Abstract
Intestinal fibrosis is a serious complication of inflammatory bowel disease (IBD). Proteinase-activated receptor (PAR) 1 is a highly conserved G protein-coupled receptor that is relevant to IBD. We investigated the expression of PAR1 in the progression of intestinal fibrosis in human tissues and mice with chronic enteritis. We acquired intestinal biopsy samples from 6 patients with stenotic UC, 6 patients with stenotic CD, and 6 patients without IBD (control individuals). Biopsy samples were analyzed through histology to test for fibrosis and through immunohistochemistry and RT‒qPCR to measure the levels of PAR1. We studied inflammation and fibrosis severity in intestinal tissues from PAR1–/– mice, and mice were given injections of the PAR1 antagonist; chronic colitis and fibrosis were induced by repetitive administration of DSS. Human intestinal fibroblasts were incubated with thrombin, a PAR1 antagonist, SB-431542 or control medium. The proliferation, activation, migration and collagen synthesis of fibroblasts were detected by CCK8 assay, immunofluorescence cytochemistry, scratch test, transwell assay, western blot, RT‒qPCR and ELISA. Compared with those in mucosal and submucosal biopsy tissue from control individuals, obviously greater levels of collagen deposition were noted in bowel biopsy tissue from patients with fibrostenotic UC or CD. Tissues from patients with fibrostenotic UC or CD had significantly greater levels of PAR1. Mice given injections of a PAR1 antagonist and of PAR1–/– mice exhibited significantly less established fibrosis than mice with chronic colitis. PAR1 inhibition of human intestinal fibroblasts reduced proliferation, differentiation, migration and collagen synthesis. Mechanistically, PAR1 antagonism effectively inhibited the phosphorylation of the Smad2 and Smad3 proteins and the Smad2/3 protein. Compared with those in control individuals, we found enhanced levels of PAR1 in fibrotic bowel tissues from patients with IBD. PAR1 promoted fibrogenesis in fibroblasts. Inhibition or knockout of the PAR1 gene in mice decreases chronic intestinal inflammation and intestinal fibrosis. This research may offer new ideas for the treatment of intestinal fibrosis complicated with chronic intestinal inflammation.