Toxicological Sciences最新文献

Thyroid hormones (THs) regulate development, growth, and metabolism. Integral to the regulation of their action are the deiodinases (Dios), metabolizing enzymes that activate (Dio1 and Dio2) and deactivate (Dio3) THs, exerting precise control over local TH action. We examined the effect of chemical interference with Dios on brain development in a rodent pregnancy model using iopanoic acid (IOP). Pregnant rat dams were exposed to 0, 5, or 10 mg/kg IOP daily by gavage from gestational day 6 to postnatal (PN) day 15. Pups were euthanized at PN0, 2, 6, and 14. Serum and brain TH and Dio activity in cortical microsomes were measured, and 2 neuroanatomical defects emblematic of TH insufficiency were examined in the brains of offspring. IOP increased serum total T4 and rT3 in dams and pups. IOP decreased Dio2 and Dio3 activity in the dam cortex and forebrain of PN0 and PN2 pups, with no effect seen on PN14. On PN2, brain T4 was increased, brain T3 was reduced, and TH-responsive genes were downregulated. A periventricular heterotopia was present in the brains of IOP-treated pups on PN14, whereas no change was seen in the numbers of parvalbumin-expressing neurons. The observation that IOP induced changes in serum THs that were not predictive of brain effects has profound implications for the interpretation of altered serum TH profiles in a chemical regulatory context as well as in a clinical setting.

Epidermal growth factor receptor (EGFR) is mostly known for its proliferative role in the liver. Our earlier investigations indicated a paradoxical cell-death-promoting facet of EGFR in the acetaminophen (APAP)-induced liver injury (AILI) model. The current study investigates this unexpected role of EGFR in promoting AILI using a hepatocyte-specific EGFR deletion mouse model. Hepatocyte-specific EGFR-deficient mice were generated by administering AAV8.TBG.Cre in EGFRfl/fl mice and were subsequently treated with a severely toxic dose (500 mg/kg) of APAP. Liver injury, regeneration, and associated signaling pathways were assessed at different time intervals. EGFR deletion did not alter early liver injury at 6 h but significantly attenuated the progression of liver injury at 12 and 24 h following APAP overdose. Consistently, the key injury-initiating events, such as APAP-protein adducts formation and early JNK activation, remained unimpaired in EGFR-deficient mice. However, EGFR deletion restricted prolonged JNK activation and its mitochondrial translocation, resulting in reduced propagation of mitochondrial damage and release of cell death drivers. Further, the replenishment of antioxidant glutathione (GSH), which is known to limit the progression of liver injury, was strikingly faster in EGFR-deficient mice. RNA-seq analysis and consequent validation revealed marked upregulation of autophagy and its transcriptional regulator, transcription factor EB, a key response to remove damaged mitochondria, in EGFR-deficient mice. Paradoxically, EGFR deletion also promoted compensatory hepatocyte proliferation, possibly secondary to decreased severity of liver injury. Overall, hepatocyte-specific EGFR deletion halted the progression of AILI. Our study established an unexpected role of EGFR in promoting AILI progression, which has wide implications in liver biology.

To address the increasing concern regarding woodsmoke (WS) exposure and better understand its effects on human health, a WS generation system was built in the Air Pollution Exposure Laboratory to facilitate future controlled human exposure studies. Ground lodgepole pine was burned to generate WS, with PM2.5 concentrations of approximately 500 µg/m3 obtained. The WS produced by this system was characterized and directly compared with diesel exhaust (DE) generated and collected at the same facility. For gases, WS showed slight increases in CO and CO2 compared with filtered air (FA), whereas DE had significantly higher levels of NOx, CO, CO2, and total volatile organic compounds than FA. The non-refractory composition of WS aerosols was approximately 98% organics, 0.2% ammonium, 1.3% nitrate, and 0.2% sulfate. Among the organic species, the fraction of oxygenated species was much higher in WS aerosols than in DE aerosols. Moreover, WS aerosols had higher concentrations of Cd compared with DE aerosols. Greater oxidative potential was also observed for WS compared with DE, with dithiothreitol consumption rates of 0.0090 nmol/min/µg. This study established a controlled human exposure platform for WS and described the methods used for analyzing and comparing the concentrations, particulate morphologies, chemical compositions, and oxidative potentials of different lab-generated pollutants. The observed differences between WS and DE in oxidative potential and amounts of gases, organic species, and metals provide a foundation for investigating how specific air pollution components differentially impact human health.

Genetic damage is an early effect of altered cell function and tumorigenesis. Analysis of epigenetic alterations in genetic damage in the context of environmental heavy metal-induced cytotoxicity highlights the importance of environment-epigenetics-genetics interactions. The mechanism through which circular RNA (circRNA), an important molecule in epigenetics, regulates cadmium (Cd)-induced DNA damage is unknown. Herein, we report that circRNA circZNF462 regulates chromatin accessibility and inhibits DNA damage after Cd exposure. Downregulation of circZNF462 was associated with DNA damage in a model of 10 μM Cd-exposed bronchial epithelial cells. Chromatin accessibility increased after Cd exposure. Downregulation of circZNF462 significantly increased chromatin accessibility, thereby increasing DNA damage. MCM5 was significantly upregulated after Cd exposure and was negatively correlated with circZNF462. Furthermore, in the Cd exposure model, downregulated circZNF462 increased the levels of MCM5 and facilitated chromatin opening. Reduction of MCM5 reversed the induction of DNA damage after Cd exposure by low levels of circZNF462. These findings underscore the role of circZNF462-regulated chromatin accessibility in Cd-induced DNA damage and suggest that the epigenetic molecule circZNF462 might serve as a potential biomarker and early intervention target for preventing environmentally related genetic damage events.

Crizotinib, a multitarget tyrosine kinase inhibitor, is the standard first-line drug used for the clinical treatment of locally advanced or metastatic ALK-positive non-small cell lung cancer. However, the liver injury induced by crizotinib is a clinical problem that needs to be solved urgently. Therefore, the mechanism underlying crizotinib-induced liver injury must be elucidated to identify prevention and treatment methods. By establishing the mouse and cell models of crizotinib-induced liver injury, we found that crizotinib induced apoptosis in mouse liver tissue, L02 cells, and HepG2 cells. After treatment with crizotinib, the N6-methyladenosine (m6A) reading protein YTHDF3 was aberrantly downregulated in mouse liver tissue and L02 cells. RNA sequencing, m6A methylated RNA immunoprecipitation sequencing (MeRIP-seq), and MeRIP-qPCR were performed to identify the target gene of Lcn2. The upregulation of LCN2 was detected in both in vitro and in vivo models. Genetic inhibition of Lcn2 resulted in a reduction in the incidence of liver cell apoptosis induced by crizotinib. Additionally, knocking down YTHDF3 increased the mRNA stability and expression level of LCN2, whereas the overexpression of YTHDF3 inhibited the expression of LCN2 and apoptosis induced by crizotinib in L02 cells. Further mechanistic studies revealed a potential association between the YTHDF3 protein and Lcn2 mRNA and that YTHDF3 may affect the stability of Lcn2 mRNA in an m6A-dependent manner. Our findings revealed that the m6A reading protein YTHDF3-LCN2-apoptosis axis plays a critical role in mediating the hepatotoxicity of crizotinib, which provides potential intervention approaches for alleviating crizotinib-induced liver injury.

Postpartum mental health disorders are a critical yet understudied aspect of maternal health. Exposure to environmental toxicants such as per- and poly-fluoroalkyl substances (PFAS) has been associated with adverse health outcomes, including reproductive and neurobehavioral dysfunction, whereas their specific effects on maternal behavior and mental health remain poorly characterized. This study investigated the effects of perinatal exposure to environmentally relevant concentrations of a PFAS mixture comprising 10 individual PFAS (PFHxA, PFPeA, PFHpA, PFBA, perfluorooctanoic acid [PFOA], PFOS, PFHxS, PFDA, and PFNA), as well as the alternative PFAS compound, perfluorobutane sulfonate (PFBS), on maternal caregiving behaviors and mental health. Female mice were exposed to the PFAS mixture (758.6 ng/l) or PFBS (7.9 ng/l) in reverse osmosis filtered water at levels detected in North Carolina drinking water, beginning before conception and continuing until the first day of birth. Maternal behaviors, including pup-directed care and nest construction, were assessed along with depressive- and anxiety-like behaviors using standardized behavioral tests. Fluoxetine was administered to a subset of animals to pharmacologically validate depressive-like outcomes. Both PFAS mixture and PFBS-exposed dams exhibited impaired maternal caregiving, including diminished nurturing behavior and poor nest building. Litters of PFBS-exposed dams emitted fewer ultrasonic vocalizations, suggesting altered maternal-offspring interaction. Dams exposed to the PFAS mixture also exhibited depressive-like behaviors that were reversed by fluoxetine treatment, whereas anxiety-like behavior was unaffected. These findings demonstrate that perinatal PFAS exposure disrupts maternal behavior and induces depressive-like phenotypes, reflecting the neurobehavioral risks of exposure during the perinatal period. This study emphasizes the potential for environmental contaminants to contribute to maternal mental health disorders and supports the need for further research on the effect of PFAS exposure in human populations.

The popularity of electronic cigarettes (e-cigs) has risen in recent years, largely due to perceptions of reduced harm compared with traditional tobacco cigarettes. E-cig use has spread into vulnerable populations such as adolescents and individuals of reproductive age, yet their safety during pregnancy remains poorly understood. E-cigs differ from conventional cigarettes in composition, and their aerosolized components may uniquely affect the uterine environment and placental function. Proper placental development, maternal vascular remodeling, and tone are essential for healthy pregnancy outcomes, but it remains unclear how e-cig aerosol components affect these processes. To address this gap, we investigated how in utero exposure to sub-ohm e-cig aerosols, with and without nicotine, affects maternal and fetal cardiovascular function, uterine vascular function, and placental morphology. Pregnant female FVB/J mice were exposed to filtered air, vehicle (propylene glycol/vegetable glycerin; PG:VG or PV), or vehicle with nicotine (PV + Nicotine) from embryonic day (E) 0.5 to E17.5 (4 h/day, 5 days/week). Maternal and fetal cardiovascular parameters were assessed at E16.5 via echocardiography and ultrasound. At E17.5, maternal, fetal, and placental tissues were collected for histological and molecular analysis. E-cig exposure resulted in maternal diastolic dysfunction, reduced uterine artery blood flow, fetal bradycardia, structural alterations in the placenta, and reduced placental sufficiency. These effects were observed in both e-cig exposure groups, with some differences between the PV and PV + Nicotine groups, suggesting that exposure to aerosolized e-cig vehicle components alone can also contribute to gestational impairments. Our findings demonstrate that e-cig exposure during pregnancy disrupts cardiovascular adaptation and fetal development, highlighting the need for reevaluation of e-cig safety during pregnancy and guiding future mechanistic studies of its effects on placental and vascular dysfunction.

Gossypol acetic acid (GAA), a medicinal form of gossypol, is a natural phenolic compound found in cottonseed, which possesses various biological activities, such as anti-fertility, antiviral, anti-inflammatory, antibacterial, and anticancer properties. However, its potential risks to aquatic organisms are poorly investigated. Here, the toxic effects on locomotor activity and the underlying mechanism were assessed in vitro and in vivo, using the zebrafish model and PC12 cells. The results showed that after treatment from 6 to 120 h post fertilization, 0.8 μM GAA significantly reduced the locomotor activity of zebrafish larvae. In addition, 0.6 and 0.8 μM GAA disrupted the dopamine neurons and the central nervous system, further inhibiting swimming activity. Furthermore, the muscle sarcomeres and hair cells of zebrafish larvae were affected after GAA exposure. Moreover, after GAA exposure, Fe2+ accumulated in the 0.6 and 0.8 μM GAA groups, and reactive oxygen species (ROS) increased, especially in the head region. In addition, apoptosis could be observed in both the head and tail muscle regions. RT-qPCR results showed that GAA dysregulated the mRNA expression of the genes correlated to mitophagy, oxidative stress, and ferroptosis pathways. The in vitro study using PC12 cells also showed that GAA could induce mitochondrial membrane potential rise, ROS generation, apoptosis, and ferroptosis. These results indicate that GAA affects locomotor activity by disrupting the nervous system and muscle in zebrafish, and its toxicity is closely related to mitochondrial dysfunction, oxidative stress, apoptosis, and ferroptosis.

Polycyclic aromatic hydrocarbons (PAHs) are a contaminant class characterized by fused aromatic rings, formed through the incomplete combustion of organic materials and petrogenic sources. Despite the abundance and toxicity of alkyl-substituted PAHs, most research and regulation focus on unsubstituted parent PAHs. Alkyl substitution of Benzo[a]pyrene (BaP), one of the most well-studied parent PAHs, drastically alters its bioactivity in zebrafish. In larval zebrafish exposed from 6 h post-fertilization (hpf), BaP caused behavioral effects but no morphological effects up to 50 µM at 120 hpf. In contrast, 8-methylbenzo[a]pyrene caused a distinct fin duplication phenotype by 0.26 µM and additional morphological effects by 1 µM. Alkyl substitution in different positions (7-, 6-, 9-, and 10-MBaP) did not elicit morphological effects at similar concentrations. This study characterized the morphological effects of 8-MBaP in zebrafish and investigated its mechanism(s) of action. Using knock-out lines, we demonstrated that 8-MBaP toxicity is Ahr2 dependent and that Cyp1a served a protective role. To identify underlying transcriptomic changes, embryos were exposed to 3 concentrations of BaP, 6-MBaP, and 8-MBaP. Whole embryos/larvae were collected at 48 and 72 hpf, which was before and during phenotype onset, respectively. Collecting RNA and morphological effects across concentration, time, and chemicals facilitated the identification of concentration-dependent transcriptional responses linked to the downstream morphological phenotypes unique to BaP methylation at the eighth position. This study improves environmental and human health hazard assessment by identifying critical structural features and mechanisms of action contributing to the toxicity of PAH mixtures in the environment.

Chemical co-exposures are important contributors to adverse biological responses yet remain poorly understood, especially in the context of prenatal development. Sonic Hedgehog (Shh) signaling is an essential developmental pathway that is sensitive to small-molecule disruption and directly linked to common and etiologically complex human birth defects. Numerous mechanistically diverse small-molecule Shh pathway antagonists have been identified, but their interactions in pathway disruption have received minimal attention. We established a tractable co-culture model in which autonomous SHH ligand production initiates this complex inter- and intracellular signal transduction cascade and culminates in activation of a GLI-responsive luminescent reporter. Compounds reported to target SHH ligand processing (RU-SKI 43, AY 9944, U18666A), SMO-mediated signal transduction (cyclopamine, vismodegib, piperonyl butoxide, cannabidiol), and GLI transcription factors (GANT 61, arsenic trioxide) reduced Shh pathway-driven reporter activity with AC50 values in the low micromolar range or below. We then evaluated chemical interactions among Shh pathway inhibitors using isobolographic analysis. Co-exposure assays revealed additive interactions from combined SMO and GLI inhibition, whereas disruption of SMO and cholesterol dynamics synergistically decreased Shh pathway activity. Unexpectedly, piperonyl butoxide synergized with other SMO inhibitors, and further characterization of piperonyl butoxide's impacts on Shh signaling supported an additional mechanism of inhibition independent of SMO. In zebrafish embryos, combined exposure to piperonyl butoxide and cyclopamine also produced a synergistic increase in craniofacial dysmorphogenesis. These findings demonstrate the importance of tractable models that recapitulate complex signal transduction pathways to empirically test for additive and synergistic chemical interactions in risk assessment.