Toxicological Sciences最新文献

6PPD-quinone (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone), a transformation product of the antiozonant 6PPD (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) is a likely causative agent of coho salmon (Oncorhynchus kisutch) pre-spawn mortality. Stormwater runoff transports 6PPD-quinone into freshwater streams, rapidly leading to neurobehavioral, respiratory distress, and rapid mortality in laboratory exposed coho salmon, but causing no mortality in many laboratory-tested species. Given this identified hazard, and potential for environmental exposure, we evaluated a set of U.S. Environmental Protection Agency's high throughput assays for their capability to detect the large potency difference between 6PPD and 6PPD-quinone observed in coho salmon and screen for bioactivities of concern. Assays included transcriptomics in larval fathead minnow (FHM), developmental and behavioral toxicity in larval zebrafish, phenotypic profiling in a rainbow trout gill cell line, acute and developmental neurotoxicity in mammalian cells, and reporter transcription factor activity in HepG2 cells. 6PPD was more consistently bioactive across assays, with distinct activity in the developmental neurotoxicity assay (mean 50th centile activity concentration = 0.91 µM). While 6PPD-quinone was less potent in FHM and zebrafish, and displayed minimal neurotoxic activity in mammalian cells, it was highly potent in altering organelle morphology in RTgill-W1 cells (phenotype altering concentration = 0.024 µM compared to 0.96 µM for 6PPD). Although in vitro sensitivity of RTgill-W1 cells may not be as sensitive as intact Coho salmon, the assay may be a promising approach to test chemicals for 6PPD-quinone-like activities. The other assays each identified unique bioactivities of 6PPD, with neurobehavioral and developmental neurotoxicity being most affected, indicating a need for further assessment of this chemical.

Prenatal exposure to the toxic metal inorganic arsenic (iAs) is associated with adverse pregnancy and fetal growth outcomes. These adverse outcomes are tied to physiological disruptions in the placenta. While iAs co-occurs in the environment with other metals such as manganese (Mn), there is a gap in the knowledge of the effects of metal-mixtures on the placenta. To address this, we exposed human placental trophoblast cells to iAs, Mn, and an iAs-Mn mixture at three concentrations and evaluated transcriptome-wide gene expression and placental migration. We hypothesized that co-exposure to iAs-Mn in a mixture would result in a synergistic/enhanced transcriptomic effect compared to either metal alone. We also anticipated that genes involved in inflammatory or immune-related pathways would be differentially expressed in relation to the mixture compared to single-metals. The results highlight that iAs exposure alone had a stronger genomic response than Mn exposure, with two-fold the number of differentially expressed genes (DEGs). When analyzing DEGs present across all concentrations of study, the iAs-Mn mixture resulted in the greatest number of DEGs. The results highlight that iAs exposure alone influences the expression of toll-like receptor-initiated response pathways including Triggering Receptor Expressed on Myeloid Cells-1 TREM. Exposure to Mn alone influenced the expression of Nicotinamide adenine dinucleotide (NAD) biosynthesis pathways. In contrast, exposure to the iAs-Mn mixtures resulted in altered expression of inflammatory and immune response-related pathways, including the Nuclear factor erythroid 2 p45-related factor 2 (NRF2)-mediated oxidative stress response pathway. Migration was unaffected by iAs, Mn or the iAs-Mn mixture. These findings provide novel toxicogenomic insights into iAs and Mn-induced placental transcriptomic dysregulations at environmentally-relevant concentrations, with implications that in utero exposure to metal mixtures can influence inflammatory and immune pathways within the placenta.

Organophosphate and pyrethroid pesticides are common contaminants in cannabis. Due to the status of cannabis as an illicit Schedule I substance at the federal level, there are no unified national guidelines in the U.S. to mitigate the health risk of pesticide exposure in cannabis. Here, we examined the change in the state-level regulations of organophosphate and pyrethroid pesticides in cannabis. The medians of pyrethroid and organophosphate pesticides specified by each state-level jurisdiction increased from zero pesticide in 2019 to 4.5 pyrethroid and 7 organophosphate pesticides in 2023, respectively. Next, we evaluated the potential connections between pyrethroids, organophosphates, cannabinoids, and Parkinson's disease using the Comparative Toxicogenomics Database (CTD). Eleven pyrethroids, 30 organophosphates, and 14 cannabinoids were associated with 95 genes to form 3,237 inferred and curated Chemical-Gene-Phenotype-Disease tetramers. Using a behavioral repulsion assay with the whole organism model Caenorhabditis elegans, we examined the effect of cannabinoids and insecticides on depleting dopamine synthesis. Exposure to chlorpyrifos and permethrin, but not Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), results in dose-dependent effects on 1-nonanol repulsive behaviors in C. elegans, indicating dopaminergic neurotoxicity (p < 0.01). Dose-dependent effects of chlorpyrifos are different in the presence of Δ9-THC and CBD (p < 0.001). As a proof of concept, this study demonstrated how to use new approach methodologies such as C. elegans and the CTD to inform further testing and pesticide regulations in cannabis by chemical class.

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 human, 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 pair-wise sequence comparison using protein sequences, instead of the biologically relevant 3-dimensional (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, ie, 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.

Because the liver plays a vital role in the clearance of exogenous chemical compounds, it is susceptible to chemical-induced toxicity. Animal-based testing is routinely used to assess the hepatotoxic potential of chemicals. While large-scale high-throughput sequencing data can indicate the genes affected by chemical exposures, we need system-level approaches to interpret these changes. To this end, we developed an updated rat genome-scale metabolic model to integrate large-scale transcriptomics data and utilized a chemical structure similarity-based ToxProfiler tool to identify chemicals that bind to specific toxicity targets to understand the mechanisms of toxicity. We used high-throughput transcriptomics data from a 5-day in vivo study where rats were exposed to different non-toxic and hepatotoxic chemicals at increasing concentrations and investigated how liver metabolism was differentially altered between the non-toxic and hepatotoxic chemical exposures. Our analysis indicated that the genes identified via toxicity target analysis and those mapped to the metabolic model showed a distinct gene expression pattern, with the majority showing upregulation for hepatotoxicants compared to non-toxic chemicals. Similarly, when we mapped the metabolic genes at the pathway level, we identified several pathways in carbohydrate, amino acid, and lipid metabolism that were significantly upregulated for hepatotoxic chemicals. Furthermore, using our system-level integration of gene expression data with the rat metabolic model, we could differentiate metabolites in these pathways that were systematically elevated or suppressed due to hepatotoxic versus non-toxic chemicals. Thus, using our combined approach, we were able to identify a set of potential gene signatures that clearly differentiated liver toxic responses from non-toxic chemicals, which helped us identify potential metabolic pathways and metabolites that are systematically associated with the toxicant exposure.

Medicinal plants are products from natural sources that have found relevance in medicine for several decades. They are rich in bioactive compounds; thus, they are widely used to treat different ailments globally. Medicinal plants have provided hope for the health care industry as most are used to synthesize modern medicines currently used in the treatment of various diseases. However, there are still concerns with respect to the mutagenic properties of medicinal plants. Over the years, researchers have embarked on various studies aimed at investigating the mutagenicity of several medicinal plants found in different regions of the world. In this review, we discussed factors that may influence plant mutagenicity and the findings of in-vitro and in-vivo mutagenicity studies of several medicinal plants from across the globe. In addition, this review considers the potential health implications of mutagenic medicinal plants and safety measures that can be used to mitigate mutagenesis in medicinal plant. To achieve this, we searched for articles reporting on medicinal plants and mutagenesis on the PubMed, Scopus and Web of Science databases. Several journal articles reported on the mutagenicity of some medicinal plants; however, it was observed that the majority of the articles reported the non-mutagenicity of medicinal plants. The findings from these studies implies that medicinal plants have good prospects in treating diseases and that they are clinically relevant. However, these reports will require further validation to determine their safety for human use as limited in-vivo studies were conducted and there are no clinical safety reports for any of the plant discussed in this review.

Ozone is an urban air pollutant, known to cause lung injury and altered function. Using established models of acute (0.8 ppm, 3 h) and episodic (1.5 ppm, 2 h, 2 times/wk, 6 wk) inhalation exposure, we observed distinct structural changes in the lung; whereas acutely, ozone primarily disrupts the bronchiolar epithelial barrier, episodic exposure causes airway remodeling. Herein we examined how these responses altered pulmonary function. A SCIREQ small animal ventilator was used to assess lung function; impedance was used to conditionally model resistance and elastance. Episodic, but not acute ozone exposure reduced the inherent and frequency-dependent tissue recoil (elastance) of the lung. Episodic ozone also increased central and high-frequency resistance relative to air control after methacholine challenge, indicating airway hyperresponsiveness. Pressure-volume (PV) loops showed that episodic ozone increased maximum lung volume, while acute ozone decreased lung volume. Episodic ozone-induced functional changes were accompanied by increases in alveolar circularization; conversely, minimal histopathology was observed after acute exposure. However, acute ozone exposure caused increases in total phospholipids, total surfactant protein D (SP-D), and low molecular weight SP-D in bronchoalveolar lavage fluid. Episodic ozone exposure only increased total SP-D. These findings demonstrate that acute and episodic ozone exposure cause distinct alterations in surfactant composition and pulmonary function. Whereas loss in PV loop area following acute ozone exposure is likely driven by increases in SP-D and inflammation, emphysematous pathology and airway hyperresponsiveness after episodic ozone appears to be the result of alterations in lung structure.

Traditional approaches for quantitatively characterizing uncertainty in risk assessment require adaptation to accommodate increased reliance on observational (vs. experimental) studies in developing toxicity values. Herein, a case study with PFOA and PFOS and vaccine response explores approaches for qualitative and-where possible-quantitative assessments of uncertainty at each step in the toxicity value development process when using observational data, including review and appraisal of individual studies, candidate study selection, dose-response modeling, and application of uncertainty factors. Each of the fifteen studies identified had uncertainties due to risk of bias in confounding, outcome, and exposure ascertainment, likely contributing to the observed inconsistencies within and across studies, and resulting in lack of candidacy for dose-response assessment. Nonetheless, two representative studies were selected to demonstrate possible methods to quantify uncertainty in the remaining steps. Data simulations indicated lack of a clear dose-response relationship; dose-response models fit to representative simulations indicated high uncertainty in both the magnitude and direction of effect with simulated BMDL values varying at least 66- and 86-fold for PFOA and PFOS. Uncertainty factor application added minimal uncertainty. Combined, a high level of uncertainty was observed, precluding the ability to confidently assess causal dose-response relationships with the observational data, alone. This case study highlights the need for quantitative uncertainty analysis when developing toxicity values with observational data and, importantly, emphasizes the need for application of additional techniques to directly assess causality and the specificity of dose-response when relying on studies of association in quantitative risk assessment.

The frequency of drug-induced liver injury (DILI) in clinical trials remains a challenge for drug developers despite advances in human hepatotoxicity models and improvements in reducing liver-related attrition in preclinical species. TAK-994, an oral orexin receptor 2 agonist, was withdrawn from phase II clinical trials due to the appearance of severe DILI. Here, we investigate the likely mechanism of TAK-994 DILI in hepatic cell culture systems examined cytotoxicity, mitochondrial toxicity, impact on drug transporter proteins, and covalent binding. Hepatic liabilities were absent in rat and non-human primate safety studies, however, murine studies initiated during clinical trials revealed hepatic single-cell necrosis following cytochrome P450 induction at clinically relevant doses. Hepatic cell culture experiments uncovered wide margins to known mechanisms of intrinsic DILI, including cytotoxicity (>100× Cmax/IC50), mitochondrial toxicity (>100× Cmax/IC50), and bile salt efflux pump inhibition (>20× Css, avg/IC50). A potential covalent binding liability was uncovered with TAK-994 following hepatic metabolism consistent with idiosyncratic DILI and the delayed-onset clinical toxicity. Although idiosyncratic DILI is challenging to detect preclinically, reductions in total daily dose and covalent binding can reduce the covalent body binding burden and, subsequently, the clinical incidence of idiosyncratic DILI.

Phthalates are known endocrine disrupting chemicals and ovarian toxicants that are used widely in consumer products. Phthalates have been shown to exert ovarian toxicity on multiple endpoints, altering transcription of genes responsible for normal ovarian function. However, the molecular mechanisms by which phthalates act on the ovary are not well understood. In this study, we hypothesized that phthalates specifically target granulosa cells within the ovarian follicle. To test our hypothesis, we cultured whole mouse antral follicles for 96 hours in the presence of vehicle or 10 µg/mL of a phthalate metabolite mixture. At the end of the culture period, follicles were dissociated into single cell suspensions and subjected to single cell RNA sequencing. We used markers from published studies to identify cell type clusters, the largest of which were granulosa and theca/stroma cells. We further identified sub-populations of granulosa, theca, and stromal cells and analyzed differentially expressed genes between the phthalate treatment and control. Granulosa cells, specifically mural granulosa cells, had the most differentially expressed genes. Pathway analysis of differentially expressed genes from the overall granulosa cell cluster revealed disruption of cell cycle and mitosis, whereas pathway analysis of the mural granulosa cell subcluster identified terms related to translation, ribosome, and endoplasmic reticulum. Our findings suggest that phthalates have both broad impacts on cell types and specific impacts on cellular subtypes, emphasizing the complexity of phthalate toxicity and highlighting how bulk sequencing can mask effects on vulnerable cell types.