Toxicological Sciences最新文献

Particulate matter (PM) containing environmentally persistent free radicals (EPFR) is formed by the incomplete combustion of organic wastes, resulting in the chemisorption of pollutants to the surface of PM containing redox-active transition metals. In prior studies in mice, EPFR inhalation impaired endothelium-dependent vasodilation. These findings were associated with aryl hydrocarbon receptor (AhR) activation in the alveolar type-II (AT-II) cells that form the air-blood interface in the lung. We thus hypothesized that AhR activation in AT-II cells promotes the systemic release of mediators that promote endothelium dysfunction peripheral to the lung. To test our hypothesis, we knocked down AhR in AT-II cells of male and female mice and exposed them to 280 µg/m3 EPFR lo (2.7e + 16 radicals/g) or EPFR (5.5e + 17 radicals/g) compared with filtered air for 4 h/day for 1 day or 5 days. AT-II-AhR activation-induced EPFR-mediated endothelial dysfunction, reducing endothelium-dependent vasorelaxation by 59%, and eNOS expression by 50%. It also increased endothelin-1 mRNA levels in the lungs and peptide levels in the plasma in a paracrine fashion, along with soluble vascular cell adhesion molecule-1 and iNOS mRNA expression, possibly via NF-kB activation. Finally, AhR-dependent increases in antioxidant response signaling, coupled to increased levels of 3-nitrotyrosine in the lungs of EPFR-exposed littermate control but not AT-II AhR KO mice suggested that ATII-specific AhR activation promotes oxidative and nitrative stress. Thus, AhR activation at the air-blood interface mediates endothelial dysfunction observed peripheral to the lung, potentially via release of systemic mediators.

Chemicals in the systemic circulation can undergo hepatic xenobiotic metabolism, generate metabolites, and exhibit altered toxicity compared with their parent compounds. This article describes a 2-chamber liver-organ coculture model in a higher-throughput 96-well format for the determination of toxicity on target tissues in the presence of physiologically relevant human liver metabolism. This 2-chamber system is a hydrogel formed within each well consisting of a central well (target tissue) and an outer ring-shaped trough (human liver tissue). The target tissue chamber can be configured to accommodate a three-dimensional (3D) spheroid-shaped microtissue, or a 2-dimensional (2D) cell monolayer. Culture medium and compounds freely diffuse between the 2 chambers. Human-differentiated HepaRG liver cells are used to form the 3D human liver microtissues, which displayed robust protein expression of liver biomarkers (albumin, asialoglycoprotein receptor, Phase I cytochrome P450 [CYP3A4] enzyme, multidrug resistance-associated protein 2 transporter, and glycogen), and exhibited Phase I/II enzyme activities over the course of 17 days. Histological and ultrastructural analyses confirmed that the HepaRG microtissues presented a differentiated hepatocyte phenotype, including abundant mitochondria, endoplasmic reticulum, and bile canaliculi. Liver microtissue zonation characteristics could be easily modulated by maturation in different media supplements. Furthermore, our proof-of-concept study demonstrated the efficacy of this coculture model in evaluating testosterone-mediated androgen receptor responses in the presence of human liver metabolism. This liver-organ coculture system provides a practical, higher-throughput testing platform for metabolism-dependent bioactivity assessment of drugs/chemicals to better recapitulate the biological effects and potential toxicity of human exposures.

Exposure to the organophosphate esters (OPEs), used as flame retardants and plasticizers, is associated with a variety of adverse health effects including an increase in the incidence of fatty liver diseases. The goal of this study was to investigate the effects of six OPEs, all detected in Canadian house dust, on the phenotype and function of HepG2 liver cells. We used high-content imaging to investigate the effects of these OPEs on cell survival, mitochondria, oxidative stress, lipid droplets, and lysosomes. Effects on the autophagy/lipophagy pathway were evaluated using confocal microscopy. The triaryl OPEs (isopropylated triphenylphosphate [IPPP], tris(methylphenyl) phosphate [TMPP], and triphenyl phosphate [TPHP]) were more cytotoxic than non-triaryl OPEs (tris(2-butoxyethyl) phosphate [TBOEP], tris(1-chloro-2-propyl) phosphate [TCIPP], and tris(1,3-dichloro-2-propyl) phosphate [TDCIPP]). Exposure to most OPEs increased total mitochondria, reduced reactive oxygen species, and increased total lipid droplet areas and lysosomal intensity. Potency ranking was done using the lowest benchmark concentration/administered equivalent dose method and toxicological prioritization index analyses to integrate all phenotypic endpoints. IPPP, TBOEP, and TPHP ranked as the most potent OPEs, whereas TMPP, TCIPP, and TDCIPP were relatively less bioactive. Confocal microscopic analysis demonstrated that IPPP reduced the colocalization of lipid droplets (PLIN2), lysosomes (LAMP1), and autophagosomes (p62), disrupting autophagy. In contrast, TBOEP rescued cells from bafilomycin A1-induced inhibition of autophagy and/or increased autophagic flux. Together, these data demonstrate that OPEs have adverse effects on HepG2 cells. Further, OPE-induced dysregulation of autophagy may contribute to the association between OPE exposure and adverse effects on liver lipid homeostasis.

Prednisone, a widely used glucocorticoid drug in human and veterinary medicine, has been reported to cause developmental toxicity. However, systematic studies about the effect of prednisone on fetal liver development are still unclear. We investigated the potential effects of maternal exposure to clinically equivalent doses of prednisone during different gestational stages on cell proliferation and apoptosis, cell differentiation, glucose and lipid metabolism, and hematopoiesis in the liver of fetal mice, and explored the potential mechanisms. Results showed that prenatal prednisone exposure (PPE) could suppress cell proliferation, inhibit hepatocyte differentiation, and promote cholangiocyte differentiation in the fetal liver. Meanwhile, PPE could result in the enhancement of glyconeogenesis and bile acid synthesis and the inhibition of fatty acid β-oxidation and hematopoiesis in the fetal liver. Further analysis found that PPE-induced alterations in liver development had obvious stage and sex differences. Overall, the alteration in fetal liver development and function induced by PPE was most pronounced during the whole pregnancy (GD0-18), and the males were relatively more affected than the females. Additionally, fetal hepatic insulin-like growth factor 1 (IGF1) signaling pathway was inhibited by PPE. In conclusion, PPE could impact fetal liver development and multiple functions, and these alterations might be partially related to the inhibition of IGF1 signaling pathway.

The exponential increase in global plastic usage has led to the emergence of nano- and microplastic (NMP) pollution as a pressing environmental issue due to its implications for human and other mammalian health. We have developed methodologies to extract solid materials from human tissue samples by saponification and ultracentrifugation, allowing for highly specific and quantitative analysis of plastics by pyrolysis-gas chromatography and mass spectrometry (Py-GC-MS). As a benchmark, placenta tissue samples were analyzed using fluorescence microscopy and automated particle count, which demonstrated the presence of >1-micron particles and fibers, but not nano-sized plastic particles. Analyses of the samples (n = 10) using attenuated total reflectance-Fourier transform infrared spectroscopy indicated presence of rayon, polystyrene, polyethylene, and unclassified plastic particles. By contrast, among 62 placenta samples, Py-GC-MS revealed that microplastics were present in all participants' placentae, with concentrations ranging widely from 6.5 to 685 µg NMPs per gram of placental tissue, averaging 126.8 ± 147.5 µg/g (mean±SD). Polyethylene was the most prevalent polymer, accounting for 54% of total NMPs and consistently found in nearly all samples (mean 68.8 ± 93.2 µg/g placenta). Polyvinyl chloride and nylon each represented approximately 10% of the NMPs by weight, with the remaining 26% of the composition represented by 9 other polymers. Together, these data demonstrate advancements in the unbiased quantitative resolution of Py-GC-MS applied to the identification and quantification of NMP species at the maternal-fetal interface. This method, paired with clinical metadata, will be pivotal to evaluating potential impacts of NMPs on adverse pregnancy outcomes.

Intensified sanitation practices amid the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak might result in the increased release of chloramine disinfectants into surface water, significantly promoting the formation of nitrosamine disinfection by-products (DBPs) in drinking water. Unfortunately, these nitrosamine DBPs exhibit significant genotoxic, carcinogenic, and mutagenic properties, whereas chlorinating disinfectants remain in global practice. The current review provides valuable insights into the occurrence, identification, contamination status, exposure limits, and toxicity of the new unregulated disinfection by-products (nitrosamine DBPs) in drinking water. As a result, concentrations of nitrosamine DBPs far exceed allowable limits in drinking water, and prolonged exposure has the potential to cause metabolic disorders, a critical step in tumor initiation and progression. Importantly, based on recent research, we have concluded the role of nitrosamines DBPs in different metabolic pathways. Remarkably, nitrosamine DBPs can induce chronic inflammation and initiate tumors by activating sphingolipid and polyunsaturated fatty acid metabolism. Regarding amino acid and nucleotide metabolism, nitrosamine DBPs can inhibit tryptophan metabolism and de novo nucleotide synthesis. Moreover, inhibition of de novo nucleotide synthesis fails to repair DNA damage induced by nitrosamines. Additionally, the accumulation of lactate induced by nitrosamine DBPs may act as a pivotal signaling molecule in communication within the tumor microenvironment. However, with the advancement of tumor metabolomics, understanding the role of nitrosamine DBPs in causing cancer by inducing metabolic abnormalities significantly lags behind, and specific mechanisms of toxic effects are not clearly defined. Urgently, further studies exploring this promising area are needed.

Organophosphorus pesticides (OPPs) having a phosphate ester moiety, such as malathion (MA) and methidathion (DMTP), are widely used and have been detected in many fatal cases of accidental exposure or suicide in Japan. In forensic toxicology, the accurate determination of blood OPP concentration is mandatory to prove death by OPP poisoning. However, fatal pesticide concentration in blood at autopsy varies depending on the circumstances surrounding the dead body. In this study, we found that 16 OPPs were degraded by human serum albumin (HSA) in a temperature-dependent fashion. The mechanism underlying MA, DMTP, azinphos-methyl, etrimfos, fenthion (MPP), pirimiphos-methyl, (E)-dimethylvinphos, (Z)-dimethylvinphos, vamidothion, edifenphos (EDDP), fosthiazate, and pyraclofos degradation involves the formation of adducts with tyrosine residues in HSA. The mass spectra obtained by liquid chromatography quadrupole Orbitrap mass spectrometry revealed that phosphate ester amino acid adducts such as Y-adduct1, Y-adduct2, Y-adduct3, Y-adduct4, and Y-adduct5 were formed in HSA solution incubated with OPPs. These results indicate that the 16 OPPs are postmortem changed by HSA. The detection of phosphate ester amino acid adducts such as Y-adduct1, Y-adduct2, Y-adduct3, Y-adduct4, and Y-adduct5, instead of MA, DMTP, azinphos-methyl, etrimfos, MPP, pirimiphos-methyl, (E)-dimethylvinphos, (Z)-dimethylvinphos, vamidothion, EDDP, fosthiazate, and pyraclofos per se, may be used to determine death by these OPPs poisoning.

Chromosome instability, a hallmark of lung cancer, is a driving mechanism for hexavalent chromium [Cr(VI)] carcinogenesis in humans. Cr(VI) induces structural and numerical chromosome instability in human lung cells by inducing DNA double-strand breaks and inhibiting homologous recombination repair and causing spindle assembly checkpoint (SAC) bypass and centrosome amplification. Great whales are long-lived species with long-term exposures to Cr(VI) and accumulate Cr in their tissue, but exhibit a low incidence of cancer. Data show Cr(VI) induces fewer chromosome aberrations in whale cells after acute Cr(VI) exposure suggesting whale cells can evade Cr(VI)-induced chromosome instability. However, it is unknown if whales can evade Cr(VI)-induced chromosome instability. Thus, we tested the hypothesis that whale cells resist Cr(VI)-induced loss of homologous recombination repair activity and increased SAC bypass and centrosome amplification. We found Cr(VI) induces similar amounts of DNA double-strand breaks after acute (24 h) and prolonged (120 h) exposures in whale lung cells, but does not inhibit homologous recombination repair, SAC bypass, or centrosome amplification, and does not induce chromosome instability. These data indicate whale lung cells resist Cr(VI)-induced chromosome instability, the major driver for Cr(VI) carcinogenesis at a cellular level, consistent with observations that whales are resistant to cancer.

To avoid adverse events in humans, toxicity studies in nonclinical species have been the foundation of safety evaluation in the pharmaceutical industry. However, it is recognized that working with animals in research is a privilege, and conscientious use should always respect the 3Rs: replacement, reduction, and refinement. In the wake of the shortages in routine nonrodent species and considering that nonanimal methods are not yet sufficiently mature, the value of the rabbit as a nonrodent species is worth exploring. Historically used in vaccine, cosmetic, and medical device testing, the rabbit is seldom used today as a second species in pharmaceutical development, except for embryo-fetal development studies, ophthalmic therapeutics, some medical devices and implants, and vaccines. Although several factors affect the decision of species selection, including pharmacological relevance, pharmacokinetics, and ADME considerations, there are no perfect animal models. In this forum article, we bring together experts from veterinary medicine, industry, contract research organizations, and government to explore the pros and cons, residual concerns, and data gaps regarding the use of the rabbit for general toxicity testing.