[Role of hydrogen sulfide in the physiology of gastrointestinal tract and in the mechanism of gastroprotection].

Hydrogen sulfide (H2S) is commonly known as a toxic gas with an unpleasant odor. However, in the human body it plays a role as a gaseous transmitter involved in the control of physiological processes. Studies published so far have shown that H2S increased synaptic long-term potentiation in the central nervous system and exerted the inflammatory and anti-inflammatory effects on vascular endothelium. These effects clearly depend on the concentration of this gaseous molecule. H2S exerts vasodilatory effect in the cardiovascular system similar to those exhibited by carbon monoxide or nitric oxide. It is believed that H2S may play a potential role in the physiology of the gastrointestinal tract including the mechanism of gastroprotection of gastric mucosa and possibly exerts a protective effect in other parts of the digestive system. The administration of L-cysteine, the precursor of H2S or NaHS, the exogenous donor of this gaseous molecule, significantly reduced gastric damage induced by ethanol, an agent that is known to induce acute gastric damage and hemorrhagic necrosis to the gastric mucosa. The administration of H2S results in increased secretion of protective bicarbonate and mucus secretions and these effects could, in part, explain the H2S-induced protection of duodenal mucosa against the damage induced by gastric acid. Despite these promising results, little is known about the therapeutic efficacy of H2S in relation to two other important gases, nitric oxide and carbon monoxide, and future studies are definitely needed to assess its usefulness in the treatment of upper and lower gastrointestinal tract disorders.