Fig. 4

Activation of SAPK/JNK pathway-mediated inhibition of p65 expression contributed to the PPI-decreased protein expression of DNMT1. a PC9 and A549 cells were exposed to increased concentration of PPI for 24 h, followed by measuring the protein expression of p65 and p50 by Western blot. The bar graphs represent the mean ± SD of p65/GAPDH of three independent experiments. b PC9 and A549 cells were treated with SP600125 (20 μM) for 2 h before exposure of the cells to PPI (1.6 μM) for an additional 24 h. Afterwards, the expression of phosphorylation of SAPK/JNK and p65 protein were detected by Western blot. c PC9 and A549 cells were transfected with control and p65 overexpression vector for 24 h before exposing the cells to PPI for an additional 24 h. Afterwards, p65 and DNMT1 protein expressions were determined using Western blot. Values in bar graphs were given as the mean ± SD from three independent experiments performed in triplicate. *Indicates significant difference as compared to the untreated control group (P < 0.05). **Indicates significant difference from PPI treated alone (P < 0.05)