Emerging role of hydrogen sulfide in colonic physiology and pathophysiology.

Hydrogen sulfide (H₂S) is a toxic gas that is now recognized as an important mediator of many physiological processes. In the colon, H₂S is produced both endogenously and by naturally occurring sulfate-reducing bacteria (SRB). The full arrays of its effects in the gastrointestinal tract are still being elucidated, but they range from motility to carcinogenesis. We examined the evidence relating to H₂S as a modulator of colonic function and disease. H₂S is implicated in modulation of colonic compliance through its action on smooth muscle. There is also evidence linking H₂S to colonic nociception, inflammatory bowel disease (IBD), and colorectal cancer. The exact mechanisms and pathways by which H₂S exerts its multitude of effects are not yet fully understood, but its involvement in physiological and pathophysiological conditions of the colon is becoming evident. Elucidating the intricate effects of H₂S in the colon and understanding the exact nature of its interactions with the colon makes pharmacological modulation of H₂S production and metabolism potential targets for treatment of a multitude of colonic conditions in the future.