The Effects And Mechanism Of IL-22 On Occludin In Colonic Mucosa Of Experimental Colitis Of Mice Model

Background:Intestinal barrier plays an important role in ulcerative colitis(UC). Protecting the integrity of intestinal barrier is thought to be a potential way for ulcerative colitis. Tight junction(TJ) plays a decisive role in intestinal barrier and its integrity is related to intestinal mucosal inflammation and a variety of cytokines.Occludin is an integral membrane protein that has been suggested to play a role in the organization and dynamic function of the epithelial tight junction(TJ).IL-22 is a newly discovered cytokines which has been widely researched;STAT3 has a major role in the downstream signalling events of the IL-22-IL-22R1system.Rrecent studies support a protective role of IL-22/STAT3 in UC,but the mechanism has not yet been defined. Here we attempt to evaluate the role of IL-22 in the animal models; Western Blotting and Immunohistochemistry would be performed to investigate the role of IL-22 in experimental colitis of mice induced by dextran sulphate sodium(DSS) and the effects of IL-22 on occludin and STAT3 in colonic mucosa.Objective:the present study aimed to investigate the role of IL-22 in experimental colitis of mice induced by dextran sulphate sodium(DSS), and discussed the effects of IL-22 on occludin and signal transducer and activator of transcription 3 (STAT 3) in colonic mucosa.Methods:Sixty Balb/c mice were evenly divided into three groups(control group, model group and IL-22 group). DSS colitis model was induced by administration of 3% DSS in drinking water, model group and IL-22 group were injected intraperitoneally with isopyknic 0.9% saline or IL-22 on the the first, the third and the fifth day. Then disease activity index (DAI), histological changes and myeloperoxidase (MPO) activity were observed. The levels of occludin and STAT 3 in colon mucosa were further detected by immunohistochemistry and Western blot. One-way analysis of variance(ANOVA) was performed for comparison among groups.Results:①DAI,histological score and MPO activity in the IL-22 group were significantly higher than the control group, but lower than the model group, and the differences were statistically significant. ②The levels of occludin:the immunohistochemistry and Western blot demonstrated that the level of occludin in the IL-22 group were significantly lower than the control group, but higher than the model group, and the differences were statistically significant. ③The levels of STAT3:the immunohistochemistry and Western blot demonstrated that the level of occludin in the IL-22 group and the model group were significantly higher than the control group,but the level of occludin in the IL-22 group were significantly higher than the model group, and the differences were statistically significant.Conclusion:IL-22 can efficiently attenuates the inflammatory reaction in the mouse model of colitis by protecting the tight junction protein- occludin, and the mechanism may be related with the STAT3.