Effects of triptolide and caspase inhibitors on DNA fragmentation in RSF. Cells were incubated with triptolide with/without caspase inhibitors for 24 h, after which fragmented DNA in the cytoplasm was measured by enzyme immunoassay and the fold induction of DNA fragmentation was calculated relative to the control value (untreated cells). Data are the mean ± S.D. for triplicate cultures and representative results from 3 independent experiments are shown. *, p < 0.05 versus cells treated with triptolide alone. Significance was evaluated by Student's t-test with a Bonferroni's correction in each caspase inhibitor study.