Figure 2 : The effect of luteolin on FasL-initiated caspase cascade. (A) HepG2 cells were treated with 20μM, 30μM, 40μM, 50μM luteolin for 16 h , and using the solvent of luteolin (DMSO) as negative control. Cells were collected and analysed by western blot using the specific anti-PARP, caspase 8 and caspase 3 antibodies. (B) HepG2 cells were pretreated with 30μM luteolin for 2h, and then treated with viriouse concentrations of FasL for another 22h. Cells lysates were detected by immunoblot analysis using indicated antibodies. (C) HepG2 cells were pretreated , post-treated with 30μM luteolin for 2h, and pari-treated luteolin and FasL (60ng/ml) for 24h. Cells lysates were detected by immunoblot analysis using indicated antibodies. (D) HepG2 cells were pretreated with z-VAD-fmk (20μM) for 30 minutes, then cells were treated with luteolin (30μM × 24h) and FasL (60ng/ml × 22h). Cells lysates were collected for detection of caspase 3 and caspase 8 cleavage by immunoblot analysis. (E) HepG 2 cells were pretreated, post-treated with 30μM luteolin for 2h, and pari-treated luteolin and FasL (60ng/ml) for 24h. Cells lysates were detected by MultiCaspase apoptosis assay.