Nitric oxide down-regulates voltage-gated Na+ channel in cardiomyocytes via transcriptional S-nitrosylation signaling pathway

Nitric oxide (NO) is produced from endothelial cells and cardiomyocytes composing the myocardium and benefits cardiac function through both vascular-dependent and -independent effects. This study was purposed to investigate the possible adverse effect of NO focusing on the voltage-gated Na + channel in cardiomyocytes. We carried out patch-clamp experiments on rat neonatal cardiomyocytes demonstrating that NOC-18, an NO donor, significantly reduced Na + channel current in a dose-dependent manner by a long-term application for 24 h, accompanied by a reduction of Nav1.5-mRNA and the protein, and an increase of a transcription factor forkhead box protein O1 (FOXO1) in the nucleus. The effect of NOC-18 on the Na + channel was blocked by an inhibitor of thiol oxidation N-ethylmaleimide or a disulfide reducing agent disulfide 1,4-Dithioerythritol, suggesting that NO is a negative regulator of the voltage-gated Na + channel through thiols in regulatory protein(s) for the channel transcription.