Endocrine disruptors and human health: is there a problem

Removal of the endocrine disrupter butyl benzyl phthalate from the environment

Butyl benzyl phthalate (BBP), an aryl alkyl ester of 1,2-benzene dicarboxylic acid, is extensively used in vinyl tiles and as a plasticizer in PVC in many commonly used products. BBP, which readily leaches from these products, is one of the most important environmental contaminants, and the increased awareness of its adverse effects on human health has led to a dramatic increase in research aimed at removing BBP from the environment via bioremediation. This review highlights recent progress in the degradation of BBP by pure and mixed bacterial cultures, fungi, and in sludge, sediment, and wastewater. Sonochemical degradation, a unique abiotic remediation technique, and photocatalytic degradation are also discussed. The degradation pathways for BBP are described, and future research directions are considered.

Assessment of estrogenic activity and total lipids in maternal biological samples (serum and breast milk)

The present study investigated estrogenic activity and total lipid levels in maternal serum and breast milk. The study was performed with 50 mothers from Fang district of northern Thailand. Maternal serum was collected 5 times, including the second trimester, pre-delivery period, delivery period, and lactating period at day 30 and day 60. Breast milk was collected 7 times, including day 1, 7, 14, 21, 30, 45, and 60 of lactation. There were the same patterns of variation between estrogenicity and total lipid levels both in serum and breast milk. The correlation between serum estrogenicity and serum total lipids was found with a correlation coefficient (r) ranging from 0.403 to 0.661. However, no correlation was found between milk estrogenicity and milk total lipids. The results therefore suggest that lipid contents might be the major factors affecting the variation of estrogenicity levels, and xenoestrogens, which the mother subjects exposed, were lipophilic pollutants. The remarkable findings were that the mean levels of estrogenicity in breast milk were approximately 8-13.5 times higher than those in maternal serum compared at the same period. However, no correlation was found between estrogenicity levels in serum and breast milk, leading to decreased accuracy in predicted infant exposure by maternal serum.

First evidence of estrogenic potential of the cyanobacterial heptotoxins the nodularin-R and the microcystin-LR in cultured mammalian cells

The estrogenic activity of cyanobacterial hepatotoxins microcystin-LR (MC-LR) and nodularin-R (NOD-R) was for the first time investigated invitro in a stably transfect cell line with an estrogen-regulated luciferase gene. Treatment of cells with NOD-R caused a dose-dependent increase in the luciferase activity. NOD-R gave rise to an induction of luciferase activity with an EC(50) value of 66.4 nM, whereas the positive control, 17beta-estradiol (E2) had an EC(50) of 9.6 pM. This indicates that NOD-R is a 6900-fold weaker inducer of luciferase than E2. In contrast, only a slight but significant activation of the luciferase gene was observed with MC-LR between 2.01 and 60.1 nM, and a maximal-induced response was observed with 10.1 nM, approximately 25% of the maximal effect obtained with 1 nM E2. The decrease in the luciferase activity at high MC-LR concentrations can be explained by a cytotoxic effect. No synergistic estrogenic effect was observed when each toxin was co-administrated with E2. However, the induction of the luciferase activity by NOD-R and MC-LR was inhibited by co-treatment with 1 microM of the pure estrogenic receptor (ER) antagonist ICI 182,780, thus proving the ER-dependency of the estrogenic effect.

Minding the calcium store: Ryanodine receptor activation as a convergent mechanism of PCB toxicity

Chronic low-level polychlorinated biphenyl (PCB) exposures remain a significant public health concern since results from epidemiological studies indicate that PCB burden is associated with immune system dysfunction, cardiovascular disease, and impairment of the developing nervous system. Of these various adverse health effects, developmental neurotoxicity has emerged as a particularly vulnerable endpoint in PCB toxicity. Arguably the most pervasive biological effects of PCBs could be mediated by their ability to alter the spatial and temporal fidelity of Ca2+ signals through one or more receptor-mediated processes. This review will focus on our current knowledge of the structure and function of ryanodine receptors (RyRs) in muscle and nerve cells and how PCBs and related non-coplanar structures alter these functions. The molecular and cellular mechanisms by which non-coplanar PCBs and related structures alter local and global Ca2+ signaling properties and the possible short and long-term consequences of these perturbations on neurodevelopment and neurodegeneration are reviewed.

Three structurally different polychlorinated biphenyl congeners (Pcb 118, 153, and 126) affect hormone production and gene expression in the human H295R in vitro model

Polychlorinated biphenyls (PCB) are ubiquitous environmental pollutants that have been linked to adverse health effects including endocrine disruption. This study compared the mono-ortho-substituted PCB 118 and di-ortho-substituted PCB 153 with the non-ortho-substituted PCB 126, for possible effects on steroid hormone production and on the expression of 10 genes encoding proteins involved in steroidogenesis. The H295R human adenocarcinoma cell line was used as an in vitro model. Cells were exposed for 48 h to solvent control (dimethyl sulfoxide, DMSO) or 6 different concentrations ranging from 40 pM to 4 muM of one of the three test compounds. All three congeners significantly increased the production of estradiol-17beta. PCB 118 produced a rise in progesterone and cortisol in a concentration-dependent manner, similar to PCB 126. Testosterone was significantly reduced in response to PCB 153 but not PCB 118 or PCB 126. All three congeners elevated aldosterone at the highest concentration tested. A significant increase was observed in CYP11B2 mRNA levels in cells exposed to the three congeners. In addition, PCB 126 upregulated CYP19, 3beta-HSD2, StAR, and HMGR mRNA levels at the highest concentration tested, and downregulated CYP21 at 40 nM. In conclusion, all three PCB congeners are capable of modulating steroidogenesis in H295R in a concentration-dependent manner, whereby the hormone profile following PCB 118 exposure resembles that of PCB 126. Where changes in gene expression profile are concerned, exposure to PCB 126 showed the greatest effects.

Practical overview of analytical methods for endocrine-disrupting compounds, pharmaceuticals and personal care products in water and wastewater

The detection of organic micropollutants, such as endocrine-disrupting compounds, pharmaceuticals and personal care products, in wastewater and the aquatic environment has brought increasing concern over their potential adverse ecological and human impacts. These compounds are generally present at trace levels (ng l(-1)) and in complex water matrices, such as wastewaters and surface waters, making their analysis difficult. Currently, no standardized analytical methods are available for the analysis of organic micropollutants in environmental waters. Owing to the diversity of physico-chemical properties exhibited by the various classes of organic micropollutants, the majority of established analytical methods described in the literature focus on a specific class of compounds, with few methods applicable to multi-class compound analysis. As such, analytical challenges and limitations contribute to the lack of understanding of the effectiveness of drinking water and wastewater treatment processes to remove organic micropollutants. This paper provides a practical overview of current analytical methods that have been developed for the analysis of multiple classes of organic micropollutants from various water matrices and describes the challenges and limitations associated with the development of these methods.

Serum levels of organochlorine pesticides in healthy adults from five regions of Spain

The aim of this study was to measure of serum levels of p,p'-dichlorodiphenyl trichloroethane (p,p'-DDT), p,p'-dichlorodiphenyl dichlorethylene (p,p'-DDE), beta-hexachlorocyclohexane (beta-HCH), and hexachlorobenzene (HCB) in healthy adults in Spain. Furthermore, we also analyzed these levels according to dietary, other lifestyle factors and anthropometric characteristics. We measured the concentrations of such organochlorine pesticides (OCPs) in serum samples collected during 1992-1996 from 953 subjects aged 35-64 years, they were residents of five Spanish regions, they were randomly selected from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. OCPs were determined by means of gas chromatography with electron-capture detection (GC-ECD). The most frequent compound found in serum was p,p'-DDE, present in 98% of the samples, followed by HCB and beta-HCH, found in 89% and 77% of samples, respectively, while p,p'-DDT could be measured only in 26% of subjects. The geometric means of serum concentrations (ng/g lipid) were 822 for p,p'-DDE, 167 for beta-HCH, and 379 for HCB. The concentrations of all OCPs were positively associated with age and body mass index, and decreased along the period of blood collection. No association was found between OCPs levels and dietary factors. The concentrations of p,p'-DDE and beta-HCB were higher in Murcia, one of southern regions, most likely associated with intensive past use of pesticides related to agricultural practices, while higher levels of HCB were found in Navarra, located in the north, maybe due to industrial use rather than agricultural application.

Responses of PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine) in MCF-7 cells are culture condition dependent

To compare the effects of the food toxin 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP) and estradiol in hormone-responsive MCF-7 cells, the cells were exposed to different concentrations of either PhIP or estradiol. The effect of various culture conditions (e.g. phenol red, FBS, vehicle (DMSO/EtOH) and seeding density) on responses was studied. Cells were continuously grown with steroid-containing or -deprived medium, or switched from steroid-containing to -deprived medium for the experiments to minimize the effect of background estrogenicity. Effects of PhIP and estradiol on cell viability and proliferation were determined by ATP analysis and Ki-67 immunocytochemistry. Expression of estrogen receptor alpha, cell stress markers (p53 and ERK) and estrogen responsive proteins (c-myc and ERK) were immunoblotted. All concentrations of estradiol induced cell proliferation, viability and changes in protein expression, typical for estrogenic responses. PhIP, however, increased viability only at low concentrations and depending on culture conditions. No changes in protein expressions by PhIP were noted, not even when switching cells from steroid-containing to -deprived medium which down-regulated the expression of proteins at basal level. Vehicle affected significantly viability, especially after exposure to PhIP, but not protein expression while medium changes affected both. In conclusion, the effects of PhIP and estradiol in MCF-7 cells are dependent on culture conditions. The detected PhIP-induced changes are weaker compared to those induced by estradiol.

Polychlorinated biphenyls in Spanish adults: determinants of serum concentrations

BACKGROUND

Polychlorinated biphenyls (PCBs) are persistent compounds that may pose an environmental hazard to humans, food being the main source of exposure for the general population.

OBJECTIVE

To measure the serum concentrations of the main PCBs in subjects from the general population in Spain, and to assess potential determinants of such concentrations.

METHODS

Serum was obtained from blood samples of 953 subjects aged 35-64 years, residents in five Spanish regions (three from the North and two from the South), randomly selected from the EPIC-Spain cohort. Blood collection took place during 1992-1996 and four PCB congeners (118, 138, 153 and 180) were determined by means of gas chromatography with electron-capture detection (GC-ECD).

RESULTS

The concentration of total PCBs was 459 ng/g lipids (or 3.1 microg/l); the corresponding figures for PCB 153 were 186 ng/g lipids and 1.25 microg/l. Men had higher values than women, PCB levels increased with age, and serum concentration of PCBs was higher in northern regions. Body mass index (BMI) was inversely related to PCB concentrations, and fish intake was the dietary factor showing the greatest association with serum PCBs. The pattern described was similar for each congener separately.

CONCLUSIONS

We found concentrations similar to those reported in European countries where blood collection was carried during the same period. Regional differences within Spain are not fully explained by anthropometric or dietary factors. The inverse association with BMI suggests that in the mid-1990s there was still ongoing or recent exposure to PCBs in Spain.

Persistent organic pollutants in fish oil supplements on the Canadian market: polychlorinated biphenyls and organochlorine insecticides

Fish and seal oil dietary supplements, marketed to be rich in omega-3 fatty acids, are frequently consumed by Canadians. Samples of these supplements (n = 30) were collected in Vancouver, Canada, between 2005 and 2007. All oil supplements were analyzed for polychlorinated biphenyls (PCBs) and organochlorine insecticides (OCs) and each sample was found to contain detectable residues. The highest SigmaPCB and SigmaDDT (1,1,1-trichloro-di-(4-chlorophenyl)ethane) concentrations (10400 ng/g and 3310 ng/g, respectively) were found in a shark oil sample while lowest levels were found in supplements prepared using mixed fish oils (anchovy, mackerel, and sardine) (0.711 ng SigmaPCB/g and 0.189 ng SigmaDDT/g). Mean SigmaPCB concentrations in oil supplements were 34.5, 24.2, 25.1, 95.3, 12.0, 5260, 321, and 519 ng/g in unidentified fish, mixed fish containing no salmon, mixed fish with salmon, salmon, vegetable with mixed fish, shark, menhaden (n = 1), and seal (n = 1), respectively. Maximum concentrations of the other OCs were generally observed in the seal oil. The hexachlorinated PCB congeners were the dominant contributors to SigmaPCB levels, while SigmaDDT was the greatest contributor to organochlorine levels. Intake estimates were made using maximum dosages on manufacturers' labels and results varied widely due to the large difference in residue concentrations obtained. Average SigmaPCB and SigmaDDT intakes were calculated to be 736 +/- 2840 ng/d and 304 +/- 948 ng/d, respectively.

Cadmium--a metallohormone?

Cadmium is a heavy metal that is often referred to as the metal of the 20th century. It is widely used in industry principally in galvanizing and electroplating, in batteries, in electrical conductors, in the manufacture of alloys, pigments, and plastics, and in the stabilization of phosphate fertilizers. As a byproduct of smelters, cadmium is a prevalent environmental contaminant. In the general population, exposure to cadmium occurs primarily through dietary sources, cigarette smoking, and, to a lesser degree, drinking water. Although the metal has no known physiological function, there is evidence to suggest that the cadmium is a potent metallohormone. This review summarizes the increasing evidence that cadmium mimics the function of steroid hormones, addresses our current understanding of the mechanism by which cadmium functions as a hormone, and discusses its potential role in development of the hormone dependent cancers.

The influence of natural organic matter and cations on the rejection of endocrine disrupting and pharmaceutically active compounds by nanofiltration

The impact of natural organic matter (NOM) and cations on the rejection of five endocrine disrupting compounds (EDCs) and pharmaceutically active compounds (PhACs) (acetaminophen, carbamazepine, estrone, gemfibrozil, oxybenzone) by nanofiltration (NF) was examined. The water matrices included membrane bioreactor (MBR) effluent, Lake Ontario water and laboratory-prepared waters modelled to represent the characteristics of the Lake Ontario water. The impact of cations in natural waters on compound rejection was also examined by doubling the natural cation concentration (calcium, magnesium, sodium) in both the Lake Ontario water and the MBR effluent. The presence of Suwannee River NOM spiked into laboratory-grade water was found to cause an increase in compound NF rejection. In addition, the presence of cations alone in laboratory-grade water did not have a significant impact on rejection with the exception of the polar compound gemfibrozil. However, when cation concentration in natural waters was increased, a significant decrease in the rejection of EDCs and PhACs was observed. This suggests that the presence of cations may result in a reduction in the association of EDCs and PhACs with NOM.

Persistent, bioaccumulative and toxic substances in fish: human health considerations

Fish are important dietary items that provide essential nutrients. Fish however, bioaccumulate monomethyl mercury (MMHg) and organo-halogenated pollutants (OHP) that are persistent bioaccumulative and toxic substances (PBTS). Unlike man-made OHP, MMHg is mainly of natural origin but background concentrations of aquatic systems are determined by the environmental Hg-methylating potential. Industrial activities can modulate environmental discharges and fish bioaccumulation of PBTS. Fish and seafood consumption are associated with human body load of PBTS, but farming practices that utilize fishmeal increase the terrestrial food chain resulting in farm-animal accumulation of PBTS. These substances are neurotoxic and endocrine active that can impact humans and wild life, but chemical characteristics of MMHg and OHP modulate interactions with animal tissues. MMHg is protein reactive with a faster metabolism (months) than OHP that are stored and slowly (years) metabolized in fat tissues. Except for brain-Hg, neither Hg nor OHP in tissues are markers of toxic effects; however, deficits in neurobehavioral test-scores of children have been shown in some fish-eating populations. These deficits are transient and within normal range, and are not prodromes of neurological diseases. Although population studies show that consumption of fish at current levels of contamination do not explain neurological disorders, endocrine activity remains controversial. Understanding risk of hazard caused by fish-PBTS consumption requires a wide range of expertise. We discuss chemical, toxic, metabolic, and ecological characteristics associated with PBTS in fish. There are proven health outcome derived from fish consumption, while risk of exposure to avoidable PBTS is a chance that can be minimized by societal actions.

Effects of birth order and maternal age on breast cancer risk: modification by whether women had been breast-fed

BACKGROUND

Early life risk factors for breast cancer have been investigated in relation to hormonal, nutritional, infectious, and genetic hypotheses. Recent studies have also considered potential health effects associated with exposure to environmental contaminants in breastmilk.

METHODS

We analyzed data from a population-based case-control study of women living in Wisconsin. Cases (n = 2016) had an incident diagnosis of invasive breast cancer in 2002-2006 reported to the statewide tumor registry. Controls (n = 1960) of similar ages were randomly selected from driver's license lists. Risk-factor information was collected during structured telephone interviews. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated from multivariable logistic regression.

RESULTS

In multivariable models, maternal age and birth order were not associated with breast cancer risk in the full study population. The odds ratio for breast cancer risk associated with having been breast-fed in infancy was 0.83 (95% CI = 0.72-0.96). In analyses restricted to breast-fed women, maternal age associations with breast cancer were null (P = 0.2). Increasing maternal age was negatively associated with breast cancer risk among women who were not breast-fed; the odds ratio for breast cancer associated with each 5-year increase in maternal age was 0.90 (0.82-1.00). Higher birth order was inversely associated with breast cancer risk among breast-fed women (for women with 3 or more older siblings compared with first-born women, OR = 0.58 [CI = 0.39-0.86]) but not among nonbreast-fed women (1.13 [0.81-1.57]).

CONCLUSION

These findings suggest that early life risk factor associations for breast cancer may differ according to breast-feeding status in infancy.

Cryptorchidism at birth in Nice area (France) is associated with higher prenatal exposure to PCBs and DDE, as assessed by colostrum concentrations

BACKGROUND

Since fetal exposure to anti-androgenic and/or estrogenic compounds has adverse effect on animal reproduction, such exposure could be harmful to human fetus. Data are scarce on cryptorchidism and human exposure to endocrine disruptors.

METHODS

We performed a prospective case-control study to assess the incidence of cryptorchidism and fetal exposure to selected chemicals in the Nice area. One hundred and fifty-one cord bloods (67 cryptorchid, 84 tightly matched controls) and 125 colostrums (56 for cryptorchid and 69 for controls) were screened for xenobiotics, including anti-androgenic dichloro-diphenyl-trichloro-ethylene (DDE), polychlorinated biphenyls (PCBs), and dibutylphthalate (and metabolite monobutylphthalate, mBP).

RESULTS

Median concentrations in colostrum were higher, although not statistically significantly, in cryptorchid versus controls. Cryptorchid boys were more likely to be classified in the most contaminated groups in colostrum for DDE, Sigma PCBs and the composite score PCB + DDE. The same trend, but again not statistically significantly was observed for mBP. Odds ratio for cryptorchidism was increased for the highest score of Sigma PCB, with a trend only for DDE and Sigma PCB + DDE versus the lowest score of those components.

CONCLUSIONS

Our results support an association between congenital cryptorchidism and fetal exposure to PCBs and possibly DDE. Higher concentrations in milk could be a marker of higher exposure or for an impaired detoxification pattern in genetically predisposed individuals.

Activation of estrogen receptor-alpha by the anion nitrite

In this study, the ability of nitrite and nitrate to mimic the effects of estradiol on growth and gene expression was measured in the human breast cancer cell line MCF-7. Similar to estradiol, treatment of MCF-7 cells with either 1 mumol/L nitrite or 1 mumol/L nitrate resulted in approximately 4-fold increase in cell growth and 2.3-fold to 3-fold increase in progesterone receptor (PgR), pS2, and cathepsin D mRNAs that were blocked by the antiestrogen ICI 182,780. The anions also recruited estrogen receptor-alpha (ERalpha) to the pS2 promoter and activated exogenously expressed ERalpha when tested in transient cotransfection assays. To determine whether nitrite or nitrate was the active anion, diphenyleneiodonium was used to inhibit oxidation/reduction reactions in the cell. The ability of diphenyleneiodonium to block the effects of nitrate, but not nitrite, on the induction of PgR mRNA and the activation of exogenously expressed ERalpha suggests that nitrite is the active anion. Concentrations of nitrite, as low as 100 nmol/L, induced a significant increase in PgR mRNA, suggesting that physiologically and environmentally relevant doses of the anion activate ERalpha. Nitrite activated the chimeric receptor Gal-ER containing the DNA-binding domain of GAL-4 and the ligand-binding domain of ERalpha and blocked the binding of estradiol to the receptor, suggesting that the anion activates ERalpha through the ligand-binding domain. Mutational analysis identified the amino acids Cys381, His516, Lys520, Lys529, Asn532, and His547 as important for nitrite activation of the receptor.

Review of the etiology of breast cancer with special attention to organochlorines as potential endocrine disruptors

Breast cancer is the most frequently diagnosed cancer among Canadian women, accounting for about 30% of all new cancer cases each year. Although the incidence of breast cancer has increased over the past 50 years, the cause of this rise is unknown. Risk factors for breast cancer may be classified into four broad categories: (1) genetic/familial, (2) reproductive/hormonal, (3) lifestyle, and (4) environmental. Established risk factors for breast cancer include older age, later age at first full-term pregnancy, no full-term pregnancies, postmenopausal obesity, and genetic factors. However, these known risk factors cannot account for the majority of cases. In the early 1990s, it was suggested that exposure to some environmental chemicals such as organochlorine compounds may play a causal role in the etiology of breast cancer through estrogen-related pathways. The relationship between organochlorines and breast cancer risk has been studied extensively in the past decade and more, and at this point there is no clear evidence to support a causal role of most organochlorine pesticides in the etiology of human breast cancer, but more evidence is needed to assess risk associated with polychlorinated biphenyls (PCBs). Future studies need to consider the combined effects of exposures, concentrate on vulnerable groups such as those with higher levels of exposure, only consider exposures occurring during the most etiologically relevant time periods, and more thoroughly consider gene-environment interactions.

Fertility and markers of male reproductive function in Inuit and European populations spanning large contrasts in blood levels of persistent organochlorines

OBJECTIVE

We synthesized the main findings from an international epidemiologic study on the impact of biopersistent organic pollutants (POPs) on human reproductive function.

DATA SOURCES AND EXTRACTION

We used a database with interview and biological data from 2,269 women and their spouses, and 18 published core papers.

DATA SYNTHESIS

The study did not provide direct evidence of hormone-like activity of the polychlorinated biphenyl (PCB) congener CB-153 and the main dichlorodiphenyltrichloroethane (DDT) metabolite, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE), as serum concentrations of these compounds were not consistently related to either endogenous or exogenous hormone activity in serum. Nevertheless several links bewteen POP exposure and biomarkers of male reproductive function were identified. First, an association between high CB-153 serum levels and low sperm counts was detected within a subgroup of men with short androgen receptor CAG repeat length. Second, a relationship between increased CB-153 serum concentrations and decreased sperm motility was seen in all four studied regions, and indications of reduced neutral alpha-glucosidase activity in seminal plasma point to a post-testicular effect. Third, damage of sperm chromatin integrity was considerably less frequent in Greenlandic Inuits compared with that in European groups, and only in the latter was impairment of sperm chromatin integrity related to POPs. Despite these effects, fertility in terms of time taken to conceive was not related to POPs except in Inuits. A likely explanation of the latter was not identified.

CONCLUSIONS

POPs may interfere with male reproductive function without major impact on fertility. The data do not provide direct evidence for endocrine disruption, hence other mechanisms should also be considered.

Atrazine interaction with estrogen expression systems

More than 40 publications have described results of atrazine responses in 17 estrogen-dependent systems and in more than a dozen different reporter and estrogen receptor-binding studies in vitro. Results from these studies have consistently failed to demonstrate that atrazine acts as an estrogen agonist. Moreover, a variety of indices of estrogen-dependent activity, in models that encompass cell incubations to whole animals, have failed to respond to atrazine. Researchers in more than a dozen laboratories have examined rats, rat tissues, human and prokaryotic cells, in addition to tissues from reptile, fish, amphibian, avian, molluscan, and insect sources, without eliciting estrogenic-like responses from atrazine. In contrast, studies of atrazine ability to antagonize estrogen-mediated responses have yielded equivocal results. Results of several studies show inhibition of estrogen-like activities by atrazine, yet many other tests have yielded negative results. Generally, in vivo models have more consistently shown that atrazine inhibits estrogen-mediated responses, whereas in more specific in vitro systems, inhibition is seldom observed. The implication is that in vivo effects of atrazine may result from inhibition of factors that are indirectly connected to the genomic interaction of estrogen (e.g., at the receptor). Potential targets of atrazine may be downstream of the ligand-receptor binding event. Atrazine may also interact with other, less specific, factors that are necessary for the completion of the estrogen-mediated response. Moreover, the apparent inhibition of cytosolic-ER binding by atrazine may, similarly, be relatively nonspecific. Observed inhibitory responses occur only at extreme doses or concentrations, i.e., several orders of magnitude greater than the level of estradiol presence in each test system. It is probable that the inhibitory effects result from very low affinity and/or low specificity interactions, which are unlikely to occur in nature. We conclude that atrazine is not an estrogen receptor agonist, but it may be a weak antagonist, when present at a high concentration under conditions of disequilibrium with estrogen. These conditions are not expected to occur as a result of normal environmental exposure.

Enhanced micronucleus formation and modulation of BCL-2:BAX in MCF-7 cells after exposure to binary mixtures

BACKGROUND

Within mixtures, interactions between different xenobiotics may occur to give rise to additive, synergistic, inhibitory and/or stimulatory effects in target cells. The role that xenobiotics individually or in mixtures, and at environmental concentrations, play in the etiology of common human diseases often remains obscure.

METHODS

In the presence or absence of lindane, chromosomal aberrations were detected in MCF-7 cells after 24-hr treatment with benzo[a]pyrene (B[a]P) or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) using the cytokinesis-block micronucleus assay. Micronuclei were scored in 1,000 binucleate cells/treatment. We investigated intracellular responses using quantitative gene expression analyses of cyclin-dependent kinase inhibitor 1A [CDKN1A (P21(WAF1/CIP1))], B-cell leukemia/lymphoma 2 (BCL-2), BCL-2-associated X (BAX), and isoforms of cytochrome P450 (CYP), CYP1A1, CYP1A2, and CYP1B1. Immunocytochemical analyses of p53, p21(Waf1/Cip1), Bcl-2 and Bax protein expression in MCF-7 cells were also carried out.

RESULTS

After exposure to binary mixtures of B[a]P plus lindane or PhIP plus lindane, a 10-fold increase in micronucleus formation resulted; these test agents individually induced 2- to 5-fold increases. Lindane increased the ratio of Bcl-2:Bax, as did 17beta-estradiol (E(2)). Although treatment with B[a]P alone was found to elevate expression of P21(WAF1/CIP1)and CYP isoenzymes, it reduced the ratio of BCL-2:BAX mRNA transcripts. Treatment with a binary mixture of 10(-8) M B[a]P plus 10(-12) M lindane or 10(-10) M E(2) reversed B[a]P-induced reductions in the ratio of Bcl-2- to Bax-positive cells. In contrast, treatments with PhIP (known to possess hormonelike properties) plus lindane or E(2) resulted in profound reductions in Bcl-2:Bax ratio.

CONCLUSIONS

Our results suggest that low-dose treatments (i.e., close to environmental levels) may increase DNA damage while influencing survival in exposed cells and that these effects may depend on the endocrine activity of test agents.

Endocrine disruptors and the thyroid gland--a combined in vitro and in vivo analysis of potential new biomarkers

BACKGROUND

There is growing evidence that, in addition to the reproductive system, the hypothalamic-pituitary-thyroid axis is a target of endocrine-disrupting compounds (EDCs). However, this is not reflected adequately in current screening and assessment procedures for endocrine activity that to date determine only general parameters of thyroid function.

OBJECTIVE AND METHODS

We used several in vitro and ex vivo assays in an attempt to identify suitable biomarkers for antithyroid action testing a selected panel of putative EDCs.

RESULTS

In vitro we detected stimulation or inhibition of iodide uptake into FRTL-5 rat thyroid cells, inhibition of thyroid hormone binding to transthyretin, agonistic or antagonistic effects in a thyroid hormone receptor-dependent reporter assay, and inhibition of thyroid peroxidase using a novel assay system based on human recombinant thyroperoxidase that might be suitable for routine screening for potential EDCs. In rats, chronic application of several EDCs led to changes in thyroid morphology, alterations of thyrotropin and thyroid hormone serum levels as well as alterations in peripheral thyroid hormone-regulated end points such as malic enzyme and type I 5'-deiodinase activity.

CONCLUSIONS

As the effects of EDCs do not reflect classic mechanisms of hormone-dependent regulation and feedback, we believe multitarget and multimodal actions of EDCs affect the hypothalamic-pituitary-thyroid axis. These complex effects require a diverse approach for screening, evaluation, and risk assessment of potential antithyroid compounds. This approach involves novel in vitro or cell-based screening assays in order to assess thyroid hormone synthesis, transport, metabolism, and action as well as in vivo assays to measure thyroid hormone-regulated tissue-specific and developmental end points in animals.

Fundulus as the premier teleost model in environmental biology: opportunities for new insights using genomics

A strong foundation of basic and applied research documents that the estuarine fish Fundulus heteroclitus and related species are unique laboratory and field models for understanding how individuals and populations interact with their environment. In this paper we summarize an extensive body of work examining the adaptive responses of Fundulus species to environmental conditions, and describe how this research has contributed importantly to our understanding of physiology, gene regulation, toxicology, and ecological and evolutionary genetics of teleosts and other vertebrates. These explorations have reached a critical juncture at which advancement is hindered by the lack of genomic resources for these species. We suggest that a more complete genomics toolbox for F. heteroclitus and related species will permit researchers to exploit the power of this model organism to rapidly advance our understanding of fundamental biological and pathological mechanisms among vertebrates, as well as ecological strategies and evolutionary processes common to all living organisms.

DUSP22/LMW-DSP2 regulates estrogen receptor-alpha-mediated signaling through dephosphorylation of Ser-118

In the previous study, we demonstrated the involvement of dual specificity phosphatase 22 (DUSP22/LMW-DSP2) in regulating the leukemia inhibitory factor/interleukin-6/signal transducer and activator of transcription 3-mediated signaling pathway. In this study, we show beta-estradiol (E2)-induced DUSP22 mRNA expression in estrogen receptor alpha (ERalpha)-positive breast cancer cells, whereas E2-induced phosphorylation and activation of ERalpha was suppressed by overexpression of DUSP22 but not catalytically inactive mutants. Furthermore, small-interfering RNA-mediated reduction of DUSP22 expression enhanced ERalpha-mediated transcription and endogenous gene expression. In fact, DUSP22 associated with ERalpha in vivo and both endogenous proteins interacted in ERalpha-positive breast cancer T47D cells. These results strongly suggest that DUSP22 acts as a negative regulator of the ERalpha-mediated signaling pathway.

Low expression of COX-2, reduced cumulus expansion, and impaired ovulation in SULT1E1-deficient mice

The SULT1E1-encoded estrogen sulfotransferase (EST) catalyzes sulfation of estrogen, resulting in its inactivation. Reduced fertility observed in SULT1E1 knockout (KO) female mice has previously been attributed to the deleterious effect of chronic exposure to high levels of circulating estrogen on placental function. We herein suggest that, in addition to placental dysfunction, this phenotype demonstrates that an excess of estrogen impairs ovulation. The role of SULT1E1 in ovulation is suggested by the substantially low ovulatory response in hCG-treated SULT1E1 KO mice; a similar effect was observed when 17beta-estradiol was administered to wild-type (WT) females. The normal rate of ovulation in SULT1E1 KO females may be restored by PGE2. Along this line, ovaries of human Chorionic Gonadotropin (hCG)-treated SULT1E1 KO mice expressed low levels of cyclooxygenase-2 (COX-2) and its downstream TSG6; moreover, their ovaries contained a reduced number of expanded cumuli. Our results demonstrate, for the first time, that estrogen inactivation may allow the expression of COX-2 and subsequent cumulus expansion, enabling normal ovulation. Our findings may be applied to novel treatments of human ovulatory failure.

GST genotypes and lung cancer susceptibility in Asian populations with indoor air pollution exposures: a meta-analysis

About half of the world's population is exposed to smoke from heating or cooking with coal, wood, or biomass. These exposures, and fumes from cooking oil use, have been associated with increased lung cancer risk. Glutathione S-transferases play an important role in the detoxification of a wide range of human carcinogens in these exposures. Functional polymorphisms have been identified in the GSTM1, GSTT1, and GSTP1 genes, which may alter the risk of lung cancer among individuals exposed to coal, wood, and biomass smoke, and cooking oil fumes. We performed a meta-analysis of 6 published studies (912 cases; 1063 controls) from regions in Asia where indoor air pollution makes a substantial contribution to lung cancer risk, and evaluated the association between the GSTM1 null, GSTT1 null, and GSTP1 105Val polymorphisms and lung cancer risk. Using a random effects model, we found that carriers of the GSTM1 null genotype had a borderline significant increased lung cancer risk (odds ratio (OR), 1.31; 95% confidence interval (CI), 0.95-1.79; p=0.10), which was particularly evident in the summary risk estimate for the four studies carried out in regions of Asia that use coal for heating and cooking (OR, 1.64; 95% CI, 1.25-2.14; p=0.0003). The GSTT1 null genotype was also associated with an increased lung cancer risk (OR, 1.49; 95% CI, 1.17-1.89; p=0.001), but no association was observed for the GSTP1 105Val allele. Previous meta- and pooled-analyses suggest at most a small association between the GSTM1 null genotype and lung cancer risk in populations where the vast majority of lung cancer is attributed to tobacco, and where indoor air pollution from domestic heating and cooking is much less than in developing Asian countries. Our results suggest that the GSTM1 null genotype may be associated with a more substantial risk of lung cancer in populations with coal exposure.

Association of serum concentration of organochlorine pesticides with dietary intake and other lifestyle factors among urban Chinese women

Concerns about the carcinogenic and endocrine-disrupting characteristics of organochlorine pesticides (OCPs) have led to a global ban on OCP use. However, OCPs persist in the environment for decades because of their long half-life. We evaluated serum levels of OCPs and their correlations with usual dietary intake and other lifestyle factors among 250 healthy women who participated as controls in the Shanghai Breast Cancer Study. Serum levels of hexachlorocyclohexane isomers (alpha-HCH, beta-HCH, gamma-HCH), dichloro-di-phenyl-trichloroethane (DDT) isomers (p,p'-DDE and p,p'-DDT), hexachlorobenzene (HCB), trans-nonachlor (TNC), and eight polychlorinated biphenyls (PCB) congeners (IUPAC no. 74, 118, 138, 153, 170, 180, 183, and 187) were measured. Lifestyle factors and usual dietary habits over the past 5 years were assessed through an in-person interview. With the exception of PCB, total OCP levels in our study population were significantly higher than those observed in other countries. Age, income, body mass index, waist-to-hip ratio, number of pregnancies, and/or total duration of breastfeeding were all significantly correlated with all types of OCPs. Of the 20 food groups evaluated, correlations with serum total OCPs were observed for eggs (r=0.13), fresh beans (r=-0.17), tea (r=0.14), and animal fat (r=0.18). Multiple regression analyses showed that age and animal fat intake were positively associated with serum total level OCPs, while leafy vegetable and fresh bean consumption was negatively associated with OCPs level. Our study suggests that dietary intake may be an important contributor of serum levels of OCPs in Chinese women.

SPR-based biosensors: a tool for biodetection of hormonal compounds

Novel cancer treatments, prevention of postmenopausal disorder, and prescription of oral contraceptives are the main developments in the design of synthetic estrogenic medication. The increasing consumption of these synthetic pharmaceuticals, in addition to human and animal natural estrogenic compound excretion, contribute to their environmental dissemination worldwide. Their assimilation as a result of consumption of food and water perturbs normal endocrine systems and leads to the emergence of human and animal diseases and malformations. These compounds are active in the organism at low concentrations. Accordingly, daily low-level exposure disrupts the natural equilibrium in the endocrine system. A method enabling quantification at such products at low levels (from pg L(-1) to ng L(-1)) is therefore required for these products. Surface plasmon resonance, essentially used for comprehension of molecular mechanisms and in drug discovery, can also be used for environmental pollutant monitoring. This technology has already been used for evaluation of the effects of chemical pollutants on specific nuclear receptors. It has been possible to determine the role of each individual compound on the disruption of the estrogen-activated cellular pathway. Development of SPR screening methods enables application of such an approach for quantification of these compounds in water.

Stable isotopes, mass spectrometry, and molecular fluxes: Applications to toxicology

In order to meet the increasing demands for safe and affordable drugs, improvements in the efficiency and accuracy of every step in drug development are required. Accordingly, new approaches for assessing drug toxicity that are faster and more precise are in demand. Numerous approaches using -omics and systems biology are being developed to meet this demand and, while promising, they have not yet provided the improvements in toxicology promised. Other innovative methodologies for predicting and assessing toxicities should therefore be explored. Here we present a novel approach for directly measuring the in vivo response of specific metabolic pathways to toxic agents. Using stable isotopes and ultra sensitive mass spectrometry, the effect of an agent on myelin synthesis, protein synthesis, or cell proliferation can be directly measured. Examples are presented where this approach is used to detect toxicity in the liver, brain, peripheral neurons, breast, and skin. Collagen synthesis, microglia proliferation, myelin synthesis, tubulin synthesis, hepatic cell proliferation, epidermal cell proliferation and mammary epithelial cell proliferation are quantitatively determined in vivo, in a high throughput manner. This approach avoids the computationally complex approach of systems biology and allows the user to observe the emergent properties of the system directly and quantitatively.

Time to pregnancy as a function of male and female serum concentrations of 2,2'4,4'5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p'-DDE)

BACKGROUND

Persistent organochlorine pollutants (POP) may affect both the female and male reproductive system in animals as well as in humans.

METHODS

Blood samples were collected from pregnant women and their partners from Greenland, Warsaw and Kharkiv, and from a cohort of Swedish fishermen's wives. Blood samples were analysed for 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p'-DDE). Information on the participants' fertility, measured as time to pregnancy (TTP), was collected. In total, 778 men and 1505 women were included in the analyses.

RESULTS

The data from Warsaw, Kharkiv and the Swedish fishermen's wives indicated no effect of either male or female exposure to POP on TTP. However, among men and women from Greenland, there seemed to be an association between serum concentrations of CB-153 and p,p'-DDE and prolonged TTP. Due to the strong intra-individual correlation between CB-153 and p,p'-DDE in the Greenlandic population, it was not possible to determine whether the risk was associated with CB-153 or p, p'-DDE or was an interaction between the two compounds.

CONCLUSIONS

The overall results of the present study create a somewhat ambiguous pattern, but give some support to the idea that dietary POP exposure might be harmful for couple fertility.

Exposure to PCB and p, p′-DDE in European and Inuit populations: impact on human sperm chromatin integrity

BACKGROUND

Persistent organochlorine pollutants (POP), such as polychlorinated biphenyls (PCB) and dichlorodiphenyldichloroethylene (p, p'-DDE), are widely found in the environment and considered potential endocrine-disrupting compounds (EDC). Their impact on male fertility is still unknown.

METHODS

To explore the hypothesis that POP is associated with altered sperm chromatin integrity, a cross-sectional study involving 707 adult males (193 Inuits from Greenland, 178 Swedish fishermen, 141 men from Warsaw, Poland, and 195 men from Kharkiv, Ukraine) was carried out. Serum levels of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153), as a proxy of the total PCB burden, and of p,p'-DDE were determined. Sperm chromatin structure assay (SCSA) was used to assess sperm DNA/chromatin integrity.

RESULTS

We found a strong and monotonically increasing DNA fragmentation index with increasing serum levels of CB-153 among European but not Inuit men, reaching a 60% higher average level in the highest exposure group. No significant associations were found between SCSA-derived parameters and p, p'-DDE serum concentrations.

CONCLUSION

These results suggest that human dietary PCB exposure might have a negative impact on the sperm chromatin integrity of adult males but additional issues, including differences in the genetic background and lifestyle habits, still need to be elucidated.

Impact of polychlorinated biphenyls contamination on estrogenic activity in human male serum

Polychlorinated biphenyls (PCBs) are thought to cause numerous adverse health effects, but their impact on estrogen signaling is still not fully understood. In the present study, we used the ER-CALUX bioassay to determine estrogenic/antiestrogenic activities of the prevalent PCB congeners and PCB mixtures isolated from human male serum. The samples were collected from residents of an area with an extensive environmental contamination from a former PCB production site as well as from a neighboring background region in eastern Slovakia. We found that the lower-chlorinated PCBs were estrogenic, whereas the prevalent higher-chlorinated PCB congeners 138, 153, 170, 180, 187, 194, 199, and 203, as well as major PCB metabolites, behaved as antiestrogens. Coplanar PCBs had no direct effect on estrogen receptor (ER) activation in this in vitro model. In human male serum samples, high levels of PCBs were associated with a decreased ER-mediated activity and an increased dioxin-like activity, as determined by the DR-CALUX assay. 17beta-Estradiol (E2) was responsible for a major part of estrogenic activity identified in total serum extracts. Significant negative correlations were found between dioxin-like activity, as well as mRNA levels of cytochromes P450 1A1 and 1B1 in lymphocytes, and total estrogenic activity. For sample fractions containing only persistent organic pollutants (POPs), the increased frequency of antiestrogenic samples was associated with a higher sum of PCBs. This suggests that the prevalent non-dioxin-like PCBs were responsible for the weak antiestrogenic activity of some POPs fractions. Our data also suggest that it might be important to pay attention to direct effects of PCBs on steroid hormone levels in heavily exposed subjects.

Liquid chromatography–tandem mass spectrometry analysis of estrogenic compounds in coastal surface water of the Baltic Sea

An analytical method has been developed for the determination of five naturally occurring estrogens (estradiol, estriol, estrone, genistein, daidzein), one synthetic hormone (ethynylestradiol) and three xenoestrogens (4-nonylphenol (NP), 4-tert-octylphenol (4-tert-OP), bisphenol A (BPA)) in coastal marine waters. The procedure includes a solid-phase extraction of approx. fifty litres of water samples on the solid-phase copolymer Oasis HLB followed by a clean-up on silica. Twenty-five percent aliquots were used for the analytical determination of the analytes using high performance liquid chromatography coupled with electrospray-ionisation tandem mass spectrometry (HPLC-ESI-MS/MS). Calculated extraction recoveries between 52 (4-tert-octylphenol) and 91% (nonylphenol) were obtained for the method developed. Matrix interferences occurring during electrospray ionisation were quantified by spiking the extracts prior to the measurements. Method detection limits ranged from 0.02 (estrone) to 1 ng L(-1) (estriol). The method was applied to determine environmental estrogens in coastal waters of the Baltic Sea. The analyses showed the presence of five compounds at levels between 0.10 (estrone) and 17 ng L(-1) (ethynylestradiol).