Kang Y J
Department of Pharmacology and Toxicology, University of North Dakota School of Medicine, Grand Forks 58202.
Toxicology. 1994 Mar 11;88(1-3):177-89. doi: 10.1016/0300-483x(94)90119-8.
Buthionine sulfoximine (BSO) inhibits proliferation of human lung carcinoma A549 cells in a manner that does not correlate with intracellular glutathione (GSH) depletion, nor does it reflect overt toxic effects of BSO. However, BSO inhibits uptake by A549 cells of cystine, which is an essential amino acid for cell growth in culture. Thus, it is hypothesized that inhibition of cellular cystine uptake is, or is partially, responsible for the antiproliferative effect of BSO. It has been shown that the gamma-glutamyl amino acid transport system plays a role in cystine transport across cell membranes. This transport system requires extracellular GSH for its operation. BSO, by inhibiting intracellular GSH synthesis, would reduce GSH export and decrease extracellular GSH levels. Therefore, the present study was undertaken to examine the effect of exogenously added GSH on BSO inhibition of cellular cystine uptake and its relationship to the antagonistic effect of GSH on BSO antiproliferation. A549 cells were treated with 10 mM BSO and exogenous GSH was added to these BSO-treated cultures. Effects of exogenous GSH on BSO antiproliferation and cellular GSH depletion were determined simultaneously as a function of time. The effect of GSH on BSO inhibition of cystine accumulation was measured using [35S]cystine. The results obtained demonstrate that exogenously added GSH partially overcame BSO antiproliferation. The GSH antagonistic effect did not correlate with repletion of intracellular GSH, but it did correlate with recovery of BSO-inhibited cystine accumulation. Exogenous GSH also enhanced proliferation of non-BSO treated cells at concentrations below 1.0 mM. The results of this study suggest that BSO inhibition of cystine uptake may represent one mechanism by which BSO exerts its antiproliferative effect. The antagonistic effect of exogenous GSH on BSO antiproliferation may result from recovery of BSO-inhibited cystine uptake, although other mechanisms responsible for the GSH antagonistic effect may also exist.
丁硫氨酸亚砜亚胺（BSO）抑制人肺癌A549细胞增殖的方式与细胞内谷胱甘肽（GSH）耗竭无关，也不反映BSO的明显毒性作用。然而，BSO抑制A549细胞对胱氨酸的摄取，而胱氨酸是培养中细胞生长所必需的氨基酸。因此，有人推测细胞胱氨酸摄取的抑制是或部分是BSO抗增殖作用的原因。已经表明，γ-谷氨酰氨基酸转运系统在胱氨酸跨细胞膜转运中起作用。该转运系统需要细胞外GSH来运作。BSO通过抑制细胞内GSH合成，会减少GSH的输出并降低细胞外GSH水平。因此，本研究旨在探讨外源性添加GSH对BSO抑制细胞胱氨酸摄取的影响及其与GSH对BSO抗增殖作用的拮抗作用的关系。用10 mM BSO处理A549细胞，并将外源性GSH添加到这些经BSO处理的培养物中。同时测定外源性GSH对BSO抗增殖作用和细胞GSH耗竭的影响随时间的变化。使用[35S]胱氨酸测量GSH对BSO抑制胱氨酸积累的影响。获得的结果表明，外源性添加的GSH部分克服了BSO的抗增殖作用。GSH的拮抗作用与细胞内GSH的补充无关，但与BSO抑制的胱氨酸积累的恢复有关。在浓度低于1.0 mM时，外源性GSH也增强了未用BSO处理的细胞的增殖。本研究结果表明，BSO对胱氨酸摄取的抑制可能是BSO发挥其抗增殖作用的一种机制。外源性GSH对BSO抗增殖作用的拮抗作用可能是由于BSO抑制的胱氨酸摄取的恢复，尽管也可能存在其他导致GSH拮抗作用的机制。
