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Up-regulation of miR-31 in human atrial fibrillation begets the arrhythmia by depleting dystrophin and neuronal nitric oxide synthase

Atrial microRNA-31 up-regulation causes dystrophin and nNOS depletion, which in turn contributes to the electrical phenotype of atrial fibrillation. Rhythm remodeling traced to tiny RNA Atrial fibrillation (AF) is characterized by abnormal heart rhythms and can be caused by a variety of risk factors ranging from obesity to diabetes. Although treatments exist, AF is famously able to recur by “remodeling” the heart tissue electrically and structurally to maintain its unsteady beat. Reilly et al. have discovered a small noncoding RNA, miR-31, that is responsible for a string of signals that allow for such remodeling. An increase in miR-31 led to depletion of neuronal nitric oxide synthase (nNOS) and repression of dystrophin (which binds nNOS in muscle cells) in the fibrillating atrial myocardium of both humans and goats. These mechanistic findings were further explored in mice. Because up-regulation of miR-31 and the resulting loss of dystrophin and nNOS in AF are specific to the atrium, it may be possible to target interventions to this remodeling pathway, thus providing a safer therapeutic option for patients with AF than those that are currently available, including ablation and ion channel blockers. Atrial fibrillation (AF) is a growing public health burden, and its treatment remains a challenge. AF leads to electrical remodeling of the atria, which in turn promotes AF maintenance and resistance to treatment. Although remodeling has long been a therapeutic target in AF, its causes remain poorly understood. We show that atrial-specific up-regulation of microRNA-31 (miR-31) in goat and human AF depletes neuronal nitric oxide synthase (nNOS) by accelerating mRNA decay and alters nNOS subcellular localization by repressing dystrophin translation. By shortening action potential duration and abolishing rate-dependent adaptation of the action potential duration, miR-31 overexpression and/or disruption of nNOS signaling recapitulates features of AF-induced remodeling and significantly increases AF inducibility in mice in vivo. By contrast, silencing miR-31 in atrial myocytes from patients with AF restores dystrophin and nNOS and normalizes action potential duration and its rate dependency. These findings identify atrial-specific up-regulation of miR-31 in human AF as a key mechanism causing atrial dystrophin and nNOS depletion, which in turn contributes to the atrial phenotype begetting this arrhythmia. miR-31 may therefore represent a potential therapeutic target in AF.