Figure 4. CP55,940 modulates phosphorylation of PI3K/Akt and ERK1/2. A: Representative western blot analysis shows that 1 μM CP55,940 enhanced H₂O₂-induced activation of p-PI3K/Akt and reduced activation of p-ERK1/2 in ARPE-19 cells. B: Protective effects of PI3K/Akt inhibitor (LY294002) on H₂O₂-induced decrease in cell viability measured by the MTT assay. ARPE-19 cells were pretreated with or without 20 μM LY294002 for 15 min in the presence or absence of 1 μM CP55,940 before exposure to 200 μM H₂O₂ for 24 h. Asterisk (*) represents the correlation significant at the p<0.05 level and suggest a significant increase in cell viability as compared to H₂O₂-treated group. Hash mark (#) represents the correlation significant at the p<0.05 level and suggest a significant decrease in cell viability as compared to CP55,940+H₂O₂-treated group. C: Protective effects of selective ERK1/2 inhibitor (U0126) on H₂O₂-induced decrease in cell viability measured by the MTT assay. ARPE-19 cells were pretreated with 20 μM U0126 for 15 min before exposure to 200 μM H₂O₂ for 24 h Asterisk (*) represents the correlation significant at the p<0.05 level and suggest a significant decrease in cell viability as compared to control group. Asteriks and hash mark (#) represents the correlation significant at the p<0.05 level and suggest a significant increase in cell viability as compared to H₂O₂-treated group. Data are expressed as mean±SEM of results in three separate experiments, each experiment performed in duplicate.