Cellular cholesterol and podocyte function in diabetic kidney disease

摘要 足细胞损伤是DKD的重要特征，肾脏脂质蓄积与DKD的发生发展密切相关。 肾小球硬化。肾小球组织中ATP结合盒转运蛋白1(ABCA1)表达降低 DKD患者的转录本，并与肾活检组织中足细胞脂滴的存在有关。 携带ABCA1功能缺失突变的丹吉尔病患者的成纤维细胞的特征是 心磷脂积聚，一种线粒体特有的磷脂。而肝脏胆固醇和胆固醇的增加 非酒精性心脏病患者心磷脂含量与线粒体功能障碍的关系 脂肪性肝炎(NASH)，高血糖诱导的线粒体超氧化物歧化 被认为是DKD患者线粒体功能障碍的主要驱动因素。这些观察结果引导我们提出了假设 ABCA1缺乏通过心磷脂依赖使足细胞易受DKD介导的损伤 线粒体功能障碍。 我们的初步数据表明，ABCA1缺乏导致线粒体膜脂改变 线粒体成分和CL蓄积与线粒体功能障碍和氧化应激的关系 使足细胞容易受到伤害。在体内，我们证明了足细胞特异性ABCA1缺乏 (PABCA1)与酯化胆固醇在肾皮质中的堆积有关，但不足以导致 蛋白尿。然而，在糖尿病环境中培养的ABCA1缺陷的足细胞更容易患DKD相关的疾病 损伤和pABCA1糖尿病小鼠加重了DKD的进展和二十二碳六烯酸的积累 富含DHA的心磷脂，一种特别容易受到活性氧(ROS)影响的心磷脂物种。这个 这些小鼠的表型可以通过用伊拉米普肽抑制心磷脂过氧化来部分挽救。 CL过氧化的抑制剂。 我们提出了三个具体目标来检验几个假说。在具体目标1中，我们将确定ABCA1 缺乏血糖和高血糖对线粒体(Dys)功能的贡献不同。在具体目标2中，我们将 探讨ABCA1缺乏对线粒体膜脂组成和流动性的影响 在特定的目标3中，我们将确定抑制心磷脂过氧化是否可以挽救ABCA1依赖 线粒体功能障碍。 这项创新性的研究旨在破译ABCA1介导的脂质区域化和CL的作用 线粒体功能障碍和足细胞损伤中的堆积。如果成功，这项研究将产生很大的影响 因为它阐明了一条在足细胞损伤中重要的新途径，并可能导致识别新的药物靶点 用于治疗DKD患者。

ABSTRACT Podocyte injury is a key feature of DKD and renal accumulation of lipid correlates with the development of glomerulosclerosis. Decreased expression of ATP-binding cassette transporter 1 (ABCA1) occurs in glomerular transcripts from patients DKD and is associated with the presence of podocyte lipid droplets in kidney biopsies. Fibroblasts from patients with Tangier disease carrying ABCA1 loss of function mutations are characterized by cardiolipin accumulation, a mitochondrial specific phospholipid. While increases in hepatic cholesterol and cardiolipin content are observed in association with mitochondrial dysfunction in patients with non-alcoholic steatohepatitis (NASH), h yperglycemia induced excess mitochondrial superoxide production has been considered the primary driver of mitochondrial dysfunction in DKD. These observations led us to hypothesize that ABCA1 deficiency renders podocytes susceptible to DKD-mediated injury via cardiolipin dependent mitochondrial dysfunction. Our preliminary data suggest that ABCA1 deficiency leads to changes in the mitochondrial membrane lipid composition and CL accumulation in association with mitochondrial dysfunction and oxidative stress in vitro rendering podocyte susceptible to injury. In vivo, we demonstrate that podocyte specific Abca1 deficiency (pABCA1) is associated with accumulation of esterified cholesterol in kidney cortex but is not sufficient to cause proteinuria. However, Abca1 deficient podocytes cultured in diabetic milieu are more susceptible to DKD-related injury and pABCA1 diabetic mice have worsened DKD progression and accumulation of docosahexaenoic acid (DHA)-rich cardiolipin, a cardiolipin species especially susceptible to reactive oxygen species (ROS). The phenotype of these mice can be partially rescued by inhibition of cardiolipin peroxidation with Elamipretide, an inhibitor of CL peroxidation. We propose three specific aims to test several hypotheses. In specific aim 1, we will determine if ABCA1 deficiency and hyperglycemia contribute differently to mitochondrial (dys)function. In specific aim 2, we will investigate the effect of ABCA1 deficiency on the lipid composition and fluidity of mitochondrial membranes and in specific aim 3, we will determine if inhibition of cardiolipin peroxidation can rescue ABCA1 dependent mitochondrial dysfunction. This innovative study is aimed at deciphering the role of ABCA1-mediated lipid compartmentalization and CL accumulation in mitochondrial dysfunction and podocyte injury. If successful, this study will have high impact as it elucidates a new pathway important in podocyte injury and may lead to the identification of new drug targets for the treatment of patients with DKD.