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Hutschalik T, Özgül O, Casini M, Szabó B, Peyronnet R, Bártulos Ó, Argenziano M, Schotten U, Matsa E. Immune response caused by M1 macrophages elicits atrial fibrillation-like phenotypes in coculture model with isogenic hiPSC-derived cardiomyocytes. Stem Cell Res Ther 2024; 15:280. [PMID: 39227896 DOI: 10.1186/s13287-024-03814-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2024] [Accepted: 06/24/2024] [Indexed: 09/05/2024] Open
Abstract
BACKGROUND Atrial fibrillation has an estimated prevalence of 1.5-2%, making it the most common cardiac arrhythmia. The processes that cause and sustain the disease are still not completely understood. An association between atrial fibrillation and systemic, as well as local, inflammatory processes has been reported. However, the exact mechanisms underlying this association have not been established. While it is understood that inflammatory macrophages can influence cardiac electrophysiology, a direct, causative relationship to atrial fibrillation has not been described. This study investigated the pro-arrhythmic effects of activated M1 macrophages on human induced pluripotent stem cell (hiPSC)-derived atrial cardiomyocytes, to propose a mechanistic link between inflammation and atrial fibrillation. METHODS Two hiPSC lines from healthy individuals were differentiated to atrial cardiomyocytes and M1 macrophages and integrated in an isogenic, pacing-free, atrial fibrillation-like coculture model. Electrophysiology characteristics of cocultures were analysed for beat rate irregularity, electrogram amplitude and conduction velocity using multi electrode arrays. Cocultures were additionally treated using glucocorticoids to suppress M1 inflammation. Bulk RNA sequencing was performed on coculture-isolated atrial cardiomyocytes and compared to meta-analyses of atrial fibrillation patient transcriptomes. RESULTS Multi electrode array recordings revealed M1 to cause irregular beating and reduced electrogram amplitude. Conduction analysis further showed significantly lowered conduction homogeneity in M1 cocultures. Transcriptome sequencing revealed reduced expression of key cardiac genes such as SCN5A, KCNA5, ATP1A1, and GJA5 in the atrial cardiomyocytes. Meta-analysis of atrial fibrillation patient transcriptomes showed high correlation to the in vitro model. Treatment of the coculture with glucocorticoids showed reversal of phenotypes, including reduced beat irregularity, improved conduction, and reversed RNA expression profiles. CONCLUSIONS This study establishes a causal relationship between M1 activation and the development of subsequent atrial arrhythmia, documented as irregularity in spontaneous electrical activation in atrial cardiomyocytes cocultured with activated macrophages. Further, beat rate irregularity could be alleviated using glucocorticoids. Overall, these results point at macrophage-mediated inflammation as a potential AF induction mechanism and offer new targets for therapeutic development. The findings strongly support the relevance of the proposed hiPSC-derived coculture model and present it as a first of its kind disease model.
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Affiliation(s)
- Thomas Hutschalik
- Ncardia Services B.V, J.H. Oortweg 21, 2333 CH, Leiden, The Netherlands
- Dept. of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, The Netherlands
| | - Ozan Özgül
- Dept. of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, The Netherlands
| | - Marilù Casini
- Regenerative Medicine and Heart Transplantation Unit, Instituto de Investigación Sanitaria La Fe, 46026, Valencia, Spain
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg Bad Krozingen and Faculty of Medicine, Freiburg im Breisgau, 79110, Germany
| | - Brigitta Szabó
- Ncardia Services B.V, J.H. Oortweg 21, 2333 CH, Leiden, The Netherlands
| | - Rémi Peyronnet
- Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg Bad Krozingen and Faculty of Medicine, Freiburg im Breisgau, 79110, Germany
| | - Óscar Bártulos
- Ncardia Services B.V, J.H. Oortweg 21, 2333 CH, Leiden, The Netherlands
| | | | - Ulrich Schotten
- Dept. of Physiology, Cardiovascular Research Institute Maastricht, Maastricht, The Netherlands
- Dept. of Cardiology, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Elena Matsa
- Ncardia Services B.V, J.H. Oortweg 21, 2333 CH, Leiden, The Netherlands.
- , Rue Edouard Belin 2, 1435, CellisticMont-Saint-Guibert, Belgium.
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland.
- National Institute for Bioprocessing Research and Training, Dublin, Ireland.
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2
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Hu D, Barajas-Martinez H, Zhang ZH, Duan HY, Zhao QY, Bao MW, Du YM, Burashnikov A, Monasky MM, Pappone C, Huang CX, Antzelevitch C, Jiang H. Advances in basic and translational research in atrial fibrillation. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220174. [PMID: 37122214 PMCID: PMC10150218 DOI: 10.1098/rstb.2022.0174] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Accepted: 03/08/2023] [Indexed: 05/02/2023] Open
Abstract
Atrial fibrillation (AF) is a very common cardiac arrhythmia with an estimated prevalence of 33.5 million patients globally. It is associated with an increased risk of death, stroke and peripheral embolism. Although genetic studies have identified a growing number of genes associated with AF, the definitive impact of these genetic findings is yet to be established. Several mechanisms, including electrical, structural and neural remodelling of atrial tissue, have been proposed to contribute to the development of AF. Despite over a century of exploration, the molecular and cellular mechanisms underlying AF have not been fully established. Current antiarrhythmic drugs are associated with a significant rate of adverse events and management of AF using ablation is not optimal, especially in cases of persistent AF. This review discusses recent advances in our understanding and management of AF, including new concepts of epidemiology, genetics and pathophysiological mechanisms. We review the current status of antiarrhythmic drug therapy for AF, new potential agents, as well as mechanism-based AF ablation. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Dan Hu
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Hector Barajas-Martinez
- Lankenau Institute for Medical Research, and Lankenau Heart Institute, Wynnwood, PA 19096, USA
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19104, USA
| | - Zhong-He Zhang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Hong-Yi Duan
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Qing-Yan Zhao
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Ming-Wei Bao
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Yi-Mei Du
- Department of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, People's Republic of China
| | - Alexander Burashnikov
- Lankenau Institute for Medical Research, and Lankenau Heart Institute, Wynnwood, PA 19096, USA
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19104, USA
| | - Michelle M. Monasky
- Arrhythmology Department, IRCCS Policlinico San Donato, San Donato Milanese, Milan 20097, Italy
| | - Carlo Pappone
- Arrhythmology Department, IRCCS Policlinico San Donato, San Donato Milanese, Milan 20097, Italy
- Vita-Salute San Raffaele University, Milan 20132, Italy
- Institute of Molecular and Translational Cardiology (IMTC), San Donato Milanese, Milan 20097, Italy
| | - Cong-Xin Huang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
| | - Charles Antzelevitch
- Lankenau Institute for Medical Research, and Lankenau Heart Institute, Wynnwood, PA 19096, USA
- Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, PA 19104, USA
| | - Hong Jiang
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan 430060, People's Republic of China
- Cardiovascular Research Institute of Wuhan University, Wuhan 430060, People's Republic of China
- Hubei Key Laboratory of Cardiology, Wuhan 430060, People's Republic of China
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3
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Zhao L, Yang Q, Tang Y, You Q, Guo X. Design, synthesis, and biological evaluation of arylmethylpiperidines as Kv1.5 potassium channel inhibitors. J Enzyme Inhib Med Chem 2022; 37:462-471. [PMID: 35012386 PMCID: PMC8757610 DOI: 10.1080/14756366.2021.2018683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Kv1.5 potassium channel, encoded by KCNA5, is a promising target for the treatment of atrial fibrillation, one of the common arrhythmia. A new series of arylmethylpiperidines derivatives based on DDO-02001 were synthesised and evaluated for their ability to inhibit Kv1.5 channel. Among them, compound DDO-02005 showed good inhibitory activity (IC50 = 0.72 μM), preferable anti-arrhythmic effects and favoured safety. These results indicate that DDO-02005 can be a promising Kv1.5 inhibitor for further studies.
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Affiliation(s)
- Lingyue Zhao
- Jiang Su Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, China.,Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Qian Yang
- Jiang Su Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, China.,Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Yiqun Tang
- Department of Clinical Pharmacy, School of Basic Medical Sciences and Clinical Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Qidong You
- Jiang Su Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, China.,Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, China
| | - Xiaoke Guo
- Jiang Su Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, China.,Department of Medicinal Chemistry, School of Pharmacy, China Pharmaceutical University, Nanjing, China
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4
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Kambayashi R, Goto A, Onozato M, Izumi-Nakaseko H, Takei Y, Matsumoto A, Kawai S, Fukushima T, Sugiyama A. Simultaneous analyses of hemodynamic and electrophysiological effects of oseltamivir along with its pharmacokinetic profile using the canine paroxysmal atrial fibrillation model. J Pharmacol Sci 2021; 148:179-186. [PMID: 34924124 DOI: 10.1016/j.jphs.2021.11.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 10/28/2021] [Accepted: 11/05/2021] [Indexed: 11/16/2022] Open
Abstract
Since information of antiviral drug oseltamivir on the anti-atrial fibrillation (AF) property is still limited, we assessed it using the canine paroxysmal AF model. Oseltamivir in doses of 3 and 30 mg/kg/10 min was intravenously infused to the isoflurane-anesthetized, chronic atrioventricular block dogs (n = 6) with monitoring hemodynamic and electrophysiological variables, in which AF was induced by 10 s of burst pacing on atrial septum. Oseltamivir decreased AF incidence and AF duration, and prolonged AF cycle length in a dose-dependent manner. The low and high doses attained the peak plasma drug concentrations of 9.7 and 96.5 μg/mL, which were approximately 100 and 1000 times greater than those observed in human clinical cases, respectively. The low dose of oseltamivir decreased mean blood pressure without altering sinoatrial or idioventricular rate, whereas its high dose reduced each of them. Oseltamivir delayed inter-atrial conduction in dose- and frequency-dependent manners, whereas it prolonged atrial effective refractory period in dose-dependent but frequency-independent manners. The high dose prolonged ventricular effective refractory period, which was not detected with the low dose. These findings can be used for repurposing oseltamivir as an anti-AF drug candidate.
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Affiliation(s)
- Ryuichi Kambayashi
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Ai Goto
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Mayu Onozato
- Department of Analytical Chemistry, Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi-shi, Chiba, 274-8510, Japan
| | - Hiroko Izumi-Nakaseko
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Yoshinori Takei
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Akio Matsumoto
- Department of Aging Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Shinichi Kawai
- Department of Inflammation & Pain Control Research, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan
| | - Takeshi Fukushima
- Department of Analytical Chemistry, Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi-shi, Chiba, 274-8510, Japan
| | - Atsushi Sugiyama
- Department of Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan; Department of Aging Pharmacology, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan; Department of Inflammation & Pain Control Research, Faculty of Medicine, Toho University, 5-21-16 Omori-nishi, Ota-ku, Tokyo, 143-8540, Japan.
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5
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Ni H, Whittaker DG, Wang W, Giles WR, Narayan SM, Zhang H. Synergistic Anti-arrhythmic Effects in Human Atria with Combined Use of Sodium Blockers and Acacetin. Front Physiol 2017; 8:946. [PMID: 29218016 PMCID: PMC5703742 DOI: 10.3389/fphys.2017.00946] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 11/08/2017] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) is the most common cardiac arrhythmia. Developing effective and safe anti-AF drugs remains an unmet challenge. Simultaneous block of both atrial-specific ultra-rapid delayed rectifier potassium (K+) current (IKur) and the Na+ current (INa) has been hypothesized to be anti-AF, without inducing significant QT prolongation and ventricular side effects. However, the antiarrhythmic advantage of simultaneously blocking these two channels vs. individual block in the setting of AF-induced electrical remodeling remains to be documented. Furthermore, many IKur blockers such as acacetin and AVE0118, partially inhibit other K+ currents in the atria. Whether this multi-K+-block produces greater anti-AF effects compared with selective IKur-block has not been fully understood. The aim of this study was to use computer models to (i) assess the impact of multi-K+-block as exhibited by many IKur blokers, and (ii) evaluate the antiarrhythmic effect of blocking IKur and INa, either alone or in combination, on atrial and ventricular electrical excitation and recovery in the setting of AF-induced electrical-remodeling. Contemporary mathematical models of human atrial and ventricular cells were modified to incorporate dose-dependent actions of acacetin (a multichannel blocker primarily inhibiting IKur while less potently blocking Ito, IKr, and IKs). Rate- and atrial-selective inhibition of INa was also incorporated into the models. These single myocyte models were then incorporated into multicellular two-dimensional (2D) and three-dimensional (3D) anatomical models of the human atria. As expected, application of IKur blocker produced pronounced action potential duration (APD) prolongation in atrial myocytes. Furthermore, combined multiple K+-channel block that mimicked the effects of acacetin exhibited synergistic APD prolongations. Synergistically anti-AF effects following inhibition of INa and combined IKur/K+-channels were also observed. The attainable maximal AF-selectivity of INa inhibition was greatly augmented by blocking IKur or multiple K+-currents in the atrial myocytes. This enhanced anti-arrhythmic effects of combined block of Na+- and K+-channels were also seen in 2D and 3D simulations; specially, there was an enhanced efficacy in terminating re-entrant excitation waves, exerting improved antiarrhythmic effects in the human atria as compared to a single-channel block. However, in the human ventricular myocytes and tissue, cellular repolarization and computed QT intervals were modestly affected in the presence of actions of acacetin and INa blockers (either alone or in combination). In conclusion, this study demonstrates synergistic antiarrhythmic benefits of combined block of IKur and INa, as well as those of INa and combined multi K+-current block of acacetin, without significant alterations of ventricular repolarization and QT intervals. This approach may be a valuable strategy for the treatment of AF.
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Affiliation(s)
- Haibo Ni
- Biological Physics Group, University of Manchester, Manchester, United Kingdom.,Space Institute of Southern China, Shenzhen, China.,Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease/Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Dominic G Whittaker
- Biological Physics Group, University of Manchester, Manchester, United Kingdom
| | - Wei Wang
- Biological Physics Group, University of Manchester, Manchester, United Kingdom
| | - Wayne R Giles
- Faculties of Kinesiology and Medicine, University of Calgary, Calgary, AB, Canada
| | - Sanjiv M Narayan
- Department of Medicine, Stanford University School of Medicine, Stanford, CA, United States
| | - Henggui Zhang
- Biological Physics Group, University of Manchester, Manchester, United Kingdom.,Space Institute of Southern China, Shenzhen, China.,Key Laboratory of Medical Electrophysiology, Ministry of Education, Collaborative Innovation Center for Prevention and Treatment of Cardiovascular Disease/Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China.,School of Computer Science and Technology, Harbin Institute of Technology, Harbin, China
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6
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Aguilar M, Feng J, Vigmond E, Comtois P, Nattel S. Rate-Dependent Role of I Kur in Human Atrial Repolarization and Atrial Fibrillation Maintenance. Biophys J 2017; 112:1997-2010. [PMID: 28494969 DOI: 10.1016/j.bpj.2017.03.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 03/06/2017] [Accepted: 03/23/2017] [Indexed: 11/24/2022] Open
Abstract
The atrial-specific ultrarapid delayed rectifier K+ current (IKur) inactivates slowly but completely at depolarized voltages. The consequences for IKur rate-dependence have not been analyzed in detail and currently available mathematical action-potential (AP) models do not take into account experimentally observed IKur inactivation dynamics. Here, we developed an updated formulation of IKur inactivation that accurately reproduces time-, voltage-, and frequency-dependent inactivation. We then modified the human atrial cardiomyocyte Courtemanche AP model to incorporate realistic IKur inactivation properties. Despite markedly different inactivation dynamics, there was no difference in AP parameters across a wide range of stimulation frequencies between the original and updated models. Using the updated model, we showed that, under physiological stimulation conditions, IKur does not inactivate significantly even at high atrial rates because the transmembrane potential spends little time at voltages associated with inactivation. Thus, channel dynamics are determined principally by activation kinetics. IKur magnitude decreases at higher rates because of AP changes that reduce IKur activation. Nevertheless, the relative contribution of IKur to AP repolarization increases at higher frequencies because of reduced activation of the rapid delayed-rectifier current IKr. Consequently, IKur block produces dose-dependent termination of simulated atrial fibrillation (AF) in the absence of AF-induced electrical remodeling. The inclusion of AF-related ionic remodeling stabilizes simulated AF and greatly reduces the predicted antiarrhythmic efficacy of IKur block. Our results explain a range of experimental observations, including recently reported positive rate-dependent IKur-blocking effects on human atrial APs, and provide insights relevant to the potential value of IKur as an antiarrhythmic target for the treatment of AF.
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Affiliation(s)
- Martin Aguilar
- Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Québec, Canada; Department of Pharmacology and Physiology/Institute of Biomedical Engineering, Université de Montréal, Montreal, Québec, Canada
| | | | - Edward Vigmond
- L'Institut de Rythmologie et Modélisation Cardiaque LIRYC, Fondation Université de Bordeaux, Hôpital Xavier-Arnozan, Pessac, France; Institut de Mathématiques de Bordeaux, Université de Bordeaux, Talence, France
| | - Philippe Comtois
- Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Québec, Canada; Department of Pharmacology and Physiology/Institute of Biomedical Engineering, Université de Montréal, Montreal, Québec, Canada
| | - Stanley Nattel
- Research Center, Montreal Heart Institute, Université de Montréal, Montreal, Québec, Canada; Department of Medicine, McGill University, Montreal, Québec, Canada; Department of Pharmacology and Therapeutics, McGill University, Montreal, Québec, Canada; Department of Medicine, Université de Montréal, Montreal, Québec, Canada; West German Heart and Vascular Center, Faculty of Medicine, University Duisburg-Essen, Essen, Germany.
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7
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Colman MA, Ni H, Liang B, Schmitt N, Zhang H. In silico assessment of genetic variation in KCNA5 reveals multiple mechanisms of human atrial arrhythmogenesis. PLoS Comput Biol 2017. [PMID: 28622331 PMCID: PMC5493429 DOI: 10.1371/journal.pcbi.1005587] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
A recent experimental study investigating patients with lone atrial fibrillation identified six novel mutations in the KCNA5 gene. The mutants exhibited both gain- and loss-of-function of the atrial specific ultra-rapid delayed rectifier K+ current, IKur. The aim of this study is to elucidate and quantify the functional impact of these KCNA5 mutations on atrial electrical activity. A multi-scale model of the human atria was updated to incorporate detailed experimental data on IKur from both wild-type and mutants. The effects of the mutations on human atrial action potential and rate dependence were investigated at the cellular level. In tissue, we assessed the effects of the mutations on the vulnerability to unidirectional conduction patterns and dynamics of re-entrant excitation waves. Gain-of-function mutations shortened the action potential duration in single cells, and stabilised and accelerated re-entrant excitation in tissue. Loss-of-function mutations had heterogeneous effects on action potential duration and promoted early-after-depolarisations following beta-adrenergic stimulation. In the tissue model, loss-of-function mutations facilitated breakdown of excitation waves at more physiological excitation rates than the wild-type, and the generation of early-after-depolarisations promoted unidirectional patterns of excitation. Gain- and loss-of-function IKur mutations produced multiple mechanisms of atrial arrhythmogenesis, with significant differences between the two groups of mutations. This study provides new insights into understanding the mechanisms by which mutant IKur contributes to atrial arrhythmias. In addition, as IKur is an atrial-specific channel and a number of IKur-selective blockers have been developed as anti-AF agents, this study also helps to understand some contradictory results on both pro- and anti-arrhythmic effects of blocking IKur. In a recent study, six mutations resulting in either gain-of-function or loss-of-function in the ultra-rapid delayed rectifier potassium current IKur, were identified to be associated with atrial fibrillation (AF). However, the causative link between the mutant IKur (either gain- or loss-of-function) and AF genesis, especially the difference and similarity between the two mutant groups, has not been elucidated. In our study, we used multiscale computational models to investigate the mechanism of arrhythmogenesis mediated by the two groups of mutations. The results suggest that the gain-of-function mutations shortened atrial action potential duration, stabilised and accelerated re-entrant excitation waves in tissue; the loss-of-function mutation promoted early-after-depolarisations following beta-adrenergic stimulation and thus wave breaks in tissue. We show these two groups of mutants carrying IKur produced multiple mechanisms of atrial arrhythmogenesis, with significant differences between the two groups. Our study provides new insights into understanding the mechanisms by which mutant IKur contributes to atrial arrhythmias. In addition, as IKur is an atrial-specific channel and a number of IKur-selective blockers have been developed as anti-AF agents, this study also helps to understand some contradictory results on both pro- and anti-arrhythmic effects of blocking IKur.
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Affiliation(s)
- Michael A. Colman
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Haibo Ni
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
| | - Bo Liang
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nicole Schmitt
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Henggui Zhang
- Biological Physics Group, School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom
- School of Computer Science and Technology, Harbin Institute of Technology, Harbin, China
- * E-mail:
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8
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Chiamvimonvat N, Chen-Izu Y, Clancy CE, Deschenes I, Dobrev D, Heijman J, Izu L, Qu Z, Ripplinger CM, Vandenberg JI, Weiss JN, Koren G, Banyasz T, Grandi E, Sanguinetti MC, Bers DM, Nerbonne JM. Potassium currents in the heart: functional roles in repolarization, arrhythmia and therapeutics. J Physiol 2017; 595:2229-2252. [PMID: 27808412 DOI: 10.1113/jp272883] [Citation(s) in RCA: 67] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 10/11/2016] [Indexed: 12/19/2022] Open
Abstract
This is the second of the two White Papers from the fourth UC Davis Cardiovascular Symposium Systems Approach to Understanding Cardiac Excitation-Contraction Coupling and Arrhythmias (3-4 March 2016), a biennial event that brings together leading experts in different fields of cardiovascular research. The theme of the 2016 symposium was 'K+ channels and regulation', and the objectives of the conference were severalfold: (1) to identify current knowledge gaps; (2) to understand what may go wrong in the diseased heart and why; (3) to identify possible novel therapeutic targets; and (4) to further the development of systems biology approaches to decipher the molecular mechanisms and treatment of cardiac arrhythmias. The sessions of the Symposium focusing on the functional roles of the cardiac K+ channel in health and disease, as well as K+ channels as therapeutic targets, were contributed by Ye Chen-Izu, Gideon Koren, James Weiss, David Paterson, David Christini, Dobromir Dobrev, Jordi Heijman, Thomas O'Hara, Crystal Ripplinger, Zhilin Qu, Jamie Vandenberg, Colleen Clancy, Isabelle Deschenes, Leighton Izu, Tamas Banyasz, Andras Varro, Heike Wulff, Eleonora Grandi, Michael Sanguinetti, Donald Bers, Jeanne Nerbonne and Nipavan Chiamvimonvat as speakers and panel discussants. This article summarizes state-of-the-art knowledge and controversies on the functional roles of cardiac K+ channels in normal and diseased heart. We endeavour to integrate current knowledge at multiple scales, from the single cell to the whole organ levels, and from both experimental and computational studies.
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Affiliation(s)
- Nipavan Chiamvimonvat
- Department of Internal Medicine, University of California, Davis, Genome and Biomedical Science Facility, Rm 6315, Davis, CA, 95616, USA.,Department of Veterans Affairs, Northern California Health Care System, Mather, CA, 95655, USA
| | - Ye Chen-Izu
- Department of Internal Medicine, University of California, Davis, Genome and Biomedical Science Facility, Rm 6315, Davis, CA, 95616, USA.,Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA.,Department of Biomedical Engineering, University of California, Davis, Genome and Biomedical Science Facility, Rm 2303, Davis, CA, 95616, USA
| | - Colleen E Clancy
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Isabelle Deschenes
- Department of Physiology and Biophysics, and Biomedical Engineering, Case Western Reserve University, Cleveland, OH, 44109, USA.,Heart and Vascular Research Center, MetroHealth Medical Center, Cleveland, OH, 44109, USA
| | - Dobromir Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Hufelandstrasse 55, 45122, Essen, Germany
| | - Jordi Heijman
- Department of Cardiology, Cardiovascular Research Institute Maastricht, Faculty of Health, Medicine, and Life Sciences, Maastricht University, Maastricht, The Netherlands
| | - Leighton Izu
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Zhilin Qu
- Division of Cardiology, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 3645 MRL, Los Angeles, CA, 90095, USA
| | - Crystal M Ripplinger
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Jamie I Vandenberg
- Victor Chang Cardiac Research Institute, 405 Liverpool Street, Darlinghurst, NSW, 2010, Australia
| | - James N Weiss
- Division of Cardiology, Cardiovascular Research Laboratory, David Geffen School of Medicine at UCLA, 3645 MRL, Los Angeles, CA, 90095, USA
| | - Gideon Koren
- Cardiovascular Research Center, Rhode Island Hospital and the Cardiovascular Institute, The Warren Alpert Medical School of Brown University, Providence, RI, 02903, USA
| | - Tamas Banyasz
- Department of Physiology, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Eleonora Grandi
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Michael C Sanguinetti
- Department of Internal Medicine, University of Utah, Nora Eccles Harrison Cardiovascular Research & Training Institute, Salt Lake City, UT, 84112, USA
| | - Donald M Bers
- Department of Pharmacology, University of California, Davis, Genome and Biomedical Science Facility, Rm 3503, Davis, CA, 95616, USA
| | - Jeanne M Nerbonne
- Departments of Developmental Biology and Internal Medicine, Cardiovascular Division, Washington University Medical School, St Louis, MO, 63110, USA
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9
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Abstract
Atrial fibrillation (AF) is associated with increased morbidity and mortality. Atrial-selective potassium (K(+)) channel blockers may represent a novel therapeutic target. The best validated atrial-specific ion currents are the acetylcholine-activated inward-rectifier K(+) current IK,ACh and ultrarapidly activating delayed-rectifier K(+) current IKur. Two-pore domain and small-conductance Ca(2+)-activated K(+) channels and Kv1.1 channels may also contribute to the atrial repolarization. We review the molecular and electrophysiologic characteristics of atrial-selective K(+) channels and their potential pathophysiologic role in AF. We summarize currently available K(+) channel blockers focusing on the most important compounds.
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Affiliation(s)
- Niels Voigt
- Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Hufelandstr. 55, Essen 45122, Germany
| | - Dobromir Dobrev
- Institute of Pharmacology, West German Heart and Vascular Center, University Duisburg-Essen, Hufelandstr. 55, Essen 45122, Germany.
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10
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Sturm AC, Kline CF, Glynn P, Johnson BL, Curran J, Kilic A, Higgins RSD, Binkley PF, Janssen PML, Weiss R, Raman SV, Fowler SJ, Priori SG, Hund TJ, Carnes CA, Mohler PJ. Use of whole exome sequencing for the identification of Ito-based arrhythmia mechanism and therapy. J Am Heart Assoc 2015; 4:JAHA.114.001762. [PMID: 26015324 PMCID: PMC4599408 DOI: 10.1161/jaha.114.001762] [Citation(s) in RCA: 15] [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: 12/19/2022]
Abstract
BACKGROUND Identified genetic variants are insufficient to explain all cases of inherited arrhythmia. We tested whether the integration of whole exome sequencing with well-established clinical, translational, and basic science platforms could provide rapid and novel insight into human arrhythmia pathophysiology and disease treatment. METHODS AND RESULTS We report a proband with recurrent ventricular fibrillation, resistant to standard therapeutic interventions. Using whole-exome sequencing, we identified a variant in a previously unidentified exon of the dipeptidyl aminopeptidase-like protein-6 (DPP6) gene. This variant is the first identified coding mutation in DPP6 and augments cardiac repolarizing current (Ito) causing pathological changes in Ito and action potential morphology. We designed a therapeutic regimen incorporating dalfampridine to target Ito. Dalfampridine, approved for multiple sclerosis, normalized the ECG and reduced arrhythmia burden in the proband by >90-fold. This was combined with cilostazol to accelerate the heart rate to minimize the reverse-rate dependence of augmented Ito. CONCLUSIONS We describe a novel arrhythmia mechanism and therapeutic approach to ameliorate the disease. Specifically, we identify the first coding variant of DPP6 in human ventricular fibrillation. These findings illustrate the power of genetic approaches for the elucidation and treatment of disease when carefully integrated with clinical and basic/translational research teams.
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Affiliation(s)
- Amy C Sturm
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Internal Medicine, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., P.F.B., R.W., S.V.R., T.J.H., P.J.M.)
| | - Crystal F Kline
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (C.F.K., J.C., P.L.J., P.J.M.)
| | - Patric Glynn
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Surgery, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (P.G., A.K., R.D.H.)
| | - Benjamin L Johnson
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.)
| | - Jerry Curran
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (C.F.K., J.C., P.L.J., P.J.M.)
| | - Ahmet Kilic
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Surgery, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (P.G., A.K., R.D.H.)
| | - Robert S D Higgins
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Surgery, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (P.G., A.K., R.D.H.)
| | - Philip F Binkley
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Internal Medicine, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., P.F.B., R.W., S.V.R., T.J.H., P.J.M.)
| | - Paul M L Janssen
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (C.F.K., J.C., P.L.J., P.J.M.)
| | - Raul Weiss
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Internal Medicine, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., P.F.B., R.W., S.V.R., T.J.H., P.J.M.)
| | - Subha V Raman
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Internal Medicine, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., P.F.B., R.W., S.V.R., T.J.H., P.J.M.)
| | - Steven J Fowler
- Cardiovascular Genetics Program, Clinical Cardiac Electrophysiology, New York University Langone Medical Center, New York, NY (S.J.F., S.G.P.) Leon H. Charney Division of Cardiology, New York University Langone Medical Center, New York, NY (S.J.F.)
| | - Silvia G Priori
- Cardiovascular Genetics Program, Clinical Cardiac Electrophysiology, New York University Langone Medical Center, New York, NY (S.J.F., S.G.P.) Molecular Cardiology, IRCCS Fondazione Salvatore Maugeri, University of Pavia, Italy (S.G.P.) Department of Cardiology, University of Pavia, Italy (S.G.P.)
| | - Thomas J Hund
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Internal Medicine, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., P.F.B., R.W., S.V.R., T.J.H., P.J.M.) Department of Biomedical Engineering, The Ohio State University, Columbus, OH (T.J.H.)
| | - Cynthia A Carnes
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) College of Pharmacy, Columbus, OH (C.A.C.)
| | - Peter J Mohler
- The Dorothy M. Davis Heart & Lung Research Institute, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., C.F.K., P.G., B.L.J., J.C., A.K., R.D.H., P.F.B., P.L.J., R.W., S.V.R., T.J.H., C.A.C., P.J.M.) Department of Internal Medicine, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (A.C.S., P.F.B., R.W., S.V.R., T.J.H., P.J.M.) Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, The Ohio State University College of Engineering, Columbus, OH (C.F.K., J.C., P.L.J., P.J.M.)
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11
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Burashnikov A, Belardinelli L, Antzelevitch C. Inhibition of IKr potentiates development of atrial-selective INa block leading to effective suppression of atrial fibrillation. Heart Rhythm 2014; 12:836-44. [PMID: 25546810 DOI: 10.1016/j.hrthm.2014.12.033] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Indexed: 12/19/2022]
Abstract
BACKGROUND The availability of safe and effective drugs for the management of atrial fibrillation (AF) remains an unmet medical need. OBJECTIVES The purpose of this study was to test the hypothesis that the inhibition of the rapidly activating delayed rectifier potassium current (IKr) greatly potentiates the development of atrial-selective sodium channel current (INa) block, leading to more effective suppression of AF. METHODS Electrophysiological and anti-AF effects of highly selective INa and IKr blockers (lidocaine and E-4031) individually and in combination were determined in canine coronary-perfused atrial and ventricular preparations. Acetylcholine (1 µM) was used to induce persistent AF. RESULTS Lidocaine (10 µM) caused a relatively small abbreviation of the action potential duration measured at 90% repolarization in both atria and ventricles, but caused atrial-selective prolongation of the effective refractory period owing to the induction of post-repolarization refractoriness. Lidocaine also caused modest atrial-selective depression of other INa-mediated parameters including excitability, maximum rate of rise of the action potential upstroke, and conduction time. E-4031 (1 µM) prolonged the action potential duration measured at 90% repolarization and effective refractory period in an atrial-predominant manner. A combination of lidocaine and E-4031 caused a greater atrial-selective depression of INa-mediated parameters. Persistent acetylcholine-mediated AF developed in 100% of atria under control conditions, in 80% (4 of 5) after pretreatment with lidocaine (10 µM), in 100% (4 of 4) after E-4031 (1 µM), and in only 14% (1 of 7) after the combination of lidocaine and E-4031. CONCLUSION Our results provide a proof of concept that IKr block greatly potentiates the effects of rapidly dissociating INa blockers to depress sodium channel-dependent parameters in the canine atria but not in the ventricles, thus contributing significantly to suppression of AF.
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12
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Colman MA, Varela M, Hancox JC, Zhang H, Aslanidi OV. Evolution and pharmacological modulation of the arrhythmogenic wave dynamics in canine pulmonary vein model. Europace 2014; 16:416-23. [PMID: 24569896 PMCID: PMC3934846 DOI: 10.1093/europace/eut349] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
Aims Atrial fibrillation (AF), the commonest cardiac arrhythmia, has been strongly linked with arrhythmogenic sources near the pulmonary veins (PVs), but underlying mechanisms are not fully understood. We aim to study the generation and sustenance of wave sources in a model of the PV tissue. Methods and results A previously developed biophysically detailed three-dimensional canine atrial model is applied. Effects of AF-induced electrical remodelling are introduced based on published experimental data, as changes of ion channel currents (ICaL, IK1, Ito, and IKur), the action potential (AP) and cell-to-cell coupling levels. Pharmacological effects are introduced by blocking specific ion channel currents. A combination of electrical heterogeneity (AP tissue gradients of 5–12 ms) and anisotropy (conduction velocities of 0.75–1.25 and 0.21–0.31 m/s along and transverse to atrial fibres) can results in the generation of wave breaks in the PV region. However, a long wavelength (171 mm) prevents the wave breaks from developing into re-entry. Electrical remodelling leads to decreases in the AP duration, conduction velocity and wavelength (to 49 mm), such that re-entry becomes sustained. Pharmacological effects on the tissue heterogeneity and vulnerability (to wave breaks and re-entry) are quantified to show that drugs that increase the wavelength and stop re-entry (IK1 and IKur blockers) can also increase the heterogeneity (AP gradients of 26–27 ms) and the likelihood of wave breaks. Conclusion Biophysical modelling reveals large conduction block areas near the PVs, which are due to discontinuous fibre arrangement enhanced by electrical heterogeneity. Vulnerability to re-entry in such areas can be modulated by pharmacological interventions.
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Affiliation(s)
- Michael A Colman
- Biological Physics Group, School of Physics & Astronomy, University of Manchester, Manchester M13 9PL, UK
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13
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Tinker A, Harmer SC. K+channels in the heart: new insights and therapeutic implications. Expert Rev Clin Pharmacol 2014; 3:305-19. [DOI: 10.1586/ecp.10.14] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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14
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Scholz EP, Carrillo-Bustamante P, Fischer F, Wilhelms M, Zitron E, Dössel O, Katus HA, Seemann G. Rotor termination is critically dependent on kinetic properties of I kur inhibitors in an in silico model of chronic atrial fibrillation. PLoS One 2013; 8:e83179. [PMID: 24376659 PMCID: PMC3869770 DOI: 10.1371/journal.pone.0083179] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 10/31/2013] [Indexed: 12/19/2022] Open
Abstract
Inhibition of the atrial ultra-rapid delayed rectifier potassium current (IKur) represents a promising therapeutic strategy in the therapy of atrial fibrillation. However, experimental and clinical data on the antiarrhythmic efficacy remain controversial. We tested the hypothesis that antiarrhythmic effects of IKur inhibitors are dependent on kinetic properties of channel blockade. A mathematical description of IKur blockade was introduced into Courtemanche-Ramirez-Nattel models of normal and remodeled atrial electrophysiology. Effects of five model compounds with different kinetic properties were analyzed. Although a reduction of dominant frequencies could be observed in two dimensional tissue simulations for all compounds, a reduction of spiral wave activity could be only be detected in two cases. We found that an increase of the percent area of refractory tissue due to a prolongation of the wavelength seems to be particularly important. By automatic tracking of spiral tip movement we find that increased refractoriness resulted in rotor extinction caused by an increased spiral-tip meandering. We show that antiarrhythmic effects of IKur inhibitors are dependent on kinetic properties of blockade. We find that an increase of the percent area of refractory tissue is the underlying mechanism for an increased spiral-tip meandering, resulting in the extinction of re-entrant circuits.
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Affiliation(s)
- Eberhard P. Scholz
- Department of Internal Medicine III, University Hospital Heidelberg, Heidelberg, Germany
- * E-mail:
| | | | - Fathima Fischer
- Department of Internal Medicine III, University Hospital Heidelberg, Heidelberg, Germany
| | - Mathias Wilhelms
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Edgar Zitron
- Department of Internal Medicine III, University Hospital Heidelberg, Heidelberg, Germany
- German Centre for Cardiovascular Research (DZHK) partner site Heidelberg/Mannheim, Heidelberg, Germany
| | - Olaf Dössel
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Hugo A. Katus
- Department of Internal Medicine III, University Hospital Heidelberg, Heidelberg, Germany
- German Centre for Cardiovascular Research (DZHK) partner site Heidelberg/Mannheim, Heidelberg, Germany
| | - Gunnar Seemann
- Institute of Biomedical Engineering, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
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15
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Colman MA, Aslanidi OV, Kharche S, Boyett MR, Garratt C, Hancox JC, Zhang H. Pro-arrhythmogenic effects of atrial fibrillation-induced electrical remodelling: insights from the three-dimensional virtual human atria. J Physiol 2013; 591:4249-72. [PMID: 23732649 PMCID: PMC3779115 DOI: 10.1113/jphysiol.2013.254987] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Chronic atrial fibrillation (AF) is associated with structural and electrical remodelling in the atria, which are associated with a high recurrence of AF. Through biophysically detailed computer modelling, this study investigated mechanisms by which AF-induced electrical remodelling promotes and perpetuates AF. A family of Courtemanche–Ramirez–Nattel variant models of human atrial cell action potentials (APs), taking into account of intrinsic atrial electrophysiological properties, was modified to incorporate various experimental data sets on AF-induced changes of major ionic channel currents (ICaL, IKur, Ito, IK1, IKs, INaCa) and on intracellular Ca2+ handling. The single cell models for control and AF-remodelled conditions were incorporated into multicellular three-dimensional (3D) atrial tissue models. Effects of the AF-induced electrical remodelling were quantified as the changes of AP profile, AP duration (APD) and its dispersion across the atria, and the vulnerability of atrial tissue to the initiation of re-entry. The dynamic behaviour of re-entrant excitation waves in the 3D models was characterised. In our simulations, AF-induced electrical remodelling abbreviated atrial APD non-uniformly across the atria; this resulted in relatively short APDs co-existing with marked regional differences in the APD at junctions of the crista terminalis/pectinate muscle, pulmonary veins/left atrium. As a result, the measured tissue vulnerability to re-entry initiation at these tissue junctions was increased. The AF-induced electrical remodelling also stabilized and accelerated re-entrant excitation waves, leading to rapid and sustained re-entry. Under the AF-remodelled condition, re-entrant scroll waves in the 3D model degenerated into persistent and erratic wavelets, leading to fibrillation. In conclusion, realistic 3D atrial tissue models indicate that AF-induced electrical remodelling produces regionally heterogeneous and shortened APD; these respectively facilitate initiation and maintenance of re-entrant excitation waves.
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Affiliation(s)
- Michael A Colman
- Professor H. Zhang: School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK.
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16
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Abstract
New antiarrhythmic drugs for treatment of atrial fibrillation should ideally be atrial selective in order to avoid pro-arrhythmic effects in the ventricles. Currently recognized atrial selective targets include atrial Nav1.5 channels, Kv1.5 channels and constitutively active Kir3.1/3.4 channels, each of which confers atrial selectivity by different mechanisms. Na(+) channel blockers with potential- and frequency-dependent action preferentially suppress atrial fibrillation because of the high excitation rate and less negative atrial resting potential, which promote drug binding in atria. Kv1.5 channels are truly atrial selective because they do not conduct repolarizing current IKur in ventricles. Constitutively active IK,ACh is predominantly observed in remodelled atria from patients in permanent atrial fibrillation (AF). A lot of effort has been invested to detect compounds which will selectively block Kir3.1/Kir3.4 in their remodelled constitutively active form. Novel drugs which have been and are being developed aim at atrial-selective targets. Vernakalant and ranolazine which mainly block atrial Na(+) channels are clinically effective. Newly designed selective IKur blockers and IK,ACh blockers are effective in animal models; however, clinical benefit in converting AF into sinus rhythm (SR) or reducing AF burden remains to be demonstrated. In conclusion, atrial-selective antiarrhythmic agents have a lot of potential, but a long way to go.
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Affiliation(s)
- Ursula Ravens
- U. Ravens: Department of Pharmacology and Toxicology, Medical Faculty Carl Gustav Carus, Dresden University of Technology, Fetscherstraße 74, D-01307 Dresden, Germany.
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17
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Abstract
The importance of potassium in maintaining stable cardiac function is a clinically understood phenomenon. Physiologically the importance of potassium in cardiac function is described by the large number of different kinds of potassium ions channels found in the heart compared to channels and membrane transport mechanisms for other ions such as sodium and calcium. Potassium is important in physiological homeostatic control of cardiac function, but is also of relevance to the diseased state, as potassium-related effects may stabilize or destabilize cardiac function. This article aims to provide a detailed understanding of potassium-mediated cardiac function. This will help the clinical practitioner evaluate how modulation of potassium ion channels by disease and pharmacological manipulation affect the cardiac patient, thus aiding in decision making when faced with clinical problems related to potassium.
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Affiliation(s)
- Ehsan Khan
- Florence Nightingale School of Nursing and Midwifery, King's College London, London, UK.
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18
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Pavri BB, Greenberg HE, Kraft WK, Lazarus N, Lynch JJ, Salata JJ, Bilodeau MT, Regan CP, Stump G, Fan L, Mehta A, Wagner JA, Gutstein DE, Bloomfield D. MK-0448, a Specific Kv1.5 Inhibitor. Circ Arrhythm Electrophysiol 2012; 5:1193-201. [DOI: 10.1161/circep.111.969782] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Background—
We evaluated the viability of I
Kur
as a target for maintenance of sinus rhythm in patients with a history of atrial fibrillation through the testing of MK-0448, a novel I
Kur
inhibitor.
Methods and Results—
In vitro MK-0448 studies demonstrated strong inhibition of I
Kur
with minimal off-target activity. In vivo MK-0448 studies in normal anesthetized dogs demonstrated significant prolongation of the atrial refractory period compared with vehicle controls without affecting the ventricular refractory period. In studies of a conscious dog heart failure model, sustained atrial fibrillation was terminated with bolus intravenous MK-0448 doses of 0.03 and 0.1 mg/kg. These data led to a 2-part first-in-human study: Part I evaluated safety and pharmacokinetics, and part II was an invasive electrophysiological study in healthy subjects. MK-0448 was well-tolerated with mild adverse experiences, most commonly irritation at the injection site. During the electrophysiological study, ascending doses of MK-0448 were administered, but no increases in atrial or ventricular refractoriness were detected, despite achieving plasma concentrations in excess of 2 μmol/L. Follow-up studies in normal anesthetized dogs designed to assess the influence of autonomic tone demonstrated that prolongation of atrial refractoriness with MK-0448 was markedly attenuated in the presence of vagal nerve simulation, suggesting that the effects of I
Kur
blockade on atrial repolarization may be negated by enhanced parasympathetic neural tone.
Conclusions—
The contribution of I
Kur
to human atrial electrophysiology is less prominent than in preclinical models and therefore is likely to be of limited therapeutic value for the prevention of atrial fibrillation.
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Affiliation(s)
- Behzad B. Pavri
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - Howard E. Greenberg
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - Walter K. Kraft
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - Nicole Lazarus
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - Joseph J. Lynch
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - Joseph J. Salata
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - Mark T. Bilodeau
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - Christopher P. Regan
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - Gary Stump
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - Li Fan
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - Anish Mehta
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - John A. Wagner
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - David E. Gutstein
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
| | - Daniel Bloomfield
- From the Department of Medicine, Division of Cardiology (B.B.P.), and Department of Pharmacology and Experimental Therapeutics (H.E.G., W.K.K.), Thomas Jefferson University, Philadelphia, PA; and Merck Sharp and Dohme Corp, Whitehouse Station, NJ (N.L., J.J.L., J.J.S., M.T.B., C.P.R., G.S., L.F., A.M., J.A.W., D.E.G., D.B.)
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Atrial-selective prolongation of refractory period with AVE0118 is due principally to inhibition of sodium channel activity. J Cardiovasc Pharmacol 2012; 59:539-46. [PMID: 22370957 DOI: 10.1097/fjc.0b013e31824e1b93] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The action of AVE0118 to prolong effective refractory period (ERP) in atria but not in ventricles is thought to be due to its inhibition of IKur. However, in nonremodeled atria, AVE0118 prolongs ERP but not action potential duration (APD70-90), which can be explained with the inhibition of sodium but not potassium channel current. ERP, APD, and the maximum rate of increase of the AP upstroke (Vmax) were measured in the canine-isolated coronary-perfused right atrial and in superfused ventricular tissue preparations. Whole-cell patch-clamp techniques were used to measure sodium channel current in HEK293 cells stably expressing SCN5A. AVE0118 (5-10 μM) prolonged ERP (P < 0.001) but not APD70 and decreased Vmax (by 15%, 10 μM, P < 0.05; n = 10 for each). Ventricular ERP, APD90, and Vmax were not changed significantly by 10 μM AVE0118 (all P = ns; n = 7). AVE0118 effectively suppressed acetylcholine-mediated persistent atrial fibrillation. AVE0118 (10 μM) reduced peak current amplitude of SCN5A-WT current by 36.5% ± 6.6% (P < 0.01; n = 7) and shifted half-inactivation voltage (V0.5) of the steady-state inactivation curve from -89.9 ± 0.5 to -96.0 ± 0.9 mV (P < 0.01; n = 7). Our data suggest that AVE0118-induced prolongation of atrial, but not ventricular ERP, is due largely to atrial-selective depression of sodium channel current, which likely contributes to the effectiveness of AVE0118 to suppress atrial fibrillation.
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Burashnikov A, Pourrier M, Gibson JK, Lynch JJ, Antzelevitch C. Rate-dependent effects of vernakalant in the isolated non-remodeled canine left atria are primarily due to block of the sodium channel: comparison with ranolazine and dl-sotalol. Circ Arrhythm Electrophysiol 2012; 5:400-8. [PMID: 22322366 DOI: 10.1161/circep.111.968305] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
BACKGROUND Several clinical trials have shown that vernakalant is effective in terminating recent onset atrial fibrillation (AF). The electrophysiological actions of vernakalant are not fully understood. METHODS AND RESULTS Here we report the results of a blinded study comparing the in vitro canine atrial electrophysiological effects of vernakalant, ranolazine, and dl-sotalol. Action potential durations (APD(50,75,90)), effective refractory period (ERP), post repolarization refractoriness (PRR), maximum rate of rise of the action potential (AP) upstroke (V(max)), diastolic threshold of excitation (DTE), conduction time (CT), and the shortest S(1)-S(1) permitting 1:1 activation (S(1)-S(1)) were measured using standard stimulation and microelectrode recording techniques in isolated normal, non-remodeled canine arterially perfused left atrial preparations. Vernakalant caused variable but slight prolongation of APD(90) (P=not significant), but significant prolongation of APD(50) at 30 μmol/L and rapid rates. In contrast, ranolazine and dl-sotalol produced consistent concentration- and reverse rate-dependent prolongation of APD(90). Vernakalant and ranolazine caused rate-dependent, whereas dl-sotalol caused reverse rate-dependent, prolongation of ERP. Significant rate-dependent PRR developed with vernakalant and ranolazine, but not with dl-sotalol. Other sodium channel-mediated parameters (ie, V(max), CT, DTE, and S(1)-S(1)) also were depressed significantly by vernakalant and ranolazine, but not by dl-sotalol. Only vernakalant elevated AP plateau voltage, consistent with blockade of ultrarapid delayed rectified potassium current and transient outward potassium current. CONCLUSIONS In isolated canine left atria, the effects of vernakalant and ranolazine were characterized by use-dependent inhibition of sodium channel-mediated parameters, and those of dl-sotalol by reverse rate-dependent prolongation of APD(90) and ERP. This suggests that during the rapid activation rates of AF, the I(Na) blocking action of the mixed ion channel blocker vernakalant takes prominence. This mechanism may explain vernakalant's anti-AF efficacy.
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Burashnikov A, Antzelevitch C. Novel pharmacological targets for the rhythm control management of atrial fibrillation. Pharmacol Ther 2011; 132:300-13. [PMID: 21867730 PMCID: PMC3205214 DOI: 10.1016/j.pharmthera.2011.08.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2011] [Accepted: 08/05/2011] [Indexed: 12/19/2022]
Abstract
Atrial fibrillation (AF) is a growing clinical problem associated with increased morbidity and mortality. Development of safe and effective pharmacological treatments for AF is one of the greatest unmet medical needs facing our society. In spite of significant progress in non-pharmacological AF treatments (largely due to the use of catheter ablation techniques), anti-arrhythmic agents (AADs) remain first line therapy for rhythm control management of AF for most AF patients. When considering efficacy, safety and tolerability, currently available AADs for rhythm control of AF are less than optimal. Ion channel inhibition remains the principal strategy for termination of AF and prevention of its recurrence. Practical clinical experience indicates that multi-ion channel blockers are generally more optimal for rhythm control of AF compared to ion channel-selective blockers. Recent studies suggest that atrial-selective sodium channel block can lead to safe and effective suppression of AF and that concurrent inhibition of potassium ion channels may potentiate this effect. An important limitation of the ion channel block approach for AF treatment is that non-electrical factors (largely structural remodeling) may importantly determine the generation of AF, so that "upstream therapy", aimed at preventing or reversing structural remodeling, may be required for effective rhythm control management. This review focuses on novel pharmacological targets for the rhythm control management of AF.
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Burashnikov A, Belardinelli L, Antzelevitch C. Atrial-selective sodium channel block strategy to suppress atrial fibrillation: ranolazine versus propafenone. J Pharmacol Exp Ther 2011; 340:161-8. [PMID: 22005044 DOI: 10.1124/jpet.111.186395] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Ranolazine has been shown to produce atrial-selective depression of sodium channel-dependent parameters and suppress atrial fibrillation (AF) in a variety of experimental models. The present study contrasts the effects of ranolazine and those of a clinically used anti-AF class IC agent, propafenone. Electrophysiological and anti-AF effects of propafenone and ranolazine were compared at clinically relevant concentrations (i.e., 0.3-1.5 and 1-10 μM, respectively) in canine isolated coronary-perfused atrial and ventricular preparations. Transmembrane action potential and pseudo-ECG were recorded. Both ranolazine and propafenone produced atrial-selective prolongation of action potential duration. Propafenone depressed sodium channel-mediated parameters [maximum rate of rise of the action potential upstroke (V(max)), conduction time, and diastolic threshold of excitation] and induced postrepolarization refractoriness to a greater degree than ranolazine, and these effects, unlike those induced by ranolazine, were not or only mildly atrial-selective at normal rates (cycle length 500 ms). At fast pacing rates, however, the effects of propafenone on V(max) and conduction time became atrial-selective, because of the elimination of diastolic interval in atria, but not in ventricles. Propafenone (1.5 μM) and ranolazine (10.0 μM) were effective in preventing the initiation of persistent acetylcholine-mediated AF (6/7 and 9/11 atria, respectively), its termination (8/10 and 8/12 atria, respectively), and subsequent reinduction (8/8 and 7/8 atria, respectively). Thus, propafenone and ranolazine both suppress AF, but ranolazine, unlike propafenone, does it with minimal effects on ventricular myocardium, suggesting a reduced potential for promoting ventricular arrhythmias.
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Burashnikov A, Petroski A, Hu D, Barajas-Martinez H, Antzelevitch C. Atrial-selective inhibition of sodium-channel current by Wenxin Keli is effective in suppressing atrial fibrillation. Heart Rhythm 2011; 9:125-31. [PMID: 21884675 DOI: 10.1016/j.hrthm.2011.08.027] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Accepted: 08/28/2011] [Indexed: 11/17/2022]
Abstract
BACKGROUND Wenxin Keli is a Chinese herb extract reported to be of benefit in the treatment of cardiac arrhythmias, cardiac inflammation, and heart failure. METHODS AND RESULTS We evaluated the electrophysiologic effects of Wenxin Keli in isolated canine arterially perfused right atrial preparations with a rim of right ventricular tissue (n = 11). Transmembrane action potentials and a pseudoelectrocardiogram were simultaneously recorded. Acetylcholine (1 μM) was used to induce atrial fibrillation (AF) and to test the anti-AF potential of Wenxin Keli (5 g/L). Wenxin Keli produced preferential abbreviation of action potential duration measured at 90% repolarization (APD(90)) in atria, but caused atrial-selective prolongation of the effective refractory period, due to the development of postrepolarization refractoriness. The maximum rate of rise of the action potential upstroke was preferentially reduced in atria. The diastolic threshold of excitation increased in both atria and ventricles, but much more in atria. The duration of the "P wave" (index of atrial conduction time) was prolonged to a much greater extent than the duration of the "QRS complex" (index of ventricular conduction time). Wenxin Keli significantly reduced I(Na) and shifted steady-state inactivation to more negative potentials in HEK293 cells stably expressing SCN5A. Wenxin Keli prevented the induction of persistent AF in 100% atria (6/6) and, in another experimental series, was found to terminate persistent acetylcholine-mediated AF in 100% of atria (3/3). CONCLUSION Wenxin Keli produces atrial-selective depression of I(Na)-dependent parameters in canine isolated coronary-perfused preparations via a unique mechanism and is effective in suppressing AF and preventing its induction, with minimal effects on the ventricular electrophysiology.
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Estes NAM, Sacco RL, Al-Khatib SM, Ellinor PT, Bezanson J, Alonso A, Antzelevitch C, Brockman RG, Chen PS, Chugh SS, Curtis AB, DiMarco JP, Ellenbogen KA, Epstein AE, Ezekowitz MD, Fayad P, Gage BF, Go AS, Hlatky MA, Hylek EM, Jerosch-Herold M, Konstam MA, Lee R, Packer DL, Po SS, Prystowsky EN, Redline S, Rosenberg Y, Van Wagoner DR, Wood KA, Yue L, Benjamin EJ. American Heart Association atrial fibrillation research summit: a conference report from the American Heart Association. Circulation 2011; 124:363-72. [PMID: 21709057 DOI: 10.1161/cir.0b013e318224b037] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Shimizu W, Horie M. Phenotypic Manifestations of Mutations in Genes Encoding Subunits of Cardiac Potassium Channels. Circ Res 2011; 109:97-109. [DOI: 10.1161/circresaha.110.224600] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Since 1995, when a potassium channel gene,
hERG
(human ether-à-go-go-related gene), now referred to as
KCNH2
, encoding the rapid component of cardiac delayed rectifier potassium channels was identified as being responsible for type 2 congenital long-QT syndrome, a number of potassium channel genes have been shown to cause different types of inherited cardiac arrhythmia syndromes. These include congenital long-QT syndrome, short-QT syndrome, Brugada syndrome, early repolarization syndrome, and familial atrial fibrillation. Genotype-phenotype correlations have been investigated in some inherited arrhythmia syndromes, and as a result, gene-specific risk stratification and gene-specific therapy and management have become available, particularly for patients with congenital long-QT syndrome. In this review article, the molecular structure and function of potassium channels, the clinical phenotype due to potassium channel gene mutations, including genotype-phenotype correlations, and the diverse mechanisms underlying the potassium channel gene–related diseases will be discussed.
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Affiliation(s)
- Wataru Shimizu
- From the Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center (W.S.), Suita, Japan, and the Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science (M.H.), Otsu, Japan
| | - Minoru Horie
- From the Division of Arrhythmia and Electrophysiology, Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center (W.S.), Suita, Japan, and the Department of Cardiovascular and Respiratory Medicine, Shiga University of Medical Science (M.H.), Otsu, Japan
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Burashnikov A, Antzelevitch C. Advances in the Pharmacologic Management of Atrial Fibrillation. Card Electrophysiol Clin 2011; 3:157-167. [PMID: 21731596 PMCID: PMC3125069 DOI: 10.1016/j.ccep.2010.10.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
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Pandit SV, Zlochiver S, Filgueiras-Rama D, Mironov S, Yamazaki M, Ennis SR, Noujaim SF, Workman AJ, Berenfeld O, Kalifa J, Jalife J. Targeting atrioventricular differences in ion channel properties for terminating acute atrial fibrillation in pigs. Cardiovasc Res 2010; 89:843-51. [PMID: 21076156 DOI: 10.1093/cvr/cvq359] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
AIMS The goal was to terminate atrial fibrillation (AF) by targeting atrioventricular differences in ionic properties. METHODS AND RESULTS Optical mapping was used to record electrical activity during carbachol (0.25-0.5 μM)-induced AF in pig hearts. The atrial-specific current, I(Kur), was blocked with 100 μM 4-aminopyridine (4-AP) or with 0.5 μM DPO-1. Hearts in AF and ventricular fibrillation (VF) were also subjected to increasing levels of extracellular K(+) ([K(+)](o): 6-12 mM), compared with controls (4 mM). We hypothesized that due to the more negative steady-state half inactivation voltage for the atrial Na(+) current, I(Na), compared with the ventricle, AF would terminate before VF in hyperkalaemia. Mathematical models were used to interpret experimental findings. The I(Kur) block did not terminate AF in a majority of experiments (6/9 with 4-AP and 3/4 with DPO-1). AF terminated in mild hyperkalaemia ([K(+)](o) ≤ 10.0 mM; N = 8). In contrast, only two of five VF episodes terminated at the maximum ([K(+)](o): 12 mM [K(+)](o)). The I(Kur) block did not terminate a simulated rotor in cholinergic AF because its contribution to repolarization was dwarfed by the large magnitude of the acetylcholine-activated K(+) current (I(K,ACh)). Simulations showed that the lower availability of the atrial Na(+) current at depolarized potentials, and a smaller atrial tissue size compared with the ventricle, could partly explain the earlier termination of AF compared with VF during hyperkalaemia. CONCLUSION I(Kur) is an ineffective anti-arrhythmic drug target in cholinergic AF. Manipulating Na(+) current 'availability' might represent a viable anti-arrhythmic strategy in AF.
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Affiliation(s)
- Sandeep V Pandit
- Center for Arrhythmia Research, University of Michigan, Ann Arbor, MI, USA.
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AZD1305 exerts atrial predominant electrophysiological actions and is effective in suppressing atrial fibrillation and preventing its reinduction in the dog. J Cardiovasc Pharmacol 2010; 56:80-90. [PMID: 20386458 DOI: 10.1097/fjc.0b013e3181e0bc6b] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Recent development of drugs for the treatment of atrial fibrillation (AF) has focused on atrial selective agents. We examined the atrioventricular differences in sodium channel block of the antiarrhythmic agent AZD1305 in atria and ventricles of anesthetized dogs in vivo, canine isolated arterially perfused preparations in vitro, and isolated myocytes using whole-cell patch-clamp techniques. AZD1305 did not change heart rate or blood pressure in vivo but prolonged action potential duration and increased effective refractory period, diastolic threshold of excitation, and conduction time preferentially in atria both in vitro and in vivo. AZD1305 reduced the maximum rate of rise of the action potential upstroke (V(max)) predominantly in atria (-51% +/- 10% in atria vs. -31% +/- 23% in ventricles; 3 microM; cycle length = 500 milliseconds). Fast sodium current (I(Na)) was blocked by AZD1305 to a greater degree in atrial versus ventricular myocytes (particularly tonic inhibition). In coronary-perfused right atria, AZD1305 very effectively prevented induction of persistent acetylcholine-mediated AF and, in a different set of atria, terminated persistent AF (in 5 of 5 and 7 of 8 atria, respectively). In conclusion, AZD1305 exerts atrial predominant sodium channel-blocking effects in vitro and in vivo and effectively suppresses AF.
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Yang T, Yang P, Roden DM, Darbar D. Novel KCNA5 mutation implicates tyrosine kinase signaling in human atrial fibrillation. Heart Rhythm 2010; 7:1246-52. [PMID: 20638934 DOI: 10.1016/j.hrthm.2010.05.032] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/15/2010] [Accepted: 05/26/2010] [Indexed: 12/19/2022]
Abstract
BACKGROUND Emerging evidence has strongly implicated hereditary determinants for atrial fibrillation (AF). Loss-of-function mutations in KCNA5 encoding the ultrarapid delayed rectifier potassium current I(Kur) have been identified in AF families. OBJECTIVE The purpose of this study was to determine the clinical and biophysical phenotypes in a KCNA5 mutation with deletion of 11 amino acids in the N-terminus of the protein, which was identified in patients with lone AF. METHODS Patients with AF confirmed by ECG were prospectively enrolled in the Vanderbilt AF Registry, which comprises clinical and genetic databases. A KCNA5 mutation was generated by mutagenesis for electrophysiologic characterization. RESULTS We identified a novel 33-bp coding region deletion in two Caucasian probands. One proband was part of a kindred that included four other members with AF, and all were mutation carriers. The mutation results in deletion of 11 amino acids in the N-terminus of the protein, a proline-rich region as a binding site for Src homology 3 (SH3) domains associated with Src-family protein tyrosine kinase (TK) pathway. In transfected cells, the mutant caused approximately 60% decreased I(Kur) versus wild-type (WT) (75 +/- 8 pA/pF vs 180 +/- 15 pA/pF, P <.01) and dominant-negative effect on WT current (105 +/- 10 pA/pF, P <.01). Pretreatment with the Src inhibitor PP2 prevented v-Src TK from 90% suppressed WT current. In contrast, the mutant channel displayed no response to v-Src TK. CONCLUSION Our data implicate abnormal atrial repolarization control due to variable TK signaling as a mechanism in familial AF and thereby suggest a role for modulation of this pathway in AF and its treatment.
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Affiliation(s)
- Tao Yang
- Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee 37323-6602, USA
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Abstract
Atrial fibrillation (AF) is a growing clinical problem associated with increased morbidity and mortality. Currently available antiarrhythmic drugs (AADs), although highly effective in acute cardioversion of paroxysmal AF, are generally only moderately successful in long-term maintenance of sinus rhythm. The use of AADs is often associated with an increased risk of ventricular proarrhythmia, extracardiac toxicity, and exacerbation of concomitant diseases such as heart failure. AF is commonly associated with intracardiac and extracardiac disease, which can modulate the efficacy and safety of AAD therapy. In light of the multifactorial intracardiac and extracardiac causes of AF generation, current development of anti-AF agents is focused on modulation of ion channel activity as well as on upstream therapies that reduce structural substrates. The available data indicate that multiple ion channel blockers exhibiting potent inhibition of peak I(Na) with relatively rapid unbinding kinetics, as well as inhibition of late I(Na) and I(Kr), may be preferable for the management of AF when considering both safety and efficacy.
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Antzelevitch C, Burashnikov A. Atrial-selective sodium channel block as a novel strategy for the management of atrial fibrillation. Ann N Y Acad Sci 2010; 1188:78-86. [PMID: 20201889 DOI: 10.1111/j.1749-6632.2009.05086.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Safe and effective pharmacologic management of atrial fibrillation (AF) is one of the greatest challenges facing an aging society. Currently available pharmacologic strategies for rhythm control of AF are associated with ventricular arrhythmias and in some cases multi-organ toxicity. Consequently, drug development has focused on atrial-selective agents such as IKur blockers. Recent studies suggest that IKur block alone may be ineffective for suppression of AF and may promote AF in healthy hearts. Recent experimental studies have demonstrated other important electrophysiologic differences between atrial and ventricular cells, particularly with respect to sodium channel function, and have identified sodium channel blockers that exploit these electrophysiologic distinctions. Atrial-selective sodium channel blockers, such as ranolazine and amiodarone, effectively suppress and/or prevent the induction of AF in experimental models, while producing little to no effect on ventricular myocardium. These findings suggest that atrial-selective sodium channel block may be a fruitful new strategy for the management of AF.
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Burashnikov A, Antzelevitch C. Advances in the Pharmacological Treatment of Atrial Fibrillation. CURRENT MEDICAL LITERATURE. CARDIOLOGY 2010; 29:1-5. [PMID: 21152111 PMCID: PMC2997698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
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Burashnikov A, Antzelevitch C. New pharmacological strategies for the treatment of atrial fibrillation. Ann Noninvasive Electrocardiol 2009; 14:290-300. [PMID: 19614642 DOI: 10.1111/j.1542-474x.2009.00305.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Atrial fibrillation (AF) is a growing clinical problem, increasing in prevalence as the population of the United States and countries around the world ages. Intensive research aimed at improving prevention, diagnosis, and treatment of AF is ongoing. Although the use and efficacy of catheter ablation-based approaches in AF treatment have increased significantly in the last decade, pharmacological agents remain the first-line therapy for rhythm management of AF. Currently available anti-AF agents are generally only moderately effective and associated with extracardiac toxicity and/or a risk for development of life-threatening ventricular arrhythmias. Included among current investigational strategies for improving the effectiveness and safety of anti-AF drugs is the development of (1) Agents that produce atrial-specific or predominant inhibition of I(Kur), I(K-ACh), or I(Na); (2) "Upstream therapies" that effect nonion channel targets that reduce atrial structural remodeling, hypertrophy, dilatation, inflammation, oxidative injury, etc; (3) Derivatives of "old" anti-AF drugs with an improved safety pharmacological profile; and (4) Gap junction therapy aimed at improving conduction without affecting sodium channels. This review focuses on new pharmacological approaches under investigation for the treatment of AF.
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Kumar K, Zimetbaum PJ. New and emerging antiarrhythmic drugs for atrial fibrillation: What may become available to the clinician in the near future. CURRENT TREATMENT OPTIONS IN CARDIOVASCULAR MEDICINE 2009; 11:373-80. [DOI: 10.1007/s11936-009-0038-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Burashnikov A, Antzelevitch C. Atrial-selective sodium channel block for the treatment of atrial fibrillation. Expert Opin Emerg Drugs 2009; 14:233-49. [PMID: 19466903 DOI: 10.1517/14728210902997939] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The pharmacological approach to therapy of atrial fibrillation (AF) is often associated with adverse effects resulting in the development of ventricular arrhythmias. As a consequence, much of the focus in recent years has been on development of atrial-selective agents. Atrial-selective sodium channel blockers have recently been shown to exist and be useful in the management of AF. This review summarizes the available data relative to current therapies, focusing on our understanding of the actions of atrial selective sodium channel blockers in suppressing and preventing the induction of AF and electrophysiological properties that confer atrial-selectivity to these antifibrillatory drugs.
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Affiliation(s)
- Alexander Burashnikov
- Research Scientist Masonic Medical Research Laboratory, 2150 Bleecker Street, Utica, NY 13501, USA
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Antzelevitch C, Burashnikov A. Atrial-selective sodium channel block as a novel strategy for the management of atrial fibrillation. J Electrocardiol 2009; 42:543-8. [PMID: 19698954 DOI: 10.1016/j.jelectrocard.2009.07.007] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2009] [Indexed: 12/19/2022]
Abstract
Pharmacological management of atrial fibrillation (AF) remains an important unmet medical need. Because available drugs for rhythm control of AF are often associated with a significant risk for development of ventricular arrhythmias or extracardiac toxicity, recent drug development has focused on agents that are atrial selective. Inhibition of the ultrarapid delayed rectifier potassium current (I(Kur)), a current exclusive to atria, is an example of an atrial-selective approach. Recent studies, however, have shown that loss-of-function mutations in KCNA5, the gene that encodes K(V)1.5, the alpha subunit of the I(Kur) channel, is associated with the development of AF and that inhibition of I(Kur) can promote the induction of AF in experimental models. Another potential atrial-selective approach has recently been identified. Experimental studies have demonstrated important atrioventricular differences in the biophysical properties of the sodium channel and have identified sodium channel blockers that can exploit electrophysiological distinctions between atria and ventricles. Atrial-selective/predominant sodium channel blockers such as ranolazine effectively suppress AF in experimental models involving canine-isolated right atrial preparations at concentrations that produce little to no effect on electrophysiological parameters in ventricular myocardium. Chronic administration of amiodarone was also found to exert atrial-selective depression of I(Na)-dependent parameters and thus to prevent the induction of AF. Ranolazine and amiodarone have in common the ability to rapidly dissociate from the sodium channel and to prolong the atrial action potential duration via inhibition of I(Kr). Our observations suggest that atrial-selective sodium channel block may be a fruitful strategy for the management of AF.
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Abraham RL, Yang T, Blair M, Roden DM, Darbar D. Augmented potassium current is a shared phenotype for two genetic defects associated with familial atrial fibrillation. J Mol Cell Cardiol 2009; 48:181-90. [PMID: 19646991 DOI: 10.1016/j.yjmcc.2009.07.020] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2009] [Revised: 07/10/2009] [Accepted: 07/23/2009] [Indexed: 12/19/2022]
Abstract
Mutations in multiple genes have been implicated in familial atrial fibrillation (AF), but the underlying mechanisms, and thus implications for therapy, remain ill-defined. Among 231 participants in the Vanderbilt AF Registry, we found a mutation in KCNQ1 (encoding the alpha-subunit of slow delayed rectifier potassium current [I(Ks)]) and separately a mutation in natriuretic peptide precursor A (NPPA) gene (encoding atrial natriuretic peptide, ANP), both segregating with early onset lone AF in different kindreds. The functional effects of these mutations yielded strikingly similar I(Ks) "gain-of-function." In Chinese Hamster Ovary (CHO) cells, coexpression of mutant KCNQ1 with its ancillary subunit KCNE1 generated approximately 3-fold larger currents that activated much faster than wild-type (WT)-I(Ks). Application of the WT NPPA peptide fragment produced similar changes in WT-I(Ks), and these were exaggerated with the mutant NPPA S64R peptide fragment. Anantin, a competitive ANP receptor antagonist, completely inhibited the changes in I(Ks) gating observed with NPPA S64R. Computational simulations identified accelerated transitions into open states as the mechanism for variant I(Ks) gating. Incorporating these I(Ks) changes into computed human atrial action potentials (AP) resulted in 37% shortening (120 vs. 192 ms at 300 ms cycle length), reflecting loss of the phase II dome which is dependent on L-type calcium channel current. We found striking functional similarities due to mutations in KCNQ1 and NPPA genes which led to I(Ks) "gain-of-function", atrial AP shortening, and consequently altered calcium current as a common mechanism between diverse familial AF syndromes.
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Affiliation(s)
- Robert L Abraham
- Division of Cardiovascular Medicine, Vanderbilt University School of Medicine, 1285A MRB IV, 2311 Pierce Avenue, Nashville, TN 37232-6602, USA
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Tamargo J, Caballero R, Gómez R, Delpón E. I(Kur)/Kv1.5 channel blockers for the treatment of atrial fibrillation. Expert Opin Investig Drugs 2009; 18:399-416. [PMID: 19335273 DOI: 10.1517/13543780902762850] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Atrial fibrillation (AF) is the most common sustained arrhythmia. Anti-arrhythmic drugs remain the mainstay of therapy, but the available class I and III anti-arrhythmic drugs are only moderately effective in long-term restoring/maintaining sinus rhythm (SR) and can produce potentially fatal ventricular pro-arrhythmia. In an attempt to identify safer and more effective anti-arrhythmic drugs, drug discovery efforts have focused on 'atrial selective drugs' that target cardiac ion channel(s) that are exclusively or predominantly expressed in the atria. The ultra-rapid activating delayed rectifier K(+) current (I(Kur)), carried by Kv1.5 channels, is a major repolarizing current in human atria, but seems to play no role in the ventricle. This finding offers the possibility of developing selective I(Kur) blockers to restore and maintain SR without a risk of ventricular pro-arrhythmia. Several I(Kur) blockers are now being developed but clinical data are still limited, so the precise role of these agents in the treatment of AF remains to be defined. In this review we analyze the possible advantages and disadvantages of the developmental I(Kur) blockers as they represent the first step for the development of potential atrial selective drugs for a more effective and safer treatment and prevention of AF.
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Affiliation(s)
- Juan Tamargo
- Universidad Complutense, School of Medicine, Department of Pharmacology, Madrid, Spain.
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Schmitt J, Ehrlich JR, Hohnloser SH. New Antiarrhythmic Drugs for the Treatment of Atrial Fibrillation. Herz 2009; 33:562-7. [DOI: 10.1007/s00059-008-3151-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Burashnikov A, Di Diego JM, Sicouri S, Ferreiro M, Carlsson L, Antzelevitch C. Atrial-selective effects of chronic amiodarone in the management of atrial fibrillation. Heart Rhythm 2008; 5:1735-42. [PMID: 19084813 DOI: 10.1016/j.hrthm.2008.09.015] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/16/2008] [Accepted: 09/13/2008] [Indexed: 12/19/2022]
Abstract
BACKGROUND Although amiodarone is one of the most effective pharmacologic agents used in clinical management of atrial fibrillation (AF), little is known about its differential effects in atrial and ventricular myocardium. OBJECTIVES This study sought to compare the electrophysiological effects of chronic amiodarone in atria and ventricles. METHODS We compared the electrophysiological characteristics of coronary-perfused atrial and ventricular wedge preparations isolated from untreated and chronic amiodarone-treated dogs (amiodarone, 40 mg/kg/day for 6 weeks, n = 12). RESULTS Chronic amiodarone prolonged action potential duration (APD(90)) predominantly in atria compared to ventricles and prolonged the effective refractory period (ERP) more than APD(90) in both ventricular and atrial preparations (particularly in the latter) due to the development of postrepolarization refractoriness. Amiodarone reduced dispersion of APD(90) in both atria and ventricles. Although the maximum rate of increase of the action potential upstroke (V(max)) was significantly lower in both atria and ventricles of amiodarone-treated hearts versus untreated controls, the reduction of V(max) was much more pronounced in atria. Amiodarone prolonged P-wave duration more significantly than QRS duration, reflecting greater slowing of conduction in atria versus ventricles. These atrioventricular distinctions were significantly accentuated at faster activation rates. Persistent acetylcholine-mediated AF could be induced in only 1 of 6 atria from amiodarone-treated versus 10 of 10 untreated dogs. CONCLUSION Our results indicate that under the conditions studied, chronic amiodarone has potent atrial-predominant effects to depress sodium channel-mediated parameters and that this action of the drug is greatly potentiated by its ability to prolong APD predominantly in the atria, thus contributing to its effectiveness to suppress AF.
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Burashnikov A, Antzelevitch C. How Do Atrial-Selective Drugs Differ From Antiarrhythmic Drugs Currently Used in the Treatment of Atrial Fibrillation? J Atr Fibrillation 2008; 1:98-107. [PMID: 21057583 DOI: 10.4022/jafib.v1i1.400] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Current pharmacologic strategies for the management of Atrial fibrillation (AF) include use of 1) sodium channel blockers, which are contraindicated in patients with coronary artery or structural heart disease because of their potent effect to slow conduction in the ventricles, 2) potassium channel blockers, which predispose to acquired long QT and Torsade de Pointes arrhythmias because of their potent effect to prolong ventricular repolarization, and 3) mixed ion channel blockers such as amiodarone, which are associated with multi-organ toxicity. Accordingly, recent studies have focused on agents that selectively affect the atria but not the ventricles. Several Atrial-selective approaches have been proposed for the management of AF, including inhibition of the Atrial-specific ultra rapid delayed rectified potassium current (IKur), acetylcholine-regulated inward rectifying potassium current (IK-ACh), or connexin-40 (Cx40). All three are largely exclusive to atria. Recent studies have proposed that an Atrial-selective depression of sodium channel-dependent parameters with agents such as ranolazine may be an alternative approach capable of effectively suppressing AF without increasing susceptibility to ventricular arrhythmias. Clinical evidence for Cx40 modulation or IK-ACh inhibition are lacking at this time. The available data suggest that Atrial-selective approaches involving a combination of INa, IKur, IKr, and, perhaps, Ito block may be more effective in the management of AF than pure IKur or INa block. The anti-AF efficacy of the Atrial-selective/predominant agents appears to be similar to that of conventionally used anti-AF agents, with the major apparent difference being that the latter are associated with ventricular arrhythmogenesis and extra cardiac toxicity.
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