Colonic luminal proteases activate colonocyte proteinase‐activated receptor‐2 and regulate paracellular permeability in mice

Luminal activation of protease‐activated receptors‐2 (PAR2) on colonocytes by trypsin or PAR2‐activating peptide increases colonic paracellular permeability (CPP). The aim of this study was to evaluate the role of proteases from endogenous and bacterial origin in the modulation of CPP and colonocyte PAR2 expression in mice. CPP was assessed with 51Cr‐EDTA after intracolonic administration of different protease inhibitors. After 12 days of oral antibiotic treatment, measurements of colonic luminal serine protease activity (CLSPA), CPP, mucosal mouse mast cell proteinase‐1 (MMCP‐1) content, immunochemistry of PAR2 and assessment of effects of PAR2 agonist (SLIGRL) and mast cell degranulator (C48/80) on CPP in Ussing chambers were performed. Immunochemistry was repeated after intracolonic trypsin administration. Colonic infusion of protease inhibitors significantly reduced CPP. In antibiotic‐treated mice, CLSPA was reduced coupled with a decrease in PAR2 expression, but with no change in CPP and MMCP‐1 content. Trypsin administration restored PAR2 expression. The increase in CPP induced by SLIGRL and C48/80 was reduced after antibiotic treatment. Protease activity of colonic content plays an important role in the regulation of mucosal barrier through activation of PAR2.