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Draskau MK, Rosenmai AK, Bouftas N, Johansson HKL, Panagiotou EM, Holmer ML, Elmelund E, Zilliacus J, Beronius A, Damdimopolou P, van Duursen M, Svingen T. AOP Report: An Upstream Network for Reduced Androgen Signaling Leading to Altered Gene Expression of Androgen Receptor-Responsive Genes in Target Tissues. ENVIRONMENTAL TOXICOLOGY AND CHEMISTRY 2024. [PMID: 39206816 DOI: 10.1002/etc.5972] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2024] [Accepted: 07/16/2024] [Indexed: 09/04/2024]
Abstract
Adverse outcome pathways (AOPs) can aid with chemical risk assessment by providing plausible links between chemical activity at the molecular level and effect outcomes in intact organisms. Because AOPs can be used to infer causality between upstream and downstream events in toxicological pathways, the AOP framework can also facilitate increased uptake of alternative methods and new approach methodologies to help inform hazard identification. However, a prevailing challenge is the limited number of fully developed and endorsed AOPs, primarily due to the substantial amount of work required by AOP developers and reviewers. Consequently, a more pragmatic approach to AOP development has been proposed where smaller units of knowledge are developed and reviewed independent of full AOPs. In this context, we have developed an upstream network comprising key events (KEs) and KE relationships related to decreased androgen signaling, converging at a nodal KE that can branch out to numerous adverse outcomes (AOs) relevant to androgen-sensitive toxicological pathways. Androgen signaling represents an extensively studied pathway for endocrine disruption. It is linked to numerous disease outcomes and can be affected by many different endocrine-disrupting chemicals. Still, pathways related to disrupted androgen signaling remain underrepresented in the AOP-wiki, and endorsed AOPs are lacking. Given the pivotal role of androgen signaling in development and function across vertebrate taxa and life stages of both sexes, this upstream AOP network serves as a foundational element for developing numerous AOPs. By connecting the upstream network with various downstream AOs, encompassing different species, it can also facilitate cross-species extrapolations for hazard and risk assessment of chemicals. Environ Toxicol Chem 2024;00:1-9. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
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Affiliation(s)
- Monica K Draskau
- National Food Institute, Technical University of Denmark, Lyngby, Denmark
| | - Anna K Rosenmai
- National Food Institute, Technical University of Denmark, Lyngby, Denmark
| | - Nora Bouftas
- Environmental Health and Toxicology, Amsterdam Institute for Life and Environment, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | | | - Eleftheria M Panagiotou
- Division of Obstetrics and Gynaecology, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
- Department of Gynecology and Reproductive Medicine, Karolinska University Hospital, Stockholm, Sweden
| | - Marie L Holmer
- National Food Institute, Technical University of Denmark, Lyngby, Denmark
| | - Emilie Elmelund
- National Food Institute, Technical University of Denmark, Lyngby, Denmark
| | - Johanna Zilliacus
- Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Anna Beronius
- Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Pauliina Damdimopolou
- Division of Obstetrics and Gynaecology, Department of Clinical Science, Intervention and Technology, Karolinska Institutet, Stockholm, Sweden
- Department of Gynecology and Reproductive Medicine, Karolinska University Hospital, Stockholm, Sweden
| | - Majorie van Duursen
- Environmental Health and Toxicology, Amsterdam Institute for Life and Environment, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Terje Svingen
- National Food Institute, Technical University of Denmark, Lyngby, Denmark
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Magurany KA, Chang X, Clewell R, Coecke S, Haugabrooks E, Marty S. A Pragmatic Framework for the Application of New Approach Methodologies in One Health Toxicological Risk Assessment. Toxicol Sci 2023; 192:kfad012. [PMID: 36782355 PMCID: PMC10109535 DOI: 10.1093/toxsci/kfad012] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
Globally, industries and regulatory authorities are faced with an urgent need to assess the potential adverse effects of chemicals more efficiently by embracing new approach methodologies (NAMs). NAMs include cell and tissue methods (in vitro), structure-based/toxicokinetic models (in silico), methods that assess toxicant interactions with biological macromolecules (in chemico), and alternative models. Increasing knowledge on chemical toxicokinetics (what the body does with chemicals) and toxicodynamics (what the chemicals do with the body) obtained from in silico and in vitro systems continues to provide opportunities for modernizing chemical risk assessments. However, directly leveraging in vitro and in silico data for derivation of human health-based reference values has not received regulatory acceptance due to uncertainties in extrapolating NAM results to human populations, including metabolism, complex biological pathways, multiple exposures, interindividual susceptibility and vulnerable populations. The objective of this article is to provide a standardized pragmatic framework that applies integrated approaches with a focus on quantitative in vitro to in vivo extrapolation (QIVIVE) to extrapolate in vitro cellular exposures to human equivalent doses from which human reference values can be derived. The proposed framework intends to systematically account for the complexities in extrapolation and data interpretation to support sound human health safety decisions in diverse industrial sectors (food systems, cosmetics, industrial chemicals, pharmaceuticals etc.). Case studies of chemical entities, using new and existing data, are presented to demonstrate the utility of the proposed framework while highlighting potential sources of human population bias and uncertainty, and the importance of Good Method and Reporting Practices.
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Affiliation(s)
| | | | - Rebecca Clewell
- 21st Century Tox Consulting, Chapel Hill, North Carolina 27517, USA
| | - Sandra Coecke
- European Commission Joint Research Centre, Ispra, Italy
| | - Esther Haugabrooks
- Coca-Cola Company (formerly Physicians Committee for Responsible Medicine), Atlanta, Georgia 30313, USA
| | - Sue Marty
- The Dow Chemical Company, Midland, Michigan 48667, USA
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Kozbenko T, Adam N, Lai V, Sandhu S, Kuan J, Flores D, Appleby M, Parker H, Hocking R, Tsaioun K, Yauk C, Wilkins R, Chauhan V. Deploying elements of scoping review methods for Adverse Outcome Pathway development: A space travel case example. Int J Radiat Biol 2022; 98:1777-1788. [PMID: 35939057 DOI: 10.1080/09553002.2022.2110306] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
Abstract
Purpose Health protection agencies require scientific information for evidence-based decision-making and guideline development. However, vetting and collating large quantities of published research to identify relevant high-quality studies is a challenge. One approach to address this issue is the use of Adverse Outcome Pathways (AOPs) that provide a framework to assemble toxicological knowledge into causally linked chains of key events across levels of biological organization to culminate in an adverse health outcome of significance. Traditionally, AOPs have been constructed using a narrative review approach where the collection of evidence that supports each pathway is based on prior knowledge of influential studies that can also be supplemented by individually selecting and reviewing relevant references. Objectives: We aimed to create a protocol for AOP weight of evidence gathering that harnesses elements of both scoping review methods and artificial intelligence tools to increase transparency while reducing bias and workload of human screeners. Methods: To develop this protocol, an existing space-health AOP in the workplan of the Organisation for Economic Co-operation and Development (OECD) AOP program was used as a case example. To balance the benefits of both scoping review tools and narrative approaches, a study protocol outlining a screening and search strategy was developed, and three reference collection workflows were tested to identify the most efficient method to inform weight of evidence. The workflows differed in their literature search strategies, and combinations of software tools used. Results: Across the three tested workflows, over 59 literature searches were completed, retrieving over 34000 references of which over 3300 were human reviewed. The most effective of the three methods used a search strategy with searches across each component of the AOP network, SWIFT Review as a pre-filtering software, and DistillerSR to create structured screening and data extraction forms. This methodology effectively retrieved relevant studies while balancing efficiency in data retrieval without compromising transparency, leading to a well-synthesized evidence base to support the AOP. Conclusions: The workflow is still exploratory in the context of AOP development, and we anticipate adaptations to the protocol with further experience. To further the systematicity, future iterations of the workflow could include structured quality assessment and risk of bias analysis. Overall, the workflow provides a transparent and unbiased approach to support AOP development, which in turn will support the need for rigorous methods to identify relevant scientific evidence while being practical to allow uptake by the broader community.
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Affiliation(s)
- Tatiana Kozbenko
- Health Canada, Ottawa, Ontario, K1A 0K9, Canada.,University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Nadine Adam
- Health Canada, Ottawa, Ontario, K1A 0K9, Canada
| | - Vita Lai
- Health Canada, Ottawa, Ontario, K1A 0K9, Canada
| | | | | | | | | | - Hanna Parker
- University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | | | - Katya Tsaioun
- Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
| | - Carole Yauk
- University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
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Hoffmann S, Aiassa E, Angrish M, Beausoleil C, Bois FY, Ciccolallo L, Craig PS, de Vries RBM, Dorne JLCM, Druwe IL, Edwards SW, Eskes C, Georgiadis M, Hartung T, Kienzler A, Kristjansson EA, Lam J, Martino L, Meek B, Morgan RL, Munoz-Guajardo I, Noyes PD, Parmelli E, Piersma A, Rooney A, Sena E, Sullivan K, Tarazona J, Terron A, Thayer K, Turner J, Verbeek J, Verloo D, Vinken M, Watford S, Whaley P, Wikoff D, Willett K, Tsaioun K. Application of evidence-based methods to construct mechanism-driven chemical assessment frameworks. ALTEX 2022; 39:499–518. [PMID: 35258090 PMCID: PMC9466297 DOI: 10.14573/altex.2202141] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Accepted: 02/28/2022] [Indexed: 11/23/2022]
Abstract
The workshop titled “Application of evidence-based methods to construct mechanism-driven chemical assessment frameworks” was co-organized by the Evidence-based Toxicology Collaboration and the European Food Safety Authority (EFSA) and hosted by EFSA at its headquarters in Parma, Italy on October 2 and 3, 2019. The goal was to explore integration of systematic review with mechanistic evidence evaluation. Participants were invited to work on concrete products to advance the exploration of how evidence-based approaches can support the development and application of adverse outcome pathways (AOP) in chemical risk assessment. The workshop discussions were centered around three related themes: 1) assessing certainty in AOPs, 2) literature-based AOP development, and 3) integrating certainty in AOPs and non-animal evidence into decision frameworks. Several challenges, mostly related to methodology, were identified and largely determined the workshop recommendations. The workshop recommendations included the comparison and potential alignment of processes used to develop AOP and systematic review methodology, including the translation of vocabulary of evidence-based methods to AOP and vice versa, the development and improvement of evidence mapping and text mining methods and tools, as well as a call for a fundamental change in chemical risk and uncertainty assessment methodology if to be conducted based on AOPs and new approach methodologies (NAM). The usefulness of evidence-based approaches for mechanism-based chemical risk assessments was stressed, particularly the potential contribution of the rigor and transparency inherent to such approaches in building stakeholders’ trust for implementation of NAM evidence and AOPs into chemical risk assessment.
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Affiliation(s)
- Sebastian Hoffmann
- Evidence-based Toxicology Collaboration (EBTC) at Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | - Elisa Aiassa
- European Food Safety Authority (EFSA), Parma, Italy
| | - Michelle Angrish
- United States Environmental Protection Agency, Office of Research and Development, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, USA
| | | | | | | | | | - Rob B. M. de Vries
- Evidence-based Toxicology Collaboration (EBTC) at Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
| | | | - Ingrid L. Druwe
- United States Environmental Protection Agency, Office of Research and Development, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, USA
| | | | - Chantra Eskes
- SeCAM, Magliaso, Switzerland
- current affiliation: European Food Safety Authority (EFSA), Parma, Italy
| | | | - Thomas Hartung
- Evidence-based Toxicology Collaboration (EBTC) at Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
- CAAT-Europe, University of Konstanz, Konstanz, Germany
| | - Aude Kienzler
- current affiliation: European Food Safety Authority (EFSA), Parma, Italy
- European Commission, Joint Research Centre, Ispra, Italy
| | | | - Juleen Lam
- California State University, East Bay, CA, USA
| | | | | | - Rebecca L. Morgan
- Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton, ON, Canada
| | | | - Pamela D. Noyes
- United States Environmental Protection Agency, Office of Research and Development, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, USA
| | - Elena Parmelli
- European Commission, Joint Research Centre, Ispra, Italy
| | - Aldert Piersma
- Centre for Health Protection (RIVM), Bilthoven, the Netherlands
| | - Andrew Rooney
- Division of the National Toxicology Program, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA
| | | | - Kristie Sullivan
- Physicians Committee for Responsible Medicine, Washington, DC, USA
| | | | | | - Kris Thayer
- United States Environmental Protection Agency, Office of Research and Development, Center for Public Health and Environmental Assessment, Research Triangle Park, NC, USA
| | | | - Jos Verbeek
- University of Eastern Finland, Kuopio, Finland
| | | | | | | | - Paul Whaley
- Evidence-based Toxicology Collaboration (EBTC) at Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
- Lancaster Environment Centre, Lancaster University, Lancaster, UK
| | | | - Kate Willett
- Humane Society International, Washington, DC, USA
| | - Katya Tsaioun
- Evidence-based Toxicology Collaboration (EBTC) at Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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Maertens A, Golden E, Luechtefeld TH, Hoffmann S, Tsaioun K, Hartung T. Probabilistic risk assessment - the keystone for the future of toxicology. ALTEX 2022; 39:3-29. [PMID: 35034131 PMCID: PMC8906258 DOI: 10.14573/altex.2201081] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2022] [Indexed: 12/12/2022]
Abstract
Safety sciences must cope with uncertainty of models and results as well as information gaps. Acknowledging this uncer-tainty necessitates embracing probabilities and accepting the remaining risk. Every toxicological tool delivers only probable results. Traditionally, this is taken into account by using uncertainty / assessment factors and worst-case / precautionary approaches and thresholds. Probabilistic methods and Bayesian approaches seek to characterize these uncertainties and promise to support better risk assessment and, thereby, improve risk management decisions. Actual assessments of uncertainty can be more realistic than worst-case scenarios and may allow less conservative safety margins. Most importantly, as soon as we agree on uncertainty, this defines room for improvement and allows a transition from traditional to new approach methods as an engineering exercise. The objective nature of these mathematical tools allows to assign each methodology its fair place in evidence integration, whether in the context of risk assessment, sys-tematic reviews, or in the definition of an integrated testing strategy (ITS) / defined approach (DA) / integrated approach to testing and assessment (IATA). This article gives an overview of methods for probabilistic risk assessment and their application for exposure assessment, physiologically-based kinetic modelling, probability of hazard assessment (based on quantitative and read-across based structure-activity relationships, and mechanistic alerts from in vitro studies), indi-vidual susceptibility assessment, and evidence integration. Additional aspects are opportunities for uncertainty analysis of adverse outcome pathways and their relation to thresholds of toxicological concern. In conclusion, probabilistic risk assessment will be key for constructing a new toxicology paradigm - probably!
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Affiliation(s)
- Alexandra Maertens
- Center for Alternatives to Animal Testing (CAAT), Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD, USA
| | - Emily Golden
- Center for Alternatives to Animal Testing (CAAT), Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD, USA
| | - Thomas H. Luechtefeld
- Center for Alternatives to Animal Testing (CAAT), Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD, USA
- ToxTrack, Baltimore, MD, USA
| | - Sebastian Hoffmann
- Center for Alternatives to Animal Testing (CAAT), Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD, USA
- seh consulting + services, Paderborn, Germany
| | - Katya Tsaioun
- Center for Alternatives to Animal Testing (CAAT), Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD, USA
| | - Thomas Hartung
- Center for Alternatives to Animal Testing (CAAT), Johns Hopkins University, Bloomberg School of Public Health, Baltimore, MD, USA
- CAAT Europe, University of Konstanz, Konstanz, Germany
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Audouze K, Zgheib E, Abass K, Baig AH, Forner-Piquer I, Holbech H, Knapen D, Leonards PEG, Lupu DI, Palaniswamy S, Rautio A, Sapounidou M, Martin OV. Evidenced-Based Approaches to Support the Development of Endocrine-Mediated Adverse Outcome Pathways: Challenges and Opportunities. FRONTIERS IN TOXICOLOGY 2021; 3:787017. [PMID: 35295112 PMCID: PMC8915810 DOI: 10.3389/ftox.2021.787017] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Accepted: 11/22/2021] [Indexed: 12/12/2022] Open
Affiliation(s)
| | - Elias Zgheib
- Université de Paris, T3S, Inserm U1124, Paris, France
| | - Khaled Abass
- Thule Institute, University of Arctic, University of Oulu, Oulu, Finland
- Department of Pesticides, Menoufia University, Menoufia, Egypt
| | - Asma H. Baig
- Centre for Pollution Research and Policy, Brunel University London, Uxbridge, United Kingdom
| | - Isabel Forner-Piquer
- Centre for Pollution Research and Policy, Brunel University London, Uxbridge, United Kingdom
| | - Henrik Holbech
- Department of Biology, University of Southern Denmark, Odense, Denmark
| | - Dries Knapen
- Zebrafishlab, Department of Veterinary Sciences, University of Antwerp, Wilrijk, Belgium
| | - Pim E. G. Leonards
- Department of Environment and Health, Vrije Universiteit Amsterdam, Amsterdam, Netherlands
| | - Diana I. Lupu
- Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden
| | - Saranya Palaniswamy
- Center for Life Course Health Research, Faculty of Medicine, University of Oulu, Oulu, Finland
| | - Arja Rautio
- Thule Institute, University of Arctic, University of Oulu, Oulu, Finland
| | - Maria Sapounidou
- Department of Chemistry, Faculty of Science and Technology, Umeå University, Umeå, Sweden
| | - Olwenn V. Martin
- Centre for Pollution Research and Policy, Brunel University London, Uxbridge, United Kingdom
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Development of a putative adverse outcome pathway network for male rat reproductive tract abnormalities with specific considerations for the androgen sensitive window of development. Curr Res Toxicol 2021; 2:254-271. [PMID: 34401750 PMCID: PMC8350458 DOI: 10.1016/j.crtox.2021.07.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2021] [Revised: 07/13/2021] [Accepted: 07/14/2021] [Indexed: 02/06/2023] Open
Abstract
Structured approaches like the adverse outcome pathway (AOP) framework offer great potential for depicting complex toxicological processes in a manner that can facilitate informed integration of mechanistic information in regulatory decisions. While this concept provides a structure for organizing evidence and facilitates consistency in evidence integration; the process, inputs, and manner in which AOPs and AOP networks are developed is still evolving. Following the OECD guiding principles of AOP development, we propose three AOPs for male reproductive tract abnormalities and derive a putative AOP network. The AOPs were developed using a fundamental understanding of the developmental biology of the organs of interest, paying close attention to the gestational timing of key events (KEs) to very specifically inform the domain of life stage applicability for the key event relationships (KERs). Chemical stressor data primarily from studies on low molecular weight phthalates (LMWPs) served to 'bound' the pathways of focus in this dynamic period of development and were integrated with the developmental biology data through an iterative process to define KEs and conclude on the extent of evidence in support of the KERs. The AOPs developed describe the linkage between 1) a decrease in Insl3 gene expression and cryptorchidism, 2) the sustained expression of Coup-tfII and hypospadias and 3) the sustained expression of Coup-tfII and altered Wolffian duct development/ epididymal agenesis. A putative AOP network linking AOP2 and AOP3 through decreased steroidogenic biosynthetic protein expression and converging of all AOPS at the population level impaired fertility adverse outcome is proposed. The network depiction specifies and displays the KEs aligned with their occurrence in gestational time. The pathways and network described herein are intended to catalyze collaborative initiatives for expansion into a larger network to enable effective data collection and inform alternative approaches for identifying stressors impacting this sensitive period of male reproductive tract development.
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Key Words
- AGD, Anogenital distance
- AO, Adverse Outcome
- AOP, Adverse Outcome Pathway
- Adverse outcome pathway
- Adverse outcome pathway network
- DBP, Dibutyl phthalate
- DEHP, Di(2-ethylhexyl)phthalate
- DHT, 5α-dihydrotestosterone
- DPP, Dipentyl phthalate
- E, Embryonic day (ED1=GD1 gestational day 1)
- GD, Gestational day (GD1=ED1 embryonic day 1)
- KE, Key event
- KER, Key event relationship
- LMWP, low molecular weight phthalate straight chain length of the esterified alcohols between 3 and 6 carbon atoms
- MPW, male programming window
- Male programming window
- Phthalate
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Goyak KO, Lewis RJ. Application of adverse outcome pathway networks to integrate mechanistic data informing the choice of a point of departure for hydrogen sulfide exposure limits. Crit Rev Toxicol 2021; 51:193-208. [PMID: 33905294 DOI: 10.1080/10408444.2021.1897085] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Acute exposure to hydrogen sulfide initiates a series of hallmark biological effects that occur progressively at increasing exposure levels: odor perception, conjunctivitis, olfactory paralysis, "knockdown," pulmonary edema, and apnea. Although effects of exposure to high concentrations of hydrogen sulfide are clear, effects associated with chronic, low-level exposure in humans is under debate, leading to uncertainty in the critical effect used in regulatory risk assessments addressing low dose exposures. This study integrates experimental animal, observational epidemiology, and occupational exposure evidence by applying a pathway-based approach. A hypothesized adverse outcome pathway (AOP) network was developed from 34 studies, composed of 4 AOPs sharing 1 molecular initiating events (MIE) and culminating in 4 adverse outcomes. A comparative assessment of effect levels and weight of evidence identified an AOP leading to a biologically-plausible, low-dose outcome relative to the other outcomes (nasal lesions, 30 ppm versus olfactory paralysis, >100 ppm; neurological effects, >80 ppm; pulmonary edema, >80 ppm). This AOP (i.e. AOP1) consists of the following key events: cytochrome oxidase inhibition (>10 ppm), neuronal cell loss (>30 ppm), and olfactory nasal lesions (defined as both neuronal cell loss and basal cell hyperplasia; >30 ppm) in rodents. The key event relationships in this pathway were supported by moderate empirical evidence and have high biological plausibility due to known mechanistic understanding and consistency in observations for diverse chemicals.
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Affiliation(s)
- Katy O Goyak
- ExxonMobil Biomedical Sciences, Inc., Annandale, NJ, USA
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