The Improvement of Intestinal Mucosal Epithelial Barrier Integrity by 1,3,4-Oxadiazole Derivatives of Pyrrolo[3,4-d]pyridazinone in Rat Experimental Colitis.

BACKGROUND AND PURPOSE: The intestinal mucosal barrier is a complex structure that separates the internal and lumen environments. An impaired intestinal barrier may lead to excessive mucosal immune system activation and further to intestinal diseases, including inflammatory bowel disease (IBD). Therefore, improving the integrity of the intestinal barrier may be a therapeutic approach to prevent or treat IBD. In this study, we aimed to elucidate the effects of the new 1,3,4-oxadiazole derivatives of pyrrolo[3,4-d]pyridazinone, compounds 7b, 10b, and 13b, in intestinal epithelial damage. METHODS: In this study, we used biobank colon and feces samples collected during our previous original experiment, in which we induced colitis in rats by trinitrobenzenesulfonic acid (TNBS) administration. We assessed the expression of tight junction (TJ) proteins, ie, claudin 1 (CLDN1), occludin (OCLN), zonula occludens 1 (ZO1), and mucus layers proteins, ie, mucin 2 (Muc2) and trefoil factor 3 (TFF3), and the goblet cells and mucus content in colon tissues. We also assessed matrix metalloproteinase 9 (MMP9) and MAP kinases (MAPKs) levels in colon tissues and the level of α1-antitrypsin (α1-AT) in feces samples. RESULTS: We found that compounds 7b and 13b at a dose of 20 mg/kg prevented TNBS-induced loss of goblet cells and mucus layer with normalizing Muc2 and TFF3 expression. Both these compounds prevented TNBS-induced loss of the TJ proteins and normalized the fecal α1-AT level. Compounds 7b and 13b (20 mg/kg) counteracted the TNBS-induced increase of MMP9 concentration and MAPK activation. CONCLUSION: New pyrrolo[3,4-d]pyridazinone derivatives normalized the colonic expression of TJ and mucus layer proteins and prevented goblet cells and mucus depletion in rats with experimental colitis, exerting a beneficial effect on mucosal epithelial barrier integrity. They protect against intestinal barrier dysfunction, and the potential mechanism may involve the inhibition of MAPKs and MMP9 activation.