The effect of low pH on breast cancer resistance protein (ABCG2)-mediated transport of methotrexate, 7-hydroxymethotrexate, methotrexate diglutamate, folic acid, mitoxantrone, topotecan, and resveratrol in in vitro drug transport models
The effect of low pH on breast cancer resistance protein (ABCG2)-mediated transport of methotrexate, 7-hydroxymethotrexate, methotrexate diglutamate, folic acid, mitoxantrone, topotecan, and resveratrol in in vitro drug transport models
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DOI：
10.1124/mol.106.028167
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发表时间：
2007-01-01
影响因子：
3.6
通讯作者：
Schellens, Jan H. M.
中科院分区：
文献类型：
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作者：
Breedveld, Pauline;Pluim, Dick;Schellens, Jan H. M.
一些细胞摄取系统（抗）叶酸功能最佳的酸性pH值。我们已经测试了这是否也适用于流出细胞的乳腺癌耐药蛋白（巴塞尔公约区域会议; ABCG 2），据报道其在生理pH下转运叶酸、甲氨蝶呤和甲氨蝶呤二谷氨酸盐和三谷氨酸盐。我们发现BCRP对1 μ M甲氨蝶呤的ATP依赖性囊泡转运在pH 5.5时比生理pH高5倍。甲氨蝶呤的转运在pH 5.5时是饱和的，表观Km和Vmax值分别为1.3 +/- 0.2 mM和44 +/- 2.5 nmol/mg蛋白/min，但在pH 7.3至6 mM甲氨蝶呤时与药物浓度呈线性关系。与最近的报道相反，我们没有检测到氨甲喋呤二谷氨酸盐在生理pH下的转运，但我们确实发现在pH 5.5下的转运。我们还发现，7-羟基-甲氨蝶呤（甲氨蝶呤的主要代谢产物）在生理pH和在完整的BCRP过表达细胞中也观察到pH效应：我们发现在pH6.5时对甲氨蝶呤和原型BCRP底物米托蒽醌的抗性水平比在生理pH时高3倍。此外，对于MDCKII-BCRP单层，我们发现白藜芦醇在pH值下是一种中性化合物
Some cellular uptake systems for (anti) folates function optimally at acidic pH. We have tested whether this also applies to efflux from cells by breast cancer resistance protein (BCRP; ABCG2), which has been reported to transport folic acid, methotrexate, and methotrexate di-and triglutamate at physiological pH. Using Spodoptera frugiperda-BCRP membrane vesicles, we showed that the ATP-dependent vesicular transport of 1 mu M methotrexate by BCRP is 5-fold higher at pH 5.5 than at physiological pH. The transport of methotrexate was saturable at pH 5.5, with apparent K m and V max values of 1.3 +/- 0.2 mM and 44 +/- 2.5 nmol/mg of protein/min, respectively, but was linear with drug concentration at pH 7.3 up to 6 mM methotrexate. In contrast to recent reports, we did not detect transport of methotrexate diglutamate at physiological pH, but we did find transport at pH 5.5. We also found that 7-hydroxy-methotrexate, the major metabolite of methotrexate, is transported by BCRP both at physiological pH and (more efficiently) at low pH. The pH effect was also observed in intact BCRP-overexpressing cells: we found a 3-fold higher level of resistance to both methotrexate and the prototypical BCRP substrate mitoxantrone at pH 6.5 as at physiological pH. Furthermore, with MDCKII-BCRP monolayers, we found that resveratrol, which is a neutral compound at pH