microRNA-10a Regulation of Inflammatory Bowel Diseases

描述（由申请人提供）：MicroRNAs （miRNA）是一类小的非编码rna，通过结合靶基因的3'-UTR作为翻译过程的内源性抑制剂，正在成为免疫系统中重要的基因表达调节剂。越来越多的证据表明，mirna作为调节炎症反应强度的有效系统，与各种人类疾病的发病机制有关。我们最近已经确定，在小鼠和人类中均保守的miR-10a在肠树突状细胞（DC）中高度表达，并通过MyD88途径通过TLR-TLR配体的相互作用受到微生物群的负调控。我们确定IL-12/IL-23p40是miR-10a的靶基因，miR-10a直接结合IL-12/IL-23p40基因的3'-UTR， miR-10a过表达抑制DC IL-12/IL-23p40的表达，抑制IL-12和IL-23的产生。IL-12和IL-23是炎症性肠病发病过程中两种重要细胞因子IL-12和IL-23共有的基因。与正常小鼠相比，结肠炎小鼠炎症性肠病变中miR-10a的表达降低，这与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。在本提案中，我们的初步数据表明，与正常个体的表达相比，克罗恩病（CD）和溃疡性结肠炎（UC）患者的肠道活检中miR-10a表达降低，这一发现表明miR-10a失调与人类IBD相关。IBD患者的NFkB激活升高，主要定位于肠固有层树突状细胞和上皮细胞。在动物模型中，过表达miR-10a可抑制DC中NFkB的表达激活和TNFa的产生，并抑制结肠炎的发展。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表达如何调节粘膜DC在微生物群响应中的激活和功能的机制。最后，我们将验证我们的假设，即DC表达miR-10a将粘膜T细胞反应转变为低水平的Th1/Th17和高水平的Treg，从而维持肠道免疫稳态和预防炎症性肠病。

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.