Analysis Of Differentially Expressed Proteins Of Ulcerative Colitis In Mice Treated With Imiquimod By ITRAQ

Objective: To study the efficacy of imiquimod(IMQ)on dextran sulfate sodium(DSS)-induced acute ulcerative colitis(UC)in mice and analyze the differentially expressed proteins of the intestinal tissue after treatment with imiquimod by isobaric tags for relative and absolute quantitation(iTRAQ).To explore the mechanism in the treatment of UC with imiquimod and provide a new reference for the treatment of UC.Methods: Sixty C57BL/6 healthy mice were randomly divided into control group,model group(DSS group),imiquimod group(IMQ group),20 mice in each group.The mice in DSS group and IMQ group drank 3% DSS solution for 7 days consecutively to induce intestinal inflammation and establish acute UC model.The mice in the control group and DSS group were given 0.4ml sterile PBS solution by intragastric administration,while the mice in IMQ group were received 0.4ml IMQ(30mg/kg)by intragastric administration at the same time from the first day of experiment.Then all the mice were sacrificed on the 8th day of the experiment.The colon was dissected out and its length was measured and recorded.Part of them were stained with hematoxylin-eosin(HE),while the rest were put into liquid nitrogen quickly and then stored at-80℃ for proteomic analysis.The weight,fecal traits and stool blood of mice in each group were recorded daily,and disease activity index(DAI)and colon histological damage score were evaluated during the experiment.Results: The mice in DSS group showed obvious symptoms of weight loss,diarrhea and mucus purulent stool,which suggested the model of UC were established successfully.Whereas imiquimod could ameliorate the symptoms of acute colitis in mice,and reduce the degree of colon shortening,weight loss,DAI and histological damage score.A total of 4170 proteins were identified by iTRAQ technology.There were 317 differentially expressed proteins in DSS group compared with control group,including 156 up-regulated proteins and 161 down-regulated proteins.In IMQ group compared with control group,253 differentially expressed proteins were detected,of which 114 were up-regulated proteins and 139 were down-regulated proteins.209 differentially expressed proteins were screen,including 81 up-regulated proteins and128 down-regulated in IMQ group compared with DSS group.Bioinformatics analysis showed that the expression of keratins were down-regulated in UC,while they were up-regulated after treatment with imiquimod.In addition,the differentially expressed proteins related to complement and coagulation cascades in DSS groupwere up-regulated.After administration of imiquimod,the related differentially expressed proteins were down-regulated.Conclusions: Imiquimod can significantly alleviate the symptoms of DSS-induced acute UC in mice,and has a therapeutic effect on UC.Its mechanism may be through increasing the expression of keratins and inhibiting the reaction of complement and coagulation cascades,which lays a theoretical foundation for further study of the mechanism of imiquimod in the treatment of UC.