Chemical Research in Toxicology最新文献

Melatonin vaping products, touted for their faster absorption than oral melatonin supplements, have been gaining popularity among adolescents as sleep aid. Here, we elucidated the response of human bronchial epithelial cells (hBECs) to high levels of melatonin from vaped aerosols, investigated the uptake of melatonin by hBECs in vitro, and characterized the chemical composition of three commercially available melatonin vapes. Melatonin vape exposure decreased the secretion of chemokines and produced an immunosuppressive gene expression signature. The tested devices contained potential contaminants, including pharmaceuticals and industrial chemicals. Further investigation is needed for melatonin vapes to determine their local and systemic toxicity.

Early derisking decisions in the development of new chemical compounds enable the identification of novel chemical candidates with improved safety profiles. In vivo studies are traditionally conducted in the early assessment of acute oral toxicity of crop protection products to avoid compounds, which are considered “very acutely toxic”, with an in vivo lethal dose of 50% (LD50) ≤ 60 mg/kg body weight. Those studies are lengthy and costly and raise ethical concerns, catalyzing the use of nonanimal alternatives. The objective of our analysis was to assess the predictive efficacy of read-across approaches for acute oral toxicity in rats, comparing the use of chemical structure information, in vitro biological data derived from the Cell Painting profiling assay on U2OS cells, or the combination of both. Our findings indicate that the classification of compounds as very acute oral toxic (LD50 ≤ 60 mg/kg) or not is possible using a read-across approach, with chemical structure information, morphological profiles, or a combination of both. When classifying compounds structurally similar to those in the training set, the chemical structure was more predictive (balanced accuracy of 0.82). Conversely, when the compounds to be classified were structurally different from those in the training set, the morphological profiles were more predictive (balanced accuracy of 0.72). Combining the two models allowed for the classification of compounds structurally similar to those in the training set to slightly improve the predictions (balanced accuracy of 0.85).

Ethidium bromide was first described as a DNA intercalator 60 years ago and, over the ensuing years, may be the most widely used fluorescent DNA stain in molecular biology, biochemistry, and histology. Noncovalent DNA binding by ethidium has been well characterized, but to date, there have been no reports of covalent DNA adduct formation by ethidium bromide. This report describes the characterization of covalent adducts generated by the reaction of ethidium with apurinic/apyrimidinic (AP) sites in DNA. Adduct formation proceeds via the reaction of the amino group(s) on ethidium with the ring-opened aldehyde residue of the AP site in DNA to yield an imine. Ethidium-AP adducts may form under a variety of circumstances due to the ubiquitous occurrence of AP sites in cellular and synthetic DNA.

Mitochondria, pivotal to cellular metabolism, serve as the primary sources of biological energy and are key regulators of intracellular calcium ion storage, crucial for maintaining cellular calcium homeostasis. Dysfunction in these organelles impairs ATP synthesis, diminishing cellular functionality. Emerging evidence implicates mitochondrial dysfunction in the etiology and progression of diverse diseases. Environmental factors that induce mitochondrial dysregulation raise significant public health concerns, necessitating a nuanced comprehension and classification of mitochondrial-related hazards. This review systematically adopts a toxicological perspective to illuminate the biological functions of mitochondria, offering a comprehensive exploration of how toxicants instigate mitochondrial dysfunction. It delves into the disruption of energy metabolism, the initiation of mitochondrial fragility and autophagy, and the induction of mutations in mitochondrial DNA by mutagens. The overarching objective is to enhance our understanding of the repercussions of mitochondrial damage on human health.

Hepatic flavin-containing monooxygenase 3 (FMO3) is arguably the most important FMO in humans from the standpoint of drug metabolism. Recently, adult hepatic FMO3 has been linked to several conditions including cardiometabolic diseases, aging, obesity, and atherosclerosis in small animals. Despite the importance of FMO3 in drug and chemical metabolism, relative to cytochrome P-450 (CYP), fewer studies have been published describing drug and chemical metabolism. This may be due to the properties of human hepatic FMO3. For example, FMO3 is thermally labile, and often methods reported in the study of human hepatic FMO3 are not optimal. Herein, I describe some practical aspects for studying human hepatic FMO3 and other FMOs.

Derived from the same natural anticoagulant as warfarin (dicoumarol), long-acting anticoagulant rodenticides (LAARs) or superwarfarins have much longer half-lives in human blood than warfarin (weeks instead of hours) and are more potent inhibitors of the same enzyme, vitamin K epoxide reductase component 1. While used effectively worldwide as rodenticides, LAARs can elicit severe, protracted, life-threatening coagulopathy in humans at blood concentrations >10 ng/mL leading to numerous accidental and intentional poisonings annually. To facilitate timely identification and quantitative analysis of LAARs in patients presenting unexplained severe, protracted, life-threatening coagulopathy, several analytical methods have been developed, all of which are based on electrospray liquid chromatography–mass spectrometry (LC–MS). In this perspective, we evaluated and compared these LC–MS methods in terms of validation, simultaneous detection of multiple LAARs, measurement of individual stereoisomers, and clinical applications.

Cytochrome P450 2D6 (CYP2D6) exhibits rich genetic polymorphism, and functional changes caused by variations are the key reasons for differences in substrate drug systemic exposure. Discovering novel variants and defining their enzymatic kinetic characteristics can contribute to the personalized application of drugs. In this study, a data chain of variant-function-structure was established through population-based sequencing, baculovirus insect cell expression, in vitro enzymatic incubation, and ultrahigh performance liquid chromatography tandem mass spectrometry. Results revealed nine novel missense mutations in the exonic regions. After the corresponding microsomes were obtained, the kinetics of the variants were investigated using dextromethorphan as a probe substrate. It was found that the activities of CYP2D6.2, 10, 17, 35, 65, R28G, T76M, and E215K were significantly reduced, while D301V almost led to loss of enzyme function. Additionally, the relative clearance rate of R25Q was significantly increased. From the molecular structure perspective, the mutation sites are distributed outside the dextromethorphan binding pocket, suggesting that they primarily influence CYP2D6 activity via allosteric modulation. These research findings provide fundamental data for the precise application of CYP2D6 substrate drugs.

Elevations in hepatic enzymes were detected in several trial patients exposed to the Alzheimer's drug atabecestat, which resulted in termination of the drug development program. Characterization of hepatic T-lymphocyte infiltrates and diaminothiazine (DIAT) metabolite-responsive, human leukocyte antigen (HLA)-DR-restricted, CD4+ T-lymphocytes in the blood of patients confirmed an immune pathogenesis. Patients with immune-mediated liver injury expressed a restricted panel of HLA-DRB1 alleles including HLA-DRB1*12:01, HLA-DRB1*13:02, and HLA-DRB1*15:01. Thus, the objectives of this study were to (i) generate DIAT-responsive T-cell clones from HLA-genotyped drug-naive donors, (ii) characterize pathways of DIAT-specific T-cell activation, and (iii) assess HLA allele restriction of the DIAT-specific T-cell response. Sixteen drug-naive donors expressing the HLA-DR molecules outlined above were recruited, and T-cell clones were generated. Cellular phenotype, function, and HLA-allele restriction were assessed using culture assays. Peptides displayed by HLA class II molecules in the presence and absence of atabecestat were analyzed by mass spectrometry. Several DIAT-responsive CD4+ clones, displaying no reactivity toward the parent drug, were successfully generated from donors expressing HLA-DRB1*12:01, HLA-DRB1*13:02, and HLA-DRB1*15:01 but not from other donors expressing other HLA-DRB1 alleles. T-cell clones were activated following direct binding of DIAT to HLA-DR proteins expressed on the surface of antigen presenting cells. DIAT binding did not alter the HLA-DRB1 peptide binding repertoire, indicative of a binding interaction with the HLA-associated peptide rather than with the HLA protein itself. DIAT-specific T-cell responses displayed HLA-DRB1*12:01, HLA-DRB1*13:02, and HLA-DRB1*15:01 restriction. These data demonstrate that DIAT displays a degree of selectivity toward HLA protein and associated peptides, with expression of certain alleles increasing and that of others decreasing, the likelihood that a drug-specific T-cell response develops.

Inhibition of thyroid peroxidase (TPO) is a known molecular initiating event for thyroid hormone dysregulation and thyroid toxicity. Consequently, TPO is a critical off-target for the design of safer agrochemicals. To date, fewer than 500 structurally characterized TPO inhibitors are known, and the most comprehensive result set generated under identical conditions encompasses approximately 1000 compounds from a subset of the ToxCast compound collection. Here we describe a collaboration between wet lab and data scientists combining a large in vitro screen and the subsequent development of an in silico model for predicting TPO inhibition. The screen encompassed more than 100,000 diverse drug-like agrochemical compounds and yielded more than 6000 structurally novel TPO inhibitors. On this foundation, we applied different machine learning techniques and compared their performance. We discuss use cases for in silico TPO models in agrochemical research and explain that model recall is of particular importance when selecting compounds from large virtual compound collections. Furthermore, we show that due to the higher structural diversity of our training data, our final model allowed better generalization than models trained on the ToxCast data set. We now have a tool to predict TPO inhibition even for molecules that are only available virtually, such as hits from virtual screenings, or compounds under consideration for inclusion in our screening collection. Structures and activity data for 34,524 compounds are provided. This data set includes almost all inhibitors, including more than 3000 proprietary structures, and a large proportion of the inactives.