The Role Of INKT Cells, CCL25/CCR9 Interaction And Hyperhomocysteinemia In The Pathogenesis Of Inflammatory Bowel Disease

Part 1 The Role of iNKT Cells and CCL25/CCR9 Interaction in the Pathogenesis of Inflammatory Bowel DiseaseBackground Natural killer T (NKT) cells share phenotypic and functional properties with both conventional natural killer cells and T cells. These cells might have an important role in the pathogenesis of ulcerative colitis (UC). The interaction of chemokine ligand 25 (CCL25) with chemokine receptor 9 (CCR9) is involved in gut-specific migration of leukocytes and induces regulatory T cells (Tregs) to migrate to the intestine in chronic ileitis.Methodology In UC patients, NKT receptor CD161, CCL25, and CCR9 expression levels were evaluated by qRT-PCR. A murine model of oxazolone-induced colitis was induced in BALB/c mice. The mRNA levels of NK1.1, CCL25 and CCR9, and pro-inflammatory cytokines in mice were evaluated. The CCR9 expression on Type I or invariant NKT (iNKT) cells, and the iNKT cells chemotaxis are observed according to flow cytometry.Results NKT receptor CD161, CCL25 and CCR9 expression levels were significantly increased in UC patients. And, the mRNA expression levels of NK1.1, CCL25 and CCR9 were increased in oxazolone-induced colitis in mice. The production of pro-inflammatory cytokines was significantly increased, especially interleukin 4 (IL-4), IL-10 and IL-13. We observed significantly increased CCR9 expression on iNKT cells. Furthermore, we found an increased iNKT population and enhanced chemotaxis during oxazolone-induced colitis.Conclusions Our study suggests that CCL25/CCR9 interactions may promote the induction and function of iNKT cells during oxazolone-induced colitis. These findings may have important implications for UC treatment and suggest a role for CCR9 inhibitors.Part 2 The Role of Hyperhomocysteinemia in the Pathogenesis of Inflammatory Bowel DiseaseBackground Hyperhomocysteinemia (HHcy) was a common phenomenon observed in patients with inflammatory bowel disease (IBD). Homosysteine is a pro-inflammatory molecule and has been identified as a risk factor for cardiovascular and cerebral diseases. The mechanism of HHcy aggravated the chronic inflammation of colon in IBD has never been explored. The aim of this study was to investigate the role and mechanism of HHcy on dextran sulfate sodium (DSS) induced-colitis.Methods Wistar rats were randomly divided into eight groups:(1) Control; (2) HHcy; (3) p38 inhibitor; (4) DSS; (5) HHcy+DSS; (6) HHcy+DSS+p38 inhibitor; (7) HHcy+DSS (21 days); and (8) HHcy+DSS+folate (21 days). Colitis was induced by 5% DSS. HHcy was induced by the normal rodent diet containing 1.7% methionine. The mRNA expression of interleukin 17 (IL-17) was detected by qRT-PCR. The protein expressions of IL-17, retinoid-related orphan nuclear receptor-yt (RORyt), p38 MAPK, phosphorylated-p38 MAPK, cytosolic phospolipaseA2 (cPLA2), phosphorylated-cPLA2 and cyclooxygenase 2 (COX2) were detected by immunoblot analysis.Results The rats of HHcy+DSS group had scientifically higher myeloperoxidase (MPO) activity, DAI score, and histological score. HHcy significantly increased the plasmatic concentration, the colonic mRNA and protein levels of IL-17. HHcy also activated p38 MAPK and cPLA2, increased the protein levels of COX2 and RORyt, as well as the plasmatic level of prostaglandin E2 (PGE2). Folate supplementation down-regulated homocysteine-induced IL-17 and RORyt expressions.Conclusions HHcy aggravated DSS-induced colitis by stimulating IL-17 expression via p38/cPLA2/COX2/PGE2 signaling pathway. The folate supplementation may represent the novel approach to treat the chronic intestinal inflammation of IBD exacerbated bv HHcv.