Abstract
Purpose :
Diabetic retinopathy (DR) is a leading cause of blindness in working-age adults. Although the loss of retinal pericytes (PC) in retinal vasculature is considered one of the early hallmarks of DR, it remains unknown how hyperglycemia selectively triggers their loss. We had shown among retinal vascular endothelial cells (EC), PC, and astrocytes, PC show increased oxidative stress and a higher rate of cell death under high glucose conditions. The aim of this study was to investigate mechanisms underlying this selective sensitivity of PC.
Methods :
Mouse retinal EC and PC were isolated as previously described. Cells were cultured in normal (5 mM) or exposed to high (30 mM) glucose to evaluate its impact on their metabolic activity. Expression levels of genes involved in inflammation, oxidative stress, mitochondrial function, and fatty acid metabolism were assessed by RT-qPCR and Western blot analysis. Cell proliferation was evaluated by counting the number of cells. The impacts of mitochondrial carbonic anhydrase (Car5a) and carnitine palmitoyl transferase 1 (Cpt1a), key regulators of oxidative metabolism, on glucose sensitivity of PC were determined by gene-specific knockdown or pharmacological inhibitors. Lipid peroxidation product acrolein levels were assessed by indirect immunofluorescence.
Results :
Incubation under high glucose conditions for 5 days significantly decreased cell numbers in retinal PC but not EC. RT-qPCR and Western blot analysis showed retinal PC express higher levels of Car5a and Cpt1a compared to EC. These results indicated that retinal PC actively utilizes mitochondrial pyruvate metabolism and fatty acid β-oxidation as energy source. Knockdown of Car5a expression by using siRNA and administration of Cpt1a inhibitor etomoxir reversed the decrease in PC cell number under high glucose conditions. Lipid peroxidation product acrolein levels were increased by high glucose condition in retinal PC but not in EC.
Conclusions :
Our findings support an important role for oxidative metabolism in retinal PC, especially under high glucose conditions, contributing to increased oxidative stress and loss of PC. Delineating the cell-specific metabolic pathways as energy source will help to find specific targets to prevent and/or slow down the progression of DR.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.