1
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Sharma AK, Singh S, Bhat M, Gill K, Zaid M, Kumar S, Shakya A, Tantray J, Jose D, Gupta R, Yangzom T, Sharma RK, Sahu SK, Rathore G, Chandolia P, Singh M, Mishra A, Raj S, Gupta A, Agarwal M, Kifayat S, Gupta A, Gupta P, Vashist A, Vaibhav P, Kathuria N, Yadav V, Singh RP, Garg A. New drug discovery of cardiac anti-arrhythmic drugs: insights in animal models. Sci Rep 2023; 13:16420. [PMID: 37775650 PMCID: PMC10541452 DOI: 10.1038/s41598-023-41942-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Accepted: 09/04/2023] [Indexed: 10/01/2023] Open
Abstract
Cardiac rhythm regulated by micro-macroscopic structures of heart. Pacemaker abnormalities or disruptions in electrical conduction, lead to arrhythmic disorders may be benign, typical, threatening, ultimately fatal, occurs in clinical practice, patients on digitalis, anaesthesia or acute myocardial infarction. Both traditional and genetic animal models are: In-vitro: Isolated ventricular Myocytes, Guinea pig papillary muscles, Patch-Clamp Experiments, Porcine Atrial Myocytes, Guinea pig ventricular myocytes, Guinea pig papillary muscle: action potential and refractory period, Langendorff technique, Arrhythmia by acetylcholine or potassium. Acquired arrhythmia disorders: Transverse Aortic Constriction, Myocardial Ischemia, Complete Heart Block and AV Node Ablation, Chronic Tachypacing, Inflammation, Metabolic and Drug-Induced Arrhythmia. In-Vivo: Chemically induced arrhythmia: Aconitine antagonism, Digoxin-induced arrhythmia, Strophanthin/ouabain-induced arrhythmia, Adrenaline-induced arrhythmia, and Calcium-induced arrhythmia. Electrically induced arrhythmia: Ventricular fibrillation electrical threshold, Arrhythmia through programmed electrical stimulation, sudden coronary death in dogs, Exercise ventricular fibrillation. Genetic Arrhythmia: Channelopathies, Calcium Release Deficiency Syndrome, Long QT Syndrome, Short QT Syndrome, Brugada Syndrome. Genetic with Structural Heart Disease: Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia, Dilated Cardiomyopathy, Hypertrophic Cardiomyopathy, Atrial Fibrillation, Sick Sinus Syndrome, Atrioventricular Block, Preexcitation Syndrome. Arrhythmia in Pluripotent Stem Cell Cardiomyocytes. Conclusion: Both traditional and genetic, experimental models of cardiac arrhythmias' characteristics and significance help in development of new antiarrhythmic drugs.
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Affiliation(s)
- Ashish Kumar Sharma
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India.
| | - Shivam Singh
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Mehvish Bhat
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Kartik Gill
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Mohammad Zaid
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Sachin Kumar
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Anjali Shakya
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Junaid Tantray
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Divyamol Jose
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Rashmi Gupta
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Tsering Yangzom
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Rajesh Kumar Sharma
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | | | - Gulshan Rathore
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Priyanka Chandolia
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Mithilesh Singh
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Anurag Mishra
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Shobhit Raj
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Archita Gupta
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Mohit Agarwal
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Sumaiya Kifayat
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Anamika Gupta
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Prashant Gupta
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Ankit Vashist
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Parth Vaibhav
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Nancy Kathuria
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Vipin Yadav
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Ravindra Pal Singh
- NIMS Institute of Pharmacy, NIMS University Rajasthan, Jaipur, Rajasthan, 303121, India
| | - Arun Garg
- MVN University, Palwal, Haryana, India
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2
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Blackwell DJ, Schmeckpeper J, Knollmann BC. Animal Models to Study Cardiac Arrhythmias. Circ Res 2022; 130:1926-1964. [PMID: 35679367 DOI: 10.1161/circresaha.122.320258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Cardiac arrhythmias are a significant cause of morbidity and mortality worldwide, accounting for 10% to 15% of all deaths. Although most arrhythmias are due to acquired heart disease, inherited channelopathies and cardiomyopathies disproportionately affect children and young adults. Arrhythmogenesis is complex, involving anatomic structure, ion channels and regulatory proteins, and the interplay between cells in the conduction system, cardiomyocytes, fibroblasts, and the immune system. Animal models of arrhythmia are powerful tools for studying not only molecular and cellular mechanism of arrhythmogenesis but also more complex mechanisms at the whole heart level, and for testing therapeutic interventions. This review summarizes basic and clinical arrhythmia mechanisms followed by an in-depth review of published animal models of genetic and acquired arrhythmia disorders.
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Affiliation(s)
- Daniel J Blackwell
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN
| | - Jeffrey Schmeckpeper
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN
| | - Bjorn C Knollmann
- Vanderbilt Center for Arrhythmia Research and Therapeutics, Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN
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3
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Iwasaki YK, Sekiguchi A, Kato T, Yamashita T. Glucocorticoid Induces Atrial Arrhythmogenesis via Modification of Ion Channel Gene Expression in Rats. Int Heart J 2022; 63:375-383. [PMID: 35354756 DOI: 10.1536/ihj.21-677] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Excess psychological stress is one of the precipitating factors for paroxysmal atrial fibrillation (AF), although the involved mechanisms are still uncertain. To test a hypothesis that one of the stress-induced hormones, glucocorticoid, is involved in the pathogenesis of stress-induced AF, we investigated whether the glucocorticoid could alter the temporal profile of cardiac ion channels gene expression, thereby leading to atrial arrhythmogenesis.Dexamethasone (DEX, 1.0 mg/kg) was injected subcutaneously in Sprague-Dawley rats. At predetermined times after DEX injection (0, 1, 3, 6, 12, and 24 hours), the mRNA levels of cardiac ion channel genes (erg, KvLQT1, Kv4.3, Kv4.2, Kv2.1, Kv1.5, Kv1.4, Kv1.2, SUR2A, Kir6.2, Kir3.4, Kir3.1 Kir2.2, Kir2.1, SCN5A, and α1C) were determined using RNase protection assay. DEX induced immediate and transient increase in the mRNA level of Kv1.5 and Kir2.2 with peaks at 6 (5.0 fold) and 3 hours (3.3 fold) after DEX injection, respectively. Patch-clamp studies revealed a significantly increased current density of the corresponding current, IKur and IK1 at 6 hours after DEX injection. Simultaneously, electrophysiological study in isolated perfused hearts showed significantly increased number of repetitive atrial responses induced by single atrial extrastimulus (3.2 ± 2.4 to 26.7 ± 16.4, P = 0.004) with shorting of the refractory period (36.4 ± 4.6 to 27.4 ± 5.5 ms, P = 0.049) after DEX injection.Glucocorticoid immediately modified Kv1.5 and Kir2.2 gene expression at pretranslational levels, thus leading to effective refractory period shortening that could be arrhythmogenic. These results implied that transient glucocorticoid-induced biochemical modification of cardiac ion channels might be one of the mechanisms underlying the stress-induced paroxysmal AF.
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Affiliation(s)
- Yu-Ki Iwasaki
- Department of Cardiovascular Medicine, Nippon Medical School
| | | | - Takeshi Kato
- Department of Cardiovascular Medicine, Graduate School of Medical Science, Kanazawa University
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4
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Wang D, Sun L, Zhang G, Liu Y, Liang Z, Zhao J, Yin S, Su M, Zhang S, Wei Y, Liu H, Liang D, Li Y. Increased Susceptibility of Atrial Fibrillation Induced by Hyperuricemia in Rats: Mechanisms and Implications. Cardiovasc Toxicol 2021; 21:192-205. [PMID: 33099748 DOI: 10.1007/s12012-020-09611-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 10/09/2020] [Indexed: 12/31/2022]
Abstract
High levels of serum uric acid is closely associated with atrial fibrillation (AF); nonetheless, the detailed mechanisms remain unknown. Therefore, this work examined the intricate mechanisms of AF triggered by hyperuricemia and the impact of the uricosuric agent benzbromarone on atrial remodeling in hyperuricemic rats. After adjusting baseline serum uric acid levels, a total of 28 healthy male adult Sprague Dawley rats were randomly divided into 4 groups, namely, control (CTR), hyperuricemia (oxonic acid potassium salt, OXO) and benzbromarone (+ BBR), and OXO withdrawal groups. Primary rat cardiomyocytes were cultured with uric acid for 24 h to investigate the direct influence of uric acid on cardiomyocytes. Results revealed that AF vulnerability and AF duration were dramatically greater in hyperuricemic rats (OXO group), while the atrial effective refractory periods (AERPs) were significantly shorter. Meanwhile, BBR treatment and withdrawal of 2% OXO administration remarkably reduced AF inducibility and shortened AF duration. Moreover, abnormal morphology of atrial myocytes, atrial fibrosis, apoptosis, and substantial sympathetic nerve sprouting were observed in hyperuricemic rats. Apoptosis and fibrosis of atria were partly mediated by caspase-3, BAX, TGF-β1, and α-smooth muscle actin. Uric acid significantly induced primary rat cardiomyocyte apoptosis and fibrosis in vitro. Also, we found that sympathetic nerve sprouting was markedly upregulated in the atria of hyperuricemia rats, and was restored by BRB or absence of OXO administration. In summary, our study confirmed that AF induced by hyperuricemic rats occurred primarily via induction of atrial remodeling, thereby providing a novel potential treatment approach for hyperuricemia-related AF.
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Affiliation(s)
- Dingyu Wang
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China
| | - Li Sun
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China
| | - Guowei Zhang
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China
| | - Yang Liu
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China
| | - Zhaoguang Liang
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China
| | - Jing Zhao
- Key Laboratory of Cardiac Diseases and Heart Failure, Harbin Medical University, Harbin, 150001, Heilongjiang Province, China
| | - Shuangli Yin
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China
| | - Mengqi Su
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China
| | - Song Zhang
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China
| | - Ying Wei
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China
| | - He Liu
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China
| | - Desen Liang
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China.
| | - Yue Li
- Department of Cardiology, The First Affiliated Hospital, Harbin Medical University, Youzheng Street 23#, Nangang District, Harbin, 150001, Heilongjiang Province, China.
- Key Laboratory of Cardiac Diseases and Heart Failure, Harbin Medical University, Harbin, 150001, Heilongjiang Province, China.
- Institute of Metabolic Disease, Heilongjiang Academy of Medical Science, Harbin, 150086, Heilongjiang Province, China.
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5
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Djalinac N, Ljubojevic-Holzer S, Matzer I, Kolesnik E, Jandl K, Lohberger B, Rainer P, Heinemann A, Sedej S, von Lewinski D, Bisping E. The role of stretch, tachycardia and sodium-calcium exchanger in induction of early cardiac remodelling. J Cell Mol Med 2020; 24:8732-8743. [PMID: 32573098 PMCID: PMC7412684 DOI: 10.1111/jcmm.15504] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Revised: 05/20/2020] [Accepted: 05/24/2020] [Indexed: 12/14/2022] Open
Abstract
Stretch and tachycardia are common triggers for cardiac remodelling in various conditions, but a comparative characterization of their role in the excitation‐transcription coupling (ETC) and early regulation of gene expression and structural changes is lacking. Here, we show that stretch and tachycardia directly induced hypertrophy of neonatal rat cardiac myocytes and also of non‐myocytes. Both triggers induced similar patterns of hypertrophy but had largely distinct gene expression profiles. ACTA1 served as good hypertrophy marker upon stretch, while RCAN1 was found increased in response to tachycardia in a rate‐dependent fashion. Mechanistically, several calcium‐handling proteins, including the sodium‐calcium exchanger (NCX), contributed to ETC. Phosphorylation of the calcium/calmodulin‐dependent protein kinase II (CaMKII) was elevated and occurred downstream of NCX activation upon tachycardia, but not stretch. Microarray profiling revealed that stretch and tachycardia regulated around 33% and 20% genes in a NCX‐dependent manner, respectively. In conclusion, our data show that hypertrophy induction by stretch and tachycardia is associated with different gene expression profiles with a significant contribution of the NCX.
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Affiliation(s)
- Natasa Djalinac
- Department of Cardiology, Medical University of Graz, Graz, Austria
| | | | - Ingrid Matzer
- Department of Cardiology, Medical University of Graz, Graz, Austria
| | - Ewald Kolesnik
- Department of Cardiology, Medical University of Graz, Graz, Austria
| | - Katharina Jandl
- Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria.,Ludwig Boltzmann Institute for Lung Vascular Research, Graz, Austria
| | - Birgit Lohberger
- Department of Orthopedics and Trauma, Medical University of Graz, Graz, Austria
| | - Peter Rainer
- Department of Cardiology, Medical University of Graz, Graz, Austria
| | - Akos Heinemann
- Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria
| | - Simon Sedej
- Department of Cardiology, Medical University of Graz, Graz, Austria
| | | | - Egbert Bisping
- Department of Cardiology, Medical University of Graz, Graz, Austria
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6
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Arase H, Yamada S, Tanaka S, Tokumoto M, Tsuruya K, Nakano T, Kitazono T. Association Between Plasma Intact Parathyroid Hormone Levels and the Prevalence of Atrial Fibrillation in Patients With Chronic Kidney Disease - The Fukuoka Kidney Disease Registry Study. Circ J 2020; 84:1105-1111. [PMID: 32507801 DOI: 10.1253/circj.cj-19-1201] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Parathyroid hormone (PTH) has been associated with cardiovascular disorders; however, it is unknown whether plasma PTH concentrations are associated with atrial fibrillation (AF) in patients with chronic kidney disease (CKD).Methods and Results:The present cross-sectional study analyzed baseline data of 3,384 patients registered in the Fukuoka Kidney Disease Registry Study, a Japanese multicenter prospective cohort study of patients with non-dialysis-dependent CKD. The outcome was prevalence of AF, and the main risk factor was plasma intact PTH concentration. Associations between plasma intact PTH concentration quartiles (Q1-Q4, from lowest to highest) and the presence of AF were analyzed using logistic regression. In all, 185 patients had AF; 22, 34, 59, and 70 patients were in Q1, Q2, Q3, and Q4 of PTH concentrations, respectively. The prevalence of AF increased incrementally with increases in plasma intact PTH. In the logistic regression model, patients with higher plasma intact PTH concentrations (Q2-Q4) had higher adjusted odds ratios (95% confidence intervals) for the prevalence of AF relative to the reference group (Q1), namely 1.33 (0.76-2.34), 1.82 ([1.06-3.13), and 1.99 (1.08-3.64), respectively (P=0.016). CONCLUSIONS Higher plasma intact PTH concentrations were significantly and incrementally associated with an increased prevalence of AF in non-dialysis-dependent CKD patients.
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Affiliation(s)
- Hokuto Arase
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University
| | - Shunsuke Yamada
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University
| | - Shigeru Tanaka
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University
| | | | - Kazuhiko Tsuruya
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University.,Department of Nephrology, Nara Medical University
| | - Toshiaki Nakano
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University
| | - Takanari Kitazono
- Department of Medicine and Clinical Science, Graduate School of Medical Sciences, Kyushu University
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7
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Melgari D, Barbier C, Dilanian G, Rücker-Martin C, Doisne N, Coulombe A, Hatem SN, Balse E. Microtubule polymerization state and clathrin-dependent internalization regulate dynamics of cardiac potassium channel: Microtubule and clathrin control of K V1.5 channel. J Mol Cell Cardiol 2020; 144:127-139. [PMID: 32445844 DOI: 10.1016/j.yjmcc.2020.05.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 05/08/2020] [Accepted: 05/09/2020] [Indexed: 12/19/2022]
Abstract
Ion channel trafficking powerfully influences cardiac electrical activity as it regulates the number of available channels at the plasma membrane. Studies have largely focused on identifying the molecular determinants of the trafficking of the atria-specific KV1.5 channel, the molecular basis of the ultra-rapid delayed rectifier current IKur. Besides, regulated KV1.5 channel recycling upon changes in homeostatic state and mechanical constraints in native cardiomyocytes has been well documented. Here, using cutting-edge imaging in live myocytes, we investigated the dynamics of this channel in the plasma membrane. We demonstrate that the clathrin pathway is a major regulator of the functional expression of KV1.5 channels in atrial myocytes, with the microtubule network as the prominent organizer of KV1.5 transport within the membrane. Both clathrin blockade and microtubule disruption result in channel clusterization with reduced membrane mobility and internalization, whereas disassembly of the actin cytoskeleton does not. Mobile KV1.5 channels are associated with the microtubule plus-end tracking protein EB1 whereas static KV1.5 clusters are associated with stable acetylated microtubules. In human biopsies from patients in atrial fibrillation associated with atrial remodeling, drastic modifications in the trafficking balance occurs together with alteration in microtubule polymerization state resulting in modest reduced endocytosis and increased recycling. Consequently, hallmark of atrial KV1.5 dynamics within the membrane is clathrin- and microtubule- dependent. During atrial remodeling, predominance of anterograde trafficking activity over retrograde trafficking could result in accumulation ok KV1.5 channels in the plasma membrane.
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Affiliation(s)
- Dario Melgari
- INSERM UMRS1166, ICAN - Institute of CardioMetabolism and Nutrition, Sorbonne Université, Paris, France
| | - Camille Barbier
- INSERM UMRS1166, ICAN - Institute of CardioMetabolism and Nutrition, Sorbonne Université, Paris, France
| | - Gilles Dilanian
- INSERM UMRS1166, ICAN - Institute of CardioMetabolism and Nutrition, Sorbonne Université, Paris, France
| | | | - Nicolas Doisne
- INSERM UMRS1166, ICAN - Institute of CardioMetabolism and Nutrition, Sorbonne Université, Paris, France
| | - Alain Coulombe
- INSERM UMRS1166, ICAN - Institute of CardioMetabolism and Nutrition, Sorbonne Université, Paris, France
| | - Stéphane N Hatem
- INSERM UMRS1166, ICAN - Institute of CardioMetabolism and Nutrition, Sorbonne Université, Paris, France; Institut de Cardiologie, Hôpital Pitié-Salpêtrière, Paris, France
| | - Elise Balse
- INSERM UMRS1166, ICAN - Institute of CardioMetabolism and Nutrition, Sorbonne Université, Paris, France.
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8
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Mulla W, Hajaj B, Elyagon S, Mor M, Gillis R, Murninkas M, Klapper-Goldstein H, Plaschkes I, Chalifa-Caspi V, Etzion S, Etzion Y. Rapid Atrial Pacing Promotes Atrial Fibrillation Substrate in Unanesthetized Instrumented Rats. Front Physiol 2019; 10:1218. [PMID: 31616316 PMCID: PMC6763969 DOI: 10.3389/fphys.2019.01218] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 09/06/2019] [Indexed: 12/19/2022] Open
Abstract
Aim The self-perpetuating nature of atrial fibrillation (AF) has been a subject of intense research in large mammalian models exposed to rapid atrial pacing (RAP). Recently, rodents are increasingly used to gain insight into the pathophysiology of AF. However, little is known regarding the effects of RAP on the atria of rats and mice. Using an implantable device for electrophysiological studies in rodents, we examined on a daily basis, the effects of continuous RAP on the developed AF substrate of unanesthetized rats and mice. Methods and Results Aggressive burst pacing did not induce AF at baseline in the large majority of rodents, but repeatedly induced AF episodes in rats exposed to RAP for more than 2 days. A microarray study of left atrial tissue from rats exposed to RAP for 2 days vs. control pacing identified 304 differentially expressed genes. Enrichment analysis and comparison with a dataset of atrial tissue from AF patients revealed indications of increased carbohydrate metabolism and changes in pathways that are thought to play critical roles in human AF, including TGF-beta and IL-6 signaling. Among 19 commonly affected genes in comparison with human AF, downregulation of FOXP1 and upregulation of the KCNK2 gene encoding the Kir2.1 potassium channel were conspicuous findings, suggesting NFAT activation. Further results included reduced expression of MIR-26 and MIR-101, which is in line with NFAT activation. Conclusion Our results demonstrate electrophysiological evidence for AF promoting effects of RAP in rats and several molecular similarities between the effects of RAP in large and small mammalian models.
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Affiliation(s)
- Wesam Mulla
- Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Regenerative Medicine and Stem Cell Research Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Barak Hajaj
- Shraga Segal Department of Microbiology, Immunology and Genetics, Faculty of Health Sciences Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Sigal Elyagon
- Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Regenerative Medicine and Stem Cell Research Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Michal Mor
- Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Roni Gillis
- Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Regenerative Medicine and Stem Cell Research Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Michael Murninkas
- Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Regenerative Medicine and Stem Cell Research Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Hadar Klapper-Goldstein
- Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Regenerative Medicine and Stem Cell Research Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Inbar Plaschkes
- National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Vered Chalifa-Caspi
- National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Sharon Etzion
- Regenerative Medicine and Stem Cell Research Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Yoram Etzion
- Cardiac Arrhythmia Research Laboratory, Department of Physiology and Cell Biology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Regenerative Medicine and Stem Cell Research Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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9
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Higashiyama A, Kokubo Y, Watanabe M, Nakao YM, Okamura T, Okayama A, Miyamoto Y. Echocardiographic Parameters and the Risk of Incident Atrial Fibrillation: The Suita Study. J Epidemiol 2019; 30:183-187. [PMID: 30930375 PMCID: PMC7064552 DOI: 10.2188/jea.je20180251] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Background Left atrial dimension (LAD) and other parameters of echocardiography have been reported to be associated with the risk of atrial fibrillation (AF). However, few studies have investigated the associations between echocardiographic parameters and the risk of AF in the Asian general population, which has a low AF incidence. Methods A prospective cohort study was performed in 1,424 individuals in the Suita study with echocardiographic parameters, including LAD, and no history of AF. After echocardiography, the participants were followed using 12-lead electrocardiography and questionnaires to detect AF incidence. The multivariable-adjusted hazard ratios (HRs) of echocardiographic parameters for AF incidence were estimated after adjustment for the risk factors of the AF risk score. Results During the median 6.0 years of follow-up, 31 AF cases occurred. The multivariable-adjusted HR of a 1-mm increase in LAD for AF was 1.18 (95% confidence interval [CI], 1.08–1.28). The multivariable-adjusted HR for AF of a 1-standard-deviation increase in LAD was higher than that of left ventricular internal dimensions in diastole, left ventricular mass, ejection fraction, and percent fractional shortening, and it was the only significant factor. In 667 participants with both LAD and LA volume (LAV) measurements, LAD and LAV were independently associated with the risk of AF incidence. Conclusions LAD on echocardiography was an independent risk factor of incident AF in the Japanese population. LAD might be useful for identifying individuals with a high risk of AF in health check-ups of the general population.
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Affiliation(s)
- Aya Higashiyama
- Department of Preventive Cardiology, National Cerebral and Cardiovascular Center
| | - Yoshihiro Kokubo
- Department of Preventive Cardiology, National Cerebral and Cardiovascular Center
| | - Makoto Watanabe
- Department of Preventive Cardiology, National Cerebral and Cardiovascular Center
| | - Yoko Masukata Nakao
- Department of Preventive Cardiology, National Cerebral and Cardiovascular Center
| | - Tomonori Okamura
- Department of Preventive Medicine and Public Health, Keio University
| | | | - Yoshihiro Miyamoto
- Department of Preventive Cardiology, National Cerebral and Cardiovascular Center
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Zhao G, Zhou J, Gao J, Liu Y, Gu S, Zhang X, Su P. Genome-wide DNA methylation analysis in permanent atrial fibrillation. Mol Med Rep 2017; 16:5505-5514. [DOI: 10.3892/mmr.2017.7221] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 04/25/2017] [Indexed: 11/06/2022] Open
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Tong M, Wang J, Ji Y, Chen X, Wang J, Wang S, Ruan L, Cui H, Zhou Y, Zhang Q, Watanabe E. Effect of eicosapentaenoic acid and pitavastatin on electrophysiology and anticoagulant gene expression in mice with rapid atrial pacing. Exp Ther Med 2017; 14:2310-2316. [PMID: 28962160 DOI: 10.3892/etm.2017.4741] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Accepted: 04/21/2017] [Indexed: 12/19/2022] Open
Abstract
Atrial remodeling is considered to be any persistent change in atrial structure or function, and is responsible for the development and perpetuation of atrial fibrillation (AF). Oxidative stress and intracellular pH regulation may also be linked to AF; however it remains unclear whether eicosapentaenoic acid (EPA) or statins have beneficial therapeutic effects. The aim of the present study was to investigate the effects of EPA and pitavastatin on the electrophysiology of and gene expressions in mice with rapidly-paced atria. Mice were treated with EPA (10 mg/g/day) or pitavastatin (30 ng/g/day) for 6 weeks, following which AF was simulated by 8-h atrial pacing at 1,800 bpm. The atrial electrophysiological properties and the expression of cardiac genes, potassium voltage-gated channel subfamily A member 5 (Kcna5), Kcn subfamily D member 2 (Kcnd2), Kv channel-interacting protein 2 (KChIP2), solute carrier family 9 member A1, thrombomodulin (TM) and tissue factor pathway inhibitor (TFPI) were examined using reverse transcription-quantitative polymerase chain reaction. In control mice, significant atrial electrical remodeling was observed (P<0.05); however, treatment with either EPA or pitavastatin ameliorated these electrophysiological changes (P>0.05). mRNA levels of Kcnd2, KChIP2 and Kcna5 were significantly upregulated in control mice (P<0.05), whereas treatment with EPA or pitavastatin attenuated this upregulation (P>0.05). Administration of pitavastatin significantly reduced the downregulation of both TFPI and TM (P<0.05). EPA treatment attenuated the TFPI downregulation compared with control mice (P>0.05), however no significant effect on TM expression was observed. In addition, both EPA (P>0.05) and pitavastatin (P<0.05) suppressed the overexpression of endothelial nitric oxide synthase. This was also exhibited in Ras-related C3 botulinum toxin substrate 1 genes (P<0.01 for both treatments). In conclusion, the results of the present study suggested that EPA and pitavastatin are able to prevent atrial electrical remodeling, thrombotic states and oxidative stress in rapidly-paced murine atria.
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Affiliation(s)
- Maoqing Tong
- Department of Cardiology, Key Laboratory of Molecular Medicine, The Affiliated Ningbo First Hospital, School of Medicine, Ningbo University, Ningbo, Zhejiang 315010, P.R. China
| | - Jiewen Wang
- Department of Gynecology and Obstetrics, The Second Affiliated Hospital of Bengbu Medical College, Bengbu, Anhui 233040, P.R. China
| | - Yunxin Ji
- Department of Psychosomatic Medicine, The Affiliated Ningbo First Hospital, School of Medicine, Ningbo University, Ningbo, Zhejiang 315010, P.R. China
| | - Xiaomin Chen
- Department of Cardiology, The Affiliated Ningbo First Hospital, School of Medicine, Ningbo University, Ningbo, Zhejiang 315010, P.R. China
| | - Jieru Wang
- Department of International Health, The Affiliated Ningbo First Hospital, School of Medicine, Ningbo University, Ningbo, Zhejiang 315010, P.R. China
| | - Shuangshuang Wang
- Department of Cardiology, The Affiliated Ningbo First Hospital, School of Medicine, Ningbo University, Ningbo, Zhejiang 315010, P.R. China
| | - Liemin Ruan
- Department of Psychosomatic Medicine, The Affiliated Ningbo First Hospital, School of Medicine, Ningbo University, Ningbo, Zhejiang 315010, P.R. China
| | - Hanbin Cui
- Department of Cardiology, The Affiliated Ningbo First Hospital, School of Medicine, Ningbo University, Ningbo, Zhejiang 315010, P.R. China
| | - Ying Zhou
- Department of Cardiology, Key Laboratory of Molecular Medicine, The Affiliated Ningbo First Hospital, School of Medicine, Ningbo University, Ningbo, Zhejiang 315010, P.R. China
| | - Qingyu Zhang
- Department of Psychosomatic Medicine, The Affiliated Ningbo First Hospital, School of Medicine, Ningbo University, Ningbo, Zhejiang 315010, P.R. China
| | - Eiichi Watanabe
- Department of Cardiology, Fujita Health University School of Medicine, Toyoake 470-1192, Japan
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12
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Yaegashi T, Kato T, Usui S, Kanamori N, Furusho H, Takashima SI, Murai H, Kaneko S, Takamura M. Short-term rapid atrial pacing alters the gene expression profile of rat liver: Cardiohepatic interaction in atrial fibrillation. Heart Rhythm 2016; 13:2368-2376. [DOI: 10.1016/j.hrthm.2016.08.036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Indexed: 11/25/2022]
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Shinohara D, Matsushita S, Yamamoto T, Inaba H, Kuwaki K, Shimada A, Amano A. Reduction of c-kit positive cardiac stem cells in patients with atrial fibrillation. J Cardiol 2016; 69:712-718. [PMID: 27499271 DOI: 10.1016/j.jjcc.2016.07.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 06/21/2016] [Accepted: 07/11/2016] [Indexed: 01/01/2023]
Abstract
BACKGROUND We aimed to determine expression patterns of cardiac stem cells in the left atrium (LA) tissue from patients with atrial fibrillation. METHODS LA appendages were obtained during open-heart surgery and processed for explant cell culture and tissue analysis (n=319). The total number of grown cells and c-kit positive cells were analyzed by flow cytometry after 4 weeks of culture. The remaining tissue was used for Masson's trichrome staining to determine the area of the fibrosis. RESULTS The diameter of the LA, as measured by echocardiography, was significantly larger in the AF group than in the sinus rhythm group. Reverse transcription polymerase chain reaction analysis revealed higher expression of collagen in the AF group and an increase in the expression of basic fibrosis growth factor and transforming growth factor-2 and -3. Masson's trichrome staining showed progression of fibrosis in the AF tissue. In addition, the expression of apoptosis-related genes were significantly higher in AF group. There was no difference in the expression of connexin-40 between groups, while the expression of connexin-43 was decreased and that of connexin-45 was increased in the AF group. The total numbers of grown cells as well as c-kit positive cells after 4 weeks of cardiac tissue culture were significantly lower in the AF group. CONCLUSION Progression of remodeling in LA tissue was observed in AF patients. The number of c-kit positive cells cultured from LA appendages was reduced in AF patients, suggesting impairments in self-renewal.
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Affiliation(s)
- Daisuke Shinohara
- Department of Cardiovascular Surgery, Juntendo University, Faculty of Medicine, Tokyo, Japan
| | - Satoshi Matsushita
- Department of Cardiovascular Surgery, Juntendo University, Faculty of Medicine, Tokyo, Japan.
| | - Taira Yamamoto
- Department of Cardiovascular Surgery, Juntendo University, Faculty of Medicine, Tokyo, Japan
| | - Hirotaka Inaba
- Department of Cardiovascular Surgery, Juntendo University, Faculty of Medicine, Tokyo, Japan
| | - Kenji Kuwaki
- Department of Cardiovascular Surgery, Juntendo University, Faculty of Medicine, Tokyo, Japan
| | - Akie Shimada
- Department of Cardiovascular Surgery, Juntendo University, Faculty of Medicine, Tokyo, Japan
| | - Atsushi Amano
- Department of Cardiovascular Surgery, Juntendo University, Faculty of Medicine, Tokyo, Japan
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Nattel S, Guasch E, Savelieva I, Cosio FG, Valverde I, Halperin JL, Conroy JM, Al-Khatib SM, Hess PL, Kirchhof P, De Bono J, Lip GYH, Banerjee A, Ruskin J, Blendea D, Camm AJ. Early management of atrial fibrillation to prevent cardiovascular complications. Eur Heart J 2014; 35:1448-56. [PMID: 24536084 DOI: 10.1093/eurheartj/ehu028] [Citation(s) in RCA: 164] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
| | | | - Irina Savelieva
- Division of Clinical Sciences, Cardiovascular Science, St George's University of London, Cranmer Terrace, London, SW17 0RE, UK
| | - Francisco G Cosio
- Cardiología Department, Hospital Universitario de Getafe, Madrid, Spain
| | - Irene Valverde
- Cardiología Department, Hospital Universitario de Getafe, Madrid, Spain
| | - Jonathan L Halperin
- Zena and Michael A. Wiener Cardiovascular Institute, Mount Sinai School of Medicine, New York, NY, USA
| | - Jennifer M Conroy
- Zena and Michael A. Wiener Cardiovascular Institute, Mount Sinai School of Medicine, New York, NY, USA
| | - Sana M Al-Khatib
- Cardiology Division, Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - Paul L Hess
- Cardiology Division, Department of Medicine, Duke University Medical Center, Durham, NC, USA
| | - Paulus Kirchhof
- University of Birmingham Centre for Cardiovascular Sciences, University of Birmingham and Sandwell and West Birmingham NHS Trust, Birmingham, UK Department of Cardiology and Angiology, Hospital of the University of Münster, Münster, Germany German Atrial Fibrillation Competence NETwork (AFNET), Münster, Germany
| | - Joseph De Bono
- University Hospitals Birmingham NHS Trust, Birmingham, UK
| | - Gregory Y H Lip
- University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Birmingham, UK
| | - Amitava Banerjee
- University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Birmingham, UK
| | - Jeremy Ruskin
- Department of Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - Dan Blendea
- Department of Medicine, Massachusetts General Hospital, Boston, MA, USA
| | - A John Camm
- Division of Clinical Sciences, Cardiovascular Science, St George's University of London, Cranmer Terrace, London, SW17 0RE, UK
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YANG DONGHUI, XI YUTAO, AI TOMOHIKO, WU GERU, SUN JUNPING, RAZAVI MEHDI, DELAPASSE SCOTT, SHURAIL MOSSAIB, GAO LIANJUN, MATHURIA NILESH, ELAYDA MACARTHUR, CHENG JIE. Vagal Stimulation Promotes Atrial Electrical Remodeling Induced by Rapid Atrial Pacing in Dogs: Evidence of a Noncholinergic Effect. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2011; 34:1092-9. [DOI: 10.1111/j.1540-8159.2011.03133.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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17
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Zigel Y, Mor M, Tzvi E, Tsviling V, Gil O, Katz A, Etzion Y. A Surface ECG-Based Algorithm to Determine the Atrial Refractoriness of Rodents During Electrophysiological Study. Cardiovasc Eng Technol 2011. [DOI: 10.1007/s13239-011-0055-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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18
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Chang D, Zhang S, Yang D, Gao L, Lin Y, Chu Z, Jiang X, Yin X, Zheng Z, Wei X, You D, Xiao X, Cong P, Bian X, Xia Y, Yang Y. Effect of epicardial fat pad ablation on acute atrial electrical remodeling and inducibility of atrial fibrillation. Circ J 2010; 74:885-94. [PMID: 20379001 DOI: 10.1253/circj.cj-09-0967] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Atrial electrical remodeling (AER) is the underlying mechanism of atrial fibrillation (AF). The present study investigated the impact of epicardial fat pad (FP) ablation on acute AER (AAER) and inducibility of AF. METHODS AND RESULTS AAER was performed in 28 mongrel dogs through 4-h rapid atrial pacing (RAP). Before RAP, 14 dogs (ablation group) underwent FP ablation, and the other 14 (control group) underwent a sham procedure. The atrial effective refractory period (ERP) and vulnerability window (VW) of AF were measured with and without bilateral cervical vagosympathetic nerve stimulation (VNS) at the high right atrium, ostium of the coronary sinus (CS) and distal CS before and after every hour of RAP. In the control group, ERP was markedly shortened in the first 2 h of RAP and then stabilized. AF was only slightly induced. After RAP, the time course of ERP with and without VNS was similar. VNS significantly shortened ERP and increased VW before and after RAP. In the ablation group, ERP was significantly prolonged after FP ablation. Moreover, neither VNS nor RAP shortened the ERP or increased the VW. AF could not be induced (VW=0). CONCLUSIONS RAP resulted in AAER, which may be mediated and aggravated by autonomic activity. Epicardial FP ablation generated denervation, which not only abolishes AF inducibility but also prevents RAP-mediated AAER.
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Affiliation(s)
- Dong Chang
- Department of Cardiology, First Affiliated Hospital of Dalian Medical University, Dalian, China
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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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21
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Tsuchiya H, Nakazato Y, Hayashi H, Suzuki T, Sekita G, Daida H. Effects of Bepridil on Atrial Electrical Remodeling in Short-Term Rapid Pacing. J Arrhythm 2009. [DOI: 10.1016/s1880-4276(09)80022-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Imai S, Saito F, Takase H, Enomoto M, Aoyama H, Yamaji S, Yokoyama K, Yagi H, Kushiro T, Hirayama A. Use of bepridil in combination with Ic antiarrhythmic agent in converting persistent atrial fibrillation to sinus rhythm. Circ J 2008; 72:709-15. [PMID: 18441448 DOI: 10.1253/circj.72.709] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND It has been reported that bepridil is as good as amiodarone in converting persistent atrial fibrillation (AF) to sinus rhythm (SR). The conversion effect of bepridil alone is not always satisfactory, however. The efficacy of pharmacological cardioversion by the combination of bepridil and a class Ic antiarrhythmic drug for persistent AF is studied. METHODS AND RESULTS The participants comprised 37 consecutive patients in whom pharmacological cardioversion was conducted to treat persistent AF (duration 22.5+/-29.6 months). Each patient first received a class Ia or Ic antiarrhythmic drug, then bepridil alone, then a combined therapy of bepridil at 200 mg/day with a class Ic antiarrhythmic drug at a routine dose. Unaccompanied use of any of the antiarrhythmic drugs achieved pharmacological cardioversion in 14 (38%) of the 37 patients (single therapy group), whereas SR was restored by combination of bepridil and a class Ic antiarrhythmic drug in 22 (combined therapy group) of the remaining 23 patients. The duration of AF was significantly longer in the combined therapy group than in the single therapy group (28.3+/-31.0 vs 7.3+/-4.1 months). CONCLUSION Combined therapy of bepridil and a class Ic antiarrhythmic drug is efficient for pharmacological cardioversion of refractory long-lasting persistent AF.
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Affiliation(s)
- Shinobu Imai
- Department of Cardiology, Nihon University Surugadai Hospital, Nihon University School of Medicine, Tokyo, Japan.
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Etzion Y, Mor M, Shalev A, Dror S, Etzion O, Dagan A, Beharier O, Moran A, Katz A. New insights into the atrial electrophysiology of rodents using a novel modality: the miniature-bipolar hook electrode. Am J Physiol Heart Circ Physiol 2008; 295:H1460-9. [PMID: 18660446 DOI: 10.1152/ajpheart.00414.2008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Studies of atrial electrophysiology (EP) in rodents are challenging, and available data are sparse. Herein, we utilized a novel type of bipolar electrode to evaluate the atrial EP of rodents through small lateral thoracotomy. In anesthetized rats and mice, we attached two bipolar electrodes to the right atrium and a third to the right ventricle. This standard setup enabled high-resolution EP studies. Moreover, a permanent implantation procedure enabled EP studies in conscious freely moving rats. Atrial EP was evaluated in anesthetized rats, anesthetized mice (ICR and C57BL6 strains), and conscious rats. Signal resolution enabled atrial effective refractory period (AERP) measurements and first time evaluation of the failed 1:1 atrial capture, which was unexpectedly longer than the AERP recorded at near normal cycle length by 27.2+/-2.3% in rats (P<0.0001; n=35), 31.7+/-8.3% in ICR mice (P=0.0001; n=13), and 57.7+/-13.7% in C57BL6 mice (P=0.015; n=4). While AERP rate adaptation was noted when 10 S1s at near normal basic cycle lengths were followed by S2 at varying basic cycle length and S3 for AERP evaluation, such rate adaptation was absent using conventional S1S2 protocols. Atrial tachypacing in rats shortened the AERP values on a timescale of hours, but a reverse remodeling phase was noted thereafter. Comparison of left vs. right atrial pacing in rats was also feasible with the current technique, resulting in similar AERP values recorded in the low right atrium. In conclusion, our findings indicate that in vivo rate adaptation of the rodent atria is different than expected based on previous ex vivo recordings. In addition, atrial electrical remodeling of rats shows unique remodeling-reverse remodeling characteristics that are described here for the first time. Further understanding of these properties should help to determine the clinical relevance as well as limitations of atrial arrhythmia models in rodents.
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Affiliation(s)
- Yoram Etzion
- Cardiac Arrhythmia Research Laboratory, Soroka University Medical Center, Beer-Sheva, Israel.
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Lu Z, Scherlag BJ, Lin J, Niu G, Fung KM, Zhao L, Ghias M, Jackman WM, Lazzara R, Jiang H, Po SS. Atrial fibrillation begets atrial fibrillation: autonomic mechanism for atrial electrical remodeling induced by short-term rapid atrial pacing. Circ Arrhythm Electrophysiol 2008; 1:184-92. [PMID: 19808412 DOI: 10.1161/circep.108.784272] [Citation(s) in RCA: 146] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
BACKGROUND The mechanism(s) for acute changes in electrophysiological properties of the atria during rapid pacing induced atrial fibrillation (AF) is not completely understood. We sought to evaluate the contribution of the intrinsic cardiac autonomic nervous system in acute atrial electrical remodeling and AF induced by 6-hour rapid atrial pacing. METHODS AND RESULTS Continuous rapid pacing (1200 bpm, 2x threshold [TH]) was performed at the left atrial appendage. Group 1 (n=7) underwent 6-hour pacing immediately followed by ganglionated plexi (GP) ablation; group 2 (n=7) underwent GP ablation immediately followed by 6-hour pacing; and group 3 (n=4) underwent administration of autonomic blockers, atropine (1 mg/kg), and propranolol (0.6 mg/kg) immediately followed by 6-hour pacing. The effective refractory period (ERP) and window of vulnerability (WOV, in milliseconds), ie, the difference between the longest and the shortest coupling interval of the premature stimulus that induced AF, were measured at 2xTH and 10xTH at the left atrium, right atrium, and pulmonary veins every hour before and after GP ablation or autonomic blockade. In group 1, ERP was markedly shortened in the first 2 hours and then stabilized both at 2xTH and 10xTH; however, WOV was progressively widened throughout the 6-hour period. After GP ablation, ERP was significantly longer than before ablation and AF could not be induced (WOV=0) at either 2xTH or 10xTH. In groups 2 and 3, rapid atrial pacing failed to shorten the ERP. AF could not be induced in 6 of 7 dogs in group 2 and all 4 dogs in group 3 during the 6-hour pacing period. CONCLUSIONS The intrinsic cardiac autonomic nervous system plays a crucial role in the acute stages of atrial electrical remodeling induced by rapid atrial pacing.
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Affiliation(s)
- Zhibing Lu
- Department of Cardiology, Renmin Hospital of Wuhan University, Wuhan, China
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Yamashita T, Sekiguchi A, Kato T, Tsuneda T, Iwasaki YK, Sagara K, Iinuma H, Sawada H, Aizawa T. Angiotensin type 1 receptor blockade prevents endocardial dysfunction of rapidly paced atria in rats. J Renin Angiotensin Aldosterone Syst 2008; 8:127-32. [PMID: 17907100 DOI: 10.3317/jraas.2007.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
INTRODUCTION Atrial fibrillation (AF) per se causes atrial endocardial dysfunction leading to local coagulation imbalance on the internal surface of the atrium, which contributes to thrombus formation in the fibrillating left atrium. MATERIALS AND METHODS To test a hypothesis that blockade of angiotensin II type 1 receptor (AT1-receptor) prevents the endocardial dysfunction by AF, we examined the effects of olmesartan on the expression of tissue factor pathway inhibitor (TFPI), thrombomodulin (TM), endothelial nitric oxide synthase (eNOS) and plasminogen activator inhibitor-1 (PAI-1) in the endocardium of the rapidly paced rat atria. RESULTS Rapid pacing induced a significant decrease in TFPI, TM and eNOS and an increase in PAI-1 protein in the left atrium. Pre-administration of low-dose olmesartan significantly prevented the down-regulation of TFPI, TM and eNOS and also attenuated the up-regulation of PAI-1. Immunohistochemistry identified these changes predominantly in the atrial endocardium. While the drug was without any effect on mRNA levels of TFPI, TM and eNOS, there was a significant decrease in its PAI-1 mRNA expression. CONCLUSIONS AT1-receptor blocker could partially prevent the atrial endocardial dysfunction by rapid atrial pacing, which would provide one theoretical basis for beneficial effects for stroke prevention in AF.
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Affiliation(s)
- Takeshi Yamashita
- The Cardiovascular Institute, Roppongi 7-3-10, Tokyo 106-0032, Japan.
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Analysis of damped oscillations during reentry: a new approach to evaluate cardiac restitution. Biophys J 2007; 94:1094-109. [PMID: 17921218 DOI: 10.1529/biophysj.107.113811] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Reentry is a mechanism underlying numerous cardiac arrhythmias. During reentry, head-tail interactions of the action potential can cause cycle length (CL) oscillations and affect the stability of reentry. We developed a method based on a difference-delay equation to determine the slopes of the action potential duration and conduction velocity restitution functions, known to be major determinants of reentrant arrhythmogenesis, from the spatial period P and the decay length D of damped CL oscillations. Using this approach, we analyzed CL oscillations after the induction of reentry and the resetting of reentry with electrical stimuli in rings of cultured neonatal rat ventricular myocytes grown on microelectrode arrays and in corresponding simulations with the Luo-Rudy model. In the experiments, P was larger and D was smaller after resetting impulses compared to the induction of reentry, indicating that reentry became more stable. Both restitution slopes were smaller. Consistent with the experimental findings, resetting of simulated reentry caused oscillations with gradually increasing P, decreasing D, and decreasing restitution slopes. However, these parameters remained constant when ion concentrations were clamped, revealing that intracellular ion accumulation stabilizes reentry. Thus, the analysis of CL oscillations during reentry opens new perspectives to gain quantitative insight into action potential restitution.
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Yoshida T, Niwano S, Niwano H, Imaki R, Satoh D, Masaki Y, Nakazato K, Soma K, Izumi T. Atrial natriuretic peptide (ANP) suppresses acute atrial electrical remodeling in the canine rapid atrial stimulation model. Int J Cardiol 2007; 123:147-54. [PMID: 17376550 DOI: 10.1016/j.ijcard.2006.12.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2006] [Revised: 11/06/2006] [Accepted: 12/11/2006] [Indexed: 11/24/2022]
Abstract
OBJECTIVES Atrial electrical remodeling is considered to play an important role in the appearance of atrial fibrillation. The effect of atrial natriuretic peptide (ANP) on atrial electrical remodeling was evaluated in a canine atrial stimulation model. METHODS In 15 beagle dogs, electrodes for pacing and recording were fixed on the atrial surface. In 10/15 dogs, rapid atrial stimulation (400 bpm) was performed for 7 h at the right atrial appendage (RAA) and the remaining 5 were used as the sham without rapid pacing. In 5/10 dogs with rapid pacing, human atrial natriuretic peptide (ANP) was infused (1.0 microg/kg/min). The effective refractory period (ERP) and the monophasic action potential duration (MAP) were evaluated at 0, 3, and 7 h after rapid pacing. The expression levels of mRNAs of ion channels or transporters were evaluated from the atrial samples of sham and after a 7 hour pacing. RESULTS In the control group with rapid pacing (n=5), the atrial ERP and MAP duration were shortened at all atrial sites, e.g., ERP from 148+/-14 ms to 109+/-8 ms at RAA, P=0.006. In contrast in the ANP group, neither the ERP nor MAP duration showed a significant shortening and the effect of ANP on hemodynamic parameter was relatively small. Expression levels of the mRNA were not significantly different between the control and ANP groups. CONCLUSIONS Administration of ANP prevented the shortening of the ERP and MAP duration in the rapid atrial stimulation model. The effect of ANP on atrial electrical remodeling was considered to be due to its direct action on the myocardium.
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Affiliation(s)
- Toru Yoshida
- Department of Emergency and Critical Care Medicine, Kitasato University School of Medicine, 1-15-1, Kitasato, Sagamihara, Kanagawa, 228-8555, Japan.
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Saygili E, Rana OR, Saygili E, Reuter H, Frank K, Schwinger RHG, Müller-Ehmsen J, Zobel C. Losartan prevents stretch-induced electrical remodeling in cultured atrial neonatal myocytes. Am J Physiol Heart Circ Physiol 2007; 292:H2898-905. [PMID: 17293496 DOI: 10.1152/ajpheart.00546.2006] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Atrial fibrillation (AF) is the most frequent arrhythmia found in clinical practice. In recent studies, a decrease in the development or recurrence of AF was found in hypertensive patients treated with angiotensin-converting enzyme inhibitors or angiotensin receptor-blocking agents. Hypertension is related to an increased wall tension in the atria, resulting in increased stretch of the individual myocyte, which is one of the major stimuli for the remodeling process. In the present study, we used a model of cultured atrial neonatal rat cardiomyocytes under conditions of stretch to provide insight into the mechanisms of the preventive effect of the angiotensin receptor-blocking agent losartan against AF on a molecular level. Stretch significantly increased protein-to-DNA ratio and atrial natriuretic factor mRNA expression, indicating hypertrophy. Expression of genes encoding for the inward rectifier K(+) current (I(K1)), Kir 2.1, and Kir 2.3, as well as the gene encoding for the ultrarapid delayed rectifier K(+) current (I(Kur)), Kv 1.5, was significantly increased. In contrast, mRNA expression of Kv 4.2 was significantly reduced in stretched myocytes. Alterations of gene expression correlated with the corresponding current densities: I(K1) and I(Kur) densities were significantly increased in stretched myocytes, whereas transient outward K(+) current (I(to)) density was reduced. These alterations resulted in a significant abbreviation of the action potential duration. Losartan (1 microM) prevented stretch-induced increases in the protein-to-DNA ratio and atrial natriuretic peptide mRNA expression in stretched myocytes. Concomitantly, losartan attenuated stretch-induced alterations in I(K1), I(Kur), and I(to) density and gene expression. This prevented the stretch-induced abbreviation of action potential duration. Prevention of stretch-induced electrical remodeling might contribute to the clinical effects of losartan against AF.
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MESH Headings
- Action Potentials/drug effects
- Angiotensin II Type 1 Receptor Blockers/pharmacology
- Angiotensin II Type 1 Receptor Blockers/therapeutic use
- Animals
- Animals, Newborn
- Antihypertensive Agents/pharmacology
- Antihypertensive Agents/therapeutic use
- Atrial Fibrillation/etiology
- Atrial Fibrillation/prevention & control
- Atrial Natriuretic Factor/genetics
- Atrial Natriuretic Factor/metabolism
- Cell Enlargement/drug effects
- Cell Shape/drug effects
- Cell Size/drug effects
- Cells, Cultured
- Gene Expression/drug effects
- Heart Atria/cytology
- Heart Atria/drug effects
- Heart Atria/metabolism
- Hypertension/complications
- Hypertension/drug therapy
- Kinetics
- Kv1.5 Potassium Channel/drug effects
- Kv1.5 Potassium Channel/metabolism
- Losartan/pharmacology
- Losartan/therapeutic use
- Mechanotransduction, Cellular/drug effects
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Potassium/metabolism
- Potassium Channels, Inwardly Rectifying/drug effects
- Potassium Channels, Inwardly Rectifying/metabolism
- Potassium Channels, Voltage-Gated/drug effects
- Potassium Channels, Voltage-Gated/genetics
- Potassium Channels, Voltage-Gated/metabolism
- RNA, Messenger/metabolism
- Rats
- Shal Potassium Channels/drug effects
- Shal Potassium Channels/metabolism
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Affiliation(s)
- Erol Saygili
- Laboratory of Muscle Research and Molecular Cardiology, Department of Internal Medicine III, University of Cologne, Kerpenerstr. 62, 50924 Cologne, Germany
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Dun W, Ozgen N, Hirose M, Sosunov EA, Anyukhovsky EP, Rosen MR, Boyden PA. Ionic mechanisms underlying region-specific remodeling of rabbit atrial action potentials caused by intermittent burst stimulation. Heart Rhythm 2006; 4:499-507. [PMID: 17399641 PMCID: PMC2040063 DOI: 10.1016/j.hrthm.2006.12.032] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/25/2006] [Accepted: 12/13/2006] [Indexed: 09/30/2022]
Abstract
BACKGROUND Pulmonary veins (PVs) and the coronary sinus (CS) play pivotal roles in triggering some episodes of atrial fibrillation. In isolated rabbit right or left atrial preparations, a 3-hour intermittent burst pacing protocol shortens action potential duration (APD) in CS and PV, but not in sinus node (SN) and left Bachmann bundle (BB) regions. OBJECTIVE The purpose of this study was to use patch clamp techniques to study the rapidly inactivating (I(to)) and sustained (I(sus)) K(+) currents as well as Ca(2+) currents (I(Ca)) in cells dispersed from intermittent burst pacing and sham PV, BB, CS, and SN regions to determine whether changes in these currents contributed to APD shortening. METHODS Real-time polymerase chain reaction was performed for transient outward K(+) and Ca(2+) channel subunit mRNAs to determine if intermittent burst pacing affected expression levels. RESULTS I(to) densities were unaffected by intermittent burst pacing in PV and Bachmann bundle cells. mRNA levels of K(V)4.3, K(V)4.2, K(V)1.4, and KChIP2 subunits of I(to) in both regions were stable. In CS cells, I(to) densities in intermittent burst pacing were greater than in sham (P <.05), but there were no parallel mRNA changes. I(Ca) density of PV cells was reduced from 14.27 +/- 2.08 pA/pF (at -5 mV) in sham to 7.52 +/- 1.65 pA/pF in intermittent burst pacing PV cells (P <.05) due to a significant shift in voltage dependence of activation. These results were seen in the absence of mRNA changes in alpha(1C) and alpha(1D) Ca(2+) channel subunits. In contrast, intermittent burst pacing had no effect on Ca(2+) current densities and kinetics of CS cells, but decreased alpha(1)C and alpha(1)D mRNA levels. CONCLUSION There is region-specific remodeling of I(to) and I(Ca) by intermittent burst pacing protocols in rabbit atrium. Increased I(to) in CS cells could account for the APD shortening observed with intermittent burst pacing, whereas an intermittent burst pacing-induced shift in voltage dependence of activation may contribute to APD shortening in PV cells.
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Affiliation(s)
- Wen Dun
- Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA
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30
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Iwasaki YK, Yamashita T, Sekiguchi A, Hatano S, Sagara K, Iinuma H, Fu LT, Kobayashi Y, Katoh T, Takano T. A method for the simultaneous analysis of mRNA levels of multiple cardiac ion channels with a multi-probe RNase protection assay. Europace 2006; 8:1011-5. [PMID: 17005589 DOI: 10.1093/europace/eul099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
AIMS Various pathological conditions can alter cardiac electrophysiological properties not only by physiological responses but also by modifying the gene expression of ion channels (electrical remodelling). To investigate the underlying mechanisms of the latter, electrophysiological alterations would require a simultaneous and comprehensive analysis of the mRNA level of the ion channel genes. METHODS AND RESULTS We designed 19 cardiac ion channel cDNA templates to analyse the corresponding mRNAs and classified them into three template sets. Those sets were a voltage-dependent K(+) channel series (rat erg, KvLQT1, Kv4.3, Kv4.2, Kv2.1, Kv1.5, Kv1.4, Kv1.2), an inwardly rectifying K(+) channel series (rat Kir6.2, SUR2A/B, Kir3.4, Kir3.1, Kir2.2, Kir2.1), and an inward cationic ion channel series (rat SCN5A, alpha1C, beta2, alpha2delta2 of cardiac L-type Ca(2+) channel and alpha1G). These cDNA templates were used to synthesize antisense digoxigenin-labelled RNA probes. An amount of the total RNA of 25 microg was adequate to analyse simultaneously the mRNA levels of the ion channel genes with the use of multi-probe RPA, and these three multi-probe template sets enabled us to evaluate the profile of the spatial and temporal transcripts of the cardiac ion channels. CONCLUSION The newly developed ion channel multi-probe RPA templates provide an aid in the comprehensive analysis of the electrical remodelling of the heart.
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Affiliation(s)
- Yu-Ki Iwasaki
- The First Department of Internal Medicine, Nippon Medical School, 1-1-5, Sendagi, Bunkyo-ku, Tokyo 1138603, Japan.
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31
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Dos Santos RW, Otaviano Campos F, Neumann Ciuffo L, Nygren A, Giles W, Koch H. ATX-II Effects on the Apparent Location of M Cells in a Computational Model of a Human Left Ventricular Wedge. J Cardiovasc Electrophysiol 2006; 17 Suppl 1:S86-S95. [PMID: 16686688 DOI: 10.1111/j.1540-8167.2006.00389.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
INTRODUCTION The apparent location of the myocytes (M cells) with the longest action potential duration (APD) in a canine left ventricular (LV) wedge have been reported to shift after application of a sea anemone toxin, ATX-II. This toxin slows inactivation of I(Na) and thus prolongs APD. Thus, M cells may exhibit dynamic functional states, rather than being a static, anatomically discrete, myocyte population. In this study, we attempted to further define and understand this phenomenon using a mathematical model of the human ventricular myocyte action potential incorporated into an in silico "wedge" preparation. Our simulations demonstrate that even under conditions of a fixed population and ratio of epicardial, M, and endocardial myocytes, the apparent anatomical position (transmural location) of the myocytes with the longest APD can shift following ATX-II treatment. This arises because the ATX-II effect, modeled as a small increase in the late or persistent Na(+) current, and consequent prolongation of APD significantly changes the electrotonic interactions between ventricular myocytes in this LV wedge preparation. METHODS AND RESULTS This LV wedge model is based on bidomain equations. It corresponds to a rectangular tissue immersed in a passive and isotropic medium that represents the superfusion bath. In this theoretical work, the three known different and discrete populations of myocytes in the human left ventricle have been included: the epicardial, M, and endocardial cells. The effects of ATX-II on I(Na) were simulated by altering the voltage-dependent steady-state inactivation of the parameters h (fast gate) and j (slow gate). As a result, in these ATX-II simulations a persistent late Na(+) current was generated in all three types of ventricular myocytes. However, the APDs were prolonged in a heterogeneous pattern. Our simulations demonstrate that after the ATX-II effects develop, alterations in transmural electrotonic interactions can produce changes in the transmural location of myocytes with the longest APD. CONCLUSIONS The combination of intercellular electrotonic interactions, which tend to reduce and smooth out the discrete transmural APD variations, and the heterogeneous effects of ATX-II, which preferentially prolong the APD of M cells, can shift the location of the ventricular myocytes. This shift results in significantly altered transmural patterns of action potential durations, which would be expected to change localized refractory period and excitability. These cellular changes give rise to alterations in the corresponding surface electrograms and may change the overall substrates for conduction and rhythm disturbances.
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Affiliation(s)
- Rodrigo Weber Dos Santos
- Department of Computer Science, Universidade Federal de Juiz de Fora, Juiz de Fora, Minas Gerais, Brazil.
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Barfield JP, Yeung CH, Cooper TG. Characterization of potassium channels involved in volume regulation of human spermatozoa. ACTA ACUST UNITED AC 2006; 11:891-7. [PMID: 16421215 DOI: 10.1093/molehr/gah208] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Fertility depends in part on the ability of the spermatozoon to respond to osmotic challenges by regulating its volume, which may rely on the movement of K+. These experiments were designed to characterize the K+ channels possibly involved in volume regulation of human ejaculated spermatozoa by simultaneously exposing them to a physiological hypo-osmotic challenge and a wide range of K+ channel inhibitors. Regulation of cellular volume, as measured by flow cytometry, was inhibited when spermatozoa were exposed to quinine (QUI; 0.3 mM), 4-aminopyridine (4AP; 4 mM) and clofilium (CLO; 10 microM) which suggests the involvement of voltage-gated K+ channels Kv1.4, Kv1.5 and Kv1.7, acid-sensitive channel TASK2 and the beta-subunit minK (IsK) in regulatory volume decrease (RVD). QUI and 4AP and, to some extent, CLO also induced hyper activation-like motility. A sensitivity of RVD to pH could not be demonstrated in spermatozoa to support the involvement of TASK2 channels. Western blotting indicated the presence of Kv1.5, TASK2, TASK3 and minK channel proteins, but not Kv1.4. Furthermore, Kv1.5, minK and TASK2 were localized to various regions of the spermatozoa. Although Kv1.4, Kv1.7, TASK2 and TASK3 channels may have important roles in human spermatozoa, Kv1.5 and minK appear to be the most likely candidates for human sperm RVD, serving as targets for non-hormonal contraception.
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Affiliation(s)
- J P Barfield
- Institute of Reproductive Medicine, University of Münster, Münster, Germany
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33
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Komatsu T, Sato Y, Tachibana H, Nakamura M, Horiuchi D, Okumura K. Randomized Crossover Study of the Long-Term Effects of Pilsicainide and Cibenzoline in Preventing Recurrence of Symptomatic Paroxysmal Atrial Fibrillation Influence of the Duration of Arrhythmia Before Therapy. Circ J 2006; 70:667-72. [PMID: 16723785 DOI: 10.1253/circj.70.667] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND There is little information on the selection of antiarrhythmic agents for long-term prevention of paroxysmal atrial fibrillation (PAF). In the present study the preventive effects of pilsicainide (Pil) and cibenzoline (Cib) were compared in patients with PAF that was defibrillated at <48 h or >or=48 h after onset. METHODS AND RESULTS A total of 60 patients (45 men, 15 women, mean age 66+/-10 years) were divided into 2 groups: Group I consisted of 22 patients in whom atrial fibrillation (AF) lasted for <48 h before cardioversion and Group II consisted of 38 patients in whom AF lasted for >or=48 h. A randomized, crossover protocol of treatment with Pil (150 mg/day) and Cib (300 mg/day) was used. Mean follow-up was 35+/-18 months. In Group I, the mean duration of maintenance of sinus rhythm was 12.3+/-2.9 months in patients treated with Pil, compared with 12.9+/-2.5 months in those givem Cib (p=NS between 2 groups). Actuarial event-free rates at 1, 3, 6, 12 months were 82%, 68%, 59% and 41%, respectively, in patients treated with Pil, and 91%, 77%, 68% and 50%, respectively, in those givenh Cib (p=NS between 2 groups). In Group II, the mean duration of maintenance of sinus rhythm was 1.6+/-0.5 months in patients treated with Pil, compared with 5.9+/-1.7 months in those given Cib (p<0.01). Actuarial event-free rates at 1, 3, 6, 12 months were 45%, 18%, 8% and 3%, respectively, in patients treated with Pil, and 63%, 45%, 29% and 16%, respectively, in those given Cib (p<0.05, at 12 months). CONCLUSIONS Prolonged tachycardia (>or=48 h) in patients with PAF seems to cause electrical remodeling. Cib, a multichannel blocker, is considered to be more effective in preventing the recurrence of PAF in the electrically remodeled atria than Pil, a pure sodium-channel blocker.
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Affiliation(s)
- Takashi Komatsu
- Second Department of Internal Medicine, Iwate Medical University School of Medicine, Morioka, Japan.
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Kubota H, Takamoto S, Furuse A, Sato M, Endo H, Fujiki T, Sudo K. Epicardial maze procedure on the beating heart with an infrared coagulator. Ann Thorac Surg 2005; 80:1081-6. [PMID: 16122491 DOI: 10.1016/j.athoracsur.2004.09.050] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2003] [Revised: 09/15/2004] [Accepted: 09/21/2004] [Indexed: 10/25/2022]
Abstract
PURPOSE Maze surgery is widely used to treat atrial fibrillation (AF) but requires cardiopulmonary bypass and longer aortic cross-clamping time. Percutaneous transcatheter pulmonary vein (PV) isolation is time consuming and relies on fluoroscopy and contrast media, and PV obstruction and cardiac tamponade are still major problems. To overcome these drawbacks, we developed an epicardial maze procedure with an infrared coagulator on the beating heart, and the aim of this study was to confirm electrophysiologically the efficacy of this method. DESCRIPTION Light from a lamp in the infrared coagulator is focused into a quartz rod, and the distal exit-plane of the rod is connected to a sapphire tip that allows 10 mm of linear photocoagulation. In an experiment in 5 dogs with AF, instead of making all of the incisions usually required for maze surgery, the infrared coagulator was applied epicardially to create a continuously overlapping linear lesion that was the same as the incision line in the maze III procedure except for the intraatrial incision. After the procedure, 11 electrodes were attached to both atria, and an electrophysiologic study was performed. EVALUATION The electrophysiologic study confirmed electrophysiologic isolation of both atrial appendages and within the PV encircling lesion. Sustained atrial fibrillation could no longer be induced. CONCLUSIONS The epicardial maze procedure was successfully performed on a beating heart with the infrared coagulator.
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Affiliation(s)
- Hiroshi Kubota
- Department of Cardiovascular Surgery, Kyorin University, Tokyo, Japan.
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35
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Yamashita T, Sekiguchi A, Iwasaki YK, Sagara K, Hatano S, Iinuma H, Aizawa T, Fu LT. Cibenzoline attenuates upregulation of Kv1.5 channel gene expression by experimental paroxysmal atrial fibrillation. Int Heart J 2005; 46:279-88. [PMID: 15876811 DOI: 10.1536/ihj.46.279] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Antiarrhythmic drugs exert their effects by inhibiting the ion channels of cardiomyocytes. However, these effects could also modify the ionic environment around them, and thereby affect the expression of ion channels, leading to biochemical enhancement or attenuation of the antiarrhythmic effects. To test this hypothesis, the physiological and biochemical effects of cibenzoline were evaluated in a rapid atrial pacing model in rats. In rats with rapid atrial pacing, pretreatment with cibenzoline significantly inhibited the increases in Kv1.5 mRNA at 2 hours and immunoreactive protein at 4 hours by 35 +/- 15% and 30 +/- 10%, respectively. These effects were observed only in the rapid atrial pacing group, not in the sham-operated group. With cibenzoline pretreatment, 4-hour rapid atrial pacing resulted in significant prolongation of the atrial refractory period compared to the untreated group even after removal of cibenzoline. In contrast, the sham and rapid atrial pacing model with and without cibenzoline pretreatment showed similar acute physiological responses to cibenzoline. In conclusion, in addition to the acute physiological effects, pretreatment with cibenzoline exerted pleiotropic effects of inhibition of Kv1.5 channel upregulation by rapid pacing, implying differences in the cibenzoline effects when administered before and after onset of paroxysmal atrial fibrillation.
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Barfield JP, Yeung CH, Cooper TG. The Effects of Putative K+ Channel Blockers on Volume Regulation of Murine Spermatozoa1. Biol Reprod 2005; 72:1275-81. [PMID: 15673604 DOI: 10.1095/biolreprod.104.038448] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Volume regulation is a necessary task for spermatozoa as the osmolarity of female tract fluids is lower than that in the epididymis and because the disruption of it in transgenic mice results in infertility. As the specific mechanisms behind this phenomenon are unknown, spermatozoa from mice were screened for sensitivities to inhibitors known to affect specific channels involved in volume regulation of somatic cells. Spermatozoa from the cauda epididymidis were exposed to physiological hypotonic conditions with and without inhibitor. Flow cytometric forward scatter measurements were taken to indicate relative sperm size at 5 and 75 min of incubation. The presence of quinine (0.8 mM), cadmium (0.2 mM), flecainide (100 microM), 4-aminopyridine (4 mM), barium (1 mM), clofilium (10 microM), and phrixotoxin (100 nM) for 75 min resulted in significantly higher forward scatter values than sperm incubated in medium without an inhibitor. These results imply that channels potentially involved in volume regulation of murine spermatozoa include the voltage-dependent Kv1.4 (also known as KCNA1), Kv1.5 (KCNA5), Kv4.1 (KCND1), Kv4.2 (KCND2), Kv4.3 (KCND3), mink (KCNE1), and acid-sensitive TASK2 (KCNK5) and TASK3 (KCNK9). Western blots confirmed the presence of Kv1.5 and TASK2 proteins in sperm plasma membranes at similar (Kv1.5) or higher (TASK2) molecular weight than in somatic cells. Incubation in a different pH did not reveal acid sensitivity of volume regulation. Volume regulation of spermatozoa may involve novel voltage-gated and pH-sensitive potassium channels, which could be valuable targets for the development of a posttesticular male contraceptive.
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Affiliation(s)
- J P Barfield
- Institute of Reproductive Medicine of the University, D-48129 Münster, Germany
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Nakazato Y, Yasuda M, Sasaki A, Iida Y, Kawano Y, Nakazato K, Tokano T, Mineda Y, Sumiyoshi M, Nakata Y, Daida H. Conversion and Maintenance of Sinus Rhythm by Bepridil in Patients With Persistent Atrial Fibrillation. Circ J 2005; 69:44-8. [PMID: 15635201 DOI: 10.1253/circj.69.44] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Bepridil has multiple ion-channel blocking effects similar to amiodarone and is expected to have anti-arrhythmic effects that are useful for the management of atrial fibrillation (AF). The aim of this study was to clarify the conversion of persistent AF and maintenance of sinus rhythm (SR) by oral bepridil. METHODS AND RESULTS Oral bepridil was administered to 112 patients (83 males, 29 females; age: 59.0+/-10.8 years) with persistent AF lasting an average of 5 months. The conversion effects and maintenance of SR after pharmacological or direct current (DC) cardioversion, as well as the incidence of adverse complications, were evaluated. In 65 of 112 (58%) patients, SR was restored within 6 months (average: 2.1 months) following bepridil administration. DC cardioversion was carried out for 21 of the remaining 47 patients with unsuccessful pharmacological conversion, and all had restoration of SR. Eventually, of the 86 patients in total who were restored to SR by either bepridil or DC cardioversion, 70 (81%) patients maintained SR after a mean follow-up of 18 months. No serious adverse complications were observed, except for marked QT prolongation in 2 cases. CONCLUSION Bepridil showed favorable conversion effects in patients with persistent AF and was highly effective for maintaining SR after pharmacological or electrical cardioversion. However, careful follow-up is necessary for the prevention of torsade de pointes caused by QT prolongation.
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Affiliation(s)
- Yuji Nakazato
- Department of Cardiology, Juntendo University School of Medicine, Tokyo, Japan.
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Ueda N, Zipes DP, Wu J. Functional and transmural modulation of M cell behavior in canine ventricular wall. Am J Physiol Heart Circ Physiol 2004; 287:H2569-75. [PMID: 15331367 DOI: 10.1152/ajpheart.00526.2004] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies have demonstrated a discrete population of midmyocardial (M) cells in the ventricular myocardium having excessive action potential duration (APD) prolongation during long activation cycle lengths (CL) and under the influence of APD-prolonging agents. However, M cells have not been found in other studies. Existing explanations for the discrepancies appear inadequate. We hypothesized that instead of being a discrete group, M cell behavior is functional and conditionally expressed. We mapped APDs on the cut-exposed transmural surfaces of arterially perfused ventricular wedges from 26 dogs during Na+ current modification with anemone toxin II (ATX-II). Compared with the endocardium, APDs were not statistically different in the parallel layer having the longest mean APD (APDL) and were significantly shorter in the epicardium in the 26 wedges before ATX-II. ATX-II (≥5 nmol/l) prolonged APD heterogeneously (midmyocardium > endocardium > epicardium). The differences increased at longer CLs. ATX-II (20.0 nmol/l) shifted the APDL layer to 32 ± 6.2% (6 wedges, CL: 4,000 ms) of the transmural thickness from the (sub)endocardium (8.6 ± 7.2%, 26 wedges, ATX-II free). We detected the presence of M cell behavior (significantly longer APDs in the APDL layer than in the endocardium and epicardium, P ≤ 0.04, CL: 4,000 ms) in the 18 wedges having ≥5 nmol/l ATX-II but not ( P > 0.36) in the other 18 wedges having ≤2.5 nmol/l ATX-II. Both the position of the APDL layer and presence of M cell-like behavior were modulated by ATX-II. The dynamic spatial modulation indicates that M cell behavior is functional and only becomes manifest under suitable conditions.
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Affiliation(s)
- Norihiro Ueda
- Krannert Institute of Cardiology, Indiana Univ. School of Medicine, 1800 N. Capitol Ave., Indianapolis, IN 46202, USA
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Berecki G, Zegers JG, Verkerk AO, Bhuiyan ZA, de Jonge B, Veldkamp MW, Wilders R, van Ginneken ACG. HERG channel (dys)function revealed by dynamic action potential clamp technique. Biophys J 2004; 88:566-78. [PMID: 15475579 PMCID: PMC1305034 DOI: 10.1529/biophysj.104.047290] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The human ether-a-go-go-related gene (HERG) encodes the rapid component of the cardiac delayed rectifier potassium current (I(Kr)). Per-Arnt-Sim domain mutations of the HERG channel are linked to type 2 long-QT syndrome. We studied wild-type and/or type 2 long-QT syndrome-associated mutant (R56Q) HERG current (I(HERG)) in HEK-293 cells, at both 23 and 36 degrees C. Conventional voltage-clamp analysis revealed mutation-induced changes in channel kinetics. To assess functional implication(s) of the mutation, we introduce the dynamic action potential clamp technique. In this study, we effectively replace the native I(Kr) of a ventricular cell (either a human model cell or an isolated rabbit myocyte) with I(HERG) generated in a HEK-293 cell that is voltage-clamped by the free-running action potential of the ventricular cell. Action potential characteristics of the ventricular cells were effectively reproduced with wild-type I(HERG), whereas the R56Q mutation caused a frequency-dependent increase of the action potential duration in accordance with the clinical phenotype. The dynamic action potential clamp approach also revealed a frequency-dependent transient wild-type I(HERG) component, which is absent with R56Q channels. This novel electrophysiological technique allows rapid and unambiguous determination of the effects of an ion channel mutation on the ventricular action potential and can serve as a new tool for investigating cardiac channelopathies.
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Affiliation(s)
- Géza Berecki
- Experimental and Molecular Cardiology Group and the Department of Physiology, Academic Medical Center, University of Amsterdam, The Netherlands.
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Birnbaum SG, Varga AW, Yuan LL, Anderson AE, Sweatt JD, Schrader LA. Structure and function of Kv4-family transient potassium channels. Physiol Rev 2004; 84:803-33. [PMID: 15269337 DOI: 10.1152/physrev.00039.2003] [Citation(s) in RCA: 268] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Shal-type (Kv4.x) K(+) channels are expressed in a variety of tissue, with particularly high levels in the brain and heart. These channels are the primary subunits that contribute to transient, voltage-dependent K(+) currents in the nervous system (A currents) and the heart (transient outward current). Recent studies have revealed an enormous degree of complexity in the regulation of these channels. In this review, we describe the surprisingly large number of ancillary subunits and scaffolding proteins that can interact with the primary subunits, resulting in alterations in channel trafficking and kinetic properties. Furthermore, we discuss posttranslational modification of Kv4.x channel function with an emphasis on the role of kinase modulation of these channels in regulating membrane properties. This concept is especially intriguing as Kv4.2 channels may integrate a variety of intracellular signaling cascades into a coordinated output that dynamically modulates membrane excitability. Finally, the pathophysiology that may arise from dysregulation of these channels is also reviewed.
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Affiliation(s)
- Shari G Birnbaum
- Div. of Neuroscience, S607, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
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41
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Libbus I, Wan X, Rosenbaum DS. Electrotonic load triggers remodeling of repolarizing current Ito in ventricle. Am J Physiol Heart Circ Physiol 2004; 286:H1901-9. [PMID: 14715504 DOI: 10.1152/ajpheart.00581.2003] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
A change in activation sequence electrically remodels ventricular myocardium, causing persistent changes in repolarizing currents (T-wave memory). However, the underlying mechanism for triggering activation sequence-dependent remodeling is unknown. Optical action potentials were mapped with high resolution from the epicardial surface of the arterially perfused canine wedge preparation (n = 23) during 30 min of baseline endocardial stimulation, followed by 40 min of epicardial stimulation, and, finally, restoration of endocardial stimulation. Immediately after the change from endocardial to epicardial stimulation, phase 1 notch amplitude of epicardial cells was attenuated by 74 +/- 8% (P < 0.001) compared with baseline and continued to diminish during the period of epicardial pacing, suggesting progressive remodeling of the transient outward current (Ito). When endocardial pacing was restored, notch amplitude did not immediately recover but remained attenuated by 23 +/- 10% (P < 0.001), also consistent with a remodeling effect. Peak Ito current measured from isolated epicardial myocytes changed by 12 +/- 4% (P < 0.025), providing direct evidence for Ito remodeling occurring on a surprisingly short time scale. The mechanism for triggering remodeling of Ito was a significant reduction (by 14 +/- 4%, P < 0.001) of upstroke amplitude in epicardial cells during epicardial stimulation. Reduction in upstroke amplitude during epicardial pacing was explained by electrotonic load on epicardial cells by fully repolarized downstream endocardial cells. These data suggest a novel mechanism for triggering electrical remodeling in the ventricle. Electrotonic load imposed by a change in activation sequence reduces upstroke amplitude, which, in turn, attenuates Ito according to its known voltage-dependent properties, triggering downregulation of current.
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Affiliation(s)
- Imad Libbus
- The Heart and Vascular Research Center and Departments of Medicine and Biomedical Engineering, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio 44109-1998, USA
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42
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Kato T, Yamashita T, Sagara K, Iinuma H, Fu LT. Progressive Nature of Paroxysmal Atrial Fibrillation-Observations From a 14-Year Follow-up Study-. Circ J 2004; 68:568-72. [PMID: 15170094 DOI: 10.1253/circj.68.568] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
BACKGROUND Atrial fibrillation (AF) is believed to occur first as paroxysmal, then be gradually perpetuated, and finally become chronic as the end result. However, this presumed clinical course has not been well confirmed. METHODS AND RESULTS The clinical course of recurrent paroxysmal AF (PAF) from its onset was examined in 171 patients (mean follow-up period: 14.1+/-8.1 years). This study population consisted of patients with no structural heart disease (n=88), ischemic heart disease (n=28), dilated or hypertrophic cardiomyopathy (n=17), valvular heart disease (n=35) or other cardiac diseases. The mean age at the onset of AF was 58.3 +/-11.8 years old. During the mean follow-up period of 14.1 years, PAF eventually developed into its chronic form in 132 patients under conventional antiarrhythmic therapy (77.2%, 5.5% of patients per year). The independent factors for early development into chronic AF were aging (hazard ratio (HR) 1.27 per 10 years, 95% confidence interval (CI) 1.06-1.47)), dilated left atrium (HR 1.39 per 10 mm, 95% CI 1.11-1.69), myocardial infarction (HR 2.33, 95% CI 1.13-4.81), and valvular diseases (HR 2.29, 95% CI 1.22-4.30). CONCLUSIONS The present long-term observations definitely and quantitatively revealed the progressive nature of PAF.
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Koh JT, Jeong BC, Kim JH, Ahn YK, Lee HS, Baik YH, Kim KK. Changes underlying arrhythmia in the transgenic heart overexpressing Refsum disease gene-associated protein. Biochem Biophys Res Commun 2004; 313:156-62. [PMID: 14672712 DOI: 10.1016/j.bbrc.2003.11.105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Previously, we identified a novel neuron-specific protein (PAHX-AP1) that binds to Refsum disease gene product (PAHX), and we developed transgenic (TG) mice that overexpress heart-targeted PAHX-AP1. These mice have atrial tachycardia and increased susceptibility to aconitine-induced arrhythmia. This study was undertaken to elucidate the possible changes in ion channels underlying the susceptibility to arrhythmia in these mice. RT-PCR analyses revealed that the cardiac expression of adrenergic beta(1)-receptor (ADRB1) was markedly lower, whereas voltage-gated potassium channel expression (Kv2.1) was higher in PAHX-AP1 TG mice compared with non-TG mice. However, the expression of voltage-sensitive sodium and calcium channels, and muscarinic receptor was not significantly different. Propranolol pretreatment, a non-specific beta-adrenoceptor antagonist, blocked aconitine-induced arrhythmia in non-TG mice, but not in PAHX-AP1 TG mice. Our results indicate that, in the PAHX-AP1 TG heart, the modulation of voltage-gated potassium channel and ADRB1 expression seem to be important in the electrophysiological changes associated with altered ion channel functions, but ADRB1 is not involved in the greater susceptibility to aconitine-induced arrhythmia.
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Affiliation(s)
- Jeong Tae Koh
- Dental Science Research Institute, Chonnam National University, Kwangju 501-190, Republic of Korea
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Wong W, Schlichter LC. Differential recruitment of Kv1.4 and Kv4.2 to lipid rafts by PSD-95. J Biol Chem 2003; 279:444-52. [PMID: 14559911 DOI: 10.1074/jbc.m304675200] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activity of voltage-gated potassium (Kv) channels, and consequently their influence on cellular functions, can be substantially altered by phosphorylation. Several protein kinases that modulate Kv channel activity are found in membrane subdomains known as lipid rafts, which are thought to organize signaling complexes in the cell. Thus, we asked whether Kv1.4 and Kv4.2, two channels with critical roles in excitable cells, are found in lipid rafts. Acylation can target proteins to raft regions; however, Kv channels are not acylated, and therefore, a different mechanism must exist to bring them into these membrane subdomains. Because both Kv1.4 and Kv4.2 interact with postsynaptic density protein 95 (PSD-95), which is acylated (specifically, palmitoylated), we examined whether PSD-95 can recruit these channels to lipid rafts. We found that a portion of Kv1.4 and Kv4.2 protein in rat brain membranes is raft-associated. Lipid raft patching and immunostaining confirmed that some Kv4.2 is in Thy-1-containing rafts in rat hippocampal neurons. Using a heterologous expression system, we determined that palmitoylation of PSD-95 was crucial to its localization to lipid rafts. We then assessed the contribution of PSD-95 to the raft association of these channels. Co-expression of PSD-95 increased the amount of Kv1.4, but not Kv4.2, in lipid rafts. Deleting the PSD-95 binding motif of Kv1.4 eliminated this recruitment, as did substituting a palmitoylation-deficient PSD-95 mutant. This work represents the first evidence that PSD-95 binding can recruit Kv channels into lipid rafts, a process that could facilitate interactions with the protein kinases that affect channel activity.
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Affiliation(s)
- Wei Wong
- Division of Cellular and Molecular Biology, Toronto Western Research Institute, University Health Network, Toronto, Ontario M5T 2S8, Canada
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45
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Watanabe H, Ma M, Washizuka T, Komura S, Yoshida T, Hosaka Y, Hatada K, Chinushi M, Yamamoto T, Watanabe K, Aizawa Y. Thyroid hormone regulates mRNA expression and currents of ion channels in rat atrium. Biochem Biophys Res Commun 2003; 308:439-44. [PMID: 12914768 DOI: 10.1016/s0006-291x(03)01420-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Atrial fibrillation is one of the common arrhythmias associated with hyperthyroidism. This study examined the effects of thyroid hormone (T3) on mRNA expression and currents of major ionic channels determining the action potential duration (APD) in the rat atrium using the RNase protection assay and the whole-cell patch-clamp technique, respectively. T3 increased the Kv1.5 mRNA expression and decreased the L-type calcium channel mRNA expression, while the Kv4.2 mRNA expression did not change. APD was shorter in hyperthyroid than in euthyroid myocytes. The ultrarapid delayed rectifier potassium currents were remarkably increased in hyperthyroid than in euthyroid myocytes, whereas the transient outward potassium currents were unchanged. L-type calcium currents were decreased in hyperthyroid than in euthyroid myocytes. T3 shifted the current-voltage relationship for calcium currents negatively. In conclusion, T3 increased the outward currents and decreased the inward currents. The resultant changes of ionic currents shortened APD, providing a substrate for atrial fibrillation.
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Affiliation(s)
- Hiroshi Watanabe
- Division of Cardiology, Niigata University Graduate School of Medical and Dental Science, 1-754 Asahimachidori, Niigata, Japan.
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46
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Abstract
INTRODUCTION Although it is well established that alterations in heart rate or activation sequence induce electrical remodeling in the atria, electrical remodeling in the ventricle is poorly understood. METHODS AND RESULTS To determine the changes in cellular repolarization that underlie ventricular electrical remodeling caused separately by altered heart rate and activation sequence, optical action potentials were recorded simultaneously from 256 sites spanning the transmural wall of the arterially perfused canine wedge preparation (n = 15). Action potentials were compared from the same sites under identical conditions [endocardial pacing, cycle length (CL) = 1,000 msec], before and after an intervening 20- to 60-minute period of remodeling induced by (1) rapid pacing (CL = 300 msec) with no change in activation sequence; (2) altered activation sequence (epicardial pacing) with no change in rate; or (3) no change in rate or activation sequence (control). Action potential duration (APD) shortened by 24.8 +/- 4.8 msec following a period of rapid heart rate (P < 0.05) but prolonged (by 12.7 +/- 1.8 msec) following a period of altered activation sequence (P < 0.05). Hence, even after restoration of baseline heart rate and activation sequence, there were persistent changes in APD from baseline, indicative of electrical remodeling. Moreover, the orientation of the maximum APD gradient across the transmural wall changed more significantly following heart rate remodeling (by 27.7 degrees +/- 4.9 degrees, P < 0.05) than following activation sequence remodeling (by 12.3 degrees +/- 2.4 degrees, P < 0.05). CONCLUSION Persistent changes in ventricular repolarization can be induced by surprisingly short periods of altered rate or activation sequence. In contrast to atrial remodeling, electrical remodeling in the ventricle can result in prolonged APD (with altered activation sequence) or reversal of APD gradient orientation (with rapid rate), suggesting that the nature of ventricular electrical remodeling induced by these two perturbations is different.
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Affiliation(s)
- Imad Libbus
- The Heart and Vascular Research Center, Department of Medicine, MetroHealth Campus, Case Western Reserve University, Cleveland, Ohio 44109-1998, USA
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Bosch RF, Scherer CR, Rüb N, Wöhrl S, Steinmeyer K, Haase H, Busch AE, Seipel L, Kühlkamp V. Molecular mechanisms of early electrical remodeling: transcriptional downregulation of ion channel subunits reduces I(Ca,L) and I(to) in rapid atrial pacing in rabbits. J Am Coll Cardiol 2003; 41:858-69. [PMID: 12628735 DOI: 10.1016/s0735-1097(02)02922-4] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
OBJECTIVES The purpose of the study was to characterize the ionic and molecular mechanisms in the very early phases of electrical remodeling in a rabbit model of rapid atrial pacing (RAP). BACKGROUND Long-term atrial fibrillation reduces L-type Ca(2+) (I(Ca,L)) and transient outward K(+) (I(to)) currents by transcriptional downregulation of the underlying ionic channels. However, electrical remodeling starts early after the onset of rapid atrial rates. The time course of ion current and channel modulation in these early phases of remodeling is currently unknown. METHODS Rapid (600 beats/min) right atrial pacing was performed in rabbits. Animals were divided into five groups with pacing durations between 0 and 96 h. Ionic currents were measured by patch clamp techniques; messenger ribonucleic acid (mRNA) and protein expression were measured by reverse transcription-polymerase chain reaction and Western blot, respectively. RESULTS L-type calcium current started to be reduced (by 47%) after 12 h of RAP and continued to decline as pacing continued. Current changes were preceded or paralleled by decreased mRNA expression of the Ca(2+) channel beta subunits CaB2a, CaB2b, and CaB3, whereas significant reductions in the alpha(1) subunit mRNA and protein expression began 24 h after pacing onset. Transient outward potassium current densities were not altered within the first 12 h, but after 24 h, currents were reduced by 48%. Longer pacing periods did not further decrease I(to). Current changes were paralleled by reduced Kv4.3 mRNA expression. Kv4.2, Kv1.4, and the auxiliary subunit KChIP2 were not affected. CONCLUSIONS L-type calcium current and I(to) are reduced in early phases of electrical remodeling. A major mechanism appears to be transcriptional downregulation of underlying ion channels, which partially preceded ion current changes.
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Affiliation(s)
- Ralph F Bosch
- Department of Cardiology, University of Tübingen, Tübingen, Germany.
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48
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Xu Y, Kumar D, Dyck JRB, Ford WR, Clanachan AS, Lopaschuk GD, Jugdutt BI. AT(1) and AT(2) receptor expression and blockade after acute ischemia-reperfusion in isolated working rat hearts. Am J Physiol Heart Circ Physiol 2002; 282:H1206-15. [PMID: 11893553 DOI: 10.1152/ajpheart.00839.2000] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We assessed ANG II type 1 (AT(1)) and type 2 (AT(2)) receptor (R) expression and functional recovery after ischemia-reperfusion with or without AT(1)R/AT(2)R blockade in isolated working rat hearts. Groups of six hearts were subjected to global ischemia (30 min) followed by reperfusion (30 min) and exposed to no drug and no ischemia-reperfusion (control), ischemia-reperfusion and no drug, and ischemia-reperfusion with losartan (an AT(1)R antagonist; 1 micromol/l), PD-123319 (an AT(2)R antagonist; 0.3 micromol/l), N(6)-cyclohexyladenosine (CHA, a cardioprotective adenosine A(1) receptor agonist; 0.5 micromol/l as positive control), enalaprilat (an ANG-converting enzyme inhibitor; 1 micromol/l), PD-123319 + losartan, ANG II (1 nmol/l), or ANG II + losartan. Compared with controls, ischemia-reperfusion decreased AT(2)R protein (Western immunoblots) and mRNA (Northern immunoblots, RT-PCR) and impaired functional recovery. PD-123319 increased AT(2)R protein and mRNA and improved functional recovery. Losartan increased AT(1)R mRNA (but not AT(1)R/AT(2)R protein) and impaired recovery. Other groups (except CHA) did not improve recovery. The results suggest that, in isolated working hearts, AT(2)R plays a significant role in ischemia-reperfusion and AT(2)R blockade induces increased AT(2)R protein and cardioprotection.
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Affiliation(s)
- Yi Xu
- Division of Cardiology, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada T6G 2R7
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Abstract
1. One essential role for potassium channels in vascular smooth muscle is to buffer cell excitation and counteract vasoconstrictive influences. Several molecular mechanisms regulate potassium channel function. The interaction of these mechanisms may be one method for fine-tuning potassium channel activity in response to various physiological and pathological challenges. 2. The most prevalent K+ channels in vascular smooth muscle are large-conductance calcium- and voltage-sensitive channels (maxi-K channels) and voltage-gated channels (Kv channels). Both channel types are complex molecular structures consisting of a pore-forming alpha-subunit and an ancillary beta-subunit. The maxi-K and Kv channel alpha-subunits assemble as tetramers and have S4 transmembrane domains that represent the putative voltage sensor. While most vascular smooth muscle cells identified to date contain both maxi-K and Kv channels, the expression of individual alpha-subunit isoforms and beta-subunit association occurs in a tissue-specific manner, thereby providing functional specificity. 3. The maxi-K channel alpha-subunit derives its molecular diversity by alternative splicing of a single-gene transcript to yield multiple isoforms that differ in their sensitivity to intracellular Ca2+ and voltage, cell surface expression and post- translational modification. The ability of this channel to assemble as a homo- or heterotetramer allows for fine-tuning control to intracellular regulators. Another level of diversity for this channel is in its association with accessory beta-subunits. Multiple beta-subunits have been identified that can arise either from separate genes or alternative splicing of a beta-subunit gene. The maxi-K channel beta-subunits modulate the channel's Ca2+ and voltage sensitivity and kinetic and pharmacological properties. 4. The Kv channel alpha-subunit derives its diverse nature by the expression of several genes. Similar to the maxi-K channel, this channel has been shown to assemble as a homo- and heterotetramer, which can significantly change the Kv current phenotype in a given cell type. Association with a number of the ancillary beta-subunits affects Kv channel function in several ways. Beta-subunits can induce inactivating properties and act as chaperones, thereby regulating channel cell-surface expression and current kinetics.
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Affiliation(s)
- Victoria P Korovkina
- Department of Physiology and Biophysics, University of Iowa, Iowa City, Iowa 52242, USA
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Kobayashi S, Reien Y, Ogura T, Saito T, Masuda Y, Nakaya H. Inhibitory effect of bepridil on hKv1.5 channel current: comparison with amiodarone and E-4031. Eur J Pharmacol 2001; 430:149-57. [PMID: 11711026 DOI: 10.1016/s0014-2999(01)01381-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Effects of bepridil on the depolarization-activated outward K(+) currents (I(out)) in rat atrial myocytes and the human cardiac K(+) (hKv1.5) channel current stably expressed in human embryonic kidney (HEK) 293 cells were examined, and compared with those of amiodarone and N-[4-[[1-[2-(6-methyl-2-pyridinyl)ethyl]-4-piperidinyl]carbonyl]phenyl] methanesulphonamide dihydrochloride dihydrate (E-4031). Membrane currents were recorded using patch-clamp techniques in enzymatically isolated rat atrial myocytes and HEK 293 cells expressing hKv1.5 channels. Bepridil potently inhibited I(out) elicited by depolarization pulses and prolonged the action potential in rat atrial cells. Bepridil also inhibited the hKv1.5 channel current with the IC(50) value of 6.6 microM. The inhibitory effects of bepridil on the currents in HEK 293 cells were voltage-dependent. Amiodarone weakly inhibited rat atrial I(out) and hKv1.5 channel current. In contrast, E-4031 at a concentration of 10 microM had little influence on these currents. Thus, bepridil inhibits hKv1.5 channel current and the inhibitory effect may be useful for the treatment of atrial fibrillation.
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Affiliation(s)
- S Kobayashi
- Department of Cardiovascular Science and Medicine, Chiba University Graduate School of Medicine, 1-8-1 Inohana, Chuo-ku, 260-8670, Chiba, Japan
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