Fig. 3.

Cytoprotective HO-1 expression by curcumin through MAPK-dependent Nrf2 activation in HepG2 cells. (A) Structure of curcumin. (B, C, D and E) Cells were treated with indicated concentrations of curcumin for indicated time periods in the absence or presence of inhibitors for MAPK pathways, and Western blotting analysis for HO-1 expression and phosphorylation of ERK, p38 MAPK and JNK and fluorescence microscopic examination for Nrf2-nuclear translocation by using green-fluorescence dye conjugated to Nrf2 antibody were performed as previously described [40]. (F) Cells were pre-incubated for 12 h with 10 µM of curcumin, and exposed for 6 h to 30 µM of ter-butylhydroperoxide in the absence or presence of 20 µM of zinc protoporphyrin IX.