Figure 7. Effects of luteolin on the ERK phosphorylation and PKA activity.

PC12 cells were seeded on poly-L-lysine-coated 100 mm dishes in normal medium for 24 h and then shifted to low serum medium (1% HS and 0.5% FBS) for 24 h prior to exposure to indicated agents. (A) Cells were treated with luteolin (20 µM) for 0 min, 15 min, 30 min and 60 min. For inhibitor treatment, cells were treated with the inhibitors U0126 for 30 min prior to exposure to luteolin (20 µM) for 15 min and 30 min. Phospho-ERK1/2 (p-ERK1/2) and total ERK1/2 proteins were analyzed by Western blotting as described in Materials and Methods. The experiments were replicated at least three times and a representative blot was shown. (B) Cells were incubated with luteolin (20 µM) for indicated period and PKA activity was detected using ELISA kit as described in Materials and Methods. For inhibitor treatment, cells were treated with the inhibitors H-89 (10 µM) and SQ22536 (500 µM) for 30 min prior to exposure to luteolin (20 µM) for 15 min. Data represent the mean ± SD of three independent experiments. *p<0.05 and **p<0.01 represents significant differences compared with 0 min group. ##p<0.01 represents significant differences compared to the respective inhibitor-non-treated group.