体外中国成人肝微粒体中氯胍活化为氯胍三嗪由CYP2C19和CYP3A4介导(英文)

目的:鉴定中国成人肝微粒体中介导氯胍(PG)活化为氯胍三嗪(CG)的细胞色素P450(CYP450).方法:分析中国成人(n=6)肝微粒体中PG活化为CG的酶促动力学,各种CYP450抑制剂对该代谢的作用及其与S-美芬妥英4′-羟化的关系.结果:6个标本中,除一个外(两酶米氏模型),PG活化为CG的酶促动力学符合米氏一酶模型;CYP3A4和CYP2E1的选择性抑制剂醋竹桃霉素(81.1％)和二乙二硫基苯甲酸(47.23％)可抑制CG生成,其它抑制剂没有明显作用;在低PG浓度时,PG的环化与S-美芬妥英4′-羟化显著相关(r=0.805,P<0.05),高浓度时相关性明显减小.结论:在中国成人肝微粒体中CYP2C19和CYP3A4参与了PG活化为CG.     

定量5-羟奥美拉唑和奥美拉唑砜以探测中国人肝微粒体中CYP2C19和CYP3A4的活性(英文)

目的:建立同时定量5-羟奥美拉唑(5-OH-OP)和奥美拉唑砜(OPS)的分析方法,探讨奥美拉唑(OP)在中国人肝微粒体中能否作为细胞色素 P450 2C19(CYP2C19)及3A4(CYP3A4)的活性表型探针药.方法:在中国人肝微粒体中进行OP的体外代谢,以高压液相色谱法(HPLC)检测主要代谢产物5-OH-OP及OPS;抗CYP2C8/9/19及抗CYR3A4的单克隆抗体被用于抑制实验;以Westem斑点法和光密度扫描定量肝微粒体中CYP2C19及CYP3A4的含量.结果:在HPLC分析中5-OH-OP及OPS有很好的洗脱,二者检测限均为0.01nmol,回收率为98％—102％并且变异系数小于9.5％;抗CYP2C8/9/19及抗CYP3A4均对5-OH-OP的生成有显著的抑制作用(P<0.05),二者的抑制作用呈底物浓度依赖,并且抗CYP3A4几乎可单独去除OPS的生成(>87％);在底物浓度为2μmol/L OP时,中国人肝微粒体中OP的5-羟化与美芬妥英的4′-羟化活性之间(r=0.72,P<0.01)、OP的5-羟化活性与CYP2C19含量之间(r=0.82,P<0.01)以及OP的硫代氧化活性与CYP3A4含量之间(r=O.78,P相似文献   

己烯雌酚对人肝微粒体内CYP3A4和CYP2C9酶的抑制作用

目的:体外实验考察己烯雌酚(DES)对细胞色素P450 3A4(CYP3A4)和细胞色素P450 2C9(CYP2C9)活性的抑制作用,以评佑DES通过抑制这两个重要的细胞色素P450(CYP)亚型而引发药物-药物相互作用的可能性.方法:混合人肝微粒体与不同浓度的DES(或阳性抑制剂),CYP3A4或CYP2C9的探针...     

N-Demethylation of clomipramine in human liver microsomes in vitro1

采用人肝微粒体应用酶促动力学分析,观察特异性细胞色素P450(CYP450)抑制剂对氯米帕明(CIM) N-去甲基代谢的作用以及CIM去甲基代谢与S-美芬妥英4′-羟化代谢的相关性,以阐明参与CIM N-去甲基代谢的CYP450的种类, 性质及其在代谢中的作用. 酶促动力学分析结果表明有高亲和力酶及具有底物别构激活特性的低亲和力酶参与了CIM的N-去甲基代谢. 抑制实验结果表明CYP 1A2特异性抑制剂呋拉茶碱（Fur）主要抑制低浓度CIM的去甲基代谢,CYP 3A4特异性抑制剂醋竹桃霉素（TAO）主要抑制高浓度CIM去甲基代谢. 相关实验发现3 μmol     

体外研究人细胞色素P450在雌二醇代谢中的作用(英文)

目的:研究雌二醇在cDNA表达的P450和人肝微粒体中的代谢机制,为在体内研究细胞色素P450活性与肿瘤发生的关系提供依据。方法:用HPLC-ECD法测定雌二醇的代谢产物。通过雌二醇在不同cDNA表达的P450中代谢,13例人肝微粒体中相关性研究,抑制剂对代谢的影响以及微粒体中17β-羟基脱氢化和2-羟基化代谢的催化动力学的研究来推断雌二醇的代谢机理。结果:在cDNA表达的P450中,催化2-羟基化代谢的P450按活性排列依次为CYP1A2、CYP3A4、CYP2C9。CYP2C9、CYP2C19和CYP2C8均具有较高的催化17β-羟基脱氢化活性。抑制CYP1A2与抑制CYP3A4对2-羟基化代谢产物生成的影响相似,可认为CYP1A2和CYP3A4在人肝微粒体中催化2-羟基化代谢的作用相近。雌二醇代谢的途径与底物浓度有关,低浓度时(1,10μmol/L)17β-羟基脱氢化为主要代谢途径;高浓度时(100μmol/L),2-羟基化成为主要代谢途径。结论:高底物浓度时,雌二醇主要由CYP1A2和CYP3A4催化代谢为2-羟基化产物。低底物浓度时,主要由CYP2C9、CYP2C19和CYP2C8催化生成17β-羟基去氢化产物。     

罗红霉素在苯巴比妥诱导的大鼠肝微粒体中的代谢

目的:研究罗红霉素在大鼠肝微粒体中的代谢,并考察罗红霉素及其代谢物对细胞色素P-450的影响.方法:采用超离心法制备了苯巴比妥诱导的大鼠肝微粒体酶.罗红霉素的体外代谢采用微粒体孵化方法,代谢物经LC-MS方法分离和分析,并通过进一步与合成对照品比较其质谱和色谱行为确定其结构.结果:在微粒体孵化液中发现了N-去甲基,N-双去甲基及O-去烷基三种代谢物.罗红霉素及其代谢物与CYP450 Fe~(2 )形成复合物的能力较弱.结论:罗红霉素在苯巴比妥诱导的大鼠肝微粒体中主要经历N-去甲基化和肟醚侧链O-去烷基化途径,两种转化途径均为NADPH依赖性.罗红霉素及其代谢物对CYP450的抑制作用较弱,     

PCR-RFLP检测CYP2C 19基因多态性验证

CYP2C19是CYP450超家族的一种同工酶。CYP2C19基因突变影响该基因的正常表达,表现为酶活性低下。CYP2C19*2和CYP2C 19*3是基因突变的主要类型。尽管CYP2C19占人肝微粒体CYP450的含量较小(0.8%~1.4%)[1],但其酶缺陷在东方人中高达15%~23%,成为其酶代谢底物产生药物效应个体差异和种族差异的主要原因,是药物代谢酶分子遗传药理学研究领域中最为关注的靶目     

大鼠肝微粒体CYP3A1/2和CYP2C9/10参与甘草次酸羟化代谢

目的:对参与18α-甘草次酸(GA)羟化代谢的细胞色素P450(cytochromeP450,CYP)亚型进行研究。方法:采用大鼠肝微粒体体外代谢GA的孵育方法和高效液相色谱(HPLC)技术,通过分析甘草次酸在肝微粒体中形成的单羟化代谢物的酶促动力学,分析其酶学模型,然后用不同的CYP同工酶选择性抑制剂和底物进行抑制实验,初步选出介导甘草次酸单羟化代谢所涉及的CYP同工酶。结果:大鼠肝微粒体羟化代谢GA呈反应时间(10～40min),底物浓度(25～200μmol/L)和蛋白浓度(0.25～1.0g/L)依赖性。GA代谢为22α-羟-GA和24-羟-GA的Vmax分别为(7.9±1.4)μmol.min-1.g-1和(3.4±1.0)μmo1.min-1.g-1,Km分别为(33±9)μmol/L和(68±18)μmol/L。抑制性研究可见:TAO和Ery剂量依赖性抑制22α-羟-GA形成,最大抑制率分别为82.4%和45.7%,而Sul无显著抑制作用;Sul剂量依赖性抑制24-羟-GA形成,抑制率依次为26.8%、45.3%和69.5%,而TAO和Ery的抑制作用不显著。红霉素N-脱甲基酶活性与22α-羟化代谢速率高度相关(r=0.864,P<0.01,n=10),与24-羟化代谢速率无明显相关(r=0.310,P>0.05,n=10)。结论:大鼠肝微粒体CYP3A1/2和CYP2C9/10分别参与了GA的C-22α和C-24羟化代谢。     

氟西汀的药代动力学及其与CYP450酶的作用

氟西汀是近年来开发的一种新型 5 羟色胺重摄取抑制剂 ,它通过选择性抑制突触间 5 羟色胺 (5 HT)的重摄取和代谢 ,增加突触间 5 HT的传递而发挥作用。氟西汀由细胞色素P45 0 (CYP45 0 )酶进行氧化代谢 ,现已证明CYP2C9,CYP2C19和CYP2D6是介导氟西汀N 去甲基代谢的主要CYP45 0同工酶。由于氟西汀及代谢产物去甲氟西汀分别为CYP2D6、CYP3A4、CYP2C19和CYP2C9的抑制剂 ,因此它可与经这些CYP同工酶催化代谢的药物产生明显的相互作用 ;从而导致不同个体间的药代动力学差异和疗效差异。     

CYP2C9和CYP2C19基因多态性对药物代谢的影响及个体化用药研究进展

CYP2C9、CYP2C19酶是细胞色素P450系统中重要的药物代谢酶,共同参与许多重要药物的体内代谢。CYP2C9、CYP2C19基因具有高度多态性,在基因编码区和非编码区存在许多碱基突变,这种突变会影响酶的活性,导致酶底物药物清除率改变,从而导致药品不良反应的发生。本文对CYP2C9、CYP2C19基因突变的发生频率及对药物代谢的影响做详细阐述。     

Evidence for involvement of polymorphic CYP2C19 and 2C9 in the N-demethylation of sertraline in human liver microsomes

AIMS: The present study was designed to define the kinetic behaviour of sertraline N-demethylation in human liver microsomes and to identify the isoforms of cytochrome P450 involved in this metabolic pathway. METHODS: The kinetics of the formation of N-demethylsertraline were determined in human liver microsomes from six genotyped CYP2C19 extensive (EM) and three poor metabolisers (PM). Selective inhibitors of and specific monoclonal antibodies to various cytochrome P450 isoforms were also employed. RESULTS: The kinetics of N-demethylsertraline formation in all EM liver microsomes were fitted by a two-enzyme Michaelis-Menten equation, whereas the kinetics in all PM liver microsomes were best described by a single-enzyme Michaelis-Menten equation similar to the low-affinity component found in EM microsomes. Mean apparent Km values for the high-and low-affinity components were 1.9 and 88 microm and V max values were 33 and 554 pmol min-1 mg-1 protein, respectively, in the EM liver microsomes. Omeprazole (a CYP2C19 substrate) at high concentrations and sulphaphenazole (a selective inhibitor of CYP2C9) substantially inhibited N-demethylsertraline formation. Of five monoclonal antibodies to various cytochrome P450 forms tested, only anti-CYP2C8/9/19 had any inhibitory effect on this reaction. The inhibition of sertraline N-demethylation by anti-CYP2C8/9/19 was greater in EM livers than in PM livers at both low and high substrate concentrations. However, anti-CYP2C8/9/19 did not abolish the formation of N-demethylsertraline in the microsomes from any of the livers. CONCLUSIONS: The polymorphic enzyme CYP2C19 catalyses the high-affinity N-demethylation of sertraline, while CYP2C9 is one of the low-affinity components of this metabolic pathway.     

中国人肝微粒体细胞色素P450 2A6的体外代谢特征

目的:观察人肝微粒体CYP2A6动力学特征.方法:采用生化分析法,体外研究化学异物对CYP2A6酶活性的影响.测定香豆素7-羟化酶的动力学参数.同时分析CYP2A6与Ⅱ相酶UGT之间的相关性.结果:CYP2A6活性差异8.8倍,K_m和V_(max)分别为0.25-1.56μmol·L~(-1)、1.41-8.70μmol·min~(-1)·g~(-1).匹鲁卡品、二乙基二硫代氨基甲酸盐、利福平明显抑制CYP2A6活性,IC_(50)值分别为 5.31μmol·L~(-1)、156.35μmol·L~(-1)和38.81μmol·L~(-1).α-萘黄酮、磺胺苯吡唑、醋竹桃霉素、酮康唑、泼尼松龙和阿奇霉素对香豆素7-羟化反应几乎无影响.CYP2A6与UGT_2之间存在显著相关性(r=0.9453,P<0.05).结论:中国人细胞色素P4502A6酶活性及动力学参数存在个体差异,CYP2A6与UGT_2之间有显著相关.除匹鲁卡品有CYP2A6选择性抑制作用外,利福平和二乙基二硫代氨基甲酸盐也明显抑制CYP2A6活性.     

Induction of diphenytriazol on cytochrome CYP1A

AIM: To study the effects of diphenytriazol on cytochrome P-450 (CYP) enzymes. METHODS: SD rats were pretreated with diphenytriazol. The catalytic activities of rat liver microsomes were determined by assaying ethoxyresorufin-O-deethylase (EROD) and pentoxyresorufin-O-dealkylase. Phenacetin and aminopyrine were se- lected as the substrate of CYP1A and CYP2B, respectively. The concentration of remaining substrate in microso- mal incubates was determined by reversed-phase high-pe…     

氯米帕明在体外人肝微粒体中的氮位去甲基代谢

采用人肝微粒体应用酶促动力学分析,观察特异性细胞色素P450(CYP450)抑制剂对氯米帕明(CIM) N-去甲基代谢的作用以及CIM去甲基代谢与S-美芬妥英4′-羟化代谢的相关性,以阐明参与CIM N-去甲基代谢的CYP450的种类, 性质及其在代谢中的作用. 酶促动力学分析结果表明有高亲和力酶及具有底物别构激活特性的低亲和力酶参与了CIM的N-去甲基代谢. 抑制实验结果表明CYP 1A2特异性抑制剂呋拉茶碱（Fur）主要抑制低浓度CIM的去甲基代谢,CYP 3A4特异性 抑制剂醋竹桃霉素（TAO）主要抑制高浓度CIM去甲基代谢. 相关实验发现3 μmol·L^-1 CIM代谢生成N-去甲基CIM的速率与200 μmol·L^-1 S-美芬妥英生成4′-羟基美芬妥英的速率无显著相关性, 提示CYP 2C19对于催化人肝微粒体中CIM的去甲基代谢仅起较为次要或很小的作用. 结果表明,CYP 1A2主要参与低浓度CIM在体外人肝微粒体N-去甲基代谢,CYP 3A4因其底物激活特性主要在高浓度CIM的去甲基代谢中起作用,CYP 2C19则作用很小.     

Effects of individual ginsenosides, ginkgolides and flavonoids on CYP2C19 and CYP2D6 activity in human liver microsomes

1. The effects of four individual ginsenosides (Rb1, Rb2, Rc and Rd), two ginkgolides (A and B) and one flavonoid (quercetin) on CYP2C19-dependent S-mephenytoin 4 cent-hydroxylation and CYP2D6-mediated bufuralol 1 cent-hydroxylation were evaluated in human liver microsomes. 2. Increasing concentrations of each test compound were added to microsomal incubation mixtures containing a well-characterized marker substrate (S-mephenytoin for CYP2C19 or bufuralol for CYP2D6) to determine their IC(50) values (compound concentration yielding 50% inhibition of a marker enzyme activity), which were estimated by graphical inspection. 3. For CYP2C19, the IC(50) values were 46, 46 and 62 micromol/L for ginsenoside Rd, quercetin and ginsenoside Rb2, respectively, whereas only ginsenoside Rd had an IC(50) value of 57 micromol/L for CYP2D6. 4. The data suggest that the tested compounds are not likely to inhibit the metabolism of the concurrent use of a given drug whose primary route of elimination is through CYP2C19 or CYP2D6.     

CYP2B6, CYP3A4, and CYP2C19 are responsible for the in vitro N-demethylation of meperidine in human liver microsomes.

Meperidine is an opioid analgesic metabolized in the liver by N-demethylation to normeperidine, a potent stimulant of the central nervous system. The purpose of this study was to identify the human cytochrome P450 (P450) enzymes involved in normeperidine formation. Our in vitro studies included 1) screening 16 expressed P450s for normeperidine formation, 2) kinetic experiments on human liver microsomes and candidate P450s, and 3) correlation and inhibition experiments using human hepatic microsomes. After normalization by its relative abundance in human liver microsomes, CYP2B6, CYP3A4, and CYP2C19 accounted for 57, 28, and 15% of the total intrinsic clearance of meperidine. CYP3A5 and CYP2D6 contributed to < 1%. Formation of normeperidine significantly correlated with CYP2B6-selective S-mephenytoin N-demethylation (r = 0.88, p < 0.0001 at 75 > microM meperidine, and r = 0.89, p < 0.0001 at 350 microM meperidine, n = 21) and CYP3A4-selective midazolam 1'-hydroxylation (r = 0.59, p < 0.01 at 75 microM meperidine, and r = 0.55, p < 0.01 at 350 microM meperidine, n = 23). No significant correlation was observed with CYP2C19-selective S-mephenytoin 4'-hydroxylation (r = 0.36, p = 0.2 at 75 microM meperidine, and r = 0.02, p = 0.9 at 350 microM meperidine, n = 13). An anti-CYP2B6 antibody inhibited normeperidine formation by 46%. In contrast, antibodies inhibitory to CYP3A4 and CYP2C8/9/18/19 had little effect (<14% inhibition). Experiments with thiotepa and ketoconazole suggested inhibition of microsomal CYP2B6 and CYP3A4 activity, whereas studies with fluvoxamine (a substrate of CYP2C19) were inconclusive due to lack of specificity. We conclude that normeperidine formation in human liver microsomes is mainly catalyzed by CYP2B6 and CYP3A4, with a minor contribution from CYP2C19.     

中国人肝微粒体中细胞色素P450酶含量和活性的个体间差异(英文)

目的:比较不同中国人肝微粒体中几种重要细胞色素P450(CYP)的酶含量和活性。方法:运用West-ern斑点分析和光密度扫描,对17个汉族、17个壮族和8个苗族受试者肝微粒体中的细胞色素P4501A2(CYP1A2)、2C9及3A4进行定量;非那西丁、甲磺丁脲、异喹胍和奥美拉唑分别用于体外测量CYP1A2、2C9、2D6及3A4的活性。结果:CYP1A2、2C9及3A4的含量和活性具有很大的个体间变异,另外CYP2D6的活性在各样本间也有很大差异;CYP3A4(32％)是中国人肝微粒体中含量最丰富的CYP,CYP2C9(19％)和CYP1A2(16％)的含量也很可观;除了CYP1A2的含量和活性具有一定的种族和性别差异外,未发现其它CYP具有种族和性别差异;CYP1A2、2C9和3A4的酶蛋白含量分别和它们的活性具有很好的相关性。结论:我们的结果为在中国人中进行药物代谢研究提供了非常有价值的信息。     

混合探针底物法同时预测细胞色素P450酶5种亚型的抑制作用

本研究建立了混合探针底物法同时预测细胞色素P450(cytochrome P-450，CYP450)酶5种亚型的抑制作用。将CYP450酶5种亚型的特异性探针底物非那西丁(CYP1A2)、右美沙芬(CYP2D6)、甲苯磺丁脲(CYP2C9)、奥美拉唑(CYP2C19)及咪达唑仑(CYP3A4)同时与人肝微粒体在体外进行孵化反应，采用液相色谱-串联质谱分析方法同时测定5个特异性底物及其生成的对应的5种代谢产物(对乙酰氨基酚、右啡烷、4-羟基甲苯磺丁脲、5-羟基奥美拉唑和1′-羟基咪达唑仑)。并选择5种细胞色素P450酶的特异性抑制剂α-萘黄酮(CYP1A2)、奎尼丁(CYP2D6)、磺胺苯吡唑(CYP2C9)、氟康唑(CYP2C19)和酮康唑(CYP3A4)加入到其所对应酶的单个探针底物及混合探针底物的反应体系中，测定生成的代谢物，计算相应IC₅₀值，对方法进行验证。5种特异性的抑制剂与混合探针底物反应后所得的IC₅₀值和与单个探针底物反应后所得的IC₅₀值具有很好的一致性且与文献报道的基本一致。本研究建立的混合探针底物法可以用于快速高通量地同时预测化合物对CYP450酶5种亚型活性的抑制作用。     

Contribution of CYP3A4, CYP2B6, and CYP2C9 isoforms to N-demethylation of ketamine in human liver microsomes.

Ketamine is a widely used drug for its anesthetic and analgesic properties; it is also considered as a drug of abuse, as many cases of ketamine illegal consumption were reported. Ketamine is N-demethylated by liver microsomal cytochrome P450 into norketamine. The identification of the enzymes responsible for ketamine metabolism is of great importance in clinical practice. In the present study, we investigated the metabolism of ketamine in human liver microsomes at clinically relevant concentrations. Liver to plasma concentration ratio of ketamine was taken into consideration. Pooled human liver microsomes and human lymphoblast-expressed P450 isoforms were used. N-demethylation of ketamine was correlated with nifedipine oxidase activity (CYP3A4-specific marker reaction), and it was also correlated with S-mephenytoin N-demethylase activity (CYP2B6-specific marker reaction). Orphenadrine, a specific inhibitor to CYP2B6, and ketoconazole, a specific inhibitor to CYP3A4, inhibited the N-demethylation of ketamine in human liver microsomes. In human lymphoblast-expressed P450, the activities of CYP2B6 were higher than those of CYP3A4 and CYP2C9 at three concentrations of ketamine, 0.005, 0.05, and 0.5 mM. When these results were extrapolated using the average relative content of these P450 isoforms in human liver, CYP3A4 was the major enzyme involved in ketamine N-demethylation. The present study demonstrates that CYP3A4 is the principal enzyme responsible for ketamine N-demethylation in human liver microsomes and that CYP2B6 and CYP2C9 have a minor contribution to ketamine N-demethylation at therapeutic concentrations of the drug.