8-hydroxy-2--deoxyguanosine and Glaucoma

This study examines retinas from a rat glaucoma model for oxidized nucleosides 8OHdG and 8OHG, biomarkers for oxidative damage of DNA and RNA, respectively. Immunohistochemical data indicate a predominant localization of 8OHdG/8OHG in retinal ganglion cells (RGCs). The levels for these oxidized DNA/RNA products were 3.2 and 2.8 fold higher at 1 and 2 weeks after intraocular pressure elevation compared to control retinas, respectively. 8OHdG/8OHG were almost exclusively associated with mitochondrial DNA/RNA: ~ 65% of 8OHdG/8OHG were associated with RNA isolated from mitochondrial fraction and ~ 35% with DNA. Furthermore, we analyzed retinas of the rd10 mouse, a model for retinitis pigmentosa, with severe degeneration of photoreceptors to determine whether high levels of 8OHdG/8OHG staining intensity in RGCs of control animals is related to the high level of mitochondrial oxidative phosphorylation necessary to support light-evoked RGC activity. No significant difference in 8OHdG/8OHG staining intensity between control and rd10 mouse retinas was observed. The results of this study suggest that high levels of 8OHdG/8OHG in RGCs of wild-type animals may lead to cell damage and progressive loss of RGCs observed during normal aging, whereas ocular hypertension-induced increase in the level of oxidatively damaged mitochondrial DNA/RNA could contribute to glaucomatous neurodegeneration.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Disease Models, Animal; DNA, Mitochondrial; Glaucoma; Intraocular Pressure; Mice; Mitochondria; Oxidative Stress; Rats; Retina; Retinal Ganglion Cells; RNA

To evaluate DNA damage markers and the antioxidant status of serum and aqueous humor in glaucoma patients.. Aqueous humor and serum samples were obtained at the time of surgery from 28 patients with glaucoma and 27 patients with cataracts. Total antioxidant status (TAS) and 8-hydroxy-2´-deoxyguanosine (8-OHdG) levels of all samples were determined by spectrophotometric and enzyme-linked immunosorbent assay methods.. Aqueous levels of 8-OHdG were higher in glaucoma patients than in the cataract group (4.61±2.97 ng/ml versus 1.98±0.70 ng/ml, p=0.002). Serum levels of 8-OHdG were also higher in glaucoma patients than in the cataract group (17.80±8.06 ng/ml versus 13.63±3.54 ng/ml, p=0.046). The TAS levels of serum (0.55±0.13 mmol/lit versus 0.70±0.14, p=0.001), and aqueous humor (0.23±0.13 mmol/lit versus 0.34±0.15, p=0.001) in glaucoma patients were lower than in cataract patients.. Our findings provide evidence that oxidative DNA damage increases and TAS decreases in the serum and aqueous humor of glaucoma patients. These findings support the hypothesis that the formation of reactive oxygen species and/or a decrease in TAS may have an important role in the pathogenesis of glaucoma.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adult; Aged; Aged, 80 and over; Antioxidants; Cataract; Cross-Sectional Studies; Deoxyguanosine; DNA Damage; Enzyme-Linked Immunosorbent Assay; Female; Glaucoma; Humans; Male; Middle Aged; Models, Statistical; Oxidative Stress; Spectrophotometry

Oxidative damage plays a pathogenic role in various chronic degenerative diseases. Oxidative damage targeting trabecular meshwork (TM) cells as a consequence of mitochondrial damage is a pathogenic mechanism for glaucoma, the most common cause of irreversible blindness worldwide. Consequences of oxidative damage are attenuated by endocellular activities involved in scavenging reactive oxidative species and DNA repair. Selected bacterial genes are highly efficient at protecting cells from oxidative DNA damage. This situation occurs for Escherichia coli formamidopyrimidine DNA glycosylase (FPG), a major DNA glycosylase that repairs oxidatively damaged DNA. Accordingly, this study was aimed at transfecting human TM cells (HTMC) with Fpg in order to increase their resistance to oxidative damage. This study demonstrates that it is feasible to increase resistance of HTMC to endogenous oxidative damage by gene transfection. These findings bear relevance for primary and secondary prevention of degenerative glaucomas and other degenerative diseases where oxidative damage plays a pathogenic role.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Cell Line, Tumor; Deoxyguanosine; DNA Damage; DNA-Formamidopyrimidine Glycosylase; Endothelial Cells; Escherichia coli; Escherichia coli Proteins; Gene Expression; Genetic Therapy; Glaucoma; Humans; Mitochondria; Oxidation-Reduction; Oxidative Stress; Reactive Oxygen Species; Recombinant Fusion Proteins; Trabecular Meshwork; Transfection

The anterior chamber of the eye is a highly specialized structure delimited by the cornea, lens, and iris. It contains the aqueous humor, secreted by the ciliary body and drained by the trabecular meshwork. Alteration of aqueous humor homeostasis plays a major role in the pathogenesis of glaucoma. The trabecular meshwork is the target tissue of glaucoma in the anterior chamber, and the development and progression of glaucoma are accompanied by accumulation of oxidative damage in this tissue. This study was conducted to comparatively evaluate the sensitivity to oxidative stress of anterior chamber tissues including the cornea, iris, and trabecular meshwork.. Cornea, iris, and trabecular meshwork fragments collected from six cornea donors were either left untreated or treated with hydrogen peroxide. Oxidative damage was determined by evaluating nucleotide oxidative modifications (8-hydroxy-2'-deoxyguanosine) and apurinic alkali-fragile sites by capillary electrophoresis.. The results indicated that the basal level of oxidative nucleotide modifications was higher in the cornea than in the iris and trabecular meshwork. The trabecular meshwork was the most sensitive tissue to oxidative damage, as after exposure to hydrogen peroxide both markers of oxidative damage dramatically increased in the trabecular meshwork but not in the cornea and iris.. Because the cornea and iris are directly exposed to light, they possess antioxidant defense mechanisms that are not activated in the trabecular meshwork. The peculiar sensitivity of the trabecular meshwork to oxidative stress is consistent with the damage selectively induced in it, triggering glaucoma's pathogenic cascade.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Cornea; Deoxyguanosine; DNA Damage; DNA Fragmentation; Electrophoresis, Capillary; Glaucoma; Glutathione Transferase; Humans; Hydrogen Peroxide; Iris; Oxidative Stress; Polymerase Chain Reaction; Polymorphism, Genetic; Trabecular Meshwork

After our studies on ganglion cell degeneration in the glaucomatous retina, the current work further confirmed the reduction of amacrine cells in the retina after the onset of glaucoma. Present study also tried to understand the possible mechanisms underlying neuronal degeneration in the glaucomatous retina. Changes of expressions in immediate early genes (IEGs), glutamate receptors (GluRs), calcium-binding proteins (CaBPs), 8-hydroxy-deoxyguanosine (8-OH-dG) and nitric oxide synthase (NOS), as well as apoptotic-related factors including caspase 3, bax, and bcl-2 were examined. IEGs such as c-fos and c-jun were induced in the retina of the glaucomatous rat as early as 2 hr after the onset of glaucoma and lasted up to 2 weeks. Expressions of GluRs and CaBPs (i.e., parvalbumin and calbindin D-28k) were observed to be increased in the retinal ganglion cell layer (GCL) and inner nuclear layer (INL) at 3 days and 1 week after the onset of glaucoma. The increase occurred well before and during the phase where significant neuronal death was observed in the GCL and INL of the glaucomatous retinae. Induction of 8-OH-dG was present in both the GCL and INL of the glaucomatous retina at 3 days after the onset of glaucoma before significant neuronal death was observed. Furthermore, confocal microscopy study showed the complete colocalization of immunohistochemical expression of caspase 3 with glial fibrillary acidic protein (GFAP), but not with neuronal nuclei (NeuN). It indicates that astrocytes and Müller cells are involved in the pathological processes of neuronal death. The relationship between the linked factors and neuronal degeneration is also discussed.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Apoptosis; Astrocytes; Calcium-Binding Proteins; Caspase 3; Caspases; Deoxyguanosine; Disease Models, Animal; Genes, Immediate-Early; Glaucoma; Glial Fibrillary Acidic Protein; Immunohistochemistry; Male; Nerve Degeneration; Neurons; Nitric Oxide Synthase; Rats; Rats, Wistar; Receptors, Glutamate; Retina; Retinal Degeneration; RNA, Messenger; Up-Regulation

Little is known about the molecular mechanisms responsible for the development of glaucoma, the leading cause of irreversible blindness worldwide. Some investigators have hypothesized that oxidative damage may be involved. We evaluated oxidative deoxyribonucleic acid (DNA) damage, in terms of 8-hydroxy-2'-deoxyguanosine (8-OH-dG), in the eyes of glaucoma patients.. Levels of 8-OH-dG were measured in the trabecular meshwork region from 42 patients with glaucoma and 45 controls of similar age and sex. Genotypes of glutathione S-transferase isoenzymes (GSTM1 and GSTT1) were assessed by polymerase chain reaction in the same DNA samples.. Levels of 8-OH-dG were significantly higher in glaucoma patients than in controls. Oxidative DNA damage in patients with glaucoma correlated significantly with intraocular pressure; in patients with primary open-angle glaucoma, it also correlated with visual field defects. GSTT1 was similar in the two groups, and had no effect on 8-OH-dG levels. Conversely, 8-OH-dG levels were significantly higher in GSTM1-null than in GSTM1-positive subjects. The GSTM1-null genotype was significantly more common in patients with primary open-angle glaucoma than in controls.. Oxidative DNA damage is significantly increased in the trabecular meshwork of glaucoma patients. GSTM1 gene deletion, which has been associated with an increased risk of cancer at various sites and molecular lesions in atherosclerosis, predisposes to more severe oxidative DNA damage in glaucoma patients. These findings may contribute to understanding the pathogenesis of glaucoma and may be useful in the prevention and treatment of this disease.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aged; Aged, 80 and over; Deoxyguanosine; DNA Damage; Female; Gene Deletion; Glaucoma; Glutathione Transferase; Humans; Male; Middle Aged; Oxidative Stress; Trabecular Meshwork