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

多药耐药相关蛋白可转运谷胱甘肽S结合物。谷胱甘肽(GSH)对足叶乙甙在MRP高表达细胞系KB/VP-4.1中的主要代谢产物葡萄糖醛酸依托泊苷转运的影响。依赖于ATP的转运不仅包括GSH结合物如[~3H]-白三烯C4，还包括[~(3 H)]依托泊苷的葡萄糖醛酸基结合物。这一结果表明MRP是一个具有广泛特异性的泵。2.丁氨酸亚磺胺(BSO)暴露降低了KB/VP-4细胞的GSH水平。在KB/VP-4细胞中，葡萄糖醛酸依托泊苷的外流速度是KB细胞(野生型细胞)的5倍。在KB/VP-4细胞中，铜、锌超氧化物歧化酶和锰超氧化物歧化酶的含量分别是KB细胞的1.5倍和6倍。这一结果表明KB/VP-4细胞可能对活性氧具有更强的抵抗力。4.细胞外超氧化物歧化酶的分子遗传学研究表明，单碱基取代导致甘氨酸与精氨酸213的交换导致其与内皮细胞表面的结合能力受损，并对类胰蛋白酶敏感。EC-SOD与细胞表面的结合是保护细胞免受外界超氧阴离子伤害的一种特别有效的方法。EC-SOD对血管内皮细胞表面保护能力的降低可能会加速肾脏、心血管功能障碍、糖尿病和高脂血症的发生；SOD同工酶的变化可能会影响受GSH等活性氧调节剂调控的ATP依赖的药物输出。

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.