Reduced Cx43 S-nitrosylation protects against cardiac stress-induced arrhythmias and myocardial injury in Duchenne Muscular Dystrophy.

AIMS: In Duchenne muscular dystrophy (DMD), connexin-43 (Cx43) delocalizes from intercalated discs to the lateral membrane of cardiomyocytes, where it forms undocked hemichannels. β-adrenergic stress induces lethal arrhythmias in DMDmdx mice that correlate with increased Cx43 S-nitrosylation and excessive hemichannel opening. Here, we aimed to determine whether S-nitrosylation of Cx43 at cysteine 271 directly contributes to β-adrenergic stress-induced arrhythmias and myocardial injury in DMD. METHODS AND RESULTS: To define the role of Cx43 S-nitrosylation in DMD cardiomyopathy, we generated DMDmdx knock-in mice carrying a cysteine-to-serine substitution at residue 271, a critical S-nitrosylation site involved in NO-dependent Cx43 hemichannel activation (DMDmdx:C271S+/-). Following β-adrenergic stimulation, DMDmdx mice exhibited a higher incidence of arrhythmogenic events and increased triggered activity in isolated cardiomyocytes compared with DMDmdx:C271S+/- mice, which more closely resembled wild-type mice. Optical mapping of isolated hearts showed that DMDmdx mice developed abnormal Ca2+ transients, prolonged action potentials, and episodes of conduction block. These abnormalities were normalized in DMDmdx:C271S+/- mice and attenuated by treatment with the Cx43 hemichannel inhibitor Gap19. Moreover, β-adrenergic stress evoked severe myocardial injury and bradycardia in DMDmdx mice, both of which were significantly attenuated in DMDmdx:C271S+/- mice. Notably, Gap19-treated DMDmdx mice were protected against myocardial injury, further supporting a direct role for Cx43 hemichannels in DMD-associated cardiac damage. CONCLUSION: These findings reveal, for the first time, a mechanistic link between Cx43 hemichannel activity, arrhythmogenesis, and myocardial injury in DMD. We conclude that S-nitrosylation of Cx43 is a fundamental NO-mediated mechanism driving β-adrenergic stress-induced arrhythmias and myocardial injury in DMDmdx mice through pathological opening of Cx43 hemichannels.