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Zhang Z, Brugada P, Weiss JN, Qu Z. Phase 2 Re-Entry Without I to: Role of Sodium Channel Kinetics in Brugada Syndrome Arrhythmias. JACC Clin Electrophysiol 2023; 9:2459-2474. [PMID: 37831035 DOI: 10.1016/j.jacep.2023.08.027] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 07/27/2023] [Accepted: 08/23/2023] [Indexed: 10/14/2023]
Abstract
BACKGROUND In Brugada syndrome (BrS), phase 2 re-excitation/re-entry (P2R) induced by the transient outward potassium current (Ito) is a proposed arrhythmia mechanism; yet, the most common genetic defects are loss-of-function sodium channel mutations. OBJECTIVES The authors used computer simulations to investigate how sodium channel dysfunction affects P2R-mediated arrhythmogenesis in the presence and absence of Ito. METHODS Computer simulations were carried out in 1-dimensional cables and 2-dimensional tissue using guinea pig and human ventricular action potential models. RESULTS In the presence of Ito sufficient to generate robust P2R, reducing sodium current (INa) peak amplitude alone only slightly potentiated P2R. When INa inactivation kinetics were also altered to simulate reported effects of BrS mutations and sodium channel blockers, however, P2R occurred even in the absence of Ito. These effects could be potentiated by delaying L-type calcium channel activation or increasing ATP-sensitive potassium current, consistent with experimental and clinical findings. INa-mediated P2R also accounted for sex-related, day and night-related, and fever-related differences in arrhythmia risk in BrS patients. CONCLUSIONS Altered INa kinetics synergize powerfully with reduced INa amplitude to promote P2R-induced arrhythmias in BrS in the absence of Ito, establishing a robust mechanistic link between altered INa kinetics and the P2R-mediated arrhythmia mechanism.
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Affiliation(s)
- Zhaoyang Zhang
- Department of Physics, School of Physical Science and Technology, Ningbo University, Ningbo, Zhejiang, China; Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Pedro Brugada
- Heart Rhythm Management Centre, Postgraduate Program in Cardiac Electrophysiology and Pacing, Universitair Ziekenhuis Brussel-Vrije Universiteit Brussel, European Reference Networks Guard-Heart, Brussels, Belgium
| | - James N Weiss
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Zhilin Qu
- Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, USA.
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2
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Abstract
Cardiac alternans arises from dynamical instabilities in the electrical and calcium cycling systems of the heart, and often precedes ventricular arrhythmias and sudden cardiac death. In this review, we integrate clinical observations with theory and experiment to paint a holistic portrait of cardiac alternans: the underlying mechanisms, arrhythmic manifestations and electrocardiographic signatures. We first summarize the cellular and tissue mechanisms of alternans that have been demonstrated both theoretically and experimentally, including 3 voltage-driven and 2 calcium-driven alternans mechanisms. Based on experimental and simulation results, we describe their relevance to mechanisms of arrhythmogenesis under different disease conditions, and their link to electrocardiographic characteristics of alternans observed in patients. Our major conclusion is that alternans is not only a predictor, but also a causal mechanism of potentially lethal ventricular and atrial arrhythmias across the full spectrum of arrhythmia mechanisms that culminate in functional reentry, although less important for anatomic reentry and focal arrhythmias.
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Affiliation(s)
- Zhilin Qu
- Departments of Medicine (Cardiology), Physiology, and Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA
| | - James N. Weiss
- Departments of Medicine (Cardiology), Physiology, and Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA
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3
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Qu Z, Liu MB, Olcese R, Karagueuzian H, Garfinkel A, Chen PS, Weiss JN. R-on-T and the initiation of reentry revisited: Integrating old and new concepts. Heart Rhythm 2022; 19:1369-1383. [PMID: 35364332 DOI: 10.1016/j.hrthm.2022.03.1224] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 03/11/2022] [Accepted: 03/23/2022] [Indexed: 12/29/2022]
Abstract
Initiation of reentry requires 2 factors: (1) a triggering event, most commonly focal excitations such as premature ventricular complexes (PVCs); and (2) a vulnerable substrate with regional dispersion of refractoriness and/or excitability, such as occurs during the T wave of the electrocardiogram when some areas of the ventricle have repolarized and recovered excitability but others have not. When the R wave of a PVC coincides in time with the T wave of the previous beat, this timing can lead to unidirectional block and initiation of reentry, known as the R-on-T phenomenon. Classically, the PVC triggering reentry has been viewed as arising focally from 1 region and propagating into another region whose recovery is delayed, resulting in unidirectional conduction block and reentry initiation. However, more recent evidence indicates that PVCs also can arise from the T wave itself. In the latter case, the PVC initiating reentry is not a separate event from the T wave but rather is causally generated from the repolarization gradient that manifests as the T wave. We call the former an "R-to-T" mechanism and the latter an "R-from-T" mechanism, which are initiation mechanisms distinct from each other. Both are important components of the R-on-T phenomenon and need to be taken into account when designing antiarrhythmic strategies. Strategies targeting suppression of triggers alone or vulnerable substrate alone may be appropriate in some instances but not in others. Preventing R-from-T arrhythmias requires suppressing the underlying dynamic tissue instabilities responsible for producing both triggers and substrate vulnerability simultaneously. The same principles are likely to apply to supraventricular arrhythmias.
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Affiliation(s)
- Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, California.
| | - Michael B Liu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Riccardo Olcese
- Department of Anesthesiology and Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Hrayr Karagueuzian
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Alan Garfinkel
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Integrative Biology and Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Peng-Sheng Chen
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - James N Weiss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
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4
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Shafaattalab S, Li AY, Gunawan MG, Kim B, Jayousi F, Maaref Y, Song Z, Weiss JN, Solaro RJ, Qu Z, Tibbits GF. Mechanisms of Arrhythmogenicity of Hypertrophic Cardiomyopathy-Associated Troponin T ( TNNT2) Variant I79N. Front Cell Dev Biol 2022; 9:787581. [PMID: 34977031 PMCID: PMC8718794 DOI: 10.3389/fcell.2021.787581] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 11/16/2021] [Indexed: 12/24/2022] Open
Abstract
Hypertrophic cardiomyopathy (HCM) is the most common heritable cardiovascular disease and often results in cardiac remodeling and an increased incidence of sudden cardiac arrest (SCA) and death, especially in youth and young adults. Among thousands of different variants found in HCM patients, variants of TNNT2 (cardiac troponin T—TNNT2) are linked to increased risk of ventricular arrhythmogenesis and sudden death despite causing little to no cardiac hypertrophy. Therefore, studying the effect of TNNT2 variants on cardiac propensity for arrhythmogenesis can pave the way for characterizing HCM in susceptible patients before sudden cardiac arrest occurs. In this study, a TNNT2 variant, I79N, was generated in human cardiac recombinant/reconstituted thin filaments (hcRTF) to investigate the effect of the mutation on myofilament Ca2+ sensitivity and Ca2+ dissociation rate using steady-state and stopped-flow fluorescence techniques. The results revealed that the I79N variant significantly increases myofilament Ca2+ sensitivity and decreases the Ca2+ off-rate constant (koff). To investigate further, a heterozygous I79N+/−TNNT2 variant was introduced into human-induced pluripotent stem cells using CRISPR/Cas9 and subsequently differentiated into ventricular cardiomyocytes (hiPSC-CMs). To study the arrhythmogenic properties, monolayers of I79N+/− hiPSC-CMs were studied in comparison to their isogenic controls. Arrhythmogenesis was investigated by measuring voltage (Vm) and cytosolic Ca2+ transients over a range of stimulation frequencies. An increasing stimulation frequency was applied to the cells, from 55 to 75 bpm. The results of this protocol showed that the TnT-I79N cells had reduced intracellular Ca2+ transients due to the enhanced cytosolic Ca2+ buffering. These changes in Ca2+ handling resulted in beat-to-beat instability and triangulation of the cardiac action potential, which are predictors of arrhythmia risk. While wild-type (WT) hiPSC-CMs were accurately entrained to frequencies of at least 150 bpm, the I79N hiPSC-CMs demonstrated clear patterns of alternans for both Vm and Ca2+ transients at frequencies >75 bpm. Lastly, a transcriptomic analysis was conducted on WT vs. I79N+/−TNNT2 hiPSC-CMs using a custom NanoString codeset. The results showed a significant upregulation of NPPA (atrial natriuretic peptide), NPPB (brain natriuretic peptide), Notch signaling pathway components, and other extracellular matrix (ECM) remodeling components in I79N+/− vs. the isogenic control. This significant shift demonstrates that this missense in the TNNT2 transcript likely causes a biophysical trigger, which initiates this significant alteration in the transcriptome. This TnT-I79N hiPSC-CM model not only reproduces key cellular features of HCM-linked mutations but also suggests that this variant causes uncharted pro-arrhythmic changes to the human action potential and gene expression.
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Affiliation(s)
- Sanam Shafaattalab
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Alison Y Li
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, BC, Canada
| | - Marvin G Gunawan
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - BaRun Kim
- Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Farah Jayousi
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Yasaman Maaref
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada
| | - Zhen Song
- UCLA Cardiac Computation Lab, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - James N Weiss
- UCLA Cardiac Computation Lab, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - R John Solaro
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL, United States
| | - Zhilin Qu
- UCLA Cardiac Computation Lab, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Glen F Tibbits
- Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, BC, Canada.,Cellular and Regenerative Medicine Centre, BC Children's Hospital Research Institute, Vancouver, BC, Canada.,Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC, Canada.,Department of Biomedical Engineering, University of British Columbia, Vancouver, BC, Canada
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5
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Abstract
BACKGROUND Three types of characteristic ST-segment elevation are associated with Brugada syndrome but only type 1 is diagnostic. Why only type 1 ECG is diagnostic remains unanswered. METHODS Computer simulations were performed in single cells, 1-dimensional cables, and 2-dimensional tissues to investigate the effects of the peak and late components of the transient outward potassium current (Ito), sodium current, and L-type calcium current (ICa,L) as well as other potassium currents on the genesis of ECG morphologies and phase 2 reentry (P2R). RESULTS Although a sufficiently large peak Ito was required to result in the type 1 ECG pattern and P2R, increasing the late component of Ito converted type 1 ECG to type 2 ECG and suppressed P2R. Increasing the peak Ito promoted spiral wave breakup, potentiating the transition from tachycardia to fibrillation, but increasing the late Ito prevented spiral wave breakup by flattening the action potential duration restitution and preventing P2R. A sufficiently large ICa,L conductance was needed for P2R to occur, but once above the critical conductance, blocking ICa,L promoted P2R. However, selectively blocking the window and late components of ICa,L suppressed P2R, countering the effect of the late Ito. Blocking either the peak or late components of sodium current promoted P2R, with the late sodium current blockade having the larger effect. As expected, increasing other potassium currents potentiated P2R, with ATP-sensitive potassium current exhibiting a larger effect than rapid and slow component of the delayed rectifier potassium current. CONCLUSIONS The peak Ito promotes type 1 ECG and P2R, whereas the late Ito converts type 1 ECG to type 2 ECG and suppresses P2R. Blocking the peak ICa,L and either the peak or the late sodium current promotes P2R, whereas blocking the window and late ICa,L suppresses P2R. These results provide important insights into the mechanisms of arrhythmogenesis and potential therapeutic targets for treatment of Brugada syndrome. Graphic Abstract: A graphic abstract is available for this article.
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Affiliation(s)
- Zhaoyang Zhang
- Department of physics, School of Physical Science and Technology, Ningbo University, Ningbo, Zhejiang 315211, China
| | - Peng-Sheng Chen
- Department of Cardiology, Cedars Sinai Medical Center, Los Aneles, CA 90048, USA
| | - James N. Weiss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
- Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, California 90095, USA
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6
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Angelini M, Pezhouman A, Savalli N, Chang MG, Steccanella F, Scranton K, Calmettes G, Ottolia M, Pantazis A, Karagueuzian HS, Weiss JN, Olcese R. Suppression of ventricular arrhythmias by targeting late L-type Ca2+ current. J Gen Physiol 2021; 153:212725. [PMID: 34698805 PMCID: PMC8552156 DOI: 10.1085/jgp.202012584] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 07/15/2021] [Accepted: 09/02/2021] [Indexed: 12/15/2022] Open
Abstract
Ventricular arrhythmias, a leading cause of sudden cardiac death, can be triggered by cardiomyocyte early afterdepolarizations (EADs). EADs can result from an abnormal late activation of L-type Ca2+ channels (LTCCs). Current LTCC blockers (class IV antiarrhythmics), while effective at suppressing EADs, block both early and late components of ICa,L, compromising inotropy. However, computational studies have recently demonstrated that selective reduction of late ICa,L (Ca2+ influx during late phases of the action potential) is sufficient to potently suppress EADs, suggesting that effective antiarrhythmic action can be achieved without blocking the early peak ICa,L, which is essential for proper excitation–contraction coupling. We tested this new strategy using a purine analogue, roscovitine, which reduces late ICa,L with minimal effect on peak current. Scaling our investigation from a human CaV1.2 channel clone to rabbit ventricular myocytes and rat and rabbit perfused hearts, we demonstrate that (1) roscovitine selectively reduces ICa,L noninactivating component in a human CaV1.2 channel clone and in ventricular myocytes native current, (2) the pharmacological reduction of late ICa,L suppresses EADs and EATs (early after Ca2+ transients) induced by oxidative stress and hypokalemia in isolated myocytes, largely preserving cell shortening and normal Ca2+ transient, and (3) late ICa,L reduction prevents/suppresses ventricular tachycardia/fibrillation in ex vivo rabbit and rat hearts subjected to hypokalemia and/or oxidative stress. These results support the value of an antiarrhythmic strategy based on the selective reduction of late ICa,L to suppress EAD-mediated arrhythmias. Antiarrhythmic therapies based on this idea would modify the gating properties of CaV1.2 channels rather than blocking their pore, largely preserving contractility.
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Affiliation(s)
- Marina Angelini
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Arash Pezhouman
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Nicoletta Savalli
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Marvin G Chang
- Department of Anesthesia and Critical Care, Massachusetts General Hospital, Harvard Medical School, Boston, MA
| | - Federica Steccanella
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Kyle Scranton
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Guillaume Calmettes
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Michela Ottolia
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,University of California, Los Angeles Cardiovascular Theme, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Antonios Pantazis
- Division of Neurobiology, Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden.,Wallenberg Center for Molecular Medicine, Linköping University, Linköping, Sweden
| | - Hrayr S Karagueuzian
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - James N Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
| | - Riccardo Olcese
- Division of Molecular Medicine, Department of Anesthesiology & Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,University of California, Los Angeles Cardiovascular Theme, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA
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8
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Fei YD, Chen M, Guo S, Ueoka A, Chen Z, Rubart-von der Lohe M, Everett TH, Qu Z, Weiss JN, Chen PS. Simultaneous activation of the small conductance calcium-activated potassium current by acetylcholine and inhibition of sodium current by ajmaline cause J-wave syndrome in Langendorff-perfused rabbit ventricles. Heart Rhythm 2020; 18:98-108. [PMID: 32763429 DOI: 10.1016/j.hrthm.2020.07.036] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2019] [Revised: 07/24/2020] [Accepted: 07/30/2020] [Indexed: 01/06/2023]
Abstract
BACKGROUND Concomitant apamin-sensitive small conductance calcium-activated potassium current (IKAS) activation and sodium current inhibition induce J-wave syndrome (JWS) in rabbit hearts. Sudden death in JWS occurs predominantly in men at night when parasympathetic tone is strong. OBJECTIVE The purpose of this study was to test the hypotheses that acetylcholine (ACh), the parasympathetic transmitter, activates IKAS and causes JWS in the presence of ajmaline. METHODS We performed optical mapping in Langendorff-perfused rabbit hearts and whole-cell voltage clamp to determine IKAS in isolated ventricular cardiomyocytes. RESULTS ACh (1 μM) + ajmaline (2 μM) induced J-point elevations in all (6 male and 6 female) hearts from 0.01± 0.01 to 0.31 ± 0.05 mV (P<.001), which were reduced by apamin (specific IKAS inhibitor, 100 nM) to 0.14 ± 0.02 mV (P<.001). More J-point elevation was noted in male than in female hearts (P=.037). Patch clamp studies showed that ACh significantly (P<.001) activated IKAS in isolated male but not in female ventricular myocytes (n=8). Optical mapping studies showed that ACh induced action potential duration (APD) heterogeneity, which was more significant in right than in left ventricles. Apamin in the presence of ACh prolonged both APD at the level of 25% (P<.001) and APD at the level of 80% (P<.001) and attenuated APD heterogeneity. Ajmaline further increased APD heterogeneity induced by ACh. Ventricular arrhythmias were induced in 6 of 6 male and 1 of 6 female hearts (P=.015) in the presence of ACh and ajmaline, which was significantly suppressed by apamin in the former. CONCLUSION ACh activates ventricular IKAS. ACh and ajmaline induce JWS and facilitate the induction of ventricular arrhythmias more in male than in female ventricles.
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Affiliation(s)
- Yu-Dong Fei
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, XinHua Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Mu Chen
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, XinHua Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shuai Guo
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Akira Ueoka
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiovascular Medicine, Okayama University Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama, Japan
| | - Zhenhui Chen
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Michael Rubart-von der Lohe
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine, Indianapolis, Indiana
| | - Thomas H Everett
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Zhilin Qu
- Department of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California
| | - James N Weiss
- Department of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology, Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Cedars-Sinai Medical Center, Los Angeles, California.
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9
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Abstract
BACKGROUND In cardiac gene therapy to improve contractile function, achieving gene expression in the majority of cardiac myocytes is essential. In preventing cardiac arrhythmias, however, this goal may not be as important since transduction efficiencies as low as 40% suppressed ventricular arrhythmias in genetically modified mice with catecholaminergic polymorphic ventricular tachycardia. METHODS Using computational modeling, we simulated 1-, 2-, and 3-dimensional tissue under a variety of conditions to test the ability of genetically engineered nonarrhythmogenic stabilizer cells to suppress triggered activity due to delayed or early afterdepolarizations. RESULTS Due to source-sink relationships in cardiac tissue, a minority (20%-50%) of randomly distributed stabilizer cells engineered to be nonarrhythmogenic can suppress the ability of arrhythmogenic cells to generate delayed and early afterdepolarizations-related arrhythmias. Stabilizer cell gene therapy strategy can be designed to correct a specific arrhythmogenic mutation, as in the catecholaminergic polymorphic ventricular tachycardia mice studies, or more generally to suppress delayed or early afterdepolarizations from any cause by overexpressing the inward rectifier K channel Kir2.1 in stabilizer cells. CONCLUSIONS This promising antiarrhythmic strategy warrants further testing in experimental models to evaluate its clinical potential.
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Affiliation(s)
- Michael B Liu
- Departments of Medicine/Cardiology (M.B.L., Z.Q., J.N.W.), David Geffen School of Medicine, University of California, Los Angeles.,Physiology (M.B.L., J.N.W.), David Geffen School of Medicine, University of California, Los Angeles
| | - Silvia G Priori
- Department of Molecular Medicine, University of Pavia, Italy (S.G.P.).,Istituti Clinici Scientifici Maugeri, IRCCS, Pavia Italy (S.G.P.).,Centro de Investigaciones Cardiovasculares Carlos III, Madrid, Spain (S.G.P.)
| | - Zhilin Qu
- Departments of Medicine/Cardiology (M.B.L., Z.Q., J.N.W.), David Geffen School of Medicine, University of California, Los Angeles.,Computational Medicine (Z.Q.), David Geffen School of Medicine, University of California, Los Angeles
| | - James N Weiss
- Departments of Medicine/Cardiology (M.B.L., Z.Q., J.N.W.), David Geffen School of Medicine, University of California, Los Angeles.,Physiology (M.B.L., J.N.W.), David Geffen School of Medicine, University of California, Los Angeles
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10
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Wu AZ, Chen M, Yin D, Everett TH, Chen Z, Rubart M, Weiss JN, Qu Z, Chen PS. Sex-specific I KAS activation in rabbit ventricles with drug-induced QT prolongation. Heart Rhythm 2020; 18:88-97. [PMID: 32707174 DOI: 10.1016/j.hrthm.2020.07.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Revised: 06/30/2020] [Accepted: 07/13/2020] [Indexed: 01/23/2023]
Abstract
BACKGROUND Female sex is a known risk factor for drug-induced long QT syndrome (diLQTS). We recently demonstrated a sex difference in apamin-sensitive small-conductance Ca2+-activated K+ current (IKAS) activation during β-adrenergic stimulation. OBJECTIVE The purpose of this study was to test the hypothesis that there is a sex difference in IKAS in the rabbit models of diLQTS. METHODS We evaluated the sex difference in ventricular repolarization in 15 male and 22 female Langendorff-perfused rabbit hearts with optical mapping techniques during atrial pacing. HMR1556 (slowly activating delayed rectifier K+ current [IKs] blocker), E4031 (rapidly activating delayed rectifier K+ current [IKr] blocker) and sea anemone toxin (ATX-II, late Na+ current [INaL] activator) were used to simulate types 1-3 long QT syndrome, respectively. Apamin, an IKAS blocker, was then added to determine the magnitude of further QT prolongation. RESULTS HMR1556, E4031, and ATX-II led to the prolongation of action potential duration at 80% repolarization (APD80) in both male and female ventricles at pacing cycle lengths of 300-400 ms. Apamin further prolonged APD80 (pacing cycle length 350 ms) from 187.8±4.3 to 206.9±7.1 (P=.014) in HMR1556-treated, from 209.9±7.8 to 224.9±7.8 (P=.003) in E4031-treated, and from 174.3±3.3 to 188.1±3.0 (P=.0002) in ATX-II-treated female hearts. Apamin did not further prolong the APD80 in male hearts. The Cai transient duration (CaiTD) was significantly longer in diLQTS than baseline but without sex differences. Apamin did not change CaiTD. CONCLUSION We conclude that IKAS is abundantly increased in female but not in male ventricles with diLQTS. Increased IKAS helps preserve the repolarization reserve in female ventricles treated with IKs and IKr blockers or INaL activators.
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Affiliation(s)
- Adonis Z Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Michael Rubart
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine, Indianapolis, Indiana
| | - James N Weiss
- Departments of Medicine (Cardiology), Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | - Zhilin Qu
- Departments of Medicine (Cardiology), Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Cedars-Sinai Medical Center, Los Angeles, California.
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Landaw J, Zhang Z, Song Z, Liu MB, Olcese R, Chen PS, Weiss JN, Qu Z. Small-conductance Ca 2+-activated K + channels promote J-wave syndrome and phase 2 reentry. Heart Rhythm 2020; 17:1582-1590. [PMID: 32333974 DOI: 10.1016/j.hrthm.2020.04.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 03/30/2020] [Accepted: 04/10/2020] [Indexed: 12/14/2022]
Abstract
BACKGROUND Small-conductance Ca2+-activated potassium (SK) channels play complex roles in cardiac arrhythmogenesis. SK channels colocalize with L-type Ca2+ channels, yet how this colocalization affects cardiac arrhythmogenesis is unknown. OBJECTIVE The purpose of this study was to investigate the role of colocalization of SK channels with L-type Ca2+ channels in promoting J-wave syndrome and ventricular arrhythmias. METHODS We carried out computer simulations of single-cell and tissue models. SK channels in the model were assigned to preferentially sense Ca2+ in the bulk cytosol, subsarcolemmal space, or junctional cleft. RESULTS When SK channels sense Ca2+ in the bulk cytosol, the SK current (ISK) rises and decays slowly during an action potential, the action potential duration (APD) decreases as the maximum conductance increases, no complex APD dynamics and phase 2 reentry can be induced by ISK. When SK channels sense Ca2+ in the subsarcolemmal space or junctional cleft, ISK can rise and decay rapidly during an action potential in a spike-like pattern because of spiky Ca2+ transients in these compartments, which can cause spike-and-dome action potential morphology, APD alternans, J-wave elevation, and phase 2 reentry. Our results can account for the experimental finding that activation of ISK induced J-wave syndrome and phase 2 reentry in rabbit hearts. CONCLUSION Colocalization of SK channels with L-type Ca2+ channels so that they preferentially sense Ca2+ in the subsarcolemmal or junctional space may result in a spiky ISK, which can functionally play a similar role of the transient outward K+ current in promoting J-wave syndrome and ventricular arrhythmias.
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Affiliation(s)
- Julian Landaw
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhaoyang Zhang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhen Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Michael B Liu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Riccardo Olcese
- Department of Anesthesiology and Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - James N Weiss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
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12
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Angelini M, Pezhouman A, Savalli N, Chang M, Calmettes G, Steccanella F, Pantazis A, Karagueuzian HS, Weiss JN, Olcese R. Potent Suppression of Ventricular Arrhythmias by Selectively Targeting Late L-type Calcium Current. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.723] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
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Affiliation(s)
- James N Weiss
- From the UCLA Cardiovascular Research Laboratory and Cardiac Arrhythmia Center, Departments of Medicine (Cardiology) (J.N.W., Z.Q., K.S.), Physiology (J.N.W.), and Radiological Sciences (K.S.), David Geffen School of Medicine at UCLA, Los Angeles, CA.
| | - Zhilin Qu
- From the UCLA Cardiovascular Research Laboratory and Cardiac Arrhythmia Center, Departments of Medicine (Cardiology) (J.N.W., Z.Q., K.S.), Physiology (J.N.W.), and Radiological Sciences (K.S.), David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Kalyanam Shivkumar
- From the UCLA Cardiovascular Research Laboratory and Cardiac Arrhythmia Center, Departments of Medicine (Cardiology) (J.N.W., Z.Q., K.S.), Physiology (J.N.W.), and Radiological Sciences (K.S.), David Geffen School of Medicine at UCLA, Los Angeles, CA
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14
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Chen M, Xu DZ, Wu AZ, Guo S, Wan J, Yin D, Lin SF, Chen Z, Rubart-von der Lohe M, Everett TH, Qu Z, Weiss JN, Chen PS. Concomitant SK current activation and sodium current inhibition cause J wave syndrome. JCI Insight 2018; 3:122329. [PMID: 30429367 DOI: 10.1172/jci.insight.122329] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2018] [Accepted: 07/17/2018] [Indexed: 12/18/2022] Open
Abstract
The mechanisms of J wave syndrome (JWS) are incompletely understood. Here, we showed that the concomitant activation of small-conductance calcium-activated potassium (SK) current (IKAS) and inhibition of sodium current by cyclohexyl-[2-(3,5-dimethyl-pyrazol-1-yl)-6-methyl-pyrimidin-4-yl]-amine (CyPPA) recapitulate the phenotypes of JWS in Langendorff-perfused rabbit hearts. CyPPA induced significant J wave elevation and frequent spontaneous ventricular fibrillation (SVF), as well as sinus bradycardia, atrioventricular block, and intraventricular conduction delay. IKAS activation by CyPPA resulted in heterogeneous shortening of action potential (AP) duration (APD) and repolarization alternans. CyPPA inhibited cardiac sodium current (INa) and decelerated AP upstroke and intracellular calcium transient. SVFs were typically triggered by short-coupled premature ventricular contractions, initiated with phase 2 reentry and originated more frequently from the right than the left ventricles. Subsequent IKAS blockade by apamin reduced J wave elevation and eliminated SVF. β-Adrenergic stimulation was antiarrhythmic in CyPPA-induced electrical storm. Like CyPPA, hypothermia (32.0°C) also induced J wave elevation and SVF. It facilitated negative calcium-voltage coupling and phase 2 repolarization alternans with spatial and electromechanical discordance, which were ameliorated by apamin. These findings suggest that IKAS activation contributes to the development of JWS in rabbit ventricles.
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Affiliation(s)
- Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Dong-Zhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Cardiovascular Division, Institute of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Adonis Z Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Shuai Guo
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Juyi Wan
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Department of Cardiothoracic Surgery, Affiliated Hospital of Southwest Medical University, Luzhou, China
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsin-Chu, Taiwan
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Michael Rubart-von der Lohe
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Zhilin Qu
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California, USA
| | - James N Weiss
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, California, USA
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA
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Wan J, Chen M, Wang Z, Everett TH, Rubart-von der Lohe M, Shen C, Qu Z, Weiss JN, Boyden PA, Chen PS. Small-conductance calcium-activated potassium current modulates the ventricular escape rhythm in normal rabbit hearts. Heart Rhythm 2018; 16:615-623. [PMID: 30445170 DOI: 10.1016/j.hrthm.2018.10.033] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Indexed: 10/27/2022]
Abstract
BACKGROUND The apamin-sensitive small-conductance calcium-activated K (SK) current IKAS modulates automaticity of the sinus node. IKAS blockade by apamin causes sinus bradycardia. OBJECTIVE The purpose of this study was to test the hypothesis that IKAS modulates ventricular automaticity. METHODS We tested the effects of apamin (100 nM) on ventricular escape rhythms in Langendorff-perfused rabbit ventricles with atrioventricular block (protocol 1) and on recorded transmembrane action potential of pseudotendons of superfused right ventricular endocardial preparations (protocol 2). RESULTS All preparations exhibited spontaneous ventricular escape rhythms. In protocol 1, apamin decreased the atrial rate from 186.2 ± 18.0 bpm to 163.8 ± 18.7 bpm (N = 6; P = .006) but accelerated the ventricular escape rate from 51.5 ± 10.7 bpm to 98.2 ± 25.4 bpm (P = .031). Three preparations exhibited bursts of nonsustained ventricular tachycardia and pauses, resulting in repeated burst termination pattern. In protocol 2, apamin increased the ventricular escape rate from 70.2 ± 13.1 bpm to 110.1 ± 2.2 bpm (P = .035). Spontaneous phase 4 depolarization was recorded from the pseudotendons in 6 of 10 preparations at baseline and in 3 in the presence of apamin. There were no changes of phase 4 slope (18.37 ± 3.55 mV/s vs 18.93 ± 3.26 mV/s, N = 3; P = .231, ), but the threshold of phase 0 activation (mV) reduced from -67.97 ± 1.53 to -75.26 ± 0.28 (P = .034). Addition of JTV-519, a ryanodine receptor 2 stabilizer, in 5 preparations reduced escape rate back to baseline. CONCLUSION Contrary to its bradycardic effect in the sinus node, IKAS blockade by apamin accelerates ventricular automaticity and causes repeated nonsustained ventricular tachycardia in normal ventricles. ryanodine receptor 2 blockade reversed the apamin effects on ventricular automaticity.
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Affiliation(s)
- Juyi Wan
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiothoracic Surgery, the Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan Province, China
| | - Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Zhuo Wang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | | | - Changyu Shen
- Richard and Susan Smith Center for Outcomes Research in Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Zhilin Qu
- Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | - James N Weiss
- Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at the University of California, Los Angeles, California
| | | | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana.
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Rees CM, Yang JH, Santolini M, Lusis AJ, Weiss JN, Karma A. The Ca 2+ transient as a feedback sensor controlling cardiomyocyte ionic conductances in mouse populations. eLife 2018; 7:36717. [PMID: 30251624 PMCID: PMC6205808 DOI: 10.7554/elife.36717] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 09/24/2018] [Indexed: 12/13/2022] Open
Abstract
Conductances of ion channels and transporters controlling cardiac excitation may vary in a population of subjects with different cardiac gene expression patterns. However, the amount of variability and its origin are not quantitatively known. We propose a new conceptual approach to predict this variability that consists of finding combinations of conductances generating a normal intracellular Ca2+ transient without any constraint on the action potential. Furthermore, we validate experimentally its predictions using the Hybrid Mouse Diversity Panel, a model system of genetically diverse mouse strains that allows us to quantify inter-subject versus intra-subject variability. The method predicts that conductances of inward Ca2+ and outward K+ currents compensate each other to generate a normal Ca2+ transient in good quantitative agreement with current measurements in ventricular myocytes from hearts of different isogenic strains. Our results suggest that a feedback mechanism sensing the aggregate Ca2+ transient of the heart suffices to regulate ionic conductances.
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Affiliation(s)
- Colin M Rees
- Physics Department, Northeastern University, Boston, United states.,Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, United States
| | - Jun-Hai Yang
- Department of Medicine (Cardiology), Cardiovascular Research Laboratory, David Geffen School of Medicine, University of California, Los Angeles, United states.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, United States
| | - Marc Santolini
- Physics Department, Northeastern University, Boston, United states.,Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, United States
| | - Aldons J Lusis
- Department of Medicine (Cardiology), Cardiovascular Research Laboratory, David Geffen School of Medicine, University of California, Los Angeles, United states.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, United States.,Department of Microbiology, David Geffen School of Medicine, University of California, Los Angeles, United States.,Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, United States
| | - James N Weiss
- Department of Medicine (Cardiology), Cardiovascular Research Laboratory, David Geffen School of Medicine, University of California, Los Angeles, United states.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, United States
| | - Alain Karma
- Physics Department, Northeastern University, Boston, United states.,Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, United States
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17
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Chen M, Yin D, Guo S, Xu DZ, Wang Z, Chen Z, Rubart-von der Lohe M, Lin SF, Everett Iv TH, Weiss JN, Chen PS. Sex-specific activation of SK current by isoproterenol facilitates action potential triangulation and arrhythmogenesis in rabbit ventricles. J Physiol 2018; 596:4299-4322. [PMID: 29917243 DOI: 10.1113/jp275681] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 06/11/2018] [Indexed: 01/09/2023] Open
Abstract
KEY POINTS It is unknown if a sex difference exists in cardiac apamin-sensitive small conductance Ca2+ -activated K+ (SK) current (IKAS ). There is no sex difference in IKAS in the basal condition. However, there is larger IKAS in female rabbit ventricles than in male during isoproterenol infusion. IKAS activation by isoproterenol leads to action potential triangulation in females, indicating its abundant activation at early phases of repolarization. IKAS activation in females induces negative Ca2+ -voltage coupling and promotes electromechanically discordant phase 2 repolarization alternans. IKAS is important in the mechanisms of ventricular fibrillation in females during sympathetic stimulation. ABSTRACT Sex has a large influence on cardiac electrophysiological properties. Whether sex differences exist in apamin-sensitive small conductance Ca2+ -activated K+ (SK) current (IKAS ) remains unknown. We performed optical mapping, transmembrane potential, patch clamp, western blot and immunostaining in 62 normal rabbit ventricles, including 32 females and 30 males. IKAS blockade by apamin only minimally prolonged action potential (AP) duration (APD) in the basal condition for both sexes, but significantly prolonged APD in the presence of isoproterenol in females. Apamin prolonged APD at the level of 25% repolarization (APD25 ) more prominently than APD at the level of 80% repolarization (APD80 ), consequently reversing isoproterenol-induced AP triangulation in females. In comparison, apamin prolonged APD to a significantly lesser extent in males and failed to restore the AP plateau during isoproterenol infusion. IKAS in males did not respond to the L-type calcium current agonist BayK8644, but was amplified by the casein kinase 2 (CK2) inhibitor 4,5,6,7-tetrabromobenzotriazole. In addition, whole-cell outward IKAS densities in ventricular cardiomyocytes were significantly larger in females than in males. SK channel subtype 2 (SK2) protein expression was higher and the CK2/SK2 ratio was lower in females than in males. IKAS activation in females induced negative intracellular Ca2+ -voltage coupling, promoted electromechanically discordant phase 2 repolarization alternans and facilitated ventricular fibrillation (VF). Apamin eliminated the negative Ca2+ -voltage coupling, attenuated alternans and reduced VF inducibility, phase singularities and dominant frequencies in females, but not in males. We conclude that β-adrenergic stimulation activates ventricular IKAS in females to a much greater extent than in males. IKAS activation plays an important role in ventricular arrhythmogenesis in females during sympathetic stimulation.
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Affiliation(s)
- Mu Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Shuai Guo
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Dong-Zhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Cardiovascular Division, Institute of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Zhuo Wang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Michael Rubart-von der Lohe
- Department of Pediatrics, Riley Heart Research Center, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.,Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan
| | - Thomas H Everett Iv
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - James N Weiss
- Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles, CA, USA
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
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19
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Yin D, Chen M, Yang N, Wu AZ, Xu D, Tsai WC, Yuan Y, Tian Z, Chan YH, Shen C, Chen Z, Lin SF, Weiss JN, Chen PS, Everett TH. Role of apamin-sensitive small conductance calcium-activated potassium currents in long-term cardiac memory in rabbits. Heart Rhythm 2018; 15:761-769. [PMID: 29325977 DOI: 10.1016/j.hrthm.2018.01.016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Indexed: 12/13/2022]
Abstract
BACKGROUND Apamin-sensitive small conductance calcium-activated K current (IKAS) is up-regulated during ventricular pacing and masks short-term cardiac memory (CM). OBJECTIVE The purpose of this study was to determine the role of IKAS in long-term CM. METHODS CM was created with 3-5 weeks of ventricular pacing and defined by a flat or inverted T wave off pacing. Epicardial optical mapping was performed in both paced and normal ventricles. Action potential duration (APD80) was determined during right atrial pacing. Ventricular stability was tested before and after IKAS blockade. Four paced hearts and 4 normal hearts were used for western blotting and histology. RESULTS There were no significant differences in either echocardiographic parameters or fibrosis levels between groups. Apamin induced more APD80 prolongation in CM than in normal ventricles (mean [95% confidence interval]: 9.6% [8.8%-10.5%] vs 3.1% [1.9%-4.3%]; P <.001). Apamin significantly lengthened APD80 in the CM model at late activation sites, indicating significant IKAS up-regulation at those sites. The CM model also had altered Ca2+ handling, with the 50% Ca2+ transient duration and amplitude increased at distal sites compared to a proximal site (near the pacing site). After apamin, the CM model had increased ventricular fibrillation (VF) inducibility (paced vs control: 33/40 (82.5%) vs 7/20 (35%); P <.001) and longer VF durations (124 vs 26 seconds; P <.001). CONCLUSION Chronic ventricular pacing increases Ca2+ transients at late activation sites, which activates IKAS to maintain repolarization reserve. IKAS blockade increases VF vulnerability in chronically paced rabbit ventricles.
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Affiliation(s)
- Dechun Yin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Mu Chen
- Department of Cardiology, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Na Yang
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Gynecological and Obstetric Ultrasound, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Adonis Z Wu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan
| | - Dongzhu Xu
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan
| | - Wei-Chung Tsai
- Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan
| | - Yuan Yuan
- Department of Cardiothoracic Surgery, Xinhua Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Zhipeng Tian
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Department of Cardiology, Central Hospital Affiliated to Shenyang Medical College, Shenyang, Liaoning, China
| | - Yi-Hsin Chan
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan
| | - Changyu Shen
- Richard and Susan Smith Center for Outcomes Research in Cardiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Shien-Fong Lin
- Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan
| | - James N Weiss
- Departments of Medicine and Physiology, University of California, Los Angeles, California
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana
| | - Thomas H Everett
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana.
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Pezhouman A, Cao H, Fishbein MC, Belardinelli L, Weiss JN, Karagueuzian HS. Atrial Fibrillation Initiated by Early Afterdepolarization-Mediated Triggered Activity during Acute Oxidative Stress: Efficacy of Late Sodium Current Blockade. ACTA ACUST UNITED AC 2018; 4. [PMID: 30393761 PMCID: PMC6214459 DOI: 10.16966/2379-769x.146] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Background The mechanism of Atrial Fibrillation (AF) that emerges spontaneously during acute oxidative stress is poorly defined and its drug therapy remains suboptimal. We hypothesized that oxidative activation of Ca-calmodulin dependent protein kinase (CaMKII) promotes Early Afterdepolarization-(EAD)-mediated triggered AF in aged fibrotic atria that is sensitive to late Na current (INa-L) blockade. Method and Results High-resolution voltage optical mapping of the Left and Right Atrial (LA & RA) epicardial surfaces along with microelectrode recordings were performed in isolated-perfused male Fisher 344 rat hearts in Langendorff setting. Aged atria (23-24 months) manifested 10-fold increase in atrial tissue fibrosis compared to young/adult (2-4 months) atria (P<0001. Spontaneous AF arose in 39 out of 41 of the aged atria but in 0 out of 12 young/adult hearts (P<001) during arterial perfusion of with 0.1 mm of hydrogen peroxide (H2O2). Optical Action Potential (AP) activation maps showed that the AF was initiated by a focal mechanism in the LA suggestive of EAD-mediated triggered activity. Cellular AP recordings with glass microelectrodes from the LA epicardial sites showing focal activity confirmed optical AP recordings that the spontaneous AF was initiated by late phase 3 EAD-mediated triggered activity. Inhibition of CaMKII activity with KN-93 (1 μM) (N=6) or its downstream target, the enhanced INa-L with GS-967 (1 μM), a specific blocker of INa-L (N=6), potently suppressed the AF and prevented its initiation when perfused 15 min prior to H2O2 (n=6). Conclusions Increased atrial tissue fibrosis combined with acute oxidative activation of CaMK II Initiate AF by EAD-mediated triggered activity. Specific block of the INa-L with GS-967 effectively suppresses the AF. Drug therapy of oxidative AF in humans with traditional antiarrhythmic drugs remains suboptimal; suppressing INa-L offers a potential new strategy for effective suppression of oxidative human AF that remains suboptimal.
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Affiliation(s)
- Arash Pezhouman
- Translational Arrhythmia Section, UCLA Cardiovascular Research Laboratory, USA
| | - Hong Cao
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, PRC
| | | | | | - James N Weiss
- Translational Arrhythmia Section, UCLA Cardiovascular Research Laboratory, USA.,Departments of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, California, USA
| | - Hrayr S Karagueuzian
- Translational Arrhythmia Section, UCLA Cardiovascular Research Laboratory, USA.,Departments of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, California, USA
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21
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Savalli N, Pantazis A, Sigg D, Weiss JN, Neely A, Olcese R. The α2δ-1 subunit remodels CaV1.2 voltage sensors and allows Ca2+ influx at physiological membrane potentials. J Gen Physiol 2017; 148:147-59. [PMID: 27481713 PMCID: PMC4969795 DOI: 10.1085/jgp.201611586] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 06/30/2016] [Indexed: 12/30/2022] Open
Abstract
Voltage-sensing domains (VSDs) in voltage-gated calcium channels sense the potential difference across membranes and interact with the pore to open it. Savalli et al. find that the accessory subunit α2δ-1 increases the sensitivity of VSDs I–III and also their efficiency of coupling to the pore. Excitation-evoked calcium influx across cellular membranes is strictly controlled by voltage-gated calcium channels (CaV), which possess four distinct voltage-sensing domains (VSDs) that direct the opening of a central pore. The energetic interactions between the VSDs and the pore are critical for tuning the channel’s voltage dependence. The accessory α2δ-1 subunit is known to facilitate CaV1.2 voltage-dependent activation, but the underlying mechanism is unknown. In this study, using voltage clamp fluorometry, we track the activation of the four individual VSDs in a human L-type CaV1.2 channel consisting of α1C and β3 subunits. We find that, without α2δ-1, the channel complex displays a right-shifted voltage dependence such that currents mainly develop at nonphysiological membrane potentials because of very weak VSD–pore interactions. The presence of α2δ-1 facilitates channel activation by increasing the voltage sensitivity (i.e., the effective charge) of VSDs I–III. Moreover, the α2δ-1 subunit also makes VSDs I–III more efficient at opening the channel by increasing the coupling energy between VSDs II and III and the pore, thus allowing Ca influx within the range of physiological membrane potentials.
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Affiliation(s)
- Nicoletta Savalli
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | - Antonios Pantazis
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | | | - James N Weiss
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | - Alan Neely
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Centro Interdisciplinario de Neurociencias de Valparaíso, Facultad de Ciencias, Universidad de Valparaíso, Valparaíso 2360102, Chile
| | - Riccardo Olcese
- Department of Anesthesiology, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095 Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
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22
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Calmettes G, Weiss JN. The emergence of egalitarianism in a model of early human societies. Heliyon 2017; 3:e00451. [PMID: 29264410 PMCID: PMC5727548 DOI: 10.1016/j.heliyon.2017.e00451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 09/18/2017] [Accepted: 11/06/2017] [Indexed: 10/30/2022] Open
Abstract
How did egalitarianism emerge in early human societies? In contrast to dominance hierarchies in non-human primates, human simple forager bands are typically egalitarian, with male hunters often serving as the collective alpha. Here we present a thermodynamics-inspired simple population model, based on stochastic optimization of dominance relationships, in which a dominance hierarchy of individuals with exclusively self-centered characteristics (the desire to dominate, resentment at being dominated) transitions spontaneously to egalitarianism as their capacity for language develops. Language, specifically gossip, allows resentment against being dominated to promote the formation of antidominance coalitions which destabilize the alpha position for individuals, leading to a phase transition in which a coalition of the full population suddenly becomes dominant. Thus, egalitarianism emerges suddenly as the optimal power-sharing arrangement in a population of selfish individuals without any inherently altruistic qualities. We speculate that egalitarianism driven by punishment for exhibiting alpha-like behavior may then set the stage for genuinely altruistic traits to propagate as predicted by game theory models. Based on model simulations, we also predict that egalitarianism is a pre-condition for adaptation of tools as weapons. Potential implications for origins of human moral belief systems are discussed.
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Affiliation(s)
| | - James N. Weiss
- Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095, United States
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23
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Ko CY, Liu MB, Song Z, Qu Z, Weiss JN. Multiscale Determinants of Delayed Afterdepolarization Amplitude in Cardiac Tissue. Biophys J 2017; 112:1949-1961. [PMID: 28494965 DOI: 10.1016/j.bpj.2017.03.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Revised: 03/02/2017] [Accepted: 03/06/2017] [Indexed: 11/17/2022] Open
Abstract
Spontaneous calcium (Ca) waves in cardiac myocytes underlie delayed afterdepolarizations (DADs) that trigger cardiac arrhythmias. How these subcellular/cellular events overcome source-sink factors in cardiac tissue to generate DADs of sufficient amplitude to trigger action potentials is not fully understood. Here, we evaluate quantitatively how factors at the subcellular scale (number of Ca wave initiation sites), cellular scale (sarcoplasmic reticulum (SR) Ca load), and tissue scale (synchrony of Ca release in populations of myocytes) determine DAD features in cardiac tissue using a combined experimental and computational modeling approach. Isolated patch-clamped rabbit ventricular myocytes loaded with Fluo-4 to image intracellular Ca were rapidly paced during exposure to elevated extracellular Ca (2.7 mmol/L) and isoproterenol (0.25 μmol/L) to induce diastolic Ca waves and subthreshold DADs. As the number of paced beats increased from 1 to 5, SR Ca content (assessed with caffeine pulses) increased, the number of Ca wave initiation sites increased, integrated Ca transients and DADs became larger and shorter in duration, and the latency period to the onset of Ca waves shortened with reduced variance. In silico analysis using a computer model of ventricular tissue incorporating these experimental measurements revealed that whereas all of these factors promoted larger DADs with higher probability of generating triggered activity, the latency period variance and SR Ca load had the greatest influences. Therefore, incorporating quantitative experimental data into tissue level simulations reveals that increased intracellular Ca promotes DAD-mediated triggered activity in tissue predominantly by increasing both the synchrony (decreasing latency variance) of Ca waves in nearby myocytes and SR Ca load, whereas the number of Ca wave initiation sites per myocyte is less important.
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Affiliation(s)
- Christopher Y Ko
- Division of Cardiology, Department of Medicine, UCLA Cardiovascular Research Laboratory, University of California, Los Angeles, California
| | - Michael B Liu
- Division of Cardiology, Department of Medicine, UCLA Cardiovascular Research Laboratory, University of California, Los Angeles, California
| | - Zhen Song
- Division of Cardiology, Department of Medicine, UCLA Cardiovascular Research Laboratory, University of California, Los Angeles, California
| | - Zhilin Qu
- Division of Cardiology, Department of Medicine, UCLA Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, California
| | - James N Weiss
- Division of Cardiology, Department of Medicine, UCLA Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California.
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24
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Korge P, John SA, Calmettes G, Weiss JN. Reactive oxygen species production induced by pore opening in cardiac mitochondria: The role of complex II. J Biol Chem 2017; 292:9896-9905. [PMID: 28450394 DOI: 10.1074/jbc.m116.768325] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 04/14/2017] [Indexed: 01/02/2023] Open
Abstract
Succinate-driven reverse electron transport (RET) through complex I is hypothesized to be a major source of reactive oxygen species (ROS) that induces permeability transition pore (PTP) opening and damages the heart during ischemia/reperfusion. Because RET can only generate ROS when mitochondria are fully polarized, this mechanism is self-limiting once PTP opens during reperfusion. In the accompanying article (Korge, P., Calmettes, G., John, S. A., and Weiss, J. N. (2017) J. Biol. Chem. 292, 9882-9895), we showed that ROS production after PTP opening can be sustained when complex III is damaged (simulated by antimycin). Here we show that complex II can also contribute to sustained ROS production in isolated rabbit cardiac mitochondria following inner membrane pore formation induced by either alamethicin or calcium-induced PTP opening. Two conditions are required to maximize malonate-sensitive ROS production by complex II in isolated mitochondria: (a) complex II inhibition by atpenin A5 or complex III inhibition by stigmatellin that results in succinate-dependent reduction of the dicarboxylate-binding site of complex II (site IIf); (b) pore opening in the inner membrane resulting in rapid efflux of succinate/fumarate and other dicarboxylates capable of competitively binding to site IIf The decrease in matrix [dicarboxylate] allows O2 access to reduced site IIf, thereby making electron donation to O2 possible, explaining the rapid increase in ROS production provided that site IIf is reduced. Because ischemia is known to inhibit complexes II and III and increase matrix succinate/fumarate levels, we hypothesize that by allowing dicarboxylate efflux from the matrix, PTP opening during reperfusion may activate sustained ROS production by this mechanism after RET-driven ROS production has ceased.
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Affiliation(s)
- Paavo Korge
- From the UCLA Cardiovascular Research Laboratory and the Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Scott A John
- From the UCLA Cardiovascular Research Laboratory and the Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Guillaume Calmettes
- From the UCLA Cardiovascular Research Laboratory and the Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - James N Weiss
- From the UCLA Cardiovascular Research Laboratory and the Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
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25
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Korge P, Calmettes G, John SA, Weiss JN. Reactive oxygen species production induced by pore opening in cardiac mitochondria: The role of complex III. J Biol Chem 2017; 292:9882-9895. [PMID: 28450391 DOI: 10.1074/jbc.m116.768317] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 04/14/2017] [Indexed: 01/02/2023] Open
Abstract
Recent evidence has implicated succinate-driven reverse electron transport (RET) through complex I as a major source of damaging reactive oxygen species (ROS) underlying reperfusion injury after prolonged cardiac ischemia. However, this explanation may be incomplete, because RET on reperfusion is self-limiting and therefore transient. RET can only generate ROS when mitochondria are well polarized, and it ceases when permeability transition pores (PTP) open during reperfusion. Because prolonged ischemia/reperfusion also damages electron transport complexes, we investigated whether such damage could lead to ROS production after PTP opening has occurred. Using isolated cardiac mitochondria, we demonstrate a novel mechanism by which antimycin-inhibited complex III generates significant amounts of ROS in the presence of Mg2+ and NAD+ and the absence of exogenous substrates upon inner membrane pore formation by alamethicin or Ca2+-induced PTP opening. We show that H2O2 production under these conditions is related to Mg2+-dependent NADH generation by malic enzyme. H2O2 production is blocked by stigmatellin, indicating its origin from complex III, and by piericidin, demonstrating the importance of NADH-related ubiquinone reduction for ROS production under these conditions. For maximal ROS production, the rate of NADH generation has to be equal or below that of NADH oxidation, as further increases in [NADH] elevate ubiquinol-related complex III reduction beyond the optimal range for ROS generation. These results suggest that if complex III is damaged during ischemia, PTP opening may result in succinate/malate-fueled ROS production from complex III due to activation of malic enzyme by increases in matrix [Mg2+], [NAD+], and [ADP].
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Affiliation(s)
- Paavo Korge
- From the UCLA Cardiovascular Research Laboratory and the Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Guillaume Calmettes
- From the UCLA Cardiovascular Research Laboratory and the Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Scott A John
- From the UCLA Cardiovascular Research Laboratory and the Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - James N Weiss
- From the UCLA Cardiovascular Research Laboratory and the Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
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26
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Abstract
Excitable systems display memory, but how memory affects the excitation dynamics of such systems remains to be elucidated. Here we use computer simulation of cardiac action potential models to demonstrate that memory can cause dynamical instabilities that result in complex excitation dynamics and chaos. We develop an iterated map model that correctly describes these dynamics and show that memory converts a monotonic first return map of action potential duration into a nonmonotonic one, resulting in a period-doubling bifurcation route to chaos.
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Affiliation(s)
- Julian Landaw
- Department of Medicine (Cardiology), University of California, Los Angeles, California 90095, USA
- Department of Biomathematics, University of California, Los Angeles, California 90095, USA
| | - Alan Garfinkel
- Department of Medicine (Cardiology), University of California, Los Angeles, California 90095, USA
- Department of Integrative Biology and Physiology, University of California, Los Angeles, California 90095, USA
| | - James N. Weiss
- Department of Medicine (Cardiology), University of California, Los Angeles, California 90095, USA
- Department of Physiology, University of California, Los Angeles, California 90095, USA
| | - Zhilin Qu
- Department of Medicine (Cardiology), University of California, Los Angeles, California 90095, USA
- Department of Biomathematics, University of California, Los Angeles, California 90095, USA
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27
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Angelini M, Pezhouman A, Savalli N, Pantazis A, Karagueuzian HS, Weiss JN, Olcese R. A New Class of Antiarrhythmics for Late I CA,L. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.1285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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28
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Rau CD, Romay MC, Tuteryan M, Wang JJC, Santolini M, Ren S, Karma A, Weiss JN, Wang Y, Lusis AJ. Systems Genetics Approach Identifies Gene Pathways and Adamts2 as Drivers of Isoproterenol-Induced Cardiac Hypertrophy and Cardiomyopathy in Mice. Cell Syst 2017; 4:121-128.e4. [PMID: 27866946 PMCID: PMC5338604 DOI: 10.1016/j.cels.2016.10.016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Revised: 09/09/2016] [Accepted: 10/19/2016] [Indexed: 10/20/2022]
Abstract
We previously reported a genetic analysis of heart failure traits in a population of inbred mouse strains treated with isoproterenol to mimic catecholamine-driven cardiac hypertrophy. Here, we apply a co-expression network algorithm, wMICA, to perform a systems-level analysis of left ventricular transcriptomes from these mice. We describe the features of the overall network but focus on a module identified in treated hearts that is strongly related to cardiac hypertrophy and pathological remodeling. Using the causal modeling algorithm NEO, we identified the gene Adamts2 as a putative regulator of this module and validated the predictive value of NEO using small interfering RNA-mediated knockdown in neonatal rat ventricular myocytes. Adamts2 silencing regulated the expression of the genes residing within the module and impaired isoproterenol-induced cellular hypertrophy. Our results provide a view of higher order interactions in heart failure with potential for diagnostic and therapeutic insights.
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Affiliation(s)
- Christoph D Rau
- Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Departments of Anesthesiology, Physiology, and Medicine, Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Milagros C Romay
- Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Mary Tuteryan
- Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Jessica J-C Wang
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Marc Santolini
- Center for Interdisciplinary Research on Complex Systems, Department of Physics, Northeastern University, Boston, MA 02115, USA
| | - Shuxun Ren
- Departments of Anesthesiology, Physiology, and Medicine, Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Alain Karma
- Center for Interdisciplinary Research on Complex Systems, Department of Physics, Northeastern University, Boston, MA 02115, USA
| | - James N Weiss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yibin Wang
- Departments of Anesthesiology, Physiology, and Medicine, Cardiovascular Research Laboratories, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Aldons J Lusis
- Department of Microbiology, Immunology and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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29
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Chiamvimonvat N, Chen-Izu Y, Clancy CE, Deschenes I, Dobrev D, Heijman J, Izu L, Qu Z, Ripplinger CM, Vandenberg JI, Weiss JN, Koren G, Banyasz T, Grandi E, Sanguinetti MC, Bers DM, Nerbonne JM. Potassium currents in the heart: functional roles in repolarization, arrhythmia and therapeutics. J Physiol 2017; 595:2229-2252. [PMID: 27808412 DOI: 10.1113/jp272883] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/11/2016] [Indexed: 12/19/2022] Open
Abstract
This is the second of the two White Papers from the fourth UC Davis Cardiovascular Symposium Systems Approach to Understanding Cardiac Excitation-Contraction Coupling and Arrhythmias (3-4 March 2016), a biennial event that brings together leading experts in different fields of cardiovascular research. The theme of the 2016 symposium was 'K+ channels and regulation', and the objectives of the conference were severalfold: (1) to identify current knowledge gaps; (2) to understand what may go wrong in the diseased heart and why; (3) to identify possible novel therapeutic targets; and (4) to further the development of systems biology approaches to decipher the molecular mechanisms and treatment of cardiac arrhythmias. The sessions of the Symposium focusing on the functional roles of the cardiac K+ channel in health and disease, as well as K+ channels as therapeutic targets, were contributed by Ye Chen-Izu, Gideon Koren, James Weiss, David Paterson, David Christini, Dobromir Dobrev, Jordi Heijman, Thomas O'Hara, Crystal Ripplinger, Zhilin Qu, Jamie Vandenberg, Colleen Clancy, Isabelle Deschenes, Leighton Izu, Tamas Banyasz, Andras Varro, Heike Wulff, Eleonora Grandi, Michael Sanguinetti, Donald Bers, Jeanne Nerbonne and Nipavan Chiamvimonvat as speakers and panel discussants. This article summarizes state-of-the-art knowledge and controversies on the functional roles of cardiac K+ channels in normal and diseased heart. We endeavour to integrate current knowledge at multiple scales, from the single cell to the whole organ levels, and from both experimental and computational studies.
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Affiliation(s)
- Nipavan Chiamvimonvat
- Department of Internal Medicine, University of California, Davis, Genome and Biomedical Science Facility, Rm 6315, Davis, CA, 95616, USA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA, 95655, USA
| | - Ye Chen-Izu
- Department of Internal Medicine, University of California, Davis, Genome and Biomedical Science Facility, Rm 6315, Davis, CA, 95616, USA.,Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA.,Department of Biomedical Engineering, University of California, Davis, Genome and Biomedical Science Facility, Rm 2303, Davis, CA, 95616, USA
| | - Colleen E Clancy
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Isabelle Deschenes
- Department of Physiology and Biophysics, and Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44109, USA.,Heart and Vascular Research Center, MetroHealth Medical Center, Cleveland, OH, 44109, USA
| | - Dobromir Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | - Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Leighton Izu
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Zhilin Qu
- Division of Cardiology, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 3645 MRL, Los Angeles, CA, 90095, USA
| | - Crystal M Ripplinger
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia
| | - James N Weiss
- Division of Cardiology, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 3645 MRL, Los Angeles, CA, 90095, USA
| | - Gideon Koren
- Cardiovascular Research Center, Rhode Island Hospital and the Cardiovascular Institute, The Warren Alpert Medical School of Brown University, Providence, RI, 02903, USA
| | - Tamas Banyasz
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Michael C Sanguinetti
- Department of Internal Medicine, University of Utah, Nora Eccles Harrison Cardiovascular Research & Training Institute, Salt Lake City, UT, 84112, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Jeanne M Nerbonne
- Departments of Developmental Biology and Internal Medicine, Cardiovascular Division, Washington University Medical School, St Louis, MO, 63110, USA
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30
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Liu MB, Ko CY, Song Z, Garfinkel A, Weiss JN, Qu Z. A Dynamical Threshold for Cardiac Delayed Afterdepolarization-Mediated Triggered Activity. Biophys J 2016; 111:2523-2533. [PMID: 27926853 PMCID: PMC5153551 DOI: 10.1016/j.bpj.2016.10.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 09/22/2016] [Accepted: 10/11/2016] [Indexed: 11/18/2022] Open
Abstract
Ventricular myocytes are excitable cells whose voltage threshold for action potential (AP) excitation is ∼-60 mV at which INa is activated to give rise to a fast upstroke. Therefore, for a short stimulus pulse to elicit an AP, a stronger stimulus is needed if the resting potential lies further away from the INa threshold, such as in hypokalemia. However, for an AP elicited by a long duration stimulus or a diastolic spontaneous calcium release, we observed that the stimulus needed was lower in hypokalemia than in normokalemia in both computer simulations and experiments of rabbit ventricular myocytes. This observation provides insight into why hypokalemia promotes calcium-mediated triggered activity, despite the resting potential lying further away from the INa threshold. To understand the underlying mechanisms, we performed bifurcation analyses and demonstrated that there is a dynamical threshold, resulting from a saddle-node bifurcation mainly determined by IK1 and INCX. This threshold is close to the voltage at which IK1 is maximum, and lower than the INa threshold. After exceeding this dynamical threshold, the membrane voltage will automatically depolarize above the INa threshold due to the large negative slope of the IK1-V curve. This dynamical threshold becomes much lower in hypokalemia, especially with respect to calcium, as predicted by our theory. Because of the saddle-node bifurcation, the system can automatically depolarize even in the absence of INa to voltages higher than the ICa,L threshold, allowing for triggered APs in single myocytes with complete INa block. However, because INa is important for AP propagation in tissue, blocking INa can still suppress premature ventricular excitations in cardiac tissue caused by calcium-mediated triggered activity. This suppression is more effective in normokalemia than in hypokalemia due to the difference in dynamical thresholds.
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Affiliation(s)
- Michael B Liu
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Christopher Y Ko
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhen Song
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Alan Garfinkel
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California
| | - James N Weiss
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Physiology, University of California, Los Angeles, Los Angeles, California
| | - Zhilin Qu
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
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31
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Korge P, Calmettes G, Weiss JN. Reactive oxygen species production in cardiac mitochondria after complex I inhibition: Modulation by substrate-dependent regulation of the NADH/NAD(+) ratio. Free Radic Biol Med 2016; 96:22-33. [PMID: 27068062 PMCID: PMC4912463 DOI: 10.1016/j.freeradbiomed.2016.04.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Revised: 03/11/2016] [Accepted: 04/06/2016] [Indexed: 01/21/2023]
Abstract
Reactive oxygen species (ROS) production by isolated complex I is steeply dependent on the NADH/NAD(+) ratio. We used alamethicin-permeabilized mitochondria to study the substrate-dependence of matrix NADH and ROS production when complex I is inhibited by piericidin or rotenone. When complex I was inhibited in the presence of malate/glutamate, membrane permeabilization accelerated O2 consumption and ROS production due to a rapid increase in NADH generation that was not limited by matrix NAD(H) efflux. In the presence of inhibitor, both malate and glutamate were required to generate a high enough NADH/NAD(+) ratio to support ROS production through the coordinated activity of malate dehydrogenase (MDH) and aspartate aminotransferase (AST). With malate and glutamate present, the rate of ROS production was closely related to local NADH generation, whereas in the absence of substrates, ROS production was accelerated by increase in added [NADH]. With malate alone, oxaloacetate accumulation limited NADH production by MDH unless glutamate was also added to promote oxaloacetate removal via AST. α-ketoglutarate (KG) as well as AST inhibition also reversed NADH generation and inhibited ROS production. If malate and glutamate were provided before rather than after piericidin or rotenone, ROS generation was markedly reduced due to time-dependent efflux of CoA. CoA depletion decreased KG oxidation by α-ketoglutarate dehydrogenase (KGDH), such that the resulting increase in [KG] inhibited oxaloacetate removal by AST and NADH generation by MDH. These findings were largely obscured in intact mitochondria due to robust H2O2 scavenging and limited ability to control substrate concentrations in the matrix. We conclude that in mitochondria with inhibited complex I, malate/glutamate-stimulated ROS generation depends strongly on oxaloacetate removal and on the ability of KGDH to oxidize KG generated by AST.
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Affiliation(s)
- Paavo Korge
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Guillaume Calmettes
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - James N Weiss
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA; Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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Karbassi E, Monte E, Chapski DJ, Lopez R, Rosa Garrido M, Kim J, Wisniewski N, Rau CD, Wang JJ, Weiss JN, Wang Y, Lusis AJ, Vondriska TM. Relationship of disease-associated gene expression to cardiac phenotype is buffered by genetic diversity and chromatin regulation. Physiol Genomics 2016; 48:601-15. [PMID: 27287924 DOI: 10.1152/physiolgenomics.00035.2016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2016] [Accepted: 06/04/2016] [Indexed: 12/11/2022] Open
Abstract
Expression of a cohort of disease-associated genes, some of which are active in fetal myocardium, is considered a hallmark of transcriptional change in cardiac hypertrophy models. How this transcriptome remodeling is affected by the common genetic variation present in populations is unknown. We examined the role of genetics, as well as contributions of chromatin proteins, to regulate cardiac gene expression and heart failure susceptibility. We examined gene expression in 84 genetically distinct inbred strains of control and isoproterenol-treated mice, which exhibited varying degrees of disease. Unexpectedly, fetal gene expression was not correlated with hypertrophic phenotypes. Unbiased modeling identified 74 predictors of heart mass after isoproterenol-induced stress, but these predictors did not enrich for any cardiac pathways. However, expanded analysis of fetal genes and chromatin remodelers as groups correlated significantly with individual systemic phenotypes. Yet, cardiac transcription factors and genes shown by gain-/loss-of-function studies to contribute to hypertrophic signaling did not correlate with cardiac mass or function in disease. Because the relationship between gene expression and phenotype was strain specific, we examined genetic contribution to expression. Strikingly, strains with similar transcriptomes in the basal heart did not cluster together in the isoproterenol state, providing comprehensive evidence that there are different genetic contributors to physiological and pathological gene expression. Furthermore, the divergence in transcriptome similarity versus genetic similarity between strains is organ specific and genome-wide, suggesting chromatin is a critical buffer between genetics and gene expression.
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Affiliation(s)
- Elaheh Karbassi
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Emma Monte
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Douglas J Chapski
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Rachel Lopez
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Manuel Rosa Garrido
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Joseph Kim
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Nicholas Wisniewski
- Department of Integrative Biology and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Christoph D Rau
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Jessica J Wang
- Department of Medicine/Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - James N Weiss
- Department of Medicine/Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California; Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Yibin Wang
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, California; Department of Medicine/Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California; Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California
| | - Aldons J Lusis
- Department of Human Genetics, David Geffen School of Medicine at UCLA, Los Angeles, California; Department of Medicine/Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California; Department of Microbiology Immunology and Molecular Genetics, David Geffen School of Medicine at UCLA, Los Angeles, California; and
| | - Thomas M Vondriska
- Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, California; Department of Medicine/Cardiology, David Geffen School of Medicine at UCLA, Los Angeles, California; Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, California
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Abstract
Although considerable progress has been made in developing ablation approaches to cure atrial fibrillation (AF), outcomes are still suboptimal, especially for persistent and long-lasting persistent AF. In this topical review, we review the arrhythmia mechanisms, both reentrant and nonreentrant, that are potentially relevant to human AF at various stages/settings. We describe arrhythmia mapping techniques used to distinguish between the different mechanisms, with a particular focus on the detection of rotors. We discuss which arrhythmia mechanisms are likely to respond to ablation, and the challenges and prospects for improving upon current ablation strategies to achieve better outcomes.
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Affiliation(s)
| | - Zhilin Qu
- UCLA Cardiovascular Research Laboratory
| | - Kalyanam Shivkumar
- Cardiac Arrhythmia Center & Neurocardiology Research Center of Excellence, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
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34
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Affiliation(s)
- James N Weiss
- From the UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA.
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Liu MB, Ko CY, Song Z, Garfinkel A, Weiss JN, Zhilin Q. Determinants of the Diastolic Calcium-Voltage Coupling Gain for Delayed Afterdepolarization Mediated Triggered Activity. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.3132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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36
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Ko CY, Nguyen TP, Sovari AA, Pezhouman A, Iyer S, Cao H, Bapat A, Vahdani N, Ghanim M, Fishbein MC, Weiss JN, Karagueuzian HS. Increased Susceptibility of Spontaneously Hypertensive Rats to Ventricular Tachyarrhythmias during the Early Stages of Hypertension. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.228] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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37
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Savalli N, Angelini M, Weiss JN, Olcese R. Gabapentinoids Suppress Early Afterdepolarizations by Uncoupling α2δ-1 Subunits from CAV1.2 Channels: Implications for CAV Channel Gating-Modifiers as a New Class of Antiarrhythmics. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.252] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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38
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Song Z, Gordan R, Weiss JN, Xie LH, Qu Z. Mitochondrial Permeability Transition Pore Opening Promotes Calcium Alternans and Waves in Ventricular Myocytes. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.2337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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39
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Song Z, Ko CY, Nivala M, Weiss JN, Qu Z. Calcium-voltage coupling in the genesis of early and delayed afterdepolarizations in cardiac myocytes. Biophys J 2016; 108:1908-21. [PMID: 25902431 DOI: 10.1016/j.bpj.2015.03.011] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 03/04/2015] [Accepted: 03/10/2015] [Indexed: 02/01/2023] Open
Abstract
Early afterdepolarizations (EADs) and delayed afterdepolarizations (DADs) are voltage oscillations known to cause cardiac arrhythmias. EADs are mainly driven by voltage oscillations in the repolarizing phase of the action potential (AP), while DADs are driven by spontaneous calcium (Ca) release during diastole. Because voltage and Ca are bidirectionally coupled, they modulate each other's behaviors, and new AP and Ca cycling dynamics can emerge from this coupling. In this study, we performed computer simulations using an AP model with detailed spatiotemporal Ca cycling incorporating stochastic openings of Ca channels and ryanodine receptors to investigate the effects of Ca-voltage coupling on EAD and DAD dynamics. Simulations were complemented by experiments in mouse ventricular myocytes. We show that: 1) alteration of the Ca transient due to increased ryanodine receptor leakiness and/or sarco/endoplasmic reticulum Ca ATPase activity can either promote or suppress EADs due to the complex effects of Ca on ionic current properties; 2) spontaneous Ca waves also exhibit complex effects on EADs, but cannot induce EADs of significant amplitude without the participation of ICa,L; 3) lengthening AP duration and the occurrence of EADs promote DADs by increasing intracellular Ca loading, and two mechanisms of DADs are identified, i.e., Ca-wave-dependent and Ca-wave-independent; and 4) Ca-voltage coupling promotes complex EAD patterns such as EAD alternans that are not observed for solely voltage-driven EADs. In conclusion, Ca-voltage coupling combined with the nonlinear dynamical behaviors of voltage and Ca cycling play a key role in generating complex EAD and DAD dynamics observed experimentally in cardiac myocytes, whose mechanisms are complex but analyzable.
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Affiliation(s)
- Zhen Song
- Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Medicine (Cardiology), University of California, Los Angeles, California
| | - Christopher Y Ko
- Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Medicine (Cardiology), University of California, Los Angeles, California
| | - Michael Nivala
- Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Medicine (Cardiology), University of California, Los Angeles, California
| | - James N Weiss
- Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Medicine (Cardiology), University of California, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Zhilin Qu
- Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Medicine (Cardiology), University of California, Los Angeles, California.
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Madhvani RV, Angelini M, Xie Y, Pantazis A, Suriany S, Borgstrom NP, Garfinkel A, Qu Z, Weiss JN, Olcese R. Targeting the late component of the cardiac L-type Ca2+ current to suppress early afterdepolarizations. ACTA ACUST UNITED AC 2016; 145:395-404. [PMID: 25918358 PMCID: PMC4411259 DOI: 10.1085/jgp.201411288] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Early afterdepolarizations (EADs) associated with prolongation of the cardiac action potential (AP) can create heterogeneity of repolarization and premature extrasystoles, triggering focal and reentrant arrhythmias. Because the L-type Ca(2+) current (ICa,L) plays a key role in both AP prolongation and EAD formation, L-type Ca(2+) channels (LTCCs) represent a promising therapeutic target to normalize AP duration (APD) and suppress EADs and their arrhythmogenic consequences. We used the dynamic-clamp technique to systematically explore how the biophysical properties of LTCCs could be modified to normalize APD and suppress EADs without impairing excitation-contraction coupling. Isolated rabbit ventricular myocytes were first exposed to H2O2 or moderate hypokalemia to induce EADs, after which their endogenous ICa,L was replaced by a virtual ICa,L with tunable parameters, in dynamic-clamp mode. We probed the sensitivity of EADs to changes in the (a) amplitude of the noninactivating pedestal current; (b) slope of voltage-dependent activation; (c) slope of voltage-dependent inactivation; (d) time constant of voltage-dependent activation; and (e) time constant of voltage-dependent inactivation. We found that reducing the amplitude of the noninactivating pedestal component of ICa,L effectively suppressed both H2O2- and hypokalemia-induced EADs and restored APD. These results, together with our previous work, demonstrate the potential of this hybrid experimental-computational approach to guide drug discovery or gene therapy strategies by identifying and targeting selective properties of LTCC.
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Affiliation(s)
- Roshni V Madhvani
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Marina Angelini
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Yuanfang Xie
- Department of Pharmacology, University of California, Davis, Davis, CA 95616
| | - Antonios Pantazis
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Silvie Suriany
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Nils P Borgstrom
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Alan Garfinkel
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Zhilin Qu
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - James N Weiss
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
| | - Riccardo Olcese
- Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095 Division of Molecular Medicine, Department of Anesthesiology, Department of Medicine (Cardiology), Department of Physiology, Department of Integrative Biology and Physiology, Cardiovascular Research Laboratory, and Brain Research Institute, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
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Prudat Y, Madhvani RV, Angelini M, Borgstom NP, Garfinkel A, Karagueuzian HS, Weiss JN, de Lange E, Olcese R, Kucera JP. Stochastic pacing reveals the propensity to cardiac action potential alternans and uncovers its underlying dynamics. J Physiol 2016; 594:2537-53. [PMID: 26563830 DOI: 10.1113/jp271573] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 11/05/2015] [Indexed: 12/30/2022] Open
Abstract
KEY POINTS Beat-to-beat alternation (alternans) of the cardiac action potential duration is known to precipitate life-threatening arrhythmias and can be driven by the kinetics of voltage-gated membrane currents or by instabilities in intracellular calcium fluxes. To prevent alternans and associated arrhythmias, suitable markers must be developed to quantify the susceptibility to alternans; previous theoretical studies showed that the eigenvalue of the alternating eigenmode represents an ideal marker of alternans. Using rabbit ventricular myocytes, we show that this eigenvalue can be estimated in practice by pacing these cells at intervals varying stochastically. We also show that stochastic pacing permits the estimation of further markers distinguishing between voltage-driven and calcium-driven alternans. Our study opens the perspective to use stochastic pacing during clinical investigations and in patients with implanted pacing devices to determine the susceptibility to, and the type of alternans, which are both important to guide preventive or therapeutic measures. ABSTRACT Alternans of the cardiac action potential (AP) duration (APD) is a well-known arrhythmogenic mechanism. APD depends on several preceding diastolic intervals (DIs) and APDs, which complicates the prediction of alternans. Previous theoretical studies pinpointed a marker called λalt that directly quantifies how an alternating perturbation persists over successive APs. When the propensity to alternans increases, λalt decreases from 0 to -1. Our aim was to quantify λalt experimentally using stochastic pacing and to examine whether stochastic pacing allows discriminating between voltage-driven and Ca(2+) -driven alternans. APs were recorded in rabbit ventricular myocytes paced at cycle lengths (CLs) decreasing progressively and incorporating stochastic variations. Fitting APD with a function of two previous APDs and CLs permitted us to estimate λalt along with additional markers characterizing whether the dependence of APD on previous DIs or CLs is strong (typical for voltage-driven alternans) or weak (Ca(2+) -driven alternans). During the recordings, λalt gradually decreased from around 0 towards -1. Intermittent alternans appeared when λalt reached -0.8 and was followed by sustained alternans. The additional markers detected that alternans was Ca(2+) driven in control experiments and voltage driven in the presence of ryanodine. This distinction could be made even before alternans was manifest (specificity/sensitivity >80% for -0.4 > λalt > -0.5). These observations were confirmed in a mathematical model of a rabbit ventricular myocyte. In conclusion, stochastic pacing allows the practical estimation of λalt to reveal the onset of alternans and distinguishes between voltage-driven and Ca(2+) -driven mechanisms, which is important since these two mechanisms may precipitate arrhythmias in different manners.
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Affiliation(s)
- Yann Prudat
- Department of Physiology, University of Bern, Bern, Switzerland
| | - Roshni V Madhvani
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Marina Angelini
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Nils P Borgstom
- Department of Bioengineering, University of California, Los Angeles, CA, USA
| | - Alan Garfinkel
- Cardiovascular Research Laboratory, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Hrayr S Karagueuzian
- Cardiovascular Research Laboratory, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - James N Weiss
- Cardiovascular Research Laboratory, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Enno de Lange
- Department of Knowledge Engineering, Maastricht University, Maastricht, The Netherlands
| | - Riccardo Olcese
- Department of Anesthesiology and Perioperative Medicine, Division of Molecular Medicine, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Cardiovascular Research Laboratory, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.,Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Jan P Kucera
- Department of Physiology, University of Bern, Bern, Switzerland
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42
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Song Z, Karma A, Weiss JN, Qu Z. Long-Lasting Sparks: Multi-Metastability and Release Competition in the Calcium Release Unit Network. PLoS Comput Biol 2016; 12:e1004671. [PMID: 26730593 PMCID: PMC4701461 DOI: 10.1371/journal.pcbi.1004671] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2015] [Accepted: 11/23/2015] [Indexed: 11/20/2022] Open
Abstract
Calcium (Ca) sparks are elementary events of biological Ca signaling. A normal Ca spark has a brief duration in the range of 10 to 100 ms, but long-lasting sparks with durations of several hundred milliseconds to seconds are also widely observed. Experiments have shown that the transition from normal to long-lasting sparks can occur when ryanodine receptor (RyR) open probability is either increased or decreased. Here, we demonstrate theoretically and computationally that long-lasting sparks emerge as a collective dynamical behavior of the network of diffusively coupled Ca release units (CRUs). We show that normal sparks occur when the CRU network is monostable and excitable, while long-lasting sparks occur when the network dynamics possesses multiple metastable attractors, each attractor corresponding to a different spatial firing pattern of sparks. We further highlight the mechanisms and conditions that produce long-lasting sparks, demonstrating the existence of an optimal range of RyR open probability favoring long-lasting sparks. We find that when CRU firings are sparse and sarcoplasmic reticulum (SR) Ca load is high, increasing RyR open probability promotes long-lasting sparks by potentiating Ca-induced Ca release (CICR). In contrast, when CICR is already strong enough to produce frequent firings, decreasing RyR open probability counter-intuitively promotes long-lasting sparks by decreasing spark frequency. The decrease in spark frequency promotes intra-SR Ca diffusion from neighboring non-firing CRUs to the firing CRUs, which helps to maintain the local SR Ca concentration of the firing CRUs above a critical level to sustain firing. In this setting, decreasing RyR open probability further suppresses long-lasting sparks by weakening CICR. Since a long-lasting spark terminates via the Kramers’ escape process over a potential barrier, its duration exhibits an exponential distribution determined by the barrier height and noise strength, which is modulated differently by different ways of altering the Ca release flux strength. Calcium (Ca) sparks, resulting from Ca-induced Ca release, are elementary events of biological Ca signaling. Sparks are normally brief, but long-lasting sparks have been widely observed experimentally under various conditions. The underlying mechanisms of spark duration or termination and the corresponding determinants remain a topic of debate. In this study, we demonstrate theoretically and computationally that normal brief sparks are excitable transients, while long-lasting sparks are multiple metastable states emerging in the diffusively coupled Ca release unit network, as a result of cooperativity and release competition among the Ca release units. Termination of a long-lasting spark is a Kramers’ escape process over a potential barrier, and the spark duration is the first-passage time, exhibiting an exponential distribution.
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Affiliation(s)
- Zhen Song
- The UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Alain Karma
- Department of Physics, Northeastern University, Boston, Massachusetts, United States of America
| | - James N. Weiss
- The UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
- Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Zhilin Qu
- The UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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43
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Affiliation(s)
- James N Weiss
- UCLA Cardiovascular Research Laboratory, Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA, 90095, USA
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44
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Clancy CE, Chen-Izu Y, Bers DM, Belardinelli L, Boyden PA, Csernoch L, Despa S, Fermini B, Hool LC, Izu L, Kass RS, Lederer WJ, Louch WE, Maack C, Matiazzi A, Qu Z, Rajamani S, Rippinger CM, Sejersted OM, O'Rourke B, Weiss JN, Varró A, Zaza A. Deranged sodium to sudden death. J Physiol 2015; 593:1331-45. [PMID: 25772289 DOI: 10.1113/jphysiol.2014.281204] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2014] [Accepted: 10/14/2014] [Indexed: 12/19/2022] Open
Abstract
In February 2014, a group of scientists convened as part of the University of California Davis Cardiovascular Symposium to bring together experimental and mathematical modelling perspectives and discuss points of consensus and controversy on the topic of sodium in the heart. This paper summarizes the topics of presentation and discussion from the symposium, with a focus on the role of aberrant sodium channels and abnormal sodium homeostasis in cardiac arrhythmias and pharmacotherapy from the subcellular scale to the whole heart. Two following papers focus on Na(+) channel structure, function and regulation, and Na(+)/Ca(2+) exchange and Na(+)/K(+) ATPase. The UC Davis Cardiovascular Symposium is a biannual event that aims to bring together leading experts in subfields of cardiovascular biomedicine to focus on topics of importance to the field. The focus on Na(+) in the 2014 symposium stemmed from the multitude of recent studies that point to the importance of maintaining Na(+) homeostasis in the heart, as disruption of homeostatic processes are increasingly identified in cardiac disease states. Understanding how disruption in cardiac Na(+)-based processes leads to derangement in multiple cardiac components at the level of the cell and to then connect these perturbations to emergent behaviour in the heart to cause disease is a critical area of research. The ubiquity of disruption of Na(+) channels and Na(+) homeostasis in cardiac disorders of excitability and mechanics emphasizes the importance of a fundamental understanding of the associated mechanisms and disease processes to ultimately reveal new targets for human therapy.
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Affiliation(s)
- Colleen E Clancy
- Department of Pharmacology, University of California, Davis, Genome Building Rm 3503, Davis, CA, 95616-8636, USA
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Ping P, Gustafsson ÅB, Bers DM, Blatter LA, Cai H, Jahangir A, Kelly D, Muoio D, O'Rourke B, Rabinovitch P, Trayanova N, Van Eyk J, Weiss JN, Wong R, Schwartz Longacre L. Harnessing the Power of Integrated Mitochondrial Biology and Physiology: A Special Report on the NHLBI Mitochondria in Heart Diseases Initiative. Circ Res 2015; 117:234-8. [PMID: 26185209 DOI: 10.1161/circresaha.117.306693] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Mitochondrial biology is the sum of diverse phenomena from molecular profiles to physiological functions. A mechanistic understanding of mitochondria in disease development, and hence the future prospect of clinical translations, relies on a systems-level integration of expertise from multiple fields of investigation. Upon the successful conclusion of a recent National Institutes of Health, National Heart, Lung, and Blood Institute initiative on integrative mitochondrial biology in cardiovascular diseases, we reflect on the accomplishments made possible by this unique interdisciplinary collaboration effort and exciting new fronts on the study of these remarkable organelles.
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Affiliation(s)
- Peipei Ping
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Åsa B Gustafsson
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Don M Bers
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Lothar A Blatter
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Hua Cai
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Arshad Jahangir
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Daniel Kelly
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Deborah Muoio
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Brian O'Rourke
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Peter Rabinovitch
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Natalia Trayanova
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Jennifer Van Eyk
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - James N Weiss
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Renee Wong
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.)
| | - Lisa Schwartz Longacre
- From the Departments of Physiology and Medicine, UCLA David Geffen School of Medicine (P.P., H.C., J.N.W.); Department of Pharmacology, Skaggs School of Pharmacy and Pharmaceutical Sciences, UC San Diego, La Jolla (Å.B.G.); Department of Pharmacology, UC Davis, Davis, CA (D.M.B.); Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, IL (L.A.B.); Center for Integrative Research on Cardiovascular Aging, Cardiovascular Services and Department of Research, Aurora Health Care, Milwaukee, WI (A.J.); Diabetes and Obesity Research Center, Sanford-Burnham Medical Research Institute, Orlando, FL (D.K.); Department of Medicine, Duke University, Durham, NC (D.M.); Department of Medicine, Division of Cardiology (B.O.R.), Department of Biomedical Engineering (N.T.), and Department of Medicine, Division of Cardiology (J.V.E.), The Johns Hopkins University School of Medicine, Baltimore, MD (B.O'R., N.T., J.V.E.); Department of Pathology, University of Washington, Seattle (P.R.); and Heart Failure and Arrhythmia Branch, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD (R.W., L.S.L.).
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Chan YH, Tsai WC, Ko JS, Yin D, Chang PC, Rubart M, Weiss JN, Everett TH, Lin SF, Chen PS. Small-Conductance Calcium-Activated Potassium Current Is Activated During Hypokalemia and Masks Short-Term Cardiac Memory Induced by Ventricular Pacing. Circulation 2015; 132:1377-86. [PMID: 26362634 DOI: 10.1161/circulationaha.114.015125] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Accepted: 06/11/2015] [Indexed: 01/26/2023]
Abstract
BACKGROUND Hypokalemia increases the vulnerability to ventricular fibrillation. We hypothesize that the apamin-sensitive small-conductance calcium-activated potassium current (IKAS) is activated during hypokalemia and that IKAS blockade is proarrhythmic. METHODS AND RESULTS Optical mapping was performed in 23 Langendorff-perfused rabbit ventricles with atrioventricular block and either right or left ventricular pacing during normokalemia or hypokalemia. Apamin prolonged the action potential duration (APD) measured to 80% repolarization (APD80) by 26 milliseconds (95% confidence interval [CI], 14-37) during normokalemia and by 54 milliseconds (95% CI, 40-68) during hypokalemia (P=0.01) at a 1000-millisecond pacing cycle length. In hypokalemic ventricles, apamin increased the maximal slope of APD restitution, the pacing cycle length threshold of APD alternans, the pacing cycle length for wave-break induction, and the area of spatially discordant APD alternans. Apamin significantly facilitated the induction of sustained ventricular fibrillation (from 3 of 9 hearts to 9 of 9 hearts; P=0.009). Short-term cardiac memory was assessed by the slope of APD80 versus activation time. The slope increased from 0.01 (95% CI, -0.09 to 0.12) at baseline to 0.34 (95% CI, 0.23-0.44) after apamin (P<0.001) during right ventricular pacing and from 0.07 (95% CI, -0.05 to 0.20) to 0.54 (95% CI, 0.06-1.03) after apamin infusion (P=0.045) during left ventricular pacing. Patch-clamp studies confirmed increased IKAS in isolated rabbit ventricular myocytes during hypokalemia (P=0.038). CONCLUSIONS Hypokalemia activates IKAS to shorten APD and maintain repolarization reserve at late activation sites during ventricular pacing. IKAS blockade prominently lengthens the APD at late activation sites and facilitates ventricular fibrillation induction.
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Affiliation(s)
- Yi-Hsin Chan
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Wei-Chung Tsai
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Jum-Suk Ko
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Dechun Yin
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Po-Cheng Chang
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Michael Rubart
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - James N Weiss
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Thomas H Everett
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Shien-Fong Lin
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.)
| | - Peng-Sheng Chen
- From Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine (Y.-H.C., W.-C.T., P.-C.C., T.H.E., S.-F.L., P.-S.C.) and Wells Center for Pediatrics Research, Department of Pediatrics (M.R.), Indiana University School of Medicine, Indianapolis; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan (Y.-H.C., P.-C.C.); Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Taiwan (W.-C.T.); Division of Cardiology, Department of Internal Medicine, Wonkwang University School of Medicine and Hospital, Jeonbuk, Republic of Korea (J.-S.K.); Department of Cardiology, First Affiliated Hospital of Harbin Medical University, China (D.Y.); Departments of Medicine (Cardiology) and Physiology, University of California, Los Angeles (J.N.W.); and Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan (S.-F.L.).
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Pezhouman A, Singh N, Song Z, Nivala M, Eskandari A, Cao H, Bapat A, Ko CY, Nguyen T, Qu Z, Karagueuzian HS, Weiss JN. Molecular Basis of Hypokalemia-Induced Ventricular Fibrillation. Circulation 2015; 132:1528-1537. [PMID: 26269574 DOI: 10.1161/circulationaha.115.016217] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Accepted: 08/05/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND Hypokalemia is known to promote ventricular arrhythmias, especially in combination with class III antiarrhythmic drugs like dofetilide. Here, we evaluated the underlying molecular mechanisms. METHODS AND RESULTS Arrhythmias were recorded in isolated rabbit and rat hearts or patch-clamped ventricular myocytes exposed to hypokalemia (1.0-3.5 mmol/L) in the absence or presence of dofetilide (1 μmol/L). Spontaneous early afterdepolarizations (EADs) and ventricular tachycardia/fibrillation occurred in 50% of hearts at 2.7 mmol/L [K] in the absence of dofetilide and 3.3 mmol/L [K] in its presence. Pretreatment with the Ca-calmodulin kinase II (CaMKII) inhibitor KN-93, but not its inactive analogue KN-92, abolished EADs and hypokalemia-induced ventricular tachycardia/fibrillation, as did the selective late Na current (INa) blocker GS-967. In intact hearts, moderate hypokalemia (2.7 mmol/L) significantly increased tissue CaMKII activity. Computer modeling revealed that EAD generation by hypokalemia (with or without dofetilide) required Na-K pump inhibition to induce intracellular Na and Ca overload with consequent CaMKII activation enhancing late INa and the L-type Ca current. K current suppression by hypokalemia and dofetilide alone in the absence of CaMKII activation were ineffective at causing EADs. CONCLUSIONS We conclude that Na-K pump inhibition by even moderate hypokalemia plays a critical role in promoting EAD-mediated arrhythmias by inducing a positive feedback cycle activating CaMKII and enhancing late INa. Class III antiarrhythmic drugs like dofetilide sensitize the heart to this positive feedback loop.
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Affiliation(s)
- Arash Pezhouman
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Neha Singh
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Zhen Song
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Michael Nivala
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Anahita Eskandari
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Hong Cao
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Aneesh Bapat
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Christopher Y Ko
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Thao Nguyen
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Zhilin Qu
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Hrayr S Karagueuzian
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - James N Weiss
- UCLA Cardiovascular Research Laboratory, Departments of Medicine (Cardiology) and Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA
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48
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Nguyen TP, Singh N, Xie Y, Qu Z, Weiss JN. Repolarization reserve evolves dynamically during the cardiac action potential: effects of transient outward currents on early afterdepolarizations. Circ Arrhythm Electrophysiol 2015; 8:694-702. [PMID: 25772542 DOI: 10.1161/circep.114.002451] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 02/20/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND Transient outward K currents (Ito) have been reported both to suppress and to facilitate early afterdepolarizations (EADs) when repolarization reserve is reduced. Here, we used the dynamic clamp technique to analyze how Ito accounts for these paradoxical effects on EADs by influencing the dynamic evolution of repolarization reserve during the action potential. METHODS AND RESULTS Isolated patch-clamped rabbit ventricular myocytes were exposed to either oxidative stress (H2O2) or hypokalemia to induce bradycardia-dependent EADs at a long pacing cycle length of 6 s, when native rabbit Ito is substantial. EADs disappeared when the pacing cycle length was shortened to 1 s, when Ito becomes negligible because of incomplete recovery from inactivation. During 6-s pacing cycle length, EADs were blocked by the Ito blocker 4-aminopyridine, but reappeared when a virtual current with appropriate Ito-like properties was reintroduced using the dynamic clamp (n=141 trials). During 1-s pacing cycle length in the absence of 4-aminopyridine, adding a virtual Ito-like current (n=1113 trials) caused EADs to reappear over a wide range of Ito conductance (0.005-0.15 nS/pF), particularly when inactivation kinetics were slow (τinact≥20 ms) and the pedestal (noninactivating component) was small (<25% of peak Ito). Faster inactivation or larger pedestals tended to suppress EADs. CONCLUSIONS Repolarization reserve evolves dynamically during the cardiac action potential. Whereas sufficiently large Ito can suppress EADs, a wide range of intermediate Ito properties can promote EADs by influencing the temporal evolution of other currents affecting late repolarization reserve. These findings raise caution in targeting Ito as an antiarrhythmic strategy.
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Affiliation(s)
- Thao P Nguyen
- From the UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles.
| | - Neha Singh
- From the UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
| | - Yuanfang Xie
- From the UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
| | - Zhilin Qu
- From the UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
| | - James N Weiss
- From the UCLA Cardiovascular Research Laboratory, Division of Cardiology, Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles
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49
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Korge P, Calmettes G, Weiss JN. Increased reactive oxygen species production during reductive stress: The roles of mitochondrial glutathione and thioredoxin reductases. Biochim Biophys Acta 2015; 1847:514-25. [PMID: 25701705 DOI: 10.1016/j.bbabio.2015.02.012] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 02/09/2015] [Accepted: 02/12/2015] [Indexed: 01/22/2023]
Abstract
Both extremes of redox balance are known to cause cardiac injury, with mounting evidence revealing that the injury induced by both oxidative and reductive stress is oxidative in nature. During reductive stress, when electron acceptors are expected to be mostly reduced, some redox proteins can donate electrons to O2 instead, which increases reactive oxygen species (ROS) production. However, the high level of reducing equivalents also concomitantly enhances ROS scavenging systems involving redox couples such as NADPH/NADP+ and GSH/GSSG. Here our objective was to explore how reductive stress paradoxically increases net mitochondrial ROS production despite the concomitant enhancement of ROS scavenging systems. Using recombinant enzymes and isolated permeabilized cardiac mitochondria, we show that two normally antioxidant matrix NADPH reductases, glutathione reductase and thioredoxin reductase, generate H2O2 by leaking electrons from their reduced flavoprotein to O2 when electron flow is impaired by inhibitors or because of limited availability of their natural electron acceptors, GSSG and oxidized thioredoxin. The spillover of H2O2 under these conditions depends on H2O2 reduction by peroxiredoxin activity, which may regulate redox signaling in response to endogenous or exogenous factors. These findings may explain how ROS production during reductive stress overwhelms ROS scavenging capability, generating the net mitochondrial ROS spillover causing oxidative injury. These enzymes could potentially be targeted to increase cancer cell death or modulate H2O2-induced redox signaling to protect the heart against ischemia/reperfusion damage.
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Affiliation(s)
- Paavo Korge
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
| | - Guillaume Calmettes
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States
| | - James N Weiss
- UCLA Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States; Department of Medicine (Cardiology), David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States; Department of Physiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, United States.
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50
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Chan YH, Tsai WC, Song Z, Ko CY, Qu Z, Weiss JN, Lin SF, Chen PS, Jones LR, Chen Z. Acute reversal of phospholamban inhibition facilitates the rhythmic whole-cell propagating calcium waves in isolated ventricular myocytes. J Mol Cell Cardiol 2015; 80:126-35. [PMID: 25596331 DOI: 10.1016/j.yjmcc.2014.12.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/23/2014] [Revised: 12/08/2014] [Accepted: 12/30/2014] [Indexed: 02/01/2023]
Abstract
Phospholamban (PLB) inhibits the activity of cardiac sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA2a). Phosphorylation of PLB during sympathetic activation reverses SERCA2a inhibition, increasing SR Ca(2+) uptake. However, sympathetic activation also modulates multiple other intracellular targets in ventricular myocytes (VMs), making it impossible to determine the specific effects of the reversal of PLB inhibition on the spontaneous SR Ca(2+) release. Therefore, it remains unclear how PLB regulates rhythmic activity in VMs. Here, we used the Fab fragment of 2D12, a monoclonal anti-PLB antibody, to test how acute reversal of PLB inhibition affects the spontaneous SR Ca(2+) release in normal VMs. Ca(2+) sparks and spontaneous Ca(2+) waves (SCWs) were recorded in the line-scan mode of confocal microscopy using the Ca(2+) fluorescent dye Fluo-4 in isolated permeabilized mouse VMs. Fab, which reverses PLB inhibition, significantly increased the frequency, amplitude, and spatial/temporal spread of Ca(2+) sparks in VMs exposed to 50 nM free [Ca(2+)]. At physiological diastolic free [Ca(2+)] (100-200 nM), Fab facilitated the formation of whole-cell propagating SCWs. At higher free [Ca(2+)], Fab increased the frequency and velocity, but decreased the decay time of the SCWs. cAMP had little additional effect on the frequency or morphology of Ca(2+) sparks or SCWs after Fab addition. These findings were complemented by computer simulations. In conclusion, acute reversal of PLB inhibition alone significantly increased the spontaneous SR Ca(2+) release, leading to the facilitation and organization of whole-cell propagating SCWs in normal VMs. PLB thus plays a key role in subcellular Ca(2+) dynamics and rhythmic activity of VMs.
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Affiliation(s)
- Yi-Hsin Chan
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA; Division of Cardiology, Department of Internal Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Linkou, Taoyuan, Taiwan
| | - Wei-Chung Tsai
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA; Division of Cardiology, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung University College of Medicine, Kaohsiung, Taiwan
| | - Zhen Song
- Division of Cardiology, Department of Medicine, University of California, Los Angeles, CA, USA
| | - Christopher Y Ko
- Division of Cardiology, Department of Medicine, University of California, Los Angeles, CA, USA
| | - Zhilin Qu
- Division of Cardiology, Department of Medicine, University of California, Los Angeles, CA, USA
| | - James N Weiss
- Division of Cardiology, Department of Medicine, University of California, Los Angeles, CA, USA
| | - Shien-Fong Lin
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA; Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan
| | - Peng-Sheng Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Larry R Jones
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Zhenhui Chen
- Krannert Institute of Cardiology and Division of Cardiology, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN, USA.
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