microRNA-dependent regulation of intestinal T-cells²

项目摘要 我们的肠道包括超过50%的我们的身体免疫细胞和紧密保持一个恒定的状态， 对外来刺激如食物颗粒和细菌的体内平衡。这种免疫“耐受性”在 慢性肠道炎症，如炎症性肠病（IBD）期间所见。不良CD 4 + T辅助因子 反应使IBD中观察到的慢性病理持续存在，从而了解分子机制 控制其功能的基因是寻找新的治疗方法的核心。一种生理适应性 对炎症的反应是代谢物的供应和需求的显著变化， 氧可用性（现在称为炎性缺氧）和转录因子缺氧的激活- 诱导因子（HIF）。虽然缺氧对T细胞基因功能有多种影响，但对后 转录调控研究不足。为了研究缺氧引起的组织保护信号， 进行了CD 4 + T细胞特异性miRNA的筛选，并鉴定了miR-29 a的选择性诱导。研究 通过遗传模型确定了Hif-2α在miR-29 a诱导中的作用，随后的实验证实了 在缺氧期间抑制miR-29 a靶基因Tbet和IFNγ（典型的TH 1标记物）。有T- Hif-2α的细胞内在缺陷显示CD 4 + T细胞中Tbet水平升高，并加重炎症 实验性结肠炎基于这些初步的研究，我们假设Hif-2α诱导miR-16表达， 29 a抑制TH 1 CD 4+细胞活化。在本提案中，我们将用三个综合的假设来解决这一问题。 调查路线。首先，我们将研究Hif-2α如何转录诱导miR-29 a，以及其功能。 Hif-2α在CD 4 + T细胞分化中的作用。第二，我们将评估miR-29 a在细胞凋亡中的作用。 调节T细胞介导的结肠炎。最后，在概念验证研究中，我们将靶向miR-29 a稳定化， 在实验性结肠炎期间体内。这些研究共同的目的是剖析Hif-2α-miR-29 a-Tbet轴在肿瘤细胞中的作用。 调节CD 4 + T细胞介导的肠道炎症。 !

Project Summary Our intestines comprise over 50% of our bodies immune cells and tightly maintains a constant state of homeostasis against foreign stimulus like food particles and bacteria. This immune “tolerance” is broken during chronic intestinal inflammation as seen during inflammatory bowel diseases (IBD). Adverse CD4+ THelper responses perpetuate the chronic pathology observed in IBD, thus understanding the molecular mechanisms that control their function is central to endeavors of finding novel therapeutic treatments. A physiologic adaptive response to inflammation is a marked shift in the supply and demand of metabolites that results in limited oxygen availability (now termed inflammatory hypoxia) and activation of the transcription factors hypoxia- inducible-factors (HIFs). While there are multiple affects of hypoxia on T cell gene function, the effects on post- transcriptional regulation are underexplored. To investigate hypoxia-elicited tissue protective signaling we performed a screen of CD4+ T cell-specific miRNAs and identified a selective induction of miR-29a. Studies with genetic models identified a role of Hif-2α in miR-29a induction and subsequent experiments demonstrated repression of the miR-29a target-genes Tbet and IFNγ (canonical TH1 markers) during hypoxia. Mice with a T- cell-intrinsic deficiency in Hif-2α displayed elevated Tbet levels in CD4+ T cells and exacerbated inflammation during experimental colitis. Based on these preliminary studies, we hypothesize that Hif-2α induction of miR- 29a suppresses TH1 CD4+ cell activation. In this proposal we will address this hypothesis with three integrated lines of investigation. Firstly, we will examine how Hif-2α transcriptionally induces miR-29a and the functional requirements for Hif-2α in CD4+ THelper differentiation. Second, we will assess the role of miR-29a in the regulation of T cell mediated colitis. Lastly, in proof of concept studies we will target miR-29a stabilization in vivo during experimental colitis. Collectively these studies aim to dissect the Hif-2α-miR-29a-Tbet axis in the regulation of CD4+ T cell-mediated intestinal inflammation.! !