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Liu X, Ren L, Yu S, Li G, He P, Yang Q, Wei X, Thai PN, Wu L, Huo Y. Late sodium current in synergism with Ca 2+/calmodulin-dependent protein kinase II contributes to β-adrenergic activation-induced atrial fibrillation. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220163. [PMID: 37122215 PMCID: PMC10150221 DOI: 10.1098/rstb.2022.0163] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023] Open
Abstract
Atrial fibrillation (AF) is frequently associated with β-adrenergic stimulation, especially in patients with structural heart diseases. The objective of this study was to determine the synergism of late sodium current (late INa) and Ca2+/calmodulin-dependent protein kinase (CaMKII)-mediated arrhythmogenic activities in β-adrenergic overactivation-associated AF. Monophasic action potential, conduction properties, protein phosphorylation, ion currents and cellular trigger activities were measured from rabbit-isolated hearts, atrial tissue and atrial myocytes, respectively. Isoproterenol (ISO, 1-15 nM) increased atrial conduction inhomogeneity index, phospho-Nav1.5 and phospho-CaMKII protein levels and late INa by 108%, 65%, 135% and 87%, respectively, and induced triggered activities and episodes of AF in all hearts studied (p < 0.05). Sea anemone toxin II (ATX-II, 2 nM) was insufficient to induce any atrial arrhythmias, whereas the propensities of AF were greater in hearts treated with a combination of ATX-II and ISO. Ranolazine, eleclazine and KN-93 abolished ISO-induced AF, attenuated the phosphorylation of Nav1.5 and CaMKII, and reversed the increase of late INa (p < 0.05) in a synergistic mode. Overall, late INa in association with the activation of CaMKII potentiates β-adrenergic stimulation-induced AF and the inhibition of both late INa and CaMKII exerted synergistic anti-arrhythmic effects to suppress atrial arrhythmic activities associated with catecholaminergic activation. This article is part of the theme issue 'The heartbeat: its molecular basis and physiological mechanisms'.
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Affiliation(s)
- Xiaoyan Liu
- Department of Cardiology, Peking University First Hospital, 8, Xishiku Street, West District, Beijing 100034, People's Republic of China
- Department of Cardiology, Cardiovascular Center, Beijing Friendship Hospital, Capital Medical University, Beijing, 100050, People's Republic of China
| | - Lu Ren
- Department of Cardiology, Peking University First Hospital, 8, Xishiku Street, West District, Beijing 100034, People's Republic of China
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA
| | - Shandong Yu
- Department of Cardiology, Peking University First Hospital, 8, Xishiku Street, West District, Beijing 100034, People's Republic of China
- Department of Cardiology, Cardiovascular Center, Beijing Friendship Hospital, Capital Medical University, Beijing, 100050, People's Republic of China
| | - Gang Li
- Department of Cardiology, Peking University First Hospital, 8, Xishiku Street, West District, Beijing 100034, People's Republic of China
| | - Pengkang He
- Department of Cardiology, Peking University First Hospital, 8, Xishiku Street, West District, Beijing 100034, People's Republic of China
| | - Qiaomei Yang
- Department of Cardiology, Peking University First Hospital, 8, Xishiku Street, West District, Beijing 100034, People's Republic of China
| | - Xiaohong Wei
- Department of Cardiology, Peking University First Hospital, 8, Xishiku Street, West District, Beijing 100034, People's Republic of China
| | - Phung N Thai
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of California, Davis, CA, 95616, USA
| | - Lin Wu
- Department of Cardiology, Peking University First Hospital, 8, Xishiku Street, West District, Beijing 100034, People's Republic of China
- Key Laboratory of Medical Electrophysiology of Ministry of Education, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, 646000, People's Republic of China
| | - Yong Huo
- Department of Cardiology, Peking University First Hospital, 8, Xishiku Street, West District, Beijing 100034, People's Republic of China
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Cheng H, Charles I, James AF, Abdala AP, Hancox JC. QT c interval and ventricular action potential prolongation in the Mecp2 Null/+ murine model of Rett syndrome. Physiol Rep 2022; 10:e15437. [PMID: 36200140 PMCID: PMC9535259 DOI: 10.14814/phy2.15437] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 07/27/2022] [Accepted: 08/06/2022] [Indexed: 06/16/2023] Open
Abstract
Rett Syndrome (RTT) is a congenital, X-chromosome-linked developmental disorder characterized by developmental delay, dysautonomia, and breathing irregularities. RTT is also associated with sudden death and QT intervals are prolonged in some RTT patients. Most individuals with RTT have mutations in the MECP2 gene. Whilst there is some evidence for QT prolongation in mouse models of RTT, there is comparatively little information on how loss of Mecp2 function affects ventricular action potentials (APs) and, to-date, none on ventricular APs from female RTT mice. Accordingly, the present study was conducted to determine ECG and ventricular AP characteristics of Mecp2Null/+ female mice. ECG recordings from 12-13 month old female Mecp2Null/+ mice showed prolonged rate corrected QT (QTc) intervals compared to wild-type (WT) controls. Although Mecp2Null/+ animals exhibited longer periods of apnoea than did controls, no correlation between apnoea length and QTc interval was observed. Action potentials (APs) from Mecp2Null/+ myocytes had longer APD90 values than those from WT myocytes and showed augmented triangulation. Application of the investigational INa,Late inhibitor GS-6615 (eleclazine; 10 μM) reduced both APD90 and AP triangulation in Mecp2Null/+ and WT myocytes. These results constitute the first direct demonstration of delayed repolarization in Mecp2Null/+ myocytes and provide further evidence that GS-6615 may have potential as an intervention against QT prolongation in RTT.
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Affiliation(s)
- Hongwei Cheng
- School of Physiology, Pharmacology and NeuroscienceUniversity WalkBristolUK
| | - Ian Charles
- School of Physiology, Pharmacology and NeuroscienceUniversity WalkBristolUK
| | - Andrew F. James
- School of Physiology, Pharmacology and NeuroscienceUniversity WalkBristolUK
| | - Ana P. Abdala
- School of Physiology, Pharmacology and NeuroscienceUniversity WalkBristolUK
| | - Jules C. Hancox
- School of Physiology, Pharmacology and NeuroscienceUniversity WalkBristolUK
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Cheng H, Charles I, James AF, Abdala AP, Hancox JC. Delayed Ventricular Repolarization and Sodium Channel Current Modification in a Mouse Model of Rett Syndrome. Int J Mol Sci 2022; 23:5735. [PMID: 35628543 DOI: 10.3390/ijms23105735] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2022] [Revised: 05/13/2022] [Accepted: 05/17/2022] [Indexed: 02/01/2023] Open
Abstract
Rett syndrome (RTT) is a severe developmental disorder that is strongly linked to mutations in the MECP2 gene. RTT has been associated with sudden unexplained death and ECG QT interval prolongation. There are mixed reports regarding QT prolongation in mouse models of RTT, with some evidence that loss of Mecp2 function enhances cardiac late Na current, INa,Late. The present study was undertaken in order to investigate both ECG and ventricular AP characteristics in the Mecp2Null/Y male murine RTT model and to interrogate both fast INa and INa,Late in myocytes from the model. ECG recordings from 8-10-week-old Mecp2Null/Y male mice revealed prolongation of the QT and rate corrected QT (QTc) intervals and QRS widening compared to wild-type (WT) controls. Action potentials (APs) from Mecp2Null/Y myocytes exhibited longer APD75 and APD90 values, increased triangulation and instability. INa,Late was also significantly larger in Mecp2Null/Y than WT myocytes and was insensitive to the Nav1.8 inhibitor A-803467. Selective recordings of fast INa revealed a decrease in peak current amplitude without significant voltage shifts in activation or inactivation V0.5. Fast INa 'window current' was reduced in RTT myocytes; small but significant alterations of inactivation and reactivation time-courses were detected. Effects of two INa,Late inhibitors, ranolazine and GS-6615 (eleclazine), were investigated. Treatment with 30 µM ranolazine produced similar levels of inhibition of INa,Late in WT and Mecp2Null/Y myocytes, but produced ventricular AP prolongation not abbreviation. In contrast, 10 µM GS-6615 both inhibited INa,Late and shortened ventricular AP duration. The observed changes in INa and INa,Late can account for the corresponding ECG changes in this RTT model. GS-6615 merits further investigation as a potential treatment for QT prolongation in RTT.
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