Developmental toxicity of short-chain chlorinated paraffins on early-stage chicken embryos in a shell-less (ex-ovo) incubation system.

Short-chain chlorinated paraffins (SCCPs) are listed as a category of globally controlled persistent organic pollutants (POPs) by the Stockholm Convention in 2017. However, SCCP toxicity, particularly their developmental toxicity in avian embryos, has not been well studied. In this study, we observed the early development of chicken embryos (Gallus gallus domesticus) by applying a shell-less (ex-ovo) incubation system developed in our previous studies. After exposing embryos at Hamburger Hamilton stage (HHS) 1 to SCCPs (control, 0.1% DMSO; SCCPs-L, 200 ng/g; SCCPs-M, 2000 ng/g; SCCPs-H, 20,000 ng/g), we observed the development of embryos from the 3rd to 9th incubation day. Exposure to SCCPs-M and -H induced a significant reduction in survival, with an LD50 of 3100 ng/g on the 9th incubation day. Significant dose-dependent decreases in body length were observed from days 4-9. We also found that SCCPs-H decreased the blood vessel length and branch number on the 4th incubation day. Additionally, SCCPs-H significantly reduced the heart rate on the 4th and 5th incubation days. These findings suggest that SCCPs may have potential of developmental and cardiovascular toxicity during the early stages of chicken embryos. Quantitative PCR of the mRNA of genes related to embryonic development showed that SLC16A10 (a triiodothyronine transporter) level decreased in the SCCPs-H group, showing a significant positive correlation with the body length of embryos. THRA level, a thyroid hormone receptor, was significantly decreased in the SCCPs-H group, whereas that of DIO3 level, a deiodinase was significantly increased. These results suggest that SCCPs exposure induces developmental delays via the thyroxine signaling pathway. Analysis of thyroid hormones (THs) in blood plasma also indicated a significant reduction in thyroxine (T4) levels in the SCCPs-H group on the 9th incubation day of embryos. In conclusion, SCCPs induce developmental toxicity by disrupting thyroid functions at the early-life stage of chicken embryos.

Seasonal variation in structural and functional distribution of periphyton in a macrolide antibiotics-contaminated river.

Periphyton, a microbial assemblage of autotrophic and heterotrophic organisms, is vital to aquatic ecosystems. While exposure to macrolide antibiotics has been confirmed to reduce the biodiversity and damage the critical ecological functions in indoor microcosm bioassays, the distribution of periphyton along a macrolide antibiotic pollution gradient in a river has yet to be determined. Herein, we established the spatiotemporal distribution of five major macrolides, i.e., azithromycin (AZI), roxithromycin (ROX), erythromycin (ERY), clarithromycin (CLA), and anhydro erythromycin (ERY-H2O) in water and periphyton of Zao River (Xi'an, China), after which we evaluated the effects on the structures, photosynthetic activity, and carbon utilization capacity of periphyton in March, June, and September 2023. In contrast with the reference sites, the macrolides were identified in all sewage treatment plants (STPs) impacted sites with concentrations ranging from 0.05 to 2.18 µg/L in water and from not detected - 9.67 µg/g in periphyton. Regarding community structure, the occurrence of macrolides was negatively linked to FirmicutesExiguobacterium undae and Exiguobacterium sibiricum, CyanobacteriaOscillatoriales and Vischeria sp., and ChlorophytaMonostroma grevillei, Selenastrum sp. LU21 and Desmodesmus subspicatus. At the functional level, only the metabolism of phenolic acids was significantly decreased in river reach with high antibiotic levels in June, compared to the other five carbon sources that were not altered. The overall photosynthetic activity of periphytic photosystem II remained unchanged in both reference and STPs impacted groups throughout three seasons. Overall, the macrolides released from STPs were correlated with the altered periphytic structures in the river, whereas a similar trend was not detected for the community functions owing to the functional redundancy. A mesocosm experiments warrants further consideration to validate the field results.

Tris(2-chloroethyl) phosphate (TCEP) exposure inhibits the epithelial-mesenchymal transition (EMT), mesoderm differentiation, and cardiovascular development in early chicken embryos.

Tris(2-chloroethyl) phosphate (TCEP) is an organophosphorus flame retardant used worldwide and has been detected in the tissues and eggs of wild birds. Our previous study reported that exposure to TCEP induced developmental delay and cardiovascular dysfunction with attenuated heart rate and vasculogenesis in early chicken embryos. This study aimed to investigate the molecular mechanisms underlying the cardiovascular effects of TCEP on chicken embryos using cardiac transcriptome analysis and to examine whether TCEP exposure affects epithelial-mesenchymal transition (EMT) and mesoderm differentiation during gastrulation. Transcriptome analysis revealed that TCEP exposure decreased the expression of cardiac conduction-related genes and transcription factors on day 5 of incubation. In extraembryonic blood vessels, the expression levels of genes related to fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) were significantly reduced by TCEP exposure and vasculogenesis was suppressed. TCEP exposure also attenuated Snail family transcriptional repressor 2 (SNAI2) and T-box transcription factor T (TBXT) signaling in the chicken primitive streak, indicating that TCEP inhibits EMT and mesoderm differentiation during gastrulation at the early developmental stage. These effects on EMT and mesoderm differentiation may be related to subsequent phenotypic defects, including suppression of heart development and blood vessel formation.

Metatranscriptomic profiles reveal the biotransformation potential of azithromycin in river periphyton.

Assessment of the interaction between the biotransformation of chemical contaminants and enzyme activity from aquatic microbial communities is critical for improving the micropollutant degradation in river remediation. Here, association mining based on metatranscriptomic analysis was initially applied to determine the genes encoding enzymes involved in the azithromycin (AZI) transformation process and the corresponding microbial hosts in periphyton, followed by revealing the dynamic variation in the community structure and function. In terms of the biotransformation potential, the highly correlated 15 enzymes were suggested to be primarily involved in AZI biotransformation, energy supply, and antibiotic resistance processes, especially aryl-alcohol dehydrogenases (EC: 1.1.1.90), hydroxylamine dehydrogenase (EC: 1.7.2.6), and monooxygenases (EC: 1.14.11.57) that were involved in the biotransformation of AZI. In the matter of community ecological function, the photosystem II (PSII) reaction center in the periphytic photosynthetic process, as indicated by Fv/Fm, was inhibited after AZI exposure, which may be attributed to the down-regulated genes enriched in the photosynthesis - antenna proteins (ko00196), photosynthesis (ko00195), and two-component system (ko02020) pathways. Furthermore, the periphytic utilization capacity for carbohydrates and phenolic acids was enhanced, which was in accordance with all the increased expression of transcripts involved in the corresponding molecular pathways, including aminobenzoate degradation (ko00627), starch and sucrose metabolism (ko00500), ABC transporters (ko02010), phosphotransferase system (ko02060), galactose metabolism (ko00052), amino sugar and nucleotide sugar metabolism (ko00520). Taken together, this study highlighted the critical role of river periphyton in the micropollutant degradation and unraveled the molecular mechanism of antibiotic biotransformation as well as the structural and functional damage in the periphyton.

A meta-analysis of randomized controlled studies on the hepatoxicity induced by polybrominated diphenyl ethers (PBDEs) in rats and mice.

Several toxicological studies were conducted to evaluate the hepatoxicity of PBDEs using different animal models, congeners, duration of exposure, and other parameters. These variations in different animal models and conditions might have an impact on extrapolating experimental results to humans. Hence, by the meta-analysis, we aimed to clarify and elucidate the species differences in hepatoxicity induced by PBDE exposure in rats and mice across different conditions and moderators. Fourteen in vivo studies that utilized rats and mice models were identified, and data such as author names, year of publication, type of PBDE congeners, rodent species, life stage of exposure, dosage, duration, and hepatoxicity indicators were extracted. The pooled standard mean difference (SMD) with a 95% confidence interval (95% CI) was used to evaluate the association between hepatoxicity and PBDE exposure across multiple approaches of measurement. Subgroup analysis, meta-regression, and interaction analysis were utilized to elucidate the species-related differences among the results of the involved studies. The pooled SMD of hepatoxicity of PBDE exposure in the involved in vivo studies was 1.82 (p = 0.016), indicating exposure to PBDE congeners and mixtures is associated with a significant increase in liver toxicity in rodents. Moreover, findings showed that rats were more sensitive to PBDEs than mice with the BDE-209 had the highest SMD value. Among the life stages of exposure, embryonic stage was found to be the most sensitive to hepatoxicity induced by PBDE congeners. Positive relationships were found between the incidence of hepatoxicity with dosage and duration of exposure to PBDE. Interaction analyses showed significant interactions between rodent species (rats or mice), dosage, length of exposure, and hepatotoxicity endpoints. Rats demonstrated an increased susceptibility to variations in organ weight, histopathological changes, mitochondrial dysfunction, and oxidative stress markers. Conversely, mice showed pronounced lipid accumulation and modifications in liver enzyme expression levels. However, significant differences were not found in terms of endoplasmic reticular stress as a mechanistic endpoint for hepatotoxicity. In conclusion, this meta-analysis showed that there might be some species-related differences in hepatoxicity induced by PBDE exposure in rats and mice depending on the parameters used. This study highlights the importance of cross-species extrapolation of results from animal models to accurately assess the potential risks to human health from exposure to PBDEs.

In silico simulations and molecular descriptors to predict in vitro transactivation potencies of Baikal seal estrogen receptors by environmental contaminants.

Baikal seals (Pusa sibirica) are vulnerable to high levels of organic pollutants. Here, we evaluated the transactivation potencies of bisphenols (BPs) and hydroxylated polychlorinated biphenyls (OH-PCBs) via the Baikal seal estrogen receptor α and ß (bsERα and bsERß) using in vitro and in silico approaches. In vitro reporter gene assays showed that most BPs and OH-PCBs exhibited estrogenic activity with bsER sub-type-specific potency. Among the BPs tested, bisphenol AF showed the lowest EC50 for both bsERs. 4'-OH-CB50 and 4'-OH-CB30 showed the lowest EC50 among OH-PCBs tested for bsERα and bsERß, respectively. 4-((4-Isopropoxyphenyl)-sulfonyl)phenol, 4'-OH-CB72, and 4'-OH-CB121 showed weak bsERα-specific transactivation. Only 4-OH-CB107 did not affect both bsERs. In silico docking simulations revealed the binding affinities of these chemicals to bsERs and partially explained the in vitro results. Using the in silico simulations and molecular descriptors as explanatory variables and the in vitro results as objective variables, the quantitative structure-activity relationship (QSAR) models constructed for classification and regression accurately separated bsER-active compounds from non-active compounds and predicted the in vitro bsERα- and bsERß-transactivation potencies, respectively. The QSAR models also suggested that chemical polarity, van der Waals surface area, bridging atom structure, position of the phenolic-OH group, and ligand interactions with key residues of the ligand binding pocket are critical variables to account for the bsER transactivation potency of the test compounds. We also succeeded in constructing computational models for predicting in vitro transactivation potencies of mouse ERs in the same manner, demonstrating the applicability of our approach independent of species-specific responses.

Developmental toxicity in early chicken embryos on exposure to an organophosphorus flame retardant, tris(2-chloroisopropyl) phosphate.

Tris(2-chloroisopropyl) phosphate (TCIPP) is an organophosphate flame retardant detected in the environment and eggs, feathers, and livers. Early-developmental-stage avian embryos are vulnerable to the toxic effects of chemicals. However, studies on the specific effects of TCIPP on avian embryonic development are limited. We aimed to investigate the toxicity of TCIPP in early chicken embryos using a previously developed shell-less incubation system. Fertilized chicken (Gallus gallus domesticus) eggs (n = 220) were exposed to 50 or 500 nmol TCIPP/(g egg) or dimethyl sulfoxide (DMSO) as a vehicle control on Day 0 of incubation. Development of 198 embryos was monitored from Days 3-9 of incubation, and 22 embryos on Day 4 and 74 embryos on Day 9 were dissected. Messenger RNA expression levels for several genes were measured in embryos on Day 4. Both TCIPP-exposed groups showed a significant reduction in survival rate. Imaging analyses revealed significant decreases in body length, head and bill length, eye diameter, and forelimb and hindlimb length in both TCIPP-treated groups. TCIPP exposure significantly impaired the development of extraembryonic blood vessels and the production of red blood cells. A TCIPP-dose-dependent decreasing trend in heart rate was observed on Days 4-7. The somitic angle increased significantly on Days 4-6, and embryos with curved somites showed cleavage in the back and gaps between somites, resulting in asymmetrical somite formation. A significant correlation was found between the somitic angle and FGF8 expression levels, suggesting that TCIPP exposure affects somite formation through an altered FGF-signaling pathway. Embryos with somitic deformities in TCIPP-exposed groups had significantly reduced survival rates, indicating that abnormal segment formation directly increased mortality. Finally, eye weight and ocular luminosity values were significantly reduced, suggesting that TCIPP may also affect eye development. Overall, these findings highlight severe toxic effects of TCIPP on avian embryonic development, including in vascularization, cardiac function, and somite and ocular development.

Multi-level assessment of the origin, feeding area and organohalogen contamination on salmon from the Baltic Sea.

The Atlantic salmon (Salmo salar) population in the Baltic Sea consists of wild and hatchery-reared fish that have been released into the sea to support salmon stocks. During feeding migration, salmon migrate to different parts of the Baltic Sea and are exposed to various biotic and abiotic stressors, such as organohalogen compounds (OHCs). The effects of salmon origin (wild or hatchery-reared), feeding area (Baltic Main Basin, Bothnian Sea, and Gulf of Finland), and OHC concentration on the differences in hepatic proteome of salmon were investigated. Multi-level analysis of the OHC concentration, transcriptome, proteome, and oxidative stress biomarkers measured from the same salmon individuals were performed to find the key variables (origin, feeding area, OHC concentrations, and oxidative stress) that best account for the differences in the transcriptome and proteome between the salmon groups. When comparing wild and hatchery-reared salmon, differences were found in xenobiotic and amino acid metabolism-related pathways. When comparing salmon from different feeding areas, the amino acid and carbohydrate metabolic pathways were notably different. Several proteins found in these pathways are correlated with the concentrations of polychlorinated biphenyls (PCBs). The multi-level analysis also revealed amino acid metabolic pathways in connection with PCBs and oxidative stress variables related to glutathione metabolism. Other pathways found in the multi-level analysis included genetic information processes related to ribosomes, signaling and cellular processes related to the cytoskeleton, and the immune system, which were connected mainly to the concentrations of Polychlorinated biphenyls and Dichlorodiphenyltrichloroethane and their metabolites. These results suggest that the hepatic proteome of salmon in the Baltic Sea, together with the transcriptome, is more affected by the OHC concentrations and oxidative stress of the feeding area than the origin of the salmon.

In vivo and in silico assessments of estrogenic potencies of bisphenol A and its analogs in zebrafish (Danio rerio): Validity of in silico approaches to predict in vivo effects.

This study assessed the estrogen-like potencies of bisphenol A (BPA) and its analogs (BPs) using in vivo and in silico approaches in zebrafish. Zebrafish embryos were exposed to 16 BPs, most of which concentration-dependently induced cytochrome P450 19A1b (CYP19A1b) expression. BPs-induced CYP19A1b expression was suppressed by fulvestrant, a nonselective high affinity antagonist for estrogen receptor (Esr) subtypes. For BPs that concentration-dependently induced CYP19A1b expression, we estimated their 50 % effective concentration (EC50) and relative potencies (REPs) with respect to the potency of BPA for inducing CYP19A1b expression. BP C2, Bis-MP, and BPAF showed lower EC50 than BPA, BPE, and BPF, while BPZ and BPB showed moderate EC50. The REP order of the BPs was BP C2 (26) > Bis-MP (24) > BPAF (21) > BPZ (5.8) > BPB (2.7) > BPE (1.5) > BPF (0.63) > 2,4'-BPF (0.22), indicating that some BPs showed greater estrogenic potencies than BPA in our system. We also constructed in silico homology models of ligand binding domains for zebrafish Esr subtypes, including Esr1, Esr2a, and Esr2b. Molecular docking simulations of ligands with the Esr subtypes revealed the interaction energies of some BPs were lower than that of BPA. The interaction energies showed significant positive correlations with their EC50 values for inducing CYP19A1b expression in vivo. This study showed that some BPA analogs have greater estrogenic potencies than BPA and that in silico simulations of interactions between ligands and Esr subtypes may help predict in vivo estrogenic potencies of untested chemicals.

What Approaches Should be Used to Prioritize Pharmaceuticals and Personal Care Products for Research on Environmental and Human Health Exposure and Effects?

Pharmaceuticals and personal care products (PPCPs) are released from multiple anthropogenic sources and thus have a ubiquitous presence in the environment. The environmental exposure and potential effects of PPCPs on biota and humans has aroused concern within the scientific community and the public. Risk assessments are commonly conducted to evaluate the likelihood of chemicals including PPCPs that pose health threats to organisms inhabiting various environmental compartments and humans. Because thousands of PPCPs are currently used, it is impractical to assess the environmental risk of all of them due to data limitations; in addition, new PPCPs are continually being produced. Prioritization approaches, based either on exposure, hazard, or risk, provide a possible means by which those PPCPs that are likely to pose the greatest risk to the environment are identified, thereby enabling more effective allocation of resources in environmental monitoring programs in specific geographical locations and ecotoxicological investigations. In the present review, the importance and current knowledge concerning PPCP occurrence and risk are discussed and priorities for future research are proposed, in terms of PPCP exposure (e.g., optimization of exposure modeling in freshwater ecosystems and more monitoring of PPCPs in the marine environment) or hazard (e.g., differential risk of PPCPs to lower vs. higher trophic level species and risks to human health). Recommended research questions for the next 10 years are also provided, which can be answered by future studies on prioritization of PPCPs. Environ Toxicol Chem 2022;00:1-14. © 2022 SETAC.

Effects of 1,3,7-tribromodibenzo-p-dioxin, a natural dioxin on chicken embryos: Comparison with effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin.

Several naturally occurring dioxins, including 1,3,7-tribromodibenzo-p-dioxin (1,3,7-TriBDD), synthesized by red algae, have been detected in the marine environment. As 1,3,7-TriBDD is accumulated in mussels and fish, predators, such as marine birds, are exposed to this congener, similar to anthropogenic dioxins (including 2,3,7,8-tetrachlorodibenzo-p-dioxin TCDD). However, little is known about the impact of 1,3,7-TriBDD exposure on the bird health. To understand the effects of 1,3,7-TriBDD on birds, the phenotypic effects and hepatic transcriptome were investigated in chicken (Gallus gallus) embryos treated with 27 µM (2.9 ng/g egg) and 137 µM (14.4 ng/g egg) 1,3,7-TriBDD. The blood glucose levels in the 1,3,7-TriBDD-treated groups were lower than those in the control group. The transcriptome analysis of 6520 sequences in the 27 and 137 µM 1,3,7-TriBDD-treated groups identified 733 and 596 differentially expressed genes (DEGs). Cytochrome P450 1A4 and 1A5 were also identified as DEGs, suggesting that the aryl hydrocarbon receptor is activated by this congener. Pathway and network analyses with DEGs suggested that 1,3,7-TriBDD may induce carcinogenic effects and metabolic alterations. These results were similar to the effects on TCDD-treated embryos. Nevertheless, the overall transcriptome results suggested that compared with TCDD, 1,3,7-TriBDD has a unique impact on insulin- and peroxisome-signaling pathways in chicken embryos. Differences in altered transcriptome profiles between 1,3,7-TriBDD- and TCDD-treated embryos may lead to different phenotypic effects: less severe effects of 1,3,7-TriBDD and more fatal effects of TCDD. Collectively, these findings warrant the further assessment of the hazard and risk of 1,3,7-TriBDD on marine animals, considering increased exposure due to climate change.

Transcriptomic Alterations in Water Flea (Daphnia magna) following Pravastatin Treatments: Insect Hormone Biosynthesis and Energy Metabolism.

Pravastatin, used for lowering cholesterol and further decreasing blood lipid, has been frequently detected in the contaminated freshwaters, whereas its long-term exposure effects on non-target aquatic invertebrates remains undetermined. Therefore, the purpose of this study was to evaluate the toxic effects of pravastatin (PRA) with the concentration gradients (0, 0.5, 50, 5000 µg/L) on a model water flea Daphnia magna (D. magna) over 21 d based on phenotypic and genome-wide transcriptomic analyses. After 21 d, exposure to PRA at 5000 µg/L significantly reduced the body length and increased the number of offspring. The 76, 167, and 499 differentially expressed genes (DEGs) were identified by using absolute log2 fold change < 1 and adj p < 0.05 as a cutoff in the 0.5, 50, and 5000 µg/L PRA treatment groups, respectively. Three pathways, including xenobiotic metabolism, insect hormone biosynthesis pathway, and energy metabolism were significantly (p < 0.05) enriched after exposure to PRA. These suggested that the upregulation of genes in insect biosynthetic hormone pathway increased the juvenile hormone III content, which further reduced the body length of D. magna. The positive effect of methyl farnesoate synthesis on the ovarian may result in the increased number of offspring. Furthermore, energy tended to be allocated to detoxification process and survival under stress conditions, as the amount of energy that an individual can invest in maintenance and growth is limited. Taken together, our results unraveled the toxic mechanism of cardiovascular and lipid pharmaceuticals in aquatic invertebrate.

Effects of exposure to oxytetracycline on the liver proteome of red seabream (Pagrus major) in a real administration scenario.

Oxytetracycline (OTC) is a widely used antibiotic in aquaculture. In this study, red seabream (Pagrus major), the most popular aquaculture species in Japan, were treated with OTC mimicking a real administration scenario in aquaculture. The treatment groups were as follows: no OTC, 40 mg/kg body wt/day (equivalent to the dose used in actual aquaculture), or 178 mg/kg body wt/day. The first exposure was conducted for a week (1st OTC exposure period), followed by a 4-week interval, and the second exposure was for one week (2nd OTC exposure period). We investigated the effects of OTC on the liver proteome with the isobaric tags for relative and absolute quantitation (iTRAQ) technology accompanied by liquid chromatography and mass spectrometry. The pathway and disease enrichment analyses of differentially abundant proteins in OTC-exposed groups compared to their respective controls showed that the abundance of proteins related to the immune and nervous systems was altered after the 1st and 2nd OTC exposures, respectively. Quantitative real-time PCR of the transcripts of immune-related genes corroborated with the results of proteome analysis. OTC exposure also modulated the expression of metabolism-related proteins after the 1st and 2nd OTC exposures. Furthermore, after four weeks of the 2nd exposure, weight loss and changes in the expression of proteins related to metabolism were observed, suggesting that OTC exposure disrupts the metabolic system and causes growth inhibition. Based on these results, we suggest that the use of OTC in aquaculture poses a health risk in fish species. Thus, we need to pay more attention to the contamination with OTC in aquaculture.

Effects of gestational exposure to bisphenol A on the hepatic transcriptome and lipidome of rat dams: Intergenerational comparison of effects in the offspring.

Our previous studies demonstrated that prenatal bisphenol A (BPA) exposure affected the hepatic transcriptome and lipidome in rat offspring in a sex- and age-dependent manner. In this study, we investigated the effects of gestational exposure to BPA on the rat dams, after weaning period, and compared them with those of their offspring. Our results showed alterations in hepatic transcriptome related to insulin signaling, circadian rhythm, and infectious disease pathways in BPA-treated dams even 4 weeks after the exposure, whereas slight modifications on the lipid profile were found. Alterations in lipid and transcriptome profiles were more prominent in the prenatally BPA-exposed offspring at postnatal day (PND) 1 and 21 than those in the dams, suggesting that in utero exposure to BPA is more serious than exposure in the adulthood. Cryptochrome-1 (Cry1) and peroxisome proliferator-activated receptor delta (Ppard) were commonly altered in both dams and offspring. Nevertheless, the results of DIABLO (Data Integration Analysis for Biomarker discovery using Latent cOmponents), showed that multi-omics data successfully distinguished the exposed dams from the corresponding controls and their offspring with a high level of accuracy. The accuracy rates in BPA50 models (including control and 50 µg BPA/kg bw/day exposed groups) were smaller than those in BPA5000 models (control and 5000 µg BPA/kg bw/day exposed groups), suggesting dose-dependent severity in BPA effects. Palmitic acid and genes related to circadian rhythm, insulin responses, and lipid metabolism (e.g., 1-acylglycerol-3-phosphate O-acyltransferase 2 (Agpat2), B-cell CLL/lymphoma 10 (Bcl10), Cry1, Harvey rat sarcoma virus oncogene (Hras), and NLR family member X1 (Nlrx1)) were identified through DIABLO models as novel biomarkers of effects of BPA across two generations.

Assessment of binding potencies of polychlorinated biphenyls and polybrominated diphenyl ethers with Baikal seal and mouse constitutive androstane receptors: Comparisons across species and congeners.

The present study evaluated the binding potencies (equilibrium dissociation constant: KD) of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) with the constitutive androstane receptor (CAR)_ligand binding domain (LBD) of the Baikal seal (bsCAR_LBD) and mouse (mCAR_LBD) using a surface plasmon resonance (SPR) biosensor. The binding affinities of individual congeners with mCAR_LBD tended to be higher than those with bsCAR_LBD but the differences were within the same order of magnitude. Notably, PBDE congeners showed higher binding affinities for both CAR_LBDs than PCB congeners. In silico docking simulations demonstrated that PBDEs had more non-covalent interactions with specific amino acid residues in both CAR_LBDs than PCBs, supporting the results of their binding affinities. Binding affinity comparisons among congeners revealed the structural requirements for higher binding; mono or di ortho-, tri meta-, and di para­chlorine substitutions for PCBs, and di or tri ortho-, mono meta-, and di para­bromine substitutions for PBDEs. The binding potencies of these congeners unlikely accounted for their previously reported CAR-mediated transactivation potencies, implying that their transactivation is regulated in a ligand-dependent, but a distinct manner from ligand binding. Risk assessment analysis showed that the KD values of individual PCB and PBDE congeners were 1-4 orders of magnitude higher than their respective hepatic concentrations in wild Baikal seal population.

Prediction of adverse effects of effluents containing phenolic compounds in the Ba River on the ovary of fish (Hemiculter leucisculus) using transcriptomic and metabolomic analyses.

The aim of this work was to evaluate the endocrine disrupting effects on the ovarian development of sharpbelly (Hemiculter leucisculus) caused by effluents containing phenolic compounds. This was achieved using integrated transcriptomic and metabolomic analyses, along with histopathological examinations. Sharpbelly, an indigenous freshwater fish widely distributed in East Asia, were collected by pole fishing from three sampling sites in the Ba River. These sampling sites include a mid-stream site near a wastewater outfall and a reference site located upstream and a far field comparison site located downstream. In sharpbelly collected near the wastewater discharge, the oocyte development was activated, compared to the other two sites. Histopathological alterations in the fish ovaries were likely due to the upregulated steroid hormone biosynthesis process, as suggested by the differentially expressed genes (e.g., hsd3b, hsd17b1) and differentially accumulated metabolites (e.g., pregnenolone). Additionally, under the stress of effluents containing phenolic compounds, genes related to the signaling pathways for oxidative phosphorylation and leukocyte transendothelial migration were dysregulated, suggesting the potential induction of inflammation and several ovarian diseases. Overall, these findings suggest that effluents containing phenolic compounds influence ovary development and reproductive function of female sharpbelly. Whether there is any resulting dysfunction of folliculogenesis, abnormality of ovulation, production of premature eggs and/or potential induction of ovarian cancers remains to be determined by further studies, for a better evaluation on effluents containing phenolic compounds to the fish fertility and the health of their offspring, and even the stability of the wild fish population. Notably, the integration of transcriptomics and metabolomics can complement the routine chemical analysis to comprehensively monitor the effects of wastewater treatment plant effluents on the health of wild fish.

Directly Reprogrammed Neurons as a Tool to Assess Neurotoxicity of the Contaminant 4-Hydroxy-2',3,5,5'-tetrachlorobiphenyl (4'OH-CB72) in Melon-Headed Whales.

Whales accumulate high levels of environmental pollutants. Exposure to polychlorinated biphenyls (PCBs) and their metabolites (OH-PCBs) could be linked to abnormal behavior, which may lead to mass stranding of marine mammals. Whales may thus suffer from adverse effects such as neuronal dysfunction, yet testing the neurotoxicity of these compounds has never been feasible for these species. This study established neurons chemically reprogrammed from fibroblasts of mass stranded melon-headed whales (Peponocephala electra) and used them for in vitro neurotoxicity assays. Exposure to 4-hydroxy-2',3,5,5'-tetrachlorobiphenyl (4'OH-CB72), a metabolite of PCBs, caused apoptosis in the reprogrammed neurons. Transcriptome analysis of 4'OH-CB72-treated whale neurons showed altered expressions of genes associated with oxidative phosphorylation, chromatin degradation, axonal transport, and neurodegenerative diseases. These results suggest that 4'OH-CB72 exposure may induce neurodegeneration through disrupted apoptotic processes. A comparison of the results with human reprogrammed neurons revealed the specific effects on the whale neurons. Our noninvasive approach using fibroblast-derived neurons is useful for hazard and risk assessments of neurotoxicity in whales.

2,3,7,8-Tetrachlorodibenzo-p-dioxin prompted differentiation to CD4+CD8-CD25+ and CD4+CD8+CD25+ Tregs and altered expression of immune-related genes in the thymus of chicken embryos.

The chicken (Gallus gallus), which has three aryl hydrocarbon receptor (AHR) isoforms (ckAHR1, ckAHR2, and ckAHR1ß) and two AHR nuclear translocator (ARNT) isoforms (ckARNT1 and ckARNT2), is highly sensitive to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and can serve as an avian model to gain an understanding of the mechanism underlying dioxin toxicity. To elucidate the mechanism of TCDD-induced immunotoxicity in avian species, we treated chicken embryos in ovo with graded concentrations of TCDD (1.5, 2.5, 3.0, 3.3, 3.5, and 4.0 µM). Initially, we measured mRNA expression levels of ckAHR and ckARNT isoforms and analyzed the T cell populations and transcriptome in the thymuses of TCDD-treated chicken embryos. Quantitative polymerase chain reaction analysis revealed that mRNA expressions of ckAHR1 and ckARNT2 were dominant in the thymus. Severe weight loss and thymus atrophy were observed in the TCDD-treated embryos. Immunophenotyping analyses demonstrated significant increases in CD4+CD8-CD25+ and CD4+CD8+CD25+ regulatory T cells (Tregs) populations following TCDD exposure, suggesting that TCDD suppresses T cell-mediated immune responses in chicken embryos. In addition, thymic transcriptome analyses intimated that alteration of the signaling pathways related to erb-b2 receptor tyrosine kinase 4 (ERBB4) and wnt family member 5A (WNT5A), and bone morphogenetic protein (BMP) may be associated with the TCDD-induced thymus atrophy. We also observed significantly altered expression levels of genes including interleukine 13 receptor subunit alpha 2 (IL13RA2), transforming growth factor beta 1 (TGFß1), collagen type III alpha 1 chain (COL3A1), and collagen type IX alpha 3 chain (COL9A3), implying immunosuppression, fibrosis development, and collagen deposition. Collectively, these findings suggest that TCDD exposure activates the ckAHR1-ckARNT2 signaling pathway and suppresses immune responses through the prompted differentiation to CD4+CD8-CD25+ and CD4+CD8+CD25+ Tregs and altered expressions of immune-related genes in the thymus of chicken embryos.

Interspecies differences in cytochrome P450-mediated metabolism of neonicotinoids among cats, dogs, rats, and humans.

Neonicotinoid insecticides are used for agricultural and non-agricultural purposes worldwide. Pets are directly exposed to neonicotinoids in veterinary products and through environmental contamination. Cytochrome P450 (CYP) is among the most significant xenobiotic metabolizing enzymes that oxidizes several chemicals, including neonicotinoids. However, CYP activities and metabolite compositions of neonicotinoid metabolites are unknown in most domesticated pet species. Our objectives were to reveal the differences in metabolites of neonicotinoids (imidacloprid, clothianidin, and acetamiprid) and CYP activities among common pet species (cats and dogs), humans, and rats. The results indicated that the CYP-mediated neonicotinoid metabolism was different depending on species and each neonicotinoid. Among these four species, the kinetics of imidacloprid metabolism indicated that rats have the highest rate of oxidation of imidacloprid to 4OH-imidacloprid, while the greatest enzyme kinetics of imidacloprid metabolism to 5OH-imidacloprid were found in rats and humans. Clothianidin was rapidly metabolized to 1-methyl-3-nitroguanidine and dm-clothianidin in rats, but cats and humans showed the lowest formation of dm-clothianidin. CYP activities in metabolism of acetamiprid to dm-acetamiprid and N-acetyl-acetamiprid were determined to be significantly higher in humans compared to other species. However, further studies should be targeted at identifying the differences in hepatic metabolism of neonicotinoids in these species using recombinant CYP enzymes.

Effects on the liver lipidome of rat offspring prenatally exposed to bisphenol A.

Bisphenol A (BPA) is a well-known endocrine disruptor that has obesogenic properties. We have previously reported sex- and age-dependent changes in hepatic transcriptome and proteome of several lipid homeostasis-related genes in rat offspring prenatally exposed to BPA. To further understand the impacts of prenatal BPA exposure, we analyzed lipidomic profiles in the postnatal day (PND) 21 and 60 rats using a high-resolution QTOF mass spectrometer coupled with a HPLC system. We found that the total lipid content was significantly decreased in PND21 females prenatally exposed to 5000 µg/kg bw/day of BPA. Levels of total fatty acids, acylcarnitines, and monoacylglycerols significantly increased in both female and male BPA-exposed rats at PND21. An elevation in total cholesterol esters and reductions in triacylglycerols and monogalactosyl diacylglycerols were found only in PND21 females prenatally exposed to BPA. Interestingly, opposite responses were observed for phospholipids and sphingolipids between PND21 females and males following BPA exposure. The effects on the body weight and total lipid content were mitigated in the latter stage, although the alterations of lipid profiles continued until PND60. A Data Integration Analysis for Biomarker discovery using Latent cOmponents (DIABLO) revealed a high correlation of the lipidome with our previously published transcriptome data. DIABLO also identified potential biomarkers of prenatal exposure to BPA; glycerol-3-phosphate dehydrogenase 1 (Gpd1) and glyceronephosphate O-acyltransferase (Gnpat), which are involved in the glycerophospholipid metabolism, in females and males, respectively. Collectively, we highlighted the sex- and age-dependent effects of prenatal BPA exposure on hepatic lipid homeostasis in rat offspring.