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39 ABSENCE OF FUNCTIONAL PROTEINASE-ACTIVATED RECEPTOR-2 (PAR2) MODULATES ISCHEMIA AND INFLAMMATORY RESPONSES IN MOUSE COLON E Hyun1, P Andrade-Gordon2, N Vergnolle1 Numerous evidences indicate the involvement of proteinases in the pathogenesis of inflammatory bowel diseases (IBD). Furthermore, higher levels of proteinase such as trypsin and tryptase that can activate PAR2 has been found in the colon of IBD patients. Our previous studies indicate that activation of PAR2 leads to colonic inflammation mediated by neurogenic mechanism. Therefore, to further study the role of PAR2 in IBD, we examined the effects of PAR2 deficiency in mice models of colonic inflammation. Colonic inflammation in C57BL6 wildtype (PAR2+/+) and PAR2-/- mice was caused by treatment with 2.5% DSS (in drinking water) or TNBS (1 mg or 2 mg in 100 µl of 40% ethanol, intracolonically). Intravital microscopy was performed, seven days after the induction of colitis, on selected venules of the colon to assess changes in leukocyte rolling, adhesion and vessel diameter. Intestinal ischemia was induced by clamping the superior mesenteric artery for 30 min. Subsequently, intravital microscopy was performed on selected intestinal venule. Additional inflammatory parameters such as macroscopic damage score, bowel thickness and myeloperoxidase (MPO) activity were measured. Lastly, weight loss was also assessed daily. For intravital microscopy experiment, PAR2-/- showed significantly lower leukocyte adherence and vessel dilation compared with the PAR2+/+ mice in all DSS, TNBS and ischemic challenges. MPO activity in PAR2-/- was significantly lower compared with PAR2+/+ mice in all three challenge as well. Treatment with DSS or TNBS resulted in higher damage score and bowel thickness in PAR2+/+ mice as compared with PAR2-/-. TNBS colitis usually provokes high mortality in C57BL6 strains, but, 92% of PAR2-/- survived after seven days from TNBS administration, where as only 36% of PAR2+/+ mice survived. Lastly, PAR2-/- treated with TNBS showed significantly lower amount of weight loss as compared with the PAR2+/+ mice. Therefore, our evidences indicate that absence of PAR2 attenuates the inflammatory responses in the mouse colon, via modulation of leukocyte recruitment. Furthermore, reduction of various clinical inflammatory parameters, such as weight loss and mortality rates in PAR2-/- mice subjected to the three different gastrointestinal inflammatory challenges, indicate a proinflammatory role of PAR2 in intestinal tissues. These results point PAR2 and the proteases that activate PAR2, as important targets for therapeutic developments in the treatment of inflammatory pathologies of the gut.
1Mucosal Inflammation Research Group, University of Calgary, Calgary, Alberta; 2RW Johnson Pharmaceutical Research Institute, Spring House, Pennsylvania, USA