线粒体功能障碍介导的PGE2/STAT3通路活化：蛋白尿促进肾小管损伤的新机制

As one of the most important markers and risk factors for progression of kidney diseases, proteinuria contributes to renal tubular epithelial cell (RTEC) injury and consequent interstitial fibrosis. We have reported that mitochondrial dysfunction confers proteinuria-induced renal tubular injury, however, the pathway downstream of mitochondrial dysfunction remains to be uncovered. Our preliminary data showed that proteinuria upregulated the expression of COX-2, mPGES-1 and EP4, whereas the protection of mitochondrial function by MnTBAP inhibited the induction of COX-2, mPGES-1 and PGE2. Moreover, proteinuria activated STAT3, a factor promoting renal injury, by phosphorylation, which was blocked by COX-2 inhibitor or EP4 siRNA. Therefore, we hypothesized that proteinuria-induced mitochondrial dysfunction mediates the activation of COX-2/mPGES-1/PGE2/EP4/STAT3 pathway and thus promotes renal tubular injury. To test this hypothesis, we will firstly confirm the effect of mitochondrial dysfunction on the expression of every component of the pathway. Furthermore, we will use RTEC specific gene knockout mouse models to study the role of COX-2, mPGES-1 and EP4 in proteinuria-induced renal tubule injury. We will also study their roles by using specific inhibitor and siRNA in vitro. These studies will elucidate the role of COX-2/mPGES-1/PGE2/EP4/STAT3 pathway in mitochondrial dysfunction-mediated RTEC injury, and could aid in the design of new therapies for the prevention of tubulointerstitial lesions in chronic kidney diseases.

蛋白尿是诱发肾小管上皮细胞损伤并导致间质纤维化的重要因素。我们前期研究揭示线粒体功能障碍介导蛋白尿诱导的肾小管损伤，但线粒体功能障碍介导自身及邻近小管细胞损伤的机制尚不清楚。预试验发现蛋白尿显著诱导环氧化酶(COX)-2、PGE2合酶mPGES-1和PGE2受体EP4的表达以及STAT3磷酸化，应用MnTBAP保护线粒体功能可抑制COX-2和mPGES-1表达、PGE2分泌和STAT3磷酸化。同时COX-2抑制剂或EP4 siRNA可阻断STAT3磷酸化并减轻肾小管损伤。由此推测：蛋白尿可通过诱导线粒体功能障碍激活COX-2/mPGES-1/PGE2/EP4/STAT3通路促进肾小管损伤。本研究将首先明确线粒体功能障碍对该通路的影响，并应用多种肾小管条件性基因敲除小鼠和细胞模型，结合特异性抑制剂和siRNA技术，阐明该通路在蛋白尿诱导肾小管损伤中的作用，为治疗蛋白尿相关肾脏病提供新思路。

蛋白尿是各类肾脏疾病中最常见的临床表现之一。在临床上，蛋白尿不仅仅是肾脏疾病的临床诊断指标，也参与了肾小管损伤的发生及慢性肾脏疾病的进展。目前，蛋白尿相关的肾小管损伤的发生机制还不十分明确，临床上也缺乏有效的针对蛋白尿相关的肾小管损伤的干预手段。本项目通过研究线粒体功能障碍及炎症通路COX-2/mPGES-1/PGE2的活化及其相互作用关系和机制探讨，阐明了：1. 蛋白尿可以显著活化COX-2/mPGES-1/PGE2信号通路，这一通路的活化参与了蛋白尿诱导的肾小管上皮细胞损伤。2. 明确了线粒体功能障碍及线粒体氧化应激对COX-2/mPGES-1/PGE2信号通路的激活作用，进而参与了蛋白尿诱导的肾小管损伤。3. 进一步研究了NLRP3炎症小体活化(已知的线粒体功能障碍相关的下游靶点)对蛋白尿诱导的COX-2/mPGES-1/PGE2通路活化的影响，为理解该通路活化提供了新视点。本项目的研究结果，不但为深入理解蛋白尿相关的肾小管损伤机制提供了新见解，也为开发有效的基于蛋白尿病理损伤作用的防治手段提供了新思路。