Fig. 2. Astaxanthin decreased XPC expression via MKK3/6-p38 MAPK activation in A549 and H1975 cells. (A and B) SB203580 (5 or 10 μM) was added to A549 or H1975 cells for 1 h before astaxanthin (5 μM) treatment for 24 h. The results (mean ± SEM) were from four independent experiments. **p < 0.01 using Student's t-test for comparison between the cells treated with astaxanthin–DMSO or a combination of astaxanthin–SB203580. (C and D) Cells were transfected with siRNA duplexes (200 nM) specific to p38 MAPK or scrambled (control) in complete medium for 24 h prior to treatment with astaxanthin (5 μM) in complete medium for 24 h. The results (mean ± SEM) were from 3 independent experiments. **p < 0.01, using Student's t-test for comparison between cells treated with astaxanthin in si-p38 MAPK RNA or si-scrambled RNA-transfected cells. (E and F) A549 or H1975 cells were transfected with MKK6E expression vector for 24 h. The results (mean ± SEM) were from 3 independent experiments. **p < 0.01 using Student's t-test for comparison of cells transfected with pcDNA3 and those transfected with MKK6E vector. After treatment, the cell extracts were examined via real-time PCR (A, C, E) and western blot (B, D, F) for determination of XPC mRNA and protein levels, respectively.