Isoobtusilactone A induces both caspase-dependent and -independent apoptosis in Hep G2 cells.
Isoobtusilactone A, a constituent isolated from the leaves of Cinnamomum kotoense, has been demonstrated by us earlier to be an agent capable of inducing apoptotic cell death of Hep G2 cells. In order to clarify if caspases alone were the sole mediator for eliciting this apoptotic process, a broad caspases inhibitor, Z-VAD.fmk, was utilized to explore this possibility. Interestingly, although Z-VAD.fmk was demonstrated to be capable of completely inhibiting isoobtusilactone A-induced oligonucleosomal DNA fragmentation, yet it could only prevent limited amount of cells from becoming apoptosis-prone. These data implied that some other mechanism(s) might be involved. Thus, the involvement of apoptosis-inducing factor (AIF), a mediator arbitrating caspase-independent apoptosis, in isoobtusilactone A-induced apoptotic process was examined. These findings indicated that isoobtusilactone A could elicit the nuclear translocation of AIF that accompanied the occurrence of large-scale DNA fragmentation. Reduction of AIF expression by AIF-siRNA transfection suppressed large-scale DNA fragmentation. Interestingly, inhibition of AIF expression by AIF-siRNA could not prevent isoobtusilactone A-induced oligonucleosomal DNA fragmentation. In the same vein, when the cells were simultaneously combined pretreatment with AIF-siRNA and Z-VAD.fmk, both large-scale DNA and oligonucleosomal DNA fragmentations could nearly be prevented. Taken together, these findings suggested that isoobtusilactone A-induced apoptotic cell death was mediated via both caspase-dependent and -independent pathways.
Liu
Tsan-Zon
TZ
Center for Gerontological Research and Graduate Institute of Medical Biotechnology, Chang-Gang University, Kwei-Shan, Taoyuan, Taiwan, ROC.
Cheng
Jiin-Tsuey
JT
Yiin
Shuenn-Jiun
SJ
Chen
Chung-Yi
CY
Chen
Ching-Hsein
CH
Wu
Mei-Jem
MJ
Chern
Chi-Liang
CL
D000473:Alkanes / Q000494:pharmacology*; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D051033:Apoptosis Inducing Factor / Q000378:metabolism; D015153:Blotting, Western; D020169:Caspases / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D027424:Cinnamomum / Q000737:chemistry*; D053938:DNA Fragmentation / Q000187:drug effects; D004587:Electrophoresis, Agar Gel; D016521:Electrophoresis, Gel, Pulsed-Field; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007202:Indicators and Reagents; D007783:Lactones / Q000494:pharmacology*; D008856:Microscopy, Fluorescence; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects
D000473:Alkanes; D000590:Amino Acid Chloromethyl Ketones; D051033:Apoptosis Inducing Factor; D007202:Indicators and Reagents; D007783:Lactones; D034741:RNA, Small Interfering; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C521340:isoobtusilactone A; D020169:Caspases