1
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Lehner AF. Reactions of deoxyribonucleotide bases with sulfooxymethyl or halomethyl polycyclic aromatic hydrocarbons induce unwinding of DNA supercoils. Toxicol Mech Methods 2024; 34:423-443. [PMID: 38133498 DOI: 10.1080/15376516.2023.2297836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 12/16/2023] [Indexed: 12/23/2023]
Abstract
Torsional stress in double-stranded DNA enables and regulates facets of chromosomal metabolism, replication, and transcription and requires regulatory enzymatic systems including topoisomerases and histone methyltransferases. As such, this machinery may be subject to deleterious effects from reactive mutagens, including ones from carcinogenic polycyclic aromatic hydrocarbon (PAH) adduct formation with DNA. Supercoiled plasmid DNA was investigated for its torsional responses to adducts formed in vitro from PAH benzylic carbocation reactive intermediates created spontaneously by release of leaving groups. PAH sulfate esters were found to (1) unwind DNA in a concentration dependent manner, and (2) provide maximum unwinding in a pattern consistent with known carcinogenicities of the parent PAHs, that is, 6-methylbenzo[a]pyrene > 7,12-methylbenz[a]anthracene > 3-methylcholanthrene > 9-methylanthracene > 7-methylbenz[a]anthracene > 1-methylpyrene. Supercoil unwinding was demonstrated to be dependent on the presence of sulfate or chloride leaving groups such that reactive carbocations were generated in situ by hydrolysis. In silico modeling of intercalative complex topology showed PAH benzylic carbocation reactive functional groups in alignment with target nucleophiles on guanine bases in a 5'-dCdG-3' pocket in agreement with known formation of nucleotide adducts. Inhibitory or modulatory effects on PAH-induced supercoil unwinding were seen with ascorbic acid and an experimental antineoplastic agent Antineoplaston A10 in agreement with their known anticarcinogenic properties. In summary, the reactive PAH intermediates studied here undoubtedly participate in well-known mutational mechanisms such as frameshifts and apurinic site generation. However, they are also capable of random disruption of chromosomal supercoiling in a manner consistent with the known carcinogenicities of the parent compounds, and this mechanism may represent an additional detrimental motif worthy of further study for a more complete understanding of chemical carcinogenicity.
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Affiliation(s)
- Andreas F Lehner
- Veterinary Diagnostic Lab, Toxicology Section, Michigan State University, East Lansing, MI, USA
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2
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Chen C, Min Y, Li X, Chen D, Shen J, Zhang D, Sun H, Bian Q, Yuan H, Wang SL. Mutagenicity risk prediction of PAH and derivative mixtures by in silico simulations oriented from CYP compound I-mediated metabolic activation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 787:147596. [PMID: 33991922 DOI: 10.1016/j.scitotenv.2021.147596] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 04/26/2021] [Accepted: 05/01/2021] [Indexed: 06/12/2023]
Abstract
PAHs and their derivatives are the main sources of mutagenicity and carcinogenicity in airborne particular matter and cause serious public health and environmental problems. Risk assessment is challenging due to the mixed nature and deficiency of toxicity data of most PAHs and their derivatives. Cytochrome P450 enzymes (CYPs) play important roles in PAH-induced carcinogenicity via metabolic activation, and CYP conformations with compound I structures strongly influence metabolic sites and metabolite species. In this study, complexes of BaP with CYP1A1, CYP1B1 or CYP2C19 compound I were successfully simulated by QM/MM methods and verified by metabolic clearance, and the mutagenicity of chemicals was then predicted by the BaP-7,8-epoxide-related metabolic conformation fitness (MCF) approach, which was validated by Ames tests, showing satisfying accuracy (R2 = 0.46-0.66). Furthermore, a prediction model of the mutagenicity risk of PAH and derivative mixtures was established based on the relative potential factor (RPF) approach and the RPF calculated from the mathematical relationship between the minimum MCF (MCFmin) and RPF, which was successfully validated by the mutagenesis of PAH and derivative mixture mimic-simulating PM2.5 samples collected in eastern China. This study provides fast reliable tools for assessing risk of the complex components of environmental PAHs and their derivatives.
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Affiliation(s)
- Chao Chen
- Key Laboratory of Modern Toxicology of Ministry of Education, Center for Global Health, School of Public Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing 211166, PR China
| | - Yue Min
- Key Laboratory of Modern Toxicology of Ministry of Education, Center for Global Health, School of Public Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing 211166, PR China; State Key Laboratory of Reproductive Medicine, Institute of Toxicology, Nanjing Medical University, 101 Longmian Avenue, Nanjing 211166, PR China
| | - Xuxu Li
- Key Laboratory of Modern Toxicology of Ministry of Education, Center for Global Health, School of Public Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing 211166, PR China; School of Nursing, Nanjing Medical University, 101 Longmian Avenue, Nanjing 211166, PR China
| | - Dongyin Chen
- School of Pharmacy, Nanjing Medical University, 101 Longmian Avenue, Nanjing 211166, PR China
| | - Jiemiao Shen
- Key Laboratory of Modern Toxicology of Ministry of Education, Center for Global Health, School of Public Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing 211166, PR China
| | - Di Zhang
- Key Laboratory of Modern Toxicology of Ministry of Education, Center for Global Health, School of Public Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing 211166, PR China
| | - Hong Sun
- Jiangsu Provincial Center for Disease Control and Prevention, 172 Jiangsu Rd., Nanjing 210009, PR China
| | - Qian Bian
- Jiangsu Provincial Center for Disease Control and Prevention, 172 Jiangsu Rd., Nanjing 210009, PR China
| | - Haoliang Yuan
- State Key Laboratory of Natural Medicines and Center of Drug Discovery, China Pharmaceutical University, 639 Longmian Avenue, Nanjing 211198, PR China
| | - Shou-Lin Wang
- Key Laboratory of Modern Toxicology of Ministry of Education, Center for Global Health, School of Public Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing 211166, PR China; State Key Laboratory of Reproductive Medicine, Institute of Toxicology, Nanjing Medical University, 101 Longmian Avenue, Nanjing 211166, PR China; School of Nursing, Nanjing Medical University, 101 Longmian Avenue, Nanjing 211166, PR China.
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3
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Gan J, Ma S, Zhang D. Non-cytochrome P450-mediated bioactivation and its toxicological relevance. Drug Metab Rev 2016; 48:473-501. [DOI: 10.1080/03602532.2016.1225756] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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4
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Coughtrie MWH. Function and organization of the human cytosolic sulfotransferase (SULT) family. Chem Biol Interact 2016; 259:2-7. [PMID: 27174136 DOI: 10.1016/j.cbi.2016.05.005] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 05/02/2016] [Indexed: 12/29/2022]
Abstract
The sulfuryl transfer reaction is of fundamental biological importance. One of the most important manifestations of this process are the reactions catalyzed by members of the cytosolic sulfotransferase (SULT) superfamily. These enzymes transfer the sulfuryl moiety from the universal donor PAPS (3'-phosphoadenosine 5'-phosphosulfate) to a wide variety of substrates with hydroxyl- or amino-groups. Normally a detoxification reaction this facilitates the elimination of a multitude of xenobiotics, although for some molecules sulfation is a bioactivation step. In addition, sulfation plays a key role in endocrine and other signalling pathways since many steroids, sterols, thyroid hormones and catecholamines exist primarily as sulfate conjugates in humans. This article summarizes much of our current knowledge of the organization and function of the human cytosolic sulfotransferases and highlights some of the important interspecies differences that have implications for, among other things, drug development and chemical safety analysis.
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Affiliation(s)
- Michael W H Coughtrie
- Faculty of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mall, Vancouver, BC, V6T 1Z3, Canada.
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5
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Barber C, Amberg A, Custer L, Dobo KL, Glowienke S, Van Gompel J, Gutsell S, Harvey J, Honma M, Kenyon MO, Kruhlak N, Muster W, Stavitskaya L, Teasdale A, Vessey J, Wichard J. Establishing best practise in the application of expert review of mutagenicity under ICH M7. Regul Toxicol Pharmacol 2015; 73:367-77. [PMID: 26248005 DOI: 10.1016/j.yrtph.2015.07.018] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Revised: 07/21/2015] [Accepted: 07/22/2015] [Indexed: 11/15/2022]
Abstract
The ICH M7 guidelines for the assessment and control of DNA reactive (mutagenic) impurities in pharmaceuticals allows for the consideration of in silico predictions in place of in vitro studies. This represents a significant advance in the acceptance of (Q)SAR models and has resulted from positive interactions between modellers, regulatory agencies and industry with a shared purpose of developing effective processes to minimise risk. This paper discusses key scientific principles that should be applied when evaluating in silico predictions with a focus on accuracy and scientific rigour that will support a consistent and practical route to regulatory submission.
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Affiliation(s)
| | - Alexander Amberg
- Sanofi-Aventis Deutschland GmbH, DSAR Preclinical Safety, Frankfurt, Germany
| | - Laura Custer
- Bristol-Myers Squibb, Drug Safety Evaluation, New Brunswick, USA
| | - Krista L Dobo
- Pfizer, Drug Safety Research and Development, Groton, CT, USA
| | - Susanne Glowienke
- Novartis Institutes for Biomedical Research, Department of Preclinical Safety, Basel, Switzerland
| | | | - Steve Gutsell
- Unilever, Safety and Environmental Assurance Centre, Colworth, Beds, UK
| | - Jim Harvey
- GlaxoSmithkline, Computational Toxicology, Ware, Herts, UK
| | | | | | - Naomi Kruhlak
- FDA Center for Drug Evaluation and Research, Silver Spring, MD, USA
| | - Wolfgang Muster
- F. Hoffmann-La Roche Ltd., Pharma Research and Early Development, Basel, Switzerland
| | | | | | | | - Joerg Wichard
- Bayer, HealthCare, Genetic Toxicology, Berlin, Germany
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6
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Squirewell EJ, Qin X, Duffel MW. Endoxifen and other metabolites of tamoxifen inhibit human hydroxysteroid sulfotransferase 2A1 (hSULT2A1). Drug Metab Dispos 2014; 42:1843-50. [PMID: 25157097 PMCID: PMC4201133 DOI: 10.1124/dmd.114.059709] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/25/2014] [Indexed: 01/07/2023] Open
Abstract
Although tamoxifen is a successful agent for treatment and prevention of estrogen-dependent breast cancer, its use has been limited by the low incidence of endometrial cancer. Human hydroxysteroid sulfotransferase 2A1 (hSULT2A1) catalyzes the formation of an α-sulfooxy metabolite of tamoxifen that is reactive toward DNA, and this has been implicated in its carcinogenicity. Also, hSULT2A1 functions in the metabolism of steroid hormones such as dehydroepiandrosterone (DHEA) and pregnenolone (PREG). These roles of hSULT2A1 in steroid hormone metabolism and in generating a reactive metabolite of tamoxifen led us to examine its interactions with tamoxifen and several of its major metabolites. We hypothesized that metabolites of tamoxifen may regulate the catalytic activity of hSULT2A1, either through direct inhibition or through serving as alternate substrates for the enzyme. We found that 4-hydroxy-N-desmethyltamoxifen (endoxifen) is a potent inhibitor of hSULT2A1-catalyzed sulfation of PREG and DHEA, with Ki values of 3.5 and 2.8 μM, respectively. In the hSULT2A1-catalyzed sulfation of PREG, 4-hydroxytamoxifen (4-OHTAM) and N-desmethyltamoxifen (N-desTAM) exhibited Ki values of 12.7 and 9.8 μM, respectively, whereas corresponding Ki values of 19.4 and 17.2 μM were observed with DHEA as substrate. A Ki value of 9.1 μM was observed for tamoxifen-N-oxide with DHEA as substrate, and this increased to 16.9 μM for the hSULT2A1-catalyzed sulfation of PREG. Three metabolites were substrates for hSULT2A1, with relative sulfation rates of 4-OHTAM > N-desTAM > > endoxifen. These results may be useful in interpreting ongoing clinical trials of endoxifen and in improving the design of related molecules.
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Affiliation(s)
- Edwin J Squirewell
- Division of Medicinal and Natural Products Chemistry, Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City, Iowa
| | - Xiaoyan Qin
- Division of Medicinal and Natural Products Chemistry, Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City, Iowa
| | - Michael W Duffel
- Division of Medicinal and Natural Products Chemistry, Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City, Iowa
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7
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Qin X, Lehmler HJ, Teesch LM, Robertson LW, Duffel MW. Chlorinated biphenyl quinones and phenyl-2,5-benzoquinone differentially modify the catalytic activity of human hydroxysteroid sulfotransferase hSULT2A1. Chem Res Toxicol 2013; 26:1474-85. [PMID: 24059442 DOI: 10.1021/tx400207q] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Human hydroxysteroid sulfotransferase (hSULT2A1) catalyzes the sulfation of a broad range of environmental chemicals, drugs, and other xenobiotics in addition to endogenous compounds that include hydroxysteroids and bile acids. Polychlorinated biphenyls (PCBs) are persistent environmental contaminants, and oxidized metabolites of PCBs may play significant roles in the etiology of their adverse health effects. Quinones derived from the oxidative metabolism of PCBs (PCB-quinones) react with nucleophilic sites in proteins and also undergo redox cycling to generate reactive oxygen species. This, along with the sensitivity of hSULT2A1 to oxidative modification at cysteine residues, led us to hypothesize that electrophilic PCB-quinones react with hSULT2A1 to alter its catalytic function. Thus, we examined the effects of four phenylbenzoquinones on the ability of hSULT2A1 to catalyze the sulfation of the endogenous substrate, dehydroepiandrosterone (DHEA). The quinones studied were 2'-chlorophenyl-2,5-benzoquinone (2'-Cl-BQ), 4'-chlorophenyl-2,5-benzoquinone (4'-Cl-BQ), 4'-chlorophenyl-3,6-dichloro-2,5-benzoquinone (3,6,4'-triCl-BQ), and phenyl-2,5-benzoquinone (PBQ). At all concentrations examined, pretreatment of hSULT2A1 with the PCB-quinones decreased the catalytic activity of hSULT2A1. Pretreatment with low concentrations of PBQ, however, increased the catalytic activity of the enzyme, while higher concentrations inhibited catalysis. A decrease in substrate inhibition with DHEA was seen following preincubation of hSULT2A1 with all of the quinones. Proteolytic digestion of the enzyme followed by LC/MS analysis indicated PCB-quinone- and PBQ-adducts at Cys55 and Cys199, as well as oxidation products at methionines in the protein. Equilibrium binding experiments and molecular modeling suggested that changes due to these modifications may affect the nucleotide binding site and the entrance to the sulfuryl acceptor binding site of hSULT2A1.
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Affiliation(s)
- Xiaoyan Qin
- Interdisciplinary Graduate Program in Human Toxicology, University of Iowa , Iowa City, Iowa 52242, United States
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8
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Qin X, Teesch LM, Duffel MW. Modification of the catalytic function of human hydroxysteroid sulfotransferase hSULT2A1 by formation of disulfide bonds. Drug Metab Dispos 2013; 41:1094-103. [PMID: 23444386 PMCID: PMC3629806 DOI: 10.1124/dmd.112.050534] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 02/26/2013] [Indexed: 01/01/2023] Open
Abstract
The human cytosolic sulfotransferase hSULT2A1 catalyzes the sulfation of a broad range of xenobiotics, as well as endogenous hydroxysteroids and bile acids. Reversible modulation of the catalytic activity of this enzyme could play important roles in its physiologic functions. Whereas other mammalian sulfotransferases are known to be reversibly altered by changes in their redox environment, this has not been previously shown for hSULT2A1. We have examined the hypothesis that the formation of disulfide bonds in hSULT2A1 can reversibly regulate the catalytic function of the enzyme. Three thiol oxidants were used as model compounds to investigate their effects on homogeneous preparations of hSULT2A1: glutathione disulfide, 5,5'-dithiobis(2-nitrobenzoic acid), and 1,1'-azobis(N,N-dimethylformamide) (diamide). Examination of the effects of disulfide bond formation with these agents indicated that the activity of the enzyme is reversibly altered. Studies on the kinetics of the hSULT2A1-catalyzed sulfation of dehydroepiandrosterone (DHEA) showed the effects of disulfide bond formation on the substrate inhibition characteristics of the enzyme. The effects of these agents on the binding of substrates and products, liquid chromatography-mass spectrometry identification of the disulfides formed, and structural modeling of the modified enzyme were examined. Our results indicate that conformational changes at cysteines near the nucleotide binding site affect the binding of both the nucleotide and DHEA to the enzyme, with the specific effects dependent on the structure of the resulting disulfide. Thus, the formation of disulfide bonds in hSULT2A1 is a potentially important reversible mechanism for alterations in the rates of sulfation of both endogenous and xenobiotic substrates.
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Affiliation(s)
- Xiaoyan Qin
- Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, The University of Iowa, Iowa City, Iowa, USA
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9
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Exposure to polycyclic aromatic hydrocarbons: bulky DNA adducts and cellular responses. EXPERIENTIA SUPPLEMENTUM (2012) 2012; 101:107-31. [PMID: 22945568 DOI: 10.1007/978-3-7643-8340-4_5] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Environmental and dietary carcinogens such as polycyclic aromatic hydrocarbons (PAHs) have been intensively studied for decades. Although the genotoxicity of these compounds is well characterized (i.e., formation of bulky PAH-DNA adducts), molecular details on the DNA damage response triggered by PAHs in cells and tissues remain to be clarified. The conversion of hazardous PAHs into carcinogenic intermediates depends on enzyme-catalyzed biotransformation. Certain cytochrome P450-dependent monooxygenases (CYPs) play a pivotal role in PAH metabolism. In particular, CYP1A1 and 1B1 catalyze oxidation of PAHs toward primary epoxide species that can further be converted into multiple follow-up products, both nonenzymatically and enzymatically. Distinct functions between these major CYP enzymes have only been appreciated since transgenic animal models had been derived. Electrophilic PAH metabolites are capable of forming stable DNA adducts or to promote depurination at damaged nucleotide sites. During the following DNA replication cycle, bulky PAH-DNA adducts may be converted into mutations, thereby affecting hot spot sites in regulatory important genes such as Ras, p53, and others. Depending on the degree of DNA distortion and cell cycle progression, PAH-DNA adducts trigger nucleotide excision repair (NER) and various DNA damage responses that might include TP53-dependent apoptosis in certain cell types. In fact, cellular responses to bulky PAH-DNA damage are complex because distinct signaling branches such as ATM/ATR, NER, TP53, but also MAP kinases, interact and cooperate to determine the overall outcome to cellular injuries initiated by PAH-DNA adducts. Further, PAHs and other xenobiotics can also confer DNA damage via an alternative route of metabolic activation, which leads to the generation of PAH semiquinone radicals and reactive oxygen species (ROS). One-electron oxidations mediated by peroxidases or other enzymes can result in PAH radical cations that mainly form unstable DNA adducts subjected to depurination. In addition, generation of ROS can also trigger multiple cellular signaling pathways not directly related to mutagenic or cytotoxic effects, including those mediated by NFκB, SAPK/JNK, and p38. In recent years, it became clear that PAHs may also be involved in inflammatory diseases, autoimmune disorders, or atherosclerosis. Further research is under way to better characterize the significance of such newly recognized systemic effects of PAHs and to reconsider risk assessment for human health.
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Akbari MR, Malekzadeh R, Shakeri R, Nasrollahzadeh D, Foumani M, Sun Y, Pourshams A, Sadjadi A, Jafari E, Sotoudeh M, Kamangar F, Boffetta P, Dawsey SM, Ghadirian P, Narod SA. Candidate gene association study of esophageal squamous cell carcinoma in a high-risk region in Iran. Cancer Res 2009. [PMID: 19826048 DOI: 10.1158/0008-5472.can-09- 1149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
There is a region with a high risk for esophageal squamous cell carcinoma (ESCC) in the northeast of Iran. Previous studies suggest that hereditary factors play a role in the high incidence of cancer in the region. We selected 22 functional variants (and 130 related tagSNPs) from 15 genes that have been associated previously with the risk of ESCC. We genotyped a primary set of samples from 451 Turkmens (197 cases and 254 controls). Seven of 152 variants were associated with ESCC at the P = 0.05 level; these single nucleotide polymorphisms were then studied in a validation set of 549 cases and 1,119 controls, which included both Turkmens and non-Turkmens. The association observed for a functional variant in ADH1B was confirmed in the validation set, and that of a tagSNP in MGMT, the association was borderline significant in the validation set, after correcting for multiple testing. The other 5 variants that were associated in the primary set were not significantly associated in the validation set. The histidine allele at codon 48 of ADH1B gene was associated with a significantly decreased risk of ESCC in the joint data set (primary and validation set) under a recessive model (odds ratio, 0.41; 95% confidence interval, 0.29-0.76; P = 4 x 10(-4)). The A allele of the rs7087131 variant of MGMT gene was associated with a decreased risk of ESCC under a dominant model (odds ratio, 0.79; 95% confidence interval, 0.64-0.96; P = 0.02). These results support the hypothesis that genetic predisposition plays a role in the high incidence of ESSC in Iran.
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Affiliation(s)
- Mohammad R Akbari
- Digestive Disease Research Center, Tehran University of Medical Sciences, Tehran, Iran
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11
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Akbari MR, Malekzadeh R, Shakeri R, Nasrollahzadeh D, Foumani M, Sun Y, Pourshams A, Sadjadi A, Jafari E, Sotoudeh M, Kamangar F, Boffetta P, Dawsey SM, Ghadirian P, Narod SA. Candidate gene association study of esophageal squamous cell carcinoma in a high-risk region in Iran. Cancer Res 2009; 69:7994-8000. [PMID: 19826048 DOI: 10.1158/0008-5472.can-09-1149] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
There is a region with a high risk for esophageal squamous cell carcinoma (ESCC) in the northeast of Iran. Previous studies suggest that hereditary factors play a role in the high incidence of cancer in the region. We selected 22 functional variants (and 130 related tagSNPs) from 15 genes that have been associated previously with the risk of ESCC. We genotyped a primary set of samples from 451 Turkmens (197 cases and 254 controls). Seven of 152 variants were associated with ESCC at the P = 0.05 level; these single nucleotide polymorphisms were then studied in a validation set of 549 cases and 1,119 controls, which included both Turkmens and non-Turkmens. The association observed for a functional variant in ADH1B was confirmed in the validation set, and that of a tagSNP in MGMT, the association was borderline significant in the validation set, after correcting for multiple testing. The other 5 variants that were associated in the primary set were not significantly associated in the validation set. The histidine allele at codon 48 of ADH1B gene was associated with a significantly decreased risk of ESCC in the joint data set (primary and validation set) under a recessive model (odds ratio, 0.41; 95% confidence interval, 0.29-0.76; P = 4 x 10(-4)). The A allele of the rs7087131 variant of MGMT gene was associated with a decreased risk of ESCC under a dominant model (odds ratio, 0.79; 95% confidence interval, 0.64-0.96; P = 0.02). These results support the hypothesis that genetic predisposition plays a role in the high incidence of ESSC in Iran.
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Affiliation(s)
- Mohammad R Akbari
- Digestive Disease Research Center, Tehran University of Medical Sciences, Tehran, Iran
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12
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Riches Z, Stanley EL, Bloomer JC, Coughtrie MWH. Quantitative evaluation of the expression and activity of five major sulfotransferases (SULTs) in human tissues: the SULT "pie". Drug Metab Dispos 2009; 37:2255-61. [PMID: 19679676 DOI: 10.1124/dmd.109.028399] [Citation(s) in RCA: 263] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Expression levels of the major human sulfotransferases (SULTs) involved in xenobiotic detoxification in a range of human tissues (i.e., SULT "pies") are not available in a form allowing comparison between tissues and individuals. Here we have determined, by quantitative immunoblotting, expression levels for the five principal human SULTs-SULT1A1, SULT1A3/4, SULT1B1, SULT1E1, and SULT2A1-and determined the kinetic properties toward probe substrates, where available, for these enzymes in cytosol samples from a bank of adult human liver, small intestine, kidney, and lung. We produced new isoform-selective antibodies against SULT1B1 and SULT2A1, which were used alongside antibodies against SULT1A3 and SULT1A1 previously produced in our laboratory or available commercially (SULT1E1). Expression levels were derived using purified recombinant enzymes to construct standard curves for each individual isoform and immunoblot. Substantial intertissue and interindividual differences in expression were observed. SULT1A1 was the major enzyme (>50% of total, range 420-4900 ng/mg cytosol protein) in the liver, followed by SULT2A1, SULT1B1, and SULT1E1. SULT1A3 was completely absent from this tissue. In contrast, the small intestine contained the largest overall amount of SULT of any of the tissues, with SULT1B1 the major enzyme (36%), closely followed by SULT1A3 (31%), and SULT1A1, SULT1E1, and SULT2A1 more minor forms (19, 8, and 6% of total, respectively). The kidney and lung contained low levels of SULT. We provide a unique data set that will add value to the study of the role and contribution of sulfation to drug and xenobiotic metabolism in humans.
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Affiliation(s)
- Zoe Riches
- Division of Medical Sciences, Centre for Oncology and Molecular Medicine, University of Dundee, Ninewells Hospital and Medical School, Dundee, United Kingdom
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13
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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
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Glatt H, Rost K, Frank H, Seidel A, Kollock R. Detoxification of promutagenic aldehydes derived from methylpyrenes by human aldehyde dehydrogenases ALDH2 and ALDH3A1. Arch Biochem Biophys 2008; 477:196-205. [PMID: 18621017 DOI: 10.1016/j.abb.2008.06.020] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2008] [Revised: 06/20/2008] [Accepted: 06/25/2008] [Indexed: 10/21/2022]
Abstract
Methylated polycyclic aromatic hydrocarbons can be metabolically activated via benzylic hydroxylation and sulpho conjugation to reactive esters, which can induce mutations and tumours. Yet, further oxidation of the alcohol may compete with this toxification. We previously demonstrated that several human alcohol dehydrogenases (ADH1C, 2, 3 and 4) oxidise various benzylic alcohols (derived from alkylated pyrenes) to their aldehydes with high catalytic efficiency. However, all these ADHs also catalysed the reverse reaction, the reduction of the aldehydes to the alcohols, with comparable or higher efficiency. Thus, final detoxification requires elimination of the aldehydes by further biotransformation. We have expressed two human aldehyde dehydrogenases (ALDH2 and 3A1) in bacteria. All pyrene aldehydes studied (1-, 2- and 4-formylpyrene, 1-formyl-6-methylpyrene and 1-formyl-8-methylpyrene) were high-affinity substrates for ALDH2 (K(m)=0.027-0.9 microM) as well as ALDH3A1 (K(m)=0.78-11 microM). Catalytic efficiencies (k(cat)/K(m)) were higher for ALDH2 than ALDH3A1 by a moderate to a very large margin depending on the substrate. Most important, they were also substantially higher than the catalytic efficiencies of the various ADHs for the reduction the aldehydes to the alcohols. These kinetic properties ensure that ALDHs, and particularly ALDH2, can complete the ADH-mediated detoxification.
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Affiliation(s)
- Hansruedi Glatt
- German Institute of Human Nutrition Potsdam-Rehbruecke, Department of Nutritional Toxicology, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany.
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15
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Oxidation of alcohols and reduction of aldehydes derived from methyl- and dimethylpyrenes by cDNA-expressed human alcohol dehydrogenases. Toxicology 2008; 245:65-75. [DOI: 10.1016/j.tox.2007.12.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2007] [Revised: 12/13/2007] [Accepted: 12/13/2007] [Indexed: 11/23/2022]
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16
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Spink DC, Wu SJ, Spink BC, Hussain MM, Vakharia DD, Pentecost BT, Kaminsky LS. Induction of CYP1A1 and CYP1B1 by benzo(k)fluoranthene and benzo(a)pyrene in T-47D human breast cancer cells: roles of PAH interactions and PAH metabolites. Toxicol Appl Pharmacol 2007; 226:213-24. [PMID: 17919675 DOI: 10.1016/j.taap.2007.08.024] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2007] [Revised: 08/23/2007] [Accepted: 08/28/2007] [Indexed: 11/18/2022]
Abstract
The interactions of polycyclic aromatic hydrocarbons (PAH) and cytochromes P450 (CYP) are complex; PAHs are enzyme inducers, substrates, and inhibitors. In T-47D breast cancer cells, exposure to 0.1 to 1 microM benzo(k)fluoranthene (BKF) induced CYP1A1/1B1-catalyzed 17beta-estradiol (E(2)) metabolism, whereas BKF levels greater than 1 muM inhibited E(2) metabolism. Time course studies showed that induction of CYP1-catalyzed E(2) metabolism persisted after the disappearance of BKF or co-exposed benzo(a)pyrene, suggesting that BKF metabolites retaining Ah receptor agonist activity were responsible for prolonged CYP1 induction. BKF metabolites were shown, through the use of ethoxyresorufin O-deethylase and CYP1A1-promoter-luciferase reporter assays to induce CYP1A1/1B1 in T-47D cells. Metabolites formed by oxidation at the C-2/C-3 region of BKF had potencies for CYP1 induction exceeding those of BKF, whereas C-8/C-9 oxidative metabolites were somewhat less potent than BKF. The activities of expressed human CYP1A1 and 1B1 with BKF as substrate were investigated by use of HPLC with fluorescence detection, and by GC/MS. The results showed that both enzymes efficiently catalyzed the formation of 3-, 8-, and 9-OHBKF from BKF. These studies indicate that the inductive effects of PAH metabolites as potent CYP1 inducers are likely to be additional important factors in PAH-CYP interactions that affect metabolism and bioactivation of other PAHs, ultimately modulating PAH toxicity and carcinogenicity.
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Affiliation(s)
- David C Spink
- Wadsworth Center, New York State Department of Health, Albany, NY 12201-0509, USA.
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17
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Kollock R, Meinl W, Schneider H, Batke M, Frank H, Seidel A, Glatt H. Efficient oxidation of promutagenic hydroxymethylpyrenes by cDNA-expressed human alcohol dehydrogenase ADH2 and its inhibition by various agents. Biochem Pharmacol 2007; 75:527-37. [PMID: 17920042 DOI: 10.1016/j.bcp.2007.08.030] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2007] [Revised: 08/28/2007] [Accepted: 08/28/2007] [Indexed: 10/22/2022]
Abstract
Alkylated polycyclic aromatic hydrocarbons can be metabolically activated via benzylic hydroxylation and sulphation to electrophilically reactive esters. However, we previously found that the predominant biotransformation route for the hepatocarcinogen 1-hydroxymethylpyrene (1-HMP) in the rat in vivo is the oxidation of the side chain by alcohol dehydrogenases (ADHs) and aldehyde dehydrogenases to the carboxylic acid. Inhibition of this pathway by ethanol (competing ADH substrate) or 4-methylpyrazole (ADH inhibitor) led to a dramatic increase in the 1-HMP-induced DNA adduct formation in rat tissues in the preceding study. In order to elucidate the role of individual ADHs in the metabolism of alkylated polycyclic aromatic hydrocarbons, we expressed the various members of the human ADH family in bacteria. Cytosolic preparations from bacteria expressing ADH2 clearly oxidized hydroxymethylpyrene isomers (1-, 2- and 4-HMP) with the highest rate. This form was purified to near homogeneity to perform detailed kinetic analyses. High catalytic efficiencies (V(max)/K(m)) were observed with HMPs. Thus, this value was 10,000-fold higher for 2-HMP than for the reference substrate, ethanol. The corresponding aldehydes were also efficiently reduced by ADH2. 4-Methylpyrazole inhibited the oxidation of the HMP isomers as well as the reverse reaction. Daidzein, cimetidine and the competing substrate ethanol were further compounds that inhibited the ADH2-mediated oxidative detoxification of 1-HMP.
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Affiliation(s)
- Ronny Kollock
- German Institute of Human Nutrition Potsdam-Rehbruecke, Department of Nutritional Toxicology, 14558 Nuthetal, Germany
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Myers SR, Ali MY, Wright T, Cunningham C. BENZO(A)PYRENE METABOLISM: ROLE OF BIOALKYLATION. Polycycl Aromat Compd 2007. [DOI: 10.1080/10406630701509104] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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19
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Bakhiya N, Batke M, Laake J, Monien BH, Frank H, Seidel A, Engst W, Glatt H. Directing Role of Organic Anion Transporters in the Excretion of Mercapturic Acids of Alkylated Polycyclic Aromatic Hydrocarbons. Drug Metab Dispos 2007; 35:1824-31. [PMID: 17639024 DOI: 10.1124/dmd.107.016964] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Excretion of mercapturic acids of a xenobiotic is a good indicator for the formation of electrophilic intermediates. However, the route of excretion, urine or feces, is important for usage of a given mercapturic acid as a biomarker in humans. In the present study we investigated the excretion routes of 1-methylpyrenyl mercapturic acid (MPMA) and 1,8-dimethylpyrenyl mercapturic acid (DMPMA) formed from the corresponding benzylic alcohols in rats. Whereas MPMA was primarily excreted in urine (72% of the total urinary and fecal level), DMPMA clearly preferred the fecal route (88%). We then examined interactions of these mercapturic acids with renal basolateral organic anion transporters (OATs) using HEK293 cells stably expressing human OAT1 and OAT3. The uptake rates of MPMA by OAT1- and OAT3-expressing cells were 2.8- and 1.7-fold, respectively, higher than that by control cells. MPMA was a competitive inhibitor of p-aminohippurate uptake by OAT1 and estrone sulfate uptake by OAT3 with K(i) values of 14.5 microM and 1.5 microM, respectively. In contrast, DMPMA was not transported by OAT1 and only modestly transported by OAT3 (1.25-fold over control). Thus, we suspect that the substrate specificities, alone or together with other factors, played a directing role in the excretion of MPMA and DMPMA. Although the mechanistic link requires verification, our results clearly show that a minute structural difference (the presence or absence of an additional methyl group in an alkylated four-ring polycyclic hydrocarbon) can strongly affect the interaction with transporter proteins and direct the excretion route of mercapturic acids.
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Affiliation(s)
- Nadiya Bakhiya
- German Institute of Human Nutrition Potsdam-Rehbrücke, Arthur-Scheunert-Allee 114-116, 14558 Nuthetal, Germany
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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.
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Affiliation(s)
- Weiling Xue
- Department of Environmental Health, University of Cincinnati Medical Center, 3223 Eden Avenue, Cincinnati, OH 45267-0056, USA
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Sharma V, Duffel MW. A Comparative Molecular Field Analysis‐Based Approach to Prediction of Sulfotransferase Catalytic Specificity. Methods Enzymol 2005; 400:249-63. [PMID: 16399353 DOI: 10.1016/s0076-6879(05)00014-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Understanding the catalytic function and substrate specificity of cytosolic sulfotransferases (SULTs) involved in drug metabolism is essential for predicting the metabolic outcomes of many xenobiotics. Although multiple isoforms of cytosolic SULTs have been identified and characterized in humans and other species, relatively little is known about the specific molecular interactions that govern their selectivity for substrates. The use of three-dimensional quantitative structure-activity relationship (3D-QSAR) techniques has emerged as a powerful tool for understanding the relationships among protein structure, catalytic function, and substrate specificity. We have found that a specific adaptation of a ligand-based 3D-QSAR method, comparative molecular field analysis (CoMFA), is particularly useful for prediction of the catalytic efficiencies of SULTs. This approach has been used to study the function of a prototypical rat hepatic phenol SULT and has now been extended to a member of the hydroxysteroid SULT family. Key aspects of this methodology incorporate strategies for finding the most meaningful bioactive conformation with respect to the protein structure, use of a model of an enzyme-substrate complex incorporating the mechanism of sulfuryl transfer, and the utilization of log(k(cat)/K(m)) as the parameter for correlation analysis. The success of this approach with members of two different families of cytosolic SULTs suggests that it may be of more general use in the study of other SULTs.
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Affiliation(s)
- Vyas Sharma
- Division of Medicinal and Natural Products Chemistry, College of Pharmacy, University of Iowa, Iowa City, USA
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22
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Tang D, Rundle A, Mooney L, Cho S, Schnabel F, Estabrook A, Kelly A, Levine R, Hibshoosh H, Perera F. Sulfotransferase 1A1 (SULT1A1) polymorphism, PAH-DNA adduct levels in breast tissue and breast cancer risk in a case-control study. Breast Cancer Res Treat 2003; 78:217-22. [PMID: 12725421 DOI: 10.1023/a:1022968303118] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Gene-environment interactions are hypothesized to be major contributors to susceptibility to environmental carcinogens and interindividual variability in cancer risk. We present findings on associations between genetic susceptibility due to inherited polymorphisms of the Phase II detoxification enzyme sulfotransferase 1A1 (SULT1A1), breast cancer risk, and polycyclic aromatic hydrocarbon (PAH)-DNA adducts. A hospital based case-control study was conducted at the New York-Presbyterian Medical Center (NYPMC). The study utilized two control groups: one comprised of women with benign breast disease (BBD) and the other comprised of women visiting NYPMC for routine gynecologic checkups (healthy controls). Blood samples were collected from cases and controls; and breast tissue from pathology blocks was collected from cases (tumor and non-tumor tissue) and BBD controls (benign tissue). PAH-DNA adduct levels were measured by immunohistochemistry in breast tissue samples, and the SULT1A1 (Arg/His) polymorphism at codon 213 was determined by PCR RFLP analyses using DNA from white blood cells. Increasing number of His alleles was modestly associated with breast cancer case-control status, when cases were compared to healthy controls (p for trend = 0.08), when cases were compared to BBD controls (p for trend = 0.08) and when cases were compared to both control groups combined (p for trend = 0.07). Contrary to our hypothesis PAH-DNA adduct levels in breast tissue were not associated with SULT1A1 genotype. Our findings are consistent with a prior report that the Arg/His polymorphism in SULT1A1 is associated with breast cancer risk.
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Affiliation(s)
- Deliang Tang
- Department of Environmental Health Sciences, Joseph L Mailman School of Public Health, Columbia University, New York City, NY 10032, USA
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23
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Flesher JW, Lehner AF, Horn J. Role of Hydroxymethyl Sulfate Esters in Aromatic Hydrocarbon Carcinogenesis. Polycycl Aromat Compd 2000. [DOI: 10.1080/10406639908020567] [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]
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24
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Tong Z, James MO. Purification and characterization of hepatic and intestinal phenol sulfotransferase with high affinity for benzo[a]pyrene phenols from channel catfish, Ictalurus punctatus. Arch Biochem Biophys 2000; 376:409-19. [PMID: 10775429 DOI: 10.1006/abbi.2000.1746] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cytosol from channel catfish liver and intestinal mucosa has high sulfotransferase activity with low concentrations of 3-, 7-, or 9-hydroxybenzo[a]pyrene. To further investigate this conjugation pathway, sulfotransferase activity toward 9-hydroxybenzo[a]pyrene was isolated from catfish intestinal and hepatic cytosol by chromatography on anion exchange and PAP-agarose affinity columns. SDS-PAGE of the active fractions showed that one major band with molecular size of about 41,000 Da was isolated from intestine, while two bands of about 41,000 and 31,000 Da were obtained from liver. Antibodies against human phenol-sulfating sulfotransferase cross-reacted strongly with the 41,000-Da bands from liver and intestine, but weakly with the hepatic 31,000-Da protein. N-Terminal sequence information could not be obtained from the pure proteins. Following digestion, an internal sequence of 20 amino acid residues was obtained from the hepatic 41,000-Da protein, which matched a sequence found in several mammalian sulfotransferases. No fish sulfotransferase sequences were available for comparison. The identity of the hepatic 31,000-Da protein was not established. The purified 41,000-Da proteins had very high activities with 3-, 7-, or 9-hydroxybenzo[a]pyrene, with K(m) values in the 40-100 nM range and V(max) 125-300 nmol/min/mg of protein. Substrate inhibition was observed when the concentrations of hydroxylated benzo[a]pyrenes were above 0.5 microM. As well as benzo[a]pyrene phenols, the purified 41,000-Da sulfotransferases catalyzed sulfation of 2-naphthol, 4-nitrophenol, 4-methylumbelliferone, 7-(hydroxymethyl)-12-methylbenz[a]anthracene, dehydroepiandrosterone, estrone, and 17beta-estradiol. Phenolic compounds were the preferred substrates for the purified enzymes.
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Affiliation(s)
- Z Tong
- Department of Medicinal Chemistry, University of Florida, Gainesville, Florida 32610, USA
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25
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Flesher JW, Horn J, Lehner AF. 9-Sulfooxymethylanthracene is an ultimate electrophilic and carcinogenic form of 9-hydroxymethylanthracene. Biochem Biophys Res Commun 1998; 251:239-43. [PMID: 9790938 DOI: 10.1006/bbrc.1998.9448] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The role of electrophilic hydroxymethyl sulfate esters in the metabolic activation, DNA-damage, mutagenicity, and complete carcinogenicity of polycyclic aromatic hydrocarbons has been elucidated considerably in recent years. The observations are in agreement with a unified hypothesis which predicts that electrophilic hydroxymethyl sulfate esters and closely related aralkylating agents are major ultimate carcinogenic forms of most, if not all, carcinogenic alkyl-substituted and even unsubstituted carcinogenic polycyclic aromatic hydrocarbons. The common final step in a chain of enzymatic substitution reactions is the formation of an aralkylating agent bearing a good leaving group. Activation of hydroxymethyl derivatives, including 9-hydroxymethylanthracene, to electrophilic mutagens has been shown to be catalyzed by 3'-phosphoadenosine-5'-phosphosulfate-dependent sulfotransferase activity. Recent studies, in a complete carcinogenic model, demonstrate that a number of sulfuric acid ester derivatives are more potent than their hydroxymethyl precursors by repeated subcutaneous injection in female Sprague-Dawley rats. In this paper, these observations have been extended to include 9-sulfooxymethylanthracene as an ultimate electrophilic and carcinogenic form of 9-hydroxymethylanthracene.
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Affiliation(s)
- J W Flesher
- Department of Pharmacology, Experimental Cancer Research Laboratory, and Graduate Center for Toxicology, Albert B. Chandler Medical Center, University of Kentucky, Lexington, Kentucky, 40536, USA.
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26
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Hong ST, Cho YS, Surh YJ, Chung AS. Inhibitory effect of hemin on mutagenicity of the electrophilic sulfuric acid ester of 6-hydroxymethylbenzo[a]pyrene. Chem Biol Interact 1998; 109:255-65. [PMID: 9566750 DOI: 10.1016/s0009-2797(97)00137-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In the present study, we examined the effects of hemin on the mutagenicity of 6-sulfooxymethylbenzo[a]pyrene (SMBP) in Salmonella typhimurium TA98 and Chinese hamster lung fibroblast (V79) cells. The compound was tested for the possible chemoprotective activity against mutagenesis induced by SMBP and its precursor, 6-hydroxymethylbenzo[a]pyrene (HMBP), activated by hepatic cytosol and PAPS in S. typhimurium TA98. Hemin not only inhibited the mutagenic activity of SMBP in V79 cells but repressed the cytotoxicity induced by this reactive ester as demonstrated by increased cell growth. The intracellular accumulation of radioactivity in V79 cells exposed to [3H]SMBP was reduced by approximately 50% when hemin (10 microM) was added to the medium. Likewise, the formation of SMBP-DNA adducts in these cells was significantly attenuated by treatment with hemin. The covalent complex formation of hemin with SMBP was confirmed by solvent extraction and reverse-phase HPLC.
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Affiliation(s)
- S T Hong
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Taejon, Japan
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27
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Flesher JW, Horn J, Lehner AF. Carcinogenicity of 1-hydroxy-3-methylcholanthrene and its electrophilic sulfate ester 1-sulfooxy-3-methylcholanthrene in Sprague-Dawley rats. Biochem Biophys Res Commun 1998; 243:30-5. [PMID: 9473474 DOI: 10.1006/bbrc.1997.8048] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Previous experiments have demonstrated that the carcinogen 1-hydroxy-3-methylcholanthrene is a metabolite of 3-methylcholanthrene. 1-Sulfooxy-3-methylcholanthrene, prepared by chemical synthesis from 1-hydroxy-3-methylcholanthrene, was shown to be a direct acting electrophilic mutagen and DNA damaging agent. These results imply that 1-hydroxy-3-methylcholanthrene could be metabolically activated to an ultimate electrophilic and carcinogenic form of 1-hydroxy-3-methylcholanthrene and 3-methylcholanthrene in a reaction catalyzed by 3'-phosphoadenosine-5'-phosphosulfate-dependent sulfotransferase activity. 1-Hydroxy-3-methylcholanthrene and its aralkylating reactive ester, 1-sulfooxy-3-methylcholanthrene, were individually administered to groups of 12 female Sprague-Dawley rats at a 0.2 mumol dose, three times weekly, for 20 doses. 1-Sulfooxy-3-methylcholanthrene induced sarcomas at the site of injection in 8 of 12 rats (66%) by 52 weeks, whereas 1-hydroxy-3-methylcholanthrene induced sarcomas at the site of injection in 5 of 12 rats (42%) by 52 weeks. These results, taken together with the results of previous experiments, strongly support the hypothesis that the activated electrophilic mutagen 1-sulfooxy-3-methylcholanthrene plays a major role as an ultimate electrophilic and carcinogenic form of 1-hydroxy-3-methylcholanthrene, a major metabolite of 3-methylcholanthrene.
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Affiliation(s)
- J W Flesher
- Department of Pharmacology, University of Kentucky, Lexington 40536, USA.
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28
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Malejka-Giganti D, Ringer DP, Vijayaraghavan P, Kiehlbauch CC, Kong J. Aryl sulfotransferase IV deficiency in rat liver carcinogenesis initiated with diethylnitrosamine and promoted with N-2-fluorenylacetamide or its C-9-oxidized metabolites. Exp Mol Pathol 1997; 64:63-77. [PMID: 9316585 DOI: 10.1006/exmp.1997.2211] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Down regulation of aryl sulfotransferase IV (AST IV) in promotion/progression of liver carcinogenesis by N-2-fluorenylacetamide (2-FAA) has been established. This study examined whether the C-9 oxidized metabolites of 2-FAA, which have recently been shown to promote diethylnitrosamine (DEN)-initiated liver carcinogenesis in male Sprague-Dawley rats, effect the above change. Hence, in DEN-initiated rats, the effects of promoting regimens of 9-OH-2-FAA or 9-oxo-2-FAA, 15 oral doses at 50 and 100 mumol/kg of body weight, were compared to those of 2-FAA at 50 mumol/kg of body weight and of the vehicle on the activity of N-hydroxy(OH)-2-FAA sulfotransferase (ST), an isozyme of AST IV and AST IV expression and distribution. Relative to the vehicle, treatment with the fluorenyl compounds led to decreased levels in hepatic N-OH-2-FAA ST activity and development of hepatic nodules and tumors which had still lower levels of the ST activity than the respective remnant livers. At approximately 8 months after treatment with the C-9-oxidized compounds at doses twice that of 2-FAA, the extents of decreases in the hepatic N-OH-2-FAA ST activity and cytosolic AST IV protein in tumors were comparable to those with 2-FAA. Immunocytochemical analysis showed close association of AST IV deficiency with neoplastic liver lesions. In comparison to N-OH-2-FAA, 9-OH-2-FAA had only low and 9-oxo-2-FAA lacked sulfate acceptor activity in the presence of male rat liver cytosol or AST IV. At 3.3-fold greater concentration than N-OH-2-FAA, 9-oxo-2-FAA inhibited (27%) the sulfate acceptor activity of N-OH-2-FAA in the presence of AST IV, which suggested interference by 9-oxo-2-FAA at the active site. Although the C-9-oxidized compounds do not appear to be substrates for N-OH-2-FAA ST, their ability to cause a decrease in N-OH-2-FAA ST activity and protein similar to that of 2-FAA supports their role in hepatocarcinogenesis. Whereas 9-OH-2-FAA had a 3.9-fold greater sulfate acceptor activity in the presence of female than male rat liver cytosol and inhibited dehydroepiandrosterone ST activity of female rat liver, N-OH-2-FAA and 9-oxo-2-FAA inhibited estrone ST activity of male rat liver, suggesting that the C-9-oxidized compounds as well as N-OH-2-FAA are substrates for STs other than AST IV.
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29
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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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30
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Flesher JW, Horn J, Lehner AF. 7-Sulfooxymethylbenz[a]anthracene is an ultimate electrophilic and carcinogenic form of 7-hydroxymethylbenz[a]anthracene. Biochem Biophys Res Commun 1997; 231:712-6. [PMID: 9070878 DOI: 10.1006/bbrc.1997.6172] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The hypothesis was tested that 7-sulfooxymethylbenz[a]anthracene (7-SBA) is an ultimate electrophilic and carcinogenic form of 7-hydroxymethylbenz[a]anthracene. In conformity with this hypothesis, 7-SBA was more carcinogenic than 7-HBA in inducing sarcomas at the site of repeated subcutaneous injection. These metabolites were individually administered to female Sprague-Dawley rats, beginning at 30 days of age, in 0.2 mumol doses given three times each week for 20 doses. One year after the first injection of 7-SBA, seven of thirteen female Sprague-Dawley rats had developed sarcomas. 7-HBA, on the other hand, had induced sarcomas at the site of injection in only two of tweleve rats. No tumors developed either in the control group given sesame oil:DMSO only or in the untreated control group. It would appear from the results summarized here that the search for an ultimate electrophilic and carcinogenic form of 7-HBA has been successful.
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Affiliation(s)
- J W Flesher
- Department of Pharmacology, A.B. Chandler Medical Center, University of Kentucky, Lexington 40536-0084, USA
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Flesher JW, Horn J, Lehner AF. 7-Sulfooxymethyl-12-methylbenz[a]anthracene is an exceptionally reactive electrophilic mutagen and ultimate carcinogen. Biochem Biophys Res Commun 1997; 231:144-8. [PMID: 9070237 DOI: 10.1006/bbrc.1997.6049] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The hypothesis was tested that an ultimate carcinogen of 7-hydroxymethyl-12-methylbenz[a]anthracene (HMBA), a major metabolite of 7,12-dimethylbenz[a]anthracene (DMBA), is a benzylic carbonium ion generated from an exceptionally reactive aralkylating metabolite, such as an electrophilic sulfate ester. In conformity with this hypothesis, sarcomas were rapidly induced in rats following repeated subcutaneous injection of HMBA (67%) or its electrophilic sulfate ester, sodium 7-sulfooxymethyl-12-methylbenz[a]anthracene (SMBA) (100%). It would appear from the results summarized here that the search for a carcinogenic metabolite of DMBA has been successful. In addition, an aralkylating electrophilic mutagen and carcinogen has been prepared from HMBA, which is itself either an ultimate carcinogen or a direct precursor of an ultimate carcinogen, i.e., a benzylic carbonium ion.
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Affiliation(s)
- J W Flesher
- Department of Pharmacology, Albert B. Chandler Medical Center, University of Kentucky, Lexington 40536, USA.
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Surh YJ. Sulfotransferase-mediated activation of some benzylic and allylic alcohols. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1996; 387:339-45. [PMID: 8794227 DOI: 10.1007/978-1-4757-9480-9_41] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Y J Surh
- Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut 06520-8034, USA
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