Liu Tsan-Zon, Cheng Jiin-Tsuey, Yiin Shuenn-Jiun, Chen Chung-Yi, Chen Ching-Hsein, Wu Mei-Jem, Chern Chi-Liang
Center for Gerontological Research and Graduate Institute of Medical Biotechnology, Chang-Gang University, Kwei-Shan, Taoyuan, Taiwan, ROC.
Food Chem Toxicol. 2008 Jan;46(1):321-7. doi: 10.1016/j.fct.2007.08.014. Epub 2007 Aug 22.
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.
异 obtusilactone A 是从土肉桂叶中分离出的一种成分，我们之前已证明它是一种能够诱导 Hep G2 细胞发生凋亡性细胞死亡的物质。为了阐明半胱天冬酶是否是引发这一凋亡过程的唯一介质，我们使用了一种广泛的半胱天冬酶抑制剂 Z-VAD.fmk 来探究这种可能性。有趣的是，尽管已证明 Z-VAD.fmk 能够完全抑制异 obtusilactone A 诱导的寡核小体 DNA 片段化，但它只能阻止有限数量的细胞变得易于凋亡。这些数据表明可能涉及其他一些机制。因此，我们研究了凋亡诱导因子（AIF），一种介导不依赖半胱天冬酶的凋亡的介质，在异 obtusilactone A 诱导的凋亡过程中的作用。这些发现表明异 obtusilactone A 可引发 AIF 的核转位，这伴随着大规模 DNA 片段化的发生。通过 AIF-siRNA 转染降低 AIF 表达可抑制大规模 DNA 片段化。有趣的是，AIF-siRNA 抑制 AIF 表达并不能阻止异 obtusilactone A 诱导的寡核小体 DNA 片段化。同样，当细胞同时用 AIF-siRNA 和 Z-VAD.fmk 进行预处理时，大规模 DNA 和寡核小体 DNA 片段化几乎都可以被阻止。综上所述，这些发现表明异 obtusilactone A 诱导的凋亡性细胞死亡是通过半胱天冬酶依赖性和非依赖性途径介导的。
