DIRECT EVIDENCE FOR INHIBITION OF FREE-RADICAL FORMATION FROM CU(I) AND HYDROGEN-PEROXIDE BY GLUTATHIONE AND OTHER POTENTIAL LIGANDS USING THE EPR SPIN-TRAPPING TECHNIQUE
DIRECT EVIDENCE FOR INHIBITION OF FREE-RADICAL FORMATION FROM CU(I) AND HYDROGEN-PEROXIDE BY GLUTATHIONE AND OTHER POTENTIAL LIGANDS USING THE EPR SPIN-TRAPPING TECHNIQUE
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DOI：
10.1016/0003-9861(92)90507-s
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发表时间：
1992-05-15
影响因子：
3.9
通讯作者：
MASON, RP
中科院分区：
文献类型：
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作者：
HANNA, PM;MASON, RP
铜诱导的氧化损伤通常归因于通过类似于Fe（II）和H2 O2的Haber-Weiss循环的机制形成高活性羟基自由基。本文用EPR自旋俘获技术研究了Cu（I）离子与H2 O2的反应。将Cu（I）溶于乙腈中，在氮气保护下，加入到含有100 mM 5，5-二甲基-1-吡咯啉N-氧化物（DMPO）的pH 7.4磷酸盐缓冲液中，观察到羟基自由基加合物。羟基自由基的形成取决于O2的存在和随后H2 O2的形成。得到的k scav k DMPO比低于那些预期的机制，涉及自由羟基自由基，并反映了干扰的亲核加成H2 O DMPO形成DMPO/。OH加合物在非螯合铜离子的存在下。向反应中加入乙醇或二甲亚砜表明还形成了高价金属中间体，可能是Cu（III）。在氨三乙酸或组氨酸溶液中加入Cu（I）后，尽管Cu（I）被完全氧化成Cu（II）并形成H2 O2，但羟基自由基的自旋捕获几乎完全被抑制. Bathocuproinedisulfonate，硫脲，还原型谷胱甘肽都稳定了铜（I）离子对氧化的O2。加入H2 O2后，三种配合物中的Cu（I）均不同程度地被氧化;然而，只有硫脲配合物在反应2 min内被完全氧化，并产生可检测到的羟基自由基。从浴铜灵二磺酸盐或谷胱甘肽络合物中未检测到自由基。总体而言，这些结果表明，铜离子在体内的有害影响减少了生化螯合剂，特别是谷胱甘肽，这可能有一个主要辊在缓和铜的毒理学效应。
Copper-induced oxidative damage is generally attributed to the formation of the highly reactive hydroxyl radical by a mechanism analogous to the Haber-Weiss cycle for Fe (II) and H 2 O 2. In the present work, the reaction between the Cu (I) ion and H 2 O 2 is studied using the EPR spin-trapping technique. The hydroxyl radical adduct was observed when Cu (I), dissolved in acetonitrile under N 2, was added to pH 7.4 phosphate buffer containing 100 m m 5, 5-dimethyl-1-pyrroline N-oxide (DMPO). Formation of the hydroxyl radical was dependent on the presence of O 2 and subsequent formation of H 2 O 2. The k scav k DMPO ratios obtained were below those expected for a mechanism involving free hydroxyl radical and reflect the interference of nucleophilic addition of H 2 O to DMPO to form the DMPO/. OH adduct in the presence of nonchelated copper ion. Addition of ethanol or dimethyl sulfoxide to the reaction suggests that a high-valent metal intermediate, possibly Cu (III), was also formed. Spin trapping of hydroxyl radical was almost completely inhibited upon addition of Cu (I) to a solution of either nitrilotriacetate or histidine, even though the copper was fully oxidized to Cu (II) and H 2 O 2 was formed. Bathocuproinedisulfonate, thiourea, and reduced glutathione all stabilized the Cu (I) ion toward oxidation by O 2. Upon addition of H 2 O 2, the Cu (I) in all three complexes was oxidized to varying degrees; however, only the thiourea complex was fully oxidized within 2 min of reaction and produced detectable hydroxyl radicals. No radicals were detected from the bathocuproinedisulfonate or glutathione complexes. Overall, these results suggest that the deleterious effects of copper ions in vivo are diminished by biochemical chelators, especially glutathione, which probably has a major roll in moderating the toxicological effects of copper.