Low Grade Mucosal Inflammation Activated The Colonic PAR-2 And Visceral Hypersensitivity In Mice

Objective:To investigate the expressions of protease-activated receptor-2(PAR-2) in colonic tissue, substance P(SP) and calcitonin gene-related peptide(CGRP) in cornu dorsale medullae spinalis, and then to explore the relationship between the activation of PAR-2 and visceral hypersensitivity in mice with DSS-induced low glade colonic mucosal imflammation.Methods:Thirty-six C57BL/6 mice were randomly divided into two groups: low grade inflammation group(group S, LGI) and control group (group A). The mice in group S were given 1.5%DSS solution for 7 days, and then distilled water for another 10 days, while the mice in group A were treated with distilled water only. The abdominal myoelectric activities(AMAs) at different levels of colorectal distension(CRD) were recorded in the 15th day.The expression of substance P(SP), calcitonin gene-related peptide(CGRP) in spine cord and the changes of PAR-2 in the colonic mucosa were detected by immunohistochemistry after CRD.Results:In the 15th, the HI in group S was 1.500±0.926. When colon distention by 15mmHg,the AMAs (27.958±1.660μV) in group S were similar to that in group A (26.947±0.854μV, P>0.05). The AMAs in group S with colonic distention by 30mmHg,45 mmHg,60mmHg were 33.455±3.786, 46.848±4.038,and 47.207±18.151 (μv) respectively, and which were significantly higher than those in group A (31.253±3.842,37.267±2.542,and 33.798±8.415(μv) (P<0.05, respectively). The integrated optical density(IOD) of PAR-2 in the distal colon(40.769±8.422) was highter than that in group A(21.718±4.131). And the IODs of SP (30.288±13.530) and CGRP (46.829±26.261) in spine cord in group were significantly higher than those in group A (SP 10.788±4.490,CGRP 13.997±3.340)(P﹤0.05 respectively). There was a positive relationship between the expression of PAR-2 and SP, or between the expression of PAR-2 and CGRP in group S (r=0.622,P<0.05, r=0.588,P<0.05). The expression of PAR-2,SP,or CGRP was a close correlation with AMAs in group S (r = 0.439-0.835, P <0.05).Conclusion:Low grade mucosal inflammation activated visceral hypersensitivity in mice, PAR-2 maybe involved its mechanisms.