Division of Pediatric Nephrology, Department of Pediatrics, University of Mississippi Medical Center, Jackson, MO 39110, USA.
Am J Nephrol. 2013;38(3):226-32. doi: 10.1159/000354357. Epub 2013 Aug 28.
BACKGROUND/AIMS: Adult and childhood obesity is an independent risk factor in development of chronic kidney disease (CKD) and its progression to end-stage kidney disease. Pathologic consequences of obesity include non-esterified fatty acid-induced oxidative stress and consequent injury. Since the serine36-phosphorylated p66shc is a newly recognized mediator of oxidative stress and kidney injury, we studied its role in oleic acid (OA)-induced production of reactive oxygen species (ROS), mitochondrial depolarization and injury in cultured renal proximal tubule cells.
Renal proximal tubule cells were used and treated with OA: ROS production, mitochondrial depolarization as well as injury were determined. Transcriptional effects of OA on the p66shc gene were determined in a reporter luciferase assay. The role of p66shc in adverse effects of OA was determined using knockdown, p66shc serine36 phosphorylation and cytochrome c binding-deficient cells.
We found that OA increased ROS production via the mitochondria - and to a less extent via the NADPH oxidase - resulting in ROS-dependent mitochondrial depolarization and consequent injury. Interestingly, OA also stimulated the promoter of p66shc. Hence, knockdown of p66shc, impairment its Ser36 phosphorylation (mutation of Ser36 residue to alanine) or cytochrome c binding (W134F mutation) significantly attenuated OA-dependent lipotoxicity.
These results offer a novel mechanism by which obesity may lead to renal tubular injury and consequently development of CKD. Manipulation of this pathway may offer therapeutic means to ameliorate obesity-dependent renal lipotoxicity.
背景/目的：成人和儿童肥胖是慢性肾脏病（CKD）发展及其进展为终末期肾病的独立危险因素。肥胖的病理后果包括非酯化脂肪酸诱导的氧化应激和随之而来的损伤。由于丝氨酸 36 磷酸化的 p66shc 是氧化应激和肾脏损伤的新发现的介质，因此我们研究了它在油酸（OA）诱导的活性氧（ROS）产生、线粒体去极化和培养的肾近曲小管细胞损伤中的作用。
使用肾近曲小管细胞并用 OA 处理：测定 ROS 产生、线粒体去极化和损伤。在报告荧光素酶测定中确定 OA 对 p66shc 基因的转录效应。使用敲低、p66shc 丝氨酸 36 磷酸化和细胞色素 c 结合缺陷细胞确定 p66shc 在 OA 不良作用中的作用。
我们发现 OA 通过线粒体增加 ROS 产生 - 并且在较小程度上通过 NADPH 氧化酶 - 导致 ROS 依赖性线粒体去极化和随后的损伤。有趣的是，OA 还刺激了 p66shc 的启动子。因此，敲低 p66shc、损害其 Ser36 磷酸化（将 Ser36 残基突变为丙氨酸）或细胞色素 c 结合（W134F 突变）显著减弱了 OA 依赖性脂毒性。
这些结果提供了一种新的机制，即肥胖可能导致肾小管损伤，进而导致 CKD 的发生。该途径的操作可能提供治疗肥胖相关肾脂毒性的手段。
