Ambra1 Deficiency Improves Retinal Inflammation in Streptozotocin-Induced Diabetic Mouse Models

Purpose To investigate the effects of <i>Ambra1</i>, which is involved in cell proliferation control in diabetic retinal inflammation, on the retina. Materials and methods <i>Ambra1</i>F/FxRosa-Cre-ER2-Tg mice and control <i>Ambra1</i>F/F mice were administered tamoxifen to generate mice with tamoxifen-dependent knockout of the <i>Ambra1</i> gene in systemic tissues (<i>Ambra1</i> conditional knockout, cKO) mice and control mice, respectively. Each mouse was administered streptozotocin (STZ) to induce type 1 diabetes. Following enucleation, immunofluorescence staining was performed, and the neuroretina was excised and cultured in the presence of 5-bromodeoxyuridine (BrdU). Staining for cyclin D3 and glutamine synthetase (GS) was performed to observe S-phase progression, localization, and characteristics. Further, we examined the expression of glial fibrillary acidic protein (GFAP), a marker of astrocytic activation in neural tissues, which is typically elevated in diabetic retinal inflammation. Results In cultured retinal tissues, BrdU staining revealed a significant increase in 5-bromodeoxyuridine (BrdU)-positive cells in <i>Ambra1</i> cKO mice compared with controls. Immunostaining for cyclin D3 showed significantly elevated expression in <i>Ambra1</i> cKO mice compared to controls, regardless of STZ treatment. However, no significant difference in cyclin D3 levels was found between STZ-treated and untreated groups within either genotype. GS staining showed no significant difference between untreated <i>Ambra1</i> cKO and control mice. Following STZ administration, GS expression increased in both groups, with the <i>Ambra1</i> cKO mice exhibiting significantly higher levels than their STZ-treated controls. Notably, the regional distribution of cyclin D3 expression closely mirrored that of GS, suggesting potential colocalization. GFAP staining showed that STZ treatment significantly increased expression in control mice; however, this increase was suppressed in <i>Ambra1</i> cKO mice. Conclusion These results indicate that loss of <i>Ambra1</i> function promotes the proliferation of Müller glia-derived cells and may contribute to the suppression of retinal inflammation under diabetic conditions. Modulating <i>Ambra1</i> activity could potentially serve as a new therapeutic approach for managing inflammation in diabetic retinopathy.