The Study On The Role Of GPR97 In The Pathogenesis Of Ibd In Mice And Its Potential Mechanism

Inflammatory Bowel Disease(IBD)is a worldwide gastrointestinal inflammatory disease.It is thought that IBD is related to the genetic factors,environment,and immune.As the pathogenesis of IBD is not clear,it can’t be cured completely so far.In addition,there are some complications in IBD patients,which affects the patients’health seriously.Therefore,it is important for clinical treatment to study the pathogenesis of IBD.G Protein-Coupled Receptors(GPCRs)are the largest protein family in mammals so far.They are important in the human body and can regulate the occurrence of many diseases,so they can serve as a drug target against some diseases.GPR97 is an adhesion G protein-coupled receptor,there are a high level of expression in various tissues and organs as well as cells.It is reported that NF-κB signaling can be activated in GPR97-knockout(KO)mice.The activation of the NF-κB signaling pathway is associated with the expression of pro-inflammatory cytokines,especially in the pathogenesis of IBD.Our previous results showed that the expression of GPR97 gene in mouse intestinal epithelial cells was down-regulated after the induction of IBD model,which indicates that GPR97 has a protective effect on the occurrence of IBD.To investigate the relationship between GPR97 and IBD,IBD model was established by DSS,clinical evaluation was performed by detecting the body weight,blood in the stool and fecal occult blood daily.On the 7th day,the IBD mice were killed and analyzed by the histopathological analysis.More serious IBD symptoms were observed in GPR97KO mice,such as more splenomegaly,shorter and thicker colon,more mucosal inflammatory infiltration.Higher level of pro-inflammatory cytokines such as IL-1β、IL-6 and TNF-αin spleen,colon and peripheral blood was detected in GPR97KO mice compared with WT mice.These results suggest that GPR97 has a protective effect on the pathogenesis of IBD.To investigate the pathogenesis of IBD by GPR97,bone marrow chimeric mice including WT→WT group and GPR97KO→WT group were constructed and IBD models were established by DSS.The clinical evaluation was detected and the results showed that there was no significant difference of IBD symptoms between the two groups,which indicated that the aggravated IBD in GPR97KO mice is not caused by hematopoietic cells.Then,the intestinal barrier function of IBD mice was examined.The data showed that the permeability of intestinal epithelial cells in GPR97KO mice was not changed.To further explore the possible molecular mechanism,the intestinal epithelial cells from WT and GPR97KO mice were isolated and NF-κB signal pathway was analyzed.The data showed that the phosphorylation level of NF-κB P65 was upregulated in the intestinal epithelial cells from GPR97KO mice.Therefore,we suppose that the aggravated IBD symptoms in GPR97KO mice are possibly associated with the higher activation of NF-κB signal pathway in intestinal epithelial cells and a higher level of pro-inflammatory cytokine production.Then,human colon carcinoma cell line HCT116 cells were used as the target cells,the expression of GPR97 was knockdown by RNA interference(RNAi)and the expression of pro-inflammatory cytokine was analyzed.The data showed that higher level of pro-inflammatory cytokines was detected after knockdown of GPR97,which verified the previous hypothesis.In conclusion,the effect of GPR97 on IBD in mice is mainly by affecting the NF-κB pathway and pro-inflammatory cytokine production in intestinal epithelial cells.The study lays the theoretical and experimental basis for the treatment of IBD using GPR97 as the therapeutic target.