PGC-1α Signaling Coordinates Susceptibility to Metabolic and Oxidative Injury in the Inner Retina

Retinal ganglion cells (RGCs), used as a common model of central nervous system injury, are particularly vulnerable to metabolic and oxidative damage. However, molecular mechanisms underlying this sensitivity have not been determined in vivo. PGC-1 alpha (encoded by PPARGC1A) regulates adaptive metabolism and oxidative stress responses in a tissue- and cell-specific manner. Aberrant PGC-1 alpha signaling is implicated in neurodegeneration, but the mechanism underlying its role in central nervous system injury remains unclear. We provide evidence from a mouse model that PGC-1 alpha expression and activity are induced in adult retina in response to metabolic and oxidative challenge. Deletion of Ppargc1a dramatically increased RGC loss, in association with dysregulated expression of PGC-1 alpha target metabolic and oxidative stress response genes, including Hmox1 (encoding H0-1), Tfam, and Vegfa. Vehicle-treated and naive Ppargc1a(-/-) mice also showed mild RGC loss, and surprisingly prominent and consistent retinal astrocyte reactivity. These cells critically regulate metabolic homeostasis in the inner retina. We show that PGC-1 alpha. signaling (not previously studied in glia) regulates detoxifying astrocyte responses to hypoxic and oxidative stresses. Finally, PGC-1 alpha expression was modulated in the inner retina with age and in a model of chronic optic neuropathy. These data implicate PGC-1 alpha signaling as an important regulator of astrocyte reactivity and RGC homeostasis to coordinate pathogenic susceptibility to metabolic and oxidative injury in the inner retina.