Formation, Reactivity, and Antiplatelet Activity of Mixed Disulfide Conjugates of Clopidogrel
作者:Haoming Zhang、D. Adam Lauver、Benedict R. Lucchesi、Paul F. Hollenberg
DOI:10.1124/mol.112.084392
日期:2013.4
In this work, we investigated the formation, reactivity, and antiplatelet activity of various mixed disulfide conjugates of clopidogrel. Our results showed that the production of the active metabolite (AM) from 2-oxoclopidogrel by human liver microsomes (HLMs) is greatly affected by the thiol reductants used. Among the 10 thiol compounds tested, glutathione (GSH) is most efficient in producing the AM at a rate of 167 pmoles AM/min/mg HLM. Interestingly, no AM but only the mixed disulfide conjugates were formed in the presence of 6-chloropyridazine-3-thiol (CPT), 2,5-dimethylfuran-3-thiol, and 3-nitropyridine-2-thiol (NPT). The mass spectrometry (MS) and MS2 spectra of the conjugates of these thiol compounds confirmed the presence of a mixed disulfide bond linkage between the AM and the thiol reductants. Kinetic studies revealed that the mixed disulfide conjugates were capable of exchanging thiols with GSH to release the AM with second order rate constants ranging from 1.2 to 28 M−1s−1. The mixed disulfide conjugates of CPT and NPT showed potent inhibition of platelet aggregation after pretreatment with 1 mM GSH, confirming that the AM is responsible for the antiplatelet activity of clopidogrel. Collectively, our results provide strong support for a cytochrome P450 (P450)-mediated bioactivation mechanism involving the initial formation of a glutathionyl conjugate, followed by thiol-disulfide exchange with another GSH molecule to release the AM. Furthermore, the stable mixed disulfide conjugates identified in this study provide a platform to quantitatively generate the therapeutic AM without the need for P450-mediated bioactivation. This property can be further explored to overcome the interindividual variability in clopidogrel therapy.
在这项工作中,我们研究了氯吡格雷的各种混合二硫化物共轭物的形成、反应性和抗血小板活性。结果表明,人肝微粒体(HLMs)从 2-oxoclopidogrel 生成活性代谢物(AM)的过程在很大程度上受到所用硫醇还原剂的影响。在测试的 10 种硫醇化合物中,谷胱甘肽(GSH)产生 AM 的效率最高,为 167 小摩尔 AM/分钟/毫克 HLM。有趣的是,在 6-氯哒嗪-3-硫醇(CPT)、2,5-二甲基呋喃-3-硫醇和 3-硝基吡啶-2-硫醇(NPT)存在下,没有形成 AM,而只形成了混合二硫化物共轭物。这些硫醇化合物共轭物的质谱(MS)和 MS2 光谱证实了 AM 与硫醇还原剂之间存在混合二硫键连接。动力学研究表明,混合二硫轭合物能够与 GSH 交换硫醇,从而释放 AM,二阶速率常数为 1.2 到 28 M-1s-1。经 1 mM GSH 预处理后,CPT 和 NPT 的混合二硫化物共轭物显示出对血小板聚集的强效抑制作用,证实 AM 是氯吡格雷抗血小板活性的原因。总之,我们的研究结果为细胞色素 P450(P450)介导的生物活化机制提供了强有力的支持,该机制涉及谷胱甘肽共轭物的初始形成,然后与另一个 GSH 分子进行硫醇-二硫化物交换,从而释放 AM。此外,本研究中发现的稳定的混合二硫化物共轭物提供了一个平台,无需 P450 介导的生物活化即可定量生成治疗 AM。可以进一步探索这一特性,以克服氯吡格雷治疗中的个体差异。