Development of a stably transfected estrogen receptor-mediated luciferase reporter gene assay in the human T47D breast cancer cell line

Detection of organic compounds with whole-cell bioluminescent bioassays

Natural and manmade organic chemicals are widely deposited across a diverse range of ecosystems including air, surface water, groundwater, wastewater, soil, sediment, and marine environments. Some organic compounds, despite their industrial values, are toxic to living organisms and pose significant health risks to humans and wildlife. Detection and monitoring of these organic pollutants in environmental matrices therefore is of great interest and need for remediation and health risk assessment. Although these detections have traditionally been performed using analytical chemical approaches that offer highly sensitive and specific identification of target compounds, these methods require specialized equipment and trained operators, and fail to describe potential bioavailable effects on living organisms. Alternatively, the integration of bioluminescent systems into whole-cell bioreporters presents a new capacity for organic compound detection. These bioreporters are constructed by incorporating reporter genes into catabolic or signaling pathways that are present within living cells and emit a bioluminescent signal that can be detected upon exposure to target chemicals. Although relatively less specific compared to analytical methods, bioluminescent bioassays are more cost-effective, more rapid, can be scaled to higher throughput, and can be designed to report not only the presence but also the bioavailability of target substances. This chapter reviews available bacterial and eukaryotic whole-cell bioreporters for sensing organic pollutants and their applications in a variety of sample matrices.

Environmental concentration of nonylphenol alters the development of urogenital and visceral organs in avian model

Nonylphenol (NP) is an endocrine disruptor with harmful effects including feminization and carcinogenesis on various organisms. This substance is a degradation product of nonylphenol ethoxylates (NPEO) that is used in several industrial and agricultural processes. In this paper, we examined the assessment of NP exposure on chick embryo development, using a concentration consistent with the environmental concentrations of NP. With this aim, NP (between 0.1 and 50 μg/egg) was injected into the yolk of egg through a small needle hole in the shell. We report the effect of NP on chick reproductive system development although the effect we observed is lower than those observed by exposition to other endocrine disruptors. However, histological analysis highlighted a decrease of intraluminal seminiferous surface area in 64.12% of case (P=0.0086) and an heterogeneous organization of the renal tubules when 10 μg/egg were injected. Moreover, an impairment of liver development with an abnormal bile spillage was observed when higher concentration of NP was injected (50 μg/egg).

Effect of microwave hydrolysis on transformation of steroidal hormones during anaerobic digestion of municipal sludge cake

Fate and removal of 16 steroidal (estrogenic, androgenic and progestogenic) hormones were studied during advanced anaerobic digestion of sludge cake using microwave (MW) pretreatment. Effect of pretreatment temperature (80, 120, 160 °C), operating temperature (mesophilic at 35 ± 2 °C, thermophilic at 55 ± 2 °C) and sludge retention time (SRT: 20, 10, 5 days) were studied employing eight lab-scale semi-continuously fed digesters. To determine the potential effect of MW hydrolysis, hormones were quantified in total (sorbed + soluble) and supernatant (soluble) phases of the digester influent and effluent streams. Seven of 16 hormones were above the method reporting limit (RL) in one or more of the samples. Hormone concentrations in total phase of un-pretreated (control) and pretreated digester feeds ranged in <157-2491 ng/L and <157-749 ng/L, respectively. The three studied factors were found to be statistically significant (95% confidence level) in removal of one or more hormones from soluble and/or total phase. MW hydrolysis of the influent resulted in both release (from sludge matrix) and attenuation of hormones in the soluble phase. Accumulation of estrone (E1) as well as progesterone (Pr) and androstenedione (Ad) in most of the digesters indicated possible microbial transformations among the hormones. Compared to controls, all pretreated digesters had lower total hormone concentrations in their influent streams. At 20 days SRT, highest total removal (E1+E2+Ad +Pr) was observed for the thermophilic control digester (56%), followed by pretreated mesophilic digesters at 120 °C and 160 °C with around 48% efficiency. In terms of conventional performance parameters, relative (to control) improvements of MW pretreated digesters at a 5-d SRT ranged in 98-163% and 57-121%, for volatile solids removal and methane production, respectively.

Effect-directed analysis to explore the polar bear exposome: identification of thyroid hormone disrupting compounds in plasma

Compounds with transthyretin (TTR)-binding potency in the blood plasma of polar bear cubs were identified with effect-directed analysis (EDA). This approach contributes to the understanding of the thyroid disrupting exposome of polar bears. The selection of these samples for in-depth EDA was based on the difference between the observed TTR-binding potency on the one hand and the calculated potency (based on known concentrations of TTR-binding compounds and their relative potencies) on the other. A library-based identification was applied to the liquid chromatography-time-of-flight-mass spectrometry (LC-ToF-MS) data by screening for matches between compound lists and the LC-ToF-MS data regarding accurate mass and isotope pattern. Then, isotope cluster analysis (ICA) was applied to the LC-ToF-MS data allowing specific screening for halogen isotope patterns. The presence of linear and branched nonylphenol (NP) was observed for the first time in polar bears. Furthermore, the presence of one di- and two monohydroxylated octachlorinated biphenyls (octaCBs) was revealed in the extracts. Linear and branched NP, 4'-OH-CB201 and 4,4'-OH-CB202 could be successfully confirmed with respect to their retention time in the analytical system. In addition, branched NP, mono- and dihydroxylated-octaCBs showed TTR-binding potencies and could explain another 32 ± 2% of the total measured activities in the extracts.

Influences of solid retention time, nitrification and microbial activity on the attenuation of pharmaceuticals and estrogens in membrane bioreactors

This study investigated the influences of solid retention time (SRT), nitrification, and microbial activity on the attenuation of pharmaceuticals and estrogens and the total estrogenic activity, using identical bench-scale membrane bioreactors. Phenacetine, acetaminophen, pentoxifylline, caffeine, bezafibrate, ibuprofen, fenoprofen, 17β-estradiol, and estrone were effectively attenuated even at short SRT (8 d). However, the attenuation efficiencies of gemfibrozil, ketoprofen, clofibric acid, and 17α-ethinylestradiol were dependent upon SRTs (20 and 80 d). Some acidic pharmaceuticals (gemfibrozil, diclofenac, bezafibrate, and ketoprofen) and 17α-ethinylestradiol were partially degraded by nitrification. Relatively high removal efficiencies were observed for 17β-estradiol and estrone (natural estrogens) compared to 17α-ethinylestradiol (synthetic estrogen) when nitrification was inhibited. Most of selected pharmaceuticals were not significantly attenuated under presumably abiotic conditions by adding sodium azide except phenacetine, acetaminophen, and caffeine. In this study, carbamazepine was found to be recalcitrant to biological wastewater treatment using membrane bioreactors regardless of the change of SRTs and microbial activity.

Assessment and molecular actions of endocrine-disrupting chemicals that interfere with estrogen receptor pathways

In all vertebrate species, estrogens play a crucial role in the development, growth, and function of reproductive and nonreproductive tissues. A large number of natural or synthetic chemicals present in the environment and diet can interfere with estrogen signaling; these chemicals are called endocrine disrupting chemicals (EDCs) or xenoestrogens. Some of these compounds have been shown to induce adverse effects on human and animal health, and some compounds are suspected to contribute to diverse disease development. Because xenoestrogens have varying sources and structures and could act in additive or synergistic effects when combined, they have multiple mechanisms of action. Consequently, an important panel of in vivo and in vitro bioassays and chemical analytical tools was used to screen, evaluate, and characterize the potential impacts of these compounds on humans and animals. In this paper, we discuss different molecular actions of some of the major xenoestrogens found in food or the environment, and we summarize the current models used to evaluate environmental estrogens.

Evaluation of an alternative in vitro test battery for detecting reproductive toxicants

The application of alternative methods in developmental and reproductive toxicology is challenging in view of the complexity of mechanisms involved. A battery of complementary test systems may provide a better prediction of developmental and reproductive toxicity than single assays. We tested twelve compounds with varying mechanisms of toxic action in an assay battery including 24 CALUX transcriptional activation assays, mouse cardiac embryonic stem cell test, ReProGlo assay, zebrafish embryotoxicity assay, and two CYP17 and two CYP19 activity assays. The battery correctly detected 11/12 compounds tested, with one false negative occurring, which could be explained by the absence of the specific mechanism of action of this compound in the battery. Toxicokinetic modeling revealed that toxic concentrations were in the range expected from in vivo reproductive toxicity data. This study illustrates added value of combining assays that contain complementary biological processes and mechanisms, increasing predictive value of the battery over individual assays.

In vitro characterization of the effectiveness of enhanced sewage treatment processes to eliminate endocrine activity of hospital effluents

Occurrence of pharmaceuticals in aquatic ecosystems is related to sewage effluents. Due to the possible adverse effects on wildlife and humans, degradation and removal of pharmaceuticals and their metabolites during wastewater treatment is an increasingly important task. The present study was part of a proof of concept study at a medium sized country hospital in western Germany that investigated efficiency of advanced treatment processes to remove toxic potencies from sewage. Specifically, the efficiency of treatment processes such as a membrane bioreactor (MBR) and ozonation to remove endocrine disruptive potentials was assessed. Estrogenic effects were characterized by use of two receptor-mediated in vitro transactivation assays, the Lyticase Yeast Estrogen Screen (LYES) and the Estrogen Receptor mediated Chemical Activated LUciferase gene eXpression (ER CALUX(®)). In addition, the H295R Steroidogenesis Assay (H295R) was utilized to detect potential disruption of steroidogenesis. Raw sewage contained measurable estrogen receptor (ER)-mediated potency as determined by use of the LYES (28.9 ± 8.6 ng/L, 0.33× concentration), which was reduced after treatment by MBR (2.3 ± 0.3 ng/L) and ozone (1.2 ± 0.4 ng/L). Results were confirmed by use of ER CALUX(®) which measured concentrations of estrogen equivalents (EEQs) of 0.2 ± 0.11 ng/L (MBR) and 0.01 ± 0.02 ng/L (ozonation). In contrast, treatment with ozone resulted in greater production of estradiol and aromatase activity at 3× and greater concentrations in H295R cells. It is hypothesized that this is partly due to formation of active oxidized products during ozonation. Substance-specific analyses demonstrated efficient removal of most of the measured compounds by ozonation. A comparison of the ER-mediated responses measured by use of the LYES and ER CALUX(®) with those from the chemical analysis using a mass-balance approach revealed estrone (E1) to be the main compound that caused the estrogenic effects. Overall, treatment of sewage by use of MBR successfully reduced estrogenicity of hospital effluents as well as substances that are able to alter sex steroid production. However, after ozonation, effluents should undergo further investigations regarding the formation of endocrine active metabolites. The results obtained as part of this study demonstrated applicability of in vitro assays for monitoring of endocrine-modulating potency of treated sewage.

Robust array-based coregulator binding assay predicting ERα-agonist potency and generating binding profiles reflecting ligand structure

Testing chemicals for their endocrine-disrupting potential, including interference with estrogen receptor (ER) signaling, is an important aspect of chemical safety testing. Because of the practical drawbacks of animal testing, the development of in vitro alternatives for the uterotrophic assay and other in vivo (anti)estrogenicity tests has high priority. It was previously demonstrated that an in vitro assay that profiles ligand-induced binding of ERα to a microarray of coregulator-derived peptides might be a valuable candidate for a panel of in vitro assays aiming at an ultimate replacement of the uterotrophic assay. In the present study, the reproducibility and robustness of this coregulator binding assay was determined by measuring the binding profiles of 14 model compounds that are recommended by the Office of Prevention, Pesticides and Toxic Substances for testing laboratory proficiency in estrogen receptor transactivation assays. With a median coefficient of variation of 5.0% and excellent correlation (R(2) = 0.993) between duplicate measurements, the reproducibility of the ERα-coregulator binding assay was better than the reproducibility of other commonly used in vitro ER functional assays. In addition, the coregulator binding assay is correctly predicting the estrogenicity for 13 out of 14 compounds tested. When the potency of the ER-agonists to induce ERα-coregulator binding was compared to their ER binding affinity, their ranking was similar, and the correlation between the EC50 values was excellent (R(2) = 0.96), as was the correlation with their potency in a transactivation assay (R(2) = 0.94). Moreover, when the ERα-coregulator binding profiles were hierarchically clustered using Euclidian cluster distance, the structurally related compounds were found to cluster together, whereas the steroid test compounds having an aromatic A-ring were separated from those with a cyclohexene A-ring. We concluded that this assay is capable of distinguishing ERα agonists and antagonists and that it even reflects the structural similarity of ERα agonists, indicating a potential to achieve identification and classification of ERα endocrine disruptors with high fidelity.

Fate of estrogenic hormones in wastewater and sludge treatment: A review of properties and analytical detection techniques in sludge matrix

Estrogenic hormones (estrone (E1), 17β-estradiol (E2), estriol (E3), 17α-ethinylestradiol (EE2)) are the major contributor to the total estrogenicity in waterways. Presence of these compounds in biosolids is also causing concern in terms of their use as soil amendment. In comparison with wastewater treatment, removal of estrogenic compounds in sewage sludge has received less attention. This paper presents a literature review regarding the source and occurrence of these pollutants in our environment. The removal pathways of estrogenic compounds in engineered systems, such as full-scale wastewater treatment plants (WWTPs), are also discussed. Review of the fate studies revealed that activated sludge system with nutrient removal shows very high (>90%) removal of estrogenic hormones in most of the cases. Although, aerobic digestion showed better attenuation of estrogenic compounds, anaerobic digestion increased the overall estrogenicity of biosolids. Finally, this paper highlights the challenges involved in analytical determination of these compounds in sewage sludge matrix.

Chlorine disinfection by-products in wastewater effluent: Bioassay-based assessment of toxicological impact

The potential ecological impact of disinfection by-products (DBPs) present in chlorinated wastewater effluents is not well understood. In this study, the chlorinated effluent of traditional wastewater treatment plants (WWTPs) and advanced water reclamation plants (AWRPs) supplying highly-treated recycled water were analyzed for nitrosamines and trihalomethanes (THMs), and a battery of bioassays conducted to assess effluent toxicity. An increase in general toxicity from DBPs was revealed for all wastewaters studied using an in vitro bioluminescence assay. Examples of androgenic activity and estrogenic activity arising from DBPs at specific sampling sites were also observed. The in vivo model (Artemia franciscana) was generally not adversely affected by exposure to DBPs from any of the chlorinated wastewaters studied. The observed toxicity could not be related to the concentrations of THMs and nitrosamines present, indicating that DBPs not monitored in this study were responsible for this. This work highlights the complexity of DBPs mixtures formed in chlorinated wastewaters, illustrating that toxicity of wastewater DBPs cannot be predicted by chemical monitoring of THMs and nitrosamines. The results suggest bioassays may be particularly useful monitoring tools in assessing toxicity arising from DBPs of these complex waters. The research concludes that DBPs formed in the chlorinated wastewaters studied can be toxic and may have a deleterious impact on aquatic organisms that are exposed to them, and therefore, that chlorination or chlorination/dechlorination may not be adequate treatment strategies for the protection of receiving waters. Chlorinated wastewater toxicity (from DBPs) is not well-understood in the Australian context, and this study serves to advise regulators on this issue.

Effect-based tools for monitoring and predicting the ecotoxicological effects of chemicals in the aquatic environment

Ecotoxicology faces the challenge of assessing and predicting the effects of an increasing number of chemical stressors on aquatic species and ecosystems. Herein we review currently applied tools in ecological risk assessment, combining information on exposure with expected biological effects or environmental water quality standards; currently applied effect-based tools are presented based on whether exposure occurs in a controlled laboratory environment or in the field. With increasing ecological relevance the reproducibility, specificity and thus suitability for standardisation of methods tends to diminish. We discuss the use of biomarkers in ecotoxicology including ecotoxicogenomics-based endpoints, which are becoming increasingly important for the detection of sublethal effects. Carefully selected sets of biomarkers allow an assessment of exposure to and effects of toxic chemicals, as well as the health status of organisms and, when combined with chemical analysis, identification of toxicant(s). The promising concept of “adverse outcome pathways (AOP)” links mechanistic responses on the cellular level with whole organism, population, community and potentially ecosystem effects and services. For most toxic mechanisms, however, practical application of AOPs will require more information and the identification of key links between responses, as well as key indicators, at different levels of biological organization, ecosystem functioning and ecosystem services.

Additive mixture effects of estrogenic chemicals in human cell-based assays can be influenced by inclusion of chemicals with differing effect profiles

A growing body of experimental evidence indicates that the in vitro effects of mixtures of estrogenic chemicals can be well predicted from the estrogenicity of their components by the concentration addition (CA) concept. However, some studies have observed small deviations from CA. Factors affecting the presence or observation of deviations could include: the type of chemical tested; number of mixture components; mixture design; and assay choice. We designed mixture experiments that address these factors, using mixtures with high numbers of components, chemicals from diverse chemical groups, assays with different in vitro endpoints and different mixture designs and ratios. Firstly, the effects of mixtures composed of up to 17 estrogenic chemicals were examined using estrogenicity assays with reporter-gene (ERLUX) and cell proliferation (ESCREEN) endpoints. Two mixture designs were used: 1) a ‘balanced’ design with components present in proportion to a common effect concentration (e.g. an EC₁₀) and 2) a ‘non-balanced’ design with components in proportion to potential human tissue concentrations. Secondly, the individual and simultaneous ability of 16 potential modulator chemicals (each with minimal estrogenicity) to influence the assay outcome produced by a reference mixture of estrogenic chemicals was examined. Test chemicals included plasticizers, phthalates, metals, PCBs, phytoestrogens, PAHs, heterocyclic amines, antioxidants, UV filters, musks, PBDEs and parabens. In all the scenarios tested, the CA concept provided a good prediction of mixture effects. Modulation studies revealed that chemicals possessing minimal estrogenicity themselves could reduce (negatively modulate) the effect of a mixture of estrogenic chemicals. Whether the type of modulation we observed occurs in practice most likely depends on the chemical concentrations involved, and better information is required on likely human tissue concentrations of estrogens and of potential modulators. Successful prediction of the effects of diverse chemical combinations might be more likely if chemical profiling included consideration of effect modulation.

Biosensor zebrafish provide new insights into potential health effects of environmental estrogens

BACKGROUND

Environmental estrogens alter hormone signaling in the body that can induce reproductive abnormalities in both humans and wildlife. Available testing systems for estrogens are focused on specific systems such as reproduction. Crucially, however, the potential for significant health impacts of environmental estrogen exposures on a variety of body systems may have been overlooked.

OBJECTIVE

Our aim was to develop and apply a sensitive transgenic zebrafish model to assess real-time effects of environmental estrogens on signaling mechanisms in a whole body system for use in integrated health assessments.

METHODS

We created a novel transgenic biosensor zebrafish containing an estrogen-inducible promoter derived with multiple tandem estrogen responsive elements (EREs) and a Gal4ff-UAS system for enhanced response sensitivity.

RESULTS

Using our novel estrogen-responsive transgenic (TG) zebrafish, we identified target tissues for environmental estrogens; these tissues have very high sensitivity even at environmentally relevant concentrations. Exposure of the TG fish to estrogenic endocrine-disrupting chemicals (EDCs) induced specific expression of green fluorescent protein (GFP) in a wide variety of tissues including the liver, heart, skeletal muscle, otic vesicle, forebrain, lateral line, and ganglions, most of which have not been established previously as targets for estrogens in fish. Furthermore, we found that different EDCs induced GFP expression with different tissue response patterns and time trajectories, suggesting different potential health effects.

CONCLUSION

We have developed a powerful new model for understanding toxicological effects, mechanisms, and health impacts of environmental estrogens in vertebrates.

The pro-apoptotic effect of quercetin in cancer cell lines requires ERβ-dependent signals

Quercetin has potentially beneficial effects on disease prevention, including cancer. An intriguing issue regarding the mechanisms of action of quercetin is the ability of this drug to modulate estrogen receptor (ER) activities. In a previous study, we demonstrated that quercetin elicited apoptosis through an ERα-dependent mechanism. However, the contribution of ERβ in quercetin-induced apoptosis remains elusive. Here, we report that quercetin, at nutritionally relevant concentrations, mimicked the 17β-estradiol (E2)-induced apoptotic effect in both ERβ1-transfected HeLa and in ERβ1-containing DLD-1 colon cancer cell lines by inducing the activation of p38. p38 activation is responsible for pro-apoptotic activation of caspase-3 and the cleavage of poly(ADP-ribose) polymerase. Notably, no inactivation or downregulation of the survival kinases (i.e., AKT and ERK1/2) or the antiapoptotic protein Bcl-2 was observed after quercetin stimulation. On the contrary, quercetin acted similarly to E2 by increasing the levels of the oncosuppressor protein PTEN and by impeding ERβ-dependent cyclin D1 promoter activity, which subsequently resulted in the transcription of the estrogen-responsive element remaining unchanged. As a whole, these data indicate that quercetin mimics the E2 effects in the presence of ERβ1, thus maintaining its anti-carcinogenic potential. In addition, the quercetin pro-apoptotic action in the presence of ERα may render it as a dual-sided protective agent against E2-related cancer in the reduction of tumour growth in organs that express ERα and/or ERβ.

Proliferation assays for estrogenicity testing with high predictive value for the in vivo uterotrophic effect

Proliferation assays based on human cell lines are the most used in vitro tests to determine estrogenic properties of compounds. Our objective was to characterise to what extent these in vitro tests provide alternatives for the in vivo Allen and Doisy test, a uterotrophic assay in immature or ovariectomised rodents with uterus weight as a crucial read-out parameter. In the present study four different human cell lines derived from three different female estrogen-sensitive tissues, i.e. breast (MCF-7/BOS and T47D), endometrial (ECC-1) and ovarian (BG-1) cells, were characterised by investigating their relative ERα and ERβ amounts, as the ERα/ERβ ratio is a dominant factor determining their estrogen-dependent proliferative responses. All four cell lines clearly expressed the ERα type and a very low but detectable amount of ERβ on both the mRNA and protein level, with the T47D cell line expressing the highest level of the ERβ type. Subsequently, a set of reference compounds representing different modes of estrogen action and estrogenic potency were used to investigate the proliferative response in the four cell lines, to determine which cell line most accurately predicts the effect observed in vivo. All four cell lines revealed a reasonable to good correlation with the in vivo uterotrophic effect, with the correlation being highest for the MCF-7/BOS cell line (R²=0.85). The main differences between the in vivo uterotrophic assay and the in vitro proliferation assays were observed for tamoxifen and testosterone. The proliferative response of the MCF-7/BOS cells to testosterone was partially caused by its conversion to estradiol by aromatase or via androstenedione to estrone. It is concluded that of the four cell lines tested, the best assay to include in an integrated testing strategy for replacement of the in vivo uterotrophic assay is the human MCF-7/BOS breast cancer cell line.

Integration of GC-MSD and ER-Calux® assay into a single protocol for determining steroid estrogens in environmental samples

There are many published studies that use either chemical or biological methods to investigate steroid estrogens in the aquatic environment, but rarer are those that combine both. In this study, gas chromatography with mass selective detection (GC-MSD) and the ER-Calux(®) estrogenicity assay were integrated into a single protocol for simultaneous determination of natural (estrone--E1, 17β-estradiol--E2, estriol--E3) and synthetic (17α-ethinylestradiol--EE2) steroid estrogens concentrations and the total estrogenic potential of environmental samples. For integration purposes, several solvents were investigated and the commonly used dimethyl sulphoxide (DMSO) in the ER-Calux(®) assay was replaced by ethyl acetate, which is more compatible with gas chromatography and enables the same sample to be analysed by both GC-MSD and the ER-Calux(®) assay. The integrated protocol was initially tested using a standard mixture of estrogens. The results for pure standards showed that the estrogenicity calculated on the basis of GC-MSD and the ER-Calux(®) assay exhibited good correlation (r(2)=0.96; α=0.94). The result remained the same when spiked waste water extracts were tested (r(2)=0.92, α=1.02). When applied to real waste water influent and effluent samples the results proved (r(2)=0.93; α=0.99) the applicability of the protocol. The main advantages of this newly developed protocol are simple sample handling for both methods, and reduced material consumption and labour. In addition, it can be applied as either a complete or sequential analysis where the ER-Calux(®) assay is used as a pre-screening method prior to the chemical analysis.

Selective activation of zebrafish estrogen receptor subtypes by chemicals by using stable reporter gene assay developed in a zebrafish liver cell line

The number of environmental chemical contaminants suspected to act as endocrine disruptor compounds by interacting with estrogen receptor (ER) signaling pathway has been continuously increasing. To study such interaction, the use of stable reporter gene assays is relevant, but species-specific in vitro screening assays are still lacking to address hazard assessment of estrogenic chemicals in aquatic vertebrates. Here, we describe the development of stable reporter gene assays based on stable expression of subtypes of zebrafish ER (zfERα, zfERβ1, and zfERβ2) coupled to estrogen response element-driven luciferase in a zebrafish liver (ZFL) cell line. The three established cell models, named ZELH-zfERα, ZELH-zfERβ1, and ZELH-zfERβ2, expressed stable and significant basal luciferase signal, which was induced by 17β-estradiol (E2) in a sensitive and dose-response manner at EC(50)s of 0.2, 0.03, and 0.05 nM, respectively. In addition, E2 significantly altered cell proliferation in ZELH-zfERα and ZELH-zfERβ2 cells, but not in parental ZFL and ZELH-zfERβ1 cells, suggesting a functionality of these two receptors to modulate endogenous gene expression in the transfected clones. The screening of various xenoestrogens from different classes in the three models resulted in different luciferase response patterns. Natural and synthetic estrogens and 1,1,1-trichloro-2-(2 chlorophenyl)-2-(4-chlorophenyl)ethane were active at lower concentrations in ZELH-zfERβ1 and ZELH-zfERβ2 than in ZELH-zfERα cells, whereas genistein and zearalenone metabolites as well as three benzophenone derivatives preferentially activated zfERα. Altogether, the newly established models provide specific and convenient in vitro tool for comparative assessment of zfERs selective activation by chemicals within ZFL cell context.

Expression of Tubb3, a beta-tubulin isotype, is regulated by androgens in mouse and rat Sertoli cells

Our previous analysis of Sertoli cell androgen receptor (AR) knockout (SCARKO) mice revealed that several cytoskeletal components are a potential target of androgen action. Here, we found that one of these components, the beta-tubulin isotype Tubb3, is differentially regulated in testes from SCARKO mice (relative to littermate controls) from Postnatal Day 10 to adulthood. The Tubb3 gene is unique in this respect, as at Day 10, no other beta-tubulin genes are significantly regulated by AR. We further characterized androgen regulation of Tubb3 in vivo and in vitro and demonstrated that it is a conserved feature in both mice and rats. To investigate whether androgens directly regulate Tubb3 expression, we screened for androgen response elements (AREs) in the Tubb3 gene. In silico analysis revealed the presence of four ARE motifs in Tubb3 intron 1, two of which bind to AR in vitro. Mutation of one of these (ARE1) strongly reduced androgen-dependent reporter gene expression. These results, coupled with the finding that the AR binds to the Tubb3 ARE region in vivo, suggest that Tubb3 is a direct target of AR. Our data strengthen the contention that androgens exert their effects on spermatogenesis, in part, through modulation of the Sertoli cell cytoskeleton. Androgen regulation of beta-tubulin has also been described in neurons, fortifying the already known similarity in microtubule organization in Sertoli cell processes and neurons, the only other cell type in which Tubb3 is known to be expressed.

Polar compounds dominate in vitro effects of sediment extracts

Sediment extracts from three polluted sites of the river Elbe basin were fractionated using a novel online fractionation procedure. Resulting fractions were screened for mutagenic, aryl hydrocarbon receptor (AhR)-mediated, transthyretin (TTR)-binding, and estrogenic activities and their potency to inhibit gap junctional intercellular communication (GJIC) to compare toxicity patterns and identify priority fractions. Additionally, more than 200 compounds and compound classes were identified using GC-MS/MS, LC-MS/MS, and HPLC-DAD methods. For all investigated end points, major activities were found in polar fractions, which are defined here as fractions containing dominantly compounds with at least one polar functional group. Nonpolar PAH fractions contributed to mutagenic and AhR-mediated activities while inhibition of GJIC and estrogenic and TTR-binding activities were exclusively observed in the polar fractions. Known mutagens in polar fractions included nitro- and dinitro-PAHs, azaarenes, and keto-PAHs, while parent and monomethylated PAHs such as benzo[a]pyrene and benzofluoranthenes were identified in nonpolar fractions. Additionally, for one sample, high AhR-mediated activities were determined in one fraction characterized by PCDD/Fs, PCBs, and PCNs. Estrone, 17β-estradiol, 9H-benz[de]anthracen-7-one, and 4-nonylphenol were identified as possible estrogenic and TTR-binding compounds. Thus, not only nonpolar compounds such as PAHs, PCBs, and PCDD/Fs but also the less characterized and investigated more polar substances should be considered as potent mutagenic, estrogenic, AhR-inducing, TTR-binding, and GJIC-inhibiting components for future studies.

Estrogenic effect of the MEK1 inhibitor PD98059 on endogenous estrogen receptor alpha and beta

Estrogens are key regulators in mammary development and breast cancer and their effects are mediated by estrogen receptors alpha (ERα) and beta (ERβ). These two receptors are ligand activated transcription factors that bind to regulatory regions in the DNA known as estrogen responsive elements (EREs). ERα and ERβ activation is subject to modulation by phosphorylation and p42/p44 MAP kinases are the best characterized ER modifying kinases. Using a reporter gene (3X-ERE-TATA-luciferase) to measure activation of endogenous ERs, we found that MEK1 inhibitor PD98059, used in concentrations insufficient to inhibit MEK1 activation of p42/p44 MAP kinases, exerted estrogenic effects on the reporter gene and on the ERE-regulated RIP 140 protein. Such estrogenic effects were observed in mammary epithelial HC11 cells and occur on unliganded ERα and ligand activated ERβ. Additionally, concentrations of PD98059 able to inhibit p42/p44 phosphorylation were not estrogenic. Further, inhibition of p42 MAP kinase expression with siRNAs also resulted in loss of PD98059 estrogenic effect. In summary, PD98059 in concentrations below the inhibitory for MEK1, exerts estrogenic effects in HC11 mammary epithelial cells.

Effect directed analysis of riverine sediments--the usefulness of Potamopyrgus antipodarum for in vivo effect confirmation of endocrine disruption

In vivo tests are not commonly used in effect directed analysis (EDA) approaches. In the present study, a novel methodology was developed whereby Potamopyrgus antipodarum, which is known to be sensitive to endocrine disrupting compounds, was used as test organism. Field sediments from a polluted site in the north of Belgium were extracted and fractionated using three coupled and automatically switched normal-phase HPLC columns. Part of the fractions were spiked to artificial sediments and tested in a sediment contact test with P. antipodarum. The other part was used for an in vitro effect confirmation with the ER-LUC and anti-AR CALUX assays. Two of the six tested fractions stimulated the reproduction of the snails, while two others inhibited the reproduction. The fractions that caused an increase in reproduction also showed an increased estrogenic potency in the ER-LUC assay. Chemical analysis revealed that one of the most prominent compounds in those fractions was bisphenol-A, which has already been reported to have a stimulating effect on the reproduction of P. antipodarum by other authors. Due to the fact that previous studies have shown that this snail is also present in the field at this certain site, it was possible to directly link the results with effects that were observed in the field. This study indicates that effect directed analyses, supported by in vivo biotests, are very useful tools in order to identify the compounds that cause adverse effects on organisms or even population level.

Estrogen-like effects of cadmium in vivo do not appear to be mediated via the classical estrogen receptor transcriptional pathway

BACKGROUND

Cadmium (Cd), a ubiquitous food contaminant, has been proposed to be an endocrine disruptor by inducing estrogenic responses in vivo. Several in vitro studies suggested that these effects are mediated via estrogen receptors (ERs).

OBJECTIVE

We performed this study to clarify whether Cd-induced effects in vivo are mediated via classical ER signaling through estrogen responsive element (ERE)-regulated genes or if other signaling pathways are involved.

METHODS

We investigated the estrogenic effects of cadmium chloride (CdCl2) exposure in vivo by applying the Organisation for Economic Co-operation and Development (OECD) rodent uterotrophic bioassay to transgenic ERE-luciferase reporter mice. Immature female mice were injected subcutaneously with CdCl2 (5, 50, or 500 µg/kg body weight) or with 17α-ethinylestradiol (EE2) on 3 consecutive days. We examined uterine weight and histology, vaginal opening, body and organ weights, Cd tissue retention, activation of mitogen-activated protein kinase (MAPK) pathways, and ERE-dependent luciferase expression.

RESULTS

CdCl2 increased the height of the uterine luminal epithelium in a dose-dependent manner without increasing the uterine wet weight, altering the timing of vaginal opening, or affecting the luciferase activity in reproductive or nonreproductive organs. However, we observed changes in the phosphorylation of mouse double minute 2 oncoprotein (Mdm2) and extracellular signal-regulated kinase (Erk1/2) in the liver after CdCl2 exposure. As we expected, EE2 advanced vaginal opening and increased uterine epithelial height, uterine wet weight, and luciferase activity in various tissues.

CONCLUSION

Our data suggest that Cd exposure induces a limited spectrum of estrogenic responses in vivo and that, in certain targets, effects of Cd might not be mediated via classical ER signaling through ERE-regulated genes.

Toxicity profiling: An integrated effect-based tool for site-specific sediment quality assessment

A toxicity profile is a toxicological "fingerprint" of an environmental sample, obtained by testing its extract in a battery of bioassays. Each represents a different mode of action. The present work explores the applicability of in vitro toxicity profiles as an effect-based tool for sediment quality assessment. For this purpose, a previously published dataset was used, in which sediment extracts from 15 different locations in the Rhine-Meuse estuary were tested in 5 different bioassays. Three useful approaches could be distinguished for applying toxicity profiles in sediment quality assessment. In the first approach, toxicity profiles are translated into hazard profiles, indicating the relative distance to the desired or acceptable sediment quality status for each toxic mode of action. Hazard profiles can be considered as location-specific characteristics; sampling locations with similar hazard profiles can be classified into clusters. This approach seems directly applicable but requires a very careful selection of a reference toxicity profile that is either measured at a reference location or is designated as a desirable or acceptable toxicity profile for that particular location. In the second approach, toxicity profiles are translated into ecological risk profiles indicating for each toxic mode of action the ratio between the actual measured bioassay response and the bioassay response level that is considered safe for environmental health. This approach has a high ecological relevance but is only feasible for a few modes of action for which toxicity data are available at the ecological level of population or higher that allow derivation of ecologically safe bioassay responses for sediment extracts. In the third approach, toxicity profiles and their derived hazard profiles are used to select samples with unusually or unexpectedly high bioassay responses for further in-depth effect-directed analysis (EDA). EDA is a powerful strategy to identify emerging compounds that contribute significantly to the toxic load on the environment. EDA is an expensive and laborious strategy, however, making it currently suitable only for investigative monitoring on a limited scale and not for routine monitoring. Future perspectives in toxicity profiling include expansion of the battery of bioassays with test methods that cover other toxic endpoints or multiple endpoints, are high throughput, and improve the ecological relevance.

Superinduction of estrogen receptor mediated gene expression in luciferase based reporter gene assays is mediated by a post-transcriptional mechanism

Several estrogenic compounds including the isoflavonoid genistein have been reported to induce a higher maximal response than the natural estrogen 17β-estradiol in in vitro luciferase based reporter gene bioassays for testing estrogenicity. The phenomenon has been referred to as superinduction. The mechanism underlying this effect and thus also its biological relevance remain to be elucidated. In the present study several hypotheses for the possible mechanisms underlying this superinduction were investigated using genistein as the model compound. These hypotheses included (i) a non-estrogen receptor (ER)-mediated mechanism, (ii) a role for an ER activating genistein metabolite with higher ER inducing activity than genistein itself, and (iii) a post-transcriptional mechanism that is not biologically relevant but specific for the luciferase based reporter gene assays. The data presented in this study indicate that induction and also superinduction of the reporter gene is ER-mediated, and that superinduction by genistein could be ascribed to stabilization of the firefly luciferase reporter enzyme increasing the bioluminescent signal during the cell-based assay. This indicates that the phenomenon of superinduction may not be biologically relevant but may rather represent a post-transcriptional effect on enzyme stability.

Performance of the flow cytometric E-screen assay in screening estrogenicity of pure compounds and environmental samples

In vitro estrogenicity screens are believed to provide a first prioritization step in hazard characterization of endocrine disrupting chemicals. When applied to complex environmental matrices or mixture samples, they have been indicated valuable in estimating the overall estrogen-mimicking load. In this study, the performance of an adapted format of the classical E-screen or MCF-7 cell proliferation assay was profoundly evaluated to rank pure compounds as well as influents and effluents of sewage treatment plants (STPs) according to estrogenic activity. In this adapted format, flow cytometric cell cycle analysis was used to allow evaluation of the MCF-7 cell proliferative effects after only 24 h of exposure. With an average EC(50) value of 2 pM and CV of 22%, this assay appears as a sensitive and reproducible system for evaluation of estrogenic activity. Moreover, estrogenic responses of 17 pure compounds corresponded well, qualitatively and quantitatively, with other in vitro and in vivo estrogenicity screens, such as the classical E-screen (R(2)=0.98), the estrogen receptor (ER) binding (R(2)=0.84) and the ER transcription activation assay (R(2)=0.87). To evaluate the applicability of this assay for complex samples, influents and effluents of 10 STPs covering different treatment processes, were compared and ranked according to estrogenic removal efficiencies. Activated sludge treatment with phosphorus and nitrogen removal appeared most effective in eliminating estrogenic activity, followed by activated sludge, lagoon and filter bed. This is well in agreement with previous findings based on chemical analysis or biological activity screens. Moreover, ER blocking experiments indicated that cell proliferative responses were mainly ER mediated, illustrating that the complexity of the end point, cell proliferation, compared to other ER screens, does not hamper the interpretation of the results. Therefore, this study, among other E-screen studies, supports the use of MCF-7 cell proliferation as estrogenicity screen for pure compounds and complex samples.

Specific in vitro toxicity of crude and refined petroleum products: II. Estrogen (alpha and beta) and androgen receptor-mediated responses in yeast assays

The present study is the second in a series aiming at a systematic inventory of specific toxic effects of oils. By employing a recombinant yeast stably transfected with human estrogen receptor-alpha (ERalpha) or -beta (ERbeta) or androgen receptor (AR) and expressing yeast enhanced green fluorescent protein, the (anti-)estrogenicity and (anti-)androgenicity of 11 crude oils and refined products were studied. None of the oils tested had significant estrogenic effects in the ERalpha assay or androgenic effects in the AR assay. However, all oils were capable of inducing estrogenic responses in the ERbeta assay, with several responses being above even the maximal response of the standard 17beta-estradiol (E2). Based on the lowest effect concentrations, the potencies of oils in all the assays were between four and seven orders of magnitude lower than those of the standards E2 or testosterone (T). The potencies of the actual individual petrochemical agonists may, however, be relatively high, considering the complex composition of oils. Additive effects, antagonistic effects, and a synergistic effect were measured in the assays upon coexposure to a fixed concentration of standard (E2 or T) and increasing concentrations of oils. To investigate whether the observed effects were receptor-mediated, coexposures to the synthetic inhibitors ICI 182,780 (ERbeta assay) or flutamide (AR assay), a fixed concentration of standard, and various concentrations of oils were performed. The results suggested that the androgenic effects were receptor mediated, whereas the estrogenic effects may be only partially mediated via the receptor. The present study indicates that oils contain compounds with possible endocrine-disrupting potential, some of them acting via the hormone receptors.

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.

Activation of transgenic estrogen receptor-beta by selected phytoestrogens in a stably transduced rat serotonergic cell line

Many flavonoids, a major group of phenolic plant-derived secondary metabolites, are known to possess estrogen-like bioactivities. However, little is known about their estrogenic properties in the central nervous system due to the lack of suitable cellular models expressing sufficient amounts of functional estrogen receptor beta (ERbeta). To overcome this deficit, we have created a cellular model, which is serotonergic in origin, to study properties of estrogenic substances by stably transducing RN46A-B14 cells derived from raphe nuclei region of the rat brain with a lentiviral vector encoding a human ERbeta. We clearly showed that the transgenic human ERbeta is a spontaneously expressed and a functional receptor. We have further assessed the estrogenicity of three different isoflavones and four different naringenin-type flavanones in this cell line utilizing a luciferase reporter gene assay. Genistein (GEN), Daidzein (DAI), Equol (EQ), Naringenin (NAR) and 8-prenylnaringenin (8-PN) showed strong estrogenic activity in a concentration-dependent manner as compared to 7-(O-prenyl)naringenin-4'-acetate (7-O-PN) which was only slightly estrogenic and 6-(1,1-dimethylallyl)naringenin (6-DMAN) that neither showed estrogenic nor anti-estrogenic activity in our model. All observed effects could be antagonized by the anti-estrogen fulvestrant. Moreover, co-treatment of cells with 17beta-estradiol (E2) and either GEN or DAI showed a slight additive effect as compared to EQ. On the other hand, 8-PN in addition to 7-O-PN, but not NAR and 6-DMAN, were able to slightly antagonize the responses triggered by E2. Our newly established cellular model may prove to be a useful tool in explicating basic physiological properties of ERbeta in the brain and may help unravel molecular and cellular mechanisms involved in serotonergic mood regulation by estrogen or potential plant-derived secondary metabolites.

Estrogenic and progestagenic effects of extracts of Justicia pectoralis Jacq., an herbal medicine from Costa Rica used for the treatment of menopause and PMS

OBJECTIVES

To investigate the biological activities of Justicia pectoralis Jacq. (Acanthaceae), an herbal medicine used in Costa Rica (CR) for the management of menopausal symptoms and dysmenorrhea.

STUDY DESIGN

The aerial parts of J. pectoralis were collected, dried and extracted in methanol. To establish possible mechanisms of action of JP for the treatment of menopausal symptoms, the estrogenic and progesterone agonists, and antiinflammatory activities were investigated.

MAIN OUTCOME MEASURES

The methanol extract (JP-M) was tested in ER and PR binding assays, a COX-2 enzyme inhibition assay, the ERbeta-CALUX assay in U2-OS cells, as well as reporter and endogenous gene assays in MCF-7 K1 cells.

RESULTS

The JP-M extract inhibited COX-2 catalytic activity (IC(50) 4.8 microg/mL); bound to both ERalpha and ERbeta (IC(50) 50 microg/mL and 23.1 microg/mL, respectively); induced estrogen-dependent transcription in the ERbeta-CALUX; and bound to the progesterone receptor (IC(50) 22.8 microg/mL). The extract also modulated the expression of endogenous estrogen responsive genes pS2, PR, and PTGES in MCF-7 cells at a concentration of 20 microg/mL. Activation of a 2 ERE-construct in transiently transfected MCF-7 cells by the extract was inhibited by the estrogen receptor antagonist ICI 182,780, indicating that the effects were mediated through the estrogen receptor. Finally, the extract weakly enhanced the proliferation of MCF-7 cells, however this was not statistically significant as compared with DMSO controls.

CONCLUSIONS

Extracts of J. pectoralis have estrogenic, progestagenic and anti-inflammatory effects, and thus have a plausible mechanism of action, explaining its traditional use for menopause and PMS.

Absence of ligand-independent transcriptional activation of the estrogen receptor via the estrogen response element in pituitary lactotrophs in primary culture

The estrogen receptor (ER) is a ligand-activated transcription factor that enhances gene expression by binding to specific regulatory DNA sequences called estrogen response elements (EREs). In some cell lines, the ER is also activated in a ligand-independent manner by multiple signaling pathways. In this study, we developed a novel adenovirus-mediated assay for promoter activation, termed LASETA, which we then used to examine whether ligand-independent activation of the ER occurred in normal pituitary lactotrophs in primary culture. In the LASETA adenovirus vector, the loxP-flanked stop sequence was deleted by prolactin (PRL) promoter-regulated expression of Cre recombinase. This led to lactotroph-specific expression of a reporter gene driven by an ERE-containing promoter. Estrogen-induced expression of the reporter protein luciferase in LASETA was specific for lactotrophs and was ER-dependent. LASETA was shown to be reliable even with varying Cre recombinase expression levels, which were caused by changes in PRL promoter activity. Using LASETA, we observed no change in ERE-mediated ER activity in the absence of estrogen after treatment of normal lactotrophs with agents such as insulin-like growth factor-1, epidermal growth factor, the adenylate cyclase activator forskolin, the extracellular signal-regulated kinase kinase inhibitor U0126, and the protein kinase A inhibitor H89. The ERE-mediated ligand-independent ER activity was induced by the growth factors and forskolin in the somatolactotroph tumor cell line GH4C1 cells. These results suggest that ERE-mediated ligand-independent activation of ER does not occur in normal lactotrophs in primary culture, and is a phenomenon likely restricted to transformed cells.

Estrogenic activities of two synthetic pyrethroids and their metabolites

Synthetic pyrethroids (SPs) are among the most common pesticides in current use, and so far, several SPs have been assessed for their potential estrogenicities by various methods. Previous studies have shown that the estrogenicities partly come from their metabolites. Although considerable information is available with respect to the metabolism and environmental degradation of SPs, little is known about the estrogenicities of the metabolites. In this study, permethrin (PM) and beta-cypermethrin (CP), as well as their metabolites (3-phenoxybenzoic alcohol (PBCOH), 3-phenoxybenzaldehyde (PBCHO) and 3-phenoxybenzoic acid (PBCOOH) were evaluated for their estrogenic activities in the MCF-7 human breast carcinoma cell line. In the MCF-7 cell proliferation assay, PM and CP exhibited significant estrogenic activities at 10(-7) mol/L, comparable to 17beta-estradiol (E2) of 10(-9) mol/L, with the relative proliferative effect ratios of 55.4% and 56.3%, respectively. The real-time quantitative polymerase chain reaction (qRT-PCR) results confirmed the estrogenicities of PM and CP with significant alteration of pS2 and ERalpha mRNA levels observed at 10(-6) mol/L. For the three major metabolites, PBCOH and PBCOOH exhibited estrogenic activities in all assays, while no significant estrogenic responses was observed for PBCHO compared to the vehicle control. In particular, PBCOH had even slightly stronger estrogenic activity than its parent compounds, indicating that metabolism may be one of the reasons for the estrogenicities of the SPs. Given the widespread use of SPs, the toxicological effects of parent compounds and their metabolites should be taken into consideration in the risk assessment of SPs.

Diastereomers of the brominated flame retardant 1,2-dibromo-4-(1,2 dibromoethyl)cyclohexane induce androgen receptor activation in the hepg2 hepatocellular carcinoma cell line and the lncap prostate cancer cell line

BACKGROUND

Reported incidences of prostate cancer and masculinization of animals indicate a release of compounds with androgenic properties into the environment. Large numbers of environmental pollutants have been screened to identify such compounds; however, not until recently was 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH) identified as the first potent activator of the human androgen receptor (hAR). TBECH has been found in beluga whales and bird eggs and has also been found to be maternally transferred in zebrafish.

OBJECTIVES

In the present study we investigated interaction energies between TBECH diastereomers (alpha, beta, gamma, and delta) and the hAR, and their ability to activate the receptor and induce prostate-specific antigen (PSA) expression in vitro.

METHODS

We performed computational modeling to determine interaction energies between the ligand and the AR ligand-binding site, and measured in vitro competitive binding assays for AR by polarization fluorometry analysis. We used enzyme-linked immunosorbent assays to determine PSA activity in LNCaP and HepG2 cells.

RESULTS

We found the gamma and delta diastereomers to be more potent activators of hAR than the alpha and beta diastereomers, which was confirmed in receptor binding studies. All TBECH diastereomers induced PSA expression in LNCaP cells even though the AR present in these cells is mutated (T877A). Modeling studies of LNCaP AR revealed that TBECH diastereomers bound to the receptor with a closer distance to the key amino acids in the ligand-binding domain, indicating stronger binding to the mutated receptor.

CONCLUSIONS

The present study demonstrates the ability of TBECH to activate the hAR, indicating that it is a potential endocrine disruptor.

Fate and removal of estrogens in municipal wastewater

Natural and synthetic estrogens are some of the most potent endocrine disrupting compounds found in municipal wastewater. Much research has been conducted on the source and fate of estrogens in wastewater treatment plants. Sorption and biodegradation are the primary removal mechanisms for estrogens in activated sludge systems, which are widely used biological treatment techniques for municipal wastewater treatment. However, when removal of estrogens in a wastewater treatment plant is incomplete, these compounds enter the environment through wastewater discharges or waste activated sludge at concentrations that can cause endocrine-reproductive system alterations in birds, reptiles and mammals. Therefore, studies have also focused on potential advanced treatment technologies with the aim of removing the compounds before discharging wastewater effluent or disposing waste sludge. This review discusses the physiological effects of these estrogens and the degree of problems estrogens pose as they enter the wastewater stream. Thereafter, this review also analyzes their fate in wastewater treatment systems and how they may reach drinking water sources. Furthermore, this review includes a discussion on various treatment technologies being investigated and future research trends for this pressing environmental issue.

Estrogenic effects of herbal medicines from Costa Rica used for the management of menopausal symptoms

OBJECTIVE

Outcomes from the Women's Health Initiative have demonstrated adverse effects associated with hormone therapy and have prioritized the need to develop new alternative treatments for the management of menopause and osteoporosis. To this end, we have been investigating natural herbal medicines used by Costa Rican women to manage menopausal symptoms.

METHODS

Seventeen plant species were collected and extracted in Costa Rica. To establish possible mechanisms of action and to determine their potential future use for menopause or osteoporosis, we investigated the estrogenic activities of the herbal extracts in an estrogen-reporter gene estrogen receptor (ER) beta-Chemically Activated Luciferase Expression assay in U2-OS cells and in reporter and endogenous gene assays in MCF-7 cells.

RESULTS

Six of the plant extracts bound to the ERs. Four of the six extracts stimulated reporter gene expression in the ER-beta-Chemically Activated Luciferase Expression assay. All six extracts modulated expression of endogenous genes in MCF-7 cells, with four extracts acting as estrogen agonists and two extracts, Pimenta dioica and Smilax domingensis, acting as partial agonist/antagonists by enhancing estradiol-stimulated pS2 mRNA expression but reducing estradiol-stimulated PR and PTGES mRNA expression. Both P. dioica and S. domingensis induced a 2ERE-luciferase reporter gene in transient transfected MCF-7 cells, which was inhibited by the ER antagonist ICI 182,780.

CONCLUSIONS

This work presents a plausible mechanism of action for many of the herbal medicines used by Costa Rican women to treat menopausal symptoms. However, it further suggests that studies of safety and efficacy are needed before these herbs should be used as alternative therapies to hormone therapy.

Urinary excretion rates of natural estrogens and androgens from humans, and their occurrence and fate in the environment: a review

Endocrine disrupting compounds (EDCs) are pollutants with estrogenic or androgenic activities at very low concentrations and are emerging as a major concern for water quality. For sewage of municipal wastewater treatment plants in cities, one of the most important sources of EDCs are natural estrogens and natural androgens (NEAs) excreted from humans. Therefore, estrogenic/androgenic potencies or relative binding affinity of the NEAs were first outlined from different sources, and data of urinary excretion rates of NEAs were summarized. To evaluate their estrogenic activities, their excretion rates of estrogen equivalent (EEQ) or testosterone (T) equivalent (TEQ) were also calculated. Based on our summary, the total excretion rates of EEQ by estrone (E1), 17beta-estradiol (E2), and estriol (E3) only accounted for 66-82% of the total excretion rate of EEQ among four different groups, and the other corresponding natural estrogens contributed 18-34%, which meant that some of the other natural estrogens may also exist in wastewater with high estrogenic activities. Based on the contribution ratio of individual androgens to the total excretion rate of TEQ, five out of 12 natural androgens, T, dihydrotestosterone (DHT), androsterone (AD), 5beta-androstanediol (beta-ADL), and androstenediol (ANL) were evaluated as the priority natural androgens, which may exist in wastewater with high androgenic activities. Published data on occurrence and fate of the NEAs including natural estrogen conjugates in the environment were also summarized here.

A novel estrogen receptor intramolecular folding-based titratable transgene expression system

The use of regulated gene expression systems is important for successful gene therapy applications. In this study, ligand-induced structural change in the estrogen receptor (ER) was used to develop a novel ER intramolecular folding-based transcriptional activation system. The system was studied using ER-variants of different lengths, flanked on either side by the GAL4-DNA-binding domain and the VP16-transactivation domain (GAL4(DBD)-ER-VP16). The ER ligands of different types showed efficient ligand-regulated transactivation. We also characterized a bidirectional transactivation system based on the ER and demonstrated its utility in titrating both reporter and therapeutic gene expression. The ligand-regulated transactivation system developed by using a mutant form of the ER (G521T, lacking affinity for the endogenous ligand 17beta-estradiol, whereas maintaining affinity for other ligands) showed efficient activation by the ligand raloxifene in living mice without significant interference from the circulating endogenous ligand. The ligand-regulated transactivation system was used to test the therapeutic efficiency of the tumor suppressor protein p53 in HepG2 (p53(+/+)) and SKBr3 (p53(-/-)/mutant-p53(+/+)) cells in culture and tumor xenografts in living mice. The multifunctional capabilities of this system should be useful for gene therapy applications, to study ER biology, to evaluate gene regulation, ER ligand screening, and ER ligand biocharacterization in cells and living animals.

Nuclear hormone receptor activity of polybrominated diphenyl ethers and their hydroxylated and methoxylated metabolites in transactivation assays using Chinese hamster ovary cells

BACKGROUND

An increasing number of studies are reporting the existence of polybrominated diphenyl ethers (PBDEs) and their hydroxylated (HO) and methoxylated (MeO) metabolites in the environment and in tissues from wildlife and humans.

OBJECTIVE

Our aim was to characterize and compare the agonistic and antagonistic activities of principle PBDE congeners and their HO and MeO metabolites against human nuclear hormone receptors.

METHODS

We tested the hormone receptor activities of estrogen receptor alpha (ERalpha), ERbeta, androgen receptor (AR), glucocorticoid receptor (GR), thyroid hormone receptor alpha(1) (TRalpha(1)), and TRbeta(1) against PBDE congeners BDEs 15, 28, 47, 85, 99, 100, 153, and 209, four para-HO-PBDEs, and four para-MeO-PBDEs by highly sensitive reporter gene assays using Chinese hamster ovary cells.

RESULTS

Of the 16 compounds tested, 6 and 2 showed agonistic activities in the ERalpha and ERbeta assays, respectively, and 6 and 6 showed antagonistic activities in these assays. 4'-HO-BDE-17 showed the most potent estrogenic activity via ERalpha/beta, and 4'-HO-BDE-49 showed the most potent anti estrogenic activity via ERalpha/beta. In the AR assay, 13 compounds showed antagonistic activity, with 4'-HO-BDE-17 in particular inhibiting AR-mediated transcriptional activity at low concentrations in the order of 10(-8) M. In the GR assay, seven compounds, including two HO-PBDEs and two MeO-PBDEs, showed weak antagonistic activity. In the TRalpha(1) and TRbeta(1) assays, only 4-HO-BDE-90 showed weak antagonistic activity.

CONCLUSIONS

Taken together, these results suggest that PBDEs and their metabolites might have multiple endocrine-disrupting effects via nuclear hormone receptors, and para-HO-PBDEs, in particular, possess more potent receptor activities compared with those of the parent PBDEs and corresponding para-MeO-PBDEs.