GSH is required to recycle ascorbic acid in cultured liver cell lines
GSH is required to recycle ascorbic acid in cultured liver cell lines
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DOI：
10.1089/152308601317203594
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发表时间：
2001-12-01
影响因子：
6.6
通讯作者：
May, JM
中科院分区：
文献类型：
--
作者：
Li, X;Qu, ZC;May, JM
肝脏是大多数哺乳动物合成抗坏血酸的部位。由于人类肝脏不能重新合成抗坏血酸，它可能与其他物种的肝脏在抗坏血酸从氧化形式再循环的能力或机制上有所不同。因此，我们比较了培养的人肝源性细胞（HepG2细胞）和大鼠肝源性细胞（H4IIE细胞）摄取和还原脱氢抗坏血酸（DHA）为抗坏血酸的能力。在培养过程中，两种细胞类型都不含有可观数量的抗坏血酸，但它们都能迅速吸收和减少DHA来生成抗坏血酸。细胞内抗坏血酸在加载DHA后积累到10-20 mM的浓度。HepG2细胞吸收和还原DHA为抗坏血酸的能力是H4IIE细胞的两倍多。在这两种细胞类型中，DHA还原降低了谷胱甘肽（GSH）的浓度，并被事先用马来酸二乙酯、丁硫氨酸亚砜和氧化苯larsine消耗谷胱甘肽所抑制。由于硫氧还蛋白还原酶，nadph依赖的DHA还原发生在两种细胞类型的隔夜透析提取物中。这些结果表明，培养的大鼠肝脏细胞合成的抗坏血酸很少，培养的人源性肝细胞比大鼠源性肝细胞具有更大的还原DHA的能力，但这两种细胞类型都主要依赖于GSH或nadph依赖的机制来从DHA中回收抗坏血酸。
Liver is the site of ascorbic acid synthesis in most mammals. As human liver cannot synthesize ascorbate de novo, it may differ from liver of other species in the capacity or mechanism for ascorbate recycling from its oxidized forms. Therefore, we compared the ability of cultured liver-derived cells from humans (HepG2 cells) and rats (H4IIE cells) to take up and reduce dehydroascorbic acid (DHA) to ascorbate. Neither cell type contained appreciable amounts of ascorbate in culture, but both rapidly took up and reduced DHA to ascorbate. Intracellular ascorbate accumulated to concentrations of 10-20 mM following loading with DHA. The capacity of HepG2 cells to take up and reduce DHA to ascorbate was more than twice that of H4IIE cells. In both cell types, DHA reduction lowered glutathione (GSH) concentrations and was inhibited by prior depletion of GSH with diethyl maleate, buthionine sulfoximine, and phenylarsine oxide. NADPH-dependent DHA reduction due to thioredoxin reductase occurred in overnight-dialyzed extracts of both cell types. These results show that cells derived from rat liver synthesize little ascorbate in culture, that cultured human-derived liver cells have a greater capacity for DHA reduction than do rat-derived liver cells, but that both cell types rely largely on GSH- or NADPH-dependent mechanisms for ascorbate recycling from DHA.