Dysregulated cystathionine-β-synthase/hydrogen sulfide signaling promotes chronic stress-induced colonic hypermotility in rats

Background: Hydrogen sulfide (H2S), an important endogenous gasotransmitter, is involved in the modulation of gastrointestinal motility, but whether it mediates the intestinal dysmotility in irritable bowel syndrome (IBS) is not known. This study explored the significance of cystathionine-beta-synthase (CBS)/H2S signaling in stress-induced colonic dysmotility. Methods: A rat model of IBS was established using chronic water avoidance stress (WAS). Colonic pathological alterations were detected histologically. Intestinal motility was determined by intestinal transit time (ITT) and fecal water content (FWC). Visceral sensitivity was assessed using the visceromotor response (VMR) to colorectal distension (CRD). Real-time PCR, Western blotting, and immunostaining were performed to identify the expression of CBS in the colon. The contractions of distal colon were studied in an organ bath system and H2S content was measured by ELISA. The effects of SAM, a selective CBS activator, on colonic dysmotility were examined. MEK1 was tested as a potential upstream effector of CBS/H2S loss. Key Results: After 10 days of WAS, the ITT was decreased and FWC was increased, and the VMR magnitude in response to CRD was enhanced. The colonic CBS expression and H2S levels were significantly declined in WAS-exposed rats, and the density of CBS-positive enteric neurons in the myenteric plexus in WAS-treated rats was lower than that in controls. SAM treatment relieved WAS-induced colonic hypermotility via increased H2S production. AZD6244, a selective inhibitor of MEK1, partially reversed CBS downregulation and colonic hypermotility in WAS-treated rats. Conclusions & Inferences: Decreased CBS/H2S signaling through increased MEK1 signaling might be important in the pathogenesis of chronic stress-induced colonic hypermotility. SAM could be administered for disorders associated with intestinal hypermotility.