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Osimitz TG, Droege W. Perspectives on interpretation of Rivera-González et al., (2021). CHEMOSPHERE 2022; 288:132599. [PMID: 34673040 DOI: 10.1016/j.chemosphere.2021.132599] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Revised: 07/19/2021] [Accepted: 10/15/2021] [Indexed: 06/13/2023]
Affiliation(s)
- Thomas G Osimitz
- Science Strategies, LLC, 1001 East Market St., Suite 202, Charlottesville, VA, 22902, USA.
| | - Wiebke Droege
- Science Strategies, LLC, 1001 East Market St., Suite 202, Charlottesville, VA, 22902, USA
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Piperonyl butoxide: Mode of action analysis for mouse liver tumour formation and human relevance. Toxicology 2020; 439:152465. [PMID: 32320717 DOI: 10.1016/j.tox.2020.152465] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 03/31/2020] [Accepted: 04/14/2020] [Indexed: 12/20/2022]
Abstract
In a 79 week bioassay the pesticide synergist piperonyl butoxide (PBO) was shown to significantly increase the incidence of hepatocellular adenoma (but not hepatocellular carcinoma) in male CD-1 mice at dietary levels of 100 and 300 mg/kg/day PBO and in female mice at a dietary level of 300 mg/kg/day. As PBO is not a genotoxic agent, a series of investigative studies were undertaken to elucidate the mode of action (MOA) for PBO-induced mouse liver tumour formation. Male CD-1 mice were fed diets to provide intakes of 0 (control), 30, 100 and 300 mg/kg/day PBO and for purposes of comparison 500 ppm sodium phenobarbital (NaPB), a known constitutive androstane receptor (CAR) activator, for 7 and 14 days. Treatment with 100 and 300 mg/kg/day PBO and 500 ppm NaPB increased relative liver weight which was associated with hepatocyte hypertrophy, with hepatocyte replicative DNA synthesis (RDS) being increased after 7 days treatment. The treatment of CD-1 mice with 30-300 mg/kg/day PBO for 14 days resulted in significant dose-dependent increases in hepatic microsomal cytochrome P450 (CYP) content and 7-pentoxyresorufin O-depentylase (PROD) activity and in hepatic Cyp2b10 mRNA levels. In contrast, PBO produced a biphasic effect on markers of activation of the peroxisome proliferator-activated receptor alpha (PPARα), with small increases in microsomal lauric acid 12-hydroxylase activity and hepatic Cyp4a10 mRNA levels being observed in mice given 100 mg/kg/day with PBO, with either no increase or a significant inhibition being observed in mice given 300 mg/kg/day PBO. The hepatic effects of PBO in male CD-1 mice were generally similar to those produced by NaPB and were reversible after the cessation of treatment for 28 days. Studies were also performed in male C57BL/6J (wild type) mice and in hepatic CAR and pregnane X receptor (PXR) knockout mice (CAR KO/PXR KO mice), where in the CAR KO/PXR KO mice PBO had little effect on markers of CAR activation, but produced some increases in markers of PPARα activation. The treatment of male CD-1 mouse hepatocytes for 4 days with 5-50 μM PBO, 10-1000 μM NaPB and 25 ng/mL epidermal growth factor (EGF) resulted in significant increases in hepatocyte RDS. While treatment of hepatocytes from one male and one female human donor with 5-500 μM PBO and 10-1000 μM NaPB for 4 days had no effect on hepatocyte RDS, treatment with EGF resulted in significant increases in RDS in both human hepatocyte preparations. In summary, PBO is predominantly a hepatic CAR activator at carcinogenic dose levels in CD-1 mice, with activation of hepatic CAR resulting in a suppression of the effect of PBO on hepatic PPARα. A robust MOA for PBO-induced mouse liver tumour formation has been established, this MOA being similar to that previously identified for NaPB and some other rodent liver CAR activators. Based on the lack of effect of PBO on RDS in human hepatocytes, it is considered that the MOA for PBO-induced mouse liver tumour formation is qualitatively not plausible for humans.
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Lake BG. Human relevance of rodent liver tumour formation by constitutive androstane receptor (CAR) activators. Toxicol Res (Camb) 2018; 7:697-717. [PMID: 30090615 PMCID: PMC6060665 DOI: 10.1039/c8tx00008e] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 03/09/2018] [Indexed: 01/01/2023] Open
Abstract
A large number of nongenotoxic chemicals have been shown to increase the incidence of liver tumours in rats and/or mice by a mode of action (MOA) involving activation of the constitutive androstane receptor (CAR). Studies with the model CAR activator phenobarbital (PB) and its sodium salt (sodium phenobarbital; NaPB) have demonstrated that the key and associative events for rat and mouse liver tumour formation include CAR activation, increased hepatocyte replicative DNA synthesis (RDS), induction of cytochrome P450 CYP2B subfamily enzymes, liver hypertrophy, increased altered hepatic foci and hepatocellular adenomas/carcinomas. The key species difference between the rat and mouse compared to humans, is that human hepatocytes are refractory to the mitogenic effects of PB/NaPB and other CAR activators. While PB/NaPB and other CAR activators stimulate RDS in rat and mouse hepatocytes in both in vitro and in vivo studies, such compounds do not stimulate RDS in cultured human hepatocytes and in in vivo studies performed in chimeric mice with humanised livers. In terms of species differences in RDS, unlike the rat and mouse, humans are similar to other species such as the Syrian hamster and guinea pig in being nonresponsive to the mitogenic effects of CAR activators. Overall, the MOA for rat and mouse liver tumour formation by PB/NaPB and other CAR activators is considered qualitatively not plausible for humans. This conclusion is supported by data from a number of epidemiological studies, which demonstrate that chronic treatment with PB does not increase the incidence of liver cancer in humans.
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Affiliation(s)
- Brian G Lake
- Centre for Toxicology , Faculty of Health and Medical Sciences , University of Surrey , Guildford , Surrey GU2 7XH , UK .
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Lake BG, Price RJ, Osimitz TG. Mode of action analysis for pesticide-induced rodent liver tumours involving activation of the constitutive androstane receptor: relevance to human cancer risk. PEST MANAGEMENT SCIENCE 2015; 71:829-834. [PMID: 25045103 DOI: 10.1002/ps.3854] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 06/30/2014] [Indexed: 06/03/2023]
Abstract
A number of non-genotoxic chemicals, including some pesticides, have been shown to increase the incidence of liver tumours in rats and/or mice. Frameworks for analysing the modes of action (MOAs) by which chemicals produce liver tumours in rodents and the relevance of such tumour data for human risk assessment have now been established. One common MOA for rodent liver tumour formation by non-genotoxic chemicals involves activation of the constitutive androstane receptor (CAR). Key and associative events for a CAR-activation MOA include receptor activation, liver hypertrophy, induction of cytochrome P450 enzyme activities, increased replicative DNA synthesis, altered hepatic foci and liver tumours. While some effects of rodent CAR activators can be observed in human liver, a major species difference is that, unlike rodents, CAR activators do not increase replicative DNA synthesis in human hepatocytes. The CAR-activation MOA for rodent liver tumour formation is thus not plausible for humans, and hence such compounds do not pose a hepatocarcinogenic hazard for humans.
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Affiliation(s)
- Brian G Lake
- Centre for Toxicology, Faculty of Health and Medical Sciences, University of Surrey, Guildford, Surrey, UK
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Kossler N, Matheis KA, Ostenfeldt N, Bach Toft D, Dhalluin S, Deschl U, Kalkuhl A. Identification of specific mRNA signatures as fingerprints for carcinogenesis in mice induced by genotoxic and nongenotoxic hepatocarcinogens. Toxicol Sci 2014; 143:277-95. [PMID: 25410580 DOI: 10.1093/toxsci/kfu248] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Long-term rodent carcinogenicity studies for evaluation of chemicals and pharmaceuticals concerning their carcinogenic potential to humans are currently receiving critical revision. Additional data from mechanistic studies can support cancer risk assessment by clarifying the underlying mode of action. In the course of the IMI MARCAR project, a European consortium of EFPIA partners and academics, which aims to identify biomarkers for nongenotoxic carcinogenesis, a toxicogenomic mouse liver database was generated. CD-1 mice were orally treated for 3 and 14 days with 3 known genotoxic hepatocarcinogens: C.I. Direct Black 38, Dimethylnitrosamine and 4,4'-Methylenedianiline; 3 nongenotoxic hepatocarcinogens: 1,4-Dichlorobenzene, Phenobarbital sodium and Piperonyl butoxide; 4 nonhepatocarcinogens: Cefuroxime sodium, Nifedipine, Prazosin hydrochloride and Propranolol hydrochloride; and 3 compounds that show ambiguous results in genotoxicity testing: Cyproterone acetate, Thioacetamide and Wy-14643. By liver mRNA expression analysis using individual animal data, we identified 64 specific biomarker candidates for genotoxic carcinogens and 69 for nongenotoxic carcinogens for male mice at day 15. The majority of genotoxic carcinogen biomarker candidates possess functions in DNA damage response (eg, apoptosis, cell cycle progression, DNA repair). Most of the identified nongenotoxic carcinogen biomarker candidates are involved in regulation of cell cycle progression and apoptosis. The derived biomarker lists were characterized with respect to their dependency on study duration and gender and were successfully used to characterize carcinogens with ambiguous genotoxicity test results, such as Wy-14643. The identified biomarker candidates improve the mechanistic understanding of drug-induced effects on the mouse liver that result in hepatocellular adenomas and/or carcinomas in 2-year mouse carcinogenicity studies.
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Affiliation(s)
- Nadine Kossler
- *Boehringer Ingelheim Pharma GmbH & Co. KG, 88400 Biberach an der Riss, Germany, H. Lundbeck A/S, 2500 Valby, Denmark and UCB Pharma S.A., 1070 Brussels, Belgium
| | - Katja A Matheis
- *Boehringer Ingelheim Pharma GmbH & Co. KG, 88400 Biberach an der Riss, Germany, H. Lundbeck A/S, 2500 Valby, Denmark and UCB Pharma S.A., 1070 Brussels, Belgium
| | - Nina Ostenfeldt
- *Boehringer Ingelheim Pharma GmbH & Co. KG, 88400 Biberach an der Riss, Germany, H. Lundbeck A/S, 2500 Valby, Denmark and UCB Pharma S.A., 1070 Brussels, Belgium
| | - Dorthe Bach Toft
- *Boehringer Ingelheim Pharma GmbH & Co. KG, 88400 Biberach an der Riss, Germany, H. Lundbeck A/S, 2500 Valby, Denmark and UCB Pharma S.A., 1070 Brussels, Belgium
| | - Stéphane Dhalluin
- *Boehringer Ingelheim Pharma GmbH & Co. KG, 88400 Biberach an der Riss, Germany, H. Lundbeck A/S, 2500 Valby, Denmark and UCB Pharma S.A., 1070 Brussels, Belgium
| | - Ulrich Deschl
- *Boehringer Ingelheim Pharma GmbH & Co. KG, 88400 Biberach an der Riss, Germany, H. Lundbeck A/S, 2500 Valby, Denmark and UCB Pharma S.A., 1070 Brussels, Belgium
| | - Arno Kalkuhl
- *Boehringer Ingelheim Pharma GmbH & Co. KG, 88400 Biberach an der Riss, Germany, H. Lundbeck A/S, 2500 Valby, Denmark and UCB Pharma S.A., 1070 Brussels, Belgium
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Elcombe CR, Peffer RC, Wolf DC, Bailey J, Bars R, Bell D, Cattley RC, Ferguson SS, Geter D, Goetz A, Goodman JI, Hester S, Jacobs A, Omiecinski CJ, Schoeny R, Xie W, Lake BG. Mode of action and human relevance analysis for nuclear receptor-mediated liver toxicity: A case study with phenobarbital as a model constitutive androstane receptor (CAR) activator. Crit Rev Toxicol 2013; 44:64-82. [PMID: 24180433 DOI: 10.3109/10408444.2013.835786] [Citation(s) in RCA: 188] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The constitutive androstane receptor (CAR) and pregnane X receptor (PXR) are important nuclear receptors involved in the regulation of cellular responses from exposure to many xenobiotics and various physiological processes. Phenobarbital (PB) is a non-genotoxic indirect CAR activator, which induces cytochrome P450 (CYP) and other xenobiotic metabolizing enzymes and is known to produce liver foci/tumors in mice and rats. From literature data, a mode of action (MOA) for PB-induced rodent liver tumor formation was developed. A MOA for PXR activators was not established owing to a lack of suitable data. The key events in the PB-induced liver tumor MOA comprise activation of CAR followed by altered gene expression specific to CAR activation, increased cell proliferation, formation of altered hepatic foci and ultimately the development of liver tumors. Associative events in the MOA include altered epigenetic changes, induction of hepatic CYP2B enzymes, liver hypertrophy and decreased apoptosis; with inhibition of gap junctional intercellular communication being an associative event or modulating factor. The MOA was evaluated using the modified Bradford Hill criteria for causality and other possible MOAs were excluded. While PB produces liver tumors in rodents, important species differences were identified including a lack of cell proliferation in cultured human hepatocytes. The MOA for PB-induced rodent liver tumor formation was considered to be qualitatively not plausible for humans. This conclusion is supported by data from a number of epidemiological studies conducted in human populations chronically exposed to PB in which there is no clear evidence for increased liver tumor risk.
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Hayashi S, Taketa Y, Inoue K, Takahashi M, Matsuo S, Irie K, Watanabe G, Yoshida M. Effects of pyperonyl butoxide on the female reproductive tract in rats. J Toxicol Sci 2013; 38:891-902. [DOI: 10.2131/jts.38.891] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Seigo Hayashi
- Division of Pathology, National Institute of Health Sciences
| | | | - Kaoru Inoue
- Division of Pathology, National Institute of Health Sciences
| | - Miwa Takahashi
- Division of Pathology, National Institute of Health Sciences
| | - Saori Matsuo
- Division of Pathology, National Institute of Health Sciences
| | - Kaoru Irie
- Division of Pathology, National Institute of Health Sciences
| | - Gen Watanabe
- Laboratory of Veterinary Physiology, Tokyo University of Agriculture and Technology
| | - Midori Yoshida
- Division of Pathology, National Institute of Health Sciences
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Tasaki M, Kuroiwa Y, Inoue T, Hibi D, Matsushita K, Ishii Y, Maruyama S, Nohmi T, Nishikawa A, Umemura T. Oxidative DNA damage andin vivomutagenicity caused by reactive oxygen species generated in the livers ofp53-proficient or -deficientgptdelta mice treated with non-genotoxic hepatocarcinogens. J Appl Toxicol 2012; 33:1433-41. [DOI: 10.1002/jat.2807] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Revised: 06/28/2012] [Accepted: 06/28/2012] [Indexed: 12/22/2022]
Affiliation(s)
- Masako Tasaki
- Division of Pathology; National Institute of Health Sciences; 1-18-1, Kamiyoga, Setagaya-ku Tokyo 158-8501 Japan
| | - Yuichi Kuroiwa
- Division of Pathology; National Institute of Health Sciences; 1-18-1, Kamiyoga, Setagaya-ku Tokyo 158-8501 Japan
| | - Tomoki Inoue
- Division of Pathology; National Institute of Health Sciences; 1-18-1, Kamiyoga, Setagaya-ku Tokyo 158-8501 Japan
| | - Daisuke Hibi
- Division of Pathology; National Institute of Health Sciences; 1-18-1, Kamiyoga, Setagaya-ku Tokyo 158-8501 Japan
| | - Kohei Matsushita
- Division of Pathology; National Institute of Health Sciences; 1-18-1, Kamiyoga, Setagaya-ku Tokyo 158-8501 Japan
| | - Yuji Ishii
- Division of Pathology; National Institute of Health Sciences; 1-18-1, Kamiyoga, Setagaya-ku Tokyo 158-8501 Japan
| | - Soichi Maruyama
- Laboratory of Veterinary Public Health, Department of Veterinary Medicine, College of Bioresource Science; Nihon University; 1866, Kameino Fujisawa-city Kanagawa 252-8510 Japan
| | - Takehiko Nohmi
- Division of Genetics and Mutagenesis; National Institute of Health Sciences; 1-18-1, Kamiyoga, Setagaya-ku Tokyo 158-8501 Japan
| | - Akiyoshi Nishikawa
- Biological Safety Research Center; National Institute of Health Sciences; 1-18-1, Kamiyoga, Setagaya-ku Tokyo 158-8501 Japan
| | - Takashi Umemura
- Division of Pathology; National Institute of Health Sciences; 1-18-1, Kamiyoga, Setagaya-ku Tokyo 158-8501 Japan
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Osimitz TG, Lake BG. Mode-of-action analysis for induction of rat liver tumors by pyrethrins: relevance to human cancer risk. Crit Rev Toxicol 2010; 39:501-11. [PMID: 19463055 DOI: 10.1080/10408440902914014] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
High doses of pyrethrins have been shown to produce liver tumors in female rats. Pyrethrins are not genotoxic agents. Pyrethrins produce liver tumors in rats by a mode of action (MOA) involving induction of hepatic xenobiotic metabolising enzymes, hypertrophy, increased cell proliferation, and the development of altered hepatic foci. The relevance of pyrethrins-induced rat liver tumors to human health was assessed by using the 2006 International Programme on Chemical Safety Human Relevance Framework. The postulated rodent tumor MOA was tested against the Bradford Hill criteria and was found to satisfy the conditions of dose and temporal concordance, biological plausibility, coherence, strength, consistency, and specificity that fit with an established mode of action for rodent liver tumor formation by phenobarbital and related compounds, which are activators of the constitutive androstane receptor. Other possible MOAs including mutagenicity, cytotoxicity, hepatic peroxisome proliferation, porphyria, and hormonal pertubation were excluded. The proposed MOA is considered not to be plausible in humans because pyrethrins, like phenobarbital, do not induce cell proliferation in human hepatocytes. Moreover, epidemiological studies with phenobarbital demonstrate that such compounds do not increase the risk of liver tumors in humans. It is concluded that pyrethrins do not pose a hepatocarcinogenic hazard for humans.
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Affiliation(s)
- Thomas G Osimitz
- Science Strategies LLC, 600 East Water Street, Suite G, Charlottesville, VA 22902, USA.
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Lake BG. Species differences in the hepatic effects of inducers of CYP2B and CYP4A subfamily forms: relationship to rodent liver tumour formation. Xenobiotica 2009; 39:582-96. [DOI: 10.1080/00498250903098184] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Jones HB, Orton TC, Lake BG. Effect of chronic phenobarbitone administration on liver tumour formation in the C57BL/10J mouse. Food Chem Toxicol 2009; 47:1333-40. [DOI: 10.1016/j.fct.2009.03.014] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 03/05/2009] [Accepted: 03/09/2009] [Indexed: 10/21/2022]
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Williams MK, Rundle A, Holmes D, Reyes M, Hoepner LA, Barr DB, Camann DE, Perera FP, Whyatt RM. Changes in pest infestation levels, self-reported pesticide use, and permethrin exposure during pregnancy after the 2000-2001 U.S. Environmental Protection Agency restriction of organophosphates. ENVIRONMENTAL HEALTH PERSPECTIVES 2008; 116:1681-8. [PMID: 19079720 PMCID: PMC2599763 DOI: 10.1289/ehp.11367] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Accepted: 08/05/2008] [Indexed: 05/13/2023]
Abstract
BACKGROUND Widespread residential pesticide use throughout the United States has resulted in ubiquitous, low-level pesticide exposure. The mix of active pesticide ingredients is changing in response to 2000-2001 regulations restricting use of the organophosphorus insecticides chlorpyrifos and diazinon. OBJECTIVES We aimed to determine the impact of U.S. Environmental Protection Agency regulations on pest infestation levels, pesticide use, and pesticides measured in indoor air samples. METHODOLOGY 511 pregnant women from inner-city New York were enrolled between 2000 and 2006. Permethrin, a pyrethroid insecticide; piperonyl butoxide (PBO), a pyrethroid synergist; chlorpyrifos; and diazinon were measured in 48-hr prenatal personal air samples. Data on pest infestation and pesticide use were collected via questionnaire. RESULTS Eighty-eight percent of women reported using pesticides during pregnancy; 55% reported using higher-exposure pesticide applications (spray cans, pest bombs and/or professional pesticide applicators). Self-reported pest sightings and use of higher-exposure applications increased significantly after the regulations were implemented (p < 0.001). PBO, cis-, and trans-permethrin were detected in 75, 19, and 18% of personal air samples, respectively. Detection frequencies of PBO and cis- and trans-permethrin increased significantly over time (p < 0.05 controlling for potential confounders). Levels and/or detection frequencies of these compounds were significantly higher among mothers reporting use of high exposure pesticide applications (p < or = 0.05). Chlorpyrifos and diazinon levels decreased significantly over time (p < 0.001). CONCLUSION In this cohort, pest infestations, use of pesticides, and use of permethrin appear to increase after the residential restriction of organophosphorus insecticides. This is one of the first studies to document widespread residential exposure to PBO.
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Affiliation(s)
- Megan K Williams
- Columbia Center for Children's Environmental Health, Mailman School of Public Health, Columbia University, 60 Haven Avenue, New York, NY 10032, USA.
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Ellinger-Ziegelbauer H, Stuart B, Wahle B, Bomann W, Ahr HJ. Comparison of the expression profiles induced by genotoxic and nongenotoxic carcinogens in rat liver. Mutat Res 2005; 575:61-84. [PMID: 15890375 DOI: 10.1016/j.mrfmmm.2005.02.004] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2004] [Revised: 01/20/2005] [Accepted: 02/23/2005] [Indexed: 05/02/2023]
Abstract
Application of recently developed gene expression techniques using microarrays in toxicological studies (toxicogenomics) facilitate the interpretation of a toxic compound's mode of action and may also allow the prediction of selected toxic effects based on gene expression changes. In order to test this hypothesis, we investigated whether carcinogens at doses known to induce liver tumors in the 2-year rat bioassay deregulate characteristic sets of genes in a short term in vivo study and whether these deregulated genes represent defined biological pathways. Male Wistar rats were dosed with the four nongenotoxic hepatocarcinogens methapyrilene (MPy, 60 mg/kg/day), diethylstilbestrol (DES, 10 mg/kg/day), Wy-14643 (Wy, 60 mg/kg/day), and piperonylbutoxide (PBO, 1200 mg/kg/day). After 1, 3, 7, and 14 days, the livers were taken for histopathological evaluation and for analysis of the gene expression profiles on Affymetrix RG_U34A arrays. The expression profile of the four nongenotoxic carcinogens were compared to the profiles of the four genotoxic carcinogens 2-nitrofluorene (2-NF), dimethylnitrosamine (DMN), 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), and aflatoxin B1 (AB1) from a similar study reported previously. By using statistical and clustering tools characteristically deregulated genes were extracted and functionally classified. Distinct cellular pathways were affected by the nongenotoxic carcinogens compared to the genotoxic carcinogens which at least partly correlated with the two-stage model of carcinogenesis. Characteristic to genotoxic carcinogens were a DNA damage response and the activation of proliferative and survival signaling. Nongenotoxic carcinogens showed responses to oxidative DNA or protein damage, as well as cell cycle progression and signs of regeneration. Many of the gene alterations found with the nongenotoxic carcinogens imply compound-specific mechanisms. Although neither a single gene nor a single pathway will be sufficient to discriminate the two classes of carcinogens, it became evident that combinations of pathway-associated gene expression profiles may be used to predict a genotoxic or nongenotoxic carcinogenic potential of a compound in short-term studies.
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Affiliation(s)
- Heidrun Ellinger-Ziegelbauer
- Bayer Healthcare AG, Department of Molecular and Genetic Toxicology, Aprather Weg 18a, 42096 Wuppertal, Germany.
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Heder AF, Hirsch-Ernst KI, Bauer D, Kahl GF, Desel H. Induction of cytochrome P450 2B1 by pyrethroids in primary rat hepatocyte cultures11Abbreviations: CYP, cytochrome P450; EGF, epidermal growth factor; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; MC, methylcholanthrene; PB, phenobarbital; PBO, piperonyl butoxide; PBREM, phenobarbital-responsive enhancer module; and PROD, pentoxyresorufin-O-depentylase. Biochem Pharmacol 2001; 62:71-9. [PMID: 11377398 DOI: 10.1016/s0006-2952(01)00639-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Numerous xenobiotics are capable of inducing their own metabolism and by enzyme induction can also lead to enhanced biotransformation of other xenobiotics. In this project, we examined the influence of pyrethroids (permethrin, cypermethrin, and fenvalerate) on the expression and activity of the phenobarbital (PB)-inducible cytochrome P450 2B1 isoform (CYP2B1) in primary rat hepatocyte cultures. Incubation of hepatocyte cultures with pyrethroids resulted in a marked CYP2B1 induction. Among the tested pyrethroids, permethrin elicited the most pronounced induction of CYP2B1 mRNA, which exceeded maximal induction achieved by PB at concentrations approximately 10-fold higher. Furthermore, permethrin induced CYP3A1 mRNA expression, while the expression of the CYP1A1 isoform, which in vivo is not responsive to PB treatment, was not significantly affected by pyrethroids. Permethrin-dependent enhancement of CYP2B1 and CYP3A1 mRNA expression was repressed by the hepatotrophic cytokine epidermal growth factor, which is known to also inhibit PB-dependent induction of CYP2B1. Several metabolites of permethrin formed by hepatocytes (3-(2',2'-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylic acid, 3-phenoxybenzyl alcohol, and 3-phenoxybenzoic acid) were ineffective in inducing CYP2B1 mRNA. Furthermore, permethrin stimulated the expression of the luciferase reporter gene under control of the CYP2B1 promoter (comprising the PB-responsive enhancer module) in transiently transfected primary hepatocyte cultures. Thus, permethrin-stimulated gene expression occurred on the transcriptional level. Taken together, these results indicate that the pyrethroid permethrin is a PB-like inducer. Due to its superior potency in induction, permethrin appears as a useful substance for mechanistic studies to elucidate the mechanism of enzyme induction by phenobarbital.
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Affiliation(s)
- A F Heder
- Department of Toxicology, Institute of Pharmacology and Toxicology, University of Goettingen, Robert-Koch-Str. 40, D-37075, Goettingen, Germany.
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Hasmall SC, Roberts RA. The nongenotoxic hepatocarcinogens diethylhexylphthalate and methylclofenapate induce DNA synthesis preferentially in octoploid rat hepatocytes. Toxicol Pathol 2000; 28:503-9. [PMID: 10930035 DOI: 10.1177/019262330002800401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Diethylhexylphthalate (DEHP), a rodent carcinogen, and 1,4-dichlorobenzene (DCB), a noncarcinogen in rat liver, are potent hepatomitogens. We have reported previously that 7-day dosing with DEHP induced a higher bromodeoxyuridine labeling index (LI) in binuclear octoploid (2x4N) rat hepatocytes than did DCB, suggesting that induction of DNA synthesis in 2x4N hepatocytes might represent a more substantial carcinogenic risk. We compared 2 additional rodent hepatocarcinogens, methylclofenapate (MCP) and phenobarbitone, with ethylene thiourea (ETU), a noncarcinogenic hepatomitogen in rat. All 3 chemicals increased hepatic LI; the 8N population had the highest LI, but only the carcinogens increased LI in the 2x4N and 4N populations. To identify the target population for induction of DNA synthesis, we used a 1-hour pulse label at the peak of induction. The results were consistent with the 7-day data, and again the highest LI was in the 8N population. The nongenotoxic rodent carcinogens MCP and DEHP induced a significant increase in the LI in the 2x4N population, whereas ETU and DCB did not. These data support the hypothesis that increased DNA synthesis within the minority 2x4N population may be more significant for subsequent hepatocarcinogenesis.
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Affiliation(s)
- S C Hasmall
- AstraZeneca Central Toxicology Laboratory, Macclesfield, Cheshire, United Kingdom.
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16
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Biegel LB, Applegate M, Sulecki LM. Effects of 5-bromo-2'deoxyuridine (BrdU) implants on hepatic cytochrome P-450 content and beta-oxidation activity in rats and mice. Drug Chem Toxicol 1999; 22:481-9. [PMID: 10445159 DOI: 10.3109/01480549909042527] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Standard regulatory toxicity tests are frequently supplemented with additional compound specific analysis. Analysis of hepatic cytochrome P-450 content, hepatic beta-oxidation activity (biochemical analysis), and cell proliferation rates are examples of these analyses that are included when past experience or similarity to other compounds, suggest that a presently tested compound may have an effect. Until now, separate subsets of animals have been designated for cell proliferation analysis and biochemical analysis, because it was unknown if implantation of 5-bromo-2'deoxyuridine (BrdU) filled osmotic pumps (BrdU implants) would effect the rate of hepatic-beta or hepatic cytochrome P-450 content. The purpose of the current study was to determine if BrdU implants had an effect on hepatic cytochrome P-450 content, beta-oxidation activity, or the measurement of these enzymes in rats and mice. The BrdU was administered through subcutaneous osmotic pump implants. The rate of hepatic peroxisomal beta-oxidation was not altered in male or female rats or mice with the BrdU implants when compared to those of the control groups. The total hepatic cytochrome P-450 content was also not altered in male or female rats or mice with the BrdU implants when compared to those of the control groups. BrdU implants do not appear to have an effect on the rate of hepatic peroxisomal beta-oxidation or the total hepatic cytochrome P-450 content in male or female rats and mice. It can be concluded that in future studies, rats or mice which are designated for cell proliferation analysis using BrdU implants are also suitable for use in evaluating chemically induced effects on hepatic peroxisomal beta-oxidation activity and/or total hepatic cytochrome P-450 content.
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Affiliation(s)
- L B Biegel
- E. I. du Pont de Nemours and Company, Haskell Laboratory for Toxicology and Industrial Medicine, Newark, DE 19714, USA
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17
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Butler WH, Gabriel KL, Osimitz TG, Preiss FJ. Oncogenicity studies of piperonyl butoxide in rats and mice. Hum Exp Toxicol 1998; 17:323-30. [PMID: 9688356 DOI: 10.1177/096032719801700607] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
1. The oncogenicity of Piperonyl butoxide (PBO) has been studied in the mouse and rat. CD-1 mice were administered PBO in the diet at target doses of 0, 30, 100 and 300 mg/kg/day for 79 weeks and Sprague-Dawley rats 0, 30, 100 and 500 mg/kg/day for 104/105 weeks. 2. At termination of the study in the mouse there was evidence of increased liver weights and an increased incidence of eosinophilic adenomas at 100 and 300 mg/kg/day in males and 300 mg/kg/day in females. 3. In rats there was increased liver weights at 100 and 500 mg/kg/day associated with hepatocyte hypertrophy in both male and female rats. There was no increased incidence of neoplasia at any site. Hypertrophy and hyperplasia of thyroid follicles was observed at 500 mg/kg/day in both sexes. 4. The observations reflect the expected changes related to the induction of the mixed function oxygenase group of enzymes. In the mouse the increased incidence of eosinophilic adenomas is not considered relevant for human risk evaluation.
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