Inhibition of Drp1 ameliorates diabetic retinopathy by regulating mitochondrial homeostasis

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 CE. (PKCE.) could induce phosphorylation of Drp1, and we found that HG induced phosphorylation of PKCE.. PKCE. inhibitor (Go 6983) or PKCE. siRNA reversed HG-induced phosphorylation of Drp1 and further mitochondrial dysfunction. The above studies indicated that HG increases mitochondrial fission via promoting PKCE./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.

Automated summary

Diabetic retinopathy (DR) is a potential blinding complication of diabetes mellitus (DM) with mitochondrial dysfunction and impaired mitophagy playing important roles. This study found that high glucose induced mitochondrial fission and dysfunction in retinal vascular endothelial cells (RMECs) through the PKCE/Drp1 signaling pathway. HG also suppressed mitophagy by down-regulating the PINK1/Parkin signaling pathway. Further research showed that Drp1 promoted the separation of Hexokinase II (HK-II) from mitochondria, thus inhibiting HK-II-PINK1-mediated mitophagy. In vivo experiments demonstrated that Mdivi-1 and Rapamycin could reverse intraretinal microvascular abnormalities in STZ-induced DR rats. These findings provide new insights into the regulation of mitochondrial homeostasis and potential treatment strategies for DR.