Fig. 7.

Celastrol induces JNK-MAPK activation to stimulate Nrf2-HO-1 pathway. (A) Celastrol increases JNK phosphorylation. Ava5 cells were incubated with 0.5 μM of celastrol, and the cell lysate was collected at the indicated time points (0–120 min). The levels phosphorylated and total proteins of ERK1/2, JNK and P38 were analyzed by Western blotting with specific antibodies. Band intensity was quantified by densitometric scanning and presented as fold-values relative to the time point of 0 min (defined as 1) following normalization against the GAPDH protein level. (B) JNK inhibitor antagonizes the inductive effect of celastrol on HO-1 expression. Ava5 cells were incubated with 0.5 M of celastrol and a MAPK inhibitor, including ERK1/2 (PD98059), JNK (SP600125), or p38 (SB203580). After 3 days treatment, HO-1 RNA levels were analyzed by qRT-PCR. Error bars denote the mean ± SD of three independent experiments.