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Chemical risk assessment still primarily relies on extrapolation of data from high-confidence in vivo studies. Emerging 21st Century Toxicology tools and approaches have potential to figure more prominently in chemical risk assessment, but many challenges in translating this research into assessments remain. One of these tools, the Adverse Outcome Pathway (AOP) Wiki provides a framework to map and evaluate adverse chemical dynamics, that is the biochemical and physiological effects that occur after chemical exposure. The AOP-guided targeted review of relevant literature, described here, shares similarities with a doctoral thesis or literature review but forces critical evaluation of each step in a pathway including those of central dogma. Additionally, it provides valuable translational regulatory relevance. Data gaps identified through this process can be targeted areas of study in the thesis itself to increase translational relevance. One of the challenges with this tool is that many AOPs are under- or undeveloped. To help fill this need, a concerted effort by subject matter experts to speed the development of AOPs supported under the Organization for Economic Cooperation and Development (OECD) framework would benefit this translational problem. As a case study, we present our experience developing AOP 460: Antagonism of Smoothened receptor leading to orofacial clefting (OECD AOP workplan project 1.101) as part of a graduate literature review. AOP development offers clear benefits to the regulatory and academic communities and increased dissemination of AOPs replete with the most current state of scientific knowledge will promote research translation and increased risk assessment capabilities.
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Dysregulation of Vascular Endothelial Growth Factor (VEGF) and its receptor (VEGFR) contributes to atherosclerosis and cardiovascular disease (CVD), making it a potential target for CVD risk assessment. High throughput screening (HTS) approaches have resulted in large-scale in vitro data, providing mechanistic information that can help assess chemical toxicity and identify molecular-initiating events (MIEs) of adverse outcome pathways (AOPs). AOPs represent a logical sequence of biological responses contributing to toxicity and are valuable tools to inform chemical risk assessments. Here, we used HTS data to formulate an AOP relating VEGF signaling perturbation to atherosclerosis. ToxCast, Tox21, and PubChem data were evaluated to obtain bio-profiles of 4165 compounds active in assays targeting VEGFR. Cheminformatics analysis identified 109 enriched structural fingerprints. Applying a subspace clustering approach based on chemical structure bioactivity yielded 12 primary targets, whose relevance to CVD was confirmed by an AI-assisted literature review. An AOP was hypothesized by coupling mechanistic relationships highlighted by HTS data with literature review findings, linking Serotonin Receptor (HTR), Estrogen Receptor Alpha (ERα), and Vasopressin Receptor (AVPR) targets with VEGFR activity, angiogenic signaling, and atherosclerosis. Several endocrine disrupting chemicals (EDCs), e.g., bisphenols, triclosan, dichlorodiphenyltrichloroethane (DDT), and polychlorinated biphenyls (PCBs), were identified as relevant chemical stressors. Subspace clustering of these chemicals evaluated potential MIEs and highlighted associations with use-case classes. By applying computational methods to profile HTS data and hypothesize a mechanistic AOP, this study proposes a data-driven approach to evaluating environmental cardiotoxicity, which could eventually supplement and reduce the need for animal testing in toxicological assessments.
This study explores how disruptions in VEGFR contribute to atherosclerosis, the buildup of plaques in arteries that can lead to CVD. By analyzing data from HTS relevant to CV health, researchers identify how different chemicals affect VEGFR and potentially cause CVD. Using these screening methods, which quickly test many chemicals, the study identifies specific biological changes leading to adverse health outcomes. This research aims to develop methods to assess chemical toxicity without relying on animal testing, making it relevant to human health. The findings link certain chemicals e.g., bisphenols and DDT, changing VEGRF activity and the development of atherosclerosis. An adverse outcome pathway (AOP) framework maps the sequence of biological events from molecular perturbations to disease, providing mechanistic insight and identifying chemicals impacting the AOP targets. This approach helps understand the risks posed by environmental chemicals and protects public health while reducing animal experiments.
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From the past to the present, many chemicals have been used for the purpose of flame retardant. Due to PBDEs' (Polybrominated diphenyl ether) lipophilic and accumulative properties, some of them are banned from the market. As an alternative to these chemicals, OPFRs (organophosphorus flame retardants) have started to be used as flame retardants. In this article, acute toxicity profiles, mutagenicity, carcinogenicity, blood-brain barrier permeability, ecotoxicity and nutritional toxicity as also AHR, ER affinity and MMP, aromatase affinity, CYP2C9, CYP3A4 interaction of the of 16 different compounds of the OPFRs were investigated using a computational toxicology method; ProTox- 3.0. According to our results, eight compounds were found to be active in terms of carcinogenic effect, whereas two compounds were found to be active for mutagenicity. On the other hand, all compounds were found to be active in terms of blood-barrier permeability. Fourteen compounds and four compounds are found to have ecotoxic and nutritional toxic potency, respectively. Eight compounds were determined as active to AhR, and four chemicals were found to be active in Estrogen Receptor alpha. Eight chemicals were found to be active in terms of mitochondrial membrane potency. Lastly, three chemicals were found to be active in aromatase enzymes. In terms of CYP interaction potencies, eight compounds were found to be active in both CYP2C9 and CYP3A4. This research provided novel insights into the potential toxic effects of OPFRs. However, further studies are needed to evaluate their toxicity. Moreover, these findings lay the groundwork for in vitro and in vivo toxicity research.
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Toxicological evaluation of substances in regulation still often relies on animal experiments. Understanding the substances' mode-of-action is crucial to develop alternative test strategies. Omics methods are promising tools to achieve this goal. Until now, most attention was focused on transcriptomics, while proteomics is not yet routinely applied in toxicology despite the large number of datasets available in public repositories. Exploiting the full potential of these datasets is hampered by differences in measurement procedures and follow-up data processing. Here we present the tool PROTEOMAS, which allows meta-analysis of proteomic data from public origin. The workflow was designed for analyzing proteomic studies in a harmonized way and to ensure transparency in the analysis of proteomic data for regulatory purposes. It agrees with the Omics Reporting Framework guidelines of the OECD with the intention to integrate proteomics to other omic methods in regulatory toxicology. The overarching aim is to contribute to the development of AOPs and to understand the mode of action of substances. To demonstrate the robustness and reliability of our workflow we compared our results to those of the original studies. As a case study, we performed a meta-analysis of 25 proteomic datasets to investigate the toxicological effects of nanomaterials at the lung level. PROTEOMAS is an important contribution to the development of alternative test strategies enabling robust meta-analysis of proteomic data. This workflow commits to the FAIR principles (Findable, Accessible, Interoperable and Reusable) of computational protocols.
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Manufactured nanomaterials (NMs) are increasingly used in a wide range of industrial applications leading to a constant increase in the market size of nano-enabled products. The increased production and use of NMs are raising concerns among different stakeholder groups with regard to their effects on human and environmental health. Currently, nanosafety hazard assessment is still widely performed using in vivo (animal) models, however the development of robust and regulatory relevant strategies is required to prioritize and/or reduce animal testing. An adverse outcome pathway (AOP) is a structured representation of biological events that start from a molecular initiating event (MIE) leading to an adverse outcome (AO) through a series of key events (KEs). The AOP framework offers great advancement to risk assessment and regulatory safety assessments. While AOPs for chemicals have been more frequently reported, the AOP collection for NMs is limited. By using existing AOPs, we aimed to generate simple and testable strategies to predict if a given NM has the potential to induce a MIE leading to an AO through a series of KEs. Firstly, we identified potential MIEs or initial KEs reported for NMs in the literature. Then, we searched the identified MIE or initial KEs as keywords in the AOP-Wiki to find associated AOPs. Finally, using two case studies, we demonstrate how in vitro strategies can be used to test the identified MIE/KEs.
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Rutas de Resultados Adversos , Nanoestructuras , Animales , Humanos , Nanoestructuras/toxicidad , Medición de RiesgoRESUMEN
Effect biomarkers can be used to elucidate relationships between exposure to environmental chemicals and their mixtures with associated health outcomes, but they are often underused, as underlying biological mechanisms are not understood. We aim to provide an overview of available effect biomarkers for monitoring chemical exposures in the general and occupational populations, and highlight their potential in monitoring humans exposed to chemical mixtures. We also discuss the role of the adverse outcome pathway (AOP) framework and physiologically based kinetic and dynamic (PBK/D) modelling to strengthen the understanding of the biological mechanism of effect biomarkers, and in particular for use in regulatory risk assessments. An interdisciplinary network of experts from the European chapter of the International Society for Exposure Science (ISES Europe) and the Organization for Economic Co-operation and Development (OECD) Occupational Biomonitoring activity of Working Parties of Hazard and Exposure Assessment group worked together to map the conventional framework of biomarkers and provided recommendations for their systematic use. We summarized the key aspects of this work here, and discussed these in three parts. Part I, we inventory available effect biomarkers and promising new biomarkers for the general population based on the H2020 Human Biomonitoring for Europe (HBM4EU) initiative. Part II, we provide an overview AOP and PBK/D modelling use that improved the selection and interpretation of effect biomarkers. Part III, we describe the collected expertise from the OECD Occupational Biomonitoring subtask effect biomarkers in prioritizing relevant mode of actions (MoAs) and suitable effect biomarkers. Furthermore, we propose a tiered risk assessment approach for occupational biomonitoring. Several effect biomarkers, especially for use in occupational settings, are validated. They offer a direct assessment of the overall health risks associated with exposure to chemicals, chemical mixtures and their transformation products. Promising novel effect biomarkers are emerging for biomonitoring of the general population. Efforts are being dedicated to prioritizing molecular and biochemical effect biomarkers that can provide a causal link in exposure-health outcome associations. This mechanistic approach has great potential in improving human health risk assessment. New techniques such as in silico methods (e.g. QSAR, PBK/D modelling) as well as 'omics data will aid this process. Our multidisciplinary review represents a starting point for enhancing the identification of effect biomarkers and their mechanistic pathways following the AOP framework. This may help in prioritizing the effect biomarker implementation as well as defining threshold limits for chemical mixtures in a more structured way. Several ex vivo biomarkers have been proposed to evaluate combined effects including genotoxicity and xeno-estrogenicity. There is a regulatory need to derive effect-based trigger values using the increasing mechanistic knowledge coming from the AOP framework to address adverse health effects due to exposure to chemical mixtures. Such a mechanistic strategy would reduce the fragmentation observed in different regulations. It could also stimulate a harmonized use of effect biomarkers in a more comparable way, in particular for risk assessments to chemical mixtures.
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Monitoreo Biológico , Exposición a Riesgos Ambientales , Biomarcadores , Exposición a Riesgos Ambientales/análisis , Monitoreo del Ambiente , Europa (Continente) , Humanos , Medición de RiesgoRESUMEN
Many drugs have the potential to cause drug-induced liver injury (DILI); however, underlying mechanisms are diverse. The concept of adverse outcome pathways (AOPs) has become instrumental for risk assessment of drug class effects. We report AOPs specific for immune-mediated and drug hypersensitivity/allergic hepatitis by considering genomic, histo- and clinical pathology data of mice and dogs treated with diclofenac. The findings are relevant for other NSAIDs and drugs undergoing iminoquinone and quinone reactive metabolite formation. We define reactive metabolites catalyzed by CYP monooxygenase and myeloperoxidases of neutrophils and Kupffer cells as well as acyl glucuronides produced by uridine diphosphoglucuronosyl transferase as molecular initiating events (MIE). The reactive metabolites bind to proteins and act as neo-antigen and involve antigen-presenting cells to elicit B- and T-cell responses. Given the diverse immune systems between mice and dogs, six different key events (KEs) at the cellular and up to four KEs at the organ level are defined with mechanistic plausibility for the onset and progression of liver inflammation. With mice, cellular stress response, interferon gamma-, adipocytokine- and chemokine signaling provided a rationale for the AOP of immune-mediated hepatitis. With dogs, an erroneous programming of the innate and adaptive immune response resulted in mast cell activation; their infiltration into liver parenchyma and the shift to M2-polarized Kupffer cells signify allergic hepatitis and the occurrence of granulomas of the liver. Taken together, diclofenac induces divergent immune responses among two important preclinical animal species, and the injury pattern seen among clinical cases confirms the relevance of the developed AOP for immune-mediated hepatitis.
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Antiinflamatorios no Esteroideos/toxicidad , Enfermedad Hepática Inducida por Sustancias y Drogas/etiología , Diclofenaco/toxicidad , Granuloma/inducido químicamente , Macrófagos del Hígado/efectos de los fármacos , Hígado/efectos de los fármacos , Neutrófilos/efectos de los fármacos , Adipoquinas/metabolismo , Animales , Enfermedad Hepática Inducida por Sustancias y Drogas/inmunología , Enfermedad Hepática Inducida por Sustancias y Drogas/metabolismo , Enfermedad Hepática Inducida por Sustancias y Drogas/patología , Citocinas/metabolismo , Perros , Granuloma/inmunología , Granuloma/metabolismo , Granuloma/patología , Mediadores de Inflamación/metabolismo , Macrófagos del Hígado/inmunología , Macrófagos del Hígado/metabolismo , Hígado/inmunología , Hígado/metabolismo , Masculino , Ratones Endogámicos C57BL , Neutrófilos/inmunología , Neutrófilos/metabolismo , Fenotipo , Transducción de Señal , Especificidad de la EspecieRESUMEN
Significant efforts are currently being made to move toxicity testing from animal experimentation to human relevant, mechanism-based approaches. In this context, the identification of molecular target(s) responsible for mechanisms of action is an essential step. Inspired by the recent concept of polypharmacology (the ability of drugs to interact with multiple targets) we argue that whole proteome virtual screening might become a breakthrough tool in toxicology reflecting the real complexity of chemical-biological interactions. Therefore, we investigated the value of performing ligand-protein binding prediction screening across the full proteome to identify new mechanisms of action for food chemicals. We applied the new approach to make a broader comparison between bisphenol A (BPA) (food-packaging chemical) and the endogenous estrogen, 17ß-estradiol (EST). Applying a novel high-throughput ligand-protein binding prediction tool (BioGPS) by the Amazon Web Services (AWS) cloud (to speed-up the calculation), we investigated the value of performing in silico screening across the full proteome (all human and rodent x-ray protein structures available in the Protein Data Bank). The strong correlation between in silico predictions and available in vitro data demonstrates the high predictive power of the method used. The most striking results obtained was that BPA was predicted to bind to many more proteins than the ones already known, most of which were common to EST. Our findings provide a new and unprecedented insight on the complexity of chemical-protein interactions, highlighting the binding promiscuity of BPA and its broader similarity compared to the female sex hormone, EST.