Proinflammatory Cytokines Suppress the Expression Level of Protease-Activated Receptor-2 through the Induction of iNOS in Rat Colon

Abstract

ABSTRACT. Protease-activated receptor (PAR)-2 plays important roles in intestinal inflammatory responses and also contributes to intestinal digestive motility. In the distal colon of a rat experimental colitis model, expression level of PAR-2 mRNA was decreased, and relaxation through PAR-2 activation was attenuated. This study shows the effects of proinflammatory cytokines on changes to PAR-2 in rat colonic smooth muscle using an organ culture method. Colonic inflammation was induced in rats by administering dextran sodium sulphate in drinking water. Organ culture of distal colonic smooth muscle layer of normal rat was performed for up to 3 days. In the experimental colitis rat, mRNA expression levels of proinflammatory cytokines such as IL-1 and TNF- increased with inflammation. After the incubation with IL-1 and TNF- for 3 days, trypsin (PAR-2 agonist)-induced relaxation was attenuated, simultaneous with suppression of PAR-2 mRNA expression. Conversely, in this preparation, mRNA expression levels of iNOS were significantly increased. When l-NMMA was added to the medium with IL-1 and TNF-, changes to PAR-2 by these cytokine recovered. Moreover, when samples were cultured with NOC-18 (slow-releasing NO donor) for 3 days, relaxation induced by trypsin and expression of PAR-2 mRNA were attenuated. These results suggest that suppression of PAR-2 expression under inflammatory conditions is at least partially induced by NO produced in the colonic muscularis externa by proinflammatory cytokines.KEY WORDS: colonic smooth muscle, inflammatory bowel disease, motility disorder, protease-activated receptor-2.

Novel role of zonulin in the pathophysiology of gastro-duodenal transit: a clinical and translational study

“…In an in-vitro assay of mouse stomach and guinea pig taenia coli, activation of PAR1 and PAR2 by their respective synthetic agonists, resulted in relaxation of the gastric fundus 22 . Other studies have reported varied results that have been dependent on the inflammatory conditions of the model and focused on www.nature.com/scientificreports/ other segments of the GI tract such as the jejunum or colon, which support a GI-segment specific, differential response to inflammation in GI function [23][24][25] . Another possible pathway by which zonulin affects GI motility is by the modulation of the innate immune system and its downstream interaction with neuro-enteric components of the GI tract 26 .…”