| Background: Intestinal mucosal barrier plays an important role in the development of ulcerative colitis(UC).When the intestinal mucosal barrier is destroyed,intestinal permeability increases,which may lead to intestinal inflammation.Tight junction(TJ)is a key component of the intestinal mucosal epithelial barrier and plays a key role in maintaining intestinal barrier function.Occludin protein is the main protein that constitutes tight junctions,plays an important role in the tight junction assembly and maintenance of intestinal barrier function,and the number of changes suggests to some extent the changes of intestinal mucosal barrier function.IL-22 is one of the IL-10 cytokine families,and its biological role depends on the activation of its downstream STAT3 signaling pathway by binding to its receptor complex.However,the role and mechanism of IL-22 on intestinal barrier tight junction proteins remains unclear and further research is needed.The aim of this study was to compare the differences in chronic UC models induced by different concentrations of DSS,select the optimal DSS concentration of UC in mice,and then establish a modelof chronic ulcerative colitis in mice by DSS(dextran sulfate sodium).Western blot and real-time PCR were used to investigate the role of IL-22 in DSS-induced chronic ulcerative colitis and its tight junction with occludin protein in intestinal mucosa.The relationship between the STAT3 protein and the STAT3 protein provides a new therapeutic target and theoretical basis for the treatment of UC.Objective: By comparing the differences in chronic UC models induced by different concentrations of DSS,the optimal DSS concentration of induced UC in mice was selected.The model of DSS chronic ulcerative colitis was induced by C57BL/6 mice to study the effect of IL-22 on DSS-induced chronic ulcerative colitis in a mouse model and its effect on tight junctions of occludin and STAT3 in intestinal mucosa.Method: Thirty female SPF C57BL/6 mice aged 6-8 weeks were randomly divided into normal control group,model control group and IL-22 intervention group,with 10 mice in each group.In addition to the normal control group,the other two groups of mice were free to drink 2.5% DSS for 3 cycles to prepare a chronic UC model for 30 days.IL-22 intervention group mice were intraperitoneally injected with IL-22 on days 6-10,16-20 and 26-30,and normal control and model control mice were intraperitoneally injected with an equal volume of 0.9% sodium chloride solution.According to the normal control group,2.0% DSS group,2.5% DSS group and 3.0% DSS group,the general conditions,disease activity index(DAI)score,mouse mortality and histopathologic score were evaluated for different concentrations of DSS.Differences in the rat chronic UC model;according to the normal control group,model control group and IL-22 intervention group,the general condition,disease activity index(DAI)score,colonic length,histopathologic score,colon tissueTNF-? The expression of mRNA and IL-6 mRNA and the tight junction of intestinal mucosa were observed by transmission electron microscopy.The therapeutic effect of IL-22 on ulcerative colitis in mice and its effect on tight junction were studied.The expression of tight junction protein occludin and the expression of STAT3 protein in the colonic mucosa of mice were detected by Western blotting and Real-time PCR.Results:(1)Compared with the normal control group,the body weight of the 2.0% DSS group,2.5% DSS group and3.0% DSS group decreased in different degrees and the DAI score increased,the difference was statistically difference(P<0.05).Compared to the normal control group,histopathologic score of the 2.0% DSS group,2.5% DSS group and 3.0%DSS group increased(P<0.01),and the difference was statistically different between the 2.0% DSS group and the 2.5% DSS group.Significance(P<0.05),there was no significant difference between the 2.5% DSS group and the 3.0%DSS group(P>0.05).(2)Compared with the normal control group,the weight of the model control group and the IL-22 intervention group decreased significantly,the DAI score and histopathological score were significantly increased(P<0.05),and the colon length was significantly shortened(P<0.05).The expression of TNF-? and IL-6 mRNA in colon tissue was significantly increased(P<0.05).Compared with the model control group,after administration of IL-22 intraperitoneal injection,the mice gained weight,DAI score and histopathological score were decreased to different degrees(P<0.05),and colon length shortening was significantly improved(P<0.05).The expression of TNF-? and IL-1 mRNA was significantly lower than that of the model control group(P<0.05).Transmission electron microscopy showed that the tight junctions between the colonic epithelium of the normal control group were consistent with dense bands,and the junction gap was narrow.The tight junctionbetween the colonic epithelium of the model control group was loose,the junction gap was enlarged,and the IL-22 intervention group was tightly constricted and narrowed.(3)Compared with the normal control group,the expression of occludin in the IL-22 intervention group was decreased by Western blot and Real-time PCR(P<0.05),but higher than the model control group.(4)Compared with the normal control group,the expression of STAT3 in IL-22 intervention group and model control group was significantly increased by Western blot and Real-time PCR(P<0.05),but IL-22 intervention group was higher than model control group.Conclusion: 1.When the DSS solution is administered periodically,the mouse chronic UC model can be successfully replicated.The mortality of the2.5% DSS group is lower and the model stability is better.2.IL-22 can effectively alleviate the inflammatory response induced by DSS in chronic ulcerative colitis in mice.The mechanism may be to increase the expression of tight junction protein occludin in intestinal mucosal barrier by regulating STAT3 pathway. |
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