The Early Pathogenesis of Diabetic Retinopathy and Its Attenuation by Sodium-Glucose Transporter 2 Inhibitors.

The early pathogenetic mechanism of diabetic retinopathy (DR) and its treatment remain unclear. Therefore, we used streptozotocin-induced diabetic mice to investigate the early pathogenic alterations in DR and the protective effect of sodium-glucose cotransporter 2 (SGLT2) inhibitors against these alterations. Retinal vascular leakage was assessed by dextran fluorescence angiography. Retinal thickness and vascular leakage were increased 2 and 4 weeks after onset of diabetes, respectively. Immunostaining showed that morphological change of microglia (amoeboid form) was observed at 2 weeks. Subsequently, increased angiopoietin-2 expression, simultaneous loss of pericytes and endothelial cells, decreased vessel density, retinal hypoxia, and increased vascular endothelial growth factor (VEGF)-A/VEGF receptor system occurred at 4 weeks. SGLT2 inhibitors (luseogliflozin and ipragliflozin) had a significant protective effect on retinal vascular leakage and retinal thickness at a low dose that did not show glucose-lowering effects. Furthermore, both inhibitors at this dose attenuated microglia morphological changes and these early pathogenic alterations in DR. In vitro study showed both inhibitors attenuated the lipopolysaccharide-induced activation of primary microglia, along with morphological changes toward an inactive form, suggesting the direct inhibitory effect of SGLT2 inhibitors on microglia. In summary, SGLT2 inhibitors may directly prevent early pathogenic mechanisms, thereby potentially playing a role in preventing DR.

Construction of a screening system for lipid-derived radical inhibitors and validation of hit compounds to target retinal and cerebrovascular diseases.

Recent studies have highlighted the indispensable role of oxidized lipids in inflammatory responses, cell death, and disease pathogenesis. Consequently, inhibitors targeting oxidized lipids, particularly lipid-derived radicals critical in lipid peroxidation, which are known as radical-trapping antioxidants (RTAs), have been actively pursued. We focused our investigation on nitroxide compounds that have rapid second-order reaction rate constants for reaction with lipid-derived radicals. A novel screening system was developed by employing competitive reactions between library compounds and a newly developed profluorescence nitroxide probe with lipid-derived radicals to identify RTA compounds. A PubMed search of the top hit compounds revealed their wide application as repositioned drugs. Notably, the inhibitory efficacy of methyldopa, selected from these compounds, against retinal damage and bilateral common carotid artery stenosis was confirmed in animal models. These findings underscore the efficacy of our screening system and suggest that it is an effective approach for the discovery of RTA compounds.