Hydroxylated metabolites of polychlorinated biphenyls and their endocrine disrupting mechanism

Hydroxylated polychlorinated biphenyls (OH-PCBs a group of main active metabolites of polychlorinated biphenyl (PCBs) which are typical persistent organic pollutants (Pops) I have been identified in wild animals and human. The endocrine disruption of OH-PCBs has been drawn great attention due to the similarity of their chemical structures to the natural estrogens and thyroid hormones. The metabolic pathways of PCBs, the levels of OHPCBs in organism, the endocrine disruption and other adverse effects of OH-PCBs are reviewed. The further investigation of OH-PCBs will not only reveal the toxicological mechanism of PCBs, but also can lay scientific basis for setting up the risk assessment of POPs contamination and early-warning system in China.

Endocrine disrupting effects on Chinese rare minnow (Gobiocypris rarus) fed with field collected Limnodrilus sp.

The potential endocrine disrupting effects and other toxicity effects on aquatic biota resulted from food uptake was simulated by feeding the laboratory cultured rare minnow(Gobiocypris rarus) with field collected Limnodrilus sp. The results indicated that the food chain processes affected significantly the growth, slightly reduced gonadosomatic indices, and elevated hepatosomatic indices. There was an obvious vitellogenin(VTG) induction, which generally only occurred in mature female, in the serum of juvenile rare minnow and mature male when fed with Limnodrilus sp. In addition, the rare minnow feeding on Limnodrilus sp. had significantly high renal indices, it meant obvious renal hyperplasia. The present work suggested that. Limnodrilus sp. from field water may contain toxic pollutants and could lead to endocrine disruption effects to the predators. It was concluded that endocrine disruptors may not only be assimilated through water, but also be bioconcentrated through food web. The results also suggested the importance of food selection in conducting the study of endocrine disruption effects using sensitive species.

Appropriateness of Largemouth Bass as a Model Species for Detection of Endocrine Dissruption

Intersex in largemouth bass (Micropterus salmoides) has been correlated with regional anthropogenic activity, but has not been causally linked to environmental factors. Four groups of hatchery-reared largemouth bass (LMB) and fathead minnows (FHM) of varying ages and sex were exposed to aqueous poultry litter mixtures, 17β- estradiol (E2), and controls. Water samples were analyzed for estrogens through liquid chromatography tandem mass spectrometry and estrogenicity through the bioluminescent yeast estrogen screen assay. Fish plasma was analyzed for the egg yolk protein vitellogenin (Vtg) using enzyme–linked immunosorbent assay and gonad tissue was examined histologically for enumeration of testicular oocytes (TO). Water chemistry revealed typical E2 conversion to Estrone with subsequent decay over the exposure periods. A modest prevalence of TO (9.4%) was detected with no apparent treatment effect. While significant Vtg induction was found in E2 exposed FHM, minimal Vtg induction was found in male LMB. Despite field findings of intersex in male LMB, this species may be poorly suited for laboratory investigations into endocrine disruption.

An in vitro investigation of endocrine disrupting effects of tricothecenes deoxynivalenol (DON), T-2, HT-2 toxins

Trichothecenes are a large family of chemically related mycotoxins. Deoxynivalenol (DON), T-2 and HT-2 toxins belong to this family and are produced by various species of Fusarium. The H295R steroidogenesis assay, regulation of steroidogenic gene expression and reporter gene assays (RGAs) for the detection of androgen, estrogen, progestagen and glucocorticoid (ant)agonist responses, have been used to assess the endocrine disrupting activity of DON, T-2 and HT-2 toxins.

H295R cells were used as a model for steroidogenesis and gene expression studies and exposed with either DON (0.1–1000 ng/ml), T-2 toxin (0.0005–5 ng/ml) or HT-2 toxin (0.005–50 ng/ml) for 48 h. We observed a reduction in hormone levels in media of exposed cells following radioimmunoassay. Cell viability was determined by four colorimetric assays and we observed reduced cell viability with increasing toxin concentrations partly explaining the significant reduction in hormone levels at the highest toxin concentration of all three trichothecenes.

Thirteen of the 16 steroidogenic genes analyzed by quantitative real time PCR (RT-qPCR) were significantly regulated (P < 0.05) by DON (100 ng/ml), T-2 toxin (0.5 ng/ml) and HT-2 toxin (5 ng/ml) compared to the control, with reference genes (B2M, ATP5B and ACTB). Whereas HMGR and CYP19 were down-regulated, CYP1A1 and CYP21 were up-regulated by all three trichothecenes. DON further up-regulated CYP17, HSD3B2, CYP11B2 and CYP11B1 and down-regulated NR5A1. T-2 toxin caused down-regulation of NR0B1 and NR5A1 whereas HT-2 toxin induced up-regulation of EPHX and HSD17B1 and down-regulation of CYP11A and CYP17. The expressions of MC2R, StAR and HSD17B4 genes were not significantly affected by any of the trichothecenes in the present study.

Although the results indicate that there is no evidence to suggest that DON, T-2 and HT-2 toxins directly interact with the steroid hormone receptors to cause endocrine disruption, the present findings indicate that exposure to DON, T-2 toxin and HT-2 toxin have effects on cell viability, steroidogenesis and alteration in gene expression indicating their potential as endocrine disruptors.

Endocrine disrupting effects of ochratoxin A at the level of nuclear receptor activation and steroidogenesis

Ochratoxin A (OTA) is a mycotoxin and extrolite of fungi which has been reported in a range of foods. This study uses mammalian reporter gene assays (RGAs) with natural steroid receptors and the H295R steroidogenesis assay to assess the endocrine disrupting activity of OTA.

At the receptor level, OTA (within a concentration range of 0.25–2500 ng/ml) did not induce an agonistic response in an oestrogen, androgen, progestagen or glucocorticoid RGA. An antagonistic effect was observed in all of the RGAs at the highest concentration tested (2500 ng/ml). However, while there was no significant cytotoxic effect observed in the MTT (thiazolyl blue tetrazolium bromide) cell viability assay at this concentration, there was a corresponding change in cell morphology which may be related to the resulting antagonistic effect.

At the hormone production level, H295R cells were used as a steroidogenesis model and exposed to OTA (within a concentration range of 0.1–1000 ng/ml). Treatment of the cells with 1000 ng/ml OTA increased the production of estradiol (117 ± 14 ng/ml) over 3 times that of the solvent control (36 ± 9 pg/ml). Western blotting confirmed an increase in aromatase protein.

Overall the results indicate that OTA does not appear to interact with steroid receptors but has the potential to cause endocrine disruption by interfering with steroidogenesis. This is the first study identifying the effect OTA may have on production of the steroid hormone estradiol.

An in vitro investigation of endocrine disrupting effects of the mycotoxin alternariol

Alternariol (AOH) is a mycotoxin commonly produced by Alternaria alternata on a wide range of foods. Few studies to date have been performed to evaluate the effects of AOH on endocrine activity. The present study makes use of in vitro mammalian cellular based assays and gene expression to investigate the ability of AOH to act as an endocrine disruptor by various modes of action. Reporter gene assays (RGAs), incorporating natural steroid hormone receptors for oestrogens, androgens, progestagens and glucocorticoids were used to identify endocrine disruption at the level of nuclear receptor transcriptional activity, and the H295R steroidogenesis assay was used to assess endocrine disruption at the level of gene expression and steroid hormone production. AOH exhibited a weak oestrogenic response when tested in the oestrogen responsive RGA and binding of progesterone to the progestagen receptor was shown to be synergistically increased in the presence of AOH. H295R cells when exposed to 0.1-1000ng/ml AOH, did not cause a significant change in testosterone and cortisol hormones but exposure to 1000ng/ml (3.87µM) AOH resulted in a significant increase in estradiol and progesterone production. In the gene expression study following exposure to 1000ng/ml (3.87µM) AOH, only one gene NR0B1 was down-regulated, whereas expression of mRNA for CYP1A1, MC2R, HSD3B2, CYP17, CYP21, CYP11B2 and CYP19 was up-regulated. Expression of the other genes investigated did not change significantly. In conclusion AOH is a weak oestrogenic mycotoxin that also has the ability to interfere with the steroidogenesis pathway.

Statistical modeling suggests that antiandrogens in effluents from wastewater treatment works contribute to widespread sexual disruption in fish living in English rivers.

BACKGROUND: The widespread occurrence of feminized male fish downstream of some wastewater treatment works has led to substantial interest from ecologists and public health professionals. This concern stems from the view that the effects observed have a parallel in humans, and that both phenomena are caused by exposure to mixtures of contaminants that interfere with reproductive development. The evidence for a "wildlife-human connection" is, however, weak: Testicular dysgenesis syndrome, seen in human males, is most easily reproduced in rodent models by exposure to mixtures of antiandrogenic chemicals. In contrast, the accepted explanation for feminization of wild male fish is that it results mainly from exposure to steroidal estrogens originating primarily from human excretion. OBJECTIVES: We sought to further explore the hypothesis that endocrine disruption in fish is multi-causal, resulting from exposure to mixtures of chemicals with both estrogenic and antiandrogenic properties. METHODS: We used hierarchical generalized linear and generalized additive statistical modeling to explore the associations between modeled concentrations and activities of estrogenic and antiandrogenic chemicals in 30 U.K. rivers and feminized responses seen in wild fish living in these rivers. RESULTS: In addition to the estrogenic substances, antiandrogenic activity was prevalent in almost all treated sewage effluents tested. Further, the results of the modeling demonstrated that feminizing effects in wild fish could be best modeled as a function of their predicted exposure to both anti-androgens and estrogens or to antiandrogens alone. CONCLUSION: The results provide a strong argument for a multicausal etiology of widespread feminization of wild fish in U.K. rivers involving contributions from both steroidal estrogens and xeno-estrogens and from other (as yet unknown) contaminants with antiandrogenic properties. These results may add farther credence to the hypothesis that endocrine-disrupting effects seen in wild fish and in humans are caused by similar combinations of endocrine-disrupting chemical cocktails.

Endocrine disrupters and human health: Could oestrogenic chemicals in body care cosmetics adversely affect breast cancer incidence in women? A review of evidence and call for further research

In the decade that has elapsed since the suggestion that exposure of the foetal/developing male to environmental oestrogens could be the cause of subsequent reproductive and developmental effects in men, there has been little definitive research to provide conclusions to the hypothesis. Issues of exposure and low potency of environmental oestrogens may have reduced concerns. However, the hypothesis that chemicals applied in body care cosmetics (including moisturizers, creams, sprays or lotions applied to axilla or chest or breast areas) may be affecting breast cancer incidence in women presents a different case scenario, not least in the consideration of the exposure issues. The specific cosmetic type is not relevant but the chemical ingredients in the formulations and the application to the skin is important. The most common group of body care cosmetic formulation excipients, namely p-hydroxybenzoic acid esters or parabens, have been shown recently to be oestrogenic in vitro and in vivo and now have been detected in human breast tumour tissue, indicating absorption (route and causal associations have yet to be confirmed). The hypothesis for a link between oestrogenic ingredients in underarm and body care cosmetics and breast cancer is forwarded and reviewed here in terms of. data on exposure to body care cosmetics and parabens, including dermal absorption; paraben oestrogenicity; the role of oestrogen in breast cancer; detection of parabens in breast tumours; recent epidemiology studies of underarm cosmetics use and breast cancer; the toxicology database; the current regulatory status of parabens and regulatory toxicology data uncertainties. Notwithstanding the major public health issue of the causes of the rising incidence of breast cancer in women, this call for further research may provide the first evidence that environmental factors may be adversely affecting human health by endocrine disruption, because exposure to oestrogenic chemicals through application of body care products (unlike diffuse environmental chemical exposures) should be amenable to evaluation, quantification and control. The exposure issues are clear and the exposed population is large, and these factors should provide the necessary impetus to investigate this potential issue of public health. Copyright (C) 2004 John Wiley Sons, Ltd.

Endocrine disrupting compounds: can they target the immune system of fish?

Endocrine disruption, in particular disruption by estrogen-active compounds, has been identified as an important ecotoxicological hazard in the aquatic environment. Research on the impact of endocrine disrupting compounds (EDCs) on wildlife has focused on disturbances of the reproductive system. However, there is increasing evidence that EDCs affect a variety of physiological systems other than the reproductive system. Here, we discuss if EDCs may be able to affect the immune system of fish, as this would have direct implications for individual fitness and population growth. Evidence suggesting an immunomodulatory role of estrogens in fish comes from the following findings: (a) estrogen receptors are expressed in piscine immune organs, (b) immune gene expression is modulated by estrogen exposure, and (c) pathogen susceptibility of fish increases under estrogen exposure.

Interference of endocrine disrupting chemicals with aromatase CYP19 expression or activity, and consequences for reproduction of teleost fish

Many natural and synthetic compounds present in the environment exert a number of adverse effects on the exposed organisms, leading to endocrine disruption, for which they were termed endocrine disrupting chemicals (EDCs). A decrease in reproduction success is one of the most well-documented signs of endocrine disruption in fish. Estrogens are steroid hormones involved in the control of important reproduction-related processes, including sexual differentiation, maturation and a variety of others. Careful spatial and temporal balance of estrogens in the body is crucial for proper functioning. At the final step of estrogen biosynthesis, cytochrome P450 aromatase, encoded by the cyp19 gene, converts androgens into estrogens. Modulation of aromatase CYP19 expression and function can dramatically alter the rate of estrogen production, disturbing the local and systemic levels of estrogens. In the present review, the current progress in CYP19 characterization in teleost fish is summarized and the potential of several classes of EDCs to interfere with CYP19 expression and activity is discussed. Two cyp19 genes are present in most teleosts, cyp19a and cyp19b, primarily expressed in the ovary and brain, respectively. Both aromatase CYP19 isoforms are involved in the sexual differentiation and regulation of the reproductive cycle and male reproductive behavior in diverse teleost species. Alteration of aromatase CYP19 expression and/or activity, be it upregulation or downregulation, may lead to diverse disturbances of the above mentioned processes. Prediction of multiple transcriptional regulatory elements in the promoters of teleost cyp19 genes suggests the possibility for several EDC classes to affect cyp19 expression on the transcriptional level. These sites include cAMP responsive elements, a steroidogenic factor 1/adrenal 4 binding protein site, an estrogen-responsive element (ERE), half-EREs, dioxin-responsive elements, and elements related to diverse other nuclear receptors (peroxisome proliferator activated receptor, retinoid X receptor, retinoic acid receptor). Certain compounds including phytoestrogens, xenoestrogens, fungicides and organotins may modulate aromatase CYP19 activity on the post-transcriptional level. As is shown in this review, diverse EDCs may affect the expression and/or activity of aromatase cyp19 genes through a variety of mechanisms, many of which need further characterization in order to improve the prediction of risks posed by a contaminated environment to teleost fish population.

Policy Development at a Local Level to Mitigate Depositing Endocrine Disruptors into Aquatic Ecosystems

Endocrine disruptors are suspected to cause disruption to organisms in aquatic environments. Intersex fish and skewed populations of females outnumbering males have been found where effluents from municipal wastewater treatment plants enter into receiving waters. The science needed to substantiate a link of these suspected pollutants as the cause of problems to human health or the environmental is in its infancy. Empirical research was used to identify suspected endocrine disruptors, their sources, and the difficulties involved in regulating these emerging contaminants. This project examined entities that are addressing endocrine disruption and provides cost-effective recommendations for municipalities to develop policies to mitigate the amount of endocrine disruptors entering into receiving waters and limiting the effects caused by endocrine disruption.

Reproductive effects of endocrine disrupting chemicals, bisphenol-A and 17β-oestradiol, on Cerastoderma edule from south-west England: field study and laboratory exposure

Endocrine disruption has rarely been reported in field populations of the edible cockle and the context with the general health of the shellfish is unclear. This study examined the reproductive state of two Cerastoderma edule populations over a 6-month period to assess their reproductive condition, the incidence of intersex and presence of parasitic infection. A further seven native sites from south-west England were examined during the peak reproductive season to identify the presence of intersex within the region. Laboratory exposures of organisms collected from field populations showed a significantly female-biased sex ratio compared with controls when exposed to the endocrine disrupting chemicals, bisphenol-A (nominal concentration: 0.1 µg L−1) and 17β-oestradiol (nominal concentration: 0.1 µg L−1), but none of the chemical exposures induced intersex. Intersex was revealed in seven out of the nine native populations of C. edule sampled at peak reproductive season. The highest incidence and most severe case of intersex were reported at Lower Anderton on the River Tamer which also had a significantly female-biased sex ratio. Additionally, the dominant trematode family was the Bucephalaidae. Parasitic infection influences the maturity of C. edule by lowering both mean gonad index and condition index. These results suggest that endocrine disrupting chemicals could be contributing factors towards the development of intersex in C. edule.

Reproductive effects of endocrine disrupting chemicals, bisphenol-A and 17β-oestradiol, on Cerastoderma edule from south-west England: field study and laboratory exposure

Endocrine disruption has rarely been reported in field populations of the edible cockle and the context with the general health of the shellfish is unclear. This study examined the reproductive state of two Cerastoderma edule populations over a 6-month period to assess their reproductive condition, the incidence of intersex and presence of parasitic infection. A further seven native sites from south-west England were examined during the peak reproductive season to identify the presence of intersex within the region. Laboratory exposures of organisms collected from field populations showed a significantly female-biased sex ratio compared with controls when exposed to the endocrine disrupting chemicals, bisphenol-A (nominal concentration: 0.1 µg L−1) and 17β-oestradiol (nominal concentration: 0.1 µg L−1), but none of the chemical exposures induced intersex. Intersex was revealed in seven out of the nine native populations of C. edule sampled at peak reproductive season. The highest incidence and most severe case of intersex were reported at Lower Anderton on the River Tamer which also had a significantly female-biased sex ratio. Additionally, the dominant trematode family was the Bucephalaidae. Parasitic infection influences the maturity of C. edule by lowering both mean gonad index and condition index. These results suggest that endocrine disrupting chemicals could be contributing factors towards the development of intersex in C. edule.

Trois expositions environnementales, un trouble : perturbations endocrine, du métabolisme monocarboné, et du microbiote intestinal maternel pendant la gestation déclenchent des phénotypes de type autistique chez le rat de type sauvage

Les Troubles du Spectre Autistique (TSA) sont caractérisés par deux principaux symptômes : des difficultés de communication sociale et des comportements stéréotypés et intérêts restreints. Les TSA touchent 5 fois plus les garçons que les filles et une augmentation de la prévalence exponentielle et continue a été observée aux États-Unis ces dernières décennies. Cette augmentation ne peut s’expliquer par les facteurs génétiques à eux seuls qui ne représentent que 5 à 15% des cas de TSA. Il est donc indispensable d’identifier de potentiels facteurs de risque environnementaux des TSA. Le but de ce travail est d’étudier différents facteurs environnementaux potentiellement modifiables dans le développement de phénotypes autistiques dans différents modèles précliniques des TSA. Les objectifs spécifiques sont : (i) caractériser les effets neurocomportementaux provoqués par une exposition périnatale simultanée à 5 perturbateurs endocriniens parmi les plus prévalent dans notre environnement quotidien (DEHP, DBP, DiNP, BDE-47, BDE-99) à de faibles doses pertinentes pour l’exposition humaine, (ii) identifier les effets neurocomportementaux associés à une altération périconceptionnelle du microbiote maternelle (iii) déterminer les effets neurocomportementaux associés à une altération périconceptionnelle du métabolisme monocarboné. Les résultats présentés dans cette thèse démontrent le potentiel de chacun de ces facteurs environnementaux d’altérer le développement cérébral fœtal. Chaque condition expérimentale a provoqué l’apparition de traits autistiques chez les rats, avec des spécificités comportementales pour chaque exposition développementale. Des déficits d’interactions sociales ont été observés dans chaque situation expérimentale, associés soit à de l’anxiété, de l’hyperactivité, des altérations d’intégration sensorimotrice, et/ou des stéréotypies. Cela nous force à considérer les TSA comme une pathologie aux multiples facettes où l’hétérogénéité des tableaux cliniques est représentative de l’hétérogénéité des causes possibles. La multitude des interactions environnementales courantes possibles avec l’épigénome pourrait être à la base de la grande diversité observée dans la sévérité des symptômes et / ou des comorbidités des TSA. Ce travail ouvre des perspectives futures de prévention ciblée des TSA fondées sur de potentielles modifications de l’environnement comme la réduction de l’exposition aux perturbateurs endocriniens, ou des supplémentations en donneurs monocarbonés (e.g. acide folique) et/ou probiotiques.

A preliminary study on assessing body burden of persistent organic pollutants (POPs) in infants through analysis of faeces

Most persistent organic pollutants (POPs) like polychlorinated biphenyls (PCBs), a range of polybrominated diphenyl ethers (PBDEs) and organochlorine pesticides (OCPs) are readily absorbed (via the ingestion and inhalation) and accumulate in fatty tissue, including adipose tissue and human milk [1]. Health effects related to exposure to these chemicals may include neurological effects, altered functioning of the nervous system and/or endocrine disruption [2-4]. The burden of environmental disease is recognized as much higher for children than adults, especially in young children under 5 years of age worldwide [5]. There is increased concern regarding the environmental impact on the health of children who have been disproportionately affected by environmental problems. For example they may be subjected to relatively higher exposure, have greater physiological susceptibility and/or suffer more extreme consequences due to growth [6-9]. It is therefore worthwhile to assess the correlation between burden of disease and exposure to xenobiotic chemical pollutants like POPs. Such assessment may provide guidance for legislative changes regarding chemical bans and give reliable advice to parents including lactating mothers.