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Zhang Y, Zhang Z, Qu Z. Curvature-mediated source and sink effects on the genesis of premature ventricular complexes in long QT syndrome. Am J Physiol Heart Circ Physiol 2024; 326:H1350-H1365. [PMID: 38551483 DOI: 10.1152/ajpheart.00004.2024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Revised: 03/13/2024] [Accepted: 03/25/2024] [Indexed: 05/08/2024]
Abstract
Premature ventricular complexes (PVCs) are spontaneous excitations occurring in the ventricles of the heart that are associated with ventricular arrhythmias and sudden cardiac death. Under long QT conditions, PVCs can be mediated by repolarization gradient (RG) and early afterdepolarizations (EADs), yet the effects of heterogeneities or geometry of the RG or EAD regions on PVC genesis remain incompletely understood. In this study, we use computer simulation to systematically investigate the effects of the curvature of the RG border region on PVC genesis under long QT conditions. We show that PVCs can be either promoted or suppressed by negative or positive RG border curvature depending on the source and sink conditions. When the origin of oscillation is in the source region and the source is too strong, a positive RG border curvature can promote PVCs by causing the source area to oscillate. When the origin of oscillation is in the sink region, a negative RG border curvature can promote PVCs by causing the sink area to oscillate. Furthermore, EAD-mediated PVCs are also promoted by negative border curvature. We also investigate the effects of wavefront curvature and show that PVCs are promoted by convex but suppressed by concave wavefronts; however, the effect of wavefront curvature is much smaller than that of RG border curvature. In conclusion, besides the increase of RG and occurrence of EADs caused by QT prolongation, the geometry of the RG border plays important roles in PVC genesis, which can greatly increase the risk of arrhythmias in cardiac diseases.NEW & NOTEWORTHY The effects of the curvature or geometry of the repolarization gradient region and wavefront curvature on the genesis of premature ventricular complexes are systematically investigated using computer modeling and simulation. Premature ventricular complexes can be promoted by either positive or negative curvature of the gradient region depending on the source and sink conditions. The underlying mechanisms of the curvature effects are revealed, which provides mechanistic insights into arrhythmogenesis in cardiac diseases.
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Affiliation(s)
- Yuhao Zhang
- Department of Physics, School of Physical Science and Technology, Ningbo University, Ningbo, People's Republic of China
| | - Zhaoyang Zhang
- Department of Physics, School of Physical Science and Technology, Ningbo University, Ningbo, People's Republic of China
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States
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2
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Guevara A, Smith CER, Caldwell JL, Ngo L, Mott LR, Lee IJ, Tapa S, Wang Z, Wang L, Woodward WR, Ng GA, Habecker BA, Ripplinger CM. Chronic nicotine exposure is associated with electrophysiological and sympathetic remodeling in the intact rabbit heart. Am J Physiol Heart Circ Physiol 2024; 326:H1337-H1349. [PMID: 38551482 DOI: 10.1152/ajpheart.00749.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 03/27/2024] [Accepted: 03/27/2024] [Indexed: 04/09/2024]
Abstract
Nicotine is the primary addictive component of tobacco products. Through its actions on the heart and autonomic nervous system, nicotine exposure is associated with electrophysiological changes and increased arrhythmia susceptibility. To assess the underlying mechanisms, we treated rabbits with transdermal nicotine (NIC, 21 mg/day) or control (CT) patches for 28 days before performing dual optical mapping of transmembrane potential (RH237) and intracellular Ca2+ (Rhod-2 AM) in isolated hearts with intact sympathetic innervation. Sympathetic nerve stimulation (SNS) was performed at the first to third thoracic vertebrae, and β-adrenergic responsiveness was additionally evaluated following norepinephrine (NE) perfusion. Baseline ex vivo heart rate (HR) and SNS stimulation threshold were higher in NIC versus CT (P = 0.004 and P = 0.003, respectively). Action potential duration alternans emerged at longer pacing cycle lengths (PCL) in NIC versus CT at baseline (P = 0.002) and during SNS (P = 0.0003), with similar results obtained for Ca2+ transient alternans. SNS shortened the PCL at which alternans emerged in CT but not in NIC hearts. NIC-exposed hearts tended to have slower and reduced HR responses to NE perfusion, but ventricular responses to NE were comparable between groups. Although fibrosis was unaltered, NIC hearts had lower sympathetic nerve density (P = 0.03) but no difference in NE content versus CT. These results suggest both sympathetic hypoinnervation of the myocardium and regional differences in β-adrenergic responsiveness with NIC. This autonomic remodeling may contribute to the increased risk of arrhythmias associated with nicotine exposure, which may be further exacerbated with long-term use.NEW & NOTEWORTHY Here, we show that chronic nicotine exposure was associated with increased heart rate, increased susceptibility to alternans, and reduced sympathetic electrophysiological responses in the intact rabbit heart. We suggest that this was due to sympathetic hypoinnervation of the myocardium and diminished β-adrenergic responsiveness of the sinoatrial node following nicotine treatment. Though these differences did not result in increased arrhythmia propensity in our study, we hypothesize that prolonged nicotine exposure may exacerbate this proarrhythmic remodeling.
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Affiliation(s)
- Amanda Guevara
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Charlotte E R Smith
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Jessica L Caldwell
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Lena Ngo
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Lilian R Mott
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - I-Ju Lee
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Srinivas Tapa
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - Zhen Wang
- Department of Pharmacology, University of California Davis, Davis, California, United States
- Shantou University Medical College, Shantou, People's Republic of China
| | - Lianguo Wang
- Department of Pharmacology, University of California Davis, Davis, California, United States
| | - William R Woodward
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon, United States
| | - G Andre Ng
- Department of Cardiovascular Sciences, University of Leicester, Leicester, United Kingdom
- National Institute for Health and Care Research, Leicester Biomedical Research Centre, Leicester, United Kingdom
- Glenfield Hospital, Leicester, United Kingdom
| | - Beth A Habecker
- Department of Chemical Physiology and Biochemistry, Oregon Health and Science University, Portland, Oregon, United States
- Department of Medicine and Knight Cardiovascular Institute, Oregon Health and Science University, Portland, Oregon, United States
| | - Crystal M Ripplinger
- Department of Pharmacology, University of California Davis, Davis, California, United States
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3
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Guevara A, Smith CER, Caldwell JL, Ngo L, Mott LR, Lee IJ, Tapa I, Wang Z, Wang L, Woodward WR, Ng GA, Habecker BA, Ripplinger CM. Chronic nicotine exposure is associated with electrophysiological and sympathetic remodeling in the intact rabbit heart. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.23.567754. [PMID: 38045290 PMCID: PMC10690259 DOI: 10.1101/2023.11.23.567754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2023]
Abstract
Nicotine is the primary addictive component in tobacco products. Through its actions on the heart and autonomic nervous system, nicotine exposure is associated with electrophysiological changes and increased arrhythmia susceptibility. However, the underlying mechanisms are unclear. To address this, we treated rabbits with transdermal nicotine (NIC, 21 mg/day) or control (CT) patches for 28 days prior to performing dual optical mapping of transmembrane potential (RH237) and intracellular Ca 2+ (Rhod-2 AM) in isolated hearts with intact sympathetic innervation. Sympathetic nerve stimulation (SNS) was performed at the 1 st - 3 rd thoracic vertebrae, and β-adrenergic responsiveness was additionally evaluated as changes in heart rate (HR) following norepinephrine (NE) perfusion. Baseline ex vivo HR and SNS stimulation threshold were increased in NIC vs. CT ( P = 0.004 and P = 0.003 respectively). Action potential duration alternans emerged at longer pacing cycle lengths (PCL) in NIC vs. CT at baseline ( P = 0.002) and during SNS ( P = 0.0003), with similar results obtained for Ca 2+ transient alternans. SNS reduced the PCL at which alternans emerged in CT but not NIC hearts. NIC exposed hearts also tended to have slower and reduced HR responses to NE perfusion. While fibrosis was unaltered, NIC hearts had lower sympathetic nerve density ( P = 0.03) but no difference in NE content vs. CT. These results suggest both sympathetic hypo-innervation of the myocardium and diminished β-adrenergic responsiveness with NIC. This autonomic remodeling may underlie the increased risk of arrhythmias associated with nicotine exposure, which may be further exacerbated with continued long-term usage. NEW & NOTEWORTHY Here we show that chronic nicotine exposure was associated with increased heart rate, lower threshold for alternans and reduced sympathetic electrophysiological responses in the intact rabbit heart. We suggest that this was due to the sympathetic hypo-innervation of the myocardium and diminished β- adrenergic responsiveness observed following nicotine treatment. Though these differences did not result in increased arrhythmia propensity in our study, we hypothesize that prolonged nicotine exposure may exacerbate this pro-arrhythmic remodeling.
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4
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Ochs AR, Boyle PM. Optogenetic Modulation of Arrhythmia Triggers: Proof-of-Concept from Computational Modeling. Cell Mol Bioeng 2023; 16:243-259. [PMID: 37810996 PMCID: PMC10550900 DOI: 10.1007/s12195-023-00781-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Accepted: 08/14/2023] [Indexed: 10/10/2023] Open
Abstract
Introduction Early afterdepolarizations (EADs) are secondary voltage depolarizations associated with reduced repolarization reserve (RRR) that can trigger lethal arrhythmias. Relating EADs to triggered activity is difficult to study, so the ability to suppress or provoke EADs would be experimentally useful. Here, we use computational simulations to assess the feasibility of subthreshold optogenetic stimulation modulating the propensity for EADs (cell-scale) and EAD-associated ectopic beats (organ-scale). Methods We modified a ventricular ionic model by reducing rapid delayed rectifier potassium (0.25-0.1 × baseline) and increasing L-type calcium (1.0-3.5 × baseline) currents to create RRR conditions with varying severity. We ran simulations in models of single cardiomyocytes and left ventricles from post-myocardial infarction patient MRI scans. Optogenetic stimulation was simulated using either ChR2 (depolarizing) or GtACR1 (repolarizing) opsins. Results In cell-scale simulations without illumination, EADs were seen for 164 of 416 RRR conditions. Subthreshold stimulation of GtACR1 reduced EAD incidence by up to 84.8% (25/416 RRR conditions; 0.1 μW/mm2); in contrast, subthreshold ChR2 excitation increased EAD incidence by up to 136.6% (388/416 RRR conditions; 50 μW/mm2). At the organ scale, we assumed simultaneous, uniform illumination of the epicardial and endocardial surfaces. GtACR1-mediated suppression (10-50 μW/mm2) and ChR2-mediated unmasking (50-100 μW/mm2) of EAD-associated ectopic beats were feasible in three distinct ventricular models. Conclusions Our findings suggest that optogenetics could be used to silence or provoke both EADs and EAD-associated ectopic beats. Validation in animal models could lead to exciting new experimental regimes and potentially to novel anti-arrhythmia treatments. Supplementary Information The online version contains supplementary material available at 10.1007/s12195-023-00781-z.
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Affiliation(s)
- Alexander R. Ochs
- Department of Bioengineering, UW Bioengineering, University of Washington, 3720 15th Ave NE N107, UW Mailbox 355061, Seattle, WA 98195 USA
| | - Patrick M. Boyle
- Department of Bioengineering, UW Bioengineering, University of Washington, 3720 15th Ave NE N107, UW Mailbox 355061, Seattle, WA 98195 USA
- Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, WA USA
- Center for Cardiovascular Biology, University of Washington, Seattle, WA USA
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Ripplinger CM, Glukhov AV, Kay MW, Boukens BJ, Chiamvimonvat N, Delisle BP, Fabritz L, Hund TJ, Knollmann BC, Li N, Murray KT, Poelzing S, Quinn TA, Remme CA, Rentschler SL, Rose RA, Posnack NG. Guidelines for assessment of cardiac electrophysiology and arrhythmias in small animals. Am J Physiol Heart Circ Physiol 2022; 323:H1137-H1166. [PMID: 36269644 PMCID: PMC9678409 DOI: 10.1152/ajpheart.00439.2022] [Citation(s) in RCA: 26] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 10/11/2022] [Accepted: 10/17/2022] [Indexed: 01/09/2023]
Abstract
Cardiac arrhythmias are a major cause of morbidity and mortality worldwide. Although recent advances in cell-based models, including human-induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM), are contributing to our understanding of electrophysiology and arrhythmia mechanisms, preclinical animal studies of cardiovascular disease remain a mainstay. Over the past several decades, animal models of cardiovascular disease have advanced our understanding of pathological remodeling, arrhythmia mechanisms, and drug effects and have led to major improvements in pacing and defibrillation therapies. There exist a variety of methodological approaches for the assessment of cardiac electrophysiology and a plethora of parameters may be assessed with each approach. This guidelines article will provide an overview of the strengths and limitations of several common techniques used to assess electrophysiology and arrhythmia mechanisms at the whole animal, whole heart, and tissue level with a focus on small animal models. We also define key electrophysiological parameters that should be assessed, along with their physiological underpinnings, and the best methods with which to assess these parameters.
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Affiliation(s)
- Crystal M Ripplinger
- Department of Pharmacology, University of California Davis School of Medicine, Davis, California
| | - Alexey V Glukhov
- Department of Medicine, Cardiovascular Medicine, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University, Washington, District of Columbia
| | - Bastiaan J Boukens
- Department Physiology, University Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands
- Department of Medical Biology, University of Amsterdam, Amsterdam University Medical Center, Amsterdam, The Netherlands
| | - Nipavan Chiamvimonvat
- Department of Pharmacology, University of California Davis School of Medicine, Davis, California
- Department of Internal Medicine, University of California Davis School of Medicine, Davis, California
- Veterans Affairs Northern California Healthcare System, Mather, California
| | - Brian P Delisle
- Department of Physiology, University of Kentucky, Lexington, Kentucky
| | - Larissa Fabritz
- University Center of Cardiovascular Science, University Heart and Vascular Center, University Hospital Hamburg-Eppendorf with DZHK Hamburg/Kiel/Luebeck, Germany
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Thomas J Hund
- Department of Internal Medicine, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio
- Department of Biomedical Engineering, Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University, Columbus, Ohio
| | - Bjorn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Na Li
- Department of Medicine, Baylor College of Medicine, Houston, Texas
| | - Katherine T Murray
- Departments of Medicine and Pharmacology, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Steven Poelzing
- Virginia Tech Carilon School of Medicine, Center for Heart and Reparative Medicine Research, Fralin Biomedical Research Institute at Virginia Tech, Roanoke, Virginia
- Department of Biomedical Engineering and Mechanics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia
| | - T Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada
- School of Biomedical Engineering, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Carol Ann Remme
- Department of Experimental Cardiology, Heart Centre, Amsterdam Cardiovascular Sciences, Heart Failure and Arrhythmias Amsterdam UMC Location University of Amsterdam, Amsterdam, The Netherlands
| | - Stacey L Rentschler
- Cardiovascular Division, Department of Medicine, Washington University in Saint Louis, School of Medicine, Saint Louis, Missouri
| | - Robert A Rose
- Department of Cardiac Sciences, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- Department of Physiology and Pharmacology, Libin Cardiovascular Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Nikki G Posnack
- Sheikh Zayed Institute for Pediatric Surgical Innovation, Children's National Hospital, Washington, District of Columbia
- Department of Pediatrics, George Washington University School of Medicine, Washington, District of Columbia
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6
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Xynogalos P, Rahm AK, Fried S, Chasan S, Scherer D, Seyler C, Katus HA, Frey N, Zitron E. Verapamil inhibits Kir2.3 channels by binding to the pore and interfering with PIP2 binding. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2022; 396:659-667. [PMID: 36445385 PMCID: PMC10042922 DOI: 10.1007/s00210-022-02342-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Accepted: 11/15/2022] [Indexed: 11/30/2022]
Abstract
Abstract
The inwardly rectifying potassium current of the cardiomyocyte (IK1) is the main determinant of the resting potential. Ion channels Kir2.1, Kir2.2, and Kir2.3 form tetramers and are the molecular correlate of macroscopic IK1 current. Verapamil is an antiarrhythmic drug used to suppress atrial and ventricular arrhythmias. Its primary mechanism of action is via blocking calcium channels. In addition, it has been demonstrated to block IK1 current and the Kir2.1 subunit. Its effect on other subunits that contribute to IK1 current has not been studied to date. We therefore analyzed the effect of verapamil on the Kir channels 2.1, 2.2, and 2.3 in the Xenopus oocyte expression system. Kir2.1, Kir2.2, and Kir2.3 channels were heterologously expressed in Xenopus oocytes. Respective currents were measured with the voltage clamp technique and the effect of verapamil on the current was measured. At a concentration of 300 µM, verapamil inhibited Kir2.1 channels by 41.36% ± 2.7 of the initial current, Kir2.2 channels by 16.51 ± 3.6%, and Kir2.3 by 69.98 ± 4.2%. As a verapamil effect on kir2.3 was a previously unknown finding, we analyzed this effect further. At wash in with 300 µM verapamil, the maximal effect was seen within 20 min of the infusion. After washing out with control solution, there was only a partial current recovery. The current reduction from verapamil was the same at − 120 mV (73.2 ± 3.7%), − 40 mV (85.5 ± 6.5%), and 0 mV (61.5 ± 10.6%) implying no voltage dependency of the block. Using site directed mutations in putative binding sites, we demonstrated a decrease of effect with pore mutant E291A and absence of verapamil effect for D251A. With mutant I214L, which shows a stronger affinity for PIP2 binding, we observed a normalized current reduction to 61.9 ± 0.06% of the control current, which was significantly less pronounced compared to wild type channels. Verapamil blocks Kir2.1, Kir2.2, and Kir2.3 subunits. In Kir2.3, blockade is dependent on sites E291 and D251 and interferes with activation of the channel via PIP2. Interference with these sites and with PIP2 binding has also been described for other Kir channels blocking drugs. As Kir2.3 is preferentially expressed in atrium, a selective Kir2.3 blocking agent would constitute an interesting antiarrhythmic concept.
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Li E, Loen V, van Ham WB, Kool W, van der Heyden MAG, Takanari H. Quantitative Analysis of the Cytoskeleton's Role in Inward Rectifier K IR 2.1 Forward and Backward Trafficking. Front Physiol 2022; 12:812572. [PMID: 35145427 PMCID: PMC8821923 DOI: 10.3389/fphys.2021.812572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Accepted: 12/23/2021] [Indexed: 11/13/2022] Open
Abstract
Alteration of the inward rectifier current IK1, carried by KIR2.1 channels, affects action potential duration, impacts resting membrane stability and associates with cardiac arrhythmias. Congenital and acquired KIR2.1 malfunction frequently associates with aberrant ion channel trafficking. Cellular processes underlying trafficking are intertwined with cytoskeletal function. The extent to which the cytoskeleton is involved in KIR2.1 trafficking processes is unknown. We aimed to quantify the dependence of KIR2.1 trafficking on cytoskeleton function. GFP or photoconvertible Dendra2 tagged KIR2.1 constructs were transfected in HEK293 or HeLa cells. Photoconversion of the Dendra2 probe at the plasma membrane and subsequent live imaging of trafficking processes was performed by confocal laser-scanning microscopy. Time constant of green fluorescent recovery (τg,s) represented recruitment of new KIR2.1 at the plasma membrane. Red fluorescent decay (τr,s) represented internalization of photoconverted KIR2.1. Patch clamp electrophysiology was used to quantify IKIR2.1. Biochemical methods were used for cytoskeleton isolation and detection of KIR2.1-cytoskeleton interactions. Cytochalasin B (20 μM), Nocodazole (30 μM) and Dyngo-4a (10 nM) were used to modify the cytoskeleton. Chloroquine (10 μM, 24 h) was used to impair KIR2.1 breakdown. Cytochalasin B and Nocodazole, inhibitors of actin and tubulin filament formation respectively, strongly inhibited the recovery of green fluorescence at the plasma membrane suggestive for inhibition of KIR2.1 forward trafficking [τg,s 13 ± 2 vs. 131 ± 31* and 160 ± 40* min, for control, Cytochalasin B and Nocodazole, respectively (*p < 0.05 vs. control)]. Dyngo-4a, an inhibitor of dynamin motor proteins, strongly slowed the rate of photoconverted channel internalization, whereas Nocodazole and Cytochalasin B had less effect [τr,s 20 ± 2 vs. 87 ± 14*, 60 ± 16 and 64 ± 20 min (*p < 0.05 vs. control)]. Cytochalasin B treatment (20 μM, 24 h) inhibited IKIR2.1. Chloroquine treatment (10 μM, 24 h) induced intracellular aggregation of KIR2.1 channels and enhanced interaction with the actin/intermediate filament system (103 ± 90 fold; p < 0.05 vs. control). Functional actin and tubulin cytoskeleton systems are essential for forward trafficking of KIR2.1 channels, whereas initial backward trafficking relies on a functional dynamin system. Chronic disturbance of the actin system inhibits KIR2.1 currents. Internalized KIR2.1 channels become recruited to the cytoskeleton, presumably in lysosomes.
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Affiliation(s)
- Encan Li
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Vera Loen
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Willem B van Ham
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Willy Kool
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Marcel A G van der Heyden
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Hiroki Takanari
- Department of Interdisciplinary Researches for Medicine and Photonics, Institute of Post-LED Photonics, University of Tokushima, Tokushima, Japan
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Reilly L, Eckhardt LL. Cardiac potassium inward rectifier Kir2: Review of structure, regulation, pharmacology, and arrhythmogenesis. Heart Rhythm 2021; 18:1423-1434. [PMID: 33857643 PMCID: PMC8328935 DOI: 10.1016/j.hrthm.2021.04.008] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Revised: 03/23/2021] [Accepted: 04/06/2021] [Indexed: 12/17/2022]
Abstract
Potassium inward rectifier channel Kir2 is an important component of terminal cardiac repolarization and resting membrane stability. This functionality is part of balanced cardiac excitability and is a defining feature of excitable cardiac membranes. “Gain-of-function” or “loss-of-function” mutations in KCNJ2, the gene encoding Kir2.1, cause genetic sudden cardiac death syndromes, and loss of the Kir2 current IK1 is a major contributing factor to arrhythmogenesis in failing human hearts. Here we provide a contemporary review of the functional structure, physiology, and pharmacology of Kir2 channels. Beyond the structure and functional relationships, we will focus on the elements of clinically used drugs that block the channel and the implications for treatment of atrial fibrillation with IK1-blocking agents. We will also review the clinical disease entities associated with KCNJ2 mutations and the growing area of research into associated arrhythmia mechanisms. Lastly, the presence of Kir2 channels has become a tipping point for electrical maturity in induced pluripotent stem cell-derived cardiomyocytes (iPS-CMs) and highlights the significance of understanding why Kir2 in iPS-CMs is important to consider for Comprehensive In Vitro Proarrhythmia Assay and drug safety testing.
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Affiliation(s)
- Louise Reilly
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin
| | - Lee L Eckhardt
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin.
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9
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Tsai YN, Hsiao YW, Lin SF, Chan YH, Hsieh YC, Tang WH, Lee AS, Huang YT, Li HY, Chao TF, Higa S, Wu TJ, Chang SL, Chen SA. Proinflammatory Cytokine Modulates Intracellular Calcium Handling and Enhances Ventricular Arrhythmia Susceptibility. Front Cardiovasc Med 2021; 8:623510. [PMID: 33796569 PMCID: PMC8007768 DOI: 10.3389/fcvm.2021.623510] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 02/22/2021] [Indexed: 11/13/2022] Open
Abstract
Background: The mechanism of Interleukin-17 (IL-17) induced ventricular arrhythmia (VA) remains unclear. This study aimed to investigate the effect of intracellular calcium (Cai) handling and VA susceptibility by IL-17. Methods: The electrophysiological properties of isolated perfused rabbit hearts under IL-17 (20 ng/ml, N = 6) and the IL-17 with neutralizer (0.4 μg/ml, N = 6) were evaluated using an optical mapping system. The action potential duration (APD) and Cai transient duration (CaiTD) were examined, and semiquantitative reverse transcriptase-polymerase chain reaction analysis of ion channels was performed. Results: There were longer APD80, CaiTD80 and increased thresholds of APD and CaiTD alternans, the maximum slope of APD restitution and induction of VA threshold in IL-17 group compared with those in IL-17 neutralizer and baseline groups. During ventricular fibrillation, the number of phase singularities and dominant frequency were both significantly greater in IL-17 group than in baseline group. The mRNA expressions of the Na+/Ca2+ exchanger, phospholamban, and ryanodine receptor Ca2+ release channel were upregulated, and the subunit of L-type Ca2+ current and sarcoplasmic reticulum Ca2+-ATPase 2a were significantly reduced in IL-17 group compared to baseline and IL-17 neutralizer group. Conclusions: IL-17 enhanced CaiTD and APD alternans through disturbances in calcium handling, which may increase VA susceptibility.
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Affiliation(s)
- Yung-Nan Tsai
- Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan.,Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Ya-Wen Hsiao
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Shien-Fong Lin
- Institute of Biomedical Engineering, National Chiao-Tung University, Hsin-Chu, Taiwan
| | - Yi-Hsin Chan
- Division of Cardiology, Chang Gung Memorial Hospital, Taoyuan, Taiwan
| | - Yu-Cheng Hsieh
- Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan.,Department of Internal Medicine, Cardiovascular Center, Taichung Veterans General Hospital, Taichung, Taiwan
| | - Wei-Hua Tang
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taipei, Taiwan.,Division of Cardiology, Department of Internal Medicine, National Yang-Ming University Hospital, Yilan, Taiwan
| | - An-Sheng Lee
- Department of Medicine, Mackay Medical College, New Taipei, Taiwan
| | - Yu-Ting Huang
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Hsing-Yuan Li
- Division of Cardiology, Department of Pediatrics, Taipei Veterans General Hospital, Taipei, Taiwan
| | - Tze-Fan Chao
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taipei, Taiwan.,Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Satoshi Higa
- Cardiac Electrophysiology and Pacing Laboratory, Division of Cardiovascular Medicine, Makiminato Central Hospital, Urasoe, Japan
| | - Tsu-Juey Wu
- Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan.,Department of Internal Medicine, Cardiovascular Center, Taichung Veterans General Hospital, Taichung, Taiwan
| | - Shih-Lin Chang
- Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taipei, Taiwan.,Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Shih-Ann Chen
- Institute of Clinical Medicine, National Yang-Ming University, Taipei, Taiwan.,Division of Cardiology, Department of Medicine, Heart Rhythm Center, Taipei Veterans General Hospital, Taipei, Taiwan.,Department of Internal Medicine, Cardiovascular Center, Taichung Veterans General Hospital, Taichung, Taiwan.,Faculty of Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan
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10
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Reilly L, Alvarado FJ, Lang D, Abozeid S, Van Ert H, Spellman C, Warden J, Makielski JC, Glukhov AV, Eckhardt LL. Genetic Loss of IK1 Causes Adrenergic-Induced Phase 3 Early Afterdepolariz ations and Polymorphic and Bidirectional Ventricular Tachycardia. Circ Arrhythm Electrophysiol 2020; 13:e008638. [PMID: 32931337 PMCID: PMC7574954 DOI: 10.1161/circep.120.008638] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Accepted: 06/23/2020] [Indexed: 11/16/2022]
Abstract
BACKGROUND Arrhythmia syndromes associated with KCNJ2 mutations have been described clinically; however, little is known of the underlying arrhythmia mechanism. We create the first patient inspired KCNJ2 transgenic mouse and study effects of this mutation on cardiac function, IK1, and Ca2+ handling, to determine the underlying cellular arrhythmic pathogenesis. METHODS A cardiac-specific KCNJ2-R67Q mouse was generated and bred for heterozygosity (R67Q+/-). Echocardiography was performed at rest, under anesthesia. In vivo ECG recording and whole heart optical mapping of intact hearts was performed before and after adrenergic stimulation in wild-type (WT) littermate controls and R67Q+/- mice. IK1 measurements, action potential characterization, and intracellular Ca2+ imaging from isolated ventricular myocytes at baseline and after adrenergic stimulation were performed in WT and R67Q+/- mice. RESULTS R67Q+/- mice (n=17) showed normal cardiac function, structure, and baseline electrical activity compared with WT (n=10). Following epinephrine and caffeine, only the R67Q+/- mice had bidirectional ventricular tachycardia, ventricular tachycardia, frequent ventricular ectopy, and/or bigeminy and optical mapping demonstrated high prevalence of spontaneous and sustained ventricular arrhythmia. Both R67Q+/- (n=8) and WT myocytes (n=9) demonstrated typical n-shaped IK1IV relationship; however, following isoproterenol, max outward IK1 increased by ≈20% in WT but decreased by ≈24% in R67Q+/- (P<0.01). R67Q+/- myocytes (n=5) demonstrated prolonged action potential duration at 90% repolarization and after 10 nmol/L isoproterenol compared with WT (n=7; P<0.05). Ca2+ transient amplitude, 50% decay rate, and sarcoplasmic reticulum Ca2+ content were not different between WT (n=18) and R67Q+/- (n=16) myocytes. R67Q+/- myocytes (n=10) under adrenergic stimulation showed frequent spontaneous development of early afterdepolarizations that occurred at phase 3 of action potential repolarization. CONCLUSIONS KCNJ2 mutation R67Q+/- causes adrenergic-dependent loss of IK1 during terminal repolarization and vulnerability to phase 3 early afterdepolarizations. This model clarifies a heretofore unknown arrhythmia mechanism and extends our understanding of treatment implications for patients with KCNJ2 mutation.
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Affiliation(s)
- Louise Reilly
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Francisco J Alvarado
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Di Lang
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Sara Abozeid
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Hannah Van Ert
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Cordell Spellman
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Jarrett Warden
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Jonathan C Makielski
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Alexey V Glukhov
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
| | - Lee L Eckhardt
- Cellular and Molecular Arrhythmia Research Program, Division of Cardiovascular Medicine, Department of Medicine, University of Wisconsin-Madison
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11
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Joca HC, Santos-Miranda A, Joviano-Santos JV, Maia-Joca RPM, Brum PC, Williams GSB, Cruz JS. Chronic Sympathetic Hyperactivity Triggers Electrophysiological Remodeling and Disrupts Excitation-Contraction Coupling in Heart. Sci Rep 2020; 10:8001. [PMID: 32409748 PMCID: PMC7224293 DOI: 10.1038/s41598-020-64949-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 04/20/2020] [Indexed: 12/31/2022] Open
Abstract
The sympathetic nervous system is essential for maintenance of cardiac function via activation of post-junctional adrenergic receptors. Prolonged adrenergic receptor activation, however, has deleterious long-term effects leading to hypertrophy and the development of heart failure. Here we investigate the effect of chronic adrenergic receptors activation on excitation-contraction coupling (ECC) in ventricular cardiomyocytes from a previously characterized mouse model of chronic sympathetic hyperactivity, which are genetically deficient in the adrenoceptor α2A and α2C genes (ARDKO). When compared to wild-type (WT) cardiomyocytes, ARDKO displayed reduced fractional shortening (~33%) and slower relaxation (~20%). Furthermore, ARDKO cells exhibited several electrophysiological changes such as action potential (AP) prolongation (~50%), reduced L-type calcium channel (LCC) current (~33%), reduced outward potassium (K+) currents (~30%), and increased sodium/calcium exchanger (NCX) activity (~52%). Consistent with reduced contractility and calcium (Ca2+) currents, the cytosolic Ca2+ ([Ca2+]i) transient from ARDKO animals was smaller and decayed slower. Importantly, no changes were observed in membrane resting potential, AP amplitude, or the inward K+ current. Finally, we modified our existing cardiac ECC computational model to account for changes in the ARDKO heart. Simulations suggest that cellular changes in the ARDKO heart resulted in variable and dyssynchronous Ca2+-induced Ca2+ release therefore altering [Ca2+]i transient dynamics and reducing force generation. In conclusion, chronic sympathetic hyperactivity impairs ECC by changing the density of several ionic currents (and thus AP repolarization) causing altered Ca2+ dynamics and contractile activity. This demonstrates the important role of ECC remodeling in the cardiac dysfunction secondary to chronic sympathetic activity.
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Affiliation(s)
- Humberto C Joca
- Department of Biochemistry and Immunology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Artur Santos-Miranda
- Department of Biochemistry and Immunology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil
- Department of Biophysics, Universidade Federal de Sao Paulo, Sao Paulo, SP, Brazil
| | | | - Rebeca P M Maia-Joca
- Department of Biochemistry and Immunology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil
| | - Patricia C Brum
- School of Physical Education and Sport, University of São Paulo, São Paulo, SP, Brazil
| | - George S B Williams
- Center for Biomedical Engineering and Technology, University of Maryland School of Medicine, Baltimore, Maryland, USA
| | - Jader S Cruz
- Department of Biochemistry and Immunology, Institute of Biological Sciences, Federal University of Minas Gerais, Belo Horizonte, MG, Brazil.
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12
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Vaidyanathan R, Van Ert H, Haq KT, Morotti S, Esch S, McCune EC, Grandi E, Eckhardt LL. Inward Rectifier Potassium Channels (Kir2.x) and Caveolin-3 Domain-Specific Interaction: Implications for Purkinje Cell-Dependent Ventricular Arrhythmias. Circ Arrhythm Electrophysiol 2019; 11:e005800. [PMID: 29326130 DOI: 10.1161/circep.117.005800] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2017] [Accepted: 11/30/2017] [Indexed: 01/05/2023]
Abstract
BACKGROUND In human cardiac ventricle, IK1 is mainly comprised Kir2.1, but Kir2.2 and Kir2.3 heterotetramers occur and modulate IK1. Long-QT syndrome-9-associated CAV3 mutations cause decreased Kir2.1 current density, but Kir2.x heterotetramers have not been studied. Here, we determine the effect of long-QT syndrome-9-CAV3 mutation F97C on Kir2.x homo- and heterotetramers and model-associated arrhythmia mechanisms. METHODS AND RESULTS Super-resolution microscopy, co-immunoprecipitation, cellular electrophysiology, on-cell Western blotting, and simulation of Purkinje and ventricular myocyte mathematical models were used. Kir2.x isoforms have unique subcellular colocalization in human cardiomyocytes and coimmunoprecipitate with Cav3. F97C-Cav3 decreased peak inward Kir2.2 current density by 50% (-120 mV; P=0.019) and peak outward by 75% (-40 mV; P<0.05) but did not affect Kir2.3 current density. FRET (Förster resonance energy transfer) efficiency for Kir2.2 with Cav3 is high, and on-cell Western blotting demonstrates decreased Kir2.2 membrane expression with F97C-Cav3. Cav3-F97C reduced peak inward and outward current density of Kir2.2/Kir2.1 or Kir2.2/Kir2.3 heterotetramers (P<0.05). Only Cav3 scaffolding and membrane domains co-immunoprecipitation with Kir2.1 and Kir2.2 and Kir2.x-N-terminal Cav3 binding motifs are required for interaction. Mathematical Purkinje, but not ventricular, myocyte model incorporating simulated current reductions, predicts spontaneous delayed after-depolarization-mediated triggered activity. CONCLUSIONS Kir2.x isoforms have a unique intracellular pattern of distribution in association with specific Cav3 domains and that critically depends on interaction with N-terminal Kir2.x Cav3-binding motifs. Long-QT syndrome-9-CAV3 mutation differentially regulates current density and cell surface expression of Kir2.x homomeric and heteromeric channels. Mathematical Purkinje cell model incorporating experimental findings suggests delayed after-depolarization-type triggered activity as a possible arrhythmia mechanism.
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Affiliation(s)
- Ravi Vaidyanathan
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Hanora Van Ert
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Kazi T Haq
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Stefano Morotti
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Samuel Esch
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Elise C McCune
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Eleonora Grandi
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.)
| | - Lee L Eckhardt
- From the Division of Cardiovascular Medicine and the Cellular and Molecular Arrhythmia Research Program, Department of Medicine, University of Wisconsin, Madison (R.V., H.V.E., S.E., E.C.M., L.L.E.); and Department of Pharmacology, University of California Davis (K.T.H., S.M., E.G.).
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13
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Johnson DM, Antoons G. Arrhythmogenic Mechanisms in Heart Failure: Linking β-Adrenergic Stimulation, Stretch, and Calcium. Front Physiol 2018; 9:1453. [PMID: 30374311 PMCID: PMC6196916 DOI: 10.3389/fphys.2018.01453] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 09/25/2018] [Indexed: 12/22/2022] Open
Abstract
Heart failure (HF) is associated with elevated sympathetic tone and mechanical load. Both systems activate signaling transduction pathways that increase cardiac output, but eventually become part of the disease process itself leading to further worsening of cardiac function. These alterations can adversely contribute to electrical instability, at least in part due to the modulation of Ca2+ handling at the level of the single cardiac myocyte. The major aim of this review is to provide a definitive overview of the links and cross talk between β-adrenergic stimulation, mechanical load, and arrhythmogenesis in the setting of HF. We will initially review the role of Ca2+ in the induction of both early and delayed afterdepolarizations, the role that β-adrenergic stimulation plays in the initiation of these and how the propensity for these may be altered in HF. We will then go onto reviewing the current data with regards to the link between mechanical load and afterdepolarizations, the associated mechano-sensitivity of the ryanodine receptor and other stretch activated channels that may be associated with HF-associated arrhythmias. Furthermore, we will discuss how alterations in local Ca2+ microdomains during the remodeling process associated the HF may contribute to the increased disposition for β-adrenergic or stretch induced arrhythmogenic triggers. Finally, the potential mechanisms linking β-adrenergic stimulation and mechanical stretch will be clarified, with the aim of finding common modalities of arrhythmogenesis that could be targeted by novel therapeutic agents in the setting of HF.
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Affiliation(s)
- Daniel M Johnson
- Department of Cardiothoracic Surgery, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, Netherlands
| | - Gudrun Antoons
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, Netherlands
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14
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Park JS, Grijalva SI, Aziz MK, Chi T, Li S, Sayegh MN, Wang A, Cho HC, Wang H. Multi-parametric cell profiling with a CMOS quad-modality cellular interfacing array for label-free fully automated drug screening. LAB ON A CHIP 2018; 18:3037-3050. [PMID: 30168827 PMCID: PMC8513687 DOI: 10.1039/c8lc00156a] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Cells are complex systems with concurrent multi-physical responses, and cell physiological signals are often encoded with spatiotemporal dynamics and further coupled with multiple cellular activities. However, most existing electronic sensors are only single-modality and cannot capture multi-parametric cellular responses. In this paper, a 1024-pixel CMOS quad-modality cellular interfacing array that enables multi-parametric cell profiling for drug development is presented. The quad-modality CMOS array features cellular impedance characterization, optical detection, extracellular potential recording, and biphasic current stimulation. The fibroblast transparency and surface adhesion are jointly monitored by cellular impedance and optical sensing modalities for comprehensive cell growth evaluation. Simultaneous current stimulation and opto-mechanical monitoring based on cardiomyocytes are demonstrated without any stimulation/sensing dead-zone. Furthermore, drug dose-dependent multi-parametric feature extractions in cardiomyocytes from their extracellular potentials and opto-mechanical signals are presented. The CMOS array demonstrates great potential for fully automated drug screening and drug safety assessments, which may substantially reduce the drug screening time and cost in future new drug development.
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Affiliation(s)
- Jong Seok Park
- The School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30308, USA.
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15
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Pathogenic mechanism of a catecholaminergic polymorphic ventricular tachycardia causing-mutation in cardiac calcium release channel RyR2. J Mol Cell Cardiol 2018; 117:26-35. [PMID: 29477366 DOI: 10.1016/j.yjmcc.2018.02.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/15/2017] [Revised: 02/14/2018] [Accepted: 02/20/2018] [Indexed: 12/27/2022]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a condition that is characterized by an abnormal heart rhythm in response to physical or emotional stress. The majority CPVT patients carry mutations in the RYR2 gene that encodes the calcium release channel/ryanodine receptor (RyR2) in cardiomyocytes. The pathogenic mechanisms that account for the clinical phenotypes of CPVT are still elusive. We have identified a de novo mutation, A165D, from a CPVT patient. We found that CPVT phenotypes are recapitulated in A165D knock-in mice. The mutant RyR2 channels enhanced sarcoplasmic reticulum Ca2+ release, triggered delayed afterdepolarization in cardiomyocytes. Structural analysis revealed that the A165D mutation is located in a loop that is involved in inter-subunit interactions in the RyR2 tetrameric structure, it disrupted conformational stability of the RyR2, which favored a closed-to-open state transition, resulting in a leaky channel. The loop also harbors several other CPVT mutations, which suggests a common pathogenic molecular mechanism of CPVT-causing mutations. Our data illustrated disease-relevant functional defects and provide a deeper mechanistic understanding of a life-threatening cardiac arrhythmia.
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16
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Lang D, Sato D, Jiang Y, Ginsburg KS, Ripplinger CM, Bers DM. Calcium-Dependent Arrhythmogenic Foci Created by Weakly Coupled Myocytes in the Failing Heart. Circ Res 2017; 121:1379-1391. [PMID: 28970285 DOI: 10.1161/circresaha.117.312050] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Revised: 09/26/2017] [Accepted: 09/29/2017] [Indexed: 12/23/2022]
Abstract
RATIONALE Intercellular uncoupling and Ca2+ (Ca) mishandling can initiate triggered ventricular arrhythmias. Spontaneous Ca release activates inward current which depolarizes membrane potential (Vm) and can trigger action potentials in isolated myocytes. However, cell-cell coupling in intact hearts limits local depolarization and may protect hearts from this arrhythmogenic mechanism. Traditional optical mapping lacks the spatial resolution to assess coupling of individual myocytes. OBJECTIVE We investigate local intercellular coupling in Ca-induced depolarization in intact hearts, using confocal microscopy to measure local Vm and intracellular [Ca] simultaneously. METHODS AND RESULTS We used isolated Langendorff-perfused hearts from control (CTL) and heart failure (HF) mice (HF induced by transaortic constriction). In CTL hearts, 1.4% of myocytes were poorly synchronized with neighboring cells and exhibited asynchronous (AS) Ca transients. These AS myocytes were much more frequent in HF (10.8% of myocytes, P<0.05 versus CTL). Local Ca waves depolarized Vm in HF but not CTL hearts, suggesting weaker gap junction coupling in HF-AS versus CTL-AS myocytes. Cell-cell coupling was assessed by calcein fluorescence recovery after photobleach during intracellular [Ca] recording. All regions in CTL hearts exhibited faster calcein diffusion than in HF, with HF-AS myocyte being slowest. In HF-AS, enhancing gap junction conductance (with rotigaptide) increased coupling and suppressed Vm depolarization during Ca waves. Conversely, in CTL hearts, gap junction inhibition (carbenoxolone) decreased coupling and allowed Ca wave-induced depolarizations. Synchronization of Ca wave initiation and triggered action potentials were observed in HF hearts and computational models. CONCLUSIONS Well-coupled CTL myocytes are effectively voltage-clamped during Ca waves, protecting the heart from triggered arrhythmias. Spontaneous Ca waves are much more common in HF myocytes and these AS myocytes are also poorly coupled, enabling local Ca-induced inward current of sufficient source strength to overcome a weakened current sink to depolarize Vm and trigger action potentials.
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Affiliation(s)
- Di Lang
- From the Department of Pharmacology, University of California, Davis
| | - Daisuke Sato
- From the Department of Pharmacology, University of California, Davis
| | - Yanyan Jiang
- From the Department of Pharmacology, University of California, Davis
| | | | | | - Donald M Bers
- From the Department of Pharmacology, University of California, Davis.
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17
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Klein MG, Shou M, Stohlman J, Solhjoo S, Haigney M, Tidwell RR, Goldstein RE, Flagg TP, Haigney MC. Role of suppression of the inward rectifier current in terminal action potential repolarization in the failing heart. Heart Rhythm 2017; 14:1217-1223. [PMID: 28396172 DOI: 10.1016/j.hrthm.2017.04.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Indexed: 11/19/2022]
Abstract
BACKGROUND The failing heart exhibits an increased arrhythmia susceptibility that is often attributed to action potential (AP) prolongation due to significant ion channel remodeling. The inwardly rectifying K+ current (IK1) has been reported to be reduced, but its contribution to shaping the AP waveform and cell excitability in the failing heart remains unclear. OBJECTIVE The purpose of this study was to define the effect of IK1 suppression on the cardiac AP and excitability in the normal and failing hearts. METHODS We used electrophysiological and pharmacological approaches to investigate IK1 function in a swine tachy-pacing model of heart failure (HF). RESULTS Terminal repolarization of the AP (TRAP; the time constant of the exponential fit to terminal repolarization) was markedly prolonged in both myocytes and arterially perfused wedges from animals with HF. TRAP was increased by 54.1% in HF myocytes (P < .001) and 26.2% in HF wedges (P = .014). The increase in TRAP was recapitulated by the potent and specific IK1 inhibitor, PA-6 (pentamidine analog 6), indicating that IK1 is the primary determinant of the final phase of repolarization. Moreover, we find that IK1 suppression reduced the ratio of effective refractory period to AP duration at 90% of repolarization, permitting re-excitation before full repolarization, reduction of AP upstroke velocity, and likely promotion of slow conduction. CONCLUSION Using an objective measure of terminal repolarization, we conclude that IK1 is the major determinant of the terminal repolarization time course. Moreover, suppression of IK1 prolongs repolarization and reduces postrepolarization refractoriness without marked effects on the overall AP duration. Collectively, these findings demonstrate how IK1 suppression may contribute to arrhythmogenesis in the failing heart.
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Affiliation(s)
- Michael G Klein
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland.
| | - Matie Shou
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Jayna Stohlman
- Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, Maryland
| | - Soroosh Solhjoo
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Myles Haigney
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Richard R Tidwell
- Department of Pathology and Laboratory Medicine, School of Medicine, The University of North Carolina, Chapel Hill, North Carolina
| | - Robert E Goldstein
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Thomas P Flagg
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, Bethesda, Maryland
| | - Mark C Haigney
- Division of Cardiology, Department of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland
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18
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Hernandez-Cascales J. Resveratrol enhances the inotropic effect but inhibits the proarrhythmic effect of sympathomimetic agents in rat myocardium. PeerJ 2017; 5:e3113. [PMID: 28382232 PMCID: PMC5376116 DOI: 10.7717/peerj.3113] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 02/21/2017] [Indexed: 01/01/2023] Open
Abstract
Background Resveratrol is a cardioprotective agent with known antiarrhythmic effects that has recently been shown to inhibit phosphodiesterase (PDE) enzyme activity. Thus, it is possible that resveratrol increases the inotropic effect of sympathomimetic agents, as PDE inhibitors do but, unlike other PDE inhibitors, its effect may not be accompanied by proarrhythmia due to its antiarrhythmic action. This work is aimed to test this hypothesis. Methods This is an “in vitro” concentration-response relationship study. The effects of noradrenaline, tyramine and isoproterenol, alone or in combination with either resveratrol or with the typical PDE inhibitor 3-isobutylmethylxantine (IBMX), were studied in electrically driven strips of right ventricle or in the spontaneously beating free wall of the right ventricle of rat heart in order to investigate inotropic or proarrhythmic effects respectively. Also, the effects of resveratrol or IBMX on the sinoatrial node rate were examined in the isolated right atria of rat heart. Results Resveratrol (10 µM and 100 µM) produces a leftward shift in the concentration-response curves for the contractile effects of noradrenaline, tyramine or isoproterenol and reduces the –log EC50 values of these three agents. IBMX produces similar effects. The spontaneous ventricular beating rate was increased by all three compounds, an effect that was further enhanced by the addition of IBMX. In contrast, resveratrol (100 µM) abolished the effects of these sympathomimetic agents on the ventricular rate. Resveratrol (1–100 µM) had no effect on the sinoatrial node rate, while IBMX produce a concentration dependent sinoatrial tachycardia. Discussion Taken together, the finding, indicate that resveratrol, like the PDE inhibitor IBMX enhances the contractile effects of sympathomimetic agents but, in contrast to IBMX, it does not enhance their proarrhythmic effect or produce sinoatrial tachycardia. This is most probably consequence of the antiarrhythmic effect of resveratrol which protect against the proarrhythmic effects resulting from PDE inhibition.
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Affiliation(s)
- Jesús Hernandez-Cascales
- Department of Pharmacology, Faculty of Medicine, University of Murcia , Espinardo-Murcia , Spain
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19
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Bers DM. Stabilizing ryanodine receptor gating quiets arrhythmogenic events in human heart failure and atrial fibrillation. Heart Rhythm 2016; 14:420-421. [PMID: 27725286 DOI: 10.1016/j.hrthm.2016.10.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2016] [Indexed: 12/01/2022]
Affiliation(s)
- Donald M Bers
- Department of Pharmacology, University of California, Davis, Davis, California.
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20
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Habecker BA, Anderson ME, Birren SJ, Fukuda K, Herring N, Hoover DB, Kanazawa H, Paterson DJ, Ripplinger CM. Molecular and cellular neurocardiology: development, and cellular and molecular adaptations to heart disease. J Physiol 2016; 594:3853-75. [PMID: 27060296 DOI: 10.1113/jp271840] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 03/15/2016] [Indexed: 12/12/2022] Open
Abstract
The nervous system and cardiovascular system develop in concert and are functionally interconnected in both health and disease. This white paper focuses on the cellular and molecular mechanisms that underlie neural-cardiac interactions during development, during normal physiological function in the mature system, and during pathological remodelling in cardiovascular disease. The content on each subject was contributed by experts, and we hope that this will provide a useful resource for newcomers to neurocardiology as well as aficionados.
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Affiliation(s)
- Beth A Habecker
- Department of Physiology and Pharmacology, Department of Medicine Division of Cardiovascular Medicine and Knight Cardiovascular Institute, Oregon Health and Science University, Portland, OR, 97239, USA
| | - Mark E Anderson
- Johns Hopkins Department of Medicine, Johns Hopkins School of Medicine, Baltimore, MD, 21287, USA
| | - Susan J Birren
- Department of Biology, Volen Center for Complex Systems, Brandeis University, Waltham, MA, 02453, USA
| | - Keiichi Fukuda
- Department of Cardiology, Keio University School of Medicine, 35-Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - Neil Herring
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
| | - Donald B Hoover
- Department of Biomedical Sciences, Center of Excellence in Inflammation, Infectious Disease and Immunity, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, TN, 37614, USA
| | - Hideaki Kanazawa
- Department of Cardiology, Keio University School of Medicine, 35-Shinanomachi, Shinjuku-ku, Tokyo, 160-8582, Japan
| | - David J Paterson
- Burdon Sanderson Cardiac Science Centre, Department of Physiology, Anatomy and Genetics, University of Oxford, Parks Road, Oxford, OX1 3PT, UK
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21
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Gardner RT, Ripplinger CM, Myles RC, Habecker BA. Molecular Mechanisms of Sympathetic Remodeling and Arrhythmias. Circ Arrhythm Electrophysiol 2016; 9:e001359. [PMID: 26810594 DOI: 10.1161/circep.115.001359] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Ryan T Gardner
- From the Department of Physiology and Pharmacology and Knight Cardiovascular Institute, Oregon Health and Science University, Portland (R.T.G., B.A.H.); Department of Pharmacology, School of Medicine, University of California, Davis (C.M.R.); and Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (R.C.M.)
| | - Crystal M Ripplinger
- From the Department of Physiology and Pharmacology and Knight Cardiovascular Institute, Oregon Health and Science University, Portland (R.T.G., B.A.H.); Department of Pharmacology, School of Medicine, University of California, Davis (C.M.R.); and Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (R.C.M.)
| | - Rachel C Myles
- From the Department of Physiology and Pharmacology and Knight Cardiovascular Institute, Oregon Health and Science University, Portland (R.T.G., B.A.H.); Department of Pharmacology, School of Medicine, University of California, Davis (C.M.R.); and Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (R.C.M.)
| | - Beth A Habecker
- From the Department of Physiology and Pharmacology and Knight Cardiovascular Institute, Oregon Health and Science University, Portland (R.T.G., B.A.H.); Department of Pharmacology, School of Medicine, University of California, Davis (C.M.R.); and Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, United Kingdom (R.C.M.).
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22
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Abstract
Any disturbance of electrical impulse formation in the heart and of impulse conduction or action potential (AP) repolarization can lead to rhythm disorders. Potassium (K(+)) channels play a prominent role in the AP repolarization process. In this review we describe the causes and mechanisms of proarrhythmic effects that arise as a response to blockers of cardiac K(+) channels. The largest and chemically most diverse groups of compound targets are Kv11.1 (hERG) and Kv7.1 (KvLQT1) channels. Finally, the proarrhythmic propensity of atrial-selective K(+) blockers inhibiting Kv1.5, Kir3.1/3.4, SK, and K2P channels is discussed.
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Affiliation(s)
- Lasse Skibsbye
- Danish Arrhythmia Research Centre, Faculty of Health and Medical Sciences, University of Copenhagen, 3 Blegdamsvej, 3 Copenhagen N DK-2200, Denmark
| | - Ursula Ravens
- Department of Pharmacology and Toxicology, Medical Faculty Carl Gustav Carus, Institut für Pharmakologie und Toxikologie, TU Dresden, Fetscherstrasse 74, Dresden D-01307, Germany.
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23
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Beta-Adrenoceptor Stimulation Reveals Ca2+ Waves and Sarcoplasmic Reticulum Ca2+ Depletion in Left Ventricular Cardiomyocytes from Post-Infarction Rats with and without Heart Failure. PLoS One 2016; 11:e0153887. [PMID: 27096943 PMCID: PMC4838269 DOI: 10.1371/journal.pone.0153887] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Accepted: 04/05/2016] [Indexed: 11/25/2022] Open
Abstract
Abnormal cellular Ca2+ handling contributes to both contractile dysfunction and arrhythmias in heart failure. Reduced Ca2+ transient amplitude due to decreased sarcoplasmic reticulum Ca2+ content is a common finding in heart failure models. However, heart failure models also show increased propensity for diastolic Ca2+ release events which occur when sarcoplasmic reticulum Ca2+ content exceeds a certain threshold level. Such Ca2+ release events can initiate arrhythmias. In this study we aimed to investigate if both of these aspects of altered Ca2+ homeostasis could be found in left ventricular cardiomyocytes from rats with different states of cardiac function six weeks after myocardial infarction when compared to sham-operated controls. Video edge-detection, whole-cell Ca2+ imaging and confocal line-scan imaging were used to investigate cardiomyocyte contractile properties, Ca2+ transients and Ca2+ waves. In baseline conditions, i.e. without beta-adrenoceptor stimulation, cardiomyocytes from rats with large myocardial infarction, but without heart failure, did not differ from sham-operated animals in any of these aspects of cellular function. However, when exposed to beta-adrenoceptor stimulation, cardiomyocytes from both non-failing and failing rat hearts showed decreased sarcoplasmic reticulum Ca2+ content, decreased Ca2+ transient amplitude, and increased frequency of Ca2+ waves. These results are in line with a decreased threshold for diastolic Ca2+ release established by other studies. In the present study, factors that might contribute to a lower threshold for diastolic Ca2+ release were increased THR286 phosphorylation of Ca2+/calmodulin-dependent protein kinase II and increased protein phosphatase 1 abundance. In conclusion, this study demonstrates both decreased sarcoplasmic reticulum Ca2+ content and increased propensity for diastolic Ca2+ release events in ventricular cardiomyocytes from rats with heart failure after myocardial infarction, and that these phenomena are also found in rats with large myocardial infarctions without heart failure development. Importantly, beta-adrenoceptor stimulation is necessary to reveal these perturbations in Ca2+ handling after a myocardial infarction.
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24
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Pfeiffer ER, Vega R, McDonough PM, Price JH, Whittaker R. Specific prediction of clinical QT prolongation by kinetic image cytometry in human stem cell derived cardiomyocytes. J Pharmacol Toxicol Methods 2016; 81:263-73. [PMID: 27095424 DOI: 10.1016/j.vascn.2016.04.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Revised: 04/08/2016] [Accepted: 04/08/2016] [Indexed: 02/06/2023]
Abstract
INTRODUCTION A priority in the development and approval of new drugs is assessment of cardiovascular risk. Current methodologies for screening compounds (e.g. HERG testing) for proarrhythmic risk lead to many false positive and false negative results, resulting in the attrition of potentially therapeutic compounds in early development, and the advancement of other candidates that cause adverse effects. With improvements in the technologies of high content imaging and human stem cell differentiation, it is now possible to directly screen compounds for arrhythmogenic tendencies in human stem cell derived cardiomyocytes (hSC-CMs). METHODS A training panel of 90 compounds consisting of roughly equal numbers of QT-prolonging and negative control (non-QT-prolonging) compounds, and a follow-up blinded study of 35 compounds including 16 from the 90 compound panel and 2 duplicates, were evaluated for prolongation of the calcium transient in hSC-CMs using kinetic image cytometry (KIC), a specialized form of high content analysis. RESULTS The KIC-hSC-CM assay identified training compounds that prolong the calcium transient with 98% specificity, 97% precision, 80% sensitivity, and 89% accuracy in predicting clinical QT prolongation by these compounds. The follow-up study of 35 blinded compounds confirmed the reproducibility and strong diagnostic accuracy of the assay. DISCUSSION The correlation of the KIC-hSC-CM results to clinical observations met or surpassed traditional preclinical assessment of cardiac risk utilizing animal models. Thus, the KIC-hSC-CM assay, which can be accomplished in high throughput and at relatively low cost, is an effective new model system for testing chemicals for cardiovascular risk.
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Affiliation(s)
| | - Raquel Vega
- Vala Sciences, Inc., San Diego, CA 92121, United States
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25
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Jaimes R, Walton RD, Pasdois P, Bernus O, Efimov IR, Kay MW. A technical review of optical mapping of intracellular calcium within myocardial tissue. Am J Physiol Heart Circ Physiol 2016; 310:H1388-401. [PMID: 27016580 DOI: 10.1152/ajpheart.00665.2015] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 03/21/2016] [Indexed: 12/18/2022]
Abstract
Optical mapping of Ca(2+)-sensitive fluorescence probes has become an extremely useful approach and adopted by many cardiovascular research laboratories to study a spectrum of myocardial physiology and disease conditions. Optical mapping data are often displayed as detailed pseudocolor images, providing unique insight for interpreting mechanisms of ectopic activity, action potential and Ca(2+) transient alternans, tachycardia, and fibrillation. Ca(2+)-sensitive fluorescent probes and optical mapping systems continue to evolve in the ongoing effort to improve therapies that ease the growing worldwide burden of cardiovascular disease. In this technical review we provide an updated overview of conventional approaches for optical mapping of Cai (2+) within intact myocardium. In doing so, a brief history of Cai (2+) probes is provided, and nonratiometric and ratiometric Ca(2+) probes are discussed, including probes for imaging sarcoplasmic reticulum Ca(2+) and probes compatible with potentiometric dyes for dual optical mapping. Typical measurements derived from optical Cai (2+) signals are explained, and the analytics used to compute them are presented. Last, recent studies using Cai (2+) optical mapping to study arrhythmias, heart failure, and metabolic perturbations are summarized.
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Affiliation(s)
- Rafael Jaimes
- Department of Biomedical Engineering, The George Washington University. Washington, District of Columbia
| | - Richard D Walton
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; Institut National de la Santé et de la Recherche Médicale, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; and L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Philippe Pasdois
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; Institut National de la Santé et de la Recherche Médicale, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; and L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Olivier Bernus
- Université de Bordeaux, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; Institut National de la Santé et de la Recherche Médicale, Centre de Recherche Cardio-Thoracique de Bordeaux U1045, Bordeaux, France; and L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Igor R Efimov
- Department of Biomedical Engineering, The George Washington University. Washington, District of Columbia; L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Université de Bordeaux, Bordeaux, France
| | - Matthew W Kay
- Department of Biomedical Engineering, The George Washington University. Washington, District of Columbia;
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26
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Ripplinger CM, Noujaim SF, Linz D. The nervous heart. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2016; 120:199-209. [PMID: 26780507 DOI: 10.1016/j.pbiomolbio.2015.12.015] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Revised: 12/29/2015] [Accepted: 12/31/2015] [Indexed: 12/23/2022]
Abstract
Many cardiac electrophysiological abnormalities are accompanied by autonomic nervous system dysfunction. Here, we review mechanisms by which the cardiac nervous system controls normal and abnormal excitability and may contribute to atrial and ventricular tachyarrhythmias. Moreover, we explore the potential antiarrhythmic and/or arrhythmogenic effects of modulating the autonomic nervous system by several strategies, including ganglionated plexi ablation, vagal and spinal cord stimulations, and renal sympathetic denervation as therapies for atrial and ventricular arrhythmias.
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Affiliation(s)
- Crystal M Ripplinger
- Department of Pharmacology, University of California Davis, 451 Health Sciences Drive, Davis, CA 95616, USA.
| | - Sami F Noujaim
- Molecular Pharmacology and Physiology, University of South Florida, 12901 Bruce B Downs Blvd, Tampa, FL 33612, USA.
| | - Dominik Linz
- Klinik für Innere Medizin III, Universitätsklinikum des Saarlandes, 66421 Homburg, Saar, Germany.
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27
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Bers DM, Chen-Izu Y. Sodium and calcium regulation in cardiac myocytes: from molecules to heart failure and arrhythmia. J Physiol 2015; 593:1327-9. [PMID: 25772288 DOI: 10.1113/jp270133] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Affiliation(s)
- Donald M Bers
- Department of Pharmacology, University of California, Davis, CA, USA
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28
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Fischer TH, Herting J, Eiringhaus J, Pabel S, Hartmann NH, Ellenberger D, Friedrich M, Renner A, Gummert J, Maier LS, Zabel M, Hasenfuss G, Sossalla S. Sex-dependent alterations of Ca2+ cycling in human cardiac hypertrophy and heart failure. Europace 2015; 18:1440-8. [PMID: 26493982 DOI: 10.1093/europace/euv313] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 08/19/2015] [Indexed: 11/12/2022] Open
Abstract
AIMS Clinical studies have shown differences in the propensity for malignant ventricular arrhythmias between women and men suffering from cardiomyopathies and heart failure (HF). This is clinically relevant as it impacts therapies like prophylactic implantable cardioverter-defibrillator implantation but the pathomechanisms are unknown. As an increased sarcoplasmic reticulum (SR) Ca(2+) leak is arrhythmogenic, it could represent a cellular basis for this paradox. METHODS/RESULTS We evaluated the SR Ca(2+) leak with respect to sex differences in (i) afterload-induced cardiac hypertrophy (Hy) with preserved left ventricular (LV) function and (ii) end-stage HF. Cardiac function did not differ between sexes in both cardiac pathologies. Human cardiomyocytes isolated from female patients with Hy showed a significantly lower Ca(2+) spark frequency (CaSpF, confocal microscopy, Fluo3-AM) compared with men (P < 0.05). As Ca(2+) spark width and duration were similar in women and men, this difference in CaSpF did not yet translate into a significant difference of the calculated SR Ca(2+) leak between both sexes at this stage of disease (P = 0.14). Epifluorescence measurements (Fura2-AM) revealed comparable Ca(2+) cycling properties (diastolic Ca(2+) levels, amplitude of systolic Ca(2+) transients, SR Ca(2+) load) in patients of both sexes suffering from Hy. Additionally, the increased diastolic CaSpF in male patients with Hy did not yet translate into an elevated ratio of cells showing arrhythmic events (Ca(2+) waves, spontaneous Ca(2+) transients) (P = 0.77). In the transition to HF, both sexes showed an increase of the CaSpF (P < 0.05) and the sex dependence was even more pronounced. Female patients had a 69 ± 10% lower SR Ca(2+) leak (P < 0.05), which now even translated into a lower ratio of arrhythmic cells in female HF patients compared with men (P < 0.001). CONCLUSION These data show that the SR Ca(2+) leak is lower in women than in men with comparable cardiac impairment. Since the SR Ca(2+) leak triggers delayed afterdepolarizations, our findings may explain why women are less prone to ventricular arrhythmias and confirm the rationale of therapeutic measures reducing the SR Ca(2+) leak.
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Affiliation(s)
- Thomas H Fischer
- Klinik für Kardiologie und Pneumologie/Herzzentrum, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Jonas Herting
- Klinik für Kardiologie und Pneumologie/Herzzentrum, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Jörg Eiringhaus
- Klinik für Kardiologie und Pneumologie/Herzzentrum, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Steffen Pabel
- Klinik für Kardiologie und Pneumologie/Herzzentrum, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Nico H Hartmann
- Klinik für Kardiologie und Pneumologie/Herzzentrum, Georg-August-Universität Göttingen, Göttingen, Germany
| | - David Ellenberger
- Institut für Medizinische Statistik, Georg-August-Universität Göttingen, Göttingen, Germany
| | - Martin Friedrich
- Abt. Thorax-, Herz- und Gefäßchirurgie, Herzzentrum, Georg-August-Universität Göttingen, Göttingen, Germany
| | - André Renner
- Abt. Thorax-, Herz-, Gefäßchirurgie, Herz- und Diabeteszentrum Nordrheinwestfalen, Bad Oeynhausen, Germany
| | - Jan Gummert
- Abt. Thorax-, Herz-, Gefäßchirurgie, Herz- und Diabeteszentrum Nordrheinwestfalen, Bad Oeynhausen, Germany
| | - Lars S Maier
- Klinik und Poliklinik für Innere Medizin II, Universitätsklinikum Regensburg, Regensburg, Germany
| | - Markus Zabel
- Klinik für Kardiologie und Pneumologie/Herzzentrum, Georg-August-Universität Göttingen, Göttingen, Germany Deutsches Zentrum für Herz-Kreislauf-Forschung (DZHK), Standort Göttingen, Germany
| | - Gerd Hasenfuss
- Klinik für Kardiologie und Pneumologie/Herzzentrum, Georg-August-Universität Göttingen, Göttingen, Germany Deutsches Zentrum für Herz-Kreislauf-Forschung (DZHK), Standort Göttingen, Germany
| | - Samuel Sossalla
- Klinik für Kardiologie und Pneumologie/Herzzentrum, Georg-August-Universität Göttingen, Göttingen, Germany Deutsches Zentrum für Herz-Kreislauf-Forschung (DZHK), Standort Göttingen, Germany
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29
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Abstract
Despite improvements in the therapy of underlying heart disease, sudden cardiac death is a major cause of death worldwide. Disturbed Na and Ca handling is known to be a major predisposing factor for life-threatening tachyarrhythmias. In cardiomyocytes, many ion channels and transporters, including voltage-gated Na and Ca channels, cardiac ryanodine receptors, Na/Ca-exchanger, and SR Ca-ATPase are involved in this regulation. We have learned a lot about the pathophysiological relevance of disturbed ion channel function from monogenetic disorders. Changes in the gating of a single ion channel and the activity of an ion pump suffice to dramatically increase the propensity for arrhythmias even in structurally normal hearts. Nevertheless, patients with heart failure with acquired dysfunction in many ion channels and transporters exhibit profound dysregulation of Na and Ca handling and Ca/calmodulin-dependent protein kinase and are especially prone to arrhythmias. A deeper understanding of the underlying arrhythmic principles is mandatory if we are to improve their outcome. This review addresses basic tachyarrhythmic mechanisms, the underlying ionic mechanisms and the consequences for ion homeostasis, and the situation in complex diseases like heart failure.
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Affiliation(s)
- Stefan Wagner
- From the Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany (S.W., L.S.M.); and Department of Pharmacology, University of California, Davis, CA (D.M.B.)
| | - Lars S Maier
- From the Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany (S.W., L.S.M.); and Department of Pharmacology, University of California, Davis, CA (D.M.B.).
| | - Donald M Bers
- From the Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany (S.W., L.S.M.); and Department of Pharmacology, University of California, Davis, CA (D.M.B.)
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30
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Lou Q, Belevych AE, Radwański PB, Liu B, Kalyanasundaram A, Knollmann BC, Fedorov VV, Györke S. Alternating membrane potential/calcium interplay underlies repetitive focal activity in a genetic model of calcium-dependent atrial arrhythmias. J Physiol 2014; 593:1443-58. [PMID: 25384790 DOI: 10.1113/jphysiol.2014.280784] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 10/23/2014] [Indexed: 01/09/2023] Open
Abstract
KEY POINTS Atrial fibrillation is often initiated and perpetuated by abnormal electrical pulses repetitively originating from regions outside the heart's natural pacemaker. In this study we examined the causal role of abnormal calcium releases from the sarcoplasmic reticulum in producing repetitive electrical discharges in atrial cells and tissues. Calsequestrin2 is a protein that stabilizes the closed state of calcium release channels, i.e. the ryanodine receptors. In the atria from mice predisposed to abnormal calcium releases secondary to the absence of calsequestrin2, we observed abnormal repetitive electrical discharges that may lead to atrial fibrillation. Here, we report a novel pathological rhythm generator. Specifically, abnormal calcium release leads to electrical activation, which in turn results in another abnormal calcium release. This process repeats itself and thus sustains the repetitive electrical discharges. These results suggest that improving the stability of ryanodine receptors might be useful to treat atrial fibrillation. ABSTRACT Aberrant diastolic calcium (Ca) release due to leaky ryanodine receptors (RyR2s) has been recently associated with atrial fibrillation (AF) and catecholaminergic polymorphic ventricular tachycardia (CPVT). However, it remains unclear how diastolic Ca release contributes to the rising of rapid repetitive focal activity, which is considered as a common AF triggering mechanism. To address this question, we conducted simultaneous voltage/Ca optical mapping in atrial tissue and one-/two-dimensional confocal imaging in atrial tissue and myocytes from wild-type (WT, n = 15) and CPVT mice lacking calsequestrin 2 (Casq2(-/-), n = 45), which promotes diastolic Ca release. During β-adrenergic stimulation (100 nM isoproterenol), only Casq2(-/-) atrial myocytes showed pacing-induced self-sustained repetitive activity (31 ± 21 s vs. none in WT). Importantly, in atrial tissue, this repetitive activity could translate to Ca-dependent focal arrhythmia. Ectopic action potential (AP) firing during repetitive activity occurred only when diastolic Ca release achieved a sufficient level of synchronization. The AP, in turn, synchronized subsequent diastolic Ca release by temporally aligning multiple sources of Ca waves both within individual myocytes and throughout the atrial tissue. This alternating interplay between AP and diastolic Ca release perpetuates the self-sustaining repetitive activity. In fact, pharmacological disruption of synchronized diastolic Ca release (by ryanodine) prevented aberrant APs; and vice versa, the inhibition of AP (by TTX or 0 Na, 0 Ca solution) de-synchronized diastolic Ca release. Taken together, these results suggest that a cyclical interaction between synchronized diastolic Ca release and AP forms a pathological rhythm generator that is involved in Ca-dependent atrial arrhythmias in CPVT.
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Affiliation(s)
- Qing Lou
- Department of Physiology & Cell Biology, College of Medicine, The Ohio State University, Columbus, OH, USA; Davis Heart & Lung Research Institute, The Ohio State University, Columbus, OH, USA
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