New screening methods for chemicals with hormonal activities using interaction of nuclear hormone receptor with coactivator

Fluorotelomer alcohols induce hepatic vitellogenin through activation of the estrogen receptor in male medaka (Oryzias latipes)

Here we report on the in vivo estrogenic effects of two fluorotelomer alcohols, such as 1H,1H,2H,2H-perfluorooctan-1-ol (6:2 FTOH) and 1H,1H,2H,2H-perfluorodecan-1-ol (8:2 FTOH), in male medaka (Oryzias latipes). An in vitro yeast two-hybrid assay indicated a significant, dose-dependent interaction between medaka estrogen receptor alpha (ERalpha) and coactivator TIF2 upon treatment with 6:2 FTOH, 8:2 FTOH or 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-nonadecafluoro-1-decanol (NFDH). The relative ranks of tested chemicals on the estrogenic effects for medaka ERalpha descended in the order of estradiol-17beta (100)>>6:2 FTOH (0.16)>NFDH (0.016)>8:2 FTOH (0.0044). In contrast, no interaction with the ERalpha was observed upon treatment with perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorododecanoic acid (PFDA) or perfluoroundecanoic acid (PFUnDA). Expression analysis of hepatic vitellogenin (VTG) protein showed estrogenic potentials with, 6:2 FTOH and 8:2 FTOH, indicative of the induction of VTG synthesis in the livers of male medaka. We also investigated mRNA expression levels of two ER subtypes (ERalpha and beta) and two VTGs (VTG I and VTG II) in the livers of male medaka following exposure to FTOHs. Quantitative real-time polymerase chain reaction analyses revealed that hepatic ERalpha, VTG I, and VTG II mRNA responded rapidly to FTOHs such as 6:2 FTOH and 8:2 FTOH after 8-h exposure, whereas no effects of these compounds on ERbeta mRNA transcription were observed. These results from both in vitro and in vivo assays strongly suggest that certain FTOHs, such as 6:2 FTOH and 8:2 FTOH, induce hepatic VTG through activation of ERalpha in male medaka.

Identification of estrogenic/anti-estrogenic compounds in diesel exhaust particulate extract

Diesel exhaust particulate extract (DEPE) was obtained from diesel exhaust particulates with Soxhlet extraction using dichloromethane. After separating DEPE into 11 fractions by liquid-liquid extraction, the neutral fraction (N) showed anti-estrogenic activity and the weak acid (phenol) fraction (WA(P)) showed estrogenic and anti-estrogenic activities by a yeast two-hybrid assay system expressing human estrogen receptor alpha. Both fractions were thoroughly fractionated by silica gel column chromatography and reversed-phase HPLC. In the WA(P) fraction, 3-methyl-4-nitrophenol and 2,6-dimethyl-4-nitrophenol were identified by LC-MS/MS as estrogenic compounds. This is the first study to identify 2,6-dimethyl-4-nitrophenol in DEPE and the first study to show that it is an estrogenic compound. In the N fraction, 1-hydroxypyrene was also identified by LC-MS/MS as an anti-estrogenic compound.

Estrogenic and anti-estrogenic activities of Cassia tora phenolic constituents

Through an estrogenic activity bioassay-guided fractionation of the 70% ethanolic extract of Cassia tora seeds two new phenolic triglucosides, torachrysone 8-O-[beta-D-glucopyranosyl(1-->3)-O-beta-D-glucopyranosyl(1-->6)-O-beta-D-glucopyranoside] (1) and toralactone 9-O-[beta-D-glucopyranosyl-(1-->3)-O-beta-D-glucopyranosyl-(1-->6)-O-beta-D-glucopyranoside] (2), along with seven known compounds were isolated. The structures of the new compounds were elucidated on the basis of spectroscopic and chemical evidence. The estrogenic activity of the fractions and the isolated compounds were investigated using the estrogen-dependent proliferation of MCF-7 cells. In addition, the yeast two hybrid assay expressing estrogen receptor alpha (ERalpha) and beta (ERbeta) and the ERalpha competitor screening assay (ligand binding screen) were used to verify the binding affinities of the isolated compounds to ER. Furthermore, a naringinase pre-treatment of the 70% alcoholic extract of Cassia tora seeds resulted in a significant increase in its estrogenic activity. From the naringinase pre-treated extract six compounds were isolated, among which 6-hydroxymusizin and aurantio-obtusin showed the most potent estrogenic activity, while torachrysone, rubrofusarin and toralactone showed a significant anti-estrogenic activity. Finally, the structure requirements responsible for the estrogenic activity of the isolated compounds were studied by investigating the activity of several synthetic compounds and chemically modifying the isolated compounds. The basic nucleus 1,3,8-trihyroxynaphthalene (T(3)HN) was found to play a principal role in the binding affinity of these compounds to ER.

Ligand-dependent interactions of the Ah receptor with coactivators in a mammalian two-hybrid assay

2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is a high affinity ligand for the aryl hydrocarbon receptor (AhR). In this study, we investigated structure-dependent differences in activation of the AhR by a series of halogenated aromatic hydrocarbons. TCDD, 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PeCDD), 2,3,7,8-tetrachlorodibenzofuran (TCDF), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), and 3,3',4,4',5-pentachlorobiphenyl (PCB126) induced CYP1A1-dependent activities in HEK293 human embryonic kidney, Panc1 pancreatic cancer, and Hepa1c1c7 mouse hepatoma cell lines. There was a structure-dependent difference in the efficacy of TCDF and PCB126 in HEK293 and Panc1 cells since induced CYP1A1 mRNA levels were lower than observed for the other congeners. A mammalian two-hybrid assay in cells transfected with GAL4-coactivator and AhR-VP16 chimeras was used to investigate structure-dependent interactions of these chimeras in Panc1, HEK293, and Hepa1c1c7 cells. The reporter construct pGAL4-luc contains five tandem GAL4 response elements linked to the luciferase gene and the GAL4-coactivator chimeras express several coactivators including steroid receptor coactivator 1 (SRC-1), SRC-2 and SRC-3, the mediator coactivator TRAP220, coactivator associated arginine methyl transferase 1 (CARM-1), and peroxisome proliferator-activated receptor gamma coactivator 1 (PGC-1). Results of the mammalian two-hybrid studies clearly demonstrate that activation of pGAL4-luc in cells transfected with VP-AhR and GAL4-coactivator chimeras is dependent on the structure of the HAH congener, cell context, and coactivator, suggesting that the prototypical HAH congeners used in this study exhibit selective AhR modulator activity.

Modeling binding equilibrium in a competitive estrogen receptor binding assay

Although the free concentration is more significant in the environmental chemistry and toxicology of receptor-mediated toxicants, few studies have been conducted to use it as a dose-metric. The relative binding affinity of three model endocrine disrupting compounds, diethylstilbestrol (DES), ethynylestradiol (EE2), and bisphenol A (BPA), were evaluated using a competitive ELISA with human estrogen receptor alpha. After measuring the available receptors and the dissociation constant for 17beta-estradiol, binding inhibition curves using the free concentration as the dose-metric were obtained by assuming species equilibrium in the ELISA system and compared with apparent inhibition curves generated using the nominal concentration as the dose-metric. Because ligand binding to estrogen receptors may reduce its free concentration in the assay system, the differences between the two curves for free and nominal concentrations are more significant for more strongly binding ligands. The ratio of a compound's nominal concentration causing 50% inhibition (IC50) to the IC50 of DES, the positive control, was strongly affected by specific assay conditions, while that estimated by modeling free concentration is independent of receptor concentration, indicating that the free concentration is a better dose-metric for a competitive binding assay.

Increased level of cellular Bip critically determines estrogenic potency for a xenoestrogen kepone in the mouse uterus

Xenoestrogen mimics estrogen-like activities primarily based on alterations of gene expression and interactions with estrogen receptor (ER)-alpha and -beta. However, the requirement for large concentrations to induce estrogenic phenotypes and low affinity for ERs has challenged the notion that prevailing xenoestrogens are significant health hazards. Here in this study, we show that under certain conditions, exposure of xenoestrogen could be potentially harmful in respect to enhanced uterine estrogenicity. Previously, we have demonstrated that estradiol-17beta up-regulates uterine Bip, a stress-related endoplasmic reticulum protein, via an ER-independent mechanism in mice. Moreover, this protein essentially involves in estradiol-17beta-mediated uterine growth response and ERalpha-dependent gene transcription. Here, we demonstrate that among three tested xenoestrogens, only kepone (>15-30 mg/kg) exerts sustained inductive response for uterine Bip expression. Interestingly, this kepone-induced Bip strongly correlates with ERalpha-dependent growth and gene expressional responses in the mouse uterus. Furthermore, these effects were strongly suppressed after knockdown of uterine Bip, via the adenovirus approach. Although kepone at 7.5 mg/kg was not effective, it was strongly stimulatory by the adenovirus-driven forced expression of uterine Bip. In contrast, the control green fluorescence protein virus was not effective in the aforementioned responses. Furthermore, the induction of uterine Bip by stress-related signals also revealed the onset of uterine growth in mice when exposed to a sublethal dose of kepone. Collectively, studies provide novel molecular evidence that Bip acts as a critical regulator to amplify estrogenic potency for a weak xenoestrogen kepone.

A field study on serum vitellogenin levels in male Reeves' pond turtles (Chinemys reevesii) from estrogen-contaminated sites and a reference site

To ascertain whether wild male turtles were influenced by environmental estrogens, we examined serum vitellogenin (VTG) levels of male Reeves' pond turtles (Chinemys reevesii) collected from four study sites (A-D) in Kyoto, Japan. Sites A-C, which were impacted by domestic or industrial wastewater and effluents from sewage treatment plants, were chosen as contaminated sites, and site D was intended as a reference site. This contaminated/reference site characterization was confirmed by measuring estrogenic activities of the water samples collected at each site for over a year. Serum VTG levels in the turtles were quantified by an enzyme-linked immunosorbent assay established previously. Estrogenic activities of the water samples were measured using a previously validated yeast two-hybrid assay and expressed as the estradiol-17beta equivalent. Estrogenic activity was observed at high levels at sites A-C, but was almost undetected at site D throughout the sampling period: the mean and range were 0.74 (<0.07-2.1), 0.52 (0.17-1.6), 1.7 (<0.07-7.3), and 0.07 (<0.07-0.62) ng/l at sites A-D, respectively. Significant differences were found only in site D versus sites A, B, and C. Therefore, site D and sites A-C were confirmed to be a reference site and contaminated ones, respectively. Overall, 320 male turtles were captured and examined. The majority of the turtles showed normal VTG values (0.10-0.74 microg/ml). Although only five turtles from sites A-C showed unusually high VTG values (1.1-5.9 microg/ml, nearly one order of magnitude higher than normal values but much lower than values in adult females), there was no significant difference in the incidence of these high values between sites A-C and site D. Moreover, among the five turtles, one turtle was captured again 2 months later, but its VTG value dropped to the normal level. The unusually high VTG values may therefore be transient elevation caused by incidental and/or individually specific agents. Excluding the unusually high values, the mean serum VTG (accompanied with the range) was 0.22 (0.10-0.74), 0.27 (0.11-0.62), 0.27 (0.17-0.68), and 0.23 (0.10-0.57) microg/ml at sites A-D, respectively. There were no significant differences in the mean VTG values among sites A-D. Although it should be clarified how and why the unusually high VTG values occurred at sites A-C, our results suggested that wild male C. reevesii turtles would not be significantly affected by xenobiotic estrogens at environmentally relevant levels in terms of serum VTG elevation.

Estrogenic activity in sediments contaminated by nonylphenol in Tokyo Bay (Japan) evaluated by vitellogenin induction in male mummichogs (Fundulus heteroclitus)

Estrogenic activity was determined in sediments collected from Tokyo Bay. Sampling was performed at five stations including the site near the sewage treatment plant. The most estrogenic sediment collected near the sewage treatment plant was fractionated into ten fractions using normal-phase high-performance liquid chromatography. Chemical analysis was carried out for each fraction and nonylphenol (NP, 20,700ngg(-1)drywt) was detected at a higher concentration than estron (2.39ngg(-1)drywt) and 17beta-estradiol (<0.7ng g(-1)dry wt). Furthermore, each fraction was administered to male mummichogs (Fundulus heteroclitus), and vitellogenin (Vtg) was measured after two weeks. The induction of Vtg was observed; this estrogenic potency could be attributed to the NP content in this fraction. This is the first report to suggest that the high NP concentration in the sediments from Tokyo Bay has the potential to induce Vtg in wild fish.

MYST opportunities for growth control: yeast genes illuminate human cancer gene functions

The MYST family of histone acetyltransferases (HATs) was initially defined by human genes with disease connections and by yeast genes identified for their role in epigenetic transcriptional silencing. Since then, many new MYST genes have been discovered through genetic and genomic approaches. Characterization of the complexes through which MYST proteins act, regions of the genome to which they are targeted and biological consequences when they are disrupted, all deepen the connections of MYST proteins to development, growth control and human cancers. Many of the insights into MYST family function have come from studies in model organisms. Herein, we review functions of two of the founding MYST genes, yeast SAS2 and SAS3, and the essential yeast MYST ESA1. Analysis of these genes in yeast has defined roles for MYST proteins in transcriptional activation and silencing, and chromatin-mediated boundary formation. They have further roles in DNA damage repair and nuclear integrity. The observation that MYST protein complexes share subunits with other HATs, histone deacetylases and other key nuclear proteins, many with connections to human cancers, strengthens the idea that coordinating distinct chromatin modifications is critical for regulation.

Corepressors of agonist-bound nuclear receptors

Nuclear receptors (NRs) rely on coregulator proteins to modulate transcription of target genes. NR coregulators can be broadly subdivided into coactivators which potentiate transcription and corepressors which silence gene expression. The prevailing view of coregulator action holds that in the absence of agonist the receptor interacts with a corepressor via the corepressor nuclear receptor (CoRNR, "corner") box motifs within the corepressor. Upon agonist binding, a conformational change in the receptor causes the shedding of corepressor and the binding of a coactivator which interacts with the receptor via NR boxes within the coregulator. This view was challenged with the discovery of RIP140 which acts as a NR corepressor in the presence of agonist and utilizes NR boxes. Since then a number of other corepressors of agonist-bound NRs have been discovered. Among them are LCoR, PRAME, REA, MTA1, NSD1, and COPR1 Although they exhibit a great diversity of structure, mechanism of repression and pathophysiological function, these corepressors frequently have one or more NR boxes and often recruit histone deacetylases to exert their repressive effects. This review highlights these more recently discovered corepressors and addresses their potential functions in transcription regulation, disease pharmacologic responses and xenobiotic metabolism.

Removal of estrogenic activity of 4-tert-octylphenol by ligninolytic enzymes from white rot fungi

4-tert-Octylphenol (4-t-OP) was treated with the white rot fungus Phanerochaete sordida YK-624 under ligninolytic condition with low-nitrogen and high-carbon culture medium. 4-t-OP completely disappeared after 5 days of treatment and the activities of ligninolytic enzymes, laccase and manganese peroxidase (MnP), were detected during this period, thus suggesting that the disappearance of 4-t-OP is related to these extracellular enzymes. Therefore, 4-t-OP was treated with laccase and MnP prepared from white rot fungi cultures. HPLC analysis demonstrated that 4-t-OP completely disappeared in the reaction mixture after 1 h of treatment with either laccase or MnP. Using the yeast two-hybrid assay system, it was also confirmed that laccase and MnP substantially removed the estrogenic activity of 4-t-OP after 1 and 2 h of treatment, respectively. These results strongly demonstrate that ligninolytic enzymes are effective in removing the estrogenic activity of 4-t-OP.

Evaluation on antagonist activities of polycyclic aromatic hydrocarbons using the yeast two-hybrid detection system for endocrine disruptors

We constructed an efficient and reliable yeast two-hybrid detection system to evaluate the estrogenic activity of endocrine disruptors (EDs) (Lee et al., Journal of Biochemistry, 131, 2002). This system employs the interaction between the human estrogen receptor beta (hERbeta) ligand binding domain and the co-activator SRC1. The extent of transcriptional activation by those chemicals correlated with estrogenic activities as measured by other assay systems. We applied this assay system to evaluate anti-estrogenic activities and found that known antagonistic compounds, 4-hydroxytamoxifen (OHT) and ICI 182,780, effectively inhibited reporter gene induction by 17beta-estradiol. We then tested the estrogenic and anti-estrogenic activities of polycyclic aromatic hydrocarbons (PAHs) using this assay system. PAHs only weakly induced the lacZ reporter gene at higher concentrations, but clearly showed an inhibitory effect on reporter gene induction by 10(-9) M 17beta-estradiol. These results suggest that PAHs are potentially anti-estrogenic and that the employed yeast detection system could be applicable to primary screening for effectors on estrogen receptor functions.

Removal of phenolic endocrine disruptors by Portulaca oleracea

Portulaca oleracea, a garden plant prevalent from spring to autumn in Japan, showed the ability to efficiently remove from water bisphenol A (BPA), which is well known as an endocrine disrupting compound (EDC) having estrogenic properties. In water culture, 50 muM BPA was almost completely removed within 24 h when the ratio of whole plant weight to the water volume was set up at 1 g to 25 ml. The estrogenic activity of the water decreased in parallel with the elimination of BPA. This plant also rapidly removed other EDCs having a phenol group including octylphenol (OP), nonylphenol (NP), 2,4-dichlorophenol (2,4-DCP) and 17beta-estradiol and, thereby, removed the endocrine disrupting activities. In addition, the ability of P. oleracea to remove BPA was not affected by BPA concentration (up to 250 microM), by cultivation in the dark, by temperatures ranging from 15 degrees C to 30 degrees C, or by pH ranging from 4 to 7. Moreover, the ability of P. oleracea to individually remove BPA, NP, and OP was the same as when they were all present. These results suggest that P. oleracea is a promising material for practical phytoremediation of landfill leachates and industrial wastewater contaminated with the tested EDCs.

beta-Cryptoxanthin, a novel natural RAR ligand, induces ATP-binding cassette transporters in macrophages

Despite its serious adverse effects, recent accumulating evidence suggests that a physiological retinoic acid receptor (RAR) agonist, all-trans retinoic acid (atRA), exhibits preventive effects on atherogenesis. Therefore, the present study was designed to explore novel natural RAR ligands with anti-atherogenic effects in order to identify and develop a drug without severe side effects. Among xanthophylls and carotenoids studied, beta-cryptoxanthin and lutein exhibited RAR ligand activity in yeast two-hybrid system that was found to be completely abolished by the RAR pan-antagonist LE540. Furthermore, these molecules can bind the RAR ligand-binding domain in the CoA-BAP system but not RXR ligand-binding domain. These results indicate that both beta-cryptoxanthin and lutein serve as ligands for RAR, but not RXR, although their binding affinity was three orders of magnitude lower than that of atRA. Additionally, when applied to macrophages, beta-cryptoxanthin indeed was found to induce the ATP-binding cassette transporter A1 (ABCA1) and ABCG1 mRNAs, which exert anti-atherosclerotic effects by preventing cholesteryl ester accumulation in macrophages. The induction of ABCA1 proteins by beta-cryptoxanthin as well as atRA was abrogated by LE540. In summary, beta-cryptoxanthin appears to be more an efficient provitamin A source than other carotenoids and xanthophylls including beta-carotene, since beta-cryptoxanthin can act not only as a RAR agonist but also a source of vitamin A. Taking into account that the pharmacodynamics difference between beta-cryptoxanthin and atRA, beta-cryptoxanthin appears to exert beneficial effects on atherogenesis through RAR activation in the manner different from atRA.

Direct determination of estrogenic and antiestrogenic activities using an enhanced plant two-hybrid system

This paper reports a simple, low-cost, and extremely sensitive reporter-gene assay system for comprehensive analysis of estrogenic activity using transgenic Arabidopsis thaliana: the EPTH system. It had the capability to detect 17beta-estradiol at a concentration of 10 pM. The system was rendered 5 times more sensitive than a previous system [Tojo, T.; Tsuda, K.; Wada, T.; Yamazaki, K. Ecotoxicol. Environ. Saf. 2006, 64, 106-114) (1)] by increasing the copy number of the transactivation domain fused to a nuclear receptor co-activator. The system can efficiently detect other estrogenic and antiestrogenic substances. Estrogenic activities were determined in treated sewage samples from four distinct sewage farms using the system. Results showed that the system can detect estrogenic activity directly and more efficiently than a yeast two-hybrid system without any manipulation for extraction and condensation of hydrophobic compounds and aseptic treatment. Furthermore, the system also is useful as a powerful tool for discovery of a new category of natural estrogenic substances that are undetectable by previous plant and yeast systems.

Modulation of Coactivator Recruitment by Cooperative Ligand Binding to Human Estrogen Receptor .ALPHA. and .BETA

Estrogen receptor (ER) is a member of the nuclear receptor superfamily, and functions as a ligand-dependent transcription factor with roles in cell growth and differentiation. In addition to endogenous estrogen, 17beta-estradiol (E(2)) and artificial antagonists, many suspected environmental estrogenic chemicals are reported to bind to ER, with various affinities and transcriptional responses. ER is also an allosteric protein and shows a positive cooperative interaction with E(2). Cooperativity affects inter-subunit interaction, and while ligand-bound ER interacts with coactivators, antagonist-bound ER does not. We therefore hypothesized that ligand-binding characteristics influence coactivator recruitment to the ER dimer, and thereby affect transcriptional activity. We investigated the interaction between ER and human Steroid Receptor Coactivator-1 (SRC-1), in the presence of compounds exhibiting various Hill coefficients. In the case of both ER subtypes (ERalpha and ERbeta), the Hill coefficients of the compounds tested correlated with the affinity of the ER-ligand complex to SRC-1, with the exception of ERbeta-4-n-nonylphenol and ER-antagonist complexes. This is the first report to investigate the relationship between Hill coefficients of ligand binding and coactivator interaction with the ER-ligand complex. We also examined the proteolytic digestion of ER using trypsin, in the presence and absence of compounds with various Hill coefficients, to investigate ligand-dependent conformational changes in ER. We used not only agonists and antagonists but also compounds of weak biological activity (partial agonists). Our results shed light on the subtle modulation of transcriptional activation by chemical agents.

Differential activation of wild-type estrogen receptor alpha and C-terminal deletion mutants by estrogens, antiestrogens and xenoestrogens in breast cancer cells

17beta-Estradiol (E2), diethylstilbestrol (DES) and several synthetic (or xenoestrogenic) compounds induced transactivation in MCF-7 or MDA-MB-231 cells transfected with wild-type estrogen receptor alpha (ERalpha) and a construct (pERE(3)) containing three tandem estrogen responsive elements (EREs) linked to a luciferase gene. In contrast, the antiestrogens ICI 182,780 and 4-hydroxytamoxifen (4-OHT) were inactive in this assay. We have investigated the effects of these compounds and several structurally-diverse estrogenic compounds on transactivation in cells transfected with pERE(3) and wild-type ERalpha, mutant ERalpha (1-553), and ERalpha (1-537) containing deletions of amino acids 595-554 and 595-538, respectively. These constructs were used to develop an in vitro assay to distinguish between different structural classes of estrogenic compounds. The results obtained using these constructs were highly cell context- and structure-dependent. Neither E2- nor diethylstilbestrol-induced transactivation in MCF-7 (or MDA-MB-231) cells transfected with pERE(3)/ERalpha (1-537) due to partial deletion of helix 12; however, octylphenol and nonlylphenol, resveratrol (a phytoestrogen), kepone and 2',3',4',5'-tetrachloro-4-biphenylol were "estrogenic" in MCF-7 cells transfected with pERE(3)/ERalpha (1-537). Moreover, the structure-dependent estrogenic activities of several synthetic estrogens (xenoestrogens) in MDA-MB-231 cells were different than those observed in MCF-7 cells. These results demonstrate that the estrogenic activity of many synthetic compounds do not require activation function 2 (AF-2) of ERalpha and are mechanistically different from E2. These data suggest that xenoestrogens are selective ER modulators (SERMs).

Endocrine effects generated by photooxidation of coplanar biphenyls in water using titanium dioxide

The oxidative photodegradation behaviors of selected three coplanar polychlorinated biphenyls (PCBs), (CB77, CB81, and CB169) using titanium dioxide (TiO(2)) in water were investigated. The main purposes were to clarify the structural relation between the original PCBs and the intermediates derived by TiO(2) oxidation and to evaluate the estrogenic and thyroid hormonal activity in the treated three coplanar PCBs during the oxidative reactions. Approximately 90% of the three coplanar PCBs decomposed within 180 min. Intermediates from the decomposition of the three coplanar PCBs, such as some hydroxylated-PCBs (OH-PCBs), carboxylic intermediates, phenolic intermediates, and other intermediates produced by the cleavage of a benzene ring were identified and quantified. In the degradation pathways, the produced amounts of OH-PCBs increased within 60 min of irradiation time. The estrogenic activity and thyroid hormonal activity of the intermediates from the three coplanar PCBs in water at 0, 60, 120, 180 and 240 min of irradiation time were assessed by using a yeast two-hybrid assay system for human estrogen receptor alpha (hERalpha) and human thyroid hormone receptor alpha (hTRalpha). The maximal estrogenic activities were induced by the solutions of decomposed PCBs with irradiation time at 60-120 min similar and slightly lower than those after the irradiation time. We found that the solutions occuring during the irradiation times of 60-120 min contained several 4-OH-PCBs substituted with OH and Cl at para- and para'-positions having estrogenic activity. The thyroid hormonal activity was not detected in the decomposed three coplanar PCBs solutions.

Oxidative degradation of BPA using TiO2 in water, and transition of estrogenic activity in the degradation pathways

The oxidative degradation behavior of bisphenol A (BPA) using titanium dioxide (TiO(2)) in water was investigated. The main purposes were to clarify the relationship with estrogenic activity from the degradation pathways demonstrated by oxidation of BPA in water. Approximately 99% of the BPA decomposed within 300 min, and gas chromatography (GC) mass spectrometry (MS) and liquid chromatography (LC) MS analysis revealed many intermediates during the degradation process. Intermediates by decomposition of BPA, such as hydroxylated-BPA (OH-BPA), carboxylic intermediates, phenolic intermediates, and other intermediates produced by the cleavage of a benzene ring were identified and quantified. Estrogenic activities of the degradation pathways of the BPA in water were assessed by using a constructed yeast two-hybrid assay system for human estrogen receptor alpha (hERalpha) and Japanese medaka fish (Oryzias latipes) estrogen receptor alpha (medERalpha). Estrogenic activity for hERalpha and medERalpha was reduced to less than 20% of the initial activity for BPA after 240 min of UV irradiation. However, estrogenic activity for medERalpha was increased by 110% from the initial activity for BPA at 60 min of UV irradiation. It was estimated that medERalpha assay was more sensitive for BPA and the intermediates than was the hERalpha assay. From these findings, we estimate that the intermediates by the oxidation of BPA have the behaviors of xenoestrogen to the aquatic wildlife in the environment.

Estrogenic Effects of Fluorotelomer Alcohols for Human Estrogen Receptor Isoforms .ALPHA. and .BETA. in Vitro

The present study demonstrates the estrogenic effects of fluorotelomer alcohols (FTOHs). In a yeast two-hybrid assay, treatment with 1H,1H,2H,2H-perfluorooctan-1-ol (6:2 FTOH), 1H,1H,2H,2H-perfluoro-decan-1-ol (8:2 FTOH) and 2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-nonadecafluoro-1-decanol (NFDH) showed a dose-dependent interaction between the human estrogen receptor (hER) isoforms hERalpha or hERbeta ligand-binding domain and coactivator TIF2, whereas there were no estrogenic effects of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) for these hERs. The estrogenic effects of FTOHs on hERalpha were higher than those on hERbeta, indicating a differential responsiveness of hERs to FTOHs. The relative ranks of tested chemicals on the estrogenic effects for hERalpha and hERbeta descended in the order of estradiol-17beta>>>6:2 FTOH>NFDH>8:2 FTOH. These results suggest that certain FTOHs including 6:2 FTOH, 8:2 FTOH and NFDH interact with hER isoforms alpha and beta in vitro. Further studies are necessary to investigate contamination levels, potential biological effects and the risks of these compounds on human health.

Anti-estrogenic Activity of Mansorins and Mansonones from the Heartwood of Mansonia gagei DRUMM

Through an anti-estrogenic bioassay-guided fractionation of the methanol extract of Mansonia gagei, three new coumarins, called mansorins I (1), II (2) and III (3) and a new naphthoquinone, mansonone I (4), were isolated. Their structures were determined based on their NMR data and CD spectroscopy. The anti-estrogenic activity of the fractions and the isolated compounds were investigated using a yeast two-hybrid assay method expressing estrogen receptors alpha (ERalpha) and beta (ERbeta). In addition, an ERalpha competitor screening system (ligand binding screen) was used to verify the binding affinities of the isolated compounds to the estrogen receptor. 1,2-Naphthoquinones (mansonones) showed more binding affinities to ER in both assay systems. All the tested compounds showed higher binding affinities to ERbeta than to ERalpha in the yeast two-hybrid assay. Mansonones F and S showed the most potent estrogen binding and estrogen antagonistic effects.

Biologically directed environmental monitoring, fate, and transport of estrogenic endocrine disrupting compounds in water: A review

Endocrine disrupting compounds (EDCs) are contaminants that may be hormonally active at low concentrations and are emerging as a major concern for water quality. Estrogenic EDCs (e-EDCs) are a subclass of EDCs that, when organisms are exposed to them, function as estrogens. Given that there are numerous e-EDCs that can negatively affect humans and wildlife, general screening techniques like biologically based assays (BBAs) may provide major advantages by estimating the total estrogenic effects of many e-EDCs in the environment. These techniques may potentially be adapted for field portable biologically directed sampling and analyses. This article summarizes available BBAs used to measure estrogenic e-EDCs in the environmental samples and also presents results relating to fate and transport of e-EDCs. Estrogenic EDCs appear to be almost ubiquitous in the environment, despite low solubility and high affinity of organic matter. Potential transport mechanisms may include: (1) transport of more soluble precursors, (2) colloid facilitated transport, (3) enhanced solubility through elevated pH, and (4) the formation of micelles by longer-chain ethoxylates. Due to their persistent and ubiquitous nature, source control strategies for e-EDCs may reduce influent concentration to wastewater treatment plants so that the post treatment effluent will decrease concentrations to estrogenically inactive levels. Alternatively if source reduction is not possible, then more testing is needed on tertiary treatment technologies and treatment efficiencies for e-EDCs. There is still a need for research on remediation and restoration approaches for habitats disturbed by elevated e-EDC concentrations.

Estrogenic activity of triterpene glycosides in yeast two-hybrid assay

Estrogenic potency of six triterpene glycosides, Holothurin A, Holotoxin A1, Frondoside A, Cucumarioside A2-2 and Cauloside C, that are natural products and semi-synthesized Ginsenoside-Rh2, were examined with yeast two-hybrid system, including expressed genes of human estrogen receptor, hERalpha, the co-activator TIF2 and lacZ as a reporter gene. Only Ginsenoside-Rh2 exhibited significant moderate estrogenic activity in the concentration range of 10(-7) to 10(-6)M. Its effect was approximately 30% of the activity of 17beta-estradiol applied at half-effective concentration. This indicates Ginsenosides-Rh2 is a weak phytoestrogen. The sea cucumber triterpene glycosides, Holothurin A, Holotoxin A1, Cucumarioside A2-2 and Frondoside A, and plant glycoside Cauloside C had no appreciable estrogenic activity. Data obtained by yeast two-hybrid assay reflect structure-activity relationship between tested compounds and 17beta-estradiol. Only Ginsenoside-Rh2 has some similarity in chemical structure with 17beta-estradiol that might explain affinity of this glycoside to the hERalpha receptor.

Identification and estrogenic characterization of impurities in commercial bisphenol A diglycidyl ether (BADGE)

A sample of commercial BADGE was fractioned by HPLC and eight impurities including novel propyl derivatives (2), (5) and (6) were identified by NMR spectrometry, FAB-MS and GC-MS. The estrogenicity, both agonist and antagonist, of fractions containing these impurities was measured with a yeast two-hybrid assay incorporating the human (hER alpha) and a competitive binding assay for hER alpha (ELISA). In the yeast two-hybrid assay, estrogenic antagonist activity was found in two fractions, while estrogenic agonist activity was not found in any. In the ELISA method, the binding affinity to hER alpha was found in three fractions. It is probable that a comprehensive assessment of the estrogenic properties of commercial BADGE, and their implications for human health, will require examination of all its components as described here.

Removal of estrogenic activity of natural steroidal hormone estrone by ligninolytic enzymes from white rot fungi

Natural steroidal hormone estrone (E1) was treated with the white rot fungus Phanerochaete sordida YK-624 under ligninolytic condition with low-nitrogen and high-carbon culture medium. E1 decreased by 98% after 5 d of treatment and the activities of ligninolytic enzymes, manganese peroxidase (MnP) and laccase, were detected during treatment, which suggested that the disappearance of E1 is related to ligninolytic enzymes produced extracellularly by white rot fungus. Therefore, E1 was treated with MnP and laccase prepared from the culture of white rot fungi. HPLC analysis demonstrated that E1 disappeared completely in the reaction mixture after 1 h of treatment with either MnP or laccase. Using the yeast two-hybrid assay system, it was also confirmed that both enzymatic treatments completely removed the estrogenic activity of E1 after 2 h. These results strongly suggest that ligninolytic enzymes are effective in removing the estrogenic activity of E1.

Formation of estrogenic products from environmental phthalate esters under light exposure

Phthalate esters (PEs) have been suspected to be environmental endocrine disruptors and the detailed mechanism remains unclear. The activities of these chemicals can be enhanced through chemical modification under the environmental conditions. We demonstrate that PEs acquire unequivocal estrogenic activity by light exposure. Through UV exposure of an aqueous PE solution, one active photoproduct, identified as 4-hydroxyPE (PE-4OH) based on its characteristic UV and mass spectra, was detected in an estrogen receptor alpha-dependent transactivation assay. PE-4OH was effectively generated by UV 290 nm. The PE-4OH production accompanied H2O2 generation in a UV dose-dependent manner. Both PE and UV irradiation were indispensable in the generation of H2O2. Addition of H2O2 to the PE solution increased PE-4OH production under UV irradiation. The PE-4OH production was also observed in the PE reaction with the Fenton reagent generating hydroxyl radical without UV irradiation. The proposed mechanism for PE-4OH production based on these results is such that by PE-mediated photosensitization H2O2 is generated from O2 and H+ and decomposed to hydroxyl radical, thus oxidizing the PE benzene ring. The PEs-4OH are remarkably active estrogenic products of PEs and would be involved in ER-mediated endocrine disruption.

Estrogenic activities of chemicals related to food contact plastics and rubbers tested by the yeast two-hybrid assay

Food contact plastics and rubbers possibly contain many kinds of chemicals such as monomers, oligomers, additives, degradation products of polymers and additives, and impurities. Among them, bisphenol A, nonylphenol, benzylbutyl phthalate, styrene oligomers and hydroxylated benzophenones have been reported to possess estrogenic activities. In this study, other chemicals related to food contact plastics and rubbers, and their metabolites induced by the S9-mixture were tested for their estrogenic activities using the yeast two-hybrid assay. Among the 150 chemicals, 10 chemicals such as bis(4-hydroxyphenyl) methane, 4-cyclohexylphenol, 4-phenylphenol, 4,4'-isopropylidenediphenol alkylphosphite, two type of styrenated phenol (including mono type), tris(nonylphenyl) phosphite, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone and 2,4-diphenyl-4-methyl-1-pentene, their metabolites and the metabolites of 6 other chemicals, such as 2-(phenylmethyl) phenol, styrenated phenol (di and tri type), 1-(N-phenylamino)naphthalene, 4-tert-butylphenylsalicylate, nonylphenol ethoxylates and 2-methyl-6-tert-butylphenol, displayed estrogenic activities. All of them contained a phenol group in their chemical structures or formed one easily by hydrolysis or metabolism. However, most of the chemicals related to food contact plastics and rubbers, and their metabolites did not show any estrogenicity.

Formation of estrogenic products from benzophenone after exposure to sunlight

Benzophenone (BP) is a suspected endocrine disrupter that is found in our environment. BP undergoes metabolic and photochemical activation. In this study, photoproducts of BP were identified using high-performance liquid chromatography and mass spectrometry and their estrogenic activity was determined using both in vitro and in vivo assays. Although BP showed no estrogenic activity, two estrogenic photoproducts were detected after irradiating an aqueous solution of BP with UV or sunlight. These active products were identified as 3-hydroxy BP (BP-3OH) and 4-hydroxyBP (BP-4OH). The formation of hydrogen peroxide H2O2) was detected with increasing levels of UV, and the addition of H2O2 to the BP solution increased BP-3OH and BP-4OH production under UV irradiation. BP hydroxylation was also observed in the reaction with the Fenton reagent generating hydroxyl radical without UV irradiation. These results suggest the involvement of photochemically generated H2O2 and hydroxyl radical in the BP hydroxylation. BP-4OH was more potent than BP-3OH for promoting estrogen receptor (ER)-mediated transcription and uterotrophic activity, although both of them showed same affinity in ER binding. In conclusion, BP can be converted into ring-hydroxylated derivatives that have estrogenic activity after exposure to light.

A simple and extremely sensitive system for detecting estrogenic activity using transgenic Arabidopsis thaliana

Numerous physiological processes are regulated by endocrine systems in animals. Endocrine-disrupting chemicals (EDCs) can affect physiological processes of organisms by binding to hormone receptors. Therefore, it is necessary to develop methods for detecting EDCs and removing them from the environment. We have developed a simple and low-cost reporter gene assay system for the comprehensive analysis of estrogenic activity using transgenic Arabidopsis thaliana. This transgenic plant constantly expresses two effector proteins: a chimeric estrogen receptor and a chimeric nuclear receptor coactivator. Estrogen-dependent interaction between the two effector proteins triggers transcriptional activation of reporter gene, beta-glucuronidase. We have demonstrated this transgenic plant's capability of detecting the existence of 17beta-estradiol at a concentration of 50 pM (13 pg/ml) in agar medium. This plant can also detect other estrogenic substances, such as diethylstilbestrol, p-n-nonylphenol, bisphenol A, and Genistein.

Application of ecotoxicogenomics for studying endocrine disruption in vertebrates and invertebrates

Chemicals released into the environment potentially disrupt the endocrine system in wild animals and humans. Developing organisms are particularly sensitive to estrogenic chemicals. Exposure to estrogens or estrogenic chemicals during critical periods of development induces persistent changes in both reproductive and nonreproductive organs, including persistent molecular alterations. Estrogen-responsive genes and critical developmental windows of various animal species, therefore, need to be identified for investigators to understand the molecular basis of estrogenic activity during embryonic development. For investigators to understand molecular mechanisms of toxicity in various species, toxicogenomics/ecotoxicogenomics, defined as the integration of genomics (transcriptomics, proteomics, metabolomics) into toxicology and ecotoxicology, need to be established as powerful tools for research. As the initial step toward using genomics to examine endocrine-disrupting chemicals, estrogen receptors and other steroid hormone receptors have been cloned in various species, including reptiles, amphibians, and fish, and alterations in the expression of these genes in response to chemicals were investigated. We are identifying estrogen-responsive genes in mouse reproductive tracts using cDNA microarrays and trying to establish microarray systems in the American alligator, roach, medaka, and water fleas (Daphnia magna). It is too early to define common estrogen-responsive genes in various animal species; however, toxicogenomics and ectotoxicogenomics provide powerful tools to help us understand the molecular mechanism of chemical toxicities in various animal species.

Effects of neonatal exposure to 4-tert-octylphenol, diethylstilbestrol, and flutamide on steroidogenesis in infantile rat testis

Exposure of neonatal testis, populated by fetal-type Leydig cells, to endocrine-active compounds may have far-reaching consequences. Our aim was to resolve the sensitivity of testosterone synthesis of infant rat (Sprague-Dawley) testis to diethylstilbestrol (DES; 0.1-1.0 mg/kg), 4-tert-octylphenol (OP; 10-100 mg/kg), and Flutamide (FLU; 2.0-25 mg/kg) given by daily sc injections from birth to postnatal day 4. Testes and serum were collected on day 14 when body and testis weight, testicular histology, circulating testosterone, LH and FSH levels, and steroidogenic acute regulatory protein (StAR) and 3beta-hydroxy-steroid-dehydrogenase (3beta-HSD) protein levels were determined. DES at each dose and FLU at 25 mg/kg dose reduced testis weight and the diameter of seminiferous cords. FLU caused some Leydig cell hyperplasia. Plasma testosterone was reduced in all DES animals, LH elevated in DES 0.5 mg/kg and FLU 25 mg/kg animals, and FSH reduced in the DES 1.0 mg/kg group. Basal testicular ex vivo progesterone and human chorionic gonadotropin (hCG)-stimulated testosterone production were decreased in DES animals. Despite a decrease in hCG-induced cyclic adenosine-3',5'-monophosphate (cAMP) production, intratesticular testosterone was increased in the FLU 10 and 25 mg/kg groups. OP 100 mg/kg elevated hCG-induced progesterone production only. No changes were seen in 3beta-HSD protein levels in any treatment group. StAR levels were reduced in DES animals. The results indicate the sensitivity of postnatal fetal-type Leydig cells to endocrine-active compounds. Suppression of StAR expression level was an early sign of the DES-induced steroidogenic lesion. FLU-induced changes suggest the importance of androgen receptor-mediated regulation of testosterone synthesis in the postnatal rat testis. Octylphenol appeared less effective in bringing about acute steroidogenic changes.

Association of increased type I collagen expression and relative stromal overgrowth in mouse epididymis neonatally exposed to diethylstilbestrol

The aim of this study was to investigate the molecular changes that underlie morphological changes in the epididymis following neonatal exposure to potent synthetic estrogen, namely diethylstilbestrol (DES). Newborn male mice were subcutaneously injected with DES or endogenous estrogen, namely 17 beta-estradiol (E2) (5 microg/mouse/day), for the first 5 days. At the age of 2, 4, and 8 weeks, epididymides of the mice were dissected. Characteristic morphological abnormality, such as relative stromal overgrowth, was observed at the age of 2 weeks in the epididymis of DES-treated mice, but not in E2-treated mice. Microarray and real-time RT-PCR analyses revealed that the expression levels of procollagen type I alpha 1 (col1a1) and col1a2 genes were markedly upregulated at the age of 2 weeks in the epididymis of DES-treated mice in comparison with the control. Western blot analysis revealed that type I collagen protein expression level in epididymis of DES-treated mice was elevated at the age of 2 weeks. In situ hybridization analysis revealed that the signals of col1a1 mRNA were detected similarly throughout the stromal tissue of epididymis at the age of 2 weeks in control and DES- and E2-treated mice. The gene expression level of epididymal type III collagen (col3a1), which is found in many stromal connective tissues as well as type I collagen, did not change at the age of 2 weeks in all groups. These results suggest that the increased type I collagen expression is associated with the relative stromal overgrowth in the epididymis of DES-treated mice.

Isoflavonoids with antiestrogenic activity from Millettia pachycarpa

Three new isoflavonoids, named millewanins G (1) and H (2) and furowanin B (3), were isolated from the leaves of Millettia pachycarpa. Their structures were elucidated on the basis of spectroscopic analyses. The antiestrogenic activity in the yeast two-hybrid assay of these isoflavonoids was examined and shown to be comparable with that of 4-hydroxytamoxifen.

Molecular responses to xenoestrogens: mechanistic insights from toxicogenomics

The xenoestrogen group of endocrine disruptors has the potential to cause reproductive and developmental effects through stimulation or disruption of sex steroid nuclear receptor signalling pathways. A more detailed understanding of the ways in which xenoestrogens interact with biological systems at the molecular level will provide a mechanistic basis for improved safety assessment. The recent sequencing of mammalian genomes has driven the development of toxicogenomic technologies, including microarray based gene expression profiling, which allow the expression levels of thousands of genes to be measured simultaneously. Since the cellular responses to xenoestrogens are predominantly mediated by estrogen receptors, which function as ligand-activated transcription factors to regulate gene expression, the application of toxicogenomics has great potential for providing insights into the molecular mechanisms of xenoestrogen action. A major challenge in applying toxicogenomics to the field of endocrine disruption is the need to define how xenoestrogen-induced changes in gene expression relate to conventional physiological and toxicological endpoints. Gene Ontology Mapping, Pathway Mapping and Phenotypic Anchoring of xenoestrogen-induced gene expression changes to cellular pathways and processes represent key steps in defining these relationships. Mechanistic insights into how xenoestrogens target specific genes and into the functional significance of xenoestrogen-induced alterations in gene expression can be further enhanced by combining transcript profiling with transgenic animal models or cell-based systems in which the estrogen receptor signalling pathways have been modified experimentally. This review illustrates how these toxicogenomic approaches are providing an unprecedented amount of mechanistic information on the molecular responses to xenoestrogens and how they are likely to impact on hazard and risk assessment.

Bioluminescent yeast assays for detecting estrogenic and androgenic activity in different matrices

In this paper we describe the construction and use of a set of bioluminescent yeast strains for the detection of compounds that can affect androgen or estrogen receptor mediated hormonal signalling. The set includes Saccharomyces cerevisiae strains expressing human androgen receptor (AR), estrogen receptor alpha (ERalpha) or estrogen receptor beta (ERbeta), along with firefly luciferase controlled by a respective hormone responsive promoter. A constitutively luminescent strain was included in the set for determining the cytotoxicity of the sample. Yeast cells were incubated with pure chemicals or complex samples for 2.5 h, after which the signal could be detected from the cell-sample mixture after simply adding the D-luciferin substrate. The assays could be completed in one day and they required no cell lysis or centrifugation steps, which makes them suitable for high-throughput analysis of samples. Due to a short incubation time the assays are directly applicable to different sample matrices, requiring no pretreatment of the samples. The assays were used to assess the hormonal activity in moisturizing lotions as an example of a complex sample matrix known to contain endocrine disrupting chemicals. Six out of eight tested moisturisers showed high estrogenic activity, whereas no androgenic activity was observed in the samples.

Estrogenic activity of 37 components of commercial sunscreen lotions evaluated by in vitro assays

Thirty-seven chemical components of commercial sunscreen lotions were evaluated for estrogen agonistic and/or antagonistic activity using two in vitro assays, (1) an ELISA-based estrogen receptor competitive binding assay (ER-ELISA) and (2) a modified yeast two-hybrid estrogen assay, with and without addition of a rat liver preparation, S9 mix. Eleven compounds, most of which were benzophenone derivatives and parabens, showed binding affinity to ER by ER-ELISA without S9 mix. Although the activities of almost all of the compounds were attenuated by addition of S9 mix, 4-octylphenylsalicylate and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone acquired estrogenic activity, suggesting metabolic activation of these compounds. Two benzophenones showed agonistic activity in the yeast two-hybrid assay without S9 mix. The activity of one of these was reduced by S9 treatment and a further two benzophenones was activated. Eight parabens were active in this assay without S9 exposure, but their activities were eliminated by S9 treatment. Benzophenones with para-phenolic hydroxyl groups and parabens with branched and/or longer linear chains were generally more potent in both bioassays. In addition, weak antagonistic activity of 4-t-butylphenyl-salicylate, 2-ethylhexyl 4-dimethylaminobenzoate and (+/-)-alpha-tocopherolacetate was observed with S9 treatment. In vivo testing of the compounds reported here to have estrogen agonistic and antagonistic activities is required to confirm their effects at an organismal level.

Evaluation of estrogenic activities of hydroxylated polycyclic aromatic hydrocarbons in cigarette smoke condensate

Estrogenic activities of cigarette smoke condensates obtained from the extraction of particulate matters from mainstream and sidestream cigarette smoke with benzene/ethanol were evaluated by using a yeast two-hybrid assay system expressing human estrogen receptor alpha (hERalpha). To identify the constituents of the cigarette smoke condensate which are responsible for the estrogenic activity, the condensate was fractionated into eleven fractions by liquid-liquid extractions. Among these fractions, the neutral fractions of mainstream and sidestream smoke showed the strongest estrogen receptor-mediated activity by the yeast two-hybrid assay. Then the neutral fractions were fractionated by medium-pressure liquid chromatography with silica gel column. In the fractions that showed strong estrogenic activity, 2-hydroxyfluorene (2-OHFle), 2- and 3-hydroxyphenanthrene (2- and 3-OHPhe), 1-hydroxypyrene (1-OHPyr) and n-propyl-p-hydroxybenzoate (n-PHB) were identified by LC- and GC-MS and HPLC with fluorescence detection. 2-OHFle, 2-OHPhe and n-PHB exhibited estrogenic activity, whereas weak activity was observed with 3-OHPhe and 1-OHPyr. Several other hydroxylated polycyclic aromatic hydrocarbons having no activity were also identified. This is a first study to identify estrogenic hydroxylated PAHs in cigarette smoke condensate. The present findings points out the necessity for detailed investigation of exposure to aerosols containing apparently estrogenic compounds.

In vitro effects of diethylstilbestrol, genistein, 4-tert-butylphenol, and 4-tert-octylphenol on steroidogenic activity of isolated immature rat ovarian follicles

Isolated rat ovarian follicles grow and produce steroid hormones in vitro and so provide a good model for studying the effects of hormonally active compounds on follicular steroidogenesis. We have evaluated the effects of diethylstilbestrol (DES), genistein (GEN) and two alkylphenols, 4-tert-butylphenol (BP) and 4-tert-octylphenol (OP) on the growth, survival, and steroid hormone and cAMP production by isolated 14-day-old rat (Sprague-Dawley) ovarian follicles. During a 5-day culture, FSH was obligatory for follicle growth and increased estradiol and testosterone secretion in a dose-dependent manner. DES (10(-6) M) caused the strongest decline in estradiol and testosterone levels but did not have detectable effects on either cAMP production or aromatase enzyme activity. GEN caused a prominent decrease in cAMP and testosterone levels without significant changes in secreted estradiol. The latter, apparently, was due to a dose-dependent stimulation of aromatase enzyme activity in the presence of genistein. Both BP and OP decreased estradiol and testosterone secretion in a dose-dependent manner while no effect on aromatase activity was observed. OP, unlike BP, decreased forskolin-induced cAMP levels. Xenoestrogens at the used concentrations did not interfere with the growth and survival of the follicles. The results indicate that isolated ovarian follicles representing intact morphological and functional units offer a sensitive model system for elucidating the female-specific reproductive effects of environmental chemicals.

Estrogenic activity of impurities in industrial grade bisphenol A

The estrogenicities of 10 compounds found as impurities in industrial grade bisphenol A (BPA) were measured by yeasttwo-hybrid assays incorporating the human estrogen receptor alpha(hERalpha) orthe medaka fish (Oryziaslatipes) estrogen receptor alpha (medERalpha). Five impurities showed greater activity than BPA itself in an agonist assay for hERalpha. p-Cumylphenol, the most active of the impurities in the hERalpha assay, was 12 times as active as BPA. The REC10 (10% relative effective concentration: 10% of the activity of 10(-8)M 17,B-estradiol) was 710 nM. Five impurities showed greater activity than BPA in an agonist assay for medERa: 4,4'-(1,3-dimethylbutylidene) bisphenol and 2-(4'-hydroxy-phenyl)-2,4,4-trimethylchroman were nearly equipotent and 9 times as active as BPA, and the REC10 values of these compounds in the medERalpha assay were 280 and 320 nM, respectively. Comparison of the experimentally determined estrogenicities of mixtures of BPA and 4,4'-(1,3-dimeth-ylbutylidene) bisphenol and those calculated by the concentrations addition (CA) method confirmed the suitability of the method for the prediction of the estrogenicities of the mixtures of BPA and its phenolic analogues. The measured estrogenicities of four samples of industrial grade BPA and laboratory grade (pure) BPA were not significantly different in either the hERalpha assay or the medERalpha assay (p > 0.05 in each case). We conclude that the impurities in industrial grade BPA, although some are of much higher estrogenic activity than BPA itself, do not significantly increase the estrogenicity of the industrial compound and therefore do not increase possible adverse health effects from such activity.

Phytoestrogens derived from red clover: an alternative to estrogen replacement therapy?

The benefits of plant extracts from soy and red clover as alternatives to conventional hormone replacement therapy (HRT) have been debated in the past. Here, an attempt has been made to summarize the biochemical and pharmacological data in the light of clinical aspects. Red clover and soy extracts contain isoflavones, which have a high affinity to estrogen receptor alpha (ERalpha), estrogen receptor beta (ERbeta), progesterone receptor (PR) and androgen receptor (AR). The higher affinity to ERbeta compared to ERalpha has been used as an explanation why red clover extracts function as food additives to treat menopausal disorders and may reduce risk of breast cancer. Biochemical analysis shows that these representatives of phytoestrogens have multiple actions beside selective estrogen receptor modulator (SERM)-activity. They act as selective estrogen enzyme modulators (SEEMs), have antioxidant activity and interact with transcription factors such as NF-kappaB. Furthermore, it is indicated that they have protective effects on osteoporosis and the cardiovascular system. Currently 40-50mg of isoflavones (biochanin A, daidzein, formononetin and genistein) are recommended as daily dose. This recommendation is based on the daily intake of phytoestrogens in a traditional Japanese diet.

Removal of estrogenic activity of endocrine-disrupting genistein by ligninolytic enzymes from white rot fungi

Endocrine-disrupting genistein was treated with the white rot fungus Phanerochaete sordida YK-624 under ligninolytic condition with low-nitrogen and high-carbon culture medium. Genistein decreased by 93% after 4 days of treatment and the activities of ligninolytic enzymes, manganese peroxidase (MnP) and laccase, were detected during treatment, thus suggesting that the disappearance of genistein is related to ligninolytic enzymes produced extracellularly by white rot fungi. Therefore, genistein was treated with MnP, laccase, and the laccase-mediator system with 1-hydroxybenzotriazole (HBT) as a mediator. HPLC analysis demonstrated that genistein disappeared almost completely in the reaction mixture after 4 h of treatment with either MnP, laccase, or the laccase-HBT system. Using the yeast two-hybrid assay system, it was also confirmed that three enzymatic treatments completely removed the estrogenic activity of genistein after 4h. These results strongly suggest that ligninolytic enzymes are effective in removing the estrogenic activity of genistein.

Some organotin compounds enhance histone acetyltransferase activity

Eukaryotic DNA is packaged into chromatin, whose basic subunit is the nucleosome, which consists of DNA and a core histone octamer. Histone acetylation is important for the regulation of gene expression and is catalyzed by histone acetyltransferase (HAT). We observed the effects of suspected endocrine-disrupting chemicals (EDCs) on HAT activity. We showed that some organotin compounds--tributyltin (TBT) and triphenyltin (TPT)--enhanced HAT activity of core histones in a dose-dependent way and other EDCs did not affect HAT activity. Organotin compounds have various influences on physical function including the hormone and immune systems, embryogenesis, and development. Dibutyltin and diphenyltin, metabolites of TBT and TPT, respectively, also promoted HAT activity, but monobutyltin, monophenyltin, and inorganic tin had no effect. Further, TBT and TPT enhanced HAT activity when nucleosomal histones were used as substrates. These data indicate that the organotin compounds have unique effects on HATs independent of their EDC activities and suggest that the varied toxicities of the organotin compounds may be caused by aberrant gene expression following altered histone acetylation.

Electrochemical detection of xenoestrogenic and antiestrogenic compounds using a yeast two-hybrid-17-β-estradiol system

The goal of this study was to determine the effects of various compounds on the 17-beta-estradiol-induced dimerization of the human estrogen receptor alpha (hERalpha), a nuclear transcription factor. For this purpose, we used a modified yeast two-hybrid (YTH) bioassay designed to study protein-protein interactions, based on the electrochemical monitoring of hERalpha dimerization and detected as beta-D-galactosidase reporter gene activity in a synthetic substrate p-aminophenyl-beta-D-galactopyranoside (pAPG). Compared with 17-beta-estradiol activity, genistein, bisphenol-A (BPA), and naringenin induced dimerization to a lower extent by four, five and six magnitudes of orders of magnitude, respectively. In the presence of physiological concentrations of 17-beta-estradiol, both tamoxifen and the analgesic drug acetaminophen inhibited hER dimerization in an antiestrogenic manner.