Schepens Eye Research Institute, Massachusetts Eye and Ear, Department of Opthalmology, Harvard Medical School, Boston, Massachusetts.
Price Vision Group, Indianapolis, Indiana.
Am J Pathol. 2019 Oct;189(10):2061-2076. doi: 10.1016/j.ajpath.2019.06.012. Epub 2019 Jul 27.
Corneal endothelium (CE) is a monolayer of mitochondria-rich cells, critical for maintaining corneal transparency compatible with clear vision. Fuchs endothelial corneal dystrophy (FECD) is a heterogeneous, genetically complex disorder, where oxidative stress plays a key role in the rosette formation during the degenerative loss of CE. Increased mitochondrial fragmentation along with excessive mitophagy activation has been detected in FECD; however, the mechanism of aberrant mitochondrial dynamics in CE cell loss is poorly understood. Here, the role of oxidative stress in mitophagy activation in FECD is investigated. Immunoblotting of FECD ex vivo specimens revealed an accumulation of PINK1 and phospho-Parkin (Ser65) along with loss of total Parkin and total Drp1. Similarly, modeling of rosette formation with menadione (MN), led to phospho-Parkin accumulation in fragmented mitochondria resulting in mitophagy-induced mitochondrial clearance, albeit possibly in a PINK1-independent manner. Loss of PINK1, phospho-Drp1, and total Drp1 was prominent after MN-induced oxidative stress, but not after mitochondrial depolarization by carbonyl cyanide m-chlorophenyl hydrazone. Moreover, MN-induced mitophagy led to degradation of Parkin along with sequestration of Drp1 and PINK1 that was rescued by mitophagy inhibition. This study shows that in FECD, intracellular oxidative stress induces Parkin-mediated mitochondrial fragmentation where endogenous Drp1 and PINK1 are sequestered and degraded by mitophagy during degenerative loss of post-mitotic cells of ocular tissue.
角膜内皮(CE)是一层富含线粒体的细胞,对于维持与清晰视力相容的角膜透明性至关重要。Fuchs 内皮角膜营养不良(FECD)是一种异质性的、遗传复杂的疾病,其中氧化应激在 CE 退行性丧失过程中的玫瑰花结形成中起着关键作用。在 FECD 中已经检测到线粒体碎片化增加以及过度的线粒体自噬激活;然而,CE 细胞丧失中线粒体异常动力学的机制尚不清楚。在这里,研究了氧化应激在 FECD 中线粒体自噬激活中的作用。FECD 体外标本的免疫印迹显示 PINK1 和磷酸化 Parkin(Ser65)的积累,以及总 Parkin 和总 Drp1 的丢失。同样,用 menadione(MN)模拟玫瑰花结形成导致磷酸化 Parkin 在碎片化的线粒体中积累,导致线粒体自噬诱导的线粒体清除,尽管可能以 PINK1 非依赖性的方式。MN 诱导的氧化应激后,PINK1、磷酸化 Drp1 和总 Drp1 的丢失很明显,但线粒体去极化用羰基氰化物 m-氯苯腙处理后则没有。此外,MN 诱导的线粒体自噬导致 Parkin 的降解,同时 Drp1 和 PINK1 的隔离,这种隔离通过线粒体自噬抑制得以挽救。这项研究表明,在 FECD 中,细胞内氧化应激诱导 Parkin 介导的线粒体碎片化,在此过程中,内源性 Drp1 和 PINK1 被隔离并通过线粒体自噬降解,导致眼组织有丝分裂后细胞的退行性丧失。