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

Purpose To investigate the effects of Ambra1, which is involved in cell proliferation control in diabetic retinal inflammation, on the retina. Materials and methods Ambra1F/FxRosa-Cre-ER2-Tg mice and control Ambra1F/F mice were administered tamoxifen to generate mice with tamoxifen-dependent knockout of the Ambra1 gene in systemic tissues (Ambra1 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 Ambra1 cKO mice compared with controls. Immunostaining for cyclin D3 showed significantly elevated expression in Ambra1 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 Ambra1 cKO and control mice. Following STZ administration, GS expression increased in both groups, with the Ambra1 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 Ambra1 cKO mice. Conclusion These results indicate that loss of Ambra1 function promotes the proliferation of Müller glia-derived cells and may contribute to the suppression of retinal inflammation under diabetic conditions. Modulating Ambra1 activity could potentially serve as a new therapeutic approach for managing inflammation in diabetic retinopathy.