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Human Family 1-4 cytochrome P450 enzymes involved in the metabolic activation of xenobiotic and physiological chemicals: an update. Arch Toxicol 2021; 95:395-472. [PMID: 33459808 DOI: 10.1007/s00204-020-02971-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 12/29/2020] [Indexed: 12/17/2022]
Abstract
This is an overview of the metabolic activation of drugs, natural products, physiological compounds, and general chemicals by the catalytic activity of cytochrome P450 enzymes belonging to Families 1-4. The data were collected from > 5152 references. The total number of data entries of reactions catalyzed by P450s Families 1-4 was 7696 of which 1121 (~ 15%) were defined as bioactivation reactions of different degrees. The data were divided into groups of General Chemicals, Drugs, Natural Products, and Physiological Compounds, presented in tabular form. The metabolism and bioactivation of selected examples of each group are discussed. In most of the cases, the metabolites are directly toxic chemicals reacting with cell macromolecules, but in some cases the metabolites formed are not direct toxicants but participate as substrates in succeeding metabolic reactions (e.g., conjugation reactions), the products of which are final toxicants. We identified a high level of activation for three groups of compounds (General Chemicals, Drugs, and Natural Products) yielding activated metabolites and the generally low participation of Physiological Compounds in bioactivation reactions. In the group of General Chemicals, P450 enzymes 1A1, 1A2, and 1B1 dominate in the formation of activated metabolites. Drugs are mostly activated by the enzyme P450 3A4, and Natural Products by P450s 1A2, 2E1, and 3A4. Physiological Compounds showed no clearly dominant enzyme, but the highest numbers of activations are attributed to P450 1A, 1B1, and 3A enzymes. The results thus show, perhaps not surprisingly, that Physiological Compounds are infrequent substrates in bioactivation reactions catalyzed by P450 enzyme Families 1-4, with the exception of estrogens and arachidonic acid. The results thus provide information on the enzymes that activate specific groups of chemicals to toxic metabolites.
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Sindi IA, Babalghith AO, Tayeb MT, Mufti AH, Naffadi H, Ekram SN, Elhawary EN, Alenezi M, Elhawary NA. Risk of Colorectal Carcinoma May Predispose to the Genetic Variants of the GST, CYP450, and TP53 Genes Among Nonsmokers in the Saudi Community. Int J Gen Med 2021; 14:1311-1323. [PMID: 33883929 PMCID: PMC8055278 DOI: 10.2147/ijgm.s294802] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 03/25/2021] [Indexed: 02/05/2023] Open
Abstract
PURPOSE Colorectal carcinoma (CRC) represents a considerable public health burden in Saudi Arabia. Several candidate genes and genetic variants have been associated with morbidity and mortality among patients with CRC. We explored whether allelic variants of the GSTM1, GSTT1, CYP450 (rs4646903 and rs1048943), and TP53 (rs1042522) genes predisposed nonsmoking Saudi individuals to increased risk for CRC. PATIENTS AND METHODS DNA from buccal cells of 158 participants (80 with CRC and 78 healthy controls) were analyzed for five SNPs using conventional PCR and TaqMan genotyping assays. The SNPStats software was utilized to choose the best interactive inheritance mode for selected SNPs (https://www.snpstats.net). RESULTS The mean age of diagnosis was 62.4±13.5 years (range, 40-83 years), with those aged 71-80 years and those aged 40-50 years accounting for the most diagnoses (35.7% and 28.6% of diagnosis, respectively). The GSTM1 and TP53 rs1042522 SNPs were associated with CRC (OR= 3.7; P< 0.0001, and OR= 1.6; P= 0.033, respectively). A plausible contribution to CRC was observed for the GSTM1 and TP53 rs1042522 SNPs (x 2 Yates= 14.7; P= 0.00013, and x 2 Yates= 11.2; P= 0.0008, respectively), while the GSTT1 null variant did not affect risk. Heterozygosity in the CYP450 (rs4646903 and rs1048943 SNPs) was associated with a significant risk for CRC. The GSTM1/GSTT1 and CYP450 rs4646903/rs1048943 SNP pairs were in linkage disequilibrium, and the associations were statistically significant (P= 0.01 and P= 4.6x10‒7, respectively). CONCLUSION The GSTM1 and TP53 rs1042522 variants can increase the development of CRC in Saudi nonsmokers. Even the presence of one copy of a variant allele in the CYP1A1 gene can predispose CRC risk. Additional studies should also examine other SNP combinations with lifestyle factors that may help prevent, rather than facilitate, colorectal tumorigenesis.
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Affiliation(s)
- Ikhlas A Sindi
- Department of Biotechnology, Faculty of Science, King Abdulaziz University, Jeddah, 21589, Saudi Arabia
- Ikhlas A Sindi Department of Biotechnology, Faculty of Science, King Abdulaziz University, Jeddah, 21589, Saudi Arabia Email
| | - Ahmed O Babalghith
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Mecca, 21955, Saudi Arabia
| | - Mohammed T Tayeb
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Mecca, 21955, Saudi Arabia
| | - Ahmad H Mufti
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Mecca, 21955, Saudi Arabia
| | - Hind Naffadi
- Common Science, First Year Deanship, Umm Al-Qura University, Mecca, Saudi Arabia
| | - Samar N Ekram
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Mecca, 21955, Saudi Arabia
- Department of Medical Oncology, King Abdullah City Hospital, Mecca, Saudi Arabia
| | - Ezzeldin N Elhawary
- MS Genomic Medicine Program, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton, UK
- Faculty of Biotechnology, October Modern Sciences and Arts University, Giza, Egypt
| | - Munaifah Alenezi
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Mecca, 21955, Saudi Arabia
| | - Nasser A Elhawary
- Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, Mecca, 21955, Saudi Arabia
- Department of Genetics, Faculty of Medicine, Ain Shams University, Cairo, Egypt
- Correspondence: Nasser A Elhawary Department of Medical Genetics, Faculty of Medicine, Umm Al-Qura University, P.O. Box 57543, Mecca, 21955, Saudi ArabiaTel +966 55 369 2180 Email
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Ning J, Wang W, Ge G, Chu P, Long F, Yang Y, Peng Y, Feng L, Ma X, James TD. Target Enzyme-Activated Two-Photon Fluorescent Probes: A Case Study of CYP3A4 Using a Two-Dimensional Design Strategy. Angew Chem Int Ed Engl 2019; 58:9959-9963. [PMID: 31099941 DOI: 10.1002/anie.201903683] [Citation(s) in RCA: 61] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 04/24/2019] [Indexed: 01/08/2023]
Abstract
The rapid development of fluorescent probes for monitoring target enzymes is still a great challenge owing to the lack of efficient ways to optimize a specific fluorophore. Herein, a practical two-dimensional strategy was designed for the development of an isoform-specific probe for CYP3A4, a key cytochrome P450 isoform responsible for the oxidation of most clinical drugs. In first dimension of the design strategy, a potential two-photon fluorescent substrate (NN) for CYP3A4 was effectively selected using ensemble-based virtual screening. In the second dimension, various substituent groups were introduced into NN to optimize the isoform-selectivity and reactivity. Finally, with ideal selectivity and sensitivity, NEN was successfully applied to the real-time detection of CYP3A4 in living cells and zebrafish. These findings suggested that our strategy is practical for developing an isoform-specific probe for a target enzyme.
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Affiliation(s)
- Jing Ning
- College of Integrative Medicine, The National & Local Joint Engineering Research Center for Drug Development of Neurodegenerative Disease, College of Pharmacy, Dalian Medical University, Dalian, 116044, China
| | - Wei Wang
- School of Pharmacy, Hunan University of Chinese Medicine, Changsha, 410208, China
| | - Guangbo Ge
- Institute of Interdisciplinary Integrative Medicine Research, Shanghai University of Traditional Chinese Medicine, Shanghai, 201203, China
| | - Peng Chu
- College of Integrative Medicine, The National & Local Joint Engineering Research Center for Drug Development of Neurodegenerative Disease, College of Pharmacy, Dalian Medical University, Dalian, 116044, China.,Center for Molecular Medicine, School of Life Science and Biotechnology, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116024, China
| | - Feida Long
- Center for Molecular Medicine, School of Life Science and Biotechnology, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116024, China
| | - Yongliang Yang
- Center for Molecular Medicine, School of Life Science and Biotechnology, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116024, China
| | - Yulin Peng
- College of Integrative Medicine, The National & Local Joint Engineering Research Center for Drug Development of Neurodegenerative Disease, College of Pharmacy, Dalian Medical University, Dalian, 116044, China
| | - Lei Feng
- College of Integrative Medicine, The National & Local Joint Engineering Research Center for Drug Development of Neurodegenerative Disease, College of Pharmacy, Dalian Medical University, Dalian, 116044, China.,Center for Molecular Medicine, School of Life Science and Biotechnology, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116024, China
| | - Xiaochi Ma
- College of Integrative Medicine, The National & Local Joint Engineering Research Center for Drug Development of Neurodegenerative Disease, College of Pharmacy, Dalian Medical University, Dalian, 116044, China.,Jiangsu Key Laboratory of New Drug Research and Clinical Pharmacy, Xuzhou Medical University, Xuzhou, 221004, China
| | - Tony D James
- Department of Chemistry, University of Bath, Bath, BA2 7AY, UK
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Ning J, Wang W, Ge G, Chu P, Long F, Yang Y, Peng Y, Feng L, Ma X, James TD. Target Enzyme‐Activated Two‐Photon Fluorescent Probes: A Case Study of CYP3A4 Using a Two‐Dimensional Design Strategy. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201903683] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Jing Ning
- College of Integrative MedicineThe National & Local Joint Engineering Research Center for Drug Development of Neurodegenerative DiseaseCollege of PharmacyDalian Medical University Dalian 116044 China
| | - Wei Wang
- School of PharmacyHunan University of Chinese Medicine Changsha 410208 China
| | - Guangbo Ge
- Institute of Interdisciplinary Integrative Medicine ResearchShanghai University of Traditional Chinese Medicine Shanghai 201203 China
| | - Peng Chu
- College of Integrative MedicineThe National & Local Joint Engineering Research Center for Drug Development of Neurodegenerative DiseaseCollege of PharmacyDalian Medical University Dalian 116044 China
- Center for Molecular Medicine, School of Life Science and BiotechnologyState Key Laboratory of Fine ChemicalsDalian University of Technology Dalian 116024 China
| | - Feida Long
- Center for Molecular Medicine, School of Life Science and BiotechnologyState Key Laboratory of Fine ChemicalsDalian University of Technology Dalian 116024 China
| | - Yongliang Yang
- Center for Molecular Medicine, School of Life Science and BiotechnologyState Key Laboratory of Fine ChemicalsDalian University of Technology Dalian 116024 China
| | - Yulin Peng
- College of Integrative MedicineThe National & Local Joint Engineering Research Center for Drug Development of Neurodegenerative DiseaseCollege of PharmacyDalian Medical University Dalian 116044 China
| | - Lei Feng
- College of Integrative MedicineThe National & Local Joint Engineering Research Center for Drug Development of Neurodegenerative DiseaseCollege of PharmacyDalian Medical University Dalian 116044 China
- Center for Molecular Medicine, School of Life Science and BiotechnologyState Key Laboratory of Fine ChemicalsDalian University of Technology Dalian 116024 China
| | - Xiaochi Ma
- College of Integrative MedicineThe National & Local Joint Engineering Research Center for Drug Development of Neurodegenerative DiseaseCollege of PharmacyDalian Medical University Dalian 116044 China
- Jiangsu Key Laboratory of New Drug Research and Clinical PharmacyXuzhou Medical University Xuzhou 221004 China
| | - Tony D. James
- Department of ChemistryUniversity of Bath Bath BA2 7AY UK
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Coumarins and P450s, Studies Reported to-Date. Molecules 2019; 24:molecules24081620. [PMID: 31022888 PMCID: PMC6515222 DOI: 10.3390/molecules24081620] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2019] [Revised: 04/19/2019] [Accepted: 04/22/2019] [Indexed: 01/08/2023] Open
Abstract
Cytochrome P450 enzymes (CYPs) are important phase I enzymes involved in the metabolism of endogenous and xenobiotic compounds mainly through mono-oxygenation reactions into more polar and easier to excrete species. In addition to their role in detoxification, they play important roles in the biosynthesis of endogenous compounds and the bioactivation of xenobiotics. Coumarins, phytochemicals abundant in food and commonly used in fragrances and cosmetics, have been shown to interact with P450 enzymes as substrates and/or inhibitors. In this review, these interactions and their significance in pharmacology and toxicology are discussed in detail.
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Rendic SP, Guengerich FP. Development and Uses of Offline and Web-Searchable Metabolism Databases - The Case of Benzo[a]pyrene. Curr Drug Metab 2018; 19:3-46. [PMID: 29219051 DOI: 10.2174/1389200219666171207123939] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Revised: 11/04/2017] [Accepted: 11/11/2017] [Indexed: 12/21/2022]
Abstract
BACKGROUND The present work describes development of offline and web-searchable metabolism databases for drugs, other chemicals, and physiological compounds using human and model species, prompted by the large amount of data published after year 1990. The intent was to provide a rapid and accurate approach to published data to be applied both in science and to assist therapy. METHODS Searches for the data were done using the Pub Med database, accessing the Medline database of references and abstracts. In addition, data presented at scientific conferences (e.g., ISSX conferences) are included covering the publishing period beginning with the year 1976. RESULTS Application of the data is illustrated by the properties of benzo[a]pyrene (B[a]P) and its metabolites. Analysis show higher activity of P450 1A1 for activation of the (-)- isomer of trans-B[a]P-7,8-diol, while P4501B1 exerts higher activity for the (+)- isomer. P450 1A2 showed equally low activity in the metabolic activation of both isomers. CONCLUSION The information collected in the databases is applicable in prediction of metabolic drug-drug and/or drug-chemical interactions in clinical and environmental studies. The data on the metabolism of searched compound (exemplified by benzo[a]pyrene and its metabolites) also indicate toxicological properties of the products of specific reactions. The offline and web-searchable databases had wide range of applications (e.g. computer assisted drug design and development, optimization of clinical therapy, toxicological applications) and adjustment in everyday life styles.
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Affiliation(s)
| | - Frederick P Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, United States
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Advanced Approaches to Model Xenobiotic Metabolism in Bacterial Genotoxicology In Vitro. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2017. [PMID: 27619490 DOI: 10.1007/10_2016_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register]
Abstract
During the past 30 years there has been considerable progress in the development of bacterial test systems for use in genotoxicity testing by the stable introduction of expression vectors (cDNAs) coding for xenobiotic-metabolizing enzymes into bacterial cells. The development not only provides insights into the mechanisms of bioactivation of xenobiotic compounds but also evaluates the roles of enzymes involved in metabolic activation or inactivation in chemical carcinogenesis. This review describes recent advances in bacterial genotoxicity assays and their future prospects, with a focus on the development and application of genetically engineering bacterial cells to incorporate some of the enzymatic activities involved in the bio-activation process of xenobiotics. Various genes have been introduced into bacterial umu tester strains encoding enzymes for genotoxic bioactivation, including bacterial nitroreductase and O-acetyltransferase, human cytochrome P450 monooxygenases, rat glutathione S-transferases, and human N-acetyltransferases and sulfotransferases. Their application has provided new tools for genotoxicity assays and for studying the role of biotransformation in chemical carcinogenesis in humans.
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Oda Y. Development and progress for three decades in umu test systems. Genes Environ 2016; 38:24. [PMID: 27980699 PMCID: PMC5131509 DOI: 10.1186/s41021-016-0054-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Accepted: 07/27/2016] [Indexed: 11/10/2022] Open
Abstract
Umu test have been widely used to predict the detection and assessment of DNA- damaging chemicals in environmental genotoxicity field for three decades. This test system is more useful with respect to simplicity, sensitivity, rapidity, and reproducibility. A review of the literature on the development of the umu test is presented in this article. The contents of this article are included a description of numerous data using the umu test. This test have been fully evaluated and used in many directions. Different genetically engineered umu systems introducing bacterial and rat or human drug metabolizing enzymes into the umu tester strains, have been successfully established and are considered as useful tools for genotoxicity assays to study the mechanisms of biotransformation in chemical carcinogenesis. Actually, we developed that two types of bacterial metabolizing enzymes and 4 types of rat and human metabolizing enzyme DNAs are expressed in these strains such as nitroreductase and O-acetyltransferase, cytochrome P450, N-acetyltransferases, sulfotransferases, and glutathione S-transferases, respectively. Due to increasing numbers of minute environmental samples and new pharmaceuticals, a high-throughput umu test system using Salmonella typhimurium TA1535/pSK1002, NM2009, and NM3009 strains provides a useful for these genotoxicity screening. I also briefly describe the first attempts to incorporate such umu tester strain into photo-genotoxicity test.
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Affiliation(s)
- Yoshimitsu Oda
- Institute of Life and Environmental Sciences, Osaka Shin-Ai College, 6-2-28 Tsurumi, Tsurumi-ku, Osaka 538-0053 Japan
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Cecropin B Represses CYP3A29 Expression through Activation of the TLR2/4-NF-κB/PXR Signaling Pathway. Sci Rep 2016; 6:27876. [PMID: 27296244 PMCID: PMC4906279 DOI: 10.1038/srep27876] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 05/25/2016] [Indexed: 12/28/2022] Open
Abstract
Cecropins are peptide antibiotics used as drugs and feed additives. Cecropin B can inhibit the expression of CYP3A29, but the underlying mechanisms remain unclear. The present study was designed to determine the mechanisms responsible for the effects of cecropin B on CYP3A29 expression, focusing on the Toll-like receptors (TLRs) and NF-κB pathways. Our results indicated that the CYP3A29 expression was inhibited by cecropin B, which was regulated by pregnane X receptor (PXR) in a time- and dose-dependent manner. Cecropin B-induced NF-κB activation played a pivotal role in the suppression of CYP3A29 through disrupting the association of the PXR/retinoid X receptor alpha (RXR-α) complex with DNA sequences. NF-κB p65 directly interacted with the DNA-binding domain of PXR, suppressed its expression, and inhibited its transactivation, leading to the downregulation of the PXR-regulated CYP3A29 expression. Furthermore, cecropin B activated pig liver cells by interacting with TLRs 2 and 4, which modulated NF-κB-mediated signaling pathways. In conclusion, cecropin B inhibited the expression of CYP3A29 in a TLR/NF-κB/PXR-dependent manner, which should be considered in future development of cecropins and other antimicrobial peptides.
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Turesky RJ, White KK, Wilkens LR, Marchand LL. Caffeine Cytochrome P450 1A2 Metabolic Phenotype Does Not Predict the Metabolism of Heterocyclic Aromatic Amines in Humans. Chem Res Toxicol 2015; 28:1603-15. [PMID: 26203673 PMCID: PMC4571451 DOI: 10.1021/acs.chemrestox.5b00177] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
2-Amino-1-methylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) are carcinogenic heterocyclic aromatic amines (HAAs) formed in well-done cooked meats. Chemicals that induce cytochrome P450 (P450) 1A2, a major enzyme involved in the bioactivation of HAAs, also form in cooked meat. Therefore, well-done cooked meat may pose an increase in cancer risk because it contains both inducers of P450 1A2 and procarcinogenic HAAs. We examined the influence of components in meat to modulate P450 1A2 activity and the metabolism of PhIP and MeIQx in volunteers during a 4 week feeding study of well-done cooked beef. The mean P450 1A2 activity, assessed by caffeine metabolic phenotyping, ranged from 6.3 to 7.1 before the feeding study commenced and from 9.6 to 10.4 during the meat feeding period: the difference in means was significant (P < 0.001). Unaltered PhIP, MeIQx, and their P450 1A2 metabolites, N(2)-(β-1-glucosiduronyl)-2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine (HON-PhIP-N(2)-Gl); N3-(β-1-glucosiduronyl)-2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine (HON-PhIP-N3-Gl); 2-amino-3-methylimidazo-[4,5-f]quinoxaline-8-carboxylic acid (IQx-8-COOH); and 2-amino-8-(hydroxymethyl)-3-methylimidazo[4,5-f]quinoxaline (8-CH2OH-IQx) were measured in urine during days 2, 14, and 28 of the meat diet. Significant correlations were observed on these days between the levels of the unaltered HAAs and their oxidized metabolites, when expressed as percent of dose ingested or as metabolic ratios. However, there was no statistically significant correlation between the caffeine P450 1A2 phenotype and any urinary HAA biomarker. Although the P450 1A2 activity varied by greater than 20-fold among the subjects, there was a large intraindividual variation of the P450 1A2 phenotype and inconsistent responses to inducers of P450 1A2. The coefficient of variation of the P450 1A2 phenotype within-individual ranged between 1 to 112% (median = 40%) during the entire course of the study. The caffeine metabolic phenotype for P450 1A2 was a poor predictor of oxidative urinary metabolites of PhIP and MeIQx and may not be a reliable measure to assess the role of HAAs in cancer risk.
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Affiliation(s)
- Robert J. Turesky
- Masonic Masonic Cancer Center and Department of Medicinal Chemistry, College of Pharmacy, 2231 6th St SE, University of Minnesota, Minneapolis, MN 55455
| | - Kami K. White
- University of Hawaii Cancer Center, University of Hawaii, Honolulu, HI 9681
| | - Lynne R. Wilkens
- University of Hawaii Cancer Center, University of Hawaii, Honolulu, HI 9681
| | - Loïc Le Marchand
- University of Hawaii Cancer Center, University of Hawaii, Honolulu, HI 9681
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Chiu KW, Hu TH, Nakano T, Chen KD, Lai CY, Hsu LW, Tseng HP, Chiu HC, Cheng YF, Goto S, Chen CL. Biological interactions of CYP2C19 genotypes with CYP3A4*18, CYP3A5*3, and MDR1-3435 in living donor liver transplantation recipients. Transplant Res 2013; 2:6. [PMID: 23617933 PMCID: PMC3643843 DOI: 10.1186/2047-1440-2-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Accepted: 04/11/2013] [Indexed: 01/10/2023] Open
Abstract
Background Polymorphisms in CYP2C19 are related to the metabolic oxidation of drugs to varying degrees. The CYP3A4*18, CYP3A5*3, and MDR1-3435 variant alleles are very important, particularly in tacrolimus metabolism in organ transplant rejection. Aim The aim of this study is o explore possible interactions among different CYP2C19 genotypes, namely, between homozygous extensive metabolizers (HomEM), heterozygous extensive metabolizers (HetEM), and poor metabolizers (PM), and the CYP3A4*18, CYP3A5*3, and MDR1-3435 variants in living donors and patients who received a living donor liver transplant (LDLT). Methods This prospective study enrolled 133 living donors and 133 corresponding recipients. On the basis of the HomEM, HetEM, and PM CYP2C19 genotypes, the distributions of CYP3A4*18 (exon 10; T878C), CYP3A5*3 (intron 3; A6986G), and MDR1-3435 (exon 26; C3435T) genotypes were analyzed for single nucleotide polymorphisms among donors and recipients. Results Among 102 HomEM genotypes, including 56 donors and 46 recipients, 91.2% of individuals harbored the T/T genotype of CYP3A4*18; 53.9% possessed G/G, and 34.3% had A/G genotypes of CYP3A5*3; and 38.2% had C/C and 50.0% had C/T genotypes at MDR1-3435. Among 130 HetEM genotypes, including 58 donors and 72 recipients, 97.7% of individuals possessed T/T genotype at CYP3A4*18; 50.0% harbored G/G and 41.5% had A/G genotypes at CYP3A5*3; and 40.0% had C/C and 49.2% had C/T genotypes at MDR1-3435. In 34 PMs, including 19 donors and 15 recipients, 88.2% had T/T genotypes at CYP3A4*18; 41.2% had G/G and 58.8% had A/G genotypes at CYP3A5*3; and 47.1% possessed C/C and 47.1% had C/T genotypes at MDR1-3435. On the basis of the CYP2C19 genotypes, no statistically significant distribution of genotypes were observed between donors and recipients for all genotypes of CYP3A4*18, CYP3A5*3, and MDR1-3435 (P >0.05). Conclusions In conclusion, the CYP2C19 genotypes do not affect the expression of CYP3A4*18, CYP3A5*3, or MDR1-3435 variants, which are independently distributed among donors and recipients during LDLT.
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Affiliation(s)
- King-Wah Chiu
- Liver Transplant Program, Kaohsiung Chang Gung Memorial Hospital, Chang Gung University, College of Medicine, Kaohsiung, Taiwan.
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Corsini A, Bortolini M. Drug-induced liver injury: the role of drug metabolism and transport. J Clin Pharmacol 2013; 53:463-74. [PMID: 23436293 DOI: 10.1002/jcph.23] [Citation(s) in RCA: 111] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Accepted: 07/17/2012] [Indexed: 12/11/2022]
Abstract
Many studies have pinpointed the significant contribution of liver-mediated drug metabolism and transport to the complexity of drug-induced liver injury (DILI). Phase I cytochrome P450 (CYP450) enzymes can lead to altered drug metabolism and formation of toxic metabolites, whilst Phase II enzymes are also associated with DILI. The emerging role of hepatic transporters in regulating the movement of endogenous and exogenous chemicals (e.g., bile acids and drugs) across cellular and tissue membranes is critical in determining the pathophysiology of liver disease as well as drug toxicity and efficacy. Genetic and environmental factors can have a significant impact on drug metabolism and transporter proteins, consequently increasing the risk of DILI in susceptible individuals. The assessment of these factors therefore represents an important approach for predicting and preventing DILI, by better understanding the pharmacological profile of a specific drug. This review focuses on the mechanisms of DILI associated with drug metabolism and hepatic transport, and how they can be influenced by underlying factors.
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Affiliation(s)
- Alberto Corsini
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Milan, Italy.
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Inami K, Yoshimitsu K, Seino H, Mochizuki M. Ruthenium porphyrin and oxidant convert N-nitrosodialkylamines into direct-acting mutagen in the Ames assay. Toxicol Res (Camb) 2013. [DOI: 10.1039/c3tx50036e] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
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Gandhi AS, Guo T, Shah P, Moorthy B, Chow DSL, Hu M, Ghose R. CYP3A-dependent drug metabolism is reduced in bacterial inflammation in mice. Br J Pharmacol 2012; 166:2176-87. [PMID: 22394353 DOI: 10.1111/j.1476-5381.2012.01933.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND AND PURPOSE Gene expression of Cyp3a11 is reduced by activation of Toll-like receptors (TLRs) by Gram-negative or Gram-positive bacterial components, LPS or lipoteichoic acid (LTA) respectively. The primary adaptor protein in the TLR signalling pathway, TIRAP, plays differential roles in LPS- and LTA-mediated down-regulations of Cyp3a11 mRNA. Here, we have determined the functional relevance of these findings by pharmacokinetic/pharmacodynamic (PK/PD) analysis of the Cyp3a substrate midazolam in mice. Midazolam is also metabolized by Cyp2c in mice. EXPERIMENTAL APPROACH Adult male C57BL/6, TIRAP+/+ and TIRAP-/- mice were pretreated with saline, LPS (2 mg·kg⁻¹) or LTA (6 mg·kg⁻¹). Cyp3a11 protein expression, activity and PK/PD studies using midazolam were performed. KEY RESULTS Cyp3a11 protein expression in LPS- or LTA-treated mice was reduced by 95% and 60% compared with saline-treated mice. Cyp3a11 activity was reduced by 70% in LPS- or LTA-treated mice. Plasma AUC of midazolam was increased two- to threefold in LPS- and LTA-treated mice. Plasma levels of 1'-OHMDZ decreased significantly only in LTA-treated mice. Both LPS and LTA decreased AUC of 1'-OHMDZ-glucuronide. In the PD study, sleep time was increased by ∼2-fold in LPS- and LTA-treated mice. LTA-mediated decrease in Cyp3a11 protein expression and activity was dependent on TIRAP. In PK/PD correlation, AUC of midazolam was increased only in LPS-treated mice compared with saline-treated mice. CONCLUSIONS AND IMPLICATIONS LPS or LTA altered PK/PD of midazolam. This is the first study to demonstrate mechanistic differences in regulation of metabolite formation of a clinically relevant drug by Gram-negative or Gram-positive bacterial endotoxins.
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Affiliation(s)
- A S Gandhi
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX, USA
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15
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Abstract
Considerable support exists for the roles of metabolism in modulating the carcinogenic properties of chemicals. In particular, many of these compounds are pro-carcinogens that require activation to electrophilic forms to exert genotoxic effects. We systematically analyzed the existing literature on the metabolism of carcinogens by human enzymes, which has been developed largely in the past 25 years. The metabolism and especially bioactivation of carcinogens are dominated by cytochrome P450 enzymes (66% of bioactivations). Within this group, six P450s--1A1, 1A2, 1B1, 2A6, 2E1, and 3A4--accounted for 77% of the P450 activation reactions. The roles of these P450s can be compared with those estimated for drug metabolism and should be considered in issues involving enzyme induction, chemoprevention, molecular epidemiology, interindividual variations, and risk assessment.
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16
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Elbarbry F, Ragheb A, Marfleet T, Shoker A. Modulation of Hepatic Drug Metabolizing Enzymes by Dietary Doses of Thymoquinone in Female New Zealand White Rabbits. Phytother Res 2012; 26:1726-30. [DOI: 10.1002/ptr.4628] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Revised: 01/17/2012] [Accepted: 01/23/2012] [Indexed: 11/07/2022]
Affiliation(s)
- Fawzy Elbarbry
- School of Pharmacy; Pacific University Oregon; Hillsboro OR 97123 USA
| | - Ahmed Ragheb
- Department of General Medicine, College of Medicine; Menofyia University; Egypt
| | - Travis Marfleet
- Department of Microbiology and Immunology, College of Medicine; University of Saskatchewan; Saskatoon SK Canada
| | - Ahmed Shoker
- Department of Medicine, Royal University Hospital; University of Saskatchewan; Saskatoon SK Canada
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17
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Ng CH, Janoo-Gilani R, Sipahimalani P, Gallagher RP, Gascoyne RD, Connors JM, Weber JP, Lai AS, Leach S, Le ND, Brooks-Wilson AR, Spinelli JJ. Interaction between organochlorines and the AHR gene, and risk of non-Hodgkin lymphoma. Cancer Causes Control 2009; 21:11-22. [PMID: 19821039 DOI: 10.1007/s10552-009-9429-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 09/04/2009] [Indexed: 12/19/2022]
Affiliation(s)
- Carmen H Ng
- BC Cancer Agency,Vancouver, BC, V5Z 1L3, Canada
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18
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Inami K, Okazawa M, Mochizuki M. Mutagenicity of aromatic amines and amides with chemical models for cytochrome P450 in Ames assay. Toxicol In Vitro 2009; 23:986-91. [DOI: 10.1016/j.tiv.2009.06.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Revised: 05/28/2009] [Accepted: 06/24/2009] [Indexed: 11/16/2022]
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19
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Ellis EM. Protection against Aflatoxin B1 in Rat—A New Look at the Link between Toxicity, Carcinogenicity, and Metabolism. Toxicol Sci 2009; 109:1-3. [DOI: 10.1093/toxsci/kfp052] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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20
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Bell L, Bickford S, Nguyen PH, Wang J, He T, Zhang B, Friche Y, Zimmerlin A, Urban L, Bojanic D. Evaluation of fluorescence- and mass spectrometry-based CYP inhibition assays for use in drug discovery. ACTA ACUST UNITED AC 2008; 13:343-53. [PMID: 18474896 DOI: 10.1177/1087057108317480] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The potential for metabolism-related drug-drug interactions by new chemical entities is assessed by monitoring the impact of these compounds on cytochrome P450 (CYP) activity using well-characterized CYP substrates. The conventional gold standard approach for in vitro evaluation of CYP inhibitory potential uses pooled human liver microsomes (HLM) in conjunction with prototypical drug substrates, often quantified by LC-MS/MS. However, fluorescent CYP inhibition assays, which use recombinantly expressed CYPs and fluorogenic probe substrates, have been employed in early drug discovery to provide low-cost, high-throughput assessment of new chemical entities. Despite its greatly enhanced throughput, this approach has been met with mixed success in predicting the data obtained with the conventional gold standard approach (HLM+LC-MS). The authors find that the predictivity of fluorogenic assays for the major CYP isoforms 3A4 and 2D6 may depend on the quality of the test compounds. Although the structurally more optimized marketed drugs yielded acceptable correlations between the fluorogenic and HLM+LC-MS/MS assays for CYPs 3A4, 2D6, and 2C9 (r2 = 0.5-0.7; p < 0.005), preoptimization, early discovery compounds yielded poorer correlations (r2 < or = 0.2) for 2 of these major isoforms, CYPs 3A4 and 2D6. Potential reasons for the observed differences are discussed.
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Affiliation(s)
- Leslie Bell
- ADME Profiling Cambridge, Metabolism and Pharmacokinetics, Global Discovery Chemistry, Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139, USA.
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21
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Yan D, Yang Y, Uchida S, Misaka S, Luo J, Takeuchi K, Inui N, Yamada S, Ohashi K, Watanabe H. Effects of ursodeoxycholic acid on the pharmacokinetics and pharmacodynamics of intravenous and oral midazolam in healthy volunteers. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2007; 377:629-36. [DOI: 10.1007/s00210-007-0217-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2007] [Accepted: 11/06/2007] [Indexed: 10/22/2022]
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22
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Du J, Xing Q, Xu L, Xu M, Shu A, Shi Y, Yu L, Zhang A, Wang L, Wang H, Li X, Feng G, He L. Systematic screening for polymorphisms in the CYP3A4 gene in the Chinese population. Pharmacogenomics 2006; 7:831-41. [PMID: 16981844 DOI: 10.2217/14622416.7.6.831] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
OBJECTIVES Cytochrome P450 3A4 (CYP3A4) is a major CYP enzyme in the liver and intestine. It is involved in the metabolism of over 50% of all drugs currently in use. The present study was designed to determine the genetic basis of CYP3A4 variability. METHODS Single nucleotide polymorphism (SNP) analysis of the CYP3A4 gene was performed on 60 healthy Chinese subjects consisting of 20 Han, 30 She and ten Dong subjects, using direct sequencing. Linkage disequilibrium, haplotype inference and Hardy-Weinberg equilibrium were also determined for these samples. RESULTS A total of 20 SNPs were found in the CYP3A4 gene, including 11 known SNPs and nine novel SNPs. The known SNPs detected in our study were CYP3A4*1B, CYP3A4*1G, CYP3A4*10, CYP3A4*13, CYP3A4*14, CYP3A4*15, CYP3A4*17, CYP3A4*18, rs3091339, rs3091430 and rs28371761, and the novel SNPs were -658 A-->C, G27A (E10K), T48A, G14284A (G167D), A15623G (N191D), C15635A (L196I), T15656C (F203L), G14199A (intron 5) and C15566T (intron 6). The allelic frequencies found in our sample varied from 1-37%. The novel SNPs detected in the CYP3A4 gene suggest that the Chinese population has different patterns of allele frequency compared with other populations. CONCLUSION Several SNPs were detected in the CYP3A4 gene. The study of genetic variants in CYP3A4 may have an important significance for the understanding of genotype and phenotype relationships.
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Affiliation(s)
- Jing Du
- Bio-X Center, Shanghai JiaoTong University, 1954 Huashan Road, Shanghai 200030, China
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23
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He P, Court MH, Greenblatt DJ, von Moltke LL. Factors influencing midazolam hydroxylation activity in human liver microsomes. Drug Metab Dispos 2006; 34:1198-207. [PMID: 16638818 DOI: 10.1124/dmd.105.008904] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The cytochrome P450 3A (CYP3A) subfamily (mainly CYP3A4 and CYP3A5) is responsible for metabolizing approximately half of currently marketed drugs, but with considerable interindividual variability in expression and function. To investigate factors contributing to this variability, rates of midazolam (MDZ) 1'-hydroxylation and CYP3A4 and CYP3A5 protein content were determined using a set of 54 human liver microsomes (HLMs). Genetic factors investigated included CYP3A4 and CYP3A5 single nucleotide polymorphisms (SNPs) and haplotypes, CYP3A4 mRNA alternative splicing, and CYP3A4 transcriptional start and polyadenylation sites. Demographic and environmental factors investigated included age, gender, and histories of smoking and alcohol consumption. MDZ 1'-hydroxylation rates varied from 0.025 to 3.106 nmol/min/mg protein, with significant correlation to CYP3A4 protein content (r(s) = 0.92, P < 0.001) but less robust correlation to CYP3A5 protein content (r(s) = 0.60, P < 0.001). We identified eight CYP3A4 SNPs (five novel) and nine CYP3A5 SNPs (one novel), as well as seven CYP3A4 and two CYP3A5 haplotypes (all novel). No influence of genotype or haplotype on MDZ 1'-hydroxylation rate was observed, although CYP3A5*3A (g.6986a>g; g.31611c>t) carriers had lower CYP3A5 protein content compared with noncarriers (P = 0.004). No alternative splicing of CYP3A4 mRNA was found. Likewise, only a single transcriptional start site and polyadenylation site for CYP3A4 mRNA were identified. Subjects with a history of alcohol consumption had 2.2-fold higher median MDZ 1'-hydroxylation (P = 0.017), whereas no influence of age, gender, or smoking was evident. In conclusion, the investigated genetic factors did not contribute substantially to the large interindividual variability in midazolam hydroxylation, although alcohol consumption has a discernable but modest influence.
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Affiliation(s)
- Ping He
- Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, MA 02111, USA
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24
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Abstract
Arylamines and heterocyclic arylamines (HAAs) are of particular interest because of demonstrated carcinogenicity in animals and humans and the broad exposure to many of these compounds. The activation of these, and also some arylamine drugs, involves N-hydroxylation, usually by cytochrome P450 (P450). P450 1A2 plays a prominent role in these reactions. However, P450 1A1 and 1B1 and other P450s are also important in humans as well as experimental animals. Some arylamines (including drugs) are N-hydroxylated predominantly by P450s other than those in Family 1. Other oxygenases can also have roles. An important issue is extrapolation between species in predicting cancer risks, as shown by the low rates of HAA activation by rat P450 1A2 and low levels of P450 1A2 expression in some nonhuman primates.
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Affiliation(s)
- Donghak Kim
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA
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25
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Noreault TL, Kostrubsky VE, Wood SG, Nichols RC, Strom SC, Trask HW, Wrighton SA, Evans RM, Jacobs JM, Sinclair PR, Sinclair JF. Arsenite decreases CYP3A4 and RXRalpha in primary human hepatocytes. Drug Metab Dispos 2005; 33:993-1003. [PMID: 15833926 DOI: 10.1124/dmd.105.003954] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Arsenic is a naturally occurring, worldwide contaminant implicated in numerous pathological conditions in humans, including cancer and several forms of liver disease. One of the contributing factors to these disorders may be the alteration of cytochrome P450 (P450) levels by arsenic. P450s are involved in the oxidative metabolism and elimination of numerous toxic chemicals. CYP3A4, a major P450 in humans, is involved in the metabolism of half of all currently used drugs. Acute exposure to arsenite decreases the induction of CYP1A1/2 proteins and activities in cultured human hepatocytes, as well as CYP3A23 in cultured rat hepatocytes. Here, in primary cultures of human hepatocytes, we assessed the effects of acute arsenite exposure on CYP3A4 and several transcription factors involved in CYP3A4 expression. The concentrations of arsenite used in these studies were nontoxic to the hepatocytes and failed to elicit an oxidative response. Treatment with arsenite in the presence of CYP3A4 inducers, rifampicin (Rif) or phenobarbital, caused major decreases in CYP3A4 mRNA, protein, and activity. In addition, the levels of CYP3A4 in untreated cells were decreased following arsenite treatment. Transcription of the CYP3A4 gene is primarily regulated by heterodimers of the retinoid X receptor alpha (RXRalpha) and the pregnane X receptor (PXR). We found that arsenite failed to affect expression of PXR or the transcription factor Sp1, yet caused a significant decrease in PXR responsiveness to Rif. Arsenite caused a large decrease in nuclear RXRalpha protein and, to a lesser extent, RXRalpha mRNA. These results suggest that arsenite inhibits both untreated and induced CYP3A4 transcription in primary human hepatocytes by decreasing the activity of PXR, as well as expression of the nuclear receptor RXRalpha.
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Affiliation(s)
- Trisha L Noreault
- Department of Pharmacology/Toxicology, Dartmouth Medical School, Hanover, New Hampshire, USA
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26
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Fujita KI, Kamataki T. Genetically engineered bacterial cells co-expressing human cytochrome P450 with NADPH-cytochrome P450 reductase: prediction of metabolism and toxicity of drugs in humans. Drug Metab Pharmacokinet 2005; 17:1-22. [PMID: 15618648 DOI: 10.2133/dmpk.17.1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Genetically engineered bacterial cells expressing human cytochrome P450 (CYP) have been developed as new tools to predict the metabolism and toxicity of drugs in humans. There are various host cells for the heterologous expression of a form of CYP. Among them, bacterial cells such as Escherichia coli (E. coli) have advantages with regard to ease of use and high yield of protein. CYP protein could be first expressed by the modification of the N-terminal amino acid sequence in E. coli cells in 1991. Since then, many forms of human CYP have been successfully expressed in E. coli cells. Since the E. coli cells do not possess endogeneous electron transport systems to support the full catalytic activity of CYP, E. coli strains co-expressing both human CYP and NADPH-cytochrome P450 reductase (OR) have been established. Each form of CYP expressed in the E. coli cells efficiently catalyzed the oxidation of a representative substrate at an efficient rate, indicating that the OR was sufficiently expressed to support the catalytic activity of CYP. According to the studies performed so far, the modification of the N-terminal amino acid sequence of CYP did not seem to affect the catalytic properties of CYP. The human CYP expressed in the E. coli cells were applicable for studies to determine a metabolic pathway(s) of drugs and to estimate kinetic parameters of drug metabolism by human CYP. Drug-drug interactions caused by inhibition of the metabolism of drugs by human CYP could also be examined by in vitro inhibition studies with CYP expressed in the E. coli cells. Recently, human CYP was co-expressed with the OR in Salmonella typhimurium (S. typhimurium) cells used for mutation assay (Ames test) by applying the technology for the expression of human CYP and the OR in E. coli cells, to evaluate whether chemicals including drugs are metabolically activated by human CYP and show mutagenicity. These strains of bacteria are considered as useful tools to study the metabolism and the toxicity of drugs in humans.
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Affiliation(s)
- Ken-Ichi Fujita
- Laboratory of Drug Metabolism, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
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27
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Minamiyama Y, Takemura S, Toyokuni S, Imaoka S, Funae Y, Hirohashi K, Yoshikawa T, Okada S. CYP3A induction aggravates endotoxemic liver injury via reactive oxygen species in male rats. Free Radic Biol Med 2004; 37:703-12. [PMID: 15288127 DOI: 10.1016/j.freeradbiomed.2004.05.022] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2004] [Revised: 05/19/2004] [Accepted: 05/21/2004] [Indexed: 11/26/2022]
Abstract
We carried out this experiment to evaluate the relationship between isoforms of cytochrome P450 (P450) and liver injury in lipopolysaccharide (LPS)-induced endotoxemic rats. Male rats were intraperitoneally administered phenobarbital (PB), a P450 inducer, for 3 days, and 1 day later, they were intravenously given LPS. PB significantly increased P450 levels (200% of control levels) and the activities (300-400% of control) of the specific isoforms (CYP), CYP3A2 and CYP2B1, in male rats. Plasma AST and ALT increased slightly more in PB-treated rats than in PB-nontreated (control) rats with LPS treatment. Furthermore, either troleandomycin or ketoconazole, specific CYP3A inhibitors, significantly inhibited LPS-induced liver injury in control and PB-treated male rats. To evaluate the oxidative stress in LPS-treated rats, in situ superoxide radical detection using dihydroethidium (DHE), hydroxy-2-nonenal (HNE)-modified proteins in liver microsomes and 8-hydroxydeoxyguanosine (8-OHdG) in liver nuclei were measured in control and PB-treated rats. DHE signal intensity, levels of HNE-modified proteins, and 8-OHdG increased significantly in PB-treated rats. LPS further increased DHE intensity, HNE-modified proteins, and 8-OHdG levels in normal and PB-treated groups. CYP3A inhibitors also inhibited the increases in these items. Our results indicate that the induction or preservation of CYP isoforms further promotes LPS-induced liver injury through mechanisms related to oxidative stress. In particular, CYP3A2 of P450 isoforms made an important contribution to this LPS-induced liver injury.
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Affiliation(s)
- Yukiko Minamiyama
- Department of Food and Health Science, Graduate School of Medicine and Dentistry, Okayama University, Okayama 700-8558, Japan.
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Ko CB, Kim SJ, Park C, Kim BR, Shin CH, Choi S, Chung SY, Noh JH, Jeun JH, Kim NS, Park R. Benzo(a)pyrene-induced apoptotic death of mouse hepatoma Hepa1c1c7 cells via activation of intrinsic caspase cascade and mitochondrial dysfunction. Toxicology 2004; 199:35-46. [PMID: 15125997 DOI: 10.1016/j.tox.2004.01.039] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2003] [Revised: 01/21/2004] [Accepted: 01/21/2004] [Indexed: 11/16/2022]
Abstract
Benzo(a)pyrene (BaP), a potent carcinogen, has been shown to induce apoptosis via activation of caspase-3. However, the upstream of caspase-3 and other apoptosis signaling remain to be elusive. Herein, we demonstrated that treatment of Hepa1c1c7 cells with BaP increased the transcriptional expression of aryl hydrocarbon nuclear transporter and cytochrome p450 1A1 in a time and dose-dependent manner but did not aromatic hydrocarbon receptor. Also, the catalytic activation of caspase-3 and caspase-9 was induced whereas that of caspase-3 and caspase-9 was not by the addition of BaP. BaP also induced the mitochondrial dysfunction, including transition of mitochondria membrane potential and cytosolic release of cytochrome c. Furthermore, a decrease in the expression of Bcl-2 to Bax ratio and phosphorylation of p53(Ser 15) were observed in BaP-treated cells. Taken together, these results demonstrated that BaP-induced apoptosis of Hepa1c1c7 cells via activation of intrinsic caspase pathway including caspase-3, caspase-9, with mitochondrial dysfunction and p53 activation.
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Affiliation(s)
- Chang-Bo Ko
- Vestibulocochlear Research Center and Department of Microbiology, Wonkwang University School of Medicine, 344-2 Shinyong-dong, Iksan, Jeonbuk 570-749, South Korea
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Marchand A, Barouki R, Garlatti M. Regulation of NAD(P)H:Quinone Oxidoreductase 1 Gene Expression by CYP1A1 Activity. Mol Pharmacol 2004; 65:1029-37. [PMID: 15044633 DOI: 10.1124/mol.65.4.1029] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The dioxin 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) induces phase I and II xenobiotic metabolizing enzymes (XME) which act sequentially to eliminate different classes of xenobiotics. The transcriptional effects of TCDD are generally mediated by the arylhydrocarbon receptor (AhR). We hypothesized that TCDD could also act indirectly, by increasing the activity of cytochrome P450 1A1 (CYP1A1), a phase I gene, which could then mediate the induction of other XME genes, such as the NAD(P)H:quinone oxidoreductase 1 (NQO1). To test this hypothesis, NQO1 gene expression was monitored after either overexpression of CYP1A1 or siRNA-mediated knock-down of CYP1A1 activity in the hepatoma cell line HepG2. Overexpression of CYP1A1 in the absence of TCDD was carried out using either adenoviral infection or the "Tet-off" system. Recombinant adenoviruses were produced encoding no protein, CYP1A1 (Ad1A1), or a mutated inactive CYP1A1 (Ad1A1mut). In the HepG2 Tet-off cell line, CYP1A1 expression was induced by the removal of doxycycline (dox) from the cell medium. Ad1A1 infection or dox removal induced CYP1A1 activity and H(2)O(2) production similarly to TCDD treatment. Moreover, in both systems, the amount of NQO1 mRNA increased to the same level as after TCDD treatment (approximately 2-fold). The UDP-glucuronosyl transferase 1A6 (UGT1A6) gene is also similarly regulated. NQO1 gene expression was not induced when mutant, inactive CYP1A1 was overexpressed or when the antioxidant N-acetyl cysteine (NAC) was added to Ad1A1. Finally, either NAC or siRNA directed against CYP1A1 mRNA decreased the induction of NQO1 gene expression by TCDD. We conclude that, after exposure to TCDD, the NQO1 gene expression can be controlled by CYP1A1 activity through an oxidative stress mediated pathway.
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Affiliation(s)
- A Marchand
- Institut National de la Santé et de la Recherche Médicale, Unité-490, 45 rue des Saints-Pères, 75006 Paris, France.
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Chen S, Nguyen N, Tamura K, Karin M, Tukey RH. The role of the Ah receptor and p38 in benzo[a]pyrene-7,8-dihydrodiol and benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide-induced apoptosis. J Biol Chem 2003; 278:19526-33. [PMID: 12637498 DOI: 10.1074/jbc.m300780200] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants in the environment. Benzo[a]pyrene (B[a]P), a prototypical member of this class of chemicals, affects cellular signal transduction pathways and induces apoptosis. In this study, the proximate carcinogen of B[a]P metabolism, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (B[a]P-7,8-dihydrodiol) and the ultimate carcinogen, B[a]P-r-7,t-8-dihydrodiol-t-9,10-epoxide(+/-) (BPDE-2) were found to induce apoptosis in human HepG2 cells. Apoptosis initiated by B[a]P-7,8-dihydrodiol was linked to activation of the Ah receptor and induction of CYP1A1, an event that can lead to the formation of BPDE-2. With both B[a]P-7,8-dihydrodiol and BPDE-2 treatment, changes in anti- and pro-apoptotic events in the Bcl-2 family of proteins correlated with the release of mitochondrial cytochrome c and caspase activation. The onset of apoptosis as monitored by caspase activation was linked to mitogen-activated protein (MAP) kinases. Utilizing mouse hepa1c1c7 cells and the Arnt-deficient BPRc1 cells, activation of MAP kinase p38 by B[a]P-7,8-dihydrodiol was shown to be Ah receptor-dependent, indicating that metabolic activation by CYP1A1 was required. This was in contrast to p38 activation by BPDE-2, an event that was independent of Ah receptor function. Confirmation that MAP kinases play a critical role in BPDE-2-induced apoptosis was shown by inhibiting caspase activation of poly(ADP-ribose)polymerase 1 (PARP-1) by chemical inhibitors of p38 and ERK1/2. Furthermore, mouse embryo p38-/- fibroblasts were shown to be resistant to the actions of BPDE-2-induced apoptosis as determined by annexin V analysis, cytochrome c release, and cleavage of PARP-1. These results confirm that the Ah receptor plays a critical role in B[a]P-7,8-dihydrodiol-induced apoptosis while p38 MAP kinase links the actions of an electrophilic metabolite like BPDE-2 to the regulation of programmed cell death.
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Affiliation(s)
- Shujuan Chen
- Laboratory of Environmental Toxicology, Department of Pharmacology, University of California, San Diego, La Jolla, California 92093-0636, USA
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Guengerich FP, Wheeler JB, Chun YJ, Kim D, Shimada T, Aryal P, Oda Y, Gillam EMJ. Use of heterologously-expressed cytochrome P450 and glutathione transferase enzymes in toxicity assays. Toxicology 2002; 181-182:261-4. [PMID: 12505322 DOI: 10.1016/s0300-483x(02)00293-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Our groups have had a long-term interest in utilizing bacterial systems in the characterization of bioactivation and detoxication reactions catalyzed by cytochrome P450 (P450) and glutathione transferase (GST) enzymes. Bacterial systems remain the first choice for initial screens with new chemicals and have advantages, including high-throughput capability. Most human P450s of interest in toxicology have been readily expressed in Escherichia coli with only minor sequence modification. These enzymes can be readily purified and used in assays of activation of chemicals. Bicistronic systems have been developed in order to provide the auxiliary NADPH-P450 reductase. Alternative systems involve these enzymes expressed together within bacteria. In one approach, a lac selection system is used with E. coli and has been applied to the characterization of inhibitors of P450s 1A2 and 1B1, as well as in basic studies involving random mutagenesis. Another approach utilizes induction of the SOS (umu) response in Salmonella typhimurium, and systems have now been developed with human P450s 1A1, 1A2, 1B1, 2C9, 2D6, 2E1, and 3A4, which have been used to report responses from heterocyclic amines. S. typhimurium his reporter systems have also been used with GSTs, first to demonstrate the role of rat GST 5-5 in the activation of dihalomethanes. These systems have been used to compare these GSTs with regard to activation of dihaloalkanes and potential toxicity.
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Affiliation(s)
- F Peter Guengerich
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, 638 Robinson Research Building, Medical Research Building I, Nashville, TN 37232-0146, USA.
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Abstract
Metabolism plays important roles in chemical carcinogenesis, both good and bad. The process of carcinogen metabolism was first recognized in the first half of the twentieth century and developed extensively in the latter half. The activation of chemicals to reactive electrophiles that become covalently bound to DNA and protein was demonstrated by Miller and Miller [Cancer 47 (1981) 2327]. Today many of the DNA adducts formed by chemical carcinogens are known, and extensive information is available about pathways leading to the electrophilic intermediates. Some concepts about the stability and reactivity of electrophiles derived from carcinogens have changed over the years. Early work in the field demonstrated the ability of chemicals to modulate the metabolism of carcinogens, a phenomenon now described as enzyme induction. The cytochrome P450 enzymes play a prominent role in the metabolism of carcinogens, both in bioactivation and detoxication. The conjugating enzymes can also play both beneficial and detrimental roles. As an example of a case in which several enzymes affect the metabolism and carcinogenicity of a chemical, aflatoxin B1 (AFB1) research has revealed insight into the myriad of reaction chemistry that can occur even with a 1s half-life for a reactive electrophile. Further areas of investigation involve the consequences of enzyme variability in humans and include areas such as genomics, epidemiology, and chemoprevention.
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Affiliation(s)
- F P Guengerich
- Department of Biochemistry, Center of Molecular Toxicology, Vanderbilt University School of Medicine, 638 Medical Research Building I, 23rd Avenue South at Pierce, Nashville, TN 37232-0146, USA.
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Oda Y, Aryal P, Terashita T, Gillam EM, Guengerich FP, Shimada T. Metabolic activation of heterocyclic amines and other procarcinogens in Salmonella typhimurium umu tester strains expressing human cytochrome P4501A1, 1A2, 1B1, 2C9, 2D6, 2E1, and 3A4 and human NADPH-P450 reductase and bacterial O-acetyltransferase. MUTATION RESEARCH-GENETIC TOXICOLOGY AND ENVIRONMENTAL MUTAGENESIS 2001; 492:81-90. [PMID: 11377247 DOI: 10.1016/s1383-5718(01)00154-1] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We investigated roles of different forms of cytochrome P450 (P450 or CYP) in the metabolic activation of heterocyclic amines (HCAs) and other procarcinogens to genotoxic metabolite(s) in the newly developed umu tester strains Salmonella typhimurium (S. typhimurium) OY1002/1A1, OY1002/1A2, OY1002/1B1, OY1002/2C9, OY1002/2D6, OY1002/2E1 and OY1002/3A4, which express respective human P450 enzymes and NADPH-cytochrome P450 reductase (reductase) and bacterial O-acetyltransferase (O-AT). These strains were established by introducing two plasmids into S. typhimurium TA1535, one carrying both P450 and the reductase cDNA in a bicistronic construct under control of an IPTG-inducible double tac promoter and the other, pOA102, carrying O-AT and umuC"lacZ fusion genes. Expression levels of CYP were found to range between 35 to 550 nmol/l cell culture in the strains tested. O-AT activities in different strains ranged from 52 to 125 nmol isoniazid acetylated/min/mg protein. All HCAs tested, and 2-aminoanthracene and 2-aminofluorene exhibited high genotoxicity in the OY1002/1A2 strain, and genotoxicity of 2-amino-3-methylimidazo [4,5-f]quinoline was detected in both the OY1002/1A1 and OY1002/1A2 strains. 3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]-indole and 3-amino-1-methyl-5H-pyrido[4,3-b]-indole were activated in the OY1002/1A1, OY1002/1B1, OY1002/1A2, and OY1002/3A4 strains. Aflatoxin B(1) exhibited genotoxicity in the OY1002/1A2, OY1002/1A1, and OY1002/3A4 strains. beta-Naphthylamine and benzo[a]pyrene did not exhibit genotoxicity in any of the strains. These results suggest that CYP1A2 is the major cytochrome P450 enzyme involved in bioactivation of HCAs.
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Affiliation(s)
- Y Oda
- Osaka Prefectural Institute of Public Health, Higashinari-ku, 537-0025, Osaka, Japan.
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Vakharia DD, Liu N, Pause R, Fasco M, Bessette E, Zhang QY, Kaminsky LS. Effect of metals on polycyclic aromatic hydrocarbon induction of CYP1A1 and CYP1A2 in human hepatocyte cultures. Toxicol Appl Pharmacol 2001; 170:93-103. [PMID: 11162773 DOI: 10.1006/taap.2000.9087] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Environmental cocontamination by polycyclic aromatic hydrocarbons (PAHs) and metals could affect the carcinogenic consequences of PAH exposure by modifying PAH induction of PAH-bioactivating CYP1A. The effect of As, Pb, Hg, or Cd (ranked as the most hazardous environmental metals by EPA and ATSDR) on CYP1A1 and 1A2 induction by benzo[a]pyrene (BaP), benzo[b]fluoranthene (BbF), dibenzo[a,h]anthracene (DBahA), benzo[a]anthracene (BaA), and benzo[k]fluoranthene (BkF) has thus been investigated in fresh human hepatocyte cultures. Induction was probed by ethoxyresorufin-O-deethylase activity, by immunoblots, and by RT-PCR. Uptake of PAHs into the hepatocytes varied according to PAH and liver donor: 84% of 5 microM BaA and 25-40% of 5 microM DBahA was taken up in 24 h. Hepatocytes retained viability up to 1 microM Cd and 5 microM Pb, Hg, or As and 5 microM PAHs. PAH induction of CYP1A in hepatocytes was variable, some cultures expressed CYP1A1 and others CYP1A1 and 1A2, and to variable extents. Induction efficiency (relative to DMSO controls) at 2.5 microM PAH concentration was in the order BkF (7.6-fold) > DBahA (6.1 fold) > BaP (5.7 fold) > BbF (3.9-fold) > BaA (2.5-fold). All four metals (1-5 microM) decreased CYP1A1/1A2 induction by some of the PAHs with dose-, metal-, and PAH-dependency. Arsenic (5 microM) decreased induction by 47% for BaP, 68% for BaA, 45% for BbF, 79% for BkF, and 53% for DBahA. Induced CYP1A2 protein was much more extensively decreased than 1A1 protein, and CYP1A2 mRNA and, to variable extents, CYP1A1 mRNA were decreased by As. Thus the metals in PAH/metal mixtures could diminish PAH carcinogenicity by decreasing induction of their bioactivation by CYP1A1/1A2.
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Affiliation(s)
- D D Vakharia
- New York State Department of Health, Wadsworth Center, Albany, New York 12201-0509, USA
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Kranendonk M, Laires A, Rueff J, Estabrook WR, Vermeulen NP. Heterologous expression of xenobiotic mammalian-metabolizing enzymes in mutagenicity tester bacteria: an update and practical considerations. Crit Rev Toxicol 2000; 30:287-306. [PMID: 10852498 DOI: 10.1080/10408440091159211] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
There is an increasing need for metabolic competent cell systems for the mechanistic studies of biotransformation of xenobiotics in toxicology in general and in genotoxicology in particular. These cell systems combine the heterologous expression of a particular mammalian biotransformation enzyme with a specific target/ end point by which a functional analysis of the expressed gene product in the (geno)toxicity of chemicals can be performed. cDNAs of an increasing number of mammalian biotransformation enzymes is being cloned. The construction of specific expression vectors permits their heterologous expression in laboratory bacteria, such as Escherichia coli strains. This development does not only allow biochemical and enzymatic studies of (pure) enzyme preparations but also facilitates the engineering of metabolically competent mutagenicity tester bacteria, thereby providing new tools for genotoxicity testing and for studying of the roles of biotransformation in chemical carcinogenesis. In this review, we describe an update as well as an evaluation of enzymes expressed in mutagenicity tester bacteria. Four types of biotransformation enzymes are now expressed in these bacteria, namely, GSTs, CYPs, NATs, and STs. The expression of these enzymes in the tester bacteria and their subsequent application in mutagenicity assays demonstrates that heterologous expression in this type of bacteria has a number implications for the functionality of the biotransformation enzymes as well as for the functioning of the tester bacteria in mutagenicity detection. We also describe here a number of practical considerations in this regard.
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Affiliation(s)
- M Kranendonk
- Department of Genetics, Faculty of Medical Sciences, Universidade Nova de Lisboa, Lisbon, Portugal.
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King LC, Adams L, Allison J, Kohan MJ, Nelson G, Desai D, Amin S, Ross JA. A quantitative comparison of dibenzo[a,l]pyrene-DNA adduct formation by recombinant human cytochrome P450 microsomes. Mol Carcinog 1999. [DOI: 10.1002/(sici)1098-2744(199910)26:2<74::aid-mc2>3.0.co;2-9] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Garner RC, Lightfoot TJ, Cupid BC, Russell D, Coxhead JM, Kutschera W, Priller A, Rom W, Steier P, Alexander DJ, Leveson SH, Dingley KH, Mauthe RJ, Turteltaub KW. Comparative biotransformation studies of MeIQx and PhIP in animal models and humans. Cancer Lett 1999; 143:161-5. [PMID: 10503897 DOI: 10.1016/s0304-3835(99)00118-4] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
MeIQx and PhIP are putative carcinogenic heterocyclic amines formed during the cooking of meat and fish. Using accelerator mass spectrometry, we have investigated the metabolism and macromolecule binding of 14C-labelled MeIQx and PhIP in human cancer patients compared to the rat. Following oral administration of MeIQx and PhIP, more DNA adducts were formed in human colon tissue compared with rats. Differences were also observed between rats and humans in the metabolite profile and urine excretion for these compounds. These results suggest humans metabolise heterocyclic amines differently to laboratory rodents and question their use as models of human risk.
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Affiliation(s)
- R C Garner
- JBUEC, Department of Biology, University of York, UK.
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38
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Kranendonk M, Fisher CW, Roda R, Carreira F, Theisen P, Laires A, Rueff J, Vermeulen NP, Estabrook RW. Escherichia coli MTC, a NADPH cytochrome P450 reductase competent mutagenicity tester strain for the expression of human cytochrome P450: comparison of three types of expression systems. Mutat Res 1999; 439:287-300. [PMID: 10023085 DOI: 10.1016/s1383-5718(98)00193-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Currently three different methods have been taken to develop new mutagenicity tester strains containing human cytochrome P450s (CYPs). Each of these use a single expression vector. In this paper we describe a fourth approach, i.e., the coexpression of a CYP and its electron-transfer flavoprotein, NADPH CYP reductase (RED), encoded by two different expression vectors. The Escherichia coli mutagenicity tester strain BMX100 has been expanded to a strain, MTC which stably expresses human RED. This new tester strain permits the biplasmid coexpression of human CYP1A2 and RED (MTC1A2). This novel strain can be used for the determination of the mutagenicity of chemicals known to be procarcinogens and metabolized by CYP1A2. The mutagenicity tester strain MTC1A2 was compared with: (i) BMX100 using the post-mitochondrial rat liver fraction (S9); (ii) BMX100 with expressing CYP1A2 alone (iii) or with expressing CYP1A2 fused to rat RED or (iv) with expressing CYP1A2, bicistronically coexpressed with rat RED. The biplasmid RED/CYP coexpression system generated a strain with the highest methoxy- and ethoxy-resorufin dealkylase activities and the highest mutagenic activities for the procarcinogens 2-aminoanthracene (2AA), aflatoxin B1 (AFB1) and 2-amino-3-methylimidazo(4,5-f)quinoline (IQ). Furthermore, the metabolism of 2AA and IQ was detected more efficiently using the MTC1A2 strain than with the BMX100 strain plus the standard rodent liver S9 metabolic system.
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Affiliation(s)
- M Kranendonk
- Department of Genetics, Faculty of Medical Sciences, New University of Lisbon, R. de Junqueira 96, P-1300, Lisbon, Portugal
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Guengerich FP, Johnson WW, Shimada T, Ueng YF, Yamazaki H, Langouët S. Activation and detoxication of aflatoxin B1. Mutat Res 1998; 402:121-8. [PMID: 9675258 DOI: 10.1016/s0027-5107(97)00289-3] [Citation(s) in RCA: 206] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Aflatoxin B1 (AFB1) is a potent hepatocarcinogen in experimental animals and a hazard to human health in several parts of the world. Implementation of rational intervention plans requires understanding of aspects of the roles of individual chemical steps involved in its disposition. AFB1 is activated to AFB1 exo-8,9-epoxide primarily by cytochrome P450 (P450) enzymes, particularly P450 3A4. However, P450 3A4 and other P450s also oxidize AFB1 to less dangerous products. The exo-epoxide is unstable in H2O (t1/2 1 s at 25 degreesC, k=0.6 s-1) and the diol product undergoes base-catalyzed rearrangement to a dialdehyde that reacts with protein lysine residues. AFB1 exo-8, 9-epoxide reacts with DNA to give adducts in high yield (>98%). This interaction is characterized by a Kd of approximately 1.4 mM, intercalation between base pairs, and rapid reaction with the guanyl N7 atom (k approximately 40 s-1). A proton field on the periphery of DNA is postulated to catalyze hydrolysis and also conjugation. Rat and especially human epoxide hydrolase show very little rate acceleration of hydrolysis of AFB1 exo- or endo-8,9-epoxide. However, glutathione transferases (GSTs) can catalyze AFB1 exo-8,9-epoxide conjugation. Kinetic analysis indicates a range of ratios of kcat/Kd varying from 10 to 1700 s-1 M-1, with the polymorphic GST M1-1 having the highest activity of the human GSTs. Studies with human hepatocytes indicate a major role for GST M1-1 in AFB1 conjugation and that the model chemoprotective agent oltipraz can act by both inducing GSTs and inhibiting P450s.
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Affiliation(s)
- F P Guengerich
- Department of Biochemistry and Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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41
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Iwata H, Fujita K, Kushida H, Suzuki A, Konno Y, Nakamura K, Fujino A, Kamataki T. High catalytic activity of human cytochrome P450 co-expressed with human NADPH-cytochrome P450 reductase in Escherichia coli. Biochem Pharmacol 1998; 55:1315-25. [PMID: 9719488 DOI: 10.1016/s0006-2952(97)00643-6] [Citation(s) in RCA: 124] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Forms of human cytochrome P450 (P450 or CYP), such as CYP1A1, CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4, were expressed or co-expressed together with human NADPH-P450 reductase in Escherichia coli. When P450 was expressed alone in E. coli, the expression level of holo-P450 ranged from 310 to 1620 nmol/L of culture. The expression level of holo-P450 decreased by co-expression with the reductase, and the level ranged from 66 to 381 nmol/L of culture. The expression level of the reductase varied depending on the forms of P450 co-expressed, and ranged from 204 to 937 U/L of culture. We assayed the catalytic activity of P450 using E. coli cells disrupted by freeze-thaw. When co-expressed with the reductase, human P450 catalyzed the oxidation of representative substrates at efficient rates. The rates appeared comparable to the reported activities of P450 in a reconstituted system containing purified preparations of P450 and the reductase.
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Affiliation(s)
- H Iwata
- Division of Drug Metabolism, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan
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Savas U, Carstens CP, Jefcoate CR. Biological oxidations and P450 reactions. Recombinant mouse CYP1B1 expressed in Escherichia coli exhibits selective binding by polycyclic hydrocarbons and metabolism which parallels C3H10T1/2 cell microsomes, but differs from human recombinant CYP1B1. Arch Biochem Biophys 1997; 347:181-92. [PMID: 9367523 DOI: 10.1006/abbi.1997.0339] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Orthologs of a previously identified CYP1B subfamily designated CYP1B1, which are constitutively expressed in mammary, uterine, and embryonic cells, have previously been functionally linked to 7,12-dimethylbenz-a-anthracene (DMBA) metabolism. A chimeric construct of mouse CYP1B1 in which the 20 NH2-terminal amino acids have been replaced by eight residues from human CYP17 has been expressed in Escherichia coli. This recombinant mouse CYP1B1 (recCYP1B1m) exhibited DMBA metabolism accurately reproducing the characteristic product distribution and specific activity of 3.4 nmol/nmol P450/min seen in C3H10T1/2 cells from which this cDNA has been cloned. The high proportion of 10,11- and 3,4-dihydrodiols and near absence of 5,6-dihyrodiol- and 7-hydroxy-DMBA metabolites are seen only in rodent microsomes where CYP1B1 is highly expressed. This distribution of products from recCYP1B1m was highly dependent on addition of epoxide hydrolase, particularly the ratio of 3,4-dihydrodiol to 4-phenol metabolites. These characteristics in addition to inhibition by antibodies raised to recCYP1B1m establish that the CYP1B1 cDNA indeed encodes the P450 responsible for polycyclic aromatic hydrocarbon (PAH) metabolism from C3H10T1/2 cells. DMBA metabolites from cDNA-expressed human CYP1B1 (recCYP1B1h) however, exhibited a different regioselectivity toward DMBA resembling human CYP1A1 catalyzed DMBA metabolism. Reconstitution of recCYP1B1m with different concentrations of NADPH-P450 reductase indicated a high affinity interaction with an apparent Km of 3 nM. Large PAH such as benz[a]pyrene, benz[e]pyrene, benz[a]anthracene, DMBA, 3-methylcholanthrene, and 1-ethynylpyrene bound to recCYP1B1m with high affinity (Kd 0.08 to 0.22 microM) concomitant with substantial spectral shifts (40% low to high spin state change). Smaller PAHs like pyrene, phenanthrene, and naphthalene neither produced spectral changes nor inhibited the spectral change caused by benz[a]pyrene. Among tested steroids, progesterone bound weakly to recCYP1B1m (Kd > 20 microM) with a comparable spectral shift and was a weak inhibitor of DMBA metabolism, but was not metabolized. While 17beta-estradiol is a substrate for human CYP1B1 we have found no evidence for binding to mouse CYP1B1. This data establishes CYP1B1 as an important contributor to activation of PAHs, particularly in extra hepatic tissues that are susceptible to cancer where CYP1B1 in contrast to CYP1A1 is constitutively expressed.
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Affiliation(s)
- U Savas
- Department of Pharmacology, Medical Science Center, 1300 University Avenue, Madison, Wisconsin 53706, USA
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Abstract
Bacterial mutagenicity assays have been widely used in genotoxicology research for two decades. We discuss the development of such assays, especially the Ames test, with particular attention to strain engineering. Genes encoding enzymes of mutagen bioactivation, including N-acetyltransferase, nitroreductase, and cytochrome P450, have been introduced into tester strains. The processing of DNA damage by the bacterial strains has also been modified in several ways, so as to enhance mutagenesis. These efforts have greatly increased the sensitivity of mutation assays and have illuminated the molecular mechanisms of mutagenesis. We also discuss the relationship between bacterial assays and in vivo mutation assays which use transgenic rodents.
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Affiliation(s)
- P D Josephy
- Guelph-Waterloo Centre for Graduate Work in Chemistry, Department of Chemistry and Biochemistry, University of Guelph, Ontario, Canada
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Blake JA, Pritchard M, Ding S, Smith GC, Burchell B, Wolf CR, Friedberg T. Coexpression of a human P450 (CYP3A4) and P450 reductase generates a highly functional monooxygenase system in Escherichia coli. FEBS Lett 1996; 397:210-4. [PMID: 8955349 DOI: 10.1016/s0014-5793(96)01196-9] [Citation(s) in RCA: 74] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The catalytic activities of recombinant cytochrome P450s expressed in E. coli have been impeded by the absence of endogenous P450 reductase. To solve this problem, we coexpressed P450 reductase with CYP3A4. Membranes from this strain contained 215 pmol P450/mg protein and a reductase activity of 1315 nmol cytochrome c reduced/min per mg. We detected 6beta-hydroxylation of testosterone and oxidation of nifedipine in vivo with turnover numbers of 15.2 and 17.3 min(-1), respectively. These values compare favourably with those obtained using an optimally reconstituted system. Our data demonstrate that a catalytically efficient human P450 system can be generated in E. coli.
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Affiliation(s)
- J A Blake
- Biomedical Research Centre, Ninewells Hospital and Medical School, Dundee, UK
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Guengerich FP, Gillam EM, Shimada T. New applications of bacterial systems to problems in toxicology. Crit Rev Toxicol 1996; 26:551-83. [PMID: 8891430 DOI: 10.3109/10408449609037477] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Bacterial systems have long been of use in toxicology. In addition to providing general models of enzymes and paradigms for biochemistry and molecular biology, they have been adapted to practical genotoxicity assays. More recently, bacteria also have been used in the production of mammalian enzymes of relevance to toxicology. Escherichia coli has been used to express cytochrome P450, NADPH-cytochrome P450 reductase, flavin-containing monooxygenase, glutathione S-transferase, quinone reductase, sulfotransferase, N-acetyltransferase, UDP-glucuronosyl transferase, and epoxide hydrolase enzymes from humans and experimental animals. The expressed enzymes have been utilized in a variety of settings, including coupling with bacterial genotoxicity assays. Another approach has involved expression of mammalian enzymes directly in bacteria for use in genotoxicity systems. Particularly with Salmonella typhimurium. Applications include both the reversion mutagenesis assay and a system using a chimera with an SOS-response indicator and a reporter.
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Affiliation(s)
- F P Guengerich
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
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47
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Abstract
This review considers current approaches to regulatory genotoxicity testing, focusing on how the use of animals can be further replaced, reduced and refined. The complementary roles of in vitro and in vivo testing, and the justification for using animals, are discussed in detail. Recommendations are made for improvements and further work, in the light of the considerable current controversy surrounding the composition and deployment of testing strategies, and the interpretation of the data generated, particularly for carcinogenicity prediction. The major problems are the oversensitivity of in vitro tests and the insensitivity of in vivo assays. On the basis of an analysis of some published databases, it is concluded that there is insufficient support for using in vivo genotoxicity assays for screening. Also, it is questionable whether the scientific benefits of using such assays always outweigh the costs to the animals involved. The considerable efforts being made to harmonise in vivo protocols and to develop improved methods for detecting genotoxicity are discussed. It is recommended that more emphasis be placed on characterising genotoxins in vitro, especially for mechanisms of activity, to optimise the benefits of any confirmatory animal tests.. Also, regulatory agencies are urged to require better-designed and more-scientifically sound protocols, in which animal numbers are minimised and data interpretation, particularly that of negative results, is facilitated. Lastly, in the development and validation of transgenic rodent systems, emphasis should be placed on developing protocols in which other acute toxicity and metabolism endpoints can be measured simultaneously with in vivo mutagenesis, while minimising animal numbers.
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Affiliation(s)
- Robert D. Combes
- FRAME, Russell & Burch House, 96–98 North Sherwood Street, Nottingham NG1 4EE, UK
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