Involvement of the α2M/LRP-1 System in Glial Stress and Antioxidant Dysregulation in the Retina of Metabolic Syndrome mice

Metabolic syndrome (MS)-induced retinopathy involves vascular, glial, and neuronal damage driven by dyslipidemia and hyperglycemia. Having previously shown α2-macroglobulin (α2M) and LRP-1 levels in Müller glia (MGCs) alongside elevated retinal α2M in MS mice, we evaluated the α2M/LRP-1 system in glial stress and antioxidant responses in MIO-M1 cells and a MS mouse model. MIO-M1 cells were treated with high glucose (HG, 30 mM) and aggregated LDL (LDLagg, 100 µg/mL) for 24 h to analyze GFAP, HO-1, α2M, and LRP-1 by western blot. Two-month-old WT and ApoE KO mice fed a fructose (FD, 10% in drinking water) or normal diet (ND) for 3 months received two intravitreal injections of anti-α2M antibody (0.5 µg/µL, 1 µL) or PBS during the final month. Retinas were evaluated for HO-1 immunofluorescence (ANOVA, Bonferroni, p≤0.05). In MIO-M1 cells, HG + LDLagg upregulated GFAP (p=0.04) while decreasing HO-1 (p=0.04) and LRP-1 (p<0.0001). In mice, treatment-diet (p=0.007) and genotype-diet (p=0.0005) interactions were significant. Retinal HO-1 increased in ApoE ND PBS vs. WT ND PBS (p=0.02) and was reversed by Ab-α2M treatment in ApoE ND (p=0.0005) and ApoE FD (p=0.01) mice. Metabolic stressors induce glial reactivity and impair antioxidant response in MIO-M1 cells, correlating with retinal α2M accumulation that alters antioxidant defenses in MS mice. Coupled with LRP-1 downregulation in MIO-M1 culture, these findings position the α2M/LRP-1 system as a target in MS-induced retinopathy.