Visceral hypersensitivity is one of the most common symptoms in patients with post-inflammatory-irritable bowel syndrome (PI-IBS). Enterochromaffin (EC) cells and 5-hydroxytryptamine (5-HT) are important in the development of visceral hyperalgesia, and EC cells are influenced by helper T-cell subtype 1 or 2 cytokine predominant environments. In the present study, the analgesic effect of cynaropicrin and its underlying mechanism on the treatment of trinitrobenzene sulfonic (TNBS)-induced PI-IBS visceral hyperalgesia rats was investigated. The results from the abdominal withdrawal reflex tests and electromyography recordings indicated that treatment with cynaropicrin significantly and dose-dependently alleviated the visceral hyperalgesia of PI-IBS rats (P<0.05). In addition, the increased colonic 5-HT content, colonic tryptophan hydroxylase expression, EC cell number and the cytokine levels, including tumor necrosis factor-α and interleukin-6 in PI-IBS rats were significantly alleviated by cynaropicrin (P<0.05). These data demonstrate that the analgesic activity of cynaropicrin on TNBS-induced PI-IBS visceral hypersensitive rats was mediated via reduction of cytokines levels. Thus, cynaropicrin as a bioactive natural product may offer promising therapeutic avenues for visceral hypersensitivity in IBS.
Keywords: cynaropicrin; enterochromaffin cell; post-inflammatory irritable bowel syndrome; visceral hyperalgesia.