Inhibition of p38-MAPK impairs MDR1 expression and function of P-gp in SGC7901/VCR cells. SGC7901/VCR cells were treated with DMSO or SB202190 (10 μM). (A) Protein levels of P-gp were detected by Western-blot analysis. A representative example of an experiment that was repeated three times is shown. (B) SGC7901/VCR cells were treated with DMSO and SB202190. Expression of MDR1 mRNA was assessed by RT-PCR. β-actin mRNA levels were measured as positive internal controls. (C) The MDR1 mRNA expression levels were normalized to those of β-actin and are the means ± SD of at least three independent experiments. Significant differences are indicated by asterisks. *, P < 0.05. (D)Effects of SB202190 on Rh123 accumulation (left) and retention (right) in SGC7901 and SGC7901/VCR cells. (left) Cells treated with SB202190 (10 μM) or vehicle control (0.1% DMSO). Rh123 (1 μg/mL) was added, and the cells were incubated for 120 min. (right) Cells were incubated with Rh123 for 120 min, washed, and resuspended in medium with SB202190 (10 μM)or vehicle control (0.1% DMSO) for 120 min. Rh123 fluorescence was measured using FAC scan. Means ± SD from three independent experiments. *P < 0.05 vs SGC7901 cells. **P < 0.05 vs vehicle control.