microRNA-10a Regulation of Inflammatory Bowel Diseases

描述(申请人提供)：microRNAs(MiRNA)是一类小的非编码RNA，通过与靶基因的3‘-UTR结合，作为翻译过程的内源性抑制因子，在免疫系统中成为基因表达的重要调节因子。越来越多的证据表明，miRNAs作为一种有效的系统来调节炎症反应的大小，并与各种人类疾病的发病机制有关。我们最近发现，miR-10a在小鼠和人的SPP中都有保守的表达，在肠道树突状细胞(DC)中高度表达，并通过MyD88途径与TLR-TLR配体相互作用而受到微生物群的负调控。我们发现IL-12/IL-23p40是炎症性肠病发病机制中的两个重要细胞因子所共有的IL-12/IL-23p40，是miR-10a的靶基因，因为miR-10a直接与IL-12/IL-23p40基因的3‘-UTR结合，而miR-10a的过表达抑制了DC IL-12/IL-23p40的表达和IL-12和IL-23的产生。MIR-10a在结肠炎小鼠炎性病变中的表达降低，与正常小鼠相比，与IL-12和IL-23的高水平相关。最近的一份报告进一步证明，miR-10a可减弱调节性T细胞(Treg)向效应T细胞的转化，并抑制Th17的分化。在本研究中，我们的初步数据显示，与正常人相比，克罗恩病(CD)和溃疡性结肠炎(UC)患者的肠道活检组织中miR-10a的表达减少，这一发现表明miR-10a的异常调节与人类IBD的相关性。IBD患者NFkB活性升高，主要定位于肠道至固有层、树突状细胞和上皮细胞。在动物模型中，miR-10a的过表达抑制了NFkB的DC表达和TNFa的产生，并抑制了结肠炎的发展。在本项目中，我们将研究miR-10a在粘膜DC中的调控靶点，以及miR-10a表达如何调节黏膜DC的激活和功能，以响应微生物区系。最后，我们将验证我们的假设，即DC表达miR-10a会改变粘膜T细胞对低水平Th1/Th17和高水平Treg的反应，从而保护肠道免疫平衡，预防炎症性肠病。

DESCRIPTION (provided by applicant): MicroRNAs (miRNA), a class of small non-coding RNAs, are emerging as important regulators of gene expression in the immune system by functioning as endogenous inhibitors of translational processes by binding to the 3'-UTR of target genes. There is increasing evidence that miRNAs function as an effective system to regulate the magnitude of inflammatory responses and have been associated with the pathogenesis of various human diseases. We have established recently that miR-10a, conserved in both mouse and human spp, was highly expressed in intestine dendritic cells (DC), and negatively regulated by microbiota through the interaction of TLR-TLR ligands via the MyD88 pathway. We identified IL-12/IL-23p40, which is shared by IL-12 and IL-23, two important cytokines in the pathogenesis of inflammatory bowel disease, as a target gene of miR-10a, in that miR-10a directly bound to the 3'-UTR of the IL-12/IL-23p40 gene, and overexpression of miR-10a inhibited DC IL-12/IL-23p40 expression and production of IL-12 and IL-23. miR-10a expression was decreased in the inflamed intestinal lesions in mice with colitis, which was correlated with high levels of IL- 12 and IL-23, compared to that in normal mice. A recent report further demonstrated that miR-10a attenuated regulatory T cell (Treg) conversion into effector T cells and inhibited Th17 differentiation. In the present proposal, our preliminary data demonstrate that miR-10a expression is decreased in intestinal biopsies of patients with Crohn's disease (CD) and ulcerative colitis (UC), when compared to its expression in normal individuals, a finding that is indicative of the relevance of dysregulated miR-10a to human IBD. NFkB activation is elevated in IBD patients and localizes primarily in the intestines to lamina propria dendritic and epithelial cells. Overexpression of miR-10a suppresses DC expression of NFkB activation and TNFa production and inhibits colitis development in an animal model. In this project, we will investigate the regulatory targets of miR-10a in mucosal DC, and the mechanisms of how miR-10a expression regulates mucosal DC activation and function in response to microbiota. Lastly, we will test our hypothesis that DC expression of miR-10a shifts mucosal T cell responses to low levesl of Th1/Th17 and high levels of Treg, which leads to preservation of intestinal immune homeostasis and prevention of inflammatory bowel disease.