Varnes M E, Biaglow J E, Roizin-Towle L, Hall E J
Int J Radiat Oncol Biol Phys. 1984 Aug;10(8):1229-33. doi: 10.1016/0360-3016(84)90323-7.
Many investigators have observed aerobic sensitization of V79, CHO and A549 (human lung carcinoma) cells upon depletion of GSH using buthionine sulfoximine (BSO). Recently we discovered that this aerobic sensitization can be reversed if WR-2721 or N-acetylcysteine is added to the cells just prior to irradiation. Reversal requires that the exogenous thiols be present during the time of irradiation. One possible explanation was that these thiols entered the cells and either increased the pool of cellular nonprotein thiols or reversed the thiol-depleted state by stimulation of GSH synthesis. Cells treated with BSO do not readily regenerate intracellular GSH because this agent irreversibly inhibits gamma-glutamyl synthetase. For A549 monolayer cultures, there is approximately 50% regeneration 6 hr after removal of 0.01 mM BSO, 20% 6 hr after 0.1 mM BSO, and only 5% 6 hr after 0.5 mM BSO. We found that addition of WR-2721 or N-acetylcysteine to BSO-treated cells did not affect the rate of regeneration of intracellular GSH. Thus, reversal of the aerobic sensitization of A549 cells by BSO cannot be explained on the basis of intracellular thiol levels alone, or by rapid reversal of BSO inhibition. In addition, diethylmaleate (DEM)-treated cells are considerably different from BSO-treated cells with respect to the ability to regenerate GSH. After removal of DEM, A549 cells immediately begin GSH resynthesis, and return to control levels occurs within 2 hr. Exogenous 5 mM GSH increases the rate of resynthesis of GSH in DEM-treated cells, but not in BSO-treated cells.
许多研究者观察到，使用丁硫氨酸亚砜胺（BSO）耗尽谷胱甘肽（GSH）后，V79、CHO和A549（人肺癌）细胞会出现需氧致敏现象。最近我们发现，如果在照射前向细胞中加入WR-2721或N-乙酰半胱氨酸，这种需氧致敏现象可以逆转。逆转要求在照射期间存在外源性硫醇。一种可能的解释是，这些硫醇进入细胞，要么增加细胞内非蛋白质硫醇的储备，要么通过刺激GSH合成来逆转硫醇耗尽状态。用BSO处理的细胞不容易再生细胞内GSH，因为这种试剂会不可逆地抑制γ-谷氨酰合成酶。对于A549单层培养物，去除0.01 mM BSO后6小时约有50%的再生，0.1 mM BSO后6小时为20%，0.5 mM BSO后6小时仅为5%。我们发现，向用BSO处理的细胞中加入WR-2721或N-乙酰半胱氨酸并不影响细胞内GSH的再生速率。因此，不能仅根据细胞内硫醇水平或BSO抑制的快速逆转来解释BSO对A549细胞需氧致敏的逆转。此外，马来酸二乙酯（DEM）处理的细胞在再生GSH的能力方面与BSO处理的细胞有很大不同。去除DEM后，A549细胞立即开始GSH再合成，并在2小时内恢复到对照水平。外源性5 mM GSH可提高DEM处理细胞中GSH的再合成速率，但对BSO处理的细胞则无此作用。
