Evaluation of Oxidative Stress and Paraoxonase Phenotypes in Pseudoexfoliation Syndrome and Pseudoexfoliation Glaucoma

Abstract

Background: Our purpose was to determine whether total oxidant and antioxidant status, total thiol levels and activities of serum paraoxonase 1, an HDL-associated antioxidant enzyme, are related with pseudoexfoliation syndrome (PEX) and pseudoexfoliation glaucoma (PG). Methods: Serum samples from 32 PEX, 30 PG, and 32 control subjects were collected at the Gulhane Military Medical Academy, Ankara. Basal paraoxonase (PON1), salt stimulated paraoxonase (stPON1), arylesterase (ARE), and total thiol levels were measured spectrophotometrically. Total antioxidant status (TAS) and total oxidant status (TOS) were determined on an autoanalyzer. Oxidative stress index (OSI) was calculated using the TAS and TOS values. PON1 phenotypes were calculated from the ratio of stPON1 to ARE. Continuous variables were compared by independent samples t-test and one-way ANOVA, except for age which was compared using Mann-Whitney U test. Categorical variables were compared using Fisher's exact test (PON1 phenotypes) or chi-square test (gender). Results: TAS levels were significantly lower in PEX and PG patients compared to controls. TOS, OSI and total thiol levels did not differ significantly among the study groups, although there was a trend towards lower TOS and total thiol levels in patients compared to controls. PON1 activities were significantly higher in PEX patients (131.37 +/- 81.20 U/L) compared to controls (95.53 +/- 55.65 U/L; p = 0.046). The PON1 phenotype which is known to have high activity towards the substrate paraoxon, but low antioxidant activity (BB phenotype) was observed significantly more in PEX patients compared to controls. Conclusions: PON1 phenotypes and lack of antioxidants might play an important role in the development of PEX/PG.