Chemical Research in Toxicology最新文献

The rapid proliferation of electronic cigarettes (ECs) has raised significant concerns about their potential health effects on both users and bystanders. This study systematically investigates the impact of EC aerosol exposure on human alveolar epithelial cells (A549), considering variations in device parameters, nicotine concentration, and exposure type. Using a gravity-based air–liquid interface exposure system, we assessed cytotoxicity and epithelial barrier integrity by measuring cell viability and transepithelial electrical resistance (TEER). Our results indicate that EC aerosol exposure significantly reduces cell viability and disrupts monolayer integrity in a dose- and device-dependent manner. Notably, VUSE (pod-type) exposure led to a 16% decrease in viability and a 41% reduction in TEER, while VOOPOO (mod-type) exposure caused a 25% viability loss and a 61% reduction in TEER. Power settings played a critical role: at 60 W, cell viability dropped by 48% at 12 mg/mL nicotine concentration compared to 29% at 0 mg/mL. Moreover, under the same number of puffs (30 puffs), firsthand exposure resulted in a 73% viability decrease, whereas secondhand exposure showed a 47% reduction, indicating substantial bystander risks associated with EC usage. These findings underscore the importance of device specifications and exposure conditions in determining EC aerosol toxicity. The observed epithelial barrier disruption suggests increased vulnerability to respiratory diseases. Given the comparable toxicity of firsthand and secondhand aerosols, regulatory measures should extend beyond direct users to include bystander protection. This study highlights the urgent need for comprehensive toxicity assessments to inform public health policies on EC use.

The toxicological interpretation of metabolomics data remains challenging, mainly due to the lack of relational knowledge of metabolic pathway perturbations and adverse outcomes. Here we propose an approach focused on the associative events defined by the adverse outcome pathway (AOP) concept to derive adverse effect predictions from toxicology metabolomics data sets by combining knowledge-driven hypothesis generation and data-driven hypothesis testing. By assessing the associative key events in an AOP, a list of plausible metabolite perturbations can be created, aiding the interpretation of the list of observed metabolite perturbations or differentially abundant metabolites (DAMs). We describe the critical steps of the interpretation and certainty assessment of the effect prediction using protoporphyrinogen oxidase (PPO) inhibition as an example. The approach could serve as a stepping stone toward creating a database of validated, toxicologically meaningful associative event signatures that can be deployed both in (early stage) research of chemical product development and in regulatory chemical safety assessment for hazard identification.

Formaldehyde (FA) is a pervasive environmental organic pollutant and a Group 1 human carcinogen. While FA has been implicated in various cancers, its genotoxic effects, including DNA damage and DNA–protein cross-linking, have proven insufficient to fully explain its role in carcinogenesis, suggesting the involvement of epigenetic mechanisms. Histone post-translational modifications (PTMs) on H3 and H4, which are critical for regulating gene expression, may contribute to FA-induced pathogenesis, as lysine and arginine residues serve as targets for FA–protein adduct formation. This study aimed to elucidate the epigenetic consequences of FA on histone methylation and acetylation patterns through a comprehensive peptide analysis. Human bronchial epithelial cells (BEAS-2B) were exposed to low-dose (0.1 mM) and high-dose (0.5 mM) FA for 1 h, and their histone extracts were analyzed using high-resolution liquid chromatography–tandem mass spectrometry-based proteomics followed by PTM-combined peptide analysis and single PTM site/type comparisons. We identified 40 peptides on histone H3 and 16 on histone H4 bearing epigenetic marks. Our findings revealed that FA exposure induced systemic alterations in H3 and H4 methylation and acetylation, including hypomethylation of H3K4 and H3K79; changes in H3K9, H3K14, H3K18, H3K23, H3K27, H3K36, H3K37, and H3R40; as well as modifications in H4K5, H4K8, H4K12, and H4K16. These FA-induced histone modifications exhibited strong parallels with epigenetic alterations observed in cancers, leukemia, and Alzheimer’s disease. This study provides novel evidence of FA-induced epigenetic toxicity, offering new insights into the potential mechanisms underlying FA-driven pathogenesis.

DNA–peptide cross-links (DpCs) are generated via the proteolytic cleavage of DNA–protein cross-links (DPCs), ubiquitous DNA lesions that block DNA replication and transcription. Translesion synthesis (TLS) DNA polymerases can facilitate replication bypass of DpC adducts in either an error-free or error-prone manner. We have previously demonstrated that local DNA sequence context significantly influences hPol η-mediated replication bypass of 5-formylcytosine (5fC)-mediated DpC lesions. However, the effects of peptide sequence on the efficiency and fidelity of the TLS bypass of 5fC-mediated DpC lesions remained unknown. In the present study, model DpCs containing three different peptides (NH₂-GGGKGLGK*GGA-COOH, NH₂-RPK*PQQFFGLM-COOH, and NH₂-RPKPQQFK*GLM-COOH, K* = oxy-lysine) were subjected to primer extension experiments in the presence of TLS polymerases. We found that in vitro replication of DpC-containing templates by hPol η was more efficient than that catalyzed by hPol l or hPol κ. HPLC-ESI-MS and HPLC-ESI-MS/MS analyses of hPol η primer extension products indicated that the replication bypass of DpC containing NH₂-RPK*PQQFFGLM-COOH was more error-prone than replication of the other two DpCs, leading to targeted C → T transitions, small deletions, and untargeted mutations downstream from the lesion. Steady-state kinetics investigation of hPol η-catalyzed nucleotide incorporation opposite the DpC lesions containing three different peptides revealed that, in all cases, error-free replication was far more efficient than incorporation of incorrect nucleotides. For mutagenic bypass, the catalytic efficiency of hPol η-mediated dAMP misincorporation opposite DpC with peptide NH₂-RPK*PQQFFGLM-COOH was higher than adenine misincorporation across from the other two DpCs and unmodified dC. These steady-state kinetic findings were further explained by molecular modeling and molecular dynamics simulations, revealing that the three different DpC lesions impose varying perturbations to the geometry of the C–G and C–A pairs at the hPol η active site. Collectively, our results reveal that the peptide sequence and conjugation chemistry of DpC lesions can influence the fidelity of lesion bypass by TLS polymerases.

Aetokthonotoxin (AETX) is an emerging environmental toxin produced by the freshwater cyanobacterium Aetokthonos hydrillicola. Accumulating in the food chain, it causes vacuolar myelinopathy, a neurological disease affecting a wide range of wildlife characterized by the development of large intramyelinic vacuoles in the white matter of the brain. So far, the mode of action of AETX is unknown. After discovering that AETX is cytostatic and arrests cancer cell lines in the G₁ phase, metabolomic profiling of AETX-treated cells as well as an assessment of the physicochemical properties of the compound suggested that AETX is a weakly acidic uncoupler of mitochondrial respiration. We confirmed this hypothesis by in vitro assays on mammalian cells, finding that AETX has the expected effects on mitochondrial network morphology, mitochondrial membrane potential, and oxygen consumption rate, resulting in affected ATP generation. We confirmed that AETX is capable of transporting protons across lipid bilayers. In summary, we demonstrate that AETX is a protonophore that uncouples oxidative phosphorylation in mitochondria, which is the primary event of AETX intoxication.

Visnagin (VNG), a furanochromone, is a major active component of the plant Ammi visnaga (L.) Lam often used for the preparation of tea products. This study aims to comprehensively investigate the mechanism of VNG-mediated CYP2A6 enzyme inactivation and the effects of VNG on the pharmacokinetics of the antitumor drug tegafur. The results demonstrate that VNG irreversibly inhibits CYP2A6 in a time-, concentration-, and NADPH-dependent manner. This time-dependent inhibition was attenuated by coincubation with letrozole, a competitive inhibitor of CYP2A6. Glutathione and hydrogen peroxide/superoxide dismutase failed to reverse the VNG-induced inactivation of CYP2A6. GSH trapping experiments provided strong evidence for the formation of epoxide and/or γ-ketoaldehyde intermediates resulting from the metabolic activation of VNG. Furthermore, pretreatment with VNG extract significantly increased the plasma C_max and area under the curve of tegafur in rats.

Toxicokinetic (TK) modeling provides critical information linking chemical exposures to tissue concentrations, predicting persistence in the body and determining the route(s) of elimination. Unfortunately, TK data are not available for most chemicals in commerce and the environment. To better understand and address these important information gaps, researchers and regulatory scientists from the international consortium of Accelerating the Pace of Chemical Risk Assessment herein present a flexible framework for characterizing the suitability of TK new approach methods (NAMs) to address chemical risk questions. High throughput toxicokinetics (HTTK) combines chemical-specific in vitro measures of TK with reproducible transparent and open-source TK models. HTTK supports the interpretation of data from in vitro bioactivity NAMs in a public health risk context and enhances the interpretation of biomonitoring data. A tiered framework has been developed focusing on two key aspects: (1) the regulatory decision context and (2) chemical properties and data. Differing levels of certainty are needed for relative risk prioritization, prospective risk assessment, and for protecting susceptible populations. Here HTTK is described with respect to measurement and modeling applications, relevant decision contexts, applicable chemistry, value of information, and certainty of predictions. In some cases, quantitative structure–property relationship (QSPR) models exist as alternatives to measurement and are discussed when they are appropriate. A series of examples applying the decision trees in specific public health scenarios are provided to illustrate that writing short responses, prompted by the decision trees and supported by the discussion and references collected here, may provide defensible written justification for or against the use of HTTK. The framework is intended to serve as a guide to chemical regulators and risk assessors who are interested to know when and where HTTK might be used for public health safety or risk decision making and when further expert guidance is needed.