1
|
Li F, Wang P, Fan T, Zhang N, Zhao L, Zhong R, Sun G. Prioritization of the ecotoxicological hazard of PAHs towards aquatic species spanning three trophic levels using 2D-QSTR, read-across and machine learning-driven modelling approaches. JOURNAL OF HAZARDOUS MATERIALS 2024; 465:133410. [PMID: 38185092 DOI: 10.1016/j.jhazmat.2023.133410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Revised: 12/24/2023] [Accepted: 12/29/2023] [Indexed: 01/09/2024]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) represent a common group of environmental pollutants that endanger various aquatic organisms via various pathways. To better prioritize the ecotoxicological hazard of PAHs to aquatic environment, we used 2D descriptors-based quantitative structure-toxicity relationship (QSTR) to assess the toxicity of PAHs toward six aquatic model organisms spanning three trophic levels. According to strict OECD guideline, six easily interpretable, transferable and reproducible 2D-QSTR models were constructed with high robustness and reliability. A mechanistic interpretation unveiled the key structural factors primarily responsible for controlling the aquatic ecotoxicity of PAHs. Furthermore, quantitative read-across and different machine learning approaches were employed to validate and optimize the modelling approach. Importantly, the optimum QSTR models were further applied for predicting the ecotoxicity of hundreds of untested/unknown PAHs gathered from Pesticide Properties Database (PPDB). Especially, we provided a priority list in terms of the toxicity of unknown PAHs to six aquatic species, along with the corresponding mechanistic interpretation. In summary, the models can serve as valuable tools for aquatic risk assessment and prioritization of untested or completely new PAHs chemicals, providing essential guidance for formulating regulatory policies.
Collapse
Affiliation(s)
- Feifan Li
- Beijing Key Laboratory of Environmental and Viral Oncology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China; Solid Waste and Chemicals Management Center, Ministry of Ecology and Environment, Beijing 100029, China
| | - Peng Wang
- Department of Neurosurgery, the First Medical Center of Chinese PLA General Hospital, Beijing 100853, China
| | - Tengjiao Fan
- Beijing Key Laboratory of Environmental and Viral Oncology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China; Department of Medical Technology, Beijing Pharmaceutical University of Staff and Workers, Beijing 100079, China
| | - Na Zhang
- Beijing Key Laboratory of Environmental and Viral Oncology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China
| | - Lijiao Zhao
- Beijing Key Laboratory of Environmental and Viral Oncology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China
| | - Rugang Zhong
- Beijing Key Laboratory of Environmental and Viral Oncology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China
| | - Guohui Sun
- Beijing Key Laboratory of Environmental and Viral Oncology, Faculty of Environment and Life, Beijing University of Technology, Beijing 100124, China.
| |
Collapse
|
2
|
Li H, Wang YG, Ma ZC, Yun-Hang G, Ling S, Teng-Fei C, Guang-Ping Z, Gao Y. A high-throughput cell-based gaussia luciferase reporter assay for measurement of CYP1A1, CYP2B6, and CYP3A4 induction. Xenobiotica 2021; 51:752-763. [PMID: 33896369 DOI: 10.1080/00498254.2021.1918800] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The induction of cytochrome P450s can result in reduced drug efficacy and lead to potential drug-drug interactions. The xenoreceptors-aryl hydrocarbon receptor (AhR), constitutive androstane receptor (CAR), and pregnane X receptor (PXR)-play key roles in CYP induction by xenobiotics. In order to be able to rapidly screen for the induction of three enzymes (CYP1A1, CYP2B6, and CYP3A4), we generated a stable AhR-responsive HepG2 cell line, a stable CAR-responsive HepG2 cell line, and a stable PXR-responsive HepG2 cell line.To validate these stable xenoreceptor-responsive HepG2 cell lines, we evaluated the induction of the different Gaussia reporter activities, as well as the mRNA and protein expression levels of endogenous CYPs in response to different inducers.The induction of luciferase activity in the stable xenoreceptor-responsive HepG2 cell lines by specific inducers occurred in a concentration dependent manner. There was a positive correlation between the induction of luciferase activities and the induction endogenous CYP mRNA expression levels. These xenoreceptor-responsive HepG2 cell lines were further validated with known CYP1A1, CYP2B6, and CYP3A4 inducers.These stable xenoreceptor-responsive HepG2 cell lines may be used in preclinical research for the rapid and sensitive detection of AhR, CAR, and PXR ligands that induce CYP450 isoforms.
Collapse
Affiliation(s)
- Han Li
- Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yu-Guang Wang
- Institute of Radiation Medicine Academy of Military Medical Sciences, Beijing, China
| | - Zeng-Chun Ma
- Institute of Radiation Medicine Academy of Military Medical Sciences, Beijing, China
| | - Gao Yun-Hang
- Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, China
| | - Song Ling
- Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, China
| | - Chen Teng-Fei
- Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, China
| | - Zhang Guang-Ping
- Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, China
| | - Yue Gao
- Institute of Radiation Medicine Academy of Military Medical Sciences, Beijing, China
| |
Collapse
|
3
|
Zhang Y, Chen X, Zhang Y. Analytical chemistry, formation, mitigation, and risk assessment of polycyclic aromatic hydrocarbons: From food processing to
in vivo
metabolic transformation. Compr Rev Food Sci Food Saf 2021; 20:1422-1456. [DOI: 10.1111/1541-4337.12705] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Revised: 12/11/2020] [Accepted: 01/01/2021] [Indexed: 01/09/2023]
Affiliation(s)
- Yiju Zhang
- National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang Key Laboratory for Agro‐Food Processing, Fuli Institute of Food Science, College of Biosystems Engineering and Food Science Zhejiang University Hangzhou China
| | - Xiaoqian Chen
- National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang Key Laboratory for Agro‐Food Processing, Fuli Institute of Food Science, College of Biosystems Engineering and Food Science Zhejiang University Hangzhou China
| | - Yu Zhang
- National Engineering Laboratory of Intelligent Food Technology and Equipment, Zhejiang Key Laboratory for Agro‐Food Processing, Fuli Institute of Food Science, College of Biosystems Engineering and Food Science Zhejiang University Hangzhou China
| |
Collapse
|
4
|
Nabi S, Bhat GA, Iqbal B, Lone MM, Lone GN, Khan MA, Dar NA. Association of Activity Altering Genotypes - Tyr113His and His139Arg in Microsomal Epoxide Hydrolase Enzyme with Esophageal Squamous Cell Carcinoma. Nutr Cancer 2019; 71:806-817. [PMID: 30633570 DOI: 10.1080/01635581.2018.1484934] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The study aimed to explore the relationship of microsomal epoxide hydrolase (mEH) exon 3 (Tyr113His) and exon 4 (His139Arg) polymorphisms and predicted mEH activity with esophageal squamous cell carcinoma (ESCC) risk. 482 histologically confirmed cases and equal number of matched controls were analyzed by polymerase chain reaction-restriction length polymorphism (PCR-RFLP). Conditional logistic regression models were used to examine the association of polymorphisms with ESCC. We noted exon 3 slow genotype (OR = 6.57; CI 3.43-12.57) as well as predicted low mEH activity (OR = 3.99; CI 2.32-6.85) was associated with the ESCC risk. Elevated ESCC risk estimates were seen in smokers independent of genotypes but the association was stronger among smokers with exon 3 variant (OR = 6.67; 3.29-13.53) and low activity (OR = 7.52; CI 3.46-16.37) genotypes. Positive family history of cancer synergistically increased ESCC risk in the individuals who harbored exon 3 (OR = 13.59; CI 5.63-32.81) or altered mEH activity genotypes (OR = 13.35; CI 5.10-34.94). Significant interaction was seen between mEH exon 3 and exon 4 genotypes (P = 0.006) and between predicted mEH activity and positive family history of cancer (P = 0.018). These findings suggest association of ESCC risk with mEH polymorphisms which get modified by tobacco smoking and positive family history of cancer.
Collapse
Affiliation(s)
- Sumaiya Nabi
- a Department of Biochemistry , University of Kashmir , Srinagar , J&K , India
| | - Gulzar Ahmad Bhat
- a Department of Biochemistry , University of Kashmir , Srinagar , J&K , India
| | - Beenish Iqbal
- a Department of Biochemistry , University of Kashmir , Srinagar , J&K , India
| | - Mohd Maqbool Lone
- b Department of Radiation Oncology , SK Institute of Medical Sciences , Srinagar , J&K , India
| | - Ghulam Nabi Lone
- c Department of CVTS , SK Institute of Medical Sciences , Srinagar , J&K , India
| | | | - Nazir Ahmad Dar
- a Department of Biochemistry , University of Kashmir , Srinagar , J&K , India
| |
Collapse
|
5
|
Trumbo-White CM, Hvastkovs EG. Electrochemical Assessment of Sequence Selective DNA Damage from Myoglogin and Cytochrome P450 Bioactivated Benzo[ a]pyrene at TP53 Oligomers. ELECTROANAL 2016. [DOI: 10.1002/elan.201600109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
| | - Eli G. Hvastkovs
- Department of Chemistry; East Carolina University; Greenville, NC
| |
Collapse
|
6
|
Risch P, Pfeifer T, Segrestaa J, Fretz H, Pothier J. Verification of the Major Metabolic Oxidation Path for the Naphthoyl Group in Chemoattractant Receptor-Homologous Molecule Expressed on Th2 Cells (CRTh2) Antagonist 2-(2-(1-Naphthoyl)-8-fluoro-3,4-dihydro-1H-pyrido[4,3-b]indol-5(2H)-yl)acetic Acid (Setipiprant/ACT-129968). J Med Chem 2015; 58:8011-35. [PMID: 26398218 DOI: 10.1021/acs.jmedchem.5b00824] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Various racemic and enantioenriched (trans)-X,Y-dihydroxy-X,Y-dihydronaphthoyl analogues as well as X-hydroxy-naphthoyl analogues of CRTh2 antagonist 2-(2-(1-naphthoyl)-8-fluoro-3,4-dihydro-1H-pyrido[4,3-b]indol-5(2H)-yl)acetic acid (1, Setipiprant/ACT-129968) were synthesized in order to gain insight into regio- and enantioselectivity of the metabolic oxidation of 1 and to verify the structures of four metabolites that were proposed earlier in a clinical ADME study. Analytical data of the synthetic standards were compared with data from samples of biological origin. The two major metabolites M7 and M9 were unambiguously verified as 2-(2-((trans)-3,4-dihydroxy-3,4-dihydronaphthalene-1-carbonyl)- and 2-(2-((trans)-5,6-dihydroxy-5,6-dihydronaphthalene-1-carbonyl)-8-fluoro-3,4-dihydro-1H-pyrido[4,3-b]indol-5(2H)-yl)acetic acid, respectively, each composed of two enantiomers with 68% and 44% ee in favor of (+)-(3S,4S)-M7 and (+)-(5S,6S)-M9, respectively. Likewise, minor metabolites M3 and M13 were identified as 2-(8-fluoro-2-(5-hydroxy-1-naphthoyl)- and 2-(8-fluoro-2-(4-hydroxy-1-naphthoyl)-1,2,3,4-tetrahydro-5H-pyrido[4,3-b]indol-5-yl)acetic acid, respectively.
Collapse
Affiliation(s)
- Philippe Risch
- Drug Discovery Department, Actelion Pharmaceuticals Ltd. , Gewerbestrasse 16, CH-4123 Allschwil, Switzerland
| | - Thomas Pfeifer
- Drug Discovery Department, Actelion Pharmaceuticals Ltd. , Gewerbestrasse 16, CH-4123 Allschwil, Switzerland
| | - Jerome Segrestaa
- Drug Discovery Department, Actelion Pharmaceuticals Ltd. , Gewerbestrasse 16, CH-4123 Allschwil, Switzerland
| | - Heinz Fretz
- Drug Discovery Department, Actelion Pharmaceuticals Ltd. , Gewerbestrasse 16, CH-4123 Allschwil, Switzerland
| | - Julien Pothier
- Drug Discovery Department, Actelion Pharmaceuticals Ltd. , Gewerbestrasse 16, CH-4123 Allschwil, Switzerland
| |
Collapse
|
7
|
Regulatory networks. Methods Mol Biol 2012. [PMID: 23086843 DOI: 10.1007/978-1-62703-059-5_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
The usefulness of mathematical models for the biological regulatory networks relies on the predictive capability of the models in order to suggest interesting hypotheses and suitable biological experiments. All mathematical frameworks dedicated to biological regulatory networks must manage a large number of abstract parameters, which are not directly measurable in the cell. The cornerstone to establish predictive models is the identification of the possible parameter values. Formal frameworks involve qualitative models with discrete values and computer-aided logic reasoning. They can provide the biologists with an automatic identification of the parameters via a formalization of some biological knowledge into temporal logic formulas. For pedagogical reasons, we focus on gene regulatory networks and develop a qualitative model of the detoxification of benzo[a]pyrene in human cells to illustrate the approach.
Collapse
|
8
|
Nandekar PP, Sangamwar AT. Cytochrome P450 1A1-mediated anticancer drug discovery: in silico findings. Expert Opin Drug Discov 2012; 7:771-89. [PMID: 22716293 DOI: 10.1517/17460441.2012.698260] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
INTRODUCTION Target-specific drugs may offer fewer side/adverse effects in comparison with other anticancer agents and thus save normal healthy cells to a greater extent. The selective overexpression of cytochrome P450 1A1 (CYP1A1) in tumor cells induces the metabolism of benzothiazole and aminoflavone compounds to their reactive species, which are responsible for DNA adduct formation and cell death. This review encompasses the novelty of CYP1A1 as an anticancer drug target and explores the possible in silico strategies that would be applicable in the discovery and development of future antitumor compounds. AREAS COVERED This review highlights the various ligand-based and target-based in silico methodologies that were efficiently used in exploration of CYP1A1 as a novel antitumor target. These methodologies include electronic structure analysis, CoMFA studies, homology modeling, molecular docking, molecular dynamics analysis, pharmacophore mapping and quantitative structure activity relationship (QSAR) studies. It also focuses on the various approaches used in the development of the lysyl amide prodrug of 5F-203 (NSC710305) and dimethanesulfonate salt of 5-aminoflavone (NSC710464) as clinical candidates from their less potent analogues. EXPERT OPINION Selective overexpression of CYP1A1 in cancer cells offers tumor-specific drug design to ameliorate the current adverse effects associated with existing antitumor agents. Medicinal chemistry and in vitro driven approaches, in combination with knowledge-based drug design and by using the currently available tools of in silico methodologies, would certainly make it possible to design and develop novel anticancer compounds targeting CYP1A1.
Collapse
Affiliation(s)
- Prajwal P Nandekar
- National Institute of Pharmaceutical Education and Research (NIPER), Department of Pharmacoinformatics, S.A.S. Nagar (Mohali), Punjab-160062, India
| | | |
Collapse
|
9
|
Sato W, Suzuki H, Sasaki T, Kumagai T, Sakaguchi S, Mizugaki M, Miyairi S, Yamazoe Y, Nagata K. Construction of a system that simultaneously evaluates CYP1A1 and CYP1A2 induction in a stable human-derived cell line using a dual reporter plasmid. Drug Metab Pharmacokinet 2010; 25:180-9. [PMID: 20460824 DOI: 10.2133/dmpk.25.180] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Human CYP1A1 and CYP1A2 genes are in a head-to-head orientation on chromosome 15 and are separated by a 23-kb intergenic space. To our knowledge, this is the first report on a stable cell line that contains the 23-kb full-length regulatory region and is able to simultaneously assess the transcriptional activation of CYP1A1 and CYP1A2 genes. The stable cell line that constitutively expresses the reporter activities was constructed by inserting the dual reporter plasmid containing the 23-kb region between the CYP1A1 and CYP1A2 genes into the chromosome. Transcriptional activation of the CYP1A1 and CYP1A2 genes was measured simultaneously using luciferase (Luc) and secreted alkaline phosphatase (SEAP) activities, respectively. To demonstrate the utility of the stable cell line, CYP1A1/1A2 induction by the majority of compounds previously identified as CYP1A1/1A2 inducers was measured. The results clearly show that all compounds caused induction of reporter activities. In addition to assessing transcriptional activation of the CYP1A1 and CYP1A2 genes by measuring reporter activities, we determined the intrinsic CYP1A1 and CYP1A2 mRNA levels by treating them with the same compounds. The results suggest that this stable cell line may be used to rapidly and accurately predict CYP1A1/1A2 induction.
Collapse
Affiliation(s)
- Wataru Sato
- Department of Environmental and Health Science, Tohoku Pharmaceutical University, Sendai, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Widersten M, Gurell A, Lindberg D. Structure–function relationships of epoxide hydrolases and their potential use in biocatalysis. Biochim Biophys Acta Gen Subj 2010; 1800:316-26. [DOI: 10.1016/j.bbagen.2009.11.014] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 11/09/2009] [Accepted: 11/23/2009] [Indexed: 10/20/2022]
|
11
|
Bebianno MJ, Barreira LA. Polycyclic aromatic hydrocarbons concentrations and biomarker responses in the clam Ruditapes decussatus transplanted in the Ria Formosa lagoon. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2009; 72:1849-1860. [PMID: 19539372 DOI: 10.1016/j.ecoenv.2009.03.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2008] [Revised: 03/02/2009] [Accepted: 03/16/2009] [Indexed: 05/27/2023]
Abstract
Clams Ruditapes decussatus were transplanted in the Ria Formosa lagoon and the variation of PAH concentrations in the whole soft tissues measured, along with a suite of biomarkers, including the following: (a) phase I and phase II metabolism of xenobiotics enzymes: benzo[a]pyrene hydroxylase (BPH) and glutathione S-transferase (GST); (b) antioxidant enzymes: superoxide dismutase, catalase and glutathione peroxidases and (c) lipid peroxidation (LPO) levels. Individual PAHs were differently accumulated and eliminated by R. decussatus. During the metabolisation of PAHs by R. decussatus BPH was clearly induced in the digestive gland. Moreover, ROS lead to the induction of protective antioxidant enzymes still causing oxidative damage to membranes. Therefore, BPH seems to be a relevant indicator of PAHs in R. decussatus.
Collapse
Affiliation(s)
- Maria J Bebianno
- CIMA, FCMA-Faculty of Marine and Environmental Sciences, University of Algarve, Campus de Gambelas, 8000-117 Faro, Portugal.
| | | |
Collapse
|
12
|
Aranda E, Ullrich R, Hofrichter M. Conversion of polycyclic aromatic hydrocarbons, methyl naphthalenes and dibenzofuran by two fungal peroxygenases. Biodegradation 2009; 21:267-81. [DOI: 10.1007/s10532-009-9299-2] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2009] [Accepted: 09/09/2009] [Indexed: 11/29/2022]
|
13
|
The role of the dioxin-responsive element cluster between the Cyp1a1 and Cyp1a2 loci in aryl hydrocarbon receptor biology. Proc Natl Acad Sci U S A 2009; 106:4923-8. [PMID: 19261855 DOI: 10.1073/pnas.0809613106] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The aryl hydrocarbon receptor (AHR) plays a central role in 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) hepatotoxicity, regulation of xenobiotic metabolism, and hepatovascular development. Each of these processes appears to be dependent on binding of the AHR to dioxin- responsive elements (DREs) within the genome. The Cyp1a1 and Cyp1a2 loci represent linked genes thought to play important roles in AHR biology. In the mouse, 8 DREs are located in the 14-kb intergenic region between the Cyp1a1 and Cyp1a2 genes. Seven of these DREs, collectively known as the DRE cluster (DREC), are located 1.4 kb upstream of the Cyp1a1 transcriptional start site and 12.6 kb upstream of the Cyp1a2 start site. To investigate the role of the DREC in each aspect of AHR biology, we generated a DREC-deficient mouse model through homologous recombination. Using this mouse model, we demonstrate that the DREC controls the adaptive up-regulation of both Cyp1a1 and Cyp1a2 genes in vivo. Using selected aspects of acute hepatic injury as endpoints, we also demonstrate that DREC null mice are more sensitive to dioxin-induced hepatotoxicity than WT mice. The results of parallel toxicologic studies using individual Cyp1a1 and Cyp1a2 null mice support the observation that up-regulation of these P450s is not the cause of many aspects of dioxin hepatotoxicity. Finally, we observed normal closure of the ductus venosus (DV) in DREC null mice. Given the 100% penetrance of patent DV in Ahr null mice, these results indicate that Cyp1a1 and Cyp1a2 do not play a dominant role in AHR-mediated vascular development.
Collapse
|
14
|
Abstract
Cancer is as a highly complex and multifactorial disease responsible for the death of hundreds of thousands of people in the western countries every year. Since cancer is clonal and due to changes at the level of the genetic material, viruses, chemical mutagens and other exogenous factors such as short-waved electromagnetic radiation that alter the structure of DNA are among the principal causes. The focus of this present review lies on the influence of the molecular structure of two well-investigated chemical carcinogens from the group of polycyclic aromatic hydrocarbons (PAHs), benzo[a]pyrene (BP) and dibenzo[a,l]pyrene (DBP). Although there is only one additional benzo ring present in the latter compound, DBP exerts much stronger genotoxic and carcinogenic effects in certain tumor models as compared to BP. Actually, DBP has been identified as the most potent tumorigen among all carcinogenic PAHs tested to date. The genotoxic effects of both compounds investigated in mammalian cells in culture or in animal models are described. Comparison of enzymatic activation, DNA binding levels of reactive diol-epoxide metabolites, efficiency of DNA adduct repair and mutagenicity provides some clues on why this compound is about 100-fold more potent in inducing tumors than BP. The data published during the past 20 years support and strengthen the idea that compound-inherent physicochemical parameters, along with inefficient repair of certain kinds of DNA lesions formed upon metabolic activation, can be considered as strong determinants for high carcinogenic potency of a chemical.
Collapse
|
15
|
Conserved genomic structure of the Cyp1a1 and Cyp1a2 loci and their dioxin responsive elements cluster. Biochem Pharmacol 2008; 77:654-9. [PMID: 19026991 DOI: 10.1016/j.bcp.2008.10.026] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2008] [Revised: 10/09/2008] [Accepted: 10/13/2008] [Indexed: 02/05/2023]
Abstract
A thorough DNA sequence analysis reveals that the mouse Cyp1a1 and Cyp1a2 loci are located with coding directions opposite to each other. The two genes are separated by approximately 13.9 kb of genomic DNA containing no open reading frames (mCyp1a1_1a2 junction). Within the mCyp1a1_1a2 junction, eight consensus dioxin responsive elements (DREs) are present and seven of the eight DREs located less than 1.4 kb upstream from the Cyp1a1 transcriptional start site. The genomic structure of mouse Cyp1a1 and Cyp1a2 loci is similar to that of human CYP1A1 and CYP1A2 loci. In the human CYP1A1 and CYP1A2 are also arranged in a head to head orientation and separated by a 23 kb genome junction (hCyp1A1_1A2). Comparative sequence analysis between these two genomic junctions demonstrated that the 1.4kb upstream region from the transcriptional start site of mouse Cyp1a1 was highly conserved with that of human CYP1A1. In contrast, there are no conserved DREs in the proximal upstream region of Cyp1a2. The "head to head" genomic structure and position of the DREs cluster region near the Cyp1a1 gene on Cyp1a1_1a2 were confirmed in cattle, dog and rat genome. These results suggest that the conservation of genomic structure of Cyp1a1 and Cyp1a2 genes, and the DREs cluster are important in mammalian biology.
Collapse
|
16
|
Polycyclic Aromatic Hydrocarbons in Food - Scientific Opinion of the Panel on Contaminants in the Food Chain. EFSA J 2008. [DOI: 10.2903/j.efsa.2008.724] [Citation(s) in RCA: 132] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
|
17
|
Wang Y, Schnetz-Boutaud NC, Kroth H, Yagi H, Sayer JM, Kumar S, Jerina DM, Stone MP. 3'-Intercalation of a N2-dG 1R-trans-anti-benzo[c]phenanthrene DNA adduct in an iterated (CG)3 repeat. Chem Res Toxicol 2008; 21:1348-58. [PMID: 18549249 PMCID: PMC2755548 DOI: 10.1021/tx7004103] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The conformation of the 1 R,2 S,3 R,4 S-benzo[ c]phenanthrene- N (2)-dG adduct, arising from trans opening of the (+)-1 S,2 R,3 R,4 S- anti-benzo[ c]phenanthrene diol epoxide, was examined in 5'- d(ATCGC XCGGCATG)-3'.5'-d(CATGCCG CGCGAT)-3', where X = 1 R,2 S,3 R,4 S-B[ c]P- N (2)-dG. This duplex, derived from the hisD3052 frameshift tester strain of Salmonella typhimurium, contains a (CG) 3 iterated repeat, a hotspot for frameshift mutagenesis. NMR experiments showed a disconnection in sequential NOE connectivity between X (4) and C (5), and in the complementary strand, they showed another disconnection between G (18) and C (19). In the imino region of the (1)H NMR spectrum, a resonance was observed at the adducted base pair X (4) x C (19). The X (4) N1H and G (18) N1H resonances shifted upfield as compared to the other guanine imino proton resonances. NOEs were observed between X (4) N1H and C (19) N (4)H and between C (5) N (4)H and G (18) N1H, indicating that base pairs X (4) x C (19) and C (5) x G (18) maintained Watson-Crick hydrogen bonding. No NOE connectivity was observed between X (4) and G (18) in the imino region of the spectrum. Chemical shift perturbations of greater than 0.1 ppm were localized at nucleotides X (4) and C (5) in the modified strand and G (18) and C (19) in the complementary strand. A total of 13 NOEs between the protons of the 1 R-B[ c]Ph moiety and the DNA were observed between B[ c]Ph and major groove aromatic or amine protons at base pairs X (4) x C (19) and 3'-neighbor C (5) x G (18). Structural refinement was achieved using molecular dynamics calculations restrained by interproton distances and torsion angle restraints obtained from NMR data. The B[ c]Ph moiety intercalated on the 3'-face of the X (4) x C (19) base pair such that the terminal ring of 1 R-B[ c]Ph threaded the duplex and faced into the major groove. The torsion angle alpha' [X (4)]-N3-C2-N2-B[ c]Ph]-C1 was calculated to be -177 degrees, maintaining an orientation in which the X (4) exocyclic amine remained in plane with the purine. The torsion angle beta' [X (4)]-C2-N2-[B[ c]Ph]-C1-C2 was calculated to be 75 degrees. This value governed the 3'-orientation of the B[ c]Ph moiety with respect to X (4). The helical rise between base pairs X (4) x C (19) and C (5) x G (18) increased and resulted in unwinding of the right-handed helix. The aromatic rings of the B[ c]Ph moiety were below the Watson-Crick hydrogen-bonding face of the modified base pair X (4) x C (19). The B[c]Ph moiety was stacked above nucleotide G (18), in the complementary strand.
Collapse
Affiliation(s)
- Yazhen Wang
- Department of Chemistry, Center in Molecular Toxicology, and the Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235
| | - Nathalie C. Schnetz-Boutaud
- Department of Chemistry, Center in Molecular Toxicology, and the Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235
| | - Heiko Kroth
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, Maryland 20892
| | - Haruhiko Yagi
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, Maryland 20892
| | - Jane M. Sayer
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, Maryland 20892
| | - Subodh Kumar
- Environmental Toxicology and Chemistry Laboratory, Great Lakes Center, State University of New York College at Buffalo, Buffalo, New York 14222
| | - Donald M. Jerina
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, Maryland 20892
| | - Michael P. Stone
- Department of Chemistry, Center in Molecular Toxicology, and the Vanderbilt-Ingram Cancer Center, Vanderbilt University, Nashville, Tennessee 37235
| |
Collapse
|
18
|
Pandey MK, Yadav S, Parmar D, Das M. Induction of hepatic cytochrome P450 isozymes, benzo(a)pyrene metabolism and DNA binding following exposure to polycyclic aromatic hydrocarbon residues generated during repeated fish fried oil in rats. Toxicol Appl Pharmacol 2005; 213:126-34. [PMID: 16263147 DOI: 10.1016/j.taap.2005.09.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Revised: 09/28/2005] [Accepted: 09/28/2005] [Indexed: 12/01/2022]
Abstract
In the present study the effect of repeated fish fried oil (RFFO) and its extract (RFFE) on hepatic cytochrome P450 (CYP) isozymes, benzo(a)pyrene (BP) metabolism and DNA adduct formation was undertaken. HPLC analysis of RFFO showed the presence of several polycyclic aromatic hydrocarbons. CYP in microsomes from control and RFFO-treated animals showed a peak at 450 nm; however, a shift of 2 nm in the SORET region along with significant induction was observed in microsomes prepared from 3-methylcholanthrene (MC)- and RFFE-treated animals. Activities of hepatic ethoxyresorufin-O-deethylase, methoxyresorufin-O-deethylase, aryl hydrocarbon hydroxylase and erythromycin-N-demethylase were found to be significantly (P < 0.05) induced following exposure of RFFE, whereas none of these enzymes were altered in RFFO-treated group. Immunoblot analysis revealed that RFFE and MC were potent inducers of CYP1A1, 1A1/2 and 3A1 isozymes, where as RFFO showed no change in these protein levels. RT-PCR analysis showed induction of cDNA of CYP1A1 and CYP3A1 by RFFE treatment. Hepatic microsomes prepared from RFFE exposed animals enhanced BP metabolism with a concomitant increase in the relative proportion of BP 7,8-diol. Hepatic microsomes prepared from animals pretreated with RFFE and MC significantly enhanced the binding of [(3)H]-BP to calf thymus DNA. The overall results suggest that exposure to RFFE may induce hepatic CYP isozymes thereby producing enhanced reactive metabolites with a potential to bind with DNA that may result in cancer.
Collapse
Affiliation(s)
- Manoj K Pandey
- Food Toxicology Laboratory, Industrial Toxicology Research Centre, MG Marg, PO Box 80, Lucknow-226001, India
| | | | | | | |
Collapse
|
19
|
Xue W, Warshawsky D. Metabolic activation of polycyclic and heterocyclic aromatic hydrocarbons and DNA damage: a review. Toxicol Appl Pharmacol 2005; 206:73-93. [PMID: 15963346 DOI: 10.1016/j.taap.2004.11.006] [Citation(s) in RCA: 587] [Impact Index Per Article: 30.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2004] [Revised: 11/01/2004] [Accepted: 11/03/2004] [Indexed: 02/07/2023]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic compounds (HACs) constitute a major class of chemical carcinogens present in the environment. These compounds require activation to electrophilic metabolites to exert their mutagenic or carcinogenic effects. There are three principal pathways currently proposed for metabolic activation of PAH and HAC: the pathway via bay region dihydrodiol epoxide by cytochrome P450 enzymes (CYPs), the pathway via radical cation by one-electron oxidation, and the ortho-quinone pathway by dihydrodiol dehydrogenase (DD). In addition to these major pathways, a brief description of a minor metabolic activation pathway, sulfonation, for PAHs that contain a primary benzylic alcoholic group or secondary hydroxyl group(s) is included in this review. The DNA damages caused through the reactive metabolites of PAH/HAC are described involving the DNA covalent binding to form stable or depurinating adducts, the formation of apurinic sites, and the oxidative damage. The review emphasizes the chemical/biochemical reactions involved in the metabolic processes and the chemical structures of metabolites and DNA adducts.
Collapse
Affiliation(s)
- Weiling Xue
- Department of Environmental Health, University of Cincinnati Medical Center, 3223 Eden Avenue, Cincinnati, OH 45267-0056, USA
| | | |
Collapse
|
20
|
Turner F, Smith G, Sachse C, Lightfoot T, Garner RC, Wolf CR, Forman D, Bishop DT, Barrett JH. Vegetable, fruit and meat consumption and potential risk modifying genes in relation to colorectal cancer. Int J Cancer 2004; 112:259-64. [PMID: 15352038 DOI: 10.1002/ijc.20404] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Epidemiological evidence shows high red meat consumption to increase the risk of colorectal cancer, while the consumption of fruit and vegetables has been shown to be protective. Many genes have been identified that encode for enzymes involved in the metabolism of dietary carcinogens or anti-carcinogens. A study of 500 incident colorectal cancer cases and population controls, matched for age, sex and general practitioner, was conducted in the United Kingdom to investigate whether 6 such genes (CYP1A1, GSTT1, GSTM1, GSTP1, EPHX1 and NQO1) modify the relationship between diet and disease risk. Usual diet was estimated using a detailed questionnaire administered by interview. Fruit and vegetable consumption were both found to protect against colorectal cancer, while overall meat and red meat consumption were found to increase risk. There was some evidence of interaction between GSTT1 and vegetable consumption (p=0.006, not adjusted for multiple tests) but no evidence of interaction with GSTM1. The protective effect of vegetables was only seen in those with deficient or intermediate GSTT1 predicted phenotype [OR 0.3, 95% confidence interval (0.1, 0.6), and OR 0.6 (0.4, 0.96), OR 1.4 (0.3, 2.4) for those with fast phenotype], and a similar result was observed for cruciferous vegetables. There was also weak evidence of interaction between red meat intake and GSTT1 (p=0.06), GSTP1 (p=0.16, with p=0.02 after adjustment for potential confounders) and NQO1 predicted phenotype (p=0.01). Because of the multiple hypotheses tested in our study, these findings require independent confirmation.
Collapse
Affiliation(s)
- Faye Turner
- Genetic Epidemiology Division, Cancer Research UK Clinical Centre, St. James's University Hospital, Leeds, United Kingdom.
| | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Shimada T, Fujii-Kuriyama Y. Metabolic activation of polycyclic aromatic hydrocarbons to carcinogens by cytochromes P450 1A1 and 1B1. Cancer Sci 2004; 95:1-6. [PMID: 14720319 PMCID: PMC11158916 DOI: 10.1111/j.1349-7006.2004.tb03162.x] [Citation(s) in RCA: 526] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2003] [Revised: 11/25/2003] [Accepted: 11/25/2003] [Indexed: 11/29/2022] Open
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitously distributed environmental chemicals. PAHs acquire carcinogenicity only after they have been activated by xenobiotic-metabolizing enzymes to highly reactive metabolites capable of attacking cellular DNA. Cytochrome P450 (CYP) enzymes are central to the metabolic activation of these PAHs to epoxide intermediates, which are converted with the aid of epoxide hydrolase to the ultimate carcinogens, diol-epoxides. Historically, CYP1A1 was believed to be the only enzyme that catalyzes activation of these procarcinogenic PAHs. However, recent studies have established that CYP1B1, a newly identified member of the CYP1 family, plays a very important role in the metabolic activation of PAHs. In CYP1B1 gene-knockout mice treated with 7,12-dimethylbenz[a]anthracene and dibenzo[a,l]pyrene, decreased rates of tumor formation were observed, when compared to wild-type mice. Significantly, gene expression of CYP1A1 and 1B1 is induced by PAHs and polyhalogenated hydrocarbons such as 2,3,7,8-tetrachlorodibenzo-p-dioxin through the arylhydrocarbon receptor. Differences in the susceptibility of individuals to the adverse action of PAHs may, in part, be due to differences in the levels of expression of CYP1A1 and 1B1 and to genetic variations in the CYP1A1 and 1B1 genes.
Collapse
Affiliation(s)
- Tsutomu Shimada
- Osaka Prefectural Institute of Public Health, Higashinari-ku, Osaka 537-0025, Japan.
| | | |
Collapse
|
22
|
Abstract
Understanding the binding of ligands in the active site of a membrane-bound protein is difficult in the absence of a crystal structure. When these proteins are the enzymes involved in drug metabolism, it leaves little option but to use site-directed mutagenesis and in vitro studies to provide critical information relating to determinants of binding affinity. Pharmacophore models and three-dimensional quantitative structure-activity relationships have been used either alone or in combination with protein homology models to provide this information for cytochrome P450s. At present, their application has been directed to the major enzymes but this may escalate in future as more in vitro data are generated for other P450s. The following review outlines the methodologies and models as well as future prospects for applying these technologies to P450s in the hope that future drugs will be selected with increased metabolic stability and fewer incidences of undesirable drug-drug interactions.
Collapse
Affiliation(s)
- Marcel J de Groot
- Department of Molecular Informatics, Structure and Design, Pfizer Global Research and Development, Sandwich Laboratories, Kent CT13 9NJ, Sandwich, UK.
| | | |
Collapse
|
23
|
Zusterzeel PL, Peters WH, Visser W, Hermsen KJ, Roelofs HM, Steegers EA. A polymorphism in the gene for microsomal epoxide hydrolase is associated with pre-eclampsia. J Med Genet 2001; 38:234-7. [PMID: 11283205 PMCID: PMC1734856 DOI: 10.1136/jmg.38.4.234] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVE Microsomal epoxide hydrolase is an important enzyme involved in the metabolism of endogenous and exogenous toxicants. Polymorphic variants of the human epoxide hydrolase gene vary in enzyme activity. We determined whether genetic variability in the gene encoding for microsomal epoxide hydrolase contributes to individual differences in susceptibility to the development of pre-eclampsia with or without the syndrome of Haemolysis, Elevated Liver enzymes, and Low Platelets (HELLP). METHODS A total of 183 non-pregnant women with a history of pre-eclampsia, 96 of whom had concurrently developed the HELLP syndrome, and 151 healthy female controls were genotyped for the 113Tyr-->His polymorphism in exon 3 and the 139His-->Arg polymorphism in exon 4 of the epoxide hydrolase gene by a polymerase chain reaction-restriction fragment length polymorphism assay. Chi-square analysis was used for statistical evaluation of differences in polymorphic rates. RESULTS In pre-eclampsia a higher frequency (29%) of the high activity genotype Tyr113 Tyr113 in exon 3 was found as compared to controls (16%, OR 2.0, 95% CI 1.2-3.7). There was no difference between groups for the 139His-->Arg polymorphism. In women with a history of pre-eclampsia, no difference in epoxide hydrolase genotypes was found between women who either did or did not develop the HELLP syndrome. In addition, a significant association was found between predicted EPHX activity and pre-eclampsia. CONCLUSIONS Women with the high activity genotype in exon 3, which could reflect differences in metabolic activation of endogenous or exogenous toxic compounds, may have enhanced susceptibility to pre-eclampsia. However, polymorphisms in the epoxide hydrolase gene do not seem to influence the risk for concurrent development of the HELLP syndrome.
Collapse
Affiliation(s)
- P L Zusterzeel
- Department of Obstetrics and Gynaecology, University Hospital Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | | | | | | | | | | |
Collapse
|
24
|
Corchero J, Pimprale S, Kimura S, Gonzalez FJ. Organization of the CYP1A cluster on human chromosome 15: implications for gene regulation. PHARMACOGENETICS 2001; 11:1-6. [PMID: 11207026 DOI: 10.1097/00008571-200102000-00001] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The sequence and organization of the CYP1A cluster on human chromosome 15 was determined. A human genomic clone from a BAC library, containing both CYP1A1 and CYP1A2 genes, was isolated and sequenced. The results of Southern blot analysis using human genomic DNA were compatible with the structure of the BAC clone. The CYP1A1 and CYP1A2 genes are separated by a 23 kb segment that contains no other open reading frames. The CYP1A1 and CYP1A2 genes are in opposite orientation, revealing that the 5' flanking region is in common between the two genes. Analysis of the sequence obtained revealed the presence of xenobiotic response elements (XREs) previously reported for CYP1A1 and CYP1A2 and several additional consensus sequences for putative XREs. The presence of all the XREs upstream of both genes suggest that some of the regulatory elements known to control CYP1A1 gene expression, could also control CYP1A2 gene expression.
Collapse
Affiliation(s)
- J Corchero
- Laboratory of Metabolism, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | | | | | | |
Collapse
|
25
|
Miller KP, Ramos KS. Impact of cellular metabolism on the biological effects of benzo[a]pyrene and related hydrocarbons. Drug Metab Rev 2001; 33:1-35. [PMID: 11270659 DOI: 10.1081/dmr-100000138] [Citation(s) in RCA: 230] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Polycyclic aromatic hydrocarbons are ubiquitous contaminants in the environment. Benzo[a]pyrene (BaP), a prototypical member of this class of chemicals, has been extensively studied for its toxic effects in laboratory animals and human populations. BaP toxicity is often mediated by oxidative metabolism to reactive intermediates that interact with macromolecules leading to alterations in target cell structure and function. More recent evidence suggests that disruption of cellular signaling pathways involved in the regulation of growth and differentiation contribute significantly to the toxicity of BaP and its metabolites. This review summarizes recent advances in our understanding of biological mechanisms of BaP toxicity at the molecular level, and the role of metabolic intermediates in carcinogenesis, atherogenesis, and teratogenesis.
Collapse
Affiliation(s)
- K P Miller
- Department of Veterinary Physiology and Pharmacology & Center for Environmental and Rural Health, Texas A&M University, College Station, USA
| | | |
Collapse
|
26
|
Harrison DJ, Hubbard AL, MacMillan J, Wyllie AH, Smith CA. Microsomal epoxide hydrolase gene polymorphism and susceptibility to colon cancer. Br J Cancer 1999; 79:168-71. [PMID: 10408710 PMCID: PMC2362155 DOI: 10.1038/sj.bjc.6690028] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
We examined polymorphisms in exons 3 and 4 of microsomal epoxide hydrolase in 101 patients with colon cancer and compared the results with 203 control samples. The frequency of the exon 3 T to C mutation was higher in cancer patients than in controls (odds ratio 3.8; 95% confidence intervals 1.8-8.0). This sequence alteration changes tyrosine residue 113 to histidine and is associated with lower enzyme activity when expressed in vitro. This suggests that putative slow epoxide hydrolase activity may be a risk factor for colon cancer. This appears to be true for both right- and left-sided tumours, but was more apparent for tumours arising distally (odds ratio 4.1; 95% confidence limits 1.9-9.2). By contrast, there was no difference in prevalence of exon 4 A to G transition mutation in cancer vs controls. This mutation changes histidine residue 139 to arginine and produces increased enzyme activity. There was no association between epoxide hydrolase genotype and abnormalities of p53 or Ki-Ras.
Collapse
Affiliation(s)
- D J Harrison
- CRC Laboratories, Department of Pathology, University of Edinburgh, UK
| | | | | | | | | |
Collapse
|
27
|
|
28
|
De Groot MJ, Vermeulen NP. Modeling the active sites of cytochrome P450s and glutathione S-transferases, two of the most important biotransformation enzymes. Drug Metab Rev 1997; 29:747-99. [PMID: 9262946 DOI: 10.3109/03602539709037596] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
- M J De Groot
- Leiden/Amsterdam Center for Drug Research, Department of Pharmacochemistry, Vrije Universiteit, Amsterdam, The Netherlands
| | | |
Collapse
|
29
|
Chary P, Harris CM, Harris TM, Lloyd RS. Differential tolerance to DNA polymerization by HIV-1 reverse transcriptase on N6 adenine C10R and C10S benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxide-adducted templates. J Biol Chem 1997; 272:5805-13. [PMID: 9038195 DOI: 10.1074/jbc.272.9.5805] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
To determine the effect of various stereoisomers of benzo[a]pyrene-7,8-dihydrodiol 9,10-epoxide (BPDE) on translesion bypass by human immunodeficiency virus-1 reverse transcriptase and its alpha-helix H mutants, six 33-mer templates were constructed bearing site- and stereospecific adducts. This in vitro model system was chosen to understand the structure-function relationships between the polymerase and damaged DNA during replication. Comparison of the replication pattern between wild type human immunodeficiency virus-1 reverse transcriptase and its mutants, using primers which were 3' to the lesion, revealed essentially similar patterns. While these primers terminated with all three of the C10R and two of the C10S BPDE-adducted templates 1 base 5' and 1 base 3' to the damaged site respectively, (+)-anti-trans-(C10S) BPDE-adducted DNA alone permitted the formation of full-length products. Utilization of a primer with its 3'-hydroxyl 1 base beyond the lesion resulted in full-length products with all the C10S BPDE-adducted templates and the (-)-syn-trans-(C10R)-BPDE-adducted template, following replication with either the wild type or mutant enzymes. However, the other two C10R BPDE-adducted templates failed to allow any primer extension, even with the wild type enzyme. Although T.P depletion studies further confirmed the differential primer extension abilities using the C10R and C10S adducted templates, their binding affinities were similar, yet distinct from the unadducted template.
Collapse
Affiliation(s)
- P Chary
- Center for Molecular Science, The University of Texas Medical Branch, Galveston, Texas 77555, USA
| | | | | | | |
Collapse
|
30
|
Shou M, Gonzalez FJ, Gelboin HV. Stereoselective epoxidation and hydration at the K-region of polycyclic aromatic hydrocarbons by cDNA-expressed cytochromes P450 1A1, 1A2, and epoxide hydrolase. Biochemistry 1996; 35:15807-13. [PMID: 8961944 DOI: 10.1021/bi962042z] [Citation(s) in RCA: 73] [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
Stereoselective epoxidation by cytochrome P450s (P450s) and regioselective hydration by epoxide hydrolase determine the carcinogenic potency of some polycyclic aromatic hydrocarbons (PAHs). In this report, cDNA-expressed human and mouse P450s 1A1 and 1A2 and epoxide hydrolase were used to characterize the stereoselective epoxidation and regioselective hydration at the K-region of benz[a]-anthracene (BA), 7,12-dimethylbenz[a]anthracene (DMBA), chrysene (CR), benzo[a]pyrene (B[a]P), dibenz[a,h]anthracene (DB[a,h]A), and benzo[c]phenanthrene (B[c]Ph) by direct chiral stationary-phase HPLC (CSP-HPLC) analyses. Our results indicated that all P450 isoforms preferentially produced major K-region, S,R-epoxides of BA (95-98%), DMBA (94-97%), B[a]P (91-96%), DB[a,h]A (94-98%), and B[c]Ph (87-92%), and major R,S-epoxide of CR (74-85%) in the presence of 3,3,3-trichloropropylene 1,2-oxide (TCPO), an inhibitor of epoxide hydrolase, suggesting that P450 enzymes exhibited the high stereoselectivity toward one of two stereoheterotopic faces of K-region double bond of the PAHs. Epoxide hydrolase either expressed from recombinant vaccinia virus or contained in human hepatoma G2 cells (HepG2) hydrated the C-O bond of epoxy-ring at the S-carbon of major metabolically-formed K-region epoxide enantiomers of BA, CR, DMBA, B[a]P, and DB[a,h]A to yield 80-98% dihydrodiols enriched in R,R-form and that at the R-carbon of B[c]Ph epoxide to yield 77-92% dihydrodiol enriched in S,S-form, suggesting that epoxide hydrolase was highly regioselective. The various enantiomeric components of dihydrodiol products in the metabolism of PAHs were apparently due to the combined effect of stereoselectivity of the P450s and regioselectivity of epoxide hydrolase. Our results provide a clear understanding of how these enzymes catalyze overall stereoselective metabolism at the K-region of the PAHs.
Collapse
Affiliation(s)
- M Shou
- Laboratory of Molecular Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | |
Collapse
|
31
|
Mumtaz MM, George JD, Gold KW, Cibulas W, DeRosa CT. ATSDR evaluation of health effects of chemicals. IV. Polycyclic aromatic hydrocarbons (PAHs): understanding a complex problem. Toxicol Ind Health 1996; 12:742-971. [PMID: 9050165 DOI: 10.1177/074823379601200601] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Polycyclic Aromatic Hydrocarbons (PAHs) are a group of chemicals that are formed during the incomplete burning of coal, oil, gas, wood, garbage, or other organic substances, such as tobacco and charbroiled meat. There are more than 100 PAHs. PAHs generally occur as complex mixtures (for example, as part of products such as soot), not as single compounds. PAHs are found throughout the environment in the air, water, and soil. As part of its mandate, the Agency for Toxic Substances and Disease Registry (ATSDR) prepares toxicological profiles on hazardous chemicals, including PAHs (ATSDR, 1995), found at facilities on the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) National Priorities List (NPL) and which pose the most significant potential threat to human health, as determined by ATSDR and the Environmental Protection Agency (EPA). These profiles include information on health effects of chemicals from different routes and durations of exposure, their potential for exposure, regulations and advisories, and the adequacy of the existing database. Assessing the health effects of PAHs is a major challenge because environmental exposures to these chemicals are usually to complex mixtures of PAHs with other chemicals. The biological consequences of human exposure to mixtures of PAHs depend on the toxicity, carcinogenic and noncarcinogenic, of the individual components of the mixture, the types of interactions among them, and confounding factors that are not thoroughly understood. Also identified are components of exposure and health effects research needed on PAHs that will allow estimation of realistic human health risks posed by exposures to PAHs. The exposure assessment component of research should focus on (1) development of reliable analytical methods for the determination of bioavailable PAHs following ingestion, (2) estimation of bioavailable PAHs from environmental media, particularly the determination of particle-bound PAHs, (3) data on ambient levels of PAHs metabolites in tissues/fluids of control populations, and (4) the need for a critical evaluation of current levels of PAHs found in environmental media including data from hazardous waste sites. The health effects component should focus on obtaining information on (1) the health effects of mixtures of PAHs particularly their noncarcinogenic effects in humans, and (2) their toxicokinetics. This report provides excerpts from the toxicological profile of PAHs (ATSDR, 1995) that contains more detailed information.
Collapse
Affiliation(s)
- M M Mumtaz
- Agency for Toxic Substances and Disease Registry, Public Health Service, U.S. Department of Health and Human Services, Atlanta, Georgia, USA.
| | | | | | | | | |
Collapse
|
32
|
Bosch I, Croop J. P-glycoprotein multidrug resistance and cancer. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1288:F37-54. [PMID: 8876632 DOI: 10.1016/0304-419x(96)00022-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- I Bosch
- Division of Pediatric Oncology, Dana-Farber Cancer Institute, Children's Hospital, Harward Medical School, Boston, MA 02115, USA
| | | |
Collapse
|
33
|
Lewis DF, Lake BG. Molecular modelling of CYP1A subfamily members based on an alignment with CYP102: rationalization of CYP1A substrate specificity in terms of active site amino acid residues. Xenobiotica 1996; 26:723-53. [PMID: 8819302 DOI: 10.3109/00498259609046745] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
1. Using a novel amino acid sequence alignment, proteins of the CYP1A subfamily have been produced from the CYP102 crystal structure template via residue replacement and energy minimization procedures. 2. Known substrates and inhibitors of CYP1A1 and CYP1A2 are shown to fit their respective active sites via key interactions with complementary amino acid residues. Substrates used in the modelling studies include: caffeine, PhIP, oestradiol, 2,4- and 2,5-diaminotoluenes, Glu-P-1, phenacetin, acetanilide, 7-methoxy and 7-ethoxyresorufins, 11-methyl cyclopenta[a]phenanthren-17-one, 7-ethoxycoumarin, aflatoxin B1, benzo[a]pyrene, benzo[a]pyrene-7,8-diol and 1'-hydroxy 3-methylcholanthrene. 3. A number of aspects relating to CYP1A substrate specificity and metabolism can be explained in terms of the enzyme models, as it is found that key interactions with active site amino acid residues direct CYP1A-mediated metabolism in the known positions.
Collapse
Affiliation(s)
- D F Lewis
- School of Biological Sciences, University of Surrey, Guildford, UK
| | | |
Collapse
|
34
|
Ford JM, Yang JM, Hait WN. P-glycoprotein-mediated multidrug resistance: experimental and clinical strategies for its reversal. Cancer Treat Res 1996; 87:3-38. [PMID: 8886447 DOI: 10.1007/978-1-4613-1267-3_1] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The study of the cellular, biochemical, and molecular biology and pharmacology of MDR has provided one of the most active and exciting areas within cancer research and one that holds great promise for translation into clinical benefit. While convincing evidence for the functional role of P-gp in mediating clinical drug resistance in humans remains elusive, studies of the clinical expression of P-gp and trials of chemosensitizers with cancer chemotherapy suggest "resistance modification" strategies may be effective in some tumors with intrinsic or acquired drug resistance. However, even if P-gp-associated MDR proves to be a relevant and reversible cause of clinical drug resistance, numerous problems remain to be solved before effective clinical chemosensitization may be achieved. Such factors as absorption, distribution, and metabolism; the effect of chemosensitizers on chemotherapeutic drug clearance; toxicity to normal tissues expressing P-gp; and the most efficacious modulator regimens all remain to be defined in vivo. Clearly, the identification of more specific, potent, and less clinically toxic chemosensitizers for clinical use remains critical to the possible success of this approach. Nonetheless, the finding that a number of pharmacological agents can antagonize a well-characterized form of experimental drug resistance provides promise for potential clinical applications. Further study of chemosensitizers in humans and the rational design of novel chemosensitizers with improved activity should define the importance of MDR in clinically resistant cancer.
Collapse
Affiliation(s)
- J M Ford
- Department of Biological Sciences, Herrin Biology Laboratories, Stanford University, CA 94305-5020, USA
| | | | | |
Collapse
|
35
|
Shou M, Korzekwa KR, Krausz KW, Crespi CL, Gonzalez FJ, Gelboin HV. Regio- and stereo-selective metabolism of phenanthrene by twelve cDNA-expressed human, rodent, and rabbit cytochromes P-450. Cancer Lett 1994; 83:305-13. [PMID: 8062229 DOI: 10.1016/0304-3835(94)90334-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The regio- and stereoselective metabolism of phenanthrene (PA) by seven cDNA-expressed human and five rodent and rabbit cytochromes P-450 has been examined using reverse-phase and chiral stationary phase high-pressure liquid chromatography (HPLC). Turnover numbers ranged from 0.2 to 55 nmol/min per nmol. Using vaccinia virus expression of P-450 enzymes in Hep G2 cells, m1A1 and m1A2 were found to be the most active P-450s. Of the human P-450s, 1A2 and 2B6 have the highest activity and 2C9 has moderate activity. Using cytochrome P-450s expressed in a lymphoblastoid cell line in presence of epoxide hydrolase (EH), human 1A1 had approximately twice the activity of human 1A2. Regioselectivities for PA metabolism were found to be both isozyme and species-dependent. Stereochemical analysis revealed that the P-450s 1A1, m1A1, m1A2, r2A1, r2B1, PB- and 3MC-treated rat liver microsomes preferentially formed 3R,4R-diol enantiomer (88-97%), whereas rabbit 4B formed the 3S,4S-diol enantiomer (72%). Eleven P-450s, 3MC and PB microsomes preferentially formed 1R,2R-diol enantiomer (80-96%). This is the same stereochemistry as the precursors to some diol epoxides that are potent carcinogens.
Collapse
Affiliation(s)
- M Shou
- Laboratory of Molecular Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892
| | | | | | | | | | | |
Collapse
|
36
|
Shou M, Korzekwa KR, Crespi CL, Gonzalez FJ, Gelboin HV. Metabolism of Benzo[a]pyrene by Seven cDNA Expressed Human Cytochromes P450. Polycycl Aromat Compd 1994. [DOI: 10.1080/10406639408014706] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
37
|
Funk M, Frank H, Oesch F, Platt K. Development of chiral stationary phases for the enantiomeric resolution of dihydrodiols of polycyclic aromatic hydrocarbons by π-donor-acceptor interactions. J Chromatogr A 1994. [DOI: 10.1016/0021-9673(94)85006-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
38
|
|
39
|
|
40
|
Koymans L, Donné-op den Kelder GM, Koppele Te JM, Vermeulen NP. Cytochromes P450: their active-site structure and mechanism of oxidation. Drug Metab Rev 1993; 25:325-87. [PMID: 8404461 DOI: 10.3109/03602539308993979] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- L Koymans
- Department of Pharmacochemistry, Faculty of Chemistry, Free University, Amsterdam, The Netherlands
| | | | | | | |
Collapse
|
41
|
Jansen EH, de Fluiter P. Detection of the enzymatic activity of cytochrome P-450 enzymes by high-performance liquid chromatography. JOURNAL OF CHROMATOGRAPHY 1992; 580:325-46. [PMID: 1400829 DOI: 10.1016/0378-4347(92)80541-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The reactions catalysed by the various cytochrome P-450 enzymes are reviewed with respect to the analysis of products by high-performance liquid chromatography (HPLC). Especially biotransformation reactions of purified cytochrome P-450 enzymes in a reconstituted system and in microsomes mainly of rat liver origin are considered. Emphasis is put on the specificity of product formation due to the individual isozymes of cytochrome P-450. It is shown that the presence of eight cytochrome P-450 isozymes can be monitored and determined by specific product formation after HPLC analysis, which is an important parameter in toxicological studies.
Collapse
Affiliation(s)
- E H Jansen
- Laboratory for Toxicology, National Institute of Public Health and Environmental Protection, Bilthoven, Netherlands
| | | |
Collapse
|
42
|
Rao SI, Duffel MW. Inhibition of rat hepatic aryl sulphotransferase IV by dihydrodiol derivatives of benzo[a]pyrene and naphthalene. Xenobiotica 1992; 22:247-55. [PMID: 1632113 DOI: 10.3109/00498259209046623] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
1. Although neither the (+)- nor (-)-enantiomer of trans-benzo[a]pyrene-7,8-dihydrodiol was a substrate for aryl sulphotransferase IV from rat liver, both enantiomers inhibited the enzyme-catalysed sulphation of 1-naphthalene-methanol with Ki values of 3.7 +/- 0.4 microM for the (+)-enantiomer, and 4.4 +/- 0.3 microM for the (-)-enantiomer. 2. Based on the magnitude of the Ki values, the binding affinity of these dihydrodiols for the aryl sulphotransferase was significantly greater than that for the corresponding phenolic derivatives of benzo[a]pyrene. That is 7-hydroxybenzo[a]pyrene and 8-hydroxybenzo[a]pyrene were both substrates for aryl sulphotransferase IV, with apparent Km values of 280 +/- 41 microM and 370 +/- 72 microM, respectively. 3. Both (+)- and (-)-trans-naphthalene-1,2-dihydrodiols were also inhibitors of aryl sulphotransferase IV, but with higher Ki values than would be expected from previously determined apparent Km and Ki values for (R)-(-)- and (S)-(+)-1,2,3,4-tetrahydro-1-naphthols, respectively.
Collapse
Affiliation(s)
- S I Rao
- Division of Medicinal and Natural Products Chemistry, College of Pharmacy, University of Iowa, Iowa City 52242
| | | |
Collapse
|
43
|
Lambard SE, Burnett AK, Wolf CR, Craft JA. The role of specific cytochromes P450 in the formation of 7,12-dimethylbenz(a)anthracene-protein adducts in rat liver microsomes in vitro. Biochem Pharmacol 1991; 42:1529-35. [PMID: 1930280 DOI: 10.1016/0006-2952(91)90421-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The role of specific cytochrome P450 (P450) isoforms in the formation of adducts of 7,12-dimethylbenz(a)anthracene metabolites and membrane proteins has been investigated in vitro with microsomal fractions prepared from rats pretreated with various isoenzyme selective inducers. The effects of isoenzyme selective inhibitors were also evaluated. Adduct formation was shown to be mediated by P450 catalysed reactions but was unaltered, relative to untreated animals, in membranes from pyrazole- and clofibrate-treated animals suggesting that CYP2E1 and CYP4A1 are not involved in this process. However, adduct formation was significantly increased in microsomes from Sudan III-, phenobarbital- and dexamethasone-treated rats, suggesting the involvement of the CYP1A, CYP2B and CYP3A subfamilies, respectively. These conclusions were further supported by the finding that adduct formation in these microsomes could be inhibited by the isoenzyme-selective inhibitors alpha-naphthoflavone, metyrapone and troleandomycin, respectively.
Collapse
Affiliation(s)
- S E Lambard
- Department of Biological Sciences, Glasgow Polytechnic, U.K
| | | | | | | |
Collapse
|
44
|
Rao SI, Duffel MW. Benzylic alcohols as stereospecific substrates and inhibitors for aryl sulfotransferase. Chirality 1991; 3:104-11. [PMID: 1863522 DOI: 10.1002/chir.530030205] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Aryl sulfotransferase IV catalyzes the 3'-phosphoadenosine-5'-phosphosulfate (PAPS)-dependent formation of sulfuric acid esters of benzylic alcohols. Since the benzylic carbon bearing the hydroxyl group can be asymmetric, the possibility of stereochemical control of substrate specificity of the sulfotransferase was investigated with benzylic alcohols. Benzylic alcohols of known stereochemistry were examined as potential substrates and inhibitors for the homogeneous enzyme purified from rat liver. For 1-phenylethanol, both the (+)-(R)- and (-)-(S)-enantiomers were substrates for the enzyme, and the kcat/Km value for the (-)-(S)-enantiomer was twice that of the (+)-(R)-enantiomer. The enzyme displayed an absolute stereospecificity with ephedrine and pseudoephedrine, and with 2-methyl-1-phenyl-1-propanol; that is, only (-)-(1R,2S)-ephedrine, (-)-(1R,2R)-pseudoephedrine, and (-)-(S)-2-methyl-1-phenyl-1-propanol were substrates for the sulfotransferase. In the case of 1,2,3,4-tetrahydro-1-naphthol, only the (-)-(R)-enantiomer was a substrate for the enzyme. Both (+)-(R)-2-methyl-1-phenyl-1-propanol and (+)-(S)-1,2,3,4-tetrahydro-1-naphthol were competitive inhibitors of the aryl sulfotransferase-catalyzed sulfation of 1-naphthalenemethanol. Thus, the configuration of the benzylic carbon bearing the hydroxyl group determined whether these benzylic alcohols were substrates or inhibitors of the rat hepatic aryl sulfotransferase IV. Furthermore, benzylic alcohols such as (+)-(S)-1,2,3,4-tetrahydro-1-naphthol represent a new class of inhibitors for the aryl sulfotransferase.
Collapse
Affiliation(s)
- S I Rao
- Division of Medicinal and Natural Products Chemistry, College of Pharmacy, University of Iowa, Iowa City 52242
| | | |
Collapse
|
45
|
Holm KA, Kindberg CG, Stobaugh JF, Slavik M, Riley CM. Stereoselective pharmacokinetics and metabolism of the enantiomers of cyclophosphamide. Preliminary results in humans and rabbits. Biochem Pharmacol 1990; 39:1375-84. [PMID: 2322319 DOI: 10.1016/0006-2952(90)90015-d] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
[R(+),S(-)]-Cyclophosphamide [(R,S)-CP] is an anticancer drug, containing a chiral phosphorous atom, which is prepared and used clinically as the racemic mixture. A new high-performance liquid chromatographic assay suitable for pharmacokinetic studies of CP enantiomers in plasma has been reported recently by this laboratory (Reid et al., Anal Chem 61: 441-446, 1989). Briefly, the assay involves ethyl acetate extraction of CP enantiomers from plasma followed by derivatization to diastereomers in a two-step process utilizing chloral and (+)-naproxen acid chloride. Chromatographic analysis was performed on a reversed phase (ODS) column with detection at 232 nm. In the present study, preliminary results on the applicability of this assay to pharmacokinetic studies are presented. Several rabbits were used to compare the influence of i.p., i.v., and oral routes of administration on the stereoselective disposition of (R,S)-CP. Following i.p. administration, S-CP was cleared faster than R-CP. Following oral administration, only R-CP was detectable in plasma, while i.v. administration resulted in minor or no stereoselective disposition. These results indicated that there was a marked stereoselective metabolism of the S-CP enantiomer, with the i.p. and oral routes producing the greatest differences due to first-pass metabolism. Incubation of rabbit-liver microsomes with (R,S)-CP demonstrated that the monooxygenase system can exhibit marked stereoselectivity in its metabolism of CP. The ratio of R-CP to S-CP in the incubation medium increased during the incubation period from 1:1 initially to 4.5:1 after 60 min. The results from the experiments with rabbits indicate that the first-pass metabolism of this drug is highly stereoselective; in contrast, cancer patients who had received (R,S)-CP as an i.v. infusion showed no stereoselectivity in the elimination of the enantiomers. Pharmacokinetic studies with cancer patients, receiving (R,S)-CP as an oral dose, are in progress in order to determine if stereoselective first-pass metabolism of this drug also occurs in humans.
Collapse
Affiliation(s)
- K A Holm
- Department of Pharmaceutical Chemistry, University of Kansas, Lawrence 66045
| | | | | | | | | |
Collapse
|
46
|
Abstract
Multi-drug-resistance protein (P-glycoprotein) turns out to be an ATP-hydrolysing transmembrane pump that increases the resistance of cells in which it is expressed by actively extruding toxic chemicals. The baffling question is how does the pump know which chemicals to extrude? Common features among its substrates are still elusive. The question raised here concerns the relationship between this pump and that known for many years as capable of extruding glutathionyl and cysteinyl S-conjugates of xenobiotics. Are excreted drugs conjugated before excretion? Does the multi-drug-resistance pump recognize a simple chemical tag put on xenobiotics by a family of transferase enzymes?
Collapse
Affiliation(s)
- I C West
- Department of Biochemistry and Genetics, University of Newcastle upon Tyne, UK
| |
Collapse
|
47
|
Abstract
In addition to their well characterized interaction with the alpha 1 subunit of the voltage-dependent L-type Ca2+ channel, certain Ca2+ antagonists have been reported to modulate an increasing number of cellular functions as diverse as extrusion of cytotoxic substances, or cleavage of cAMP by phosphodiesterase. Some of these interactions (such as the reversal of multidrug resistance by Ca2+ antagonists for the treatment of lymphoma patients) have already been exploited clinically; some (such as protection of ischemic tissue by Ca2+ antagonists interacting with mitochondrial sites) open new therapeutic issues. In this survey of the non-L-type channel Ca2+ antagonist target structures known to date, Gerald Zernig evaluates the available data and emphasizes common characteristics shared by the seemingly diverse target structures. Research on these sites might help to understand yet unexplained effects of Ca2+ antagonists and possibly lead to the development of novel drugs with higher selectivity for non-L-type Ca2+ channel structures.
Collapse
Affiliation(s)
- G Zernig
- Institut für Biochemische Pharmakologie, Innsbruck, Austria
| |
Collapse
|
48
|
Kirby GM, Bend JR, Smith IR, Hayes MA. The role of glutathione S-transferases in the hepatic metabolism of benzo[a]pyrene in white suckers (Catostomus commersoni) from polluted and reference sites in the Great Lakes. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. C, COMPARATIVE PHARMACOLOGY AND TOXICOLOGY 1990; 95:25-30. [PMID: 1971553 DOI: 10.1016/0742-8413(90)90077-m] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
1. Orally administered 3H-benzo[a]pyrene (3H-BaP) was excreted in the bile of White Suckers predominantly as water soluble metabolites some of which were hydrolyzed by arylsulfatase or beta-glucuronidase. 2. Non-hydrolysible polar metabolites comprised a substantial proportion of biliary metabolites. 3. HPLC analysis revealed fluorescent and 3H-labelled peaks which co-eluted with standards of the glucuronide and sulfate conjugates of BaP. 4. The most polar peak co-chromatographed with a double-radiolabelled metabolite produced in vitro with 3H-BaP and 35S-glutathione. 5. Inhibition of epoxide hydrolase in vitro reduced all water soluble metabolites except the glutathione conjugate of BaP. 6. Glutathione conjugation represents a major hepatic detoxication pathway of BaP in White Suckers.
Collapse
Affiliation(s)
- G M Kirby
- Department of Pathology, University of Guelph, Ontario, Canada
| | | | | | | |
Collapse
|
49
|
Affiliation(s)
- G T Tucker
- Department of Pharmacology and Therapeutics, University of Sheffield, Royal Hallamshire Hospital, U.K
| | | |
Collapse
|
50
|
Hildebrandt P, Greinert R, Stier A, Taniguchi H. Resonance Raman study on the structure of the active sites of microsomal cytochrome P-450 isozymes LM2 and LM4. EUROPEAN JOURNAL OF BIOCHEMISTRY 1989; 186:291-302. [PMID: 2598933 DOI: 10.1111/j.1432-1033.1989.tb15208.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The isozymes 2 and 4 of rabbit microsomal cytochrome P-450 (LM2, LM4) have been studied by resonance Raman spectroscopy. Based on high quality spectra, a vibrational assignment of the porphyrin modes in the frequency range between 100-1700 cm-1 is presented for different ferric states of cytochrome P-450 LM2 and LM4. The resonance Raman spectra are interpreted in terms of the spin and ligation state of the heme iron and of heme-protein interactions. While in cytochrome P-450 LM2 the six-coordinated low-spin configuration is predominantly occupied, in the isozyme LM4 the five-coordinated high-spin form is the most stable state. The different stability of these two spin configurations in LM2 and LM4 can be attributed to the structures of the active sites. In the low-spin form of the isozymes LM4 the protein matrix forces the heme into a more rigid conformation than in LM2. These steric constraints are removed upon dissociation of the sixth ligand leading to a more flexible structure of the active site in the high-spin form of the isozyme LM4. The vibrational modes of the vinyl groups were found to be characteristic markers for the specific structures of the heme pockets in both isozymes. They also respond sensitively to type-I substrate binding. While in cytochrome P-450 LM4 the occupation of the substrate-binding pocket induces conformational changes of the vinyl groups, as reflected by frequency shifts of the vinyl modes, in the LM2 isozyme the ground-state conformation of these substituents remain unaffected, suggesting that the more flexible heme pocket can accommodate substrates without imposing steric constraints on the porphyrin. The resonance Raman technique makes structural changes visible which are induced by substrate binding in addition and independent of the changes associated with the shift of the spin state equilibrium: the high-spin states in the substrate-bound and substrate-free enzyme are structurally different. The formation of the inactive form, P-420, involves a severe structural rearrangement in the heme binding pocket leading to drastic changes of the vinyl group conformations. The conformational differences of the active sites in cytochromes P-450 LM2 and LM4 observed in this work contribute to the understanding of the structural basis accounting for substrate and product specificity of cytochrome P-450 isozymes.
Collapse
Affiliation(s)
- P Hildebrandt
- Max-Planck-Institut für Biophysikalische Chemie, Abteilung Spektroskopie, Göttingen, FRG
| | | | | | | |
Collapse
|