Chemical Research in Toxicology最新文献

Breast cancer resistance protein (BCRP), an important ATP-binding cassette transporter, is mainly responsible for drug efflux from cells, especially in high-expressing tumor cells, and is closely associated with multidrug resistance (MDR). Numerous studies have demonstrated that the inhibition of BCRP can reverse MDR, so inhibiting BCRP is considered to be a promising strategy for cancer treatment. Alkaloids are the primary bioactive ingredients in various traditional Chinese medicines (TCMs), some of which have been reported to reverse MDR by inhibiting BCRP. Our objective was to identify potential inhibitors of BCRP from 130 alkaloids, evaluate the reversion of MDR in TMZ-resistant U251T and T98G cells, and clarify the structure–activity relationships of alkaloids in BCRP inhibition. Among them, eight alkaloids, including sempervirine, reserpine, coptisine chloride, geissoschizine methyl ether, vincristine sulfate, tetrahydroberberine, cyclovirobuxine, and berberrubine, exhibited significant inhibition (>50%) of BCRP in BCRP-MDCK cells, with IC₅₀ ranging from 16.95–94.13 μM. Co-treatment with the inhibitor increased Temozolomide (TMZ) cytotoxicity in TMZ-resistant U251T and T98G cells, with IC₅₀ values declining by 2.1–97.3%. For sempervirine, coptisine chloride, and reserpine, the inhibition appeared to be even greater than the positive inhibitor KO143. Molecular docking analyses elucidated that the inhibitory effect of alkaloids on BCRP was related to π–π stacked, π–alkyl, and π–Sulfur interactions. The pharmacophore model illustrated that aromatic rings and hydrophobic groups may play a critical role in the potency of alkaloid inhibition on BCRP. Taken together, our findings provide valuable information for optimizing alkaloid structure and developing BCRP inhibitors with improved potency and specificity to reverse clinical MDR.

Triclocarban (TCC) is an antiseptic ingredient incorporated into many skin-contact hygiene products, raising public health concerns for its frequent detection in the general population. As the central metabolic organ, the liver plays a key role in lipid synthesis and metabolism; however, the in vivo effects of TCC on hepatic lipid homeostasis remain largely unclear. Herein, a percutaneous TCC exposure model was established based on human-relevant concentrations. An integrated multiomics approach, including hepatic transcriptomics and lipidomics, was applied to explore TCC effects on the liver. We discovered that continuous dermal absorption of TCC significantly disturbed hepatic lipid profiles, as manifested by the decrease in energy storage lipid triacylglycerol (TG) and its synthetic precursor diacylglycerol (DG). Integrated analysis of transcriptomics and targeted validation revealed that TG reduction could result from the decline in lipogenesis, acceleration of fatty acid β-oxidation, and elevated secretion of very-low-density lipoproteins (VLDLs). Cell membrane homeostasis was also disrupted through altering hepatocellular phosphatidylcholine (PC) and phosphatidylethanolamine (PE) levels, which may be related to the activation of endoplasmic reticulum (ER) stress, resulting in the promotion of hepatocyte apoptosis. Together, this work provides novel insights into the causal relationship between TCC exposure and the hepatic metabolic homeostasis.

Cisplatin (DDP) is widely utilized in the clinical treatment of malignant tumors, but its effectiveness is significantly compromised by the adverse effects of acute kidney injury (AKI). Renal tubular cells are primarily responsible for DDP-induced AKI (DDP-AKI); however, the responses of heterogeneous renal tubular cells to DDP exposure have not been thoroughly explored. In this study, we employed a targeted metabolomics approach to investigate the metabolic responses of renal tubular cells in DDP-AKI rats. Tubular cells were isolated from the renal cortex and outer medulla, and a chemical derivatization-based liquid chromatography–tandem mass spectrometry (LC–MS/MS) metabolomics method was applied. Our findings revealed distinct metabolic profiles in tubular cells from the renal cortex and outer medulla, with outer medullary cells exhibiting greater sensitivity to DDP exposure. Further analyses identified the tryptophan pathway as a critical factor contributing to these regional differences. Additional functional investigations showed that intermediate metabolites of the tryptophan pathway alleviated DDP cytotoxicity in both cortical and outer medullary tubular cells primarily through modulation of the Bcl2/Bax and Caspase-3 pathway. This study enhances our understanding of the metabolic characteristics of tubular cells across heterogeneous renal regions in DDP-AKI and facilitates further exploration of the underlying mechanisms of DDP-induced nephrotoxicity.

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.