Hydrogen sulfide and the vasculature: a novel vasculoprotective entity and regulator of nitric oxide bioavailability?

Introduction Reactive nitrogen species (RNS) in the heart and vasculature (H2S) biosynthesis H2S measurement, catabolism and removal H2S in the heart and vasculature Evidence for 'cross-talk' between nitric oxide and H2S Evidence for the formation of a novel intermediate between nitric oxide and H2S at physiological pH Concluding remarks Hydrogen sulfide (H2S) is a well known and pungent toxic gas that has recently been shown to be synthesised in man from the amino acids cystathionine, homocysteine and cysteine by at least two distinct enzymes; cystathionine-gamma-lyase and cystathionine-beta-synthase. In the past few years, H2S has emerged as a novel and increasingly important mediator in the cardiovascular system but delineating the precise physiology and pathophysiology of H2S is proving to be complex and difficult to unravel with disparate findings reported with cell types, tissue types and animal species reported. Therefore, in this review we summarize the mechanisms by which H2S has been proposed to regulate blood pressure and cardiac function, discuss the mechanistic discrepancies reported in the literature as well as the therapeutic potential of H2S. We also examine the methods of H2S detection in biological fluids, processes for H2S removal and discuss the reported blood levels of H2S in man and animal models of cardiovascular pathology. We also highlight the complex interaction of H2S with nitric oxide in regulating cardiovascular function in health and disease.