Patients with Duchene Muscular Dystrophy (DMD) commonly present severe ventricular arrhythmias that contribute to heart failure. Arrhythmias and lethality are also consistently observed in adult Dmdmdx mice, a mouse model of DMD, after acute β-adrenergic stimulation. These pathological features were previously linked to aberrant expression and remodeling of the cardiac gap junction protein connexin 43 (Cx43). Here, we report that remodeled Cx43 protein forms Cx43 hemichannels in the lateral membrane of Dmdmdx cardiomyocytes and that the β -adrenergic agonist isoproterenol (Iso) aberrantly activates these hemichannels. Block of Cx43 hemichannels or a reduction in Cx43 levels (using Dmdmdx:Cx43+/- mice) prevents the abnormal increase in membrane permeability, plasma membrane depolarization and Iso-evoked electrical activity in these cells. Additionally, Iso treatment promotes nitric oxide (NO) production and S-nitrosylation of Cx43 hemichannels in Dmdmdx heart. Importantly, inhibition of NO production prevents arrhythmias evoked by Iso. We found that NO directly activates Cx43 hemichannels by S-nitrosylation of cysteine at the position 271. Our results demonstrate that opening of remodeled and S-nitrosylated Cx43 hemichannels play a key role in the development of arrhythmias in DMD mice and may serve as therapeutic targets to prevent fatal arrhythmias in DMD patients.
Mauricio A. Lillo, Eric Himelman, Natalia Shirokova, Lai-Hua Xie, Diego Fraidenraich, Jorge E. Contreras