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Zonyfar C, Ngnamsie Njimbouom S, Mosalla S, Kim JD. GTransCYPs: an improved graph transformer neural network with attention pooling for reliably predicting CYP450 inhibitors. J Cheminform 2024; 16:119. [PMID: 39472986 PMCID: PMC11524008 DOI: 10.1186/s13321-024-00915-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Accepted: 10/10/2024] [Indexed: 11/02/2024] Open
Abstract
State‑of‑the‑art medical studies proved that predicting CYP450 enzyme inhibitors is beneficial in the early stage of drug discovery. However, accurate machine learning-based (ML) in silico methods for predicting CYP450 inhibitors remains challenging. Here, we introduce GTransCYPs, an improved graph neural network (GNN) with a transformer mechanism for predicting CYP450 inhibitors. This model significantly enhances the discrimination between inhibitors and non-inhibitors for five major CYP450 isozymes: 1A2, 2C9, 2C19, 2D6, and 3A4. GTransCYPs learns information patterns from molecular graphs by aggregating node and edge representations using a transformer. The GTransCYPs model utilizes transformer convolution layers to process features, followed by a global attention-pooling technique to synthesize the graph-level information. This information is then fed through successive linear layers for final output generation. Experimental results demonstrate that the GTransCYPs model achieved high performance, outperforming other state-of-the-art methods in CYP450 prediction.Scientific contributionThe prediction of CYP450 inhibition via computational techniques utilizing biological information has emerged as a cost-effective and highly efficient approach. Here, we presented a deep learning (DL) architecture based on GNN with transformer mechanism and attention pooling (GTransCYPs) to predict CYP450 inhibitors. Four GTransCYPs of different pooling technique were tested on an experimental tasks on the CYP450 prediction problem for the first time. Graph transformer with attention pooling algorithm achieved the best performances. Comparative and ablation experiments provide evidence of the efficacy of our proposed method in predicting CYP450 inhibitors. The source code is publicly available at https://github.com/zonwoo/GTransCYPs .
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Affiliation(s)
- Candra Zonyfar
- Department of Computer Science and Electronic Engineering, Sun Moon University, Asan, 31460, Republic of Korea
| | | | - Sophia Mosalla
- Division of Computer Science and Engineering, Sun Moon University, Asan, 31460, Republic of Korea
| | - Jeong-Dong Kim
- Department of Computer Science and Electronic Engineering, Sun Moon University, Asan, 31460, Republic of Korea.
- Division of Computer Science and Engineering, Sun Moon University, Asan, 31460, Republic of Korea.
- Genome-based BioIT Convergence Institute, Sun Moon University, Asan, 31460, Republic of Korea.
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2
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Luo Y, Li J, Gu Z, Huang Y. Graphene quantum dots blocking the channel egresses of cytochrome P450 enzyme (CYP3A4) reveals potential toxicity. Sci Rep 2023; 13:21091. [PMID: 38036640 PMCID: PMC10689800 DOI: 10.1038/s41598-023-48618-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 11/28/2023] [Indexed: 12/02/2023] Open
Abstract
Graphene quantum dots (GQDs) have garnered significant attention, particularly in the biomedical domain. However, extensive research reveals a dichotomy concerning the potential toxicity of GQDs, presenting contrasting outcomes. Therefore, a comprehensive understanding of GQD biosafety necessitates a detailed supplementation of their toxicity profile. In this study, employing a molecular dynamics (MD) simulation approach, we systematically investigate the potential toxicity of GQDs on the CYP3A4 enzyme. We construct two distinct simulation systems, wherein a CYP3A4 protein is enveloped by either GQDs or GOQDs (graphene oxide quantum dots). Our results elucidate that GQDs come into direct contact with the bottleneck residues of Channels 2a and 2b of CYP3A4. Furthermore, GQDs entirely cover the exits of Channels 2a and 2b, implying a significant hindrance posed by GQDs to these channels and consequently leading to toxicity towards CYP3A4. In-depth analysis reveals that the adsorption of GQDs to the exits of Channels 2a and 2b is driven by a synergistic interplay of hydrophobic and van der Waals (vdW) interactions. In contrast, GOQDs only partially obstruct Channel 1 of CYP3A4, indicating a weaker influence on CYP3A4 compared to GQDs. Our findings underscore the potential deleterious impact of GQDs on the CYP3A4 enzyme, providing crucial molecular insights into GQD toxicology.
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Affiliation(s)
- Yuqi Luo
- Department of Gastrointestinal and Hepatobiliary Surgery, Shenzhen Longhua District Central Hospital, No. 187, Guanlan Road, Longhua District, Shenzhen, 518110, Guangdong Province, China.
| | - Jinjun Li
- Department of Gastrointestinal and Hepatobiliary Surgery, Shenzhen Longhua District Central Hospital, No. 187, Guanlan Road, Longhua District, Shenzhen, 518110, Guangdong Province, China
| | - Zonglin Gu
- College of Physical Science and Technology, Yangzhou University, Jiangsu, 225009, China
| | - Yaoxing Huang
- Department of Gastrointestinal and Hepatobiliary Surgery, Shenzhen Longhua District Central Hospital, No. 187, Guanlan Road, Longhua District, Shenzhen, 518110, Guangdong Province, China.
- Department of Gastroenterology, Guangzhou First People's Hospital, School of Medicine, South China University of Technology, Guangzhou, 510180, Guangdong Province, China.
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3
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Alqahtani MA, El-Ghiaty MA, El-Kadi AOS. Mercury and methylmercury differentially modulate hepatic cytochrome P450 1A1 and 1A2 in vivo and in vitro. J Biochem Mol Toxicol 2023; 37:e23243. [PMID: 36245390 DOI: 10.1002/jbt.23243] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 08/16/2022] [Accepted: 10/06/2022] [Indexed: 11/08/2022]
Abstract
The cytochrome P450 1 A (CYP1A) subfamily enzymes are involved in the metabolic activation of several xenobiotics to toxic metabolites and reactive intermediates, resulting ultimately in carcinogenesis. Mercury and halogenated aromatic hydrocarbons (HAHs), typified by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are persistent environmental pollutants involved in the modulation of aryl hydrocarbon receptor (AHR) gene battery, including cytochrome P450 (CYP) genes. We previously investigated the effect of coexposure to either inorganic or organic mercury (Hg+2 and MeHg) with TCDD on CYP1A1 in vitro. Thus, we examined the impact of coexposure to Hg+2 or MeHg and TCDD on AHR-regulated genes (Cyp1a1/1a2) in vivo and in vitro. Therefore, male C57BL/6 mice were injected intraperitoneally with MeHg or Hg+2 (2.5 mg/kg) in the absence and presence of TCDD (15 μg/kg) for 6 or 24 h. The concentration-dependent effect of MeHg was examined in murine hepatoma Hepa1c1c7 cells. In vivo, both MeHg and Hg2+ inhibited the TCDD-mediated induction of Cyp1a1/1a2 mRNA levels. However, Only Hg2+ was able to inhibit the TCDD-mediated induction at posttranscriptional levels of CYP1A1/1A2 protein and catalytic activity, suggesting differential modulation effects by Hg+2 and MeHg. In addition, the inhibitory role of HO-1 (Heme oxygenase-1) on CYP1A activity induced by TCDD was investigated using a HO-1 competitive inhibitor, tin-mesoporphyrin, that partially restored the MeHg-mediated decrease in CYP1A1 activity. This study demonstrates that MeHg, alongside Hg2+ , can differentially modulate the TCDD-induced AHR-regulated genes (Cyp1a1/1a2) at different expression levels in C57BL/6 mice liver and Hepa1c1c7 cells.
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Affiliation(s)
- Mohammed A Alqahtani
- Department of Pharmaceutical Sciences, 2142 J Katz Group-Rexall Centre for Pharmacy and Health Research Edmonton, University of Alberta Ringgold Standard Institution, Edmonton, Alberta, Canada
| | - Mahmoud A El-Ghiaty
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada
| | - Ayman O S El-Kadi
- Faculty of Pharmacy and Pharmaceutical Sciences, 2142 J Katz Group-Rexall Centre for Pharmacy and Health Research, University of Alberta, Edmonton, Alberta, Canada
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4
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Liao J, Xie L, Shi H, Cui S, Lan F, Luo Z, Ma X. Development of an efficient transient expression system for Siraitia grosvenorii fruit and functional characterization of two NADPH-cytochrome P450 reductases. PHYTOCHEMISTRY 2021; 189:112824. [PMID: 34102591 DOI: 10.1016/j.phytochem.2021.112824] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Revised: 05/24/2021] [Accepted: 05/24/2021] [Indexed: 06/12/2023]
Abstract
Siraitia grosvenorii (Luo hanguo or monk fruit) is a valuable medicinal herb for which the market demand has increased dramatically worldwide. As promising natural sweeteners, mogrosides have received much attention from researchers because of their extremely high sweetness and lack of calories. Nevertheless, owing to the absence of genetic transformation methods, the molecular mechanisms underlying the regulation of mogroside biosynthesis have not yet been fully elucidated. Therefore, an effective method for gene function analysis needs to be developed for S. grosvenorii fruit. As a powerful approach, transient expression has become a versatile method to elucidate the biological functions of genes and proteins in various plant species. In this study, PBI121 with a β-glucuronidase (GUS) marker and tobacco rattle virus (TRV) were used as vectors for overexpression and silencing, respectively, of the SgCPR1 and SgCPR2 genes in S. grosvenorii fruit. The effectiveness of transient expression was validated by GUS staining in S. grosvenorii fruit, and the expression levels of SgCPR1 and SgCPR2 increased significantly after infiltration for 36 h. In addition, TRV-induced gene silencing suppressed the expression of SgCPR1 and SgCPR2 in S. grosvenorii fruit. More importantly, the production of the major secondary metabolites mogrol, mogroside IIE (MIIE) and mogroside III (MIII) was activated by the overexpression of SgCPR1 and SgCPR2 in S. grosvenorii fruit, with levels 1-2 times those in the control group. Moreover, the accumulation of mogrol, MIIE and MIII was decreased in the SgCPR1 and SgCPR2 gene silencing assays. Therefore, this transient expression approach was available for S. grosvenorii fruit, providing insight into the expression of the SgCPR1 and SgCPR2 genes involved in the mogroside biosynthesis pathway. Our study also suggests that this method has potential applications in the exploration of the molecular mechanisms, biochemical hypotheses and functional characteristics of S. grosvenorii genes.
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Affiliation(s)
- Jingjing Liao
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100193, China
| | - Lei Xie
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100193, China
| | - Hongwu Shi
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100193, China
| | - Shengrong Cui
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100193, China
| | - Fusheng Lan
- Guilin GFS Monk Fruit Corp, Guilin, 541006, China
| | - Zuliang Luo
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100193, China.
| | - Xiaojun Ma
- Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, 100193, China.
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5
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Identification of human cytochrome P450 isozymes involved in the oxidative metabolism of carfentanil. Toxicol Lett 2021; 343:28-33. [PMID: 33652071 DOI: 10.1016/j.toxlet.2021.02.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 02/23/2021] [Accepted: 02/25/2021] [Indexed: 11/23/2022]
Abstract
Carfentanil is an ultra-potent opioid with an analgesic potency 10,000 times that of morphine but has received little scientific investigation. In the present study, the human cytochrome P450 (CYP) isozymes catalyzing the oxidative metabolism of carfentanil were investigated. Using UHPLC-HRMS, Michaelis-Menten kinetics of formation for three major metabolites norcarfentanil (M1), pharmaceutical active metabolite 4-[(1-oxopropyl)phenylamino]-1-(2-hydroxyl-2-phenylethyl)-4-piperidinecarboxylic acid methyl ester (M11), and 4-[(1-oxopropyl)phenylamino]-1-(2-oxo-2-phenylethyl)-4-piperidinecarboxylic acid methyl ester (M15) were determined. Isozymes catalyzing the formation of the low abundant, highly active metabolite 1-[2-(2-hydroxylphenyl)ethyl]-4-[(1-oxopropyl)phenylamino]-4-piperidinecarboxylic acid methyl ester (M13) were also identified. Selective P450 inhibition studies with pooled human liver microsomes (HLMs) and recombinant CYP isozymes suggested that metabolites M1, M11, and M15 were predominantly formed by isozyme CYP3A5, followed by CYP3A4. Isozymes CYP2C8 and CYP2C9 also made contributions but to a much lesser extent. Highly potent metabolite M13 was predominantly formed by isozyme CYP2C9, followed by CYP2C8. These findings indicate that CYP3A5, CYP3A4, CYP2C8 and CYP2C9 play a major role in the transformation of carfentanil to M1 (norcarfentanil), M11, M13 and M15 through N-dealkylation of piperidine ring, hydroxylation of phenethyl group and ketone formation on phenethyl linker by human liver micrsomes.
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6
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Donato MT, Castell JV, Gómez-Lechón MJ. The Coumarin 7-Hydroxylation Microassay in Living Hepatic Cells in Culture. Altern Lab Anim 2020. [DOI: 10.1177/026119299802600206] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Coumarin 7-hydroxylation was evaluated in hepatic cells from various species, cultured in 96-well plates. This microassay involved incubating living cultured cells with the substrate, followed by fluorimetric quantification of the product released into the culture supernatant, after hydrolysis of the conjugates of 7-hydroxycoumarin that were formed. Fluorescence was measured directly in the wells by using a microplate fluorescence reader. The major advantages of this technique are its simplicity and automation, the small number of cells required, the reduction in sample handling and assay time, and the possibility of performing repeated assays with the same cell monolayer, since no injury to cells is detectable during the assay. By using this microassay, it was shown that human hepatocytes hydroxylated coumarin at higher rates than did rabbit, dog or rat hepatocytes, and that no appreciable metabolic activity was observed in hepatoma cells (Hep G2 and FaO). In addition, methoxsalen was found to be a potent inhibitor of cytochrome P4502A6 activity in living human hepatocytes.
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Affiliation(s)
- M. Teresa Donato
- Unidad de Hepatologia Experimental, Centro de Investigation, Hospital Universitario La Fe, Avda. Campanar 21, 46009 Valencia, Spain
| | - José V. Castell
- Unidad de Hepatologia Experimental, Centro de Investigation, Hospital Universitario La Fe, Avda. Campanar 21, 46009 Valencia, Spain
| | - Maria José Gómez-Lechón
- Unidad de Hepatologia Experimental, Centro de Investigation, Hospital Universitario La Fe, Avda. Campanar 21, 46009 Valencia, Spain
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7
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Functional expression of two NADPH-cytochrome P450 reductases from Siraitia grosvenorii. Int J Biol Macromol 2018; 120:1515-1524. [DOI: 10.1016/j.ijbiomac.2018.09.128] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 09/21/2018] [Accepted: 09/21/2018] [Indexed: 12/16/2022]
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8
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Ai CZ, Liu Y, Li W, Chen DM, Zhu XX, Yan YW, Chen DC, Jiang YZ. Computational explanation for bioactivation mechanism of targeted anticancer agents mediated by cytochrome P450s: A case of Erlotinib. PLoS One 2017. [PMID: 28628631 PMCID: PMC5476264 DOI: 10.1371/journal.pone.0179333] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
EGFR inhibitors, even with therapeutics superiorities in anticancer, can cause idiosyncratic pulmonary and hepatic toxicities that are associated with the reactive electrophile bioactivated by Cytochrome P450s (P450s). Until now, neither has the electrophilic intermediate been caught experimentally, nor has the subtle mechanism been declared. Herein, the underlying mechanism of bioactivation mediated by P450s was explored by DFT calculations for a case of EGFR inhibitor, Erlotinib. Based on the calculation and analysis, we suggest that with other metabolites, reactive electrophiles of Erlotinib: epoxide and quinine-imine, can be generated by several steps along the oxidative reaction pathway. The generation of epoxide needs two steps: (1) the addition of Erlotinib to Compound I (Cpd I) and (2) the rearrangement of protons. Whereas, quinine-imine needs a further oxidation step (3) via which quinone is generated and ultimately turns into quinine-imine. Although both reactive electrophiles can be produced for either face-on or side-on pose of Erlotinib, the analysis of energy barriers indicates that the side-on path is preferred in solvent environment. In the rate-determining step, e.g. the addition of Erlotinib to the porphyrin, the reaction barrier for side-on conformation is decreased in aqueous and protein environment compared with gas phase, whereas, the barrier for face-on pose is increased in solvent environment. The simulated mechanism is in good agreement with the speculation in previous experiment. The understanding of the subtle mechanism of bioactivation of Erlotinib will provide theoretical support for toxicological mechanism of EGFR inhibitors.
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Affiliation(s)
- Chun-Zhi Ai
- Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, Guangdong, China
| | - Yong Liu
- School of Life Science and Medicine, Dalian University of Technology, Panjin, Liaoning, China
| | - Wei Li
- College of Medicine, Yangzhou University, Yangzhou, Jiangsu, China
| | - De-Meng Chen
- Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
- School of Dentistry, University of California, Los Angeles, California, United States of America
| | - Xin-Xing Zhu
- Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, Guangdong, China
| | - Ya-Wei Yan
- Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, Guangdong, China
| | - Du-Chu Chen
- Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, Guangdong, China
| | - Yi-Zhou Jiang
- Institute for Advanced Study, Shenzhen University, Shenzhen, Guangdong, China
- * E-mail:
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9
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Parkinson A. An Overview of Current Cytochrome P450 Technology for Assessing the Safety and Efficacy of New Materials. Toxicol Pathol 2016. [DOI: 10.1177/019262339602400107] [Citation(s) in RCA: 120] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Studies of xenobiotic biotransformation by in vitro techniques are destined to play an increasingly important role in assessing the safety and efficacy of drugs and other new chemical entities. The first part of this article summarizes some of the in vitro techniques that have been developed to evaluate xenobiotics as inducers of liver microsomal cytochrome P450. The second part provides an overview of reaction phenotyping, an in vitro technology for determining which human P450 enzyme or enzymes are involved in the biotransformation of xenobiotics.
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Affiliation(s)
- Andrew Parkinson
- Department of Pharmacology, Toxicology and Therapeutics, Center for Environmental and Occupational Health, University of Kansas Medical Center, Kansas City, Kansas 66160-7417, XenoTech L.L.C., 3800 Cambridge, Kansas City, Kansas 66103
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10
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Faqi AS, Holm KA. Metabolism and Drug–Drug Interaction in Pregnant Mother/Placenta/Fetus. METHODS IN PHARMACOLOGY AND TOXICOLOGY 2016. [DOI: 10.1007/7653_2016_64] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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11
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Whitelaw DA, Tonkin R, Meints CE, Wolthers KR. Kinetic analysis of electron flux in cytochrome P450 reductases reveals differences in rate-determining steps in plant and mammalian enzymes. Arch Biochem Biophys 2015; 584:107-15. [PMID: 26361974 DOI: 10.1016/j.abb.2015.09.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 09/02/2015] [Accepted: 09/03/2015] [Indexed: 11/19/2022]
Abstract
Herein, we compare the kinetic properties of CPR from Arabidopsis thaliana (ATR2), with CPR from Artemisia annua (aaCPR) and human CPR (hCPR). While all three CPR forms elicit comparable rates for cytochrome c(3+) turnover, NADPH reduction of the FAD cofactor is ∼50-fold faster in aaCPR and ATR2 compared to hCPR, with a kobs of ∼500 s(-1) (6 °C). Stopped-flow analysis of the isolated FAD-domains reveals that NADP(+)-FADH2 charge-transfer complex formation is also significantly faster in the plant enzymes, but the rate of its decay is comparable for all three proteins. In hCPR, transfer of a hydride ion from NADPH to FAD is tightly coupled to subsequent FAD to FMN electron transfer, indicating that the former catalytic event is slow relative to the latter. In contrast, interflavin electron transfer is slower than NADPH hydride transfer in aaCPR and ATR2, occurring with an observed rate constant of ∼50 s(-1). Finally, the transfer of electrons from FMN to cytochrome c(3+) is rapid (>10(3) s(-1)) in all three enzymes and does not limit catalytic turnover. In combination, the data reveal differences in rate-determining steps between plant CPR and their mammalian equivalent in mediating the flux of reducing equivalents from NADPH to external electron acceptors.
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Affiliation(s)
- Douglas A Whitelaw
- Department of Chemistry, University of British Columbia, Okanagan Campus, 3247 University Way, Kelowna BC, V1V 1V7, Canada
| | - Rochelle Tonkin
- Department of Chemistry, University of British Columbia, Okanagan Campus, 3247 University Way, Kelowna BC, V1V 1V7, Canada
| | - Carla E Meints
- Department of Chemistry, University of British Columbia, Okanagan Campus, 3247 University Way, Kelowna BC, V1V 1V7, Canada
| | - Kirsten R Wolthers
- Department of Chemistry, University of British Columbia, Okanagan Campus, 3247 University Way, Kelowna BC, V1V 1V7, Canada.
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Matsuda K, Takahashi A, Middlebrooks CD, Obara W, Nasu Y, Inoue K, Tamura K, Yamasaki I, Naya Y, Tanikawa C, Cui R, Figueroa JD, Silverman DT, Rothman N, Namiki M, Tomita Y, Nishiyama H, Kohri K, Deguchi T, Nakagawa M, Yokoyama M, Miki T, Kumon H, Fujioka T, Prokunina-Olsson L, Kubo M, Nakamura Y, Shuin T. Genome-wide association study identified SNP on 15q24 associated with bladder cancer risk in Japanese population. Hum Mol Genet 2014; 24:1177-84. [PMID: 25281661 DOI: 10.1093/hmg/ddu512] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Through genome-wide association analysis and an independent replication study using a total of 1131 bladder cancer cases and 12 558 non-cancer controls of Japanese populations, we identified a susceptibility locus on chromosome 15q24. SNP rs11543198 was associated with bladder cancer risk with odds ratio (OR) of 1.41 and P-value of 4.03 × 10(-9). Subgroup analysis revealed rs11543198 to have a stronger effect in male smokers with OR of 1.66. SNP rs8041357, which is in complete linkage disequilibrium (r(2) = 1) with rs11543198, was also associated with bladder cancer risk in Europeans (P = 0.045 for an additive and P = 0.025 for a recessive model), despite much lower minor allele frequency in Europeans (3.7%) compared with the Japanese (22.2%). Imputational analysis in this region suggested CYP1A2, which metabolizes tobacco-derived carcinogen, as a causative candidate gene. We also confirmed the association of previously reported loci, namely SLC14A1, APOBEC3A, PSCA and MYC, with bladder cancer. Our finding implies the crucial roles of genetic variations on the chemically associated development of bladder cancer.
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Affiliation(s)
- Koichi Matsuda
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Atsushi Takahashi
- Center for Integrative Medical Science, The Institute of Physical and Chemical Research (RIKEN), Kanagawa, Japan
| | - Candace D Middlebrooks
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, USA
| | - Wataru Obara
- Department of Urology, Iwate Medical University School of Medicine, Iwate, Japan
| | - Yasutomo Nasu
- Department of Urology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Keiji Inoue
- Department of Urology, School of Medicine, Kochi University, Koichi, Japan
| | - Kenji Tamura
- Department of Urology, School of Medicine, Kochi University, Koichi, Japan
| | - Ichiro Yamasaki
- Department of Urology, School of Medicine, Kochi University, Koichi, Japan
| | - Yoshio Naya
- Department of Urology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Chizu Tanikawa
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Ri Cui
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, The University of Tokyo, Tokyo, Japan
| | - Jonine D Figueroa
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, USA
| | - Debra T Silverman
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, USA
| | - Nathaniel Rothman
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, USA
| | - Mikio Namiki
- Department of Integrative Cancer Therapy and Urology, Kanazawa University Graduate School of Medical Science, Ishikawa, Japan
| | - Yoshihiko Tomita
- Department of Urology, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Hiroyuki Nishiyama
- Department of Urology, Faculty of Medicine, University of Tsukuba, Ibaragi, Japan
| | - Kenjiro Kohri
- Department of Nephro-urology, Nagoya City University Graduate School of Medical Sciences, Aichi, Japan
| | - Takashi Deguchi
- Department of Urology, Graduate School of Medicine, Gifu University, Gifu, Japan
| | - Masayuki Nakagawa
- Department of Urology, Graduate School of Medical and Dental Sciences, Kagoshima University, Kagoshima, Japan
| | - Masayoshi Yokoyama
- Department of Urology, Ehime University Graduate School of Medicine, Ehime, Japan
| | - Tsuneharu Miki
- Department of Urology, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan
| | - Hiromi Kumon
- Department of Urology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Tomoaki Fujioka
- Department of Urology, Iwate Medical University School of Medicine, Iwate, Japan
| | - Ludmila Prokunina-Olsson
- Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, USA
| | - Michiaki Kubo
- Center for Integrative Medical Science, The Institute of Physical and Chemical Research (RIKEN), Kanagawa, Japan
| | - Yusuke Nakamura
- Department of Medicine and Department of Surgery, Center for Personalized Therapeutics, The University of Chicago, Chicago, IL, USA
| | - Taro Shuin
- Department of Urology, School of Medicine, Kochi University, Koichi, Japan
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13
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Induction of cytochrome P450 3A1 expression by diallyl disulfide: Protective effects against cyclophosphamide-induced embryo-fetal developmental toxicity. Food Chem Toxicol 2014; 69:312-9. [DOI: 10.1016/j.fct.2014.04.024] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 04/02/2014] [Accepted: 04/12/2014] [Indexed: 02/01/2023]
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14
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Xu M, Ju W, Hao H, Wang G, Li P. Cytochrome P450 2J2: distribution, function, regulation, genetic polymorphisms and clinical significance. Drug Metab Rev 2014; 45:311-52. [PMID: 23865864 DOI: 10.3109/03602532.2013.806537] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Cytochrome P450 2J2 (CYP2J2) is an enzyme mainly found in human extrahepatic tissues, with predominant expression in the cardiovascular systems and lower levels in the intestine, kidney, lung, pancreas, brain, liver, etc. During the past 15 years, CYP2J2 has attracted much attention for its epoxygenase activity in arachidonic acid (AA) metabolism. It converts AA to four epoxyeicosatrienoic acids (EETs) that have various biological effects, especially in the cardiovascular systems. In recent publications, CYP2J2 is shown highly expressed in various human tumor cells, and its EET metabolites are demonstrated to implicate in the pathologic development of human cancers. CYP2J2 is also a human CYP that involved in phase I xenobiotics metabolism. Antihistamine drugs and many other compounds were identified as the substrates of CYP2J2, and studies have demonstrated that these substrates have a broad structural diversity. CYP2J2 is found not readily induced by known P450 inducers; however, its expression could be regulated in some pathological conditions, might through the activator protein-1(AP-1), the AP-1-like element and microRNA let-7b. Several genetic mutations in the CYP2J2 gene have been identified in humans, and some of them have been shown to have potential associations with some diseases. With the increasing awareness of its roles in cancer disease and drug metabolism, studies about CYP2J2 are still going on, and various inhibitors of CYP2J2 have been determined. Further studies are needed to delineate the roles of CYP2J2 in disease pathology, drug development and clinical practice.
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Affiliation(s)
- Meijuan Xu
- State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, China
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15
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Simtchouk S, Eng JL, Meints CE, Makins C, Wolthers KR. Kinetic analysis of cytochrome P450 reductase from Artemisia annua reveals accelerated rates of NADH-dependent flavin reduction. FEBS J 2013; 280:6627-42. [PMID: 24299267 DOI: 10.1111/febs.12567] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 09/06/2013] [Accepted: 10/09/2013] [Indexed: 11/26/2022]
Abstract
Cytochrome P450 reductase from Artemisia annua (aaCPR) is a diflavin enzyme that has been employed for the microbial synthesis of artemisinic acid (a semi-synthetic precursor of the anti-malarial drug, artemisinin) based on its ability to transfer electrons to the cytochrome P450 monooxygenase, CYP71AV1. We have isolated recombinant aaCPR (with the N-terminal transmembrane motif removed) from Escherichia coli and compared its kinetic and thermodynamic properties with other CPR orthologues, most notably human CPR. The FAD and FMN redox potentials and the macroscopic kinetic constants associated with cytochrome c(3+) reduction for aaCPR are comparable to that of other CPR orthologues, with the exception that the apparent binding affinity for the oxidized coenzyme is ~ 30-fold weaker compared to human CPR. CPR from A. annua shows a 3.5-fold increase in uncoupled NADPH oxidation compared to human CPR and a strong preference (85 100-fold) for NADPH over NADH. Strikingly, reduction of the enzyme by the first and second equivalent of NADPH is much faster in aaCPR, with rates of > 500 and 17 s(-1) at 6 °C. We also optically detect a charge-transfer species that rapidly forms in < 3 ms and then persists during the reductive half reaction. Additional stopped-flow kinetic studies with NADH and (R)-[4-(2) H]NADPH suggest that the accelerated rate of flavin reduction is attributed to the relatively weak binding affinity of aaCPR for NADP(+) .
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Affiliation(s)
- Svetlana Simtchouk
- Department of Chemistry, University of British Columbia, Kelowna, BC, Canada
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16
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Konstandi M, Cheng J, Gonzalez FJ. Sex steroid hormones regulate constitutive expression of Cyp2e1 in female mouse liver. Am J Physiol Endocrinol Metab 2013; 304:E1118-28. [PMID: 23548611 PMCID: PMC3651618 DOI: 10.1152/ajpendo.00585.2012] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
CYP2E1 is of paramount toxicological significance because it metabolically activates a large number of low-molecular-weight toxicants and carcinogens. In this context, factors that interfere with Cyp2e1 regulation may critically affect xenobiotic toxicity and carcinogenicity. The aim of this study was to investigate the role of female steroid hormones in the regulation of CYP2E1, as estrogens and progesterone are the bases of contraceptives and hormonal replacement therapy in menopausal women. Interestingly, a fluctuation in the hepatic expression pattern of Cyp2e1 was revealed in the different phases of the estrous cycle of female mice, with higher Cyp2e1 expression at estrus (E) and lower at methestrus (ME), highly correlated with that in plasma gonadal hormone levels. Depletion of sex steroids by ovariectomy repressed Cyp2e1 expression to levels similar to those detected in males and cyclic females at ME. Hormonal supplementation brought Cyp2e1 expression back to levels detected at E. The role of progesterone appeared to be more prominent than that of 17β-estradiol. Progesterone-induced Cyp2e1 upregulation could be attributed to inactivation of the insulin/PI3K/Akt/FOXO1 signaling pathway. Tamoxifen, an anti-estrogen, repressed Cyp2e1 expression potentially via activation of the PI3K/Akt/FOXO1 and GH/STAT5b-linked pathways. The sex steroid hormone-related changes in hepatic Cyp2e1 expression were highly correlated with those observed in Hnf-1α, β-catenin, and Srebp-1c. In conclusion, female steroid hormones are clearly involved in the regulation of CYP2E1, thus affecting the metabolism of a plethora of toxicants and carcinogenic agents, conditions that may trigger several pathologies or exacerbate the outcomes of various pathophysiological states.
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Affiliation(s)
- Maria Konstandi
- Department of Pharmacology, School of Medicine, University of Ioannina, GR-45110, Ioannina, Greece.
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17
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Li J, Wei DQ, Wang JF, Li YX. A negative cooperativity mechanism of human CYP2E1 inferred from molecular dynamics simulations and free energy calculations. J Chem Inf Model 2011; 51:3217-25. [PMID: 22077825 DOI: 10.1021/ci2004016] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Human cytochrome P450 2E1 (CYP2E1) participates in the metabolism of over 2% of all the oral drugs. A hallmark peculiar feature of this enzyme is that it exhibits a pronounced negative cooperativity in substrate binding. However the mechanism by which the negative cooperativity occurs is unclear. Here, we performed molecular dynamics simulations and free energy calculations on human CYP2E1 to examine the structural differences between the substrate-free and the enzymes with one and two aniline molecules bound. Our results indicate that although the effector substrate does not bind in the active site cavity, it still can directly interact with the active site residues of human CYP2E1. The interaction of the effector substrate with the active site leads to a reorientation of active site residues, which thereby weakens the interactions of the active substrate with this site. We also identify a conserved residue T303 that plays a crucial role in the negative cooperative binding on the short-range effects. This residue is a key factor in the positioning of substrates and in proton delivery to the active site. Additionally, a long-range effect of the effector substrate is identified in which F478 is proposed to play a key role. As located in the interface between the active and effector sites, this residue structurally links the active and effector sites and is found to play a significant role in affecting substrate access and ligand positioning within the active site. In the negative cooperative binding, this residue can decrease the interactions of the active substrate with the active site by π-π stacking which then lowers the hydroxylation activity for the active substrate. These findings are in agreement with previous experimental observations and thus provide detailed atomistic insight into the poorly understood mechanism of the negative cooperativity in human CYP2E1.
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Affiliation(s)
- Jue Li
- College of Life Science and Biotechnology and State Key Laboratory of Microbial Metabolism, Shanghai Jiao Tong University, Shanghai 200240, China
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18
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Oxidative stress and oxidative damage in chemical carcinogenesis. Toxicol Appl Pharmacol 2011; 254:86-99. [PMID: 21296097 DOI: 10.1016/j.taap.2009.11.028] [Citation(s) in RCA: 297] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2008] [Revised: 11/29/2009] [Accepted: 11/29/2009] [Indexed: 12/13/2022]
Abstract
Reactive oxygen species (ROS) are induced through a variety of endogenous and exogenous sources. Overwhelming of antioxidant and DNA repair mechanisms in the cell by ROS may result in oxidative stress and oxidative damage to the cell. This resulting oxidative stress can damage critical cellular macromolecules and/or modulate gene expression pathways. Cancer induction by chemical and physical agents involves a multi-step process. This process includes multiple molecular and cellular events to transform a normal cell to a malignant neoplastic cell. Oxidative damage resulting from ROS generation can participate in all stages of the cancer process. An association of ROS generation and human cancer induction has been shown. It appears that oxidative stress may both cause as well as modify the cancer process. Recently association between polymorphisms in oxidative DNA repair genes and antioxidant genes (single nucleotide polymorphisms) and human cancer susceptibility has been shown.
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Abstract
While the normal inflammatory cascade is self-limiting and crucial for host protection against invading pathogens and in the repair of damaged tissue, a wealth of evidence suggests that chronic inflammation is the engine driving carcinogenesis. Over a period of almost 150 years the link between inflammation and cancer development has been well established. In this chapter we discuss the fundamental concepts and mechanisms behind normal inflammation as it pertains to wound healing. We further discuss the association of inflammation and its role in carcinogenesis, highlighting the different stages of cancer development, namely tumour initiation, promotion and progression. With both the innate and adaptive arms of the immune system being central to the inflammatory process, we examine the role of a number of immune effectors in contributing to the carcinogenic process. In addition, we highlight the influences of host genetics in altering cancer risk.
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Affiliation(s)
- Stephen G Maher
- Department of Surgery, Institute of Molecular Medicine, Trinity College Dublin and St. James's Hospital, Dublin 8, Ireland.
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20
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Abstract
Abstract
Objective
Although the human small intestine serves primarily as an absorptive organ for nutrients and water, it also has the ability to metabolise drugs. Interest in the small intestine as a drug-metabolising organ has been increasing since the realisation that it is probably the most important extrahepatic site of drug biotransformation.
Key findings
Among the metabolising enzymes present in the small intestinal mucosa, the cytochromes P450 (CYPs) are of particular importance, being responsible for the majority of phase I drug metabolism reactions. Many drug interactions involving induction or inhibition of CYP enzymes, in particular CYP3A, have been proposed to occur substantially at the level of the intestine rather than exclusively within the liver, as originally thought. CYP3A and CYP2C represent the major intestinal CYPs, accounting for approximately 80% and 18%, respectively, of total immunoquantified CYPs. CYP2J2 is also consistently expressed in the human gut wall. In the case of CYP1A1, large interindividual variation in the expression levels has been reported. Data for the intestinal expression of the polymorphic CYP2D6 are conflicting. Several other CYPs, including the common hepatic isoform CYP2E1, are expressed in the human small intestine to only a very low extent, if at all. The distribution of most CYP enzymes is not uniform along the human gastrointestinal tract, being generally higher in the proximal regions of the small intestine.
Summary
This article reviews the current state of knowledge of CYP enzyme expression in human small intestine, the role of the gut wall in CYP-mediated metabolism, and how this metabolism limits the bioavailability of orally administered drugs. Possible interactions between drugs and CYP activity in the small intestine are also discussed.
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Affiliation(s)
- Kirstin Thelen
- Institute of Pharmaceutical Technology, Goethe University, Frankfurt am Main, Germany
| | - Jennifer B Dressman
- Institute of Pharmaceutical Technology, Goethe University, Frankfurt am Main, Germany
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21
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Klaunig JE, Kamendulis LM, Hocevar BA. Oxidative stress and oxidative damage in carcinogenesis. Toxicol Pathol 2009; 38:96-109. [PMID: 20019356 DOI: 10.1177/0192623309356453] [Citation(s) in RCA: 627] [Impact Index Per Article: 39.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Carcinogenesis is a multistep process involving mutation and the subsequent selective clonal expansion of the mutated cell. Chemical and physical agents including those that induce reative oxygen species can induce and/or modulate this multistep process. Several modes of action by which carcinogens induce cancer have been identified, including through production of reactive oxygen species (ROS). Oxidative damage to cellular macromolecules can arise through overproduction of ROS and faulty antioxidant and/or DNA repair mechanisms. In addition, ROS can stimulate signal transduction pathways and lead to activation of key transcription factors such as Nrf2 and NF-kappaB. The resultant altered gene expression patterns evoked by ROS contribute to the carcinogenesis process. Recent evidence demonstrates an association between a number of single nucleotide polymorphisms (SNPs) in oxidative DNA repair genes and antioxidant genes with human cancer susceptibility. These aspects of ROS biology will be discussed in the context of their relationship to carcinogenesis.
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Affiliation(s)
- James E Klaunig
- Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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22
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Fisher CD, Lickteig AJ, Augustine LM, Ranger-Moore J, Jackson JP, Ferguson SS, Cherrington NJ. Hepatic cytochrome P450 enzyme alterations in humans with progressive stages of nonalcoholic fatty liver disease. Drug Metab Dispos 2009; 37:2087-94. [PMID: 19651758 PMCID: PMC2769034 DOI: 10.1124/dmd.109.027466] [Citation(s) in RCA: 252] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2009] [Accepted: 07/27/2009] [Indexed: 12/11/2022] Open
Abstract
Members of the cytochrome P450 (P450) enzyme families CYP1, CYP2, and CYP3 are responsible for the metabolism of approximately 75% of all clinically relevant drugs. With the increased prevalence of nonalcoholic fatty liver disease (NAFLD), it is likely that patients with this disease represent an emerging population at significant risk for alterations in these important drug-metabolizing enzymes. The purpose of this study was to determine whether three progressive stages of human NALFD alter hepatic P450 expression and activity. Microsomes isolated from human liver samples diagnosed as normal, n = 20; steatosis, n = 11; nonalcoholic steatohepatitis (NASH) (fatty liver), n = 10; and NASH (no longer fatty), n = 11 were analyzed for P450 mRNA, protein, and enzyme activity. Microsomal CYP1A2, CYP2D6, and CYP2E1 mRNA levels were decreased with NAFLD progression, whereas CYP2A6, CYP2B6, and CYP2C9 mRNA expression increased. Microsomal protein expression of CYP1A2, CYP2C19, CYP2D6, CYP2E1, and CYP3A4 tended to decrease with NAFLD progression. Likewise, functional activity assays revealed decreasing trends in CYP1A2 (p = 0.001) and CYP2C19 (p = 0.05) enzymatic activity with increasing NAFLD severity. In contrast, activity of CYP2A6 (p = 0.001) and CYP2C9 (diclofenac, p = 0.0001; tolbutamide, p = 0.004) was significantly increased with NAFLD progression. Increased expression of proinflammatory cytokines tumor necrosis factor alpha and interleukin 1beta was observed and may be responsible for observed decreases in respective P450 activity. Furthermore, elevated CYP2C9 activity during NAFLD progression correlated with elevated hypoxia-induced factor 1alpha expression in the later stages of NAFLD. These results suggest that significant and novel changes occur in hepatic P450 activity during progressive stages of NAFLD.
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Affiliation(s)
- Craig D. Fisher
- Department of Pharmacology and Toxicology (C.D.F., A.J.L., L.M.A., N.J.C.) and
| | - Andrew J. Lickteig
- Department of Pharmacology and Toxicology (C.D.F., A.J.L., L.M.A., N.J.C.) and
| | - Lisa M. Augustine
- Department of Pharmacology and Toxicology (C.D.F., A.J.L., L.M.A., N.J.C.) and
| | - James Ranger-Moore
- Division of Epidemiology and Biostatistics (J.R.-M.), University of Arizona, Tucson, Arizona
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23
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Probing possible egress channels for multiple ligands in human CYP3A4: a molecular modeling study. J Mol Model 2009; 16:607-14. [PMID: 19727863 DOI: 10.1007/s00894-009-0571-5] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2009] [Accepted: 07/29/2009] [Indexed: 10/20/2022]
Abstract
Human cytochrome P450 (CYP) 3A4 extensively contributes to metabolize 50% of the marketed drugs. Recently, a CYP3A4 structure with two molecules of ketoconazole (2KT) was identified. However, channels for egresses of these inhibitors are unexplored. Thus, we applied molecular dynamics simulations followed by channel analyses. Two simulations of empty and 2KT-bound CYP3A4 results revealed the multiple ligand-induced conformational changes in channel forming regions, which appear to be important for the regulation of channels. In addition, we observed that the channel-3 entrance is closed due to the large structural deviation of the key residues from Phe-cluster. F215 and F220 are known as entrance blockers of channel-2 in metyrapone-bound CYP3A4. Currently, F220 blocks the channel-3 along with F213 and F241. Therefore, it suggested that channel-1 and 2 could potentially serve as egress routes for 2KT. It is also supported by the results from MOLAxis analyses, in which the frequency of channel occurrence and bottleneck radius during simulation favor channel-1 and 2. Several bottleneck residues of these channels may have critical roles in 2KT egresses, especially S119. Our modeling study for multiple ligand-channeling of CYP3A4 could be very helpful to gain new insights into channel selectivity of CYP3A4.
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24
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Asha S, Vidyavathi M. Cunninghamella – A microbial model for drug metabolism studies – A review. Biotechnol Adv 2009; 27:16-29. [DOI: 10.1016/j.biotechadv.2008.07.005] [Citation(s) in RCA: 136] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2008] [Revised: 07/03/2008] [Accepted: 07/31/2008] [Indexed: 01/16/2023]
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25
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Huang FF, Chai CL, Zhang Z, Liu ZH, Dai FY, Lu C, Xiang ZH. The UDP-glucosyltransferase multigene family in Bombyx mori. BMC Genomics 2008; 9:563. [PMID: 19038024 PMCID: PMC2633020 DOI: 10.1186/1471-2164-9-563] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2008] [Accepted: 11/27/2008] [Indexed: 12/18/2022] Open
Abstract
Background Glucosidation plays a major role in the inactivation and excretion of a great variety of both endogenous and exogenous compounds. A class of UDP-glycosyltransferases (UGTs) is involved in this process. Insect UGTs play important roles in several processes, including detoxication of substrates such as plant allelochemicals, cuticle formation, pigmentation, and olfaction. Identification and characterization of Bombyx mori UGT genes could provide valuable basic information for this important family and explain the detoxication mechanism and other processes in insects. Results Taking advantage of the newly assembled genome sequence, we performed a genome-wide analysis of the candidate UGT family in the silkworm, B. mori. Based on UGT signature and their similarity to UGT homologs from other organisms, we identified 42 putative silkworm UGT genes. Most of them are clustered on the silkworm chromosomes, with two major clusters on chromosomes 7 and 28, respectively. The phylogenetic analysis of these identified 42 UGT protein sequences revealed five major groups. A comparison of the silkworm UGTs with homologs from other sequenced insect genomes indicated that some UGTs are silkworm-specific genes. The expression patterns of these candidate genes were investigated with known expressed sequence tags (ESTs), microarray data, and RT-PCR method. In total, 36 genes were expressed in tissues examined and showed different patterns of expression profile, indicating that these UGT genes might have different functions. Conclusion B. mori possesses a largest insect UGT gene family characterized to date, including 42 genes. Phylogenetic analysis, genomic organization and expression profiles provide an overview for the silkworm UGTs and facilitate their functional studies in future.
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Affiliation(s)
- Fei-Fei Huang
- The Key Sericultural Laboratory of Agricultural Ministry, Institute of Sericulture and Systems Biology, Southwest University, Chongqing 400715, PR China.
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26
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Knaak JB, Dary CC, Power F, Thompson CB, Blancato JN. Physicochemical and Biological Data for the Development of Predictive Organophosphorus Pesticide QSARs and PBPK/PD Models for Human Risk Assessment. Crit Rev Toxicol 2008; 34:143-207. [PMID: 15112752 DOI: 10.1080/10408440490432250] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
A search of the scientific literature was carried out for physiochemical and biological data [i.e., IC50, LD50, Kp (cm/h) for percutaneous absorption, skin/water and tissue/blood partition coefficients, inhibition ki values, and metabolic parameters such as Vmax and Km] on 31 organophosphorus pesticides (OPs) to support the development of predictive quantitative structure-activity relationship (QSAR) and physiologically based pharmacokinetic and pharmacodynamic (PBPK/PD) models for human risk assessment. Except for work on parathion, chlorpyrifos, and isofenphos, very few modeling data were found on the 31 OPs of interest. The available percutaneous absorption, partition coefficients and metabolic parameters were insufficient in number to develop predictive QSAR models. Metabolic kinetic parameters (Vmax, Km) varied according to enzyme source and the manner in which the enzymes were characterized. The metabolic activity of microsomes should be based on the kinetic activity of purified or cDNA-expressed cytochrome P450s (CYPs) and the specific content of each active CYP in tissue microsomes. Similar requirements are needed to assess the activity of tissue A- and B-esterases metabolizing OPs. A limited amount of acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and carboxylesterase (CaE) inhibition and recovery data were found in the literature on the 31 OPs. A program is needed to require the development of physicochemical and biological data to support risk assessment methodologies involving QSAR and PBPK/PD models.
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Affiliation(s)
- James B Knaak
- Department of Pharmacology and Toxicology, School of Medicine and Biomedical Sciences, SUNY at Buffalo, Buffalo, New York 14214, USA.
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27
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Nakashima A, Kawashita H, Masuda N, Saxer C, Niina M, Nagae Y, Iwasaki K. Identification of cytochrome P450 forms involved in the 4-hydroxylation of valsartan, a potent and specific angiotensin II receptor antagonist, in human liver microsomes. Xenobiotica 2008; 35:589-602. [PMID: 16192110 DOI: 10.1080/00498250500158175] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Valsartan is known to be excreted largely as unchanged compound and is minimally metabolized in man. Although the only notable metabolite is 4-hydroxyvaleryl metabolite (4-OH valsartan), the responsible enzyme has not been clarified at present. The current in vitro studies were conducted to identify the cytochrome P450 (CYP) enzymes involved in the formation of 4-OH valsartan. Valsartan was metabolized to 4-OH valsartan by human liver microsomes and the Eadie-Hofstee plots were linear. The apparent Km and Vmax values for the formation of 4-OH valsartan were 41.9-55.8 microM and 27.2-216.9 pmol min(-1) mg(-1) protein, respectively. There was good correlation between the formation rates of 4-OH valsartan and diclofenac 4'-hydroxylase activities (representative CYP2C9 activity) of 11 individual microsomes (r = 0.889). No good correlation was observed between any of the other CYP enzyme marker activities (CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4 and CYP4A). Among the recombinant CYP enzymes examined (CYPs 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, 3A4, 3A5 and 4A11), CYP2C9 notably catalysed 4-hydroxylation of valsartan. For the specific CYP inhibitors or substrates examined (furafylline, diclofenac, S(+)-mephenytoin, quinidine and troleandomycin), only diclofenac inhibited the formation of 4-OH valsartan. These results showed that CYP2C9 is the only form responsible for 4-hydroxylation of valsartan in human liver microsomes. Although CYP2C9 is involved in valsartan metabolism, CYP-mediated drug-drug interaction between valsartan and other co-administered drugs would be negligible.
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Affiliation(s)
- A Nakashima
- Preclinical Development Department, Tsukuba Research Institue, Novartis Pharma K. K., Ibaraki, Japan
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28
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Isin EM, Guengerich FP. Substrate binding to cytochromes P450. Anal Bioanal Chem 2008; 392:1019-30. [PMID: 18622598 DOI: 10.1007/s00216-008-2244-0] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2008] [Revised: 06/10/2008] [Accepted: 06/11/2008] [Indexed: 01/08/2023]
Abstract
P450s have attracted tremendous attention owing to not only their involvement in the metabolism of drug molecules and endogenous substrates but also the unusual nature of the reaction they catalyze, namely, the oxidation of unactivated C-H bonds. The binding of substrates to P450s, which is usually viewed as the first step in the catalytic cycle, has been studied extensively via a variety of biochemical and biophysical approaches. These studies were directed towards answering different questions related to P450s, including mechanism of oxidation, substrate properties, unusual substrate oxidation kinetics, function, and active-site features. Some of the substrate binding studies extending over a period of more than 40 years of dedicated work have been summarized in this review and categorized by the techniques employed in the binding studies.
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Affiliation(s)
- Emre M Isin
- Biotransformation Section, Department of Discovery DMPK & Bioanalytical Chemistry, AstraZeneca R & D Mölndal, 431 83, Mölndal, Sweden.
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29
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Multiple NADPH–cytochrome P450 reductases from Trypanosoma cruzi. Mol Biochem Parasitol 2008; 160:42-51. [DOI: 10.1016/j.molbiopara.2008.03.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2007] [Revised: 03/12/2008] [Accepted: 03/13/2008] [Indexed: 11/22/2022]
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30
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Collom SL, Laddusaw RM, Burch AM, Kuzmic P, Perry MD, Miller GP. CYP2E1 substrate inhibition. Mechanistic interpretation through an effector site for monocyclic compounds. J Biol Chem 2007; 283:3487-3496. [PMID: 18056994 DOI: 10.1074/jbc.m707630200] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
In this study we offer a mechanistic interpretation of the previously known but unexplained substrate inhibition observed for CYP2E1. At low substrate concentrations, p-nitrophenol (pNP) was rapidly turned over (47 min(-1)) with relatively low K(m) (24 microM); nevertheless, at concentrations of >100 microM, the rate of pNP oxidation gradually decreased as a second molecule bound to CYP2E1 through an effector site (K(ss) = 260 microm), which inhibited activity at the catalytic site. 4-Methylpyrazole (4MP) was a potent inhibitor for both sites through a mixed inhibition mechanism. The K(i) for the catalytic site was 2.0 microM. Although we were unable to discriminate whether an EIS or ESI complex formed, the respective inhibition constants were far lower than K(ss). Bicyclic indazole (IND) inhibited catalysis through a single CYP2E1 site (K(i) = 0.12 microM). Similarly, 4MP and IND yielded type II binding spectra that reflected the association of either two 4MP or one IND molecule(s) to CYP2E1, respectively. Based on computational docking studies with a homology model for CYP2E1, the two sites for monocyclic molecules, pNP and 4MP, exist within a narrow channel connecting the active site to the surface of the enzyme. Because of the presence of the heme iron, one site supports catalysis, whereas the other more distal effector site binds molecules that can influence the binding orientation and egress of molecules for the catalytic site. Although IND did not bind these sites simultaneously, the presence of IND at the catalytic site blocked binding at the effector site.
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Affiliation(s)
- Samuel L Collom
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | - Ryan M Laddusaw
- Department of Chemistry, Ouachita Baptist University, Arkadelphia, Arkansas 71998
| | - Amber M Burch
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | | | - Martin D Perry
- Department of Chemistry, Ouachita Baptist University, Arkadelphia, Arkansas 71998
| | - Grover P Miller
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205.
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Kim HJ, Lee SB, Guengerich FP, Park YI, Dong MS. Effects of N-terminal modification of recombinant human cytochrome P450 1A2 on catalytic activity. Xenobiotica 2007; 37:356-65. [PMID: 17455110 DOI: 10.1080/00498250601178189] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
1. The high-level expression of mammalian cytochrome P450 in bacteria usually requires modification of the amino-terminal region of the enzyme. The effect of altering amino acids in the N-terminus of human recombinant CYP1A2 on its catalytic activity was investigated herein. 2. Rates of 7-ethoxyresorufin O-deethylation by CYP1A2a (a form made by altering the amino acids LLL of CYP1A2 to RER at positions 3-5) in reconstituted systems were significantly low compared with those of other CYP1A2 N-terminal variants at a low ratio of cytochrome P450 to NADPH-cytochrome P450 reductase, but not at higher reductase concentrations. 3. CYP1A2a-dependent ethoxyresorufin O-deethylase activity in a cumene hydroperoxide-supported system was approximately 2-fold higher than other CYP1A2 N-terminal variants. 4. Our results suggest that modification of three N-terminal amino acids in CYP1A2 alters the interaction between CYP1A2 and the reductase in reconstituted phospholipid vesicles and in the bicistronic membranes.
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Affiliation(s)
- H-J Kim
- School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea
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Hvastkovs EG, So M, Krishnan S, Bajrami B, Tarun M, Jansson I, Schenkman JB, Rusling JF. Electrochemiluminescent arrays for cytochrome P450-activated genotoxicity screening. DNA damage from benzo[a]pyrene metabolites. Anal Chem 2007; 79:1897-906. [PMID: 17261025 PMCID: PMC2323608 DOI: 10.1021/ac061975q] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Arrays suitable for genotoxicity screening are reported that generate metabolites from cytochrome P450 enzymes (CYPs) in thin-film spots. Array spots containing DNA, various human cyt P450s, and electrochemiluminescence (ECL) generating metallopolymer [Ru(bpy)2PVP10]2+ were exposed to H2O2 to activate the enzymes. ECL from all spots was visualized simultaneously using a CCD camera. Using benzo[a]pyrene as a test substrate, enzyme activity for producing DNA damage in the arrays was found in the order CYP1B1 > CYP1A2 > CYP1A1 > CYP2E1 > myoglobin, the same as the order of their metabolic activity. Thus, these arrays estimate the relative propensity of different enzymes to produce genotoxic metabolites. This is the first demonstration of ECL arrays for high-throughput in vitro genotoxicity screening.
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Collom SL, Jamakhandi AP, Tackett AJ, Radominska-Pandya A, Miller GP. CYP2E1 active site residues in substrate recognition sequence 5 identified by photoaffinity labeling and homology modeling. Arch Biochem Biophys 2007; 459:59-69. [PMID: 17222385 PMCID: PMC1994253 DOI: 10.1016/j.abb.2006.10.028] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2006] [Revised: 10/20/2006] [Accepted: 10/24/2006] [Indexed: 11/22/2022]
Abstract
Despite its biological importance, our knowledge of active site structure and relevance of critical amino acids in CYP2E1 catalytic processes remain limited. In this study, we identified CYP2E1 active site residues using photoaffinity labeling with 7-azido-4-methylcoumarin (AzMC) coupled with a CYP2E1 homology model. In the absence of light, AzMC was an effective competitor against substrate p-nitrophenol oxidation by CYP2E1. Photoactivation of AzMC led to a concentration-dependent loss in CYP2E1 activity and structural integrity resulting from the modification of both heme and protein. The photo-labeling reaction degraded heme and produced a possible heme adduct. Probe incorporation into the protein occurred at multiple sites within substrate recognition sequence 5 (SRS-5). Based on a CYP2E1 homology model, we hypothesize AzMC labels SRS-5 residues, Leu363, Val364, and Leu368, in the active site. In addition, we propose a series of phenylalanines, especially Phe106, mediate contacts with the coumarin.
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Affiliation(s)
- Samuel L. Collom
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Arvind P. Jamakhandi
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Alan J. Tackett
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Anna Radominska-Pandya
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
| | - Grover P. Miller
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA
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Wang Y, Wang S, Liu Y, Yan L, Dou G, Gao Y. Characterization of metabolites and cytochrome P450 isoforms involved in the microsomal metabolism of aconitine. J Chromatogr B Analyt Technol Biomed Life Sci 2006; 844:292-300. [PMID: 16949890 DOI: 10.1016/j.jchromb.2006.07.059] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2005] [Revised: 06/21/2006] [Accepted: 07/15/2006] [Indexed: 12/01/2022]
Abstract
Aconitine, a major Aconitum alkaloid, is well known for its high toxicity that induces severe arrhythmias leading to death. The current study investigated the metabolism of aconitine and the effects of selective cytochrome P450 (CYP) inhibitors on the metabolism of aconitine in rat liver microsomes. The metabolites were separated and assayed by liquid chromatography-ion trap mass spectrometry (LC/MS(n)) and further identified by comparison of their mass spectra and chromatographic behaviors with reference substances. Various selective inhibitors of CYP were used to identify the isoforms of CYP, that involved in the metabolism of aconitine. A total of at least six metabolites were found and characterized in rat liver microsomal incubations. Result showed that the inhibitor of CYP 3A had an inhibitory effect on aconitine metabolism in a concentration-dependant manner, the inhibitor of CYP1A1/2 had a modest inhibitory effect, whereas inhibitors of CYP2B1/2, 2D and 2E1 had no obvious inhibitory effects on aconitine metabolism. Aconitine might be metabolized by CYP 3A and CYP1A1/2 isoforms in rat liver microsome.
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Affiliation(s)
- Yuguang Wang
- Department of Pharmacology and Toxicology, Beijing Institute of Radiation Medicine, Beijing 100850, PR China
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Choudhuri S, Klaassen CD. Structure, function, expression, genomic organization, and single nucleotide polymorphisms of human ABCB1 (MDR1), ABCC (MRP), and ABCG2 (BCRP) efflux transporters. Int J Toxicol 2006; 25:231-59. [PMID: 16815813 DOI: 10.1080/10915810600746023] [Citation(s) in RCA: 263] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The ATP-binding cassette (ABC) transporters constitute a large family of membrane proteins, which transport a variety of compounds through the membrane against a concentration gradient at the cost of ATP hydrolysis. Substrates of the ABC transporters include lipids, bile acids, xenobiotics, and peptides for antigen presentation. As they transport exogenous and endogenous compounds, they reduce the body load of potentially harmful substances. One by-product of such protective function is that they also eliminate various useful drugs from the body, causing drug resistance. This review is a brief summary of the structure, function, and expression of the important drug resistance-conferring members belonging to three subfamilies of the human ABC family; these are ABCB1 (MDR1/P-glycoprotein of subfamily ABCB), subfamily ABCC (MRPs), and ABCG2 (BCRP of subfamily ABCG), which are expressed in various organs. In the text, the transporter symbol that carries the subfamily name (such as ABCB1, ABCC1, etc.) is used interchangeably with the corresponding original names, such as MDR1P-glycoprotein, MRP1, etc., respectively. Both nomenclatures are maintained in the text because both are still used in the transporter literature. This helps readers relate various names that they encounter in the literature. It now appears that P-glycoprotein, MRP1, MRP2, and BCRP can explain the phenomenon of multidrug resistance in all cell lines analyzed thus far. Also discussed are the gene structure, regulation of expression, and various polymorphisms in these genes. Because genetic polymorphism is thought to underlie interindividual differences, including their response to drugs and other xenobiotics, the importance of polymorphism in these genes is also discussed.
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Affiliation(s)
- Supratim Choudhuri
- Division of Biotechnology and GRAS Notice Review, Office of Food Additive Safety, Center for Food Safety and Nutrition, U.S. Food and Drug Administration, College Park, Maryland, USA.
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Elbarbry F, Wilby K, Alcorn J. Validation of a HPLC method for the determination of p-nitrophenol hydroxylase activity in rat hepatic microsomes. J Chromatogr B Analyt Technol Biomed Life Sci 2006; 834:199-203. [PMID: 16497568 DOI: 10.1016/j.jchromb.2006.02.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2005] [Revised: 12/23/2005] [Accepted: 02/07/2006] [Indexed: 10/25/2022]
Abstract
We report a HPLC-UV method for determination of p-nitrophenol (PNP) hydroxylation to 4-nitrocatechol (4NC) as a marker for CYP2E1 activity in rat hepatic microsomes. Proteins were precipitated by addition of 50 microL phosphoric acid (50%, v/v in water) to 500 microL microsomal suspensions. Following vortex mixing and centrifugation the supernatant (20 microL) was injected onto a Supelcosil C(18) column (150 mm x 4.6 mm, 5 microm), and mobile phase (22% acetonitrile, 0.1% trifluoroacetic acetic acid, 0.5% triethylamine) delivered at 1.0 mL/min produced resolved peaks for internal standard, 4NC, and PNP in < 11 min. Calibration curves were linear (r(2) = 0.999) from 0.1 to 40 microM with intra- and inter-day precision < 12% and accuracy >90%. The method's improved sensitivity (LOQ = 0.1 microM) and minimal sample processing allowed rapid monitoring of PNP hydroxylase activity in fetal, neonatal, juvenile, and adult rat livers.
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Affiliation(s)
- Fawzy Elbarbry
- College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Sask., Canada S7N5C9
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Cotreau MM, von Moltke LL, Greenblatt DJ. The influence of age and sex on the clearance of cytochrome P450 3A substrates. Clin Pharmacokinet 2005; 44:33-60. [PMID: 15634031 DOI: 10.2165/00003088-200544010-00002] [Citation(s) in RCA: 202] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cytochrome P450s (CYPs) are an important family of enzymes in the metabolism of many therapeutic agents and endogenous metabolic reactions. The CYP3A subfamily is especially prominent in these metabolic activities. This review article focuses on how the factors of age and sex may influence the in vivo activity of human CYP3A. The functional activity of CYP3A varies based on issues such as interaction with one or more substrates and between individuals and/or localisation. For CYP3A substrates, intrinsic clearance is the component of total clearance that is contributed by the enzymes. Depending on the route of administration and the contribution of hepatic blood flow to overall clearance, sensitivities to changes in CYP3A activities may differ. Additionally, age may influence the hepatic blood flow and, in turn, affect CYP3A activity. A review of the literature regarding age influences on the clearance of CYP3A substrates does suggest that age can affect the clearance of certain CYP3A substrates.CYP3A is responsible for a large number of endogenous metabolic reactions involving steroid hormones, and enzyme activity has been reported to be induced and/or inhibited in the presence of some sex steroids. Based on published studies for most CYP3A substrates, sex does not appear to influence clearance; however, with certain substrates significant sex-related differences are found. In such cases, women primarily have higher clearance than men.
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Affiliation(s)
- Monette M Cotreau
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
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Vandebriel RJ. Gene polymorphisms within the immune system that may underlie drug allergy. Naunyn Schmiedebergs Arch Pharmacol 2003; 369:125-32. [PMID: 14530905 DOI: 10.1007/s00210-003-0804-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2003] [Accepted: 08/19/2003] [Indexed: 01/13/2023]
Abstract
Drug allergy encompasses a broad spectrum of different diseases. It occurs in some individuals, whereas it does not occur in many others. This suggests, among others, the involvement of hereditary factors, and thus of gene polymorphisms. Since drug metabolising enzymes as well as the immune system itself may be responsible for drug allergy, gene polymorphisms are relevant in both systems. While already some information exists on gene polymorphisms of drug metabolising enzymes that result in drug allergy, little information is available on gene polymorphisms within the immune system that result in such allergy. This review sets out to provide an avenue for future research aimed at discovering such polymorphisms. To this end, immune mechanisms that underlie drug allergy will be discussed. A pivotal mechanism underlying several types of drug allergy, immediate-type (type I) hypersensitivity, is also a hallmark of asthma, and therefore drug allergy and asthma share a range of candidate genes. Research on asthma has come relatively far in establishing associations of disease with polymorphisms in these genes. Therefore, these polymorphisms and their associations with asthma will be discussed. These studies on asthma provide us with lessons on how to conduct such studies on drug allergy.
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Affiliation(s)
- Rob J Vandebriel
- Laboratory for Toxicology, Pathology and Genetics, National Institute of Public Health and the Environment, P.O. Box 1, 3720, BA Bilthoven, The Netherlands.
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Lee SJ, Buhler DR. Cloning, tissue distribution, and functional studies of a new cytochrome P450 3A subfamily member, CYP3A45, from rainbow trout (Oncorhynchus mykiss) intestinal ceca. Arch Biochem Biophys 2003; 412:77-89. [PMID: 12646270 DOI: 10.1016/s0003-9861(03)00029-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
In trout and mammals, the major extrahepatic expression site for CYP3A forms is in the intestine. A cDNA encoding a new CYP3A subfamily member was isolated from rainbow trout intestinal ceca by reverse transcriptase-polymerase chain reaction (RT-PCR), followed by rapid amplification of cDNA ends (RACE)-PCR. In a set of two primers for PCR, a consensus sequence in the highly conserved regions in 17 CYP3A sequences was used for one primer, and the second primer was designed based on adapter sequence ligated on the 5(') and 3(') cDNA ends. The 3(') and 5(') end nucleotide sequences of RACE-PCR products were used for the priming sites for the full-length cDNA in RT-PCR. The resulting 2615-bp cDNA contained an open reading frame of 1554 bp encoding a 518-amino acid residue protein (M(r)=59057.13, pI=6.15) with 26 amino acid differences from that of the previously cloned rainbow trout CYP3A27. The cDNA was assigned as CYP3A45 by the P450 Nomenclature Committee. The deduced amino acid sequence of rainbow trout CYP3A45 was 94% identical with trout CYP3A27, 72% with killifish CYP3A56, and 71% with both medaka CYP3A40 and killifish CYP3A30 in positional alignment comparisons. Northern blotting by a CYP3A45-specific nucleotide probe showed that the major expression site was the intestinal ceca rather than the liver in both male and female trout. Recombinant baculovirus containing a CYP3A45 cDNA (Bv-3A45) was constructed under polyhedrin promoter of the Autographa californica nuclear polyhedrosis virus and used to express CYP3A45 protein in Spodoptera frugiperda cells. The Western blot showed that the expressed CYP3A45 protein comigrated with purified LMC5 P450 and was recognized by anti-LMC5 polyclonal antibodies. The expressed CYP3A45 showed catalytic activities for the 6 beta-, 2 beta-, and 16 beta-hydroxytestosterones of 1.76, 0.193, and 0.078 nmol/min/nmol CYP3A45, respectively. In summary, a second form of CYP3A with steroid hydroxylase activity, CYP3A45, has been cloned from rainbow trout and the major site of expression was in the intestinal tissues.
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Affiliation(s)
- Su Jun Lee
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, OR 97331-7301, USA
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Ma X, Wang H, Xin J, Zhang T, Tu Z. Identification of cytochrome P450 1A2 as enzyme involved in the microsomal metabolism of Huperzine A. Eur J Pharmacol 2003; 461:89-92. [PMID: 12586202 DOI: 10.1016/s0014-2999(03)01290-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Huperzine A is a reversible and selective cholinesterase inhibitor approved for the treatment of Alzheimer's disease. To identify which cytochrome P450 (CYP) isoenzymes are involved in the metabolism of Huperzine A, an in vitro study was performed with rat liver microsomes and immunoinhibition and chemical inhibition methods. Huperzine A metabolism was analyzed with high-performance liquid chromatography (HPLC) and expressed as Huperzine A disappearance rate. Result showed that 76.2% of Huperzine A metabolism was inhibited by CYP1A2 antibody and 17.8% by CYP3A1/2 antibody. Inhibitory effects produced by CYP2C11 and 2E1 antibodies were minor. The CYP1A2 substrate phenacetin showed an inhibitory effect of 70.3%. In conclusion, Huperzine A metabolism in rat liver microsomes is mediated primarily by CYP1A2, with a probable secondary contribution of CYP3A1/2. CYP2C11 and 2E1 are likely not involved in Huperzine A metabolism.
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Affiliation(s)
- Xiaochao Ma
- State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institute for Biological Science, Chinese Academy of Sciences, Shanghai 200031, China
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Abstract
Metabolism alone does not adequately account for the observed intersubject variability in drug disposition or response. Carrier-mediated processes, or transporters, are increasingly recognized to be importantly involved in drug absorption, distribution, and excretion. Thus for many drugs, transport and metabolism must be considered together to better predict drug disposition in vivo. Accordingly, this review will outline relevant background information regarding drug transporters and the role of such transporters in the drug disposition process.
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Affiliation(s)
- Richard B Kim
- Division of Clinical Pharmacology, Department of Medicine, Vanderbilt University School of Medicine, 572 RRB1, 23rd Avenue at Pierce Avenue, Nashville, TN 37323-6602, USA.
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Lieu C, Shi J, Donat F, Van Horn R, Brian W, Newton J, Delbressine L, Vos R. Fondaparinux sodium is not metabolised in mammalian liver fractions and does not inhibit cytochrome P450-mediated metabolism of concomitant drugs. Clin Pharmacokinet 2002; 41 Suppl 2:19-26. [PMID: 12383041 DOI: 10.2165/00003088-200241002-00003] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
OBJECTIVE To investigate the in vitro metabolism of the antithrombotic agent fondaparinux sodium in mammalian liver fractions and to evaluate its potential inhibitory effect on human cytochrome P450 (CYP)-mediated metabolism of other drugs. METHODS Metabolism was evaluated by incubating radioisotope-labelled fondaparinux sodium with postmitochondrial liver fractions of rat, rabbit, monkey or human origin (three subjects). Human liver microsomal preparations and an NADPH-generating system were incubated with phenacetin, coumarin, tolbutamide, S-mephenytoin, bufuralol, chlorzoxazone or nifedipine. These are selectively metabolised by CYP isoforms: CYP1A2, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1 or CYP3A4, respectively. Experiments were designed to determine apparent K(i) (inhibitory constant) values for fondaparinux sodium against each CYP isoform, by varying concentrations of fondaparinux sodium and the selective substrate. Each experiment included control reaction mixtures containing an isoform-selective inhibitor. After incubation, the mixtures were analysed by LC-MS/MS or with fluorometric detection. RESULTS All liver fractions were enzymatically active, as demonstrated by degradation of [(14)C]testosterone. No metabolism of fondaparinux sodium was detectable in postmitochondrial liver fractions. Apparent K(i) values for fondaparinux sodium against the CYP isoforms could not be determined because the oxidative metabolism of the isoform-selective CYP substrates was not significantly inhibited in pooled microsomal reaction mixtures. In the presence of selective CYP inhibitors, metabolism of each substrate was significantly reduced, confirming that inhibition could be observed in these assays. CONCLUSION The demonstrated lack of mammalian hepatic metabolism of fondaparinux sodium is consistent with animal and human studies. The absence of inhibition of the human CYP isoforms commonly involved in the metabolism of drugs suggests that clinical treatment with fondaparinux sodium is unlikely to interfere with the pharmacokinetics and metabolism of a wide range of other drugs which are associated with CYP inhibition.
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Affiliation(s)
- Carolyne Lieu
- Sanofi-Synthelabo Research Division, Great Valley, Pennsylvania, USA
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Abstract
Dramatic developmental changes in the physiological and biochemical processes that govern drug pharmacokinetics and pharmacodynamics occur during the first year of life. These changes may have significant consequences for the way infants respond to and deal with drugs. The ontogenesis of systemic clearance mechanisms is probably the most critical determinant of a pharmacological response in the developing infant. In recent years, advances in molecular techniques and an increased availability of fetal and infant tissues have afforded enhanced insight into the ontogeny of clearance mechanisms. Information from these studies is reviewed to highlight the dynamic and complex nature of developmental changes in clearance mechanisms in infants during the first year of life. Hepatic and renal elimination mechanisms constitute the two principal clearance pathways of the developing infant. Drug metabolising enzyme activity is primarily responsible for the hepatic clearance of many drugs. In general, when compared with adult activity levels normalised to amount of hepatic microsomal protein, hepatic cytochrome P450-mediated metabolism and the phase II reactions of glucuronidation, glutathione conjugation and acetylation are deficient in the neonate, but sulfate conjugation is an efficient pathway at birth. Parturition triggers the dramatic development of drug metabolising enzymes, and each enzyme demonstrates an independent rate and pattern of maturation. Marked interindividual variability is associated with their developmental expression, making the ontogenesis of hepatic metabolism a highly variable process. By the first year of life, most enzymes have matured to adult activity levels. When compared with adult values, renal clearance mechanisms are compromised at birth. Dramatic increases in renal function occur in the ensuing postpartum period, and by 6 months of age glomerular filtration rate normalised to bodyweight has approached adult values. Maturation of renal tubular functions exhibits a more protracted time course of development, resulting in a glomerulotubular imbalance. This imbalance exists until adult renal tubule function values are approached by 1 year of age. The ontogeny of hepatic biliary and renal tubular transport processes and their impact on the elimination of drugs remain largely unknown. The summary of the current understanding of the ontogeny of individual pathways of hepatic and renal elimination presented in this review should serve as a basis for the continued accruement of age-specific information concerning the ontogeny of clearance mechanisms in infants. Such information can only help to improve the pharmacotherapeutic management of paediatric patients.
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Affiliation(s)
- Jane Alcorn
- Division of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536-0082, USA
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Takahashi E, Fujita KI, Kamataki T, Arimoto-Kobayashi S, Okamoto K, Negishi T. Inhibition of human cytochrome P450 1B1, 1A1 and 1A2 by antigenotoxic compounds, purpurin and alizarin. Mutat Res 2002; 508:147-56. [PMID: 12379470 DOI: 10.1016/s0027-5107(02)00212-9] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Recently we have shown that anthraquinone food pigments such as purpurin and alizarin suppress the genotoxic activities of several mutagens including heterocyclic amines and polycyclic aromatic hydrocarbons in the Drosophila DNA repair test and in the Ames test. To investigate the mechanism of this inhibition, we have now examined the effects of these anthraquinone pigments on enzymes that metabolize xenobiotics. The activities of eight human recombinant cytochrome P450 (CYP) isozymes were measured in the presence of purpurin, alizarin or carminic acid. Purpurin and alizarin strongly inhibited the activities of CYP1A1, CYP1A2 and CYP1B1, and weakly suppressed those of CYP2A6 and CYP2E1 in a dose-dependent manner, but did not inhibit those of CYP2C19, CYP3A4 and CYP3A5. Carminic acid did not affect the activities of any CYPs tested. CYP1B1 was the most strongly affected CYP molecule by purpurin and alizarin among CYPs examined in this study. From kinetic analysis, it was shown that the inhibition by purpurin on CYP1B1 was both competitive and non-competitive, and that by alizarin was competitive. The values of slopes obtained from Lineweaver-Burk plots are proportional to the square of purpurin concentration. This observation suggests that two molecules of purpurin are interacting with one molecule of CYP1B1. The K(m) value of CYP1B1 was 11 microM, and the K(i) value of purpurin and alizarin against CYP1B1 was 0.7 microM(2) and 0.5 microM, respectively. We also examined the effects of these pigments on the mutagenicities of MeIQx and B[a]P in the Ames test, using Salmonella typhimurium TA1538 co-expressing each form of human CYP and NADPH-cytochrome P450 reductase (OR). The mutagenicity of MeIQx in TA1538 1A2/OR or 1B1/OR was suppressed by purpurin and alizarin but not by carminic acid. Purpurin also reduced the mutagenicity of B[a]P in TA1538 1A1/OR or 1B1/OR. These results suggest that the antigenotoxic activities of purpurin and alizarin can be explained by inhibition of CYP activities responsible for activating the mutagens.
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Affiliation(s)
- Eizo Takahashi
- Faculty of Pharmaceutical Sciences, Okayama University, Tsushima, Okayama 700-8530, Japan
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Ueng YF, Don MJ, Peng HC, Wang SY, Wang JJ, Chen CF. Effects of Wu-chu-yu-tang and its component herbs on drug-metabolizing enzymes. JAPANESE JOURNAL OF PHARMACOLOGY 2002; 89:267-73. [PMID: 12184732 DOI: 10.1254/jjp.89.267] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The compound herbal medicine Wu-chu-yu-tang is used for the treatment of migraine and vomiting accompanying a cold. To assess the interactions of herb and drug metabolism, effects of Wu-chu-yu-tang on hepatic and renal cytochrome P450 (CYP), UDP-glucuronosyl transferase (UGT) and glutathione S-transferase (GST) were studied in C57BL/6J mice. Treatment of mice with 5 g/kg per day Wu-chu-yu-tang for 3 days caused 2.5-fold and 2.9-fold increases of liver microsomal 7-ethoxyresorufin O-deethylation (EROD) and 7-methoxyresorufin O-demethylation activities, respectively. However, CYP activities toward 7-ethoxycoumarin, benzphetamine, N-nitrosodimethylamine, erythromycin and nifedipine, and conjugation activities of UGT and GST were not affected. In kidney, Wu-chu-yu-tang-treatment had no effects on Cyp, UGT and GST activities. Among the four component herbs of Wu-chu-yu-tang, only Evodiae Fructus (Wu-chu-yu) extract increased EROD activity and CYP1a2 protein level. In E. Fructus, rutaecarpine, evodiamine and dehydroevodiamine are the main active alkaloids. At the doses corresponding to their contents in Wu-chu-yu-tang, rutaecarpine-treatment increased hepatic EROD activity, whereas evodiamine and dehydroevodiamine had no effects. These results demonstrated that ingestion of Wu-chu-yu-tang elevated mouse hepatic Cyp1a2 activity and protein level. E. Fructus and rutaecarpine contributed at least in part to the CYP1a2 induction by Wu-chu-yu-tang. Patients should be cautioned about the drug interaction of Wu-chu-yu-tang and CYP1A2 substrates.
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Affiliation(s)
- Yune-Fang Ueng
- National Research Institute of Chinese Medicine, Taipei, Taiwan.
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Kobayashi K, Urashima K, Shimada N, Chiba K. Substrate specificity for rat cytochrome P450 (CYP) isoforms: screening with cDNA-expressed systems of the rat. Biochem Pharmacol 2002; 63:889-96. [PMID: 11911841 DOI: 10.1016/s0006-2952(01)00843-7] [Citation(s) in RCA: 151] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
In this study, we performed a screening of the specificities of rat cytochrome P450 (CYP) isoforms for metabolic reactions known as the specific probes of human CYP isoforms, using 13 rat CYP isoforms expressed in baculovirus-infected insect cells or B-lymphoblastoid cells. Among the metabolic reactions studied, diclofenac 4-hydroxylation (DFH), dextromethorphan O-demethylation (DMOD) and midazolam 4-hydroxylation were specifically catalyzed by CYP2C6, CYP2D2 and CYP3A1/3A2, respectively. These results suggest that diclofenac 4-hydroxylation, dextromethorphan O-demethylation and midazolam 4-hydroxylation are useful as catalytic markers of CYP2C6, CYP2D2 and CYP3A1/3A2, respectively. On the other hand, phenacetin O-deethylation and 7-ethoxyresorufin O-deethylation were catalyzed both by CYP1A2 and by CYP2C6. Benzyloxyresorufin O-dealkylation and pentoxyresorufin O-dealkylation were also catalyzed by CYP1A2 in addition to CYP2B1. Bufuralol 1'-hydroxylation was extensively catalyzed by CYP2D2 but also by CYP2C6 and CYP2C11. p-Nitrophenol 2-hydroxylation and chlorzoxazone 6-hydroxylation were extensively catalyzed by CYP2E1 but also by CYP1A2 and CYP3A1. Therefore, it is necessary to conduct further study to clarify whether these activities in rat liver microsomes are useful as probes of rat CYP isoforms. In contrast, coumarin 7-hydroxylation and S- and R-mephenytoin 4'-hydroxylation did not show selectivity toward any isoforms of rat CYP studied. Therefore, activities of coumarin 7-hydroxylation and S- and R-mephenytoin 4'-hydroxylation are not able to be used as catalytic probes of CYP isoforms in rat liver microsomes. These results may provide useful information regarding catalytic probes of rat CYPs for studies using rat liver microsomal samples.
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Affiliation(s)
- Kaoru Kobayashi
- Laboratory of Biochemical Pharmacology and Toxicology, Faculty of Pharmaceutical Sciences, Chiba University, Chiba, Japan.
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Chen C, Thakker DR. The fallacy of using adrenochrome reaction for measurement of reactive oxygen species formed during cytochrome p450-mediated metabolism of xenobiotics. J Pharmacol Exp Ther 2002; 300:417-20. [PMID: 11805199 DOI: 10.1124/jpet.300.2.417] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The adrenochrome reaction (oxidation of epinephrine to adrenochrome) has been widely employed as a standard assay for reactive oxygen species, produced under a variety of conditions, including those produced during cytochrome P450 (CYP)-mediated oxidation of substrates such as cyclosporine. However, it has been reported that epinephrine and adrenochrome can be metabolized by hepatic microsomes and that adrenochrome can also be metabolized by NADPH-CYP reductase. Thus, in the present report, we provide evidence that measurement of adrenochrome cannot be used as an index of reactive oxygen species generated during CYP-mediated metabolism of xenobiotics because adrenochrome and its precursor, epinephrine, interact with the CYP enzyme system as substrates and inhibitors. Our results indicated that adrenochrome was moderately stable in phosphate buffer but degraded rapidly (over 50% consumed in less than 2 min) by (cloned and expressed) CYP3A4 and CYP reductase in the presence of NADPH. Furthermore, both epinephrine and adrenochrome were found to be inhibitors of CYP3A4-mediated oxidation of testosterone. Together, these results lead to the conclusion that the use of adrenochrome reaction for measurement of reactive oxygen species formed during CYP3A4-mediated metabolism of xenobiotics is inappropriate.
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Affiliation(s)
- Cuiping Chen
- Division of Drug Delivery and Disposition, School of Pharmacy, The University of North Carolina at Chapel Hill, 27599-7360, USA
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Abstract
This chapter is an update of the data on substrates, reactions, inducers, and inhibitors of human CYP enzymes published previously by Rendic and DiCarlo (1), now covering selection of the literature through 2001 in the reference section. The data are presented in a tabular form (Table 1) to provide a framework for predicting and interpreting the new P450 metabolic data. The data are formatted in an Excel format as most suitable for off-line searching and management of the Web-database. The data are presented as stated by the author(s) and in the case when several references are cited the data are presented according to the latest published information. The searchable database is available either as an Excel file (for information contact the author), or as a Web-searchable database (Human P450 Metabolism Database, www.gentest.com) enabling the readers easy and quick approach to the latest updates on human CYP metabolic reactions.
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Affiliation(s)
- Slobodan Rendic
- Faculty of Pharmacy and Biochemistry, University of Zagreb, Croatia.
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Lee SJ, Hedstrom OR, Fischer K, Wang-Buhler JL, Sen A, Cok I, Buhler DR. Immunohistochemical localization and differential expression of cytochrome P450 3A27 in the gastrointestinal tract of rainbow trout. Toxicol Appl Pharmacol 2001; 177:94-102. [PMID: 11740908 DOI: 10.1006/taap.2001.9289] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
In mammals the cytochrome P450 3A (CYP3A) subfamily isoforms are primarily expressed in liver and intestines with lesser amounts found in other tissues. The aim of this study was to examine the cellular localization and the expression pattern of CYP3A27 in the gastrointestinal tract (GI tract) of a freshwater teleost species, the rainbow trout (Oncorhynchus mykiss), a fish model used extensively for toxicological and carcinogenesis research. Using an avidin biotinylated enzyme complex and 3,3'-diaminobenzidine staining, strong cytoplasmic immunohistochemical staining was observed for CYP3A27 protein in hepatocytes and in enterocytes of the intestinal ceca and the proximal descending intestine when probed with a polyclonal antibody raised against rainbow trout P450 LMC5, a CYP3A protein. The intensity of epithelial staining decreased distally along the GI tract with faint staining observed in the epithelial cells examined near the vent. Western blot analysis was supportive of the immunohistochemistry results. Northern blot analysis also demonstrated that CYP3A27 mRNA was expressed along the entire GI tract. The major area of CYP3A27 mRNA expression was in the intestinal ceca, followed by the proximal descending intestine, at levels that were about three- to five-fold and two- to four-fold, respectively, greater than seen in the liver of the fish studied. Monooxygenase activities of intestinal ceca microsomes against testosterone and progesterone confirmed the presence of active CYP3A enzyme in this tissue. These results suggest that the intestine of rainbow trout may possesses substantial capacity for first-pass metabolism of xenobiotics by CYP3A27, which makes it an excellent model in which to study the consequence of such metabolism.
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Affiliation(s)
- S J Lee
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis, Oregon 97331, USA
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Abstract
The systematic development and application of biomarkers in environmental health risk assessment is a relatively new field. At first, the major interest was in biomarkers of exposure, borrowing concepts from pharmacology, then it moved from the external estimates of exposure to internal measures of dose, and ultimately, to markers of target dose. While these markers provide evidence of exposures, they do not provide evidence of that toxicological damage has occurred. For this reason, measurements of DNA adducts and protein adducts are of interest, since they may provide bridges between exposures and disease end-points. In parallel, more quantitative and more sensitive end-points for diseases have been sought. Again, with advancing techniques in cytogenetics, extensive studies were conducted on such markers as chromosomal aberrations, micronuclei and other changes deemed to represent genomic damage. However, these types of end-points are quite unspecific for application to new hazards of uncertain human toxic (carcinogenic) potential. Recent work focusing on more specific early-effect markers such as certain oncogenes and tumour-suppressor genes have substantial promise as shown by work with aflatoxins and vinyl chloride. Such studies have also enhanced mechanistic insight. The advances in molecular genetics have led to an upsurge in interest in most susceptibility factors, and identification of polymorphisms of various enzymes has become possible. Ongoing search for "ultra-high risk" individuals may be fruitful, but probably only relevant to a small segment of potentially exposed populations. Factors associated with a small differential risk, however theoretically or mechanistically important, offer only little practical use.
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Affiliation(s)
- H Vainio
- WHO, International Agency for Research on Cancer, Unit of Chemoprevention, 150 Cours Albert Thomas, F-69372 Lyon, France.
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