Wagenknecht B, Roth W, Gulbins E, Wolburg H, Weller M
Laboratory of Molecular Neuro-Oncology, Department of Neurology, University of Tübingen, Tübingen, Germany.
Cell Death Differ. 2001 Jun;8(6):595-602. doi: 10.1038/sj.cdd.4400848.
Most human malignant glioma cell lines are susceptible to CD95 ligand (CD95L)-induced apoptosis. Here, we report that glioma cells are also susceptible to the cytotoxic effects of exogenous C2-ceramide. This form of cell death exhibits some morphological features of apoptosis as assessed by electron microscopy, but is unaffected by the broad spectrum caspase inhibitor, zVAD-fmk. Further, CD95L-induced apoptosis is synergistically enhanced by coexposure of the glioma cells to CD95L and C2-ceramide. CD95L-induced caspase 3-like activity, cytochrome c release and cleavage of caspases 3, 8, 9 and poly(ADP-ribose)polymerase (PARP) increase substantially after cotreatment with CD95L and C2-ceramide compared with CD95L treatment alone. None of these events occur in response to cytotoxic concentrations of C2-ceramide alone. C2-ceramide does not alter CD95 expression. Gene transfer-mediated enhancement of CD95 expression results not only in increased susceptibility to CD95L, but also in increased sensitivity to C2-ceramide. We conclude that (i) synergistic induction of apoptosis by C2-ceramide and CD95L depend on a cross-talk between the two signal transduction pathways and that (ii) C2-ceramide, independently of its sensitizing effects on CD95-dependent caspase activation, is also capable of triggering an apoptotic signaling cascade that is unaffected by zVAD-fmk-mediated caspase inhibition, but promoted by high levels of CD95 expression.
大多数人类恶性胶质瘤细胞系对CD95配体（CD95L）诱导的凋亡敏感。在此，我们报告胶质瘤细胞对外源性C2-神经酰胺的细胞毒性作用也敏感。通过电子显微镜评估，这种细胞死亡形式表现出一些凋亡的形态学特征，但不受广谱半胱天冬酶抑制剂zVAD-fmk的影响。此外，胶质瘤细胞同时暴露于CD95L和C2-神经酰胺时，CD95L诱导的凋亡会协同增强。与单独用CD95L处理相比，CD95L与C2-神经酰胺联合处理后，CD95L诱导的半胱天冬酶3样活性、细胞色素c释放以及半胱天冬酶3、8、9和聚（ADP-核糖）聚合酶（PARP）的裂解显著增加。单独使用细胞毒性浓度的C2-神经酰胺时，这些事件均未发生。C2-神经酰胺不改变CD95的表达。基因转移介导的CD95表达增强不仅导致对CD95L的敏感性增加，还导致对C2-神经酰胺的敏感性增加。我们得出结论：（i）C2-神经酰胺和CD95L协同诱导凋亡依赖于两条信号转导途径之间的相互作用；（ii）C2-神经酰胺独立于其对CD95依赖性半胱天冬酶激活的致敏作用，也能够触发一个不受zVAD-fmk介导的半胱天冬酶抑制影响，但受高水平CD95表达促进的凋亡信号级联反应。
