LC/BRY-treated cells exhibit sustained MAPK activation and MEK inhibitors oppose mitochondrial damage and apoptosis in cells treated with these agents.

(A) U937 cells were exposed to either BRY or LC/BRY for the indicated intervals and analyzed for the presence of phosphorylated ERK expression as described in “Materials and methods.” (B,C) Cells were pretreated with the designated MEK inhibitors (PD98059 [●], U0126 [○], SL327 [▪]) for 1 hour before the addition of LC/BRY. Following a 24-hour exposure, the cells were either (B) assayed for loss of mitochondrial membrane permeability by determining the percentage of cells exhibiting low levels of DiOC₆; values are expressed as the percentage inhibition of LC/BRY-mediated mitochondrial damage compared to cells that were not exposed to MEK inhibitors or (C) the percentage of apoptotic cells was determined by morphologic analysis as above. In each case, values represent the means for triplicate experiments (± SEM).