Department of Ophthalmology, The Affiliated Wuxi People's Hospital of Nanjing Medical University, Wuxi, PR China.
Center of Clinical Research, The Affiliated Wuxi People's Hospital of Nanjing Medical University, Wuxi, PR China.
Exp Eye Res. 2022 Jul;220:109095. doi: 10.1016/j.exer.2022.109095. Epub 2022 Apr 28.
Diabetic retinopathy (DR) is a potentially blinding complication resulting from diabetes mellitus (DM). Retinal vascular endothelial cells (RMECs) dysfunction occupies an important position in the pathogenesis of DR, and mitochondrial disorders play a vital role in RMECs dysfunction. However, the detailed mechanisms underlying DR-induced mitochondrial disorders in RMECs remain elusive. In the present study, we used High glucose (HG)-induced RMECs in vitro and streptozotocin (STZ)-induced Sprague-Dawley rats in vivo to explore the related mechanisms. We found that HG-induced mitochondrial dysfunction via mitochondrial Dynamin-related protein 1(Drp1)-mediated mitochondrial fission. Drp1 inhibitor, Mdivi-1, rescued HG-induced mitochondrial dysfunction. Protein Kinase Cδ (PKCδ) could induce phosphorylation of Drp1, and we found that HG induced phosphorylation of PKCδ. PKCδ inhibitor (Go 6983) or PKCδ siRNA reversed HG-induced phosphorylation of Drp1 and further mitochondrial dysfunction. The above studies indicated that HG increases mitochondrial fission via promoting PKCδ/Drp1 signaling. Drp1 induces excessive mitochondrial fission and produces damaged mitochondrial, and mitophagy plays a key role in clearing damaged mitochondrial. Our study showed that HG suppressed mitophagy via inhibiting LC3B-II formation and p62 degradation. 3-MA (autophagy inhibitor) aggravated HG-induced RMECs damage, while rapamycin (autophagy agonist) rescued the above phenomenon. Further studies were identified that HG inhibited mitophagy by down-regulation of the PINK1/Parkin signaling pathway, and PINK1 siRNA aggravated HG-induced RMECs damage. Further in-depth study, we propose that Drp1 promotion of Hexokinase II (HK-II) separation from mitochondria, thus inhibiting HK-II-PINK1-mediated mitophagy. In vivo, we found that intraretinal microvascular abnormalities (IRMA), including retinal vascular leakage, acellular capillaries, and apoptosis were increased in STZ-induced DR rats, which were reversed by pretreatment with Mdivi-1 or Rapamycin. Altogether, our findings provide new insight into the mechanisms underlying the regulation of mitochondrial homeostasis and provide a potential treatment strategy for Diabetic retinopathy.
糖尿病视网膜病变（DR）是一种由糖尿病（DM）引起的潜在致盲并发症。视网膜血管内皮细胞（RMECs）功能障碍在 DR 的发病机制中占有重要地位，而线粒体紊乱在 RMECs 功能障碍中起着至关重要的作用。然而，DR 诱导的 RMECs 中线粒体紊乱的确切机制仍不清楚。在本研究中，我们使用体外高糖（HG）诱导的 RMECs 和体内链脲佐菌素（STZ）诱导的 Sprague-Dawley 大鼠来探讨相关机制。我们发现 HG 通过线粒体动力相关蛋白 1（Drp1）介导的线粒体分裂诱导线粒体功能障碍。Drp1 抑制剂 Mdivi-1 挽救了 HG 诱导的线粒体功能障碍。蛋白激酶 Cδ（PKCδ）可诱导 Drp1 磷酸化，我们发现 HG 诱导 PKCδ 磷酸化。PKCδ 抑制剂（Go 6983）或 PKCδ siRNA 逆转了 HG 诱导的 Drp1 磷酸化和进一步的线粒体功能障碍。上述研究表明，HG 通过促进 PKCδ/Drp1 信号增加线粒体分裂。Drp1 诱导过度的线粒体分裂并产生受损的线粒体，而自噬在清除受损线粒体方面起着关键作用。我们的研究表明，HG 通过抑制 LC3B-II 的形成和 p62 的降解来抑制自噬。3-MA（自噬抑制剂）加重了 HG 诱导的 RMECs 损伤，而雷帕霉素（自噬激动剂）挽救了上述现象。进一步的研究表明，HG 通过下调 PINK1/Parkin 信号通路抑制自噬，而 PINK1 siRNA 加重了 HG 诱导的 RMECs 损伤。进一步深入研究，我们提出 Drp1 促进己糖激酶 II（HK-II）与线粒体分离，从而抑制 HK-II-PINK1 介导的自噬。在体内，我们发现 STZ 诱导的 DR 大鼠视网膜内微血管异常（IRMA）增加，包括视网膜血管渗漏、无细胞毛细血管和细胞凋亡，用 Mdivi-1 或雷帕霉素预处理可逆转这些异常。总之，我们的研究结果为调节线粒体动态平衡的机制提供了新的见解，并为糖尿病视网膜病变提供了一种潜在的治疗策略。
