Molecular regulatory mechanism of TRPV4-mediated calcium-dependent 5-HT secretion from enterochromaffin cells and its involvement in ulcerative colitis.

Although acetylcholine (ACh) released by the vagus nerve can stimulate enterochromaffin cells (ECs) to secrete 5-hydroxytryptamine (5-HT), the precise regulatory mechanism underlying this process and its association with the pathogenesis of ulcerative colitis (UC) remain unclear. In this study, we aimed to investigate whether TRPV4-mediated calcium influx in ECs is involved the process of ACh promoting 5-HT secretion which leads to UC. In vitro experiments, western blotting, cellular calcium imaging, and patch clamp were applied to ECs, and dextran sulfate sodium (DSS)-induced UC of mouse model was used in vivo. Carbachol (CCh), a stable analog of ACh, activated mAChR/IP3/IP3R pathway to increase intracellular [Ca2+]ilevels in ECs, in which both TRPV4 channels and RyR were activated in response to CCh. The selective TRPV4 antagonist HC067047 inhibited the calcium signals and membrane currents induced by IP3/IP3R, as well as 5-HT secretion. In addition, selective blocker of RyR (Dantrolene) also significantly inhibited CCh-induced calcium signals and membrane currents. In vivo experiments, HC067047 significantly suppressed the synthesis and release of 5-HT from ECs and alleviated DSS-induced UC in mice. Taken together, this study reveals a novel mAChR/IP3/IP3R /TRPV4/5-HT pathway in ECs is likely involved in the pathogenesis of UC. Targeting this pathway holds a promise for the potential prevention and treatment of UC.