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Increasing evidence shows that 2,3,7,8-tetrachlorodibenzo- p -dioxin(TCDD) enhances inflammation, and inflammation has a significant negative impact on fertility. Therefore, the aim of this study was to investigate the effects of TCDD on testis inflammation. Pregnant mice and primary Sertoli cells were treated with TCDD, and male offspring and Sertoli cells were treated with lipopolysaccharides(LPS). We then measured testis apoptotic cells, proinflammatory cytokines, and observed the Klotho/PDLIM2/p65 pathway. In vivo results revealed that TCDD further enhanced LPS-increased testis apoptotic cells and concentrations of testicular proinflammatory cytokines (IL1β, IL18, and IL12) (p < 0.05). An in vitro investigation showed the levels of proinflammatory cytokines were increased in TCDD + LPS-treated cells compared with LPS-treated cells (p < 0.05). Compared with the LPS-treated cells, expression of Klotho and PDLIM2 was significantly decreased in TCDD + LPS-treated cells (p < 0.05), while expression of p65 and NLRP3 were significantly increased in the cotreatment cells (p < 0.05). However, the addition of Klotho to the TCDD + LPS-cotreated cells significantly increased PDLIM2 and decreased p65 activation and NLRP3 (p < 0.05). Meanwhile, mRNA levels and the secretion of proinflammatory cytokines were both suppressed by exogenous Klotho (p < 0.05). Administration of Klotho decreased TCDD + LPS-induced cytokines and apoptosis in mice (p < 0.05). Taken together, TCDD may increase testicular inflammation by affecting the secretion of proinflammatory cytokines in Sertoli cells via the Klotho/PDLIM2/p65 pathway, which influences the testicular microenvironment and induces germ cell apoptosis. [ABSTRACT FROM AUTHOR]

Abstract The mediator of dioxin toxicity, aryl hydrocarbon receptor (AHR), has also important physiological functions. Selective AHR modulators (SAHRMs) share some effects of dioxins, except for their marked toxicity. We recently characterised toxicologically two novel SAHRMs, prodrugs IMA-08401 and IMA-07101 in rats, demonstrating that they are far less deleterious than the most toxic AHR-agonist, TCDD. Here, we analysed the in vitro toxicity and in silico AHR binding of the respective active, deacetylated metabolites, IMA-06201 (N-ethyl- N -phenyl-5-chloro-1,2-dihydro-4-hydroxy-1-methyl-2-oxo-quinoline-3-carboxamide) and IMA-06504 (N-(4-trifluoromethylphenyl)-1,2-dihydro-4-hydroxy-5-methoxy-1-methyl-2-oxo-quinoline-3-carboxamide). In H4IIE rat hepatoma cells, IMA-06201 and IMA-06504 induced CYP1A1 with comparable potencies and efficacies to those of TCDD. They had little effect on cell viability as assessed by LDH leakage and MTT reduction assays, and were not mutagenic in the Ames test, but IMA-06504 elicited a maximally 2.7-fold increase in micronuclei. Molecular docking simulations showed that similar to TCDD, they occupy the central region of AHR ligand binding cavity. Hence, while showing low to negligible in vitro toxicity, these novel SAHRMs bind to the AHR qualitatively in a similar fashion to TCDD, and appear comparably powerful AHR agonists. Combined with our earlier results demonstrating that they seem considerably less toxic in vivo than TCDD, these compounds are thus highly interesting new SAHRMs. Highlights • IMA-06201 and IMA-06504 are selective AHR modulators. • As CYP1A1 inducers, they appear comparable to TCDD in potency and efficacy. • They also show low to negligible cytotoxicity and mutagenicity in vitro. • Based on in silico modelling, their binding to the AHR resembles that of TCDD. • Therefore, they have potential as drug compound candidates and research tools. [ABSTRACT FROM AUTHOR]

Abstract: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is highly toxic and affects the cardiovascular system, brain, and skin by AhR-dependent and other mechanisms, as well as causing metabolic impairments and cancer. The involvement of the respiratory system has not yet been studied. TCDD in the blood was measured and biomarkers of oxidative stress and inflammation were analysed in 2016 in the exhaled breath condensate (EBC) of the last eight male survivors (mean age 72.4 ± 1.3 years) from 80 workers intoxicated with TCDD during the production of herbicides from 1965 to 1968. The results were compared with their findings in 2010 to evaluate a trend. Malondialdehyde, 4-hydroxy-trans-nonenale, and 8-isoprostaglandin F2α (8-isoprostane), in addition to markers of the oxidation of nucleic acids and proteins 8-hydroxy-2-deoxyguanosine, 8-hydroxyguanosine, 5-(hydroxymethyl)uracil, o-tyrosine, and 3-nitrotyrosine, as well as markers of inflammation leukotrienes and anti-inflammatory lipoxins, were analysed in EBC by liquid chromatography-electrospray ionisation-tandem mass spectrometry. In addition, the patients underwent chest X-ray, spirometry and fractional exhaled nitric oxide (FeNO) examinations. The control group included 7 men (66 ± 16 years) with comparable lifestyle factors. The median plasma TCDD level lowered from 155 (28-553) ng/kg fat in 2010 to 112 (46-390) ng/kg fat in 2016, i.e., 50 years after exposure. The mean TCDD body deposit was 5.0 ± 3.7 µg. Serum TCDD level in the pooled sample of the controls was 12 ng/kg fat. All markers of oxidative stress, LTB4 and LTC4, remained overexpressed in patients and anti-inflammatory lipoxins were under-expressed compared to controls (all p < 0.01). The mean FeNO and spirometry results were within the reference values. Borderline X-ray findings and combined lung function impairments were seen in the patients with the lower TCDD plasma levels. Differences in the expression of the biomolecular markers in EBC as compared to controls were not associated with lung impairments and the respiratory parameters measured. Therefore, these EBC markers can be used to evaluate systemic oxidative stress and inflammation in tissues and the endovascular, atherosclerotic, neurotoxic, and metabolic effects of TCDD.Graphical abstract: [ABSTRACT FROM AUTHOR]

The environmental polycyclic aromatic hydrocarbons (PAH) and dioxins are carcinogens and their adverse effects have been largely attributed to the activation of AhR. Hesperetin is a flavonone found abundantly in citrus fruits and has been shown to be a biologically active agent. In the present study, the effect of hesperetin on the nuclear translocation of AhR and the downstream gene expression was investigated in MCF-7 cells. Confocal microscopy indicated that 7, 12-dimethylbenz[α]anthracene (DMBA) or 2,3,7,8-tetrachlorodibenzo- p- dioxin (TCDD) -induced nuclear translocation of AhR was deterred by hesperetin treatment. The reduced nuclear translocation could also be observed in Western analysis. Reporter-gene assay further illustrated that the induced XRE transactivation was weakened by the treatment of hesperetin. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay demonstrated that the gene expressions of CYP1A1 , 1A2 , and 1B1 followed the same pattern of AhR translocation. These results suggested that hesperetin counteracted AhR transactivation and suppressed the downstream gene expression. [ABSTRACT FROM AUTHOR]

The aryl hydrocarbon receptor (AHR) is not essential to survival, but does act as a key regulator of many normal physiological events. The role of this receptor in toxicological processes has been studied extensively, primarily employing the high-affinity ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). However, regulation of physiological responses by endogenous AHR ligands remains to be elucidated. Here, we review developments in this field, with a focus on 6-formylindolo[3,2-b]carbazole (FICZ), the endogenous ligand with the highest affinity to the receptor reported to date. The binding of FICZ to different isoforms of the AHR seems to be evolutionarily well conserved and there is a feedback loop that controls AHR activity through metabolic degradation of FICZ via the highly inducible cytochrome P450 1A1. Several investigations provide strong evidence that FICZ plays a critical role in normal physiological processes and can ameliorate immune diseases with remarkable efficiency. Low levels of FICZ are pro-inflammatory, providing resistance to pathogenic bacteria, stimulating the anti-tumor functions, and promoting the differentiation of cancer cells by repressing genes in cancer stem cells. In contrast, at high concentrations FICZ behaves in a manner similar to TCDD, exhibiting toxicity toward fish and bird embryos, immune suppression, and activation of cancer progression. The findings are indicative of a dual role for endogenously activated AHR in barrier tissues, aiding clearance of infections and suppressing immunity to terminate a vicious cycle that might otherwise lead to disease. There is not much support for the AHR ligand-specific immune responses proposed, the differences between FICZ and TCDD in this context appear to be explained by the rapid metabolism of FICZ. [ABSTRACT FROM AUTHOR]

Uveitis is characterized as a common cause of blindness worldwide. Aryl hydrocarbon receptor (AhR), a ligand-activated nuclear receptor, has been implicated to play a role in human uveitis, although the exact mechanisms remain poorly understood. The purpose of this study was to enhance our knowledge concerning the role of AhR during intraocular inflammation. We immunized wild-type and AhR-knockout C57BL/6J mice with IRBP651–670 to induce experimental autoimmune uveitis (EAU). Disease severity was evaluated with both clinical and histopathological grading. Blood–retinal barrier (BRB) integrity was tested by Evans blue and tight junction proteins qualifications. Apoptosis was measured using TdT-mediated dUTP nick end labeling staining. Macrophage/microglia activation and polarization were studied by immunofluorescence and Western blot. Following EAU induction, AhR−/− mice had more severe clinical and histopathological manifestations of uveitis than AhR+/+ mice. Increased vascular permeability and apoptotic cells were observed in AhR−/− EAU mice when compared with AhR+/+ EAU mice. In addition, AhR−/− EAU mice showed evidence of a significantly increased macrophage/microglia cells and a stronger polarization from the M2 to the M1 phenotype as compared to AhR+/+ EAU mice. The levels of pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-1β were increased in AhR−/− EAU mice, which was associated with the activation of NF-κB and signal transducers and activators of transcription (STAT) pathways. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an agonist of AhR, caused a significant decrease in the clinical and histopathological manifestations, preserved BRB integrity, reduced apoptotic cells, inhibited macrophage/microglia activation, and shifted their polarization from M1 toward M2. Moreover, decreased expression of pro-inflammatory cytokines including TNF-α, IL-6, and IL-1β and inhibition of NF-κB and STAT pathways were found in EAU mice following TCDD treatment. In conclusion, AhR activation with TCDD exhibits an immunomodulatory effect by reducing BRB breakdown, inhibiting retinal cell apoptosis, and reducing pro-inflammatory cytokine expression during EAU. The underlying mechanism may involve the modulation of macrophages/microglia polarization and the downregulation of NF-κB and STAT pathways. [ABSTRACT FROM AUTHOR]

The effects of body fat mass on the elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was examined in mice. When male C57BL/6J mice are fed a high-fat, simple carbohydrate diet (HFD) for 13 weeks, they develop an obese phenotype. In contrast, A/J mice fed an HFD do not become obese. After 13 weeks on a normal diet (ND) or HFD, male C57BL/6J and A/J mice received a single dose by gavage of 0.1 or 5.0 µg of 2,3,7,8-tetrachloro[1,6-3H] dibenzo-p-dioxin per kg body weight. Using classical pharmacokinetics, the blood elimination half-life of TCDD was approximately 10 and 2 times longer in the C57BL/6J on the HFD compared with the mice on the ND at 0.1 and 5.0 µg/kg doses, respectively. The diet did not increase the blood half-life of TCDD in the A/J mice, which did not get obese. Using a physiologically based pharmacokinetic model for TCDD that incorporated experimentally derived percent body fat mass and tissue partition coefficients, as well as data on hepatic sequestration, did not provide accurate predictions to the data and could not explain the increase in half-life of TCDD in the HFD groups. This work demonstrates that obesity influences the half-life of TCDD, but other undetermined factors are involved in its elimination because the increase in body fat mass, decreases in cytochrome P4501A2, and altered partition coefficients could not completely explain the prolonged half-life. [ABSTRACT FROM AUTHOR]

2,3,7,8-Tetrachlorodibenzo- p -dioxin (TCDD) and other aryl hydrocarbon receptor (AhR) agonists have been shown to regulate bone development and remodeling in a species-, ligand-, and age-specific manner, however the underlying mechanisms remain poorly understood. In this study, we characterized the effect of 0.01–30 μg/kg TCDD on the femoral morphology of male and female juvenile mice orally gavaged every 4 days for 28 days and used RNA-Seq to investigate gene expression changes associated with the resultant phenotype. Micro-computed tomography revealed that TCDD dose-dependently increased trabecular bone volume fraction (BVF) 2.9- and 3.3-fold in male and female femurs, respectively. Decreased serum tartrate-resistant acid phosphatase (TRAP) levels, combined with a reduced osteoclast surface to bone surface ratio and repression of femoral proteases (cathepsin K, matrix metallopeptidase 13), suggests that TCDD impaired bone resorption. Increased osteoblast counts at the trabecular bone surface were consistent with a reciprocal reduction in the number of bone marrow adipocytes, suggesting AhR activation may direct mesenchymal stem cell differentiation towards osteoblasts rather than adipocytes. Notably, femoral expression of transmembrane glycoprotein NMB ( Gpnmb ; osteoactivin), a positive regulator of osteoblast differentiation and mineralization, was dose-dependently induced up to 18.8-fold by TCDD. Moreover, increased serum levels of 1,25-dihydroxyvitamin D 3 were in accordance with the renal induction of 1α-hydroxylase Cyp27b1 and may contribute to impaired bone resorption. Collectively, the data suggest AhR activation tipped the bone remodeling balance towards bone formation, resulting in increased bone mass with reduced marrow adiposity. [ABSTRACT FROM AUTHOR]

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent organic pollutant (POP), an unintentional byproduct of various industrial processes, and a human carcinogen. The expression of the cytochrome P450 1A (cyp1a) gene is upregulated in the presence of TCDD through activating the aryl hydrocarbon receptor pathway in a dose-dependent manner. Several essential response elements, including the 8 potential xenobiotic response elements in the cyp1a promoter region, have been identified to be the main functional parts for the response to TCDD. Thus, we aimed to develop a convenient and sensitive biomonitoring tool to examine the level of POPs in the environment and evaluate its potential human health risks by TCDD. Here, we established a transgenic zebrafish model with a red fluorescent reporter gene (mCherry) using the truncated cyp1a promoter. Under exposure to TCDD, the expression pattern of mCherry in the reporter zebrafish mirrored that of endogenous cyp1a mRNA, and the primary target tissues for TCDD were the brain vessels, liver, gut, cloaca, and skin. Our results indicated that exposure of the embryos to TCDD at concentrations as low as 0.005 nM for 48 h, which did not elicit morphologic abnormalities in the embryos, markedly increased mCherry expression. In addition, the reporter embryos responded to other POPs, and primary liver cell culture of zebrafish revealed that Cyp1a protein was mainly expressed in the cytoplasm of liver cells. Furthermore, our transgenic fish embryos demonstrated that TCDD exposure can regulate the expression levels of several tumor-related factors, including epidermal growth factor, TNF-α, C-myc, proliferating cell nuclear antigen, TGF-β, serine/threonine kinase (Akt), and phosphorylated Akt, suggesting that our transgenic fish can be used as a sensitive model to evaluate the carcinogenicity induced by TCDD exposure. [ABSTRACT FROM AUTHOR]

Infectious agents are a significant risk factor for preterm birth (PTB); however, the simple presence of bacteria is not sufficient to induce PTB in most women. Human and animal data suggest that environmental toxicant exposures may act in concert with other risk factors to promote PTB. Supporting this “second hit” hypothesis, we previously demonstrated exposure of fetal mice (F1 animals) to the environmental endocrine disruptor 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) leads to an increased risk of spontaneous and infection-mediated PTB in adult animals. Surprisingly, adult F1males also confer an enhanced risk of PTB to their control partners. Herein, we used a recently established model of ascending group B Streptococcus (GBS) infection to explore the impact of a maternal versus paternal developmental TCDD exposure on infection-mediated PTB in adulthood. Group B Streptococcus is an important contributor to PTB in women and can have serious adverse effects on their infants. Our studies revealed that although gestation length was reduced in control mating pairs exposed to low-dose GBS, dams were able to clear the infection and bacterial transmission to pups was minimal. In contrast, exposure of pregnant F1females to the same GBS inoculum resulted in 100% maternal and fetal mortality. Maternal health and gestation length were not impacted in control females mated to F1males and exposed to GBS; however, neonatal survival was reduced compared to controls. Our data revealed a sex-dependent impact of parental TCDD exposure on placental expression of Toll-like receptor 2 and glycogen production, which may be responsible for the differential impact on fetal and maternal outcomes in response to GBS infection. [ABSTRACT FROM AUTHOR]

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The effects of the most potent aryl hydrocarbon receptor (AhR) agonist 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) on bile acid (BA) homeostasis was examined in male and female wild-type and AhR-null mice shortly after 4-day exposure, rather than at a later time when secondary non-AhR dependent effects are more likely to occur. TCDD had similar effects on BA homeostasis in male and female mice. TCDD decreased the concentration of total-(Σ) BAs in liver by approximately 50% (all major BA categories except for the non-6,12-OH BAs), without decreasing the expression of the rate limiting BA synthetic enzyme (Cyp7a1) or altering the major BA regulatory pathways (FXR) in liver and intestine. Even though the Σ-BAs in liver were markedly decreased, the Σ-BAs excreted into bile were not altered. TCDD decreased the relative amount of 12-OH BAs (TCA, TDCA, CA, DCA) in bile and increased the biliary excretion of TCDCA and its metabolites (TαMCA, TUDCA); this was likely due to the decreased Cyp8b1 (12α-hydroxylase) in liver. The concentration of Σ-BAs in serum was not altered by TCDD, indicating that serum BAs do not reflect BA status in liver. However, proportions of individual BAs in serum reflected the decreased expression of Cyp8b1. All these TCDD-induced changes in BA homeostasis were absent in AhR-null mice. In summary, through the AhR, TCDD markedly decreases BA concentrations in liver and reduces the 12α-hydroxylation of BAs without altering Cyp7a1 and FXR signaling. The TCDD-induced decrease in Σ-BAs in liver did not result in a decrease in biliary excretion or serum concentrations of Σ-BAs. [ABSTRACT FROM AUTHOR]

2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) is an environmental contaminant and its toxicity is mediated by the aryl hydrocarbon receptor (AHR). Mechanisms of TCDD cardiovascular toxicity consist of oxidative stress, growth factor modulation, and ionic current alteration. It is indicated that the rodent cardiovascular system is a target for TCDD cardiomyopathy. Here, our understanding of TCDD cardiovascular toxicity is reviewed. [ABSTRACT FROM AUTHOR]

FICZ and TCDD, two high-affinity AhR ligands, are reported to have opposite effects on T cell differentiation with TCDD inducing regulatory T cells and FICZ inducing Th17 cells. This dichotomy has been attributed to ligand-intrinsic differences in AhR activation, although differences in sensitivity to metabolismcomplicate the issue. TCDD is resistant to AhR-induced metabolism and produces sustained AhR activation following a single dose in the lg/kg range, whereas FICZ is rapidly metabolized and AhR activation is transient. Nonetheless, prior studies comparing FICZ with TCDD have generally used the same 10-50 lg/kg dose range, and thus the two ligands would not equivalently activate AhR. We hypothesized that highaffinity AhR ligands can promote CD4þ T cell differentiation into both Th17 cells and Tregs, with fate depending on the extent and duration of AhR activation. We compared the immunosuppressive effects of TCDD and FICZ, along with two other rapidly metabolized ligands (ITE and 11-Cl-BBQ) in an acute alloresponse mouse model. The dose and timing of administration of each ligand was optimized for TCDD-equivalent Cyp1a1 induction. When optimized, all of the ligands suppressed the alloresponse in conjunction with the induction of Foxp3- Tr1 cells on day 2 and the expansion of natural Foxp3þ Tregs on day 10. In contrast, a low dose of FICZ induced transient expression of Cyp1a1 and did not induce Tregs or suppress the alloresponse but enhanced IL-17 production. Interestingly, low doses of the other ligands, including TCDD, also increased IL-17 production on day 10. These findings support the conclusion that the dose and the duration of AhR activation by high-affinity AhR ligands are the primary factors driving the fate of T cell differentiation. [ABSTRACT FROM AUTHOR]

Toxic potencies of xenobiotics such as halogenated aromatic hydrocarbons inducing 2,3,7,8-tetrachlorodibenzo-p-dioxin/2,3,7,8-tetrachlorodibenzofuran (TCDD/TCDF)-like effects were investigated by quantitative structure–toxicity relationships (QSTR) using their aryl hydrocarbon receptor (AhR) binding affinity data. A descriptor pool was created using the SPARTAN 10, DRAGON 6.0 and ADMET 8.0 software packages, and the descriptors were selected using QSARINS (v.2.2.1) software. The QSTR models generated for AhR binding affinities of chemicals with TCDD/TCDF-like effects were internally and externally validated in line with the Organization of Economic Co–operation and Development (OECD) principles. The TCDD-based model had six descriptors from DRAGON 6.0 and ADMET 8.0, whereas the TCDF-based model had seven descriptors from DRAGON 6.0. The predictive ability of the generated models was tested on a diverse group of chemicals including polychlorinated/brominated biphenyls, dioxins/furans, ethers, polyaromatic hydrocarbons with fused heterocyclic rings (i.e. phenoxathiins, thianthrenes and dibenzothiophenes) and polyaromatic hydrocarbons (i.e. halogenated naphthalenes and phenanthrenes) with no AhR binding data. For the external set chemicals, the structural coverage of the generated models was 90% and 89% for TCDD and TCDF-like effects, respectively. [ABSTRACT FROM PUBLISHER]

The aim of this study was to assess the effect of different concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on selected parameters of equine gametes under controlled in vitro conditions. Assessments covered maturation of oocytes as well as sperm-cell function and structure. In the first part of the experiment, the influence of different concentrations of TCDD (0.32 ng, 3.2 ng, and 32 ng/mL) on in vitro maturation (IVM) of equine oocytes was evaluated. During IVM, 28.38% of the oocytes reached the metaphase II (matured) stage at a TCDD concentration of 0.32 ng/mL and only 5.14% at a concentration of 3.2 ng/mL. In group, with the highest concentration of TCDD in the medium (32 ng), matured oocytes were not observed. In the second part of experiment, the influence of TCDD (0.32 ng, 3.2 ng, and 32 ng/mL) on sperm parameters, such as motility, plasma membrane integrity, acrosome integrity, mitochondrial activity, lipid peroxidation (LPO), apoptosis, and chromatin status, was evaluated. The present study demonstrates that moderate concentrations of TCDD may activate population of motile sperm cells under in vitro conditions with no influence on sperm-cell structure or LPO. Moreover, the modulation of motility function of sperm was confirmed by the detection of the evident increase of cell number with high mitochondrial potential. Dioxins exert negative impact on both female and male reproductive systems. Thus, an overall analysis of both systems will advance scientific knowledge on the impact of toxic agents on the reproductive system. [ABSTRACT FROM AUTHOR]

Objectives To conduct a cross-sectional morbidity survey among 245 former employees of a pesticide production plant exposed to 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) in New Zealand. Methods Demographic factors and health information were collected in face-to-face interviews. TCDD, lipids, thyroid hormones, glucose and immunoglobulin G (IgG) were determined in non-fasting blood. For 111 participants, a neurological examination was conducted. Associations between health outcomes and working in a TCDD exposed job (prevalence 49%) and serum TCDD concentration ≥ 10 pg/g lipid (18%) were assessed using logistic regression whilst controlling for age, gender, smoking, body mass index and ethnicity. Results Diabetes was more common in those who had worked in TCDD exposed jobs (OR 4.0, 95%CI 1.0–15.4) and in those with serum TCDD ≥ 10 pg/g (OR 3.1, 95%CI 0.9–10.7). Non-fasting glucose levels > 6.6 mmol/l were more common in those with TCDD exposed jobs (OR 3.6, 95%CI 1.0–12.9), as were serum free thyroxine 4 < 12.8 pmol/l (OR 4.5, 95%CI 1.4–14.4), triglycerides > 1.7 mmol/l (OR 2.5, 95%CI 1.1–5.7) and high density lipoprotein cholesterol (HDL) < 1 mmol/l (OR 4.0, 95%CI 1.2–13.2). IgG was negatively associated with TCDD (linear regression p = 0.05). The neurological examination revealed a higher frequency of abnormal reflexes in those with serum TCDD ≥ 10 pg/g (OR 4.8, 95%CI 1.1–21.0). Conclusions In this occupationally exposed population, TCDD was associated with an increased risk of diabetes and a range of subclinical responses in multiple systems (peripheral nervous system, immune system, thyroid hormones and lipid metabolism), several decades after last exposure. These results need to be interpreted with caution due to the small study size and the cross-sectional nature of the study. [ABSTRACT FROM AUTHOR]

The inhibition of bone healing in humans is a well-established effect associated with cigarette smoking, but the underlying mechanisms are still unclear. Recent work using animal cell lines have implicated the aryl hydrocarbon receptor (AhR) as a mediator of the anti-osteogenic effects of cigarette smoke, but the complexity of cigarette smoke mixtures makes understanding the mechanisms of action a major challenge. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, dioxin) is a high-affinity AhR ligand that is frequently used to investigate biological processes impacted by AhR activation. Since there are dozens of AhR ligands present in cigarette smoke, we utilized dioxin as a prototype ligand to activate the receptor and explore its effects on pro-osteogenic biomarkers and other factors critical to osteogenesis using a human osteoblast-like cell line. We also explored the capacity for AhR antagonists to protect against dioxin action in this context. We found dioxin to inhibit osteogenic differentiation, whereas co-treatment with various AhR antagonists protected against dioxin action. Dioxin also negatively impacted cell adhesion with a corresponding reduction in the expression of integrin and cadherin proteins, which are known to be involved in this process. Similarly, the dioxin-mediated inhibition of cell migration correlated with reduced expression of the chemokine receptor CXCR4 and its ligand, CXCL12, and co-treatment with antagonists restored migratory capacity. Our results suggest that AhR activation may play a role in the bone regenerative response in humans exposed to AhR activators, such as those present in cigarette smoke. Given the similarity of our results using a human cell line to previous work done in murine cells, animal models may yield data relevant to the human setting. In addition, the AhR may represent a potential therapeutic target for orthopedic patients who smoke cigarettes, or those who are exposed to secondhand smoke or other environmental sources of aryl hydrocarbons. [ABSTRACT FROM AUTHOR]

Significant prolonged aryl hydrocarbon receptor (AHR) activation, classically exhibited following exposure to 2,3,7,8- tetrachlorodibenzo-p-dioxin, can cause a variety of undesirable toxicological effects. Novel pharmaceutical chemistries also have the potential to cause activation of AHR and consequent toxicities in pre-clinical species and man. Previous methods either employed relatively expensive and low-throughput primary hepatocyte dosing with PCR endpoint, or low resolution overexpressing reporter gene assays. We have developed, validated and applied an in vitro microtitre plate imaging-based medium throughput screening assay for the assessment of endogenous species-specific AHR activation potential via detection of induction of the surrogate transcriptional target Cytochrome P450 CYP1A1. Routine testing of pharmaceutical drug development candidate chemistries using this assay can influence the chemical design process and highlight AHR liabilities. This assay should be introduced such that human AHR activation liability is flagged early for confirmatory testing. [ABSTRACT FROM AUTHOR]

Several cohort studies have reported that dioxin and dioxin-like polychlorinated biphenyls might impair the nervous system and lead to neurological or neurodegenerative diseases in the elder people, but there is limited research on the involved mechanism. By using microarray analysis, we figured out the differentially expressed genes between brain samples from SD rats after low-dose (0.1 μg/(kg▪bw)) dioxin exposure for six months and controls. To investigate the function changes in the course of dioxin exposure, Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed on the differentially expressed genes. And the changes of several picked genes have been verified by real-time PCR. A total of 145 up-regulated and 64 down-regulated genes were identified. The metabolic processes, interleukin-1 secretion and production were significantly associated with the differentially expressed genes. And the genes regulated by dioxin also clustered to cholinergic synapse and long-term potentiation. Candidate biomarker genes such as egr1 , gad2 , gabrb3 , abca1 , ccr5 and pycard may be toxicological targets for dioxin. Furthermore, synaptic plasticity and neuro-immune system may be two principal affected areas by dioxin. [ABSTRACT FROM AUTHOR]

Infection of kidney cells (MDBK) with Bovine Herpesvirus 1 (BoHV-1) is affected by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), which accelerates BoHV-1-induced apoptosis and increases virus replication. Herein, to elucidate the mechanism through TCDD modifies BoHV-1 infection, we analyzed the modulation of a members of Sirtuin proteins family in MDBK cells. We found that mitochondrial SIRT3 was upregulated during infection. This change was accompanied by cytoskeletal rearrangements and cell extensions. All these trends were drastically modified by TCDD. We hypothesize that, taken together, these results might further clarify the processes responsible for the action of TCDD on the BoHV-1 replication, resulting in enhanced virus production. [ABSTRACT FROM AUTHOR]

Recently, we found that 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) – the most toxic dioxin – affected multiple cellular processes in AhR -knocked-down granulosa cells, including the expression of genes and the abundance of proteins. Such alterations may imply the involvement of noncoding RNAs in the remodeling of intracellular regulatory tracks. The aims of the current study were to examine the effects of TCDD on the expression of lncRNAs in AhR -knocked-down granulosa cells of pigs and to indicate potential target genes for differentially expressed lncRNAs (DELs). In the current study, the abundance of AhR protein in porcine granulosa cells was reduced by 98.9% at 24 h after AhR targeted siRNA transfection. Fifty-seven DELs were identified in the AhR -deficient cells treated with TCDD mostly after 3 h (3 h: 56, 12 h: 0, 24 h: 2) after the dioxin treatment. This number was 2.5 times higher than that of intact TCDD-treated granulosa cells. The high number of DELs identified in the early stages of the TCDD action may be associated with a rapid defensive response of cells to harmful actions of this persistent environmental pollutant. In contrast to intact TCDD-treated granulosa cells, AhR -deficient cells were characterized by a broader representation of DELs enriched in GO terms related to the immune response and regulation of transcription and cell cycle. The obtained results support the notion that TCDD may act in an AhR-independent manner. They increase our knowledge on the intracellular mechanism of TCDD action and may in the future contribute to better coping with detrimental consequences of human and animal exposure to TCDD. [Display omitted] • TCDD affected the expression of lncRNAs in AhR-deficient granulosa cells. • DEL action in the cells focused on cell cycle, transcription and immune response. • Identified DELs targeted genes related to non-canonical TCDD pathways. • Number of DELs was 2.5 times higher in AhR-deficient cells than in intact cells. • The highest DEL number was found in both cell types at 3 h of TCDD treatment. [ABSTRACT FROM AUTHOR]

Arsenic trioxide (ATO) is a highly toxic arsenical which has been successfully exploited for treating acute promyelocytic leukemia (APL). Unfortunately, its therapeutic efficacy is accompanied by serious toxicities with undeciphered mechanisms. Cytochrome P450 1A (CYP1A) enzymes undergo modulation by arsenicals, with ensuing critical consequences regarding drug clearance or procarcinogen activation. Here, we investigated the potential of ATO to alter basal and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced CYP1A1/1A2 expressions. Mouse-derived hepatoma Hepa-1c1c7 cells were exposed to 0.63, 1.25, and 2.5 μM ATO with or without 1 nM TCDD. ATO increased TCDD-induced CYP1A1/1A2 mRNA, protein, and activity. Constitutively, ATO induced Cyp1a1/1a2 transcripts and CYP1A2 protein. ATO increased AHR nuclear accumulation and subsequently increased XRE-luciferase reporter activity. ATO enhanced CYP1A1 mRNA and protein stabilities. In conclusion, ATO up-regulates CYP1A in Hepa-1c1c7 cells transcriptionally, post-transcriptionally, and post-translationally. Therefore, ATO can be implicated in clearance-related interactions with CYP1A1/1A2 substrates, or in excessive activation of environmental procarcinogens. [Display omitted] • ATO up-regulates both constitutive and inducible expressions of CYP1A enzymes. • ATO up-regulates CYP1A enzymes transcriptionally through an AHR-dependent mechanism. • ATO up-regulates CYP1A1 enzyme post-transcriptionally through enhancing its mRNA stability. • ATO up-regulates CYP1A1 enzyme post-translationally through enhancing its protein stability. [ABSTRACT FROM AUTHOR]

2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD), the most toxic congener of dioxins, has a proven reproductive toxicity. Due to the lack of evidence on the multigenerational female reproductive toxicity of TCDD through the maternal exposure, the current study aims to evaluate, on the one hand, the acute reproductive toxicity of TCDD on adult female pre-gestational exposed to a critical single dose of TCDD (25 μg/kg) for a week (group referred to as AFnG; adult female/non-gestation). On the other hand, the transcription, hormonal and histological effects of TCDD on the females of two generations F1 and F2, were also investigated after the exposure of pregnant females to TCDD on gestational day 13 (GD13) (group referred to as AFG; adult female/gestation). First, our data showed alternations in the ovarian expressional pattern of certain key genes involved in the detoxification of TCDD as well as in the biosynthesis of steroidal hormones. The expression of Cyp1a1 was highly induced in TCDD-AFnG group, but reduced in both F1 and F2. While the transcripts levels of Cyp11a1 and 3βhsd2 were decreased, Cyp19a1 transcripts were increased as a function of TCDD exposure. This was synchronized with a dramatic increase in the level of estradiol hormone in the females of both experimental groups. Beside a significant reduce in their size and weight, ovaries of TCDD-exposed females showed serious histological alterations marked by atrophy of the ovary, congestion in the blood vessels, necrosis in the layer of granular cells, dissolution of the oocyte and nucleus of ovarian follicles. Finally, the female fertility was dramatically affected across generations with a reduced male\female ratio. Our data indicate that the exposure of pregnant female to TCDD has serious negative effects in the female productive system across generations and suggest the use of hormonal alternation as biomarker to monitor and assess the indirect exposure of these generations to TCDD. [Display omitted] • Pregnant mice on gestation day 13 were exposed to a single dose of TCDD. • Transgenerational effects of TCDD were evaluated in ovaries of F1 and F2. • CYP19A1 expression was remarkably increased in F1 and F2. • Estradiol hormone was seriously increased in mother as well in F1 and F2. • Female fertility was dramatically affected across generations F1 and F2. [ABSTRACT FROM AUTHOR]

• The zebrafish ear is necessary to detect changes in motion, sound, and gravity. • Embryos exposed to TCDD lack structural components of the developing ear. • TCDD exposure impairs formation of the fusion plate and alters pillar topography. • The semicircular canals of the ear are required to detect changes in movement. • Following TCDD exposure embryos fail to establish semicircular canals. Dioxins are a class of highly toxic and persistent environmental pollutants that have been shown through epidemiological and laboratory-based studies to act as developmental teratogens. 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most potent dioxin congener, has a high affinity for the aryl hydrocarbon receptor (AHR), a ligand activated transcription factor. TCDD-induced AHR activation during development impairs nervous system, cardiac, and craniofacial development. Despite the robust phenotypes previously reported, the characterization of developmental malformations and our understanding of the molecular targets mediating TCDD-induced developmental toxicity remains limited. In zebrafish, TCDD-induced craniofacial malformations are produced, in part, by the downregulation of SRY-box transcription factor 9b (sox9b) , a member of the SoxE gene family. sox9b , along with fellow SoxE gene family members sox9a and sox10 , have important functions in the development of the otic placode, the otic vesicle, and, ultimately, the inner ear. Given that sox9b is a known target of TCDD and that transcriptional interactions exist among SoxE genes, we asked whether TCDD exposure impaired the development of the zebrafish auditory system, specifically the otic vesicle, which gives rise to the sensory components of the inner ear. Using immunohistochemistry, in vivo confocal imaging, and time-lapse microscopy, we assessed the impact of TCDD exposure on zebrafish otic vesicle development. We found exposure resulted in structural deficits, including incomplete pillar fusion and altered pillar topography, leading to defective semicircular canal development. The observed structural deficits were accompanied by reduced collagen type II expression in the ear. Together, our findings reveal the otic vesicle as a novel target of TCDD-induced toxicity, suggest that the function of multiple SoxE genes may be affected by TCDD exposure, and provide insight into how environmental contaminants contribute to congenital malformations. [ABSTRACT FROM AUTHOR]

Environmental toxicants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor (AhR), are known to induce host toxicity and structural shifts in the gut microbiota. Key bacterial populations with similar or opposing functional responses to AhR ligand exposure may potentially help regulate expression of genes associated with immune dysfunction. To examine this question and the mechanisms for AhR ligand-induced bacterial shifts, C57BL/6 gnotobiotic mice were colonized with and without segmented filamentous bacteria (SFB) – an immune activator. Mice were also colonized with polysaccharide A producing Bacteroides fragilis – an immune suppressor to serve as a commensal background. Following colonization, mice were administered TCDD (30 μg/kg) every 4 days for 28 days by oral gavage. Quantified with the nCounter® mouse immunology panel, opposing responses in ileal gene expression (e.g., genes associated with T-cell differentiation via the class II major histocompatibility complex) as a result of TCDD dosing and SFB colonization were observed. Genes that responded to TCDD in the presence of SFB did not show a significant response in the absence of SFB, and vice versa. Regulatory T-cells examined in the mesenteric lymph-nodes, spleen, and blood were also less impacted by TCDD in mice colonized with SFB. TCDD-induced shifts in abundance of SFB and B. fragilis compared with previous studies in mice with a traditional gut microbiome. With regard to the mouse model colonized with individual populations, results indicate that TCDD-induced host response was significantly modulated by the presence of SFB in the gut microbiome, providing insight into therapeutic potential between AhR ligands and key commensals.

One of the hallmarks of the acute toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a drastically reduced feed intake by an unknown mechanism. To further elucidate this wasting syndrome, we followed the effects of a single large dose (100 μg/kg) of TCDD on the serum levels of several energy balance-influencing hormones, clinical chemistry variables, and hepatic aryl hydrocarbon receptor (AHR) expression in two rat strains that differ widely in their TCDD sensitivities, for up to 10 days. TCDD affected most of the analytes in sensitive Long-Evans rats, while there were few alterations in the resistant Han/Wistar strain. However, analyses of feed-restricted unexposed Long-Evans rats indicated several of the perturbations to be secondary to energy deficiency. Notable increases in ghrelin and glucagon occurred in TCDD-treated Long-Evans rats alone, which links these hormones to the wasting syndrome. The newly found energy balance regulators, insulin-like growth factor 1 and fibroblast growth factor 21 (FGF-21), appeared to function in concert in body weight loss-induced metabolic state, and FGF-21 was putatively linked to increased lipolysis induced by TCDD. Finally, we demonstrate a reverse set of changes in the AHR protein and mRNA response to TCDD and feed restriction, suggesting that AHR might function also as a physiological regulator, possibly involved in the maintenance of energy balance.

A common feature of nuclear receptors (NRs) is the transformation of external cell signals into specific transcriptions of the signal molecule. Signal molecules function as ligands for NRs and, after their uptake, activated NRs form homo- or heterodimers at promoter recognition sequences of the specific genes in the nucleus. Another common feature of NRs is their dependence on coactivators, which bridge the basic transcriptional machinery and other cofactors to the target genes, in order to initiate transcription and to unwind histone-bound DNA for exposing additional promoter recognition sites via their histone acetyltransferase (HAT) function. In this review, we focus on our recent findings related to the recruitment of steroid receptor coactivator 1 (SRC1/NCoA1) by the estrogen receptor-α (ERα) and by the arylhydrocarbon receptor/arylhydrocarbon receptor nuclear translocator 1 (AhR/ARNT1) complex. We also describe the extension of our previously published findings regarding the binding between ARNT1.1 exon16 and SRC1e exon 21, via in silico analyses of androgen receptor (AR) NH2-carboxyl-terminal interactions, the results of which were verified by in vitro experiments. Based on these data, we suggest a newly derived tentative binding site of nuclear coactivator 2/glucocorticoid receptor interacting protein-1/transcriptional intermediary factor 2 (NCOA-2/ GRIP-1/TIF-2) for ARNT1.1 exon 16. Furthermore, results obtained by immunoprecipitation have revealed a second leucine-rich binding site for hARNT1.1 exon 16 in SRC1e exon 21 (LSSTDLL). Finally, we discuss the role of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as an endocrine disruptor for estrogen related transcription.

The prototype dioxin congener 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is known to exert anti-estrogenic effects via activation of the aryl hydrocarbon receptor (AhR) by interfering with the regulation of oestrogen homeostasis and the estrogen receptor α (ERα) signalling pathway. The AhR/ER cross-talk is considered to play a crucial role in TCDD- and E2-dependent mechanisms of carcinogenesis, though the concerted mechanism of action in the liver is not yet elucidated. The present study investigated TCDD's impact on the transcriptional cross-talk between AhR and ERα and its modulation by 17β-estradiol (E2) in the human hepatoma cell line HepG2, which is AhR-responsive but ERα-negative. Transient transfection assays with co-transfection of hERα and supplementation of receptor antagonists showed anti-estrogenic action of TCDD via down-regulation of E2-induced ERα signaling. In contrast, enhancement of AhR signaling dependent on ERα was observed providing evidence for increased cytochrome P450 (CYP) induction to promote E2 metabolism. However, relative mRNA levels of major E2-metabolizing CYP1A1 and 1B1 and the main E2-detoxifying catechol-O-methyltransferase were not affected by the co-treatments. This study provides new evidence of a TCDD-activated AhR-mediated molecular AhR/ERα cross-talk mechanism at transcriptional level via indirect inhibition of ERα and enhanced transcriptional activity of AhR in HepG2 cells.

A hydrophilic interaction liquid chromatography (HILIC)−ultra high-pressure liquid chromatography (UHPLC) coupled with tandem mass spectrometry (MS/MS) method was developed and applied to profile metabolite changes in human Huh-7 cells exposed to the potent aryl hydrocarbon receptor (AHR) ligand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Comparisons of sensitivity (limit of detection as low as 0.01 µM) and reproducibility (84% of compounds had an interday relative standard deviation (RSD) less than 10.0%; 83% of compounds had an intraday RSD less than 15.0%) were assessed for all the metabolites. The exposure of Huh-7 cells to the hepatotoxic carcinogen TCDD at low doses (1 nM and 10 nM for 4 h and 24 h, respectively) was reflected by the disturbance of amino acid metabolism, energy metabolism (glycolysis, TCA cycle), and nucleic acid metabolism. TCDD caused a significant decrease in amino acids such as serine, alanine, and proline while promoting an increase in arginine levels with 24 h treatment. Energy metabolism intermediates such as phosphoenolpyruvate and acetyl−CoA and nucleosides such as UMP, XMP, and CMP were also markedly decreased. These results support the application of HILIC−UHPLC−MS/MS for robust and reliable analysis of the cellular response to environmentally relevant toxicants at lower doses.

Background: The neurological effects of short-term dioxin exposure during the fetal period is an important health risk in humans. Here, we investigated the effects of dioxin on neural differentiation using human embryonic stem cells (hESCs) to evaluate human susceptibility to dioxin. Methods: Using an enzymatic bulk passage, neural differentiation from human ESCs was carried out. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) was added to various stages of culture. The expression levels of the neuronal markers microtubule-associated protein 2 (MAP2) and thyroxine hydroxylase (TH) were measured by RT-qPCR and image analysis of immunostaining. Results: Although early-stage neuronal cells are quite resistant to TCDD, the numbers of neural rosettes and increases in mRNA expression levels and the number of cells positive for MAP2 and TH were significant by temporal exposure at embryoid body stage (Day9-exposure group). In contrast, the TCDD exposures against ESCs (Day0-exposure group) and differentiated neural cells (Day35-exposure group) were not affected at all. The increment was similarly observed by continuous exposure of TCDD from Day9 through Day60. Conclusions: These results indicated that dioxin exposure during the early stage of differentiation from hESCs increases the contents of neuronal cells, especially TH-positive neuronal cells. Regulations of aryl hydrocarbon receptor (AHR) signaling in an early stage of embryogenesis should be investigated extensively to understand the mechanism underlying the increase in neuronal cell populations and to apply the knowledge to regenerative medicine.

Here, we investigate the role of RelB in the regulation of genes which were identified to be induced in an aryl hydrocarbon receptor (AhR)-dependent manner and critically involved in regulation of immune responses. We analyzed the expression of genes of the AhR gene battery, cytokines, and immune regulatory enzymes in bone marrow-derived macrophages (BMM) and thymus of B6 wildtype (wt) mice and RelB knockout (RelB−/−) mice after treatment with various AhR ligands. The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced expression of indoleamine 2,3-dioxygenase 1 (IDO1) and IDO2 was significantly repressed in thymus of RelB−/− mice but not in BMM derived from RelB−/− mice. Interestingly, the induced and basal expression of the cytokines interleukin (IL)-17A, IL-22, and CCL20 required the functional expression of RelB. The RelB-dependent expression of CCL20 was induced by the AhR ligands TCDD and 6-formylindolo[3,2-b]carbazole (FICZ), whereas indole-3-carbinol (I3C) suppressed CCL20 in lipopolysaccharide (LPS)-activated wt BMM. The LPS-induced expression of IL-6 and IL-10 was enhanced by TCDD and FICZ, whereas I3C significantly suppressed these cytokines in BMM. The exposure to FICZ led to higher increases of IL-17A and IL-22 mRNA compared to the effect of TCDD or I3C in thymus of wt mice. On the other hand, TCDD was the strongest inducer of CYP1A1, AhR Repressor (AhRR), and IDO2. In summary, these findings provide evidence for the important role of RelB in the transcriptional regulation of cytokines and enzymes induced by AhR ligands.

IMA-08401 (C2) is a novel aryl hydrocarbon receptor (AHR) agonist and selective AHR modulator (SAHRM) that is structurally similar to laquinimod (LAQ). Both compounds are converted to the AHR-active metabolite DELAQ (IMA-06201) in vivo. SAHRMs have been proposed as therapeutic options for various autoimmune disorders. Clinical trials on LAQ have not reported any significant toxic outcomes and C2 has shown low toxicity in rats; however, their functional resemblance to the highly toxic AHR agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) raises questions. Here, we characterize the hepatic transcriptomic changes induced by acute (single-dose) and subacute exposure (repeated dosing for 5 days followed by a 5-day recovery period) to C2 in Sprague-Dawley rats. Exposure to C2 leads to activation of the AHR, as shown by altered transcription of Cyp1a1. We identify a heightened response early after exposure that drops off by day 10. Acute exposure to C2 leads to changes to transcription of genes involved in antiviral and antibacterial responses, which highlights the immunomodulator effects of this AHR agonist. Subacute exposure causes an oxidative stress response in the liver, the consequences of which require further study on target tissues such as the CNS and immune system, both of which may be compromised in this patient population.

Dioxins and related compounds induce morphological abnormalities in developing animals in an aryl hydrocarbon receptor (AhR)-dependent manner. Here we review the studies in which 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is used as a prototypical compound to elucidate the pathogenesis of morphological abnormalities. TCDD-induced cleft palate in fetal mice involves a delay in palatogenesis and dissociation of fused palate shelves. TCDD-induced hydronephrosis, once considered to be caused by the anatomical obstruction of the ureter, is now separated into TCDD-induced obstructive and non-obstructive hydronephrosis, which develops during fetal and neonatal periods, respectively. In the latter, a prostaglandin E2 synthesis pathway and urine concentration system are involved. TCDD-induced abnormal development of prostate involves agenesis of the ventral lobe. A suggested mechanism is that AhR activation in the urogenital sinus mesenchyme by TCDD modulates the wingless-type MMTV integration site family (WNT)/β-catenin signaling cascade to interfere with budding from urogenital sinus epithelium. TCDD exposure to zebrafish embryos induces loss of epicardium progenitor cells and heart malformation. AHR2-dependent downregulation of Sox9b expression in cardiomyocytes is a suggested underlying mechanism. TCDD-induced craniofacial malformation in zebrafish is considered to result from the AHR2-dependent reduction in SRY-box 9b (SOX9b), probably partly via the noncoding RNA slincR, resulting in the underdevelopment of chondrocytes and cartilage.

Chemokines are components of the skin microenvironment, which enable immune cell chemotaxis. Traditionally, transcription factors involved in inflammatory signaling (eg, NFjB) are important mediators of chemokine expression. To what extent xenobiotics and their associated receptors control chemokine expression is poorly understood. The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor known to mediate physiological responses in the skin through the regulation of genes involved in xenobiotic metabolism, epidermal differentiation, and immunity. Here, we demonstrate that AHR activation within primary mouse keratinocytes regulates the expression of a neutrophil directing chemokine (C-X-C motif) ligand 5 (Cxcl5). AHR-mediated regulation of Cxcl5 is because of direct transcriptional activity upon treatment with AHR agonists such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Additionally, AHR mediates enhanced induction of Cxcl5 upon exposure to an agonist and the inflammatory cytokine interleukin 1 beta. This synergy is confined primarily to keratinocytes, as dermal fibroblasts did not achieve the same level of combinatorial induction. AHR-specific antagonists were able to reduce basal and induced levels of Cxcl5, demonstrating the potential for pharmacological intervention. Exposure of C57BL/6 J mice to ultraviolet (UV) light followed by topical treatment with the AHR agonist formylindolo(3,2-b)carbazole (FICZ) significantly induced Cxcl5 expression in skin compared with UV alone, and this response was absent in Ahr-/- mice. These results establish AHR as an important mediator of Cxcl5, with implications for the treatment of inflammatory skin diseases. [ABSTRACT FROM AUTHOR]

Dioxins have come to the agenda first in 1976 after the "Seveso Accident". It is a general term and they are one of the persistent organic pollutants, and made of two rings of benzene with carbon, chlorine and oxygen atoms. They are toxic and carsinogenic. The mostly known compound is 2,3,7,8-tetraklorodinezo-p-dioksin (TCDD), which is the most toxic compound among dioxins. They stay in nature and do not dissolve in water, but they dissolve in adipose tissue, so they accumulate in humans. Their half-life changes between 7 and 8 years. The emitted dioxins from the regarding sources, are transmitted to the ground and plants by rain, and they are taken by animals and humans via food chain. Although this route is the most frequent one, they are also taken by respiratory system. They show biologic-toxic effects in humans. These effects are seen in thyroid functions, reproductive and endocrinologic systems, and carsinogenic effects such as sarcomas of soft tissue, lung cancer and nonhodgkin lymphoma can also be observed. In prevention, the reduction of occurance of these substances as by-products; limitation of exportation and importation; periodic control of related sectors and increasing the awareness of the related population are important. In Turkey, according to the Stockholm Convention; there is a "National Application Plan" and an inventory developed by the Ministry of Food, Agriculture and Livestock. [ABSTRACT FROM AUTHOR]

Polychlorinated dibenzo-p-dioxins (PCDDs) are highly toxic to humans. The search for novel and effective methods and materials for detecting or removing these gas pollutants is becoming more important and urgent. With its high specific surface area, abundance, and variety of potential applications, phosphorene has attracted much research interest. In this study, density functional theory was used to study the interactions between a doped phosphorene sheet and a tetrachlorodibenzo-p-dioxin (TCDD) molecule. The initial configurations of the TCDD and metallic (Ca or Ti) or nonmetallic (S and Se) dopants were investigated during the TCDD–phosphorene interaction study. Adsorption energy, isosurface of electron density difference, and density of states analysis were utilized to explore the interactions between TCDD and phosphorene. The results indicated that Ca dopant effectively improved the interaction between TCDD and phosphorene. Se dopant reduced the interaction between TCDD and phosphorene. Combining interactions between TCDD and the pristine, Ca-doped, and Se-doped phosphorenes, phosphorene could be a promising candidate for TCDD sensing and removal. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) is an increasingly attractive remediation alternative for the sequestration of dioxins at contaminated sites globally. However, the potential for AC to reduce the bioavailability of dioxins in mammals and the residing gut microbiota has received less attention. This question was partially answered in a recent study examining 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD)-induced hallmark toxic responses in mice administered with TCDD sequestered by AC or freely available in corn oil by oral gavage. Results from that study support the use of AC to significantly reduce the bioavailability of TCDD to the host. Herein, we examined the bioavailability of TCDD sequestered to AC on a key murine gut commensal and the influence of AC on the community structure of the gut microbiota. The analysis included qPCR to quantify the expression of segmented filamentous bacteria (SFB) in the mouse ileum, which has responded to TCDD-induced host toxicity in previous studies and community structure via sequencing the 16S ribosomal RNA (rRNA) gene. The expression of SFB 16S rRNA gene and functional genes significantly increased with TCDD administered with corn oil vehicle. Such a response was absent when TCDD was sequestered by AC. In addition, AC appeared to have a minimal influence on murine gut community structure and diversity, affecting only the relative abundance of Lactobacillaceae and two other groups. Results of this study further support the remedial use of AC for eliminating bioavailability of TCDD to host and subsequent influence on the gut microbiome. [ABSTRACT FROM AUTHOR]

Several genotoxic and non-genotoxic agents have been reported to cause delayed genetic damage in the progeny of the exposed cells. Such induced genomic instability (IGI) may be a driving force in carcinogenesis, and it is thus highly important to understand the cellular events accompanying it. The aim of this study was to investigate whether 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) affects mitochondrial integrity and can consequently induce genomic instability. Mitochondrial integrity was evaluated by measuring mitochondrial superoxide production, mitochondrial membrane potential, and mitochondrial activity. Micronucleus formation was used to assess immediate genetic damage and IGI. The assays were performed either immediately, 8 or 15 d after the exposure. Mitochondrial superoxide production was increased by TCDD immediately after the exposure. No consistent effects on mitochondrial integrity were observed at later time points, although slightly decreased mitochondrial membrane potential at 8 d and increased mitochondrial superoxide potential production at 15 after exposure were observed in the TCDD-exposed cells. TCDD did not cause immediate genetic damage, and significant IGI was not observed. In conclusion, the present results suggest that immediate TCDD-induced increase in mitochondrial superoxide level does not lead to persistent loss of mitochondrial integrity or IGI in human SH-SY5Y neuroblastoma cells. [ABSTRACT FROM AUTHOR]

2,3,7,8-Tetrachlorodibenzo- p -dioxin (TCDD; polycyclic aromatic hydrocarbon) is a persistent and ubiquitous environmental contaminant that causes a wide variety of deleterious effects. In this study, the DNA damage and apoptotic activity induced by TCDD was examined using in silico and in vitro approaches. In silico study showed that conformational changes and energies involved in the binding of TCDD to cytochrome P450 1B1 (CYP1B1) were crucial for its target proteins. Moreover, activated TCDD had high affinity to bind with aryl hydrocarbon receptor (AhR), with a binding energy of −564.7 Kcal/mol. Further, TCDD-CYP1B1 complex showed strong binding affinity for caspase 3, showing a binding energy of −518.5 Kcal/mol, and the docking of caspase inhibitors in the complex showed weak interaction with low binding energy as compared to TCDD-CYP1B1 caspase complexes. Interestingly, TCDD-induced apoptosis was significantly suppressed in Ac-DEVD-CMK-pretreated cells. The DNA damage activity of TCDD was quantified by comet tail formation and γ-H2AX foci formation in HaCaT cells. The role of CYP1B1 and AhR in DNA damage and apoptosis was demonstrated, and clotrimazole as well as knockdown of CYP1B1 and AhR could inhibit TCDD activation and suppress DNA damage followed by apoptosis in HaCaT cells. Moreover, TCDD increased expression of p53 and PUMA and our data showed that TCDD induced DNA damage followed by p53-mediated apoptosis. This study highlights the critical role of CYP1B1 and AhR in TCDD activity and proposes that inhibition of these key molecules might serve as a potential therapeutic approach for treatment of allergy and cancer. [ABSTRACT FROM AUTHOR]

Environmental toxicants such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor (AhR), are known to induce host toxicity and structural shifts in the gut microbiota. Key bacterial populations with similar or opposing functional responses to AhR ligand exposure may potentially help regulate expression of genes associated with immune dysfunction. To examine this question and the mechanisms for AhR ligand-induced bacterial shifts, C57BL/6 gnotobiotic mice were colonized with and without segmented filamentous bacteria (SFB) – an immune activator. Mice were also colonized with polysaccharide A producing Bacteroides fragilis – an immune suppressor to serve as a commensal background. Following colonization, mice were administered TCDD (30 μg/kg) every 4 days for 28 days by oral gavage. Quantified with the nCounter® mouse immunology panel, opposing responses in ileal gene expression (e.g., genes associated with T-cell differentiation via the class II major histocompatibility complex) as a result of TCDD dosing and SFB colonization were observed. Genes that responded to TCDD in the presence of SFB did not show a significant response in the absence of SFB, and vice versa. Regulatory T-cells examined in the mesenteric lymph-nodes, spleen, and blood were also less impacted by TCDD in mice colonized with SFB. TCDD-induced shifts in abundance of SFB and B. fragilis compared with previous studies in mice with a traditional gut microbiome. With regard to the mouse model colonized with individual populations, results indicate that TCDD-induced host response was significantly modulated by the presence of SFB in the gut microbiome, providing insight into therapeutic potential between AhR ligands and key commensals. [ABSTRACT FROM AUTHOR]

Contaminant involvement in the pathophysiology of obesity is widely recognized. It has been shown that low dose and chronic exposure to endocrine disruptor compounds (EDCs) potentiated diet- induced obesity. High and acute exposure to 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD), a persistent organic pollutant (POP) and an EDC with anti-estrogenic property, causes wasting syndrome . However at lower doses, the TCDD metabolic effects remain poorly understood. We investigated the obesogenic effect during chronic exposure of TCDD at 1 μg/kg body weight (bw)/week in adult C57BL/6J mice fed with a high fat diet (HFD) and exposed from 10 to 42 weeks old to TCDD or equal volume of vehicle by intragastric gavage. Under these conditions, TCDD was obesogenic in adult mice (7% in males and 8% in females), which was linked to fat mass. A sex effect was observed in the fat mass distribution in adipose tissue and in the hepatic triglyceride content evolution. In visceral fat pad weight, we observed a decrease (11%) in males and an increase (14%) in females. The hepatic triglyceride content increase (41%) in females only. TCDD failed to induce any change in plasma parameters regarding glucose and lipid homeostasis. Messenger ribonucleic acid (mRNA) levels involved in adipose tissue and hepatic metabolism, inflammation, xenobiotic metabolism and endocrine disruption were differently regulated between males and females. In conclusion, these results provide new evidence that dioxin, a POP and EDC can be obesogenic for adult mice with multi-organ effects. [ABSTRACT FROM AUTHOR]

The study was conducted in order to compare the in vitro effect of 2,3,7,8-tetrachlorodibenzo-pdioxin (TCDD), 3,3′,4,4′,5-pentachlorobiphenyl (PCB 126) and 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) on the number of apoptotic cells and the activity of caspase-3 in chicken ovarian follicles. The ovarian stroma, white (WF) and yellowish (YF) prehierarchical follicles and fragments of the theca and granulosa layers of the 3 largest preovulatory follicles (F3-F1) were in vitro exposed to TCDD (10 nM), PCB 126 (10 nM) and PCB 153 (10 μM) for 24 h. After incubation the number of apoptotic cells and caspase-3 activity were determined by TUNEL method and fluorometric assay, respectively. PCB 126 and PCB 153 increased the number of apoptotic cells in the ovarian stroma while TCDD and PCB 126 elevated it in the WF follicles. Under the control conditions, caspase-3 activity steadily increased along with maturation of the follicles, reaching the highest level in the theca layer of the F1 follicle. The activity of this enzyme in the granulosa layer of F3-F1 follicles was on average 60% lower in comparison to the stroma. Exposure to TCDD elevated caspase-3 activity in prehierarchical follicles and in the granulosa layer of F2 and F1 preovulatory follicles. On the contrary, PCB 126 exerted a suppressive effect on caspase-3 activity in the WF follicles and the granulosa layer of the F2 follicle, and PCB 153 in the theca layer of F2 and F1 and the granulosa layer of the F3 follicle. In conclusion, the results indicate that TCDD and PCBs affect apoptosis in chicken ovarian follicles and in consequence may disrupt follicle development. [ABSTRACT FROM AUTHOR]

This reminiscing review article is an account of the author's fascination and involvements with mass spectrometry from the perspective of an organic chemist with an interest in natural product chemistry. It covers a period from 1961 through the mid 1990s as mass spectrometry evolved form a novelty technique to become a most widely used analytical technique. Following a brief synopsis of my pathway to mass spectrometry, my research efforts in this field are presented with a focus mainly on evolving principles and technologies which I had personal involvements with. To provide historical perspectives, discussions of these developments are accompanied by brief outlines of the relevant state-of-the-art, shedding light on the technical and conceptual challenges encountered during those early days in mass spectrometry. Examples are presented of my involvements with basic and applied research in mass spectrometry during graduate studies at Stanford University and close to three decade tenure in pharmaceutical research at Syntex Research. My basic research interests focused mainly on principles of electron ionization induced fragmentation mechanisms, with an emphasis on steroids and other model compounds. Extensive deuterium labeling evidence was used to determine the fragmentation mechanisms of the diagnostically significant ions in the spectra of numerous model compounds, uncovering examples of wide-ranging hydrogen transfers, skeletal rearrangements, methyl and phenyl migrations, stereoselective fragmentations and low and high energy fragmentation processes. Depiction of the industrial research phase of my career includes comments on the pivotal role mass spectrometry played on advancing modern pharmaceutical research. Examples are presented of involvements with instrumental developments and a few select cases of applied research, including studies of bile mechanisms in vertebrates, identification of bisphenol-A leaching from sterilized polycarbonate containers, high sensitivity TCDD analyses and other projects. Reflecting on my services for the mass spectrometry society, involvements with the co-founding and 12 year chairing of the Asilomar Conference on Mass Spectrometry and founding of the Bay Area Mass Spectrometry regional MS discussion group, as part of my services for the mass spectrometry community, are presented in some detail. © 2016 Wiley Periodicals, Inc. Mass Spec Rev 36:520-542, 2017 [ABSTRACT FROM AUTHOR]

2,3,7,8-Tetrachlorodibenzo- p -dioxin (TCDD) is a toxic man-made chemical compound contaminating the environment. An exposure of living organisms to TCDD may result in numerous disorders, including reproductive pathologies. The aim of the current study was to examine the effects of TCDD on the transcriptome of porcine granulosa cell line AVG-16. By employing next-generation sequencing (NGS) we aimed to identify genes potentially involved in the mechanism of TCDD action and toxicity in porcine granulosa cells. The AVG-16 cells were treated with TCDD (100 nM) for 3, 12 or 24 h, and afterwards total cellular RNA was isolated and sequenced. In TCDD-treated cells we identified 141 differentially expressed genes (DEGs; p adjusted < 0.05 and log2 fold change ≥1.0). The DEGs were assigned to GO term, covering biological processes, molecular functions and cellular components. Due to the large number of genes with altered expression, in the current study we analyzed only the genes involved in follicular growth, development and functioning. The obtained results showed that TCDD may affect ovarian follicle fate by influencing granulosa cell cycle, proliferation and DNA repair. The demonstrated over-time changes in the quantity and quality of genes being affected by TCDD treatment showed that the effects of TCDD on granulosa cells changed dramatically between 3-, 12- and 24-h of cell culture. This finding indicate that timing of gene expression measurement is critical for drawing correct conclusions on detailed relationships between the TCDD-affected genes and resulting intracellular processes. These conclusions have to be confirmed and extended by research involving proteomic and functional studies. [ABSTRACT FROM AUTHOR]

The aryl hydrocarbon receptor (AHR) mediates the toxicity of dioxins, but also plays important physiological roles. Selective AHR modulators, which elicit some effects imparted by this receptor without causing the marked toxicity of dioxins, are presently under intense scrutiny. Two novel such compounds are IMA-08401 ( N-acetyl-N-phenyl-4-acetoxy-5-chloro-1,2-dihydro-1-methyl-2-oxo-quinoline-3-carboxamide ) and IMA-07101 ( N-acetyl-N- ( 4-trifluoromethylphenyl ) -4-acetoxy-1,2-dihydro-5-methoxy-1-methyl-2-oxo-quinoline-3-carboxamide ). They represent, as diacetyl prodrugs, AHR-active metabolites of the drug compounds laquinimod and tasquinimod, respectively, which are intended for the treatment of autoimmune diseases and cancer. Here, we toxicologically assessed the novel compounds in Sprague-Dawley rats, after a single dose (8.75–92.5 mg/kg) and 5-day repeated dosing at the highest doses achievable (IMA-08401: 100 mg/kg/day; and IMA-07101: 75 mg/kg/day). There were no overt clinical signs of toxicity, but body weight gain was marginally retarded, and the treatments induced minimal hepatic extramedullary haematopoiesis. Further, both the absolute and relative weights of the thymus were significantly decreased. Cyp1a1 gene expression was substantially increased in all tissues examined. The hepatic induction profile of other AHR battery genes was distinct from that caused by 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD). The only marked alterations in serum clinical chemistry variables were a reduction in triglycerides and an increase in 3-hydroxybutyrate. Liver and kidney retinol and retinyl palmitate concentrations were affected largely in the same manner as reported for TCDD. In vitro , the novel compounds activated CYP1A1 effectively in H4IIE cells. Altogether, these novel compounds appear to act as potent activators of the AHR, but lack some major characteristic toxicities of dioxins. They therefore represent promising new selective AHR modulators. [ABSTRACT FROM AUTHOR]