Increased Plasma Levels of 8-Hydroxy-2′-deoxyguanosine (8-OHdG) in Patients with Pseudoexfoliation Glaucoma

PURPOSE: To investigate systemic oxidative stress-induced DNA damage in patients with pseudoexfoliation glaucoma (PXG), we estimated plasma levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG) as a marker for oxidative DNA damage in comparison to controls. In addition, we also examined a combined effect of lysyl oxidase-like 1 (LOXL1) polymorphism status and 8-OHdG levels on PXG risk. MATERIALS AND METHODS: A retrospective case-control study was performed to estimate plasma levels of 8-OHdG in 41 PXG patients and 45 nonglaucomatous controls using the enzyme-linked immunosorbent assay (ELISA). The assay was performed in duplicate on an automated ELISA analyzer. Two common polymorphisms (rs1048661 and rs3835942) in LOXL1 gene were genotyped by Sanger sequencing. RESULTS: The mean and median levels of 8-OHdG were significantly increased in the PXG cases (p=0.032) and male subjects (p=0.041). Subjects with levels greater than the third quartile (75% percentile) exhibited a significant increased risk of PXG (odds ratio = 4.06, 95% confidence interval (CI = 1.11–14.80, p=0.029)). Within- and between-group comparisons showed that the mean levels were higher in individuals carrying the LOXL1 risk variant (G/G), but not statistically significant. In logistic regression analysis, both 8-OHdG (p=0.044) and rs3835942 (p=0.012) showed a statistically significant effect on the PXG outcome. However, the effect was lost when age, sex, and rs1048661 were included. A significant positive correlation was observed between 8-OHdG levels and intraocular pressure (R=0.284, p=0.008) and cup/disc ratio (R=0.233, p=0.031). Furthermore, in receiver operating characteristic analysis, the area under the curve was statistically significant (p=0.032) with a value of 0.635 (95% CI = 0.518–0.751). CONCLUSION: The study demonstrates an association of increased plasma levels of 8-OHdG in patients with PXG, supporting the role of oxidative stress, and increased oxidative DNA damage in PXG development.