Alterations in glutamate cysteine ligase content in the retina of two retinitis pigmentosa animal models

Retinitis Pigmentosa (RP) comprises a group of rare genetic retinal disorders in which one of several different mutations induces photoreceptor death. Oxidative stress and glutathione (GSH) alterations may be related to the pathogenesis of RP. GSH has been shown to be present in high concentrations in the retina. In addition, the retina has the capability to synthesize GSH. In this study, we tested whether the two subunits of glutamate cysteine ligase, the rate-limiting enzyme in GSH synthesis, and the concentrations of retinal GSH, oxidized glutathione (GSSG), cysteine (Cys) and glutamate are altered in the retina of two different RP mice models. Retinas from C3H and rd1 mice at different postnatal days (P7, P11, P15, P19, P21 and P28) and from C57BL/6 and rd10 mice at P21 were obtained. Western blot analysis was performed to determine the protein content of catalytic and modulatory subunits from glutamate cysteine ligase (GCLC and GCLM, respectively). In another set of experiments, control and rdl mice were administered buthinine sulfoximine, a glutathione synthase inhibitor, or paraquat. GSH, GSSG, glutamate and Cys concentrations were determined, by HPLC. A decrease in retinal GCLC content was observed in C3H and rdl mice with age, nevertheless, there was an increase in retinal GCLC in rdl mice compared to control retinas at P19. No modifications in GCLM content with age and no difference between GCLM content in rdl and control retinas were observed. The GSH concentration decreased in the rdl retinas compared with control ones at P15, it increased at P19, and was again similar at P21 and P28. No changes in GSSG concentration in control retinas with age were observed; the GSSG levels in rdl retinas were similar from P7 to P19 and then increased significantly at P21 and P28. Glutamate concentration was increased in the rdl retinas compared to control mice from P7 to P15 and were comparable at P21 and P28. The Cys concentrations was measured in control and rdl retinas, but no significant changes were observed between them. BSO administration decreases GSH retinal concentration in control and rdl mice, while paraquat administration induced an increase in GSH retinal concentration in control mice and a decrease in GSH in rdl mice retina. Retinal GCLC was significantly increased in rd10 mice at P21 as well as GSSG. Our results suggest alterations in retinal GCLC content and GSH and/or its precursors in these two RP animal models. Regulation of the enzymes related to GSH metabolism and the retinal concentration of glutamate may be a possible target to delay especially cone death in RP. (C) 2016 Elsevier Inc. All rights reserved.