Figure 6. Mitogen-activated protein kinase (MAPK) were activated by H₂O₂ in ARPE-19 cells. A: Human RPE cells were exposed to 200 μM H₂O₂ for various time points (30, 60, 120 min) and cell lysates were prepared. The phosphorylated and total protein levels of p38 mitogen-activated protein kinase (p38MAPK), extracellular signal regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) were detected with specific antibodies, using western blot analysis as described in the Methods. β-actin served as the loading control. Figures were selected as representative data from three independent experiments. B: After 24-h exposure to H₂O₂, cell viability was measured with an MTT assay. Each value represents the mean±SEM of three independent experiments (n=3 experiments, *p<0.05).