title: Reduction in Na(+) current by angiotensin II is mediated by PKCα in mouse and human-induced pluripotent stem cell-derived cardiomyocytes.
abstract: 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.
  
  
  
  We tested whether ANGII can alter ventricular conduction and Na(+) current using transgenic mice with cardiomyocyte-restricted overexpression of ANGII type 1 receptor (AT1R).
  
  
  
  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.
  
  
  
  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 NaV1.5 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.
  
  
  
  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.
authors.affiliation: Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Faculty of Pharmacy, Université de Montréal, Montreal, Quebec, Canada.
authors.forename: Sophie
authors.initials: S
authors.lastname: Mathieu
authors.affiliation: Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Department of Physiology, Faculty of Medicine, Université de Montréal, Montreal, Quebec, Canada.
authors.forename: Nabil
authors.initials: N
authors.lastname: El Khoury
authors.affiliation: Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Faculty of Pharmacy, Université de Montréal, Montreal, Quebec, Canada.
authors.forename: Katy
authors.initials: K
authors.lastname: Rivard
authors.affiliation: Research Center, Montreal Heart Institute, Montreal, Quebec, Canada.
authors.forename: Roselle
authors.initials: R
authors.lastname: Gélinas
authors.affiliation: Research Center, Montreal Heart Institute, Montreal, Quebec, Canada.
authors.forename: Philippe
authors.initials: P
authors.lastname: Goyette
authors.affiliation: Lady Davis Institute, Sir Mortimer B. Davis-Jewish General Hospital, McGill University, Montreal, Quebec, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Paradis
authors.affiliation: Ottawa University, Ottawa, Ontario, Canada.
authors.forename: Mona
authors.initials: M
authors.lastname: Nemer
authors.affiliation: Research Center, Montreal Heart Institute, Montreal, Quebec, Canada; Faculty of Pharmacy, Université de Montréal, Montreal, Quebec, Canada. Electronic address: celine.fiset@icm-mhi.org.
authors.forename: Céline
authors.initials: C
authors.lastname: Fiset
mesh_terms: D000200:Action Potentials; D000804:Angiotensin II / Q000378:metabolism*; D000818:Animals; D006329:Heart Conduction System / Q000503:physiopathology; D006801:Humans; D057026:Induced Pluripotent Stem Cells / Q000502:physiology; D051379:Mice; D032383:Myocytes, Cardiac / Q000378:metabolism*; D051571:Protein Kinase C-alpha / Q000378:metabolism*; D015222:Sodium Channels / Q000502:physiology*
chemical_list: D015222:Sodium Channels; D000804:Angiotensin II; D051571:Protein Kinase C-alpha
keywords: Angiotensin II type 1 receptor; Arrhythmia; Na(+) current; Protein kinase Cα; Ventricular conduction; hiPSC-CM