1
|
Foley B, Hopperstad K, Gamble J, Lynn SG, Thomas RS, Deisenroth C. Technical evaluation and standardization of the human thyroid microtissue assay. Toxicol Sci 2024; 199:89-107. [PMID: 38310358 DOI: 10.1093/toxsci/kfae014] [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] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2024] Open
Abstract
The success and sustainability of U.S. EPA efforts to reduce, refine, and replace in vivo animal testing depends on the ability to translate toxicokinetic and toxicodynamic data from in vitro and in silico new approach methods (NAMs) to human-relevant exposures and health outcomes. Organotypic culture models employing primary human cells enable consideration of human health effects and inter-individual variability but present significant challenges for test method standardization, transferability, and validation. Increasing confidence in the information provided by these in vitro NAMs requires setting appropriate performance standards and benchmarks, defined by the context of use, to consider human biology and mechanistic relevance without animal data. The human thyroid microtissue (hTMT) assay utilizes primary human thyrocytes to reproduce structural and functional features of the thyroid gland that enable testing for potential thyroid-disrupting chemicals. As a variable-donor assay platform, conventional principles for assay performance standardization need to be balanced with the ability to predict a range of human responses. The objectives of this study were to (1) define the technical parameters for optimal donor procurement, primary thyrocyte qualification, and performance in the hTMT assay, and (2) set benchmark ranges for reference chemical responses. Thyrocytes derived from a cohort of 32 demographically diverse euthyroid donors were characterized across a battery of endpoints to evaluate morphological and functional variability. Reference chemical responses were profiled to evaluate the range and chemical-specific variability of donor-dependent effects within the cohort. The data-informed minimum acceptance criteria for donor qualification and set benchmark parameters for method transfer proficiency testing and validation of assay performance.
Collapse
Affiliation(s)
- Briana Foley
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA
| | - Kristen Hopperstad
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA
| | - John Gamble
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA
- Oak Ridge Institute for Science and Education, Oak Ridge, Tennessee 37831, USA
| | - Scott G Lynn
- Office of Pesticide Programs, U.S. Environmental Protection Agency, Washington, District of Columbia 20460, USA
| | - Russell S Thomas
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA
| | - Chad Deisenroth
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, USA
| |
Collapse
|
2
|
Hopperstad K, Deisenroth C. Development of a bioprinter-based method for incorporating metabolic competence into high-throughput in vitro assays. Front Toxicol 2023; 5:1196245. [PMID: 37215384 PMCID: PMC10192685 DOI: 10.3389/ftox.2023.1196245] [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] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2023] [Accepted: 04/21/2023] [Indexed: 05/24/2023] Open
Abstract
The acceptance and use of in vitro data for hazard identification, prioritization, and risk evaluation is partly limited by uncertainties associated with xenobiotic metabolism. The lack of biotransformation capabilities of many in vitro systems may under- or overestimate the hazard of compounds that are metabolized to more or less active metabolites in vivo. One approach to retrofitting existing bioassays with metabolic competence is the lid-based Alginate Immobilization of Metabolic Enzymes (AIME) method, which adds hepatic metabolism to conventional high-throughput screening platforms. Here, limitations of the lid-based AIME method were addressed by incorporating bioprinting, which involved depositing S9-encapsulated microspheres into standard 384-well plates with requisite cofactors for phase I and II hepatic metabolism. Objectives of this study included: 1) compare the lid-based and AIME bioprinting methods by assessing the enzymatic activity of a common cytochrome P450 (CYP) enzyme, 2) use biochemical assays with the bioprinting method to characterize additional measures of phase I and II metabolic activity, and 3) evaluate the bioprinting method by screening 25 chemicals of known metabolism-dependent bioactivity in the VM7Luc estrogen receptor transactivation (ERTA) assay. A comparison of the two methods revealed comparable precision and dynamic range. Activity of additional CYP enzymes and glucuronidation was observed using the AIME bioprinting method. The ERTA experiment identified 19/21 ER-active test chemicals, 14 of which were concordant with expected biotransformation effects (73.7%). Additional refinement of the AIME bioprinting method has the potential to expand high-throughput screening capabilities in a robust, accessible manner to incorporate in vitro metabolic competence.
Collapse
|
3
|
Deisenroth C, DeGroot DE, Zurlinden T, Eicher A, McCord J, Lee MY, Carmichael P, Thomas RS. The Alginate Immobilization of Metabolic Enzymes Platform Retrofits an Estrogen Receptor Transactivation Assay With Metabolic Competence. Toxicol Sci 2021; 178:281-301. [PMID: 32991717 DOI: 10.1093/toxsci/kfaa147] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The U.S. EPA Endocrine Disruptor Screening Program utilizes data across the ToxCast/Tox21 high-throughput screening (HTS) programs to evaluate the biological effects of potential endocrine active substances. A potential limitation to the use of in vitro assay data in regulatory decision-making is the lack of coverage for xenobiotic metabolic processes. Both hepatic- and peripheral-tissue metabolism can yield metabolites that exhibit greater activity than the parent compound (bioactivation) or are inactive (bioinactivation) for a given biological target. Interpretation of biological effect data for both putative endocrine active substances, as well as other chemicals, screened in HTS assays may benefit from the addition of xenobiotic metabolic capabilities to decrease the uncertainty in predicting potential hazards to human health. The objective of this study was to develop an approach to retrofit existing HTS assays with hepatic metabolism. The Alginate Immobilization of Metabolic Enzymes (AIME) platform encapsulates hepatic S9 fractions in alginate microspheres attached to 96-well peg lids. Functional characterization across a panel of reference substrates for phase I cytochrome P450 enzymes revealed substrate depletion with expected metabolite accumulation. Performance of the AIME method in the VM7Luc estrogen receptor transactivation assay was evaluated across 15 reference chemicals and 48 test chemicals that yield metabolites previously identified as estrogen receptor active or inactive. The results demonstrate the utility of applying the AIME method for identification of false-positive and false-negative target assay effects, reprioritization of hazard based on metabolism-dependent bioactivity, and enhanced in vivo concordance with the rodent uterotrophic bioassay. Integration of the AIME metabolism method may prove useful for future biochemical and cell-based HTS applications.
Collapse
Affiliation(s)
- Chad Deisenroth
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | - Danica E DeGroot
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | - Todd Zurlinden
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | - Andrew Eicher
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | - James McCord
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | - Mi-Young Lee
- Safety and Environmental Assurance Centre, Unilever, Colworth Science, Park, Bedford, Sharnbrook MK44 1LQ, UK
| | - Paul Carmichael
- Safety and Environmental Assurance Centre, Unilever, Colworth Science, Park, Bedford, Sharnbrook MK44 1LQ, UK
| | - Russell S Thomas
- Center for Computational Toxicology and Exposure, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| |
Collapse
|
4
|
Souder JP, Gorelick DA. ahr2, But Not ahr1a or ahr1b, Is Required for Craniofacial and Fin Development and TCDD-dependent Cardiotoxicity in Zebrafish. Toxicol Sci 2020; 170:25-44. [PMID: 30907958 DOI: 10.1093/toxsci/kfz075] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that binds environmental toxicants and regulates gene expression. AHR also regulates developmental processes, like craniofacial development and hematopoiesis, in the absence of environmental exposures. Zebrafish have 3 paralogs of AHR: ahr1a, ahr1b, and ahr2. Adult zebrafish with mutations in ahr2 exhibited craniofacial and fin defects. However, the degree to which ahr1a and ahr1b influence ahr2 signaling and contribute to fin and craniofacial development are not known. We compared morphology of adult ahr2 mutants and ahr1a;ahr1b single and double mutant zebrafish. We found that ahr1a;ahr1b single and double mutants were morphologically normal whereas ahr2 mutant zebrafish demonstrated fin and craniofacial malformations. At 5 days post fertilization, both ahr1a;ahr1b and ahr2 mutant larvae were normal, suggesting that adult phenotypes are due to defects in maturation or maintenance. Next, we analyzed the function of zebrafish AHRs activated by environmental ligands. The prototypical AHR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), induces toxicity in humans and rodents via AHR and causes cardiotoxicity in zebrafish embryos. It has been shown that embryos with mutations in ahr2 are resistant to TCDD toxicity, yet it is unclear whether ahr1 receptors are required. Furthermore, though AHR was shown to interact with estrogen receptor alpha following TCDD treatment, it is not known whether this interaction is constitutive or context-dependent. To determine whether estrogen receptors are constitutive cofactors for AHR signaling, we used genetic and pharmacologic techniques to analyze TCDD-dependent toxicity in estrogen receptor and ahr mutant embryos. We found that embryos with mutations in ahr1a;ahr1b or estrogen receptor genes are susceptible to TCDD toxicity whereas ahr2 mutant embryos are TCDD-resistant. Moreover, pharmacologic blockade of nuclear estrogen receptors failed to prevent TCDD toxicity. These findings suggest that ahr1 genes do not have overlapping functions with ahr2 in fin and craniofacial development or TCDD-dependent toxicity, and that estrogen receptors are not constitutive partners of ahr2.
Collapse
Affiliation(s)
- Jaclyn P Souder
- Medical Scientist Training Program & Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, Alabama, 35294.,Department of Molecular and Cellular Biology, Center for Precision Environmental Health, Baylor College of Medicine, Houston, Texas, 77030
| | - Daniel A Gorelick
- Medical Scientist Training Program & Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, Alabama, 35294.,Department of Molecular and Cellular Biology, Center for Precision Environmental Health, Baylor College of Medicine, Houston, Texas, 77030
| |
Collapse
|
5
|
Rock KD, St Armour G, Horman B, Phillips A, Ruis M, Stewart AK, Jima D, Muddiman DC, Stapleton HM, Patisaul HB. Effects of Prenatal Exposure to a Mixture of Organophosphate Flame Retardants on Placental Gene Expression and Serotonergic Innervation in the Fetal Rat Brain. Toxicol Sci 2020; 176:203-223. [PMID: 32243540 PMCID: PMC7357193 DOI: 10.1093/toxsci/kfaa046] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
There is a growing need to understand the potential neurotoxicity of organophosphate flame retardants (OPFRs) and plasticizers because use and, consequently, human exposure, is rapidly expanding. We have previously shown in rats that developmental exposure to the commercial flame retardant mixture Firemaster 550 (FM 550), which contains OPFRs, results in sex-specific behavioral effects, and identified the placenta as a potential target of toxicity. The placenta is a critical coordinator of fetal growth and neurodevelopment, and a source of neurotransmitters for the developing brain. We have shown in rats and humans that flame retardants accumulate in placental tissue, and induce functional changes, including altered neurotransmitter production. Here, we sought to establish if OPFRs (triphenyl phosphate and a mixture of isopropylated triarylphosphate isomers) alter placental function and fetal forebrain development, with disruption of tryptophan metabolism as a primary pathway of interest. Wistar rat dams were orally exposed to OPFRs (0, 500, 1000, or 2000 μg/day) or a serotonin (5-HT) agonist 5-methoxytryptamine for 14 days during gestation and placenta and fetal forebrain tissues collected for analysis by transcriptomics and metabolomics. Relative abundance of genes responsible for the transport and synthesis of placental 5-HT were disrupted, and multiple neuroactive metabolites in the 5-HT and kynurenine metabolic pathways were upregulated. In addition, 5-HTergic projections were significantly longer in the fetal forebrains of exposed males. These findings suggest that OPFRs have the potential to impact the 5-HTergic system in the fetal forebrain by disrupting placental tryptophan metabolism.
Collapse
Affiliation(s)
- Kylie D Rock
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27619
| | - Genevieve St Armour
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27619
| | - Brian Horman
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27619
| | - Allison Phillips
- Nicholas School of the Environment, Duke University, Durham, North Carolina 27708
| | - Matthew Ruis
- Nicholas School of the Environment, Duke University, Durham, North Carolina 27708
| | - Allison K Stewart
- Molecular Education, Technology, and Research Innovation Center, North Carolina State University, Raleigh, North Carolina 27695
| | - Dereje Jima
- Center for Human Health and the Environment, North Carolina State University, Raleigh, North Carolina 27695
- Bioinformatics Research Center, North Carolina State University, Raleigh, North Carolina 27695
| | - David C Muddiman
- Molecular Education, Technology, and Research Innovation Center, North Carolina State University, Raleigh, North Carolina 27695
| | - Heather M Stapleton
- Nicholas School of the Environment, Duke University, Durham, North Carolina 27708
| | - Heather B Patisaul
- Department of Biological Sciences, North Carolina State University, Raleigh, North Carolina 27619
- Center for Human Health and the Environment, North Carolina State University, Raleigh, North Carolina 27695
| |
Collapse
|
6
|
Deisenroth C, Soldatow VY, Ford J, Stewart W, Brinkman C, LeCluyse EL, MacMillan DK, Thomas RS. Development of an In Vitro Human Thyroid Microtissue Model for Chemical Screening. Toxicol Sci 2020; 174:63-78. [PMID: 31808822 PMCID: PMC8061085 DOI: 10.1093/toxsci/kfz238] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Thyroid hormones (TH) are essential for regulating a number of diverse physiological processes required for normal growth, development, and metabolism. The US EPA Endocrine Disruptor Screening Program (EDSP) has identified several molecular thyroid targets relevant to hormone synthesis dynamics that have been adapted to high-throughput screening (HTS) assays to rapidly evaluate the ToxCast/Tox21 chemical inventories for potential thyroid disrupting chemicals (TDCs). The uncertainty surrounding the specificity of active chemicals identified in these screens and the relevance to phenotypic effects on in vivo human TH synthesis are notable data gaps for hazard identification of TDCs. The objective of this study was to develop a medium-throughput organotypic screening assay comprised of reconstructed human thyroid microtissues to quantitatively evaluate the disruptive effects of chemicals on TH production and secretion. Primary human thyroid cells procured from qualified euthyroid donors were analyzed for retention of NK2 homeobox 1 (NKX2-1), Keratin 7 (KRT7), and Thyroglobulin (TG) protein expression by high-content image analysis to verify enrichment of follicular epithelial cells. A direct comparison of 2-dimensional (2D) and 3-dimensional (3D) 96-well culture formats was employed to characterize the morphology, differential gene expression, TG production, and TH synthesis over the course of 20 days. The results indicate that modeling human thyroid cells in the 3D format was sufficient to restore TH synthesis not observed in the 2D culture format. Inhibition of TH synthesis in an optimized 3D culture format was demonstrated with reference chemicals for key molecular targets within the thyroid gland. Implementation of the assay may prove useful for interpreting phenotypic effects of candidate TDCs identified by HTS efforts currently underway in the EDSP.
Collapse
Affiliation(s)
- Chad Deisenroth
- National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | | | - Jermaine Ford
- Research Cores Unit, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Research Triangle Park, North Carolina 27711
| | - Wendy Stewart
- National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | - Cassandra Brinkman
- National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| | | | - Denise K. MacMillan
- Research Cores Unit, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Research Triangle Park, North Carolina 27711
| | - Russell S. Thomas
- National Center for Computational Toxicology, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711
| |
Collapse
|
7
|
Bai D, Li Q, Xiong Y, Zhao J, Bai L, Shen P, Yuan L, Wu P. Editor's Highlight: Effects of Intraperitoneal Injection of SnS2 Flowers on Mouse Testicle. Toxicol Sci 2019; 161:388-400. [PMID: 29069489 DOI: 10.1093/toxsci/kfx220] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
SnS2 nanoflowers (SnS2 NFs) have been widely used in photoelectric and catalytic applications. However, its explosure and reproductive toxicity is unknown. The aim of this study was to investigate the effect of exposure to 3 different sized-SnS2 flowers (dose: 38 mg/kg; size: 50, 80, and 200 nm) in testes of mice for 4 weeks by intraperitoneal injection. Though the body weight of mice treated or not with SnS2 NFs was not different, and SnS2 NFs were distributed to the organs including liver, kidney, spleen, heart, brain, and testis, more distribution SnS2 NFs (50 and 80 nm) were found in testicle tissues compared with SnS2 flowers (200 nm) in those tissues. The results of sperm count and survival analysis, histopathological evaluation, and qRT-PCR detection showed that there was moderate reproductive toxicity induced by the small-sized SnS2 NFs in testicle tissues. Furthermore, elevated malondialdehyde level and decreased superoxide dismutase activity were also observed in the SnS2 NFs (dose: 38 mg/kg; size: 50 and 80 nm) treated groups. Likewise, the qRT-PCR data indicated that SnS2 NFs can induce apoptosis and inflammation responses. Although the pro-inflammation marker of TNF-α, IL-1β, iNOS, and COX-2 at the mRNA levels were higher expression in 50 and 80 nm groups than that in control and 200 nm group, no statistical significance existed between 50 and 80 nm groups. Accordingly, the repeated-dose toxicity of SnS2 NFs in testicle tissues was also observed in a dose-dependent manner by intraperitoneal injection of SnS2 NFs (size: 50 nm; 0.38, 3.8, and 38 mg/kg) for 4 weeks, when determined by sperm count, survival rate, and qRT-PCR analysis. In addition, transmission electron microscopy showed that the ultrastructural abnormalities formed by the small-sized SnS2 NFs in testes were more severe than those formed by the large-sized SnS2 in testes. Taken together, these findings implied that the SnS2 NFs activated inflammation responses that signified apoptosis in murine testes. This study provided useful information for risk analysis and regulation of SnS2 NFs by administration agencies.
Collapse
Affiliation(s)
- Disi Bai
- Department of Applied Physics, Institute of Advanced Materials Physics, Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Faculty of Science, Tianjin University, Tianjin 300072, People's Republic of China
| | - Qingzhao Li
- School of Public Health, North China University of Science and Technology, Tangshan, Hebei 063210, People's Republic of China
| | - Yanjie Xiong
- Department of Pathology, North China University of Science and Technology Affiliated Hospital, Tangshan, Hebei 063000, People's Republic of China
| | - Junjian Zhao
- Department of Pathology, North China University of Science and Technology Affiliated Hospital, Tangshan, Hebei 063000, People's Republic of China
| | - Liyuan Bai
- Tangshan Environmental Monitoring Center of Heibei Province, Tangshan, Hebei 063000, People's Republic of China
| | - Peijun Shen
- Center of Environmental Monitoring of Tangshan, Tangshan, Hebei 063000, People's Republic of China
| | - Lu Yuan
- School of Public Health, North China University of Science and Technology, Tangshan, Hebei 063210, People's Republic of China
| | - Ping Wu
- Department of Applied Physics, Institute of Advanced Materials Physics, Tianjin Key Laboratory of Low Dimensional Materials Physics and Preparing Technology, Faculty of Science, Tianjin University, Tianjin 300072, People's Republic of China
| |
Collapse
|
8
|
Cheng WY, Zhang Q, Schroeder A, Villeneuve DL, Ankley GT, Conolly R. Editor's Highlight: Computational Modeling of Plasma Vitellogenin Alterations in Response to Aromatase Inhibition in Fathead Minnows. Toxicol Sci 2016; 154:78-89. [PMID: 27503384 DOI: 10.1093/toxsci/kfw142] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In vertebrates, conversion of testosterone into 17β-estradiol (E2) is catalyzed by cytochrome P450 (CYP) 19A aromatase. An important role of E2 in oviparous vertebrates such as fish is stimulation of hepatic synthesis of the glycolipoprotein vitellogenin (VTG), an egg yolk precursor essential to oocyte development and larval survival. In fathead minnows (FHMs) (Pimephales promelas) exposed to the aromatase inhibitor fadrozole, plasma VTG levels do not change in concert with plasma E2 levels. Specifically, while plasma VTG and E2 levels both drop quickly when aromatase is first inhibited, the recovery of plasma VTG upon cessation of aromatase inhibition is substantially delayed relative to the recovery of plasma E2. We modified an existing computational model of the FHM hypothalamic-pituitary-gonadal axis to evaluate alternative hypotheses that might explain this delay. In the first hypothesis, a feedback loop involving active transport of VTG from the blood into the ovary is used. The activity of the transporter is negatively regulated by ovarian VTG. In the second hypothesis, a type 1 coherent feed-forward loop is implemented in the liver. This loop has 2 arms, both requiring E2 activation. The first arm describes direct, canonical E2-driven transcriptional induction of VTG, and the second describes an E2-driven intermediate transcriptional regulator that is also required for VTG synthesis. Both hypotheses accurately described the observed VTG dynamics. This result could be used to guide design of laboratory experiments intended to determine if either of the motifs, or perhaps even both of them, actually do control VTG dynamics in FHMs exposed to aromatase inhibitors.
Collapse
Affiliation(s)
- Wan-Yun Cheng
- *Oak Ridge Institute for Science and Education; Tennessee.,Integrated Systems Toxicology Division, National Health and Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina
| | - Qiang Zhang
- Department of Environmental Health, Rollins School of Public Health, Emory University, Georgia
| | - Anthony Schroeder
- Math, Science & Technology Department, University of Minnesota Crookston, Minnesota
| | - Daniel L Villeneuve
- Mid-Continent Ecology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Minnesota
| | - Gerald T Ankley
- Mid-Continent Ecology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Minnesota
| | - Rory Conolly
- Integrated Systems Toxicology Division, National Health and Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina;
| |
Collapse
|
9
|
Borgert CJ, Becker RA, Carlton BD, Hanson M, Kwiatkowski PL, Sue Marty M, McCarty LS, Quill TF, Solomon K, Van Der Kraak G, Witorsch RJ, Yi KD. Does GLP enhance the quality of toxicological evidence for regulatory decisions? Toxicol Sci 2016; 151:206-13. [PMID: 27208076 PMCID: PMC4880141 DOI: 10.1093/toxsci/kfw056] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
There is debate over whether the requirements of GLP are appropriate standards for evaluating the quality of toxicological data used to formulate regulations. A group promoting the importance of non-monotonic dose responses for endocrine disruptors contend that scoring systems giving primacy to GLP are biased against non-GLP studies from the literature and are merely record-keeping exercises to prevent fraudulent reporting of data from non-published guideline toxicology studies. They argue that guideline studies often employ insensitive species and outdated methods, and ignore the perspectives of subject-matter experts in endocrine disruption, who should be the sole arbiters of data quality. We believe regulatory agencies should use both non-GLP and GLP studies, that GLP requirements assure fundamental tenets of study integrity not typically addressed by journal peer-review, and that use of standardized test guidelines and GLP promotes consistency, reliability, comparability, and harmonization of various types of studies used by regulatory agencies worldwide. This debate suffers two impediments to progress: a conflation of different phases of study interpretation and levels of data validity, and a misleading characterization of many essential components of GLP and regulatory toxicology. Herein we provide clarifications critical for removing those impediments.
Collapse
Affiliation(s)
- Christopher J Borgert
- Dept. Physiol. Sciences, Univ. FL College of Veterinary Medicine, Applied Pharmacology and Toxicology, Inc, and C.E.H.T, Gainesville, Florida 32605;
| | - Richard A Becker
- American Chemistry Council, Washington, District of Columbia 20002
| | - Betsy D Carlton
- Bluestar Silicones USA Corp 10520 Whitestone Rd., Raleigh, North Carolina 27615
| | - Mark Hanson
- Department of Environment and Geography, University of Manitoba, Winnipeg, Manitoba, Canada
| | | | - Mary Sue Marty
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan 48674
| | - Lynn S McCarty
- Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, Michigan 48674
| | - Terry F Quill
- Quill Law Group, LLC, Washington, District of Columbia 20006
| | - Keith Solomon
- University of Guelph, Centre for Toxicology, School of Environmental Science, Guelph, Ontario N1G 2W1, Canada
| | - Glen Van Der Kraak
- Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Raphael J Witorsch
- Department of Physiology & Biophysics, School of Medicine, Virginia Commonwealth University, Richmond, Virginia 23298-0551
| | - Kun Don Yi
- Syngenta Crop Protection, Inc, Greensboro, North Carolina 27419-8300
| |
Collapse
|
10
|
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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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
| |
Collapse
|