Reduction in Na⁺ current by angiotensin II is mediated by PKCα in mouse and human-induced pluripotent stem cell-derived cardiomyocytes

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• 作者：Sophie Mathieu ; PhD^* ; ^&dagger ; ; Nabil El Khoury ; MSc^* ; ^&Dagger ; ; Katy Rivard ; PhD^* ; ^&dagger ; ; Roselle Gé ; linas ; PhD^* ; Philippe Goyette ; PhD^* ; Pierre Paradis ; PhD^§ ; ; Mona Nemer ; PhD^║ ; Cé ; line Fiset ; PhD^* ; ^&dagger ; ; ^{celine.fiset@icm-mhi.org" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Angiotensin II type 1 receptor ; Na+ current ; Arrhythmia ; Ventricular conduction ; hiPSC-CM ; Protein kinase Cα
• 刊名：Heart Rhythm
• 出版年：2016
• 出版时间：June 2016
• 年：2016
• 卷：13
• 期：6
• 页码：1346-1354
• 全文大小：2524 K

文摘

Ventricular arrhythmias and sudden cardiac deaths are among the leading causes of mortality in patients with heart failure, and the underlying mechanisms remain incompletely understood. Chronic elevation of angiotensin II (ANGII) is known to be one of the main contributors to heart failure.

Objective

We tested whether ANGII can alter ventricular conduction and Na⁺ current using transgenic mice with cardiomyocyte-restricted overexpression of ANGII type 1 receptor (AT1R).

Methods

We used surface electrocardiograms along with current- and voltage-clamp techniques to characterize the electrophysiological properties of AT1R mice while the underlying regulatory mechanisms were explored using reverse transcription/quantitative polymerase chain reaction, Western blots, and immunofluorescence techniques.

Results

Electrophysiological data indicated that chronic AT1R activation in ventricular myocytes caused a 60% reduction in Na⁺ current density that slowed the maximal velocity of the action potential upstroke, leading to a prolongation of the QRS complex. These changes occur independently of cardiac hypertrophy, suggesting a direct role for ANGII/AT1R in slowing ventricular conduction. Western blots demonstrated a selective increase in sarcolemmal protein kinase Cα (PKCα) in AT1R mice, indicating PKCα activation. Furthermore, immunofluorescence analysis showed reorganization of PKCα expression to sarcolemma and colocalization with Na_V1.5 in AT1R myocytes. The involvement of PKCα in regulating Na⁺ current was subsequently demonstrated in human-induced pluripotent stem cell–derived cardiomyocytes where ANGII treatment reduced Na⁺ current density. Concomitant treatment with αV5-3, a PKCα translocation inhibitor peptide, blocked the ANGII effect.

Conclusion

Overall, this study suggests that in mouse and human cardiomyocytes, PKCα is an important mediator of the ANGII-induced reduction in Na⁺ current and may contribute to ventricular arrhythmias.