Abstract
Purpose :
Diabetic retinopathy continues to progress even after termination of hyperglycemia, suggesting a ‘metabolic memory’ phenomenon. Mitochondria play a central role in the development of diabetic retinopathy, and in the metabolic memory phenomenon associated with its progression. Mitochondria are very dynamic, and their fission and fusion allow exchange of the components to segregate functional and damaged elements. We have shown that mitochondrial fragmentation is increased and fusion protein (Mfn2) is decreased in hyperglycemia, and re-institution of normal glycemia has no beneficial effect on mitochondrial fragmentation. Our aim was to investigate the role of regulation of Mfn2 in the continued compromised mitochondrial dynamics in diabetic retinopathy.
Methods :
Using human retinal endothelial cells, incubated in high (20mM; HG) D-glucose for four days, followed by normal (5mM; NG) D-glucose for four days, without or with a Mfn2 activator (leflunomide;100µM; HG-NG and HG-NG/Lef groups), GTPase activity of Mfn2 and mitochondrial fragmentation were analyzed. Effect of leflunomide on continued mitochondrial dysfunction was evaluated by quantifying ROS (Mitosox), membrane depolarization (JC-1 staining) and mitochondrial DNA damage (oxidatively modified DNA and extended length PCR), and on the removal of the damaged mitochondria (mitophagy).
Results :
In HG-NG group, NG failed to ameliorate glucose-induced decrease in Mfn2 GTPase activity and mitochondrial dysfunction, and the damaged mitochondria continued to accumulate. Addition of leflunomide during the normal glucose incubation, which had followed four days of high glucose exposure (HG-NG/Lef group), ameliorated decrease in the GTPase activity of Mfn2 and mitochondrial fragmentation. In the same cell preparation, mitochondrial dysfunction was prevented, and removal of the damaged mitochondria was enhanced.
Conclusions :
Thus, supplementing good glycemic control with therapies targeting mitochondrial dynamics should help maintain mitochondrial homeostasis, and slow down the progression of diabetic retinopathy.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.