Abstract

Since our initial demonstrations that hydrogen sulfide (H2S) may function as a neuromodulator in the brain and a smooth muscle relaxant in the vascular system, accumulating evidence shows that H2S may function as a signaling molecule. We and others also found that H2S has a cytoprotective effect. Because H2S is well-known toxic gas, a cytoprotective role has been overlooked. H2S protects neurons from oxidative stress. It also protects cardiac muscle from ischemia-reperfusion injury. The finding led to the application of H2S to the bypass surgery patients in Phase II clinical trial. Cystathionine β–synthase (CBS) and cystathionine γ–lyase (CSE) are well known as H2S-producing enzymes. We recently demonstrated that the other H2S-producing enzyme, 3-mercaptopyruvate sulfurtransferase (3MST) along with cysteine aminotransferase (CAT) is localized to neurons in the brain and to the vascular endothelium. However, the regulation of H2S production by 3MST/CAT pathway had not been well understood. The present study shows that H2S production by 3MST/CAT pathway is regulated by Ca2+ and that H2S protects retinal photoreceptor cells from light induced degeneration by suppressing excessive Ca2+ influx caused by intense light.

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