Antioxidants Reduce Cell Death in a Model of Retinitis Pigmentosa: Relationship With Glutathione Metabolism

Abstract

Purpose: : In previous studies we have shown that the use of a combination of antioxidants drastically reduced the number of rod photoreceptors displaying oxidatively damaged DNA, and delayed the degeneration process in rd1 mice. In an effort to understand the mechanisms exerted by antioxidants in the degenerated retina, we have analyzed changes in the levels of several proteins and oxidative stress markers in the rd1 retina at postnatal day 11 (PN 11) when treated with antioxidants.

Methods: : Mice of rd1 origin were treated daily from PN3 by oral infusion with a mix of antioxidants (zeaxanthin, lutein, -lipoic acid) dissolved in olive oil and GSH (in water) and with the aqueous and lipid extract from Lycium barbarum until PN10. Retina was dissected and homogenized in prechilled 0.2 M potassium phosphate buffer, pH 7.0. This homogenate was used to assay malondialdehyde (MDA) and glutathione (GSH) concentration, as well as glutathione peroxidase (GPx) and glutathione reductase (GSSG-R) activities were measured as oxidative stress markers. Inmunostaining for nuclear factor kappaB (NF-ΚB) was also performed. MDA and GSH concentration was measured by liquid chromatography, and GPx and GSSG-R was measured spectrophotometrically.

Results: : Antioxidants increased GPx activity and GSH levels in rd1 retinas. There was no difference in GSSG-R activity between untreated and antioxidant treated mice. A high correlation was established between GSH concentration and GPx activity and, interestingly, there was a negative correlation between GSH retinal concentration and number of TUNEL positive cells. Localization of NF-ΚB showed no differences between treated and untreated rd1 retinas.

Conclusions: : The present results and previous findings show that antioxidants reduce cell death in rd1 retina, but, herein we demonstrate the importance of improving thiol homeostasis, and thereby decrease oxidative stress, in order to protect retinal death.

Keywords: antioxidants • photoreceptors • retina