Wispriyono B, Matsuoka M, Igisu H, Matsuno K
Department of Environmental Toxicology, University of Occupational and Environmental Health, Kitakyushu 807-8555, Japan.
J Pharmacol Exp Ther. 1998 Oct;287(1):344-51.
N-acetylcysteine (NAC) has been known not only to stimulate synthesis of glutathione but also to affect the gene regulation. In our study, effects of NAC on the cytotoxicity of cadmium (Cd) were examined in LLC-PK1 cells. Preincubation and subsequent incubation with 1 mM NAC almost completely suppressed Cd-induced cellular damage evaluated either by trypan blue exclusion or lactate dehydrogenase leakage. This almost complete protection required the presence of NAC during Cd exposure. Treatment with 1 mM NAC increased the intracellular glutathione level approximately 2-fold. Inhibition of this increase by buthionine sulfoximine did not abolish the protection by NAC. One mM NAC also suppressed Cd-induced increase of c-Fos protein although NAC alone did not change the protein content. The inhibition of transcriptions by actinomycin D did not affect the protection by NAC. Thus, NAC-induced protection appeared to be independent of glutathione level or the transcriptional activation of genes including c-fos. However, treatment with NAC markedly lowered the uptake of Cd into cells although it did not affect the efflux clearly. Addition of NAC during the exposure to Cd suppressed Cd-induced cellular damage but the suppression decreased when the duration of the exposure without NAC increased. These results suggest that NAC-induced protection against Cd cytotoxicity is mainly due to the lowered uptake of Cd into the cells.
N-乙酰半胱氨酸（NAC）不仅已知能刺激谷胱甘肽的合成，还能影响基因调控。在我们的研究中，检测了NAC对LLC-PK1细胞中镉（Cd）细胞毒性的影响。用1 mM NAC预孵育并随后孵育几乎完全抑制了通过台盼蓝排斥法或乳酸脱氢酶泄漏评估的Cd诱导的细胞损伤。这种几乎完全的保护作用在Cd暴露期间需要NAC的存在。用1 mM NAC处理使细胞内谷胱甘肽水平增加了约2倍。丁硫氨酸亚砜胺对这种增加的抑制并没有消除NAC的保护作用。1 mM NAC也抑制了Cd诱导的c-Fos蛋白增加，尽管单独的NAC并没有改变蛋白含量。放线菌素D对转录的抑制并没有影响NAC的保护作用。因此，NAC诱导的保护作用似乎独立于谷胱甘肽水平或包括c-fos在内的基因的转录激活。然而，用NAC处理显著降低了细胞对Cd的摄取，尽管它对流出没有明显影响。在暴露于Cd期间添加NAC抑制了Cd诱导的细胞损伤，但当无NAC暴露的持续时间增加时，这种抑制作用减弱。这些结果表明，NAC诱导的对Cd细胞毒性的保护作用主要是由于细胞对Cd的摄取降低。
