CYP2 D6的基因多态性与药物临床应用

CYP2D6是CYP酶系中重要的一种氧化代谢酶,参与多种药物的代谢。 CYP2D6具有基因多态性,这是构成药物代谢个体差异和种族差异的基础,它主要参与心血管类、抗精神病类、镇痛药、以及一些抗癌药物等的代谢。研究 CYP2D6基因多态性与药物代谢个体差异的相关性,有助于减轻药物不良反应,提高治疗效果,实施个体化给药。     

细胞色素P4502D6与药物代谢

细胞色素P4502D6（CYP2D6）是一种重要的P450系氧化代谢酶,除参与代谢一些内源性物质和某些环境中毒性化合物外,主要是参怀多种重要药物的代谢,如作用于心血管和中枢神经系统的药物。CYP2D6参与代谢的药物占总P450代谢药物的30％,同时对手性药物的代谢还呈现立体选择性。研究还发现CYP2D6对药物的代谢呈现明显的个体和种族差异,引起这种差异的主要原因是CYP2D6具有的基因多态性,此外还有一些非基因因素,如药物的影响等。目前,CYP2D6的生物学特征已被基本确定,这将十分有助于对CYP2D6的深入研究,从而为临床合理用药提供科学依据。     

细胞色素P4502D6基因多态性和药物相互作用

细胞色素P4502D6（CYP2D6）是一种重要的P450系氧化代谢酶,参与多种重要药物的代谢.CYP2D6具有基因多态性,对药物的代谢呈现明显的个体差异.而且CYP2D6能被多种药物竞争性抑制和诱导,药物联用时易产生相互作用.本文从CYP2D6的基因多态性与代谢表型、底物竞争作用、代谢酶的诱导和抑制等方面,探讨CYP2D6基因多态性与药物相互作用的关系.     

CYP2D6基因多态性与抗精神病药物的个体化应用

CYP2D6是一种重要的细胞色素P450酶,存在着显著的基因多态性.CYP2D6在抗精神病类药物的代谢中发挥着重要作用,与许多抗精神病药物药动学及药效学的个体间变异存在着密切联系,检测CYP2D6基因型有助于患者抗精神病药物治疗方案的选择和调整,提高用药的安全性和有效性.本文综述CYP2D6基因多态性对抗精神病药物的药动学、不良反应及药物相互作用的影响,探讨了CYP2D6基因型检测在抗精神病个体化治疗中的应用前景.     

CYP2D6基因多态性及其临床意义

CYP2D6是CYP酶系中重要的一种氧化代谢酶,参与多种药物的代谢.CYP2D6具有基因多态性,使药物代谢在不同种族之间,甚至在同种族不同人群中产生较大的差异,从而影响药物的疗效.因此,深入了解CYP2D6基因的多态性以及对药物代谢的影响,对指导临床合理用药和调整用药方案具有重大意义.     

CYP2D6基因多态性及对美托洛尔代谢的影响

CYP2D6是一种重要的P450系氧化代谢酶,主要参与多种重要药物的代谢。CYP2D6基因多态性会引起药物代谢有显著的个体和种族差异。美托洛尔为选择性β1受体阻滞剂,临床应用上存在巨大个体差异,主要在肝脏经多条途径代谢,大约70%的代谢由CYP2D6介导,CPY2D6基因多态性对美托洛尔代谢有较大影响。本文从CYP2D6的基因多态性及它对美托洛尔代谢的影响这两方面作一综述。     

与细胞色素P_(450)2D6相关的药物相互作用研究

细胞色素P450（CYP）是一组结构和功能相关的超家族基因编码同工酶。人体内参与药物代谢的CYP有17个基因家族，42个亚家族，64个酶。众所周知，在人体内许多因素如遗传因素、年龄、性别、疾病和环境都可以影响CYP的活性。本文着重综述了近年来国内、外文献报道的与CYP2D6相关的药物相互作用。CYP2D6是一种重要的细胞色素药物代谢酶，除参与代谢一些内源性物质和某些环境中毒性化合物外，主要是参与多种药物的代谢。CYP2D6参与代谢的药物占总CYP代谢药物的30％，同时对手性药物的代谢还呈现立体选择性。CYP2D6是临床上重要的肝药酶之一，与之相关的药物相互作用也十分多见。了解CYP2D6的底物以及相关的药物相互作用对临床合理用药具有十分重要的意义。     

CYP2D6基因多态性及对药物代谢的影响

CYP2D6代谢酶是细胞色素P450家族中的成员之一,是参与Ⅰ相代谢和众多内源性物质和不同药物消除的酶。虽然它在肝脏中的含量大约只占肝脏总量的2%,但在临床上却参与了25%以上的常用药物的代谢活动。在所有参与药物代谢的细胞色素P450基因家族中,CYP2D6是唯一不能被诱导的酶,这种酶具有广泛的多态性,这种多态性对酶的药物代谢功能具有重要影响,CYP2D6的这种多态性和药物代谢功能所表现的对个体活性的差异,在遗传药理学上具有重要意义。本文从CYP2D6基因多态性和它对药物代谢的影响这两方面进行了阐述。     

肠道细胞色素P450代谢酶研究进展

细胞色素P450(CYP450s)为肠道主要I相代谢酶,目前发现有CYP1A1、CYP2C9、CYP2C19、CYP2J2、CYP2D6、CYP3A4、CYP3A5 7种同工酶。肠道CYP在药物代谢及药物相互作用中发挥重要作用,与药物疗效及不良反应密切相关。基因多态性及个体差异均影响药物代谢,导致临床疗效差别。该文就肠道CYP各亚型相关研究进展做一综述。     

基于药物基因组学的选择性5-羟色胺再摄取抑制剂个体化治疗抑郁症

选择性5-羟色胺再摄取抑制剂(SSRIs)是当前治疗抑郁症的一线药物,CYP2D6、CYP2C19基因多态性会影响SSRIs的代谢,进而影响其疗效与安全性.目前我国临床医师对抑郁症患者基于基因多态性的SSRIs个体化治疗实践相对较少.该文就CYP2D6、CYP2C19基因型及其对SSRIs治疗的影响进行综述,以期为抑郁...     

Modeling human cytochrome P450 2D6 metabolism and drug-drug interaction by a novel panel of knockout and humanized mouse lines

The highly polymorphic human cytochrome P450 2D6 enzyme is involved in the metabolism of up to 25% of all marketed drugs and accounts for significant individual differences in response to CYP2D6 substrates. Because of the differences in the multiplicity and substrate specificity of CYP2D family members among species, it is difficult to predict pathways of human CYP2D6-dependent drug metabolism on the basis of animal studies. To create animal models that reflect the human situation more closely and that allow an in vivo assessment of the consequences of differential CYP2D6 drug metabolism, we have developed a novel straightforward approach to delete the entire murine Cyp2d gene cluster and replace it with allelic variants of human CYP2D6. By using this approach, we have generated mouse lines expressing the two frequent human protein isoforms CYP2D6.1 and CYP2D6.2 and an as yet undescribed variant of this enzyme, as well as a Cyp2d cluster knockout mouse. We demonstrate that the various transgenic mouse lines cover a wide spectrum of different human CYP2D6 metabolizer phenotypes. The novel humanization strategy described here provides a robust approach for the expression of different CYP2D6 allelic variants in transgenic mice and thus can help to evaluate potential CYP2D6-dependent interindividual differences in drug response in the context of personalized medicine.     

Molecular genetics of CYP2D6: clinical relevance with focus on psychotropic drugs

Cytochrome P450 CYP2D6 is the most extensively characterized polymorphic drug-metabolizing enzyme. A deficiency of the CYP2D6 enzyme is inherited as an autosomal recessive trait; these subjects (7% of Caucasians, about 1% of Orientals) are classified as poor metabolizers. Among the rest (extensive metabolizers), enzyme activity is highly variable, from extremely high in ultrarapid metabolizers, to markedly reduced in intermediate metabolizers. The CYP2D6 gene is highly polymorphic, with more than 70 allelic variants described so far. Of these, more than 15 encode an inactive or no enzyme at all. Others encode enzyme with reduced, "normal" or increased enzyme activity. The CYP2D6 gene shows marked interethnic variability, with interpopulation differences in allele frequency and existence of "population-specific" allelic variants, for instance among Orientals and Black Africans. The CYP2D6 enzyme catalyses the metabolism of a large number of clinically important drugs including antidepressants, neuroleptics, some antiarrhythmics, lipophilic beta-adrenoceptor blockers and opioids. The present-day knowledge on the influence of the genetic variability in CYP2D6 on the clinical pharmacokinetics and therapeutic effects/adverse effects of psychotropic drugs is reviewed.     

Comparative metabolic capabilities and inhibitory profiles of CYP2D6.1, CYP2D6.10, and CYP2D6.17.

Polymorphisms in the cytochrome P450 2D6 (CYP2D6) gene are a major cause of pharmacokinetic variability in human. Although the poor metabolizer phenotype is known to be caused by two null alleles leading to absence of functional CYP2D6 protein, the large variability among individuals with functional alleles remains mostly unexplained. Thus, the goal of this study was to examine the intrinsic enzymatic differences that exist among the several active CYP2D6 allelic variants. The relative catalytic activities (enzyme kinetics) of three functionally active human CYP2D6 allelic variants, CYP2D6.1, CYP2D6.10, and CYP2D6.17, were systematically investigated for their ability to metabolize a structurally diverse set of clinically important CYP2D6-metabolized drugs [atomoxetine, bufuralol, codeine, debrisoquine, dextromethorphan, (S)-fluoxetine, nortriptyline, and tramadol] and the effects of various CYP2D6-inhibitors [cocaine, (S)-fluoxetine, (S)-norfluoxetine, imipramine, quinidine, and thioridazine] on these three variants. The most significant difference observed was a consistent but substrate-dependent decease in the catalytic efficiencies of cDNA-expressed CYP2D6.10 and CYP2D6.17 compared with CYP2D6.1, yielding 1.32 to 27.9 and 7.33 to 80.4% of the efficiency of CYP2D6.1, respectively. The most important finding from this study is that there are mixed effects on the functionally reduced allelic variants in enzyme-substrate affinity or enzyme-inhibitor affinity, which is lower, higher, or comparable to that for CYP2D6.1. Considering the rather high frequencies of CYP2D6*10 and CYP2D6*17 alleles for Asians and African Americans, respectively, these data provide further insight into ethnic differences in CYP2D6-mediated drug metabolism. However, as with all in vitro to in vivo extrapolations, caution should be applied to the clinical consequences.     

Polymorphic cytochrome P450 2D6: humanized mouse model and endogenous substrates

Cytochrome P450 2D6 (CYP2D6) is the first well-characterized polymorphic phase I drug-metabolizing enzyme, and more than 80 allelic variants have been identified for the CYP2D6 gene, located on human chromosome 22q13.1. Human debrisoquine and sparteine metabolism is subdivided into two principal phenotypes--extensive metabolizer and poor metabolizer--that arise from variant CYP2D6 genotypes. It has been estimated that CYP2D6 is involved in the metabolism and disposition of more than 20% of prescribed drugs, and most of them act in the central nervous system or on the heart. These drug substrates are characterized as organic bases containing one nitrogen atom with a distance about 5, 7, or 10 A from the oxidation site. Aspartic acid 301 and glutamic acid 216 were determined as the key acidic residues for substrate-enzyme binding through electrostatic interactions. CYP2D6 transgenic mice, generated using a lambda phage clone containing the complete wild-type CYP2D6 gene, exhibits enhanced metabolism and disposition of debrisoquine. This transgenic mouse line and its wild-type control are models for human extensive metabolizers and poor metabolizers, respectively, and would have broad application in the study of CYP2D6 polymorphism in drug discovery and development, and in clinical practice toward individualized drug therapy. Endogenous 5-methoxyindole- thylamines derived from 5-hydroxytryptamine were identified as high-affinity substrates of CYP2D6 that catalyzes their O-demethylations with high enzymatic capacity and specificity. Thus, polymorphic CYP2D6 may play an important role in the interconversions of these psychoactive tryptamines, including a crucial step in a serotonin-melatonin cycle.     

In Vitro Functional Assessment of 22 Newly Identified CYP2D6 Allelic Variants in the Chinese Population

Cytochrome P450 2D6 (CYP2D6) is one of the most widely investigated CYPs related to genetic polymorphisms and is responsible for one‐quarter of the currently used clinical drugs. We previously detected 22 novel, non‐synonymous, mutated sites in the Chinese population, but nothing is known about the functional effects of these mutations in terms of specific CYP2D6 substrates. In this study, wild‐type CYP2D6, two common allelic variants and 22 newly reported CYP2D6 isoforms were transiently expressed in 293FT cells, and the enzymatic activities of these variants were systematically assessed using dextromethorphan and bufuralol as the probing substrates. Consequently, 19 and 21 allelic variants were found to exhibit significantly decreased enzymatic activities for dextromethorphan and bufuralol, respectively. Of 22 novel CYP2D6 variants, six allelic isoforms (CYP2D6.89, CYP2D6.92, CYP2D6.93, CYP2D6.96, E215K and R440C) exhibited absent or extremely reduced metabolic activities compared with those observed for the wild‐type enzyme. Our in vitro functional data can be useful for CYP2D6 phenotype prediction and provide valuable information for the study of clinical impact of these newly found CYP2D6 variants in China.     

Isolation, sequence and genotyping of the drug metabolizer CYP2D6 gene in the Colombian population

Cytochrome P450 2D6 monooxygenase metabolizes several commonly used drugs, particularly psychotropics and cardiovascular agents. The gene that encodes this isoenzyme is highly polymorphic, with 1-10% of the population carrying mutations that produce an inactive enzyme, and 1-29% of individuals who possess additional copies of functional CYP2D6 genes. The genotypic features of the CYP2D6 gene have already been studied in many ethnic groups; however, the genetic characteristics of this enzyme are unknown in the Colombian population. The allelic variants and mutations of this polymorphic isoenzyme are the main cause of interindividual and interethnic differences in the therapeutic efficacy and adverse effects at standard doses of drugs metabolized by the products of the CYP2D6 gene. In the present study we have isolated, sequenced and genotyped the CYP2D6 gene in the Colombian population. The distribution of allelic frequencies of 10 alleles associated with normal, diminished or increased CYP2D6 activity has been studied in 121 healthy volunteers. The commonest alleles detected in the Colombian people were the functional alleles *1 (38.8%) and *2 (37%). Among the seven nonfunctional alleles studied in our sample, we found frequencies of 19.4%, 1.6%, 1.2% and 0.8%, for the *4, *17, *3 and *5 alleles, respectively. The alleles *6, *7 and *8 could not be identified in any of the subjects studied. The frequency of the duplicate allele was 1.2%. In this Colombian sample, 91.7% of the individuals were normal metabolizers (EM), 6.6% were poor metabolizers (PM), and 1.7% were ultrarapid metabolizers (UM). These results show that the allelic distribution of the CYP2D6 gene in the Colombian population of mestizo-prevalent subjects is compatible with the genomic assembly of the constitutive tri-ethnic origin of this Latin American country.     

Genetic and environmental influences on therapeutic and toxicity outcomes: studies with CYP2A6

The idea that the liver enzyme cytochrome P450 2A6 (CYP2A6), known also as nicotine C-oxidase, is one of the determinants of smoking addiction and smoking behavior is primarily based on its role in nicotine metabolism and disposition. The results of studies linking the CYP2A6 genetic polymorphism with smoking dependence and smoking behavior however remain controversial. The most likely causes of the controversies appeared to be consideration given to a few allelic variants coupled with the uses of the CYP2A6 alleles lacking in vivo phenotypic validation. In the present review, we summarize research findings on biological significance of CYP2A6 and gene polymorphisms together with a discussion on CYP2A6 inhibitors that hold the promise of uses in smoking cessation. In addition, we provide the phenotype/genotype information derived from our systematic investigation on the relationship between CYP2A6 genotypes, smoking habits and coumarin metabolism phenotypes in a group of 393 normal adults (197 women and 196 men), 16 to 60 years of age, whose exposure to cadmium and lead were also determined, enabling us to assess the CYP2A6 phenotypic variability associated with CYP2A6 genotypes and environmental exposure. The results indicate that the phenotype of CYP2A6 enzyme in liver is an outcome of interactions between the CYP2A6 gene, cadmium, nicotine and possibly its metabolites.     

In vitro assessment of the allelic variants of cytochrome P450

The cytochrome P450 (CYP) superfamily is one of the most important groups of enzymes involved in drug metabolism. It is responsible for the metabolism of a large number of drugs. Many CYP isoforms are expressed polymorphically, and catalytic alterations of allelic variant proteins can affect the metabolic activities of many drugs. The CYP2D6, CYP2C9, CYP2C19, and CYP2B6 genes are particularly polymorphic, whereas CYP1A1, CYP1A2, CYP2E1, and CYP3A4 are relatively well conserved without common functional polymorphisms. In vitro studies using cDNA expression systems are useful tools for evaluating functional alterations of the allelic variants of CYP, particularly for low-frequency alleles. Recombinant CYPs have been successfully expressed in bacteria, yeast, baculoviruses, and several mammalian cells. Determination of CYP variant-mediated kinetic parameters (Km and Vmax) in vitro can be useful for predicting drug dosing and clearance in humans. This review focuses on the advantages and disadvantages of the various cDNA-expression systems used to determine the kinetic parameters for CYP allelic variants, the methods for determining the kinetic parameters, and the findings of in vitro studies on highly polymorphic CYPs, including CYP2D6, CYP2C9, CYP2C19, and CYP2B6.     

Effect of CYP2D6 variants on venlafaxine metabolism in vitro

1.?CYP2D6 is an important member of the cytochrome P450 (CYP450) enzyme superfamily, we recently identified 22 CYP2D6 alleles in the Han Chinese population. The aim of this study was to assess the catalytic activities of these allelic isoforms and their effects on the metabolism of venlafaxine in vitro.

2.?The wild-type and 24 CYP2D6 variants were expressed in insect cells, and each variant was characterized using venlafaxine as the substrate. Reactions were performed at 37?°C with 5–500?μM substrate (three variants was adjusted to 1000?μM) for 50?min. By using high-performance liquid chromatography to detect the products, the kinetic parameters K_m, V_max, and intrinsic clearance (V_max/K_m) of O-desmethylvenlafaxine were determined.

3.?Among the 22 CYP2D6 variants, the intrinsic clearance (V_max/K_m) values of all variants were significantly decreased (from 0.2% to 84.5%) compared with wild-type CYP2D6*1. In addition, the kinetic parameters of two CYP2D6 variants could not be detected because they have no detectable enzyme activity.

4.?The comprehensive in vitro assessment of CYP2D6 variants provides significant insights into allele-specific activity towards venlafaxine in vivo.     

Genetic analysis of the interethnic difference between Chinese and Caucasians in the polymorphic metabolism of debrisoquine and codeine

Summary The Far Eastern and Caucasian populations are strikingly different with respect to the debrisoquine/sparteine hydroxylation polymorphism. The number of poor metabolizers, as defined for Caucasians, is very low among Chinese and Japanese. We investigated the molecular basis for this difference by analysis of the CYP2D6 gene in 115 Chinese subjects, combined with phenotypic classification of codeine and debrisoquine metabolism.A correlation between the rates of metabolism of these two drugs and genotype, as analyzed by RFLP using XbaI, was observed among the Chinese. A high frequency (37%) of alleles indicative of gene insertions (reflected by Xba I 44kb fragments) was recorded in the Chinese, but was not associated with the poor metabolizer phenotype, as it is in Caucasians. PCR amplification of part of the CYP2D6 gene with mutation specific primers for CYP2D6A (29A) and CYP2D6B (29B) allelic variants revealed that the XbaI 44kb fragment in Chinese apparently contains a functional CYP2D6 gene, in contrast to the situation among Caucasians.The results provide a molecular explanation of the interethnic difference in the metabolism of drugs affected by the debrisoquine hydroxylation polymorphism.