Curcumin pretreatment activates Nrf2/ARE signaling. (A) Effects of curcumin treatment alone at the indicated concentrations for 12 h on total Nrf2 levels. In the following experiments, primary rat astrocytes were treated with MeHg (5 μM for 6 h) in the absence or presence of curcumin pretreatment (2, 5, 10 or 20 μM for 12 h). (B, C) Effects of curcumin pretreatment on the expression level of total Nrf2 and Keap1. (D, E) Effects of curcumin pretreatment on the expression level of nuclear and cytoplasmic Nrf2. Histone H3 and β-actin were used as the internal control of the nucleus and cytoplasm, respectively. (F) Representative images of Nrf2 localiztion by immunofluorescence staining. Green fluorescence (FITC) indicates Nrf2 and blue (DAPI) indicates the nucleus. Scale bar: 100 μm. (G–I) Effects of curcumin pretreatment on the protein expression level of the Nrf2 target genes, HO-1 and NQO1. Data are expressed as mean ± SD of at least three independent experiments. *P < 0.05 vs. MeHg group. Cur, curcumin; MeHg, methylmercury.