Studies On The Mechanism Of Dracorhodin Perchlorate And Magnolol-induced Tumor Cell Apoptosis

This dissertation reports mechanisms of dracorhodin perchlorate-induced cell death in human cervical carcinoma HeLa, human melanoma A375-S2, and human premyelocytic leukemia HL-60 cells and mechanism of magnolol-induced HeLa cell death.The studies demonstrate that dracorhodin perchlorate inhibited the proliferation of A375-S2, HeLa, HL-60, human breast cancer MCF-7 and human histocytic lymphoma U937 cells in a dose- and time-dependent manner. MTT assay, photomicroscopical observation and DNA agarose gel electrophoresis showed that dracorhodin perchlorate induced cell apoptosis in HeLa, A375-S2 and HL-60 cells.In dracorhodin perchlorate-treated HeLa cells caspase-3, 8, 9 activities increased followed by the degradation of caspase-3 substrates, ICAD (inhibitor of caspase dependent DNase) and PARP (poly-(ADP-ribose) polymerase). Caspase 1 inhibitor, Ac-YVAD-cmk, and a caspase 10 inhibitor z-AEVD-fmk also reduced dracorhodin perchlorate-induced HeLa cell death. Fas expression was up-regulated and the Fas agonistic antibody CH-11 has a synergistic effect with dracorhodin perchlorate. The drug decreased the expression of anti-apoptotic mitochondrial protein, Bcl-X_L, but not Bcl-2, increased the expression of pro-apoptotic protein, Bax. It also caused the lost of mitochondrial membrane potential. Pretreatment with Ac-YVAD-cmk reduced DNA fragmentation, attenuated degradation of procaspase-3 and its substrates, ICAD and PARP, however, it did not affect the activation of caspase-8; suggesting caspase-1 may play its role upstream to caspase-3 in dracorhodin perchlorate induced HeLa cell apoptosis. Dracorhodin perchlorate increased the expression of p53 and p21^WAF1 proteins. The cell death was partially reduced by MEK inhibitor (PD98059), JNK MAPK inhibitor (SP600125) and p38 MAPK inhibitor (SB 203580); the drug induced sustained phosphorylation of JNK, phosphorylation of ERK at 3～6 h, and phosphorylation of p38 at 24～36 h, indicating different roles of these MAPK at different stages of cell death.In dracorhodin perchlorate-treated A375-S2 cells, caspase-3, -8, -9, and -10...