巨噬细胞中mTORC1调控Th17反应及炎症性肠病的机制研究

The mechanism of inflammatory bowel disease (IBD) remains unclear even recent studies indicate its nature of autoimmunity. Based on the pivotal role of adaptive immunity in IBD, the latest researches have focused on the relationship of IBD to Th17 response,a new type of adaptive immunity distinct from the classical Th1 and Th2 response, however, the mechanism by which the Th17 response is initiated needs further study.In a preliminary study, our team compared the profile of inflammatory cytokines and chemokines in the serum of mice who conditionally suffered TSC1 depletion (which means mTORC1 is constitutively activated)in macrophages to that of normal mice, and found that IL-1, IL-6 and IL-17 is dramatically up-regulated, which suggests strong Th17 response has been initiated.Taking into account the success of using mTORC1 specific inhibitors to treat people or mice suffering from IBD, also the pivotal role of Th17 response in the process of IBD, our project is aimed to study: 1, whether mTORC1 in macrophages can directly issue Th17 response and trigger IBD; 2,whether mTORC1 in macrophages mediate Th17 response and IBD promoted by risk factors such as DSS; 3, the mechanism by which mTORC1 in macrophages mediates Th17 response and IBD. This project hopefully will not only provide a theoretic foundation for clinical treatment of IBD using mTORC1 inhibitors, but also discover some biomarkers even in the subclinical phase of IBD.

炎症性肠病(IBD)的病因复杂，大量研究显示免疫反应在其致病机制中起着至关重要的作用。最新研究把焦点集中在Th17反应与IBD的密切关系上，然而，在获得性免疫中，抗原呈递细胞通过何种机制调节Th17反应仍不清楚。本课题组构建了巨噬细胞中可诱导型特异敲除TSC1（致mTORC1持续性激活）的小鼠模型，检测了血清中的炎症因子表达谱，发现在敲除组小鼠血清中IL-1、IL-6和IL-17急剧升高，提示发生了强烈的Th17反应。鉴于临床上或动物模型中mTORC1特异抑制剂治疗IBD的成功尝试，本项目旨在研究：1，巨噬细胞能否通过mTORC1通路直接诱导Th17反应及IBD；2，巨噬细胞中mTORC1是否介导DSS诱发的Th17反应及IBD；3，mTORC1调控Th17反应与IBD的机制。本项目的潜在意义在于：1，为mTORC1抑制剂的临床应用提供依据；2，发现亚临床期的分子标志物。

结肠上皮细胞在溃疡性结肠炎致病机制中的作用当前仍不清楚。在本课题中，我们揭示了溃疡性结肠炎发病初期结肠上皮细胞募集TH17细胞从而促进溃疡性结肠炎的新机制。首先，雷帕霉素机制性靶蛋白复合物1（mTORC1）在患溃疡性结肠炎的小鼠的结肠上皮中过度激活。其次，在结肠上皮细胞中特异性敲除TSC1（mTORC1内源性负调控蛋白）以诱导mTORC1持续性激活mTOR加剧了DSS诱导的溃疡性结肠炎。反之，特异性敲除RPTOR(mTORC1核心组分)以诱导mTORC1持续性失活可减轻溃疡性结肠炎。敲除TSC1敲除增强了结肠上皮中COX2、白介素-1、白介素-6、及白介素-23的表达及黏膜固有层中TH17细胞的浸润，而敲除RPTOR的结果正好相反。重要的是，抑制COX2逆转了TSC1敲除所诱导的这些炎症介质的升高，并随之减弱了小鼠溃疡性结肠炎的症状及病理学改变，提示mTORC1介导的溃疡性结肠炎依赖于COX2的表达。更进一步，mTORC1磷酸化了STAT3的S727位点，从而增强STAT3与COX2启动子区的结合并促进了COX2的转录。与此相符合，在溃疡性结肠炎患者的结肠病灶组织中，mTORC1活性与COX2表达均显著增强且呈强正相关。综上所述，我们的研究展现了肠上皮细胞中的mTORC1在溃疡性结肠炎致病机制中的关键作用，并建立了结肠上皮细胞-TH17细胞-溃疡性结肠炎发生之间的全新联系，提示利用rapamycin抑制mTORC1活性可以有效缓解溃疡性结肠炎，为防治溃疡性结肠炎提供了新的理论依据。