Hydrogen sulfide: a gasotransmitter of clinical relevance

Though the existence of hydrogen sulfide (H2S) in biological tissues has been known for over 300 years, it is the most recently appreciated of the gasotransmitters as a physiologic messenger molecule. The enzymes cystathionine gamma-lyase (CSE) and cystathionine beta-synthase (CBS) had long been speculated to generate H2S, and inhibitors of these enzymes had been employed to characterize influences of H2S in various organs. Definitive evidence that H2S is a physiologic regulator came with the development of mice with targeted deletion of CSE and CBS. Best characterized is the role of H2S, formed by CSE, as an endothelial derived relaxing factor that normally regulates blood pressure by acting through ATP-sensitive potassium channels. H2S participates in various phases of the inflammatory process, predominantly exerting anti-inflammatory actions. Currently, the most advanced efforts to develop therapeutic agents involve the combination of H2S donors with nonsteroidal anti-inflammatory drugs (NSAIDs). The H2S releasing moiety provides cytoprotection to gastric mucosa normally adversely affected by NSAIDs while the combination of H2S and inhibition of prostaglandin synthesis may afford synergistic anti-inflammatory influences.