Dietary Lipoic Acid Attenuates Oxidative Stress and Retinal Ganglion Cell Loss in the DBA/2J Mouse Model of Glaucoma

Abstract

Purpose: : Data from DBA/2J mice with high intraocular pressure (IOP) suggest retinal ganglion cells (RGCs) are targets of oxidative stress in glaucoma. To address the role of oxidative stress in RGC loss in glaucoma we treated DBA/2J mice with alpha-lipoic acid (ALA), a dietary supplement with antioxidant properties, and then examined retinal oxidative stress and RGC numbers within the retina and optic nerve.

Methods: : Six-month-old DBA/2J mice were fed control or ALA supplemented (600 mg ALA/kg diet) chow for 16 weeks. RGCs were retrogradely labeled with fluorogold (FG) one week prior to tissue collection, immunolabeled with NeuN, and counted using unbiased stereology. Control and ALA treated optic nerves were fixed and processed for digital light microscopy. Western blotting, QPCR and immnocytochemistry were used to examine oxidative stress markers in control and ALA treated DBA/2J retinas.

Results: : Mice received an average dose of 64.15 mg ALA/kg over the course of the study. No significant differences in weight gain, food consumption or average lifetime IOP (18.6 mmHg vs. 18.4 mmHg) were observed between control and ALA groups. Immunoreactivity for 3NT and 8OHdG, markers of oxidative damage, localized to RGCs and appeared decreased in ALA retinas compared to control retinas. Message and protein levels for NOS2 were decreased 50% in ALA retinas. Significant increases in the antioxidant ceruloplasmin (109% for mRNA) and heme oxygenase-1 (114% for protein) levels were observed in ALA retinas. Finally, ALA treatment increased the number of NeuN+ (2086 ± 286 vs. 1203 ± 232 cells/mm2) and FG+ (1242 ± 253 vs. 566 ± 161 cells/mm2) cells in wholemount retinas compared to controls.

Conclusions: : Together these data suggest ALA attenuates oxidative stress in this chronic model of glaucoma by lowering NOS2 expression and increasing levels of antioxidant proteins, which resulted in greater numbers of RGCs. Further examination of this dietary supplement and its role in RGC neuroprotection in glaucoma is warranted.

Keywords: neuroprotection • retina: proximal (bipolar, amacrine, and ganglion cells) • oxidation/oxidative or free radical damage