Effects of luteolin on Nrf2 target gene expression.

<p>(<b>A and D</b>) PC12 cells were cultured in serum-free medium and then incubated with 6-OHDA (100 µM) for 8 and 12 h. Levels of HO-1 and Nrf2 mRNA were measured by RT-Q-PCR and normalized to β-actin as described in the Materials and Methods. (<b>B, C, and E</b>) PC12 cells were treated with luteolin (10 or 20 µM) or tiron (0.5 and 5 mM) for 30 min before 6-OHDA (100 µM) insult for 8 h. RNA was then prepared for RT-Q-PCR analysis. Data represent the mean ± SD of three independent experiments. *, <i>p</i><0.05; **, <i>p</i><0.01 represent significant differences compared with the vehicle control (without 6-OHDA). ##, <i>p</i><0.01 represents significant differences compared with the 6-OHDA-treated vehicle. (<b>F and G</b>) Contribution of Nrf2 activation to HO-1 expression in response to 6-OHDA. PC12 cells were transfected transiently with nonspecific (scrambled) siRNA or with Nrf2-specific siRNA before 6-OHDA (100 µM) treatment. Effects of Nrf2 siRNA on the expression of Nrf2 and HO-1 after 6-OHDA treatment for 8 h were measured by RT-Q-PCR. Data represent the mean ± SD of three independent experiments. **<i>p</i><0.01 represents significant differences compared with the vehicle control (without 6-OHDA). #, p<0.05; ##, <i>p</i><0.01 represent significant differences compared with the scrambled siRNA-transfected group.