miR-125a对炎症性肠病肠黏膜组织内CD4+T细胞和上皮屏障功能的调节作用研究

Inflammatory bowel diseases (IBD), including Crohn’s disease and ulcerative colitis, are idiopathic, chronic inflammatory disorders of the gastrointestinal tract. Abnormal immune responses in intestinal mucosa toward commensal microbiota together with intestinal mucosal barrier defects, persistent mucosal infection, genetic and environmental factors may be associated with the etiology and pathogenesis of human IBD. MicroRNAs (miR) are small non-coding RNAs that play a role in inducing RNA silencing and post-transcriptional regulation of gene expression by binding to the 3’-untranslated region of target mRNAs, leading to mRNA degradation or translational inhibition. miR-125a has been found to be highly expressed in T cells, and regulate the functions of Treg cells through the IL-6-STAT3 signaling pathway. Our precious study has shown that miR-125a expression is decreased in intestinal mucosal CD4+ T cells and epithelial cells from IBD patients. Mice lacking miR-125a developed more severe colitis induced by 2,4,6-trinitro-benzene sulfonic acid (TNBS), and importantly, CD4+ T cells isolated from inflamed colon of miR-125-/- mice produced higher levels of IFN-g and IL-17 compared with wild-type controls. Therefore, we hypothesize that miR-125a may play a critical role in intestinal mucosal inflammation. In this study, we will study the expression of miR-125a in peripheral blood mononuclear cells and inflamed mucosa from IBD patients, investigate the potential role of miR-125a in regulating T cell immune responses in intestinal mucosa and epithelial barrier function, and try to determine the target genes (i.e., Ets-1) of miR-125a. Experimental murine models of chronic intestinal inflammation will be established in both miR-125a deficient mice and Ets-1 transgenic mice to determine the potential roles of miR-125a and its target gene Ets-1 in the pathogenesis of IBD. Our study will provide new theoretical basis for IBD immunological therapy.

炎症性肠病(IBD)可能与肠黏膜屏障损伤、免疫调节异常、遗传和环境等因素有关。microRNA(miR)是一类内源性非编码RNA，通过与靶基因结合调控其功能。研究表明miR-125a高表达于T细胞，通过IL-6-STAT3信号，密切调节Treg细胞效应。我们前期研究发现miR-125a在IBD患者CD4+ T细胞和肠上皮细胞表达降低；TNBS诱导miR-125a-/-小鼠发生严重结肠炎，肠黏膜内CD4+ T细胞表达IFN-g和IL-17A增多。据此我们提出miR-125a可能参与肠道炎症发生。本课题主要研究miR-125a在IBD患者肠黏膜表达，分析对肠黏膜内CD4+ T细胞激活、增殖分化和肠上皮屏障功能的调节作用。验证miR-125a靶基因Ets-1，利用miR-125a-/-和Ets-1转基因小鼠建立结肠炎模型，阐明它们在肠黏膜炎症发生中的免疫调节作用，为IBD临床治疗寻求新的靶点。

炎症性肠病（inflammatory bowel disease, IBD）可能与肠黏膜屏障损伤、免疫调节异常、遗传和环境等因素有关。microRNA（miR）是一类内源性非编码RNA，通过与靶基因结合调控其功能。重点研究在炎症性肠病（IBD）肠黏膜炎症发生时，miR-125a对肠黏膜组织内CD4+ T细胞增殖分化的免疫调节作用，以及对肠上皮屏障功能的调节效应。我们研究发现miR-125a主要表达在肠黏膜组织内CD4+ T细胞，通过IL-6-STAT3信号，密切调节Treg细胞效应。miR-125a在IBD患者CD4+ T细胞和肠上皮细胞表达降低；一些促炎症细胞因子（如IL-6、TNF-a）能够显著降低miR-125a表达。体外细胞培养发现miR-125a慢病毒转染的IBD患者CD4+ T细胞表达IL-17A、RORC、IFN-g、TNF-a mRNA显著降低，有效抑制IBD患者CD4+ T细胞向Th1和Th17细胞分化。TNBS诱导miR-125a-/-小鼠发生严重结肠炎，肠黏膜内CD4+ T细胞表达IFN-g和IL-17A增多。Luciferase分析证实了EST-1是miR-125a的靶基因。构建ETS-1转基因小鼠，发现DSS诱导ETS-1转基因小鼠发生严重的结肠炎。本课题阐明了miR-125a-ETS-1信号通路在IBD肠黏膜炎症发生过程中起着重要免疫调节作用，通过靶向调控该基因表达以及下游靶基因ETS-1的功能有可能用于临床上治疗IBD的发生发展。