Contribution of glutathione to multidrug resistance and the its regulation with active oxygen modulators

多药耐药相关蛋白（MRP）已被证明转运谷胱甘肽S-结合物。谷胱甘肽（GSH）对多药耐药蛋白（MRP）高表达细胞株KB/VP-4.1中依托泊苷代谢产物葡萄糖醛酸依托泊苷转运的影响。ATP依赖性转运不仅包括[^3H]-白三烯C4等GSH结合物，还包括[^3H]依托泊苷的葡萄糖醛酸结合物。这一结果表明MRP是一个具有广泛特异性的泵。2.丁硫氨酸亚砜（BSO）暴露降低KB/VP-4细胞的GSH水平。葡萄糖醛酸基依托泊苷从KB/VP-4的流出比从KB细胞（野生型细胞）快5倍。3. KB/VP-4细胞中铜、锌、锰超氧化物歧化酶含量分别是KB细胞的1.5倍和6倍。4.细胞外超氧化物歧化酶的分子遗传学研究表明，细胞外超氧化物歧化酶与内皮细胞表面结合能力降低，对胰蛋白酶样蛋白酶的敏感性降低。EC-SOD与细胞表面的结合是保护细胞免受外部超氧阴离子的特别有效的方式。EC-SOD对内皮细胞表面保护能力的降低可能会加速肾功能、心血管功能障碍、糖尿病和高脂血症的发生，SOD同工酶的改变可能会影响由GSH等活性氧调节剂控制的ATP依赖性药物输出。

Multidrug resistance-associated protein (MRP) has shown to transport glutathione S-conjugate. The effect of glutathione (GSH) on the transport of glucuronosyl etoposide, a major metabolite of etoposide in MRP overexpressing cell line KB/VP-4.1.The involvement of MRP in the transport of drug conjugates was investigated using membrane vesicles prepared from KB/VP-4 cells. The ATP-dependent transport of not only GSH-conjugate such as [^3H]-leukotriene C4, but also glucuronosyl conjugate of [^3H] etoposide. This result demonstrates that MRP is a pump with a broad specificity.2.The butionine sulfoximine (BSO)-exposure reduced the GSH level inKB/VP-4 cells. The efflux of glucuronosyl etoposide was5-times faster from KB/VP-4 than from KB cells (wild type cells). BSO abolished the increased efflux of drug from KB/VP-4.3.In KB/VP-4 cells, the contents of copper, zinc-superoxide dismutase and manganese-superoxide dismutase were 1.5-fold and 6-fold higher than those in KB cells, respectively. This result shows that KB/VP-4 cell might to be more resistant to active oxygens.4.Molecular genetic studies of extracellular-superoxide dismutase have shown that a single base substitution generating the exchange of glycine for arginine 213 causes the impairment of its binding ability to endothelial cell surface and susceptibility to trypsin-like proteinases. The binding of EC-SOD to cell surface is an especially efficient way of protecting cells against external superoxide anion. The decrease of the protective capacity on the endothelial surface by EC-SOD might accelerate the renal, cardiovascular dysfunctions, diabetes and hyperlipidemia.The change of SOD isozyme might affect on the ATP-dependent export of drug which are controlled by active oxygen modulators such as GSH.