Oxidative Stress in Neurodegeneration & Neuroprotection in Glaucoma

Columbia University Health Sciences, New York NY

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Abstract

DESCRIPTION (provided by applicant): Our recent studies of human glaucoma and in vivo and in vitro experimental models collectively support that oxidative stress is a major component of cellular events during glaucomatous neurodegeneration. We hypothesize based on the findings of these studies that (1) oxidative stress reduces the ability of retinal ganglion cells (RGCs) and axons to cope with the elevated intraocular pressure (IOP)-related stress in glaucoma and facilitates neurodegenerative injury (by generating direct neurotoxicity and also secondary neurodegenerative consequences, such as glial dysfunction and neuroinflammation); and (2) by suppressing or eliminating the harmful consequences of oxidative stress, antioxidant treatment can protect against neurodegenerative injury. Proposed project will test the validity of this hypothesis in a mouse model of glaucoma with experimentally induced ocular hypertension by anterior chamber microbead/viscoelastic injections in one eye. We will use two experimental paradigms to analyze the temporal effects of increased or decreased oxidative stress on glaucomatous neuronal injury. In the first experimental paradigm, we will analyze the effects of deficient antioxidant response on neuronal injury in experimentally induced glaucoma in superoxide dismutase 1 (SOD1)-/- versus C57BL/6J (wild-type) mice. This analysis will determine whether overloaded oxidative stress in SOD1-/- mice increases the susceptibility to neuronal injury in experimental glaucoma. In the second experimental paradigm, we will analyze the effects of a pharmacological antioxidant treatment on neuronal injury in wild-type mice with experimental glaucoma. Animals will receive Tempol (an antioxidant protecting against multiple oxidants, such as superoxide, peroxynitrite, and hydroxyl radicals) or vehicle (saline) using subcutaneously implanted osmotic mini-pumps for drug delivery by constant infusion. This analysis will determine whether pharmacological inhibition of oxidative stress acts to break the cycle of events leading to neurodegenerative injury, and whether antioxidant treatment has any potential as a neuroprotective strategy for glaucoma. We will determine neuronal injury by counting RGC axons and somas in their entirety using an imaging-based improved methodology free from sampling bias. We will also determine SOD1-/- and Tempol effects on oxidative stress-related major molecular outcomes of glaucoma, including retina and optic nerve protein carbonyl and HNE levels reflecting oxidative modifications and a redox- sensitive transcription factor, NF-?B that regulates glial immune/inflammatory responses in glaucoma. The data will be statistically compared between experimental groups matched for the cumulative IOP exposure (and axon loss within each group) at different time points during an experimental period of up to 12 weeks. This project is expected to determine the pathogenic importance of oxidative stress for glaucomatous neurodegeneration and the potential of antioxidant treatment as a neuroprotection strategy in glaucoma. The new information will also have broad implications useful for other ocular and neurodegenerative diseases.