Nitric oxide augments single persistent Na+ channel currents via the cGMP/PKG signaling pathway in Kenyon cells isolated from cricket mushroom bodies

Nitrergic modulation of ion channel function in regulating neuronal excitability

Nitric oxide (NO) signaling in the brain provides a wide range of functional properties in response to neuronal activity. NO exerts its effects through different signaling pathways, namely, through the canonical soluble guanylyl cyclase-mediated cGMP production route and via post-translational protein modifications. The latter pathways comprise cysteine S-nitrosylation and 3-nitrotyrosination of distinct tyrosine residues. Many ion channels are targeted by one or more of these signaling routes, which leads to their functional regulation under physiological conditions or facilities their dysfunction leading to channelopathies in many pathologies. The resulting alterations in ion channel function changes neuronal excitability, synaptic transmission, and action potential propagation. Transient and activity-dependent NO production mediates reversible ion channel modifications via cGMP and S-nitrosylation signaling, whereas more pronounced and longer-term NO production during conditions of elevated oxidative stress leads to increasingly cumulative and irreversible protein 3-nitrotyrosination. The complexity of this regulation and vast variety of target ion channels and their associated functional alterations presents a challenging task in assessing and understanding the role of NO signaling in physiology and disease.

Nitric oxide down-regulates voltage-gated Na+ channel in cardiomyocytes possibly through S-nitrosylation-mediated signaling

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, a disulfide reducing agent disulfide 1,4-Dithioerythritol, or a FOXO1 activator paclitaxel, suggesting that NO is a negative regulator of the voltage-gated Na⁺ channel through thiols in regulatory protein(s) for the channel transcription.