Induction of vascular endothelial growth factor by 4-hydroxynonenal and its prevention by glutathione precursors in retinal pigment epithelial cells

Abstract

Although 4-hydroxynonenal, a highly reactive lipid peroxidation product, is implicated in several age-related disorders such as Alzheimer's and Parkinson's diseases, its role in age-related macular degeneration is not known. The purpose of this study was to determine whether 4-hydroxynonenal increases vascular endothelial growth factor (VEGF) expression in human retinal pigment epithelial cells (ARPE-19), a source of VEGF in choroidal neovascularization observed in age-related macular degeneration. In addition, it was the purpose of this study to assess whether glutathione (GSH) and GSH precursors can inhibit the effects of 4-hydroxynonenal. At 1 μM, 4-hydroxynonenal did not alter cell viability, but elevated VEGF secretion and mRNA expression by 35% ( p<0.05) and 1.9-fold ( p<0.05), respectively. However, at concentrations 5 μM and above, 4-hydroxynonenal reduced VEGF secretion as well as cell viability. At 1 and 10 μM, 4-hydroxynonenal did not induce apoptosis in ARPE-19 cells. 4-Hydroxynonenal (1 μM) reduced intracellular GSH by 25% ( p<0.05) and increased oxidative stress by 50% ( p<0.05). GSH precursor pretreatment for 1 h, which increased intracellular GSH levels by 50% ( p<0.05), as well as GSH co-treatment, inhibited the VEGF-inductive and cytotoxic effects of 4-hydroxynonenal. Thus, 4-hydroxynonenal (1 μM) induces VEGF expression and secretion in ARPE-19 cells. This effect is likely due to GSH depletion and an associated increase in intracellular oxidative stress, resulting in increased VEGF mRNA levels. 4-Hydroxynonenal-mediated VEGF secretion as well as cytotoxicity can be reversed with GSH precursor pretreatment or GSH co-treatment.