Acute Hyperglycemia-Induced Inflammation in MIO-M1 Cells: The Role of Aldose Reductase.

Diabetic retinopathy (DR), traditionally considered a microvascular complication, is now recognized as a neuroinflammatory disorder involving retinal glial cells. Aldose reductase (AKR1B1), a key enzyme in the polyol pathway, has been implicated in the hyperglycemia-induced inflammatory response in various cell types, although its role in retinal Müller glial cells under acute glucose stress remains unclear. This study investigates AKR1B1 activity and its contribution to inflammatory signaling in MIO-M1 human Müller cells exposed to acute hyperglycemia. AKR1B1 expression and activity, as well as NF-κB activation and COX-2 expression, were evaluated. Sorbinil, a specific AKR1B1 inhibitor, was used to determine the enzyme's contribution to acute hyperglycemia-induced inflammation. Acute high-glucose treatment significantly increased AKR1B1 activity and sorbitol accumulation without affecting cell viability. In addition, activation of NF-κB and increased expression of cyclooxygenase-2 (COX-2) were observed, both of which were significantly reduced by Sorbinil. Our findings highlight the role of macroglia as active contributors to early inflammatory events in DR and suggest that transient hyperglycemic spikes are sufficient to trigger AKR1B1-dependent glial activation.