Contribution of human cytochrome<i>P</i>-450 isoforms to the metabolism of the simplest phenothiazine neuroleptic promazine
作者:Jacek Wójcikowski、Lydiane Pichard-Garcia、Patrick Maurel、Władysława A Daniel
DOI:10.1038/sj.bjp.0705195
日期:2003.4
The aim of the present study was to identify human cytochrome P‐450 isoforms (CYPs) involved in 5‐sulphoxidation and N‐demethylation of the simplest phenothiazine neuroleptic promazine in human liver.
The experiments were performed in the following in vitro models: (A) a study of promazine metabolism in liver microsomes—(a) correlations between the rate of promazine metabolism and the level and activity of CYPs; (b) the effect of specific inhibitors on the rate of promazine metabolism (inhibitors: CYP1A2—furafylline, CYP2D6—quinidine, CYP2A6+CYP2E1—diethyldithiocarbamic acid, CYP2C9—sulfaphenazole, CYP2C19—ticlopidine, CYP3A4—ketoconazole); (B) promazine biotransformation by cDNA‐expressed human CYPs (Supersomes 1A1, 1A2, 2A6, 2B6, 2C9, 2C19, 2E1, 3A4); (C) promazine metabolism in a primary culture of human hepatocytes treated with specific inducers (rifampicin—CYP3A4, CYP2B6 and CYP2C inducer, 2,3,7,8‐tetrachlordibenzeno‐p‐dioxin (TCDD)—CYP1A1/1A2 inducer).
In human liver microsomes, the formation of promazine 5‐sulphoxide and N‐desmethylpromazine was significantly correlated with the level of CYP1A2 and ethoxyresorufin O‐deethylase and acetanilide 4‐hydroxylase activities, as well as with the level of CYP3A4 and cyclosporin A oxidase activity. Moreover, the formation of N‐desmethylpromazine was correlated well with S‐mephenytoin 4′‐hydroxylation.
Furafylline (a CYP1A2 inhibitor) and ketoconazole (a CYP3A4 inhibitor) significantly decreased the rate of promazine 5‐sulphoxidation, while furafylline and ticlopidine (a CYP2C19 inhibitor) significantly decreased the rate of promazine N‐demethylation in human liver microsomes.
The cDNA‐expressed human CYPs generated different amounts of promazine metabolites, but the rates of CYP isoforms to catalyse promazine metabolism at therapeutic concentration (10 μM) was as follows: 1A1>2B6>1A2>2C9>3A4>2E1>2A6>2D6>2C19 for 5‐sulphoxidation and 2C19>2B6>1A1>1A2>2D6>3A4>2C9>2E1>2A6 for N‐demethylation. The highest intrinsic clearance (Vmax/Km) was found for CYP1A subfamily, CYP3A4 and CYP2B6 in the case of 5– sulphoxidation, and for CYP2C19, CYP1A subfamily and CYP2B6 in the case of N‐demethylation.
In a primary culture of human hepatocytes, TCDD (a CYP1A subfamily inducer), as well as rifampicin (mainly a CYP3A4 inducer) induced the formation of promazine 5‐sulphoxide and N‐desmethylpromazine.
Regarding the relative expression of various CYPs in human liver, the obtained results indicate that CYP1A2 and CYP3A4 are the main isoforms responsible for 5‐sulphoxidation, while CYP1A2 and CYP2C19 are the basic isoforms that catalyse N‐demethylation of promazine in human liver. Of the other isoforms studied, CYP2C9 and CYP3A4 contribute to a lesser degree to promazine 5‐sulphoxidation and N‐demethylation, respectively. The role of CYP2A6, CYP2B6, CYP2D6 and CYP2E1 in the investigated metabolic pathways of promazine seems negligible.
British Journal of Pharmacology (2003) 138, 1465–1474. doi:10.1038/sj.bjp.0705195
本研究的目的是在人类肝脏中确定参与简单吩噻嗪抗精神病药物普罗迷嗪(promazine)5-硫氧化和N-脱甲基作用的人类细胞色素P-450异构体(CYPs)。
实验是在以下体外模型中进行的:(A) 研究普罗迷嗪在肝微粒体中的代谢——(a) 普罗迷嗪代谢速率与CYPs的水平和活性的相关性;(b) 特异性抑制剂对普罗迷嗪代谢速率的影响(抑制剂:CYP1A2—呋拉西林,CYP2D6—金鸡纳碱,CYP2A6 + CYP2E1—二乙基二硫代碳酸盐,CYP2C9—磺胺苯唑,CYP2C19—噻氯匹啶,CYP3A4—酮康唑);(B) cDNA表达的重组人CYPs催化普罗迷嗪的生物转化(使用的CYPs为Supersomes 1A1, 1A2, 2A6, 2B6, 2C9, 2C19, 2E1, 3A4);(C) 在人原代肝细胞培养物中,普罗迷嗪在特定诱导剂处理下的代谢(利福霉素——CYP3A4、CYP2B6和CYP2C诱导剂,2,3,7,8-四氯二苯并-dioxin(TCDD)——CYP1A1/1A2诱导剂)。
在人肝微粒体中,普罗迷嗪5-硫氧化物和N-脱甲基普罗迷嗪的形成与CYP1A2的水平以及乙氧基苦味酸O-脱乙基酶和对硝基苯酚N-羟化酶的活性显著相关,同时也与CYP3A4的水平和环孢素A氧化酶的活性显著相关。此外,N-脱甲基普罗迷嗪的形成与S-甲乙双键酶的活性良好相关。
呋拉西林(CYP1A2抑制剂)和酮康唑(CYP3A4抑制剂)显著降低了普罗迷嗪5-硫氧化的速率,而呋拉西林和噻氯匹啶(CYP2C19抑制剂)显著降低了人肝微粒体中普罗迷嗪N-脱甲基的速率。
cDNA表达的人CYPs生成了不同量的普罗迷嗪代谢物,但在治疗浓度(10 μM)下,各CYP异构体催化普罗迷嗪代谢的速率如下:5-硫氧化为1A1 > 2B6 > 1A2 > 2C9 > 3A4 > 2E1 > 2A6 > 2D6 > 2C19;N-脱甲基为2C19 > 2B6 > 1A1 > 1A2 > 2D6 > 3A4 > 2C9 > 2E1 > 2A6。在5-硫氧化中,CYP1A亚家族、CYP3A4和CYP2B6具有最高的固有清除率(Vmax/Km);在N-脱甲基中,CYP2C19、CYP1A亚家族和CYP2B6具有最高的固有清除率。
在人原代肝细胞培养物中,TCDD(CYP1A亚家族诱导剂)以及利福霉素(主要是CYP3A4诱导剂)诱导了普罗迷嗪5-硫氧化物和N-脱甲基普罗迷嗪的形成。
根据各种CYP在人类肝脏中的相对表达水平,结果显示CYP1A2和CYP3A4是负责5-硫氧化的主要异构体,而CYP1A2和CYP2C19是催化普罗迷嗪N-脱甲基作用的基本异构体。在研究的其他异构体中,CYP2C9和CYP3A4分别对普罗迷嗪的5-硫氧化和N-脱甲基作用有较小的贡献。CYP2A6、CYP2B6、CYP2D6和CYP2E1在普罗迷嗪研究代谢途径中的作用似乎可以忽略不计。
British Journal of Pharmacology (2003) 138, 1465–1474. doi:10.1038/sj.bjp.0705195