To 2,3,7,8-tetrachlorodibenzo-p-dioxin Research Articles

Levels of polychlorinated dibenzo-p-dioxins, dibenzofurans (PCDD/Fs) and dioxin-like PCBs in free range eggs from Vietnam, including potential health risks

Chicken and duck eggs collected from three different areas in Vietnam were examined for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). These regions included a background area, an area sprayed with Agent Orange and the Bien Hoa airbase area where Agent Orange was handled by the US Army. The latter area now is inhabited and people keep their own laying hens. Egg samples were first screened with an in vitro reporter gene bioassay and a selection was analyzed by GC/HRMS. Samples from Bien Hoa airbase showed very high PCDD/F levels, up to 249pg dioxin-equivalents (TEQ)/g fat, mainly due to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). In the sprayed areas, levels (3.2–8.2pgTEQg−1) were comparable to those observed in background areas (3.2–8.2pgTEQg−1 fat). The estimated average consumption of 22gd−1 of the highly contaminated eggs will result in a 2-fold exceedance of the current exposure limits for adults and 5-fold for children, even without considering other contaminated food sources. This indicates a potential health risk from consumption of these highly contaminated eggs, which were not yet considered as a source for exposure to PCDD/Fs of people living in the highly contaminated areas.

0313 An assessment of the impact of misclassification error on an estimate of effect for occupational exposure to TCDD-contaminated chemicals and ischaemic heart disease0313 An assessment of the impact of misclassification error on an estimate of effect for occupational exposure to TCDD-contaminated chemicals and ischaemic heart disease

ObjectivesTo quantify the effect of exposure and disease misclassification on the odds ratio (OR) for ischaemic heart disease (IHD) mortality in a retrospective cohort study of trichlorophenol workers exposed to...

Activation of the aryl hydrocarbon receptor during development leads to an altered CD4+ T cell response to influenza A virus infection (IRC2P.448)

Abstract Epidemiological evidence suggests developmental exposures to certain pollutants correlate with lower antibody responses to childhood immunizations, but the mechanism by which this occurs is unknown. The transcription factor aryl hydrocarbon receptor (AhR) is activated by a variety of chemicals, expressed by immune cells, and has been shown to influence immune function, such as CD4+ T cell subset specification and function. The effect of maternal exposure to AhR ligands on the function of CD4+ T cells has never been directly examined. We report here the consequences of developmental triggering of the AhR on the CD4+ T cell response to influenza virus infection. Mice developmentally exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the prototypical AhR ligand, have fewer activated, virus-specific CD4+ T cells, Th1, and T follicular helper cells, yet an increase in regulatory T cells in their lung draining lymph nodes. Consistent with this, developmentally exposed mice have a reduction in their class-switched, virus-specific antibody response. By using reciprocal adoptive transfers, we demonstrate that the effects of developmental activation of the AhR on CD4+ T cells occur through both direct and indirect pathways. These findings suggest changes in the functional capacity of CD4+ T cells may be a key contributor to the decreased antibody response to immunizations observed in children of mothers exposed to AhR-binding chemicals.

Dioxin-induced fetal growth retardation: the role of a preceding attenuation in the circulating level of glucocorticoid.

Exposure of pregnant rats to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) at a low dose causes developmental disorders such as growth retardation and sexual immaturity in their pups. Our previous studies have demonstrated that TCDD attenuates the expression of pituitary luteinizing hormone in fetuses, resulting in the impairment of sexual behavior after they reach maturity. In this study, we focused on growth disturbance and investigated whether TCDD affects the expression of growth hormone (GH), another pituitary hormone which is essential for normal development in perinatal pups. The result showed that maternal exposure to TCDD (1 µg/kg) at gestational day (GD) 15 reduced the fetal expression of GH from the onset at GD18. In accordance with this, TCDD attenuated the pup weight during the perinatal period. We then examined the effect of TCDD on the serum concentration of corticosterone, which plays a key role in the proliferation of GH-producing cells, and found that TCDD reduces the circulating level of corticosterone in the mothers at GD18 and the male fetuses at GD19. The reduction in fetuses seems to be due to increased inactivation rather than reduced synthesis, because TCDD induces the fetal expression of hepatic enzymes participating in the metabolism of glucocorticoids without changing the expression of steroidogenic proteins in the pituitary-adrenal axis. Supplying corticosterone to TCDD-exposed mothers restored or tended to restore a TCDD-induced reduction in pup weight as well as the levels of pituitary GH mRNA and serum GH. These results suggest that TCDD lowers GH expression and growth retardation owing, at least partially, to a reduction in the circulating level of glucocorticoid in pregnant mothers and their fetuses.

Relative Potency for Altered Humoral Immunity Induced by Polybrominated and Polychlorinated Dioxins/Furans in Female B6C3F1/N Mice

The use of brominated flame retardants and incineration of bromine-containing materials has lead to an increase in polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) in the environment. Measurable amounts of PBDD/Fs have been detected in soil, seafood, and human breast milk and serum. Studies indicate that the relative potencies of some PBDD/Fs based on enzyme induction are equivalent to those of some polychlorinated dibenzo-p-dioxins and dibenzofurans. To assess the humoral immunity relative potencies of PBDD/Fs and compare them to their chlorinated analogs, female B6C3F1/N mice received a single oral exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,7,8-tetrabromodibenzofuran (TBDF), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 1,2,3,7,8-pentabromodibenzofuran (1PeBDF), 1,2,3,7,8-pentachlorodibenzofuran (1PeCDF), 2,3,4,7,8-pentabromodibenzofuran (4PeBDF), 2,3,4,7,8-pentachlorodibenzofuran (4PeCDF), 2,3-dibromo-7,8-dichlorodibenzo-p-dioxin (DBDCDD), or 2,3,7-tribromodibenzo-p-dioxin (TriBDD). Inhibition of the immunoglobulin M (IgM) antibody forming cell response was measured 4 days following immunization with sheep red blood cells. The data were fit to a Hill model to estimate the ED50 for inhibition. Expression of xenobiotic metabolizing enzyme (XME) and thyroxine transport protein (Ttr) genes in liver was measured by PCR to assess aryl hydrocarbon-mediated responses. TCDD, TBDF, TCDF, 1PeBDF, 4PeBDF, 4PeCDF, and DBDCDD suppressed the IgM antibody response and Ttr gene expression, and upregulated phase I XME genes. 1PeCDF suppressed the IgM antibody response but only upregulated phase I XME genes; TriBDD had no effect on antibody response. The rank order of potency (ED50) for these chemicals was TCDD>TBDF>4PeBDF>TCDF/4PeCDF/1PeBDF>1PeCDF. Whereas TCDD was the most potent compound tested, the brominated analogs were more potent than their chlorinated analogs, suggesting that these compounds should be considered in toxic equivalency factor evaluation and risk assessment.

MP29-02 INCREASED EXPRESSION OF ARYL HYDROCARBON RECEPTOR IN CLEAR CELL RENAL CELL CARCINOMA AND INFILTRATING LYMPHOCYTES: IMPLICATIONS FOR CANCER INVASION, PROGNOSIS AND TUMOR IMMUNITY

You have accessJournal of UrologyKidney Cancer: Basic Research II1 Apr 2014MP29-02 INCREASED EXPRESSION OF ARYL HYDROCARBON RECEPTOR IN CLEAR CELL RENAL CELL CARCINOMA AND INFILTRATING LYMPHOCYTES: IMPLICATIONS FOR CANCER INVASION, PROGNOSIS AND TUMOR IMMUNITY Masaru Ishida, Shuji Mikami, Takeo Kosaka, Ryuichi Mizuno, Eiji Kikuchi, Akira Miyajima, Ken Nakagawa, Yasunori Okada, and Mototsugu Oya Masaru IshidaMasaru Ishida More articles by this author , Shuji MikamiShuji Mikami More articles by this author , Takeo KosakaTakeo Kosaka More articles by this author , Ryuichi MizunoRyuichi Mizuno More articles by this author , Eiji KikuchiEiji Kikuchi More articles by this author , Akira MiyajimaAkira Miyajima More articles by this author , Ken NakagawaKen Nakagawa More articles by this author , Yasunori OkadaYasunori Okada More articles by this author , and Mototsugu OyaMototsugu Oya More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2014.02.744AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Aryl hydrocarbon receptor (AhR) is involved in xenobiotic-induced toxicity, and it is also associated with cancer cell invasion and tumor immunity. The aim of this study is to investigate the clinical significance of expression of AhR in RCC and infiltrating lymphocytes. Furthermore, we elucidate the role of AhR in cancer cells by regulating the expression using its ligand or siRNA for AhR in vitro. METHODS A total of 120 RCC patients were included in the study. The median age was 60 years (25 to 87) and the median follow-up was 63 months (0.3 to 151). The AhR expression in cancer cells and infiltrating lymphocytes in stromal tissues adjacent to cancer nests was investigated by immunohistochemistry and its associations with the clinicopathological parameters and prognosis were analyzed. AhR signal pathway was activated by exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a ligand of AhR, or AhR expression was down-regulated by siRNA in an RCC cell line, 786-O. Subsequently, cancer cell invasion and expression of MMPs were investigated using MatrigelTM and real-time quantitative PCR. RESULTS The AhR expression in RCC and infiltrating lymphocytes was significantly higher in clear cell RCC compared to non-clear cell RCC (p < 0.05). Therefore, further experiments were confined to clear cell RCC. AhR in RCC was associated with the smoking history (p = 0.007), gender (p = 0.002) and histological grade (p = 0.02). The number of AhR-positive lymphocytes was significantly associated with AhR expression in RCC (p < 0.01), pathological T (p < 0.05), pathological N (p < 0.05), vascular invasion (p < 0.01) and metastasis (p < 0.05). A multivariate analysis revealed that the histological grade (p < 0.001), vascular invasion (p < 0.01) and AhR in cancer cells (p < 0.001) were independent prognostic factors for the PFS. The 5-year PFS rates were 80.5% in the low AhR RCC and 20.4% in the high AhR RCC (p < 0.001). TCDD treatment enhanced the cell invasion through MatrigelTM (p < 0.05) together with up-regulating the expression of MMP-1 and MMP-9 (p < 0.05). The cell invasion through MatrigelTM was inhibited in comparison to the cells transfected with a non-targeting siRNA (p < 0.05) together with the down-regulation of MMP-1 and MMP-9 (p < 0.05). CONCLUSIONS These results suggest that AhR in cancer cells regulates invasion of RCC and that AhR may be involved in tumor immunity. AhR could therefore be a potentially attractive therapeutic target for the control of RCC. © 2014FiguresReferencesRelatedDetails Volume 191Issue 4SApril 2014Page: e304-e305 Advertisement Copyright & Permissions© 2014MetricsAuthor Information Masaru Ishida More articles by this author Shuji Mikami More articles by this author Takeo Kosaka More articles by this author Ryuichi Mizuno More articles by this author Eiji Kikuchi More articles by this author Akira Miyajima More articles by this author Ken Nakagawa More articles by this author Yasunori Okada More articles by this author Mototsugu Oya More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Toxicological Impact of Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on Some Hormonal Profiles and Hematological Parameters in Goats

Female Baladi goats were used to investigate the toxicological effects of 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD) on some serum hormones andblood features. Animals were divided into two groups, group 1: served as control, group 2: animals were orallyadministeredwith three repeated doses (0.23µg/Kg body weight) of TCDD with 2 days intervalbetween dosing. Results revealed that exposure toTCDD induced reduction in serum estradiol, progesterone and prolactin levels and elevation in glucocorticoid hormone cortisol throughout the different studied periods (48h, 96h and 16 days commenced the last intoxicated dose). The adverse impact of TCDD on goat reproductive hormones was confirmed by histopatholgical observations on their uteri and ovaries after 16 days commenced the last intoxicated dose. Intoxication of goats with TCDD showed also marked decreases in hemoglobin (Hb) concentrat ion, red blood cell count (RBC) , packed cellvolume (PCV), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) OriginalResearch Article

Comparison of intake and systemic relative effect potencies of dioxin-like compounds in female rats after a single oral dose

Risk assessment for mixtures of dioxin-like compounds uses the toxic equivalency factor (TEF) approach. Although current WHO-TEFs are mostly based on oral administration, they are commonly used to determine toxicity equivalencies (TEQs) in human blood or tissues. However, the use of "intake" TEFs to calculate systemic TEQs in for example human blood, has never been validated. In this study, intake and systemic relative effect potencies (REPs) for 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PeCDD), 2,3,4,7,8-pentachlorodibenzofuran (4-PeCDF), 3,3',4,4',5-pentachlorobiphenyl (PCB-126), 2,3',4,4',5-pentachlorobiphenyl (PCB-118) and 2,3,3',4,4',5-hexachlorobiphenyl (PCB-156) were compared in rats. The effect potencies were calculated based on administered dose and liver, adipose or plasma concentrations in female Sprague-Dawley rats 3 days after a single oral dose, relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Hepatic ethoxyresorufin-O-deethylase activity and gene expression of Cyp1a1, 1a2, 1b1 and aryl hydrocarbon receptor repressor in liver and peripheral blood lymphocytes were used as endpoints. Results show that plasma-based systemic REPs were generally within a half log range around the intake REPs for all congeners tested, except for 4-PeCDF. Together with our previously reported systemic REPs from a mouse study, these data do not warrant the use of systemic REPs as systemic TEFs for human risk assessment. However, further investigation for plasma-based systemic REPs for 4-PeCDF is desirable.

Circulating Soluble CD27 and CD30 in Workers Exposed to 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD)

Previous studies suggest that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure may be associated with non-Hodgkin lymphoma (NHL) but findings remain inconclusive. There is a need for mechanistic studies to evaluate the biologic plausibility of this association. In this cross-sectional study, we investigated changes in plasma levels of interleukin 1 receptor antagonist (IL1RA) and soluble (s)CD27 and sCD30 which have been found to be predictive of lymphoma, among workers of a cohort occupationally exposed to TCDD. Eighty-five workers who had been exposed to TCDD more than 30 years before blood collection were included in the current investigation. Plasma level of the markers was measured by ELISA. Current plasma levels of TCDD were determined by high-resolution gas chromatography/isotope dilution high-resolution mass spectrometry. TCDD blood levels at time of last exposure were estimated using a one-compartment first order kinetic model. Exposure-response analyses showed no significant association between blood levels of sCD27, and sCD30 and current and estimated TCDD levels at time of last exposure. IL1RA showed a borderline significant decrease with increasing plasma TCDD levels (P = 0.07), which reached formal statistical significance when excluding subjects with chronic diseases. In conclusion, no clear dose-response relationship was observed between the measured markers and TCDD level. However, there was a suggestion that markers in particular IL1RA tended to decrease with increasing TCDD levels. This observation is consistent with our earlier observation on decreasing cytokine levels, suggesting immunosuppression, with increasing exposures. These findings possibly provide new insights in the etiology of NHL and the mechanisms through which TCDD can increase lymphoma risk.

Maternal dioxin exposure and pregnancy outcomes over 30 years of follow-up in Seveso

Animal evidence suggests an association between exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and adverse pregnancy outcomes. Epidemiologic studies report inconsistent results, but are limited by narrow range of exposure, small sample size, and lack of a biologic measure of highest lifetime exposure. On July 10, 1976, a chemical explosion in Seveso, Italy resulted in the highest known residential exposure to TCDD. In 1996, we initiated the Seveso Women's Health Study (SWHS), a retrospective cohort of TCDD exposure and reproductive health. Individual-level TCDD was measured in serum collected soon after the explosion. After 20years of follow-up, we found no association between maternal TCDD in 1976 serum or estimated at pregnancy and spontaneous abortion (SAB), fetal growth, or gestational length. Here, we present an updated analysis of TCDD exposure and adverse pregnancy outcomes from a subsequent follow-up of the SWHS cohort in 2008–2009.SWHS women had 1211 post-explosion pregnancies through the 2008–2009 follow-up. We found no association between TCDD estimated at pregnancy and SAB, fetal growth, or gestational length. However, we found a non-significant inverse association between maternal 1976 serum TCDD and birthweight (adjusted β=−22.8, 95% CI: −80.1, 34.6). The association was stronger among first post-explosion births, but remained non-significant (adjusted β=−47.7, 95% CI: −107.3, 11.9). SWHS is the first study to be able to consider two potentially relevant measures of TCDD exposure: highest lifetime dose and in utero. Our results, although non-significant, suggest that highest dose may be more relevant in epidemiologic studies of TCDD and pregnancy outcomes.

Peroxiredoxin I protein, a potential biomarker of hydronephrosis in fetal mice exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin

ObjectiveIn previous studies, we established an animal model of human congenital hydronephrosis with exposure of developing mice to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), but the etiopathogenesis is not entirely clear. The present study was to identify the changes that may be involved in the etiology at the protein level. MethodsC57BL/6J mice fetuses were treated with TCDD. Comparative proteomic analysis was adopted to identify the proteins associated with hydronephrosis induced by TCDD. ResultsTwo-dimensional electrophoresis display revealed that 19 protein spots were differentially expressed in the upper urinary tract tissues in fetal mice after exposure to TCDD. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) identified 12 up-regulated proteins: peroxiredoxin I (Prx I), cadherin 6, gamma-actin, radixin, desmin, type II transforming growth factor-beta receptor, chromogranin B, serum albumin precursor, transferrin, hypothetical protein LOC70984, lipk protein, and zinc finger protein 336. Histochemical staining indicated that Prx I protein was positively expressed in the ureteric epithelium in the treated group, and not in the control group, which is consistent with MALDI-TOF-MS. ConclusionPrx I protein may be a potential biomarker or responsive protein of hydronephrosis in fetal mice induced by TCDD.

Serum TCDD and TEQ concentrations among Seveso women, 20 years after the explosion.

The Seveso Women's Health Study (SWHS) is a historical cohort study of the female population residing near Seveso, Italy, on 10 July 1976, when a chemical explosion resulted in the highest known residential exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Individual TCDD concentration was measured in serum collected near the time of the explosion, and in 1996, we collected adequate blood for TCDD and total dioxin toxic equivalent (TEQ) measurement. Polychlorinated dibenzo-p-dioxins, dibenzofurans, and biphenyls were measured in 1996 serum for a sample (n=225, 23%) of the SWHS cohort and WHO 2005 TEQs were calculated. We examined characteristics that predict 1996 TCDD concentrations and estimated TCDD elimination half-life over the 20-year period since the explosion. Median lipid-adjusted TCDD and total TEQ concentrations in 1996 serum were 7.3 and 26.2 p.p.t., respectively. Initial 1976 TCDD and age at explosion were the strongest predictors of 1996 TCDD. The TCDD elimination half-life was 7.1 years for women older than 10 years in 1976, but was shorter in those who were younger. Twenty years after the explosion, TCDD concentrations in this SWHS sample, the majority of who were children in 1976, remain elevated relative to background. These data add to the limited data available on TCDD elimination half-life in children.

Ultrahigh resolution mass spectrometry-based metabolic characterization reveals cerebellum as a disturbed region in two animal models

In the previous reports about cognitive dysfunction, cerebellum was thought to be a less affected tissue by genetic or environmental alterations in comparison to other tissues in the brain including hippocampus under the same conditions. In this work, we investigated two types of metabolomic alterations inside the cerebellum tissue. The first one addressed the differences in the metabolomics profiles between Transgenic (Tg) CRND8 of Alzheimer's disease mice and non-transgenic (non-Tg) littermates. The second one addressed the metabolic differences between wild type mice exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and wild type mice which are not exposed to this toxic compound. For these two investigations, ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS) was implemented. As a result, the significant changes of each comparison were tentatively annotated by the high mass accuracy generated from the measurements in the negative ion mode. The biosynthesis of amino acids was also enhanced pronouncedly, and perturbation of purine metabolism was also observed in Tg mice compared to non-Tg littermates. In another animal model, the reduced levels of amino acids were found whereas the intermediate levels in purine metabolism and fatty acids including fatty acid conjugated metabolites were elevated in cerebellar tissues of mice exposed to TCDD compared to control group. Collectively, it was demonstrated that FT-ICR/MS was a powerful tool for interpretation of the elemental compositions of the peaks, revealing that the metabolic perturbations in cerebellar tissues of mice were induced by either genetic manipulation or environmental factor. Therefore, the non-targeted approach, alternatively, provides various metabolic phenotypes for the systems-level mirror of the complex etiology of neurotoxicity in the cerebellum.

2,3,7,8-Tetrachlorodibenzo-p-dioxin Slows the Progression of Experimental Cutaneous Leishmaniasis in Susceptible BALB/c and SCID Mice

In a model of experimental cutaneous leishmaniasis, pre-exposure of Leishmania major-resistant mice to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), an aryl hydrocarbon receptor agonist, causes suppression of the protective anti-parasite T helper 1 response while paradoxically also reducing parasite burdens in those animals. In this study, we examined if TCDD exposure could also reduce parasite burdens in L. major-susceptible BALB/c mice. In the highest dose group (160 µg/Kg), TCDD treatment caused a significant reduction of parasite burdens by 10-fold after three weeks while also causing a significant lymphoid atrophy indicating suppression of the non-protective T helper 2 response. A dose-dependent delay of foot lesion progression was also observed such that lesion size in the highest dose group was less than half that of controls after 35 days of infection. Importantly, although TCDD exposure initially reduced disease severity and prolonged the course of disease by as much as three fold in some animals, this effect was transitory and TCDD did not induce resistance to L. major infection. Because TCDD exposure reduced L. major burdens in both resistant and susceptible mice, we hypothesized that TCDD reduces L. major burdens in mice by a mechanism that does not involve adaptive immunity. To test this, severe combined immunodeficient (SCID) mice were used. In mice infected with a moderate number of L. major (10,000), TCDD treatment caused a time- and dose-dependent decrease of parasite burdens by nearly 100-fold after six weeks in the highest dose group (200 µg/Kg). A significant and dose-dependent delay of foot lesion progression was also observed in these animals. These results indicate that TCDD exposure can reduce the severity of leishmanial disease in mice independent of adaptive immunity.

Effects of maternal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin on parvalbumin- and calbindin-immunoreactive neurons in the limbic system and superior colliculus in rat offspring

Previous studies have reported that maternal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces socioemotional and cognitive disturbances in rat offspring. In the present study, the effects of maternal TCDD exposure on putative inhibitory interneurons were investigated in the medial prefrontal cortex (mPFC), basolateral amygdala (BLA), hippocampus (HP), and superior colliculus (SC) in rat offspring. Dams were given TCDD (1.0μg/kg) on gestational day 15. When offspring rats reached adulthood (14 weeks old), parvalbumin (PV)- and calbindin (Calb)-immunoreactive neurons were immunohistochemically investigated. The histological investigations indicated that the mean area of the mPFC had increased, whereas the mean area of the SC decreased in the exposed male rats. In the exposed female rats, the mean SC area increased. Furthermore, the number and area of PV-immunoreactive neurons increased in the mPFC of the female exposed rats. In contrast, the number of PV-immunoreactive neurons in the BLA, HP, and SC decreased in the male and female exposed rats. The number of Calb-immunoreactive neurons decreased in the HP of the male and female exposed rats and the SC of the female exposed rats. Because PV- and Calb-immunoreactive neurons, which are putatively GABAergic, have been implicated in various higher brain functions, the effects of TCDD on socioemotional and cognitive functions might be mediated partly through these alterations in PV- and Calb-immunoreactive neurons in these areas.

Serum metabolomic pertubations among workers exposed to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD)

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been associated with multiple health effects. Mechanistic studies using metabolomics could provide supporting evidence for such associations by identifying relevant biological pathways. In this study, we investigated metabolic perturbations in a cohort of TCDD exposed workers to better understand TCDD related health effects. Eighty one workers who had been exposed to TCDD in the past and 63 nonexposed workers were included in the study. Serum metabolites were detected using ultra high pressure liquid chromatography coupled online to a Q-TOF Premier mass spectrometer with a scan range of 70-1,000 m/z. Current plasma levels of TCDD were determined by high-resolution gas chromatography/isotope dilution high resolution mass spectrometry. TCDD blood levels at the time of last exposure were estimated using a one-compartment first order kinetic model. Differentially expressed metabolites were identified using linear regression models, partial least squares regression (PLSr) and a regression-based Bayesian variable selection approach. Features that were present in all quality control samples and had a coefficient of variation <30% were included in the analyses (n = 421 features). Adjusted linear regression analysis showed several significant perturbations (n = 27; P < 0.05) but these observations did not survive multiple testing correction (q value > 0.05). PLSr analyses and Bayesian variable selection regression analyses revealed no obvious metabolic perturbations associated with TCDD levels. This is the first metabolomic analysis related to TCDD exposure in humans. No significant metabolic features were identified. It is concluded that TCDD exposure at levels present in this study does not lead to significant perturbations of the serum metabolome.

Impaired Cardiovascular Function Caused by Different Stressors Elicits a Common Pathological and Transcriptional Response in Zebrafish Embryos

Zebrafish embryos have been widely used to study the genes and processes needed for normal vertebrate heart development. We recently observed that exposure to 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD) or retinoic acid (RA) produces very similar signs of heart failure in developing zebrafish via divergent molecular pathways. The fact that diverse stressors and mutations cause severe pericardial edema and circulatory collapse in developing zebrafish has been largely unexplored. We hypothesized that unrelated chemicals can trigger a common pathological response leading to the same end-stage heart failure. To test this hypothesis, we compared the effects of TCDD, RA, carbaryl, valproic acid, and morpholino oligonucleotide (MO) knockdown of TBX5 on the developing heart in zebrafish embryos. These model stressors have all been previously reported to affect zebrafish heart development, and elicited very similar signs of embryonic heart failure. Microarray analysis showed that one cluster of 92 transcripts affected by these different treatments was significantly downregulated by all treatments. This gene cluster is composed of transcripts required for chromosome assembly, DNA replication, and cell cycle progression. We refer to this cluster as the cell cycle gene cluster (CCGC). Immunohistochemistry revealed that downregulation of the CCGC precedes a halt in cardiomyocyte proliferation in the hearts of zebrafish exposed to any of the treatments. Previous work has shown that the initial response to TCDD is a decrease in cardiac output. Since this precedes the signs of edema, heart failure, and fall in CCGC expression, we postulated that any factor that decreases cardiac output will produce the same syndrome of heart failure responses. To test this, we used MO knockdown of cardiac troponin T2 (TNNT2) to specifically block contractility. The TNNT2-MO produced exactly the same signs of cardiotoxicity as the other treatments, including downregulation of the signature CCGC. Our results indicate that agents altering cardiac output can have amplified consequences during specific periods in development.

In utero and lactational exposure to 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin modulates dysregulation of the lipid metabolism in mouse offspring fed a high‐calorie diet

Exposure to environmental chemicals, including dioxins, is a risk factor for type 2 diabetes mellitus in humans. This study explored the hypothesis that in utero and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most toxic congener among dioxins, aggravates this disease state later in adulthood. Pregnant C57Bl/6 J mice were administered either a single oral dose of TCDD (3.0 µg kg(-1) body weight) or corn oil on gestational day 12.5. The male pups born to these two groups of dams were given either a regular diet or a high-calorie diet, after postnatal day (PND) 28. The four groups of investigated offspring were thus termed T-R (TCDD regular diet), T-H (TCDD high-calorie diet), V-R (vehicle regular diet), and V-H (vehicle high-calorie diet). The mice were regularly monitored for body weight, blood pressure and glucose, until they reached 26 weeks of age. Mice in the V-H group were significantly obese at weeks 15 and 26, but they exhibited no diabetes-associated signs of insulin resistance or hypertension. However, metabolic syndrome-related alterations with marginal signs of liver damage were found at week 26. Pronounced signs of dysregulated lipid metabolism with altered gene expression and liver inflammation were already present at week 15, whereas such alterations were suppressed in the T-H group. Although the mechanism is unclear, this study showed that in utero and lactational exposure to low-dose TCDD does not aggravate obesity-induced disease states, such as adult-onset diabetes, but instead attenuates the dysregulation of lipid metabolism brought on by a high-calorie diet.

TCDD Inhibition of Canonical Wnt Signaling Disrupts Prostatic Bud Formation in Mouse Urogenital Sinus

In mice, in utero exposure to 2,3,7,8-tetrachlorodibenzo-p- dioxin (TCDD) reduces the number of dorsolateral prostatic buds resulting in a smaller dorsolateral prostate and prevents formation of ventral buds culminating in ventral prostate agenesis. The genes and signaling pathways affected by TCDD that are responsible for disrupting prostate development are largely unknown. Here we show that treatment of urogenital sinus (UGS) organ cultures with known inhibitors of canonical Wnt signaling also inhibits prostatic bud formation. In support of the hypothesis that TCDD decreases canonical Wnt signaling, we identify inhibitory effects of TCDD on multiple components of the canonical Wnt signaling pathway in the UGS that temporally coincide with the inhibitory effect of TCDD on prostatic bud formation: (1) expression of R-spondins (Rspo2 and Rspo3) that promote canonical Wnt signaling is reduced; (2) expression of Lef1, Tcf1, and Wif1, established canonical Wnt target genes, is decreased; (3) expression of Lgr5, a RSPO receptor that activates canonical Wnt signaling, is reduced; and (4) expression of Dickkopfs (Dkks), inhibitors of canonical Wnt signaling, is not increased by TCDD. Thus, the TCDD-induced reduction in canonical Wnt signaling is associated with a decrease in activators (Rspo2 and Rspo3) rather than an increase in inhibitors (Dkk1 and Dkk2) of the pathway. This study focuses on determining whether treatment of TCDD-exposed UGS organ cultures with RSPO2 and/or RSPO3 is capable of rescuing the inhibitory effects of TCDD on canonical Wnt signaling and prostatic bud formation. We discovered that each RSPO alone or in combination partially rescues TCDD inhibition of both canonical Wnt signaling and prostatic bud formation.

Effect of tocopherol on biochemical blood parameters in pleuritis-induced rats treated with 2,3,7,8-tetrachlorodibenzo-p-dioxin

The aim of this study was to evaluate the effect of tocopherol on pleuritis-induced rats exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Rats were treated with a single TCDD dose of 5 μg/kg body weight (b.w.) and then for 3 weeks they were daily supplemented with tocopherol at a dose of 30 mg/kg b.w. The inflammation was initiated by intrapleural injection of a single dose of 1% carrageenin solution in a volume of 0.15 ml. Changes in biochemical blood parameters were measured three times at the 24th, 72nd and 120th hour of pleuritis and the blood was collected from 20 animals of each group of rats (group with the control inflammation; group treated with TCDD and with control inflammation; group treated with TCDD, supplemented with tocopherol and with the inflammation). The following biochemical parameters were measured: tumor necrosis factor (TNF), interleukin-1 (IL-1), IL-2, IL-4, IL-6, procollagen, telopeptide, fibrinogen, cholesterol, urea, creatinine, aspartate aminotransferase (AspAT) and alanine aminotransferase (AlAT). Daily supplementation of tocopherol caused significant changes in the level of TNF, IL-1, IL-4, IL-6, urea, creatinine, AspAT and AlAT. According to the results of these studies, we suggest that tocopherol supplementation in high doses could act as a protective treatment to improve liver metabolism.