Decreased levels of s-nitrosylated Cx43 prevent arrhythmogenicity and myocardial infarction upon cardiac stress in duchenne muscular dystrophy.

Abstract

Connexin43 (Cx43) plays a critical role in action potential propagation and cardiac contractility. In healthy cardiomyocytes, Cx43 is located at the intercalated disk, however, in cardiac diseases such as hypertrophic and dilated cardiomyopathy, it is remodelled to the lateral side of ventricular cardiomyocytes. In Duchenne muscular dystrophy (DMD) mice, lateralized cardiac Cx43 is found forming hemichannels at the plasma membrane that activate upon cardiac stress evoking triggered activity and arrhythmogenic behaviours. S-nitrosylated levels of Cx43 strongly correlate with changes in membrane excitability in cardiomyocytes from DMD mice. To unequivocally demonstrate a direct role of S-nitrosylated Cx43 in DMD cardiomyopathy, we developed a specific knockin mouse line, in which the Cx43 site for S-nitrosylation, cysteine 271, was specifically substituted for a serine (Cx43C271S). We then crossed the C271S mouse line with DMD mice to obtain DMD:Cx43C271S+/- mice with reduced levels of S-nitrosylated Cx43. Littermate mice (4-6-month-old) were used to assess isoproterenol-induced cardiac stress and, consequently, heart dysfunction in WT, DMD and DMD:Cx43C271S+/- mice. DMD mice displayed increased number of arrhythmogenic events, but without changes in RR and QRS complexes within 1-h post-isoproterenol treatment. However, elevated number of deadly arrhythmias, bradycardia, and increased QRS complex duration were detected in DMD mice for 24-h following isoproterenol stimulation. Strikingly, the number of arrhythmogenic events were significantly reduced in DMD:Cx43C271S+/- mice. β-adrenergic stimulation with isoproterenol induced cardiac hypertrophy, myocardial infarction, and 40% mortality in DMD mice, which was prevented in DMD:Cx43C271S+/- mice. Therefore, these findings strongly suggest that S-nitrosylation of Cx43 proteins at site cysteine 271 represents a fundamental nitric oxide-mediated mechanism involved in the induction of arrythmias and myocardial infarction in DMD mice after β-adrenergic stress.