Figure 5. Galangin-induced TRAIL-mediate apoptosis is associated with up-regulation of proteasome activity.

(a) Caki cells were treated with 30 μM galangin for 24 h. After lysis of cells, the proteasome activity was determined as described in the Materials and Methods. As a positive control, 1 μM MG132 was used. (b) Caki cells were treated with indicated concentrations of galangin for 24 h. Protein levels of PSMA5 and PSMD4 were determined by western blotting. Actin was used as a loading control. (cropped, full-length blots are in Supplementary Fig. S8). (c) Caki cells were treated with 30 μM galangin for the indicated time periods and loaded with a H₂DCF-DA fluorescent dye. H₂DCF-DA fluorescence intensity was detected by flow cytometry. P.C. (Positive control; 20 μM shogaol) (d) Caki cells were pretreated with 5 mM NAC and 2 mM GEE for 30 min, and then stimulated with 30 μM galangin plus 50 ng/ml TRAIL for 24 h. Apoptosis was analyzed as the sub G1 population by FACS analysis. The protein expression levels of PARP and actin were determined by Western blotting. The level of actin was used as a loading control. (cropped, full-length blots are in Supplementary Fig. S8).