Hidden Antioxidative Functions of Reduced Nicotinamide Adenine Dinucleotide Coexisting with Hemoglobin.
Hidden Antioxidative Functions of Reduced Nicotinamide Adenine Dinucleotide Coexisting with Hemoglobin.
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与血红蛋白共存的还原型烟酰胺腺嘌呤二核苷酸的隐藏抗氧化功能。
DOI：
10.1021/acschembio.7b00174
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发表时间：
2017
影响因子：
4
通讯作者：
Sakai H
中科院分区：
文献类型：
--
作者：
Yamada M;Sakai H
红细胞（RBC）中的亚铁氧合血红蛋白（HbO 2）总是缓慢地自动氧化形成高铁血红蛋白（metHb）。然而，metHb的水平总是保持低于0.5%的细胞内metHb还原酶系统与辅酶，如还原的烟酰胺腺嘌呤二核苷酸（NADH），并通过超氧化物歧化酶（SOD）和过氧化氢酶（CAT），消除活性氧。毫无疑问，没有相应的酶系统，NADH不能还原metHb。然而，我们的研究表明，高浓度的NADH（正常水平的100倍，与HbO 2等摩尔）延迟HbO 2在没有酶系统的高度纯化的Hb溶液中的自氧化。此外，在添加氧化剂如H2 O2、NO和NaNO 2的情况下观察到NADH对metHb形成的抑制作用。我们的机制评估阐明了极高的pseudo-CAT和pseudo-SOD活性的NADH共存的HbO 2，和反应性的NADH与NO。我们准备了一个模型的红细胞（Hb-vesicles，Hb-V）封装纯化的HbO 2溶液和NADH，但没有酶系统的脂质体。我们证实了NADH对自氧化和氧化剂诱导的metHb形成的抑制作用。此外，静脉内给予这些Hb-Vs的大鼠引起metHb形成的显着延迟约50%相比，没有NADH共封装的情况下。基于这些结果，我们阐明了一个新的作用，即通过与血红蛋白相互作用的抗氧化作用，除了其经典的辅酶的作用。
Ferrous oxyhemoglobin (HbO2) in red blood cells (RBCs) invariably and slowly autoxidizes to form ferric methemoglobin (metHb). However, the level of metHb is always maintained below 0.5% by intracellular metHb reduction of enzymatic systems with coenzymes, such as reduced nicotinamide adenine dinucleotide (NADH), and by superoxide dismutase (SOD) and catalase (CAT), which eliminate reactive oxygen species. Unquestionably, NADH cannot reduce metHb without the corresponding enzymatic system. Our study, however, demonstrated that a high concentration of NADH (100-fold of normal level, equimolar to HbO2) retarded autoxidation of HbO2in a highly purified Hb solution with no enzymatic system. Furthermore, an inhibitory effect of NADH on metHb formation was observed with additions of oxidants such as H2O2, NO, and NaNO2. Our mechanism assessment elucidated extremely high pseudo-CAT and pseudo-SOD activities of NADH with coexistence of HbO2, and reactivity of NADH with NO. We prepared a model of RBCs (Hb-vesicles, Hb-V) encapsulating purified HbO2solution and NADH, but no enzymatic system within liposome. We confirmed the inhibitory effect of NADH on both autoxidation and oxidant-induced metHb formation. In addition, an intravenous administration of these Hb-Vs to rats caused significant retardation of metHb formation by approximately 50% compared to the case without NADH coencapsulation. Based on these results, we elucidated a new role of NADH, that is, antioxidative effect via interaction with Hb, in addition to its classical role as a coenzyme.