Oxidative stress markers in visual cortex and red blood cells in a chronic glaucoma model in rats

Abstract

Purpose: Although considered an eye disease, glaucoma damages structures of the brain, including the lateral geniculate nucleus and the visual cortex.<br /> The aim of the present study was to establish the antioxidant status in visual cortex homogenates and red blood cells in an experimental glaucoma model

Methods: Female Wistar rats (n= 12) were operated under a microscope. Two episcleral veins were cauterized in order to elevate intraocular pressure. Six animals received the episcleral venous occlusion (G), while other six received a sham procedure (C).<br /> In order to assess the occurrence of oxidative stress the following markers were evaluated at 45 days after the surgery in left and right visual cortex: spontaneous chemiluminescence (CL), lipid peroxidation marker (TBARS), total antioxidant capacity (TRAP), thioredoxin reductase (TR) and glutathione peroxidase (GPx). In red blood cells superoxide dismutase (SOD), catalase (CAT) and total glutathione (GSH+GSSG) were measured. Unpaired t-test was used.

Results: Results in visual cortex showed: a - CL increased 89% in left cortex and 104% in right cortex in G vs C (CL Control (cpm/mg protein): left cortex 1878±210 p<0.001, right cortex 1617±171 p<0.001).; b -TBARS increased 75% in left cortex and 78% in right cortex in G vs C (TBARS Control (pmol/mg protein): left cortex 2.74±0.13 p< 0.001, right cortex 2.58±0.15 p < 0.001), c -TR decreased 34% in left cortex and 54% in right cortex in G vs C (TR Control (nmol/min.mg protein): left cortex 5.6±0.8 p< 0.05, right cortex 6.0±0.5 p<0.001) and d- GPx increased 51% in left cortex and 71% in right cortex in G vs C (GPx control (nmol/min.mg protein): left cortex 7.1±0.4 p< 0.05, right cortex 7.9±0.5 p<0.001). In red blood cells the activity of SOD increased 48% in G vs C (SOD control (U/mg protein): 0.92±0.10 p<0.01). The rest of the parameters evaluated in visual cortex and red blood cells showed no significant changes.

Conclusions: Reactive oxygen species are increased in this glaucoma model evidenced by an increase in TBARS and CL values. The decrease in TR and a compensatory up-regulation of SOD and GPx may be a consequence of an increase in oxidative process.