Perazine at therapeutic drug concentrations inhibits human cytochrome P450 isoenzyme 1A2 (CYP1A2) and caffeine metabolism – an in vitro study

The aim of the present study was to estimate the inhibitory effect of perazine, a phenothiazine neuroleptic with piperazine structure in a side chain, on human CYP1A2 activity measured as a rate of caffeine 3-N- and 1-N-demethylation. Moreover, the influence of perazine on other caffeine metabolic pathways such as 7-N-demethylation (CYP1A2, CYP2C8/9, CYP3A4) and 8-hydroxylation (CYP3A4, CYP1A2, CYP2C8/9) was also determined. The Dixon analysis showed that in both human liver microsomes and Supersomes CYP1A2 perazine potently and to a similar degree inhibited caffeine 3-N-demethylation (K_i = 3.5 μM) and 1-N-demethylation (K_i = 5 μM). Perazine moderately diminished the rate of caffeine 7-N-demethylation in Supersomes CYP1A2 (K_i = 11.5 μM) and liver microsomes (K_i = 20 μM), and attenuated C-8-hydroxylation (K_i = 15.5μM) in Supersomes CYP1A2. On the other hand, perazine weakly inhibited caffeine C-8-hydroxylation in liver microsomes (K_i = 98 μM). About 80% of basal CYP1A2 activity was reduced by the therapeutic concentrations of perazine (5–10 μM).The obtained results show that perazine at its therapeutic concentrations is a potent inhibitor of human CYP1A2. Hence, taking account of CYP1A2 contribution to the metabolism of endogenous substances (steroids), drugs (xanthine derivatives, phenacetin, propranolol, imipramine, phenothiazine neuroleptics, clozapine) and carcinogenic compounds, the inhibition of CYP1A2 by perazine may be of physiological, pharmacological and toxicological importance.     

细胞色素P450 2C19单碱基突变位点CYP2C19m1的分析

目的:CYP2C19ml是引起CYP2C19酶活性缺陷的主要等位基因,有83%左右的慢代谢者含有CYP2C19ml等位基因,本文试图建立一步PCR测定CYP2C19ml等位基因的方法。方法:根据等位基因特异扩增(ASA)原理设计两对分别特异扩增野生型等位基因和突变型等位基因的引物,建立了一步PCR测定CYP2C19ml等位基因的方法。结果:对39位随机受试者进行了基因分型研究,发现3位CYP2C19ml纯合子、18位CYP2C19ml杂合子,其余18位为野生型纯合子。结论:说明效法能够用于测定CYP2C19ml等住基因,并且证明该法具有简便、快速和污染少的优点。     

细胞色素P450 2C19单碱基突变位点CYP2C19m1的分析

目的:CYP2C19ml是引起CYP2C19酶活性缺陷的主要等位基因,有83％左右的慢代谢者含有CYP2C19ml等位基因,本文试图建立一步PCR测定CYP2C19ml等位基因的方法。方法:根据等位基因特异扩增(ASA)原理设计两对分别特异扩增野生型等位基因和突变型等位基因的引物,建立了一步PCR测定CYP2C19ml等位基因的方法。结果:对39位随机受试者进行了基因分型研究,发现3位CYP2C19ml纯合子、18位CYP2C19ml杂合子,其余18位为野生型纯合子。结论:说明效法能够用于测定CYP2C19ml等住基因,并且证明该法具有简便、快速和污染少的优点。     

Association between blood carisoprodol:meprobamate concentration ratios and CYP2C19 genotype in carisoprodol-drugged drivers: decreased metabolic capacity in heterozygous CYP2C19*1/CYP2C19*2 subjects?

Carisoprodol is metabolized to meprobamate by the cytochrome P450 enzyme CYP2C19, encoded by the polymorphic CYP2C19 gene. Most studies on carisoprodol metabolism have been carried out on individuals phenotyped for CYP2C19 activity using the probe drug S-mephenytoin. We aimed to investigate whether the ratio of carisoprodol to meprobamate in a 'real life' setting could be predicted by CYP2C19 genotype or, more specifically, if high carisoprodol : meprobamate ratios in drugged drivers could be ascribed to the presence of mutant CYP2C19 alleles. From original material comprising 358 blood samples from apprehended drivers, two polarized groups were selected; a high-ratio group of 11 subjects where the carisoprodol : meprobamate ratio was >1 and a low-ratio control group of 23 subjects where the ratio was <0.31. Genotyping was carried out for the CYP2C19*2, CYP2C19*3 and CYP2C19*4 alleles. DNA samples from 94 healthy blood donors were used as reference material. The number of mutant alleles in the high-ratio and low-ratio groups was significantly higher and lower, respectively, than in the reference material. The increased number of mutant alleles in the high-ratio group was not due to the presence of many poor metabolizers, but to a high number of heterozygous individuals with the genotype CYP2C19*1/*2. This result indicates a gene dosage effect where the carisoprodol : meprobamate ratio reflects the number of active CYP2C19 alleles. The metabolism of carisoprodol to meprobamate is dependent on CYP2C19 genotype. Heterozygous individuals with the CYP2C19*1/*2 genotype have a reduced capacity for metabolizing carisoprodol, and should probably be regarded as intermediate metabolizers of this drug.     

Identification of CYP3A4 and CYP2C8 as the major cytochrome P450 s responsible for morphine N -demethylation in human liver microsomes

1. The aim was to identify the cytochrome P450 (CYP) enzymes responsible for the N -demethylation of morphine in vitro. 2. In human liver microsomes, normorphine formation followed Michaelis-Menten kinetics with mean K m and V max of 12.4 ± 2.2 mM and 1546 ± 121 pmol?min ? 1?mg ? 1, respectively. In microsomes from a panel of 14 human livers phenotyped for 10 CYP enzymes, morphine N -demethylation correlated with testosterone 6 β -hydroxylation (r = 0.91, p <0.001) and paclitaxel 6- α hydroxylation (r = 0.72, p <0.001), two specific markers of CYP3A4 and CYP2C8, respectively. Normorphine formation decreased when incubated in the presence of troleandomycin or quercetin (by 46 and 33-36%, respectively), which further corroborates the contribution of CYP3A4 and CYP2C8. 3. Among eight recombinant human CYP enzymes tested, CYP3A4 and CYP2C8 exhibited the highest intrinsic clearance. More than 90% of morphine N -demethylation could be accounted for via the action of both CYP3A4 and CYP2C8. 4. The in vitro findings suggest that hepatic CYP3A4, and to a lesser extent CYP2C8, play an important role in the metabolism of morphine into normorphine.     

Effect of fermented red ginseng on cytochrome P450 and P‐glycoprotein activity in healthy subjects,as evaluated using the cocktail approach

AimsWe assessed the drug interaction profile of fermented red ginseng with respect to the activity of major cytochrome (CYP) P450 enzymes and of a drug transporter protein, P‐glycoprotein (P‐gp), in healthy volunteers.MethodsThis study was an open‐label crossover study. The CYP probe cocktail drugs caffeine, losartan, dextromethorphan, omeprazole, midazolam and fexofenadine were administered before and after 2 weeks of fermented red ginseng administration. Plasma samples were collected, and tolerability was assessed. Pharmacokinetic parameters were calculated, and the 90% confidence intervals (CIs) of the geometric mean ratios of the parameters were determined from logarithmically transformed data. Values were compared between before and after fermented red ginseng administration using analysis of variance (anova).ResultsFifteen healthy male subjects were evaluated, none of whom were genetically defined as a poor CYP2C9, CYP2C19 or CYP2D6 metabolizer based on genotyping. Before and after fermented red ginseng administration, the geometric least‐square mean metabolic ratio (90% CI) was 0.901 (0.830–0.979) for caffeine (CYP1A2) to paraxanthine, 0.774 (0.720–0.831) for losartan (CYP2C9) to EXP3174, 1.052 (0.925–1.197) for omeprazole (CYP2C19) to 5‐hydroxyomeprazole, 1.150 (0.860–1.538) for dextromethorphan (CYP2D6) to dextrorphan, and 0.816 (0.673–0.990) for midazolam (CYP3A4) to 1‐hydroxymidazolam. The geometric mean ratio of the area under the curve of the last sampling time (AUC_last) for fexofenadine (P‐gp) was 1.322 (1.112–1.571).ConclusionNo significantly different drug interactions were observed between fermented red ginseng and the CYP probe substrates following the two‐week administration of concentrated fermented red ginseng. However, the inhibition of P‐gp was significantly different between fermented red ginseng and the CYP probe substrates. The use of fermented red ginseng requires close attention due to the potential for increased systemic exposure when it is used in combination with P‐gp substrate drugs.     

Relative roles of CYP2C19 and CYP3A4/5 in midazolam 1′-hydroxylation

1. During the characterization of recombinant CYP2C19, it was observed that this enzyme metabolized midazolam, which is generally regarded as CYP3A4/5 substrate, and we therefore decided to pursue this observation further.

2. CYP2C19 showed a Michaelis-Menten pattern for midazolam 1′-hydroxylation and was inhibited by (+)-N-3-benzylnirvanol and S-mephenytoin, which are a standard potent inhibitor and a substrate of CYP2C19, respectively.

3. The inhibitory potency by CYP3A4/5 inhibitor on the midazolam 1′-hydroxylation in human liver microsomes (HLM) was correlated with the CYP3A4/5 specific catalytic activity, but such correlation was not observed in CYP2C19 enzyme. The in vitro intrinsic clearance value for midazolam 1′-hydroxylation was not changed by the addition of (+)-N-3-benzylnirvanol in four individual HLM preparations.

4. These results indicated that although CYP2C19 is capable of catalyzing midazolam 1′-hydroxylation, CYP3A4/5 play a more important role.     

Evaluation of lansoprazole as a probe for assessing cytochrome P450 2C19 activity and genotype–phenotype correlation in childhood

Purpose

Lansoprazole, a cytochrome P450 2C19 (CYP2C19) substrate, has been widely used in children to manage acid-related diseases. CYP2C19 exhibits marked genetic polymorphisms, and distribution of these polymorphisms varies among different ethnic groups. There is limited data regarding the use of probe drugs for determining CYP2C19 activity in children. The aim of this study was to evaluate lansoprazole as an in vivo phenotyping probe for assessing CYP2C19 activity in children.

Methods

The CYP2C19*2, *3, and *17 variants were determined in 244 children. Three hours after a single oral dose of lansoprazole (n?=?94) or omeprazole (n?=?19), plasma lansoprazole and 5-hydroxy lansoprazole or omeprazole and 5-hydroxy omeprazole concentrations were analyzed by high-performance liquid chromatography.

Results

The CYP2C19*17 was the most frequent variant allele (24.4%). The group of patients with CYP2C19*17*17 genotype had a 70% lower (p?CYP2C19*1*1 genotype group, whereas the CYP2C19*2*2 group had 6.9-fold higher (p?*17*17 [mean ± standard deviation (SD); 2.8?±?2.1] group and higher in the *2*2 group (63.5?±?12.2) compared with that of the *1*1 genotype group (6.1?±?4.5).

Conclusion

According to our results from a Turkish pediatric population, lansoprazole is a suitable probe drug for phenotyping CYP2C19. The CYP2C19*2 and *17 variants should be taken into consideration in predicting the clinical outcome of therapy with lansoprazole in the pediatric population.

     

Tobacco smoke-dependent changes in cytochrome P450 1A1, 1A2, and 2E1 protein expressions in fetuses, newborns, pregnant rats, and human placenta

Tobacco smoke (TS) was described as a mixture of numerous cytochrome P450 (P450) substrates, inducers, and inhibitors. These inducers and inhibitors may modify drug clearance and xenobiotic or endogenous metabolism affecting P450s expression. In the present study, the effect of gestation and TS on: (1) cytochrome P450 CYP1A1, CYP1A2, and CYP2E1 protein expressions, and (2) cytochrome P450-linked microsomal enzyme activities, were studied in fetal rat liver, rat, and human placenta and in newborn and adult rat hepatic and extrahepatic tissues. Non-pregnant and pregnant 4-month-old female Wistar rats were exposed to TS (500, 1,000, or 1,500 mg carbon monoxide per m³ air) in a toxicological chamber for 3 weeks (6 h daily, 5 days weekly). Human placentas were sampled from non-smoking, passive smoking, or active smoking primiparas. The efficacy of exposure was assessed by measuring urine cotinine levels. The TS-dependent inductory effect on the expression of CYP1A1 and 1A2 and related monooxygenase activities, and the inhibitory/inductory effect on CYP2E1 expression in rat tissues were observed. Pregnancy was associated with decreased levels of constitutive CYP1A1 and 2E1 in hepatic and extrahepatic tissues, TS-inducible CYP1A2 expression in the liver, and CYP1A1 expression in lungs and heart, but had no inhibitory effect on TS-inducible CYP1A1 and 2E1 expression, EROD, and P450-cooperated enzyme activities in the liver, kidney, and, in the latter case, in the heart. The presence of TS-induced CYP1A1 protein was confirmed in rat and human placenta and showed in newborn liver and lungs. CYP1A2 and 2E1 proteins were detectable in fetal rat liver. It was concluded that the expression of CYP1A1, 1A2, and 2E1, which metabolize some drugs and activate carcinogens, is controlled by age-, pregnancy-, and tissue-specific regulatory mechanisms in rats. Gestational differences in the regulation of expression of CYP1A subfamily members are not excluded. CYP1A1 and 2E1, but not CYP1A2 inductory mechanisms seem to be functional in fetal liver at day 21 of pregnancy but they appeared to be uninducible under a TS exposure. In TS-exposed pregnant females and fetuses the effects of metabolic activation of CYP1A1 and 1A2 substrates might be reduced because of lower CYP expressions or poor induction, respectively.This paper was presented partially at the following congresses: 7th European ISSX Meeting, Budapest 1999; Eurotox 1999, Oslo; 11th World Conference on Tobacco OR Health, Chicago, 2000; EUROTOX 2001, Istanbul; 6th International ISSX Meeting, Munich, 2001     

Use of cafeine as a probe for rapid determination of cytochrome P-450 CYP1A2 activity in humans

目的：建立快速测定细胞色素Ｐ４５０ＣＹＰ１Ａ２酶活性的高压液相色谱方法．方法：取３００μＬ血浆样品，用β羟乙基茶碱作内标，经５ｍＬ氯仿／异丙醇（９∶１）萃取处理后，用００５％的乙酸、乙腈和甲醇作为基本流动相，采用梯度洗脱程序在ＯＤＳ柱上分离待测组分，紫外检测波长２８２ｎｍ．结果：无内源性物质干扰测定．次黄嘌呤、内标和咖啡因快速基线分离，三者的保留时间均小于１３分钟．次黄嘌呤和咖啡因的检测下限均为０１μｍｏｌ·Ｌ－１，线性范围分别为１－１００μｍｏｌ·Ｌ－１和１－２００μｍｏｌ·Ｌ－１，相关系数分别为０９９９９和０９９８７，变异系数分别小于６％和１０％．两者的平均相对回收率为９６％－１０８％．结论：本方法快速、灵敏，可用于人群ＣＹＰ１Ａ２酶活性研究．     

中国汉族和回族药物代谢酶细胞色素P450(CYP)3A4、CYP2C9、CYP2C19及CYP2D6基因多态性分析

目的对中国汉族、回族健康人群细胞色素P450(CYP)3A4、CYP2C9、CYP2C19及CYP2D6进行基因多态性分析,比较汉族和回族健康人群基因表型和基因频率分布。方法多聚酶链反应-限制性片段长度多态性(PCR-RFLP)法,对300名志愿者的几种基因进行分型。结果汉族、回族CYP3A4*5等位基因频率均为0,CYP3A4*18等位基因频率分别为0.18,0.19;汉族、回族CYP2C9*2等位基因频率分别为0.01,0.05;CYP2C9*13等位基因频率均为0;汉族、回族CYP2C19*2等位基因频率分别为0.39,0.50;CYP2C19*3等位基因频率分别为0.05,0.05;汉族、回族CYP2D6*10等位基因频率分别为0.57,0.39。结论汉族、回族健康人群的CYP3A4*18、CYP2C9*2、CYP2C19*2、CYP2C19*3均没有显著性差异;在汉族、回族健康人群中未发现CYP3A4*5和CYP2C9*13突变;汉族、回族CYP2D6*10等位基因频率有显著性差异(P<0.01);回族人群CYP2D6中速代谢型(*10/*10)频率为13.4%,明显低于汉族的33.1%(P<0.01)。     

黄酮类化合物对细胞色素P450 CYP1，2E1，3A4和19的影响

黄酮类化合物广泛存在于蔬菜、坚果、水果和饮料及中草药中，可诱导或抑制多种细胞色素P450的活性。本篇综述主要集中回顾黄酮类化合物对于细胞色素P450 CYP1，2E1，3A4和19的影响。归纳总结了该类物质抑制和诱导细胞色素P450的多种机制，如刺激特定的受体、稳定相关mRNA等。并总结了该类物质对细胞色素P450的影响体内和体外水平的研究结果并非总是一致的原因，如体内外的浓度的差异、基因和其他环境因素的影响。由于黄酮类化合物可通过影响细胞色素P450的活性影响药物代谢从而导致药物不良反应和药物相互作用，因此在将该类物质与其他药物合用时应高度重视。     

Omeprazole limited sampling strategies to predict area under the concentration–time curve ratios: implications for cytochrome P450 2C19 and 3A phenotyping

Purpose  

To develop a limited sampling strategy (LSS) to predict area under the concentration–time curve (AUC) ratios of omeprazole (AUC_OPZ) to its metabolites 5-hydroxyomeprazole (AUC_5OH) and omeprazole sulfone (AUC_SUL) as phenotyping parameters for cytochrome P450 (CYP) 2C19 and 3A.     

Cytochrome P450 2W1 (CYP2W1) – ready for use as the biomarker and drug target for cancer?

1.?This article aims to evaluate the potentials of using cytochrome P450 2W1 (CYP2W1) as a biomarker and a drug target of cancer because of its characteristic cancer-specific expression.

2.?Discrepant findings comparing the expression levels of CYP2W1 in cancer and non-cancer samples were reported. In general, the expression followed a developmental pattern. The demethylation status of CpG island and the expression levels of CYP2W1 genes was positively correlated.

3.?CYP2W1 was able to activate several procarcinogens, anticancer pro-drugs and to metabolise many endogenous substances including fatty acids and lysophospholipids.

4.?CYP2W1 expression level was suggested to serve as an independent prognostic biomarker in colorectal cancer and hepatocellular carcinoma. The correlation of genetic polymorphisms of CYP2W1 and cancer risk was uncertain.

5.?Further characterisation of CYP2W1 structure is suggested to link to its functions. More studies are warranted to reveal the true status and the regulation of CYP2W1 expression across normal and cancer tissues. Catalytic activity of CYP2W1 should be tested on a wider spectrum of endogenous and exogenous substances before its use as the drug target. Larger size of clinical samples can be included to verify the potential of CYP2W1 as the prognostic or cancer risk biomarker.     

Determination of caffeine and five metabolites simultaneously by HPLC and application on evaluating the activity of CYP1A2, CYP2A6, NAT2 and XO in Chinese healthy volunteers

HPLC同时检测咖啡因及其代谢产物并在健康中国人群中CYP1A2,CYP2A6,NATR和XO酶活性评价中的应用@陈尧$Pharmacogenetics Research Institute, Central South University!Changsha 410078, Hunan, China @欧阳冬生$Pharmacogenetics Research Institute, Central South Univer     

Dried chicory root modifies the activity and expression of porcine hepatic CYP3A but not 2C – Effect of in vitro and in vivo exposure

Hepatic cytochrome P450 expression and activity are dependent on many factors, including dietary ingredients. In the present study, we investigated the in vivo and in vitro effect of chicory root on hepatic CYP3A and 2C in male pigs. Chicory feeding increased the expression of CYP3A29 mRNA but not CYP2C33. Correspondingly, CYP3A activity was increased by chicory feeding, while CYP2C activity was not affected. Additionally, the in vitro effect of chicory extract on the CYP3A activity was investigated. It was shown that CYP3A activity in the microsomes from male pigs was inhibited, but this effect was eliminated by pre-incubation. In both male and female pigs the CYP3A activity was increased in the presence of chicory after pre-incubation. Furthermore, gender-related differences in mRNA expression and activity were observed. CYP3A mRNA expression was greater in female pigs; this was not reflected on activity. For CYP2C, no difference in mRNA expression was observed, while CYP2C activity was greater in female pigs. Surprisingly, the expression of the constitutive androstane receptor, pregnane X receptor and aryl hydrocarbon receptor did not differ with feed or gender. In conclusion, chicory root modifies the expression and activity of CYP3A in vivo and in vitro, while CYP2C is not affected.     

Halowax 1051 affects steroidogenesis, 17β-hydroxysteroid dehydrogenase (17β-HSD) and cytochrome P450arom (CYP19) activity, and protein expression in porcine ovarian follicles

We evaluated the effect of Halowax 1051 on ovarian follicular testosterone (T) and estradiol (E2) secretion determined by EIA and on the expression of 17β-HSD and CYP19 analyzed by Western blot. 17β-HSD and CYP19 activity were determined indirectly by measuring the conversion of androstenedione (A4) to T and T to E2, respectively. Additionally, CYP19 activity by dibenzylfluorescein assay. Follicles were exposed to 1–1000 pg/ml of Halowax 1051 for 24, 48 or 72 h. It was found that Halowax 1051, in all doses used, increased basal T secretion concomitant with a decrease in basal E2 secretion. Inhibitory action on 17β-HSD and stimulatory action on CYP19 (activity and protein expression) under the influence of 1 pg/ml, and opposite effect under the influence of 10–1000 pg/ml was noted. In conclusion, we suggest non-linear dose–response effect of Halowax 1051 on steroidogenesis and steroidogenic enzymes activity and protein expression.     

细胞色素P450(CYP)3A5与CYP2C19基因多态性对伏立康唑在健康人体的药代动力学特征的影响

目的研究中国健康人体内细胞色素P450(CYP)3A5、CYP2C19基因多态性对伏立康唑药代动力学的影响。方法用RFLP-PCR法对受试者进行全血CYP3A5、CYP2C19基因分型;建立人血浆中伏立康唑的LC-MS测定方法,检测血药浓度;并对受试者单次口服伏立康唑200 mg后的系列血药浓度进行测定。结果伏立康唑200 mg,CYP2C19突变纯合子的AUC0-36、AUC0-∞值均显著高于野生组;也显著高于突变杂合组;而CL/F值则明显低于野生组。T1/2﹑Cmax等在各组间无统计学差异;伏立康唑各药代动力学参数在CYP3A5各组间均无统计学差异。结论中国人体内CYP2C19基因多态性对伏立康唑的药代动力学过程有显著影响;而CYP3A5基因多态性对伏立康唑的药代动力学过程无明显影响。     

Induction and decline of hepatic cytochromes P4501A1 and 1A2 in rats exposed to hyperoxia are not paralleled by changes in glutathione S-transferase-α

We investigated the effects of hyperoxia on the activities of hepatic ethoxyresorufin 0-deethylase (EROD) (CYP1A1), methoxyresorufin 0-demethylase (MROD) (CYP1A2), and glutathione transferase-α (GST-α), and the status of protein thiols (PSH) in male Sprague-Dawley rats. Twenty-four h of hyperoxia more than doubled EROD and MROD activities, which were increased 7.6- and 3.3-fold, respectively, after 48 h of hyperoxia. The increases in EROD and MROD activities were paralleled by enhanced CYP1A1/1A2 apoproteins contents, as detected by Western analysis. At 60 h of hyperoxia, by which time hyperoxic Sprague-Dawley rats display marked respiratory distress, pulmonary edema, and other markers of pulmonary dysfunction, the activities and levels of hepatic CYP1A1 and 1A2 had declined dramatically and returned to levels observed in air-breathing control animals. Hepatic activities of GST-α, as well as PSH status, were not altered significantly in the hyperoxic animals at any time point. The marked induction and subsequent decline of hepatic CYP1A1/1A2 activities in rats exposed to hyperoxia suggest that these enzymes may contribute to the mechanisms of injury and/or to adaptive responses to hyperoxic exposures in vivo.