miR-138通过Sirt1/Tristetraprolin参与糖尿病肾病炎症导致足细胞损伤的机制

Podocyte injury caused by inflammation is the most important factor leading to the occurrence and development of diabetic nephropathy (DN), although the mechanism is still not clear.. Our previous study showed that the expressions of miR-138 and inflammatory cytokines were increased and the expressions of Sirt1 and anti-inflammatory protein Tristetraprolin (TTP) were decreased in blood, urine and renal tissues of DN patients. The similar results were found in mouse podocytes treated with high glucose. Additionally, in mouse podocytes, inhibition of miR-138 expression by the specific inhibitor could cause the expressions of Sirt1 and TTP increased, while the expression of TTP could be decreased by the inhibition of Sirt1, companied with the inflammatory factors expressions up-regulated.. Accordingly, we assume that miR-138 participate in the podocyte injury caused by inflammation in diabetic nephropathy through Sirt1/Tristetraprolin .. This project intends to test the blood, urine and renal tissues of DN patients, podocytes and db/db mice through cellular and molecular biology techniques to determine: 1) the relationship between miR-138 expressions and proteinuria or inflammation of DN; 2) the role of miR-138 in the podocyte injury caused by inflammation of DN; 3) the molecular mechanisms of miR-138 participate in the podocyte injury caused by inflammation of DN through Sirt1/Tristetraprolin. And these contents will provide a new perspective and experimental basis for discovering the mechanism and new therapy target of DN.

炎症造成的足细胞损伤对糖尿病肾病(DN)发生发展至关重要，但机制尚未阐明。我们前期实验发现，DN患者肾组织、血/尿标本及高糖培养小鼠足细胞中miR-138及炎性因子表达增多，Sirt1与抗炎蛋白Tristetraprolin(TTP)表达下降。抑制miR-138表达可导致足细胞Sirt1与TTP表达增多；而抑制Sirt1表达后，TTP表达减少，炎性因子增多。据此我们假设：miR-138通过Sirt1调节TTP参与DN炎症，进而导致足细胞损伤。本课题拟利用患者血、尿、肾组织标本、足细胞及db/db鼠，通过细胞分子生物学技术确定miR-138的表达与DN蛋白尿及炎症反应的关系；明确miR-138在DN炎症造成足细胞损伤过程中的作用；探讨miR-138通过Sirt1对TTP的表达调控、参与DN炎症导致足细胞损伤的分子机制，为探明DN发生机制并寻找新的治疗靶点提供新视角和科学实验依据。

炎症蛋白的异常表达是糖尿病肾病肾脏足细胞损伤及产生蛋白尿的重要因素。目前研究显示体内60%的蛋白质的表达调控过程有miRNA的参与，但miRNA是否参与糖尿病肾病炎症反应及其机制仍不清楚。本课题的研究目的是探索miR-138在糖尿病肾病中参与炎症蛋白表达进而导致足细胞损伤及蛋白尿的分子机制。在DN患者标本中，我们发现肾脏纤维化、硬化及足细胞线粒体肿胀可能与miR-138表达升高有关。利用db/db小鼠构建糖尿肾病动物模型进行体内研究，发现miR-138可能通过下调SIRT1的表达使p38磷酸化并抑制TTP的表达，激活炎性因子，导致db/db小鼠肾脏足细胞损伤并出现蛋白尿；尾静脉注射miR-138 shRNA，能增加SIRT1在肾小球的表达量，抑制p38的磷酸化，激活TTP可抑制下游炎性因子表达，足细胞得到修复，尿蛋白减少。在细胞水平，我们发现高糖条件下miR-138表达上调，并直接下调SIRT1表达，使p38-MAPK磷酸化、抗炎蛋白TTP的表达下降，上调炎性因子表达，足细胞长期处于炎症状态下而失去正常的结构和功能。转染miR-138 shRNA，可提高高糖培养的足细胞中SIRT1的表达量，抑制p38的磷酸化，激活TTP进而抑制下游炎性因子表达，足细胞得到修复。高糖培养的足细胞转染SIRT1的激动剂SRT1720亦能有效缓解足细胞的损伤情况。我们的研究结果表明miR-138-SIRT1-p38-TTP的调节轴可能在糖尿病肾病中起关键作用。这些发现可能对糖尿病肾病的认识和未来的治疗有一定的价值。