Estrogenic Activity Of Bisphenol A Research Articles

Complete degradation of bisphenol A and nonylphenol by a composite of biogenic manganese oxides and Escherichia coli cells with surface-displayed multicopper oxidase CotA

Endocrine-disrupting chemicals (EDCs) are a large group of environmental toxicants that pose serious risks to public health. In this study, we report a new method for the complete degradation of EDCs using a dual oxidation-action composite of biogenic manganese oxides and engineered Escherichia coli cells with surface-expressed multicopper oxidase CotA. The cotA gene from a Mn2+-oxidizing bacterium was constructed as a fusion gene “inaQ-N/cotA” with an anchoring motif inaQ-N from Pseudomonas syringae and was expressed in E. coli cells to display catalytic CotA on the cell surface. Under prolonged Mn2+-enriched culturing conditions, the engineered cells were capable of forming microspherical aggregated composites that were mainly composed of ramsdellite (MnO2). The ability of the composite to degrade two EDCs, bisphenol A (BPA) and nonylphenol (NP), was investigated. GC–MS assays identified 7 and 10 degraded intermediates using the 13C isotope from 13C-labeled BPA and 13C-labeled NP, respectively. The appearance of 13CO2 from both reaction mixtures revealed mineralization pathways of BPA and NP by this composite. Bioassays using Caenorhabditis elegans as an indicator organism demonstrated that the estrogenic activity of BPA and NP was eliminated by these degradation processes. The reaction of the composite proceeded at an acidic pH and room temperature. A consecutive three-round treatment process showed comparable levels of degradation by the composite in repeated reactions and showed that the activity could be easily recovered. Moreover, the superoxide radical levels of BPA-degradation and NP-degradation were monitored during the 24 h reaction time, and possible BPA-degradation and NP-degradation pathways by the composite were proposed.

Bisphenol A Effects on Gonadotroph Function: Disruption of Pituitary Cell-Cell Communication?

Since the publication of a joint International Programme on Chemical Safety report in 2002 assessing the scientific knowledge of endocrine disruptors, there has been a dramatic increase in both awareness of the risk they may pose and studies of potential health implications for humans and wildlife (1). Of all the endocrine disruptors studied to date, there has been considerable focus on bisphenol A (BPA), in particular on its effects on the reproductive axis (2). BPA is a widely used industrial chemical, which has been found in 95% of urine samples from adults in the United States (3), with contaminated food and water accounting for 90% of exposure (4). Although most studies have focused on the estrogenic activity of BPA, it has also been shown to bind to androgen and thyroid hormone receptors, suggesting that it may disrupt multiple endocrine systems. In the reproductive axis, BPA has been reported to adversely affect several end points of fertility, advance puberty, and induce polycystic ovarian syndrome (2). In this edition of Endocrinology, Eckstrum et al (5) describe effects of BPA on gonadotrophs during an important pituitary developmental window in neonatal mice. The authors have found that the gene encoding intracellular adhesion molecule-5 (Icam5) (also known as telencephalin) is more highly expressed in the pituitary of day-old female mice compared with their male littermates. They go on to show that the RNA and protein are predominantly expressed in gonadotrophs, with increased expression during the early postnatal period (up to d 20), with a continued higher expression in females than males. The disrupting effect of BPA on this expression is demonstrated in females and males in ex vivo cultures, and in females in vivo, with lower expression of Icam5. This work builds on previous studies describing effects on BPA exposure in utero by the same group, where different effects on the reproductive axis were described, consistent with the concept that specific windows of the development of endocrine axes may be differentially affected by the same endocrine disruptor. What is the potential role of Icam5 in normal pituitary function? Expression of this gene has previously been considered to occur only in the telencephalon, where it has a role in the regulation of the interactions between axonal protrusions and dendritic spines, which form neuronal synapses. Loss of Icam5 in knockout mice leads to a reduction in filopodia, which develop into dendritic spines (6) and increased spinal maturation, overexpression the reverse. This kind of cell-cell interaction leading to functional connectivity has been described in the pituitary, where homotypic cell networks have been shown to exist, with important roles in the regulation of cell function at both the level of secretion (7) and gene expression (8). The proteins regulating this cell network formation have not been identified, but those with a function similar to that described for ICAM5 are likely to be mediators, making it a likely candidate. In the neonate, it is possible that ICAM5 mediates the formation of the gonadotroph network described by Budry et al (9). This network begins its development before birth, and it would be interesting to determine whether there is a window of Icam5 expression in these early gonadotrophs. In the adult, ICAM5 was only found in a subset of gonadotrophs, what could be its role

Molecular docking of bisphenol A and its nitrated and chlorinated metabolites onto human estrogen-related receptor-gamma

A xenoestrogen and known endocrine disruptor, bisphenol A (BPA) binds the human estrogen-related receptor-gamma (ERRγ) with high affinity (Kd≈5.5nM). It is likely that BPA undergoes oxidative biotransformation by hypochlorite/hypochlorous acid (−OCl/HOCl) and peroxynitrite (PN) and the products formed in these reactions may serve as secondary estrogens and contribute to the toxicodynamics of BPA. Therefore, in the present study we have examined the formation of chlorinated and nitrated BPA in reactions of BPA with −OCl/HOCl and PN(+CO2) performed around the neutral pH. We have identified four major products in these reactions and they include 3-chloro-BPA (CBPA), 3,3′-dichloro-BPA (DCBPA), 3-nitro-BPA (NBPA) and 3,3′-dinitro-BPA (DNBPA). Towards understanding the toxicodynamics and estrogenic activity of BPA in biological systems, we have performed molecular docking of BPA, CBPA, DCBPA, DNBPA and NBPA onto the ERRγ using AutoDock 4.2 software and compared the binding energies with those of estradiol, the natural ligand. Based on the genetic algorithm, the three best conformations were selected and averaged for each ligand and a detailed analysis of molecular interactions based on free energies of binding (kcal/mol) was computed. The results indicate the following rank order of binding to ERRγ: BPA (−8.78±0.06)>CBPA (−8.53±0.41)>NBPA (−7.36±0.74)>DCBPA (−5.24±0.17)>DNBPA (−4.95±0.78)>estradiol (−4.94±1.04). The docking studies revealed that the OH group of one of the phenyl rings forms a hydrogen bond with Glu275/Arg316, while the OH group of other phenyl ring was bound to Asp346. These results suggest that both BPA and its putative chlorinated and nitrated metabolites have strong binding affinity compared to estradiol.

A REVIEW RECENT DEVELOPMENT ON ANALYTICAL METHODS FOR DETERMINATION OF BISPHENOL A IN FOOD AND BIOLOGICAL SAMPLES

Bisphenol A (BPA) is an industrial chemical with major applications in the production of polycarbonate plastics and epoxy resins. Polycarbonate is used in food storage containers, while epoxy resins are used in the internal coating for food and beverage cans. Residues of unreacted BPA in polycarbonate plastic containers and epoxy coating can migrate into foods, and thus humans of different age groups have been inevitably exposed to BPA. A significant amount of work has been conducted since the estrogenic activity of BPA was reported again in the 1990s to investigate the presence of BPA in both various food and biological samples. Methods based on liquid chromatography (LC) with various ultra violet (UV), fluorescence, electrochemical detection (ECD), mass spectrometry (MS), tandem mass spectrometry (MS/MS), gas chromatography (GC) with MS and MS/MS, and enzyme linked immunosorbent assays (ELISA) have been developed for determination of BPA in food and biological samples over the past 10–15 years with significant improvements in method detection limits. This review is to give an overview of the recent development of the determination of BPA in food and biological samples and to identify knowledge gaps to further improve the analytical methods for BPA.

Iron deficiency augments bisphenol A-induced oxidative stress in rats

Bisphenol A (BPA), an estrogenic environmental contaminant is also known for oxidative stress-inducing effect. Malnutrition is recognized as a confounding factor in oxidative stress. However, little is known about effect of malnutrition on oxidative stress induced by BPA or other endocrine disrupting chemicals (EDCs). We studied effect of malnutrition (iron deficiency) in rats chronically exposed to low levels of BPA taking into consideration the oxidative stress and antioxidant status in liver, kidney and gonads. Iron deficiency significantly elevated level of lipid peroxidation in BPA-exposed rats. Similarly, decrease in reduced glutathione level was more significant in rats maintained on iron deficient diet compared to those maintained on normal diet. Iron deficiency also significantly modulated activities of vital antioxidant enzymes in all the tissues. Female rats showed more vulnerability than males to iron-deficiency modulated effects of BPA on the above parameters. This study demonstrated that malnutrition, especially iron deficiency, might act as a confounding factor in EDC-induced oxidative stress. However, more studies may be needed to confirm effect of nutritional factors on estrogenic activity of BPA or other EDCs.

Comparisons of polychromatic and monochromatic UV-based treatments of bisphenol-A in water via toxicity assessments

Polychromatic ultraviolet irradiation, such as from medium pressure (MP) Hg lamps may enhance the UV degradation of environmental pollutants as compared to low pressure (LP) Hg UV sources emitting monochromatic irradiation. Typically, studies involving destruction of environmental pollutants such as endocrine disrupting compounds (EDCs) are based on measurement of the parent compound decay using analytical chemistry, but such information is insufficient to determine an effective treatment endpoint because the identity and biological activity of many transformation products remain unknown. Bioanalytical methods to assess residual biological activity of a treated water offers one means to compare removal efficiency of EDC activity between MP- and LP-UV lamps under photolysis and UV/H2O2 oxidation. In this study, changes in estrogenic activity of bisphenol-A (BPA) as a function of UV treatment were evaluated using both an in vitro yeast estrogen screen and in vivo vitellogenin assay with Japanese medaka (Oryzias latipes) fish. Decay of BPA parent compound and formation of degradation products were followed using HPLC analysis. Results demonstrated that MP-UV direct photolysis more effectively removed BPA and associated estrogenic activity compared to LP-UV lamps. UV in combination with H2O2 significantly removed estrogenic activity in vitro and in vivo compared to direct photolysis; however, no significant difference in removal rates was found between the two lamps under UV/H2O2 oxidation. Furthermore, the UV/H2O2 process was effective for reducing embryo toxicity of BPA, but resulted in the production of acidic intermediates, causing acute toxicity and delayed hatching in some medaka embryos.

Retinoic Acid Inhibits Uterotrophic Activity of Bisphenol A in Adult Ovariectomized Rats

Bisphenol A (BPA) is used in the production of polycarbonate and epoxy resins. The weak estrogenic activity of BPA has been confirmed by both in vitro and in vivo assays. Retinal acetate has been reported to inhibit the adverse effects of BPA on male mice reproduction. All-trans-retinoic acid (ATRA) is a potent natural derivative of vitamin A and is reported to inhibit the estrogen-induced proliferation of human breast carcinoma cells. In this study, we investigated the possible inhibitory effects of ATRA on the estrogenic activity of BPA by a standard in vivo uterotrophic assay. Proliferated and apoptotic uterine cells were identified by 5-bromo-2'deoxyuridine (BrdU) incorporation and terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay. We observed that ATRA supplementation significantly inhibits a BPA-induced uterine weight increase in adult ovariectomized rats. However, there were no significant differences in the increases in the numbers of BrdU-positive cells and TUNEL-positive cells between the BPA and BPA+ATRA groups. These results show that ATRA may have an inhibitory effect on the estrogenic activity of BPA in an in vivo assay.

Dietary Psyllium Protects Immature Rats from Estrogenic Activity of Bisphenol A

This study was conducted to determine whether dietary psyllium (PSY) can protect against the estrogenic activity of Bisphenol A (BPA) in a rat uterotrophic bioassay. Fifteen immature female rats were fed a commercial diet (blank diet), a blank diet containing 0.1% BPA (control diet), or a blank diet with 0.1% BPA and 5% PSY (PSY diet) for 6 days. The uterine weight of the control group was significantly higher than of the blank group. The uterine weight and the uterine BPA levels of the PSY group were significantly lower than the control group. Serum BPA concentrations and liver BPA levels of the PSY group tended to decrease compared to the control group. However, BPA excretions in feces were significantly higher in the PSY group than in the control group (p<0.01). These observations indicate that dietary PSY feeding can protect against the estrogenic activity of BPA in rats.

The effect of bisphenol A and chlorinated derivatives of bisphenol A on the level of serum vitellogenin in Japanese medaka (Oryzias latipes)

2,2-bis (4-hydroxyphenyl) propane or Bisphenol A (BPA), has been reported to behave as an endocrine disrupter below acute toxic levels, and is widely present in the water environment. Although BPA is easily chlorinated, very little is reported on the effect of chlorinated BPA to the aquatic organisms. In this study, the estrogenic activities of BPA and its chlorinated derivatives were evaluated by the induction of vitellogenin (VTG) in the serum of mature male Japanese medaka. In addition, the effect of sodium hypochlorite on the decomposition of BPA was tested. The relative potencies of estrogenic activities of chlorinated BPA descended in the order 3,3'-diCIBPA>BPA> or =3-CIBPA>3,3',5-triCIBPA, and no estrogenic activity was observed in 3,3',5,5'-tetraCIBPA. Lowest Observed Effect Concentration (LOEC) and No Observed Effect Concentration (NOEC) for both 3-CIBPA and 3,3'-diCIBPA were 500 microg/L and 200 microg/L, respectively. LOEC for 3,3',5-triCIBPA was >500 microg/L. When BPA was reacted with sodium hypochlorite (24 hours; residual chlorine at 1 ppm), however, complete decomposition of BPA and its chlorinated derivatives was observed. The decrease in BPA and its chlorinated derivatives paralleled the decrease in estrogenic potency evaluated by the induction of vitellogenin (VTG) in the serum of mature male Japanese medaka.

Synthesis and estrogenic activity of bisphenol a mono- and di-beta-D-glucopyranosides, plant metabolites of bisphenol A.

The syntheses and characterization of bisphenol A mono- and di-beta-D-glucopyranosides were undertaken to confirm that these compounds are major plant metabolities of bisphenol A (BPA) and to allow an assessment of their estrogenicity. Synthesis involved the glucosidation of unprotected BPA with glucose penta-acetate with phosphorus oxychloride as catalyst. The estrogenic activity of BPA and its mono- and di-beta-D-glucopyranosides were measured with an enzyme-linked immunosorbent assay (ELISA)-based estrogen receptor competitive binding assay and with a yeast two-hybrid assay adapted to a chemiluminescent reporter gene (for beta-galactosidase). Both methods showed that the estrogenicity of BPA was eliminated by formation of the di-glucoside, but whereas the ELISA-based method indicated that reduced activity remained in the monoglucoside, the yeast two-hybrid method showed the monoglucoside to be inactive. Presumably these results reflect the more complex interactions of test compound and cellular components required to demonstrate estrogenicity in the yeast two-hybrid assay. As these processes parallel those in mammalian cells, the yeast two-hybrid method is likely to be the more realistic assay. The uptake and metabolism of BPA by plants offers the possibility of phytoremediation of contaminated water, but also provides an additional route for the compound to enter the human food chain.

Effects of perinatal exposure to bisphenol A on play behavior of female and male juvenile rats.

In higher vertebrates, estrogen can exert an organizational effect on sexually dimorphic areas of the central nervous system (CNS) during the perinatal phase of development. The possibility that estrogenic pollutants may mimic estrogen action on the CNS during development and produce long-lasting or irreversible effects is an issue of great concern. Bisphenol A (BPA), a compound widely used in the food industry and in dentistry, has proven estrogenic actions. To study its potential developmental effects on behavior, we gave female Sprague-Dawley rats 40 microg/kg/day BPA from conception to weaning postnatal day 21 and 400 microg/kg/day BPA from gestation day 14 to postnatal day 6. After exposure, we studied social behavior in a play situation in juvenile male and female offspring. The attempt to use play behavior to study the effects of BPA yielded some interesting results. We observed an early action of BPA on several behavioral categories in both males and females. In particular we observed a masculinization of female behavior in two behavioral categories (play with females and sociosexual exploration), an effect probably mediated by the estrogenic activity of BPA in the CNS. These long-lasting effects of BPA could have important consequences at individual and population levels.

The activity of bisphenol A depends on both the estrogen receptor subtype and the cell type.

Bisphenol A (BPA), a monomer of plastic used in consumer products, is abundant in the environment and enters the body by ingestion or adsorption. In order to characterize the estrogenic effect of BPA, we performed luciferase assay on three independent cell lines derived from different tissues transfected with either human ERalpha cDNA or ERbeta cDNA. The estrogenic activities of BPA were detectable in all cell lines via both ERalpha and ERbeta. In 293T cells and Hec-1 cells, the estrogenic activities were significantly decreased when cells expressing ERalpha were incubated with 10(-6) M BPA in the presence of 10(-8) M 17beta-estradiol (E2) while the activities via ERbeta were essentially unchanged in the same conditions. Interestingly, no reduction of estrogenic activity was detected in HOS-TE85 cells via either ERalpha or ERbeta. Our results indicate that BPA only acts as an agonist of estrogen via ERbeta whereas it has dual actions as an agonist and antagonist in some types of cells via ERalpha. Thus, the activity of BPA may depend on the ER subtype and the tissue involved.

Differential Interactions of Bisphenol A and 17.BETA.-estradiol with Estrogen Receptor .ALPHA.(ER.ALPHA.) and ER.BETA..

Bisphenol A (BPA), a monomer of plastic used in consumer products, is abundant in the environment and enters the body by ingestion or adsorption. We developed a cell based transcription assay system using a reporter gene under the transcriptional control of estrogen receptor alpha (ERalpha) as well as ERbeta and performed chloramphenicol acetyltransferase (CAT) assay on HeLa cells transfected with either human ERalpha cDNA or ERbeta cDNA to characterize the estrogenic effect of BPA. Estrogenic activity of BPA was detectable at a concentration of 10(-9) M and the activity increased in a dose dependent manner between concentrations of 10(-9) M and 10(-6) M of BPA for both ERalpha and ERbeta. The estrogenic activity of 17beta-estradiol at a concentration of 10(-8) M was almost compatible with that of BPA at the concentration of 10(-6) M of BPA for ERalpha as well as ERbeta. CAT activity was significantly decreased when cells expressing ERalpha were incubated with 10(-6) M of BPA and 10(-8) M of 17beta-estradiol while the activity was essentially the same for ERbeta in the same condition, indicating that BPA exhibits only agonistic action for ERbeta whereas it has dual actions as an agonist and antagonist of estrogen for ERalpha. These results indicates that BPA exerts its effects in ER subtype specific way, thus suggesting that the mode of action of endocrine disruptors are more complex than thought.