Taxifolin protects retinal pigment epithelium cells against oxidative stress induced apoptosis

Abstract

Purpose : Oxidative stress which induce retinal pigment epithelial (RPE) cell damage has been suggested to be an important factor in the pathogenesis of age-related macular degeneration (AMD). Taxifolin, a kind of flavanonol, has been shown to exhibit significant antioxidant properties .The purpose of this study was to investigate the potential protective effects of taxifolin in culture RPE cells during oxidative stress and its mechanisms.

Methods : Primary human RPE cells were treated with different concentrations of taxifolin as well as 0.4 μM H₂O₂ for 24 h. Cell viability was determined by the MTT assay. Apoptosis was quantitatively measured by annexin V/propidium iodide (PI) double staining and the expression levels of PARP was evaluated by western blotting. Reactive oxygen species (ROS) were measured using a commercially available ROS detection system. Phase II enzymes NAD(P)H quinine oxidoreductase 1 (NQO1), hemeoxygenase-1 (HO-1), glutamate-cysteine ligase modifier subunit (GCLM), expression were examined with real time PCR and western blotting. The nuclear localization of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) protein were detected with western blotting.

Results : Treatment of taxifolin (100 μM) could decrease the apoptosis induced by H₂O₂ (0.4 mM) from 51.3% to 15.4%. Reactive oxygen species (ROS) were measured using a commercially available ROS detection system. It was found that taxifolin could abolish the generation of ROS induced by H₂O₂ in a dose dependent manner. Therefore, taxifolin clearly reduced H₂O₂-induced cell viability decrease, cell apoptosis, and intracellular generation of ROS. Moreover, taxifolin inhibited the H₂O₂-induced caspase-3 activation. Activation of the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway was involved in the protective effect of taxifolin on the RPE cells. In addition, treatment with taxifolin activated the Nrf2-ARE pathway by inducing Nrf2 nuclear localization. Consequently, Phase II enzymes NQO1, HO-1, GCLM, and GCLC mRNA and proteins were increased.

Conclusions : Taxifolin protects retinal pigment epithelium cells against oxidative stress-induced cell apoptosis and the potential mechanism is possibly related with the activation of the Nrf2 as well as the Phase II antioxidant enzyme system.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.