Chemical Research in Toxicology最新文献

The many-decade use of perfluorooctanesulfonic acid (PFOS) in firefighting foams and other products has resulted in their accumulation in water sources and terrestrial environments. Long-term exposure of PFOS has been linked to detrimental effects on human health. PFOS, primarily manufactured through electrochemical fluorination (ECF), yielded both linear and branched isomers. While progress has been made in understanding the health impacts of linear PFOS exposure on human health, there is far less understanding about the toxicological effects and bioaccumulative potential of their branched isomers. In this study, the bioaccumulation potential of linear PFOS and five different branched isomers in the long-chain fatty acid (LCFA) transport protein from Escherichia coli (E. coli) is investigated using molecular dynamics simulations. The bioaccumulative potential of the PFOS isomers was assessed by computing their binding strength at both the low-affinity site and the high-affinity site in comparison with natural ligands. The binding characteristics of PFOS isomers from in silico examinations are in good agreement with in vitro cellular studies. Our study demonstrates a preferential bioaccumulation potential for certain branched isomers rather than linear PFOS. The low hydrogen bonding network of disubstituted isomers compared to monosubstituted isomers at the low-affinity site corroborates with their minimal abundance in the in vitro studies. The interactions between the PFOS isomers with residues ARG_157 and GLU_319 determine their binding potential. Additionally, the location of −CF₃ substitutions in branched PFOS isomers plays a crucial role in governing their overall bioaccumulation potential, providing insight about the bioaccumulation potential in living organisms.

Bisphenol A analogs (BPs), used as BPA alternatives, have drawn great concerns due to their potential adverse effects. Studies have shown that reactive metabolites (RMs) formed in vitro and in vivo could covalently bind to nucleophilic macromolecules to elicit toxicity. However, the bioactivation potential of BPs and their capacity to covalently modify amino acid residues within proteins have been poorly characterized. Thus, this study systematically characterized the metabolic activation of eight BPs and their reactivity toward cysteine. Using N-acetylcysteine (NAC) as a trapping agent to capture RMs, we developed a novel nontargeted fragment screening strategy for cysteine adduct identification and mechanistic exploration. Integrating calculated electron affinity results, mechanistic analyses revealed a common activation pathway across multiple BPs involving oxidation, ipso-addition, and ipso-substitution. Also, the abundances of cysteine adducts correlated with metabolic rates of individual BPs, underscoring structure–reactivity relationships. These results provided critical mechanistic insight into BPs bioactivation, implicating their potential toxicity risk and supporting environmental risk evaluation.

The distribution of 7-(deoxyadenosin-N⁶-yl)-aristolactam I (ALI-dA) in mice treated with the same amount of aristolochic acid I (AA-I) at different dosage rates was investigated. The results showed a distinct organ distribution pattern of ALI-dA, with the highest adduct levels observed in the bladders of mice that received chronic doses of AA-I. In contrast, in mice that received AA-I acutely, the highest levels were found in the kidneys and were over ten times higher than those observed with chronic exposure. These results indicate that, in addition to the cumulative dose, the rate at which humans are exposed to AA-I is an under-recognized risk factor in the development of aristolochic acid nephropathy.

Detecting and quantifying peroxynitrite (ONOO^–) under physiological conditions is challenging due to its low steady-state levels, resulting from typically low fluxes of nitric oxide (^•NO) and superoxide (O₂^•–), as well as its short half-life caused by rapid reactions with cellular and extracellular targets. Low-molecular-weight boronate probes that react rapidly with ONOO^– to form stable and characteristic products represent the most promising class of redox probes for ONOO^– detection and quantitative analyses in chemical and biological systems. Because boronates also respond to other nucleophilic oxidants, including hydrogen peroxide (H₂O₂), novel approaches to selectively detect ONOO^– are needed. Here, we report our studies on the application of boronobenzyl (Bz-BA) derivatives of the fluorescent coumarin-pyridine (CP) construct for specific detection of ONOO^–. We demonstrate that the probe containing a boronate moiety in the ortho position to the fluorophore (CP-Bz-o-BA) reacts rapidly with ONOO^– and forms the corresponding cyclization product on the minor, ONOO^–-specific pathway. We characterized the reaction kinetics and stoichiometry of CP-Bz-o-BA with ONOO^– and identified the hydroxybenzyl derivative as the major and stable product, with cyclic and nitrated derivatives as the minor, but ONOO^–-specific products. Liquid chromatography–mass spectrometry analyses of cell extracts confirmed the formation of the same products in RAW 264.7 macrophages activated to produce ONOO^–, demonstrating the occurrence of the same chemistry and its applicability for specific detection of ONOO^– in biological settings. Interestingly, the CP-Bz-o-BA probe reacts with H₂O₂ significantly faster (∼5-fold) than the previously reported aromatic boronates (e.g., coumarin-7-boronic acid, CBA), which we attribute to the presence of the positive charge of the pyridinium cation in proximity to the boronic acid moiety.

Arsenite-contaminated groundwater poses a major health concern affecting millions of people. Chronic exposure to elevated levels of inorganic arsenic is implicated in carcinogenesis, with impaired DNA repair and dysregulated DNA and histone modifications as key factors. Using human A549 lung carcinoma cells, we investigated the persistence of acute arsenite-induced cellular stress at the epigenetic and transcriptional levels after 24 h of exposure to 1–25 μM NaAsO₂, reflecting low to high acute exposure scenarios, followed by a 48 h arsenite-free postincubation period. The primary objective was to analyze alterations in acetylation and methylation marks on both bulk histone H3 and specific DNA repair gene loci. We conducted immunochemical and proteomic analyses to assess alterations in histone modification patterns. Transient effects were observed at both methylated and acetylated residues, with hypoacetylation specifically detected at promoters of certain DNA repair genes, including MLH1, MSH2, MPG, and XPA. Among all modifications analyzed, H3K18ac exhibited the most pronounced decline, suggesting its preferential sensitivity toward arsenite. H3 hypoacetylation was further observed in noncancerous human BEAS-2B lung cells, indicating that this effect is not cancer cell-specific. Mechanistically, in A549 cells, increased total HDAC or decreased HAT activity could be excluded. Instead, a persistent moderate decline in HDAC activity and a delayed, pronounced induction of HAT activity suggest targeted arsenite interactions with specific enzymes of the histone acetylation regulatory network.

In view of the toxic effects of persistent organic pollutants (POPs), fast and effective assessment of their concentrations in marine mammals is important for understanding individual and population-level health impacts. This study developed an ultrasonic-based method that is less time-consuming, uses minimal solvent, and thus is more sustainable than the gold standard Soxhlet method for accurate analysis of organochlorine pesticides (OCs), polychlorinated biphenyls (PCBs), and benzene hexachlorides (BHC) in false killer whale blubber. This method was developed by comparing concentrations of POPs obtained using the traditional Soxhlet and novel ultrasonic extraction methods using blubber from false killer whales (n = 4) that were stranded in the Hawaiian Islands. The average total POPs extracted from the four killer whales and adjusted for lipid weight (lw) were 11,379.57 ± 3,303.03 ng/g lw for Soxhlet extraction and 14,310.39 ± 4,469.00 ng/g lw for the ultrasonic method, indicating a greater extraction efficiency of the ultrasonic method. The results further revealed that false killer whale FKW2013018 (∑OCs 15,447.38 ± 812.17 ng/g lw and ∑PCBs 5,205.32 ± 253.46 ng/g lw) and false killer whale FKW2016016 (∑OCs 18,164.90 ± 1,433.15 ng/g lw and ∑PCBs 4,913.32 ± 447.29 ng/g lw) accumulated organochlorines and PCBs at very high and potentially toxic levels. The low ratio of 4,4′-DDT/4,4′-DDE (0.026 ± 0.004) using both extraction methods indicated that the stranded false killer whales experienced long-term exposure to 4,4′-DDT, leading to bioaccumulation of the stable 4,4′-DDE metabolite. The levels of OCs, PCBs, and BHCs in this study were below toxic threshold levels. However, in view of the susceptibility of cetaceans with reduced lipid content to the toxic effects of POPs, cetaceans with low lipid content (as a result of starvation, fasting, or extended migration events) may be at higher risk of the negative health impacts of organic pollutants.

3-Chlorotyrosine, a product of hypochlorous-acid-induced protein tyrosine chlorination in inflamed tissues, has been considered a marker of oxidative inflammation in vivo. However, it has been proposed that the dichlorination of tyrosine might serve as a more reliable biomarker for inflammation than tyrosine monochlorination. Hemoglobin adduction plays an important role in the biomonitoring of chemical exposures in humans. An increased level of 3-chlorotyrosine in the hemoglobin of breast cancer patients has been reported as breast cancer is associated with high levels of oxidative stress. In this study, we discovered the presence of 3,5-dichlorotyrosine in tryptic peptides of human hemoglobin by high-resolution tandem mass spectrometry. The peptides containing 3,5-dichlorotyrosine, 3-chlorotyrosine, and methionine sulfoxide were quantified using nanoflow liquid chromatography tandem mass spectrometry. The results show that the extents of chlorination at α-Tyr-42 and β-Tyr-130, dichlorination at α-Tyr-24, and oxidation at α-Met-32 are significantly higher in the globin of breast cancer patients compared with those in healthy subjects. Moreover, the extents of dichlorination at α-Tyr-24 and chlorination at β-Tyr-130 are significantly higher in patients with stage III breast cancer than in healthy subjects. To our knowledge, this is the first report on the identification and quantification of 3,5-dichlorotyrosine in human hemoglobin. Our results suggest that chlorination and dichlorination of tyrosine in human hemoglobin are vital inflammatory biomarkers of breast cancer.

Although recent progress has been made, structure-based methods such as molecular docking are still underexplored in the context of toxicity prediction. These approaches offer added value, particularly in addressing challenges such as activity cliffs─i.e., caused by stereoisomerism─that are difficult to capture by conventional Quantitative Structure–Activity Relationship (QSAR) methods. In this study, we investigated the ability of docking scoring functions and protein–ligand interaction fingerprints to rank the potential hazard of compounds targeting the human mitochondrial complexes I and III (CI, NADH:ubiquinone oxidoreductase and CIII, cytochrome bc₁ complex). We applied an induced fit docking protocol to account for binding site flexibility and performed a set of binding energy minimizations for rescoring of representative binding modes. Both individual scoring functions and consensus scoring approaches achieved acceptable rank correlation to experimentally derived data from CIII (Spearman r: 0.89 and 0.86). Moreover, consensus interaction fingerprints that combine molecular interactions from both docking outputs captured differences of inhibitor subtypes at CIII. Follow-up in vitro testing confirmed an isomerism-dependent activity cliff of E-/Z-Fenpyroximate at CI. These findings support the utility of using consensus docking and scoring as a screening-level tool for prioritizing compounds based on interpretable predicted relative binding affinities at CI and CIII.

Copper-based pesticide exposures have been linked to increased Parkinson’s disease (PD) risk through oxidative stress, mitochondrial dysfunction, and neuroinflammation, yet their metabolic effects in PD remain poorly understood. Using high-resolution metabolomics (HRM) data from 642 PD patients and 277 controls from the Parkinson’s Environment and Gene (PEG) study, we evaluated alterations associated with chronic copper pesticide exposure. Composite and individual copper pesticide estimates were derived within a 500-m buffer around residential and workplace addresses over 5 years prior to the blood draw. Metabolome-wide association studies (MWAS) using partial least-squares (PLS) and empirical Bayes linear models were conducted to identify copper-associated metabolites, and pathway enrichment was performed using the Mummichog algorithm with 100 permutations to identify enriched metabolic pathways. In the primary analysis of the composite copper metric, we detected 215 copper-associated metabolite features, 88 of which were annotated, while none of them survived the FDR < 0.05 threshold. In individual-pesticide analyses, only copper sulfate (pentahydrate) yielded significant results: 57 metabolite features passed the FDR < 0.05 threshold (51 in PD patients, 4 in controls, and 2 in the full sample). The strongest metabolite association was with a phosphatidylcholine, PC(22:2(13Z,16Z)/16:1(9Z)) (β = 0.07, p = 1.51 × 10^–05). Pathway enrichment supported involvement of inflammation metabolism, lipid metabolism, amino acid metabolism, etc. These findings suggest that chronic copper pesticide exposure is linked to serum metabolic changes, particularly in inflammation-related metabolism pathways. Given the cross-sectional study design, these associations should be interpreted cautiously, as they do not establish causality.

Environmental pollutants can induce multiorgan damage, with the digestive tract particularly susceptible. Diabetic enteropathy is a significant complication of type 2 diabetes mellitus (T2D). However, the relationship between environmental pollutant exposure and T2D-associated intestinal injury has not been previously explored. In this study, T2D mice were subjected to polystyrene microplastics (PS-MPs, 100 μg/day, 3 weeks) and bisphenol A (BPA, 100 μg/kg/day, 2 weeks). Metabolomics and 16S rRNA sequencing were used to detect changes in colonic metabolites and gut microbial composition. Caco-2 cells were utilized to investigate the functions of the altered metabolites. Compared to the T2D group, mice exposed to PS-MPs and BPA exhibited shorter colon length and reduced levels of gut barrier proteins ZO-1 and Occludin. Metabolomics analysis revealed that PS-MPs primarily affected colonic long-chain fatty acids (LCFAs) and adenosine metabolism, while BPA disrupted α-ketoisovaleric acid (KIVA) and pyruvic acid (PyrA) homeostasis. Moreover, PS-MPs exposure altered the abundance of Duncaniella and Olsenella, while BPA primarily affected Phocaeicola, Olsenella, and Variovorax. In vitro experiments showed that palmitoleic acid (C16:1), γ-linolenic acid (C18:3), adenosine (Ado), and KIVA promoted the expression of ZO-1 in Caco-2 cells. Our findings provide valuable insights into the impact of environmental pollutants on intestinal injury in T2D, underscoring the importance of environmental contaminant management, particularly in susceptible populations.