Impaired S-nitrosylation of Cx43 prevents arrhythmogenicity and myocardial injury upon cardiac stress in Duchenne Muscular Dystrophy

Connexin-43 (Cx43) plays a critical role in the propagation of action potentials and cardiac contractility. In healthy cardiomyocytes, Cx43 is mainly located at the intercalated disk; however, Cx43 remodeling is observed in cardiac pathologies and is linked with arrhythmogenesis and sudden cardiac death. Using a mouse model of Duchenne muscular dystrophy (DMD), we previously demonstrated that Cx43 localizes to the lateral side of dystrophic cardiomyocytes, forming undocked hemichannels. {beta}-adrenergic signaling-induced cardiac stress promotes S-nitrosylation and the opening of undocked Cx43 hemichannels leading to disrupted cardiac membrane excitability and deadly arrhythmogenic behaviors. To establish the direct role of S-nitrosylated Cx43 in DMD cardiomyopathy, we generated knockin DMDmdx mice with reduced levels of S-nitrosylated Cx43, by replacing cysteine 271 with a serine in one Cx43 of the unique site for S-nitrosylation of Cx43 (DMDmdx:C271S+/-). Immunofluorescence analysis revealed that cardiac Cx43 lateralization in DMDmdx:C271S+/- mice was similar to DMDmdx mice, indicating that the genetic modification did not prevent Cx43 remodeling. Upon isoproterenol treatment, DMDmdx mice displayed a higher incidence of arrhythmogenic events when compared to DMDmdx:C271S+/- mice, which more closely resemble wild-type mice. Optical mapping imaging in isolated hearts showed that DMDmdx mice displayed aberrant Ca2+ signaling and prolonged action potentials, which is restored in DMDmdx:C271S+/- mice. Isoproterenol treatment evoked severe myocardial injury in DMDmdx mice, which was significantly attenuated in DMDmdx:C271S+/- mice. Notably, DMDmdx mice treated with Gap19, a Cx43 hemichannel blocker, exhibited cardioprotection against myocardial injury. We concluded that S-nitrosylation of Cx43 proteins is a fundamental NO-mediated mechanism involved in arrhythmias and myocardial injury in DMDmdx, occurring through the opening of hemichannels following {beta}-adrenergic stress.