mTOR/YY1/p53通路在糖尿病肾病肾小管上皮细胞转分化中的作用及槲皮素的干预效应

Epithelial-to-mesenchymal transition (EMT) is essential for the development of renal fibrosis in diabetic nephropathy (DN). Our previous studies demonstrated that mammalian target of rapamycin (mTOR) could promote the pathogenesis of EMT in the renal tubule epithelial cells, but the underlying mechanism remained incompletely known. Yin-Yang1 (YY1) and p53 have been reported to be involved in the development of EMT in carcinogenesis. The results of our preliminary experiments showed that under diabetic conditions, activated mTOR could stimulate the expression of YY1 but reduce the amount of p53 in the renal tubule epithelial cells. Meanwhile, YY1 siRNA could remarkably up-regulate the expression of p53, and inhibit the development of EMT. Therefore, we hypothesize that under diabetic conditions, mTOR can activate YY1, and then inhibit the expression and activity of p53, leading to EMT. The current project is aimed to investigate the role of the YY1/p53 signaling pathway in mTOR-mediated EMT, using renal tubular epithelial cells, db/db mice and YY1 conditional knock-out db/db mice. Furthermore, we will investigate the inhibitory effect of quercetin on EMT via the mTOR/YY1/p53 signaling pathway. The project will not only provide theoretical and experimental evidence for flavonoids to treat DN, but also facilitate the development of more novel drugs against DN.

肾小管上皮细胞转分化（EMT）是糖尿病肾病（DN）肾纤维化形成的重要机制。我们前期研究发现，mTOR促进了DN肾小管EMT发生，但机制未明。文献证实Yin-Yang1（YY1）、p53参与了肿瘤EMT发生。预实验证实，糖尿病/高糖状态下，在肾小管上皮细胞中mTOR激活可增加YY1并降低p53表达；沉默YY1可上调p53表达，抑制EMT发生。据此，我们提出假设：在DN发生过程中，活化的mTOR可激活YY1，进而抑制p53的表达和活性，最终促进肾小管EMT发生。本项目拟以高糖培养的肾小管上皮细胞、db/db小鼠及YY1条件性基因敲除db/db小鼠为对象，研究mTOR通过YY1/p53通路，促进DN肾小管EMT发生的机制；并在此基础上，证实槲皮素通过调控mTOR/YY1/p53通路，阻抑肾小管EMT发生，为将黄酮类天然化合物用于DN防治提供理论和实验依据，并为寻找新的DN防治药物提供新思路。

肾脏纤维化是糖尿病肾病重要的病理特征，其中肾小管上皮细胞-间质转分化在肾脏纤维化的病理进程中极为重要，然而其具体分子机制尚未完全阐明。本研究通过细胞实验、动物模型以及肾脏病理等研究，采用基因转染技术，证实在体外培养的肾小管上皮细胞中，高糖可通过激活mTORC1/YY1信号通路，增加YY1的蛋白水平并促进其入核，而mTORC1的特异性抑制剂能够显著降低YY1的表达及核转录。在糖尿病肾病db/db小鼠的肾脏组织中，YY1的蛋白水平和核转位显著升高。而YY1的高表达可以上调高葡萄糖培养的HK-2细胞及小鼠肾皮质中的α-SMA表达和活性，最终导致肾纤维化的发生。过表达YY1可以通过增加α-SMA表达促进上皮-间质转化过程，进而加重db/m小鼠的肾纤维化。相反的，沉默YY1则可以逆转肾纤维化。总之，这些结果表明，上调的YY1在HG诱导的EMT相关蛋白表达失调中起关键作用，最终导致DN的肾纤维化。本项目的研究阐明了mTORC1/YY1通路参与调控肾小管上皮-间质转分化的分子机制，揭示mTORC1/YY1通路，尤其是YY1在糖尿病肾病肾纤维化病理进程中的作用，为糖尿病肾病防治药物的研发提供新的靶标，为糖尿病肾病的临床治疗策略提供新的思路。