细胞色素P450酶电化学生物传感器的构建及其药物代谢应用

药物代谢过程是药物在体内产生药效和毒性的主要过程,发展廉价、方便、快速、高通量的体外药物代谢研究方法对新药的开发和设计、给药的方法和剂量、临床药物的检测等都有重要的指导意义. 细胞色素P450酶（CYP450酶）在药物的I相反应中起到关键作用,以电极代替辅酶NADPH提供CYP450酶催化反应过程中需要的两个电子,构建CYP450酶电化学生物传感器可实现药物的初步筛选. 大量研究表明,CYP450酶在电极表面合适的固定方法与电极材料可有效提高传感器的检测性能. 本文主要综述近年来CYP450酶电化学生物传感器的构建及其在药物代谢研究方面的应用,并展望其研发前景.     

LC-MS检测肝微粒体孵育液中系列化合物

肝脏是最重要的药物代谢器官之一,肝微粒体孵育试验可在亚细胞水平确定药物代谢稳定性、药酶抑制、活性代谢物生成等重要特性。对孵育液中药物进行定性定量检测是一项关键性试验,本文利用液相色谱-离子阱质谱技术,成功地对肝微粒体孵育液中两个系列化合物进行了定性定量分析,探讨了样品前处理的重要影响因素。     

高效液相色谱-串联质谱及特异性抑制剂探针方法研究异嗪皮啶的体外CYP450代谢产物及代谢亚型

利用高效液相色谱-串联质谱及特异性抑制剂探针方法研究了异嗪皮啶在大鼠肝微粒体CYP450中的代谢产物及代谢亚型。结果表明,异嗪皮啶在大鼠肝微粒体的代谢时间为2 h最佳,其主要代谢产物有5种。CYP 3A,CYP 2C,CYP 2E1等亚型为异嗪皮啶在大鼠肝微粒体内的主要代谢酶。本方法为进一步研究药物-药物相互作用提供了依据。     

基于DNA定向固定化技术构建毛细管固定化酶微反应器的研究进展

生物酶影响着物质代谢和质能转换等生命活动,生物体内某些酶的活性变化会导致疾病的发生。发展新型的酶分析方法对深刻理解生物代谢过程、疾病诊断和药物研发等具有重要意义。毛细管电泳（CE）具有分离效率高、分析速度快、操作简单和样品消耗少以及可与多种检测手段联用等优点,在酶分析研究中越来越受到关注。CE酶分析主要包括离线和在线两种模式,其中,固定化酶微反应器与毛细管电泳联用（CE-IMER）的在线酶分析已经成为主要的酶分析方法之一。CE-IMER充分结合了固定化酶和CE的优势,将游离酶固定在毛细管内,不仅可以显著提高酶的稳定性和重复使用性,而且可以实现纳升规模溶液的自动化酶分析,进而显著降低酶分析成本。目前已有大量方法制备IMER用于CE酶分析,然而如何构建性能良好、可再生使用、酶固载量大、自动化程度高的CE-IMER一直是该领域重点研究的问题。DNA定向固定化技术（DDI）可以充分利用DNA分子的碱基互补配对（A-T,C-G）,在温和的生理条件下特异性固定生物大分子。由于短链双螺旋DNA分子具有较强的机械刚性和物理化学稳定性,通过DDI将酶固定在载体表面,有利于降低传质阻力,提高酶与底物的接触能力,进而促进酶促分析过程。该文主要综述了利用DDI构建新型IMER在CE酶分析中的应用现状,并对其未来发展进行了展望。     

一种细胞色素P4502C8基因多态-CYP2C8.3的结构和功能

细胞色素P450超级家族在代谢众多的外源性化学物质方面发挥重要的作用.细胞色素P4502C8是人体肝脏中主要负责代谢抗癌药物紫杉醇的酶,它至少负责代谢5%的临床药物.细胞色素P450 2C8的基因多态性与用药个体化有着密切的关系.CYP2C8.3是常见的P450 2C8的基因多态之一,其发生了双点突变,分别是R139K...     

代谢组学中的分离分析科学*

代谢组学从概念的提出到现在已经有十多年的时间,它已被广泛应用于药物开发、疾病、微生物和植物等生命科学各个领域的研究,成为系统生物学不可或缺的一部分。代谢组学关注生物体系新陈代谢网络下游的小分子,分离分析科学是代谢组学技术平台的重要组成部分,与其它分析化学技术共同肩负着生物样本中代谢物全组分定性、定量的重任。本文结合我们研究组的工作,主要介绍气相色谱、液相色谱以及毛细管电泳等分离分析技术在代谢组中的应用和进展,以期对读者有所启迪。     

微量量热法筛选抑菌特效药的研究

用微量最热计连续测定细菌代谢过程中的热显变化，可获得反映细菌代谢规律的完整的热谱图以按指数生长模型对指数生长期进行处理，可计算出细菌正常代谢的生长速率常数L’．若在培养基中加入合成药物，使细菌在药物抑制作用下生长，也可获得完整的热谱图，从而计算出在药物抑制作用下细菌的生长速率常数．本义对福氏志贺氏Zb菌和金黄色葡萄球莉在四种合成药物抑制作用下的热谱进行了测定，并计算了生长速率常数，找出了细菌生长速率常数与所用药物浓度之间的定量关系，可为筛选抑菌药物和确定用药显提供定量依据’1基本原理设细菌在代谢过…     

液相色谱-质谱联用技术结合多探针底物法研究人参皂苷Rb1的体外代谢

以奥美拉唑、 苯妥英、 卡马西平和非那西丁为检测肝药酶细胞色素P450酶(CYP450)亚型的专属探针药物, 通过原型药物减少量测定法考察药物体外代谢的变化, 评价人参皂苷Rb1对CYP450不同亚型酶的作用. 结果表明, P2C9, P2C19和P3A4实验组与对照组差异不显著, P1A2实验组与对照组差异显著, 表明人参皂苷Rb1能诱导P1A2亚型酶的活性, 促进底物与酶反应, 加快底物的代谢, 而对P2C9, P2C19和P3A4三个亚型酶有弱的诱导或无诱导作用. 根据快速分离液相色谱-质谱联用(RRLC-MS/MS)检测结果推断, 人参皂苷Rb1在CYP450酶中的代谢产物可转化为人参皂苷Rb1氧化产物(Rb1+O)及人参皂苷Rd和F2.     

瑞芬太尼在人体中的代谢动力学研究

建立了用液相色谱-串联质谱技术进行瑞芬太尼代谢动力学研究的方法。比较了不同停药时间对瑞芬太尼浓度及代谢产物的影响。瑞芬太尼浓度测定采用串联质谱的选择反应监测技术,以m/z377>345为定量离子对,定量检出限为0.5μg/L。代谢产物的测定采用液质联用技术,同时测定二级质谱。在停药8min后,瑞芬太尼代谢90%。氧化和水解是瑞芬太尼的主要代谢反应,瑞芬太尼在人体中形成4种代谢物。该研究方法简单、快速、灵敏,具有广泛的应用性。     

锰的生理作用及其与健康的关系

（1）通过含锰酶或锰激活酶发挥生理作用 锰是体内多种酶的活性基因或辅助因子,又是某些酶的激活剂,参与体内多方面的物质代谢,具有重要的生理作用。精氨酸酶是与尿素生成有关的酶。其活性与从食物中摄取的锰量有关。锰超氧化物歧化酶（Mn—SOD）可清除过氧化物,主要存在于线粒体内。丙酮酸羧化酶也是含锰酶,在葡萄糖生成过程中起重要作用。     

Characterization of the biotransformation pathways of clomiphene, tamoxifen and toremifene as assessed by LC-MS/(MS) following in vitro and excretion studies

The use of selective oestrogen receptor modulators has been prohibited since 2005 by the World Anti-Doping Agency regulations. As they are extensively cleared by hepatic and intestinal metabolism via oxidative and conjugating enzymes, a complete investigation of their biotransformation pathways and kinetics of excretion is essential for the anti-doping laboratories to select the right marker(s) of misuse. This work was designed to characterize the chemical reactions and the metabolizing enzymes involved in the metabolic routes of clomiphene, tamoxifen and toremifene. To determine the biotransformation pathways of the substrates under investigation, urine samples were collected from six subjects (three females and three males) after oral administration of 50 mg of clomiphene citrate or 40 mg of tamoxifen or 60 mg of toremifene, whereas the metabolizing enzymes were characterized in vitro, using expressed cytochrome P450s and uridine diphosphoglucuronosyltransferases. The separation, identification and determination of the compounds formed in the in vivo and in vitro experiments were carried out by liquid chromatography coupled with mass spectrometry techniques using different acquisition modes. Clomiphene, tamoxifen and toremifene were biotransformed to 22, 23 and 18 metabolites respectively, these phase I reactions being catalyzed mainly by CYP3A4 and CYP2D6 isoforms and, to a lesser degree, by CYP3A5, CYP2B6, CYP2C9, CYP2C19 isoforms. The phase I metabolic reactions include hydroxylation in different positions, N-oxidation, dehalogenation, carboxylation, hydrogenation, methoxylation, N-dealkylation and combinations of them. In turn, most of the phase I metabolites underwent conjugation reaction to form the corresponding glucuro-conjugated mainly by UGT1A1, UGT1A3, UGT1A4, UGT2B7, UGT2B15 and UGT2B17 isoenzymes.     

Identification of cytochrome P450 isoforms involved in the metabolism of artocarpin and assessment of its drug–drug interaction

Artocarpin isolated from an agricultural plant Artocarpus communis has shows anti‐inflammation and anticancer activities. In this study, we utilized recombinant human UDP‐glucuronosyltransferasesupersomes (UGTs) and human liver microsomes to explore its inhibitory effect on UGTs and cytochrome p450 enzymes (CYPs). Chemical inhibition studies and screening assays with recombinant human CYPs were used to identify if CYP isoform is involved in artocarpin metabolism. Artocarpin showed strong inhibition against UGT1A3, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B7, CYP2C8 and CYP3A4. In particular, artocarpin exhibited competitive inhibition against CYP3A4 and noncompetitive inhibition against UGT1A3 and UGT1A7. The half inhibition concentration values for CYP3A4, UGT1A3 and UGT1A7 were 4.67, 3.82 and 4.82 μm , and the inhibition kinetic parameters for them were 0.78, 2.67 and 3.14 μm , respectively. After artocarpin was incubated in human liver microsomes and determined by HPLC, we observed its main metabolites (M1 and M2). In addition, we proved that CYP2D6 played the key role in the biotransformation of artocarpin in human liver microsomes. The result of molecular docking further confirmed that artocarpin interacted with CYP2D6, CYP2C8 and CYP3A4 through hydrogen bonds. This study provided preliminary results for further research on artocarpin or artocarpin‐containing herbs.     

Corydaline inhibits multiple cytochrome P450 and UDP-glucuronosyltransferase enzyme activities in human liver microsomes

Corydaline is a bioactive alkaloid with various antiacetylcholinesterase, antiallergic, and antinociceptive activities found in the medicinal herb Corydalis Tubers. The inhibitory potential of corydaline on the activities of seven major human cytochrome P450 and four UDP-glucuronosyltransferase enzymes in human liver microsomes was investigated using LC-tandem MS. Corydaline was found to inhibit CYP2C19-catalyzed S-mephenytoin-4'-hydroxylatoin and CYP2C9-catalyzed diclofenac 4-hydroxylation, with K(i) values of 1.7 and 7.0 mM, respectively. Corydaline also demonstrated moderate inhibition of UGT1A1-mediated 17b-estradiol 3-glucuronidation and UGT1A9-mediated propofol glucuronidation with K(i) values of 57.6 and 37.3 mM, respectively. In the presence of corydaline, CYP3A-mediated midazolam hydroxylation showed a decrease with increasing preincubation time in a dose-dependent manner with K(i) values of 30.0 mM. These in vitro results suggest that corydaline should be evaluated for potential pharmacokinetic drug interactions in vivo due to potent inhibition of CYP2C19 and CYP2C9.     

UGT1A1 and UGT1A9 Are Responsible for Phase II Metabolism of Tectorigenin and Irigenin In Vitro

Tectorigenin and irigenin are biologically active isoflavones of Belamcanda chinensis (L.) DC. Previous studies indicated that both compounds could be metabolized in vivo; however, the kinetic parameters of enzymes involved in the metabolization of tectorigenin and irigenin have not been identified. The aim of this study was to investigate UGTs involved in the glucuronidation of tectorigenin and irigenin and determine enzyme kinetic parameters using pooled human liver microsomes (HLMs) and recombinant UGTs. Glucuronides of tectorigenin and irigenin were identified using high-performance liquid chromatography (HPLC) coupled with mass spectrometry and quantified by HPLC using a response factor method. The results showed that tectorigenin and irigenin were modified by glucuronidation in HLMs. One metabolite of tectorigenin (M) and two metabolites of irigenin (M1 and M2) were detected. Chemical inhibition and recombinant enzyme experiments revealed that several enzymes could catalyze tectorigenin and irigenin glucuronidation. Among them, UGT1A1 and UGT1A9 were the primary enzymes for both tectorigenin and irigenin; however, the former mostly produced irigenin glucuronide M1, while the latter mostly produced irigenin glucuronide M2. These findings suggest that UGT1A1 and UGT1A9 were the primary isoforms metabolizing tectorigenin and irigenin in HLMs, which could be involved in drug–drug interactions and, therefore, should be monitored in clinical practice.     

Cytochrome P450 reaction phenotyping and inhibition and induction studies of pinostrobin in human liver microsomes and hepatocytes

Pinostrobin (PI, 5‐hydroxy‐7‐methoxyflavanone) is a natural flavonoid known for its rich pharmacological activities. The objective of this study was to identify the human liver cytochrome P450 (CYP450) isoenzymes involved in the metabolism of PI. A single hydoxylated metabolite was obtained from PI after an incubation with pooled human liver microsomes (HLMs). The relative contributions of different CYP450s were evaluated using CYP450‐selective inhibitors in HLMs and recombinant human CYP450 enzymes, and the results revealed the major involvement of CYP1A2, CYP2C9 and CYP2E1 in PI metabolism. We also evaluated the ability of PI to inhibit and induce human cytochrome P450 enzymes in vitro . High‐performance liquid chromatography and liquid chromatography–tandem mass spectrometry analytical techniques were used to estimate the enzymatic activities of seven drug‐metabolizing CYP450 isozymes in vitro . In HLMs, PI did not inhibit CYP 1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6 or CYP3A4 (IC₅₀ > 100 μm ). In the induction studies, PI had minimal effects on CYP1A2, CYP2B6and CYP3A4 activity. Based on these results, PI would not be expected to cause clinically significant CYP450 inhibition or induction.     

Validated assay for studying activity profiles of human liver UGTs after drug exposure: inhibition and induction studies

UDP-glucuronsyltransferases (UGTs) are a family of conjugating enzymes that participate in the metabolism of many drugs. The study of potential drug–drug interactions involving UGTs has been largely hindered by the limited availability of selective functional assays for individual UGT enzymes. We propose a sensitive and reproducible procedure for the activity measurements of four major human hepatic UGT forms. The assays are based on analysis and quantification by high-performance liquid chromatography–tandem mass spectrometry of glucuronides formed from selective probe substrates, namely, β-estradiol (UGT1A1, 3-glucuronide), 1-naphthol (UGT1A6), propofol (UGT1A9), and naloxone (UGT2B7). The analytical methods developed in the present study have been validated under good laboratory practice compliance following FDA recommendations. The assays can be easily applied to both phenotyping UGT reactions in liver-derived cellular and subcellular systems, and drug–drug interaction in vitro studies. Chemical inhibition of UGTs was tested in human liver microsomes at substrate concentrations lower than the corresponding K _M values. Under these conditions, selective inhibition of UGT2B7 by fluconazole and low amitriptyline concentrations were observed, whereas diclofenac and quinidine were shown as non-enzyme-selective inhibitors of UGTs. Induction of UGTs was studied in primary human hepatocytes and HepG2 cells cultured in 96-well plates. Aryl hydrocarbon receptor ligands (except indirubin in hepatocytes) increased the UGT1A1 activity in both cell models. The highest effects were observed in HepG2 cells exposed to indirubin (21-fold over the control) and omeprazole or β-naphthoflavone (about sixfold). Although variable effects were observed in other UGT enzymes, the degree of induction was generally lower than that for UGT1A1.     

A UPLC-MS/MS assay of the "Pittsburgh cocktail": six CYP probe-drug/metabolites from human plasma and urine using stable isotope dilution

The efficiency of drug metabolism by a single enzyme can be measured as the fractional metabolic clearance which can be used as a measure of whole body activity for that enzyme. Measurement of activity of multiple enzymes simultaneously is feasible using a cocktail approach, however, analytical approach using different assays for drug probes can be cumbersome. A quantitative ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) based method for the rapid measurement of six cytochrome P450 (CYP) probe drugs and their relevant metabolites is described. The six specific probe substrates/metabolites are caffeine/paraxanthine (CYP1A2), flurbiprofen/4'-hydroxyflurbiprofen (CYP2C9), mephenytoin/4'-hydroxymephenytoin (CYP2C19), debrisoquine/4-hydroxydebrisoquine (CYP2D6), chlorzoxazone/6'-hydroxychlorzoxazone (CYP2E1) and dapsone/N-monoacetyldapsone (NAT2). These probes were quantified by stable isotope dilution from plasma and urine. The present workflow provides a robust, fast and sensitive assay for the "Pittsburgh cocktail", and has been successfully applied to a clinical phenotyping study of liver disease. A representative group of 17 controls and patients with chronic liver disease were administered orally caffeine (100 mg), chlorzoxazone (250 mg), debrisoquine (10 mg), mephenytoin (100 mg), flurbiprofen (50 mg) and dapsone (100 mg). Urine (0 through 8 h) and plasma (4 and 8 h) samples were analyzed for drug/metabolite amounts by stable isotope dilution UPLC-MS/MS. The phenotypic activity of drug metabolizing enzymes was investigated with 17 patient samples. Selected reaction monitoring (SRM) was optimized for each drug and metabolite. In the method developed, analytes were resolved by reversed-phase by development of a gradient using a water/methanol solvent system. SRM of each analyte was performed in duplicate on a triple quadrupole mass spectrometer utilizing an 8 min analytical method each, one with the source operating in the positive mode and one in the negative mode, using the same solvent system. This method enabled quantification of each drug (caffeine, chlorzoxazone, debrisoquine, mephenytoin, flurbiprofen, and dapsone) and its resulting primary metabolite in urine or plasma in patient samples. The method developed and the data herein demonstrate a robust quantitative assay to examine changes in CYP enzymes both independently or as part of a cocktail. The clinical use of a combination of probe drugs with UPLC-MS/MS is a highly efficient tool for the assessment of CYP enzyme activity in liver disease.     

Biochemical and analytical development of the CIME cocktail for drug fate assessment in humans

Phenotyping based on drug metabolism activity appears to be informative regarding mechanism‐based interactions during drug development. We report here the first steps of the development of the innovative CIME cocktail. This cocktail is designed not only for the major cytochrome P450, with caffeine, amodiaquine, tolbutamide, omeprazole, dextromethorphan and midazolam as substrates of CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6 and CYP3A, respectively, but also phase II enzymes UGT 1A1/6/9 with acetaminophen, P‐gp and OATP1B1 with digoxin and rosuvastatin, and renal function with memantine. An assay combining ultra‐performance liquid chromatography using a 1.7 µm particle size column with tandem mass spectrometry (UPLC/MS/MS) was set up for the simultaneous quantification of the 20 substrates and metabolites after extraction from human plasma using solid‐phase extraction. The method was validated in the spirit of the FDA guidelines. Mean accuracy ranged from 87.7 to 115%, the coefficient of variance (CV%) of intra‐ and inter‐run from 1.7 to 16.4% and from 1.6 to 14.9%, respectively, and for the limit of quantification (LOQ) with ten lots of plasma, accuracy ranged from 84 to 115% and CV% precision was <16%. Short‐term stability was evaluated in eluate (4 h, room temperature), plasma (24 h, room temperature), the autosampler (24 h, 4°C) and in three freeze/thaw cycles in plasma. All except three analytes were stable under these conditions. For the three others a specific process can be followed. This robust, fast and sensitive assay in human plasma provides an analytical tool for ten‐probe drugs of the CIME cocktail. Clinical samples will be assayed in the near future using this new assay method. Copyright © 2010 John Wiley & Sons, Ltd.     

Long-range effects of a peripheral mutation on the enzymatic activity of cytochrome P450 1A2

The human cytochrome P450 1A2 is an important drug metabolizing and procarcinogen activating enzyme. An experimental study found that a peripheral mutation, F186L, at ～26 ? away from the enzyme's active site, caused a significant reduction in the enzymatic activity of 1A2 deethylation reactions. In this paper, we explored the effects of this mutation by carrying out molecular dynamics simulations and structural analyses. We found that the long-range effects of the F186L mutation were through a change in protein flexibility and a collective protein motion that caused the main substrate access channel to be mostly closed in the mutant. Our work is the first that combined both access channel analysis and protein motion analysis to elucidate mechanisms of mutation-induced allostery in a CYP protein. Such structural modeling and analysis approaches may be applied to other CYP proteins and other enzymes with buried active sites and may help guide protein engineering and drug design.