Estradiol Protects RPE Cells From Oxidative Stress by Induction of ER- β

Abstract

Methods: : Cultured ARPE-19 cells were subjected to oxidative stress with t-butyl hydroxide (t-BH) or hydrogen peroxide (H₂O₂). Drug treatment was done 2 hours before H₂O₂ insult. Reactive oxygen species (ROS) were measured by H₂DCFDA fluorescence. Apoptosis was measured using a cell-death ELISA kit, while mitochondrial potential was measured using the JC-1 assay. Gene expression was quantified using qRT-PCR. Estrogen receptor (ER) and β protein expression was detected using Western blot analysis.

Results: : ARPE-19 cells upon exposure to oxidative stress show significant elevation of ROS, increased apoptosis, loss of mitochondrial potential and reduced ATP synthesis. All of these cellular and biochemical changes were reduced by 17β- estradiol treatment. Estradiol mediated effects were reversed by an ER antagonist indicating that a specific, receptor-mediated mechanism was responsible for these anti-oxidant effects. Estradiol treatment up regulated the expression of ER-β and antioxidant gene GPx2. Estradiol also reduced H₂O₂ induced reduction of mitochondria specific superoxide dismutase (MnSOD).

Conclusions: : 17-β Estradiol protects ARPE-19 cells by preventing oxidative stress induced mitochondrial damage. The anti-oxidant effects of 17-β Estradiol involve specific genomic pathways including induction of the ER subtype ER-β and cellular anti-oxidant genes. This study suggests that estrogen analogs might be useful for the treatment of early acute macular degeneration.

Keywords: age-related macular degeneration • oxidation/oxidative or free radical damage • gene/expression