Delivery of exogenous tetrahydrobiopterin (BH4) to cells of target organs:: Role of salvage pathway and uptake of its precursor in effective elevation of tissue BH4
Delivery of exogenous tetrahydrobiopterin (BH4) to cells of target organs:: Role of salvage pathway and uptake of its precursor in effective elevation of tissue BH4
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DOI：
10.1016/j.ymgme.2005.09.002
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发表时间：
2005-12-01
影响因子：
3.8
通讯作者：
Wakasugi, OK
中科院分区：
文献类型：
--
作者：
Hasegawa, H;Sawabe, K;Wakasugi, OK
靶器官（如肝脏）中的细胞通常不含有完全还原形式的四氢生物蝶呤（BH4）。相反，它们短暂地从细胞外液中吸收BH4，瞬间氧化BH4，然后几乎全部排出。然而，在细胞培养物中加入BH4后，观察到BH4的少量但稳定的积累。这种积累被甲氨蝶呤（一种二氢叶酸还原酶抑制剂）抑制，这种现象最初是基于使用已建立的细胞系（如RBL2H3和PC12）进行的体外研究结果提出的。这些细胞也吸收双氢生物蝶呤（BH2）并将其还原为具有酶活性的BH4。它们在BH4处理后积累可用BH4的能力归因于BH2的掺入，在典型的实验中，BH2是由细胞和BH4的自动氧化产生的。到目前为止，各种细胞系的大多数细胞在培养中表现相似。我们对单个小鼠的体内研究表明，给药sepapterin、BH2和BH4在提高靶器官BH4水平方面相当有效。在我们的细胞培养系统中，甲氨蝶呤也抑制了补充BH4、BH2或sepapterin后BH4在各种组织中的积累。由此可见，补充后BH4的升高主要是通过一种“挽救途径”，其中BH2是通过二氢叶酸还原酶的作用产生BH4的关键中间体。(c) 2005爱思唯尔公司版权所有。
Cells in target organs such as liver do not generally incorporate tetrahydrobiopterin (BH4) in its fully reduced form. Instead, they transiently take up BH4 from the extracellular fluid, instantaneously oxidize it and then expel virtually all of it. However, a small but stable accumulation of BH4 was observed after BH4 administration to the cell cultures. This accumulation was inhibited by methotrexate, an inhibitor of dihydrofolate reductase, a phenomenon that was first suggested based on results of in vitro studies which used established cell lines such as RBL2H3 and PC12. These cells also take up dihydrobiopterin (BH2) and reduce it to enzymically active BH4. Their ability to accumulate usable BH4 upon BH4 administration was attributed to the incorporation of BH2, which in typical experiments was produced by the cells as well as by auto-oxidation of BH4. Most cells of the various cell lines so far examined behaved similarly in culture. Our in vivo work with individual mice demonstrated that administration of sepiapterin, BH2, and BH4 was comparably effective in raising BH4 levels in target organs. BH4 accumulation in various tissues after supplementation with BH4, BH2 or sepiapterin was also inhibited by methotrexate, as in the case of our cell culture system. It was concluded that the elevation in BH4 by supplementation was mainly through a "salvage pathway" that included BH2 as the key intermediate in the production of BH4 through the action of dihydrofolate reductase. (c) 2005 Elsevier Inc. All rights reserved.