The gasotransmitter role of hydrogen sulfide

A novel concept of "gasotransmitter" arrived recently. Gasotransmitters are small molecules of endogenous gases with important physiological functions. Their production and metabolism are enzymatically regulated, and their effects are not dependent on specific membrane receptors. Following the identification of nitric oxide and carbon monoxide as gasotransmitters, hydrogen sulfide (H2S) may be qualified as the third gasotransmitter. Recent studies have shown that H 2 S is generated from vascular smooth muscle cells (SMCs), catalyzed by specific H2S-generating enzyme. At physiologically relevant concentrations, H2S relaxes vascular tissues, an effect mediated by the activation of ATP-sensitive K+ (K-ATP) channels in vascular SMCs. H-2 S directly alters the activity of K-ATP channels without the involvement of second messengers. Furthermore, the endogenous production of H2S in the cardiovascular system is likely regulated by nitric oxide, whereas the vasorelaxant effect of nitric oxide is inhibited by H2S. It is anticipated that future studies will better reveal the molecular mechanisms underlying the effect of H2S on K-ATP channel proteins, the interaction of H2S and other gasotransmitters in cardiovascular system, the endogenous stimulators and inhibitors of H2S metabolism, the role of H2S in the regulation of heart function, and the abnormal H2S production and action under various pathophysiological conditions.