Abstract
Purpose :
Oxidative stress in the pathogenesis of neurodegenerative diseases is generally associated with damage to cellular macromolecules, including DNA and RNA. This study evaluates the level of oxidized nucleosides 8-hydroxydeoxyguanosine (8OHdG) and 8-hydroxyguanosine (8OHG), biomarkers for oxidative damage of DNA and RNA, respectively, in the retinas of rat experimental glaucoma models
Methods :
The experimental glaucoma model was generated by trabecular laser photocoagulation in 3-month-old Brown Norway rats. Apoptotic cells in glaucomatous retinas were detected with TUNEL staining. Spatial distribution of 8OHdG/8OHG in control and experimental retinas was analyzed with immunohistochemistry using DNA and RNA Oxidative Damage Marker monoclonal antibodies. The levels of 8OHdG/8OHG in retinal mitochondrial DNA/RNA samples were measured with DNA/RNA Oxidative Damage ELISA Kit
Results :
8OHdG/8OHG in the retina were predominantly localized to retinal ganglion cell (RGC) somas. The immunostaining intensities for these oxidatively damaged DNA/RNA nucleosides were significantly higher at 1 and 2 weeks after intraocular pressure (IOP) elevation compared to controls. Analysis of different cellular fractions indicates that 8OHdG/8OHG is almost exclusively associated with mitochondrial DNA/RNA, with approximately 65% of oxidized product associated with RNA isolated from mitochondrial fraction and the remaining 35% with mitochondrial DNA. Quantitative analysis of 8OHdG/8OHG in mitochondrial DNA/RNA isolated from retinas of experimental animals 1 and 2 weeks after IOP elevation showed approximately a 3.2 and 2.8 fold increase in the levels of oxidized DNA/RNA, respectively, compared to that of control animals
Conclusions :
The observed high levels of 8OHdG/8OHG in RGCs of wild-type animals may lead to mitochondrial dysfunction and contribute to cell damage and progressive loss of RGCs during normal aging. Ocular hypertension is associated with a significant increase in the level of oxidatively damaged mitochondrial DNA/RNA, which in turn could contribute to the increased rate of RGC dysfunction and death in glaucoma
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.