Abstract
OBJECTIVE: Diabetic retinopathy (DR) is characterised by chronic neuroinflammation where the NLRP3 inflammasome plays a pivotal role. This study investigated the therapeutic potential and underlying mechanism of combining systemic metformin (MET) with intravitreal MCC950, a specific NLRP3 inhibitor, in a rodent model of DR. METHODS: A type 2 diabetic rat model was induced by high-fat diet and streptozotocin (STZ) injection. Diabetic rats were divided into DR, MET, MCC950 and MET+MCC950 treatment groups. Body weight and blood glucose were monitored. Retinal structural changes were assessed by HE and PAS staining. Apoptosis was detected by TUNEL assay, and oxidative stress was evaluated by ROS fluorescence. The expression and interaction of key proteins within the NEK7/NLRP3 pathway were analysed by Western blot and immunofluorescence. RESULTS: The DR group exhibited significant retinal thinning, increased acellular capillaries, elevated apoptosis and oxidative stress. While monotherapies showed partial improvement, the MET+MCC950 combination yielded the most robust protective effects, nearly restoring retinal morphology and significantly reducing apoptosis and ROS levels. Mechanistically, combination therapy most effectively suppressed the activation of the NEK7/NLRP3 inflammasome pathway, as evidenced by decreased protein levels of NEK7, NLRP3, ASC, cleaved-Caspase-1 and IL-1β. Immunofluorescence confirmed enhanced NEK7/NLRP3 interaction in DR, which was markedly inhibited by the combination treatment. A significant positive correlation was found between ROS levels and NEK7 expression. CONCLUSION: The study demonstrates that the combination of systemic metformin and intravitreal MCC950 confers superior protection against DR by synergistically inhibiting the NEK7/NLRP3 inflammasome pathway, resulting in reduced oxidative stress, apoptosis and inflammatory response. This novel combinational strategy presents a promising therapeutic approach for DR.