Chimienti F, Jourdan E, Favier A, Seve M
Laboratoire de Biologie du Stress Oxydant, Université J. Fourier, La Tronche, France.
Free Radic Biol Med. 2001 Nov 15;31(10):1179-90. doi: 10.1016/s0891-5849(01)00701-8.
To analyze the effects of high concentrations of zinc ions on oxidative stress protection, we developed an original model of zinc-resistant HeLa cells (HZR), by using a 200 microM zinc sulfate-supplemented medium. Resistant cells specifically accumulate high zinc levels in intracellular vesicles. These resistant cells also exhibit high expression of metallothioneins (MT), mainly located in the cytoplasm. Exposure of HZR to Zn-depleted medium for 3 or 7 d decreases the intracellular zinc content, but only slightly reduces MT levels of resistant cells. No changes of the intracellular redox status were detected, but zinc resistance enhanced H2O2-mediated cytotoxicity. Conversely, zinc-depleted resistant cells were protected against H2O2-induced cell death. Basal- and oxidant-induced DNA damage was increased in zinc resistant cells. Moreover, measurement of DNA damage on zinc-depleted resistant cells suggests that cytoplasmic metal-free MT ensures an efficient protection against oxidative DNA damage, while Zn-MT does not. This newly developed Zn-resistant HeLa model demonstrates that high intracellular concentrations of zinc enhance oxidative DNA damage and subsequent cell death. Effective protection against oxidative damage is provided by metallothionein under nonsaturating zinc conditions. Thus, induction of MT by zinc may mediate the main cellular protective effect of zinc against oxidative injury.
为了分析高浓度锌离子对氧化应激保护的影响，我们通过使用添加了200微摩尔硫酸锌的培养基，建立了一种抗锌的HeLa细胞（HZR）原始模型。抗性细胞在细胞内囊泡中特异性地积累高锌水平。这些抗性细胞还表现出金属硫蛋白（MT）的高表达，主要位于细胞质中。将HZR暴露于缺锌培养基3天或7天会降低细胞内锌含量，但仅略微降低抗性细胞的MT水平。未检测到细胞内氧化还原状态的变化，但锌抗性增强了H2O2介导的细胞毒性。相反，缺锌的抗性细胞对H2O2诱导的细胞死亡具有保护作用。在抗锌细胞中，基础和氧化剂诱导的DNA损伤增加。此外，对缺锌抗性细胞的DNA损伤测量表明，细胞质中无金属的MT可有效保护细胞免受氧化性DNA损伤，而锌结合的MT则不能。这个新建立的抗锌HeLa模型表明，细胞内高浓度的锌会增强氧化性DNA损伤和随后的细胞死亡。在非饱和锌条件下，金属硫蛋白可有效保护细胞免受氧化损伤。因此，锌诱导MT可能介导了锌对氧化损伤的主要细胞保护作用。
