Metabolic Vulnerability as a Diseased Target for Glaucoma

Project Summary Retinal ganglion cell (RGC) axons degenerate after functional decline in glaucoma, a circumstance potentially caused, but certainly exacerbated by, energy deficit, indicating that metabolic dysfunction contributes to glaucomatous degeneration. High intraocular pressure (IOP) in glaucoma results in hypoxia that promotes glycolysis through upregulation of glycolysis-associated genes, but also mitochondrial recycling, and downregulation of genes encoding for oxidative phosphorylation (OxPhos). A critical question is whether RGC metabolic reprogramming from OxPhos to glycolysis is initiated by IOP-associated hypoxia, and whether repeated reprogramming and development of pseudohypoxia underlies the significant energy stress and dysfunction observed in the glaucomatous retina. The long-term goal of this work is to leverage our understanding of retinal metabolism to maintain visual function despite the stressors inherent in glaucomatous neurodegeneration. The overall objective of this proposal is to determine the impact of IOP-mediated damage on retinal and optic nerve head metabolic resilience. Our central hypothesis is that ocular hypertension (OHT)-associated hypoxia transitions into pseudohypoxia, destabilizing neural and glial metabolism and mitochondrial homeostasis, with downstream negative impact on RGCs in the retina and ONH. This hypothesis derives from our recent analysis indicating that mitochondria and availability of energy substrates, both targets of hypoxia-associated regulation, contribute to the metabolic challenges of RGCs. The rationale for the work is that investigating metabolic cooperation and dysfunction in glaucomatous retina will identify new therapeutic targets for a disease that has no mechanism-based interventions. Guided by strong preliminary data, the aims of this proposal will address a critical element of the retinal energy management in glaucoma by revealing 1) whether OHT is the impetus for metabolic reprogramming, followed by adaptation as pseudohypoxia, in the glaucomatous retina; 2) how metabolic coupling is managed among neurons and glia in the normal and ocular hypertensive retina; 3) how RGCs, Müller glia, and ONH astrocytes respond to and manage metabolic challenge on a cell-by-cell basis. Overall, this work will enable us to determine how RGCs, Müller glia, and ONH astrocytes respond metabolically to IOP increase, whether those changes persist long-term, and how we might promote metabolic resilience. The approach is innovative by taking the position that insight will only come from investigating the metabolic dependencies of the primary cell types impacted during the development of glaucoma pathology. In addition, we will apply new cutting-edge approaches to the investigation of mitochondria such as cell- specific mitochondrial isolation followed by metabolomics and co-detection of protein and gene expression through spatial transcriptomics. This proposal is significant because we will reveal mitochondrial-specific metabolic dysregulation amenable to therapeutic intervention.