细胞色素P—450 CYP2D6基因分型与表型的吻合率

研究细胞色素Ｐ４５０－２Ｄ６基因分型测定方法及其与表型的吻合率。方法：利用等位基因特异扩增法基本原理,对ＣＹＰ２Ｄ６酶缺陷等位基因ＣＹＰ２Ｄ６＊３,＊４,＊６和＊７进行测定。结果;通过１６８例基因分型,并将结果与表型对照,发现同时测定ＣＹＰ２Ｄ６＊３,＊４,＊６和＊７等位基因时,１２５例快代谢者和４３例慢代谢者的基因分型结果与表型结果的吻合率为１００％。     

ＣＹＰ２Ｃ１９和ＣＹＰ２Ｃ９等位基因在中国人群中多态性分布

目的：探讨细胞色素Ｐ４５０（ＣＹＰ）２Ｃ１９（ＣＹＰ２Ｃ１９）和ＣＹＰ２Ｃ９在中国人群中的等位基因多态性分布，分析影响上述基因多态性的因素。方法：应用聚合酶链反应—变性高效液相（ＰＣＲ—ＤＨＰＬＣ）技术分析了１５０例癫痫患ＣＹＰ２Ｃ１９外显子４（＊３）、外显５（＊２）和ＣＹＰ２Ｃ９外显子７（＊３）的等位基因变异，观察这二种基因多态性在癫痫患中分布的特征。结果：１５０例癫痫患ＣＹＰ２Ｃ１９＊３、ＣＹＰ２Ｃ１９＊２和ＣＹＰ２Ｃ９＊３均为野生型的发生率为３８、７％，ＣＹＰ２Ｃ１９＊２、ＣＹＰ２Ｃ１９＊３和ＣＹＰ２Ｃ９＊３等位基因频率分别为３４．３％、５．３％和７．３％。ＣＹＰ２Ｃ１９＊２和ＣＹＰ２Ｃ１９＊３等位基因分布频率存在性别之间的显差异，Ｐ值分别为Ｐ＜Ｏ．０５、Ｐ＜Ｏ．０１；而ＣＹＰ２Ｃ９＊３的等位基因分布频率不存在性别之间的显差异。ＣＹＰ２Ｃ１９基因型存在性别之间的显差异，Ｐ＜Ｏ．０１。存在ＣＹＰ２Ｃ９＊３等位基因多态性的个体一定出现ＣＹＰ２Ｃ１９＊２的等位基因多态性。结论：性别因素可能对ＣＹＰ２Ｃ１９酶的活性产生影响，应用同时经ＣＹＰ２Ｃ９和ＣＹＰ２Ｃ１９代谢的药物时，需进行基团型测定。     

细胞色素P450同工酶在外源物代谢中的作用

细胞色素Ｐ４５０酶系（ＣＹＰ）中的Ｐ４５０Ⅰ￣Ｐ４５０Ⅳ家族是代谢外来化合物的主要酶系。环境致癌主要是ＣＹＰ１Ａ的底物，ＣＹＰ２Ｄ６的突出特征是它的遗传多态性，而ＣＹＰ２Ｅ１主要参与乙醇等小分子化合物的代谢，ＣＹＰ３Ａ则是参与大多数临床口服药物代谢的主要同工酶。本文综述了细胞色素Ｐ４５０铎外源性化合物代谢转换及调控研究，对ＣＹＰ１Ａ、ＣＹＰ２Ｅ的诱导机制及ＣＹＰ３Ａ的主要抑制机制也作了叙述。     

利用右美沙芬区分细胞色素P4502D6纯合子与杂合子快代谢者

本研究目的是建立准确的细胞色素Ｐ４５０２Ｄ６（ＣＹＰ２Ｄ６）的右美沙芬表型测定法，以发现ＣＹＰ２Ｄ６纯合子与杂合子快代谢者的表型差异。通过提高右美沙芬的检测灵敏度（１ｎｇ·ｍｌ－１）而建立的ＨＰＬＣ分析法，对已知基因型的３组共１６８位受试者进行表型测定。结果发现不仅快代谢者与慢代谢者在代谢率上有很大差异，纯合子快代谢者与杂合子快代谢者之间在代谢率上也有差异。提示ＣＹＰ２Ｄ６基因表达时，基因拷贝数起一定的作用     

细胞色素氧化酶P4501A2与药物代谢

细胞色素氧化酶Ｐ４５０１Ａ２（ＣＹＰ１Ａ２）在药物代谢、前致癌物激活的过程中起重要的作用。现已发现越来越多的药物由ＣＹＰ１Ａ２催化代谢，这些物包括非那西丁、咖啡因，丙咪嗪、氯氮平、他克林、普萘洛尔和美西律等。不同个体之间体内ＣＹＰ１Ａ２的活性差异是引起这些药物在代谢和效应上个体差异的主要原因之一。     

细胞色素P450 2D6等位基因CYP2D6C的特异扩增法测定

细胞色素Ｐ４５０２Ｄ６（ＣＹＰ２Ｄ６）第２７０３－５位ＡＡＧ缺失造成表达产物第２８１位赖氨酸缺失的等位基因称为ＣＹＰ２Ｄ６Ｃ．利用等位基因特异扩增法（ＡＳＡ）原理,建立了ＡＳＡ－ＰＣＲ测定ＣＹＰ２Ｄ６的方法．经３９６例测定,说明本法快捷,污染少．测定结果显示ＣＹＰ２Ｄ６Ｃ不属于ＣＹＰ２Ｄ６酶缺陷等位基因,表型仍为快代谢．     

质子泵抑制剂与药物的相互作用

质子泵抑制剂奥美拉唑、兰索拉唑和盘托拉唑主要经细胞色素Ｐ４５０（ＣＹＰ）的异构酶ＣＹＰ２Ｃ１９代谢消除。研究表明,三个质子泵抑制剂对其它经ＣＹＰ系列代谢的药物皆表现出较弱的相互作用,少数文献报道这一相互作用无临床相关性,并且未发现剂量与不良反应的相关性。预示了该类药物临床使用或合用的安全性。     

P-450特异性化学抑制剂在外源化合物代谢中的作用

已知细胞色素Ｐ４５０（ｃｙｔｏｃｈｒｏｍｅＰ４５０,ＣＹＰ）单加氧酶系统在机体对外源化合物代谢中占有主导地位。随着研究水平的提高和手段的增加,人们对ＣＹＰ同工酶在外源化合物代谢中作用的认识日趋深入。近年来的大量研究已证实,人ＣＹＰ酶蛋白很难纯化,但化学抑制剂在确定参与外源化合物代谢的ＣＹＰ类型上却是非常有效的工具药［１～４］,化学抑制剂为预测药物间的相互作用,提供了有效的研究手段。１　人ＣＹＰ同工酶与外源化合物代谢ＣＹＰ是一组含亚铁血红素蛋白的超家族（ｓｕｐｅｒｆａｍｉｌｙ）,主要位于肝微粒…     

肝病患者药物代谢酶细胞色素P450酶1A2,多态性N—乙酰化 …

目的以咖啡因为代谢探针，研究肝患者咖啡因代物比值（ｃａｆｆｅｉｎｅ ｍｅｔａｂｏｌｉｔｅ ｒａｔｉｏｓ，ＣＭＲｓ）的变化，探讨ＣＭＲｓ作为药工谢酶细胞色素Ｐ４５０酶１Ａ２（ＣＹＰ１Ａ２）、多态性Ｎ－乙酰基转移酶（ＮＡＴ２）、黄嘌呤氧化化酶（ＸＯ）的活性指标，用于调整某些药物用药方案的可行性。方法：选择健康受者３０例，慢性肝病受试者３０例。采用高效液相色谱（ＨＰＬＣ）法测定受试者尿液３０例，慢性肝病     

CYP2D6表面型决定16名中国汉族受试者普罗帕酮对映体药物动力学 …

目的：研究ＣＹＰ２Ｄ６表达型在汉族健康受试者普罗帕桐对映体代谢中的作用。和右美沙芬进行代谢分型后得到的７名极快代谢得（ＶＥＭ）和９名中速代谢者（ＩＭ）。单剂量口服消旋普罗帕酮４００ｍｇ,抽取０－１５ｈ静脉血,运用反相高压液相色谱法加柱前衍生化,定量分析血浆中普罗帕酮对映体深度。结果：两种ＣＹＰ２Ｄ６表现型的Ｓ－Ｐｒｏ代谢均较Ｒ－Ｐｒｏ慢,血浆浓度升高。此外ＩＭ中Ｒ－Ｐｒｏ对映体在ＶＥＭ和ＩＭ中的代     

The effect of liver cirrhosis on the regulation and expression of drug metabolizing enzymes

Cirrhosis is the end stage of many forms of liver pathologies including hepatitis. The liver is known for its vital role in the processing of xenobiotics, including drugs and toxic compounds. Cirrhosis causes changes in the architecture of the liver leading to changes in blood flow, protein binding, and drug metabolizing enzymes. Drug metabolizing enzymes are primarily decreased due to loss of liver tissue. However, not all enzyme activities are reduced and some are only altered in specific cases. There is a great deal of discrepancy between various reports on cytochrome p450 alterations in liver cirrhosis, likely due to differences in disease severity and other underlying conditions. In general, however, CYP1A and CYP3A levels and related enzyme activities are usually reduced and CYP2C, CYP2A, and CYP2B are mostly unaltered. Both alcohol dehyrogenases and aldehyde dehydrogenases are altered in liver cirrhosis, although the etiology of the disease may determine the expression of alcohol dehydrogenases. Glucuronidation is mainly preserved, but there are a number of factors that determine whether glucuronidation is affected in patients with liver cirrhosis. Low sulphation rates are usually found in patients with liver disease but a decrease in sulfatase activity compensates for the decrease in sulphation rates. In all cases, a reduction in drug metabolizing enzyme activities in liver cirrhosis contributes to decreased clearance of drugs seen in patients with liver abnormalities. The reduction in drug metabolizing enzyme activity must be taken into consideration when adjusting doses, especially in patients with severe liver disease.     

Hepatic drug metabolizing enzymes induced by clofibrate in rasH2 mice

Hepatic drug metabolizing enzyme activities were determined, after treatment with clofibrate, in transgenic mice carrying human c-Ha-ras (rasH2 mice). Changes in the drug metabolizing enzyme activities in these mice by gene integration were also evaluated. Male and female rasH2 mice (Tg) and the litter mates not carrying the gene (non-Tg) received orally 500 mg/kg of clofibrate or the vehicle for 12 consecutive days. Liver homogenate and microsomes were prepared and the contents and activities of cytochrome P450 (CYP), cytochrome b5 content and enzyme activities related to peroxisome proliferation were determined. Relative liver weights, CYP4A and activities of catalase and carnitine palmitoyl transferase increased to the same extent in Tg and non-Tg mice treated with clofibrate. In Tg and non-Tg groups that received vehicle, contents and activities of CYP and cytchrome b5 contents were comparable. It was concluded that gene integration did not alter drug metabolizing enzymes and responses to clofibrate.     

The role of cytochrome P450 enzymes in the metabolism of risperidone and its clinical relevance for drug interactions

In the recent years it has been increasingly recognized that pharmacogenetical factors play an important role in the drug treatment. These factors may influence the appearance of side-effects and drug interactions due to interindividual differences in the activity of metabolizing enzymes. Risperidone in humans is mainly metabolized to 9-hydroxyrisperidone by the polymorphic cytochrome enzyme P450 2D6 (CYP2D6). Plasma concentrations of risperidone and 9-hydroxyrisperidone show large interindividual variability, which may be partly related to the activity of the CYP2D6 enzyme. Around seven percent of Caucasians have a genetically inherited impaired activity of the CYP2D6 enzyme. Debrisoquine metabolic ratio (a marker of CYP2D6 activity) and the number of CYP2D6 active genes have been related to risperidone plasma concentrations among patients during steady-state conditions. A large number drugs have been described to be metabolized by CYP2D6, and it is therefore important to evaluate the clinical significance of the impaired metabolism and possible drug interactions on the enzyme. Since risperidone/9-hydroxyrisperidone ratio strongly correlates with CYP2D6 enzyme activity and the number of CYP2D6 active genes, thus it might be a useful tool in clinical practice to estimate the possible risk of drug interactions due to impaired CYP2D6 enzyme activity. CYP3A4 is the most abundant drug metabolizing enzyme in humans, and in vitro and in vivo results suggest also a role for the enzyme in risperidone metabolism. The consideration of the implication of cytochrome P450 enzymes in risperidone metabolism may help to individualize dose schemes in order to avoid interactions and potentially dangerous side-effects, such us QTc interval lengthening among patients with cardiac risk factors.     

Drug-metabolizing enzymes in the skin of man, rat, and pig

The mammalian skin has long been considered to be poor in drug metabolism. However, many reports clearly show that most drug metabolizing enzymes also occur in the mammalian skin albeit at relatively low specific activities. This review summarizes the current state of knowledge on drug metabolizing enzymes in the skin of human, rat, and pig, the latter, because it is often taken as a model for human skin on grounds of anatomical similarities. However only little is known about drug metabolizing enzymes in pig skin. Interestingly, some cytochromes P450 (CYP) have been observed in the rat skin which are not expressed in the rat liver, such as CYP 2B12 and CYP2D4. As far as investigated most drug metabolizing enzymes occur in the suprabasal (i.e. differentiating) layers of the epidermis, but the rat CYP1A1 rather in the basal layer and human UDP-glucuronosyltransferase rather in the stratum corneum. The pattern of drug metabolizing enzymes and their localization will impact not only the beneficial as well as detrimental properties of drugs for the skin but also dictate whether a drug reaches the blood flow unchanged or as activated or inactivated metabolite(s).     

Drug-Metabolizing Enzymes in the Skin of Man,Rat, and Pig

The mammalian skin has long been considered to be poor in drug metabolism. However, many reports clearly show that most drug metabolizing enzymes also occur in the mammalian skin albeit at relatively low specific activities. This review summarizes the current state of knowledge on drug metabolizing enzymes in the skin of human, rat, and pig, the latter, because it is often taken as a model for human skin on grounds of anatomical similarities. However only little is known about drug metabolizing enzymes in pig skin. Interestingly, some cytochromes P450 (CYP) have been observed in the rat skin which are not expressed in the rat liver, such as CYP 2B12 and CYP2D4. As far as investigated most drug metabolizing enzymes occur in the suprabasal (i.e. differentiating) layers of the epidermis, but the rat CYP1A1 rather in the basal layer and human UDP-glucuronosyltransferase rather in the stratum corneum. The pattern of drug metabolizing enzymes and their localization will impact not only the beneficial as well as detrimental properties of drugs for the skin but also dictate whether a drug reaches the blood flow unchanged or as activated or inactivated metabolite(s).     

Effect of chronic disulfiram administration on the activities of CYP1A2, CYP2C19, CYP2D6, CYP2E1, and N-acetyltransferase in healthy human subjects

AIMS: Short-term disulfiram administration has been shown to selectively inhibit CYP2E1 activity but the effects of chronic disulfiram administration on the activities of drug metabolizing enzymes is unclear. The purpose of this study was to evaluate the effects of disulfiram given for 11 days on selected drug metabolizing enzyme activities. METHODS: Seven healthy volunteers were given disulfiram 250 mg daily for 11 days. Activities of the drug metabolizing enzymes CYP1A2, CYP2C19, CYP2D6, CYP2E1 and N-acetyltransferase were determined using the probe drugs caffeine, mephenytoin, debrisoquine, chlorzoxazone, and dapsone, respectively. Chlorzoxazone was administered before disulfiram administration and after the second and eleventh doses of disulfiram, while the other probe drugs were given before disulfiram administration and after the eleventh disulfiram dose. RESULTS: Disulfiram administration markedly inhibited chlorzoxazone 6-hydroxylation by more than 95%, but did not affect metabolism of debrisoquine or mephenytoin. Caffeine N3-demethylation was decreased by 34% (P < 0.05). Monoacetyldapsone concentrations were markedly elevated by disulfiram administration resulting in a nearly 16-fold increase in the dapsone acetylation index, calculated as the plasma concentration ratio of monoacetyldapsone to dapsone. CYP-mediated dapsone N-hydroxylation was not significantly altered. CONCLUSIONS: These data suggest that disulfiram-mediated inhibition is predominantly selective for CYP2E1. The magnitude of CYP2E1 inhibition was similar after both acute and chronic disulfiram administration. The effects on caffeine N3-demethylation (CYP1A2) and dapsone metabolism suggest that chronic disulfiram administration may affect multiple drug metabolizing enzymes, which could potentially complicate the use of chronically administered disulfiram as a diagnostic inhibitor of CYP2E1.     

Clinical pharmacogenetics and potential application in personalized medicine

The current 'fixed-dosage strategy' approach to medicine, means there is much inter-individual variation in drug response. Pharmacogenetics is the study of how inter-individual variations in the DNA sequence of specific genes affect drug responses. This article will highlight current pharmacogenetic knowledge on important drug metabolizing enzymes, drug transporters and drug targets to understand interindividual variability in drug clearance and responses in clinical practice and potential use in personalized medicine. Polymorphisms in the cytochrome P450 (CYP) family may have had the most impact on the fate of pharmaceutical drugs. CYP2D6, CYP2C19 and CYP2C9 gene polymorphisms and gene duplications account for the most frequent variations in phase I metabolism of drugs since nearly 80% of drugs in use today are metabolised by these enzymes. Approximately 5% of Europeans and 1% of Asians lack CYP2D6 activity, and these individuals are known as poor metabolizers. CYP2C9 is another clinically significant drug metabolising enzyme that demonstrates genetic variants. Studies into CYP2C9 polymorphism have highlighted the importance of the CYP2C9*2 and CYP2C9*3 alleles. Extensive polymorphism also occurs in a majority of Phase II drug metabolizing enzymes. One of the most important polymorphisms is thiopurine S-methyl transferases (TPMT) that catalyzes the S-methylation of thiopurine drugs. With respect to drug transport polymorphism, the most extensively studied drug transporter is P-glycoprotein (P-gp/MDR1), but the current data on the clinical impact is limited. Polymorphisms in drug transporters may change drug's distribution, excretion and response. Recent advances in molecular research have revealed many of the genes that encode drug targets demonstrate genetic polymorphism. These variations, in many cases, have altered the targets sensitivity to the specific drug molecule and thus have a profound effect on drug efficacy and toxicity. For example, the beta (2)-adrenoreceptor, which is encoded by the ADRB2 gene, illustrates a clinically significant genetic variation in drug targets. The variable number tandem repeat polymorphisms in serotonin transporter (SERT/SLC6A4) gene are associated with response to antidepressants. The distribution of the common variant alleles of genes that encode drug metabolizing enzymes, drug transporters and drug targets has been found to vary among different populations. The promise of pharmacogenetics lies in its potential to identify the right drug at the right dose for the right individual. Drugs with a narrow therapeutic index are thought to benefit more from pharmacogenetic studies. For example, warfarin serves as a good practical example of how pharmacogenetics can be utilized prior to commencement of therapy in order to achieve maximum efficacy and minimum toxicity. As such, pharmacogenetics has the potential to achieve optimal quality use of medicines, and to improve the efficacy and safety of both prospective and licensed drugs.     

Proteomic analysis for the impact of hypercholesterolemia on expressions of hepatic drug transporters and metabolizing enzymes

1. Our objective is to investigate the alterations of hepatic drug transporters and metabolizing enzymes in hypercholesterolemia. Male Sprague–Dawley rats were fed high-cholesterol chows for 8 weeks to induce hypercholesterolemia. Protein levels of hepatic drug transporters and metabolizing enzymes were analyzed by iTRAQ labeling coupled with LC TRIPLE-TOF.

2. Total 239 differentially expressed proteins were identified using proteomic analysis. Among those, protein levels of hepatic drug transporters (MRP2, ABCD3, OAT2, SLC25A12, SCL38A3, SLC2A2 and SLC25A5) and metabolizing enzymes (CYP2B3, CYP2C7, CYP2C11, CYP2C13, CYP4A2 and UGT2B) were markedly reduced, but the levels of CYP2C6 and CYP2E1 were increased in hypercholesterolemia group compared to control. Decreased expressions of drug transporters MRP2 and OAT2 were further confirmed by real time quantitative PCR (RT-qPCR) and western blot.

3. Ingenuity pathway analysis revealed that these differentially expressed proteins were regulated by various signaling pathways including nuclear receptors and inflammatory cytokines. One of the nuclear receptor candidates, liver X receptor alpha (LXRα), was further validated by RT-qPCR and western blot. Additionally, LXRα agonist T0901317 rescued the reduced expressions of MRP2 and OAT2 in HepG2 cells in hypercholesterolemic serum treatment.

4. Our present results indicated that hypercholesterolemia affected the expressions of various drug transporters and metabolizing enzymes in liver via nuclear receptors pathway. Especially, decreased function of LXRα contributes to the reduced expressions of MRP2 and OAT2.     

St. John's wort extract induces CYP3A and CYP2E1 in the Swiss Webster mouse.

This investigation was designed to determine the ability of St. John's wort (SJW), a readily available antidepressant, to induce various hepatic drug metabolizing enzymes. SJW (140 or 280 mg/kg/day) was administered to male Swiss Webster mice for 1, 2, or 3 weeks. Enzymatic activity was analyzed in hepatic microsomes for all of the following drug metabolizing enzymes: CYP3A, CYP1A, CYP2E1, and UDP-glucuronosyltransferase (UDPGT). The catalytic activity of CYP1A was unchanged from control following any dose or duration of SJW, while both CYP3A and CYP2E1 catalytic activities were increased 2-fold by both SJW concentrations but only following 3 weeks of administration. Results from Western immunoblotting studies supported the changes in catalytic activity, as protein levels for CYP2E1 and CYP3A were increased (2.5-fold and 6-fold, respectively) following 3 weeks of SJW administration. Additionally, the catalytic activity of the conjugation enzyme UDPGT was unchanged from control following all SJW treatments. These results indicate that in the mouse moderate doses of SJW cause an increase in the catalytic activity and polypeptide levels of CYP2E1 and CYP3A but only following 21 days of administration, while the catalytic activity of CYP1A and UDPGT activity remain unaffected.