Oxidative metabolism of combretastatin A-1 produces quinone intermediates with the potential to bind to nucleophiles and to enhance oxidative stress via free radicals
Oxidative metabolism of combretastatin A-1 produces quinone intermediates with the potential to bind to nucleophiles and to enhance oxidative stress via free radicals
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DOI：
10.1021/tx7002195
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发表时间：
2007-12-01
影响因子：
4.1
通讯作者：
Wardman, Peter
中科院分区：
文献类型：
--
作者：
Folkes, Lisa K.;Christlieb, Martin;Wardman, Peter
康布他汀是基于二苯乙烯的微管蛋白解聚剂，具有针对肿瘤血管系统的选择性活性；两种变体（A-1和A-4）目前正在进行临床试验。考布他汀 A-1 (CA1) 比考布他汀 A-4 (CA4) 具有更强的抗肿瘤作用。我们假设这反映了 CA1 中第二个（邻位）酚部分赋予的增强的反应性。 CA1 被过氧化物酶、酪氨酸酶或 Fe(III) 氧化生成具有相应邻醌 Q1 质量特征的物质。给小鼠施用CA1-双(磷酸盐)后，在肝脏中检测到GSH与Q1亲核加成形成的对苯二酚-硫醚缀合物Q1H(2)-SG。在竞争中，Q1 在 pH 7.4 下经过几分钟的电环闭环，产生第二种邻醌产物 Q2，其特征在于精确质量和 NMR。该产品也是由人早幼粒细胞白血病（HL-60）细胞在体外产生的，前提是添加了超氧化物歧化酶。 Q2 对谷胱甘肽 (GSH) 和抗坏血酸具有高度反应性，以催化方式刺激氧气消耗。通过 EPR 表征了 CA1 自氧化过程中形成的自由基中间体，并研究了 GSH 和抗坏血酸对信号的影响。使用脉冲辐射解来引发选择性单电子氧化或还原，并从 CA1 氧化或 Q2 还原时形成的自由基的不同吸收光谱提供进一步的证据，表明 CA1 氧化时形成两种不同的醌。结果证明了 CA1 和 CA4 药理学特性之间的根本差异，这为它们在体内的不同活性提供了两种可能的解释：对可能与蛋白质硫醇和可能与核酸结合的醌中间体的氧化激活，以及通过增强超氧化物/过氧化氢产生来刺激氧化应激。体内 GSH 缀合物 Q1H(2)-SG 的观察提供了与当前 CA1-二（磷酸盐）（OXi4503）临床试验相关的氧化代谢新标记。
Combretastatins are stilbene-based, tubulin depolymerization agents with selective activity against the tumor vasculature; two variants (A-1 and A-4) are currently undergoing clinical trials. Combretastatin A-1 (CA1) has a greater antitumor effect than combretastatin A-4 (CA4). We hypothesized that this reflects the enhanced reactivity conferred by the second (ortho) phenolic moiety in CA1. Oxidation of CA1 by peroxidase, tyrosinase, or Fe(III) generates a species with mass characteristics of the corresponding ortho-quinone Q1. After administration of CA1-bis(phosphate) to mice, the hydroquinone-thioether conjugate Q1H(2)-SG, formed from the nucleophilic addition of GSH to Q1, was detected in liver. In competition, electrocyclic ring closure of Q1, over a few minutes at pH 7.4, leads to a second ortho-quinone product Q2, characterized by exact mass and NMR. This product was also generated by human promyelocytic leukemia (HL-60) cells in vitro, provided that superoxide dismutase was added. Q2 is highly reactive toward glutathione (GSH) and ascorbate, stimulating oxygen consumption in a catalytic manner. Free radical intermediates formed during autoxidation of CA1 were characterized by EPR, and the effects of GSH and ascorbate on the signals were studied. Pulse radiolysis was used to initiate selective one-electron oxidation or reduction and provided further evidence, from the differing absorption spectra of the radicals formed on oxidation of CA1 or reduction of Q2, that two different quinones were formed on oxidation of CA1. The results demonstrate fundamental differences between the pharmacological properties of CA1 and CA4 that provide two possible explanations for their differential activities in vivo: oxidative activation to a quinone intermediate likely to bind to protein thiols and possibly to nucleic acids and stimulation of oxidative stress by enhancing superoxide/hydrogen peroxide production. The observation of the GSH conjugate Q1H(2)-SG in vivo provides a new marker for oxidative metabolism of relevance to current clinical trials of CA1-bis(phosphate) (OXi4503).