Frontiers in toxicology最新文献

Acute intoxication with high levels of organophosphate (OP) cholinesterase inhibitors can cause cholinergic crisis, which is associated with acute, life-threatening parasympathomimetic symptoms, respiratory depression and seizures that can rapidly progress to status epilepticus (SE). Clinical and experimental data demonstrate that individuals who survive these acute neurotoxic effects often develop significant chronic morbidity, including behavioral deficits. The pathogenic mechanism(s) that link acute OP intoxication to chronic neurological deficits remain speculative. Cellular senescence has been linked to behavioral deficits associated with aging and neurodegenerative disease, but whether acute OP intoxication triggers cellular senescence in the brain has not been investigated. Here, we test this hypothesis in a rat model of acute intoxication with the OP diisopropylfluorophosphate (DFP). Adult male Sprague-Dawley rats were administered DFP (4 mg/kg, s.c.). Control animals were administered an equal volume (300 µL) of sterile phosphate-buffered saline (s.c.). Both groups were subsequently injected with atropine sulfate (2 mg/kg, i.m.) and 2-pralidoxime (25 mg/kg, i.m.). DFP triggered seizure activity within minutes that rapidly progressed to SE, as determined using behavioral seizure criteria. Brains were collected from animals at 1, 3, and 6 months post-exposure for immunohistochemical analyses of p16, a biomarker of cellular senescence. While there was no immunohistochemical evidence of cellular senescence at 1-month post-exposure, at 3- and 6-months post-exposure, p16 immunoreactivity was significantly increased in the CA3 and dentate gyrus of the hippocampus, amygdala, piriform cortex and thalamus, but not the CA1 region of the hippocampus or the somatosensory cortex. Co-localization of p16 immunoreactivity with cell-specific biomarkers, specifically, NeuN, GFAP, S100β, IBA1 and CD31, revealed that p16 expression in the brain of DFP animals is neuron-specific. The spatial distribution of p16-immunopositive cells overlapped with expression of senescence associated β-galactosidase and with degenerating neurons identified by FluoroJade-C (FJC) staining. The co-occurrence of p16 and FJC was positively correlated. This study implicates cellular senescence as a novel pathogenic mechanism underlying the chronic neurological deficits observed in individuals who survive OP-induced cholinergic crisis.

Introduction: In toxicology, steps are being taken towards more mechanism-focused and human relevant approaches to risk assessment, requiring new approaches and methods. Additionally, there is increasing emphasis by regulators on risk assessment of immunotoxicity. Methods: Here we present data from a peripheral blood mononuclear cell (PBMC) system whereby a varied set of stimuli, including those against the TCR and Toll-like receptors, enable readouts of cytokine and prostaglandin E2 (PGE2) production with monocyte, T cell and B cell viability, proliferation, and associated activation markers. In addition to results on the impact of the stimuli used, initial profiling data for a case study chemical, curcumin, is presented, illustrating how the system can be used to generate information on the impact of exogenous materials on three major constituent immune cell subsets for use in risk assessment and to direct follow-on studies. Results: The different stimuli drove distinct responses, not only in relation to the "quantity" of the response but also the "quality". Curcumin had a limited impact on the B cell parameters measured, with the stimuli used, and it was noted that in contrast to T cells where there was either no impact or a reduction in viability and proliferation with increasing concentration, for B cells there was a small but significant increase in both measurements at curcumin concentrations below 20 µM. Similarly, whilst expression of activation markers by T cells was reduced by the highest concentration of curcumin, they were increased in B cells. Curcumin only impacted the viability of stimulated monocytes at the highest concentration and had differential impact on different activation markers. Levels of all cytokines and PGE2 were reduced at higher concentrations. Discussion: Although the platform has certain limitations, it nevertheless enables assessment of healthy baseline monocyte, T-, and B-cell responses, and scrutiny of the impact of different stimuli to detect potential immune suppression or enhancement from exogenous materials. In the case of curcumin, a pattern of responses indicative of immune suppressive / anti-inflammatory effects was detected. It is an accessible, highly modifiable system that can be used to screen materials and guide further studies, providing a holistic, integrated picture of effects.

In the European regulatory context, rodent in vivo studies are the predominant source of neurotoxicity information. Although they form a cornerstone of neurotoxicological assessments, they are costly and the topic of ethical debate. While the public expects chemicals and products to be safe for the developing and mature nervous systems, considerable numbers of chemicals in commerce have not, or only to a limited extent, been assessed for their potential to cause neurotoxicity. As such, there is a societal push toward the replacement of animal models with in vitro or alternative methods. New approach methods (NAMs) can contribute to the regulatory knowledge base, increase chemical safety, and modernize chemical hazard and risk assessment. Provided they reach an acceptable level of regulatory relevance and reliability, NAMs may be considered as replacements for specific in vivo studies. The European Partnership for the Assessment of Risks from Chemicals (PARC) addresses challenges to the development and implementation of NAMs in chemical risk assessment. In collaboration with regulatory agencies, Project 5.2.1e (Neurotoxicity) aims to develop and evaluate NAMs for developmental neurotoxicity (DNT) and adult neurotoxicity (ANT) and to understand the applicability domain of specific NAMs for the detection of endocrine disruption and epigenetic perturbation. To speed up assay time and reduce costs, we identify early indicators of later-onset effects. Ultimately, we will assemble second-generation developmental neurotoxicity and first-generation adult neurotoxicity test batteries, both of which aim to provide regulatory hazard and risk assessors and industry stakeholders with robust, speedy, lower-cost, and informative next-generation hazard and risk assessment tools.

[This corrects the article DOI: 10.3389/ftox.2023.1212509.].

Introduction: The Adverse Outcome Pathway (AOP) concept facilitates rapid hazard assessment for human health risks. AOPs are constantly evolving, their number is growing, and they are referenced in the AOP-Wiki database, which is supported by the OECD. Here, we present a study that aims at identifying well-defined biological areas, as well as gaps within the AOP-Wiki for future research needs. It does not intend to provide a systematic and comprehensive summary of the available literature on AOPs but summarizes and maps biological knowledge and diseases represented by the already developed AOPs (with OECD endorsed status or under validation). Methods: Knowledge from the AOP-Wiki database were extracted and prepared for analysis using a multi-step procedure. An automatic mapping of the existing information on AOPs (i.e., genes/proteins and diseases) was performed using bioinformatics tools (i.e., overrepresentation analysis using Gene Ontology and DisGeNET), allowing both the classification of AOPs and the development of AOP networks (AOPN). Results: AOPs related to diseases of the genitourinary system, neoplasms and developmental anomalies are the most frequently investigated on the AOP-Wiki. An evaluation of the three priority cases (i.e., immunotoxicity and non-genotoxic carcinogenesis, endocrine and metabolic disruption, and developmental and adult neurotoxicity) of the EU-funded PARC project (Partnership for the Risk Assessment of Chemicals) are presented. These were used to highlight under- and over-represented adverse outcomes and to identify and prioritize gaps for further research. Discussion: These results contribute to a more comprehensive understanding of the adverse effects associated with the molecular events in AOPs, and aid in refining risk assessment for stressors and mitigation strategies. Moreover, the FAIRness (i.e., data which meets principles of findability, accessibility, interoperability, and reusability (FAIR)) of the AOPs appears to be an important consideration for further development.

Background: The interstitial testicular Leydig cells are responsible for the production of testosterone, which functionally deteriorate with normal aging. Decreased expression of mitochondrial steroidogenic interactome proteins and diminished mitochondrial function in aging Leydig cells suggest that mitochondrial dynamics play a role in maintaining adequate levels of testosterone. Optic atrophy 1 (OPA1) protein regulates mitochondrial dynamics and cristae formation in many cell types. Previous studies showed that increasing OPA1 expression in dysfunctional Leydig cells restored mitochondrial function and recovered androgen production to levels found in healthy Leydig cells. These findings suggested that mitochondrial dynamics may be a promising target to ameliorate diminished testosterone levels in aging males. Methods: We used twelve-month-old rats to explore the relationship between mitochondrial dynamics and Leydig cell function. Isolated Leydig cells from aged rats were treated ex vivo with the cell-permeable mitochondrial fusion promoter 4-Chloro-2-(1-(2-(2,4,6-trichlorophenyl)hydrazono)ethyl) phenol (mitochondrial fusion promoter M1), which enhances mitochondrial tubular network formation. In parallel, rats were treated with 2 mg/kg/day M1 for 6 weeks before Leydig cells were isolated. Results: Ex vivo M1-treated cells showed enhanced mitochondrial tubular network formation by transmission electron microscopy, enhanced Leydig cell mitochondrial integrity, improved mitochondrial function, and higher testosterone biosynthesis compared to controls. However, in vivo treatment of aged rats with M1 not only failed to re-establish testosterone levels to that of young rats, it also led to further reduction of testosterone levels and increased apoptosis, suggesting M1 toxicity in the testis. The in vivo M1 toxicity seemed to be tissue-specific, however. Conclusion: Promoting mitochondrial fusion may be one approach to enhancing cell health and wellbeing with aging, but more investigations are warranted. Our findings suggest that fusion promoters could potentially enhance the productivity of aged Leydig cells when carefully regulated.

Introduction: Skin sensitization, which leads to allergic contact dermatitis, is a key toxicological endpoint with high occupational and consumer prevalence. This study optimized several in vitro assays listed in OECD skin sensitization test guidelines for use on a quantitative high-throughput screening (qHTS) platform and performed in silico model predictions to assess the skin sensitization potential of prioritized compounds from the Tox21 10K compound library. Methods: First, we screened the entire Tox21 10K compound library using a qHTS KeratinoSens^TM (KS) assay and built a quantitative structure-activity relationship (QSAR) model based on the KS results. From the qHTS KS screening results, we prioritized 288 compounds to cover a wide range of structural chemotypes and tested them in the solid phase extraction-tandem mass spectrometry (SPE-MS/MS) direct peptide reactivity assay (DPRA), IL-8 homogeneous time-resolved fluorescence (HTRF) assay, CD86 and CD54 surface expression in THP1 cells, and predicted in silico sensitization potential using the OECD QSAR Toolbox (v4.5). Results: Interpreting tiered qHTS datasets using a defined approach showed the effectiveness and efficiency of in vitro methods. We selected structural chemotypes to present this diverse chemical collection and to explore previously unidentified structural contributions to sensitization potential. Discussion: Here, we provide a skin sensitization dataset of unprecedented size, along with associated tools, and analysis designed to support chemical assessments.

Emerging contaminants, including pharmaceuticals, personal care products, microplastics, and per- and poly-fluoroalkyl substances, pose a major threat to both ecosystems and human health in Southeast Asia. As this region undergoes rapid industrialization and urbanization, the increasing presence of unconventional pollutants in water bodies, soil, and various organisms has become an alarming concern. This review comprehensively examines the environmental challenges posed by emerging contaminants in Southeast Asia and recent progress in toxicity testing methods. We discuss the diverse range of emerging contaminants found in Southeast Asia, shedding light on their causes and effects on ecosystems, and emphasize the need for robust toxicological testing methods. This review is a valuable resource for researchers, policymakers, and environmental practitioners working to mitigate the impacts of emerging contaminants and secure a sustainable future for Southeast Asia.