Characterization of medaka (Oryzias latipes) AHRs and the comparison of two model fishes-Medaka vs. zebrafish: The subform-specific sensitivity to dioxin.

Dioxins and the emerging dioxin-like compounds (DLCs) have recruited increasing concerns about their environmental contamination, toxicity, health impacts, and mechanisms. Based on the structural similarity of dioxins and many DLCs, their toxicity was predominantly mediated by the dioxin receptor (aryl hydrocarbon receptor, AHR) in animals (including human), which can be different in expression and function among species and then possibly produce the species-specific risk or toxicity. To date, characterizing the AHR of additional species other than human and rodents can increase the accuracy of toxicity/risk evaluation and increase knowledge about AHR biology. As a key model, the medaka AHR has not been clearly characterized. Through genome survey and phylogenetic analysis, we identified four AHRs (olaAHR1a, olaAHR1b, olaAHR2a, and olaAHR2b) and two ARNTs (olaARNT1 and olaARNT2). The medaka AHR pathway was conserved in expression in nine tested tissues, of which olaAHR2a represented the predominant subform with greater abundance. Medaka AHRs and ARNTs were functional and could be efficiently transactivated by the classical dioxin congener 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), although olaAHR1a did not seem to cooperate with olaARNT2. In terms of function/sensitivity, the EC50 values of medaka olaAHR1a (9.01 ± 1.43 nM), olaAHR1b (4.00 ± 1.10 nM), olaAHR2a (8.75 ± 3.34 nM), and olaAHR2b (3.06 ± 0.81 nM) showed slight differences; however, they were all at the nM level. The sensitivity of four medaka AHRs to TCDD was similar to that of zebrafish dreAHR2 (the dominant form, EC50 = 3.14 ± 4.19 nM), but these medaka AHRs were more sensitive than zebrafish dreAHR1b (EC50 = 27.05 ± 18.51 nM). The additional comparison also indicated that the EC50 values in various species were usually within the nM range, but AHRs of certain subforms/species can vary by one or two orders of magnitude. In summary, the present study will enhance the understanding of AHR and help improve research on the ecotoxicity of dioxins/DLCs.

Toxicological evaluation of TBBPA by common carp (Cyprinus carpio) about the in vivo/vitro disturbance of the AHR pathway.

Tetrabromobisphenol A (TBBPA) is a widely used plastic additive with high bioaccumulation potential and toxicity on both humans and wildlife. Currently, research on its ecotoxicity and the underlying mechanism is limited. Using common carp (Cyprinus carpio), we evaluated the toxicity of TBBPA, especially focusing on its alteration of a key metabolism-related pathway aryl hydrocarbon receptor (AHR), using in vivo/vitro assays and in silico simulation. The 96 h LC50 of TBBPA of common carp was 4.2 mg/L and belonged to the acute toxic level II. The bioaccumulation potential of TBBPA follows the role of liver > gill > brain and varies between 3- and 14-day exposure. On the AHR pathway respect, as expected, the metabolism-related cyp1a1 and cyp1b1 were upregulated in the liver and brain. Ahr2, the receptor, was also upregulated in the brain under TBBPA exposure. The alteration of gene expression was tissue-specific while the difference between 3- or 14-day exposure was minor. AHR inhibition assay indicated the 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD)-induced AHR transactivation can be inhibited by TBBPA suggesting it is not a potent agonist but a competitive antagonist. In silico analysis indicated TBBPA can be successfully docked into the binding cavity with similar poses but still have AHR-form-specific interactions. Molecular dynamics simulation proved TBBPA can be more flexible than the coplanar ligand TCDD, especially in ccaAHR1b with greater root-mean-square deviation (RMSD), of which TCDD-induced transactivation seemed not to be blocked by TBBPA. This research increased the understanding of TBBPA toxicity and alteration of the AHR pathway, and pointed out the need to perform additional toxicology evaluation of emerging contaminants, especially on non-model species.

Functional characterization of common carp (Cyprinus carpio) AHRs: Subform-specific sensitivity to dioxin and interspecies differences.

Dioxins are widely known to bioaccumulate in the body and produce a wide spectrum of toxic effects on both humans and wildlife. In addition, some novel sorts of compounds that were similar in structure and effect were gradually identified and termed dioxin-like compounds (DLCs). The toxicity of dioxins as well as DLCs is predominantly mediated by the dioxin receptor (aryl hydrocarbon receptor, AHR) in animals, which is usually differentially expressed and functionally distinct (especially the sensitivity to dioxins) among species, possibly resulting in species-specific variations in the toxicity of dioxins. Therefore, detailed functional exploration of the AHRs of a given species, such as the common carp (which is a vital wild and commercial species with a broad geological distribution) in the current study, will enable a comprehensive ecotoxicity evaluation. Through genome survey and phylogenetic analysis, we identified three AHRs (AHR1a, AHR1b, and AHR2) and two ARNTs (ARNT1 and ARNT2). AHR2 was observed to have greater expression abundance in the gill and brain, and may serve as the predominant subform. Those AHRs and ARNTs are functional, and the AHRs can be efficiently transactivated by the classical dioxin congener 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). We individually determined the EC50 values of AHR1a (0.41 ± 0.24 nM), AHR1b (12.80 ± 3.28 nM), and AHR2 (0.64 ± 0.49 nM), and found that: 1) The AHR sensitivities of common carp and zebrafish (phylogenetically close species) are relatively similar. AHR1a and the predominant form AHR2 have greater sensitivity to TCDD. 2) ARNT1 and ARNT2 do not produce different sensitivities, but with distinct induction fold, of a given AHR transactivation when cooperating as the partner; 3) Distinct AHR subforms of the same or distinct species can have even one or two orders of magnitude differences in sensitivity. In summary, the current study will add to the knowledge of AHR biology and help improve ecotoxicology research on dioxins and DLCs.

Subacute exposure to dechlorane 602 dysregulates gene expression and immunity in the gut of mice.

Dechlorane 602 (Dec 602) has biomagnification potential. Our previous studies suggested that exposure to Dec 602 for 7 days induced colonic inflammation even after 7 days of recovery. To shed some light on the underlying mechanisms, disturbances of gut immunity and gene expression were further studied. Adult C57BL/6 mice were administered orally with Dec 602 for 7 days, then allowed to recover for another 7 days. Colonic type 3 innate lymphoid cells (ILC3s) in lamina propria lymphocytes (LPLs) and lymphocytes in mesenteric lymph nodes (MLNs) were examined by flow cytometry. Expressions of genes in the gut were determined by RNA-Seq. It was found that Dec 602 exposure up-regulated the percentage of CD4+ T cells in MLNs. The mean fluorescent intensity (MFI) of interleukin (IL)- 22 in LPLs was decreased, while the MFI of IL-17a as well as the percentage of IL-17a+ ILC3s in LPLs were increased after exposure to Dec 602. Genes involved in the formation of blood vessels and epithelial-mesenchymal transition were up-regulated by Dec 602. Ingenuity pathway analysis of differentially expressed genes predicted that exposure to Dec 602 resulted in the activation of liver X receptor/retinoid X receptor (LXR/RXR) and suppression of muscle contractility. Our results, on one hand, verified that the toxic effects of Dec 602 on gut immunity could last for at least 14 days, and on the other hand, these results predicted other adverse effects of Dec 602, such as muscle dysfunction. Overall, our studies provided insights for the further investigation of Dec 602 and other emerging environmental pollutants.

Gut microbiota of Anabas testudineus (Bloch, 1792) in the e-waste dismantling region: In situ status and relationship with internal metal burden.

Due to the production of large quantities of electronic waste (e-waste), unsafe dismantling has caused serious pollution as well as toxicological impacts on both wildlife and humans. As an important aspect of physiology and health, the wildlife's gut microbiota and its changes induced by pollution have been recruiting increasing concerns. To reveal the gut microbiota-related ecotoxicology induced by e-waste dismantling, this study resolves the gut microbiota profile of Anabas testudineus, a native highly adapted nonmodel fish under the in situ exposure, and reveals whether and how the microbiota was altered. The comparisons are made by collecting samples from different e-waste polluted sites in Guiyu (a town in South China) and a nearby reference (nonpolluted) site. The overall gut microbiota landscape of A. testudineus is similar to that of other reported fishes, with an average of ∼300 OTUs, and constituted by Firmicutes (34.51%), Fusobacteria (29.16%) as the major phyla. Obviously different liver metal burdens/fingerprints were observed between the e-waste and reference sites. Accordingly, although the alpha-diversity (ACE, Simpson, and Shannon) of the gut microbiota did not significantly vary, a detailed exploration of the microbiota constitution indicated significant differences at various taxonomic levels, including a series of significantly different species and biomarkers, and showing site-specific beta-diversity clustering patterns. Interestingly, a few bacteria with greater abundance in the fish gut of e-waste polluted sites were also reported to present in other contaminated environments, have a role in wastewater treatment, be capable to transform metal, etc. Redundancy analysis (RDA) and Pearson association analyses indicated significant associations between Mn and Cetobacterium somerae (Pearson r = 0.3612, p = 0.0008) and between Pb and Clostridium colicanis (Pearson r = 0.5151, p < 0.0001). In summary, pollution from e-waste dismantling may have a role in altering the fish gut microbiota, and this research provides insights for better understanding e-waste ecotoxicology and improving future conservation.

Toxic effect of triphenyl phosphate (TPHP) on Cyprinus carpio and the intestinal microbial community response.

Triphenyl phosphate (TPHP) is a kind of organophosphorus flame retardants, and its use is increasing annually. However, the toxic effect associated with exposure to it has not been adequately investigated. Therefore, in this study, we determined the toxic dose of TPHP in the economic fish species, Cyprinus carpio. Acute and subacute toxicity tests were conducted, and the enrichment of TPHP in the gills, brain, intestines, and liver were determined by Liquid Chromatography-Mass Spectrometry, and the response of carp gut microbial community to TPHP stress was determined using 16 S rRNA gene high-throughput sequencing. Results showed that the 96-h LC50 of TPHP in carp was 7 mg/L. At the 7 d, the order of TPHP absorption was as follows (from highest to lowest): gills > intestine > liver > brain, but at the 28 d and the purification period, the order of TPHP absorption was brain > gills > intestine > liver. TPHP exposure at 3.5 mg/L decreased α-diversity of the intestinal microbial community (p < 0.05), and altered community composition, in particular the relative abundance of dominant microbial populations. Functional profiles of the microbial communities predicted based on 16 S rRNA gene data showed upregulation in the degradation of exogenous substances and energy metabolism of the TPHP-treated groups (p < 0.05), suggesting that intestinal microbial taxa play a role in reducing TPHP toxicity. The results provide insights that could facilitate risk assessments of TPHP pollutants in aquatic environments and the management of associated water pollution.

Characterization and algicidal activity of bacteria from the phycosphere of the harmful alga Karenia mikimotoi.

Harmful algal blooms (HABs) are detrimental to aquatic ecosystems; thus, economical and practical HAB control methods are needed. We analyzed a microbial community closely related to the alga Karenia mikimotoi, which has HABs that can be toxic to aquatic environments. We studied the relationship between algicidal bacteria and the microbial community of K. mikimotoi culture using culture-dependent and culture-independent methods. Bacterial strains Marinobacter sp. (O-7) and Pseudomonas sp. (D-2) were isolated from a K. mikimotoi seawater culture containing a mixed microbial community and determined to have algicidal activity. Both strains produced alga-lysing substances that were toxic to K. mikimotoi. The algicidal extracellular substances produced by D-2 were stable at temperatures ranging from - 80 to 120 °C but sensitive to strong acidic/alkaline conditions. The substances produced by O-7 were inactivated at high temperatures and strong alkaline conditions. Extracellular substances produced by O-7 and D-2 caused K. mikimotoi and Prorocentrum donghaiense cell lysis, but no changes or inhibitory effects occurred in two other chlorophyta groups. O-7 and D-2 exhibited significantly greater algicidal activity during the logarithmic growth phase of K. mikimotoi growth compared to the stationary phase. Culture-independent analysis of the microbial community in association with K. mikimotoi was made using Illumina MiSeq sequencing. Phylogenetic analysis showed that Proteobacteria was the dominant bacterial population in the phycosphere of K. mikimotoi, containing Marinobacter sp. and Pseudomonas sp.. The Marinobacter was abundant and accounted for 5.3% of the total. Our results indicate that certain bacterial species from K. mikimotoi culture might be effective for removal of HABs.

Gradient adhesion modification of polyacrylamide/alginate-calcium tough hydrogels.

Strong hydrogel adhesion requires the synergy of adhesion and cohesion. Gradient adhesive-tough hydrogels can balance adhesion and cohesion, however, their construction is still a challenging task. Here, we used ethylenediaminetetraacetic acid (EDTA) on-side coordination-induced diffusion chelating Ca2+ to form an adhesive surface in a polyacrylamide/alginate-calcium (PAAm/Alg-Ca2+) tough hydrogel as a facile method for the construction of gradient adhesive-tough hydrogels. The adhesion energy of a gradient adhesive-tough hydrogel to skin is increased by 128% compared with PAAm/Alg-Ca2+ tough hydrogels and the elongation at break is two times higher than that of PAAm/Alg hydrogels. In addition, gradient adhesive-tough hydrogels also exhibit wide linear sensitivity (the gauge factor (GF) = 0.196 (0% < ε < 400%); GF = 0.260 (400% < ε < 650%)) as a wearable strain sensor to monitor human motions. This work provides a versatile strategy for the design of gradient adhesive-tough hydrogels and also provides a practical model for the development of wearable strain sensors.

The aryl hydrocarbon receptor: A predominant mediator for the toxicity of emerging dioxin-like compounds.

The aryl hydrocarbon receptor (AHR) is a member of the basic helix-loop-helix/Per-ARNT-Sim (bHLH-PAS) family of transcription factors and has broad biological functions. Early after the identification of the AHR, most studies focused on its roles in regulating the expression of drug-metabolizing enzymes and mediating the toxicity of dioxins and dioxin-like compounds (DLCs). Currently, more diverse functions of AHR have been identified, indicating that AHR is not just a dioxin receptor. Dioxins and DLCs occur ubiquitously and have diverse health/ecological risks. Additional research is required to identify both shared and compound-specific mechanisms, especially for emerging DLCs such as polyhalogenated carbazoles (PHCZs), polychlorinated diphenyl sulfides (PCDPSs), and others, of which only a few investigations have been performed at present. Many of the toxic effects of emerging DLCs were observed to be predominantly mediated by the AHR because of their structural similarity as dioxins, and the in vitro TCDD-relative potencies of certain emerging DLC congeners are comparable to or even greater than the WHO-TEFs of OctaCDD, OctaCDF, and most coplanar PCBs. Due to the close relationship between AHR biology and environmental science, this review begins by providing novel insights into AHR signaling (canonical and non-canonical), AHR's biochemical properties (AHR structure, AHR-ligand interaction, AHR-DNA binding), and the variations during AHR transactivation. Then, AHR ligand classification and the corresponding mechanisms are discussed, especially the shared and compound-specific, AHR-mediated effects and mechanisms of emerging DLCs. Accordingly, a series of in vivo and in vitro toxicity evaluation methods based on the AHR signaling pathway are reviewed. In light of current advances, future research on traditional and emerging DLCs will enhance our understanding of their mechanisms, toxicity, potency, and ecological impacts.

Adhesive and tough hydrogels: from structural design to applications.

In recent years, multifunctional hydrogels have garnered great interest. Usually, there is a contradiction between the toughness and interface adhesion of traditional hydrogels. In engineering and medical applications, hydrogels need to have good adhesive properties and toughness. The design of functional hydrogels with strong adhesion and high toughness is key to their application. In this review, the research progress of adhesive and tough hydrogels in recent years is outlined. Specifically, the structural design (such as integrated, layered, and gradient structures) and applications (such as cartilage repair, drug delivery, strain sensors, tissue adhesives, soft actuators, and supercapacitors) of adhesive and tough hydrogels are classified and discussed, providing new insights on their design and development.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on spontaneous movement of human neuroblastoma cells.

Aryl hydrocarbon receptor (AhR) plays important roles in the interferences of dioxin exposure with the occurrence and development of tumors. Neuroblastoma is a kind of malignant tumor with high mortality and its occurrence is getting higher in dioxin exposed populations. However, there is still a lack of direct evidence of influences of dioxin on neuroblastoma cell migration. SK-N-SH is a human neuroblastoma cell line which has been used to reveal 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced dysregulation of certain promigratory gene. Thus, in this study, we employed SK-N-SH cells to investigate the effects of TCDD on the spontaneous movement of neuroblastoma cells, which is a short-range cell migratory behavior related to clone formation and tumor metastasis in vitro. Using unlabeled live cell imaging and high content analysis, we characterized the spontaneous movement under a full-nutrient condition in SK-N-SH cells. We found that the spontaneous movement of SK-N-SH cells was inhibited after 36- or 48-h treatment with TCDD at relative low concentrations (10-10 or 2 × 10-10 M). The TCDD-treated cells were unable to move as freely as that of control cells, resulting in less diffusive trajectories and a decreased displacement of the movement. In line with this cellular effect, the expression of pro-adhesive genes was significantly induced in time- and concentration-dependent manners after TCDD treatment. In addition, with the presence of AhR antagonist, CH223191, the effects of TCDD on the gene expression and the spontaneous cell movement were effectively reversed. Thus, we proposed that AhR-mediated up-regulation of pro-adhesive genes might be involved in the inhibitory effects of dioxin on the spontaneous movement of neuroblastoma cells. To our knowledge, this is the first piece of direct evidence about the influence of dioxin on neuroblastoma cell motility.

Determination of polyhalogenated carbazoles in soil using gas chromatography-triple quadrupole tandem mass spectrometry.

Polyhalogenated carbazoles (PHCZs) are emerging environmental contaminants that have caused wide concerns due to their dioxin-like toxicity and environmental persistence. It would be desirable to determine all of these chemicals using a simple analytical method. Within this study, a simple and sensitive method combining accelerated solvent extraction (ASE) with gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS) was established to simultaneously analyze eleven frequently detected PHCZs in soil, including CCZ-3, CCZ-36, CCZ-1368, CCZ-2367, BCZ-3, BCZ-27, BCZ-36, BCZ-136, BCZ-1368, 1-B-36-CCZ, 18-B-36-CCZ. The calibration curves of the target analytes showed good linearity (R2 > 0.99, level = 6), and method detection limits (MDLs) ranging from 1.5 to 14.6 pg g-1. The average recoveries of the analytes in soil samples ranged from 64% to 126% with the RSD ranging from 2.0% to 10%. The developed method was successfully used for determination of these eleven PHCZs in soil samples from a tie-dye area in southwest China. Total concentrations of these eleven PHCZs ranging up to 46.3 ng g-1 dw. CCZ-36, BCZ-3, CCZ-3, 1-B-36-CCZ, 18-B-36-CCZ, and BCZ-1368 were the most abundant compounds in soil.

Characterization of the Aryl Hydrocarbon Receptor (AhR) Pathway in Anabas testudineus and Mechanistic Exploration of the Reduced Sensitivity of AhR2a.

Field investigations have revealed the ability of the climbing perch Anabas testudineus to survive in highly contaminated water bodies. The aryl hydrocarbon receptor (AhR) pathway is vital in mediating the toxicity of aromatic hydrocarbon contaminants, and genotypic variation in the AhR can confer resistance to these contaminants. Thus, we characterized the AhR pathway in A. testudineus in order to understand the mechanism(s) underlying the resistance of this species to contaminants and to broaden current knowledge on teleost AhR. In A. testudineus, four AhRs, two AhR nuclear translocators (ARNTs), and one AhR repressor (AhRR) were found. Transient transfection assays revealed that AhR1a, AhR1b, and AhR2b were functional, whereas AhR2a was poorly activated by the potent agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Two ARNTs (partner of AhR) and one AhRR (repressor of AhR) all were functional with each of the active AhR. As a major form, the insensitivity of AhR2a might serve as a potential mechanism for A. testudineus' reduced sensitivity to severe contamination. We explored the key residues that may account for AhR2a's insensitivity in silico and then functionally validated them in vitro. Two sites (VCS322-324, M370) in its ligand-binding domain (LBD) were proved critical for its sensitivity to TCDD. This systematic exploration of the AhR pathway showed that most members have maintained their traditional functions as expected, whereas a nonfunctionalization event has occurred for AhR2a.

The toxic effects of in situ exposure of a native fish species (Anabas testudineus) to electronic waste pollution.

In recent decades, crude recycling of electronic waste (e-waste) has caused serious pollution and threatened wild organisms in certain regions. It is therefore valuable to investigate the pollution-induced toxic effects in situ using native fish species. Unlike the death or decline observed in other species, Anabas testudineus can better adapt to severe e-waste pollution. Using it as a model, the true status of this wild organism was revealed. We collected A. testudineus from two polluted sites (st1 and st2) and conducted transcriptome analyses of the liver, gill, and kidney. Clear whole-transcriptome differences were found between polluted and clean sites and between differentially polluted sites (st1 and st2). Pathway analysis revealed that long-term e-waste pollution would cause significant hypoxia, oxidative stress, and potentially apoptosis. Accordingly, several defensive responses were elicited including 'oxidation-reduction' and the 'unfolded protein response'. Certain biological processes, including 'DNA repair' and 'endoplasmic reticulum stress response', were altered in a tissue- or burden-specific pattern suggesting transcriptome plasticity in response to distinct burdens. This study revealed the toxic impacts of e-waste pollution on wild organisms using a native fish species. Additionally, due to its highly adaptive nature, A. testudineus could be a suitable test species for such severe conditions in the wild or otherwise.

Aryl hydrocarbon receptor activity of polyhalogenated carbazoles and the molecular mechanism.

Polyhalogenated carbazoles (PHCZs) are a class of contaminants identified with persistence and bioaccumulation property from previous studies. However, the toxic effect and mechanism of PHCZs are not fully understood. In this study, eleven PHCZs, including four chlorocarbazoles, four bromocarbazoles and two bromo/chlorocarbazoles were screened for their potential aryl hydrocarbon receptor (AhR) activity by using a dioxin responsive element-driven luciferase reporter assay. We found that nine PHCZs significantly activated AhR in a concentration-dependent manner. Their potencies of AhR activation were 1000 to 100,000 folds less than that of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent AhR ligand. The relative AhR activation potency of the nine PHCZs followed the order 2,3,6,7-tetrachloro-9H-carbazole >2,7-dibromo-9H-carbazole >1,3,6-tribromo-9H-carbazole >1,3,6,8-tetrachloro-9H-carbazole >1,3,6,8-tetrabromo-9H-carbazole >1-bromo-3,6-dichloro-9H-carbazole >3,6-dibromo-9H-carbazole >3-bromo-9H-carbazole >1,8-dibromo-3,6-dichloro-9H-carbazole, which was partly in line with the induction of AhR-mediated CYP1A1 expression. In silico analysis indicated that the nine PHCZs could be docked into the same pocket as TCDD due to their high structural similarity. However, the shrunk size of the heterocyclic moieties in PHCZs relative to that in TCDD dramatically decreased the complex stability provided by inter-molecular interactions. Moreover, two distinguished docking poses adopted by the nine PHCZs were found, in which one was illustrated by 2367-CCZ and 27-BCZ while the other symbolized by TCDD and the left seven agonists. The differential antagonizing effects of CH223191 on PHCZ-induced AhR activity supported such pose differentiation. The present experimental and in silico data provide new direct evidence of PHCZ-AhR interaction which sheds light on AhR-associated toxicological study and risk assessment of PHCZs.

Transcriptomic analysis of Anabas testudineus and its defensive mechanisms in response to persistent organic pollutants exposure.

The freshwater climbing perch (Anabas testudineus) can tolerate water environments contaminated with persistent organic pollutants (POPs). The mechanisms underlying this tolerance are unknown. We used de novo transcriptomic analysis to investigate the defensive mechanisms of A. testudineus against POPs based on its genetic features and biological responses to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure. Our results revealed a specific expansion of cytochrome P450 (CYP) 3A subfamily, which may be involved in the elimination of certain POPs. In xenobiotic responses, the aryl-hydrocarbon receptor (AhR) pathway represents a critical signaling mechanism, and we characterized four AhR and two AhR nuclear translocator homologs and one AhR repressor (AhRR) gene in A. testudineus. TCDD-induced AhRR and CYP1A mRNA upregulation suggests that negative-feedback regulation of AhR signaling through AhRR helps avoid excessive xenobiotic responses. Furthermore, liver and gill transcriptomic profiles were markedly altered after TCDD exposure, with some of the altered genes being related to common defensive responses reported in other species. Based on the newly identified TCDD-altered genes, several A. testudineus-specific responses are proposed, such as enhanced fatty acid ß-oxidation. The genetic features of CYP3A subfamily and AhR pathway and the TCDD-induced defensive biological processes elucidated here enhance our understanding of A. testudineus defensive responses against POPs.

Type 3 innate lymphoid cells are altered in colons of C57BL/6 mice with dioxin exposure.

Type 3 innate lymphoid cells (ILC3s) are distributed in the gut and regulate inflammation by secreting cytokines, including interferon (IFN)-γ and interleukin (IL)-17. The maintenance and function of ILC3s involve the activity of aryl hydrocarbon receptor (AhR), a potent ligand of which is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), one of the most toxic dioxin congeners. Thus, TCDD exposure might affect ILC3s. To obtain in vivo evidence supporting this notion, we exposed female C57BL/6 mice orally to TCDD (low/high doses: 0.1/10 µg/kg body weight) during pregnancy and lactation periods, and after the exposure, evaluated the mothers and offspring for alterations in ILC3 differentiation and function in the colon. ILC3 frequency among colonic lamina propria lymphocytes was preferentially diminished in the offspring, and, in parallel, the median fluorescence intensity (MFI) of retinoic acid receptor-related orphan receptor (ROR)γt, which is associated with ILC3 differentiation, was also decreased in ILC3s. Conversely, the percentages of two subsets of the cells, one positive for natural cytotoxicity receptor NKp46 and the other for IL-17a, were increased in TCDD-exposed mothers and offspring. Moreover, the percentage of IFN-γ+ ILC3s was increased specifically in the mothers, but this was in conjunction with a significant decrease in the MFI of IFN-γ, which suggests that the IFN-γ+ ILC3 subset was functionally altered. In conclusion, maternal exposure to TCDD suppresses ILC3 differentiation in the offspring and influences ILC3 function in distinct manners in the mother and offspring. Our study provides new insights into the intergenerational interference of dioxins in colonic ILC3s.

Metabolic profiling study on potential toxicity in male mice treated with Dechlorane 602 using UHPLC-ESI-IT-TOF-MS.

Dechlorane 602 (Dec 602), a chlorinated flame retardant, has been widely detected in different environmental matrices and biota. However, toxicity data for Dec 602 seldom have been reported. A metabolomics study based on ultra-high performance liquid chromatography coupled with ion trap time-of-flight mass spectrometry was employed to study the urine and sera metabolic profiles of mice administered with Dec 602 (0, 0.001, 0.1, and 10 mg/kg body weight per day) for 7 days. A significant difference in metabolic profiling was observed between the Dec 602 treated group and the control group by multivariate analysis, which directly reflected the metabolic perturbations caused by Dec 602. The metabolomics analyses of urine from Dec 602-exposed animals exhibited an increase in the levels of thymidine and tryptophan as well as a decrease in the levels of tyrosine, 12,13-dihydroxy-9Z-octadecenoic acid, 2-hydroxyhexadecanoic acid and cuminaldehyde. The metabolomics analyses of sera showed a decrease in the levels of kynurenic acid, daidzein, adenosine, xanthurenic acid and hypoxanthine from Dec 602-exposed animals. These findings indicated Dec 602 induced disturbance in phenylalanine, tyrosine and tryptophan biosynthesis, tryptophan metabolism, tyrosine metabolism, pyrimidine metabolism, purine metabolism, ubiquinone and other terpenoid-quinone biosynthesis; phenylalanine metabolism and aminoacyl-tRNA biosynthesis. Significant alterations of immune and neurotransmitter-related metabolites (tyrosine, tryptophan, kynurenic acid, and xanthurenic acid) suggest that the toxic effects of Dec 602 may contribute to its interactions with the immune and neuronal systems. This study demonstrated that the UHPLC-ESI-IT-TOF-MS-based metabolomic approach can obtain more specific insights into the potential toxic effects of Dec 602 at molecular level.

Effects of Acute Low-Dose Exposure to the Chlorinated Flame Retardant Dechlorane 602 and Th1 and Th2 Immune Responses in Adult Male Mice.

BACKGROUND: Although the chlorinated flame retardant Dechlorane (Dec) 602 has been detected in food, human blood, and breast milk, there is limited information on potential health effects, including possible immunotoxicity. OBJECTIVES: We determined the immunotoxic potential of Dec 602 in mice by examining the expression of phenotypic markers on thymocyte and splenic lymphocyte subsets, Th1/Th2 transcription factors, and the production of cytokines and antibodies. METHODS: Adult male C57BL/6 mice were orally exposed to environmentally relevant doses of Dec 602 (1 and 10 µg/kg body weight per day) for 7 consecutive days. Thymocyte and splenic CD4 and CD8 subsets and splenocyte apoptosis were examined by flow cytometric analysis. Cytokine expression was measured at both the mRNA and the protein levels. Levels of the transcription factors Th1 (T-bet and STAT1) and Th2 (GATA3) were determined using quantitative real-time polymerase chain reaction (qPCR). Serum levels of immunoglobulins IgG1, IgG2a, IgG2b and IgE were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: Splenic CD4+ and CD8+ T cell subsets were decreased compared with vehicle controls, and apoptosis was significantly increased in splenic CD4+ T cells. Expression (mRNA and protein) of Th2 cytokines [interleukin (IL)-4, IL-10, and IL-13] increased, and that of Th1 cytokines [IL-2, interferon (IFN)-γ and tumor necrosis factor (TNF)-α] decreased. The Th2 transcriptional factor GATA3 increased, whereas the Th1 transcriptional factors T-bet and STAT1 decreased. As additional indicators of the Th2-Th1 imbalance, production of IgG1 was significantly increased, whereas IgG2a was reduced. CONCLUSIONS: To our knowledge, we are the first to report evidence of the effects of Dec 602 on immune function in mice, with findings indicating that Dec 602 exposure favored Th2 responses and reduced Th1 function. CITATION: Feng Y, Tian J, Xie HQ, She J, Xu SL, Xu T, Tian W, Fu H, Li S, Tao W, Wang L, Chen Y, Zhang S, Zhang W, Guo TL, Zhao B. 2016. Effects of acute low-dose exposure to the chlorinated flame retardant dechlorane 602 and Th1 and Th2 immune responses in adult male mice. Environ Health Perspect 124:1406-1413; http://dx.doi.org/10.1289/ehp.1510314.