Mitophagy is a principle mechanism to degrade damaged mitochondria through PARK2-dependent or PARK2-independent pathway. Mitophagy has been identified to play an important role in acute kidney disease, whereas its role in renal fibrosis remains ill-defined. We sought to investigate the involvement and regulation of mitophagy in renal tubular epithelial cell(RTEC) injury and renal fibrosis after unilateral ureteral obstruction(UUO). Mitochondrial damageand mitochondrial reactive oxygen species (ROS) production was increased in kidney after obstruction of the left ureter. Mitophagy was increased in kidneys following UUO and HK-2 cells under hypoxia exposure, assessed by electron microscopy of mitophagosome, colocalization of MitotrackerRed-stained mitochondria and LC3 staining. The upregulation of PINK1, PARK2, and LC3 II in mitochondrial fraction was observed in the obstructed kidney and hypoxia-exposed HK-2 cells. Pink1 or Park2 gene deletion markedly increased mtROS production, mitochondrial damage, TGFβ1 expression in RTEC, and renal fibrosis in UUO. Mitochondrial recruitment of Drp1 was also induced after UUO. The Drp1 inhibitor, Mdivi-1, decreased mitochondrial PINK1, PARK2 and LC3II level, increased mtROS production both in vivo and in vitro, activated TGFβ1-Smad2/3 signaling in HK-2 cells under hypoxia and worsened renal fibrosis following UUO. The upregulation of TGFβ1 signaling in hypoxia-treated HK-2 cells due to PINK1 or PARK2 silencing, or worsened renal fibrosis after UUO due to Pink1-or Park2-KO mice was rescued by mitoTEMPO, a mitochondria-targeted antioxidant. The findings of this study suggest that Drp1-regulated PARK2-dependent mitophagy plays a critical role in hypoxia-induced renal tubular epithelial cell injury and renal fibrosis in UUO.

线粒体是通过依赖于PARK2或非依赖于PARK2的途径降解受损线粒体的主要机制。线粒体已被确定在急性肾脏疾病中起重要作用，而其在肾纤维化中的作用仍不清楚。我们试图研究线粒体在单侧输尿管梗阻（UUO）后肾小管上皮细胞（RTEC）损伤和肾纤维化中的参与和调节。左输尿管阻塞后，肾脏线粒体损伤和线粒体活性氧（ROS）产生增加。缺氧暴露下UUO和HK-2细胞后肾脏的线粒体增多，通过电镜观察线粒体，线粒体红色染色的线粒体和LC3染色的共定位。在阻塞的肾脏和缺氧暴露的HK-2细胞中观察到线粒体组分中PINK1，PARK2和LC3 II的上调。Pink1或Park2基因缺失明显增加了mtROS的产生，线粒体损伤，RTEC中TGFβ1的表达以及UUO中的肾纤维化。UUO后也诱导Drp1的线粒体募集。Drp1抑制剂Mdivi-1可降低体内和体外线粒体PINK1，PARK2和LC3II的水平，增加mtROS的产生，在缺氧状态下，HK-2细胞中的TGFβ1-Smad2/ 3信号激活，并在UUO后加重肾纤维化。通过线粒体靶向的抗氧化剂mitoTEMPO拯救了由于PINK1或PARK2沉默导致的缺氧处理过的HK-2细胞中TGFβ1信号的上调，或由于粉红色1或Park2-KO小鼠引起的UUO后肾纤维化恶化。这项研究的发现表明，Drp1调节的PARK2依赖性线粒体在缺氧引起的UUO肾小管上皮细胞损伤和肾纤维化中起关键作用。