Role of PPARalpha in acute kidney injury

描述(由申请人提供)：我们建议研究底物氧化、脂毒性和近曲小管细胞死亡之间的关系。我们已经证明，使用配体激活PPARpha，或通过转基因小鼠增加近端小管中PPARpha的表达，可以改善缺血再灌注损伤(IRI)和顺铂肾毒性模型中的肾功能。我们的初步研究表明，与野生型小鼠相比，单侧缺血和单侧输尿管梗阻(UUO)的PPARpha TG小鼠的近端小管细胞死亡和间质纤维化显著减少。我们的中心假说预测，近端小管和周细胞PPARpha的表达和活性增加阻断了肾小管间质炎症和肾纤维化，这是 从急性到慢性肾脏疾病(CKD)的进展。具体目的1.确定近端小管(PT)-PPARα增加是否可阻断肾小管间质纤维化。我们假设近端小管PPARpha的表达增加可以减轻肾纤维化。我们将使用野生型、遗传缺陷的PPARpha小鼠和PPARpha转基因小鼠以及两种肾脏纤维化的动物模型来确定脂肪酸氧化、脂蛋白增加 在肾纤维化模型中，脂肪酶活性和自噬增加有助于降低脂毒性和防止近端小管细胞死亡。具体目的2.研究近端小管(PT)-PPARα增加减少肾纤维化的机制。我们将阐述PPARpha表达减少肾纤维化的几个独立机制：1)通过改变UUO小鼠的巨噬细胞表型；2)通过增加UUO逆转后的结构修复；3)通过减少肾间质中的肌成纤维细胞的增殖。具体目的3.确定PPARpha减轻小鼠肾周细胞肾纤维化的细胞机制。我们的初步研究表明，从UUO小鼠分离的周细胞中，PPARpha的表达以及脂肪酸氧化基因的表达显著减少。我们建议从野生型小鼠分离和培养小鼠肾周细胞1)确定PPARpha过表达对周细胞向肌成纤维细胞转化的影响，2)确定PPARpha介导的脂肪酸氧化增加、中性脂质积累减少以及脂肪生成的改变是否有助于体外培养周细胞向肌成纤维细胞的转化，3)确定细胞自噬增加对周细胞向肌成纤维细胞转化的作用，以及4)确定PPARpha缺陷在原代周细胞向肌成纤维细胞转化中的作用。总之，这些研究将进一步促进我们对周细胞代谢和功能的了解，并应为治疗慢性肾脏疾病提供额外的治疗靶点。

DESCRIPTION (provided by applicant): We propose to examine the relationship between substrate oxidation, lipotoxicity and proximal tubule cell death. We have shown that activation of PPARalpha using a ligand, or by increased expression of PPARalpha in the proximal tubule using transgenic mice ameliorates kidney function in the ischemia reperfusion injury (IRI), and cisplatin model of nephrotoxicity. Our preliminary studies demonstrate a significant reduction in proximal tubule cell death and reduced interstitial fibrosis in PPARalpha Tg mice subjected to both unilateral ischemia and Unilateral Ureteral Obstruction (UUO), when compared to wild type mice. Our central hypothesis predicts that increased expression and activity of proximal tubule and pericyte PPARalpha interdict tubulo-interstitial inflammation and renal fibrosis, a hallmark of the progression from Acute to Chronic Kidney Disease (CKD). Specific Aim 1. To determine whether increased proximal tubule (PT)-PPARalpha interdicts with tubulo-interstitial fibrosis. We hypothesize that increased expression of proximal tubule PPARalpha attenuates renal fibrosis. We will use wild type, genetically deficient PPARalpha mice, and PPARalpha transgenic mice and two animal models of renal fibrosis to determine if increased fatty acid oxidation, lipoprotein lipase activity, and increased autophagy contribute to reduced lipotoxicity and prevent proximal tubule cell death in models of renal fibrosis. Specific Aim 2. To examine the mechanisms by which increased proximal tubule (PT)-PPARalpha reduces renal fibrosis. We will address several independent mechanisms by which PPARalpha expression could reduce renal fibrosis: 1) by changing macrophage phenotype in UUO mice 2) by increasing structural repair after reversal of UUO and 3) by reducing myofibroblast proliferation in renal interstitium. Specific Aim 3. To determine cellular mechanisms by which PPARalpha reduces renal fibrosis in mouse kidney pericytes. Our preliminary studies show that PPARalpha expression as well as expression of fatty acid oxidation genes are significantly reduced in pericytes isolated from UUO mice. We propose to isolate and culture mouse kidney pericytes from wild type mice 1) to determine the effects of PPARalpha overexpression on pericyte to myofibroblasts transition in vitro, 2) to determine whether PPARalpha mediated increase in fatty acid oxidation, reduced neutral lipid accumulation, and changes on adipogenesis contribute to the transition from pericytes to myofibroblasts in vitro, 3) to determine the role of increased cellular autophagy on pericyte to myofibroblasts transition, and 4) to determine the role of PPARalpha deficiency on primary pericytes transition to myofibroblasts. Altogether these studies will further advance our knowledge of pericyte metabolism and function and should provide additional therapeutic targets to manage chronic kidney disease.