α1D Adrenergic Receptor Antagonism Protects Against High Glucose-Induced Mitochondrial Dysfunction and Blood Retinal Barrier Breakdown in ARPE-19 Cells.

Diabetic retinopathy (DR) is a microvascular complication of diabetes mellitus and a leading cause of blindness in the working-age population. Current pharmacological treatments counteract DR's later stages without targeting the earlier disease phases. Using computational approaches, our group previously identified the α1D and α2C adrenoceptors (α1DR and α2CR) as new putative drug targets for DR. Therefore, the aim of this work was to validate the role of these receptors in an in vitro model of DR, i.e., retinal pigmented epithelial cells (ARPE-19) challenged with high glucose (HG, 50 mM). We examined the effects of selective α1DR and α2CR agonists and antagonists on hyperglycemia-induced mitochondrial dysfunction and blood retinal barrier breakdown. Seahorse XFe was employed to assess the oxygen consumption rate and extracellular acidification rate. The integrity of the ARPE-19 barrier was evaluated through transepithelial electrical resistance measurements and a sodium fluorescein permeability test. α1DR pharmacological modulation through the α1DR antagonist BMY 7378 (0.1-1 µM, 24 h), but not α2CR, significantly attenuated HG-induced mitochondrial dysfunction. BMY 7378 (0.1-1 µM, 48 h) also prevented HG-mediated damage to retinal epithelial integrity. In contrast, the α1DR agonist phenylephrine (1-10 μM, 24 h) further reduced ARPE-19 mitochondrial activity compared to HG, indicating that α1D activation is directly implicated in DR-mediated mitochondrial dysfunction. In conclusion, the current in vitro study validated α1DR as a pharmacological target for DR.