Modulation of Oxidative Stress Responses by Vitamin E, or Vitamin A plus Vitamin C Treatment in Human Retinal Pigment Epithelial Cells

Abstract

The purpose of this study was to characterize the potential of vitamins to protect the retinal pig-ment epithelium (RPE) from oxidative stress (OS). We have previously shown that OS induces the expression of AP1 transcription factors (FOSB, CFOS and ATF3), but is modulated by pretreatment with vitamin C (200 μ M). We propose that OS-induced AP1 expression can be used as a biomarker of OS to test the efficacy of vitamins to limit the impact of OS in the RPE. Here we examined the efficacy of vitamin E or combined vitamin A plus vitamin C to modulate OS-induced AP1 expression in the RPE. We pretreated human ARPE-19 cells with vitamin E (0 - 7.5 μ M) or with combined vitamin A (10 or 15 μ M) plus vitamin C (50 or 100 μ M) for 3 days prior to exposure to 500 μ M H2O2 OS for 1 - 4 h. AP1 expression was assessed using qRT-PCR. Pretreatment with ≥2.5 μ M vitamin E significantly decreased OS-induced AP1 expression at 1 - 4 h OS, compared to controls. Lower doses of vitamin E were ineffective at modulating OS responses. Pretreatment with 100 μ M vitamin C combined with 15 μ M vitamin A protected RPE cells from OS-induced AP1 expression. There is an additive and potentially protective effect of 100 μ M vitamin C and 15 μ M vitamin A on FOSB expression at 4 h, and a potentially protective effect of 100 μ M vitamin C and 15 μ M vitamin A on CFOS expression at 1 h OS. A protective effect was also seen with 15 μ M vitamin A pretreatment alone on ATF3 expression. Thus, “sub-therapeutic” levels of multiple vitamins may protect RPE cells better than higher doses of a single vitamin. This OS-induced AP1 expression biomarker assay may be useful to identify complex antioxidant formulations as therapeutics for degenerative diseases that are thought to be caused by OS, like age-related macular degeneration.