mTOR调控急性缺血性肾损伤修复期M1/M2型巨噬细胞生物学活性的机制研究

Acute renal ischemia-reperfusion injury (IRI) is common and associated with increased morbidity and mortality among hospitalized patients with increased risks of chronic kidney disease and even end stage of renal disease in the future. The exact reparative mechnism of renal IRI remain unknown. Macrophages, consisting of M1 and M2 subpopulations, play diverse roles in inflammation and tissue repair, which determine the outcome of renal IRI. Our previous experiment and published data suggested that mTOR signaling mediated kidney inflammatory injury and subsequent fibrosis. Our later investigation showed significant activation of mTOR in both M1 and M2 macrophage. Therefore, we propose the hypothesis that mTOR plays a key role in regulating different functions of renal M1 and M2 macrophage. Inhibition of mTOR in M1 but activation of mTOR in M2 during the reparative phase of renal IRI may help to facilitate kidney recovery. In this experiment, we will modify the activity of Rheb/mTOR in primary macrophages by gene transfection in vitro. Native macrophages of CD11b-DTR mice will be specifically ablated during IRI reparative phase, followed by adoptive transfer of gene-modulated macrophages through mice tail veins. Our study, for the first time, investigates the role of mTOR signaling in regulating bioactivities of M1/M2 macrophages during renal IRI reparative stage, which will help to improve our understandings on the pathogenesis of renal IRI and raise the novel therapeutic targets of acute kidney injury.

肾脏急性缺血再灌注损伤（IRI）是临床常见危重病，预后差，其转归的机制不清。M1/M2型巨噬细胞在肾脏IRI过程中分别发挥促炎症/促修复作用。我们前期实验证实mTOR是调控肾脏炎症损伤－修复的关键通路，且发现mTOR活性在分化的M1及M2型巨噬细胞中均显著上调。为此，我们推测：mTOR同时介导肾脏M1/M2型巨噬细胞的不同生物学功能，在肾脏IRI修复期选择性抑制M1型而上调M2型巨噬细胞的mTOR活性将促进肾脏修复。我们将在肾脏IRI修复期敲除CD11b-DTR转基因小鼠的固有巨噬细胞，通过基因转染调节M1/M2型巨噬细胞Rheb/mTOR活性，将转染后细胞过继转输至巨噬细胞缺失的受体小鼠，评估小鼠肾脏损伤的转归。本课题将首次从基因、蛋白及细胞功能层面研究mTOR对肾脏IRI修复期M1/M2型巨噬细胞活性的调控作用，探讨介导肾脏巨噬细胞促修复作用的分子机制，旨在为临床干预治疗提供理论依据。

急性肾损伤（AKI）是临床常见危重病，可进行性发展为慢性肾脏病（CKD）甚至终末期肾病（ESRD），目前机制仍不清楚，临床缺乏有效的干预手段。本课题主要探讨mTOR信号通路在AKI炎症损伤过程中调控免疫效应细胞活性的机制。本课题通过构建缺血再灌注损伤及脓毒血症所致AKI小鼠模型，研究mTOR信号通路在AKI过程中调控肾脏巨噬细胞、调节型T细胞（Treg）、肾间质成纤维细胞及肾小管上皮细胞等炎症效应细胞活性的分子机制。我们的研究发现mTOR信号通路在脓毒血症AKI过程中调控肾脏巨噬细胞炎症活性，抑制mTOR信号通路有助于缓解脓毒血症所致AKI的肾功能损害及相关纤维化的发展（American Journal of Nephrology. 2015; 42(4): 305-17.）。更为值得注意的是，本课题同时发现在AKI发生发展过程中，mTOR通路对不同炎症细胞发挥不同调节作用，mTOR信号通路活化能显著抑制肾脏调节型T细胞（Treg）的活性，而抑制Treg细胞的mTOR信号通路明显增加其调控AKI炎症损伤的能力，经过体外条件性干预的Treg细胞移植在缺血性AKI中具有明显的肾脏保护作用（Journal of Immunology. 2016; 197(10): 3917-3926.）。通过本课题研究，我们揭示了mTOR通路在肾脏不同炎症效应细胞中（巨噬细胞、Treg细胞、成纤维细胞及肾小管上皮细胞等）具有截然不同的调控作用。本课题阐述了AKI发生发展过程中，mTOR通路发挥复杂的、互为影响的生物学效应，所发表的研究成果对以mTOR为靶点治疗AKI向CKD发展提供了理论依据，同时也为细胞移植治疗在AKI的开展提供了一系列实验基础。