Toxicology and human health assessment of decabromodiphenyl ether

Selenomethionine alleviates decabromodiphenyl ether-induced oxidative stress and ferroptosis via the NRF2/GPX4 pathway in the chicken brain

Decabromodiphenyl ether (BDE209) is a toxic environmental pollutant that can cause neurotoxicity, behavioral abnormalities, and cognitive impairment in animals. However, the specific mechanisms of BDE209-induced neurological injury and effective preventative and therapeutic interventions are lacking. Even though selenomethionine (Se-Met) has a significant detoxification effect and protects the nervous system, it remains unclear whether Se-Met can counteract the toxic effects of BDE209. For the in vivo test, we randomly divided 60 1-week-old hy-line white variety chicks into the Con, BDE209, Se-Met, and BDE209 +Se-Met groups. In vitro experiments were performed, exposing chick embryo brain neurons to BDE209, Se-Met, N-Acetylcysteine (NAC, a ROS inhibitor), and RSL3 (a GPX4 inhibitor). We demonstrated that BDE209 induced oxidative stress and ferroptosis in the chicken brain, which mainly manifested as mitochondrial atrophy, cristae breakage, increased Fe2+ and MDA content, decreased antioxidant enzyme activity, and the inhibition of the NRF2/GPX4 signaling pathway in the brain neurons. However, Se-Met supplementation reversed these changes by activating the NRF2/GPX4 pathway, reducing mitochondrial damage, enhancing antioxidant enzyme activity, and alleviating ferroptosis. This study provides insight into the mechanism of BDE209-related neurotoxicity and suggests Se-Met as an effective preventative and control measure against BDE209 poisoning.

Long-lived molecular anions of brominated diphenyl ethers

Resonance electron attachment in a series of brominated diphenyl ethers, namely 4-bromodiphenyl ether (BDPE), 4-bromophenyl ether (BPE), and decabromodiphenyl ether (DBDE), was investigated in the gas phase by means of dissociative electron attachment spectroscopy. In addition to channels of dissociation into stable fragments, long-lived molecular negative ions with an average lifetime relative to autodetachment of the order of 60 µs were found for the last two molecules. In the case of BDPE and BPE, the most intense dissociation channel is the bromine anion, and for DBDE-the [C6Br5O]- anion. The [C6Br5O]- anion sequentially decomposes with the elimination of the bromide anion on a microsecond time scale, which is confirmed by the registration of metastable ions with an apparent mass of 12.8 a.m.u. The electron affinity of the studied molecules and the appearance energy of fragment ions were estimated with CAM-B3LYP/6-311+G(d,p).

Estrogens and development of the rete testis, efferent ductules, epididymis and vas deferens

Estrogen has always been considered the female hormone and testosterone the male hormone. However, estrogen's presence in the testis and deleterious effects of estrogen treatment during development have been known for nearly 90 years, long before estrogen receptors (ESRs) were discovered. Eventually it was learned that testes actually synthesize high levels of estradiol (E2) and sequester high concentrations in the reproductive tract lumen, which seems contradictory to the overwhelming number of studies showing reproductive pathology following exogenous estrogen exposures. For too long, the developmental pathology of estrogen has dominated our thinking, even resulting in the "estrogen hypothesis" as related to the testicular dysgenesis syndrome. However, these early studies and the development of an Esr1 knockout mouse led to a deluge of research into estrogen's potential role in and disruption of development and function of the male reproductive system. What is new is that estrogen action in the male cannot be divorced from that of androgen. This paper presents what is known about components of the estrogen pathway, including its synthesis and target receptors, and the need to achieve a balance between androgen- and estrogen-action in male reproductive tract differentiation and adult functions. The review focuses on what is known regarding development of the male reproductive tract, from the rete testis to the vas deferens, and examines the expression of estrogen receptors and presence of aromatase in the male reproductive system, traces the evidence provided by estrogen-associated knockout and transgenic animal models and discusses the effects of fetal and postnatal exposures to estrogens. Hopefully, there will be enough here to stimulate discussions and new investigations of the androgen:estrogen balance that seems to be essential for development of the male reproductive tract.

Decabromodiphenyl ether (BDE-209) exposure to lactating mice perturbs steroidogenesis and spermatogenesis in adult male offspring

Decabromodiphenyl ether (BDE-209) is widely used as a flame retardant in many products like electronic equipments, plastics, furniture and textiles. BDE-209, a thyroid hormones (THs)-disrupting chemical, affects male reproductive health through altered THs status in mouse model. The present study was designed in continuation to our earlier work to elucidate whether early life exposure to BDE-209 has a long term potential risk to male reproductive health. This study, therefore, aimed to evaluate the effect of maternal BDE-209 exposure during lactation and to elucidate possible mechanism(s) of its action on male reproduction in adult Parkes mice offspring. Lactating female Parkes mice were orally gavaged with 500, and 700 mg/kg body weight of BDE-209 in corn oil from postnatal day (PND) 1 to PND 28 along with 6-propyl-2-thiouracil (PTU)-treated positive controls and vehicle-treated controls. Male pups of lactating dams were euthanized at PND 75. Maternal BDE-209 exposure during lactation markedly affected histoarchitecture of testis and testosterone production with concomitant down-regulation in the expression of various steroidogenic markers in adult offspring. Maternal exposure to BDE-209 during lactation also interfered with germ cell dynamics and oxidative status in testes of adult mice offspring. A decreased expression of connexin 43 and androgen receptor was also evident in testes of these mice offspring; further, number, motility and viability of spermatozoa were also adversely affected in these mice. The results thus provide evidences that maternal exposure to BDE-209 during lactation causes reproductive toxicity in adult mice offspring.

Decarbromodiphenyl ether (BDE-209) promotes monocyte-endothelial adhesion in cultured human aortic endothelial cells through upregulating intercellular adhesion molecule-1

There is growing evidence that exposure to persistent organic pollutants (POPs) is statistically associated with incidence of cardiovascular disease (CVD) or its risk factors. Decarbromodiphenyl ether (BDE-209) is a new POP which exists extensively in human tissues, but its potential effects on CVD have so far received less focus. The adhesion of circulating monocytes to endothelial cells is one of the critical underlying steps in the initiation and development of CVD. In the present study, we investigated the effect of BDE-209 on the adhesion of THP-1 monocytes to human aortic endothelial cells (HAECs) and identified the molecular mechanisms involved. Our results showed that 6.25, 12.5 and 25 µM of BDE-209 exposures caused significant increases in monocyte-endothelial cell adhesion, in a dose-dependent manner. Mechanistically, BDE-209 exposure increased the expression of intercellular adhesion molecule-1 (ICAM-1). Moreover, the up-regulation of ICAM-1 was accompanied by a decrease in the expression of microRNA-141 (miR-141). Furthermore, the up-regulation of ICAM-1 and the increased adhesion induced by BDE-209 could be reversed by miR-141 supplement. Taken together, our results show that BDE-209 potentiates monocyte-endothelial cell interaction via miR-141/ICAM-1 pathway in HAECs.

Decabromodiphenyl ether (BDE-209) enhances foam cell formation in human macrophages via augmenting Toll-like receptor 4-dependent lipid uptake

Growing epidemiological evidence is substantiating an association between exposure to persistent organic pollutants (POPs) and incidence of atherosclerosis. Decabromodiphenyl ether (BDE-209) is a new POP which presents extensively in human populations; whether this contaminant is potentially arteriosclerotic remains unclear. In this study, we investigated the effects of BDE-209 on macrophage-derived foam cell formation, a hallmark of early atherosclerosis, using THP-1-derived macrophages incubated with oxidized low-density lipoprotein (oxLDL) as a foam cell model. The results showed that 6.25, 12.5 and 25.0 μM of BDE-209 significantly enhanced lipid accumulation inside the foam cells, in a dose-dependent manner. Further mechanism assays suggested that BDE-209 significantly increased the expression of Toll-like receptor 4 (TLR4), a signal transducing integral membrane protein mediating lipid uptake in macrophages, at both the mRNA and protein levels. In contrast, there was no significant changes for several key regulators involving in lipid efflux, lipogenesis, and lipid oxidation in macrophages. Furthermore, the augmented lipid accumulation was almost completely abrogated by treatment with an anti-TLR4 antibody. Together, these data illustrate that BDE-209 enhances oxLDL-induced macrophage foam cell formation via augmenting TLR4-dependent lipid uptake in the cells.

Chemical alternatives assessment of different flame retardants - A case study including multi-walled carbon nanotubes as synergist

Flame retardants (FRs) are a diverse group of chemicals used as additives in a wide range of products to inhibit, suppress, or delay ignition and to prevent the spread of fire. Halogenated FRs (HFRs) are widely used because of their low impact on other material properties and the low loading levels necessary to meet the required flame retardancy. Health and environmental hazards associated with some halogenated FRs have driven research for identifying safer alternatives. A variety of halogen-free FRs are available on the market, including organic (phosphorus and nitrogen based chemicals) and inorganic (metals) materials. Multi-walled carbon nanotubes (MWCNT) have been demonstrated to act as an effective/synergistic co-additive in some FR applications and could thereby contribute to reducing the loading of FRs in products and improving their performance. As part of the FP7 project DEROCA we carried out a chemical alternatives assessment (CAA). This is a methodology for identifying, comparing and selecting safer alternatives to chemicals of concern based on criteria for categorising human and environmental toxicity as well as environmental fate. In the project we assessed the hazard data of different halogen-free FRs to be applied in 5 industrial and consumer products and here we present the results for MWCNT, aluminium diethylphosphinate, aluminium trihydroxide, N-alkoxy hindered amines and red phosphorus compared to the HFR decabromodiphenylether. We consulted the REACH guidance, the criteria of the U.S.-EPA Design for Environment (DfE) and the GreenScreen® Assessment to assess and compare intrinsic properties affecting the hazard potential. A comparison/ranking of exposure reference values such as Derived No Effect Levels (DNELs) showed that FRs of concern are not identified by a low DNEL. A comparison based on hazard designations according to the U.S.-EPA DfE and GreenScreen® for human health endpoints, aquatic toxicity and environmental fate showed that the major differences between FRs of concern and their proposed alternatives are the potential for bioaccumulation and CMR (carcinogenic, mutagenic or reprotoxic) effects. As most alternatives are inorganic chemicals, persistence (alone) is not a suitable criterion. From our experiences in carrying out a CAA we conclude: i) REACH registration dossiers provide a comprehensive source of hazard information for an alternative assessment. It is important to consider that the presented data is subject to changes and its quality is variable. ii) Correct identification of the chemicals is crucial to retrieve the right data. This can be challenging for mixtures, reaction products or nanomaterials or when only trade names are available. iii) The quality of the data and the practice on how to fill data gaps can have a huge impact on the results and conclusions. iv) Current assessment criteria have mainly been developed for organic chemicals and create challenges when applied to inorganic solids, including nanomaterials. It is therefore crucial to analyse and report uncertainties for each decision making step.

Factors influencing leaching of PBDEs from waste cathode ray tube plastic housings

Samples of waste cathode ray tube (CRT) plastic housings were exposed to Milli-Q® water containing dissolved humic matter at concentrations of 0, 100 and 1000mgL(-1) as leaching fluid under laboratory conditions, and polybrominated diphenyl ethers (PBDEs) determined in the resulting leachate. Despite the relatively hydrophobic physicochemical properties of PBDEs, concentrations of ƩPBDEs in the leachate from the leaching experiments in this study ranged from 14,000 to 200,000ngL(-1). PBDE leaching appears to be a second order process, whereby a period of initially intense dissolution of more labile PBDEs is followed by a slower stage corresponding to external diffusion of the soluble residue in the material. The bulk of transfer of PBDEs to the leaching fluid occurs within the first 6h of contact, during which time we suggest that the most labile PBDEs are "washed" off the surface of the CRT plastics. The predominant congeners in the chips were BDE-209 (2600mgkg(-1)) and BDE 183 (220mgkg(-1)). The impacts on PBDE leaching of leachate pH and temperature were also examined. Increasing the temperature of leaching fluids from 20 to 80°C, enhances the leachability of BDE-209 and BDE-99 from plastics. In all cases, the alkaline pH8.5 examined, resulted in the greatest PBDE concentrations in leachate. Agitation of the waste/leachate mixture enhances PBDE leaching from CRT plastics. Potential evidence for debromination of heavy congeners to the lower brominated and more bioavailable BDEs was observed. Specifically, BDEs-47, -85 and -100 were detected in the leachates, but were absent from the CRT plastics themselves.

Bisphenol-A and Sleep Adequacy among Adults in the National Health and Nutrition Examination Surveys

STUDY OBJECTIVES

To evaluate bisphenol-A (BPA) level and its relationship to sleep adequacy in a nationally representative sample of U.S. adults.

METHODS

A population-based cross-sectional study was conducted using 2005-2010 National Health and Nutrition Examination Survey whereby data were collected using in-person interviews, physical examination and laboratory testing. BPA level was measured in urine samples and analyzed as loge-transformed variable and in quartiles (< 0.9 ng/mL; 0.9 to < 1.9 ng/mL; 1.9 to < 3.7 ng/mL; 3.7+ ng/mL). Sleep adequacy was operationalized with three questions: "How much sleep do you usually get at night on weekdays or workdays?", "Have you ever told a doctor or other health professionals that you have trouble sleeping?" and "Have you ever been told by a doctor or other health professional that you have a sleep disorder?" Sleep duration was further categorized as (< 6 h, ≥ 6 h); (< 7 h, 7-8 h, > 8 h); (< 5 h, 5-6 h, 7-8 h, ≥ 9 h). Linear, binary, and ordinal logistic regression models were constructed.

RESULTS

Loge-transformed BPA level was inversely related to sleep duration defined, in hours, as a continuous variable, a dichotomous variable (≥ 6, < 6), or an ordinal variable (≥ 9, 7-8, 5-6, < 5), after adjustment for confounders. Help-seeking behavior for sleep problems and diagnosis with sleep disorders were not significantly associated with loge-transformed BPA level in fully adjusted models.

CONCLUSIONS

Loge-transformed BPA level may be associated with fewer hours of sleep among U.S. adults, with implications for prevention. Further research involving diverse populations are needed to confirm these study findings.

Occurrence and Profiles of the Artificial Endocrine Disruptor Bisphenol A and Natural Endocrine Disruptor Phytoestrogens in Urine from Children in China

BACKGROUND

Exposure to artificial or natural endocrine disruptors, such as bisphenol A (BPA) and phytoestrogens has been demonstrated to have health effects, especially in children. Biomonitoring of BPA and phytoestrogens in human urine can be used to assess the intake levels of these compounds.

METHODS

In this study, BPA and phytoestrogens in urine specimens (n = 256) collected from children in China were measured by liquid chromatography (LC)-tandem mass spectrometry (MS/MS).

RESULTS

BPA was detected in most specimens, with a geometric mean concentration of 1.58 ng/mL. For the first time, levels of urinary phytoestrogens in Chinese children were reported. Daidzein and enterolactone are the typical isoflavones and lignans compounds in urine, respectively.

CONCLUSIONS

Relatively high levels of urinary BPA indicate an increasing risk of BPA exposure to Chinese children. Urinary concentrations of daidzein in Chinese children are higher when compared with those reported in the U.S. children, while concentrations of urinary enterolactone and enterodiols are significantly lower. This suggests a significant difference in phytoestrogen intake between the children from China and from the U.S.

Methods for studying human organogenesis

This review details methods for utilizing D & C suction abortus specimens as a source of human fetal organs to study the morphogenetic and molecular mechanisms of human fetal organ development. By this means it is possible to design experiments elucidating the molecular mechanisms of human fetal organ development and to compare and contrast human developmental mechanisms with that of laboratory animals. Finally human fetal organs can be grown in vivo as grafts to athymic mice, thus allowing ethical analysis of potential adverse effects of environmental toxicants.

A review of the carcinogenic potential of bisphenol A

The estrogenic properties of bisphenol A (BPA), a ubiquitous synthetic monomer that can leach into the food and water supply, have prompted considerable research into exposure-associated health risks in humans. Endocrine-disrupting properties of BPA suggest it may impact developmental plasticity during early life, predisposing individuals to disease at doses below the oral reference dose (RfD) established by the Environmental Protection Agency in 1982. Herein, we review the current in vivo literature evaluating the carcinogenic properties of BPA. We conclude that there is substantial evidence from rodent studies indicating that early-life BPA exposures below the RfD lead to increased susceptibility to mammary and prostate cancer. Based on the definitions of "carcinogen" put forth by the International Agency for Research on Cancer and the National Toxicology Program, we propose that BPA may be reasonably anticipated to be a human carcinogen in the breast and prostate due to its tumor promoting properties.

Soy but not bisphenol A (BPA) or the phytoestrogen genistin alters developmental weight gain and food intake in pregnant rats and their offspring

Endocrine disrupting compounds (EDCs) are hypothesized to promote obesity and early puberty but their interactive effects with hormonally active diets are poorly understood. Here we assessed individual and combinatorial effects of soy diet or the isoflavone genistein (GEN; administered as the aglycone genistin GIN) with bisphenol A (BPA) on body weight, ingestive behavior and female puberal onset in Wistar rats. Soy-fed dams gained less weight during pregnancy and, although they consumed more than dams on a soy-free diet during lactation, did not become heavier. Their offspring (both sexes), however, became significantly heavier (more pronounced in males) pre-weaning. Soy also enhanced food intake and accelerated female pubertal onset in the offspring. Notably, pubertal onset was also advanced in females placed on soy diet at weaning. Males exposed to BPA plus soy diet, but not BPA alone, had lighter testes. BPA had no independent effects.

Tracking the sources of polybrominated diphenyl ethers in birds: foraging in waste management facilities results in higher DecaBDE exposure in males

Differences in feeding ecology are now recognized as major determinants of inter-individual variations in contaminant profiles of free-ranging animals, but exceedingly little attention has been devoted to the role of habitat use. Marked inter-individual variations and high levels of polybrominated diphenyl ethers (PBDEs) (e.g., DecaBDE) have previously been documented in ring-billed gulls (Larus delawarensis) breeding in a colony near Montreal (QC, Canada). However, the environmental sources of these compounds, and thus the reasons causing these large inter-individual variations remain unidentified. In the present study, we used GPS-based telemetry (±5 to 10m precision) to track ring-billed gulls from this colony to reconstruct their movements at the landscape level. We related habitat use of individual gulls (n=76) to plasma concentrations (ng/g ww) and relative contributions (percentages) to Σ38PBDEs of major congeners in the internationally restricted PentaBDE and current-use DecaBDE mixtures. Male gulls that visited waste management facilities (WMFs; i.e., landfills, wastewater treatment plants and related facilities; 25% of all GPS-tracked males) exhibited greater DecaBDE (concentrations and percentages) and lower PentaBDE (percentages) relative to those that did not. In contrast, no such relationships were found in females. Moreover, in males, DecaBDE (concentrations and percentages) increased with percentages of time spent in WMFs (i.e., ~5% of total foraging time), while PentaBDE (percentages) decreased. No relationships between percentages of time spent in other habitats (i.e., urban areas, agriculture fields, and St. Lawrence River) were found in either sex. These findings suggest that animals breeding in the vicinity of WMFs as well as mobile species that only use these sites for short stopovers to forage, could be at risk of enhanced DecaBDE exposure.

Effects of two polybrominated diphenyl ethers (BDE-47, BDE-209) on the swimming behavior, population growth and reproduction of the rotifer Brachionus plicatilis

Polybrominated diphenyl ethers (PBDEs) are new kinds of persistent organic pollutants (POPs) and their potential threats to the equilibrium and sustainability of marine ecosystems have raised worldwide concerns. Here, two kinds of PBDEs, tetra-BDE (BDE-47) and deca-BDE (BDE-209) were applied, and their toxic effects on the swimming behavior, population growth and reproduction of Brachionus plicatilis were investigated. The results showed that: (1) The actual concentrations of BDE-47 and -209 in the seawater phase measured by GC-MS (Gas Chromatography-Mass Spectrometer) were much lower than their nominal concentrations. (2) In accordance with the 24-hr acute tests, BDE-209 did not show any obvious swimming inhibition to rotifers, but a good correlation did exist between the swimming inhibition rate and BDE-47 concentration suggesting that BDE-47 is more toxic than BDE-209. (3) Both BDE-47 and -209 had a significant influence on the population growth and reproduction parameters of B. plicatilis including the population growth rate, the ratio of ovigerous females/non-ovigerous females (OF/NOF), the ratio of mictic females/amictic females (MF/AF), resting egg production and the mictic rate, which indicate that these parameters in B. plicatilis population were suitable for monitoring and assessing PBDEs. Our results suggest that BDE-47 and -209 are not acute lethal toxicants and may pose a low risk to marine rotifers at environmental concentrations for short-term exposure. They also accumulate differently into rotifers. Further research data are needed to understand the mechanisms responsible for the effects caused by PBDEs and to assess their risks accurately.

The effects of postnatal exposure to low-dose bisphenol-A on activity-dependent plasticity in the mouse sensory cortex

Bisphenol-A (BPA) is a monomer used in the production of polycarbonate plastics, epoxies and resins and is present in many common household objects ranging from water bottles, can linings, baby bottles, and dental resins. BPA exposure has been linked to numerous negative health effects throughout the body, although the mechanisms of BPA action on the developing brain are still poorly understood. In this study, we sought to investigate whether low dose BPA exposure during a developmental phase when brain connectivity is being organized can cause long-term deleterious effects on brain function and plasticity that outlast the BPA exposure. Lactating dams were orally exposed to 25 μg/kg/day of BPA (one half the U.S. Environmental Protection Agency's 50 μg/kg/day rodent dose reference) or vehicle alone from postnatal day (P)5 to P21. Pups exposed to BPA in their mother's milk exhibited deficits in activity-dependent plasticity in the visual cortex during the visual critical period (P28). To determine the possible mechanisms underlying BPA action, we used immunohistochemistry to examine histological markers known to impact cortical maturity and developmental plasticity and quantified cortical dendritic spine density, morphology, and dynamics. While we saw no changes in parvalbumin neuron density, myelin basic protein expression or microglial density in BPA-exposed animals, we observed increases in spine density on apical dendrites in cortical layer five neurons but no significant alterations in other morphological parameters. Taken together our results suggest that exposure to very low levels of BPA during a critical period of brain development can have profound consequences for the normal wiring of sensory circuits and their plasticity later in life.

Extent and mechanisms of brominated flame retardant emissions from waste soft furnishings and fabrics: A critical review

Use of brominated flame retardants (BFRs) in soft furnishings has occurred for over thirty years with the phase out of polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD) only relatively recently begun. As products treated with BFRs reach the end of their lifecycle they enter the waste stream, thereby constituting an important and increasing reservoir of these chemicals. This review highlights the dearth of data on the extent and potential mechanisms of BFR emissions from waste soft furnishings. However, insights into what may occur are provided by scrutiny of the larger (though still incomplete) database related to BFR emissions from electronic waste (e-waste). In many countries, municipal landfills have historically been the primary disposal method of waste consumer products and therefore represent a substantial reservoir of BFRs. Published data for BFR emissions to both air and water from landfill and other waste disposal routes are collated, presented and reviewed. Reported concentrations of PBDEs in landfill leachate range considerably from <1ngL(-1) to 133,000ngΣPBDEL(-1). In addition to direct migration of BFRs from waste materials; there is evidence that some higher brominated flame retardants are able to undergo degradation and debromination during waste treatment, that in some instances may lead to the formation of more toxic and bioavailable compounds. We propose that waste soft furnishings be treated with the same concern as e-waste, given its potential as a reservoir and source of environmental contamination with BFRs.

Green tea potentially ameliorates bisphenol a-induced oxidative stress: an in vitro and in silico study

The present investigation was an attempt to elucidate oxidative stress induced by bisphenol A on erythrocytes and its amelioration by green tea extract. For this, venous blood samples from healthy human adults were collected in EDTA vials and used for preparation of erythrocytes suspension. When erythrocyte suspensions were treated with different concentrations of BPA/H2O2, a dose-dependent increase in hemolysis occurred. Similarly, when erythrocytes suspensions were treated with either different concentrations of H2O2 (0.05-0.25 mM) along with BPA (50 μg/mL) or 0.05 mM H2O2 along with different concentrations of BPA (50-250 μg/mL), dose-dependent significant increase in hemolysis occurred. The effect of BPA and H2O2 was found to be additive. For the confirmation, binding capacity of bisphenol A with erythrocyte proteins (hemoglobin, catalase, and glutathione peroxidase) was inspected using molecular docking tool, which showed presence of various hydrogen bonds of BPA with the proteins. The present data clearly indicates that BPA causes oxidative stress in a similar way as H2O2 . Concurrent addition of different concentrations (10-50 μg/mL) of green tea extract to reaction mixture containing high dose of bisphenol A (250 μg/mL) caused concentration-dependent amelioration in bisphenol A-induced hemolysis. The effect was significant (P < 0.05). It is concluded that BPA-induced oxidative stress could be significantly mitigated by green tea extract.

Green tea potentially ameliorates bisphenol a-induced oxidative stress: an in vitro and in silico study

The present investigation was an attempt to elucidate oxidative stress induced by bisphenol A on erythrocytes and its amelioration by green tea extract. For this, venous blood samples from healthy human adults were collected in EDTA vials and used for preparation of erythrocytes suspension. When erythrocyte suspensions were treated with different concentrations of BPA/H₂O₂, a dose-dependent increase in hemolysis occurred. Similarly, when erythrocytes suspensions were treated with either different concentrations of H₂O₂ (0.05–0.25 mM) along with BPA (50 μg/mL) or 0.05 mM H₂O₂ along with different concentrations of BPA (50–250 μg/mL), dose-dependent significant increase in hemolysis occurred. The effect of BPA and H₂O₂ was found to be additive. For the confirmation, binding capacity of bisphenol A with erythrocyte proteins (hemoglobin, catalase, and glutathione peroxidase) was inspected using molecular docking tool, which showed presence of various hydrogen bonds of BPA with the proteins. The present data clearly indicates that BPA causes oxidative stress in a similar way as H₂O₂ . Concurrent addition of different concentrations (10–50 μg/mL) of green tea extract to reaction mixture containing high dose of bisphenol A (250 μg/mL) caused concentration-dependent amelioration in bisphenol A-induced hemolysis. The effect was significant (P < 0.05). It is concluded that BPA-induced oxidative stress could be significantly mitigated by green tea extract.

Bisphenol-A: epigenetic reprogramming and effects on reproduction and behavior

Bisphenol A (BPA) is a synthetic compound used in the production of many polycarbonate plastics and epoxy resins. It is one of the most widely produced chemicals in the world today and is found in most canned goods, plastics, and even household dust. Exposure to BPA is almost universal: most people have measurable amounts of BPA in both urine and serum. BPA is similar in structure to estradiol and can bind to multiple targets both inside and outside the nucleus, in effect acting as an endocrine disruptor. Research on BPA exposure has accelerated in the past decade with findings suggesting that perinatal exposure to BPA can negatively impact both male and female reproduction, create alterations in behavior, and act as a carcinogen. BPA can have both short term and long term effects with the latter typically occurring through epigenetic mechanisms such as DNA methylation. This review will draw on both human and animal studies in an attempt to synthesize the literature and examine the effects of BPA exposure on reproduction, behavior, and carcinogenesis with a focus on the potential epigenetic mechanisms by which it acts.

Sex-specific Esr2 mRNA expression in the rat hypothalamus and amygdala is altered by neonatal bisphenol A exposure

Perinatal life is a critical window for sexually dimorphic brain organization, and profoundly influenced by steroid hormones. Exposure to endocrine-disrupting compounds may disrupt this process, resulting in compromised reproductive physiology and behavior. To test the hypothesis that neonatal bisphenol A (BPA) exposure can alter sex-specific postnatal Esr2 (Erβ) expression in brain regions fundamental to sociosexual behavior, we mapped Esr2 mRNA levels in the principal nucleus of the bed nucleus of the stria terminalis (BNSTp), paraventricular nucleus (PVN), anterior portion of the medial amygdaloid nucleus (MeA), super optic nucleus, suprachiasmatic nucleus, and lateral habenula across postnatal days (PNDs) 0-19. Next, rat pups of both sexes were subcutaneously injected with 10 μg estradiol benzoate (EB), 50 μg/kg BPA (LBPA), or 50 mg/kg BPA (HBPA) over the first 3 days of life and Esr2 levels were quantified in each region of interest (ROI) on PNDs 4 and 10. EB exposure decreased Esr2 signal in most female ROIs and in the male PVN. In the BNSTp, Esr2 expression decreased in LBPA males and HBPA females on PND 10, thereby reversing the sex difference in expression. In the PVN, Esr2 mRNA levels were elevated in LBPA females, also resulting in a reversal of sexually dimorphic expression. In the MeA, BPA decreased Esr2 expression on PND 4. Collectively, these data demonstrate that region- and sex-specific Esr2 expression is vulnerable to neonatal BPA exposure in regions of the developing brain critical to sociosexual behavior in rat.

Exposure assessment and health risk of poly-brominated diphenyl ether (PBDE) flame retardants in the indoor environment of elementary school students in Korea

This study assessed the health risks of elementary school students' exposure to PBDEs via different possible pathways in children's facilities. After PBDE contamination was measured, exposure was demonstrated to occur through multiple routes, including inhalation of indoor dust, dermal contact with products' surfaces and children's hands, and incidental dust ingestion. Samples were collected from various children's facilities (30 elementary schools, 31 private academies, 12 living rooms and bedrooms in houses, 5 public libraries of children's literature, and 3 large hypermalls) in summer (Jul-Sep, 2008) and winter (Jan-Feb, 2009). The hazard index (HI) was estimated for non-carcinogens and PBDEs, such as TeBDE, PeBDE, HxBDE, OcBDE, and DeBDE. PBDEs were detected in all floor dust samples, 99% of indoor air samples, 94% of product-wipe samples, and 86% of hand wipe samples. The average levels of PBDEs ranged from 0.19 to 1.06 ng/m(3) in indoor air, 4623 to 6,650 ng/g-dust in floor dust, 0.012 to 0.103 ng/cm(2) on product surfaces, and 7.89 to 25.38 ng/hand on the surface of children's hands. The HI for school children via multimedia and multipathway exposure to PBDEs did not exceed 1.0. The exposure to PBDEs at home (approximately 80%) was dominant. The contribution rates of PBDE risk were 77% and 15% via dust ingestion at home and at elementary school, respectively; thus, intake of floor dust was determined to be the primary route of exposure.

Sex differences in the association of urinary bisphenol-A concentration with selected indices of glucose homeostasis among U.S. adults

PURPOSE

Emerging evidence suggests that exposure to endocrine disruptors may initiate or exacerbate adiposity and associated health problems. This study examined sex differences in the association of urinary level of bisphenol-A (BPA) with selected indices of glucose homeostasis among U.S. adults.

METHODS

Data analyses were performed using a sample of 1586 participants from the 2005 to 2008 National Health and Nutrition Examination Surveys. BPA level and the ratio of BPA-to-creatinine level were defined as log-transformed variables and in quartiles. Selected indices of glucose homeostasis were defined using fasting glucose and insulin data. Multivariate linear and logistic regression models for the hypothesized relationships were constructed after controlling for age, sex, race, education, marital status, smoking status, physical activity, total dietary intake, and urinary creatinine concentration.

RESULTS

Taking the first quartile as a referent, the third quartile of BPA level was positively associated with log-transformed level of insulin and β-cell function (homeostasis model assessment for β-cell function) as well as insulin resistance (log-transformed homeostasis model assessment for insulin resistance; homeostasis model assessment for insulin resistance ≥2.5), with significant BPA-by-sex interaction; these associations were stronger among males than among females. Irrespective of sex, the ratio of BPA-to-creatinine level was not predictive of indices of glucose homeostasis.

CONCLUSIONS

A complex association may exist between BPA and hyperinsulinemia among adult U.S. men. Prospective cohort studies are needed to further elucidate endocrine disruptors as determinants of adiposity-related disturbances.

Evaluation of simple in vitro to in vivo extrapolation approaches for environmental compounds

As part of an effort to support in silico/in vitro based risk assessment, we evaluated the accuracy associated with conducting simple in vitro to in vivo extrapolation (IVIVE) for environmental compounds using available in vitro human metabolism data. The IVIVE approach was applied to a number of compounds with a wide range of properties spanning the diversity of characteristics of environmental compounds, and where possible the resulting estimates of the in vivo steady-state blood concentration were compared with estimates derived on the basis of human in vivo kinetic data. There appears to be a systematic bias in the estimation of intrinsic clearance (Clint) from in vitro versus in vivo data, with in vitro based estimates underestimating in vivo clearance for small values of Clint but with the opposite relationship at large values of Clint. Nevertheless, the resulting estimates of Css were in good agreement. The chief drawback of the simple approach used in this study, which performs the IVIVE prediction for the parent compound only, is that it is not applicable for toxicity associated with a metabolite.

Regulatory decisions on endocrine disrupting chemicals should be based on the principles of endocrinology

For years, scientists from various disciplines have studied the effects of endocrine disrupting chemicals (EDCs) on the health and wellbeing of humans and wildlife. Some studies have specifically focused on the effects of low doses, i.e. those in the range that are thought to be safe for humans and/or animals. Others have focused on the existence of non-monotonic dose-response curves. These concepts challenge the way that chemical risk assessment is performed for EDCs. Continued discussions have clarified exactly what controversies and challenges remain. We address several of these issues, including why the study and regulation of EDCs should incorporate endocrine principles; what level of consensus there is for low dose effects; challenges to our understanding of non-monotonicity; and whether EDCs have been demonstrated to produce adverse effects. This discussion should result in a better understanding of these issues, and allow for additional dialog on their impact on risk assessment.

Effects of decabromodiphenyl ether (BDE-209) on the avoidance response, survival, growth and reproduction of earthworms (Eisenia fetida)

The effects of decabromodiphenyl ether (BDE-209) on avoidance response, survival, growth, and reproduction of earthworms (Eisenia fetida) were investigated under laboratory conditions using natural and artificial soils as substrate. Results showed that no significant avoidance response was observed when earthworms were exposed to 0.1-1000 mg/kg of BDE-209 for 48 h. After 28-days exposure, no significant effects on survival and growth of adult earthworms was induced by 0.1-1000 mg/kg of BDE-209 indicating the Lowest Observed Effect Level (LOEL) of BDE-209 on their survival and body weight was more than 1000 mg/kg. Except for a significant decrease in the number of juveniles per hatched cocoon in artificial soils at 1000 mg/kg of BDE-209, no significant effects on reproductive parameters (e.g. cocoon production per earthworms, weight per cocoon and cocoon hatchability) were observed. These results suggest that adult earthworms have a strong tolerance for BDE-209 exposure in soils, but a potential toxicity does exist for earthworm embryos or juveniles.

A critique of the European Commission document, "State of the Art Assessment of Endocrine Disrupters"

In this commentary, we critique a recently finalized document titled "State of the Art Assessment of Endocrine Disrupters" (SOA Assessment). The SOA Assessment was commissioned by the European Union Directorate-General for the Environment to provide a basis for developing scientific criteria for identifying endocrine disruptors and reviewing and possibly revising the European Community Strategy on Endocrine Disrupters. In our view, the SOA Assessment takes an anecdotal approach rather than attempting a comprehensive assessment of the state of the art or synthesis of current knowledge. To do the latter, the document would have had to (i) distinguish between apparent associations of outcomes with exposure and the inference of an endocrine-disruption (ED) basis for those outcomes; (ii) constitute a complete and unbiased survey of new literature since 2002 (when the WHO/IPCS document, "Global Assessment of the State-of-the-Science of Endocrine Disruptors" was published); (iii) consider strengths and weaknesses and issues in interpretation of the cited literature; (iv) follow a weight-of-evidence methodology to evaluate evidence of ED; (v) document the evidence for its conclusions or the reasoning behind them; and (vi) present the evidence for or reasoning behind why conclusions that differ from those drawn in the 2002 WHO/IPCS document need to be changed. In its present form, the SOA Assessment fails to provide a balanced and critical assessment or synthesis of literature relevant to ED. We urge further evidence-based evaluations to develop the needed scientific basis to support future policy decisions.

Neonatal Bisphenol A exposure alters sexually dimorphic gene expression in the postnatal rat hypothalamus

Developmental exposure to Bisphenol A (BPA), a component of polycarbonate and epoxy resins, has been purported to adversely impact reproductive function in female rodents. Because neonatal life is a critical window for the sexual dimorphic organization of the hypothalamic-pituitary-gonadal (HPG) axis, interference with this process could underlie compromised adult reproductive physiology. The goal of the present study was to determine if neonatal BPA exposure interferes with sex specific gene expression of estrogen receptor alpha (ERα), ER beta (ERβ) and kisspeptin (Kiss1) in the anterior and mediobasal hypothalamus. Long Evans (LE) neonatal rats were exposed to vehicle, 10μg estradiol benzoate (EB), 50mg/kg BPA or 50μg/kg BPA by subcutaneous injection daily from postnatal day 0 (PND 0) to PND 2. Gene expression was assessed by in situ hybridization on PNDs 4 and 10. Within the anterior hypothalamus ERα expression was augmented by BPA in PND 4 females, then fell to male-typical levels by PND 10. ERβ expression was not altered by BPA on PND 4, but significantly decreased or eliminated in both sexes by PND 10. Kiss1 expression was diminished by BPA in the anterior hypothalamus, especially in females. There were no significant impacts of BPA in the mediobasal hypothalamus. Collectively, BPA effects did not mirror those of EB. The results show that neonatal hypothalamic ER and Kiss1 expression is sensitive to BPA exposure. This disruption may alter sexually dimorphic hypothalamic organization and underlie adult reproductive deficiencies. Additionally, the discordant effects of EB and BPA indicate that BPA likely disrupts hypothalamic organization by a mechanism other than simply acting as an estrogen mimic.

Effects of in utero exposure to Bisphenol A or diethylstilbestrol on the adult male reproductive system

The objective of this study was to determine whether in utero exposure to Bisphenol A (BPA) induced reproductive tract abnormalities in the adult male testis. Using the C57/Bl6 mouse, we examined sex-organ weights, anogenital distance, and testis histopathology in adult males exposed in utero via oral gavage to sesame oil, 50 µg/kg BPA, 1000 µg/kg BPA, or 2 µg/kg diethylstilbestrol (DES) as a positive control from gestational days 10 to 16. No changes in sperm production or germ cell apoptosis were observed in adult testes after exposure to either chemical. Adult mRNA levels of genes associated with sexual maturation and differentiation, GATA4 and ID2, were significantly lower only in DES-exposed testes. In summary, the data indicate no gross alterations in spermatogenesis after in utero exposure to BPA or DES. At the molecular level, in utero exposure to DES, but not BPA, leads to decreased mRNA expression of genes associated with Sertoli cell differentiation.

Preimplantation exposure to bisphenol A (BPA) affects embryo transport, preimplantation embryo development, and uterine receptivity in mice

To investigate the effects of bisphenol A (BPA) on embryo and uterine factors in embryo implantation, timed pregnant C57BL6 females were treated subcutaneously with 0, 0.025, 0.5, 10, 40, and 100mg/kg/day BPA from gestation days 0.5-3.5. In 100mg/kg/day BPA-treated females, no implantation sites were detected on day 4.5 but retention of embryos in the oviduct and delayed embryo development were detected on day 3.5. When untreated healthy embryos were transferred to pseudopregnant females treated with 100mg/kg/day BPA, no implantation sites were detected on day 4.5. In 40 mg/kg/day BPA-treated females, delayed implantation and increased perinatal lethality of their offspring were observed. Implantation seemed normal in the rest BPA-treated groups or the female offspring from 40 mg/kg/day BPA-treated group. These data demonstrate the adverse effects of high doses of BPA on processes critical for embryo implantation: embryo transport, preimplantation embryo development, and establishment of uterine receptivity.

Bisphenol A increases mammary cancer risk in two distinct mouse models of breast cancer

Bisphenol A (BPA) is an industrial plasticizer that leaches from food containers during normal usage, leading to human exposure. Early and chronic exposure to endocrine-disrupting environmental contaminants such as BPA elevates the potential for long-term health consequences. We examined the impact of BPA exposure on fetal programming of mammary tumor susceptibility as well as its growth promoting effects on transformed breast cancer cells in vivo. Fetal mice were exposed to 0, 25, or 250 μg/kg BPA by oral gavage of pregnant dams. Offspring were subsequently treated with the known mammary carcinogen, 7,12-dimethylbenz[a]anthracene (DMBA). While no significant differences in postnatal mammary development were observed, both low- and high-dose BPA cohorts had a statistically significant increase in susceptibility to DMBA-induced tumors compared to vehicle-treated controls. To determine if BPA also promotes established tumor growth, MCF-7 human breast cancer cells were subcutaneously injected into flanks of ovariectomized NCR nu/nu female mice treated with BPA, 17beta-estradiol, or placebo alone or combined with tamoxifen. Both estradiol- and BPA-treated cohorts formed tumors by 7 wk post-transplantation, while no tumors were detected in the placebo cohort. Tamoxifen reversed the effects of estradiol and BPA. We conclude that BPA may increase mammary tumorigenesis through at least two mechanisms: molecular alteration of fetal glands without associated morphological changes and direct promotion of estrogen-dependent tumor cell growth. Both results indicate that exposure to BPA during various biological states increases the risk of developing mammary cancer in mice.

Degradation of gas phase decabromodiphenyl ether by resonant interaction with low-energy electrons

Resonance electron attachment in a series of brominated phenyl ethers, including decabromodiphenyl ether (DBDE), was investigated in the gas phase by means of electron transmission spectroscopy (ETS) and dissociative electron attachment spectroscopy (DEAS). Attachment of thermal electrons to DBDE leads to various dissociative decay channels of the temporary molecular anion. In contrast to other bromophenyl ethers, the bromide anion is not the most intense negative fragment. The neutral counterparts of the observed [Br(2)](-) and [C(6)Br(4)O](-) anion fragments are ascribed to the closed-shell species octabromodibenzofuran and hexabromobenzene, respectively, although their formation implies complex atomic rearrangements. Density functional theory calculations are employed to evaluate electron affinities, thermodynamic energy thresholds for production of the anion fragments observed in the DEA spectra and the proton affinities of the corresponding neutral radicals. Since DBDE is one of the most widespread organic pollutants, the present gas-phase DEA study can provide indications on the reaction mechanisms which occur in vivo and cause injuries to living cells.