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.
Although glaucoma is a leading cause of blindness, current treatment strategies are not sufficient to prevent disease progression. Therefore, improved treatments are strongly needed to prevent progressive injury to specific nerve cells (called optic nerve) and continuous loss of visual function in patients with glaucoma. To accomplish this important goal, our experimental research aims to identify specific molecular alterations that cause the death of nerve cells in glaucoma. Our recent studies of human donor eyes with glaucoma, animal models, and cell cultures using up-to-date analysis techniques have suggested oxidative stress-related mechanisms. In the proposed project, we specifically aim to test the importance of oxidative stress in an experimental model of glaucoma in mice and determine whether antioxidant treatment provides protection against nerve degeneration. We expect that this project will provide important information about the oxidative stress-related component of glaucoma, and thereby help develop new treatment possibilities for millions of Americans suffering from this blinding disease.
|Hondur, Gözde; Gökta?, Emre; Al-Aswad, Lama et al. (2018) Age-related changes in the peripheral retinal nerve fiber layer thickness. Clin Ophthalmol 12:401-409|
|Hondur, Gözde; Göktas, Emre; Yang, Xiangjun et al. (2017) Oxidative Stress-Related Molecular Biomarker Candidates for Glaucoma. Invest Ophthalmol Vis Sci 58:4078-4088|
|Tezel, Gülgün (2016) Applying proteomics to research for optic nerve regeneration in glaucoma: what's on the horizon? Expert Rev Proteomics :1-3|
|Yang, Xiangjun; Hondur, Gözde; Tezel, Gülgün (2016) Antioxidant Treatment Limits Neuroinflammation in Experimental Glaucoma. Invest Ophthalmol Vis Sci 57:2344-54|
|Yang, Xiangjun; Hondur, Gözde; Li, Ming et al. (2015) Proteomics Analysis of Molecular Risk Factors in the Ocular Hypertensive Human Retina. Invest Ophthalmol Vis Sci 56:5816-30|