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Yamada T. Application of humanized mice to toxicology studies: Evaluation of the human relevance of the mode of action for rodent liver tumor formation by activators of the constitutive androstane receptor (CAR). J Toxicol Pathol 2021; 34:283-297. [PMID: 34629731 PMCID: PMC8484926 DOI: 10.1293/tox.2021-0027] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/08/2021] [Indexed: 12/31/2022] Open
Abstract
The constitutive androstane receptor (CAR)-mediated mode of action (MOA) for phenobarbital (PB)-induced rodent liver tumor formation has been established, with increased hepatocyte proliferation, which is a key event in tumor formation. Previous studies have demonstrated that PB and other CAR-activators stimulate proliferation in cultured rodent hepatocytes, but not in cultured human hepatocytes. However, in the genetically humanized CAR and pregnane X receptor (PXR) mouse (hCAR/hPXR mouse, downstream genes are still mouse), PB increased hepatocyte proliferation and tumor production in vivo. In contrast to the hCAR/hPXR mouse, studies with chimeric mice with human hepatocytes (PXB-mouse, both receptor and downstream genes are human) demonstrated that PB did not increase human hepatocyte proliferation in vivo. PB increased hepatocyte proliferation in a chimeric mouse model with rat hepatocytes, indicating that the lack of human hepatocyte proliferation is not due to any functional defect in the chimeric mouse liver environment. Gene expression analysis demonstrated that the downstream genes of CAR/PXR activation were similar in hCAR/hPXR and CD-1 mice, but differed from those observed in chimeric mice with human hepatocytes. These findings strongly support the conclusion that the MOA for CAR-mediated rodent liver tumor formation is qualitatively implausible for humans. Indeed, epidemiological studies have found no causal link between PB and human liver tumors. There are many similarities with respect to hepatic effects and species differences between rodent CAR and peroxisome proliferator-activated receptor α activators. Based on our research, the chimeric mouse with human hepatocytes (PXB-mouse) is reliable for human cancer risk assessment of test chemicals.
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Affiliation(s)
- Tomoya Yamada
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-8558, Japan
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2
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Weight of evidence and human relevance evaluation of the benfluralin mode of action in rodents (Part I): Liver carcinogenesis. Regul Toxicol Pharmacol 2020; 117:104758. [PMID: 32798612 DOI: 10.1016/j.yrtph.2020.104758] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 07/18/2020] [Accepted: 07/31/2020] [Indexed: 01/11/2023]
Abstract
Benfluralin, an herbicide of the dinitroaniline class used in weed control, was first registered in the United States in 1970. Increased incidence of liver tumors was observed in the 2 year dietary carcinogenicity studies. A review of the toxicology database provides evidence that the mode of action (MOA) of benfluralin responsible for hepatocellular adenoma and carcinoma in rodents depends on activation of the constitutive androstane (CAR)/pregnane X (PXR) receptors, that triggers enzyme induction and altered gene expression leading to hepatocyte proliferation. After prolonged exposures at high dose levels, altered hepatic foci and liver tumors are observed. This hepatocarcinogenic MOA has been described in rodents following long-term dietary exposures to other CAR/PXR activator chemicals, such as phenobarbital, and is generally considered as non-relevant in humans due to differences between human and rodent responses. We analyzed the existing and newly acquired toxicology data to establish that the hepatocarcinogenic MOA of benfluralin in rodents includes the same key events previously described in the rodent MOA of phenobarbital. A weight of evidence approach was taken to establish temporal and dose-related concordance of the causal key events supporting the conclusion that rodent liver carcinogenicity of benfluralin is unlikely to be relevant for human cancer risk.
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Becker RA, Dellarco V, Seed J, Kronenberg JM, Meek B, Foreman J, Palermo C, Kirman C, Linkov I, Schoeny R, Dourson M, Pottenger LH, Manibusan MK. Quantitative weight of evidence to assess confidence in potential modes of action. Regul Toxicol Pharmacol 2017; 86:205-220. [DOI: 10.1016/j.yrtph.2017.02.017] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 02/17/2017] [Accepted: 02/18/2017] [Indexed: 12/31/2022]
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4
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Colnot T, Dekant W. Approaches for grouping of pesticides into cumulative assessment groups for risk assessment of pesticide residues in food. Regul Toxicol Pharmacol 2017; 83:89-99. [DOI: 10.1016/j.yrtph.2016.12.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 12/06/2016] [Accepted: 12/07/2016] [Indexed: 01/25/2023]
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5
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Williams GM, Aardema M, Acquavella J, Berry SC, Brusick D, Burns MM, de Camargo JLV, Garabrant D, Greim HA, Kier LD, Kirkland DJ, Marsh G, Solomon KR, Sorahan T, Roberts A, Weed DL. A review of the carcinogenic potential of glyphosate by four independent expert panels and comparison to the IARC assessment. Crit Rev Toxicol 2016; 46:3-20. [DOI: 10.1080/10408444.2016.1214677] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Gary M. Williams
- Department of Pathology, New York Medical College, Valhalla, NY, USA
| | | | - John Acquavella
- Department of Clinical Epidemiology, Aarhus University, Aarhus, Denmark
| | - Sir Colin Berry
- Department of Pathology, Queen Mary, University of London, London, UK
| | | | | | | | - David Garabrant
- Department of Occupational Medicine and Epidemiology, EpidStat Institute, University of Michigan, Ann Arbor, MI, USA
| | - Helmut A. Greim
- Department of Toxicology and Environmental Hygiene, Technical University of Munich, Munich, Germany
| | | | | | - Gary Marsh
- Department of Biostatistics, Center for Occupational Biostatistics & Epidemiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA, USA
| | | | - Tom Sorahan
- Department of Occupational Epidemiology, University of Birmingham, Birmingham, UK
| | - Ashley Roberts
- Intertek Regulatory & Scientific Consultancy, Mississauga, ON, Canada
| | - Douglas L. Weed
- DLW Consulting Services, LLC, University of New Mexico School of Medicine, Albuquerque, NM, USA
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6
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Williams GM, Berry C, Burns M, de Camargo JLV, Greim H. Glyphosate rodent carcinogenicity bioassay expert panel review. Crit Rev Toxicol 2016; 46:44-55. [DOI: 10.1080/10408444.2016.1214679] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
| | - Colin Berry
- Queen Mary, University of London, London, UK
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Bal-Price A, Lein PJ, Keil KP, Sethi S, Shafer T, Barenys M, Fritsche E, Sachana M, Meek MEB. Developing and applying the adverse outcome pathway concept for understanding and predicting neurotoxicity. Neurotoxicology 2016; 59:240-255. [PMID: 27212452 DOI: 10.1016/j.neuro.2016.05.010] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Revised: 05/13/2016] [Accepted: 05/13/2016] [Indexed: 12/12/2022]
Abstract
The Adverse Outcome Pathway (AOP) concept has recently been proposed to support a paradigm shift in regulatory toxicology testing and risk assessment. This concept is similar to the Mode of Action (MOA), in that it describes a sequence of measurable key events triggered by a molecular initiating event in which a stressor interacts with a biological target. The resulting cascade of key events includes molecular, cellular, structural and functional changes in biological systems, resulting in a measurable adverse outcome. Thereby, an AOP ideally provides information relevant to chemical structure-activity relationships as a basis for predicting effects of structurally similar compounds. AOPs could potentially also form the basis for qualitative and quantitative predictive modeling of the human adverse outcome resulting from molecular initiating or other key events for which higher-throughput testing methods are available or can be developed. A variety of cellular and molecular processes are known to be critical for normal function of the central (CNS) and peripheral nervous systems (PNS). Because of the biological and functional complexity of the CNS and PNS, it has been challenging to establish causative links and quantitative relationships between key events that comprise the pathways leading from chemical exposure to an adverse outcome in the nervous system. Following introduction of the principles of MOA and AOPs, examples of potential or putative adverse outcome pathways specific for developmental or adult neurotoxicity are summarized and aspects of their assessment considered. Their possible application in developing mechanistically informed Integrated Approaches to Testing and Assessment (IATA) is also discussed.
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Affiliation(s)
- Anna Bal-Price
- European Commission Joint Research Centre, Institute for Health and Consumer Protection, Ispra, Italy.
| | - Pamela J Lein
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, CA 95616, USA
| | - Kimberly P Keil
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, CA 95616, USA
| | - Sunjay Sethi
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California Davis, Davis, CA 95616, USA
| | - Timothy Shafer
- Integrated Systems Toxicology Division, Office of Research and Development, U.S. Environmental Protection Agency, RTP, USA
| | - Marta Barenys
- IUF-Leibniz Research Institute for Environmental Medicine, Düsseldorf, Germany
| | - Ellen Fritsche
- IUF-Leibniz Research Institute for Environmental Medicine, Düsseldorf, Germany
| | - Magdalini Sachana
- European Commission Joint Research Centre, Institute for Health and Consumer Protection, Ispra, Italy
| | - M E Bette Meek
- McLaughlin Centre for Risk Science, University of Ottawa, Ottawa, Canada
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8
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Luijten M, Olthof ED, Hakkert BC, Rorije E, van der Laan JW, Woutersen RA, van Benthem J. An integrative test strategy for cancer hazard identification. Crit Rev Toxicol 2016; 46:615-39. [PMID: 27142259 DOI: 10.3109/10408444.2016.1171294] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Assessment of genotoxic and carcinogenic potential is considered one of the basic requirements when evaluating possible human health risks associated with exposure to chemicals. Test strategies currently in place focus primarily on identifying genotoxic potential due to the strong association between the accumulation of genetic damage and cancer. Using genotoxicity assays to predict carcinogenic potential has the significant drawback that risks from non-genotoxic carcinogens remain largely undetected unless carcinogenicity studies are performed. Furthermore, test systems already developed to reduce animal use are not easily accepted and implemented by either industries or regulators. This manuscript reviews the test methods for cancer hazard identification that have been adopted by the regulatory authorities, and discusses the most promising alternative methods that have been developed to date. Based on these findings, a generally applicable tiered test strategy is proposed that can be considered capable of detecting both genotoxic as well as non-genotoxic carcinogens and will improve understanding of the underlying mode of action. Finally, strengths and weaknesses of this new integrative test strategy for cancer hazard identification are presented.
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Affiliation(s)
- Mirjam Luijten
- a Centre for Health Protection, National Institute for Public Health and the Environment (RIVM) , Bilthoven , the Netherlands
| | - Evelyn D Olthof
- a Centre for Health Protection, National Institute for Public Health and the Environment (RIVM) , Bilthoven , the Netherlands
| | - Betty C Hakkert
- b Centre for Safety of Substances and Products, National Institute for Public Health and the Environment (RIVM) , Bilthoven , the Netherlands
| | - Emiel Rorije
- b Centre for Safety of Substances and Products, National Institute for Public Health and the Environment (RIVM) , Bilthoven , the Netherlands
| | | | - Ruud A Woutersen
- d Netherlands Organization for Applied Scientific Research (TNO) , Zeist , the Netherlands
| | - Jan van Benthem
- a Centre for Health Protection, National Institute for Public Health and the Environment (RIVM) , Bilthoven , the Netherlands
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Kleinstreuer NC, Sullivan K, Allen D, Edwards S, Mendrick DL, Embry M, Matheson J, Rowlands JC, Munn S, Maull E, Casey W. Adverse outcome pathways: From research to regulation scientific workshop report. Regul Toxicol Pharmacol 2016; 76:39-50. [PMID: 26774756 PMCID: PMC11027510 DOI: 10.1016/j.yrtph.2016.01.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 01/12/2016] [Indexed: 01/20/2023]
Abstract
An adverse outcome pathway (AOP) helps to organize existing knowledge on chemical mode of action, starting with a molecular initiating event such as receptor binding, continuing through key events, and ending with an adverse outcome such as reproductive impairment. AOPs can help identify knowledge gaps where more research is needed to understand the underlying mechanisms, aid in chemical hazard characterization, and guide the development of new testing approaches that use fewer or no animals. A September 2014 workshop in Bethesda, Maryland considered how the AOP concept could improve regulatory assessments of chemical toxicity. Scientists from 21 countries, representing industry, academia, regulatory agencies, and special interest groups, attended the workshop, titled Adverse Outcome Pathways: From Research to Regulation. Workshop plenary presentations were followed by breakout sessions that considered regulatory acceptance of AOPs and AOP-based tools, criteria for building confidence in an AOP for regulatory use, and requirements to build quantitative AOPs and AOP networks. Discussions during the closing session emphasized a need to increase transparent and inclusive collaboration, especially with disciplines outside of toxicology. Additionally, to increase impact, working groups should be established to systematically prioritize and develop AOPs. Multiple collaborative projects and follow-up activities resulted from the workshop.
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Affiliation(s)
- Nicole C Kleinstreuer
- National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA.
| | - Kristie Sullivan
- Physicians Committee for Responsible Medicine, Washington, DC, USA
| | - David Allen
- Integrated Laboratory Systems, Inc., Research Triangle Park, NC, USA
| | - Stephen Edwards
- National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, NC, USA
| | - Donna L Mendrick
- National Center for Toxicological Research, U.S. Food and Drug Administration, Jefferson, AR, USA
| | - Michelle Embry
- ILSI Health and Environmental Sciences Institute, Washington, DC, USA
| | | | | | - Sharon Munn
- Joint Research Centre, European Commission, Ispra, Italy
| | - Elizabeth Maull
- National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | - Warren Casey
- National Toxicology Program Interagency Center for the Evaluation of Alternative Toxicological Methods, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
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10
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Berry C. The dangers of hazards. Toxicol Res (Camb) 2016; 5:373-376. [PMID: 30090352 PMCID: PMC6062252 DOI: 10.1039/c5tx00472a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Accepted: 01/11/2016] [Indexed: 01/17/2023] Open
Abstract
Concerns about the quality and reproducibility of scientific papers have emphasised the uncertainty of observations in the biological sciences. Focussing on this problem in the types of science that often underlie regulations affecting population exposures has clear implications for regulatory studies. Recent comments on the IARC process of hazard identification in the field of carcinogenesis have identified problems in dealing with public information content and regulatory value of the Monograph system. What is the value of a system that does not clearly identify its methodology for defining a hazard and which does not provide realistic estimates of risk?
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Affiliation(s)
- Colin Berry
- Queen Mary - Pathology , London College Gardens , Dulwich , London SE21 7BE , UK .
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11
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Lapenna S, Gemen R, Wollgast J, Worth A, Maragkoudakis P, Caldeira S. Assessing herbal products with health claims. Crit Rev Food Sci Nutr 2016; 55:1918-28. [PMID: 24915414 DOI: 10.1080/10408398.2012.726661] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Herbs, herbal extracts, or phytochemicals are broadly used as foods, drugs, and as traditional medicines. These are well regulated in Europe, with thorough controls on both safety and efficacy or validity of health claims. However, the distinction between medicines and foods with health claims is not always clear. In addition, there are several cases of herbal products that claim benefits that are not scientifically demonstrated. This review details the European Union (EU) legislative framework that regulates the approval and marketing of herbal products bearing health claims as well as the scientific evidence that is needed to support such claims. To illustrate the latter, we focus on phytoecdysteroid (PE)-containing preparations, generally sold to sportsmen and bodybuilders. We review the limited published scientific evidence that supports claims for these products in humans. In addition, we model the in silico binding between different PEs and human nuclear receptors and discuss the implications of these putative bindings in terms of the mechanism of action of this family of compounds. We call for additional research to validate the safety and health-promoting properties of PEs and other herbal compounds, for the benefit of all consumers.
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Affiliation(s)
- Silvia Lapenna
- a European Commission, Joint Research Centre (JRC), Institute for Health and Consumer Protection (IHCP), Public Health Policy Support Unit, Ispra (VA) , Italy
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Low dose evaluation of the antiandrogen flutamide following a Mode of Action approach. Toxicol Appl Pharmacol 2015; 289:515-24. [PMID: 26485406 DOI: 10.1016/j.taap.2015.10.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2015] [Revised: 10/06/2015] [Accepted: 10/14/2015] [Indexed: 12/22/2022]
Abstract
The dose-response characterization of endocrine mediated toxicity is an on-going debate which is controversial when exploring the nature of the dose-response curve and the effect at the low-end of the curve. To contribute to this debate we have assessed the effects of a wide range of dose levels of the antiandrogen flutamide (FLU) on 7-week male Wistar rats. FLU was administered by oral gavage at doses of 0, 0.001, 0.01, 0.1, 1 and 10mg/kg/day for 28 days. To evaluate the reproducibility, the study was performed 3 times. The molecular initiating event (MIE; AR antagonism), the key events (LH increase, Leydig cell proliferation and hyperplasia increases) and associated events involved in the mode of action (MOA) of FLU induced testicular toxicity were characterized to address the dose response concordance. Results showed no effects at low doses (<0.1mg/kg/day) for the different key events studied. The histopathological changes (Leydig cell hyperplasia) observed at 1 and 10mg/kg/day were associated with an increase in steroidogenesis gene expression in the testis from 1mg/kg/day, as well as an increase in testosterone blood level at 10mg/kg/day. Each key event dose-response was in good concordance with the MOA of FLU on the testis. From the available results, only monotonic dose-response curves were observed for the MIE, the key events, associated events and in effects observed in other sex related tissues. All the results, so far, show that the reference endocrine disruptor FLU induces threshold effects in a standard 28-day toxicity study on adult male rats.
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Evans RM, Scholze M, Kortenkamp A. Examining the feasibility of mixture risk assessment: A case study using a tiered approach with data of 67 pesticides from the Joint FAO/WHO Meeting on Pesticide Residues (JMPR). Food Chem Toxicol 2015; 84:260-9. [DOI: 10.1016/j.fct.2015.08.015] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 08/07/2015] [Accepted: 08/15/2015] [Indexed: 12/28/2022]
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Becker RA, Patlewicz G, Simon TW, Rowlands JC, Budinsky RA. The adverse outcome pathway for rodent liver tumor promotion by sustained activation of the aryl hydrocarbon receptor. Regul Toxicol Pharmacol 2015; 73:172-90. [PMID: 26145830 DOI: 10.1016/j.yrtph.2015.06.015] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 06/19/2015] [Accepted: 06/22/2015] [Indexed: 12/29/2022]
Abstract
An Adverse Outcome Pathway (AOP) represents the existing knowledge of a biological pathway leading from initial molecular interactions of a toxicant and progressing through a series of key events (KEs), culminating with an apical adverse outcome (AO) that has to be of regulatory relevance. An AOP based on the mode of action (MOA) of rodent liver tumor promotion by dioxin-like compounds (DLCs) has been developed and the weight of evidence (WoE) of key event relationships (KERs) evaluated using evolved Bradford Hill considerations. Dioxins and DLCs are potent aryl hydrocarbon receptor (AHR) ligands that cause a range of species-specific adverse outcomes. The occurrence of KEs is necessary for inducing downstream biological responses and KEs may occur at the molecular, cellular, tissue and organ levels. The common convention is that an AOP begins with the toxicant interaction with a biological response element; for this AOP, this initial event is binding of a DLC ligand to the AHR. Data from mechanistic studies, lifetime bioassays and approximately thirty initiation-promotion studies have established dioxin and DLCs as rat liver tumor promoters. Such studies clearly show that sustained AHR activation, weeks or months in duration, is necessary to induce rodent liver tumor promotion--hence, sustained AHR activation is deemed the molecular initiating event (MIE). After this MIE, subsequent KEs are 1) changes in cellular growth homeostasis likely associated with expression changes in a number of genes and observed as development of hepatic foci and decreases in apoptosis within foci; 2) extensive liver toxicity observed as the constellation of effects called toxic hepatopathy; 3) cellular proliferation and hyperplasia in several hepatic cell types. This progression of KEs culminates in the AO, the development of hepatocellular adenomas and carcinomas and cholangiolar carcinomas. A rich data set provides both qualitative and quantitative knowledge of the progression of this AOP through KEs and the KERs. Thus, the WoE for this AOP is judged to be strong. Species-specific effects of dioxins and DLCs are well known--humans are less responsive than rodents and rodent species differ in sensitivity between strains. Consequently, application of this AOP to evaluate potential human health risks must take these differences into account.
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Affiliation(s)
- Richard A Becker
- Regulatory and Technical Affairs Department, American Chemistry Council (ACC), Washington, DC 20002, USA.
| | - Grace Patlewicz
- DuPont Haskell Global Centers for Health and Environmental Sciences, Newark, DE 19711, USA
| | - Ted W Simon
- Ted Simon LLC, 4184 Johnston Road, Winston, GA 30187, USA
| | - J Craig Rowlands
- The Dow Chemical Company, Toxicology & Environmental Research & Consulting, 1803 Building Washington Street, Midland, MI 48674, USA
| | - Robert A Budinsky
- The Dow Chemical Company, Toxicology & Environmental Research & Consulting, 1803 Building Washington Street, Midland, MI 48674, USA
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Meek M(B, Lipscomb JC. Gaining acceptance for the use of in vitro toxicity assays and QIVIVE in regulatory risk assessment. Toxicology 2015; 332:112-23. [DOI: 10.1016/j.tox.2015.01.010] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 12/31/2014] [Accepted: 01/14/2015] [Indexed: 12/01/2022]
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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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Autrup H, Barile FA, Blaauboer BJ, Degen GH, Dekant W, Dietrich D, Domingo JL, Gori GB, Greim H, Hengstler JG, Kacew S, Marquardt H, Pelkonen O, Savolainen K, Vermeulen NP. Principles of Pharmacology and Toxicology Also Govern Effects of Chemicals on the Endocrine System. Toxicol Sci 2015; 146:11-5. [PMID: 26026993 DOI: 10.1093/toxsci/kfv082] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The present debate on chemicals with Hormonal activity, often termed 'endocrine disruptors', is highly controversial and includes challenges of the present paradigms used in toxicology and in hazard identification and risk characterization. In our opinion, chemicals with hormonal activity can be subjected to the well-evaluated health risk characterization approach used for many years including adverse outcome pathways. Many of the points arguing for a specific approach for risk characterization of chemicals with hormonal activity are based on highly speculative conclusions. These conclusions are not well supported when evaluating the available information.
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Affiliation(s)
- Herman Autrup
- International Union of Toxicologists, Institute of Public Health, University of Aarhus, Aarhus, Denmark
| | - Frank A Barile
- College of Pharmacy and Health Sciences, St John's University, Queens, New York, USA
| | - Bas J Blaauboer
- Division of Toxicology, Institute for Risk Assessment Sciences, Utrecht University, Utrecht, The Netherlands
| | - Gisela H Degen
- Leibniz Research Centre for Working Environment and Human Factors (IfADo), TU Dortmund, Dortmund, Germany
| | - Wolfgang Dekant
- Department of Toxicology, University of Wuerzburg, Wuerzburg, Germany;
| | - Daniel Dietrich
- Faculty of Biology, University of Konstanz, Konstanz, Germany
| | - Jose L Domingo
- Laboratory of Toxicology and Environmental Health, School of Medicine, IISPV, Universitat 'Rovira i Virgili', Reus, Spain
| | | | | | - Jan G Hengstler
- Leibniz Research Centre for Working Environment and Human Factors (IfADo), TU Dortmund, Dortmund, Germany
| | - Sam Kacew
- McLaughlin Centre for Risk Assessment, University of Ottawa, Ottawa, Canada
| | | | - Olavi Pelkonen
- Department of Pharmacology and Toxicology, University of Oulu, Oulu, Finland
| | - Kai Savolainen
- Nanosafety Research Centre, Finnish Institute of Occupational Health, Helsinki Finland
| | - Nico P Vermeulen
- Department of Chemistry & Pharmaceutical Sciences, Vrije Universiteit, Amsterdam, The Netherlands
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18
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Claxton LD. The history, genotoxicity, and carcinogenicity of carbon-based fuels and their emissions: Part 5. Summary, comparisons, and conclusions. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2015; 763:103-47. [DOI: 10.1016/j.mrrev.2014.10.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2014] [Revised: 10/04/2014] [Accepted: 10/06/2014] [Indexed: 12/19/2022]
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Meek MEB, Palermo CM, Bachman AN, North CM, Jeffrey Lewis R. Mode of action human relevance (species concordance) framework: Evolution of the Bradford Hill considerations and comparative analysis of weight of evidence. J Appl Toxicol 2014; 34:595-606. [PMID: 24777878 PMCID: PMC4321063 DOI: 10.1002/jat.2984] [Citation(s) in RCA: 135] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2013] [Revised: 11/28/2013] [Accepted: 12/03/2013] [Indexed: 12/30/2022]
Abstract
The mode of action human relevance (MOA/HR) framework increases transparency in systematically considering data on MOA for end (adverse) effects and their relevance to humans. This framework continues to evolve as experience increases in its application. Though the MOA/HR framework is not designed to address the question of "how much information is enough" to support a hypothesized MOA in animals or its relevance to humans, its organizing construct has potential value in considering relative weight of evidence (WOE) among different cases and hypothesized MOA(s). This context is explored based on MOA analyses in published assessments to illustrate the relative extent of supporting data and their implications for dose-response analysis and involved comparisons for chemical assessments on trichloropropane, and carbon tetrachloride with several hypothesized MOA(s) for cancer. The WOE for each hypothesized MOA was summarized in narrative tables based on comparison and contrast of the extent and nature of the supporting database versus potentially inconsistent or missing information. The comparison was based on evolved Bradford Hill considerations rank ordered to reflect their relative contribution to WOE determinations of MOA taking into account increasing experience in their application internationally. This clarification of considerations for WOE determinations as a basis for comparative analysis is anticipated to contribute to increasing consistency in the application of MOA/HR analysis and potentially, transparency in separating science judgment from public policy considerations in regulatory risk assessment.
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Affiliation(s)
- M E Bette Meek
- University of Ottawa, One Stewart Street, Suite 309, Ottawa, Ontario, K1N 6N5, Canada
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20
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Endocrine effects of chemicals: Aspects of hazard identification and human health risk assessment. Toxicol Lett 2013; 223:280-6. [DOI: 10.1016/j.toxlet.2013.03.022] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2012] [Revised: 02/27/2013] [Accepted: 03/08/2013] [Indexed: 01/26/2023]
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Testai E, Galli CL, Dekant W, Marinovich M, Piersma AH, Sharpe RM. A plea for risk assessment of endocrine disrupting chemicals. Toxicology 2013; 314:51-9. [DOI: 10.1016/j.tox.2013.07.018] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Accepted: 07/30/2013] [Indexed: 12/20/2022]
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Scholz S, Sela E, Blaha L, Braunbeck T, Galay-Burgos M, García-Franco M, Guinea J, Klüver N, Schirmer K, Tanneberger K, Tobor-Kapłon M, Witters H, Belanger S, Benfenati E, Creton S, Cronin MT, Eggen RI, Embry M, Ekman D, Gourmelon A, Halder M, Hardy B, Hartung T, Hubesch B, Jungmann D, Lampi MA, Lee L, Léonard M, Küster E, Lillicrap A, Luckenbach T, Murk AJ, Navas JM, Peijnenburg W, Repetto G, Salinas E, Schüürmann G, Spielmann H, Tollefsen KE, Walter-Rohde S, Whale G, Wheeler JR, Winter MJ. A European perspective on alternatives to animal testing for environmental hazard identification and risk assessment. Regul Toxicol Pharmacol 2013; 67:506-30. [DOI: 10.1016/j.yrtph.2013.10.003] [Citation(s) in RCA: 127] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 10/02/2013] [Accepted: 10/16/2013] [Indexed: 12/20/2022]
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Scientific Opinion on the relevance of dissimilar mode of action and its appropriate application for cumulative risk assessment of pesticides residues in food. EFSA J 2013. [DOI: 10.2903/j.efsa.2013.3472] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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Rorije E, Aldenberg T, Buist H, Kroese D, Schüürmann G. The OSIRIS Weight of Evidence approach: ITS for skin sensitisation. Regul Toxicol Pharmacol 2013; 67:146-56. [DOI: 10.1016/j.yrtph.2013.06.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Revised: 06/11/2013] [Accepted: 06/12/2013] [Indexed: 01/24/2023]
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Meek ME, Boobis A, Cote I, Dellarco V, Fotakis G, Munn S, Seed J, Vickers C. New developments in the evolution and application of the WHO/IPCS framework on mode of action/species concordance analysis. J Appl Toxicol 2013; 34:1-18. [PMID: 24166207 PMCID: PMC6701984 DOI: 10.1002/jat.2949] [Citation(s) in RCA: 194] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 09/19/2013] [Indexed: 01/25/2023]
Abstract
The World Health Organization/International Programme on Chemical Safety mode of action/human relevance framework has been updated to reflect the experience acquired in its application and extend its utility to emerging areas in toxicity testing and non-testing methods. The underlying principles have not changed, but the framework’s scope has been extended to enable integration of information at different levels of biological organization and reflect evolving experience in a much broader range of potential applications. Mode of action/species concordance analysis can also inform hypothesis-based data generation and research priorities in support of risk assessment. The modified framework is incorporated within a roadmap, with feedback loops encouraging continuous refinement of fit-for-purpose testing strategies and risk assessment. Important in this construct is consideration of dose–response relationships and species concordance analysis in weight of evidence. The modified Bradford Hill considerations have been updated and additionally articulated to reflect increasing experience in application for cases where the toxicological outcome of chemical exposure is known. The modified framework can be used as originally intended, where the toxicological effects of chemical exposure are known, or in hypothesizing effects resulting from chemical exposure, using information on putative key events in established modes of action from appropriate in vitro or in silico systems and other lines of evidence. This modified mode of action framework and accompanying roadmap and case examples are expected to contribute to improving transparency in explicitly addressing weight of evidence considerations in mode of action/species concordance analysis based on both conventional data sources and evolving methods.
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Affiliation(s)
- M E Meek
- Chemical Risk Assessment, McLaughlin Centre for Population Health Risk Assessment, 1 Stewart Street, Ottawa, Ontario, Canada, K1N 6N5
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Andersen ME, Preston RJ, Maier A, Willis AM, Patterson J. Dose–response approaches for nuclear receptor-mediated modes of action for liver carcinogenicity: Results of a workshop. Crit Rev Toxicol 2013; 44:50-63. [DOI: 10.3109/10408444.2013.835785] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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A framework for fit-for-purpose dose response assessment. Regul Toxicol Pharmacol 2013; 66:234-40. [DOI: 10.1016/j.yrtph.2013.03.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2012] [Revised: 03/20/2013] [Accepted: 03/22/2013] [Indexed: 01/07/2023]
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Dourson M, Becker RA, Haber LT, Pottenger LH, Bredfeldt T, Fenner-Crisp PA. Advancing human health risk assessment: integrating recent advisory committee recommendations. Crit Rev Toxicol 2013; 43:467-92. [PMID: 23844697 PMCID: PMC3725687 DOI: 10.3109/10408444.2013.807223] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Revised: 05/16/2013] [Accepted: 05/17/2013] [Indexed: 11/13/2022]
Abstract
Over the last dozen years, many national and international expert groups have considered specific improvements to risk assessment. Many of their stated recommendations are mutually supportive, but others appear conflicting, at least in an initial assessment. This review identifies areas of consensus and difference and recommends a practical, biology-centric course forward, which includes: (1) incorporating a clear problem formulation at the outset of the assessment with a level of complexity that is appropriate for informing the relevant risk management decision; (2) using toxicokinetics and toxicodynamic information to develop Chemical Specific Adjustment Factors (CSAF); (3) using mode of action (MOA) information and an understanding of the relevant biology as the key, central organizing principle for the risk assessment; (4) integrating MOA information into dose-response assessments using existing guidelines for non-cancer and cancer assessments; (5) using a tiered, iterative approach developed by the World Health Organization/International Programme on Chemical Safety (WHO/IPCS) as a scientifically robust, fit-for-purpose approach for risk assessment of combined exposures (chemical mixtures); and (6) applying all of this knowledge to enable interpretation of human biomonitoring data in a risk context. While scientifically based defaults will remain important and useful when data on CSAF or MOA to refine an assessment are absent or insufficient, assessments should always strive to use these data. The use of available 21st century knowledge of biological processes, clinical findings, chemical interactions, and dose-response at the molecular, cellular, organ and organism levels will minimize the need for extrapolation and reliance on default approaches.
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Affiliation(s)
- Michael Dourson
- Toxicology Excellence for Risk Assessment, Cincinnati, OH, USA.
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von Stackelberg K. A Systematic Review of Carcinogenic Outcomes and Potential Mechanisms from Exposure to 2,4-D and MCPA in the Environment. J Toxicol 2013; 2013:371610. [PMID: 23533401 PMCID: PMC3600329 DOI: 10.1155/2013/371610] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 05/18/2012] [Accepted: 07/11/2012] [Indexed: 12/21/2022] Open
Abstract
Chlorophenoxy compounds, particularly 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxy)acetic acid (MCPA), are amongst the most widely used herbicides in the United States for both agricultural and residential applications. Epidemiologic studies suggest that exposure to 2,4-D and MCPA may be associated with increased risk non-Hodgkins lymphoma (NHL), Hodgkin's disease (HD), leukemia, and soft-tissue sarcoma (STS). Toxicological studies in rodents show no evidence of carcinogenicity, and regulatory agencies worldwide consider chlorophenoxies as not likely to be carcinogenic or unclassifiable as to carcinogenicity. This systematic review assembles the available data to evaluate epidemiologic, toxicological, pharmacokinetic, exposure, and biomonitoring studies with respect to key cellular events noted in disease etiology and how those relate to hypothesized modes of action for these constituents to determine the plausibility of an association between exposure to environmentally relevant concentrations of 2,4-D and MCPA and lymphohematopoietic cancers. The combined evidence does not support a genotoxic mode of action. Although plausible hypotheses for other carcinogenic modes of action exist, a comparison of biomonitoring data to oral equivalent doses calculated from bioassay data shows that environmental exposures are not sufficient to support a causal relationship. Genetic polymorphisms exist that are known to increase the risk of developing NHL. The potential interaction between these polymorphisms and exposures to chlorophenoxy compounds, particularly in occupational settings, is largely unknown.
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Affiliation(s)
- Katherine von Stackelberg
- E Risk Sciences, LLP, 12 Holton Street, Allston, MA 02134, USA
- Harvard Center for Risk Analysis, 401 Park Drive, Landmark 404J, Boston, MA 02215, USA
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Lewis RW, Botham JW. A review of the mode of toxicity and relevance to humans of the triketone herbicide 2-(4-methylsulfonyl-2-nitrobenzoyl)-1,3-cyclohexanedione. Crit Rev Toxicol 2013; 43:185-99. [DOI: 10.3109/10408444.2013.764279] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Vermeire T, Aldenberg T, Buist H, Escher S, Mangelsdorf I, Pauné E, Rorije E, Kroese D. OSIRIS, a quest for proof of principle for integrated testing strategies of chemicals for four human health endpoints. Regul Toxicol Pharmacol 2013; 67:136-45. [PMID: 23385135 DOI: 10.1016/j.yrtph.2013.01.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Revised: 01/20/2013] [Accepted: 01/23/2013] [Indexed: 01/07/2023]
Abstract
Chemical substances policies in Europe are aiming towards chemical safety and at the same time a reduction in animal testing. These goals are alleged to be reachable by mining as many relevant data as possible, evaluate these data with regard to validity, reliability and relevance, and use of these data in so-called Integrated Testing Strategies (ITS). This paper offers an overview of four human health endpoints that were part of the EU-funded OSIRIS project, aiming to develop ITS fit for the EU chemicals legislation REACH. The endpoints considered cover their categorical as well as continuous characteristics: skin sensitisation, repeated dose toxicity, mutagenicity and carcinogenicity. Detailed papers are published elsewhere in this volume. The stepwise ITS approach developed takes advantage of existing information, groups information about similar substances and integrates exposure considerations. The different and possibly contradictory information is weighted and the respective uncertainties taken into account in a weight of evidence (WoE) approach. In case of data gaps, the ITS proposes the most appropriate method to acquire the missing information. Each building block for the ITS, i.e. each in vivo test, in vitro test, (Q)SAR model or human evidence, is evaluated with regard to quality.
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Affiliation(s)
- Theo Vermeire
- National Institute for Public Health and the Environment (RIVM), Antonie van Leeuwenhoeklaan 9, 3721 MA Bilthoven, The Netherlands.
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de Camargo JLV. Chemical carcinogenesis - mode of action to inform quantitative human risk. BMC Proc 2013; 7 Suppl 2:K10. [PMID: 24764467 PMCID: PMC3624635 DOI: 10.1186/1753-6561-7-s2-k10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Affiliation(s)
- João Lauro V de Camargo
- Department of Pathology - Faculty of Medicine, São Paulo State University, UNESP, Botucatu, São Paulo, Brazil
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Hall AP, Elcombe CR, Foster JR, Harada T, Kaufmann W, Knippel A, Küttler K, Malarkey DE, Maronpot RR, Nishikawa A, Nolte T, Schulte A, Strauss V, York MJ. Liver hypertrophy: a review of adaptive (adverse and non-adverse) changes--conclusions from the 3rd International ESTP Expert Workshop. Toxicol Pathol 2012; 40:971-94. [PMID: 22723046 DOI: 10.1177/0192623312448935] [Citation(s) in RCA: 278] [Impact Index Per Article: 23.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Preclinical toxicity studies have demonstrated that exposure of laboratory animals to liver enzyme inducers during preclinical safety assessment results in a signature of toxicological changes characterized by an increase in liver weight, hepatocellular hypertrophy, cell proliferation, and, frequently in long-term (life-time) studies, hepatocarcinogenesis. Recent advances over the last decade have revealed that for many xenobiotics, these changes may be induced through a common mechanism of action involving activation of the nuclear hormone receptors CAR, PXR, or PPARα. The generation of genetically engineered mice that express altered versions of these nuclear hormone receptors, together with other avenues of investigation, have now demonstrated that sensitivity to many of these effects is rodent-specific. These data are consistent with the available epidemiological and empirical human evidence and lend support to the scientific opinion that these changes have little relevance to man. The ESTP therefore convened an international panel of experts to debate the evidence in order to more clearly define for toxicologic pathologists what is considered adverse in the context of hepatocellular hypertrophy. The results of this workshop concluded that hepatomegaly as a consequence of hepatocellular hypertrophy without histologic or clinical pathology alterations indicative of liver toxicity was considered an adaptive and a non-adverse reaction. This conclusion should normally be reached by an integrative weight of evidence approach.
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Affiliation(s)
- A P Hall
- AstraZeneca Pharmaceuticals, Alderley Park, Macclesfield, Cheshire, UK.
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