Binge Alcohol Exposure Triggers Atrial Fibrillation Through T-Type Ca 2+ Channel Upregulation via Protein Kinase C (PKC) / Glycogen Synthesis Kinase 3β (GSK3β) / Nuclear Factor of Activated T-Cells (NFAT) Signaling　- An Experimental Account of Holiday Heart Syndrome

The association between binge alcohol ingestion and atrial fibrillation (AF), often termed "holiday heart syndrome", has long been recognized. However, the underlying cellular and molecular mechanisms are unknown. An experimental model of binge alcohol-induced AF was developed to elucidate the mechanisms linking acute ethanol exposure to changes in ion channel transcription and AF susceptibility. AF-susceptibility during transesophageal electrical stimulation was enhanced 8 h after, but not immediately or 24 h after, acute alcohol intake. T-type calcium channel (TCC) blockade and calcineurin inhibition diminished the AF-promoting effect of ethanol. Long-term (8-24 h) exposure to ethanol augmented TCC isoform-expression (Ca 3.1 and Ca 3.2) and currents in cardiomyocytes, accompanied by upregulation of the transcription factors, Csx/Nkx2.5 and nuclear factor of activated T-cells (NFAT), in the nucleus, and of phospho-glycogen synthesis kinase 3β (GSK3β) in the cytosol. Inhibition of protein kinase C (PKC) during the 7- to 8-h period following ethanol exposure attenuated susceptibility to AF, whereas acute exposure did not. GSK3β inhibition itself upregulated TCC expression and increased AF susceptibility. The present study results suggest a crucial role for TCC upregulation in the AF substrate following binge alcohol-drinking, resulting from ethanol-induced PKC-activation that hyperphosphorylates GSK3β to cause enhanced calcineurin-NFAT-Csx/Nkx2.5 signaling. These observations elucidate for the first time the potential mechanisms underlying the clinically well-recognized, but mechanistically enigmatic, "holiday heart syndrome".