HIF-1α/PPAR-γ/SIRT1 axis drives astrocyte senescence and regulates endothelial function via GDNF/NRTN in diabetic retinopathy

BACKGROUND: Diabetic retinopathy (DR) is a leading cause of blindness in working-age populations. Astrocyte senescence is highly prevalent in DR, but the underlying regulatory mechanism remains unclear. This study aims to investigate the role of the HIF-1α/PPAR-γ/SIRT1 axis in regulating retinal astrocyte senescence and endothelial function in DR. METHODS: Mouse retinal astrocytes were exposed to high glucose (30 mM) to mimic diabetic conditions. Senescence was evaluated by β-galactosidase staining. Signaling pathways were manipulated using HIF-1α inhibitor (PX-478), PPAR-γ inhibitor (T0070907), SIRT1 agonist (SRT2104), and autophagy inhibitor (3-MA). Protein and mRNA levels of key factors were detected by Western blot and RT-qPCR. Astrocytes and retinal microvascular endothelial cells were co-cultured in Transwell systems to assess paracrine regulation on endothelial migration, proliferation, and apoptosis. RESULTS: High glucose induced astrocyte senescence, inflammatory activation, and downregulation of GDNF and NRTN, accompanied by elevated HIF-1α and PPAR-γ, and reduced SIRT1 expression and autophagy activity. Inhibiting HIF-1α or activating SIRT1 attenuated senescence, apoptosis, and inflammation, restored autophagy, and upregulated GDNF/NRTN secretion. HIF-1α negatively regulated SIRT1 expression via PPAR-γ. Senescent astrocytes impaired endothelial function through reduced GDNF/NRTN; overexpression of GDNF or NRTN in astrocytes preserved endothelial migration and proliferation, and inhibited apoptosis. CONCLUSION: HIF-1α/PPAR-γ/SIRT1 axis mediates high glucose-induced astrocyte senescence via autophagy dysfunction. Senescent astrocytes disrupt retinal endothelial homeostasis by reducing GDNF/NRTN secretion. Targeting this axis may represent a novel neurovascular protective therapeutic strategy for DR.