In Vitro Hepatic Oxidative Biotransformation of Trimethoprim
In Vitro Hepatic Oxidative Biotransformation of Trimethoprim
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DOI：
10.1124/dmd.115.065193
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发表时间：
2015-09-01
影响因子：
3.9
通讯作者：
Pearce, Robin E.
中科院分区：
文献类型：
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作者：
Goldman, Jennifer L.;Leeder, J. Steven;Pearce, Robin E.
自20世纪60年代以来，甲氧苄啶（TMP）已被广泛使用，无论是单独使用还是与磺胺甲恶唑联合使用。不幸的是，关于细胞色素P450酶（P450）在TMP初级代谢产物形成中所起作用的信息很少。因此，我们进行了体外研究，以鉴定和更全面地表征催化六种TMP初级代谢产物形成的P450：TMP 1-N-氧化物（1-NO-TMP）和3-N-氧化物（3-NO-TMP）、3 '-和4'-去甲基-TMP、苄醇（C α-OH-TMP）和TMP的N-乙酰半胱氨酸（NAC）加合物（C α-NAC-TMP）。人肝微粒体（HLM）中每种TMP代谢产物的形成动力学与单酶Michaelis-Menten动力学一致，Km值明显高于（>= 10倍）TMP治疗浓度（50 mM）。一组HLM中代谢产物形成速率与标志物P450活性之间的相关性研究沿着使用选择性P450抑制剂与合并HLM孵育的抑制研究的综合结果表明，1-NO-TMP、C α-NAC-TMP和C α-OH-TMP主要由CYP 3A 4形成。相反，3-NO-TMP主要由CYP 1A 2在HLM中形成，并被α-萘啶酮抑制。4 '-去甲基-TMP被认为是一种反应性TMP代谢物前体，由几种P450形成，包括CYP 3A 4，与多种P450活性相关，但主要受酮康唑抑制（高达50%），表明CYP 3A 4对TMP 4'-去甲基化有重要贡献。TMP 3 '-去甲基化由多种P450催化，包括CYP 2C 9，与CYP 2C 9活性相关，并被磺胺苯吡唑抑制（高达40%）。总体而言，CYP 2C 9和CYP 3A 4似乎是TMP主要代谢的最重要贡献者。
Trimethoprim (TMP) has been widely used since the 1960s, both alone and in combination with sulfamethoxazole. Unfortunately, information regarding the role that cytochrome P450 enzymes (P450s) play in the formation of TMP primary metabolites is scarce. Hence, we undertook in vitro studies to identify and more fully characterize the P450s that catalyze formation of six TMP primary metabolites: TMP 1-N-oxide (1-NO-TMP) and 3-N-oxide (3-NO-TMP), 3'- and 4'-desmethyl-TMP, a benzylic alcohol (C alpha-OH-TMP), and an N-acetyl cysteine (NAC) adduct of TMP (C alpha-NAC-TMP). Formation kinetics for each TMP metabolite in human liver microsomes (HLMs) were consistent with single-enzyme Michaelis-Menten kinetics, and Km values were markedly above (>= 10-fold) the therapeutic concentrations of TMP (50 mM). The combined results from correlation studies between rates of metabolite formation and marker P450 activities in a panel of HLMs along with inhibition studies utilizing selective P450 inhibitors incubated with pooled HLMs suggested that 1-NO-TMP, C alpha-NAC-TMP, and C alpha-OH-TMP were predominantly formed by CYP3A4. In contrast, 3-NO-TMP was formed predominantly by CYP1A2 in HLMs and inhibited by alpha-naphthoflavone. 4'-Desmethyl-TMP, which is believed to be a reactive TMP metabolite precursor, was formed by several P450s, including CYP3A4, correlated with multiple P450 activities, but was inhibited primarily by ketoconazole (up to 50%), suggesting that CYP3A4 makes a major contribution to TMP 4'-demethylation. TMP 3'-demethylation was catalyzed by multiple P450s, including CYP2C9, correlated with CYP2C9 activity, and was inhibited by sulfaphenazole (up to 40%). Overall, CYP2C9 and CYP3A4 appear to be the most significant contributors to TMP primary metabolism.