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Baze A, Wiss L, Horbal L, Biemel K, Asselin L, Richert L. Comparison of in vitro thyroxine (T4) metabolism between Wistar rat and human hepatocyte cultures. Toxicol In Vitro 2024; 96:105763. [PMID: 38142784 DOI: 10.1016/j.tiv.2023.105763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Revised: 10/24/2023] [Accepted: 12/05/2023] [Indexed: 12/26/2023]
Abstract
In vitro assays remain relatively new in exploring human relevance of liver, in particular nuclear receptor-mediated perturbations of the hypothalamus-pituitary-thyroid axis seen in rodents, mainly in the rat. Consistent with in vivo data, we confirm that thyroid hormone thyroxine metabolism was 9 times higher in primary rat hepatocytes (PRH) than in primary human hepatocytes (PHH) cultured in a 2D sandwich (2Dsw) configuration. In addition, thyroxine glucuronide (T4-G) was by far the major metabolite formed in both species (99.1% in PRH and 69.7% in PHH) followed by thyroxine sulfate (T4-S, 0.7% in PRH and 18.1% in PHH) and triiodothyronine/reverse triiodothyronine (T3/rT3, 0.2% in PRH and 12.2% in PHH). After a 7-day daily exposure to orphan receptor-mediated liver inducers, T4 metabolism was strongly increased in PRH, almost exclusively through increased T4-G formation. These results were consistent with the inductions of glucuronosyltransferase Ugt2b1 and canalicular transporter Mrp2. PHH also responded to activation of the three nuclear receptors, with mainly induction of glucuronosyltransferase UGT1A1 and canalicular transporter MRP2. Despite this, T4 disappearance rate and secreted T4 metabolites were only slightly increased in PHH. Overall, our data highlight that cryopreserved hepatocytes in 2Dsw culture allowing long-term exposure and species comparison are of major interest in improving liver-mediated human safety assessment.
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Affiliation(s)
- Audrey Baze
- KaLy-Cell SAS, 20A rue du Général Leclerc, 67115 Plobsheim, France
| | - Lucille Wiss
- KaLy-Cell SAS, 20A rue du Général Leclerc, 67115 Plobsheim, France
| | - Liliia Horbal
- Pharmacelsus GmbH, Science Park 2, 66123 Saarbrüken, Germany
| | - Klaus Biemel
- Pharmacelsus GmbH, Science Park 2, 66123 Saarbrüken, Germany
| | - Laure Asselin
- KaLy-Cell SAS, 20A rue du Général Leclerc, 67115 Plobsheim, France
| | - Lysiane Richert
- KaLy-Cell SAS, 20A rue du Général Leclerc, 67115 Plobsheim, France; Zylan SAS, 8 rue de la Haute Corniche, 67210 Obernai, France.
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2
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De Boever S, Devisscher L, Vinken M. Unraveling the micro- and nanoplastic predicament: A human-centric insight. Sci Total Environ 2024; 916:170262. [PMID: 38253106 DOI: 10.1016/j.scitotenv.2024.170262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2023] [Revised: 01/02/2024] [Accepted: 01/16/2024] [Indexed: 01/24/2024]
Abstract
Micro- and nanoplastics are vast anthropogenic pollutants in our direct surroundings with a robust environmental stability and a potential for a long-lasting and increasing global circulation. This has raised concerns among the public and policy makers for human health upon exposure to these particles. The micro- and nanoplastic burden on humans is currently under debate, along with criticism on the experimental approaches used in hazard assessment. The present review presents an overview of the human-relevant aspects associated with the current micro-and nanoplastic burden. We focus on environmental circulation and the estimation of exposure quantities to humans, along with a state-of-the-art overview of particle accumulation in over 15 human organs and other specimen. Additionally, data regarding particle characteristics used in toxicity testing was extracted from 91 studies and discussed considering their environmental and human relevance.
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Affiliation(s)
- Sybren De Boever
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, 1090 Brussels, Belgium.
| | - Lindsey Devisscher
- Gut-Liver Immunopharmacology Unit, Basic and Applied Medical Sciences, Liver Research Centre Ghent, Faculty of Medicine and Health Sciences, Universiteit Gent, Corneel Heymanslaan 10, 9000 Ghent, Belgium
| | - Mathieu Vinken
- Entity of In Vitro Toxicology and Dermato-Cosmetology, Department of Pharmaceutical and Pharmacological Sciences, Faculty of Medicine and Pharmacy, Vrije Universiteit Brussel, Laarbeeklaan 103, 1090 Brussels, Belgium
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3
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Botham J, Lewis RW, Travis KZ, Baze A, Richert L, Codrea E, Semino Beninel G, Garcin JC, Strupp C. Species differences and human relevance of the toxicity of 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors and a new approach method in vitro for investigation. Arch Toxicol 2023; 97:991-999. [PMID: 36800004 PMCID: PMC10025182 DOI: 10.1007/s00204-023-03458-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 02/02/2023] [Indexed: 02/18/2023]
Abstract
The mode of action (MoA) of the 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitor herbicides in mammals is well described and is generally accepted to be due to a build-up of excess systemic tyrosine which is associated with the range of adverse effects reported in laboratory animals. What is less well accepted is the basis for the marked difference in the effects of HPPD inhibitors that has been observed across experimental species and humans, where some species show significant toxicities whereas in other species exposure causes few effects. The activity of the catabolic enzyme tyrosine aminotransferase (TAT) varies across species including humans and it is hypothesized that this primarily accounts for the different levels of tyrosinemia observed between species and leads to the subsequent differences in toxicity. The previously reported activities of TAT in different species showed large variation, were inconsistent, have methodological uncertainties and could lead to a reasonable challenge to the scientific basis for the species difference in response. To provide clarity, a new method was developed for the simultaneous and systematic measurement of TAT in vitro using robust methodologies in a range of mammalian species including human. The results obtained showed general correlation between high TAT activity and low in vivo toxicity when using a model based on hepatic cytosol and a very convincing correlation when using a primary hepatocyte model. These data fully support the role of TAT in explaining the species differences in toxicity. Moreover, this information should give greater confidence in selecting the most appropriate animal model (the mouse) for human health risk assessment and for key classification and labeling decision-making.
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Affiliation(s)
| | | | - Kim Z Travis
- Regulatory Science Associates, Inverkip, Scotland, UK
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Rosol TJ, Witorsch RJ. Ethyl acrylate (EA) exposure and thyroid carcinogenicity in rats and mice with relevance to human health. Regul Toxicol Pharmacol 2021; 124:104961. [PMID: 34015422 DOI: 10.1016/j.yrtph.2021.104961] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Revised: 05/03/2021] [Accepted: 05/13/2021] [Indexed: 12/28/2022]
Abstract
Ethyl acrylate (EA) was classified by IARC as a Group-2B Carcinogen based, in part, on data suggesting increased incidence of thyroid neoplasia in rats and mice exposed chronically to EA vapors. We examined chronic exposure of rats and mice to EA vapors, evaluated the data on the incidence of thyroid follicular neoplasia, and determined the relevance of thyroid tumors to human health risk. The data revealed a small statistically significant increase in thyroid tumors in EA-exposed male rats and mice. The tumor incidences were within the range of historical controls and were not consistently dose-dependent. Most thyroid tumors in exposed animals were benign. Chronic exposure of EA to rats and mice (drinking water or gavage) and dogs (capsules) had no evidence of thyroid neoplasia. Results from chronic studies, in vivo and in vitro data, and ToxCastTM/Tox 21 HTPS did not support genotoxic/mutagenic potential for EA. This suggests that the associations between EA exposure and thyroid neoplasia represent chance or random observations rather than a compound-mediated effect. Due to species-specific physiological differences, the hypothalamic-pituitary-thyroid axis of rodents is more sensitive to endocrine disruptive chemicals than that of humans which further suggests that findings in rodents have questionable relevance to human health.
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Affiliation(s)
- Thomas J Rosol
- Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH, 45701, USA.
| | - Raphael J Witorsch
- Department of Physiology and Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, VA, 23298, USA.
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5
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Bomann W, Tinwell H, Jenkinson P, Kluxen FM. Metribuzin-induced non-adverse liver changes result in rodent-specific non-adverse thyroid effects via uridine 5'-diphospho-glucuronosyltransferase (UDPGT, UGT) modulation. Regul Toxicol Pharmacol 2021; 122:104884. [PMID: 33596450 DOI: 10.1016/j.yrtph.2021.104884] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 01/19/2021] [Accepted: 02/01/2021] [Indexed: 11/18/2022]
Abstract
Metribuzin is a herbicide that inhibits photosynthesis and has been used for over 40 years. Its main target organ is the liver and to some extent the kidney in rats, dogs, and rabbits. Metribuzin shows a specific thyroxine (T4) profile in rat studies with T4 increases at low doses and T4 decreases at higher doses. Only the T4 decreases occur together with histopathological changes in the thyroid and weight changes of liver and thyroid. A set of experiments was conducted to investigate metribuzin's endocrine disruptor potential according to European guidance and regulations. The results indicate that a liver enzyme modulation, i.e. of the uridine 5'-diphospho-glucuronosyltransferase (UDPGT, UGT), is most likely responsible for both increased and decreased plasma thyroxine level and for thyroid histopathological observations. Animals with high T4 levels show low UGT activity, while animals with low T4 levels show high UGT activity. A causal relationship was inferred, since other potentially human-relevant mode of action (MOA) pathways were excluded in dedicated studies, i.e. inhibition of deiodinases (DIO), inhibition of thyroid peroxidase (TPO) or of the sodium importer system (NIS). This liver metabolism-associated MOA is considered not relevant for human hazard assessment, due to species differences in thyroid homeostasis between humans and rats and, more importantly, based on experimental data showing that metribuzin affects UGT activity in rat but not in human hepatocytes. Further, we discuss whether or not increased T4 levels in the rat, in the absence of histopathological changes, should be considered as adverse and therefore used as an appropriate hazard model for humans. Based on a weight of evidence approach, metribuzin should not be classified as an endocrine disruptor with regard to the thyroid modality.
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Affiliation(s)
- Werner Bomann
- Toxconsult, 9393 W 110th Street, 51 Corporate Woods, Suite 500, Overland Park, KS, 66210, USA.
| | - Helen Tinwell
- Bayer.SAS, 16 rue Jean-Marie Leclair, 69009, Lyon, France
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Kawamura S, Otani M, Miyamoto T, Abe J, Ihara R, Inawaka K, Fantel AG. Different effects of an N-phenylimide herbicide on heme biosynthesis between human and rat erythroid cells. Reprod Toxicol 2021; 99:27-38. [PMID: 33249232 DOI: 10.1016/j.reprotox.2020.11.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 10/28/2020] [Accepted: 11/22/2020] [Indexed: 01/10/2023]
Abstract
Rat developmental toxicity including embryolethality and teratogenicity (mainly ventricular septal defects and wavy ribs) were produced by S-53482, an N-phenylimide herbicide that inhibits protoporphyrinogen oxidase (PPO) common to chlorophyll and heme biosynthesis. The sequence of key biological events in the mode of action has been elucidated as follows: inhibition of PPO interferes with normal heme synthesis, which causes loss of blood cells leading to fetal anemia, embryolethality and the development of malformations. In this study we investigated whether the rat is a relevant model for the assessment of the human hazard of the herbicide. To study effects on heme biosynthesis, human erythroleukemia, human cord blood, and rat erythroleukemia cells were treated with the herbicide during red cell differentiation. Protoporphyrin IX, a marker of PPO inhibition, and heme were determined. We investigated whether synchronous maturation of primitive erythropoiesis, which can contribute to massive losses of embryonic blood, occurs in rats. The population of primitive erythroblasts was observed on gestational days 11 through 14. Heme production was suppressed in rat erythroid cells. In contrast, heme reduction was not seen in both human erythroid cells when PPO was inhibited. Rats underwent synchronous maturation in primitive erythropoiesis. Our results combined with epidemiological findings that patients with deficient PPO are not anemic led us to conclude that human erythroblasts are resistant to the herbicide. It is suggested that the rat would be an inappropriate model for assessing the developmental toxicity of S-53482 in humans as rats are specifically sensitive to PPO inhibition by the herbicide.
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Affiliation(s)
- Satoshi Kawamura
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan.
| | - Mitsuhiro Otani
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Taiki Miyamoto
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Jun Abe
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Ryo Ihara
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Kunifumi Inawaka
- Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., 1-98, Kasugade-naka 3-chome, Konohana-ku, Osaka, 554-8558, Japan
| | - Alan G Fantel
- Department of Pediatrics, University of Washington, 1959 NE Pacific St. Box 366320, Seattle, WA 98195-6320, USA
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Strupp C, Quesnot N, Weber-Parmentier C, Richert L, Bomann WH, Singh P. Weight of Evidence and Human Relevance Evaluation of the Benfluralin Mode of Action in Rats (Part II): Thyroid carcinogenesis. Regul Toxicol Pharmacol 2020; 117:104736. [PMID: 32798613 DOI: 10.1016/j.yrtph.2020.104736] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Revised: 07/10/2020] [Accepted: 07/13/2020] [Indexed: 11/08/2022]
Abstract
Benfluralin is an herbicide of the dinitroaniline class used to control grasses and weeds. In a 2 year dietary study in rats, benfluralin increased incidences of thyroid follicular adenoma and carcinoma at high dietary concentrations (≥2500 ppm). The benfluralin toxicology database suggests the mode of action (MOA) is initiated by induction of liver metabolizing enzymes, particularly thyroid hormone specific UGTs, a major pathway for T4 clearance in rats. As reported with phenobarbital, this effect triggers negative feedback regulation, increasing thyroid stimulating hormone (TSH) release into circulating blood. When sustained over time, this leads to thyroid changes such as follicular hypertrophy, hyperplasia and thyroid follicular tumors with chronic exposures. The described MOA was previously established in rat studies with various chemical activators of xenobiotic receptors in the liver. It is generally considered as non-relevant in humans, due to differences between humans and rats in T4 turnover and susceptibility to this carcinogenic MOA. A structured methodology based on the IPCS/MOA/Human Relevance framework was used in the evaluation of available benfluralin data, and the conclusion was determined that the carcinogenic potential of benfluralin in the thyroid is not relevant in humans.
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Affiliation(s)
- Christian Strupp
- Gowan, Highlands House, Basingstoke Road, Spencers Wood Reading, Berkshire, RG7 1NT, United Kingdom.
| | - Nicolas Quesnot
- Charles River Laboratories Evreux, 27005, Evreux Cedex, France.
| | | | | | - Werner H Bomann
- ToxConsult®, 9393 W 110th Street, 51 Corporate Woods, Suite 500, Overland Park, KS, 66210, USA.
| | - Pramila Singh
- Charles River Laboratories Evreux, 27005, Evreux Cedex, France.
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8
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Strupp C, Quesnot N, Richert L, Moore J, Bomann WH, Singh P. 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] [What about the content of this article? (0)] [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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Colnot T, Melching-Kollmuß S, Semino G, Dekant W. A flow scheme for cumulative assessment of pesticides for adverse liver effects. Regul Toxicol Pharmacol 2020; 116:104694. [PMID: 32621977 DOI: 10.1016/j.yrtph.2020.104694] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 04/15/2020] [Accepted: 05/28/2020] [Indexed: 12/17/2022]
Abstract
The European Food Safety Authority (EFSA) is developing approaches to cumulative risk assessment by assigning pesticides to cumulative assessment groups (CAGs). For assignment to CAGs, EFSA relies on common toxic effects (CTEs) on the target system. The developed flow scheme for assignment to liver CAGs sequentially assesses the consistency of the CTE, its adversity, its potential to be secondary to other toxicities, its human relevance, and the relation of the NOAEL for the CTE to the overall NOAEL. If the responses to all questions are "yes", allocation to a CAG is supported; "no" stops the process.
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Affiliation(s)
| | | | | | - Wolfgang Dekant
- Department of Toxicology, University of Würzburg, Versbacher Strasse 9, 97078, Würzburg, Germany.
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Lake BG, Price RJ, Scott MP, Chatham LR, Vardy A, Osimitz TG. 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] [What about the content of this article? (0)] [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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11
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Bos PMJ, Gosens I, Geraets L, Delmaar C, Cassee FR. Pulmonary toxicity in rats following inhalation exposure to poorly soluble particles: The issue of impaired clearance and the relevance for human health hazard and risk assessment. Regul Toxicol Pharmacol 2019; 109:104498. [PMID: 31604110 DOI: 10.1016/j.yrtph.2019.104498] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 10/04/2019] [Accepted: 10/07/2019] [Indexed: 11/19/2022]
Abstract
Intensive discussions are ongoing about the interpretation of pulmonary effects observed in rats exposed to poorly soluble particles. Alveolar clearance differs between rats and humans and becomes impaired in rats at higher exposure concentrations. Some have doubted the human relevance of toxic effects observed in rats under impaired clearance conditions and have suggested that experimental exposures should stay below concentrations inducing impaired clearance. However, for regulatory purposes, insight in potential health effects at relatively high concentrations is needed to fully understand the hazard. Many aspects of impaired particle clearance remain unclear, hampering human health hazard and risk assessment. For an adequate evaluation of the impact of impaired clearance on pulmonary toxicity, a clear definition of alveolar clearance is needed that enables to quantitatively relate the level of impairment to the induction of adverse pulmonary health effects. Also, information is needed on the mechanism of action and the appropriate dose metric for the pulmonary effects observed. In absence of these data, human hazard and risk assessment can only be performed in a pragmatic way. Unless available data clearly point out otherwise, rat pulmonary toxicity including lung inflammation and tumour formation, needs to be considered relevant for human hazard and risk assessment.
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Affiliation(s)
- Peter M J Bos
- National Institute for Public Health and the Environment, Bilthoven, the Netherlands
| | - Ilse Gosens
- National Institute for Public Health and the Environment, Bilthoven, the Netherlands
| | - Liesbeth Geraets
- National Institute for Public Health and the Environment, Bilthoven, the Netherlands
| | - Christiaan Delmaar
- National Institute for Public Health and the Environment, Bilthoven, the Netherlands
| | - Flemming R Cassee
- National Institute for Public Health and the Environment, Bilthoven, the Netherlands; Institute for Risk Assessment Sciences, Utrecht University, Utrecht, the Netherlands.
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12
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Laube B, Michaelsen S, Meischner V, Hartwig A, Epe B, Schwarz M. Classification or non-classification of substances with positive tumor findings in animal studies: Guidance by the German MAK commission. Regul Toxicol Pharmacol 2019; 108:104444. [PMID: 31433998 DOI: 10.1016/j.yrtph.2019.104444] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2019] [Revised: 08/10/2019] [Accepted: 08/14/2019] [Indexed: 12/19/2022]
Abstract
One of the important tasks of the German Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (known as the MAK Commission) is in the evaluation of a potential for carcinogenicity of hazardous substances at the workplace. Often, this evaluation is critically based on data on carcinogenic responses seen in animal studies and, if positive tumor responses have been observed, this will mostly lead to a classification of the substance under investigation into one of the classes for carcinogens. However, there are cases where it can be demonstrated with a very high degree of confidence that the tumor findings in the experimental animals are not relevant for humans at the workplace and, therefore, the MAK Commission will not classify the respective substance into one of the classes for carcinogens. This paper will summarize the general criteria used by the MAK Commission for the categorization into "carcinogen" and "non-carcinogen" and compare this procedure with those used by other national and international organizations.
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Affiliation(s)
- Britta Laube
- Scientific Secretariat of the Senate Commission on the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission), Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Department of Food Chemistry and Toxicology, Karlsruhe, Germany
| | - Sandra Michaelsen
- Scientific Secretariat of the Senate Commission on the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission), Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Department of Food Chemistry and Toxicology, Karlsruhe, Germany
| | - Veronika Meischner
- Scientific Secretariat of the Senate Commission on the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission), Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Department of Food Chemistry and Toxicology, Karlsruhe, Germany
| | - Andrea Hartwig
- Food Chemistry and Toxicology, Institute of Applied Bioscience, Karlsruhe Institute of Technology (KIT), Adenauerring 20a, 76131, Karlsruhe, Germany
| | - Bernd Epe
- Institute of Pharmacy and Biochemistry, University of Mainz, Staudingerweg 5, D-55099, Mainz, Germany
| | - Michael Schwarz
- Dept. of Experimental and Clinical Pharmacology and Toxicology, Dept. Toxicology, Eberhard Karls University, Wilhelmstr. 56, 72074, Tübingen, Germany.
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Bartsch R, Brinkmann B, Jahnke G, Laube B, Lohmann R, Michaelsen S, Neumann I, Greim H. Human relevance of follicular thyroid tumors in rodents caused by non-genotoxic substances. Regul Toxicol Pharmacol 2018; 98:199-208. [PMID: 30076866 DOI: 10.1016/j.yrtph.2018.07.025] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Revised: 07/27/2018] [Accepted: 07/28/2018] [Indexed: 12/31/2022]
Abstract
Chronic stimulation of the thyroid gland of rodents by TSH leads to thyroid follicular hyperplasia and subsequently to thyroid follicular adenomas and carcinomas. However, the interpretations of rodent thyroid tumors are contradictory. The U.S. Food and Drug Administration (FDA) concluded that findings with drugs that lead to increased levels of thyroid-stimulating hormone (TSH) in rats are not relevant to humans, whereas the U.S. Environmental Protection Agency (US EPA) concluded that chemicals that produce rodent thyroid tumors may pose a carcinogenic hazard for humans although the thyroid of rodents appears to be more sensitive to a carcinogenic stimulus than that of humans. Meanwhile, based on the CLP Criteria of the European Chemicals Agency (ECHA), rodent thyroid tumors caused by the induction of uridine-diphosphate-glucuronosyl transferases (UDGT) were assessed as not relevant to humans. To clarify these discrepant positions, the function and regulation of the thyroid gland are described and the types of thyroid tumors and the causes of their development in humans and animals are examined. Based on these data and the evidence that so far, except radiation, no chemical is known to increase the incidence of thyroid tumors in humans, it is concluded that rodent thyroid tumors resulting from continuous stimulation of the thyroid gland by increased TSH levels are not relevant to humans. Consequently, compounds that induce such tumors do not warrant classification as carcinogenic.
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Affiliation(s)
- Ruediger Bartsch
- Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Department of Food Chemistry and Toxicology, Karlsruhe, Germany
| | - Britta Brinkmann
- Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Department of Food Chemistry and Toxicology, Karlsruhe, Germany
| | - Gunnar Jahnke
- Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Department of Food Chemistry and Toxicology, Karlsruhe, Germany
| | - Britta Laube
- Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Department of Food Chemistry and Toxicology, Karlsruhe, Germany
| | - Ruth Lohmann
- Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Department of Food Chemistry and Toxicology, Karlsruhe, Germany
| | - Sandra Michaelsen
- Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Department of Food Chemistry and Toxicology, Karlsruhe, Germany
| | - Ingrid Neumann
- Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Department of Food Chemistry and Toxicology, Karlsruhe, Germany
| | - Helmut Greim
- Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Department of Food Chemistry and Toxicology, Karlsruhe, Germany.
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