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Rubenstein DS, Rubenstein MA, Cummins JR, Belinskiy BP, Cox CL. The spiral wave frequency effect in atrial fibrillation. Biophys J 2024; 123:782-798. [PMID: 38341756 PMCID: PMC10995432 DOI: 10.1016/j.bpj.2024.02.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 12/19/2023] [Accepted: 02/05/2024] [Indexed: 02/13/2024] Open
Abstract
A spiral wavefront (WF), generated by a cardiac rotor that drifts between surface electrodes during atrial fibrillation, exhibits frequency changes inconsistent with classical Doppler effect (CDE) phenomena. Recent clinical studies reveal three repeatedly observed events--1) side-dependent frequency changes across the path of the rotor, 2) one additional WF strike on the higher frequency side, and 3) a reversal of WF strike sequence--which constitute a diametrical property of spinning WF sources. A linear ray model is first used to reveal and develop the diametrical phenomena. Mathematical models of an Archimedean spiral and a spiral generated by the diffusion equation are developed and compared. Each formulation predicts the diametrical property that CDE does not capture and illuminates the occurrence of a strong side and weak side with respect to the rotor path. Whereas CDE exhibits higher and lower frequencies from approaching and receding sources of WFs, respectively, spiral rotors generate higher and lower frequencies on opposite sides of the migration path. This motivates the reconsideration of mapping and ablation strategies that have traditionally been based on identifying sites of the dominant frequency. While this research aims to characterize the path of a spiral rotor during atrial fibrillation accurately, the results are applicable in other fields of science and engineering in which rotating spiral waves occur.
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Affiliation(s)
- Donald S Rubenstein
- Department of Medicine, Prisma Health Upstate Campus, Greenville, South Carolina
| | | | - James R Cummins
- Department of Mathematics, University of Tennessee at Chattanooga, Chattanooga, Tennessee
| | - Boris P Belinskiy
- Department of Mathematics, University of Tennessee at Chattanooga, Chattanooga, Tennessee
| | - Christopher L Cox
- Department of Mathematics, University of Tennessee at Chattanooga, Chattanooga, Tennessee.
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2
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Carvajal C, Yan J, Nani A, DeSantiago J, Wan X, Deschenes I, Ai X, Fill M. Isolated Cardiac Ryanodine Receptor Function Varies Between Mammals. J Membr Biol 2024; 257:25-36. [PMID: 38285125 DOI: 10.1007/s00232-023-00301-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 11/24/2023] [Indexed: 01/30/2024]
Abstract
Concerted robust opening of cardiac ryanodine receptors' (RyR2) Ca2+ release 1oplasmic reticulum (SR) is fundamental for normal systolic cardiac function. During diastole, infrequent spontaneous RyR2 openings mediate the SR Ca2+ leak that normally constrains SR Ca2+ load. Abnormal large diastolic RyR2-mediated Ca2+ leak events can cause delayed after depolarizations (DADs) and arrhythmias. The RyR2-associated mechanisms underlying these processes are being extensively studied at multiple levels utilizing various model animals. Since there are well-described species-specific differences in cardiac intracellular Ca2+ handing in situ, we tested whether or not single RyR2 function in vitro retains this species specificity. We isolated RyR2-rich heavy SR microsomes from mouse, rat, rabbit, and human ventricular muscle and quantified RyR2 function using identical solutions and methods. The single RyR2 cytosolic Ca2+ sensitivity was similar across these species. However, there were significant species differences in single RyR2 mean open times in both systole and diastole-like solutions. In diastole-like solutions, single rat/mouse RyR2 open probability and frequency of long openings (> 6 ms) were similar, but these values were significantly greater than those of either single rabbit or human RyR2s. We propose these in vitro single RyR2 functional differences across species stem from the species-specific RyR2 regulatory environment present in the source tissue. Our results show the single rabbit RyR2 functional attributes, particularly in diastole-like conditions, replicate those of single human RyR2 best among the species tested.
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Affiliation(s)
- Catherine Carvajal
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA
| | - Jiajie Yan
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA
- Department of Physiology & Cell Biology, College of Medicine, The Ohio State University, 333 W. 10Th Avenue, Columbus, OH, 43210, USA
| | - Alma Nani
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA
| | - Jaime DeSantiago
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA
| | - Xiaoping Wan
- Department of Physiology & Cell Biology, College of Medicine, The Ohio State University, 333 W. 10Th Avenue, Columbus, OH, 43210, USA
| | - Isabelle Deschenes
- Department of Physiology & Cell Biology, College of Medicine, The Ohio State University, 333 W. 10Th Avenue, Columbus, OH, 43210, USA
| | - Xun Ai
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA.
- Department of Physiology & Cell Biology, College of Medicine, The Ohio State University, 333 W. 10Th Avenue, Columbus, OH, 43210, USA.
| | - Michael Fill
- Department of Physiology & Biophysics, Section of Cellular Signaling, Rush University Medical Center, 1750 W. Harrison Avenue, Chicago, IL, 60612, USA.
- Department of Molecular Biophysics & Physiology, Rush University Medical Center, 1750 West Harrison Street, Columbus, OH, 43210, USA.
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3
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Shi R, Reichardt M, Fiegle DJ, Küpfer LK, Czajka T, Sun Z, Salditt T, Dendorfer A, Seidel T, Bruegmann T. Contractility measurements for cardiotoxicity screening with ventricular myocardial slices of pigs. Cardiovasc Res 2023; 119:2469-2481. [PMID: 37934066 PMCID: PMC10651213 DOI: 10.1093/cvr/cvad141] [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: 11/08/2022] [Revised: 05/22/2023] [Accepted: 07/10/2023] [Indexed: 11/08/2023] Open
Abstract
AIMS Cardiotoxicity is one major reason why drugs do not enter or are withdrawn from the market. Thus, approaches are required to predict cardiotoxicity with high specificity and sensitivity. Ideally, such methods should be performed within intact cardiac tissue with high relevance for humans and detect acute and chronic side effects on electrophysiological behaviour, contractility, and tissue structure in an unbiased manner. Herein, we evaluate healthy pig myocardial slices and biomimetic cultivation setups (BMCS) as a new cardiotoxicity screening approach. METHODS AND RESULTS Pig left ventricular samples were cut into slices and spanned into BMCS with continuous electrical pacing and online force recording. Automated stimulation protocols were established to determine the force-frequency relationship (FFR), frequency dependence of contraction duration, effective refractory period (ERP), and pacing threshold. Slices generated 1.3 ± 0.14 mN/mm2 force at 0.5 Hz electrical pacing and showed a positive FFR and a shortening of contraction duration with increasing pacing rates. Approximately 62% of slices were able to contract for at least 6 days while showing stable ERP, contraction duration-frequency relationship, and preserved cardiac structure confirmed by confocal imaging and X-ray diffraction analysis. We used specific blockers of the most important cardiac ion channels to determine which analysis parameters are influenced. To validate our approach, we tested five drug candidates selected from the Comprehensive in vitro Proarrhythmia Assay list as well as acetylsalicylic acid and DMSO as controls in a blinded manner in three independent laboratories. We were able to detect all arrhythmic drugs and their respective mode of action on cardiac tissue including inhibition of Na+, Ca2+, and hERG channels as well as Na+/Ca2+ exchanger. CONCLUSION We systematically evaluate this approach for cardiotoxicity screening, which is of high relevance for humans and can be upscaled to medium-throughput screening. Thus, our approach will improve the predictive value and efficiency of preclinical cardiotoxicity screening.
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Affiliation(s)
- Runzhu Shi
- Institute for Cardiovascular Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Göttingen, Germany
- International Research Training Group 1816, University Medical Center Göttingen, Göttingen, Germany
| | - Marius Reichardt
- Institute for Cardiovascular Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Göttingen, Germany
- Institute for X-ray Physics, University of Göttingen, Göttingen, Germany
| | - Dominik J Fiegle
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Linda K Küpfer
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Titus Czajka
- Institute for X-ray Physics, University of Göttingen, Göttingen, Germany
| | - Zhengwu Sun
- Walter-Brendel-Centre of Experimental Medicine, Hospital of the University Munich, Munich, Germany
| | - Tim Salditt
- Institute for X-ray Physics, University of Göttingen, Göttingen, Germany
- Cluster of Excellence ‘Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells’ (MBExC), University of Göttingen, Göttingen, Germany
| | - Andreas Dendorfer
- Walter-Brendel-Centre of Experimental Medicine, Hospital of the University Munich, Munich, Germany
- German Centre of Cardiovascular Research (DZHK), Munich Heart Alliance, Munich, Germany
| | - Thomas Seidel
- Institute of Cellular and Molecular Physiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany
| | - Tobias Bruegmann
- Institute for Cardiovascular Physiology, University Medical Center Göttingen, Humboldtallee 23, 37073 Göttingen, Göttingen, Germany
- Cluster of Excellence ‘Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells’ (MBExC), University of Göttingen, Göttingen, Germany
- German Center for Cardiovascular Research (DZHK), Partner site Göttingen, Göttingen, Germany
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4
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Schmeckpeper J, Kim K, George SA, Blackwell DJ, Brennan JA, Efimov IR, Knollmann BC. RyR2 inhibition with dantrolene is antiarrhythmic, prevents further pathological remodeling, and improves cardiac function in chronic ischemic heart disease. J Mol Cell Cardiol 2023; 181:67-78. [PMID: 37285929 PMCID: PMC10526741 DOI: 10.1016/j.yjmcc.2023.05.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 04/30/2023] [Accepted: 05/31/2023] [Indexed: 06/09/2023]
Abstract
Diastolic Ca2+ leak due to cardiac ryanodine receptor (RyR2) hyperactivity has been widely documented in chronic ischemic heart disease (CIHD) and may contribute to ventricular tachycardia (VT) risk and progressive left-ventricular (LV) remodeling. Here we test the hypothesis that targeting RyR2 hyperactivity can suppress VT inducibility and progressive heart failure in CIHD by the RyR2 inhibitor dantrolene. METHODS AND RESULTS: CIHD was induced in C57BL/6 J mice by left coronary artery ligation. Four weeks later, mice were randomized to either acute or chronic (6 weeks via implanted osmotic pump) treatment with dantrolene or vehicle. VT inducibility was assessed by programmed stimulation in vivo and in isolated hearts. Electrical substrate remodeling was assessed by optical mapping. Ca2+ sparks and spontaneous Ca2+ releases were measured in isolated cardiomyocytes. Cardiac remodeling was quantified by histology and qRT-PCR. Cardiac function and contractility were measured using echocardiography. Compared to vehicle, acute dantrolene treatment reduced VT inducibility. Optical mapping demonstrated reentrant VT prevention by dantrolene, which normalized the shortened refractory period (VERP) and prolonged action potential duration (APD), preventing APD alternans. In single CIHD cardiomyocytes, dantrolene normalized RyR2 hyperactivity and prevented spontaneous intracellular Ca2+ release. Chronic dantrolene treatment not only reduced VT inducibility but also reduced peri-infarct fibrosis and prevented further progression of LV dysfunction in CIHD mice. CONCLUSIONS: RyR2 hyperactivity plays a mechanistic role for VT risk, post-infarct remodeling, and contractile dysfunction in CIHD mice. Our data provide proof of concept for the anti-arrhythmic and anti-remodeling efficacy of dantrolene in CIHD.
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Affiliation(s)
- Jeffrey Schmeckpeper
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Kyungsoo Kim
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Sharon A George
- Department of Biomedical Engineering, the George Washington University, Washington DC, USA; Department of Biomedical Engineering, Northwestern University, Chicago, IL, USA
| | - Daniel J Blackwell
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Jaclyn A Brennan
- Department of Biomedical Engineering, the George Washington University, Washington DC, USA
| | - Igor R Efimov
- Department of Biomedical Engineering, the George Washington University, Washington DC, USA; Department of Biomedical Engineering, Northwestern University, Chicago, IL, USA
| | - Bjorn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN, USA.
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Eisen B, Binah O. Modeling Duchenne Muscular Dystrophy Cardiomyopathy with Patients' Induced Pluripotent Stem-Cell-Derived Cardiomyocytes. Int J Mol Sci 2023; 24:ijms24108657. [PMID: 37240001 DOI: 10.3390/ijms24108657] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 05/05/2023] [Accepted: 05/10/2023] [Indexed: 05/28/2023] Open
Abstract
Duchenne muscular dystrophy (DMD) is an X-linked progressive muscle degenerative disease caused by mutations in the dystrophin gene, resulting in death by the end of the third decade of life at the latest. A key aspect of the DMD clinical phenotype is dilated cardiomyopathy, affecting virtually all patients by the end of the second decade of life. Furthermore, despite respiratory complications still being the leading cause of death, with advancements in medical care in recent years, cardiac involvement has become an increasing cause of mortality. Over the years, extensive research has been conducted using different DMD animal models, including the mdx mouse. While these models present certain important similarities to human DMD patients, they also have some differences which pose a challenge to researchers. The development of somatic cell reprograming technology has enabled generation of human induced pluripotent stem cells (hiPSCs) which can be differentiated into different cell types. This technology provides a potentially endless pool of human cells for research. Furthermore, hiPSCs can be generated from patients, thus providing patient-specific cells and enabling research tailored to different mutations. DMD cardiac involvement has been shown in animal models to include changes in gene expression of different proteins, abnormal cellular Ca2+ handling, and other aberrations. To gain a better understanding of the disease mechanisms, it is imperative to validate these findings in human cells. Furthermore, with the recent advancements in gene-editing technology, hiPSCs provide a valuable platform for research and development of new therapies including the possibility of regenerative medicine. In this article, we review the DMD cardiac-related research performed so far using human hiPSCs-derived cardiomyocytes (hiPSC-CMs) carrying DMD mutations.
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Affiliation(s)
- Binyamin Eisen
- Cardiac Research Laboratory, Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 3200003, Israel
| | - Ofer Binah
- Cardiac Research Laboratory, Department of Physiology, Biophysics and Systems Biology, Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa 3200003, Israel
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6
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Forkmann M, Busch S. [Should we treat asymptomatic premature ventricular contractions?]. Herzschrittmacherther Elektrophysiol 2023; 34:131-135. [PMID: 36941444 DOI: 10.1007/s00399-023-00934-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Accepted: 02/24/2023] [Indexed: 03/23/2023]
Abstract
Premature ventricular contractions (PVC) are a common arrhythmia. Therapy is indicated in case of frequent symptomatic PVC or deterioration of left ventricular function. Asymptomatic patients should be evaluated critically for possible PVC-associated symptoms. Catheter ablation of PVCs in patients with normal left ventricular ejection fraction (LVEF) is safe and effective. PVC-induced cardiomyopathy should be considered in unexplained LVEF dysfunction with a PVC burden of at least 10%. If ECG and echocardiography do not clearly rule out structural heart disease (SHD) or the clinical presentation raises suspicion of SHD, cardiac magnetic resonance imaging should be performed. If SHD has been excluded, the guidelines recommend catheter ablation as primary therapy in frequent monomorphic PVC, regardless of symptoms. To prevent PVC-induced cardiomyopathy, ablation can also be considered in asymptomatic patients with a PVC burden > 20%. Also, in patients with known SHD frequent PVC can aggravate LV dysfunction and catheter ablation should be considered.
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Affiliation(s)
- Mathias Forkmann
- II. Med. Klinik für Kardiologie und Angiologie, Klinikum Coburg, Ketschendorfer Str. 33, 96450, Coburg, Deutschland.
| | - Sonia Busch
- II. Med. Klinik für Kardiologie und Angiologie, Klinikum Coburg, Ketschendorfer Str. 33, 96450, Coburg, Deutschland
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7
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Muser D, Santangeli P, Liang JJ. Mechanisms of Ventricular Arrhythmias and Implications for Catheter Ablation. Card Electrophysiol Clin 2022; 14:547-558. [PMID: 36396177 DOI: 10.1016/j.ccep.2022.07.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Ventricular arrhythmias present with a wide spectrum of clinical manifestations, from mildly symptomatic frequent premature ventricular contractions to life-threatening events. Pathophysiologically, idiopathic ventricular arrhythmias occur in the absence of structural heart disease or ion channelopathies. Ventricular arrhythmias in the context of structural heart disease are usually determined by scar-related reentry and are associated with increased mortality. Catheter ablation is safe and highly effective in treating ventricular arrhythmias. The proper characterization of the arrhythmogenic substrate is essential for accurate procedural planning. We provide an overview on the main mechanisms of ventricular arrhythmias and their implications for catheter ablation.
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Affiliation(s)
- Daniele Muser
- Cardiothoracic Department, Udine University Hospital, Udine 33100, Italy; Electrophysiology Section, Division of Cardiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA
| | - Pasquale Santangeli
- Electrophysiology Section, Division of Cardiology, Hospital of the University of Pennsylvania, 3400 Spruce Street, Philadelphia, PA 19104, USA
| | - Jackson J Liang
- Electrophysiology Section, Division of Cardiology, University of Michigan, Frankel Cardiovascular Center, 1425 E. Ann Street, Ann Arbor, MI 48109, USA.
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8
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Qu Z, Liu MB, Olcese R, Karagueuzian H, Garfinkel A, Chen PS, Weiss JN. R-on-T and the initiation of reentry revisited: Integrating old and new concepts. Heart Rhythm 2022; 19:1369-1383. [PMID: 35364332 DOI: 10.1016/j.hrthm.2022.03.1224] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 03/11/2022] [Accepted: 03/23/2022] [Indexed: 12/29/2022]
Abstract
Initiation of reentry requires 2 factors: (1) a triggering event, most commonly focal excitations such as premature ventricular complexes (PVCs); and (2) a vulnerable substrate with regional dispersion of refractoriness and/or excitability, such as occurs during the T wave of the electrocardiogram when some areas of the ventricle have repolarized and recovered excitability but others have not. When the R wave of a PVC coincides in time with the T wave of the previous beat, this timing can lead to unidirectional block and initiation of reentry, known as the R-on-T phenomenon. Classically, the PVC triggering reentry has been viewed as arising focally from 1 region and propagating into another region whose recovery is delayed, resulting in unidirectional conduction block and reentry initiation. However, more recent evidence indicates that PVCs also can arise from the T wave itself. In the latter case, the PVC initiating reentry is not a separate event from the T wave but rather is causally generated from the repolarization gradient that manifests as the T wave. We call the former an "R-to-T" mechanism and the latter an "R-from-T" mechanism, which are initiation mechanisms distinct from each other. Both are important components of the R-on-T phenomenon and need to be taken into account when designing antiarrhythmic strategies. Strategies targeting suppression of triggers alone or vulnerable substrate alone may be appropriate in some instances but not in others. Preventing R-from-T arrhythmias requires suppressing the underlying dynamic tissue instabilities responsible for producing both triggers and substrate vulnerability simultaneously. The same principles are likely to apply to supraventricular arrhythmias.
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Affiliation(s)
- Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, California.
| | - Michael B Liu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Riccardo Olcese
- Department of Anesthesiology and Perioperative Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Hrayr Karagueuzian
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Alan Garfinkel
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Integrative Biology and Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Peng-Sheng Chen
- Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, California
| | - James N Weiss
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
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Hong H, Cao X, Deng T, Meng XM, Li YM, Zhu LJ, Lv J, Li X, Yu SG, Zhu BM. Acupuncture at Neiguan suppresses PVCs occurring post-myocardial infarction by alleviating inflammation and fibrosis. Chin Med 2022; 17:52. [PMID: 35484628 PMCID: PMC9047269 DOI: 10.1186/s13020-022-00606-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Accepted: 04/07/2022] [Indexed: 02/08/2023] Open
Abstract
Background Acupuncture at Neiguan (PC6) has long been used for treating cardiovascular diseases, but its antiarrhythmic effect and the underlying mechanisms have not yet been well investigated, especially regarding premature ventricular complexes (PVCs) that occur post-myocardial infarction (MI). The purpose of this study was to study the antiarrhythmic effect of manual acupuncture applied to PC6 for a relatively long period (28 days) and to elucidate the mechanism in mice. Methods An MI mouse model was generated by ligating the left anterior descending coronary artery in male C57/BL6 mice (n = 31). Manual acupuncture at PC6 was applied seven times weekly for 4 weeks. The state of myocardial injury was characterized by electrocardiography (ECG) and echocardiography. Inflammation was detected by ELISA and immunohistochemical stanning. Fibrosis was evaluated by Masson’s trichrome staining. RNA sequencing was used to explore the differentially expressed genes (DEGs) among the different groups after treatment. Results Acupuncture at PC6 lowered the incidence of spontaneous PVCs after MI injury (1/9, 11%) compared to that in mice without acupuncture treatment (6/9, 67%) and improved the ejection fraction from 31.77% in the MI mice to 44.18% in the MI + PC6 mice. Fibrosis was reduced after PC6 treatment. RNA-seq showed many DEGs involved in the immune system and inflammatory response pathway. Further studies confirmed that inflammation at the circulation level and cardiac tissue was inhibited in MI + PC6 mice, accompanied by suppressed sympathetic activation. Conclusions In conclusion, 28-day treatment of acupuncture at PC6 reduced spontaneous PVCs and improved systolic function, possibly by suppressing inflammatory response-mediated fibrosis and sympathetic hyperactivity.
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Affiliation(s)
- Hao Hong
- Regenerative Medicine Research Center, West China Hospital, Sichuan University, Keyuan Road 4, Gaopeng Street, Chengdu, 610041, Sichuan, China
| | - Xin Cao
- Acupuncture and Tuina School/Third Teaching Hospital, Chengdu University of Traditional Chinese Medicine, Shierqiao Road 37, Jinniu District, Chengdu, 610075, Sichuan, China
| | - Tian Deng
- Regenerative Medicine Research Center, West China Hospital, Sichuan University, Keyuan Road 4, Gaopeng Street, Chengdu, 610041, Sichuan, China
| | - Xiang-Min Meng
- Regenerative Medicine Research Center, West China Hospital, Sichuan University, Keyuan Road 4, Gaopeng Street, Chengdu, 610041, Sichuan, China
| | - Yu-Meng Li
- Regenerative Medicine Research Center, West China Hospital, Sichuan University, Keyuan Road 4, Gaopeng Street, Chengdu, 610041, Sichuan, China
| | - Li-Juan Zhu
- Acupuncture and Tuina School/Third Teaching Hospital, Chengdu University of Traditional Chinese Medicine, Shierqiao Road 37, Jinniu District, Chengdu, 610075, Sichuan, China
| | - Jing Lv
- Acupuncture and Tuina School/Third Teaching Hospital, Chengdu University of Traditional Chinese Medicine, Shierqiao Road 37, Jinniu District, Chengdu, 610075, Sichuan, China
| | - Xuan Li
- Acupuncture and Tuina School/Third Teaching Hospital, Chengdu University of Traditional Chinese Medicine, Shierqiao Road 37, Jinniu District, Chengdu, 610075, Sichuan, China
| | - Shu-Guang Yu
- Acupuncture and Tuina School/Third Teaching Hospital, Chengdu University of Traditional Chinese Medicine, Shierqiao Road 37, Jinniu District, Chengdu, 610075, Sichuan, China.
| | - Bing-Mei Zhu
- Regenerative Medicine Research Center, West China Hospital, Sichuan University, Keyuan Road 4, Gaopeng Street, Chengdu, 610041, Sichuan, China.
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Pandey V, Xie LH, Qu Z, Song Z. Mitochondrial Contributions in the Genesis of Delayed Afterdepolarizations in Ventricular Myocytes. Front Physiol 2021; 12:744023. [PMID: 34721066 PMCID: PMC8551757 DOI: 10.3389/fphys.2021.744023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Accepted: 09/02/2021] [Indexed: 11/17/2022] Open
Abstract
Mitochondria fulfill the cell's energy demand and affect the intracellular calcium (Ca2+) dynamics via direct Ca2+ exchange, the redox effect of reactive oxygen species (ROS) on Ca2+ handling proteins, and other signaling pathways. Recent experimental evidence indicates that mitochondrial depolarization promotes arrhythmogenic delayed afterdepolarizations (DADs) in cardiac myocytes. However, the nonlinear interactions among the Ca2+ signaling pathways, ROS, and oxidized Ca2+/calmodulin-dependent protein kinase II (CaMKII) pathways make it difficult to reveal the mechanisms. Here, we use a recently developed spatiotemporal ventricular myocyte computer model, which consists of a 3-dimensional network of Ca2+ release units (CRUs) intertwined with mitochondria and integrates mitochondrial Ca2+ signaling and other complex signaling pathways, to study the mitochondrial regulation of DADs. With a systematic investigation of the synergistic or competing factors that affect the occurrence of Ca2+ waves and DADs during mitochondrial depolarization, we find that the direct redox effect of ROS on ryanodine receptors (RyRs) plays a critical role in promoting Ca2+ waves and DADs under the acute effect of mitochondrial depolarization. Furthermore, the upregulation of mitochondrial Ca2+ uniporter can promote DADs through Ca2+-dependent opening of mitochondrial permeability transition pores (mPTPs). Also, due to much slower dynamics than Ca2+ cycling and ROS, oxidized CaMKII activation and the cytosolic ATP do not appear to significantly impact the genesis of DADs during the acute phase of mitochondrial depolarization. However, under chronic conditions, ATP depletion suppresses and enhanced CaMKII activation promotes Ca2+ waves and DADs.
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Affiliation(s)
- Vikas Pandey
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Lai-Hua Xie
- Department of Cell Biology and Molecular Medicine, Rutgers New Jersey Medical School, Newark, NJ, United States
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Department of Computational Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
| | - Zhen Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA, United States
- Peng Cheng Laboratory, Shenzhen, China
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Sato D, Uchinoumi H, Bers DM. Increasing SERCA function promotes initiation of calcium sparks and breakup of calcium waves. J Physiol 2021; 599:3267-3278. [PMID: 33963531 PMCID: PMC8249358 DOI: 10.1113/jp281579] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 05/04/2021] [Indexed: 01/16/2023] Open
Abstract
KEY POINTS Increasing sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) pump activity enhances sarcoplasmic reticulum calcium (Ca) load, which increases both ryanodine receptor opening and driving force of Ca release flux. Both of these effects promote Ca spark formation and wave propagation. However, increasing SERCA activity also accelerates local cytosolic Ca decay as the wave front travels to the next cluster, which limits wave propagation. As a result, increasing SERCA pump activity has a biphasic effect on the propensity of arrhythmogenic Ca waves, but a monotonic effect to increase Ca spark frequency and amplitude. ABSTRACT Waves of sarcoplasmic reticulum (SR) calcium (Ca) release can cause arrhythmogenic afterdepolarizations in cardiac myocytes. Ca waves propagate when Ca sparks at one Ca release unit (CRU) recruit new Ca sparks in neighbouring CRUs. Under normal conditions, Ca sparks are too small to recruit neighbouring Ca sparks where Ca sensitivity is also low. However, under pathological conditions such as a Ca overload or ryanodine receptor (RyR) sensitization, Ca sparks can be larger and propagate more readily as macro-sparks or full Ca waves. Increasing SERCA pump activity promotes SR Ca load, which promotes RyR opening and increases driving force of the Ca release flux from SR to cytosol, promoting Ca waves. However, high sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) activity can also decrease local cytosolic [Ca] as it approaches the next CRU, thereby reducing wave appearance and propagation. In this study, we use a physiologically detailed model of subcellular Ca cycling and experiments in phospholamban-knockout mice, to show how Ca waves are initiated and propagate and how different conditions contribute to the generation and propagation of Ca waves. We show that reducing diffusive coupling between Ca sparks by increasing SERCA activity prevents Ca waves by reducing [Ca] at the next CRU, as do Ca buffers, low intra-SR Ca diffusion and distance between CRUs. Increasing SR Ca uptake rate has a biphasic effect on Ca wave propagation; initially it enhances Ca spark probability and amplitude and CRU coupling, thereby promoting arrhythmogenic Ca wave propagation, but at higher levels SR Ca uptake can abort those arrhythmogenic Ca waves.
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Affiliation(s)
- Daisuke Sato
- Department of Pharmacology, University of California, Davis School of Medicine, California, USA
| | - Hitoshi Uchinoumi
- Department of Pharmacology, University of California, Davis School of Medicine, California, USA.,Department of Cardiology, Yamaguchi University School of Medicine, Yamaguchi, Japan
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis School of Medicine, California, USA
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12
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Takahashi M, Yokoshiki H, Mitsuyama H, Watanabe M, Temma T, Kamada R, Hagiwara H, Takahashi Y, Anzai T. SK channel blockade prevents hypoxia-induced ventricular arrhythmias through inhibition of Ca 2+/voltage uncoupling in hypertrophied hearts. Am J Physiol Heart Circ Physiol 2021; 320:H1456-H1469. [PMID: 33635168 DOI: 10.1152/ajpheart.00777.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 02/17/2021] [Indexed: 11/22/2022]
Abstract
Ventricular arrhythmia (VA) is the major cause of death in patients with left ventricular (LV) hypertrophy and/or acute ischemia. We hypothesized that apamin, a blocker of small-conductance Ca2+-activated K+ (SK) channels, alters Ca2+ handling and exhibits anti-arrhythmic effects in ventricular myocardium. Spontaneous hypertensive rats were used as a model of LV hypertrophy. A dual optical mapping of membrane potential (Vm) and intracellular calcium (Cai) was performed during global hypoxia (GH) on the Langendorff perfusion system. The majority of pacing-induced VAs during GH were initiated by triggered activities. Pretreatment of apamin (100 nmol/L) significantly inhibited the VA inducibility. Compared with SK channel blockers (apamin and NS8593), non-SK channel blockers (glibenclamide and 4-AP) did not exhibit anti-arrhythmic effects. Apamin prevented not only action potential duration (APD80) shortening (-18.7 [95% confidence interval, -35.2 to -6.05] ms vs. -2.75 [95% CI, -10.45 to 12.65] ms, P = 0.04) but also calcium transient duration (CaTD80) prolongation (14.52 [95% CI, 8.8-20.35] ms vs. 3.85 [95% CI, -3.3 to 12.1] ms, P < 0.01), thereby reducing CaTD80 - APD80, which denotes "Cai/Vm uncoupling" (33.22 [95% CI, 22-48.4] ms vs. 6.6 [95% CI, 0-14.85] ms, P < 0.01). The reduction of Cai/Vm uncoupling was attributable to less prolonged Ca2+ decay constant and suppression of diastolic Cai increase by apamin. The inhibition of VA inducibility and changes in APs/CaTs parameters caused by apamin was negated by the addition of ouabain, an inhibitor of Na+/K+ pump. Apamin attenuates APD shortening, Ca2+ handling abnormalities, and Cai/Vm uncoupling, leading to inhibition of VA occurrence in hypoxic hypertrophied hearts.NEW & NOTEWORTHY We demonstrated that hypoxia-induced ventricular arrhythmias were mainly initiated by Ca2+-loaded triggered activities in hypertrophied hearts. The blockades of small-conductance Ca2+-activated K+ channels, especially "apamin," showed anti-arrhythmic effects by alleviation of not only action potential duration shortening but also Ca2+ handling abnormalities, most notably the "Ca2+/voltage uncoupling."
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Affiliation(s)
- Masayuki Takahashi
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
- Department of Cardiovascular Medicine, National Hospital Organization Hokkaido Medical Center, Sapporo, Japan
| | - Hisashi Yokoshiki
- Department of Cardiovascular Medicine, Sapporo City General Hospital, Sapporo, Japan
| | - Hirofumi Mitsuyama
- Department of Cardiovascular Medicine, Hokkaido Ohno Memorial Hospital, Sapporo, Japan
| | - Masaya Watanabe
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Taro Temma
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Rui Kamada
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Hikaru Hagiwara
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Yumi Takahashi
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
| | - Toshihisa Anzai
- Department of Cardiovascular Medicine, Hokkaido University Graduate School of Medicine, Sapporo, Japan
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13
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Boycott HE, Nguyen MN, Vrellaku B, Gehmlich K, Robinson P. Nitric Oxide and Mechano-Electrical Transduction in Cardiomyocytes. Front Physiol 2020; 11:606740. [PMID: 33384614 PMCID: PMC7770138 DOI: 10.3389/fphys.2020.606740] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 11/23/2020] [Indexed: 12/22/2022] Open
Abstract
The ability§ of the heart to adapt to changes in the mechanical environment is critical for normal cardiac physiology. The role of nitric oxide is increasingly recognized as a mediator of mechanical signaling. Produced in the heart by nitric oxide synthases, nitric oxide affects almost all mechano-transduction pathways within the cardiomyocyte, with roles mediating mechano-sensing, mechano-electric feedback (via modulation of ion channel activity), and calcium handling. As more precise experimental techniques for applying mechanical stresses to cells are developed, the role of these forces in cardiomyocyte function can be further understood. Furthermore, specific inhibitors of different nitric oxide synthase isoforms are now available to elucidate the role of these enzymes in mediating mechano-electrical signaling. Understanding of the links between nitric oxide production and mechano-electrical signaling is incomplete, particularly whether mechanically sensitive ion channels are regulated by nitric oxide, and how this affects the cardiac action potential. This is of particular relevance to conditions such as atrial fibrillation and heart failure, in which nitric oxide production is reduced. Dysfunction of the nitric oxide/mechano-electrical signaling pathways are likely to be a feature of cardiac pathology (e.g., atrial fibrillation, cardiomyopathy, and heart failure) and a better understanding of the importance of nitric oxide signaling and its links to mechanical regulation of heart function may advance our understanding of these conditions.
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Affiliation(s)
- Hannah E. Boycott
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford, United Kingdom
| | - My-Nhan Nguyen
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford, United Kingdom
| | - Besarte Vrellaku
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford, United Kingdom
| | - Katja Gehmlich
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford, United Kingdom
- Institute of Cardiovascular Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Paul Robinson
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
- Division of Cardiovascular Medicine, Radcliffe Department of Medicine and British Heart Foundation Centre of Research Excellence Oxford, University of Oxford, Oxford, United Kingdom
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14
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Du B, Chakraborty P, Azam MA, Massé S, Lai PFH, Niri A, Si D, Thavendiranathan P, Abdel-Qadir H, Billia F, Nanthakumar K. Acute Effects of Ibrutinib on Ventricular Arrhythmia in Spontaneously Hypertensive Rats. JACC: CARDIOONCOLOGY 2020; 2:614-629. [PMID: 34396273 PMCID: PMC8352013 DOI: 10.1016/j.jaccao.2020.08.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 08/26/2020] [Accepted: 08/30/2020] [Indexed: 12/19/2022]
Abstract
Background The Bruton's Tyrosine Kinase Inhibitor ibrutinib is associated with ventricular arrhythmia (VA) and sudden death. However, the pro-arrhythmic electrophysiological dysregulation that results from ibrutinib with age and cardiovascular disease is unknown. Objectives This study sought to investigate the acute effects of ibrutinib on left ventricular (LV) VA vulnerability, cytosolic calcium dynamics, and membrane electrophysiology in old and young spontaneous hypertensive rats (SHRs). Methods Langendorff-perfused hearts of young (10 to 14 weeks) and old (10 to 14 months) SHRs were treated with ibrutinib (0.1 μmol/l) or vehicle for 30 min. Simultaneously, LV epicardial action potential and cytosolic calcium transients were optically mapped following an incremental pacing protocol. Calcium and action potential dynamics parameters were analyzed. VA vulnerability was assessed by electrically inducing ventricular fibrillations (VFs) in each heart. Western blot analysis was performed on LV tissues. Results Ibrutinib treatment resulted in higher vulnerability to VF in old SHR hearts (27.5 ± 7.5% vs. 5.7 ± 3.7%; p = 0.026) but not in young SHR hearts (8.0 ± 4.9% vs. 0%; p = 0.193). In old SHR hearts, following ibrutinib treatment, action potential duration (APD) alternans (p = 0.008) and APD alternans spatial discordance (p = 0.027) were more prominent. Moreover, calcium transient duration 50 was longer (p = 0.032), calcium amplitude alternans ratio was significantly lower (p = 0.001), and time-to-peak of calcium amplitude was shorter (p = 0.037). In young SHR hearts, there were no differences in calcium and APD dynamics. Conclusions Ibrutinib-induced VA is associated with old age in SHR. Acute dysregulation of calcium and repolarization dynamics play important roles in ibrutinib-induced VF.
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Key Words
- AF, atrial fibrillation
- AMPK, adenosine monophosphate-activated protein kinase
- APD, action potential duration
- CA, calcium alternans
- CaMKII, Ca2+/calmodulin-dependent protein kinase II
- CaT, calcium transient
- CaTD, calcium transient duration
- DAD, delayed afterdepolarization
- EAD, early afterpolarization
- LV, left ventricular
- PI3K, phosphoinositide 3-kinase
- PLB, phospholamban
- SCaE, spontaneous calcium elevation
- SHR, spontaneous hypertension rat
- SR, sarcoplasmic reticulum
- VA, ventricular arrhythmia
- VF, ventricular fibrillation
- action potential duration alternans
- calcium handling
- ibrutinib
- spatial discordant repolarization
- ventricular arrythmias
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Affiliation(s)
- Beibei Du
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, Toronto, Ontario, Canada.,Department of Cardiology, The Third Hospital of Jilin University, Jilin Provincial Cardiovascular Research Institute, Changchun, China
| | - Praloy Chakraborty
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, Toronto, Ontario, Canada
| | - Mohammed Ali Azam
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, Toronto, Ontario, Canada
| | - Stéphane Massé
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, Toronto, Ontario, Canada
| | - Patrick F H Lai
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, Toronto, Ontario, Canada
| | - Ahmed Niri
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, Toronto, Ontario, Canada
| | - Daoyuan Si
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, Toronto, Ontario, Canada.,Department of Cardiology, The Third Hospital of Jilin University, Jilin Provincial Cardiovascular Research Institute, Changchun, China
| | - Paaladinesh Thavendiranathan
- Ted Rogers Program in Cardiotoxicity Prevention, Peter Munk Cardiac Center, Toronto General Hospital, University Health Network, University of Toronto, Toronto, Ontario, Canada
| | - Husam Abdel-Qadir
- Ted Rogers Program in Cardiotoxicity Prevention, Peter Munk Cardiac Center, Toronto General Hospital, University Health Network, University of Toronto, Toronto, Ontario, Canada
| | - Filio Billia
- Ted Rogers Program in Cardiotoxicity Prevention, Peter Munk Cardiac Center, Toronto General Hospital, University Health Network, University of Toronto, Toronto, Ontario, Canada
| | - Kumaraswamy Nanthakumar
- The Hull Family Cardiac Fibrillation Management Laboratory, Toronto General Hospital, Toronto, Ontario, Canada
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15
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Multisite phosphorylation of the cardiac ryanodine receptor: a random or coordinated event? Pflugers Arch 2020; 472:1793-1807. [PMID: 33078311 DOI: 10.1007/s00424-020-02473-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/03/2020] [Accepted: 10/02/2020] [Indexed: 10/23/2022]
Abstract
Many proteins are phosphorylated at more than one phosphorylation site to achieve precise tuning of protein function and/or integrate a multitude of signals into the activity of one protein. Increasing the number of phosphorylation sites significantly broadens the complexity of molecular mechanisms involved in processing multiple phosphorylation sites by one or more distinct kinases. The cardiac ryanodine receptor (RYR2) is a well-established multiple phospho-target of kinases activated in response to β-adrenergic stimulation because this Ca2+ channel is a critical component of Ca2+ handling machinery which is responsible for β-adrenergic enhancement of cardiac contractility. Our review presents a selective overview of the extensive, often conflicting, literature which focuses on identifying reliable lines of evidence to establish if multiple RYR2 phosphorylation is achieved randomly or in a specific sequence, and whether phosphorylation at individual sites is functionally specific and additive or similar and can therefore be substituted.
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16
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Bhagwan JR, Mosqueira D, Chairez-Cantu K, Mannhardt I, Bodbin SE, Bakar M, Smith JGW, Denning C. Isogenic models of hypertrophic cardiomyopathy unveil differential phenotypes and mechanism-driven therapeutics. J Mol Cell Cardiol 2020; 145:43-53. [PMID: 32531470 PMCID: PMC7487780 DOI: 10.1016/j.yjmcc.2020.06.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 05/18/2020] [Accepted: 06/05/2020] [Indexed: 12/14/2022]
Abstract
BACKGROUND Hypertrophic cardiomyopathy (HCM) is a prevalent and complex cardiovascular condition. Despite being strongly associated with genetic alterations, wide variation of disease penetrance, expressivity and hallmarks of progression complicate treatment. We aimed to characterize different human isogenic cellular models of HCM bearing patient-relevant mutations to clarify genetic causation and disease mechanisms, hence facilitating the development of effective therapeutics. METHODS We directly compared the p.β-MHC-R453C and p.ACTC1-E99K HCM-associated mutations in human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and their healthy isogenic counterparts, generated using CRISPR/Cas9 genome editing technology. By harnessing several state-of-the-art HCM phenotyping techniques, these mutations were investigated to identify similarities and differences in disease progression and hypertrophic signaling pathways, towards establishing potential targets for pharmacological treatment. CRISPR/Cas9 knock-in of the genetically-encoded calcium indicator R-GECO1.0 to the AAVS1 locus into these disease models resulted in calcium reporter lines. RESULTS Confocal line scan analysis identified calcium transient arrhythmias and intracellular calcium overload in both models. The use of optogenetics and 2D/3D contractility assays revealed opposing phenotypes in the two mutations. Gene expression analysis highlighted upregulation of CALM1, CASQ2 and CAMK2D, and downregulation of IRF8 in p.β-MHC-R453C mutants, whereas the opposite changes were detected in p.ACTC1-E99K mutants. Contrasting profiles of nuclear translocation of NFATc1 and MEF2 between the two HCM models suggest differential hypertrophic signaling pathway activation. Calcium transient abnormalities were rescued with combination of dantrolene and ranolazine, whilst mavacamten reduced the hyper-contractile phenotype of p.ACTC1-E99K hiPSC-CMs. CONCLUSIONS Our data show that hypercontractility and molecular signaling within HCM are not uniform between different gene mutations, suggesting that a 'one-size fits all' treatment underestimates the complexity of the disease. Understanding where the similarities (arrhythmogenesis, bioenergetics) and differences (contractility, molecular profile) lie will allow development of therapeutics that are directed towards common mechanisms or tailored to each disease variant, hence providing effective patient-specific therapy.
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Affiliation(s)
- Jamie R Bhagwan
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK.
| | - Diogo Mosqueira
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK.
| | - Karolina Chairez-Cantu
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK
| | - Ingra Mannhardt
- Department of Experimental Pharmacology and Toxicology, Cardiovascular Research Center, University Medical Center Hamburg-Eppendorf, and DZHK (German Center for Cardiovascular Research), partner site Hamburg/Kiel/Lübeck, Hamburg, Germany
| | - Sara E Bodbin
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK
| | - Mine Bakar
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK
| | - James G W Smith
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK; Faculty of Medicine and Health Sciences, Norwich Medical School, University of East Anglia,NR4 7UQ, UK
| | - Chris Denning
- Division of Cancer & Stem Cells, Biodiscovery Institute, University of Nottingham, NG7 2RD, UK.
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17
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Abstract
Premature ventricular complexes (PVCs) are extremely common, found in the majority of individuals undergoing long-term ambulatory monitoring. Increasing age, a taller height, a higher blood pressure, a history of heart disease, performance of less physical activity, and smoking each predict a greater PVC frequency. Although the fundamental causes of PVCs remain largely unknown, potential mechanisms for any given PVC include triggered activity, automaticity, and reentry. PVCs are commonly asymptomatic but can also result in palpitations, dyspnea, presyncope, and fatigue. The history, physical examination, and 12-lead ECG are each critical to the diagnosis and evaluation of a PVC. An echocardiogram is indicated in the presence of symptoms or particularly frequent PVCs, and cardiac magnetic resonance imaging is helpful when the evaluation suggests the presence of associated structural heart disease. Ambulatory monitoring is required to assess PVC frequency. The prognosis of those with PVCs is variable, with ongoing uncertainty regarding the most informative predictors of adverse outcomes. An increased PVC frequency may be a risk factor for heart failure and death, and the resolution of systolic dysfunction after successful catheter ablation of PVCs demonstrates that a causal relationship can be present. Patients with no or mild symptoms, a low PVC burden, and normal ventricular function may be best served with simple reassurance. Either medical treatment or catheter ablation are considered first-line therapies in most patients with PVCs associated with symptoms or a reduced left ventricular ejection fraction, and patient preference plays a role in determining which to try first. If medical treatment is selected, either β-blockers or nondihydropyridine calcium channel blockers are reasonable drugs in patients with normal ventricular systolic function. Other antiarrhythmic drugs should be considered if those initial drugs fail and ablation has been declined, has been unsuccessful, or has been deemed inappropriate. Catheter ablation is the most efficacious approach to eradicate PVCs but may confer increased upfront risks. Original research remains necessary to identify individuals at risk for PVC-induced cardiomyopathy and to identify preventative and therapeutic approaches targeting the root causes of PVCs to maximize effectiveness while minimizing risk.
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Affiliation(s)
- Gregory M. Marcus
- Electrophysiology Section, Division of Cardiology, University of California, San Francisco
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18
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Exploring Impaired SERCA Pump-Caused Alternation Occurrence in Ischemia. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2019; 2019:8237071. [PMID: 31827590 PMCID: PMC6885202 DOI: 10.1155/2019/8237071] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 10/08/2019] [Indexed: 12/24/2022]
Abstract
Impaired sarcoplasmic reticulum (SR) calcium transport ATPase (SERCA) gives rise to Ca2+ alternans and changes of the Ca2+release amount. These changes in Ca2+ release amount can reveal the mechanism underlying how the interaction between Ca2+ release and Ca2+ uptake induces Ca2+ alternans. This study of alternans by calculating the values of Ca2+ release properties with impaired SERCA has not been explored before. Here, we induced Ca2+ alternans by using an impaired SERCA pump under ischemic conditions. The results showed that the recruitment and refractoriness of the Ca2+ release increased as Ca2+ alternans occurred. This indicates triggering Ca waves. As the propagation of Ca waves is linked to the occurrence of Ca2+ alternans, the “threshold” for Ca waves reflects the key factor in Ca2+ alternans development, and it is still controversial nowadays. We proposed the ratio between the diastolic network SR (NSR) Ca content (Cansr) and the cytoplasmic Ca content (Cai) (Cansr/Cai) as the “threshold” of Ca waves and Ca2+ alternans. Diastolic Cansr, Cai, and their ratio were recorded at the onset of Ca2+ alternans. Compared with certain Cansr and Cai, the “threshold” of the ratio can better explain the comprehensive effects of the Ca2+ release and the Ca2+ uptake on Ca2+ alternans onset. In addition, these ratios are related with the function of SERCA pumps, which vary with different ischemic conditions. Thus, values of these ratios could be used to differentiate Ca2+ alternans from different ischemic cases. This agrees with some experimental results. Therefore, the certain value of diastolic Cansr/Cai can be the better “threshold” for Ca waves and Ca2+ alternans.
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19
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van Opbergen CJM, den Braven L, Delmar M, van Veen TAB. Mitochondrial Dysfunction as Substrate for Arrhythmogenic Cardiomyopathy: A Search for New Disease Mechanisms. Front Physiol 2019; 10:1496. [PMID: 31920701 PMCID: PMC6914828 DOI: 10.3389/fphys.2019.01496] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Accepted: 11/25/2019] [Indexed: 12/12/2022] Open
Abstract
Arrhythmogenic cardiomyopathy (ACM) is a familial heart disease, associated with ventricular arrhythmias, fibrofatty replacement of the myocardial mass and an increased risk of sudden cardiac death (SCD). Malignant ventricular arrhythmias and SCD largely occur in the pre-clinical phase of the disease, before overt structural changes occur. To prevent or interfere with ACM disease progression, more insight in mechanisms related to electrical instability are needed. Currently, numerous studies are focused on the link between cardiac arrhythmias and metabolic disease. In line with that, a potential role of mitochondrial dysfunction in ACM pathology is unclear and mitochondrial biology in the ACM heart remains understudied. In this review, we explore mitochondrial dysfunction in relation to arrhythmogenesis, and postulate a link to typical hallmarks of ACM. Mitochondrial dysfunction depletes adenosine triphosphate (ATP) production and increases levels of reactive oxygen species in the heart. Both metabolic changes affect cardiac ion channel gating, electrical conduction, intracellular calcium handling, and fibrosis formation; all well-known aspects of ACM pathophysiology. ATP-mediated structural remodeling, apoptosis, and mitochondria-related alterations have already been shown in models of PKP2 dysfunction. Yet, the limited amount of experimental evidence in ACM models makes it difficult to determine whether mitochondrial dysfunction indeed precedes and/or accompanies ACM pathogenesis. Nevertheless, current experimental ACM models can be very useful in unraveling ACM-related mitochondrial biology and in testing potential therapeutic interventions.
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Affiliation(s)
- Chantal J M van Opbergen
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Lyanne den Braven
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, Netherlands
| | - Mario Delmar
- Division of Cardiology, NYU School of Medicine, New York, NY, United States
| | - Toon A B van Veen
- Department of Medical Physiology, Division of Heart & Lungs, University Medical Center Utrecht, Utrecht, Netherlands
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20
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Kim SS, Kim HK, Park HW, Jeong MH, Lim KS, Kee HJ, Ryu YH, Kim HB, Na JY, Ki YJ, Park KH, Choi DH, Lee KH, Yoon NS, Cho JG. Effect of Renal Denervation on Suppression of PVC and QT Prolongation in a Porcine Model of Acute Myocardial Infarction. Korean Circ J 2019; 50:38-49. [PMID: 31642212 PMCID: PMC6923235 DOI: 10.4070/kcj.2019.0106] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Revised: 07/12/2019] [Accepted: 08/14/2019] [Indexed: 12/16/2022] Open
Abstract
Background and Objectives Antiarrhythmic effect of renal denervation (RDN) after acute myocardial infarction (AMI) remains unclear. The goal of this study was to evaluate the effect of RDN on ventricular arrhythmia (VA) after AMI in a porcine model. Methods Twenty pigs were randomly divided into 2 groups based on RDN (RDN, n=10; Sham, n=10). After implanting a loop recorder, AMI was induced by occlusion of the middle left anterior descending coronary artery. Catheter-based RDN was performed for each renal artery immediately after creating AMI. Sham procedure used the same method, but a radiofrequency current was not delivered. Electrocardiography was monitored for 1 hour to observe VA. One week later, the animals were euthanized and the loop recorder data were analyzed. Results Ventricular fibrillation event rate and the interval from AMI creation to first VA in acute phase were not different between the 2 groups. However, the incidence of premature ventricular complex (PVC) was lower in the RDN than in the Sham. Additionally, RDN inhibited prolongation of the corrected QT (QTc) interval after AMI. The frequency of non-sustained or sustained ventricular tachycardia, arrhythmic death was lower in the RDN group in the early period. Conclusions RDN reduced the incidence of PVC, inhibited prolongation of the QTc interval, and reduced VA in the early period following an AMI. These results suggest that RDN might be a therapeutic option in patients with electrical instability after AMI.
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Affiliation(s)
- Sung Soo Kim
- Department of Cardiology, Chosun University Hospital, Gwangju, Korea
| | - Hyun Kuk Kim
- Department of Cardiology, Chosun University Hospital, Gwangju, Korea
| | - Hyung Wook Park
- Department of Cardiovascular Medicine, Chonnam National University Medical School, Gwangju, Korea.
| | - Myung Ho Jeong
- Department of Cardiovascular Medicine, Chonnam National University Medical School, Gwangju, Korea.
| | - Kyung Seob Lim
- Futuristic Animal Resource and Research Center, Korea Research Institute of Bioscience and Biotechnology, Ochang, Korea
| | - Hae Jin Kee
- Biomedical Research Institute, Chonnam National University Hospital, Gwangju, Korea
| | - Yu Hee Ryu
- Biomedical Research Institute, Chonnam National University Hospital, Gwangju, Korea
| | - Han Byul Kim
- Biomedical Research Institute, Chonnam National University Hospital, Gwangju, Korea
| | - Joo Young Na
- Biomedical Research Institute, Chonnam National University Hospital, Gwangju, Korea
| | - Young Jae Ki
- Department of Cardiology, Chosun University Hospital, Gwangju, Korea
| | - Keun Ho Park
- Department of Cardiology, Chosun University Hospital, Gwangju, Korea
| | - Dong Hyun Choi
- Department of Cardiology, Chosun University Hospital, Gwangju, Korea
| | - Ki Hong Lee
- Department of Cardiovascular Medicine, Chonnam National University Medical School, Gwangju, Korea
| | - Nam Sik Yoon
- Department of Cardiovascular Medicine, Chonnam National University Medical School, Gwangju, Korea
| | - Jeong Gwan Cho
- Department of Cardiovascular Medicine, Chonnam National University Medical School, Gwangju, Korea
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21
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Han D, Xue X, Yan Y, Li G. Dysfunctional Cav1.2 channel in Timothy syndrome, from cell to bedside. Exp Biol Med (Maywood) 2019; 244:960-971. [PMID: 31324123 DOI: 10.1177/1535370219863149] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Timothy syndrome is a rare disorder caused by CACNA1C gene mutations and characterized by multi-organ system dysfunctions, including ventricular arrhythmias, syndactyly, dysmorphic facial features, intermittent hypoglycemia, immunodeficiency, developmental delay, and autism. Because of the low morbidity and high mortality at a young age, it remains a huge challenge to establish a diagnosis and treatment system to manage Timothy syndrome patients. Here, we aim to provide a detailed review of Timothy syndrome, discuss the mechanisms underlying dysfunctional Cav1.2 due to CACNA1C mutations, and provide some new emerging evidences in treating Timothy syndrome from cell to bedside, promoting the management of this rare disease. Impact statement The knowledge of Timothy syndrome (TS) caused by dysfunctional Cav1.2 channel due to CACNA1C mutations is rapidly evolving as novel technologies of electrophysiology are introduced and our understanding of the mechanisms of TS develops. In this review, we focus on the TS-related dysfunctional Cav1.2 and the underlying mechanisms. We update TS-related CACNA1C mutations in a precise way over the past 20 years and summarize all reported TS patients based on their clinical presentations and molecular mechanisms, respectively. We hope this review will provide a new comprehensive way to better understand the electrophysiological mechanisms underlying TS from cell to bedside, promoting the management of TS in practice.
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Affiliation(s)
- Dan Han
- 1 Department of Cardiology, the First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P. R. China.,2 Department of Cardiovascular Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P.R. China*These authors contributed equally to this work and should be considered to share first authorship
| | - Xiaolin Xue
- 1 Department of Cardiology, the First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P. R. China
| | - Yang Yan
- 2 Department of Cardiovascular Surgery, First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P.R. China*These authors contributed equally to this work and should be considered to share first authorship
| | - Guoliang Li
- 1 Department of Cardiology, the First Affiliated Hospital of Xi'an Jiaotong University, Shaanxi 710061, P. R. China
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22
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Bazmi M, Escobar AL. How Ca 2+ influx is attenuated in the heart during a "fight or flight" response. J Gen Physiol 2019; 151:722-726. [PMID: 31004065 PMCID: PMC6572000 DOI: 10.1085/jgp.201912338] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Bazmi and Escobar highlight a recent investigation of the mechanisms that regulate Ca2+ influx during sympathetic stimulation.
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Affiliation(s)
- Maedeh Bazmi
- Quantitative Systems Biology Program, School of Natural Sciences, University of California, Merced, Merced, CA
| | - Ariel L Escobar
- Department of Bioengineering, School of Engineering, University of California, Merced, Merced, CA
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23
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Dharmawan T, Nakajima T, Ohno S, Iizuka T, Tamura S, Kaneko Y, Horie M, Kurabayashi M. Identification of a novel exon3 deletion of RYR2 in a family with catecholaminergic polymorphic ventricular tachycardia. Ann Noninvasive Electrocardiol 2019; 24:e12623. [PMID: 30615235 PMCID: PMC6850420 DOI: 10.1111/anec.12623] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 11/01/2018] [Accepted: 11/13/2018] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND RYR2, encoding cardiac ryanodine receptor, is the major responsible gene for catecholaminergic polymorphic ventricular tachycardia (CPVT). Meanwhile, KCNJ2, encoding inward-rectifier potassium channel (IK1 ), can be the responsible gene for atypical CPVT. We recently encountered a family with CPVT and sought to identify a responsible gene variant. METHODS A targeted panel sequencing (TPS) was employed in the proband. Copy number variation (CNV) in RYR2 was identified by focusing on read numbers in the TPS and long-range PCR. Cascade screening was conducted by a Sanger method and long-range PCR. KCNJ2 wild-type (WT) or an identified variant was expressed in COS-1 cells, and whole-cell currents (IK1 ) were recorded using patch-clamp techniques. RESULTS A 40-year-old female experienced cardiopulmonary arrest while cycling. Her ECG showed sinus bradycardia with prominent U-waves (≥0.2 mV). She had left ventricular hypertrabeculation at apex. Exercise induced frequent polymorphic ventricular arrhythmias. Her sister died suddenly at age 35 while bouldering. Her father and paternal aunt, with prominent U-waves, received permanent pacemaker due to sinus node dysfunction. The initial TPS and cascade screening identified a KCNJ2 E118D variant in all three symptomatic patients. However, after focusing on read numbers, we identified a novel exon3 deletion of RYR2 (RYR2-exon3 deletion) in all of them. Functional analysis revealed that KCNJ2 E118D generated IK1 indistinguishable from KCNJ2 WT, even in the presence of catecholaminergic stimulation. CONCLUSIONS Focusing on the read numbers in the TPS enabled us to identify a novel CNV, RYR2-exon3 deletion, which was associated with phenotypic features of this family.
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Affiliation(s)
- Tommy Dharmawan
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Tadashi Nakajima
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Seiko Ohno
- Department of Bioscience and Genetics, National Cerebral and Cardiovascular Center, Suita, Japan.,Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan
| | - Takashi Iizuka
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Shuntaro Tamura
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Yoshiaki Kaneko
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Minoru Horie
- Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science, Otsu, Japan.,Center for Epidemiologic Research in Asia, Shiga University of Medical Science, Otsu, Japan
| | - Masahiko Kurabayashi
- Department of Cardiovascular Medicine, Gunma University Graduate School of Medicine, Maebashi, Japan
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24
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Han D, Tan H, Sun C, Li G. Dysfunctional Nav1.5 channels due to SCN5A mutations. Exp Biol Med (Maywood) 2018; 243:852-863. [PMID: 29806494 DOI: 10.1177/1535370218777972] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The voltage-gated sodium channel 1.5 (Nav1.5), encoded by the SCN5A gene, is responsible for the rising phase of the action potential of cardiomyocytes. The sodium current mediated by Nav1.5 consists of peak and late components (INa-P and INa-L). Mutant Nav1.5 causes alterations in the peak and late sodium current and is associated with an increasingly wide range of congenital arrhythmias. More than 400 mutations have been identified in the SCN5A gene. Although the mechanisms of SCN5A mutations leading to a variety of arrhythmias can be classified according to the alteration of INa-P and INa-L as gain-of-function, loss-of-function and both, few researchers have summarized the mechanisms in this way before. In this review article, we aim to review the mechanisms underlying dysfunctional Nav1.5 due to SCN5A mutations and to provide some new insights into further approaches in the treatment of arrhythmias. Impact statement The field of ion channelopathy caused by dysfunctional Nav1.5 due to SCN5A mutations is rapidly evolving as novel technologies of electrophysiology are introduced and our understanding of the mechanisms of various arrhythmias develops. In this review, we focus on the dysfunctional Nav1.5 related to arrhythmias and the underlying mechanisms. We update SCN5A mutations in a precise way since 2013 and presents novel classifications of SCN5A mutations responsible for the dysfunction of the peak (INa-P) and late (INa-L) sodium channels based on their phenotypes, including loss-, gain-, and coexistence of gain- and loss-of function mutations in INa-P, INa-L, respectively. We hope this review will provide a new comprehensive way to better understand the electrophysiological mechanisms underlying arrhythmias from cell to bedside, promoting the management of various arrhythmias in practice.
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Affiliation(s)
- Dan Han
- 1 Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, P.R. China
| | - Hui Tan
- 2 Department of Respiratory Medicine, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, P.R. China
| | - Chaofeng Sun
- 1 Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, P.R. China
| | - Guoliang Li
- 1 Department of Cardiovascular Medicine, First Affiliated Hospital of Xi'an Jiaotong University, Xi'an 710061, P.R. China
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25
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Koleske M, Bonilla I, Thomas J, Zaman N, Baine S, Knollmann BC, Veeraraghavan R, Györke S, Radwański PB. Tetrodotoxin-sensitive Na vs contribute to early and delayed afterdepolarizations in long QT arrhythmia models. J Gen Physiol 2018; 150:991-1002. [PMID: 29793933 PMCID: PMC6028491 DOI: 10.1085/jgp.201711909] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2017] [Revised: 03/30/2018] [Accepted: 04/30/2018] [Indexed: 01/08/2023] Open
Abstract
Neuronal Na+ channels contribute to catecholaminergic polymorphic ventricular tachycardia in the heart, but their role in other types of arrhythmias is unknown. Koleske et al. show that they contribute to early and delayed afterdepolarizations common to long QT, catecholaminergic polymorphic ventricular tachycardia, and overlap phenotypes. Recent evidence suggests that neuronal Na+ channels (nNavs) contribute to catecholamine-promoted delayed afterdepolarizations (DADs) and catecholaminergic polymorphic ventricular tachycardia (CPVT). The newly identified overlap between CPVT and long QT (LQT) phenotypes has stoked interest in the cross-talk between aberrant Na+ and Ca2+ handling and its contribution to early afterdepolarizations (EADs) and DADs. Here, we used Ca2+ imaging and electrophysiology to investigate the role of Na+ and Ca2+ handling in DADs and EADs in wild-type and cardiac calsequestrin (CASQ2)-null mice. In experiments, repolarization was impaired using 4-aminopyridine (4AP), whereas the L-type Ca2+ and late Na+ currents were augmented using Bay K 8644 (BayK) and anemone toxin II (ATX-II), respectively. The combination of 4AP and isoproterenol prolonged action potential duration (APD) and promoted aberrant Ca2+ release, EADs, and DADs in wild-type cardiomyocytes. Similarly, BayK in the absence of isoproterenol induced the same effects in CASQ2-null cardiomyocytes. In vivo, it prolonged the QT interval and, upon catecholamine challenge, precipitated wide QRS polymorphic ventricular tachycardia that resembled human torsades de pointes. Treatment with ATX-II produced similar effects at both the cellular level and in vivo. Importantly, nNav inhibition with riluzole or 4,9-anhydro-tetrodotoxin reduced the incidence of ATX-II–, BayK-, or 4AP-induced EADs, DADs, aberrant Ca2+ release, and VT despite only modestly mitigating APD prolongation. These data reveal the contribution of nNaVs to triggered arrhythmias in murine models of LQT and CPVT-LQT overlap phenotypes. We also demonstrate the antiarrhythmic impact of nNaV inhibition, independent of action potential and QT interval duration, and provide a basis for a mechanistically driven antiarrhythmic strategy.
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Affiliation(s)
- Megan Koleske
- Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Ingrid Bonilla
- Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH
| | - Justin Thomas
- Division of Pharmacy Practice and Sciences, College of Pharmacy, The Ohio State University, Columbus, OH
| | - Naveed Zaman
- Division of Pharmacology, College of Pharmacy, The Ohio State University, Columbus, OH
| | - Stephen Baine
- Division of Pharmacology, College of Pharmacy, The Ohio State University, Columbus, OH
| | - Bjorn C Knollmann
- Division of Clinical Pharmacology, Vanderbilt University Medical School, Nashville, TN
| | - Rengasayee Veeraraghavan
- Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH.,Department of Biomedical Engineering, College of Engineering, The Ohio State University, Columbus, OH
| | - Sándor Györke
- Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH.,Department of Physiology and Cell Biology, College of Medicine, The Ohio State University, Columbus, OH
| | - Przemysław B Radwański
- Dorothy M. Davis Heart and Lung Research Institute, College of Medicine, The Ohio State University Wexner Medical Center, Columbus, OH .,Division of Pharmacy Practice and Sciences, College of Pharmacy, The Ohio State University, Columbus, OH.,Division of Pharmacology, College of Pharmacy, The Ohio State University, Columbus, OH
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26
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Cao ZZ, Tian YJ, Hao J, Zhang PH, Liu ZP, Jiang WZ, Zeng ML, Zhang PP, Ma JH. Barbaloin inhibits ventricular arrhythmias in rabbits by modulating voltage-gated ion channels. Acta Pharmacol Sin 2018; 39:357-370. [PMID: 29072259 DOI: 10.1038/aps.2017.93] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 06/17/2017] [Indexed: 12/15/2022] Open
Abstract
Barbaloin (10-β-D-glucopyranosyl-1,8-dihydroxy-3-(hydroxymethyl)-9(10H)-anthracenone) is extracted from the aloe plant and has been reported to have anti-inflammatory, antitumor, antibacterial, and other biological activities. Here, we investigated the effects of barbaloin on cardiac electrophysiology, which has not been reported thus far. Cardiac action potentials (APs) and ionic currents were recorded in isolated rabbit ventricular myocytes using whole-cell patch-clamp technique. Additionally, the antiarrhythmic effect of barbaloin was examined in Langendorff-perfused rabbit hearts. In current-clamp recording, application of barbaloin (100 and 200 μmol/L) dose-dependently reduced the action potential duration (APD) and the maximum depolarization velocity (Vmax), and attenuated APD reverse-rate dependence (RRD) in ventricular myocytes. Furthermore, barbaloin (100 and 200 μmol/L) effectively eliminated ATX II-induced early afterdepolarizations (EADs) and Ca2+-induced delayed afterdepolarizations (DADs) in ventricular myocytes. In voltage-clamp recording, barbaloin (10-200 μmol/L) dose-dependently inhibited L-type calcium current (ICa.L) and peak sodium current (INa.P) with IC50 values of 137.06 and 559.80 μmol/L, respectively. Application of barbaloin (100, 200 μmol/L) decreased ATX II-enhanced late sodium current (INa.L) by 36.6%±3.3% and 71.8%±6.5%, respectively. However, barbaloin up to 800 μmol/L did not affect the inward rectifier potassium current (IK1) or the rapidly activated delayed rectifier potassium current (IKr) in ventricular myocytes. In Langendorff-perfused rabbit hearts, barbaloin (200 μmol/L) significantly inhibited aconitine-induced ventricular arrhythmias. These results demonstrate that barbaloin has potential as an antiarrhythmic drug.
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27
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Walker MA, Gurev V, Rice JJ, Greenstein JL, Winslow RL. Estimating the probabilities of rare arrhythmic events in multiscale computational models of cardiac cells and tissue. PLoS Comput Biol 2017; 13:e1005783. [PMID: 29145393 PMCID: PMC5689829 DOI: 10.1371/journal.pcbi.1005783] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 09/18/2017] [Indexed: 11/24/2022] Open
Abstract
Ectopic heartbeats can trigger reentrant arrhythmias, leading to ventricular fibrillation and sudden cardiac death. Such events have been attributed to perturbed Ca2+ handling in cardiac myocytes leading to spontaneous Ca2+ release and delayed afterdepolarizations (DADs). However, the ways in which perturbation of specific molecular mechanisms alters the probability of ectopic beats is not understood. We present a multiscale model of cardiac tissue incorporating a biophysically detailed three-dimensional model of the ventricular myocyte. This model reproduces realistic Ca2+ waves and DADs driven by stochastic Ca2+ release channel (RyR) gating and is used to study mechanisms of DAD variability. In agreement with previous experimental and modeling studies, key factors influencing the distribution of DAD amplitude and timing include cytosolic and sarcoplasmic reticulum Ca2+ concentrations, inwardly rectifying potassium current (IK1) density, and gap junction conductance. The cardiac tissue model is used to investigate how random RyR gating gives rise to probabilistic triggered activity in a one-dimensional myocyte tissue model. A novel spatial-average filtering method for estimating the probability of extreme (i.e. rare, high-amplitude) stochastic events from a limited set of spontaneous Ca2+ release profiles is presented. These events occur when randomly organized clusters of cells exhibit synchronized, high amplitude Ca2+ release flux. It is shown how reduced IK1 density and gap junction coupling, as observed in heart failure, increase the probability of extreme DADs by multiple orders of magnitude. This method enables prediction of arrhythmia likelihood and its modulation by alterations of other cellular mechanisms.
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Affiliation(s)
- Mark A. Walker
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, United States of America
| | - Viatcheslav Gurev
- TJ Watson Research Center, IBM, Yorktown Heights, NY, United States of America
| | - John J. Rice
- TJ Watson Research Center, IBM, Yorktown Heights, NY, United States of America
| | - Joseph L. Greenstein
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, United States of America
| | - Raimond L. Winslow
- Department of Biomedical Engineering and Institute for Computational Medicine, Johns Hopkins University, Baltimore, MD, United States of America
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28
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Enriquez A, Frankel DS, Baranchuk A. Pathophysiology of ventricular tachyarrhythmias : From automaticity to reentry. Herzschrittmacherther Elektrophysiol 2017; 28:149-156. [PMID: 28567491 DOI: 10.1007/s00399-017-0512-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2017] [Accepted: 05/15/2017] [Indexed: 02/01/2023]
Abstract
Ventricular arrhythmias are a heterogeneous group of arrhythmias and may arise in patients with cardiomyopathy or structurally normal hearts. The electrophysiologic mechanisms responsible for the initiation and maintenance of ventricular tachycardia include enhanced automaticity, triggered activity, and reentry. Differentiating between these three mechanisms can be challenging and usually requires an invasive electrophysiology study. Establishing the underlying mechanism in a particular patient is helpful to define the optimal therapeutic approach, including the selection of pharmacologic agents or delineation of an ablation strategy.
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Affiliation(s)
- Andres Enriquez
- Section of Cardiac Electrophysiology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
| | - David S Frankel
- Section of Cardiac Electrophysiology, Hospital of the University of Pennsylvania, Philadelphia, PA, USA
| | - Adrian Baranchuk
- Heart Rhythm Service, Kingston General Hospital, Queen's University, Kingston, ON, Canada.
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29
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Bai J, Yin R, Wang K, Zhang H. Mechanisms Underlying the Emergence of Post-acidosis Arrhythmia at the Tissue Level: A Theoretical Study. Front Physiol 2017; 8:195. [PMID: 28424631 PMCID: PMC5371659 DOI: 10.3389/fphys.2017.00195] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Accepted: 03/15/2017] [Indexed: 11/17/2022] Open
Abstract
Acidosis has complex electrophysiological effects, which are associated with a high recurrence of ventricular arrhythmias. Through multi-scale cardiac computer modeling, this study investigated the mechanisms underlying the emergence of post-acidosis arrhythmia at the tissue level. In simulations, ten Tusscher-Panfilov ventricular model was modified to incorporate various data on acidosis-induced alterations of cellular electrophysiology and intercellular electrical coupling. The single cell models were incorporated into multicellular one-dimensional (1D) fiber and 2D sheet tissue models. Electrophysiological effects were quantified as changes of action potential profile, sink-source interactions of fiber tissue, and the vulnerability of tissue to the genesis of unidirectional conduction that led to initiation of re-entry. It was shown that acidosis-induced sarcoplasmic reticulum (SR) calcium load contributed to delayed afterdepolarizations (DADs) in single cells. These DADs may be synchronized to overcome the source-sink mismatch arising from intercellular electrotonic coupling, and produce a premature ventricular complex (PVC) at the tissue level. The PVC conduction can be unidirectionally blocked in the transmural ventricular wall with altered electrical heterogeneity, resulting in the genesis of re-entry. In conclusion, altered source-sink interactions and electrical heterogeneity due to acidosis-induced cellular electrophysiological alterations may increase susceptibility to post-acidosis ventricular arrhythmias.
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Affiliation(s)
- Jieyun Bai
- School of Computer Science and Technology, Harbin Institute of TechnologyHarbin, China
| | - Renli Yin
- State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of TechnologyHarbin, China
| | - Kuanquan Wang
- School of Computer Science and Technology, Harbin Institute of TechnologyHarbin, China
| | - Henggui Zhang
- School of Computer Science and Technology, Harbin Institute of TechnologyHarbin, China.,Biological Physics Group, School of Physics and Astronomy, University of ManchesterManchester, UK.,Space Institute of Southern ChinaShenzhen, China
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30
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Chen-Izu Y, Izu LT. Mechano-chemo-transduction in cardiac myocytes. J Physiol 2017; 595:3949-3958. [PMID: 28098356 DOI: 10.1113/jp273101] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Accepted: 12/15/2016] [Indexed: 12/31/2022] Open
Abstract
The heart has the ability to adjust to changing mechanical loads. The Frank-Starling law and the Anrep effect describe exquisite intrinsic mechanisms the heart has for autoregulating the force of contraction to maintain cardiac output under changes of preload and afterload. Although these mechanisms have been known for more than a century, their cellular and molecular underpinnings are still debated. How does the cardiac myocyte sense changes in preload or afterload? How does the myocyte adjust its response to compensate for such changes? In cardiac myocytes Ca2+ is a crucial regulator of contractile force and in this review we compare and contrast recent studies from different labs that address these two important questions. The 'dimensionality' of the mechanical milieu under which experiments are carried out provide important clues to the location of the mechanosensors and the kinds of mechanical forces they can sense and respond to. As a first approximation, sensors inside the myocyte appear to modulate reactive oxygen species while sensors on the cell surface appear to also modulate nitric oxide signalling; both signalling pathways affect Ca2+ handling. Undoubtedly, further studies will add layers to this simplified picture. Clarifying the intimate links from cellular mechanics to reactive oxygen species and nitric oxide signalling and to Ca2+ handling will deepen our understanding of the Frank-Starling law and the Anrep effect, and also provide a unified view on how arrhythmias may arise in seemingly disparate diseases that have in common altered myocyte mechanics.
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Affiliation(s)
- Ye Chen-Izu
- Department of Pharmacology, University of California, Davis, CA, 95616, USA.,Department of Biomedical Engineering, University of California, Davis, CA, 95616, USA.,Department of Internal Medicine/Division of Cardiology, University of California, Davis, CA, 95616, USA
| | - Leighton T Izu
- Department of Pharmacology, University of California, Davis, CA, 95616, USA
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31
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Liu MB, Ko CY, Song Z, Garfinkel A, Weiss JN, Qu Z. A Dynamical Threshold for Cardiac Delayed Afterdepolarization-Mediated Triggered Activity. Biophys J 2016; 111:2523-2533. [PMID: 27926853 PMCID: PMC5153551 DOI: 10.1016/j.bpj.2016.10.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2016] [Revised: 09/22/2016] [Accepted: 10/11/2016] [Indexed: 11/18/2022] Open
Abstract
Ventricular myocytes are excitable cells whose voltage threshold for action potential (AP) excitation is ∼-60 mV at which INa is activated to give rise to a fast upstroke. Therefore, for a short stimulus pulse to elicit an AP, a stronger stimulus is needed if the resting potential lies further away from the INa threshold, such as in hypokalemia. However, for an AP elicited by a long duration stimulus or a diastolic spontaneous calcium release, we observed that the stimulus needed was lower in hypokalemia than in normokalemia in both computer simulations and experiments of rabbit ventricular myocytes. This observation provides insight into why hypokalemia promotes calcium-mediated triggered activity, despite the resting potential lying further away from the INa threshold. To understand the underlying mechanisms, we performed bifurcation analyses and demonstrated that there is a dynamical threshold, resulting from a saddle-node bifurcation mainly determined by IK1 and INCX. This threshold is close to the voltage at which IK1 is maximum, and lower than the INa threshold. After exceeding this dynamical threshold, the membrane voltage will automatically depolarize above the INa threshold due to the large negative slope of the IK1-V curve. This dynamical threshold becomes much lower in hypokalemia, especially with respect to calcium, as predicted by our theory. Because of the saddle-node bifurcation, the system can automatically depolarize even in the absence of INa to voltages higher than the ICa,L threshold, allowing for triggered APs in single myocytes with complete INa block. However, because INa is important for AP propagation in tissue, blocking INa can still suppress premature ventricular excitations in cardiac tissue caused by calcium-mediated triggered activity. This suppression is more effective in normokalemia than in hypokalemia due to the difference in dynamical thresholds.
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Affiliation(s)
- Michael B Liu
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Christopher Y Ko
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Zhen Song
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California
| | - Alan Garfinkel
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Integrative Biology and Physiology, University of California, Los Angeles, Los Angeles, California
| | - James N Weiss
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Physiology, University of California, Los Angeles, Los Angeles, California
| | - Zhilin Qu
- Cardiovascular Research Laboratory, University of California, Los Angeles, Los Angeles, California; Department of Medicine, University of California, Los Angeles, Los Angeles, California; Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California.
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32
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Liang F, Fan P, Jia J, Yang S, Jiang Z, Karpinski S, Kornyeyev D, Pagratis N, Belardinelli L, Yao L. Inhibitions of late INa and CaMKII act synergistically to prevent ATX-II-induced atrial fibrillation in isolated rat right atria. J Mol Cell Cardiol 2016; 94:122-130. [PMID: 27066997 DOI: 10.1016/j.yjmcc.2016.04.001] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Revised: 03/23/2016] [Accepted: 04/06/2016] [Indexed: 12/19/2022]
Abstract
AIMS Increases in late Na(+) current (late INa) and activation of Ca(2+)/calmodulin-dependent protein kinase (CaMKII) are associated with atrial arrhythmias. CaMKII also phosphorylates Nav1.5, further increasing late INa. The combination of a CaMKII inhibitor with a late INa inhibitor may be superior to each compound alone to suppress atrial arrhythmias. Therefore, we investigated the effect of a CaMKII inhibitor in combination with a late INa inhibitor on anemone toxin II (ATX-II, a late INa enhancer)-induced atrial arrhythmias. METHODS AND RESULTS Rat right atrial tissue was isolated and preincubated with either the CaMKII inhibitor autocamtide-2-related inhibitory peptide (AIP), the late INa inhibitor GS458967, or both, and then exposed to ATX-II. ATX-II increased diastolic tension and caused fibrillation of isolated right atrial tissue. AIP (0.3μmol/L) and 0.1μmol/L GS458967 alone inhibited ATX-II-induced arrhythmias by 20±3% (mean±SEM, n=14) and 34±5% (n=13), respectively, whereas the two compounds in combination inhibited arrhythmias by 81±4% (n=10, p<0.05, vs either AIP or GS458967 alone or the calculated sum of individual effects of both compounds). AIP and GS458967 also attenuated the ATX-induced increase of diastolic tension. Consistent with the mechanical and electrical data, 0.3μmol/L AIP and 0.1μmol/L GS458967 each inhibited ATX-II-induced CaMKII phosphorylation by 23±3% and 32±4%, whereas the combination of both compounds inhibited CaMKII phosphorylation completely. CONCLUSION The effects of an enhanced late INa to induce arrhythmic activity and activation of CaMKII in atria are attenuated synergistically by inhibitors of late INa and CaMKII.
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Affiliation(s)
- Faquan Liang
- Gilead Sciences, Inc., Fremont, CA 94555, United States.
| | - Peidong Fan
- Gilead Sciences, Inc., Fremont, CA 94555, United States
| | - Jessie Jia
- Gilead Sciences, Inc., Fremont, CA 94555, United States
| | - Suya Yang
- Gilead Sciences, Inc., Fremont, CA 94555, United States
| | - Zhan Jiang
- Gilead Sciences, Inc., Fremont, CA 94555, United States
| | | | | | | | | | - Lina Yao
- Gilead Sciences, Inc., Fremont, CA 94555, United States
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Boyden PA, Dun W, Stuyvers BD. What is a Ca(2+) wave? Is it like an Electrical Wave? Arrhythm Electrophysiol Rev 2016; 4:35-9. [PMID: 26835097 DOI: 10.15420/aer.2015.4.1.35] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 02/25/2015] [Indexed: 11/04/2022] Open
Abstract
Arrhythmia subcellular mechanisms are constantly being explored. Recent knowledge has shown that travelling Ca(2+) waves in cardiac cells are critical for delayed afterdepolarisations and in some cases, early afterdepolarisations. In this review, we comment on the properties of cardiac Ca(2+) waves and abnormal Ca(2+) releases in terms of properties used to describe electrical waves; propagation, excitability and refractoriness.
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Affiliation(s)
| | - Wen Dun
- Department of Pharmacology, Columbia University, New York
| | - Bruno D Stuyvers
- Faculty of Medicine, Division of Biomedical Sciences, Memorial University of Newfoundland, St. John's, NL, Canada
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Mesubi OO, Anderson ME. Atrial remodelling in atrial fibrillation: CaMKII as a nodal proarrhythmic signal. Cardiovasc Res 2016; 109:542-57. [PMID: 26762270 DOI: 10.1093/cvr/cvw002] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 01/05/2016] [Indexed: 01/10/2023] Open
Abstract
CaMKII is a serine-threonine protein kinase that is abundant in myocardium. Emergent evidence suggests that CaMKII may play an important role in promoting atrial fibrillation (AF) by targeting a diverse array of proteins involved in membrane excitability, cell survival, calcium homeostasis, matrix remodelling, inflammation, and metabolism. Furthermore, CaMKII inhibition appears to protect against AF in animal models and correct proarrhythmic, defective intracellular Ca(2+) homeostasis in fibrillating human atrial cells. This review considers current concepts and evidence from animal and human studies on the role of CaMKII in AF.
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Affiliation(s)
- Olurotimi O Mesubi
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA Department of Medicine, The Johns Hopkins University School of Medicine, 1830 E. Monument Street, Suite 9026, Baltimore, MD 21287, USA
| | - Mark E Anderson
- Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA Department of Medicine, The Johns Hopkins University School of Medicine, 1830 E. Monument Street, Suite 9026, Baltimore, MD 21287, USA Department of Physiology and the Program in Cellular and Molecular Medicine, The Johns Hopkins School of Medicine, Baltimore, MD, USA
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Hernandez-Hernandez G, Alvarez-Lacalle E, Shiferaw Y. Role of connectivity and fluctuations in the nucleation of calcium waves in cardiac cells. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:052715. [PMID: 26651731 DOI: 10.1103/physreve.92.052715] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Indexed: 06/05/2023]
Abstract
Spontaneous calcium release (SCR) occurs when ion channel fluctuations lead to the nucleation of calcium waves in cardiac cells. This phenomenon is important since it has been implicated as a cause of various cardiac arrhythmias. However, to date, it is not understood what determines the timing and location of spontaneous calcium waves within cells. Here, we analyze a simplified model of SCR in which calcium release is modeled as a stochastic processes on a two-dimensional network of randomly distributed sites. Using this model we identify the essential parameters describing the system and compute the phase diagram. In particular, we identify a critical line which separates pinned and propagating fronts, and show that above this line wave nucleation is governed by fluctuations and the spatial connectivity of calcium release units. Using a mean-field analysis we show that the sites of wave nucleation are predicted by localized eigenvectors of a matrix representing the network connectivity of release sites. This result provides insight on the interplay between connectivity and fluctuations in the genesis of SCR in cardiac myocytes.
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Affiliation(s)
- Gonzalo Hernandez-Hernandez
- Department of Physics & Astronomy, California State University, Northridge, 18111 Nordhoff Street, Northridge, CA 91330, USA
| | - Enric Alvarez-Lacalle
- Physics Department, Universitat Politècnica de Catalunya, BarcelonaTech, Barcelona, Spain
| | - Yohannes Shiferaw
- Department of Physics & Astronomy, California State University, Northridge, 18111 Nordhoff Street, Northridge, CA 91330, USA
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Liu MB, de Lange E, Garfinkel A, Weiss JN, Qu Z. Delayed afterdepolarizations generate both triggers and a vulnerable substrate promoting reentry in cardiac tissue. Heart Rhythm 2015; 12:2115-24. [PMID: 26072025 PMCID: PMC4583816 DOI: 10.1016/j.hrthm.2015.06.019] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Indexed: 11/23/2022]
Abstract
BACKGROUND Delayed afterdepolarizations (DADs) have been well characterized as arrhythmia triggers, but their role in generating a tissue substrate vulnerable to reentry is not well understood. OBJECTIVE The purpose of this study was to test the hypothesis that random DADs can self-organize to generate both an arrhythmia trigger and a vulnerable substrate simultaneously in cardiac tissue as a result of gap junction coupling. METHODS Computer simulations in 1-dimensional cable and 2-dimensional tissue models were performed. The cellular DAD amplitude was varied by changing the strength of sarcoplasmic reticulum calcium release. Random DAD latency and amplitude in different cells were simulated using gaussian distributions. RESULTS Depending on the strength of spontaneous sarcoplasmic reticulum calcium release and other conditions, random DADs in cardiac tissue resulted in the following behaviors: (1) triggered activity (TA); (2) a vulnerable tissue substrate causing unidirectional conduction block and reentry by inactivating sodium channels; (3) both triggers and a vulnerable substrate simultaneously by generating TA in regions next to regions with subthreshold DADs susceptible to unidirectional conduction block and reentry. The probability of the latter 2 behaviors was enhanced by reduced sodium channel availability, reduced gap junction coupling, increased tissue heterogeneity, and less synchronous DAD latency. CONCLUSION DADs can self-organize in tissue to generate arrhythmia triggers, a vulnerable tissue substrate, and both simultaneously. Reduced sodium channel availability and gap junction coupling potentiate this mechanism of arrhythmias, which are relevant to a variety of heart disease conditions.
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Affiliation(s)
- Michael B Liu
- UCLA Cardiovascular Research Laboratory; Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California
| | - Enno de Lange
- UCLA Cardiovascular Research Laboratory; Department of Knowledge Engineering, Maastricht University, Maastricht, The Netherlands
| | - Alan Garfinkel
- UCLA Cardiovascular Research Laboratory; Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California; Department of Integrative Biology and Physiology, University of California, Los Angeles, California
| | - James N Weiss
- UCLA Cardiovascular Research Laboratory; Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California; Department of Integrative Biology and Physiology, University of California, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Zhilin Qu
- UCLA Cardiovascular Research Laboratory; Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California.
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Affiliation(s)
- Bruce B. Lerman
- From the Division of Cardiology, Department of Medicine, Cornell University, Medical Center, New York, NY
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Greene D, Shiferaw Y. Approximate analytical solutions for excitation and propagation in cardiac tissue. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:042719. [PMID: 25974539 DOI: 10.1103/physreve.91.042719] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2015] [Indexed: 06/04/2023]
Abstract
It is well known that a variety of cardiac arrhythmias are initiated by a focal excitation in heart tissue. At the single cell level these currents are typically induced by intracellular processes such as spontaneous calcium release (SCR). However, it is not understood how the size and morphology of these focal excitations are related to the electrophysiological properties of cardiac cells. In this paper a detailed physiologically based ionic model is analyzed by projecting the excitation dynamics to a reduced one-dimensional parameter space. Based on this analysis we show that the inward current required for an excitation to occur is largely dictated by the voltage dependence of the inward rectifier potassium current (I(K1)), and is insensitive to the detailed properties of the sodium current. We derive an analytical expression relating the size of a stimulus and the critical current required to induce a propagating action potential (AP), and argue that this relationship determines the necessary number of cells that must undergo SCR in order to induce ectopic activity in cardiac tissue. Finally, we show that, once a focal excitation begins to propagate, its propagation characteristics, such as the conduction velocity and the critical radius for propagation, are largely determined by the sodium and gap junction currents with a substantially lesser effect due to repolarizing potassium currents. These results reveal the relationship between ion channel properties and important tissue scale processes such as excitation and propagation.
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Affiliation(s)
- D'Artagnan Greene
- Department of Physics and Astronomy, California State University, Northridge, California 91330, USA
| | - Yohannes Shiferaw
- Department of Physics and Astronomy, California State University, Northridge, California 91330, USA
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Perspective: a dynamics-based classification of ventricular arrhythmias. J Mol Cell Cardiol 2015; 82:136-52. [PMID: 25769672 DOI: 10.1016/j.yjmcc.2015.02.017] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Revised: 02/05/2015] [Accepted: 02/20/2015] [Indexed: 02/04/2023]
Abstract
Despite key advances in the clinical management of life-threatening ventricular arrhythmias, culminating with the development of implantable cardioverter-defibrillators and catheter ablation techniques, pharmacologic/biologic therapeutics have lagged behind. The fundamental issue is that biological targets are molecular factors. Diseases, however, represent emergent properties at the scale of the organism that result from dynamic interactions between multiple constantly changing molecular factors. For a pharmacologic/biologic therapy to be effective, it must target the dynamic processes that underlie the disease. Here we propose a classification of ventricular arrhythmias that is based on our current understanding of the dynamics occurring at the subcellular, cellular, tissue and organism scales, which cause arrhythmias by simultaneously generating arrhythmia triggers and exacerbating tissue vulnerability. The goal is to create a framework that systematically links these key dynamic factors together with fixed factors (structural and electrophysiological heterogeneity) synergistically promoting electrical dispersion and increased arrhythmia risk to molecular factors that can serve as biological targets. We classify ventricular arrhythmias into three primary dynamic categories related generally to unstable Ca cycling, reduced repolarization, and excess repolarization, respectively. The clinical syndromes, arrhythmia mechanisms, dynamic factors and what is known about their molecular counterparts are discussed. Based on this framework, we propose a computational-experimental strategy for exploring the links between molecular factors, fixed factors and dynamic factors that underlie life-threatening ventricular arrhythmias. The ultimate objective is to facilitate drug development by creating an in silico platform to evaluate and predict comprehensively how molecular interventions affect not only a single targeted arrhythmia, but all primary arrhythmia dynamics categories as well as normal cardiac excitation-contraction coupling.
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Sato D, Bartos DC, Ginsburg KS, Bers DM. Depolarization of cardiac membrane potential synchronizes calcium sparks and waves in tissue. Biophys J 2015; 107:1313-7. [PMID: 25229139 DOI: 10.1016/j.bpj.2014.07.053] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 03/05/2014] [Accepted: 07/15/2014] [Indexed: 10/24/2022] Open
Abstract
The diastolic membrane potential (Vm) can be hyperpolarized or depolarized by various factors such as hyperkalemia or hypokalemia in the long term, or by delayed afterdepolarizations in the short term. In this study, we investigate how Vm affects Ca sparks and waves. We use a physiologically detailed mathematical model to investigate individual factors that affect Ca spark generation and wave propagation. We focus on the voltage range of -90 ∼ -70 mV, which is just below the Vm for sodium channel activation. We find that Vm depolarization promotes Ca wave propagation and hyperpolarization prevents it. This finding is directly validated in voltage clamp experiments with Ca waves using isolated rat ventricular myocytes. Ca transport by the sodium-calcium exchanger (NCX) is determined by Vm as well as Na and Ca concentrations. Depolarized Vm reduces NCX-mediated efflux, elevating [Ca]i, and thus promoting Ca wave propagation. Moreover, depolarized Vm promotes spontaneous Ca releases that can cause initiation of multiple Ca waves. This indicates that during delayed afterdepolarizations, Ca release units (CRUs) interact with not just the immediately adjacent CRUs via Ca diffusion, but also further CRUs via fast (∼0.1 ms) changes in Vm mediated by the voltage and Ca-sensitive NCX. This may contribute significantly to synchronization of Ca waves among multiple cells in tissue.
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Affiliation(s)
- Daisuke Sato
- Department of Pharmacology, University of California, Davis, Davis, California.
| | - Daniel C Bartos
- Department of Pharmacology, University of California, Davis, Davis, California
| | - Kenneth S Ginsburg
- Department of Pharmacology, University of California, Davis, Davis, California
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Davis, California.
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Horváth B, Hegyi B, Kistamás K, Váczi K, Bányász T, Magyar J, Szentandrássy N, Nánási PP. Cytosolic calcium changes affect the incidence of early afterdepolarizations in canine ventricular myocytes. Can J Physiol Pharmacol 2015; 93:527-34. [PMID: 25928391 DOI: 10.1139/cjpp-2014-0511] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
This study was designed to investigate the influence of cytosolic Ca(2+) levels ([Ca(2+)]i) on action potential duration (APD) and on the incidence of early afterdepolarizations (EADs) in canine ventricular cardiomyocytes. Action potentials (AP) of isolated cells were recorded using conventional sharp microelectrodes, and the concomitant [Ca(2+)]i was monitored with the fluorescent dye Fura-2. EADs were evoked at a 0.2 Hz pacing rate by inhibiting the rapid delayed rectifier K(+) current with dofetilide, by activating the late sodium current with veratridine, or by activating the L-type calcium current with BAY K8644. These interventions progressively prolonged the AP and resulted in initiation of EADs. Reducing [Ca(2+)]i by application of the cell-permeant Ca(2+) chelator BAPTA-AM lengthened the AP at 1.0 Hz if it was applied alone, in the presence of veratridine, or in the presence of BAY K8644. However, BAPTA-AM shortened the AP if the cells were pretreated with dofetilide. The incidence of the evoked EADs was strongly reduced by BAPTA-AM in dofetilide, moderately reduced in veratridine, whereas EAD incidence was increased by BAPTA-AM in the presence of BAY K8644. Based on these experimental data, changes in [Ca(2+)]i have marked effects on APD as well as on the incidence of EADs; however, the underlying mechanisms may be different, depending on the mechanism of EAD generation. As a consequence, reduction of [Ca(2+)]i may eliminate EADs under some, but not all, experimental conditions.
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Affiliation(s)
- Balázs Horváth
- a Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, Hungary.,b Faculty of Pharmacy, University of Debrecen, Debrecen, Hungary
| | - Bence Hegyi
- a Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, Hungary
| | - Kornél Kistamás
- a Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, Hungary
| | - Krisztina Váczi
- a Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, Hungary
| | - Tamás Bányász
- a Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, Hungary
| | - János Magyar
- a Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, Hungary.,c Division of Sport Physiology, Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Norbert Szentandrássy
- a Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, Hungary.,d Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, Hungary
| | - Péter P Nánási
- a Department of Physiology, Faculty of Medicine, University of Debrecen, H-4012 Debrecen, Nagyerdei krt 98, Hungary.,d Department of Dental Physiology and Pharmacology, Faculty of Dentistry, University of Debrecen, Hungary
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Xiong F, Yin Y, Dubé B, Pagé P, Vinet A. Electrophysiological changes preceding the onset of atrial fibrillation after coronary bypass grafting surgery. PLoS One 2014; 9:e107919. [PMID: 25247814 PMCID: PMC4172567 DOI: 10.1371/journal.pone.0107919] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Accepted: 08/24/2014] [Indexed: 12/02/2022] Open
Abstract
BACKGROUND The incidence of Post-CABG atrial fibrillation (AF) lies between 25% and 40%. It worsens morbidity and raises post-operative costs. Detection of incoming AF soon enough for prophylactic intervention would be helpful. The study is to investigate the electrophysiological changes preceding the onset of AF and their relationship to the preoperative risk. METHODS AND RESULTS Patients were recorded continuously for the first four days after coronary artery bypass grafting surgery (CABG) with three unipolar electrodes sutured to the atria (AEG). The patients experiencing an AF lasting more than 10 minutes were selected and the two hours before the onset were analyzed. Four variables were found to show significant changes in the two hours prior to the first prolonged AF: increasing rate of premature atrial activation, increasing incidence of short transient arrhythmias, acceleration of heart rate, and rise of low frequency content of heart rate. The main contrast was between the first and last hour before AF onset. Preoperative risk was not predictive of the onset time of AF and did not correlate with the amplitude of changes prior to AF. CONCLUSIONS Post-CABG AF were preceded by electrophysiological changes occurring in the last hour before the onset of the arrhythmia, whereas none of these changes was found to occur in all AF patients. The risk was a weighted sum of factors related to the density of premature activations and the state of atrial substrate reflected by the sinus rhythm and its frequency content prior to AF. Preoperative risk score seems unhelpful in setting a detection threshold for the AF onset.
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Affiliation(s)
- Feng Xiong
- Research Center, Hôpital du Sacré-Cœur de Montréal, Université de Montréal, Montréal, Canada
- Montréal Heart Institute, Université de Montréal, Montréal, Canada
| | - Yalin Yin
- Research Center, Hôpital du Sacré-Cœur de Montréal, Université de Montréal, Montréal, Canada
| | - Bruno Dubé
- Research Center, Hôpital du Sacré-Cœur de Montréal, Université de Montréal, Montréal, Canada
- Biomedical Engineering Institute, Université de Montréal, Montréal, Canada
| | - Pierre Pagé
- Research Center, Hôpital du Sacré-Cœur de Montréal, Université de Montréal, Montréal, Canada
- Montréal Heart Institute, Université de Montréal, Montréal, Canada
- Department of Surgery, Université de Montréal, Montréal, Canada
| | - Alain Vinet
- Research Center, Hôpital du Sacré-Cœur de Montréal, Université de Montréal, Montréal, Canada
- Biomedical Engineering Institute, Université de Montréal, Montréal, Canada
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Wang P, Tang M, Gao L, Luo H, Wang G, Ma X, Duan Y. Roles of I(f) and intracellular Ca2+ release in spontaneous activity of ventricular cardiomyocytes during murine embryonic development. J Cell Biochem 2013; 114:1852-62. [PMID: 23463619 DOI: 10.1002/jcb.24527] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 02/21/2013] [Indexed: 01/01/2023]
Abstract
In recent years, the contribution of I(f), an important pacemaker current, and intracellular Ca(2+) release (ICR) from sarcoplasmic reticulum to pacemaking and arrhythmia has been intensively studied. However, their functional roles in embryonic heart remain uncertain. Using patch clamp, Ca(2+) imaging, and RT-PCR, we found that I(f) regulated the firing rate in early and late stage embryonic ventricular cells, as ivabradine (30 µM), a specific blocker of I(f), slowed down action potential (AP) frequency. This inhibitory effect was even stronger in late stage cells, though I(f) was down-regulated. In contrast to I(f), ICR was found to be indispensable for the occurrence of APs in ventricular cells of different stages, because abolishment of ICR with ryanodine and 2-aminoethoxydiphenyl borate (2-APB), specific blockers of ryanodine receptors (RyRs) and inositol trisphosphate receptors (IP3Rs), completely abolished APs. In addition, we noticed that RyR- and IP3R-mediated ICR coexisted in early-stage ventricular cells and RyRs functionally dominated. While at late stage RyRs, but not IP3Rs, mediated ICR. In both early and late stage ventricular cells, Na-Ca exchanger current (I(Na/Ca)) mediated ICR-triggered depolarization of membrane potential and resulted in the initiation of APs. We also observed that different from I(f), which presented as the substantial component of the earlier diastolic depolarization current, application of ryanodine, and/or 2-APB slowed the late phase of diastolic depolarization. Thus, we conclude that in murine embryonic ventricular cells I(f) regulates firing rate, while RyRs and IP3Rs (early stage) or RyRs (late stage)-mediated ICR determines the occurrence of APs.
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Affiliation(s)
- Peng Wang
- Department of Physiology, Tongji Medical College of Huazhong University of Science and Technology, Wuhan, China
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XU GUOJUN, GAN TIANYI, TANG BAOPENG, CHEN ZUHENG, MAHEMUTI AILIMAN, JIANG TAO, SONG JIANGUO, GUO XIA, LI YAODONG, ZHOU XIANHUI, ZHANG YU, LI JINXIN. Alterations in the expression of atrial calpains in electrical and structural remodeling during aging and atrial fibrillation. Mol Med Rep 2013; 8:1343-52. [DOI: 10.3892/mmr.2013.1684] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 08/16/2013] [Indexed: 11/06/2022] Open
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Renal denervation suppresses ventricular arrhythmias during acute ventricular ischemia in pigs. Heart Rhythm 2013; 10:1525-30. [PMID: 23851058 DOI: 10.1016/j.hrthm.2013.07.015] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2013] [Indexed: 12/13/2022]
Abstract
BACKGROUND Increased sympathetic activation during acute ventricular ischemia is involved in the occurrence of life-threatening arrhythmias. OBJECTIVE To test the effect of sympathetic inhibition by renal denervation (RDN) on ventricular ischemia/reperfusion arrhythmias. METHODS Anesthetized pigs, randomized to RDN or SHAM treatment, were subjected to 20 minutes of left anterior descending coronary artery (LAD) occlusion followed by reperfusion. Infarct size, hemodynamics, premature ventricular contractions, and spontaneous ventricular tachyarrhythmias were analyzed. Monophasic action potentials were recorded with an epicardial probe at the ischemic area. RESULTS Ventricular ischemia resulted in an acute reduction of blood pressure (-29%) and peak left ventricular pressure rise (-40%), which were not significantly affected by RDN. However, elevation of left ventricular end-diastolic pressure (LVEDP) during LAD ligation was attenuated by RDN (ΔLVEDP: +1.8 ± 0.6 mm Hg vs +9.7 ± 1 mm Hg in the SHAM group; P = .046). Infarct size was not affected by RDN compared to SHAM. RDN significantly reduced spontaneous ventricular extrabeats (160 ± 15/10 min in the RDN group vs 422 ± 36/10 min in the SHAM group; P = .021) without affecting coupling intervals. In 5 of 6 SHAM-treated animals, ventricular fibrillation (VF) occurred during LAD occlusion. By contrast, only 1 of 7 RDN-treated animals experienced VF (P = .029). Beta-receptor blockade by atenolol showed comparable effects. Neither VF nor transient shortening of monophasic action potential duration during reperfusion was inhibited by RDN. CONCLUSIONS RDN reduced the occurrence of ventricular arrhythmias/fibrillation and attenuated the rise in LVEDP during left ventricular ischemia without affecting infarct size, changes in ventricular contractility, blood pressure, and reperfusion arrhythmias. Therefore, RDN may protect from ventricular arrhythmias during ischemic events.
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Shryock JC, Song Y, Rajamani S, Antzelevitch C, Belardinelli L. The arrhythmogenic consequences of increasing late INa in the cardiomyocyte. Cardiovasc Res 2013; 99:600-11. [PMID: 23752976 DOI: 10.1093/cvr/cvt145] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
This review presents the roles of cardiac sodium channel NaV1.5 late current (late INa) in generation of arrhythmic activity. The assumption of the authors is that proper Na(+) channel function is necessary to the maintenance of the transmembrane electrochemical gradient of Na(+) and regulation of cardiac electrical activity. Myocyte Na(+) channels' openings during the brief action potential upstroke contribute to peak INa and initiate excitation-contraction coupling. Openings of Na(+) channels outside the upstroke contribute to late INa, a depolarizing current that persists throughout the action potential plateau. The small, physiological late INa does not appear to be critical for normal electrical or contractile function in the heart. Late INa does, however, reduce the net repolarizing current, prolongs action potential duration, and increases cellular Na(+) loading. An increase of late INa, due to acquired conditions (e.g. heart failure) or inherited Na(+) channelopathies, facilitates the formation of early and delayed afterpolarizations and triggered arrhythmias, spontaneous diastolic depolarization, and cellular Ca(2+) loading. These in turn increase the spatial and temporal dispersion of repolarization time and may lead to reentrant arrhythmias.
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Affiliation(s)
- John C Shryock
- Department of Biology, Cardiovascular Therapeutic Area, Gilead Sciences, Foster City, CA, USA
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Abstract
Ca(2+) waves were probably first observed in the early 1940s. Since then Ca(2+) waves have captured the attention of an eclectic mixture of mathematicians, neuroscientists, muscle physiologists, developmental biologists, and clinical cardiologists. This review discusses the current state of mathematical models of Ca(2+) waves, the normal physiological functions Ca(2+) waves might serve in cardiac cells, as well as how the spatial arrangement of Ca(2+) release channels shape Ca(2+) waves, and we introduce the idea of Ca(2+) phase waves that might provide a useful framework for understanding triggered arrhythmias.
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Affiliation(s)
- Leighton T Izu
- Department of Pharmacology, University of California, Davis, USA.
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Sicouri S, Belardinelli L, Antzelevitch C. Antiarrhythmic effects of the highly selective late sodium channel current blocker GS-458967. Heart Rhythm 2013; 10:1036-43. [PMID: 23524321 DOI: 10.1016/j.hrthm.2013.03.023] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/22/2013] [Indexed: 12/14/2022]
Abstract
BACKGROUND Previous studies have shown that late sodium channel current (INa) blockers such as ranolazine can exert antiarrhythmic effects by suppressing early and delayed afterdepolarization (EAD and DAD)-induced triggered activity. OBJECTIVE To evaluate the electrophysiological properties of GS-458967 (GS967), a potent and highly selective late INa blocker, in canine Purkinje fibers (PFs) and pulmonary vein (PV) and superior vena cava (SVC) sleeve preparations. METHODS Transmembrane action potentials were recorded from canine PFs and PV and SVC sleeve preparations by using standard microelectrode techniques. The rapidly activating delayed rectifier potassium channel current blocker E-4031 (2.5-5 µM) and the late INa agonist ATX-II (10 nM) were used to induce EADs in PFs. Isoproterenol (1 µM), high calcium ([Ca(2+)]o = 5.4 mM), or their combination was used to induce DADs and triggered activity. RESULTS In PFs, GS967 (10-300 nM) caused a significant concentration-dependent reduction in action potential duration without altering the maximum rate of rise of the action potential upstroke, action potential amplitude, or resting membrane potential at any rate studied (basic cycle lengths of 1000, 500, and 300 ms) or concentration evaluated (n = 5; P < .05). GS967 (30-100 nM) abolished EADs and EAD-induced triggered activity elicited in PFs by exposure to E-4031 (n = 4) or ATX-II (n = 4). In addition, GS967 reduced or abolished DADs and suppressed DAD-induced triggered activity elicited in PFs (n = 4) and PV (n = 4) and SVC (n = 3) sleeve preparations by exposure to isoproterenol, high calcium, or their combination. CONCLUSIONS Our data suggest that the selective inhibition of late INa with GS967 can exert antiarrhythmic effects by suppressing EAD- and DAD-mediated extrasystolic activity in PFs and PV and SVC sleeve preparations.
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Affiliation(s)
- Serge Sicouri
- Masonic Medical Research Laboratory, Utica, New York 13501-1787, USA.
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Miura M, Murai N, Hattori T, Nagano T, Stuyvers BD, Shindoh C. Role of reactive oxygen species and Ca(2+) dissociation from the myofilaments in determination of Ca(2+) wave propagation in rat cardiac muscle. J Mol Cell Cardiol 2012; 56:97-105. [PMID: 23266595 DOI: 10.1016/j.yjmcc.2012.12.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2012] [Revised: 11/14/2012] [Accepted: 12/10/2012] [Indexed: 11/30/2022]
Abstract
Ca(2+) waves are initiated not only by Ca(2+) leak from the sarcoplasmic reticulum (SR), but also by Ca(2+) dissociation from the myofilaments in the myocardium with nonuniform contraction. We investigated whether contractile properties and the production of reactive oxygen species (ROS) affect Ca(2+) wave propagation. Trabeculae were obtained from 76 rat hearts. Force was measured with a strain gauge, sarcomere length with a laser diffraction technique, and [Ca(2+)](i) with fura-2 and a CCD camera (24°C, 2.0mmol/L [Ca(2+)](o)). ROS production was estimated from 2',7'-dichlorofluorescein (DCF) fluorescence. Trabeculae were regionally exposed to a jet of solution containing 1) 10mmol/L Ca(2+) to initiate Ca(2+) waves by SR Ca(2+) leak due to Ca(2+) overload within the jet-exposed region, and 2) 0.2mmol/L Ca(2+) or 5mmol/L caffeine to initiate such waves by Ca(2+) dissociation from the myofilaments due to nonuniform contraction. Ca(2+) waves were induced by stimulus trains for 7.5s. Ten-percent muscle stretch increased DCF fluorescence and accelerated Ca(2+) waves initiated due to both Ca(2+) overload and nonuniform contraction. Preincubation with 3μmol/L diphenyleneiodonium or 10μmol/L colchicine suppressed the increase in DCF fluorescence but suppressed acceleration of Ca(2+) waves initiated only due to Ca(2+) overload. Irrespective of preincubation with colchicine, reduction of force after the addition of 10μmol/L blebbistatin did not decelerate Ca(2+) waves initiated due to Ca(2+) overload, while it did decelerate waves initiated due to nonuniform contraction. These results suggest that Ca(2+) wave propagation is modulated by ROS production through an intact microtubule network only during stretch and may be additionally modulated by Ca(2+) dissociated from the myofilaments in the case of nonuniform contraction.
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Affiliation(s)
- Masahito Miura
- Department of Clinical Physiology, Health Science, Tohoku University Graduate School of Medicine, Sendai 980-8574, Japan.
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