The concept of gaseous molecules as signalling messengers began to emerge in the 1980s with the discovery of endothelial derived relaxing factor, later identified as the gas, nitric oxide. Carbon monoxide and, more recently, hydrogen sulphide have also emerged as important modulators of signal transduction. Hydrogen sulphide is better known as a highly toxic gas with the unforgettable odour of rotten eggs. The beneficial effects of dietary garlic on blood pressure and the vasculature have been shown to be mediated largely by the conversion of garlic-derived polysulphides into hydrogen sulphide by red blood cells. Production of hydrogen sulphide has been attributed to two enzymes in the cysteine biosynthesis pathway, cystathionine β-synthase and cystathionine γ-lyase.
A study published in the journal Science now shows that genetically modified mice lacking cystathionine γ-lyase have reduced levels of hydrogen sulphide in the serum, heart, aorta, and other tissues. The mice showed pronounced hypertension and diminished endothelium-dependent vasorelaxation, providing the first direct evidence that hydrogen sulphide is a physiological vasodilator and regulator of blood pressure.
Hydrogen sulphide has also been shown to cause a drastic reduction in metabolic demand which may provide benefit in the treatment of myocardial ischaemia and reperfusion.