Li W, Zhao Y, Chou I N
Department of Microbiology, Boston University School of Medicine, MA 02118.
Toxicology. 1993 Jan 29;77(1-2):65-79. doi: 10.1016/0300-483x(93)90138-i.
To understand the mechanisms of Cd2+ and Ni2+ cytotoxicity, we have studied the effects of these two metal ions on the organization of cytoskeletal elements, microtubules (MT) and microfilaments (MF), cytoskeletal protein sulfhydryls and cellular glutathione (GSH) in cultured 3T3 cells. At a metal ion dose that caused 95% inhibition of DNA synthesis, Cd2+ (10 microM, 16 h exposure) induced MT depolymerization whereas Ni2+ (2 mM, 20 h exposure) elicited MT aggregation and bundling. Under these conditions, Cd2+ and Ni2+ also caused MF aggregation and redistribution. Furthermore, exposure of cells to Cd2+ resulted in a dose-dependent increase in cytoskeletal protein sulfhydryls and cellular GSH levels. In contrast, treatment of cells with Ni2+ resulted in a dose-dependent decrease in cytoskeletal protein sulfhydryls as well as cellular GSH content. Time course studies showed that cells exposed to 10 microM Cd2+ exhibited a biphasic response in regulating their cytoskeletal protein sulfhydryls and cellular GSH, e.g. an initial decrease followed by a steady recovery and overshooting upon prolonged incubation. However, restoration of cytoskeletal protein sulfhydryls occurred approximately 2 h after commencement of cellular GSH recovery in Cd(2+)-treated cells. These results suggest that cellular GSH may play an important role in regulating cytoskeletal protein sulfhydryls. On the other hand, decrease of cellular GSH induced by Ni2+ might facilitate oxidation of cytoskeletal protein sulfhydryls and formation of disulfide bonds between individual MT polymers which would favor MT aggregation in Ni(2+)-exposed cells. In addition, we also demonstrated that elevation of cellular GSH in Cd(2+)-treated cells probably resulted from new GSH synthesis.
为了解镉离子（Cd2+）和镍离子（Ni2+）的细胞毒性机制，我们研究了这两种金属离子对培养的3T3细胞中细胞骨架成分、微管（MT）和微丝（MF）的组织、细胞骨架蛋白巯基以及细胞内谷胱甘肽（GSH）的影响。在导致DNA合成95%抑制的金属离子剂量下，Cd2+（10微摩尔，暴露16小时）诱导微管解聚，而Ni2+（2毫摩尔，暴露20小时）引起微管聚集和成束。在这些条件下，Cd2+和Ni2+还导致微丝聚集和重新分布。此外，细胞暴露于Cd2+会导致细胞骨架蛋白巯基和细胞内GSH水平呈剂量依赖性增加。相反，用Ni2+处理细胞会导致细胞骨架蛋白巯基以及细胞内GSH含量呈剂量依赖性降低。时间进程研究表明，暴露于10微摩尔Cd2+的细胞在调节其细胞骨架蛋白巯基和细胞内GSH方面表现出双相反应，例如最初下降，随后稳定恢复，并在长时间孵育后出现超调。然而，在Cd2+处理的细胞中，细胞骨架蛋白巯基的恢复大约在细胞内GSH恢复开始后2小时发生。这些结果表明，细胞内GSH可能在调节细胞骨架蛋白巯基方面发挥重要作用。另一方面，Ni2+诱导的细胞内GSH减少可能促进细胞骨架蛋白巯基的氧化以及单个微管聚合物之间二硫键的形成，这将有利于Ni2+暴露细胞中的微管聚集。此外，我们还证明，Cd2+处理细胞中细胞内GSH的升高可能是由于新的GSH合成。
