细胞色素P450酶系在药物代谢中的作用

该文从细胞色素P450概述、参与药物代谢的人类细胞色素P450亚型、细胞色素P450与药物的相互作用、细胞色素P450多态性在药物不良反应中的作用及细胞色素P450酶系产生药物不良反应的机制等方面综述细胞色素P450酶系对药物代谢的影响，为指导临床合理用药，避免药物不良反应及个体化用药提供参考。     

药物代谢酶细胞色素P450 2C9研究进展

P450 2C9是人体中重要的药物代谢酶。P450 2C9基因编码区的多态性造成氨基酸序列的变化。主要包括P450 2C9*2和P450 2C9*3两种突变体，变异纯合子对P450 2C9底物的代谢能力明显降低。P450 2C9的底物包括甲苯磺丁脲、苯妥英、S-法华令、氟西汀、洛沙坦等。P450 2C9可被利福平诱导，被胺碘酮和氟康唑等多种药物抑制。     

细胞色素P450酶基因多态性的研究进展及临床意义

细胞色素P450（cytochrome P450,CYP）是重要的药物代谢酶,参与催化多种内源和外源化合物,特别是多种临床药物的生物转化。CYP存在广泛的基因多态性和表型多态性,体现在个体对于各种化合物的代谢存在明显差异。本文综述了CYP的基因多态性、与药物代谢相关的CYP各亚型的特点和临床意义,主要目的是合理解释和预测临床上药物间相互作用和药物不良反应等,为实现临床个体化给药提供科学依据。     

细胞色素P450基因突变及其效应的研究进展

细胞色素P450(CYP450)作为一组重要的氧化酶在人体药物代谢中发挥着重要作用，随着基因组学的发展，其基因多态性逐步得到深入研究。近年来，对于CYP450的研究重点也逐渐由基因定位和单纯的突变位点发现，转移到等位基因功能多态性和基因突变导致的酶学改变这些基因与蛋白的效应关系上来。本文综述了CYP450新的单核苷酸多态性的出现及相应功能的研究进展。     

细胞色素P450酶系和药物不良反应

细胞色素P450酶系在药物代谢中扮演了重要角色。本描述了许多环境和基因的因素,这些因素调整人体酶和它们的药物底物的活性。在一些情况下,细胞色素P450酶具有基因的多态性,导致对某些药物在表型上明显慢和明显快的代谢。慢代谢（PMs）易发生与浓度相关的药物不良反应,而快代谢（EMs）则对药物相互作用易感;其中抑制的相互作用可能会由于血浆浓度的增中而导致毒性。药物代谢被改变是药物不良反应的重要原因。     

细胞色素P450与药物代谢的研究现状

细胞色素P450(CYP)在众多中西药物代谢中起着非常重要的作用。本文综述了与药物代谢相关的CYP亚型、CYP与药物相互作用的关系及中药对CYP的影响，旨在合理解释和预测临床上药物间相互作用和药物不良反应等。同时选择适当的药物作为探针来评价CYP的活性，为实现临床个体化给药提供科学依据。     

药物代谢中的肝细胞色素P450

肝细胞色素Ｐ４５０参与许多外源性物质（包括药物）的生物转化。本文从肝细胞色素Ｐ４５０在体内的分布及命名,被诱导和抑制的机制,对映体代谢的选择性与代谢差异遗传多态性以及国内外关于Ｐ４５０的研究方法等方面介绍了该领域研究的新进展。     

细胞色素P450酶与药物代谢的研究进展与评价

目的：评价细胞色素P450酶与药物代谢的研究进展,以供临床医师合理用药参考。方法：查阅近年来国内、外的相关文献资料,进行归纳和分析。结果与结论：肝细胞色素P450酶系参与人体许多内、外源性物质（包括药物）的分解和代谢。P450酶系在体内的分布、结构和功能在药物代谢和临床疾病诊断过程中有着十分重要的药理作用和临床意义。     

细胞色素P450酶系和药物的不良反应

细胞色素P450酶系在药物代谢中扮演了重要角色.本文描述了许多环境的和基因的因素,这些因素调整人体酶和它们的药物底物的活性.在一些情况下,细胞色素P450酶具有基因的多态性,导致对某些药物在表型上明显慢和明显快的代谢.慢代谢者(PMs)易发生与浓度相关的药物不良反应,而快代谢者(EMs)则对药物相互作用易感;其中抑制的相互作用可能会由于血浆浓度的增加而导致毒性.药物代谢被改变是药物不良反应的重要原因.     

细胞色素P450的基因多态性与药物代谢

细胞色素P450（cytochrome P450，CYP）是重要的药物代谢酶，参与催化多种内源和外源化合物，特别是多种临床药物的生物转化。CYP存在广泛的基因多态性和表型多态性，使其对于各种化合物的代谢存在统计学个体差异。核受体是配体依赖性转录因子超家族，与药物代谢过程中的基因表达调控密切相关，被外源物质活化后诱导或抑制CYP基因的表达。现综述CYP与药物代谢、CYP的基因多态性、CYP表达的诱导机制、核受体及其配体诱导CYP表达及近年研究CYP450的各种实验方法。     

加替沙星和环丙沙星对大鼠肝细胞色素P450酶系的影响

目的 研究加替沙星和环丙沙星对大鼠肝微粒体细胞色素P450酶系的影响。方法 加替沙星和环丙沙星400 mg.kg-1灌胃给药大鼠,qd,7天后,用差速离心法制备大鼠肝微粒体,用Lowry法测定蛋白浓度,用分光光度计法检测6种肝微粒体细胞色素P450酶含量及活性,并用单因素方差分析进行统计。结果 加替沙星组的6种细胞色素P450酶的活性与空白对照组相比差异无统计学意义;而环丙沙星能抑制6种细胞色素P450酶中的b5、NADPH-CytC还原酶、氨基比林N-脱甲基酶、红霉素N-脱甲基酶和7-乙氧基香豆素脱烃酶的活性,对CYP450酶系有选择性抑制作用。结论 加替沙星对大鼠肝微粒体CYP450酶系无显著性影响,而环丙沙星对CYP450酶系有选择性抑制作用。     

大鼠肝微粒体细胞色素P450酶系检测方法学研究

目的 :建立大鼠肝微粒体蛋白含量以及肝微粒体细胞色素P4 5 0酶系含量与活性测定的紫外和荧光分光光度方法。方法 :应用差速离心法提取大鼠肝微粒体 ,Lowery法测定肝微粒体蛋白浓度 ,应用紫外和荧光分光光度法测定肝微粒体细胞色素P4 5 0酶系含量及活性。结果 :牛血清白蛋白标准曲线的线性范围为 2 5～ 2 5 0mg·L-1,最低检测限为2 5mg·L-1,相关系数r为 0 .9975 ;紫外分光光度法测定细胞色素P4 5 0和细胞色素b5含量及NADPH CytC还原酶活性的结果显示方法灵敏 ;测定氨基比林N 脱甲基酶、红霉素N 脱甲基酶活性的甲醛标准曲线 ,线性范围为 0 .0 5～ 0 .5mmol·L-1,最低检测限为 0 .0 5mmol·L-1,相关系数r为 0 .9988;测定 7 乙氧基香豆素脱烃酶活性的resorufin标准曲线线性范围为 1～ 8μmol·L-1,最低检测限为 1μmol·L-1,相关系数r为 0 .9998。结论 :紫外和荧光分光光度方法测定大鼠肝微粒体细胞色素P4 5 0酶系中 6种酶的含量及活性的灵敏可靠 ,重复性较好。     

新型抗抑郁药的代谢与细胞色素P450介导的药物相互作用

新型抗抑郁药(选择性5-羟色胺再摄取抑制剂,SSRI)疗效肯定,耐受性好,已得到广泛应用。SSRI剂既是P 450酶的底物又是P 450酶的抑制剂,其重要特征是对P 450酶的抑制。当SSRI剂与P 450酶的其他底物合用时,可能发生明显的具有临床意义的药物相互作用。     

Small Intestinal Cytochromes P450

Abstract

Small intestinal cytochromes P450 (P450) provide the principal, initial source of biotransformation of ingested xenobiotics. The consequences of such biotransformation are detoxification by facilitating excretion, or toxification by bioactivation. P450s occur at highest concentrations in the duodenum, near the pylorus, and at decreasing concentrations distally — being lowest in the ileum. Highest concentrations occur from midvillus to villous tip, with little or none occurring in the crypts of Lieberkuehn. Microsomal P4503A, 2C8-10, and 2D6 forms have been identified in human small intestine, and P450s 2B1, possibly 2B2, 2A1, and 3A1/2 were located in endoplasmic reticulum of rodent small intestine, while P4502B4 has been purified to electrophoretic homogeneity from rabbit intestine. Some evidence indicates a differential distribution of P450 forms along the length of the small intestine and even along the villus. Rat intestinal P450s are inducible by xenobiotics — with phenobarbital (PB) inducing P4502B1, 3-methylcholanthrene (3-MC) inducing P4501A1, and dexamethasone inducing two forms of P4503A. Induction is most effectively achieved by oral administration of the agents, and is rapid — aryl hydrocarbon hydroxylase (AHH) was increased within 1 h of administration of, for example, 3-MC. AHH, 7-ethoxycoumarin O-deethylase (ECOD), and 7-ethoxyresorufin O-deethylase (EROD) have been used most frequently as substrates to characterize intestinal P450s. Dietary factors affect intestinal P450s markedly — iron restriction rapidly decreased intestinal P450 to beneath detectable values; selenium deficiency acted similarly but was less effective; Brussels sprouts increased intestinal AHH activity 9.8-fold, ECOD activity 3.2-fold, and P450 1.9-fold; fried meat and dietary fat significantly increased intestinal EROD activity; a vitamin A-deficient diet increased, and a vitamin A-rich diet decreased intestinal P450 activities; and excess cholesterol in the diet increased intestinal P450 activity. The role of intestinal P450 in toxifying or detoxifying specific xenobiotics has been clearly demonstrated to only a limited extent. However, elevated intestinal P450 levels have been indirectly linked to gastrointestinal cancer. Intestinal metabolism of 2,2,2-trifluoroethanol produces intestinal lesions with consequent systemic bacterial infection.     

细胞色素P450酶在癌症研究中的应用

细胞色素P450酶是体内代谢转换的重要酶系.现从细胞色素P450酶在活性调节、代谢表型、致癌 物活化、抗癌药物代谢、肿瘤组织中特异表达和肿瘤基因治疗等方面综述细胞色素P450酶的特点及其在癌症研究中的应用潜力.     

Time-dependent inhibition of human drug metabolizing cytochromes P450 by tricyclic antidepressants

AIMS

To investigate time-dependent inhibition (TDI) of human drug metabolizing CYP enzymes by tricyclic antidepressants (TCAs).

METHODS

CYP1A2, CYP2C9, CYP2C19, CYP2D6 and CYP3A/CYP3A4 activities were investigated following co- and preincubation with TCAs using human liver microsomes (HLM) and human recombinant CYP proteins (expressed in Escherichia coli) as the enzyme sources. A two-step incubation method was employed to examine the in vitro mechanism-based inactivation (MBI) criteria. Potential metabolite–intermediate complex (MIC) formation was studied by spectral analysis.

RESULTS

TCAs generally exhibited significant TDI of recombinant CYP1A2, CYP2C19 and CYP2D6 (>10% positive inhibition differences between co- and preincubation conditions). TDI of recombinant CYP2C9 was minor (<10%), and was minor or absent in experiments utilizing recombinant CYP3A4 or HLM as the enzyme sources. Where observed, TDI of recombinant CYP occurred via alkylamine MIC formation, but evidence to support similar behaviour in HLM was limited. Indeed, only secondary amine TCAs reduced the apparent P450 content of HLM (3–6%) consistent with complexation. As a representative TCA, nortriptyline fulfilled the in vitro MBI criteria using recombinant CYP2C19 and CYP3A4 (K_I and k_inact values of 4 µm and 0.19 min⁻¹, and 70 µm and 0.06 min⁻¹), but not with the human liver microsomal enzymes.

CONCLUSIONS

TCAs appear to have minimal potential for MBI of human liver microsomal CYP enzymes involved in drug metabolism. HLM and recombinant CYP (expressed in E. coli) are not equivalent enzyme sources for evaluating the TDI associated with some drugs.

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Much of the literature evidence for mechanism-based inactivation (MBI) of CYP by tricyclic antidepressants is limited to studies in rat liver microsomes.
• One report from this laboratory characterized MBI of human recombinant CYP2C8 by nortriptyline.

WHAT THIS STUDY ADDS

• Tricyclic antidepressants form alkylamine metabolite-intermediate complexes with human recombinant CYP enzymes (expressed in Escherichia coli) relatively easily, resulting in time-dependent inhibition.
• Evidence to support similar irreversible inhibition using human liver microsomal (HLM) fractions is limited.
• HLM and recombinant CYP (expressed in E. coli) are not equivalent enzyme sources for evaluating the time-dependent inhibition of human drug metabolizing CYP that is associated with some drugs.

     

Human cytochromes mediating gepirone biotransformation at low substrate concentrations

Biotransformation of gepirone to 1-(2-pyrimidinyl)-piperazine (1-PP) and 3'-OH-gepirone, as well as two other hydroxylated metabolites, was studied in vitro using a human liver microsomal preparation and heterologously expressed human CYP3A4 and CYP2D6. The focus was on a low range of gepirone concentrations (1000 nM and below). Liver microsomes formed 1-PP and 3'-OH-gepirone with similar reaction velocities. Two other hydroxylated metabolites (2-OH- and 5-OH-gepirone) were also formed, but pure reference standards were not available for purposes of quantitative analysis. The CYP3A inhibitor ketoconazole completely eliminated 1-PP formation, reduced 3'-OH-gepirone formation to less than 20% of control, and reduced 2-OH-gepirone formation to 7% of control. All metabolites were formed by expressed CYP3A4; however, CYP2D6 formed 3'-OH- and 5-OH-gepirone, but not 1-PP or 2-OH-gepirone. Based on estimated relative abundances of the two isoforms in human liver, CYP3A4 was predicted to account for more than 95% of net clearance of gepirone in vivo at low concentrations approaching the therapeutic range. CYP2D6 would account for less than 5% of net clearance. The findings are consistent with previous in vitro studies of gepirone using higher substrate concentrations.