The Role Of Tyrosine Phosphatase Shp2 In Exacerbating Intestinal Inflammation By Restraining IL-10-mediated Anti-Inflammatory Property Of Macrophage

Inflammatory bowel disease(IBD)is an autoimmune disease characterized by chronic intestinal non-specific inflammation,mainly including Crohn’s Disease(CD)and ulcerative colitis(UC),with a higher and higher incidence rate in our country during the recent twenty years.The pathogenesis of IBD may associated with genetic factors,lifestyle and environmental factors,but the specific pathogenesis still remains unclear.Shp2,a non-receptor tyrosine phosphatase that is widely expressed in the body,is encoded by the PTPN11 gene.And it is highly expressed in most types of immune cells,and its importance in the immune system is receiving increasing attention.Some scientists have analyzed the polymorphism of the PTPN11 gene in UC and CD patients and concluded that PTPN11 is a susceptibility gene in UC patients,suggesting that Shp2 may be involved in the pathogeneis of IBD.However,the role of Shp2 in the regulation of macrophages in gut microenvironment and its effect on intestinal immune homeostasis in the pathogenesis of IBD have not been studied yet.To explore this issue,we collected peripheral blood mononuclear cells(PBMCs)from UC and CD patients for detection of Shp2 expression and found that the expression of Shp2 in the PBMCs of UC and CD patients was significantly higher than that of normal people.To further investigate the involvement of Shp2 in the pathophysiology and regulation of IBD,we constructed a conditional-knockout-mice with Shp2 knockout in macrophage(Shp2M KO).Dextran sulfate sodium salt(DSS)was dissolved in drinking water to establish acute colitis model.Shp2M KO mice showed more mild intestinal inflammation and a more complete intestinal barrier than WT mice.And the levels of inflammatory cytokines such as TNF-α,IL-6 and IL-1β in the rat and intestine were lower than those in WT,but there was no effect on the secretion of inflammatory factors such as IFN-y and IL-17 from T cells.In chronic colitis model,the colonic tumors were significantly less in Shp2M KO intestine than WT with less gathering of intestinal macrophages and less inflammatory cytokines.However,with PAMPs stimulation in vitro,the absence of Shp2 did not affect the level of inflammatory cytokines in macrophage.Further studies found that IL-10 can significantly inhibit the production of TNF-α and IL-6 after stimulation by LPS.This inhibitory effect was significantly enhanced after the deletion of Shp2.Furthermore,we found that Shp2 knockdown significantly enhanced IL-10-induced STAT3 phosphorylation in macrophages and promoted the expression of SOCS3,a target of IL-10/STAT3 signaling.In order to verify that Shp2 is involved in the regulation of IL-10 inhibition of colitis at an in vivo level,intraperitoneal injection of anti-IL-10 was performed to neutralize IL-10.The results showed that WT and KO injected with anti-IL-10 neutralizing antibody no longer have significant differences in the weight loss,colon length,intestinal tissue damage and intestinal inflammatory factor levels.This study revealed that tyrosine phosphatase Shp2 plays an important role in the positive regulation of inflammatory bowel disease and proves the important role of IL-10 in this regulatory process.It helps to provide a new perspective to further elucidate the pathogenesis of inflammatory bowel disease and to provide new ideas and theoretical basis for the treatment of inflammatory bowel disease.