The estrogenicity of bisphenol A-related diphenylalkanes with various substituents at the central carbon and the hydroxy groups

Biotransformation of bisphenol F by human and rat liver subcellular fractions

Bisphenol F [4,4'-dihydroxydiphenyl-methane] (BPF) has a broad range of applications in industry (liners lacquers, adhesives, plastics, coating of drinks and food cans). Free monomers of this bisphenol can be released into the environment and enter the food chain, very likely resulting in the exposure of humans to low doses of BPF. This synthetic compound has been reported to be estrogenic. A study of BPF distribution and metabolism in rats has demonstrated the formation of many metabolites, with multiple biotransformation pathways. In the present work we investigated the in vitro biotransformation of radio-labelled BPF using rat and human liver subcellular fractions. BPF metabolites were separated, isolated by high-performance liquid chromatography (HPLC), and analysed by mass spectrometry (MS), MS(n), and nuclear magnetic resonance (NMR). Many of these metabolites were characterized for the first time in mammals and in humans. BPF is metabolised into the corresponding glucuronide and sulfate (liver S9 fractions). In addition to these phase II biotransformation products, various hydroxylated metabolites are formed, as well as structurally related apolar metabolites. These phase I metabolic pathways are dominant for incubations carried out with liver microsomes and also present for incubations carried out with liver S9 fractions. The formation of the main metabolites, namely meta-hydroxylated BPF and ortho-hydroxylated BPF (catechol BPF) is P450 dependent, as is the formation of the less polar metabolites characterized as BPF dimers. Both the formation of a catechol and of dimeric metabolites correspond to biotransformation pathways shared by BPF, other bisphenols and estradiol.

Identification of estrogenic and antiestrogenic activities of respirable diesel exhaust particles by bioassay-directed fractionation

Bioassay-directed fractionation was performed to identify causative chemical groups of DEPs with estrogenic and antiestrogenic activities. Bioassay-directed fractionation consists of a cell bioassay (E-SCREEN) in conjunction with acid-base partitioning (F1 and F2) and silica gel column fractionation of neutral fractions (F3-F7). Crude extract (CE) of DEPs in dichloromethane (DCM) exhibited both estrogenic and antiestrogenic activity. Estrogenic activity of CE and some fractions (F1, F2, F3, F5 and F6) was induced through estrogen receptor (ER)-mediated pathways. In particular, the acid polar fraction (F2) of DEPs, which contains phenols, induced high levels of estrogenic activity compared to other fractions. The estrogenic activity of F2 (610.80 pg-bio-EEQ/g-DEPs) was higher than that of the total estrogenic activity of CE (222.22 pg-bio-EEQ/g-DEPs). This result indicates that the estrogenic activity induced by causative estrogenic fraction (F2) may be antagonized by unidentified chemicals in DEPs. On the other hand, non-polar fractions (F3 and F4) of DEPs include aliphatic and chlorinated hydrocarbon, polyaromatic hydrocarbons, and their alkyl derivatives, which play an important role in the antiestrogenic activity of DEPs. In particular, F4, which contains PAH and its derivatives, showed the highest antiestrogenic activity. Since in our previous study, dibenzo(a, h)anthracene and chrysene were identified in F4, and these chemicals have antiestrogenic activity, we assume that these chemicals are the major causative chemicals with antiestrogenic activity in DEPs. In contrast to the estrogenic activity of DEPs, antiestrogenic activity of CE was stronger than that of antiestrogenic fractions (F3 and F4) at non-cytotoxic concentrations, indicating that additive or synergistic effects by unidentified chemicals contained in DEPs occurred.

Derivation of a bisphenol A oral reference dose (RfD) and drinking-water equivalent concentration

Human exposure to bisphenol A (BPA) is due to that found in the diet, and BPA and its metabolites were detected at parts per billion (or less) concentrations in human urine, milk, saliva, serum, plasma, ovarian follicular fluid, and amniotic fluid. Adverse health effects in mice and rats may be induced after parenteral injection or after massive oral doses. Controlled ingestion trials in healthy adult volunteers with 5 mg d16-BPA were unable to detect parent BPA in plasma despite exquisitely sensitive (limit of detection = 6 nM) methods, but by 96 h 100% of the administered dose was recovered in urine as the glucuronide. The extensive BPA glucuronidation following ingestion is not seen after parenteral injection; only the parent BPA binds plasma proteins and estrogen receptors (ER). The hypothesis that BPA dose-response may be described by a J- or U-shape curve was not supported by toxicogenomic data collected in fetal rat testes and epididymes (after repeated parenteral exposure at 2-400,000 microg/kg-d), where a clear monotonic dose-response both in the numbers of genes and magnitude of individual gene expression was evident. There is no clear indication from available data that the BPA doses normally consumed by humans pose an increased risk for immunologic or neurologic disease. There is no evidence that BPA poses a genotoxic or carcinogenic risk and clinical evaluations of 205 men and women with high-performance liquid chromatography (HPLC)-verified serum or urinary BPA conjugates showed (1) no objective signs, (2) no changes in reproductive hormones or clinical chemistry parameters, and (3) no alterations in the number of children or sons:daughters ratio. Results of benchmark dose (BMD10 and BMDL10) calculations and no-observed-adverse-effect level (NOAEL) inspections of all available and reproducible rodent studies with oral BPA found BMD and NOAEL values all greater than the 5 mg/kg-d NOAELs from mouse and rat multigeneration reproduction toxicity studies. While allometric and physiologically based pharmacokinetic (PBPK) models were constructed for interspecies scaling of BPA and its interaction with ER, multigeneration feeding studies with BPA at doses spanning 5 orders of magnitude failed to identify signs of developmental toxicity or adverse changes in reproductive tract tissues; the 5-mg/kg-d NOAELs identified for systemic toxicity in rats and mice were less than the oral NOAELs for reproductive toxicity. Thus, it is the generalized systemic toxicity of ingested BPA rather than reproductive, immunologic, neurobehavioral, or genotoxic hazard that represents the point of departure. Using U.S. Environmental Protection Agency (EPA) uncertainty factor guidance and application of a threefold database uncertainty factor (to account for the fact that the carcinogenic potential of transplacental BPA exposure has yet to be fully defined and comprehensive neurobehavioral and immunotoxicologic evaluations of BPA by relevant routes and at relevant doses have yet to be completed) to the administered dose NOAEL results in an oral RfD of 0.016 mg/kg-d. Assuming the 70-kg adult consumes 2 L of water each day and adopting the default 20% U.S. EPA drinking water relative source contribution yields a 100 microg/L BPA total allowable concentration (TAC).

Synthetic endocrine disruptors in the environment and water remediation by advanced oxidation processes

The present study is an overview of the literature on classes and types of compounds described as "endocrine disruptors" and their treatability in water by advanced oxidation processes, which generate hydroxyl radicals in water. The review is limited to details of the destruction of three classes of endocrine disruptors, namely bisphenols, alkylphenols and phthalates, which are among the most highly suspected endocrine disrupting compounds that interfere with the hormonal system of wildlife. It was found that photocatalysis with titanium dioxide was the most frequently tested advanced oxidation method most likely due its potential to render complete mineralization. There is sufficient research also with direct and indirect photolysis and ozonation, which were less effective for the overall mineralization but more representative of the conditions existing in real water treatment plants.

Bisphenol-A and chlorinated derivatives in adipose tissue of women

Bisphenol-A (BPA) and chlorinated derivatives (Cl(x)BPA) were investigated in adipose tissue of women in Southeast Spain. BPA was above limit of detection (LOD) in 11 out of 20 samples (55%). Among Cl(x)BPA, Cl(2)BPA was the most frequent (80%) and abundant, constituting 94.6% of total chlorinated BPA in adipose tissue. Mean +/- S.D. of BPA, monochloro-BPA (ClBPA), dichloro-BPA (Cl(2)BPA), and trichloro-BPA (Cl(3)BPA) were 5.83 +/- 3.48, 3.05 +/- 0.28, 9.21 +/- 9.26, and 0.74 +/- 0.15 ng/g of adipose tissue, respectively. No tetrachloro-BPA (Cl(4)BPA) was found above LOD. There are no published data on BPA in human adipose tissue or on Cl(x)BPA in adipose tissue or blood, limiting comparisons. BPA levels were similar (w/w) to findings in blood (w/v) in other populations and below levels reported in placenta tissue (w/w). Because of the estrogen mimicking effects of BPA and its Cl(x)BPA, further research is needed to explore their combined effects on human health and trends in human exposure.

Antiestrogenic potentials of ortho-PCB congeners by single or complex exposure

Di-ortho PCB congeners 52, 138, 153 and 180, and the mono-ortho coplanar congener 118 have been detected as a complex mixture in human tissue in Korea. This study examined the antiestrogenic effects of samples exposed to single or combination treatment of the ortho-PCB congeners. In order to determined the combined toxicity, a sample mixture (M1, M2, M3, M4, and M5) was designed based on the ortho-PCB congeners found in Korean human tissue. With the exception of PCB 52, the ortho-PCB congeners (PCB 118, 138, 153, and 180) showed weak antiestrogenic activity. The antiestrogenic activity of di-ortho PCB congeners (PCB 138, 153, and 180) was induced by the depletion of endogenous E2 as well as through the ER-dependent pathway, whereas the antiestrogenic activity of mono-ortho PCB 118 was only induced through the depletion of endogenous E2. When the MCF7-BUS cells were treated with mixtures containing the no effective concentration (10(-6) M) of the PCB congeners, M3 (PCB 118 + PCB 138 + PCB 180) and M4 (PCB 118 + PCB 138) had an antiestrogenic effect but the other mixtures (M1; PCB 52 + PCB 118 + PCB 138 + PCB 180, M2; PCB 118 + PCB 138 + PCB 153 + PCB 180, M5; PCB 118 + PCB 180) did not. Although the mechanism for the interaction between the PCB congeners is not completely understood, it was presumed that exposure to a mixture of the PCB congeners might have synergistic effects on their antiestrogenicity through the ER-independent pathway.

Developmental Toxicity by Exposure to Bisphenol A Diglycidyl Ether during Gestation and Lactation Period in Sprague-dawley Male Rats

OBJECTIVES

Bisphenol A diglycidyl ether (BADGE) is the major component in commercial liquid epoxy resins, which are manufactured by co-reacting bisphenol A with epichlorohydrin. This study was performed to show the developmental effects of prenatal and postnatal exposures to BADGE in male rat offspring.

METHODS

Mated female rats were divided into four groups, each containing 12 rats. The dosing solutions were prepared by thoroughly mixing BADGE in corn oil at the 0, 375, 1500 and 3000 mg/kg/day concentrations. Mated females were dosed once daily by oral gavage on gestation day (GD) 6 - 20 and postnatal day (PND) 0 - 21. Pregnant female dams were observed general symptoms and body weight. Also, male pups were observed the general symptoms, body weight, developmental parameters (e.g. anogenital distance, pina detachment, incisor eruption, nipple retention, eye opening, testis descent), organ pathologic changes and hormone levels of plasma.

RESULTS

Pregnant rats treated with BADGE died at a rate of about 70% in the 1500 mg/kg/day group and all rats treated with 3000 mg/kg/day died. Body weight, for male pups treated with doses of 375 mg/kg/day, was significantly lower than in the control group at PND 42, 56, and 63 (p<0.05). Evaluation of body characteristics including; separation of auricle, eruption of incisor, separation of eyelid, nipple retention, descent of testis, and separation of the prepuce in the BADGE treated group showed no difference in comparisons with the control group. AGD and adjusted AGD (mm/kg) for general developmental items in BADGE 375 mg/kg/day treated pups tended to be longer than in controls, however, these differences were not statistically significant. Relative weights of adrenal gland, lung (p<0.05), brain, epididymis, prostate, and testis (p<0.01) were heavier than in control in measures at PND 9 weeks. There were no significant changes in comparisons of histological findings of these organs. Loss of spermatids was observed in the seminiferous tubule at PND 9 weeks, but no weight changes were observed. The plasma estrogen levels were similar in the control and treatment groups at PND 3, 6 and 9 weeks. The plasma testosterone levels in the control group tended to increase with age. However, in the BADGE 375 mg/kg/day treated male pups it did not tend to increase.

CONCLUSIONS

These findings suggest that BADGE is a chemical that has developmental effects consistent with it being an endocrine disruptor.

Oestrogenicity of paper and cardboard extracts used as food containers

Bisphenol-A (BPA), dibutyl phthalate (DBP), and di-2-ethylhexyl phthalate (DEHP), which are common chemical residues in food-packaging materials, were investigated in paper and cardboard containers used for take-away food. The oestrogenicity of aqueous extracts was tested in E-Screen bioassay and analysis carried out by high-performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC/MS). Oestrogenicity was demonstrated in 90% of extracts (geometric mean [GM] = 11.97 pM oestradiol equivalents g(-1)). DEHP, DBP, and BPA (GM = 341.74, 37.59, and 2.38 ng g(-1) of material) were present in 77.50, 67.50, and 47.50% of samples, respectively. In bivariate analyses, no significant association was found between the levels of these chemicals and oestrogenicity in cardboard/paper extracts. A close-to-significant association was found between oestrogenicity and DBP (beta = 1.25; p = 0.06) in paper extracts, which reached statistical significance in multivariate analysis (beta = 1.61; p = 0.03). Paper and cardboard used in food packaging may contribute to the inadvertent exposure of consumers to endocrine-disrupting chemicals.

Disposition and metabolic profiling of bisphenol F in pregnant and nonpregnant rats

The distribution of bisphenol F (4,4'-dihydroxydiphenyl-methane, BPF) was studied in female Sprague-Dawley rats. Pregnant and nonpregnant animals were gavaged with a single dose of 7 or 100 mg/kg [3H]BPF and were kept for 96 h in metabolic cages. The excretion of BPF residues occurred mainly in urine (43-54% of the administered dose), which was found to contain at least six different metabolites, and to a lesser extent in feces (15-20% of the administered dose). Sulfatase treatment and subsequent high-performance liquid chromatography analyses suggest that the major urinary metabolite (more than 50% of the radioactivity present in urine) is a sulfate conjugate of BPF. At 96 h, BPF residues were detectable in all tissues examined with the largest amounts in the liver (0.5% of the dose). In pregnant rats dosed at day 17 of gestation, BPF residues were detected in the uterus, placenta, amniotic fluid, and fetuses (0.9-1.3% of the administered dose). Large amounts of radioactivity (8-10% of the dose) were still located in the digestive tract lumen at the end of the study. After administration of a single oral dose of [3H]BPF, 46% of the distributed radioactivity was excreted in bile over a 6 h period. In rats, BPF and/or its metabolites very likely undergo enterohepatic cycling, which could be responsible for the relatively high amounts of residues still excreted 4 days after BPF administration. This bisphenol is efficiently absorbed and distributed to the reproductive tract in female rats, and its residues pass the placental barrier at a late stage of gestation in rats.

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.

Antiestrogenic activities of Ginkgo biloba extracts

Most climacteric and postmenopausal women appear to have vasomotor symptoms as well as a high risk of osteoporosis and cardiovascular disease. Although exogenous estrogens can reduce these symptoms, women are reluctant to use hormone replacement therapy (HRT) due to its undesirable side effects, such as irregular bleeding and an increased risk of breast cancer. A previous study suggested that Ginkgo biloba extracts (GBE) have estrogenic activity and might be suitable as an alternative to HRT. However, there are no reports of the preventive effect of GBE on breast cancer, which is the side effect of classical HRT. In this study, it was confirmed that GBE exhibits estrogenic and antiestrogenic activity depending on the E2 and GBE concentration, via estrogen receptor (ER)-dependent and ER-independent pathways. In addition, GBE reduced the E2 levels by stimulating the E2 metabolism and inhibiting E2 synthesis, which indicates that GBE can induce antiestrogenic activity via the depletion of E2. Furthermore, GBE might have similar action to selective arylhydrocarbon receptor modulators (SAhRMs), which induce antiestrogenic activity through cross-talk between the arylhydrocarbon receptor (AhR) and ER. In conclusion, GBE has a biphasic effect on estrogen, and can be considered as a potential alternative to HRT with chemopreventive effects on breast cancer. However, further studies on animals and humans will be required.

Impact of reaction conditions on the laccase-catalyzed conversion of bisphenol A

The oxidative conversion of aqueous BPA catalyzed by laccase from Trametes versicolor was conducted in a closed, temperature-controlled system containing buffer for pH control. The effects of medium pH, buffer concentration, temperature and mediators and the impacts of dissolved wastewater constituents on BPA conversion were investigated. The optimal pH for BPA conversion was approximately 5, with greater than half maximal conversion and good enzyme stability in the range of 4-7. The stability of the enzyme was not impacted by buffer concentration, nor was BPA conversion. Despite the observation that the enzyme tended to be inactivated at elevated temperatures, enhanced conversion of BPA was observed up until a reaction temperature of 45 degrees C. Of the mediators studied, ABTS was most successful at enhancing the conversion of BPA. Dissolved wastewater constituents that were studied included various inorganic salts, organic compounds and heavy metal ions. BPA conversion was inhibited in the presence of anions such as sulfite, thiosulfate, sulfide, nitrite and cyanide. The metal ions Fe(III) and Cu(II) and the halogens chloride and fluoride substantially suppressed BPA conversion, but the presence of selected organic compounds did not significantly reduce the conversion of BPA.

Biphasic effects of kaempferol on the estrogenicity in human breast cancer cells

Dietary flavonoids have attracted a great deal of attention as agents for preventing estrogen-related diseases, such as postmenopausal symptoms, and for reducing the risk of estrogen-dependent cancer. Kaempferol is one of the most commonly found dietary phytoestrogen. The aim of this study was to investigate the estrogenic and/or antiestrogenic effect of kaempferol, which can confirm its potency as a preventive agent against estrogen-related diseases. Kaempferol has both estrogenic and antiestrogenic activity, which are biphasic response on estrogen receptor. The estrogenic activity of kaempferol induced via ER-mediated pathway depending on E2 concentration (< or = 10(-12) M). Kaempferol (10(-5) M) also caused antiproliferative effect on MCF-7 cell in the presence of E2 (10(-11) M) and restored to the addition of excess E2 (10(-7) M), which confirms that antiproliferation of kaempferol was induced via ER-dependent pathway. However, at 10(-4) M, concentration higher than the concentrations at which the estrogenic effects of kaempferol are detected (10(-5) M), kaempferol induced strong antiproliferative effect, but were unaffected by the addition of excess E2 (10(-7) M) indicating that kaempferol exerts antiproliferation via ER-independent pathway. In particular, kaempferol blocked the focus formation induced by E2, which confirms that kaempferol might inhibit the malignant transformation caused by estrogens. Therefore, we suggested that kaempferol might regulate a suitable level of estrogenic activity in the body and is expected to have potential beneficial effects in preventing estrogen imbalance diseases (breast cancer, osteoporosis, cardiovascular disease and etc.).

Estrogenic effects of marijuana smoke condensate and cannabinoid compounds

Chronic exposure to marijuana produces adverse effects on the endocrine and reproductive systems in humans; however, the experimental evidence for this presented thus far has not been without controversy. In this study, the estrogenic effect of marijuana smoke condensate (MSC) was evaluated using in vitro bioassays, viz., the cell proliferation assay, the reporter gene assay, and the ER competitive binding assay. The results of these assays were compared with those of three major cannabinoids, i.e., THC, CBD, and CBN. The estrogenic effect of MSC was further confirmed by the immature female rat uterotrophic assay. MSC stimulated the estrogenicity related to the ER-mediated pathway, while neither THC, CBD, nor CBN did. Moreover, treatment with 10 and 25 mg/kg MSC induced significant uterine response, and 10 mg/kg MSC resulted in an obvious change in the uterine epithelial cell appearance. MSC also enhanced the IGFBP-1 gene expression in a dose-dependent manner. To identify the constituents of MSC responsible for its estrogenicity, the MSC fractionated samples were examined using another cell proliferation assay, and the estrogenic active fraction was analyzed using GC-MS. In the organic acid fraction that showed the strongest estrogenic activity among the seven fractions of MSC, phenols were identified. Our results suggest that marijuana abuse is considered an endocrine-disrupting factor. Furthermore, these results suggest that the phenolic compounds contained in MSC play a role in its estrogenic effect.

Antiestrogenic effects of marijuana smoke condensate and cannabinoid compounds

The antiestrogenic effects of marijuana smoke condensate (MSC) and three major cannabinoids, ie., delta9-tetrahydrocannabinol (THC), cannabidiol (CBD), and cannabinol (CBN), were evaluated using in vitro bioassays, viz., the human breast cancer cell proliferation assay, the recombinant human estrogen receptor (ER) competitive binding assay, and the reporter gene assay. The inhibitory effects on estrogen were also examined using the ethoxyresorufin-O-deethylase (EROD) assay, the aromatase assay, and the 17beta-estradiol (E2) metabolism assay. The results showed that MSC induced the antiestrogenic effect via the ER-mediated pathway, while THC, CBD, and CBN did not have any antiestrogenic activity. This suggests that the combined effects of the marijuana smoke components are responsible for the antiestrogenicity of marijuana use. In addition, MSC induced the CYP1A activity and the E2 metabolism, but inhibited the aromatase activity, suggesting that the antiestrogenic activity of MSC is also related to the indirect ER-dependent pathway, as a result of the depletion of the in situ E2 level available to bind to the ER. In conclusion, pyrogenic products including polycyclic aromatic hydrocarbons (PAHs) in the non-polar fraction, which is the most biologically active fraction among the seven fractions of MSC, might be responsible for the antiestrogenic effect.

Combination of in vitro bioassays encompassing different mechanisms to determine the endocrine-disrupting effects of river water

In this study, the total toxic effects of river water samples were assessed using a series of cell culture bioassays which encompassed different mechanisms, based on specific modes of action. River water samples were collected from three tributaries of the Youngsan River in the western portion of Korea. We confirmed that Youngsan River water was polluted with a complex mixture of estrogenic and dioxin-like compounds. The total toxic effects of the downstream water samples were found to be higher than that of the upstream water samples. In the upstream water samples, total estrogenic activity was measured to be between 0.005 and 0.049 ng-EEQ/l (17beta-estradiol-equivalent concentration) and no CYP1A activity was detected. In the downstream water samples, however, total estrogenic activity was measured to be between 0.021 ng-EEQ/l and 1.918 ng-EEQ/l, and total CYP1A activity was between 0.63 and 3.55 microg-MEQ/l (3-methylcholanthrene-equivalent concentration). When assessed according to a concentration-response curve, downstream water sample extracts exerted dual actions on estrogen receptors, depending on the concentration volume of the samples. The concentration volume range proximal to the original water sample exhibited estrogenic activity, whereas antiestrogenic activity was observed at high concentration volumes (more than 5 times concentration) in the extracts. This study involved a combination of in vitro bioassays, designed to encompass different mechanisms. The bioassays used included the estrogen receptor binding affinity test, E-screen assay, aromatase assay, and EROD assay. These tests provided a great deal of useful information regarding the potency and action modes of estrogenicity and antiestrogenicity inherent in the sampled river water. Although further study is necessary to determine the relationship between toxic responses in in vitro bioassay systems and chronic toxicity in aquatic organisms, our approach is expected to be fairly accurate with regard to the detection of endocrine-disrupting effects in an aquatic environment.

Piezoelectric immunosensor for bisphenol A based on signal enhancing step with 2-methacrolyloxyethyl phosphorylcholine polymeric nanoparticle

An immunoassay in which BPA competed with a BPA-horseradish peroxidase conjugate for binding to anti-BPA antibodies, coupled to a piezoelectric (PZ) immunosensor, was able to detect 0.1 ng mL(-1) BPA. To enhance the sensitivity of the assay, we tested nanoparticles approximately 200 nm in diameter, coupled to anti-BPA antibodies, to increase the mass change on the surface of the immunosensor and thereby increase the frequency shift detected. This second step, using nanoparticles coated with anti-BPA antibodies, improved the sensitivity of the assay by approximately eight times at BPA concentrations below 10 ng mL(-1). Field emission-scanning electron microscopy (FE-SEM) showed that polymeric 2-methacrolyloxyethyl phosphorylcholine (MPC) nanoparticles coupled to antibodies remained monodisperse on the surface of the immunosensor and therefore produced stable signals in the immunosensors. Since the frequency shift detected in the assay mainly originated from the mass change on the surface of the PZ crystal, the colloidal stability of the antibody-conjugated particles used in the enhancement step played an extremely important role in achieving a stable and highly sensitive signal.

High-performance liquid chromatographic analysis of bisphenol A and 4-nonylphenol in serum, liver and testis tissues after oral administration to rats and its application to toxicokinetic study

A sensitive and simple method based on solid-phase extraction (SPE) and HPLC with fluorescence detection for the determination of bisphenol A (BPA) and 4-nonylphenol (4-NP) in rat serum, liver and testis tissues has been developed. The chromatographic conditions consisted of a C18 column and mobile phase composition of acetonitrile and water with flow rate of 1.0 ml/min. The fluorescence detection was performed at excitation and emission wavelengths of 227 nm and 313 nm, respectively. Under these conditions, BPA and 4-NP were well separated and showed good linearities in the ranges of 0.01-50.0 microg/ml for BPA and 0.15-150.0 microg/ml for 4-NP with correlation coefficients greater than 0.999. The detection limits of serum and tissue samples were 2.8 ng/ml and 1.4 ng/g for BPA and 5.6 ng/ml and 2.8 ng/g for 4-NP at a signal-to-noise ratio (S/N) of 3. The intra-assay and the inter-assay precisions were better than 11.4%. Recoveries of BPA and 4-NP were 78.6-95.0% and 80.2-93.4%, respectively. The proposed method was applied to a toxicokinetic study of BPA and 4-NP including individual and combined oral administration to rats. The results showed that 4-NP remarkably altered the toxicokinetic parameters of BPA in testis, while parameters of BPA were not obviously altered in serum and liver under the experimental conditions investigated. On the other hand, there was no significant difference in the toxicokinetics of 4-NP when administered with BPA.

Effects of bisphenol A-related diphenylalkanes on vitellogenin production in male carp (Cyprinus carpio) hepatocytes and aromatase (CYP19) activity in human H295r adrenocortical carcinoma cells

The present study investigated the effects of the known xenoestrogen bisphenol A (BPA) relative to eight BPA-related diphenylalkanes on estrogen receptor (ER)-mediated vitellogenin (vtg) production in hepatocytes from male carp (Cyprinus carpio), and on aromatase (CYP19) activity in the human adrenocortical H295R carcinoma cell line. Of the eight diphenylalkanes, only 4,4'-(hexafluoropropylidene)diphenol (BHF) and 2,2'-bis(4-hydroxy-3-methylphenyl)propane (BPRO) induced vtg, i.e., to a maximum of 3% to 4% (at 100 microM) compared with 8% for BPA relative to the maximum induction by 17beta-estradiol (E2, 1 microM). Bisphenol A diglycidyl ether (BADGE) was a potent antagonist of vtg production with an IC50 of 5.5 microM, virtually 100% inhibition of vtg at 20 microM, and an inhibitive (IC50) potency about one-tenth that of the known ER antagonist tamoxifen (IC50, 0.6 microM). 2,2'-Diallyl bisphenol A, 4,4'-(1,4-phenylene-diisopropylidene)bisphenol, BPRO, and BHF were much less inhibitory with IC50 concentrations of 20-70 microM, and relative potencies of 0.03 and 0.009 with tamoxifen. Bisphenol ethoxylate showed no anti-estrogenicity (up to 100 microM), and 4,4'-isopropylidene-diphenol diacetate was only antagonistic at 100 microM. When comparing the (anti)estrogenic potencies of these bisphenol A analogues/diphenylalkanes, anti-estrogenicity occurred at lower concentrations than estrogenicity. 4,4'-Isopropylidenebis(2,6-dimethylphenol) (IC50, 2.0 microM) reduced E2-induced (EC50, 100 nM) vtg production due to concentration-dependent cytotoxicity as indicated by a parallel decrease in MTT activity and vtg, whereas the remaining diphenylalkanes did not cause any cytotoxicity relative to controls. None of the diphenylalkanes (up to 100 microM) induced EROD activity indicating that concentration-dependent, CYP1A enzyme-mediated metabolism of E2, or any Ah-receptor-mediated interaction with the ER, was not a likely explanation for the observed anti-estrogenic effects. At concentrations as great as 100 microM, none of the diphenylalkanes directly inhibited aromatase (CYP19) activity in H295R cells. Environmental exposure of fish to BPA and related diphenylalkanes, depending on the structure, may pose anti-estrogenic, and to a lesser extent estrogenic, risks to development and reproduction.

Bisphenol A removal from water by activated carbon. Effects of carbon characteristics and solution chemistry

The present study aimed to analyze the behavior of different activated carbons in the adsorption and removal of bisphenol A (2-2-bis-4-hydroxypheniyl propane) from aqueous solutions in order to identify the parameters that determine this process. Two commercial activated carbons and one prepared in our laboratory from almond shells were used; they were texturally and chemically characterized, obtaining the surface area, pore size distribution, mineral matter content, elemental analysis, oxygen surface groups, and pH of the point of zero charge (pH(PZC)), among other parameters. Adsorption isotherms of bisphenol A and adsorption capacities were obtained. The capacity of the carbons to remove bisphenol A was related to their characteristics. Thus, the adsorption of bisphenol A on activated carbon fundamentally depends on the chemical nature of the carbon surface and the pH of the solution. The most favorable experimental conditions for this process are those in which the net charge density of the carbon is zero and the bisphenol A is in molecular form. Under these conditions, the adsorbent-adsorbate interactions that govern the adsorption mechanism are enhanced. Influences of the mineral matter present in the carbon samples and the solution chemistry (pH and ionic strength) were also analyzed. The presence of mineral matter in carbons reduces their adsorption capacity because of the hydrophilic nature of the matter. The presence of electrolytes in the solution favor the adsorption process because of the screening effect produced between the positively charged carbon surface and the bisphenol A molecules, with a resulting increase in adsorbent-adsorbate interactions.

Bisphenol A in canned foods in New Zealand: an exposure assessment

Exposure to bisphenol A (BPA) from the consumption of canned and bottled food has been determined for New Zealand adults. Eighty different canned foods purchased from retail outlets in Christchurch, New Zealand, between November 2003 and February 2004 were analysed for BPA concentration by gas chromatography/mass spectrometry. BPA was detected in all foods analysed except for soft drinks. Concentrations ranged from < 10 to 29 microg kg(-1), except for individual samples of tuna, corned beef and coconut cream, which were 109, 98 and 191 microg kg(-1) , respectively. The limit of quantitation was <10 microg kg(-1) for foods of low fat content (< 1%) and <20 microg kg(-1) for foods containing >1% fat. Mean concentration data were combined with 24-h dietary recall information for 4399 individual consumers. Mean and maximum exposures were 0.008 and 0.29 microg kg(-1) bw day(-1), respectively, well below the temporary tolerable daily intake of 10 microg kg(-1) bw day(-1) given by the European Commission in 2002. The results of the present survey suggest that the levels of BPA identified in canned foods are unlikely to be of concern to adult health, and there is no reason for consumers to change their consumption patterns as a result of these findings. When the concentration data found in the current survey are applied to an oestrogenicity model for an adult male, the contribution of BPA to the total oestrogenicity from 16 food components is 7%. The impact of this level of oestrogenicity remains unclear.

Development and validation of a capillary high-performance liquid chromatography/electrospray tandem mass spectrometric method for the quantification of bisphenol A in air samples

Bisphenol A (BPA) is a toxic industrial chemical that affects the endocrine system even at low concentrations. A new method, based on capillary high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (HPLC/ESI-MS/MS) analysis, has been developed to determine BPA in atmospheric samples. The method involves collection of air samples (typically 2 m(3)) on glass fiber filters, with ultrasonic extraction and sample concentration under vacuum before analysis. HPLC analysis was performed isocratically at a flow rate of 10 microL min(-1) using a capillary reversed-phase column and MS/MS analysis in negative ion multiple reaction monitoring (MRM) mode, using BPA-d(16) as internal standard. The present method provides linear response in the range 0.007-3.5 microg/filter (R(2) > 0.999) and is characterized by high accuracy (mean bias 2%) and good reproducibility (mean RSD 5%). High sensitivity (LOD = 2 ng/m(3) based on 2 m(3) of air collected), specificity, and speed of the analysis make the present method suitable for routine determination of BPA in the atmosphere, both for ambient and personnel monitoring.

Degradation of Bisphenol A by White Rot Fungi, Stereum hirsutum and Heterobasidium insulare, and Reduction of Its Estrogenic Activity

Two lignin-degrading basidiomycetes, Stereum hirsutum and Heterobasidium insulare, were used to degrade bisphenol A (BPA) in culture, and the estrogenic activity of the degradation products was examined using MCF-7 cell proliferation assays (E-screen) and analysis of pS2 mRNA expression in MCF 7 cells. Both S. hirsutum and H. insulare showed high resistance to BPA 100 ppm, and their mycelial growth was fully completed within 8 d of incubation at 30 degrees C. It took 7 to 14 d to achieve complete degradation (ca. 99%) of BPA by both fungi. MCF-7 cells proliferated actively at a BPA concentration of 10(-5) M. However, cell line proliferation was significantly inhibited when the cells were incubated in BPA culture media containing S. hirsutum and H. insulare. Similar results were obtained regarding pS2 mRNA expression. The pS2 mRNA expression levels decreased by 1.5-fold in supernatant from BPA treated with S. hirsutum and H. insulare compared with those treated with BPA alone.

In vivo imaging of activated estrogen receptors in utero by estrogens and bisphenol A

Environmental estrogens are of particular concern when exposure occurs during embryonic development. Although there are good models to study estrogenic activity of chemicals in adult animals, developmental exposure is much more difficult to test. The weak estrogenic activity of the environmental estrogen bisphenol A (BPA) in embryos is controversial. We have recently generated transgenic mice that carry a reporter construct with estrogen-responsive elements coupled to luciferase. We show that, using this in vivo model in combination with the IVIS imaging system, activation of estrogen receptors (ERs) by maternally applied BPA and other estrogens can be detected in living embryos in utero. Eight hours after exposure to 1 mg/kg BPA, ER transactivation could be significantly induced in the embryos. This was more potent than would be estimated from in vitro assays, although its intrinsic activity is still lower than that of diethylstilbestrol and 17beta-estradiol dipropionate. On the basis of these results, we conclude that the estrogenic potency of BPA estimated using in vitro assays might underestimate its estrogenic potential in embryos.

Review of the toxicology, human exposure and safety assessment for bisphenol A diglycidylether (BADGE)

BADGE (whose chemical names are bisphenol A diglycidylether and 2,2-bis(4-(2,3-epoxypropyl)phenyl)propane) is the lowest molecular weight oligomer in commercial epoxy resins and the major component in commercial liquid epoxy resins. The major application areas for epoxy resins are protective coatings and civil engineering. Additional applications include printed circuit boards, composites, adhesives and tooling, while a relatively small amount of epoxy resins (< 10%) finds use in protective coatings inside food and drink cans. The use of BADGE in food-contact applications was first regulated through EC Directive 2002/16/EC and amended in EC Directive 2004/13/EC with migration levels in food-contact applications being generally well below the regulatory thresholds. The paper discusses the commercial use of BADGE focusing on the current knowledge of human exposure from canned food applications. To assess the safety of this application, the exposure data are compared with no adverse effect levels (NOAEL) from various toxicological investigations with BADGE including reproductive and developmental assays, endocrine toxicity investigations, and sub-chronic and chronic assays. Consumer exposure to BADGE is almost exclusively from migration of BADGE from can coatings into food. Using a worst-case scenario that assumes BADGE migrates at the same level into all types of food, the estimated per capita daily intake for a 60-kg individual is approximately 0.16 microg kg(-1) body weight day(-1). A review of one- and two-generation reproduction studies and developmental investigations found no evidence of reproductive or endocrine toxicity, the upper ranges of dosing being determined by maternal toxicity. The lack of endocrine toxicity in the reproductive and developmental toxicological tests is supported by negative results from both in vivo and in vitro assays designed specifically to detect oestrogenic and androgenic properties of BADGE. An examination of data from sub-chronic and chronic toxicological studies support a NOAEL of 50 mg kg(-1) body weight day(-1) from the 90-day study, and a NOAEL of 15 mg kg(-1) body weight day(-1) (male rats) from the 2-year carcinogenicity study. Both NOAELS are considered appropriate for risk assessment. Comparing the estimated daily human intake of 0.16 microg kg(-1) body weight day(-1) with the NOAELS of 50 and 15 mg kg(-1) body weight day(-1) shows human exposure to BADGE from can coatings is between 250,000 and 100,000-fold lower than the NOAELs from the most sensitive toxicology tests. These large margins of safety together with lack of reproductive, developmental, endocrine and carcinogenic effects supports the continued use of BADGE for use in articles intended to come into contact with foodstuffs.

Steroid activities comparison of natural and food wrap compounds in human breast cancer cell lines

In this study, we tested and compared the endocrine disruption activities of compounds in materials used to package foods (bisphenol A, bisphenol F, and bisphenol A diglycidylether BADGE) with natural molecules (genistein, apigenin, kaempferol, and tangeretin) in the human breast cancer cell lines MCF-7 (ER(+)) and MDA-MB453 (AR(+); GR(+)). Octylphenol was also chosen as a xenoestrogen reference. Two compounds had no estrogenic activity: BADGE and tangeretin. Genistein was the most active compound in the E-Screen assay with MCF-7, followed by octylphenol, bisphenol F, bisphenol A and apigenin, with kaempferol the least potent. All estrogenic compounds competed with 17beta-estradiol for binding to the MCF-7 ER and their estrogenic effects were abolished in the presence of tamoxifen, an ER antagonist. In MDA-MB453 cells transfected with pMMTVneo-Luc, all compounds had anti-androgenic activities, with octylphenol the most potent. Kaempferol, genistein, and apigenin were more potent anti-androgens than bisphenols A or F. The natural compounds had a biphasic effect on luciferase activity. At high concentrations, genistein (10(-5)M) and apigenin (10(-6)M) acted as GR agonists in transfected MDA-MB453 cells. Furthermore, apigenin, at a concentration of 10(-5)M, may act as a partial androgen receptor (AR) agonist, as nilutamide, an AR antagonist, inhibited its activity by 26%.

Oxidation of bisphenol A, 17beta-estradiol, and 17alpha-ethynyl estradiol and byproduct estrogenicity

A human breast cancer cell line (MCF-7) was used to investigate the cumulative estrogenicity profiles elicited during the oxidation of three estrogenic compounds [bisphenol A (BPA), 17beta-estradiol (E2), and 17alpha-ethynyl estradiol (EE2)]. High-performance liquid chromatography (HPLC) with a method detection limit (MDL) of approximately 1 nM was used to measure the initial and final concentrations of test compounds during oxidation. Both chlorination and ozonation removed from 75% to >99% of the test compounds in distilled water. Increasing contact time and chlorination dose improved compound removal. Chlorination byproducts of BPA, E2, and EE2 elicited low levels of estrogenicity over an extended period of time. For equivalent molar oxidant dosages, ozone and chlorine had comparable residual proliferative effect values and >99% loss of the parent compounds. For oxidation studies of estrogenic chemicals, ammonium chloride was found to adequately quench residual chlorine without interfering with cell culture assay. Oxidation of test compounds with chlorine and ozone resulted in a similar estrogenicity trend, with a relative higher level of estrogenicity elicited during the early phases of oxidation, which gradually dissipated over the extended exposure time to a stable point. Oxidation with ozone resulted in the rapid transformation of test compounds, reaching a stabilized estrogenic level in 10 min, whereas for chlorination it took more than 120 min for elicited estrogenicity to stabilize.

Study on anti-androgenic effects of bisphenol a diglycidyl ether (BADGE), bisphenol F diglycidyl ether (BFDGE) and their derivatives using cells stably transfected with human androgen receptor, AR-EcoScreen

We studied in vitro hormonal activity of bisphenol A diglycidyl ether (BADGE) and bisphenol F diglycidyl ether (BFDGE), which are used as a material of interior coating for food cans. We also examined related compounds such as 2,2-bis[4-(3-chloro-2-hydroxypropoxy)phenyl]propane (BADGE.2HCl), and bis[4-(3-chloro-2-hydroxypropoxy)phenyl]methane (BFDGE.2HCl) etc. For this purpose, we constructed two stably transfected CHO-K1 cell lines (AR-EcoScreen for androgenic activity and c-luc for cell toxicity evaluation). One stably expresses luciferase with induction of androgen. The other stably expresses luciferase without androgen induction. Also, we have determined the androgenic and anti-androgenic effects of the test chemicals by reporter gene assay with these cell lines. None of the chemicals tested by this assay exhibited androgen agonistic activity. However, BADGE.2HCl and BFDGE.2HCl had the conspicuous antagonistic activity for androgen. These compounds had a high binding affinity for androgen receptor. Furthermore, these two compounds did not show the estrogenic activity in vitro assays. On the contrary, bisphenol A and bisphenol F exhibited anti-androgenic activity in vitro in addition to the estrogenic activity. These results suggest that these chlorohydroxy compounds of BADGE and BFDGE act as androgen antagonist through the process of binding to androgen receptor.

Environmental fate of bisphenol A and its biological metabolites in river water and their xeno-estrogenic activity

Monitoring of bisphenol A [BPA; 2,2-bis(4-hydroxyphenyl)propane] and its biological metabolites [4,4'-dihydroxy-alphamethylstilbene (DHMS), 2,2-bis(4-hydroxyphenyl)-1-propanol (BPA-OH), 2,2-bis(4-hydroxyphenyl)propanoic acid (BPA-COOH), and 2-(3,4-dihydroxyphenyl)-2-(4-hydroxyphenyl)propane (3-OH-BPA)] in river waters was performed by solid-phase extraction and GC/MS determination. The concentrations of BPA, BPA-COOH, BPA-OH, and 3-OH-BPA in the river water ranged from 2 to 230 (8.8 x 10(-12) to 1.0 x 10(-9) M), from 5 to 75 (1.9 x 10(-11) to 2.9 x 10(-10) M), from 3 to 16 (1.2 x 10(-11) to 6.6 x 10(-11) M), and from 3 to 11 (1.2 x 10(-11) to 4.5 x 10(-11) M) ng L(-1), respectively. DHMS, an intermediate in the main degradation pathway of BPA, was not detected in any water sample. Under the aerobic conditions in the river water, BPA disappeared within 8 d of incubation, but BPA-COOH, BPA-OH, and tetraol remained in the supernatant after 14 d of incubation. For the xeno-estrogenic activity of BPA and the metabolites, their ability to bind to recombinant human estrogen receptor alpha in competition with fluorescence-labeled 17beta-estradiol was measured. Fifty percent inhibitory concentrations (IC50) of BPA, DHMS, 3-OH-BPA, and BPA-OH were approximately 1 x 10(-5), 1 x 10(-6), 3 x 10(-5), and 1 x 10(-2) M, respectively. In human cultured MCF-7 breast cancer cells, BPA increased cell numbers in a dose-dependent manner at concentrations from 10(-7) to 10(-5) M. For the BPA metabolites, DOHMS, 3-OH-BPA, and BPA-COOH caused the cells proliferation at concentrations from 10(-9) to 10(-6), from 10(-7) to 10(-6), and from 10(-5) to 10(-4) M, respectively. BPA-OH did not cause MCF-7 cells proliferation. These results indicate that BPA is mainly metabolized through oxidative rearrangement by bacteria in the river water, and intermediate bisphenols via minor metabolic pathways exist in river water. The presence of the bisphenols having the xeno-estrogenic effect suggests the necessity of monitoring those in river water, in the effluent waters from sewage plants, or in landfill leachate.

Bisphenol A causes hyperactivity in the rat concomitantly with impairment of tyrosine hydroxylase immunoreactivity

We examined the effects of bisphenol A, an endocrine disruptor, on rat behavioral and cellular responses. Single intracisternal administration of bisphenol A (0.2-20 microg) into 5-day-old male Wistar rats caused significant hyperactivity at 4-5 weeks of age. Rats were about 1.6-fold more active in the nocturnal phase after administration of both 2 and 20 microg of bisphenol A than were control rats. The response was dose-dependent. Based on DNA macroarray analyses of the midbrain, bisphenol A decreased by more than twofold gene expression levels of the dopamine D4 receptor at 4 weeks of age and the dopamine transporter at 8 weeks of age. Furthermore, bisphenol A decreased by more than twofold gene expression levels of the dopamine D4 receptor at 4 weeks of age and the dopamine transporter at 8 weeks of age. We conclude that bisphenol A affected central dopaminergic system activity, resulting in hyperactivity due most likely to a large reduction of tyrosine hydroxylase activity in the midbrain.

Estrogenic activities of Ginkgo biloba extracts

Ginkgo biloba extracts (GBE) are extracted from the leaves of Ginkgo biloba tree. GBE contains 24% of phytoestrogens, which is kaempferol, quercetin, and isorhamnetin. It has been reported that phytoestrogens could be a part of SERMs (Selective estrogen receptor modulators) and possibly the alternative HRT (Hormone replacement therapy) for postmenopausal women. The goal of this study was to investigate the potencies of GBE and its major components (quercetin, kaempferol, isorhamnetin) for estrogenic effect, which confirms the capacity as an alternative HRP. It was found that GBE and its major components exerted a dual action on ER-alpha and ER-beta in competitive binding assay. The binding affinity of these chemicals to ER-beta was higher than to ER-alpha. In the E-screen assay, these chemicals induced cell proliferation in ER-positive MCF-7 cell, but not in ER-negative MDA-MB-231 cells. The cell proliferation induced by these chemicals was blocked by tamoxifen. Also, GBE and its major components induced pS2 and PR (progesterone receptor) transcription in MCF-7 cells. Therefore these results indicated that GBE and its major components had the weak estrogenic activities through the estrogen response pathway by an interaction with the ER. In conclusion, we provided the evidence of potential estrogenic activities of GBE, which could be useful as an alternative HRP. However, further studies are required to assess the physiological significance of GBE in animals and humans.

Correlation of Analyte Structures with Biosensor Responses Using the Detection of Phenolic Estrogens as a Model

The apparent increase in hormone-induced cancers and disorders of the reproductive tract in wildlife and humans has led to a search for an accurate and reliable method for monitoring endocrine-disrupting chemicals (EDCs). This study presents a generic approach that may allow researchers to establish screening procedures for potential EDCs by correlating the analyte structures with biosensor responses and explain possible reaction mechanisms. A simple amperometric tyrosinase-based biosensor (Tyr-CPE) has been developed for the detection of phenolic EDCs. The investigation of the enzymatic oxidation of selected phenolic estrogens was first carried out using UV-vis spectroscopy. The result was used to correlate sensor responses to enzymatic activity. Natural phytoestrogen polyphenols, including resveratrol (RES), genistein (GEN), and quercetin (QRC), were compared with synthetic estrogens, for example, bisphenol A (BPhA), nonylphenol (NPh), and diethylstilbestrol (DES). The Tyr-CPE biosensor resulted in rapid, simple, and accurate measurement of phenolic estrogens with varying degrees of sensitivity, selectivity, and response times. The sensor responses have been evaluated for the detection of binary and tertiary mixtures of EDCs and natural estrogens. The results showed that BPhA could be successfully discriminated in a composite mixture containing NPh and DES at various ratios. In the case of natural phenolic estrogens GEN, RES, and QRC, the sensor allows the determination of a total phenolic content. The sensor was also validated for the detection of BPhA in a real environmental water sample, and the results was compared with standard ASTM method 9065. Mechanistically, our results indicated that the number of OH groups, the nature and the position of aryl ring substituents, or both could affect the detection limit and the biosensor sensitivity.

Estrogenic effects of food wrap packaging xenoestrogens and flavonoids in female Wistar rats: a comparative study

The objective of this study was to compare the estrogenicity of xenoestrogens found in food wrap packaging and phytoestrogen flavonoids. Uterotrophic and vaginal cornification assays were performed on immature and ovariectomized rats. Genistein, bisphenol F, and octylphenol were identified as estrogenic only in immature rats. Using vaginal cornification as a more specific estrogenic parameter, all tested compounds except tangeretin were active in immature rats. While apigenin and kaempferol appeared to have low estrogenic activity, they potentialized the uterotrophic effect of 17beta-estradiol in immature rats. These data showed that (i) phytoestrogens like genistein can be as potent or even more estrogenic than compounds found in food wrap packaging, (ii) immature rats appear to be a more sensitive in vivo model than ovariectomized rats in term of estrogenicity, (iii) the vaginal cornification assay could be a sensitive and useful test to detect weak estrogenic compounds to which humans can be exposed via food.

Down-regulation of inducible nitric oxide synthase and tumor necrosis factor-alpha expression by bisphenol A via nuclear factor-kappaB inactivation in macrophages

Bisphenol A [BPA, 2,2bis(4hydroxyphenyl)propane] is reported to have estrogenic activity; however, its influence on cytokine production or immune system function remains unclear. In this study, we investigated the effects of BPA on the production of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-alpha), and on the level of inducible nitric oxide synthase (iNOS) and TNF-alpha gene expression in mouse macrophages. BPA alone did not affect NO or TNF-alpha production. In contrast, BPA inhibited lipopolysaccharide (LPS)-induced NO and TNF-alpha production, and the levels of iNOS and TNF-alpha mRNA in a dose-dependent manner. Treatment with ICI 182.780, an estrogenreceptor antagonist, inhibited the suppressive effects of BPA. Transient expression and electrophoretic mobility shift assays with NF-kappaB binding sites revealed that BPA reduced the levels of the LPS-induced NF-kappaB transcription factor complex. These results demonstrate that BPA may affect the regulation of the immune system function by reducing NO and TNF-alpha production via the inhibition of NF-kappaB transactivation mediated through the estradiol receptor.

[Studies on estrogenic activities of food additives with human breast cancer MCF-7 cells and mechanism of estrogenicity by BHA and OPP]

Estrogenic activities of more than 90 chemicals including food additives, foodstuffs of plant origin, and some chemicals, which could be orally ingested, were examined by assaying estrogen receptor (ER)-dependent proliferation of MCF-7 cells. Among 66 food additives, 17 compounds stimulated the proliferation, but their concentrations giving maximal cell yield were higher than that of 17 beta-estradiol and their estrogenic activities were weak. Flavonoids had relatively strong estrogenic activities. In the assay of ER competitive binding to human ER alpha and ER beta in vitro, the antioxidant t-butylhydroxyanisole (BHA) had the capacity to compete with 17 beta-estradiol, while the capacity of o-phenyl phenol (OPP) was too small to calculate. Both BHA and OPP induced a decrease in gene expression of ER alpha and an increase in that of progesterone receptor in a time-dependent manner. These effects were similar to that of 17 beta-estradiol, a though much higher concentrations were required for these compounds than 17 beta-estradiol. These results may suggest that we should be careful not to ingest excessive food additives.

In vitro assay of hydrolysis and chlorohydroxy derivatives of bisphenol A diglycidyl ether for estrogenic activity

Bisphenol A diglycidyl ether (BADGE) is an epoxy resin monomer. Epoxy-based solution coatings are used in many applications as additives for a variety of plastic coatings in food packaging. It is well known that unreacted BADGE can migrate from epoxy-based packing materials into foods. Not only BADGE but also its derivatives can easily migrate into foods and it is likely that we intake BADGE and its derivatives through food or drink. Recently, endocrine disrupting chemicals (EDCs) have attracted attention because they have been shown to affect reproduction in wildlife. The estrogenic activity of BADGE derivatives has not previously been investigated. Therefore, we investigated the estrogenic activity of the BADGE derivatives, dihydrolysed BADGE (BADGE-4OH) and chlorohydroxy BADGE (BADGE-2Cl), using breast cancer cell (T47D) proliferation assay and estrogen receptor (ER) (alpha) binding assay. These chemicals exhibited T47D cell proliferation at concentrations of 10(-14)-10(-4) M. However, these chemicals did not bind to ER (alpha) in the binding assay.

Metabolism of bisphenol a in primary cultured hepatocytes from mice, rats, and humans

Studies have shown that in the rat, bisphenol A (BPA) is metabolized and eliminated primarily as a monoglucuronide, a metabolite without estrogenic activity. The purpose of this study was to determine the extent of monoglucuronide formation in monolayers of hepatocytes from rats, mice, and humans. Noncytotoxic concentrations of BPA (10, 20, and 35 microM; 1.0 microCi), as assessed by lactate dehydrogenase leakage, were incubated with isolated hepatocytes for 0-6 h. Media were collected and analyzed for metabolites by radiochemical high performance liquid chromatography and liquid chromatography-tandem mass spectrometry. The metabolites identified include a monoglucuronide (major metabolite), a sulfate conjugate, and a glucuronide/sulfate diconjugate (minor metabolites). In hepatocytes of male Fischer-344 rats, the predominate metabolite was the diconjugate (glucuronide/sulfate). Under these conditions, the extent of metabolism by 3 h was similar in all species tested because all BPA was converted to conjugates by 3 h. Initial rates of metabolism in hepatocytes followed the order of mice > rats > humans. However, when extrapolated to the whole liver (i.e., cells per liver), the hepatic capacity for BPA glucuronidation is predicted to be humans > rats > mice. This research was supported in part by The Society of Plastics Industry Inc., and Southwest Environmental Health Science Center (ES 06694).

Sulfation of bisphenol A abolished its estrogenicity based on proliferation and gene expression in human breast cancer MCF-7 cells

Bisphenol A, an endocrine-disrupting chemical, is widely used in many consumer products. We previously showed the sulfoconjugation of bisphenol A catalyzed by a human thermostable phenol sulfotransferase, ST1A3. The estrogenic potency of bisphenol A sulfate was compared with that of bisphenol A by an E-screen assay using human breast cancer MCF-7 cells. An increase in the expression level of an estrogen-responsive pS2 gene was also examined using MCF-7 cells after exposure to bisphenol A and its sulfate for their estrogenicity. Bisphenol A sulfate did not exhibit estrogenic effects at 0.1 microM (E-screen assay) and 1 mM (pS2 gene expression) compared with bisphenol A, which exhibited the effects at 3 nM (E-screen assay) and 1 microM (pS2 gene expression), respectively. We have therefore evaluated major roles of cytosolic phenol sulfotransferase in the human liver. Bisphenol A sulfation in human liver cytosols was inhibited by more than 90% by p-nitrophenol and quercetin, a typical substrate and specific inhibitor of phenol sulfotransferase, respectively. These results indicated that the estrogenicity of bisphenol A was abolished through its sulfation catalyzed by a human hepatic thermostable phenol sulfotransferase.

Estrogenic effect of a series of bisphenol analogues on gene and protein expression in MCF-7 breast cancer cells

Bisphenols constitute a family of compounds, which includes many substances that have as a common chemical structure two phenolic rings joined together through a bridging carbon. In the present study, we aimed to determine whether several events triggered by 17 beta-estradiol (E(2)) in MCF-7 breast cancer cells were also observed in response to various bisphenol-A (BPA) analogues. We studied the expression of estrogen controlled genes by measuring the induction of pS2 (mRNA and protein) and progesterone receptor (PgR) as well as the expression of a luciferase reporter gene transfected into MVLN cells. These data were compared to the cell proliferation potency and effectiveness as the latest expression of estrogen controlled functions. Bisphenols showed an agonistic effect in all our assays, suggesting that these compounds may act through all the response pathways triggered by the natural hormone. We found differences between the assays in the potency of bisphenols, defined as the minimum concentration required to produce a maximal effect. In the cell proliferation assay, all tested compounds needed a lower concentration than in the other assays to give maximal response. Our results suggest that the polarity and nature of the substituent in the central carbon determines the estrogenic potency. Presence of two propyl chains at the central carbon appears to confer the greatest potency in both gene and protein expression assays.

Identification of estrogenic activity of chlorinated bisphenol A using a GFP expression system

A green fluorescent protein (GFP)-reporter vector regulated by an estrogen response element (ERE) was constructed and transfected into human breast carcinoma MCF7 cells. Stable transfectants were selected and their GFP fluorescence intensity was measured using a quantitative fluorescent imaging system. 17β-estradiol (E(2)) and bisphenol A (BPA) induced a dose-dependent increase in GFP intensity in the cells, reaching maximum response at 5×10(-10) and 10(-5) M, respectively. Using this GFP expression system, we examined the estrogenicity of mono-, di-, tri-, and tetra-chlorinated BPAs, which were detected in wastewater from waste-paper recycling plants using sodium hypochlorite as a bleaching agent. 3-ClBPA and 3,3'-diClBPA showed similar estrogenicities, effective at lower concentrations than parent BPA. On the other hand, the maximum activities of BPA and 3,3',5-triClBPA, whose EC(50) were similar, were higher than other chlorinated BPAs. This is the first demonstration of the estrogenicity of chlorinated BPAs. Since polychlorinated BPAs were not easily biodegraded, chlorinated BPAs might be more severe endocrine disruptors than BPA.

Determination of bisphenol A in rat brain by microdialysis and column switching high-performance liquid chromatography with fluorescence detection

A sensitive column switching HPLC-fluorescence detection for determination of bisphenol A (BPA) in rat brain by coupling with microdialysis was developed. A microdialysis probe was inserted into the hypothalamus of rat brain and an artificial cerebrospinal fluid was used for perfusion. BPA in brain dialysate was subjected to a fluorescent derivatization with 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl), and the excess reagent was removed by a column-switching technique. Separation was carried out on two ODS semimicro-columns with the mobile phase of acetonitrile-H(2)O-methanol-tetrahydrofuran (55:10:35:2.5, v/v) and acetonitrile-0.1 M acetate buffer (pH 3.0)-methanol (35:10:55, v/v) at a flow rate of 0.10 and 0.15 mL/min for a precolumn and a separation column, respectively. Fluorescence intensity was monitored at 475 nm with excitation of 350 nm. BPA could be sensitively detected at 0.3 ppb in 60 micro L brain microdialysate at a signal-to-noise ratio of 3. By the proposed method, concentrations of BPA in rat brain and plasma were monitored for 8 h after single i.v. or oral administration. It is proved that BPA is capable of penetrating the blood-brain barrier. The ratio of the area under the concentration-time curve of BPA in rat brain to that in blood was estimated to be about 3.0-3.8%.