Toxicological Sciences最新文献

Human health reference values (HHRVs) developed by US governmental agencies and professional organizations are derived for specific purposes related to their organizational or statutory mandates, and for individual chemicals or substance groups (e.g. manganese compounds). Choosing an appropriate chemical-specific value should be based on the risk assessment need and the specific exposure context, along with a basic understanding of the various types and the intended purposes of each available HHRV. In this overview, HHRVs have been broadly organized into 3 main categories: values for the general public, occupational exposure limits, and emergency response values. The goal of this overview is to equip the reader with a greater understanding of HHRVs, how they are meant to be applied, and key aspects to consider in selecting the most appropriate value. These key aspects include target population (e.g. general public of all ages vs. working-age adults), duration and frequency of exposure, health effect severity, confidence in the data set, use of well-documented and contemporary derivation methods, transparency and documentation of the value derivation, and the thoroughness of the review process. Chemical- and exposure scenario-specific needs should determine which HHRV is most appropriate; however, a most appropriate HHRV may not be available for every chemical and situation. Therefore, we present both considerations and limitations to guide the selection of an alternate HHRV based on suitability for the assessment scenario from among the available chemical-specific values.

Exposures to per- and polyfluoroalkyl substances (PFAS) are associated with various adverse health outcomes, and a wide range of PFAS compounds have been detected in human serum, the environment, and food. Toxicokinetic models, however, have been developed for only a subset of the compounds of interest. To facilitate reverse dosimetry and risk assessment for the less studied PFAS compounds in food, we developed and evaluated an approach to adapt existing toxicokinetic models for nonhuman primates to predict human serum levels. The approach was validated with perfluorooctanoic acid and perfluorooctanesulfonic acid data and applied to perfluorohexanesulfonate. Results indicate that the approach yields similar dosimetry estimates to those of other models, particularly those used for regulatory purposes, suggesting the methodology can be leveraged to inform decision-making in data-sparse spaces. Applying and adapting the framework will improve our ability to connect dietary PFAS exposures to endpoints of concern for a wide range of PFAS compounds.

Congenital heart defects (CHDs) are common birth defects attributed to genetic and environmental factors, such as pharmaceuticals and chemicals. Identifying modifiable environmental factors and understanding their impact on heart development is crucial for mitigating chemical-induced CHDs. Given the increasing number of chemical agents, efficient high-throughput systems are essential to evaluate their teratogenic potential during cardiovascular development, which is a major concern for chemical safety. In this study, we developed 3 transgenic zebrafish reporter lines, myl7:EGFP, kdrl:mRFP, and gata1:mKate2, which enable real-time visualization of myocardial and endocardial development and cardiac function based on blood flow. These transgenic embryos were used to investigate the teratogenic effects of chemicals well known to induce heart defects in mammals, including humans. Our real-time imaging revealed that the teratogens induced significant malformations in cardiac morphogenesis, including abnormal heart tube formation, incomplete cardiac looping, and reduced heart chamber size. These teratogens also disrupted the expression of cardiac progenitor markers, suggesting impaired cardiac progenitor development. These defects were detected at the early stages (4-48 h post-fertilization), suggesting that the stages of progenitor development to heart looping were most susceptible to teratogen exposure, i.e. the critical period for teratogen-induced heart defects. Functional defects, such as impaired blood flow, were observed using real-time imaging of the gata1-reporter line. This study demonstrates the utilization of transgenic zebrafish embryo models for high-throughput teratogenicity testing, which also allows us to analyze the mechanisms underlying chemical-induced heart defects. Therefore, our zebrafish models would contribute to the identification and reduction of risks associated with CHDs.

Astrocytes, the most abundant glial cells in the central nervous system (CNS), play essential roles in maintaining neuronal homeostasis, synaptic regulation, and blood-brain barrier integrity. However, these cells can undergo senescence-a cellular state characterized by irreversible growth arrest and the secretion of proinflammatory factors-in response to aging and pathological stressors, contributing to synaptic dysfunction and neurodegenerative diseases. This review examines the molecular mechanisms driving astrocytic senescence, including oxidative stress, DNA damage, and inflammatory signaling pathways such as NF-κB and the senescence-associated secretory phenotype. A particular focus is placed on the diverse array of known chemical inducers of astrocyte senescence, such as pesticides and heavy metals, which provide critical insights into the processes governing cellular aging in the brain. By analyzing the effects of these inducers, we highlight their implications for neurodegenerative disease progression and brain aging. Understanding astrocytic senescence offers new insights into age-related neuropathology and presents promising avenues for targeted therapies in neurodegenerative disorders induced by environmental toxicants.

Exposure to the ambient air pollutant ozone induces acute and chronic respiratory health effects in part by causing inflammation of the airways. Several aspects of the inflammatory response to ozone can be modeled in vitro using primary human bronchial epithelial cells (HBECs) cultured at an air-liquid interface. We tested two commonly used HBEC culture media systems, one proprietary and one non-proprietary, to identify which system yielded the most in vivo-like pro-inflammatory response to acute ozone exposure as reflected by gene expression. Cells from 6 donors were grown in each culture system in parallel, followed by examination of epithelial morphology and cell type proportions prior to ozone exposure. Cultures grown in the proprietary system were notably thicker and contained more ciliated and secretory cells, as well as internal cyst-like structures. The transcriptomic response to acute ozone exposure (0.5 parts per million ozone × 2 h) was strongly affected by media type. HBECs grown in the proprietary system exhibited minimal changes after ozone, with only 7 differentially expressed genes (DEGs). In contrast, HBECs grown in the non-proprietary system exhibited a more dynamic response with 128 DEGs, including hallmark response genes indicative of inflammation (CXCL8) and oxidative stress (HMOX1). Gene set enrichment analysis using the 128 DEGs further corroborated upregulation of oxidative stress and inflammation pathways. In total, our results indicate that the choice of HBEC culture media should be carefully considered to best model the in vivo response to ozone.

Alcohol intake is a risk factor for the development of osteopenia. Ethanol perturbs gene expression in osteoblasts and osteoclasts and disrupts growth plate morphology. Hepatic metabolism of ethanol to acetate elevates concentrations of acetate in the circulation. We investigated whether acetate could, in part, mediate the toxicity of ethanol in bone and on chondrocyte differentiation. When ethanol and acetate were compared by gavage for 4 consecutive days, none of 11 selected genes involved in bone homeostasis were significantly affected by acetate, but acetate responses significantly correlated with ethanol responses. Intraperitoneal injection with acetate to transiently elevate serum acetate for 4 consecutive days significantly increased expression of 2 markers of osteoclast differentiation, calcitonin receptor (Calcr) and Ocstamp. Early chondrogenic differentiation of ATDC5 cells for 7 days in vitro, characterized by aggrecan (Acan) and collagen 2a1 (Col2a1) mRNA expression and proteoglycan production, was inhibited by both 50 mM ethanol and 5 mM acetate. Ethanol effects were not blocked by the alcohol dehydrogenase inhibitor 4-methylpyrazole. 50 mM ethanol retarded both ATDC5 cell growth and culture medium acidification. Inhibition of chondrogenic differentiation by 5 mM acetate was associated with elevated phosphorylation of extracellular signal-regulated kinase (ERK)1 and ERK2 and decreased expression of transcription factors Sox9 and Runx2. In acetate-exposed cells, blocking of ERK1 and ERK2 phosphorylation with Trametinib prevented further reduction of Acan and Col2a1 mRNA expression. We conclude that ethanol-derived acetate mediates at least part of the induction of Calcr and Ocstamp expression and that acetate mimics the effects of ethanol on early chondrogenic differentiation.

Per- and polyfluoroalkyl substances (PFAS) are persistent and widespread contaminants. Epidemiological effects of PFAS include increased serum cholesterol, decreased immune response to vaccination and disease, and increased incidence of cancer; however, PFAS modes of action remain unclear. Herein, we analyzed gene expression data from human liver spheroids that were exposed to several concentrations of 24 different PFAS. Benchmark concentration (BMC) response modeling was used to identify the 250 lowest gene BMCs for each PFAS. Hierarchical clustering analysis revealed 4 functionally diverse gene sets. Each gene set was affected by a distinct group of PFAS, whereas individual PFAS were usually part of more than 1 PFAS group. The biological roles of these gene sets relate to: (1) cholesterol biogenesis and cholesterol clearance (downregulated by 7 fluorocarbon or longer PFAS), putatively through discordance of cholesterol sensing by SCAP and LXR due to membrane integration of PFAS; (2) lipolysis (upregulated by 8 carbon or shorter PFAS); (3) innate immunity (downregulated by most PFAS); and (4) adaptive immunity (downregulated by sulfonate-type PFAS). The distinctions between the 4 PFAS groups suggest that PFAS can act through at least 4 independent mechanisms. The molecular characteristics of each PFAS group may be useful for understanding the molecular interactions leading to their effect on gene expression. Inclusion of some PFAS congeners in more than one PFAS group suggests that individual PFAS can act through multiple unrelated molecular interactions. This transcriptomic analysis offers a major advancement to the understanding of the molecular mechanisms underlying the effects of PFAS exposure and provides guidance for future work that may strengthen links between PFAS exposure and their proposed effects on human health.

Pyrethroid insecticides represent a broad class of chemicals used widely in agriculture and household applications. Human studies show mixed effects of maternal pyrethroid exposure on fetal growth and neurodevelopment. Assessment of shared pyrethroid metabolites as a biomarker for exposure obscures effects of specific chemicals within this broader class. To better characterize pyrethroid effects on fetal development, we investigated maternal exposure to permethrin, a type I pyrethroid, and α-cypermethrin, a type II pyrethroid, on fetal development in mice. Pregnant CD1 mice were exposed to permethrin (1.5, 15, or 50 mg/kg), α-cypermethrin (0.3, 3, or 10 mg/kg), or corn oil vehicle via oral gavage on gestational days (GDs) 6 to 16. Effects on fetal growth, placental toxicity, and neurodevelopment were evaluated at GD 16. Cypermethrin, but not permethrin, significantly reduced fetal growth and altered placental layer morphology. Placental RNAseq analysis revealed downregulation of genes involved in extracellular matrix remodeling in response to α-cypermethrin. Both pyrethroids induced shifts in fetal dorsal forebrain microglia morphology from ramified to ameboid states; however, the effects of α-cypermethrin were more pronounced. The α-cypermethrin transcriptome of fetal dorsal forebrain implicated altered glutamate receptor signaling, synaptogenesis, and c-AMP signaling. Coregulated gene modules in individual placenta and fetal dorsal forebrain pairs were correlated and overlapped in biological processes characterizing synapses, mitotic cell cycle, and chromatin organization, suggesting placenta-fetal brain shared mechanisms with α-cypermethrin exposure. In summary, maternal exposure to the type II pyrethroid α-cypermethrin, but not type I pyrethroid permethrin, significantly affected placental development, fetal growth, and neurodevelopment, and these effects were linked.

In pharmaceutical drug development, animal tests are traditionally required to conduct comprehensive toxicity assessments before initiating human clinical trials. However, animal tests are time-consuming and can hinder the rapid development of drugs needed to combat urgent health crises, such as the COVID-19 pandemic. Therefore, faster non-animal alternatives are critical to accelerating preclinical toxicity assessments. Molnupiravir, an antiviral medication authorized for emergency use to treat COVID-19, is an oral pro-drug that is metabolized into its active form, N4-hydroxycytidine (NHC). The developmental toxicity of molnupiravir was initially identified in preclinical animal studies. The present study aims to determine whether in vitro assays using gastruloids-three-dimensional aggregates of pluripotent stem cells that mimic axial elongation morphogenesis of early embryos-can effectively detect the developmental toxicity of molnupiravir in a clinically relevant context. In our experiments, NHC at 20 μM significantly impaired the morphological progression and altered the gene expression profiles in gastruloids derived from mouse P19C5 stem cells. Similarly, in a human embryonic stem cell-based morphogenesis model, NHC reduced the aggregate size at 10 μM and induced significant gene expression changes at concentrations as low as 2.5 μM. Notably, these NHC concentrations are comparable to the plasma levels observed in humans (approximately 10.8 μM) following administration of the clinically recommended dose of molnupiravir. These findings demonstrate that gastruloid-based assays can reliably detect the developmental toxicity of NHC at clinically relevant concentrations, supporting their utility as non-animal tools for expediting preclinical developmental toxicity assessments.

Animal models are widely used during drug development. The selection of suitable animal model relies on various factors such as target biology, animal resource availability, and legacy species. It is imperative that the selected animal species exhibit the highest resemblance to humans, in terms of target biology as well as the similarity in the target protein. The current practice to address cross-species protein similarity relies on pairwise sequence comparison using protein sequences, instead of the biologically relevant 3D structure of proteins. We developed a novel quantitative machine learning pipeline using 3D structure-based feature data from the Protein Data Bank, nominal data from UNIPROT, and bioactivity data from ChEMBL, all of which were matched for human and animal data. Using the XGBoost regression model, similarity scores between targets were calculated and based on these scores, the best animal species for a target was identified. For real-world application, targets from an alternative source, i.e. AlphaFold, were tested using the model, and the animal species that had the most similar protein to the human counterparts were predicted. These targets were then grouped based on their associated phenotype such that the pipeline could predict an optimal animal species.