Department of Medicine, Ningbo First Hospital, Zhejiang University, Ningbo, China.
Department of Nephrology, Second Xiangya Hospital, Central South University, Changsha, China.
Clin Sci (Lond). 2018 Jun 26;132(12):1297-1314. doi: 10.1042/CS20180005. Print 2018 Jun 29.
Renal tubular injury is increasingly being recognized as an early characteristic of diabetic nephropathy (DN). Mitochondrial dynamic alterations and redox protein p66Shc-mediated oxidative stress are both critical for ensuing diabetic tubular cell injury and apoptosis; whether these two processes are interlinked remains unclear. In the present study, we observed changes in mitochondrial morphology and expression of associated proteins in tubules of patients with DN. We demonstrated mitochondrial fragmentation as an important pathogenic feature of tubular cell injury that is linked to oxidative stress and p66Shc up-regulation. In renal proximal tubular cells, alterations in mitochondrial dynamics and expression of fission-fusion proteins were observed under high glucose (HG) ambience, along with p66Shc Ser36 phosphorylation. Gene ablation of p66Shc alleviated HG-induced mitochondrial fragmentation, down-regulated Fis1 and reduced p66Shc-Fis1 binding, increased Mfn1 expression, and disrupted interactions between Mfn1 and proapoptotic Bak. Overexpression of p66Shc exacerbated these changes, whereas overexpression of dominant-negative p66Shc Ser36 mutant had a marginal effect under HG, indicating that p66Shc phosphorylation as a prerequisite in the modulation of mitochondrial dynamics. Disrupted mitochondrial dynamics and enhanced Mfn1-Bak interactions modulated by p66Shc led to loss of mitochondrial voltage potential, cytochrome release, excessive ROS generation, and apoptosis. Taken together, these results link p66Shc to mitochondrial dynamic alterations in the pathogenesis of DN and unveil a novel mechanism by which p66Shc mediates HG-induced mitochondrial fragmentation and proapoptotic signaling that results in oxidative injury and apoptosis in the tubular compartment in human diabetic nephropathy.
肾小管损伤越来越被认为是糖尿病肾病 (DN) 的早期特征。线粒体动力学改变和氧化应激相关的 p66Shc 蛋白是导致随后的糖尿病肾小管细胞损伤和凋亡的关键因素；这两个过程是否相互关联尚不清楚。本研究观察了 DN 患者肾小管中线粒体形态和相关蛋白表达的变化。我们证明了线粒体碎片化是肾小管细胞损伤的一个重要致病特征，与氧化应激和 p66Shc 上调有关。在高糖 (HG) 环境下，在肾近端小管细胞中观察到线粒体动力学改变和分裂融合蛋白表达改变，同时伴有 p66Shc Ser36 磷酸化。p66Shc 基因缺失减轻了 HG 诱导的线粒体碎片化，下调了 Fis1 并减少了 p66Shc-Fis1 结合，增加了 Mfn1 表达，并破坏了 Mfn1 和促凋亡 Bak 之间的相互作用。p66Shc 的过表达加剧了这些变化，而 HG 下过表达显性负性 p66Shc Ser36 突变体的作用微不足道，表明 p66Shc 磷酸化是调节线粒体动力学的前提。p66Shc 调节的线粒体动力学破坏和 Mfn1-Bak 相互作用增强导致线粒体电压势能丧失、细胞色素 c 释放、ROS 生成过多和细胞凋亡。综上所述，这些结果将 p66Shc 与 DN 发病机制中的线粒体动力学改变联系起来，并揭示了 p66Shc 介导 HG 诱导的线粒体碎片化和促凋亡信号的新机制，导致人类糖尿病肾病肾小管区氧化损伤和细胞凋亡。
