Ethanol-induced atrial fibrillation results from late INa and can be prevented by ranolazine

Abstract Background Ethanol consumption is the most important self-triggered cause of atrial fibrillation (AF). As abstinence often fails, alternative therapies are needed. CaMKII-activation upon ethanol with consecutive Ca2+-leak from the sarcoplasmic reticulum (SR) appears to be an important pathomechanism for ethanol-induced AF, but is not a druggable target. CaMKII has previously been shown to induce late sodium current (late INa) which could be proarrhythmogenic. Purpose We hypothesized that late INa might be involved in the development of AF upon acute ethanol exposition and that thus, the antianginal drug ranolazine (an inhibitor of late INa) could be repurposed to prevent ethanol-induced AF. Methods Acute effects of ethanol were investigated in vivo and in vitro as compared to vehicle. The occurrence of AF in vivo was assessed by programmed electrical stimulation in mice. To test the role of late INa, we used ranolazine in vivo and in vitro, as well as tetrodotoxin in vitro. We measured late INa and cytosolic sodium concentration, recorded stimulated action potentials and spontaneous delayed afterdepolarizations (DAD), and assessed SR Ca2+-leak by recording Ca2+-sparks. Mechanistically, we inhibited CaMKII using AIP and used NaV1.5 S571A mice to specifically investigate the role of CaMKII-mediated late INa. Human biopsies were acquired during surgery and were used for cell isolation or chunk incubation. Results Ethanol acutely induced late INa, sodium overload, SR Ca2+-leak and delayed afterdepolarizations in isolated atrial cardiomyocytes, as well as atrial fibrillation in vivo (10 of 10 mice). All of these cellular ethanol effects were prevented by pharmacologic inhibition of late INa. Importantly, ranolazine prevented the development of AF upon ethanol exposure in vivo. Mechanistically, CaMKII-activation and, accordingly, CaMKII-dependent NaV1.5 phosphorylation (S571) were increased by ethanol exposure. Indeed, the phosphoresistant NaV1.5 S571A mutation prevented late INa, SR Ca2+-leak and in vivo AF upon ethanol, demonstrating a critical role of CaMKII-mediated NaV1.5 phosphorylation for acute ethanol effects. Conclusion We show that ethanol acutely induces late INa upstream of arrhythmogenic SR Ca2+-leak and delayed afterdepolarizations, dependent on NaV1.5 S571 phosphorylation, leading to atrial fibrillation in vivo. Importantly, these effects as well as AF in vivo can be prevented using the late INa inhibitor ranolazine. We suggest that this antianginal drug could be repurposed to prevent ethanol-induced AF.Late INa (Patch-Clamp)In vivo AF (programmed stimulation)