Wagner B A, Buettner G R, Burns C P
Department of Medicine, University of Iowa College of Medicine, Iowa City 52242.
Cancer Res. 1992 Nov 1;52(21):6045-51.
The ether lipid antineoplastic agents have no known interaction with DNA, but rather they appear to target membranes. The primary mechanism of action is unknown but effects on membrane biology are documented. We have studied the effect of two ether lipids on membrane lipids and examined the hypothesis that membrane peroxidative damage may be involved in their mechanism of action. With the use of cells having membranes enriched in polyunsaturated fatty acids of the omega-3 family of fatty acids, we have demonstrated that the prototypical ether lipid 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine and a thioether lipid analogue, 1-O-hexadecylmercapto-2-methoxymethyl-rac-glycero-3-phosphocholine , increase membrane lipid peroxidation and cytotoxicity in a time- and drug concentration-dependent manner. The oxidative cofactors Fe2+ and ascorbic acid were required. The pattern of cell death did not fully correspond to the peroxidation, since cofactors were required for peroxidation but not cytotoxicity. However, the rate of decrease in cell viability after exposure to the drug and cofactors corresponded to the peroxidation rate. In addition, when L1210 cells modified with the monounsaturated fatty acid oleic acid or unmodified cells were used, there was no ether lipid-enhanced peroxidation, and the cells were significantly less sensitive to the drug, with or without cofactors. The lipid-soluble antioxidant vitamin E inhibited 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine peroxidation and cytotoxicity in a concentration-dependent manner in the presence of cofactors but not consistently without them. Depletion of cellular glutathione content of L1210 cells using L-buthionine-(SR)-sulfoximine resulted in 40% augmentation of cofactor-facilitated cytotoxicity of 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine and a borderline effect on peroxidation. Another ether lipid, the thio compound 1-O-hexadecylmercapto-2-methoxymethyl-rac-glycero-3-phosphocholine , enhanced peroxidation in the presence of cofactors with kinetics corresponding to those of cytotoxicity. In the presence of ether lipid and cofactors the intensity of ascorbate free radical increased, consistent with oxidative stress. We conclude that the ether lipids stimulate membrane lipid peroxidation in a time- and drug concentration-dependent manner in the presence of oxidative cofactors. Even though peroxidation may not fully explain the cytotoxic effect of the ether lipid class of anticancer drugs, this observation provides further information on the nature of the membrane damage induced by the drugs. Since the ether lipids generate no known free radical intermediates directly, this suggests that membrane damage indirectly results in a process involving a peroxidative reaction.
醚脂类抗肿瘤药物与DNA之间尚无已知的相互作用，相反，它们似乎作用于细胞膜。其主要作用机制尚不清楚，但对膜生物学的影响已有文献记载。我们研究了两种醚脂对膜脂的作用，并检验了膜过氧化损伤可能参与其作用机制的假说。利用富含ω-3脂肪酸家族多不饱和脂肪酸的细胞膜的细胞，我们已证明典型的醚脂1-O-十八烷基-2-O-甲基-rac-甘油-3-磷酸胆碱和一种硫醚脂类似物1-O-十六烷基巯基-2-甲氧基甲基-rac-甘油-3-磷酸胆碱，以时间和药物浓度依赖性方式增加膜脂过氧化和细胞毒性。需要氧化辅因子Fe2+和抗坏血酸。细胞死亡模式与过氧化并不完全对应，因为过氧化需要辅因子，但细胞毒性不需要。然而，暴露于药物和辅因子后细胞活力的下降速率与过氧化速率相对应。此外，当使用用单不饱和脂肪酸油酸修饰的L1210细胞或未修饰的细胞时，不存在醚脂增强的过氧化，并且无论有无辅因子，细胞对药物的敏感性均显著降低。脂溶性抗氧化剂维生素E在有辅因子存在时以浓度依赖性方式抑制1-O-十八烷基-2-O-甲基-rac-甘油-3-磷酸胆碱的过氧化和细胞毒性，但在没有辅因子时并非始终如此。使用L-丁硫氨酸-(SR)-亚砜亚胺耗尽L1210细胞的细胞内谷胱甘肽含量导致1-O-十八烷基-2-O-甲基-rac-甘油-3-磷酸胆碱的辅因子促进的细胞毒性增加40%，对过氧化有临界影响。另一种醚脂，硫化合物1-O-十六烷基巯基-2-甲氧基甲基-rac-甘油-3-磷酸胆碱，在有辅因子存在时增强过氧化，其动力学与细胞毒性的动力学相对应。在有醚脂和辅因子存在时，抗坏血酸自由基的强度增加，与氧化应激一致。我们得出结论，在氧化辅因子存在下，醚脂以时间和药物浓度依赖性方式刺激膜脂过氧化。尽管过氧化可能无法完全解释醚脂类抗癌药物的细胞毒性作用，但这一观察结果为药物诱导的膜损伤的性质提供了进一步的信息。由于醚脂不会直接产生已知的自由基中间体，这表明膜损伤间接导致了一个涉及过氧化反应的过程。
