Disruption of glucocorticoid action by environmental chemicals: potential mechanisms and relevance

Research status of anti-obesogenic functional foods: mechanism of endocrine-disrupting chemicals and glucocorticoid receptor pathway

Obesity due to excessive fat accumulation, affects health and quality of life and increases the risk of diseases such as type 2 diabetes and cardiovascular conditions. Traditional causes, such as calorie excess and sedentary behavior, do not fully explain the obesity epidemic, leading to the hypothesis that endocrine-disrupting chemicals or obesogens contribute to obesity. The obesogenic mechanisms of representative obesogenic substances, such as bisphenols, have been discussed, mainly focusing on their interactions with estrogen receptors. Based on several studies showing that obesogens induce obesity by mimicking glucocorticoids, this review focused on the role of the glucocorticoid receptor pathway. In addition, the anti-obesogenic bioactive substances that have been studied to this date along with their inhibitory mechanisms were discussed.

Evaluating Mixtures of Urinary Phthalate Metabolites and Serum Per-/Polyfluoroalkyl Substances in Relation to Adolescent Hair Cortisol: The HOME Study

Results of toxicological studies indicate that phthalates and per-/polyfluoroalkyl substances (PFAS), 2 classes of endocrine-disrupting chemicals, may alter the functioning of the hypothalamic-pituitary-adrenocortical (HPA) axis. We evaluated the associations of urinary phthalate metabolites and serum PFAS during gestation and childhood with adolescent hair cortisol concentrations (pg/mg hair) at age 12 years, an integrative marker of HPA axis activity (n = 205 mother-child pairs; Cincinnati, Ohio; enrolled 2003-2006). We used quantile-based g-computation to estimate associations between mixtures of urinary phthalate metabolites or serum PFAS and hair cortisol. We also examined whether associations of individual phthalate metabolites or PFAS with cortisol varied by the timing of exposure. We found that a 1-quartile increase in all childhood phthalate metabolites was associated with 35% higher adolescent hair cortisol (phthalate mixture ψ = 0.13; 95% confidence interval: 0.03, 0.22); these associations were driven by monoethyl phthalate, monoisobutyl phthalate, and monobenzyl phthalate. We did not find evidence that phthalate metabolites during gestation or serum PFAS mixtures were related to adolescent hair cortisol concentrations. We found suggestive evidence that higher childhood concentrations of individual PFAS were related to higher and lower adolescent hair cortisol concentrations. Our results suggest that phthalate exposure during childhood may contribute to higher levels of chronic HPA axis activity.

A comparative study of human and zebrafish glucocorticoid receptor activities of natural and pharmaceutical steroids

Introduction

The action of environmental steroids on the human glucocorticoid receptor (hGR) has been pointed out with the risk to impair physiological immune and metabolic processes regulated by this nuclear receptor. However, there is still a lack of mechanistic information regarding their ability to interact with GR in aquatic species.

Methods

To investigate ligand activation differences between hGR and zebrafish GR (zfGR), we tested several natural and synthetic steroids using reporter cell lines expressing hGR or zfGR.

Results and discussion

Almost all the glucocorticoids tested (dexamethasone, cortisol, bimedrazol, medrol, cortivazol and fluticasone) are agonists of the two receptors with similar potencies. The dissociated glucocorticoids, RU24782 and RU24858 are agonists of both zfGR and hGR but with a better potency for the latter. On the other hand, the synthetic glucocorticoid forbimenol and the mineralocorticoid aldosterone are agonist on hGR but antagonist on zfGR. The other steroids tested, androgens and progestins, are all antagonists of both GRs with equal or lower potency on zfGR than on hGR. Surprisingly, the lower efficacy and potency on zfGR of aldosterone, forbimenol and the dissociated glucocorticoids is not related to their affinity for the receptors which would suggest that it could be related to less efficacious recruitment of coactivators by zfGR compared to hGR.

Establishment of killer whale (Orcinus orca) primary fibroblast cell cultures and their transcriptomic responses to pollutant exposure

Populations of killer whale (Orcinus orca) contain some of the most polluted animals on Earth. Yet, the knowledge on effects of chemical pollutants is limited in this species. Cell cultures and in vitro exposure experiments are pertinent tools to study effects of pollutants in free-ranging marine mammals. To investigate transcriptional responses to pollutants in killer whale cells, we collected skin biopsies of killer whales from the Northern Norwegian fjords and successfully established primary fibroblast cell cultures from the dermis of 4 out of 5 of them. Cells from the individual with the highest cell yield were exposed to three different concentrations of a mixture of persistent organic pollutants (POPs) that reflects the composition of the 10 most abundant POPs found in Norwegian killer whales (p,p'-DDE, trans-nonachlor, PCB52, 99, 101, 118, 138, 153, 180, 187). Transcriptional responses of 13 selected target genes were studied using digital droplet PCR, and whole transcriptome responses were investigated utilizing RNA sequencing. Among the target genes analysed, CYP1A1 was significantly downregulated in the cells exposed to medium (11.6 µM) and high (116 µM) concentrations of the pollutant mixture, while seven genes involved in endocrine functions showed a non-significant tendency to be upregulated at the highest exposure concentration. Bioinformatic analyses of RNA-seq data indicated that 13 and 43 genes were differentially expressed in the cells exposed to low and high concentrations of the mixture, respectively, in comparison to solvent control. Subsequent pathway and functional analyses of the differentially expressed genes indicated that the enriched pathways were mainly related to lipid metabolism, myogenesis and glucocorticoid receptor regulation. The current study results support previous correlative studies and provide cause-effect relationships, which is highly relevant for chemical and environmental management.

[Simultaneous determination of 24 corticosteroids in sediments based on ultrasonic extraction, solid-phase extraction, liquid chromatography, and tandem mass spectrometry]

Corticosteroids (CSs) are widely used to treat various inflammatory and immune diseases in humans and animals, such as arthritis and lupus. Thus far, CSs have been frequently detected in diverse pollution sources, such as in the influent and effluent of traditional wastewater treatment plants, livestock farms, and aquaculture. Owing to incomplete removal or limited treatment, CSs can enter the water environment and eventually be adsorbed in the sediment. Due to hydrodynamic effects, CSs can re-enter the surface water through the resuspension of sediments, and pose a hazard to the ecosystem and human health via the enrichment of aquatic organisms and transmission through the food chain. Therefore, trace analysis of CSs in sediments is significant for exploring their prevalence and behavior in multiple environments. However, existing research mainly focuses on the determination of glucocorticoids in water samples, and studies on the systematic quantitative analysis of CSs in environmental solid samples with more complex matrices are scarce. Moreover, majority of previous investigations focused on a limited number of glucocorticoids, making it important to widen the range of target compounds to be studied, including mineralocorticoids. In this study, the main factors which could influence the accuracy and sensitivity in the determination of 24 target CSs were systematically optimized in the sample pretreatment and instrument analysis. A novel method based on ultrasonic extraction coupled with solid phase extraction (SPE) for sample pretreatment was developed for the simultaneous determination of the 24 CSs in sediments using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sediment sample was ground to homogenize the particle sizes after freeze-drying. The analytes from 2.0 g of the sample were ultrasonicated and extracted with methanol-acetone (1∶1, v/v). After concentrating and diluting each extract, SPE was performed. The water sample was extracted and purified using hydrophile-lipophile balance (HLB) cartridges, following which the extract was further purified with LC-NH2 cartridges. The extracts were concentrated using a rotary evaporator, dried under a gentle stream of nitrogen, and re-dissolved in methanol for instrumental analysis. Chromatographic separation was conducted on an Agilent ZORBAX Eclipse Plus C8 column (100 mm×2.1 mm, 1.8 μm), with a column flow rate of 0.3 mL/min and a gradient of mobile phases A (water with 0.1% acetic acid) and B (acetonitrile). The column temperature was set to 30 ℃ and the injection volume was fixed at 5 μL. Electrospray ionization MS in the dynamic multiple reaction monitoring (DMRM) and selected ion monitoring (SIM) modes were performed in the positive mode for the qualitative and quantitative analysis of the target compounds. Quantitation of the target compounds was carried out using the internal standard method. The effects of different extraction solvents, purification conditions, and MS conditions on the recoveries of the target compounds were investigated. The limits of detection (LODs) (S/N≥3) and limits of quantification (LOQs) (S/N≥10) of all 24 compounds were in the ranges of 0.14-1.25 μg/kg and 0.26-2.26 μg/kg, respectively. The correlation coefficients of linear calibration curves were higher than 0.995 in the range of 1.0-100 μg/L. The recoveries of the 24 CSs at 5, 20, and 50 μg/kg spiked levels ranged from 64.9% to 125.1% with relative standard deviations of 0.4%-12.6% (n=5). The developed method was applied to analyze the CSs in three sediment samples from the rivers of the Pearl River Delta. In all, 11 target compounds were detected in these samples, with contents in the range of 1.25-29.38 μg/kg. The characteristic of this method is efficient, sensitive, reliable, and suitable for the trace determination of varieties of natural and synthesized CSs in environmental sediments.

mRNA expression and protein-protein interaction (PPI) network analysis of adrenal steroidogenesis in response to exposure to phthalates in rats

Phthalate esters such as di-butyl phthalate (DBP) and di-ethyl hexyl phthalate (DEHP) used in personal care and consumer products and medical devices have potential to affect human health. We studied the effect of DBP and DEHP on critical enzymes of glucocorticoid biosynthesis pathway in the adrenal gland and pro-inflammatory cytokines in the serum in male Wistar rats. DEHP and DBP treatment altered the mRNA expression of enzymes of glucocorticoid biosynthesis pathway accompanied by a reduction in glucocorticoid production and elevation in the level of glucocorticoid regulated pro-inflammatory cytokines indicating a cascading effect of phthalates. The analysis of PPI (protein - protein interaction) network involving Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and Gene Ontology (GO) of enzymes through STRING database revealed that all the proteins have the maximum level of interaction with the selected number of proteins. The STRING database analysis together with in vivo data indicates the potential effects of phthalates on various targets of steroidogenesis pathway with a global biological impact.

Differential regulation of the glucocorticoid receptor nucleocytoplasmic shuttling by TPR-domain proteins

A dimer of the heat-shock protein of 90-kDa (Hsp90) represents the critical core of the chaperone complex associated to the glucocorticoid receptor (GR) oligomer. The C-terminal end of the Hsp90 dimer shapes a functional acceptor site for co-chaperones carrying tetratricopeptide repeat (TPR) domains, where they bind in a mutually exclusive and competitive manner. They impact on the biological properties of the GR•Hsp90 complex and are major players of the GR transport machinery. Recently, we showed that the overexpression of a chimeric TPR peptide influences the subcellular distribution of GR. In this study, the functional role of endogenous proteins carrying TPR or TPR-like sequences on GR subcellular distribution was characterized. It is demonstrated that, contrarily to the positive influence of FKBP52 on GR nuclear accumulation, FKBP51 and 14-3-3 impaired this property. While SGT1α showed no significant effect, the overexpression of the Ser/Thr phosphatase PP5 resulted in a nearly equal nuclear-cytoplasmic redistribution of GR rather than its typical cytoplasmic localization in the absence of steroid. This observation led to analyse the influence of the phosphorylation status of GR, which resulted not linked to its nucleo-cytoplasmic shuttling mechanism. Nonetheless, it was evidenced that both PP5 and FKBP52 are related to the anchorage of the GR to nucleoskeleton structures. The influence of these TPR domain proteins on the steroid-dependent transcriptional activity of GR was also characterized. It is postulated that the pleiotropic actions of the GR in different cell types may be the consequence of the relative abundance of different TPR-domain interacting co-chaperones.

Long-term Effects of Maternal Separation on Anxiety-Like Behavior and Neuroendocrine Parameters in Adult Balb/c Mice

Introduction: Disruption of maternal care using maternal separation (MS) models has provided significant evidence of the deleterious long-term effects of early life stress. Several preclinical studies investigating MS showed multiple behavioral and biomolecular alterations. However, there is still conflicting results from MS studies, which represents a challenge for reliability and replicability of those findings. Objective: To address that, this study was conducted to investigate whether MS would affect anxiety-like behaviors using a battery of classical tasks, as well as central and peripheral stress-related biomarkers. Methods: Male Balb/c mice were exposed to MS from postnatal day (PND) 2 to 14 for 180-min per day. Two independent cohorts were performed to evaluate both baseline and anxiety-like behavior responses to MS at PND60. We performed composite scores to evaluate MS effects on anxiety and risk assessment phenotypes. Also, we assessed mRNA gene expression in the medial pre-frontal cortex (mPFC) of glucocorticoid and mineralocorticoid receptors (GR and MR) using real-time PCR and peripheral corticosterone levels (CORT) to investigate possible neurobiological correlates to anxiety behaviors. Results: We found increased anxiety-like behavior and decreased risk assessment and exploratory behaviors in MS mice. The animals exposed to MS also presented a decrease in MR mRNA expression and higher levels of CORT compared to controls. Conclusions: Our findings reinforce the body of evidence suggesting that long-term MS induces effects on anxiety and risk assessment phenotypes following the exposure to a standardized MS protocol. Moreover, MS affected the expression of MR mRNA and induced significant changes on CORT response. This data highlights that the reprograming MS effects on HPA axis could be mediate by MR gene expression in mPFC and chronic overactivity of peripheral CORT levels.

Associations of per-/polyfluoroalkyl substances with glucocorticoids and progestogens in newborns

BACKGROUND

Exposure to per-/polyfluoroalkyl substances (PFASs) can disrupt endocrine hormones in humans. Prior studies have focused on the harmful effects of the two traditional per-/polyfluoroalkyl substances (PFASs), perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). Other PFASs, used as the replacements of PFOS and PFOA, are widely and increasingly detected in humans. Whether these replacements influence glucocorticoids and progestogens in newborns remains unknown.

OBJECTIVE

To investigate the associations between exposures of PFOS, PFOA and their replacements and glucocorticoids and progestogens in newborns.

METHODS

We measured the concentrations of 13 PFASs, 3 glucocorticoids (11-deoxycortisol, cortisol and cortisone) and 2 progestogens [progesterone, 17-hydroxyprogesterone (17OHP)] in the cord sera of 374 neonates in a birth cohort from Wuhan, China, between 2013 and 2014. We evaluated the associations of each PFAS with glucocorticoids and progestogens using multiple linear regression models, and multiple comparisons were additionally corrected via false discovery rates (FDR).

RESULTS

Out of the 13 PFASs, 9 were detected in over 95% of cord sera. The Chinese specific PFOS replacement - 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA, trade name F-53B) was positively associated with 13.13% change in cortisol in girls (95% CI = 4.47%, 22.52%, for each IQR increase in 6:2 Cl-PFESA). Seven PFASs had positive associations with the precursor of cortisol, namely 11-deoxycortisol (percent change ranged from 6.41% to 11.24%, for each IQR increase in PFASs). Perfluorobutane sulfonate (PFBS) in cord sera was positively associated with progesterone in the linear model, whereas PFOS and perfluorohexane sulfonate (PFHxS) levels were associated with progesterone in the quartile models. No PFASs were related to 17OHP or cortisone.

CONCLUSIONS

In this study, PFOS, PFOA and/or their replacements were positively associated with progesterone, cortisol and 11-deoxycortisol in newborns. These results suggested that not only PFOS and PFOA, but also other PFASs have potential impacts on glucocorticoids and progestogens in newborns.

Glucocorticoid and mineralocorticoid receptors and corticosteroid homeostasis are potential targets for endocrine-disrupting chemicals

Endocrine-disrupting chemicals (EDCs) have received significant concern, since they ubiquitously exist in the environment and are able to induce adverse health effects on human and wildlife. Increasing evidence shows that the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR), members of the steroid receptor subfamily, are potential targets for EDCs. GR and MR mediate the actions of glucocorticoids and mineralocorticoids, respectively, which are two main classes of corticosteroids involved in many physiological processes. The effects of EDCs on the homeostasis of these two classes of corticosteroids have also gained more attention recently. This review summarized the effects of environmental GR/MR ligands on receptor activity, and disruption of corticosteroid homeostasis. More than 130 chemicals classified into 7 main categories were reviewed, including metals, metalloids, pesticides, bisphenol analogues, flame retardants, other industrial chemicals and pharmaceuticals. The mechanisms by which EDCs interfere with GR/MR activity are primarily involved in ligand-receptor binding, nuclear translocation of the receptor complex, DNA-receptor binding, and changes in the expression of endogenous GR/MR genes. Besides directly interfering with receptors, enzyme-catalyzed synthesis and prereceptor regulation pathways of corticosteroids are also important targets for EDCs. The collected evidence suggests that corticosteroids and their receptors should be considered as potential targets for safety assessment of EDCs. The recognition of relevant xenobiotics and their underlying mechanisms of action is still a challenge in this emerging field of research.

Variation in scale cortisol concentrations of a wild freshwater fish: Habitat quality or seasonal influences?

A significant body of literature suggests that aquatic pollutants can interfere with the physiological function of the fish hypothalamic-pituitary-interrenal (HPI) axis, and eventually impair the ability to cope with subsequent stressors. For this reason, development of accurate techniques to assess fish stress responses have become of growing interest. Fish scales have been recently recognized as a biomaterial that accumulates cortisol, hence it can be potentially used to assess chronic stress in laboratory conditions. We, therefore, aimed to evaluate the applicability of this novel method for cortisol assessment in fish within their natural environment. Catalan chub (Squalius laietanus) were sampled from two sites; a highly polluted and a less polluted (reference) site, in order to examine if habitat quality could potentially influence the cortisol deposition in scales. We also evaluated the seasonal variation in scale cortisol levels by sampling fish at three different time points during spring-summer 2014. In each sampling, blood was collected to complement the information provided by the scales. Our results demonstrated that blood and scale cortisol levels from individuals inhabiting the reference site were significantly correlated, therefore increasing the applicability of the method as a sensitive-individual measure of fish HPI axis activity, at least in non-polluted habitats. Since different environmental conditions could potentially alter the usefulness of the technique, results highlight that further validation is required to better interpret hormone fluctuations in fish scales. Scale cortisol concentrations were unaffected by habitat quality although fish from the polluted environment presented lower circulating cortisol levels. We detected a seasonal increase in scale cortisol values concurring with an energetically costly period for the species, supporting the idea that the analysis of cortisol in scales reveals changes in the HPI axis activity. Taken together, the present study suggests that cortisol levels in scales are more likely to be influenced by mid-term, intense energetically demanding periods rather than by long-term stressors. Measurement of cortisol in fish scales can open the possibility to study novel spatio-temporal contexts of interest, yet further research is required to better understand its biological relevance.

Trace analysis of corticosteroids (CSs) in environmental waters by liquid chromatography-tandem mass spectrometry

Natural and synthetic corticosteroids (CSs) are a class of steroid hormones which could potentially disturb the corticosteroid signaling pathways in wildlife and humans. In this study, a sensitive and robust analytical method using solid phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for simultaneous analysis of sub-ng/L concentrations of 26 CSs in highly complex natural water matrices. The method performance was validated for WWTP influent, effluent, surface water and finished drinking water. Low practical quantification levels (PQLs) were achieved as 0.008-0.16 ng/L in finished drinking water, 0.019-0.50 ng/L in surface water, 0.047-1.5 ng/L in WWTP effluent, and 0.10-3.1 ng/L in WWTP influent, respectively, with the recoveries ranging from 70% to 130%. The cleanup performance and matrix interferences were also evaluated. This method was then applied to the analysis of target CSs in WWTP influent and effluent samples collected from a local WWTP, as well as surface water downstream of the WWTP outfall, detecting an average summed CS concentration of 744 ng/L in influent, 23.4 ng/L in effluent and 10.9 ng/L in surface water. Four synthetic CSs (triamcinolone acetonide, fluocinolone acetonide, clobetasol propionate, and fluticasone propionate) were found poorly removed in the WWTP. The developed method provides a tool to obtain occurrence data of corticosteroids in environmental waters, which will permit assessing their risk to environmental organisms.

Chronic exposure to inhaled, traffic-related nitrogen dioxide and a blunted cortisol response in adolescents

BACKGROUND

Chronic health effects of traffic-related air pollution, like nitrogen dioxide (NO₂), are well-documented. Animal models suggested that NO₂ exposures dysregulate cortisol function.

OBJECTIVES

We evaluated the association between traffic-related NO₂ exposure and adolescent human cortisol concentrations, utilizing measures of the cortisol diurnal slope.

METHODS

140 adolescents provided repeated salivary cortisol samples throughout one day. We built a land use regression model to estimate chronic NO₂ exposures based on home and school addresses. We then generated model-based estimates of the association between cortisol and NO₂ exposure one year prior to cortisol sampling, examining changes in cortisol diurnal slope. The final model was adjusted other criteria pollutants, measures of psychosocial stress, anthropometry, and other demographic and covariates.

RESULTS

We observed a decrease in diurnal slope in cortisol for adolescents exposed to the estimated 75th percentile of ambient NO₂ (high exposure) relative to those exposed at the 25th percentile (low exposure). For a highly exposed adolescent, the log cortisol was lower by 0.06 µg/dl at waking (95% CI: -0.15, 0.02), 0.07 µg/dl at 30 min post waking (95% CI: -0.15, 0.02), and higher by 0.05 µg/dl at bedtime (95% CI: 0.05, 0.15), compared to a low exposed adolescent. For an additional interquartile range of exposure, the model-based predicted diurnal slope significantly decreased by 0.12 (95% CI: -0.23, -0.01).

CONCLUSIONS

In adolescents, we found that increased, chronic exposure to NO₂ and the mixture of pollutants from traffic sources was associated with a flattened diurnal slope of cortisol, a marker of an abnormal cortisol response which we hypothesize may be a mechanism through which air pollution may affect respiratory function and asthma in adolescents.

An ex vivo assay for screening glucocorticoid signaling disruption based on glucocorticoid-response gene transcription in Xenopus tails

There is a pressing need for developing in vivo or ex vivo assays to screen the glucocorticoid (GC) signaling disruption of chemicals. Thus, we aimed to establish an ex vivo assay for screening GC signaling disruption based on the GC-response gene transcription in Xenopus laevis tails cultured ex vivo. Firstly, we investigated effects of corticosterone (CORT, a main GC in frogs) on GC-response gene expression, and determined the six genes as molecular endpoints for assaying the GC signaling disruption. CORT in the range of 1.56-400nmol/L was found to up-regulate transcription of the six GC-response genes, exhibiting comparable or higher sensitivity than previously reported assays. To validate this ex vivo assay, then, we examined effects of dexamethasone (a known GC signaling agonist) on GC-response gene expression. Dexamethasone displayed an agonistic action in a concentration-dependent manner, further demonstrating the efficiency of the established assay. Finally, we applied the ex vivo assay to evaluate the GC signaling disruption of bisphenol A (BPA). In accordance with previous reports, we found a concentration-dependent agonistic activity of BPA, showing that the established assay is effective for detecting the GC signaling disrupting activity of environmental chemicals. Correspondingly, the GC signaling agonistic actions of CORT and BPA in ex vivo tails accorded with the observations in vivo, indicating that the ex vivo assay is able to detect the actions of chemicals in vivo. Overall, we established an ex vivo assay that can effectively screen GC signaling disruption of environmental chemicals.

Polychlorinated Biphenyl-Related Alterations of the Expression of Essential Genes in Harbour Seals (Phoca vitulina) from Coastal Sites in Canada and the United States

As long-lived marine mammals found throughout the temperate coastal waters of the North Pacific and Atlantic Oceans, harbour seals (Phoca vitulina) have become an invaluable sentinel of food-web contamination. Their relatively high trophic position predisposes harbour seals to the accumulation of harmful levels of persistent organic pollutants (POPs). We obtained skin/blubber biopsy samples from live-captured young harbour seals from various sites in the northeastern Pacific (British Columbia, Canada, and Washington State, USA) as well as the northwestern Atlantic (Newfoundland and Quebec, Canada). We developed harbour seal-specific primers to investigate the potential impact of POP exposure on the expression of eight important genes. We found correlations between the blubber mRNA levels of three of our eight target genes and the dominant persistent organic pollutant in seals [polychlorinated biphenyls (PCBs)] including estrogen receptor alpha (Esr1: r ² = 0.12, p = 0.038), thyroid hormone receptor alpha (Thra: r ² = 0.16; p = 0.028), and glucocorticoid receptor (Nr3c1: r ² = 0.12; p = 0.049). Age, sex, weight, and length were not confounding factors on the expression of genes. Although the population-level consequences are unclear, our results suggest that PCBs are associated with alterations of the expression of genes responsible for aspects of metabolism, growth and development, and immune function. Collectively, these results provide additional support for the use of harbour seals as indicators of coastal food-web contamination.

Human exposure to endocrine disrupting compounds: Their role in reproductive systems, metabolic syndrome and breast cancer. A review

Endocrine disrupting chemicals (EDCs) are released into the environment from different sources. They are mainly used in packaging industries, pesticides and food constituents. Clinical evidence, experimental models, and epidemiological studies suggest that EDCs have major risks for humans by targeting different organs and systems in the body (e.g. reproductive system, breast tissue, adipose tissue, pancreas, etc.). Due to the ubiquity of human exposure to these compounds the aim of this review is to describe the most recent data on the effects induced by phthalates, bisphenol A and parabens in a critical window of exposure: in utero, during pregnancy, infants, and children. The interactions and mechanisms of toxicity of EDCs in relation to human general health problems, especially those broadening the term of endocrine disruption to 'metabolic disruption', should be deeply investigated. These include endocrine disturbances, with particular reference to reproductive problems and breast, testicular and ovarian cancers, and metabolic diseases such as obesity or diabetes.

Evaluation of tetrabromobisphenol A effects on human glucocorticoid and androgen receptors: A comparison of results from human- with yeast-based in vitro assays

The incidence of immune-related diseases increased over the last years in industrialized countries, suggesting a contribution of environmental factors. Impaired glucocorticoid action has been associated with immune disorders. Thus, there is an increasing interest to identify chemicals disrupting glucocorticoid action. The widely used flame retardant tetrabromobisphenol A (TBBPA) was reported earlier to potently inhibit glucocorticoid receptor (GR) and moderately androgen receptor (AR) activity in yeast-based reporter gene assays. To further characterize possible GR disrupting effects of TBBPA, transactivation experiments using a human HEK-293 cell-based reporter gene assay and cell-free receptor binding experiments were performed in the present study. Both, transactivation and GR binding experiments failed to detect any activity of TBBPA on GR function. Molecular docking calculations supported this observation. Additionally, the current study could confirm the antiandrogenic activity of TBBPA seen in the yeast assay, although the effect was an order of magnitude less pronounced in the HEK-293 cell-based system. In conclusion, TBBPA does not directly affect GR function and, considering its rapid metabolism and low concentrations found in humans, it is unlikely to cause adverse effects by acting through AR. This study emphasizes the use of cell-free assays in combination with cell-based assays for the in vitro evaluation of endocrine disrupting chemicals.

Impact of biosolids and wastewater effluent application to agricultural land on corticosterone content in lettuce plants

We studied corticosterone occurrence in lettuce plants grown on three biosolids amended soils under irrigation with either tap water or secondary wastewater effluent. Corticosterone was examined as it has possible implications for human health. It is a major glucocorticoid, and as such has an effect on regulation of metabolism, immune functions and stress response. The plants were grown in 220-L lysimeters packed with 3 soils which represent a wide range of physicochemical properties. Lettuce was grown in cycles (two in summer and two in winter) during 3 years, and in every spring season the sludges were re-applied. Corticosterone was quantified using ELISA and LCMS, and was found in the biosolids, tap water, wastewater effluent and lettuce plants. The respective ranges of concentrations were: 11-92 ng g(-1), 0.5-1.6 ng L(-1), 4.2-4.7 ng L(-1); and 1-900 ng g(-1) dry weight. A positive relationship was found between corticosterone concentrations in winter-grown lettuces and the plants fresh weight. The corticosterone content of the plants did not correspond with either the type of irrigation water or the biosolids type and rate of application or the soil properties.

Using exposomics to assess cumulative risks and promote health

Under the exposome paradigm all nongenetic factors contributing to disease are considered to be 'environmental' including chemicals, drugs, infectious agents, and psychosocial stress. We can consider these collectively as environmental stressors. Exposomics is the comprehensive analysis of exposure to all environmental stressors and should yield a more thorough understanding of chronic disease development. We can operationalize exposomics by studying all the small molecules in the body and their influence on biological pathways that lead to impaired health. Here, we describe methods by which this may be achieved and discuss the application of exposomics to cumulative risk assessment in vulnerable populations. Since the goal of cumulative risk assessment is to analyze, characterize, and quantify the combined risks to health from exposures to multiple agents or stressors, it seems that exposomics is perfectly poised to advance this important area of environmental health science. We should therefore support development of tools for exposomic analysis and begin to engage impacted communities in participatory exposome research. A first step may be to apply exposomics to vulnerable populations already studied by more conventional cumulative risk approaches. We further propose that recent migrants, low socioeconomic groups with high environmental chemical exposures, and pregnant women should be high priority populations for study by exposomics. Moreover, exposomics allows us to study interactions between chronic stress and environmental chemicals that disrupt stress response pathways (i.e., 'stressogens'). Exploring the impact of early life exposures and maternal stress may be an interesting and accessible topic for investigation by exposomics using biobanked samples.

Do persistent organic pollutants interact with the stress response? Individual compounds, and their mixtures, interaction with the glucocorticoid receptor

Persistent organic pollutants (POPs) are toxic substances, highly resistant to environmental degradation, which can bio-accumulate and have long-range atmospheric transport potential (UNEP, 2001). The majority of studies on endocrine disruption have focused on interferences on the sexual steroid hormones and so have overlooked disruption to glucocorticoid hormones. Here the endocrine disrupting potential of individual POPs and their mixtures has been investigated in vitro to identify any disruption to glucocorticoid nuclear receptor transcriptional activity. POP mixtures were screened for glucocorticoid receptor (GR) translocation using a GR redistribution assay (RA) on a CellInsight™ NXT high content screening (HCS) platform. A mammalian reporter gene assay (RGA) was then used to assess the individual POPs, and their mixtures, for effects on glucocorticoid nuclear receptor transactivation. POP mixtures did not induce GR translocation in the GR RA or produce an agonist response in the GR RGA. However, in the antagonist test, in the presence of cortisol, an individual POP, p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE), was found to decrease glucocorticoid nuclear receptor transcriptional activity to 72.5% (in comparison to the positive cortisol control). Enhanced nuclear transcriptional activity, in the presence of cortisol, was evident for the two lowest concentrations of perfluorodecanoic acid (PFOS) potassium salt (0.0147mg/ml and 0.0294mg/ml), the two highest concentrations of perfluorodecanoic acid (PFDA) (0.0025mg/ml and 0.005mg/ml) and the highest concentration of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) (0.0000858mg/ml). It is important to gain a better understanding of how POPs can interact with GRs as the disruption of glucocorticoid action is thought to contribute to complex diseases.

Reprint of "In silico methods in the discovery of endocrine disrupting chemicals"

The prevalence of sex hormone-dependent cancers, reproductive problems, obesity, and cardiovascular complications has risen especially in the Western world. It has been suggested, that the exposure to various endocrine disrupting chemicals (EDCs) contributes to the development and progression of these diseases. EDCs can interfere with various proteins: nuclear steroid hormone receptors, such as estrogen-, androgen-, glucocorticoid- and mineralocorticoid receptors (ER, AR, GR, MR), and enzymes that are involved in steroid hormone synthesis and metabolism, for example hydroxysteroid dehydrogenases (HSDs). Numerous chemicals are known as endocrine disruptors. However, the mechanism of action for most of these EDCs is still unknown. It is exhaustive and time consuming to test in vitro all chemicals - potential EDCs - used in industry, agriculture or as food preservatives against their effects on the endocrine system. Computational methods, such as virtual screening, quantitative structure activity relationships and docking, are already well recognized and used in drug development. The same methods could also aid the research on EDCs. So far, the computational methods in the search of EDCs have been retrospective. There are, however, some prospective studies reporting the use of in silico methods: five studies reporting the identification of previously unknown 17β-HSD3 inhibitors, MR agonists, and ER antagonists/agonists. This review provides an overview of case studies and in silico methods that are used in the search of EDCs. This article is part of a Special Issue entitled 'CSR 2013'.

Polychlorinated biphenyl exposure and corticosterone levels in seven polar seabird species

The role of polychlorinated biphenyls (PCBs) on exposure-related endocrine effects has been poorly investigated in wild birds. This is the case for stress hormones including corticosterone (CORT). Some studies have suggested that environmental exposure to PCBs and altered CORT secretion might be associated. Here we investigated the relationships between blood PCB concentrations and circulating CORT levels in seven free-ranging polar seabird species occupying different trophic positions, and hence covering a wide range of PCB exposure. Blood ∑₇PCB concentrations (range: 61-115,632 ng/g lw) were positively associated to baseline or stress-induced CORT levels in three species and negatively associated to stress-induced CORT levels in one species. Global analysis suggests that in males, baseline CORT levels generally increase with increasing blood ∑₇PCB concentrations, whereas stress-induced CORT levels decrease when reaching high blood ∑₇PCB concentrations. This study suggests that the nature of the PCB-CORT relationships may depend on the level of PCB exposure.

Metabolic disruption in context: Clinical avenues for synergistic perturbations in energy homeostasis by endocrine disrupting chemicals

The global epidemic of metabolic disease is a clear and present danger to both individual and societal health. Understanding the myriad factors contributing to obesity and diabetes is essential for curbing their decades-long expansion. Emerging data implicate environmental endocrine disrupting chemicals (EDCs) in the pathogenesis of metabolic diseases such as obesity and diabetes. The phenylsulfamide fungicide and anti-fouling agent tolylfluanid (TF) was recently added to the list of EDCs promoting metabolic dysfunction. Dietary exposure to this novel metabolic disruptor promoted weight gain, increased adiposity, and glucose intolerance as well as systemic and cellular insulin resistance. Interestingly, the increase in body weight and adipose mass was not a consequence of increased food consumption; rather, it may have resulted from disruptions in diurnal patterns of energy intake, raising the possibility that EDCs may promote metabolic dysfunction through alterations in circadian rhythms. While these studies provide further evidence that EDCs may promote the development of obesity and diabetes, many questions remain regarding the clinical factors that modulate patient-specific consequences of EDC exposure, including the impact of genetics, diet, lifestyle, underlying disease, pharmacological treatments, and clinical states of fat redistribution. Currently, little is known regarding the impact of these factors on an individual's susceptibility to environmentally-mediated metabolic disruption. Advances in these areas will be critical for translating EDC science into the clinic to enable physicians to stratify an individual's risk of developing EDC-induced metabolic disease and to provide direction for treating exposed patients.

Endocrine disrupting compounds affecting corticosteroid signaling pathways in Czech and Swiss waters: potential impact on fish

This study investigated the occurrence of corticosteroid signaling disruptors in wastewaters and rivers in the Czech Republic and in Switzerland. 36 target compounds were detected using HPLC-MS/MS, with up to 6.4 μg/L for azole antifungals that indirectly affect corticosteroid signaling. Glucocorticoid receptor (GR)-mediated activity was determined using the GR-CALUX bioassay with dexamethasone equivalent concentrations ranging from <LOD-2.6, 19-37, and 78-542 ng/L for river water, treated, and untreated wastewater, respectively. For most samples, the chemically predicted GR-mediated response was higher than that determined by the bioassay. Correspondingly, antiglucocorticoid activity was observed in some fractions. The fish plasma model (FPM), which predicts plasma concentrations, was applied to evaluate the potential of detected pharmaceuticals to cause receptor-mediated effects in fish. With one exception, medroxyprogesterone, the FPM applied to individual compounds predicted fish plasma concentrations to be below the level of human therapeutic plasma concentrations. To account for the activity of the sum of GR-active compounds, we introduce the "cortisol equivalents fish plasma concentration" approach, through which an increase in fish glucocorticoid plasma levels comparable to 0.9-83 ng/mL cortisol after exposure to the analyzed river waters was estimated. The results suggest that these chemicals may impact wild fish.

Screening of bisphenol A, triclosan and paraben analogues as modulators of the glucocorticoid and androgen receptor activities

A homeostasis of the glucocorticoid and androgen endocrine system is essential to human health. Their disturbance can lead to various diseases, for example cardiovascular, inflammatory and autoimmune diseases, infertility, cancer. Fifteen widely used industrial chemicals that disrupt endocrine activity were selected for evaluation of potential (anti)glucocorticoid and (anti)androgenic activities. The human breast carcinoma MDA-kb2 cell line was utilized for reporter gene assays, since it expresses both the androgen and the glucocorticoid-responsive reporter. Two new antiandrogens, 4,4'-sulfonylbis(2-methylphenol) (dBPS) and 4,4'-thiodiphenol (THIO), and two new antiglucocorticoids, bisphenol Z and its analog bis[4-(2-hydroxyethoxy)phenyl] sulfone (BHEPS) were identified. Moreover, four new glucocorticoid agonists (methyl paraben, ethyl paraben, propyl paraben and bisphenol F) were found. To elucidate the structure-activity relationship of bisphenols, we performed molecular docking experiments with androgen and glucocorticoid receptor. These docking experiments had shown that bulky structures such as BHEPS and bisphenol Z act as antiglucocorticoid, because they are positioned toward helix H12 in the antagonist conformation and could therefore be responsible for H12 conformational change and the switch between agonistic and antagonistic conformation of receptor. On the other hand smaller structures cannot interact with H12. The results of in vitro screening of fifteen industrial chemicals as modulators of the glucocorticoid and androgen receptor activities demand additional in vivo testing of these chemicals for formulating any relevant hazard identification to human health.

Adipocytes under assault: environmental disruption of adipose physiology

The burgeoning obesity epidemic has placed enormous strains on individual and societal health mandating a careful search for pathogenic factors, including the contributions made by endocrine disrupting chemicals (EDCs). In addition to evidence that some exogenous chemicals have the capacity to modulate classical hormonal signaling axes, there is mounting evidence that several EDCs can also disrupt metabolic pathways and alter energy homeostasis. Adipose tissue appears to be a particularly important target of these metabolic disruptions. A diverse array of compounds has been shown to alter adipocyte differentiation, and several EDCs have been shown to modulate adipocyte physiology, including adipocytic insulin action and adipokine secretion. This rapidly emerging evidence demonstrating that environmental contaminants alter adipocyte function emphasizes the potential role that disruption of adipose physiology by EDCs may play in the global epidemic of metabolic disease. Further work is required to better characterize the molecular targets responsible for mediating the effects of EDCs on adipose tissue. Improved understanding of the precise signaling pathways altered by exposure to environmental contaminants will enhance our understanding of which chemicals pose a threat to metabolic health and how those compounds synergize with lifestyle factors to promote obesity and its associated complications. This knowledge may also improve our capacity to predict which synthetic compounds may alter energy homeostasis before they are released into the environment while also providing critical evidentiary support for efforts to restrict the production and use of chemicals that pose the greatest threat to human metabolic health. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.

Molecular docking revealed potential disruptors of glucocorticoid receptor-dependent reporter gene expression

Glucocorticoids are an essential part of the endocrine system that is responsible for a variety of functions such as regulation of immune activity, appropriate brain function, and fetal development. Disturbance of glucocorticoid signaling can lead to various cardiovascular, inflammatory, and autoimmune diseases, so the identification of chemicals that can modulate activity of the glucocorticoid receptor (GR) is crucial. In this study, molecular docking was utilized to find new agonists and antagonists of the GR. The best hits were further tested on the in vitro model of MDA-kb2 cells expressing luciferase activity in a GR-dependent manner. Nine new potential modulators of the receptor, belonging to six structurally diverse classes, were identified. Six of them, tetramethrin and cypermethrin, diethyl hexyl phthalate and diphenyl isophthalate, naphthol AS-OL and dicumyl peroxide, induced luciferase activity; while the other three, bisphenol P, bisphenol M, and Antioxidant 425, suppressed luciferase activity. Of the nine potential GR modulators, only bisphenol M displayed appreciable binding affinity for the receptor.

Benchmarking organic micropollutants in wastewater, recycled water and drinking water with in vitro bioassays

Thousands of organic micropollutants and their transformation products occur in water. Although often present at low concentrations, individual compounds contribute to mixture effects. Cell-based bioassays that target health-relevant biological endpoints may therefore complement chemical analysis for water quality assessment. The objective of this study was to evaluate cell-based bioassays for their suitability to benchmark water quality and to assess efficacy of water treatment processes. The selected bioassays cover relevant steps in the toxicity pathways including induction of xenobiotic metabolism, specific and reactive modes of toxic action, activation of adaptive stress response pathways and system responses. Twenty laboratories applied 103 unique in vitro bioassays to a common set of 10 water samples collected in Australia, including wastewater treatment plant effluent, two types of recycled water (reverse osmosis and ozonation/activated carbon filtration), stormwater, surface water, and drinking water. Sixty-five bioassays (63%) showed positive results in at least one sample, typically in wastewater treatment plant effluent, and only five (5%) were positive in the control (ultrapure water). Each water type had a characteristic bioanalytical profile with particular groups of toxicity pathways either consistently responsive or not responsive across test systems. The most responsive health-relevant endpoints were related to xenobiotic metabolism (pregnane X and aryl hydrocarbon receptors), hormone-mediated modes of action (mainly related to the estrogen, glucocorticoid, and antiandrogen activities), reactive modes of action (genotoxicity) and adaptive stress response pathway (oxidative stress response). This study has demonstrated that selected cell-based bioassays are suitable to benchmark water quality and it is recommended to use a purpose-tailored panel of bioassays for routine monitoring.

Chronic exposure to a low dose of ingested petroleum disrupts corticosterone receptor signalling in a tissue-specific manner in the house sparrow (Passer domesticus)

Stress-induced concentrations of glucocorticoid hormones (including corticosterone, CORT) can be suppressed by chronic exposure to a low dose of ingested petroleum. However, endocrine-disrupting chemicals could interfere with CORT signalling beyond the disruption of hormone titres, including effects on receptors in different target tissues. In this study, we examined the effects of 6 weeks of exposure to a petroleum-laced diet (1% oil weight:food weight) on tissue mass and intracellular CORT receptors in liver, fat, muscle and kidney (metabolic tissues), spleen (an immune tissue) and testes (a reproductive tissue). In the laboratory, male house sparrows were fed either a 1% weathered crude oil (n = 12) or a control diet (n = 12); glucocorticoid receptors and mineralocorticoid receptors were quantified using radioligand binding assays. In oil-exposed birds, glucocorticoid receptors were lower in one metabolic tissue (liver), higher in another metabolic tissue (fat) and unchanged in four other tissues (kidney, muscle, spleen and testes) compared with control birds. We saw no differences in mineralocorticoid receptors between groups. We also saw a trend towards reduced mass of the testes in oil-exposed birds compared with controls, but no differences in fat, kidney, liver, muscle or spleen mass between the two groups. This is the first study to examine the effects of petroleum on CORT receptor density in more than one or two target tissues. Given that a chronic low dose of ingested petroleum can affect stress-induced CORT titres as well as receptor density, this demonstrates that oil can act at multiple levels to disrupt an animal's response to environmental stressors. This also highlights the potential usefulness of the stress response as a bioindicator of chronic crude oil exposure.

A chemical screening procedure for glucocorticoid signaling with a zebrafish larva luciferase reporter system

Glucocorticoid stress hormones and their artificial derivatives are widely used drugs to treat inflammation, but long-term treatment with glucocorticoids can lead to severe side effects. Test systems are needed to search for novel compounds influencing glucocorticoid signaling in vivo or to determine unwanted effects of compounds on the glucocorticoid signaling pathway. We have established a transgenic zebrafish assay which allows the measurement of glucocorticoid signaling activity in vivo and in real-time, the GRIZLY assay (Glucocorticoid Responsive In vivo Zebrafish Luciferase activitY). The luciferase-based assay detects effects on glucocorticoid signaling with high sensitivity and specificity, including effects by compounds that require metabolization or affect endogenous glucocorticoid production. We present here a detailed protocol for conducting chemical screens with this assay. We describe data acquisition, normalization, and analysis, placing a focus on quality control and data visualization. The assay provides a simple, time-resolved, and quantitative readout. It can be operated as a stand-alone platform, but is also easily integrated into high-throughput screening workflows. It furthermore allows for many applications beyond chemical screening, such as environmental monitoring of endocrine disruptors or stress research.

In silico methods in the discovery of endocrine disrupting chemicals

The prevalence of sex hormone-dependent cancers, reproductive problems, obesity, and cardiovascular complications has risen especially in the Western world. It has been suggested, that the exposure to various endocrine disrupting chemicals (EDCs) contributes to the development and progression of these diseases. EDCs can interfere with various proteins: nuclear steroid hormone receptors, such as estrogen-, androgen-, glucocorticoid- and mineralocorticoid receptors (ER, AR, GR, MR), and enzymes that are involved in steroid hormone synthesis and metabolism, for example hydroxysteroid dehydrogenases (HSDs). Numerous chemicals are known as endocrine disruptors. However, the mechanism of action for most of these EDCs is still unknown. It is exhaustive and time consuming to test in vitro all chemicals - potential EDCs - used in industry, agriculture or as food preservatives against their effects on the endocrine system. Computational methods, such as virtual screening, quantitative structure activity relationships and docking, are already well recognized and used in drug development. The same methods could also aid the research on EDCs. So far, the computational methods in the search of EDCs have been retrospective. There are, however, some prospective studies reporting the use of in silico methods: five studies reporting the identification of previously unknown 17β-HSD3 inhibitors, MR agonists, and ER antagonists/agonists. This review provides an overview of case studies and in silico methods that are used in the search of EDCs. This article is part of a Special Issue entitled 'CSR 2013'.

Impact of cadmium exposure during pregnancy on hepatic glucocorticoid receptor methylation and expression in rat fetus

Adverse fetal environment due to maternal undernutrition or exposure to environmental chemicals alters glucocorticoid (GC) metabolism increasing the risk of metabolic disorders in adulthood. In this study, we investigated the effects of maternal exposure to cadmium (Cd, 50 ppm) during pregnancy in the methylation of fetal hepatic glucocorticoid receptor promoter (GR) and the correlation with its expression and that of the DNA methyltransferases (DNMT1a and 3a). We also studied the expression of liver phosphoenolpyruvate carboxykinase (PEPCK) and acyl-CoA oxidase (AOX), two enzymes involved in the metabolism of carbohydrates and lipids respectively. The methylation of the rat GR gene exon 1₁₀ (GR1₁₀) in nucleotides -2536 to -2361 was analyzed by pyrosequencing. Quantitative real time PCR was used to assess hepatic GR, PEPCK and AOX mRNA, and their protein levels using Western blotting analysis. Differential methylation was noted across groups at all CpG sites in the GR exon 1₁₀ in a sex-dependent manner. In males, CpG were more methylated than the controls (185±21%, p<0.001) but only CpG sites 1,6,7 and 9 showed a significantly different extent of methylation. In addition, a lower expression of GR (mRNA and protein) was found. On the contrary, in females, CpG were less methylated than the controls (62±11%, p<0.05) and overexpressed, affecting PEPCK and AOX expression, which did not change in males. The GR methylation profile correlates with DNMT3a expression which may explain epigenetic sex-dependent changes on GR1₁₀ promoter induced by Cd treatment. In conclusion, Cd exposure during pregnancy affects fetal liver DNMT3a resulting in sex-dependent changes in methylation and expression of GR1₁₀. Although these effects do not seem to be directly involved in the low birth weight and height, they may have relevant implications for long-term health.

Species-specific differences in the inhibition of human and zebrafish 11β-hydroxysteroid dehydrogenase 2 by thiram and organotins

Dithiocarbamates and organotins can inhibit enzymes by interacting with functionally essential sulfhydryl groups. Both classes of chemicals were shown to inhibit human 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2), which converts active cortisol into inactive cortisone and has a role in renal and intestinal electrolyte regulation and in the feto-placental barrier to maternal glucocorticoids. In fish, 11β-HSD2 has a dual role by inactivating glucocorticoids and generating the major androgen 11-ketotestosterone. Inhibition of this enzyme may enhance glucocorticoid and diminish androgen effects in fish. Here, we characterized 11β-HSD2 activity of the model species zebrafish. A comparison with human and mouse 11β-HSD2 revealed species-specific substrate preference. Unexpectedly, assessment of the effects of thiram and several organotins on the activity of zebrafish 11β-HSD2 showed weak inhibition by thiram and no inhibition by any of the organotins tested. Sequence comparison revealed the presence of an alanine at position 253 on zebrafish 11β-HSD2, corresponding to cysteine-264 in the substrate-binding pocket of the human enzyme. Substitution of alanine-253 by cysteine resulted in a more than 10-fold increased sensitivity of zebrafish 11β-HSD2 to thiram. Mutating cysteine-264 on human 11β-HSD2 to serine resulted in 100-fold lower inhibitory activity. Our results demonstrate significant species differences in the sensitivity of human and zebrafish 11β-HSD2 to inhibition by thiram and organotins. Site-directed mutagenesis revealed a key role of cysteine-264 in the substrate-binding pocket of human 11β-HSD2 for sensitivity to sulfhydryl modifying agents.

Associations between complex OHC mixtures and thyroid and cortisol hormone levels in East Greenland polar bears

The multivariate relationship between hair cortisol, whole blood thyroid hormones, and the complex mixtures of organohalogen contaminant (OHC) levels measured in subcutaneous adipose of 23 East Greenland polar bears (eight males and 15 females, all sampled between the years 1999 and 2001) was analyzed using projection to latent structure (PLS) regression modeling. In the resulting PLS model, most important variables with a negative influence on cortisol levels were particularly BDE-99, but also CB-180, -201, BDE-153, and CB-170/190. The most important variables with a positive influence on cortisol were CB-66/95, α-HCH, TT3, as well as heptachlor epoxide, dieldrin, BDE-47, p,p'-DDD. Although statistical modeling does not necessarily fully explain biological cause-effect relationships, relationships indicate that (1) the hypothalamic-pituitary-adrenal (HPA) axis in East Greenland polar bears is likely to be affected by OHC-contaminants and (2) the association between OHCs and cortisol may be linked with the hypothalamus-pituitary-thyroid (HPT) axis.

Relationships between POPs and baseline corticosterone levels in black-legged kittiwakes (Rissa tridactyla) across their breeding cycle

Chronic exposure to persistent organic pollutants (POPs) in wildlife might alter the response to environmental changes through interference with the regulation of stress hormones. Here, we examined the relationship between blood concentrations of several POPs and baseline plasma corticosterone levels in the black-legged kittiwake (Rissa tridactyla) during three distinct periods in the breeding season. The concentrations of POPs and corticosterone increased, whereas body mass decreased progressively from the pre-laying period to the incubation and the chick rearing period. ∑PCB (polychlorinated biphenyls) correlated positively with the baseline corticosterone levels during the pre-laying period, which might suggest that PCBs affect the regulation of corticosterone. However, this relationship was not found during the incubation or the chick rearing period. Possible explanations are discussed with emphasis on how total stress/allostatic load is handled during different periods and conditions.

Induction of SCEs and DNA fragmentation in bovine peripheral lymphocytes by in vitro exposure to tolylfluanid-based fungicide

The potential for genotoxic and cytotoxic effects of tolylfluanid-based fungicide (50% active agent) was evaluated using sister chromatid exchange (SCE) and proliferation indices (PI) in cultured bovine peripheral lymphocytes. For the detection of possible genetic damage, DNA fragmentation assay was also applied. Bovine lymphocytes cultured for 72 h were treated with the fungicide at the final concentrations of 1.75, 3.5, 8.75, and 17.5 μg/mL for the last 24 and 48 h of culture without S9 metabolic activation, and during the last 2 h of culture with S9 metabolic activation. In the SCE assays no evidence for genotoxic activity of the fungicide was found in treatments of 24 h without and 2 h with S9. After the 24 h exposure to tolylfluanid, a weak decrease in the PI was observed. With the prolonged exposure time (48 h), dose dependence in the increase of SCE frequencies was observed. Moreover, after 48 h exposure slight fragmentation of DNA at the concentrations of 3.5 and 8.75 μg/mL was demonstrated. SCE quantification is the most widely used approach for the assessment of genotoxic/cytogenetic effects of chemical compounds. Positive results in the assay at 48 h exposure indicated a potential of the fungicide to increase frequency of chromosomal damage (replication injuries) that is the confirmation of early effect of exposure.

Stress hormone masculinizes female morphology and behaviour

Sex steroids play major roles in vertebrate sexual differentiation. Unexpectedly, we now find that exposure to elevated levels of the naturally occurring stress hormone cortisol can also masculinize sexually dimorphic morphological characters and behaviour in adult female mosquitofish (Gambusia affinis) in a dose-dependent manner. Females masculinized by cortisol developed elongated anal fins with distal tip features similar to those of mature males. Most masculinized females also attempted to copulate when placed with normal females. Although the mechanism of masculinization is currently unknown, we propose a role for an enzyme that both inactivates cortisol and catalyzes the final step in synthesis of a major teleost androgen. This mechanism may also help explain some previously reported effects of stress on sexual development across vertebrate taxa. Our findings underscore the need to understand the full range of chemicals, both naturally occurring hormones and human-produced endocrine disruptors, that can influence sexual differentiation and reproductive function.

Plasma cortisol concentrations and lifestyle in a population of outdoor workers

The aim of this study was to assess whether exposure to urban pollution in outdoor workers, may alter plasma cortisol concentrations also in relation to the effect of smoking and drinking habits. The research was carried out on 498 outdoor police workers, divided into three groups; Group A: traffic policemen (TP), Group B: drivers (D), Group C: Other duties (OD). To evaluate separately the effect of using alcohol and smoking, each group was divided into three subgroups: (1) non-smokers and non-drinkers, (2) smokers and non-drinkers, (3) non-smokers and drinkers. Our results show cortisol mean values were significantly higher in the TP group compared to the D and OD groups without significant differences between the last two groups. The results suggest that exposure to pollutants associated with urban psychosocial stress may play a more important role on plasma cortisol levels than smoking and alcohol.

Environmental endocrine disruptors promote adipogenesis in the 3T3-L1 cell line through glucocorticoid receptor activation

The burgeoning obesity and diabetes epidemics threaten health worldwide, yet the molecular mechanisms underlying these phenomena are incompletely understood. Recently, attention has focused on the potential contributions of environmental pollutants that act as endocrine disrupting chemicals (EDCs) in the pathogenesis of metabolic diseases. Because glucocorticoid signaling is central to adipocyte differentiation, the ability of EDCs to stimulate the glucocorticoid receptor (GR) and drive adipogenesis was assessed in the 3T3-L1 cell line. Various EDCs were screened for glucocorticoid-like activity using a luciferase reporter construct, and four (bisphenol A (BPA), dicyclohexyl phthalate (DCHP), endrin, and tolylfluanid (TF)) were shown to significantly stimulate GR without significant activation of the peroxisome proliferator-activated receptor-gamma. 3T3-L1 preadipocytes were then treated with EDCs and a weak differentiation cocktail containing dehydrocorticosterone (DHC) in place of the synthetic dexamethasone. The capacity of these compounds to promote adipogenesis was assessed by quantitative oil red O staining and immunoblotting for adipocyte-specific proteins. The four EDCs increased lipid accumulation in the differentiating adipocytes and also upregulated the expression of adipocytic proteins. Interestingly, proadipogenic effects were observed at picomolar concentrations for several of the EDCs. Because there was no detectable adipogenesis when the preadipocytes were treated with compounds alone, the EDCs are likely promoting adipocyte differentiation by synergizing with agents present in the differentiation cocktail. Thus, EDCs are able to promote adipogenesis through the activation of the GR, further implicating these compounds in the rising rates of obesity and diabetes.

High-resolution mass spectrometric identification and quantification of glucocorticoid compounds in various wastewaters in the Netherlands

In the past two decades much research effort has focused on the occurrence, effects, and risks of estrogenic compounds. However, increasing emissions of new emerging compounds may also affect the action of hormonal pathways other than the estrogenic hormonal axis. Recently, a suite of novel CALUX bioassays has become available that enables looking further than estrogenic effects only. By employing these bioassays, we recently showed high glucocorticogenic activity in wastewaters collected at various sites in The Netherlands. However, since bioassays provide an integrated biological response, the identity of the responsible biological compounds remained unknown. Therefore, our current objective was to elucidate the chemical composition of the wastewater extracts used in our previous study by means of LC-high-resolution Orbitrap MS/MS and to determine if the compounds quantified could account for the observed glucocorticoid responsive (GR) CALUX bioassay response. The mass spectrometric analysis revealed the presence of various glucocorticoids in the range of 13-1900 ng/L. In extracts of hospital wastewater-collected prior to sewage treatment-several glucocorticoids were identified (cortisol 275-301 ng/L, cortisone 381-472 ng/L, prednisone 117-545 ng/L, prednisolone 315-1918 ng/L, and triamcinolone acetonide 14-41 ng/L) which are used to treat a great number of human pathologies. A potency balance calculation based on the instrumental analyses and relative potencies (REPs) of the individual glucocorticoids supports the conclusion that triamcinolone acetonide (REP = 1.3), dexamethasone (REP = 1), and prednisolone (REP = 0.2) are the main contributors to the glucocorticogenic activity in the investigated wastewater extracts. The action of these compounds is concentration additive and the overall glucocorticogenic activity can be explained to a fairly large extent by their contribution.

The glucocorticoid-activating enzyme 11beta-hydroxysteroid dehydrogenase type 1 has broad substrate specificity: Physiological and toxicological considerations

The primary function of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) is to catalyze the conversion of inactive to active glucocorticoid hormones and to modulate local glucocorticoid-dependent gene expression. Thereby 11beta-HSD1 plays a key role in the regulation of metabolic functions and in the adaptation of the organism to energy requiring situations. Importantly, elevated 11beta-HSD1 activity has been associated with metabolic disorders, and recent investigations with rodent models of obesity and type 2 diabetes provided evidence for beneficial effects of 11beta-HSD1 inhibitors, making this enzyme a promising therapeutic target. Several earlier and recent studies, mainly performed in vitro, revealed a relatively broad substrate spectrum of 11beta-HSD1 and suggested that this enzyme has additional functions in the metabolism of some neurosteroids (7-oxy- and 11-oxyandrogens and -progestins) and 7-oxysterols, as well as in the detoxification of various xenobiotics that contain reactive carbonyl groups. While there are many studies on the effect of inhibitors on cortisone reduction and circulating glucocorticoid levels and on the transcriptional regulation of 11beta-HSD1 in obesity and diabetes, only few address the so-called alternative functions of this enzyme. We review recent progress on the biochemical characterization of 11beta-HSD1, with a focus on cofactor and substrate specificity and on possible alternative functions of this enzyme.

Adrenocortical function of Arctic-breeding glaucous gulls in relation to persistent organic pollutants

Unpredictable changes in the environment stimulate the avian hypothalamo-pituitary-adrenal axis to produce corticosterone, which induces behavioural and metabolic changes that enhance survival in the face of adverse environmental conditions. In addition to profound environmental perturbations, such as severe weather conditions and unpredictable food shortages, many Arctic-breeding birds are also confronted with chronic exposure to persistent organic pollutants (POPs), some of which are known to disrupt endocrine processes. This study investigated the adrenocortical function of a top predator in the Arctic marine environment, the glaucous gull (Larus hyperboreus). High concentrations of organochlorines, brominated flame retardants and metabolically-derived products in blood plasma of incubating glaucous gulls were associated with high baseline corticosterone concentrations in both sexes and a reduced stress response in males. Contaminant-related changes in corticosterone concentration occurred over and above differences in body condition and seasonal variation. Chronically high corticosterone concentrations and/or a compromised adrenocortical response to stress can have negative effects on the health of an individual. The results of the present study suggest that exposure to POPs may increase the vulnerability of glaucous gulls to environmental stressors and thus could potentially compromise their ability to adapt to the rapidly changing environmental conditions associated with climate change that are currently seen in the Arctic.

Endocrine disrupters as obesogens

The recent dramatic rise in obesity rates is an alarming global health trend that consumes an ever increasing portion of health care budgets in Western countries. The root cause of obesity is thought to be a prolonged positive energy balance. Hence, the major focus of preventative programs for obesity has been to target overeating and inadequate physical exercise. Recent research implicates environmental risk factors, including nutrient quality, stress, fetal environment and pharmaceutical or chemical exposure as relevant contributing influences. Evidence points to endocrine disrupting chemicals that interfere with the body's adipose tissue biology, endocrine hormone systems or central hypothalamic-pituitary-adrenal axis as suspects in derailing the homeostatic mechanisms important to weight control. This review highlights recent advances in our understanding of the molecular targets and mechanisms of action for these compounds and areas of future research needed to evaluate the significance of their contribution to obesity.

Minireview: the case for obesogens

Obesity and obesity-related disorders, such as type 2 diabetes, hypertension, and cardiovascular disease, are epidemic in Western countries, particularly the United States. The conventional wisdom holds that obesity is primarily the result of a positive energy balance, i.e. too many calories in and too few calories burned. Although it is self-evident that fat cannot be accumulated without a higher caloric intake than expenditure, recent research in a number of laboratories suggests the existence of chemicals that alter regulation of energy balance to favor weight gain and obesity. These obesogens derail the homeostatic mechanisms important for weight control, such that exposed individuals are predisposed to weight gain, despite normal diet and exercise. This review considers the evidence for obesogens, how they might act, and where future research is needed to clarify their relative contribution to the obesity epidemic.