Figure 4

Pterostilbene activates caspase via ERK1/2 and p38MAPK signaling pathways.

(A) After 24 h of drug exposure, cells were stained with JC-1 fluorescent dye, and mitochondrial membrane potential was detected by flow cytometry. (B) SUDHL-4, NU-DUL-1, DB and OCI-LY8 cells were treated with pterostilbene (60 μM) for 24 h and stained with DCFH-DA; then the level of ROS was detected by flow cytometry and data are presented as the mean fluorescence intensity. Values are presented as the means ± SEM of three independent experiments. *p < 0.05, compared to the vehicle control group. (C) After pterostilbene treatment for 48 h, the expression of cleaved caspase-3, cleaved caspase-8, caspase-9, cleaved caspase substrate, Bcl-2, Bax and PARP were monitored by western blotting. (D) SUDHL-4 and NU-DUL-1 cells were pretreated with or without 50 μM of pan-caspase inhibitor Z-VAD-FMK for 1 h and then exposed to 60 μM pterostilbene for 24 h. *p < 0.05. (E) SUDHL-4 and NU-DUL-1 cells were treated with pterostilbene (20, 40 or 60 μM) for 48 h, then the expression of phospho(p)-ERK1/2, ERK1/2, p-p38MAPK and p38MAPK were monitored by western blotting. Quantitative results of p-ERK1/2 and p-p38MAPK protein levels, which were adjusted with the total ERK1/2 and p38MAPK protein levels and expressed as multiples of induction beyond each respective control. Values represent the means ± SEM of three independent experiments. *p < 0.05, compared to the vehicle control group.