1
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Wang R, Qu Z, Huang X. Dissecting the roles of calcium cycling and its coupling with voltage in the genesis of early afterdepolarizations in cardiac myocyte models. PLoS Comput Biol 2024; 20:e1011930. [PMID: 38416778 PMCID: PMC10927084 DOI: 10.1371/journal.pcbi.1011930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Revised: 03/11/2024] [Accepted: 02/19/2024] [Indexed: 03/01/2024] Open
Abstract
Early afterdepolarizations (EADs) are abnormal depolarizations during the plateau phase of the action potential, which are known to be associated with lethal arrhythmias in the heart. There are two major hypotheses for EAD genesis based on experimental observations, i.e., the voltage (Vm)-driven and intracellular calcium (Ca)-driven mechanisms. In ventricular myocytes, Ca and Vm are bidirectionally coupled, which can affect each other's dynamics and result in new dynamics, however, the roles of Ca cycling and its coupling with Vm in the genesis of EADs have not been well understood. In this study, we use an action potential model that is capable of independent Vm and Ca oscillations to investigate the roles of Vm and Ca coupling in EAD genesis. Four different mechanisms of EADs are identified, which are either driven by Vm oscillations or Ca oscillations alone, or oscillations caused by their interactions. We also use 5 other ventricular action potential models to assess these EAD mechanisms and show that EADs in these models are mainly Vm-driven. These mechanistic insights from our simulations provide a theoretical base for understanding experimentally observed EADs and EAD-related arrhythmogenesis.
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Affiliation(s)
- Rui Wang
- Department of Physics, South China University of Technology, Guangzhou, China
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California, United States of America
| | - Xiaodong Huang
- Department of Physics, South China University of Technology, Guangzhou, China
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2
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Horváth B, Szentandrássy N, Almássy J, Dienes C, Kovács ZM, Nánási PP, Banyasz T. Late Sodium Current of the Heart: Where Do We Stand and Where Are We Going? Pharmaceuticals (Basel) 2022; 15:ph15020231. [PMID: 35215342 PMCID: PMC8879921 DOI: 10.3390/ph15020231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 02/07/2022] [Accepted: 02/09/2022] [Indexed: 02/05/2023] Open
Abstract
Late sodium current has long been linked to dysrhythmia and contractile malfunction in the heart. Despite the increasing body of accumulating information on the subject, our understanding of its role in normal or pathologic states is not complete. Even though the role of late sodium current in shaping action potential under physiologic circumstances is debated, it’s unquestioned role in arrhythmogenesis keeps it in the focus of research. Transgenic mouse models and isoform-specific pharmacological tools have proved useful in understanding the mechanism of late sodium current in health and disease. This review will outline the mechanism and function of cardiac late sodium current with special focus on the recent advances of the area.
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Affiliation(s)
- Balázs Horváth
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
| | - Norbert Szentandrássy
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
- Department of Basic Medical Sciences, Faculty of Dentistry, University of Debrecen, 4032 Debrecen, Hungary
| | - János Almássy
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
| | - Csaba Dienes
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
| | - Zsigmond Máté Kovács
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
| | - Péter P. Nánási
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
- Department of Dental Physiology and Pharmacology, University of Debrecen, 4032 Debrecen, Hungary
| | - Tamas Banyasz
- Department of Physiology, University of Debrecen, 4032 Debrecen, Hungary; (B.H.); (N.S.); (J.A.); (C.D.); (Z.M.K.); (P.P.N.)
- Correspondence: ; Tel.: +36-(52)-255-575; Fax: +36-(52)-255-116
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3
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Gonano LA, Mattiazzi A. Targeting late ICaL to close the window to ventricular arrhythmias. J Gen Physiol 2021; 153:212726. [PMID: 34699586 PMCID: PMC8552155 DOI: 10.1085/jgp.202113009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Affiliation(s)
- Luis A Gonano
- Centro de Investigaciones Cardiovasculares Horacio Cingolani, CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
| | - Alicia Mattiazzi
- Centro de Investigaciones Cardiovasculares Horacio Cingolani, CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Argentina
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4
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Hutchings DC, Pearman CM, Madders GWP, Woods LS, Eisner DA, Dibb KM, Trafford AW. PDE5 Inhibition Suppresses Ventricular Arrhythmias by Reducing SR Ca 2+ Content. Circ Res 2021; 129:650-665. [PMID: 34247494 PMCID: PMC8409902 DOI: 10.1161/circresaha.121.318473] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
[Figure: see text].
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Affiliation(s)
- David C Hutchings
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Charles M Pearman
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - George W P Madders
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Lori S Woods
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - David A Eisner
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Katharine M Dibb
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
| | - Andrew W Trafford
- Unit of Cardiac Physiology, Division of Cardiovascular Sciences, Faculty of Biology Medicine and Health, University of Manchester, Manchester Academic Health Sciences Centre, United Kingdom
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5
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Abstract
Atrial fibrillation (AF) is the most common cardiac arrhythmia, largely associated to morbidity and mortality. Over the past decades, research in appearance and progression of this arrhythmia have turned into significant advances in its management. However, the incidence of AF continues to increase with the aging of the population and many important fundamental and translational underlaying mechanisms remain elusive. Here, we review recent advances in molecular and cellular basis for AF initiation, maintenance and progression. We first provide an overview of the basic molecular and electrophysiological mechanisms that lead and characterize AF. Next, we discuss the upstream regulatory factors conducting the underlying mechanisms which drive electrical and structural AF-associated remodeling, including genetic factors (risk variants associated to AF as transcriptional regulators and genetic changes associated to AF), neurohormonal regulation (i.e., cAMP) and oxidative stress imbalance (cGMP and mitochondrial dysfunction). Finally, we discuss the potential therapeutic implications of those findings, the knowledge gaps and consider future approaches to improve clinical management.
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6
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Kistamás K, Hézső T, Horváth B, Nánási PP. Late sodium current and calcium homeostasis in arrhythmogenesis. Channels (Austin) 2020; 15:1-19. [PMID: 33258400 PMCID: PMC7757849 DOI: 10.1080/19336950.2020.1854986] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The cardiac late sodium current (INa,late) is the small sustained component of the sodium current active during the plateau phase of the action potential. Several studies demonstrated that augmentation of the current can lead to cardiac arrhythmias; therefore, INa,late is considered as a promising antiarrhythmic target. Fundamentally, enlarged INa,late increases Na+ influx into the cell, which, in turn, is converted to elevated intracellular Ca2+ concentration through the Na+/Ca2+ exchanger. The excessive Ca2+ load is known to be proarrhythmic. This review describes the behavior of the voltage-gated Na+ channels generating INa,late in health and disease and aims to discuss the physiology and pathophysiology of Na+ and Ca2+ homeostasis in context with the enhanced INa,late demonstrating also the currently accessible antiarrhythmic choices.
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Affiliation(s)
- Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary
| | - Tamás Hézső
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary
| | - Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen , Debrecen, Hungary.,Department of Dental Physiology, Faculty of Dentistry, University of Debrecen , Debrecen, Hungary
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7
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Kistamás K, Veress R, Horváth B, Bányász T, Nánási PP, Eisner DA. Calcium Handling Defects and Cardiac Arrhythmia Syndromes. Front Pharmacol 2020; 11:72. [PMID: 32161540 PMCID: PMC7052815 DOI: 10.3389/fphar.2020.00072] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 01/24/2020] [Indexed: 12/13/2022] Open
Abstract
Calcium ions (Ca2+) play a major role in the cardiac excitation-contraction coupling. Intracellular Ca2+ concentration increases during systole and falls in diastole thereby determining cardiac contraction and relaxation. Normal cardiac function also requires perfect organization of the ion currents at the cellular level to drive action potentials and to maintain action potential propagation and electrical homogeneity at the tissue level. Any imbalance in Ca2+ homeostasis of a cardiac myocyte can lead to electrical disturbances. This review aims to discuss cardiac physiology and pathophysiology from the elementary membrane processes that can cause the electrical instability of the ventricular myocytes through intracellular Ca2+ handling maladies to inherited and acquired arrhythmias. Finally, the paper will discuss the current therapeutic approaches targeting cardiac arrhythmias.
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Affiliation(s)
- Kornél Kistamás
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,Division of Cardiovascular Sciences, School of Medical Sciences, University of Manchester, Manchester, United Kingdom
| | - Roland Veress
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Balázs Horváth
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Tamás Bányász
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Péter P Nánási
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,Department of Dental Physiology, Faculty of Dentistry, University of Debrecen, Debrecen, Hungary
| | - David A Eisner
- Division of Cardiovascular Sciences, School of Medical Sciences, University of Manchester, Manchester, United Kingdom
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8
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Jiao L, Machuki JO, Wu Q, Shi M, Fu L, Adekunle AO, Tao X, Xu C, Hu X, Yin Z, Sun H. Estrogen and calcium handling proteins: new discoveries and mechanisms in cardiovascular diseases. Am J Physiol Heart Circ Physiol 2020; 318:H820-H829. [PMID: 32083972 DOI: 10.1152/ajpheart.00734.2019] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Estrogen deficiency is considered to be an important factor leading to cardiovascular diseases (CVDs). Indeed, the prevalence of CVDs in postmenopausal women exceeds that of premenopausal women and men of the same age. Recent research findings provide evidence that estrogen plays a pivotal role in the regulation of calcium homeostasis and therefore fine-tunes normal cardiomyocyte contraction and relaxation processes. Disruption of calcium homeostasis is closely associated with the pathological mechanism of CVDs. Thus, this paper maps out and summarizes the effects and mechanisms of estrogen on calcium handling proteins in cardiac myocytes, including L-type Ca2+ channel, the sarcoplasmic reticulum Ca2+ release channel named ryanodine receptor, sarco(endo)plasmic reticulum Ca2+-ATPase, and sodium-calcium exchanger. In so doing, we provide theoretical and experimental evidence for the successful design of estrogen-based prevention and treatment therapies for CVDs.
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Affiliation(s)
- Lijuan Jiao
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | | | - Qi Wu
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Mingjin Shi
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Lu Fu
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | | | - Xi Tao
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Chenxi Xu
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Xide Hu
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Zeyuan Yin
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Hong Sun
- Department of Physiology, Xuzhou Medical University, Xuzhou, Jiangsu, China
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9
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Sugiyama A, Hagiwara-Nagasawa M, Kambayashi R, Goto A, Chiba K, Naito AT, Kanda Y, Matsumoto A, Izumi-Nakaseko H. Analysis of electro-mechanical relationship in human iPS cell-derived cardiomyocytes sheets under proarrhythmic condition assessed by simultaneous field potential and motion vector recordings. J Pharmacol Sci 2019; 140:317-320. [DOI: 10.1016/j.jphs.2019.07.006] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Revised: 07/06/2019] [Accepted: 07/12/2019] [Indexed: 11/24/2022] Open
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10
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Huang X, Song Z, Qu Z. Determinants of early afterdepolarization properties in ventricular myocyte models. PLoS Comput Biol 2018; 14:e1006382. [PMID: 30475801 PMCID: PMC6283611 DOI: 10.1371/journal.pcbi.1006382] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Revised: 12/06/2018] [Accepted: 09/17/2018] [Indexed: 12/20/2022] Open
Abstract
Early afterdepolarizations (EADs) are spontaneous depolarizations during the repolarization phase of an action potential in cardiac myocytes. It is widely known that EADs are promoted by increasing inward currents and/or decreasing outward currents, a condition called reduced repolarization reserve. Recent studies based on bifurcation theories show that EADs are caused by a dual Hopf-homoclinic bifurcation, bringing in further mechanistic insights into the genesis and dynamics of EADs. In this study, we investigated the EAD properties, such as the EAD amplitude, the inter-EAD interval, and the latency of the first EAD, and their major determinants. We first made predictions based on the bifurcation theory and then validated them in physiologically more detailed action potential models. These properties were investigated by varying one parameter at a time or using parameter sets randomly drawn from assigned intervals. The theoretical and simulation results were compared with experimental data from the literature. Our major findings are that the EAD amplitude and takeoff potential exhibit a negative linear correlation; the inter-EAD interval is insensitive to the maximum ionic current conductance but mainly determined by the kinetics of ICa,L and the dual Hopf-homoclinic bifurcation; and both inter-EAD interval and latency vary largely from model to model. Most of the model results generally agree with experimental observations in isolated ventricular myocytes. However, a major discrepancy between modeling results and experimental observations is that the inter-EAD intervals observed in experiments are mainly between 200 and 500 ms, irrespective of species, while those of the mathematical models exhibit a much wider range with some models exhibiting inter-EAD intervals less than 100 ms. Our simulations show that the cause of this discrepancy is likely due to the difference in ICa,L recovery properties in different mathematical models, which needs to be addressed in future action potential model development. Early afterdepolarizations (EADs) are abnormal depolarizations during the plateau phase of action potential in cardiac myocytes, arising from a dual Hopf-homoclinic bifurcation. The same bifurcations are also responsible for certain types of bursting behaviors in other cell types, such as beta cells and neuronal cells. EADs are known to play important role in the genesis of lethal arrhythmias and have been widely studied in both experiments and computer models. However, a detailed comparison between the properties of EADs observed in experiments and those from mathematical models have not been carried out. In this study, we performed theoretical analyses and computer simulations of different ventricular action potential models as well as different species to investigate the properties of EADs and compared these properties to those observed in experiments. While the EAD properties in the action potential models capture many of the EAD properties seen in experiments, the inter-EAD intervals in the computer models differ a lot from model to model, and some of them show very large discrepancy with those observed in experiments. This discrepancy needs to be addressed in future cardiac action potential model development.
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Affiliation(s)
- Xiaodong Huang
- Department of Physics, South China University of Technology, Guangzhou, China
| | - Zhen Song
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
| | - Zhilin Qu
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
- * E-mail:
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11
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Zhang JC, Wu HL, Chen Q, Xie XT, Zou T, Zhu C, Dong Y, Xiang GJ, Ye L, Li Y, Zhu PL. Calcium-Mediated Oscillation in Membrane Potentials and Atrial-Triggered Activity in Atrial Cells of Casq2 R33Q/R33Q Mutation Mice. Front Physiol 2018; 9:1447. [PMID: 30450052 PMCID: PMC6224359 DOI: 10.3389/fphys.2018.01447] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 09/24/2018] [Indexed: 12/11/2022] Open
Abstract
Aim: We investigated the underlying mechanisms in atrial fibrillation (AF) associated with R33Q mutation and Ca2+-triggered activity. Methods and Results: We examined AF susceptibility with intraesophageal burst pacing in the sarcoplasmic reticulum (SR) Ca2+ leak model calsequestrin 2 R33Q (Casq2R33Q/R33Q) mice. Atrial trigger appeared in R33Q mice but not WT mice (17.24%, 5/29 vs. 0.00%, 0/32, P < 0.05). AF was induced by 25 Hz pacing in R33Q mice (48.27%, 14/29 vs. 6.25%, 2/32, P < 0.01). The mice were given 1.5 mg/kg isoproterenol (Iso), and the incidences of AF increased (65.51%, 19/29 vs. 9.21%, 3/32, P < 0.01). Electrophysiology experiments and the recording of intracellular Ca2+ indicated significant increases in the Ca2+ sparks (5.24 ± 0.75 100 μM-1.s-1 vs. 0.29 ± 0.04 100 μM-1.s-1, n = 20, P < 0.05), intracellular free Ca2+ (0.238 ± 0.009 μM vs. 0.172 ± 0.006 μM, n = 20, P < 0.05), Ca2+ wave (11.74% vs. 2.24%, n = 20, P < 0.05), transient inward current (ITi) (-0.56 ± 0.02 pA/pF vs. -0.42 ± 0.01 pA/pF, n = 10, P < 0.05), and oscillation in membrane potentials (10.71%, 3/28 vs. 4.16%, 1/24, P < 0.05) in the R33Q group, but there was no significant difference in the L-type calcium current. These effects were enhanced by Iso, and the inhibition of calmodulin-dependent protein kinase II (CaMKII) by 1 μM KN93 reversed the effects of Iso on Ca2+ sparks (5.01 ± 0.66 100 μm-1.s-1 vs. 11.33 ± 1.63 100 μm-1.s-1, P < 0.05), intracellular Ca2+ (0.245 ± 0.005 μM vs. 0.324 ± 0.008 μM, P < 0.05), Ca2+ wave (12.35% vs. 17.83%, P < 0.05), ITi (-0.61 ± 0.02 pA/pF vs. -0.78 ± 0.03 pA/pF, n = 10, P < 0.05), and oscillation in membrane potential (17.85% 5/28 vs. 32.17% 9/28, P < 0.05). The reduction of ryanodine receptor 2 (RyR2) stable subunits (Casq2, triadin, and junctin) rather than RYR2 and the increase in CaMKII, phosphor-CaMKII, phosphor-RyR2 (Ser 2814), SERCA, and NCX1.1 was reflected in the R33Q group. Conclusion: This study demonstrates that the increase in spontaneous calcium elevations corresponding to ITi that may trigger the oscillation in membrane potentials in the R33Q group, thereby increasing the risk of AF. The occurrence of spontaneous calcium elevations in R33Q atrial myocytes is due to the dysfunction of RyR2 stable subunits, CaMKII hyperactivity, and CaMKII-mediated RyR phosphorylation. An effective therapeutic strategy to intervene in Ca2+-induced AF associated with the R33Q mutation may be through CaMKII inhibition.
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Affiliation(s)
- Jian-Cheng Zhang
- Department of Cardiology, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Hong-Lin Wu
- Department of Cardiology, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Qian Chen
- Department of Critical Care Medicine Division Four, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Xiao-Ting Xie
- Department of Cardiology, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Tian Zou
- Department of Cardiology, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Chao Zhu
- Department of Cardiology, General Hospital of People's Liberation Army, Beijing, China
| | - Ying Dong
- Department of Cardiology, General Hospital of People's Liberation Army, Beijing, China
| | - Guo-Jian Xiang
- Department of Cardiology, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
| | - Lei Ye
- National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore
| | - Yang Li
- Department of Cardiology, General Hospital of People's Liberation Army, Beijing, China
| | - Peng-Li Zhu
- Department of Geriatric Medicine, Fujian Provincial Center for Geriatrics, Fujian Provincial Hospital, Provincial Clinical Medicine College of Fujian Medical University, Fuzhou, China
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12
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Johnson DM, Antoons G. Arrhythmogenic Mechanisms in Heart Failure: Linking β-Adrenergic Stimulation, Stretch, and Calcium. Front Physiol 2018; 9:1453. [PMID: 30374311 PMCID: PMC6196916 DOI: 10.3389/fphys.2018.01453] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Accepted: 09/25/2018] [Indexed: 12/22/2022] Open
Abstract
Heart failure (HF) is associated with elevated sympathetic tone and mechanical load. Both systems activate signaling transduction pathways that increase cardiac output, but eventually become part of the disease process itself leading to further worsening of cardiac function. These alterations can adversely contribute to electrical instability, at least in part due to the modulation of Ca2+ handling at the level of the single cardiac myocyte. The major aim of this review is to provide a definitive overview of the links and cross talk between β-adrenergic stimulation, mechanical load, and arrhythmogenesis in the setting of HF. We will initially review the role of Ca2+ in the induction of both early and delayed afterdepolarizations, the role that β-adrenergic stimulation plays in the initiation of these and how the propensity for these may be altered in HF. We will then go onto reviewing the current data with regards to the link between mechanical load and afterdepolarizations, the associated mechano-sensitivity of the ryanodine receptor and other stretch activated channels that may be associated with HF-associated arrhythmias. Furthermore, we will discuss how alterations in local Ca2+ microdomains during the remodeling process associated the HF may contribute to the increased disposition for β-adrenergic or stretch induced arrhythmogenic triggers. Finally, the potential mechanisms linking β-adrenergic stimulation and mechanical stretch will be clarified, with the aim of finding common modalities of arrhythmogenesis that could be targeted by novel therapeutic agents in the setting of HF.
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Affiliation(s)
- Daniel M Johnson
- Department of Cardiothoracic Surgery, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, Netherlands
| | - Gudrun Antoons
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, Maastricht, Netherlands
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13
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Bögeholz N, Pauls P, Dechering DG, Frommeyer G, Goldhaber JI, Pott C, Eckardt L, Müller FU, Schulte JS. Distinct Occurrence of Proarrhythmic Afterdepolarizations in Atrial Versus Ventricular Cardiomyocytes: Implications for Translational Research on Atrial Arrhythmia. Front Pharmacol 2018; 9:933. [PMID: 30186171 PMCID: PMC6111493 DOI: 10.3389/fphar.2018.00933] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Accepted: 07/30/2018] [Indexed: 12/11/2022] Open
Abstract
Background: Principal mechanisms of arrhythmia have been derived from ventricular but not atrial cardiomyocytes of animal models despite higher prevalence of atrial arrhythmia (e.g., atrial fibrillation). Due to significant ultrastructural and functional differences, a simple transfer of ventricular proneness toward arrhythmia to atrial arrhythmia is critical. The use of murine models in arrhythmia research is widespread, despite known translational limitations. We here directly compare atrial and ventricular mechanisms of arrhythmia to identify critical differences that should be considered in murine models for development of antiarrhythmic strategies for atrial arrhythmia. Methods and Results: Isolated murine atrial and ventricular myocytes were analyzed by wide field microscopy and subjected to a proarrhythmic protocol during patch-clamp experiments. As expected, the spindle shaped atrial myocytes showed decreased cell area and membrane capacitance compared to the rectangular shaped ventricular myocytes. Though delayed afterdepolarizations (DADs) could be evoked in a similar fraction of both cell types (80% of cells each), these led significantly more often to the occurrence of spontaneous action potentials (sAPs) in ventricular myocytes. Interestingly, numerous early afterdepolarizations (EADs) were observed in the majority of ventricular myocytes, but there was no EAD in any atrial myocyte (EADs per cell; atrial myocytes: 0 ± 0; n = 25/12 animals; ventricular myocytes: 1.5 [0–43]; n = 20/12 animals; p < 0.05). At the same time, the action potential duration to 90% decay (APD90) was unaltered and the APD50 even increased in atrial versus ventricular myocytes. However, the depolarizing L-type Ca2+ current (ICa) and Na+/Ca2+-exchanger inward current (INCX) were significantly smaller in atrial versus ventricular myocytes. Conclusion: In mice, atrial myocytes exhibit a substantially distinct occurrence of proarrhythmic afterdepolarizations compared to ventricular myocytes, since they are in a similar manner susceptible to DADs but interestingly seem to be protected against EADs and show less sAPs. Key factors in the generation of EADs like ICa and INCX were significantly reduced in atrial versus ventricular myocytes, which may offer a mechanistic explanation for the observed protection against EADs. These findings may be of relevance for current studies on atrial level in murine models to develop targeted strategies for the treatment of atrial arrhythmia.
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Affiliation(s)
- Nils Bögeholz
- Clinic for Cardiology II - Electrophysiology, University Hospital Münster, Münster, Germany
| | - Paul Pauls
- Clinic for Cardiology II - Electrophysiology, University Hospital Münster, Münster, Germany.,Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Dirk G Dechering
- Clinic for Cardiology II - Electrophysiology, University Hospital Münster, Münster, Germany
| | - Gerrit Frommeyer
- Clinic for Cardiology II - Electrophysiology, University Hospital Münster, Münster, Germany
| | - Joshua I Goldhaber
- Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA, United States
| | - Christian Pott
- Department of Cardiology, Schuechtermann-Klinik, Bad Rothenfelde, Germany
| | - Lars Eckardt
- Clinic for Cardiology II - Electrophysiology, University Hospital Münster, Münster, Germany
| | - Frank U Müller
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
| | - Jan S Schulte
- Institute of Pharmacology and Toxicology, University of Münster, Münster, Germany
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14
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Prajapati C, Pölönen RP, Aalto-Setälä K. Simultaneous recordings of action potentials and calcium transients from human induced pluripotent stem cell derived cardiomyocytes. Biol Open 2018; 7:bio.035030. [PMID: 29970475 PMCID: PMC6078349 DOI: 10.1242/bio.035030] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) offer a unique in vitro platform to study cardiac diseases, as they recapitulate many disease phenotypes. The membrane potential (Vm) and intracellular calcium (Ca2+) transient (CaT) are usually investigated separately, because incorporating different techniques to acquire both aspects concurrently is challenging. In this study, we recorded Vm and CaT simultaneously to understand the interrelation between these parameters in hiPSC-CMs. For this, we used a conventional patch clamp technique to record Vm, and synchronized this with a Ca2+ imaging system to acquire CaT from same hiPSC-CMs. Our results revealed that the CaT at 90% decay (CaT90) was longer than action potential (AP) duration at 90% repolarization (APD90). In addition, there was also a strong positive correlation between the different parameters of CaT and AP. The majority of delayed after depolarizations (DADs) observed in the Vm recording were also characterized by elevations in the intracellular Ca2+ level, but in some cases no abnormalities were observed in CaT. However, simultaneous fluctuations in CaT were always observed during early after depolarizations (EADs) in Vm In summary, simultaneous recording of Vm and CaT broadens the understanding of the interrelation between Vm and CaT and could be used to elucidate the mechanisms underlying arrhythmia in cardiac disease condition.
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Affiliation(s)
| | | | - Katriina Aalto-Setälä
- BioMediTech, University of Tampere, 33520 Tampere, Finland .,Faculty of Medicine and Life Science, University of Tampere, 33520 Tampere, Finland.,Heart Hospital, Tampere University Hospital, 33520 Tampere, Finland
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15
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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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16
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Liu W, Kim TY, Huang X, Liu MB, Koren G, Choi BR, Qu Z. Mechanisms linking T-wave alternans to spontaneous initiation of ventricular arrhythmias in rabbit models of long QT syndrome. J Physiol 2018; 596:1341-1355. [PMID: 29377142 DOI: 10.1113/jp275492] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 01/23/2018] [Indexed: 01/23/2023] Open
Abstract
KEY POINTS T-wave alternans (TWA) and T-wave lability (TWL) are precursors of ventricular arrhythmias in long QT syndrome; however, the mechanistic link remains to be clarified. Computer simulations show that action potential duration (APD) prolongation and slowed heart rates promote APD alternans and chaos, manifesting as TWA and TWL, respectively. Regional APD alternans and chaos can exacerbate pre-existing or induce de novo APD dispersion, which combines with enhanced ICa,L to result in premature ventricular complexes (PVCs) originating from the APD gradient region. These PVCs can directly degenerate into re-entrant arrhythmias without the need for an additional tissue substrate or further exacerbate the APD dispersion to cause spontaneous initiation of ventricular arrhythmias. Experiments conducted in transgenic long QT rabbits show that PVC alternans occurs at slow heart rates, preceding spontaneous intuition of ventricular arrhythmias. ABSTRACT T-wave alternans (TWA) and irregular beat-to-beat T-wave variability or T-wave lability (TWL), the ECG manifestations of action potential duration (APD) alternans and variability, are precursors of ventricular arrhythmias in long QT syndromes. TWA and TWL in patients tend to occur at normal heart rates and are usually potentiated by bradycardia. Whether or how TWA and TWL at normal or slow heart rates are causally linked to arrhythmogenesis remains unknown. In the present study, we used computer simulations and experiments of a transgenic rabbit model of long QT syndrome to investigate the underlying mechanisms. Computer simulations showed that APD prolongation and slowed heart rates caused early afterdepolarization-mediated APD alternans and chaos, manifesting as TWA and TWL, respectively. Regional APD alternans and chaos exacerbated pre-existing APD dispersion and, in addition, APD chaos could also induce APD dispersion de novo via chaos desynchronization. Increased APD dispersion, combined with substantially enhanced ICa,L , resulted in a tissue-scale dynamical instability that gave rise to the spontaneous occurrence of unidirectionally propagating premature ventricular complexes (PVCs) originating from the APD gradient region. These PVCs could directly degenerate into re-entrant arrhythmias without the need for an additional tissue substrate or could block the following sinus beat to result in a longer RR interval, which further exacerbated the APD dispersion giving rise to the spontaneous occurrence of ventricular arrhythmias. Slow heart rate-induced PVC alternans was observed in experiments of transgenic LQT2 rabbits under isoproterenol, which was associated with increased APD dispersion and spontaneous occurrence of ventricular arrhythmias, in agreement with the theoretical predictions.
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Affiliation(s)
- Weiqing Liu
- Department of Medicine, University of California, Los Angeles, California, USA.,School of Science, Jiangxi University of Science and Technology, Ganzhou, China
| | - Tae Yun Kim
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA
| | - Xiaodong Huang
- Department of Medicine, University of California, Los Angeles, California, USA.,Department of Physics, South China University of Technology, Guangzhou, China
| | - Michael B Liu
- Department of Medicine, University of California, Los Angeles, California, USA
| | - Gideon Koren
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA
| | - Bum-Rak Choi
- Cardiovascular Research Center, Division of Cardiology, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, Rhode Island, USA
| | - Zhilin Qu
- Department of Medicine, University of California, Los Angeles, California, USA.,Department of Biomathematics, University of California, Los Angeles, California, USA
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17
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Yang HY, Firth JM, Francis AJ, Alvarez-Laviada A, MacLeod KT. Effect of ovariectomy on intracellular Ca 2+ regulation in guinea pig cardiomyocytes. Am J Physiol Heart Circ Physiol 2017; 313:H1031-H1043. [PMID: 28778911 DOI: 10.1152/ajpheart.00249.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 07/17/2017] [Accepted: 08/02/2017] [Indexed: 01/30/2023]
Abstract
This study addressed the hypothesis that long-term deficiency of ovarian hormones after ovariectomy (OVx) alters cellular Ca2+-handling mechanisms in the heart, resulting in the formation of a proarrhythmic substrate. It also tested whether estrogen supplementation to OVx animals reverses any alterations to cardiac Ca2+ handling and rescues proarrhythmic behavior. OVx or sham operations were performed on female guinea pigs using appropriate anesthetic and analgesic regimes. Pellets containing 17β-estradiol (1 mg, 60-day release) were placed subcutaneously in selected OVx animals (OVx + E). Cardiac myocytes were enzymatically isolated, and electrophysiological measurements were conducted with a switch-clamp system. In fluo-4-loaded cells, Ca2+ transients were 20% larger, and fractional sarcoplasmic reticulum (SR) Ca2+ release was 7% greater in the OVx group compared with the sham group. Peak L-type Ca2+ current was 16% larger in OVx myocytes with channel inactivation shifting to more positive membrane potentials, creating a larger "window" current. SR Ca2+ stores were 22% greater in the OVx group, and these cells showed a higher frequency of Ca2+ sparks and waves and shorter wave-free intervals. OVx myocytes showed higher frequencies of early afterdepolarizations, and a greater percentage of these cells showed delayed afterdepolarizations after exposure to isoprenaline compared with sham myocytes. The altered Ca2+ regulation occurring in the OVx group was not observed in the OVx + E group. These findings suggest that long-term deprivation of ovarian hormones in guinea pigs lead to changes in myocyte Ca2+-handling mechanisms that are considered proarrhythmogenic. 17β-Estradiol replacement prevented these adverse effects.NEW & NOTEWORTHY Ovariectomized guinea pig cardiomyocytes have higher frequencies of Ca2+ waves, and isoprenaline-challenged cells display more early afterdepolarizations, delayed afterdepolarizations, and extra beats compared with sham myocytes. These alterations to Ca2+ regulation were not observed in myocytes from ovariectomized guinea pigs supplemented with 17β-estradiol, suggesting that ovarian hormone deficiency modifies cardiac Ca2+ regulation, potentially creating proarrhythmic substrates.
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Affiliation(s)
- Hsiang-Yu Yang
- National Heart and Lung Institute, Imperial College London, London, United Kingdom; and.,Division of Cardiovascular Surgery, Department of Surgery, Tri-Service General Hospital, National Defence Medical Center, Taipei, Taiwan
| | - Jahn M Firth
- National Heart and Lung Institute, Imperial College London, London, United Kingdom; and
| | - Alice J Francis
- National Heart and Lung Institute, Imperial College London, London, United Kingdom; and
| | - Anita Alvarez-Laviada
- National Heart and Lung Institute, Imperial College London, London, United Kingdom; and
| | - Kenneth T MacLeod
- National Heart and Lung Institute, Imperial College London, London, United Kingdom; and
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18
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Osadchii OE. Role of abnormal repolarization in the mechanism of cardiac arrhythmia. Acta Physiol (Oxf) 2017; 220 Suppl 712:1-71. [PMID: 28707396 DOI: 10.1111/apha.12902] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In cardiac patients, life-threatening tachyarrhythmia is often precipitated by abnormal changes in ventricular repolarization and refractoriness. Repolarization abnormalities typically evolve as a consequence of impaired function of outward K+ currents in cardiac myocytes, which may be caused by genetic defects or result from various acquired pathophysiological conditions, including electrical remodelling in cardiac disease, ion channel modulation by clinically used pharmacological agents, and systemic electrolyte disorders seen in heart failure, such as hypokalaemia. Cardiac electrical instability attributed to abnormal repolarization relies on the complex interplay between a provocative arrhythmic trigger and vulnerable arrhythmic substrate, with a central role played by the excessive prolongation of ventricular action potential duration, impaired intracellular Ca2+ handling, and slowed impulse conduction. This review outlines the electrical activity of ventricular myocytes in normal conditions and cardiac disease, describes classical electrophysiological mechanisms of cardiac arrhythmia, and provides an update on repolarization-related surrogates currently used to assess arrhythmic propensity, including spatial dispersion of repolarization, activation-repolarization coupling, electrical restitution, TRIaD (triangulation, reverse use dependence, instability, and dispersion), and the electromechanical window. This is followed by a discussion of the mechanisms that account for the dependence of arrhythmic vulnerability on the location of the ventricular pacing site. Finally, the review clarifies the electrophysiological basis for cardiac arrhythmia produced by hypokalaemia, and gives insight into the clinical importance and pathophysiology of drug-induced arrhythmia, with particular focus on class Ia (quinidine, procainamide) and Ic (flecainide) Na+ channel blockers, and class III antiarrhythmic agents that block the delayed rectifier K+ channel (dofetilide).
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Affiliation(s)
- O. E. Osadchii
- Department of Health Science and Technology; University of Aalborg; Aalborg Denmark
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19
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Vandersickel N, Van Nieuwenhuyse E, Seemann G, Panfilov AV. Spatial Patterns of Excitation at Tissue and Whole Organ Level Due to Early Afterdepolarizations. Front Physiol 2017; 8:404. [PMID: 28690545 PMCID: PMC5479889 DOI: 10.3389/fphys.2017.00404] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 05/29/2017] [Indexed: 01/08/2023] Open
Abstract
Early after depolarizations (EAD) occur in many pathological conditions, such as congenital or acquired channelopathies, drug induced arrhythmias, and several other situations that are associated with increased arrhythmogenicity. In this paper we present an overview of the relevant computational studies on spatial EAD dynamics in 1D, 2D, and in 3D anatomical models and discuss the relation of EADs to cardiac arrhythmias. We also discuss unsolved problems and highlight new lines of research in this area.
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Affiliation(s)
| | | | - Gunnar Seemann
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg · Bad Krozingen, Medical Center, University of FreiburgFreiburg, Germany.,Faculty of Medicine, University of FreiburgFreiburg, Germany
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20
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Edwards AG, Louch WE. Species-Dependent Mechanisms of Cardiac Arrhythmia: A Cellular Focus. CLINICAL MEDICINE INSIGHTS-CARDIOLOGY 2017; 11:1179546816686061. [PMID: 28469490 PMCID: PMC5392019 DOI: 10.1177/1179546816686061] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Accepted: 11/20/2016] [Indexed: 12/17/2022]
Abstract
Although ventricular arrhythmia remains a leading cause of morbidity and mortality, available antiarrhythmic drugs have limited efficacy. Disappointing progress in the development of novel, clinically relevant antiarrhythmic agents may partly be attributed to discrepancies between humans and animal models used in preclinical testing. However, such differences are at present difficult to predict, requiring improved understanding of arrhythmia mechanisms across species. To this end, we presently review interspecies similarities and differences in fundamental cardiomyocyte electrophysiology and current understanding of the mechanisms underlying the generation of afterdepolarizations and reentry. We specifically highlight patent shortcomings in small rodents to reproduce cellular and tissue-level arrhythmia substrate believed to be critical in human ventricle. Despite greater ease of translation from larger animal models, discrepancies remain and interpretation can be complicated by incomplete knowledge of human ventricular physiology due to low availability of explanted tissue. We therefore point to the benefits of mathematical modeling as a translational bridge to understanding and treating human arrhythmia.
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Affiliation(s)
- Andrew G Edwards
- Center for Biomedical Computing, Simula Research Laboratory, Lysaker, Norway.,Center for Cardiological Innovation, Simula Research Laboratory, Lysaker, Norway.,Department of Biosciences, University of Oslo, Oslo, Norway
| | - William E Louch
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.,K.G. Jebsen Cardiac Research Centre and Center for Heart Failure Research, University of Oslo, Oslo, Norway
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21
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Vornanen M. Electrical Excitability of the Fish Heart and Its Autonomic Regulation. FISH PHYSIOLOGY 2017. [DOI: 10.1016/bs.fp.2017.04.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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22
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Role of CaMKII and PKA in Early Afterdepolarization of Human Ventricular Myocardium Cell: A Computational Model Study. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2016; 2016:4576313. [PMID: 28053652 PMCID: PMC5178856 DOI: 10.1155/2016/4576313] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2016] [Accepted: 10/31/2016] [Indexed: 11/30/2022]
Abstract
Early afterdepolarization (EAD) plays an important role in arrhythmogenesis. Many experimental studies have reported that Ca2+/calmodulin-dependent protein kinase II (CaMKII) and β-adrenergic signaling pathway are two important regulators. In this study, we developed a modified computational model of human ventricular myocyte to investigate the combined role of CaMKII and β-adrenergic signaling pathway on the occurrence of EADs. Our simulation results showed that (1) CaMKII overexpression facilitates EADs through the prolongation of late sodium current's (INaL) deactivation progress; (2) the combined effect of CaMKII overexpression and activation of β-adrenergic signaling pathway further increases the risk of EADs, where EADs could occur at shorter cycle length (2000 ms versus 4000 ms) and lower rapid delayed rectifier K+ current (IKr) blockage (77% versus 85%). In summary, this study computationally demonstrated the combined role of CaMKII and β-adrenergic signaling pathway on the occurrence of EADs, which could be useful for searching for therapy strategies to treat EADs related arrhythmogenesis.
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23
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Huang X, Kim TY, Koren G, Choi BR, Qu Z. Spontaneous initiation of premature ventricular complexes and arrhythmias in type 2 long QT syndrome. Am J Physiol Heart Circ Physiol 2016; 311:H1470-H1484. [PMID: 27765749 DOI: 10.1152/ajpheart.00500.2016] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2016] [Accepted: 10/03/2016] [Indexed: 02/07/2023]
Abstract
The occurrence of early afterdepolarizations (EADs) and increased dispersion of repolarization are two known factors for arrhythmogenesis in long QT syndrome. However, increased dispersion of repolarization tends to suppress EADs due to the source-sink effect, and thus how the two competing factors cause initiation of arrhythmias remains incompletely understood. Here we used optical mapping and computer simulation to investigate the mechanisms underlying spontaneous initiation of arrhythmias in type 2 long QT (LQT2) syndrome. In optical mapping experiments of transgenic LQT2 rabbit hearts under isoproterenol, premature ventricular complexes (PVCs) were observed to originate from the steep spatial repolarization gradient (RG) regions and propagated unidirectionally. The same PVC behaviors were demonstrated in computer simulations of tissue models of rabbits. Depending on the heterogeneities, these PVCs could lead to either repetitive focal excitations or reentry without requiring an additional vulnerable substrate. Systematic simulations showed that cellular phase 2 EADs were either suppressed or confined to the long action potential region due to the source-sink effect. Tissue-scale phase 3 EADs and PVCs occurred due to tissue-scale dynamical instabilities caused by RG and enhanced L-type calcium current (ICa,L), occurring under both large and small RG. Presence of cellular EADs was not required but potentiated PVCs when RG was small. We also investigated how other factors affect the dynamical instabilities causing PVCs. Our main conclusion is that tissue-scale dynamical instabilities caused by RG and enhanced ICa,L give rise to both the trigger and the vulnerable substrate simultaneously for spontaneous initiation of arrhythmias in LQT2 syndrome.
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Affiliation(s)
- Xiaodong Huang
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California.,Department of Physics, South China University of Technology, Guangzhou, China; and
| | - Tae Yun Kim
- Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, Rhode Island
| | - Gideon Koren
- Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, Rhode Island
| | - Bum-Rak Choi
- Division of Cardiology, Cardiovascular Research Center, Rhode Island Hospital, Warren Alpert Medical School of Brown University, Providence, Rhode Island
| | - Zhilin Qu
- Department of Medicine (Cardiology), David Geffen School of Medicine, University of California, Los Angeles, California; .,Department of Biomathematics, David Geffen School of Medicine, University of California, Los Angeles, California
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24
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Ben Jehuda R, Barad L. Patient Specific Induced Pluripotent Stem Cell-Derived Cardiomyocytes for Drug Development and Screening In Catecholaminergic Polymorphic Ventricular Tachycardia. J Atr Fibrillation 2016; 9:1423. [PMID: 27909533 DOI: 10.4022/jafib.1423] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 07/18/2016] [Accepted: 07/19/2016] [Indexed: 12/25/2022]
Abstract
Catecholaminergic polymorphic ventricular tachycardia (CPVT), an inherited arrhythmia often leading to sudden cardiac death in children and young adults, is characterized by polymorphic/bidirectional ventricular tachycardia induced by adrenergic stimulation associated with emotionally stress or physical exercise. There are two forms of CPVT: 1. CPVT1 is caused by mutations in the RYR2 gene, encoding for ryanodine receptor type 2. CPVT1 is the most common form of CPVT in the population, and is inherited by a dominant mechanism. 2. CPVT2 is caused by mutations in the CASQ2 gene, encoding for cardiac calsequestrin 2 and is inherited by recessive mechanism. Patient-specific induced Pluripotent Stem Cells (iPSC) have the ability to differentiate into cardiomyocytes carrying the patient's genome including CPVT-linked mutations and expressing the disease phenotype in vitro at the cellular level. The potency for in vitro modeling using iPSC-derived cardiomyocytes (iPSC-CMs) has been exploited to investigate a variety of inherited diseases including cardiac arrhythmias such as CPVT. In this review we attempted to cover the majority of CPVT patient specific iPSC research studies previously published. CPVT patient-specific iPSC model enables the in vitro investigation of the molecular and cellular disease-mechanisms by the means of electrophysiologycal and Ca+2 imaging methodologies. Furthermore, this in vitro model allows the screening of various antiarrhythmic drugs, specifically for each patient, also known as "personalized medicine".
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Affiliation(s)
- Ronen Ben Jehuda
- Department of Physiology, Biophysics and Systems Biology; The Rappaport Institute; Ruth and Bruce Rappaport Faculty of Medicine; Department of Biotechnology, Technion, Haifa, Israel
| | - Lili Barad
- Department of Physiology, Biophysics and Systems Biology; The Rappaport Institute; Ruth and Bruce Rappaport Faculty of Medicine
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25
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Himeno Y, Asakura K, Cha CY, Memida H, Powell T, Amano A, Noma A. A human ventricular myocyte model with a refined representation of excitation-contraction coupling. Biophys J 2016. [PMID: 26200878 DOI: 10.1016/j.bpj.2015.06.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cardiac Ca(2+)-induced Ca(2+) release (CICR) occurs by a regenerative activation of ryanodine receptors (RyRs) within each Ca(2+)-releasing unit, triggered by the activation of L-type Ca(2+) channels (LCCs). CICR is then terminated, most probably by depletion of Ca(2+) in the junctional sarcoplasmic reticulum (SR). Hinch et al. previously developed a tightly coupled LCC-RyR mathematical model, known as the Hinch model, that enables simulations to deal with a variety of functional states of whole-cell populations of a Ca(2+)-releasing unit using a personal computer. In this study, we developed a membrane excitation-contraction model of the human ventricular myocyte, which we call the human ventricular cell (HuVEC) model. This model is a hybrid of the most recent HuVEC models and the Hinch model. We modified the Hinch model to reproduce the regenerative activation and termination of CICR. In particular, we removed the inactivated RyR state and separated the single step of RyR activation by LCCs into triggering and regenerative steps. More importantly, we included the experimental measurement of a transient rise in Ca(2+) concentrations ([Ca(2+)], 10-15 μM) during CICR in the vicinity of Ca(2+)-releasing sites, and thereby calculated the effects of the local Ca(2+) gradient on CICR as well as membrane excitation. This HuVEC model successfully reconstructed both membrane excitation and key properties of CICR. The time course of CICR evoked by an action potential was accounted for by autonomous changes in an instantaneous equilibrium open probability of couplons. This autonomous time course was driven by a core feedback loop including the pivotal local [Ca(2+)], influenced by a time-dependent decay in the SR Ca(2+) content during CICR.
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Affiliation(s)
- Yukiko Himeno
- Biosimulation Research Center, College of Life Sciences, Ritsumeikan University, Shiga, Japan
| | - Keiichi Asakura
- Biosimulation Research Center, College of Life Sciences, Ritsumeikan University, Shiga, Japan; Nippon Shinyaku Co., Ltd., Kyoto, Japan
| | - Chae Young Cha
- Biosimulation Research Center, College of Life Sciences, Ritsumeikan University, Shiga, Japan; Oxford Centre for Diabetes Endocrinology and Metabolism, University of Oxford, Oxford, UK
| | - Hiraku Memida
- Biosimulation Research Center, College of Life Sciences, Ritsumeikan University, Shiga, Japan
| | - Trevor Powell
- Department of Pharmacology, University of Oxford, Oxford, UK
| | - Akira Amano
- Biosimulation Research Center, College of Life Sciences, Ritsumeikan University, Shiga, Japan
| | - Akinori Noma
- Biosimulation Research Center, College of Life Sciences, Ritsumeikan University, Shiga, Japan.
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Markandeya YS, Kamp TJ. Rational strategy to stop arrhythmias: Early afterdepolarizations and L-type Ca2+ current. ACTA ACUST UNITED AC 2016; 145:475-9. [PMID: 26009542 PMCID: PMC4442792 DOI: 10.1085/jgp.201511429] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Affiliation(s)
- Yogananda S Markandeya
- Department of Medicine and Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705 Department of Medicine and Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705
| | - Timothy J Kamp
- Department of Medicine and Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705 Department of Medicine and Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI 53705
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27
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Song Z, Ko CY, Nivala M, Weiss JN, Qu Z. Calcium-voltage coupling in the genesis of early and delayed afterdepolarizations in cardiac myocytes. Biophys J 2016; 108:1908-21. [PMID: 25902431 DOI: 10.1016/j.bpj.2015.03.011] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Revised: 03/04/2015] [Accepted: 03/10/2015] [Indexed: 02/01/2023] Open
Abstract
Early afterdepolarizations (EADs) and delayed afterdepolarizations (DADs) are voltage oscillations known to cause cardiac arrhythmias. EADs are mainly driven by voltage oscillations in the repolarizing phase of the action potential (AP), while DADs are driven by spontaneous calcium (Ca) release during diastole. Because voltage and Ca are bidirectionally coupled, they modulate each other's behaviors, and new AP and Ca cycling dynamics can emerge from this coupling. In this study, we performed computer simulations using an AP model with detailed spatiotemporal Ca cycling incorporating stochastic openings of Ca channels and ryanodine receptors to investigate the effects of Ca-voltage coupling on EAD and DAD dynamics. Simulations were complemented by experiments in mouse ventricular myocytes. We show that: 1) alteration of the Ca transient due to increased ryanodine receptor leakiness and/or sarco/endoplasmic reticulum Ca ATPase activity can either promote or suppress EADs due to the complex effects of Ca on ionic current properties; 2) spontaneous Ca waves also exhibit complex effects on EADs, but cannot induce EADs of significant amplitude without the participation of ICa,L; 3) lengthening AP duration and the occurrence of EADs promote DADs by increasing intracellular Ca loading, and two mechanisms of DADs are identified, i.e., Ca-wave-dependent and Ca-wave-independent; and 4) Ca-voltage coupling promotes complex EAD patterns such as EAD alternans that are not observed for solely voltage-driven EADs. In conclusion, Ca-voltage coupling combined with the nonlinear dynamical behaviors of voltage and Ca cycling play a key role in generating complex EAD and DAD dynamics observed experimentally in cardiac myocytes, whose mechanisms are complex but analyzable.
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Affiliation(s)
- Zhen Song
- Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Medicine (Cardiology), University of California, Los Angeles, California
| | - Christopher Y Ko
- Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Medicine (Cardiology), University of California, Los Angeles, California
| | - Michael Nivala
- Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Medicine (Cardiology), University of California, Los Angeles, California
| | - James N Weiss
- Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Medicine (Cardiology), University of California, Los Angeles, California; Department of Physiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Zhilin Qu
- Cardiovascular Research Laboratory, University of California, Los Angeles, California; Department of Medicine (Cardiology), University of California, Los Angeles, California.
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28
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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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29
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Tikkanen E, Haverinen J, Egginton S, Hassinen M, Vornanen M. Effects of prolonged anoxia on electrical activity of the heart in Crucian carp (Carassius carassius). J Exp Biol 2016; 220:445-454. [DOI: 10.1242/jeb.145177] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 11/15/2016] [Indexed: 01/08/2023]
Abstract
The effects of sustained anoxia on cardiac electrical excitability were examined in the anoxia-tolerant Crucian carp (Carassius carassius). The electrocardiogram (ECG) and expression of excitation-contraction coupling genes were studied in fish acclimatised to normoxia in summer (+18°C) or winter (+2°C), and in winter fish after 1, 3 and 6 weeks of anoxia. Anoxia induced a sustained bradycardia from a heart rate of 10.3±0.77 to 4.1±0.29 bpm (P<0.05) after 5 weeks, and heart rate slowly recovered to control levels when oxygen was restored. Heart rate variability greatly increased under anoxia, and completely recovered under re-oxygenation. The RT interval increased from 2.8±0.34 s in normoxia to 5.8±0.44 s under anoxia (P<0.05), which reflects a doubling of the ventricular action potential (AP) duration. Acclimatisation to winter induced extensive changes in gene expression relative to summer-acclimatised fish, including depression in those coding for the sarcoplasmic reticulum calcium pump (Serca2-q2) and ATP-sensitive K+ channels (Kir6.2) (P<0.05). Genes of delayed rectifier K+ (kcnh6) and Ca2+ channels (cacna1c) were up-regulated in winter fish (P<0.05). In contrast, the additional challenge of anoxia caused only minor changes in gene expression, e.g. depressed expression of Kir2.2b K+ channel gene (kcnj12b), whereas expression of Ca2+ (cacna1a, -c and –g) and Na+ channel genes (scn4a and scn5a) were not affected. These data suggest that low temperature pre-conditions the Crucian carp heart for winter anoxia, whereas sustained anoxic bradycardia and prolongation of AP duration are directly induced by oxygen shortage without major changes in gene expression.
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Affiliation(s)
- Elisa Tikkanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
| | - Jaakko Haverinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
| | | | - Minna Hassinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
| | - Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
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30
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Bögeholz N, Pauls P, Bauer BK, Schulte JS, Dechering DG, Frommeyer G, Kirchhefer U, Goldhaber JI, Müller FU, Eckardt L, Pott C. Suppression of Early and Late Afterdepolarizations by Heterozygous Knockout of the Na+/Ca2+ Exchanger in a Murine Model. Circ Arrhythm Electrophysiol 2015; 8:1210-8. [PMID: 26338832 DOI: 10.1161/circep.115.002927] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2015] [Accepted: 08/13/2015] [Indexed: 11/16/2022]
Abstract
BACKGROUND The Na(+)/Ca(2+) exchanger (NCX) has been implied to cause arrhythmias. To date, information on the role of NCX in arrhythmogenesis derived from models with increased NCX expression, hypertrophy, and heart failure. Furthermore, the exact mechanism by which NCX exerts its potentially proarrhythmic effect, ie, by promoting early afterdepolarization (EAD) or delayed afterdepolarization (DAD) or both, is unknown. METHODS AND RESULTS We investigated isolated cardiomyocytes from a murine model with heterozygous knockout of NCX (hetKO) using the patch clamp and Ca(2+) imaging techniques. Action potential duration was shorter in hetKO with IKtot not being increased. The rate of spontaneous Ca(2+) release events and the rate of DADs were unaltered; however, DADs had lower amplitude in hetKO. A DAD triggered a spontaneous action potential significantly less often in hetKO when compared with wild-type. The occurrence of EADs was also drastically reduced in hetKO. ICa activity was reduced in hetKO, an effect that was abolished in the presence of the Ca(2+) buffer BAPTA. CONCLUSIONS Genetic suppression of NCX reduces both EADs and DADs. The following molecular mechanisms apply: (1) Although the absolute number of DADs is unaffected, an impaired translation of DADs into spontaneous action potentials results from a reduced DAD amplitude. (2) EADs are reduced in absolute number of occurrence, which is presumably a consequence of shortened action potential duration because of reduced NCX activity but also reduced ICa the latter possibly being caused by a direct modulation of Ca(2+)-dependent ICa inhibition by reduced NCX activity. This is the first study to demonstrate that genetic inhibition of NCX protects against afterdepolarizations and to investigate the underlying mechanisms.
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Affiliation(s)
- Nils Bögeholz
- From the Division of Electrophysiology, Department of Cardiovascular Medicine (N.B., P.P., B.K.B., D.G.D., G.F., L.E., C.P.) and Institute of Pharmacology and Toxicology (P.P., B.K.B., J.S.S., U.K., F.U.M.), University Hospital Münster, Münster, Germany; and Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (J.I.G.).
| | - Paul Pauls
- From the Division of Electrophysiology, Department of Cardiovascular Medicine (N.B., P.P., B.K.B., D.G.D., G.F., L.E., C.P.) and Institute of Pharmacology and Toxicology (P.P., B.K.B., J.S.S., U.K., F.U.M.), University Hospital Münster, Münster, Germany; and Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (J.I.G.)
| | - B Klemens Bauer
- From the Division of Electrophysiology, Department of Cardiovascular Medicine (N.B., P.P., B.K.B., D.G.D., G.F., L.E., C.P.) and Institute of Pharmacology and Toxicology (P.P., B.K.B., J.S.S., U.K., F.U.M.), University Hospital Münster, Münster, Germany; and Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (J.I.G.)
| | - Jan S Schulte
- From the Division of Electrophysiology, Department of Cardiovascular Medicine (N.B., P.P., B.K.B., D.G.D., G.F., L.E., C.P.) and Institute of Pharmacology and Toxicology (P.P., B.K.B., J.S.S., U.K., F.U.M.), University Hospital Münster, Münster, Germany; and Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (J.I.G.)
| | - Dirk G Dechering
- From the Division of Electrophysiology, Department of Cardiovascular Medicine (N.B., P.P., B.K.B., D.G.D., G.F., L.E., C.P.) and Institute of Pharmacology and Toxicology (P.P., B.K.B., J.S.S., U.K., F.U.M.), University Hospital Münster, Münster, Germany; and Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (J.I.G.)
| | - Gerrit Frommeyer
- From the Division of Electrophysiology, Department of Cardiovascular Medicine (N.B., P.P., B.K.B., D.G.D., G.F., L.E., C.P.) and Institute of Pharmacology and Toxicology (P.P., B.K.B., J.S.S., U.K., F.U.M.), University Hospital Münster, Münster, Germany; and Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (J.I.G.)
| | - Uwe Kirchhefer
- From the Division of Electrophysiology, Department of Cardiovascular Medicine (N.B., P.P., B.K.B., D.G.D., G.F., L.E., C.P.) and Institute of Pharmacology and Toxicology (P.P., B.K.B., J.S.S., U.K., F.U.M.), University Hospital Münster, Münster, Germany; and Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (J.I.G.)
| | - Joshua I Goldhaber
- From the Division of Electrophysiology, Department of Cardiovascular Medicine (N.B., P.P., B.K.B., D.G.D., G.F., L.E., C.P.) and Institute of Pharmacology and Toxicology (P.P., B.K.B., J.S.S., U.K., F.U.M.), University Hospital Münster, Münster, Germany; and Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (J.I.G.)
| | - Frank U Müller
- From the Division of Electrophysiology, Department of Cardiovascular Medicine (N.B., P.P., B.K.B., D.G.D., G.F., L.E., C.P.) and Institute of Pharmacology and Toxicology (P.P., B.K.B., J.S.S., U.K., F.U.M.), University Hospital Münster, Münster, Germany; and Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (J.I.G.)
| | - Lars Eckardt
- From the Division of Electrophysiology, Department of Cardiovascular Medicine (N.B., P.P., B.K.B., D.G.D., G.F., L.E., C.P.) and Institute of Pharmacology and Toxicology (P.P., B.K.B., J.S.S., U.K., F.U.M.), University Hospital Münster, Münster, Germany; and Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (J.I.G.)
| | - Christian Pott
- From the Division of Electrophysiology, Department of Cardiovascular Medicine (N.B., P.P., B.K.B., D.G.D., G.F., L.E., C.P.) and Institute of Pharmacology and Toxicology (P.P., B.K.B., J.S.S., U.K., F.U.M.), University Hospital Münster, Münster, Germany; and Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (J.I.G.)
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31
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Zimik S, Vandersickel N, Nayak AR, Panfilov AV, Pandit R. A Comparative Study of Early Afterdepolarization-Mediated Fibrillation in Two Mathematical Models for Human Ventricular Cells. PLoS One 2015; 10:e0130632. [PMID: 26125185 PMCID: PMC4488347 DOI: 10.1371/journal.pone.0130632] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Accepted: 05/21/2015] [Indexed: 02/06/2023] Open
Abstract
Early afterdepolarizations (EADs), which are abnormal oscillations of the membrane potential at the plateau phase of an action potential, are implicated in the development of cardiac arrhythmias like Torsade de Pointes. We carry out extensive numerical simulations of the TP06 and ORd mathematical models for human ventricular cells with EADs. We investigate the different regimes in both these models, namely, the parameter regimes where they exhibit (1) a normal action potential (AP) with no EADs, (2) an AP with EADs, and (3) an AP with EADs that does not go back to the resting potential. We also study the dependence of EADs on the rate of at which we pace a cell, with the specific goal of elucidating EADs that are induced by slow or fast rate pacing. In our simulations in two- and three-dimensional domains, in the presence of EADs, we find the following wave types: (A) waves driven by the fast sodium current and the L-type calcium current (Na-Ca-mediated waves); (B) waves driven only by the L-type calcium current (Ca-mediated waves); (C) phase waves, which are pseudo-travelling waves. Furthermore, we compare the wave patterns of the various wave-types (Na-Ca-mediated, Ca-mediated, and phase waves) in both these models. We find that the two models produce qualitatively similar results in terms of exhibiting Na-Ca-mediated wave patterns that are more chaotic than those for the Ca-mediated and phase waves. However, there are quantitative differences in the wave patterns of each wave type. The Na-Ca-mediated waves in the ORd model show short-lived spirals but the TP06 model does not. The TP06 model supports more Ca-mediated spirals than those in the ORd model, and the TP06 model exhibits more phase-wave patterns than does the ORd model.
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Affiliation(s)
- Soling Zimik
- Department of Physics, Centre for Condensed Matter Theory, Indian Institute of Science, Bangalore, Karnataka, India
| | - Nele Vandersickel
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - Alok Ranjan Nayak
- Department of Physics, Centre for Condensed Matter Theory, Indian Institute of Science, Bangalore, Karnataka, India
- Robert Bosch Centre for Cyber Physical Systems, Indian Institute of Science, Bangalore, Karnataka, India
| | - Alexander V. Panfilov
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
- Moscow Institute of Physics and Technology (State University), Dolgoprudny, Moscow Region, Russia
| | - Rahul Pandit
- Department of Physics, Centre for Condensed Matter Theory, Indian Institute of Science, Bangalore, Karnataka, India
- Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore, Karnataka, India
- * E-mail:
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32
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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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Assessment of anti-arrhythmic activity of antipsychotic drugs in an animal model: Influence of non-cardiac α1-adrenergic receptors. Eur J Pharmacol 2015; 748:10-7. [DOI: 10.1016/j.ejphar.2014.12.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 11/28/2014] [Accepted: 12/10/2014] [Indexed: 01/09/2023]
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34
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Vandersickel N, Kazbanov IV, Defauw A, Pijnappels DA, Panfilov AV. Decreased repolarization reserve increases defibrillation threshold by favoring early afterdepolarizations in an in silico model of human ventricular tissue. Heart Rhythm 2015; 12:1088-96. [PMID: 25623180 DOI: 10.1016/j.hrthm.2015.01.033] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Indexed: 11/27/2022]
Affiliation(s)
- Nele Vandersickel
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium.
| | - Ivan V Kazbanov
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - Arne Defauw
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - Daniël A Pijnappels
- Department of Cardiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Alexander V Panfilov
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium; Laboratory of Mathematical Modeling in Physiology and Medicine, Ural Federal University, Ekaterinburg, Russia
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35
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EAD and DAD mechanisms analyzed by developing a new human ventricular cell model. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 116:11-24. [PMID: 25192800 DOI: 10.1016/j.pbiomolbio.2014.08.008] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2014] [Accepted: 08/09/2014] [Indexed: 12/31/2022]
Abstract
It has long been suggested that the Ca(2+)-mechanisms are largely involved in generating the early afterdepolarization (EAD) as well as the delayed afterdepolarization (DAD). This view was examined in a quantitative manner by applying the lead potential analysis to a new human ventricular cell model. In this ventricular cell model, the tight coupled LCC-RyR model (CaRU) based on local control theory (Hinch et al. 2004) and ion channel models mostly based on human electrophysiological data were included to reproduce realistic Ca(2+) dynamics as well as the membrane excitation. Simultaneously, the Ca(2+) accumulation near the Ca(2+) releasing site was incorporated as observed in real cardiac myocytes. The maximum rate of ventricular repolarization (-1.02 mV/ms) is due to IK1 (-0.55 mV/ms) and the rest is provided nearly equally by INCX (-0.20 mV/ms), INaL (-0.16 mV/ms) and INaT (-0.13 mV/ms). These INaL and INaT components are due to closure of the voltage gate, which remains partially open during the plateau potential. DADs could be evoked by applying high-frequency stimulations supplemented by a partial Na(+)/K(+) pump inhibition, or by a microinjection of Ca(2+). EADs was evoked by retarding the inactivation of INaL. The lead potential (VL) analysis revealed that IK1 and IKr played the primary role to reverse the AP repolarization to depolarizing limb of EAD. ICaL and INCX amplified EAD, while the remaining currents partially antagonized dVL/dt. The maximum rate of rise of EAD was attributable to the rapid activation of both ICaL (45.5%) and INCX (54.5%).
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Nordin C. The proarrhythmic effect of hypoglycemia: evidence for increased risk from ischemia and bradycardia. Acta Diabetol 2014; 51:5-14. [PMID: 24212718 DOI: 10.1007/s00592-013-0528-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 10/24/2013] [Indexed: 12/13/2022]
Abstract
Hypoglycemia increases the risk for both overall and sudden death. At a cellular level, hypoglycemia causes alterations in the physiology of myocardial tissue that are identical to proarrhythmic medications. Reduced serum glucose blocks the repolarizing K(+) channel HERG, which leads to action potential and QT prolongation and is uniformly associated with risk for torsades de pointes ventricular tachycardia. The sympathetic response induced by hypoglycemia also increases the risk of arrhythmias from Ca(2+) overload, which occur with sympathomimetic medications and excessive beta adrenergic stimulation. Thus, hypoglycemia can be considered a proarrhythmic event. This review focuses on emerging evidence for two other important changes induced by hypoglycemia that promote arrhythmias: ischemia and bradycardia. Studies of patients with "insulin shock" therapy from the early twentieth century and other more recent data strongly suggest that hypoglycemia can cause ischemia of myocardial tissue, both in association with coronary artery obstructions and by cellular mechanisms. Ischemia induces multiple proarrhythmic responses. Since ischemia itself reduces the possibility of using energy substrates other than glucose, hypoglycemia may generate positive feedback for electrophyisologic destabilization. Recent studies also show that hypoglycemia can cause bradycardia and heart block. Bradycardia is known to cause action potential prolongation and potentiate the development of torsades de pointes, particularly with low-serum K(+) which can be induced by hypoglycemic episodes. Thus, hypoglycemia-induced bradycardia may also create a dynamic, positive feedback for the development of arrhythmias and sudden death. These studies further support the hypothesis that hypoglycemia is a proarrhythmic event.
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Affiliation(s)
- Charles Nordin
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA,
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Vandersickel N, Kazbanov IV, Nuitermans A, Weise LD, Pandit R, Panfilov AV. A study of early afterdepolarizations in a model for human ventricular tissue. PLoS One 2014; 9:e84595. [PMID: 24427289 PMCID: PMC3888406 DOI: 10.1371/journal.pone.0084595] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Accepted: 11/15/2013] [Indexed: 12/13/2022] Open
Abstract
Sudden cardiac death is often caused by cardiac arrhythmias. Recently, special attention has been given to a certain arrhythmogenic condition, the long-QT syndrome, which occurs as a result of genetic mutations or drug toxicity. The underlying mechanisms of arrhythmias, caused by the long-QT syndrome, are not fully understood. However, arrhythmias are often connected to special excitations of cardiac cells, called early afterdepolarizations (EADs), which are depolarizations during the repolarizing phase of the action potential. So far, EADs have been studied mainly in isolated cardiac cells. However, the question on how EADs at the single-cell level can result in fibrillation at the tissue level, especially in human cell models, has not been widely studied yet. In this paper, we study wave patterns that result from single-cell EAD dynamics in a mathematical model for human ventricular cardiac tissue. We induce EADs by modeling experimental conditions which have been shown to evoke EADs at a single-cell level: by an increase of L-type Ca currents and a decrease of the delayed rectifier potassium currents. We show that, at the tissue level and depending on these parameters, three types of abnormal wave patterns emerge. We classify them into two types of spiral fibrillation and one type of oscillatory dynamics. Moreover, we find that the emergent wave patterns can be driven by calcium or sodium currents and we find phase waves in the oscillatory excitation regime. From our simulations we predict that arrhythmias caused by EADs can occur during normal wave propagation and do not require tissue heterogeneities. Experimental verification of our results is possible for experiments at the cell-culture level, where EADs can be induced by an increase of the L-type calcium conductance and by the application of I blockers, and the properties of the emergent patterns can be studied by optical mapping of the voltage and calcium.
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Affiliation(s)
- Nele Vandersickel
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
- * E-mail:
| | - Ivan V. Kazbanov
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
| | - Anita Nuitermans
- Department of Theoretical Biology, Utrecht University, Utrecht, The Netherlands
| | - Louis D. Weise
- Department of Physics and Astronomy, Ghent University, Ghent, Belgium
- Department of Theoretical Biology, Utrecht University, Utrecht, The Netherlands
| | - Rahul Pandit
- Center for Condensed Matter Theory - Department of Physics, Indian Institute of Science, Bangalore, India
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Heijman J, Zaza A, Johnson DM, Rudy Y, Peeters RLM, Volders PGA, Westra RL. Determinants of beat-to-beat variability of repolarization duration in the canine ventricular myocyte: a computational analysis. PLoS Comput Biol 2013; 9:e1003202. [PMID: 23990775 PMCID: PMC3749940 DOI: 10.1371/journal.pcbi.1003202] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Accepted: 06/10/2013] [Indexed: 12/26/2022] Open
Abstract
Beat-to-beat variability of repolarization duration (BVR) is an intrinsic characteristic of cardiac function and a better marker of proarrhythmia than repolarization prolongation alone. The ionic mechanisms underlying baseline BVR in physiological conditions, its rate dependence, and the factors contributing to increased BVR in pathologies remain incompletely understood. Here, we employed computer modeling to provide novel insights into the subcellular mechanisms of BVR under physiological conditions and during simulated drug-induced repolarization prolongation, mimicking long-QT syndromes type 1, 2, and 3. We developed stochastic implementations of 13 major ionic currents and fluxes in a model of canine ventricular-myocyte electrophysiology. Combined stochastic gating of these components resulted in short- and long-term variability, consistent with experimental data from isolated canine ventricular myocytes. The model indicated that the magnitude of stochastic fluctuations is rate dependent due to the rate dependence of action-potential (AP) duration (APD). This process (the “active” component) and the intrinsic nonlinear relationship between membrane current and APD (“intrinsic component”) contribute to the rate dependence of BVR. We identified a major role in physiological BVR for stochastic gating of the persistent Na+ current (INa) and rapidly activating delayed-rectifier K+ current (IKr). Inhibition of IKr or augmentation of INa significantly increased BVR, whereas subsequent β-adrenergic receptor stimulation reduced it, similar to experimental findings in isolated myocytes. In contrast, β-adrenergic stimulation increased BVR in simulated long-QT syndrome type 1. In addition to stochastic channel gating, AP morphology, APD, and beat-to-beat variations in Ca2+ were found to modulate single-cell BVR. Cell-to-cell coupling decreased BVR and this was more pronounced when a model cell with increased BVR was coupled to a model cell with normal BVR. In conclusion, our results provide new insights into the ionic mechanisms underlying BVR and suggest that BVR reflects multiple potentially proarrhythmic parameters, including increased ion-channel stochasticity, prolonged APD, and abnormal Ca2+ handling. Every heartbeat has an electrical recovery (repolarization) interval that varies in duration from beat to beat. Excessive beat-to-beat variability of repolarization duration has been shown to be a risk marker of potentially fatal heart-rhythm disorders, but the contributing subcellular mechanisms remain incompletely understood. Computational models have greatly enhanced our understanding of several basic electrophysiological mechanisms. We developed a detailed computer model of the ventricular myocyte that can simulate beat-to-beat changes in repolarization duration by taking into account stochastic changes in the opening and closing of individual ion channels responsible for all main ion currents. The model accurately reproduced experimental data from isolated myocytes under both physiological and pathological conditions. Using the model, we identified several mechanisms contributing to repolarization variability, including stochastic gating of ion channels, duration and morphology of the repolarization phase, and intracellular calcium handling, thereby providing insights into its basis as a proarrhythmic marker. Our computer model provides a detailed framework to study the dynamics of cardiac electrophysiology and arrhythmias.
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Affiliation(s)
- Jordi Heijman
- Department of Knowledge Engineering, Maastricht University, Maastricht, The Netherlands
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, The Netherlands
- Institute of Pharmacology, Faculty of Medicine, University Duisburg-Essen, Essen, Germany
| | - Antonio Zaza
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano, Italy
| | - Daniel M. Johnson
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, The Netherlands
| | - Yoram Rudy
- Cardiac Bioelectricity and Arrhythmia Center, Washington University in St. Louis, St. Louis, Missouri, United States of America
| | - Ralf L. M. Peeters
- Department of Knowledge Engineering, Maastricht University, Maastricht, The Netherlands
| | - Paul G. A. Volders
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Centre, Maastricht, The Netherlands
- * E-mail: (PGAV); (RLW)
| | - Ronald L. Westra
- Department of Knowledge Engineering, Maastricht University, Maastricht, The Netherlands
- * E-mail: (PGAV); (RLW)
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Orchard CH, Bryant SM, James AF. Do t-tubules play a role in arrhythmogenesis in cardiac ventricular myocytes? J Physiol 2013; 591:4141-7. [PMID: 23652596 DOI: 10.1113/jphysiol.2013.254540] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The transverse (t-) tubules of mammalian ventricular myocytes are invaginations of the surface membrane. The function of many of the key proteins involved in excitation-contraction coupling is located predominantly at the t-tubules, which thus form a Ca(2+)-handling micro-environment that is central to the normal rapid activation and relaxation of the ventricular myocyte. Although cellular arrhythmogenesis shares many ion flux pathways with normal excitation-contraction coupling, the role of the t-tubules in such arrhythmogenesis has not previously been considered. In this brief review we consider how the location and co-location of proteins at the t-tubules may contribute to the generation of arrhythmogenic delayed and early afterdepolarisations, and how the loss of t-tubules that occurs during heart failure may alter the generation of such arrhythmias, as well as contributing to other types of arrhythmia as a result of changes of electrical heterogeneity within the whole heart.
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Affiliation(s)
- C H Orchard
- C. H. Orchard: University of Bristol, School of Physiology and Pharmacology, Medical Sciences Building, University Walk, Bristol BS8 1TD, UK.
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Lee HC, Rudy Y, Po-Yuan P, Sheu SH, Chang JG, Cui J. Modulation of KCNQ1 alternative splicing regulates cardiac IKs and action potential repolarization. Heart Rhythm 2013; 10:1220-8. [PMID: 23608591 DOI: 10.1016/j.hrthm.2013.04.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Indexed: 10/26/2022]
Abstract
BACKGROUND Slow delayed-rectifier potassium current (IKs) channels, made of the pore-forming KCNQ1 and auxiliary KCNE1 subunits, play a key role in determining action potential duration (APD) in cardiac myocytes. The consequences of drug-induced KCNQ1 splice alteration remain unknown. OBJECTIVE To study the modulation of KCNQ1 alternative splicing by amiloride and the consequent changes in IKs and action potentials (APs) in ventricular myocytes. METHODS Canine endocardial, midmyocardial, and epicardial ventricular myocytes were isolated. Levels of KCNQ1a and KCNQ1b as well as a series of splicing factors were quantified by using the reverse transcriptase-polymerase chain reaction and Western blot. The effect of amiloride-induced changes in the KCNQ1b/total KCNQ1 ratio on AP was measured by using whole-cell patch clamp with and without isoproterenol. RESULTS With 50 μmol/L of amiloride for 6 hours, KCNQ1a at transcriptional and translational levels increased in midmyocardial myocytes but decreased in endo- and epicardial myocytes. Likewise, changes in splicing factors in midmyocardial were opposite to that in endo- and epicardial myocytes. In midmyocardial myocytes amiloride shortened APD and decreased isoproterenol-induced early afterdepolarizations significantly. The same amiloride-induced effects were demonstrated by using human ventricular myocyte model for AP simulations under beta-adrenergic stimulation. Moreover, amiloride reduced the transmural dispersion of repolarization in pseudo-electrocardiogram. CONCLUSIONS Amiloride regulates IKs and APs with transmural differences and reduces arrhythmogenicity through the modulation of KCNQ1 splicing. We suggested that the modulation of KCNQ1 splicing may help prevent arrhythmia.
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Affiliation(s)
- Hsiang-Chun Lee
- Department of Biomedical Engineering, Cardiac Bioelectricity and Arrhythmia Center, Washington University in St. Louis, St Louis, Missouri 63130-4899, USA
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Bourgonje VJA, Vos MA, Ozdemir S, Doisne N, Acsai K, Varro A, Sztojkov-Ivanov A, Zupko I, Rauch E, Kattner L, Bito V, Houtman M, van der Nagel R, Beekman JD, van Veen TAB, Sipido KR, Antoons G. Combined Na(+)/Ca(2+) exchanger and L-type calcium channel block as a potential strategy to suppress arrhythmias and maintain ventricular function. Circ Arrhythm Electrophysiol 2013; 6:371-9. [PMID: 23515266 DOI: 10.1161/circep.113.000322] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND L-type calcium channel (LTCC) and Na(+)/Ca(2+) exchanger (NCX) have been implicated in repolarization-dependent arrhythmias, but also modulate calcium and contractility. Although LTCC inhibition is negative inotropic, NCX inhibition has the opposite effect. Combined block may, therefore, offer an advantage for hemodynamics and antiarrhythmic efficiency, particularly in diseased hearts. In a model of proarrhythmia, the dog with chronic atrioventricular block, we investigated whether combined inhibition of NCX and LTCC with SEA-0400 is effective against dofetilide-induced torsade de pointes arrhythmias (TdP), while maintaining calcium homeostasis and hemodynamics. METHODS AND RESULTS Left ventricular pressure (LVP) and ECG were monitored during infusion of SEA-0400 and verapamil in anesthetized dogs. Different doses were tested against dofetilide-induced TdP in chronic atrioventricular block dogs. In ventricular myocytes, effects of SEA-0400 were tested on action potentials, calcium transients, and early afterdepolarizations. In cardiomyocytes, SEA-0400 (1 μmol/L) blocked 66±3% of outward NCX, 50±2% of inward NCX, and 33±9% of LTCC current. SEA-0400 had no effect on systolic calcium, but slowed relaxation, despite action potential shortening, and increased diastolic calcium. SEA-0400 stabilized dofetilide-induced lability of repolarization and suppressed early afterdepolarizations. In vivo, SEA-0400 (0.4 and 0.8 mg/kg) had no effect on left ventricular pressure and suppressed dofetilide-induced TdPs dose dependently. Verapamil (0.3 mg/kg) also inhibited TdP, but caused a 15±8% drop of left ventricular pressure. A lower dose of verapamil without effects on left ventricular pressure (0.06 mg/kg) was not antiarrhythmic. CONCLUSIONS In chronic atrioventricular block dogs, SEA-0400 treatment is effective against TdP. Unlike specific inhibition of LTCC, combined NCX and LTCC inhibition has no negative effects on cardiac hemodynamics.
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Affiliation(s)
- Vincent J A Bourgonje
- Department of Medical Physiology, Division of Heart and Lungs, University Medical Center Utrecht, University of Utrecht, Utrecht, The Netherlands
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Xie Y, Grandi E, Puglisi JL, Sato D, Bers DM. β-adrenergic stimulation activates early afterdepolarizations transiently via kinetic mismatch of PKA targets. J Mol Cell Cardiol 2013; 58:153-61. [PMID: 23481579 DOI: 10.1016/j.yjmcc.2013.02.009] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Revised: 01/25/2013] [Accepted: 02/11/2013] [Indexed: 02/04/2023]
Abstract
Sympathetic stimulation regulates cardiac excitation-contraction coupling in hearts but can also trigger ventricular arrhythmias caused by early afterdepolarizations (EADs) in pathological conditions. Isoproterenol (ISO) stimulation can transiently cause EADs which could result from differential kinetics of L-type Ca current (ICaL) vs. delayed rectifier potassium current (IKs) effects, but multiple PKA targets complicate mechanistic analysis. Utilizing a biophysically detailed model integrating Ca and β-adrenergic signaling, we investigate how different phosphorylation kinetics and targets influence β-adrenergic-induced transient EADs. We found that: 1) The faster time course of ICaL vs. IKs increases recapitulates experimentally observed ISO-induced transient EADs (which are due to ICaL reactivation). These EADs disappear at steady state ISO and do not occur during more gradual ISO application. 2) This ICaL vs. IKs kinetic mismatch with ISO can also induce transient EADs due to spontaneous sarcoplasmic reticulum (SR) Ca release and Na/Ca exchange current. The increased ICaL, SR Ca uptake and action potential duration (APD) raise SR Ca to cause spontaneous SR Ca release, but eventual IKs activation and APD shortening abolish these EADs. 3) Phospholemman (PLM) phosphorylation decreases both types of EADs by increasing outward Na/K-ATPase current (INaK) for ICaL-mediated EADs, and reducing intracellular Na and Ca loading for SR Ca-release-mediated EADs. Slowing PLM phosphorylation kinetics abolishes this protective effect. 4) Blocking phospholamban (PLB) phosphorylation has little effect on ICaL-mediated transient EADs, but abolishes SR Ca-release-mediated transient EADs by limiting SR Ca loading. 5) RyR phosphorylation has little effect on either transient EAD type. Our study emphasizes the importance of understanding non-steady state kinetics of several systems in mediating β-adrenergic-induced EADs and arrhythmias.
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Affiliation(s)
- Yuanfang Xie
- Department of Pharmacology, University of California Davis, Davis, CA, USA
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43
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Electrical storm: recent pathophysiological insights and therapeutic consequences. Basic Res Cardiol 2013; 108:336. [DOI: 10.1007/s00395-013-0336-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Revised: 01/29/2013] [Accepted: 02/04/2013] [Indexed: 01/01/2023]
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Stokke MK, Tovsrud N, Louch WE, Øyehaug L, Hougen K, Sejersted OM, Swift F, Sjaastad I. I(CaL) inhibition prevents arrhythmogenic Ca(2+) waves caused by abnormal Ca(2+) sensitivity of RyR or SR Ca(2+) accumulation. Cardiovasc Res 2013; 98:315-25. [PMID: 23417043 DOI: 10.1093/cvr/cvt037] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AIMS Arrhythmogenic Ca(2+) waves result from uncontrolled Ca(2+) release from the sarcoplasmic reticulum (SR) that occurs with increased Ca(2+) sensitivity of the ryanodine receptor (RyR) or excessive Ca(2+) accumulation during β-adrenergic stimulation. We hypothesized that inhibition of the L-type Ca(2+) current (I(CaL)) could prevent such Ca(2+) waves in both situations. METHODS AND RESULTS Ca(2+) waves were induced in mouse left ventricular cardiomyocytes by isoproterenol combined with caffeine to increase RyR Ca(2+) sensitivity. I(CaL) inhibition by verapamil (0.5 µM) reduced Ca(2+) wave probability in cardiomyocytes during electrostimulation, and during a 10 s rest period after ceasing stimulation. A separate type of Ca(2+) release events occurred during the decay phase of the Ca(2+) transient and was not prevented by verapamil. Verapamil decreased Ca(2+) spark frequency, but not in permeabilized cells, indicating that this was not due to direct effects on RyR. The antiarrhythmic effect of verapamil was due to reduced SR Ca(2+) content following I(CaL) inhibition. Computational modelling supported that the level of I(CaL) inhibition obtained experimentally was sufficient to reduce the SR Ca(2+) content. Ca(2+) wave prevention through reduced SR Ca(2+) content was also effective in heterozygous ankyrin B knockout mice with excessive SR Ca(2+) accumulation during β-adrenergic stimulation. CONCLUSION I(CaL) inhibition prevents diastolic Ca(2+) waves caused by increased Ca(2+) sensitivity of RyR or excessive SR Ca(2+) accumulation during β-adrenergic stimulation. In contrast, unstimulated early Ca(2+) release during the decay of the Ca(2+) transient is not prevented, and merits further study to understand the full antiarrhythmic potential of I(CaL) inhibition.
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Affiliation(s)
- Mathis K Stokke
- Institute for Experimental Medical Research, Oslo University Hospital and University of Oslo, Oslo, Norway.
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Choi BR. Calcium measurements from whole heart using Rhod-2. Methods Mol Biol 2013; 937:217-228. [PMID: 23007589 DOI: 10.1007/978-1-62703-086-1_13] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Calcium recording from whole heart is an important technique to investigate role of calcium in cardiac arrhythmias. Intracellular calcium can be recorded from multiple locations using imaging devices and organic dyes or genetic probe (Tallini et al. PNAS 103(12):4753-4758, 2006) from whole heart. Here, we describe the optical apparatus and the method to record intracellular calcium transients.
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Affiliation(s)
- Bum-Rak Choi
- Cardiovascular Research Center, Rhode Island Hospital and Brown Medical School, Providence, RI, USA.
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Johnson DM, Heijman J, Bode EF, Greensmith DJ, van der Linde H, Abi-Gerges N, Eisner DA, Trafford AW, Volders PGA. Diastolic spontaneous calcium release from the sarcoplasmic reticulum increases beat-to-beat variability of repolarization in canine ventricular myocytes after β-adrenergic stimulation. Circ Res 2012; 112:246-56. [PMID: 23149594 DOI: 10.1161/circresaha.112.275735] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
RATIONALE Spontaneous Ca(2+) release (SCR) from the sarcoplasmic reticulum can cause delayed afterdepolarizations and triggered activity, contributing to arrhythmogenesis during β-adrenergic stimulation. Excessive beat-to-beat variability of repolarization duration (BVR) is a proarrhythmic marker. Previous research has shown that BVR is increased during intense β-adrenergic stimulation, leading to SCR. OBJECTIVE We aimed to determine ionic mechanisms controlling BVR under these conditions. METHODS AND RESULTS Membrane potentials and cell shortening or Ca(2+) transients were recorded from isolated canine left ventricular myocytes in the presence of isoproterenol. Action-potential (AP) durations after delayed afterdepolarizations were significantly prolonged. Addition of slowly activating delayed rectifier K(+) current (I(Ks)) blockade led to further AP prolongation after SCR, and this strongly correlated with exaggerated BVR. Suppressing SCR via inhibition of ryanodine receptors, Ca(2+)/calmodulin-dependent protein kinase II inhibition, or by using Mg(2+) or flecainide eliminated delayed afterdepolarizations and decreased BVR independent of effects on AP duration. Computational analyses and voltage-clamp experiments measuring L-type Ca(2+) current (I(CaL)) with and without previous SCR indicated that I(CaL) was increased during Ca(2+)-induced Ca(2+) release after SCR, and this contributes to AP prolongation. Prolongation of QT, T(peak)-T(end) intervals, and left ventricular monophasic AP duration of beats after aftercontractions occurred before torsades de pointes in an in vivo dog model of drug-induced long-QT1 syndrome. CONCLUSIONS SCR contributes to increased BVR by interspersed prolongation of AP duration, which is exacerbated during I(Ks) blockade. Attenuation of Ca(2+)-induced Ca(2+) release by SCR underlies AP prolongation via increased I(CaL.) These data provide novel insights into arrhythmogenic mechanisms during β-adrenergic stimulation besides triggered activity and illustrate the importance of I(Ks) function in preventing excessive BVR.
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Affiliation(s)
- Daniel M Johnson
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Maastricht University Medical Center, Maastricht, The Netherlands
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Arrhythmogenic mechano-electric heterogeneity in the long-QT syndrome. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2012; 110:347-58. [DOI: 10.1016/j.pbiomolbio.2012.07.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 07/16/2012] [Indexed: 11/23/2022]
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Kujala K, Paavola J, Lahti A, Larsson K, Pekkanen-Mattila M, Viitasalo M, Lahtinen AM, Toivonen L, Kontula K, Swan H, Laine M, Silvennoinen O, Aalto-Setälä K. Cell model of catecholaminergic polymorphic ventricular tachycardia reveals early and delayed afterdepolarizations. PLoS One 2012; 7:e44660. [PMID: 22962621 PMCID: PMC3433449 DOI: 10.1371/journal.pone.0044660] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Accepted: 08/06/2012] [Indexed: 12/23/2022] Open
Abstract
Background Induced pluripotent stem cells (iPSC) provide means to study the pathophysiology of genetic disorders. Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a malignant inherited ion channel disorder predominantly caused by mutations in the cardiac ryanodine receptor (RyR2). In this study the cellular characteristics of CPVT are investigated and whether the electrophysiological features of this mutation can be mimicked using iPSC -derived cardiomyocytes (CM). Methodology/Principal Findings Spontaneously beating CMs were differentiated from iPSCs derived from a CPVT patient carrying a P2328S mutation in RyR2 and from two healthy controls. Calcium (Ca2+) cycling and electrophysiological properties were studied by Ca2+ imaging and patch-clamp techniques. Monophasic action potential (MAP) recordings and 24h-ECGs of CPVT-P2328S patients were analyzed for the presence of afterdepolarizations. We found defects in Ca2+ cycling and electrophysiology in CPVT CMs, reflecting the cardiac phenotype observed in the patients. Catecholaminergic stress led to abnormal Ca2+ signaling and induced arrhythmias in CPVT CMs. CPVT CMs also displayed reduced sarcoplasmic reticulum (SR) Ca2+ content, indicating leakage of Ca2+ from the SR. Patch-clamp recordings of CPVT CMs revealed both delayed afterdepolarizations (DADs) during spontaneous beating and in response to adrenaline and also early afterdepolarizations (EADs) during spontaneous beating, recapitulating the changes seen in MAP and 24h-ECG recordings of patients carrying the same mutation. Conclusions/Significance This cell model shows aberrant Ca2+ cycling characteristic of CPVT and in addition to DADs it displays EADs. This cell model for CPVT provides a platform to study basic pathology, to screen drugs, and to optimize drug therapy.
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Affiliation(s)
- Kirsi Kujala
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
| | - Jere Paavola
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Anna Lahti
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
| | - Kim Larsson
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
| | - Mari Pekkanen-Mattila
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
| | - Matti Viitasalo
- Department of Cardiology, Helsinki University Hospital, Helsinki, Finland
| | - Annukka M. Lahtinen
- Research Program’s Unit Molecular Medicine, University of Helsinki, Helsinki, Finland
| | - Lauri Toivonen
- Department of Cardiology, Helsinki University Hospital, Helsinki, Finland
| | - Kimmo Kontula
- Department of Medicine, University of Helsinki, Helsinki, Finland
| | - Heikki Swan
- Department of Medicine, University of Helsinki, Helsinki, Finland
| | - Mika Laine
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
- Department of Cardiology, Helsinki University Hospital, Helsinki, Finland
| | - Olli Silvennoinen
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
- Tampere University Hospital, Tampere, Finland
| | - Katriina Aalto-Setälä
- Institute of Biomedical Technology, University of Tampere, Tampere, Finland
- BioMediTech, Tampere, Finland
- Heart Center, Tampere, Finland
- * E-mail:
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Negative electro-mechanical windows are required for drug-induced Torsades de Pointes in the anesthetized guinea pig. J Pharmacol Toxicol Methods 2012; 66:125-34. [DOI: 10.1016/j.vascn.2012.03.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2012] [Revised: 03/13/2012] [Accepted: 03/29/2012] [Indexed: 11/17/2022]
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50
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Prolonged Action Potential and After depolarizations Are Not due to Changes in Potassium Currents in NOS3 Knockout Ventricular Myocytes. JOURNAL OF SIGNAL TRANSDUCTION 2012; 2012:645721. [PMID: 22970362 PMCID: PMC3434404 DOI: 10.1155/2012/645721] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Revised: 07/13/2012] [Accepted: 07/16/2012] [Indexed: 02/01/2023]
Abstract
Ventricular myocytes deficient in endothelial nitric oxide synthase (NOS3(-/-)) exhibit prolonged action potential (AP) duration and enhanced spontaneous activity (early and delayed afterdepolarizations) during β-adrenergic (β-AR) stimulation. Studies have shown that nitric oxide is able to regulate various K(+) channels. Our objective was to examine if NOS3(-/-) myocytes had altered K(+) currents. APs, transient outward (I(to)), sustained (I(Ksus)), and inward rectifier (I(K1)) K(+) currents were measured in NOS3(-/-) and wild-type (WT) myocytes. During β-AR stimulation, AP duration (measured as 90% repolarization-APD(90)) was prolonged in NOS3(-/-) compared to WT myocytes. Nevertheless, we did not observe differences in I(to), I(Ksus), or I(K1) between WT and NOS3(-/-) myocytes. Our previous work showed that NOS3(-/-) myocytes had a greater Ca(2+) influx via L-type Ca(2+) channels with β-AR stimulation. Thus, we measured β-AR-stimulated SR Ca(2+) load and found a greater increase in NOS3(-/-) versus WT myocytes. Hence, our data suggest that the prolonged AP in NOS3(-/-) myocytes is not due to changes in I(to), I(Ksus), or I(K1). Furthermore, the increase in spontaneous activity in NOS3(-/-) myocytes may be due to a greater increase in SR Ca(2+) load. This may have important implications for heart failure patients, where arrhythmias are increased and NOS3 expression is decreased.
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