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

多药耐药相关蛋白（MRP）可转运谷胱甘肽s缀合物。谷胱甘肽（GSH）对MRP过表达细胞株KB/VP-4.1中依托泊苷主要代谢物葡萄糖醛基依托泊苷运输的影响。利用KB/VP-4细胞制备的膜泡研究了MRP在药物偶联物运输中的作用。atp依赖的转运不仅包括[^3H]-白三烯C4等谷胱甘肽偶联物，还包括[^3H]依托油苷的葡萄糖醛酸偶联物。结果表明，MRP是一种具有广泛特异性的泵。butionine亚砜（BSO）暴露降低了inKB/VP-4细胞的GSH水平。KB/VP-4细胞的葡萄糖醛基依托opo苷外排速度比野生型细胞快5倍。BSO消除了KB/VP-4.3中增加的药物外排。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比KB细胞高1.5倍和6倍。结果表明，KB/VP-4细胞可能具有更强的抗活性氧能力。细胞外超氧化物歧化酶的分子遗传学研究表明，产生甘氨酸交换精氨酸213的单碱基取代导致其与内皮细胞表面的结合能力受损，并对胰蛋白酶样蛋白酶易感性受损。EC-SOD与细胞表面结合是保护细胞免受外部超氧阴离子侵害的一种特别有效的方法。EC-SOD降低内皮细胞表面的保护能力可能加速肾功能、心血管功能障碍、糖尿病和高脂血症的发生。SOD同工酶的变化可能影响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.