Protective effect of canolol from oxidative stress-induced cell damage in ARPE-19 cells via an ERK mediated antioxidative pathway

Purpose: Oxidative stress damage to retinal pigment epithelial (RPE) cells is thought to play a critical role in the pathogenesis of age-related macular degeneration (AMD). This study was conducted to investigate the protective effect of canolol against oxidative stress-induced cell death in ARPE-19 cells and its underlying mechanism. Methods: ARPE-19 cells, a human retinal pigment epithelial cell line, were subjected to oxidative stress with 150 μM t-butyl hydroxide (t-BH) in the presence/absence of canolol in different concentrations. Cell viabilities were monitored by a 3-(4, 5-dimethylthiazol-2-yl)-2, 5 diphenyl tetrazolium bromide (MTT) assay. The apoptosis was measured by flow cy tometry using Annexin V-FITC and PI staining and intracellular reactive oxygen species (ROS) levels were measured by a fluorescence spectrophotometer. Gene expression of NF-E2-related factor ( Nrf-2), heme oxygenase-1 (HO-1), catalase and glutathione S-transferase-pi (GST-pi) were measured by a reverse transcription polymerase chain reaction (RT–PCR) assay. Activation of the extracellular signal regulated kinase (ERK) protein was evaluated by western blot analysis. Results: Canolol showed relatively high safety for ARPE-19 cells and recovered the cell death caused by t-BH dosedependently at a concentration of 50–200 μM. Canolol also reduced t-BH-induced intracellular ROS generation and thus protected ARPE-19 cells from cell apoptosis. HO-1, catalase, GST-pi, and Nrf-2 were elevated in ARPE-19 cells after treatment with different concentrations of canolol for 24 h. Finally, canolol was found to activate extracellular signal regulated kinase (ERK) phosphorylation in ARPE-19 cells under the condition, with or without t-BH. Conclusions: Canolol protected ARPE-19 cells from t-BH-induced oxidative damage and the protective mechanism was associated, at least partly, with the upregulation (activation) of antioxidative enzymes, probably through an ERK mediated pathway. This suggests that canolol offers a remarkable protective effect against oxidative damage of RPE cells and may have a therapeutic effect on AMD and other oxidative stress-related retinal diseases.