Effect And Mechanism Of Schistosoma Japonicum Infection On DSS-induced Colitis

Background and aimInflammatory bowel disease(IBD)presenting by chronic and complicated inflammation lesions of intestinal tract includes ulcerative colitis(UC)and Crohn's disease(CD).According to epidemiology investigations,IBD mainly occured in white people living in North America and Europe.Among them,the morbidity of UC and CD in Europe were respectively 505/100,000 and 322/100,000 accompanying with the incidence rate of 24.3/100,000 for UC and 12.7/100,000 for CD,while the incidence rate of UC in Asian was only 6.3/100,000 at the same period.In recent years,the incidence and morbidity of IBD present ascendant trend all around the world and almost 5 million patients are suffering from IBD which is one of the regular digestive diseases in China now.Since IBD could be easily recurrent without effective means of radical treatment,and patients are more likely to develop IBD in the second and third decade of life or at their senectitude,the impact of IBD on patients' social communication,work and quality of life is high and it brings patients with serious physical,mental and economic burden.No mention the complications such as intestinal perforation,intestinal obstruction and even colorectal cancer.Therefore,exploring the occurrence and development mechanism and finding out the effective therapeutic targets of IBD will be beneficial to the comprehension and treatment of IBD as well as improving the quality of life of IBD patients.In the 1990s,"IBD hygiene hypothesis" was first proposed,which stated that children in extremely hygienic environments that might impede the proper maturation of their immune system were predisposed to IBD later in life.According to the animal and clinical investigations,helminth-infection was suggested to decrease the susceptibility or prevent the development of IBD.After exposure to Trichuris suis ova,IBD patients got significantly remission.Schistosoma(S.)which is a kind of common parasitic worm in China plays an important role in allergic and autoimmune diseases such as type 1 diabetes mellitus,rheumatoid arthritis and IBD.It was reported that mice infected with S.mansoni eggs or larvae could prevent trichlorophthalenesulfonic acid(TNBS)/sodium dextran sulfate(DSS)induced colitis while the mechanism about how helminths regulate IBD is still elusive.Here we aimed to explore the effects and mechanism of S.japonicum infection on DSS-induced colitis model.Methods1.Mice were randomly divided into 4 groups:Con group(control),DSS group(3%DSS),CER+DSS group(infection with S.japonicum + 3%DSS);CER group(infection with S.japonicum).Mice from CER+DSS group and CER group were administrated with 20±2 cercariae of S.japonicum percutaneously.And mice from CER+DSS group and DSS group colitis were induced by 3%DSS 4 weeks post infection.Weight change,colon length and disease activity index(DAI)were observed and evaluated.And histological score(HS)was assessed after H&E staining.Inflammatory cells in colon tissues were tested by immunofluorescence.2.Inflammatory cytokines were examined by CBA,flow cytometry and real time-PCR.Expressions of NF-?B and endoplasmic reticulum stress(ERS)relative proteins were detected by western blot and real time-PCR.3.TUNEL and cleaved-caspase3(C-C3)were examined to exam apoptosis level in colon tissues.In addition,Bcl-2 and Bax were investigated by western blot.Results1.Liver from CER+DSS and CER mice showed scatteredly yellow egg tuberous.Compared to CER+DSS group,mice from DSS group presented less weight loss(p<0.0001),longer colon(p=0.004),less inflammatory cells infiltration,and less disease activity index(p=0.005)as well as histopathological score(p=0.004).No difference exited between mice from Con group and CER group.2.The expressions of IL-6,IL-10 and IFNy in serum of CER+DSS mice were significantly lower than those of DSS mice(p<0.001)tested by CBA and flow cytometry.There was no significant difference in the expression of inflammatory cytokines between mice from Con group and CER group.Real-time PCR showed that the expression of IL-6 in colon tissue of DSS mice was significantly higher than that of CER+DSS mice(p<0.001),and the expressions of IL-10 and IFNy were also higher than those of CER+DSS mice(p<0.01 and p<0.05,respectively).There was no significant difference in the expression of inflammatory cytokines and transcription factors other than IL-10(p<0.05)in colon tissues between Con mice and CER mice.The expression of P-P65 and P-I?B? protein in colon tissues of CER+DSS group was significantly decreased compared with DSS group.The expression levels of IRE1?,IRE1?,GRP78 and CHOP protein in colon tissues of CER+DSS group were significantly lower than those of DSS group,especially IRE1? and IRE1?(p<0.01 and p<0.05,respectively).No significant difference showed in mice between CER group and Con group.3.According to the immunofluorescence and TUNEL examination,much more CC3 positive cells and TUNEL positive cells showed in colon tissues of DSS mice than those of CER+DSS mice,especially for CC3.The expression levels of Bcl-2 protein in colon tissues of CER+DSS mice,DSS mice and CER mice were significantly lower than that of Con mice,and CER+DSS mice got significantly higher Bcl-2 expression than that of DSS group(p<0.05).The expression levels of Bax protein in colon tissues of CER+DSS mice,DSS mice and CER mice were significantly higher than that of Con mice,while CER+DSS mice presented less expression of Bax than that of DSS mice without statistically difference.ConclusionThese result indicated that exposure to S.japonicum attenuated inflammatory response in DSS-induced colitis model.Apart from Thl/Th2/Thl7 pathway,NF-?B pathway and ER stress showed enormous potential in mitigating inflammation and decreasing enterocytes apoptosis in DSS-induced colitis.Thus,NF-?B pathway as well as ERS led a new way to understand the relationship between helminth infection and IBD,especially ERS,which may offer new therapeutic methods for IBD.