Fig. 2. Apoptosis and expression of vascular endothelial growth factor (VEGF)-A and B-cell leukemia/lymphoma (Bcl)-2 after treatment of retinal pigment epithelial (RPE) cells with H₂O₂. (A) Effects of H₂O₂ on apoptosis of RPE cells. The RPE cells were treated with various concentrations of H₂O₂ for 16 hours. Cell apoptosis was 3.26% for RPE at 100 µM H₂O₂ compared to 3.82% for the control, but the difference was not significant. Cell apoptosis decreased at 200 µM H₂O₂ (2.65%) but increased at 300 and 400 µM of H₂O₂ (10.42%, 17.99%). Means were significantly different than the control (p < 0.05). Each bar shows the mean ± standard deviation of results of three or more independent experiments. The asterisk indicates a statistically significant difference within the group (^*increased, ^**decreased, p < 0.05). (B) Expression of VEGF-A after exposure to H₂O₂. VEGF-A excretion into the medium was measured using enzyme-linked immunosorbent assay. VEGF-A expression increased after addition of 50, 100, or 200 µM H₂O₂ to RPE cells. However, after being treated with 300 and 400 µM H₂O₂, VEGF-A expression decreased. Data are expressed as the mean ± standard deviation of the results of three or more independent experiments. Means were statistically significant compared to the control at all concentrations of H₂O₂ (p < 0.05). (C) Expression of Bcl-2 mRNA after exposure to H₂O₂. Cells were cultured with various concentrations of H₂O₂ for 16 hours (0, 100, 200, and 300 µM). Expression of Bcl-2 mRNA decreased as oxidative stress increased. Data are expressed as the mean ± standard deviation of the results of three or more independent experiments. Means were statistically significant compared with the control at all concentrations of H₂O₂ (p < 0.05).