Figure 9.

Inhibition of procaspase 9 function also blocks the potentiation of bile acid-induced apoptosis by MAPK inhibition. DCA increases apoptosis in hepatocytes, which is potentiated by MAPK inhibition and blocked by expression of either Bcl-2, Bcl-_XL, dominant negative procaspase 9 or the peptide inhibitor of caspase 9, LEHD-fmk. Cells were infected with poly-l-lysine–conjugated adenoviruses to express either dominant negative procaspase 9 or a null virus. Cells were infected with recombinant adenoviruses to express either Bcl-2, Bcl-_XL or a null virus. Twenty-four hours after infection, cells were pretreated with either vehicle control or LEHD-fmk (40 μM) and cells were subsequently treated with DCA (50 μM) and either vehicle control or PD98059 (50 μM), and the percentage of apoptosis was determined 360 min after addition of H-33342. Data are the means of three experiments ± SEM. No difference in the apoptotic profile was observed comparing CMV poly-l-lysine virus infected to CMV recombinant virus-infected cells. (Inset) LEHD prevents cleavage of procaspase 3 but not procaspase 8 2 h after exposure. Cells were pretreated with either vehicle or LEHD-fmk (20 μM) followed 30 min afterward by DCA (50 μM) and either vehicle control or PD98059 (50 μM), and the expression of p20-cleaved caspase 8 and p17-cleaved caspase 3 determined 120 min after addition. Data are representative of two experiments.