Tu1983 Activation of TRPA1, but Not of TRPV1, Improves Gut Motility in a Murine Model of Postoperative Ileus

Abstract

Background and Aim: Agonists of transient receptor potential vanilloid (TRPV1) and transient receptor potential ankyrin 1 (TRPA1) have been reported to induce contraction of intestinal smooth muscle In Vitro, but it is unclear whether activation of TRPV1 or TRPA1 affects gastrointestinal (GI) transit In Vivo. In this study, we investigated the effects of capsaicin (TRPV1 agonist), allyl isothiocyanate (AITC, TRPA1 agonist), cinnamaldehyde (CA, TRPA1 agonist), daikenchuto (TU-100, TRPA1/TRPV1 agonist), and 6-shogaol (6SG, TRPA1/TRPV1 agonist), the main constituent of TU-100, on murine postoperative ileus (POI) induced by surgical manipulation of mouse intestines. TU-100, a traditional Japanese medicine that has been prescribed to improve paralytic POI in Japan, is currently undergoing clinical trials on various intestinal diseases such as postoperative ileus, functional constipation, and Crohn's disease in the USA (http://clinicaltrials.gov/ct2/results?term=TU-100). Methods: Male C57Bl/ 6 mice underwent laparotomy and large bowel manipulation. Fluorescein isothiocyanatedextran (FD70) was administered orally at 23.5 h postoperatively, and the mice were killed at 30 min post gavage. GI transit was estimated by calculating the geometric center (GC) value. Serotonin release from RIN-14B cell, an enterochromaffin-like cell line, was measured by EIA. Results: Colonic manipulation decreased small intestinal transit to 70.2±2.7% of control. TRPA1 agonists (AITC, CA, TU-100, and 6SG) significantly improved the delayed GI transit induced by intestinal manipulation by 68.3±12.9%, 83.6±9.8%, 65.7±13.8%, and 26.3±6.7%, respectively. On the other hand, the TRPV1 agonist capsaicin had no effect. Freshly isolated intestinal epithelial cells and RIN-14B cells expressed abundant TRPA1 mRNA but no TRPV1 mRNA. POI was induced in TRPV1-deficient mice to a similar degree as in wild-type mice, and TU-100 was effective in POI of TRPV1-deficient mice. AITC, CA, TU-100, and 6SG stimulated RIN-14B cell to release serotonin. Conclusions: These results suggest that TRPA1 is essential to induction and alleviation of POI while TRPV1 stimulation may play little role. Stimulation of TRPA1 may be a novel therapeutic approach for the treatment of POI.