Characterization of novel dihydrothienopyridinium and thienopyridinium metabolites of ticlopidine in vitro: Role of peroxidases, cytochromes P450, and monoamine oxidases
Characterization of novel dihydrothienopyridinium and thienopyridinium metabolites of ticlopidine in vitro: Role of peroxidases, cytochromes P450, and monoamine oxidases
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DOI：
10.1124/dmd.32.1.49
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发表时间：
2004-01-01
影响因子：
3.9
通讯作者：
O'Connell, TN
中科院分区：
文献类型：
--
作者：
Dalvie, DK;O'Connell, TN
噻氯匹定是一种抑制二磷酸腺苷诱导的血小板聚集的药物。噻氯匹定的代谢研究表明，主要代谢途径为N-脱烷基化、N-氧化和噻吩环氧化。然而，噻氯匹定具有一些与环状叔胺（如1-甲基-4-苯基-1，2，3，6-四氢吡啶和四氢异喹啉）相似的结构特征，后者通过亚胺（二氢吡啶）物质转化为神经毒性吡啶代谢物。目前的体外研究检查了噻氯匹定通过细胞色素P450（P450）、过氧化物酶和单胺氧化酶（MAO）进行类似转化的潜力。这些研究的结果表明，噻氯匹定通过中间体2-电子氧化产物噻吩并二氢吡啶代谢物（M5），通过P450、辣根过氧化物酶和髓过氧化物酶，以及在较小程度上通过MAO，发生总体4-电子氧化，生成新型噻吩并吡啶代谢物（M6）。通过液相色谱（LC）-串联质谱和LC-NMR表征这些代谢产物的结构。杆状病毒表达的P450的定性研究揭示了P450 3A 4参与这种转化。有趣的是，M5是过氧化物酶介导的反应中的主要代谢产物，对空气氧化或反硝化相当稳定。其亲电性较低，不形成氰化物、谷胱甘肽或N-乙酰半胱氨酸加合物。另一方面，M6是P450催化噻氯匹定氧化的主要代谢产物。本研究的结果表明，除了噻氯匹定的噻吩环代谢外，该化合物的四氢吡啶部分与其他环状叔胺一样易受2-电子和4-电子氧化的影响。
Ticlopidine is an agent that inhibits adenosine diphosphate-induced platelet aggregation. Metabolic studies with ticlopidine have indicated that the principal routes of metabolism are N-dealkylation, N-oxidation, and oxidation of the thiophene ring. However, ticlopidine shares some structural features that are similar to those of cyclic tertiary amines such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and tetrahydroisoquinolines, which are converted to neurotoxic pyridinium metabolites, via the iminium (dihydropyridinium) species. The current in vitro studies examined the potential of ticlopidine to undergo a similar conversion by cytochrome P450 (P450), peroxidases, and monoamine oxidase (MAO). The results from these studies have suggested that ticlopidine undergoes an overall 4-electron oxidation to the novel thienopyridinium metabolite (M6) via the intermediate 2-electron oxidation product, the thienodihydropyridinium metabolite (M5) by P450, horseradish peroxidase, and myeloperoxidase and, to a lesser extent, by MAO. The structures of these metabolites were characterized by liquid chromatography (LC)-tandem mass spectrometry and LC-NMR. Qualitative studies with baculovirus-expressed P450s revealed the involvement of P450 3A4 in this conversion. Interestingly, M5 was the primary metabolite in the peroxidase-mediated reactions and was quite stable to air oxidation or disproportionation. It was less electrophilic and did not form cyanide, glutathione, or N-acetylcysteine adducts. On the other hand, M6 was the major metabolite in P450-catalyzed oxidation of ticlopidine. The results from this study have revealed that in addition to metabolism of the thiophene ring of ticlopidine, the tetrahydropyridine moiety of the compound is susceptible to a 2-electron and a 4-electron oxidation like other cyclic tertiary amines.