The developmental toxicity of bisphenol A in rats and mice

Nitrogen-doped titanium dioxide/schwertmannite nanocomposites as heterogeneous photo-Fenton catalysts with enhanced efficiency for the degradation of bisphenol A

Potential health risks related to environmental endocrine disruptors (EEDs) have aroused research hotspots at the forefront of water treatment technologies. Herein, nitrogen-doped titanium dioxide/schwertmannite nanocomposites (N-TiO2/SCH) have been successfully developed as heterogeneous catalysts for the degradation of typical EEDs via photo-Fenton processes. Due to the sustainable Fe(III)/Fe(II) conversion induced by photoelectrons, as-prepared N-TiO2/SCH nanocomposites exhibit much enhanced efficiency for the degradation of bisphenol A (BPA; ca. 100% within 60 min under visible irradiation) in a wide pH range of 3.0-7.8, which is significantly higher than that of the pristine schwertmannite (ca. 74.5%) or N-TiO2 (ca. 10.8%). In this photo-Fenton system, the efficient degradation of BPA is mainly attributed to the oxidation by hydroxyl radical (•OH) and singlet oxygen (1O2). Moreover, the possible catalytic mechanisms and reaction pathway of BPA degradation are systematically investigated based on analytical and photoelectrochemical analyses. This work not only provides a feasible means for the development of novel heterogeneous photo-Fenton catalysts, but also lays a theoretical foundation for the potential application of mineral-based materials in wastewater treatment.

Hormone effects of eighteen bisphenol analogues and their effects on cellular homeostasis and the typical signal pathways

Through the transfer chain of surroundings from feed to the farmed-animals and ultimately the corresponding livestock and poultry products, people are exposed to large amounts of bisphenol analogues (BPs), such as rational emissions from manufacturing plants, feed packaging bags and food packaging contact. Some BPs have been reported to show certain toxicological effects, especially, estrogen and endocrine disrupting effect. With the increasing application of BPs, the problem is becoming more and more serious. We systematically studied the hormonal effects of 18 BPs and their effects on cell homeostasis and classical signaling pathways by using classical E-SCREEN assay, fluorescent probes and western blotting. The results confirmed the estrogen-like effect of 13 BPs and 6 BPs obtained high docking scores (Scores < -9.0) for the three receptors simultaneously with the main interactions of hydrophobic, hydrogen and π-stacking of T-type bonds. BPAP regulates cells via apoptosis and steroid signaling pathway by intracellular ROS and mitochondrial followed the caspase pathway. BPE and BPS were involved in the classical NF-κB and Hippo signaling pathways. All data provides scientific basis for the safety risk assessment of endocrine disrupting and cellular homeostasis evaluation of BPs as chronic environmental pollution.

Exploring the potential of ToxCast™ data for mechanism-based prioritization of chemicals in regulatory context: Case study with priority existing chemicals (PECs) under K-REACH

Recent studies have highlighted the potential of ToxCast™ database to mechanism-based prioritization of chemicals. To explore the applicability of ToxCast data in the context of regulatory inventory chemicals, we screened 510 priority existing chemicals (PECs) regulated under the Act on the Registration and Evaluation of Chemical Substances (K-REACH) using ToxCast bioassays. In our analysis, a hit-call data matrix containing 298984 chemical-gene interactions was computed for 949 bioassays with the intended target genes, which enabled the identification of the putative toxicity mechanisms. Based on the reactivity to the chemicals, we analyzed 412 bioassays whose intended target gene families were cytochrome P450, oxidoreductase, transporter, nuclear receptor, steroid hormone, and DNA-binding. We also identified 141 chemicals based on their reactivity in the bioassays. These chemicals are mainly in consumer products including colorants, preservatives, air fresheners, and detergents. Our analysis revealed that in vitro bioactivities were involved in the relevant mechanisms inducing in vivo toxicity; however, this was not sufficient to predict more hazardous chemicals. Overall, the current results point to a potential and limitation in using ToxCast data for chemical prioritization in regulatory context in the absence of suitable in vivo data.

Study of eighteen typical bisphenol analogues as agonist or antagonist for androgen and glucocorticoid at sub-micromolar concentrations in vitro

Bisphenol A and its substitutions are commonly used to manufacture epoxy resins, plastic materials and different kinds of daily necessities. In this process, a large number of bisphenol analogues (BPs) are continuously released directly/indirectly into the environment. Through the chain of environment-feed-farmed-animals-livestock and poultry products, BPs present the low concentration but chronic exposure for surroundings and environment. In addition, BPs have been revealed by extensive studies as emerging endocrine disruptors, whose effects on androgens/glucocorticoids have rarely been mentioned in previous reports. The (anta-) agonist/antagonist properties of 18 classic BPs were investigated in vitro: We assessed the cytotoxicity and examined the luciferase induction values of BPs in MDA-kb2 cells, incubated single or co-incubated with dihydrotestosterone (DHT), dexamethasone, flutamide and RU486 for 24 h. From the concentration of 10^-10 to 10^-5 M, BPs had negligible cytotoxicity for MDA-kb2 cells, except for 4,4'-(9-Fluorenylidene)diphenol with the IC₅₀ 1.32 μM. All 18 BPs had the response to androgen/glucocorticoid receptors (AR/GR). BPs at nanomolar and trace concentrations are agonists, while BPs at micromolar and higher concentrations are antagonists. Molecular docking showed that BPs interact with AR/GR through hydrophobic bonds, hydrogen bonds, T-type π-stacking and water-bridge. These experimental data demonstrate the universality of the endocrine-disrupting effects of BPs and suggest the urgency of paying attention to the usages of BPs.

Maternal and developmental toxicity of Bisphenol-A in SWR/J mice

Bisphenol-A (BPA), an organic compound with two phenol functional groups, is a widely used industrial plasticizer with known estrogenic properties. It is used in the manufacture of epoxy resins and polycarbonate plastics. This study was designed to evaluate and assess the possible toxicity arising from the oral administration of BPA to pregnant mice. Pregnant SWR/J mice (15 mice/group) were administrated oral doses of BPA (125, 250 and 500 mg/kg/day) over the course of five-day intervals during gestation (D1-5, D6-10 and D11-15), while control groups received only corn oil. The results indicated that BPA was associated with a reduction in the body weight of the pregnant mice from around 2–3 days after administration until the end of gestation. The greatest effects were evident when the BPA was given during the later stages of pregnancy, and with higher doses. They also showed marked reduction in food intake and, to a lesser extent, in water intake. Furthermore, doses of BPA induced a reduction in implantation sites, lower foetal body weight and increased mortality rates. Abortion and foetal resorption rates were not affected by BPA administration, however. The above findings were concluded by discussing the possible mechanisms involved in producing these effects.

Fighting Bisphenol A-Induced Male Infertility: The Power of Antioxidants

Bisphenol A (BPA), a well-known endocrine disruptor present in epoxy resins and polycarbonate plastics, negatively disturbs the male reproductive system affecting male fertility. In vivo studies showed that BPA exposure has deleterious effects on spermatogenesis by disturbing the hypothalamic–pituitary–gonadal axis and inducing oxidative stress in testis. This compound seems to disrupt hormone signalling even at low concentrations, modifying the levels of inhibin B, oestradiol, and testosterone. The adverse effects on seminal parameters are mainly supported by studies based on urinary BPA concentration, showing a negative association between BPA levels and sperm concentration, motility, and sperm DNA damage. Recent studies explored potential approaches to treat or prevent BPA-induced testicular toxicity and male infertility. Since the effect of BPA on testicular cells and spermatozoa is associated with an increased production of reactive oxygen species, most of the pharmacological approaches are based on the use of natural or synthetic antioxidants. In this review, we briefly describe the effects of BPA on male reproductive health and discuss the use of antioxidants to prevent or revert the BPA-induced toxicity and infertility in men.

Gestational Exposure to Bisphenol A Affects Testicular Morphology, Germ Cell Associations, and Functions of Spermatogonial Stem Cells in Male Offspring

Exposure to bisphenol A (BPA) in the gestational period damages the reproductive health of offspring; detailed evidence regarding BPA-induced damage in testicular germ cells of offspring is still limited. In this study, pregnant mice (F0) were gavaged with three BPA doses (50 μg, 5 mg, and 50 mg/kg body weight (bw)/day; tolerable daily intake (TDI), no-observed-adverse-effect-level (NOAEL), and lowest-observed-adverse-effect level (LOAEL), respectively) on embryonic days 7 to 14, followed by investigation of the transgenerational effects of such exposure in male offspring. We observed that the NOAEL- and LOAEL-exposed F1 offspring had abnormalities in anogenital distance, nipple retention, and pubertal onset (days), together with differences in seminiferous epithelial stages and testis morphology. These effects were eradicated in the next F2 and F3 generations. Moreover, there was an alteration in the ratio of germ cell population and the apoptosis rate in germ cells increased in F1 offspring at the LOAEL dose. However, the total number of spermatogonia remained unchanged. Finally, a reduction in the stemness properties of spermatogonial stem cells in F1 offspring was observed upon LOAEL exposure. Therefore, we provide evidence of BPA-induced disruption of physiology and functions in male germ cells during the gestational period. This may lead to several reproductive health issues and infertility in offspring.

Paternal Exposure to Bisphenol-A Transgenerationally Impairs Testis Morphology, Germ Cell Associations, and Stemness Properties of Mouse Spermatogonial Stem Cells

Bisphenol-A (BPA) exposure in an adult male can affect the reproductive system, which may also adversely affect the next generation. However, there is a lack of comprehensive data on the BPA-induced disruption of the association and functional characteristics of the testicular germ cells, which the present study sought to investigate. Adult male mice were administered BPA doses by gavage for six consecutive weeks and allowed to breed, producing generations F1-F4. Testis samples from each generation were evaluated for several parameters, including abnormal structure, alterations in germ cell proportions, apoptosis, and loss of functional properties of spermatogonial stem cells (SSCs). We observed that at the lowest-observed-adverse-effect level (LOAEL) dose, the testicular abnormalities and alterations in seminiferous epithelium staging persisted in F0-F2 generations, although a reduced total spermatogonia count was found only in F0. However, abnormalities in the proportions of germ cells were observed until F2. Exposure of the male mice (F0) to BPA alters the morphology of the testis along with the association of germ cells and stemness properties of SSCs, with the effects persisting up to F2. Therefore, we conclude that BPA induces physiological and functional disruption in male germ cells, which may lead to reproductive health issues in the next generation.

Neuro-toxic and Reproductive Effects of BPA

Background:

Bisphenol A (BPA) is one of the highest volume chemicals produced worldwide. It has recognized activity as an endocrine-disrupting chemical and has suspected roles as a neurological and reproductive toxicant. It interferes in steroid signaling, induces oxidative stress, and affects gene expression epigenetically. Gestational, perinatal and neonatal exposures to BPA affect developmental processes, including brain development and gametogenesis, with consequences on brain functions, behavior, and fertility.

Methods:

This review critically analyzes recent findings on the neuro-toxic and reproductive effects of BPA (and its ana-logues), with focus on neuronal differentiation, synaptic plasticity, glia and microglia activity, cognitive functions, and the central and local control of reproduction.

Results:

BPA has potential human health hazard associated with gestational, peri- and neonatal exposure. Beginning with BPA’s disposition, this review summarizes recent findings on the neurotoxicity of BPA and its analogues, on neuronal dif-ferentiation, synaptic plasticity, neuro-inflammation, neuro-degeneration, and impairment of cognitive abilities. Furthermore, it reports the recent findings on the activity of BPA along the HPG axis, effects on the hypothalamic Gonadotropin Releas-ing Hormone (GnRH), and the associated effects on reproduction in both sexes and successful pregnancy.

Conclusion:

BPA and its analogues impair neuronal activity, HPG axis function, reproduction, and fertility. Contrasting re-sults have emerged in animal models and human. Thus, further studies are needed to better define their safety levels. This re-view offers new insights on these issues with the aim to find the “fil rouge”, if any, that characterize BPA’s mechanism of action with outcomes on neuronal function and reproduction.

Estrogen and Bisphenol A in Hypertension

PURPOSE OF REVIEW

Cardiovascular disease (CVD) is a non-subsiding disease that remains a leading cause of morbidity and mortality. CVD has been associated with endocrine disruptors, such as bisphenol A (BPA). This review critically summarizes existing findings on BPA and hypertension, with particular attention to genomic, non-genomic, molecular, and cellular mechanisms of action that render BPA as a cardiovascular estrogenic disruptor.

RECENT FINDINGS

Owing to its similar estrogenic structure, BPA has been shown to affect various phenotypes that are regulated by the natural hormone, estrogen. Indeed, BPA has been shown to interact with estrogen receptors, located both in the cell membrane and in the cytoplasm/nucleus. Given that estrogen plays an important role in cardiovascular physiology, a contributing role for BPA in CVD would not be unexpected. Existing literature, though limited, established BPA as a source of disruption in cardiovascular health, particularly hypertension. However, effects of BPA are largely dependent on the dose, patient gender, tissue, and developmental stage of the exposed tissue/organ. Accumulating evidence argues for an adverse effect of BPA on blood pressure, with this effect being gender, dose, and time specific. Thus, comprehensive studies which take these factors and other parameters, like epigenetic factors, into account are warranted before a thorough understanding is at hand.

Metabonomics reveals bisphenol A affects fatty acid and glucose metabolism through activation of LXR in the liver of male mice

Bisphenol-A (BPA) is a representative environmental endocrine disrupting chemical that is widely used in the production of polycarbonate plastics and epoxy resins. Many studies have confirmed BPA to be closely associated with metabolic diseases, reproductive system diseases, and sex hormone-dependent cancers. In this study, we aimed to systematically elucidate the molecular action of BPA on liver fatty acid and glucose metabolism and the reasons for BPA-induced hypoglycemia through a metabonomics approach. C57BL/6 mice were orally treated with BPA (1, 10, 50, 250 μg/kg) for 35 days and the liver metabonomics and histopathology, molecular docking, mRNA expression levels and activities of enzymes were analyzed. Based on the high-resolution mass spectrometry (MS) for metabonomics and on various software and bioinformatic analysis methods, we found that BPA could affect fatty acid and glucose metabolism, block the TCA cycle, and BPA also regulated the nuclear receptor LXR caused hypoglycemia, thereby affecting the normal metabolic functions of the liver.

Involvement of the Endocrine-Disrupting Chemical Bisphenol A (BPA) in Human Placentation

Background: Endocrine-disrupting chemicals (EDCs) are environmental chemicals/toxicants that humans are exposed to, interfering with the action of multiple hormones. Bisphenol A (BPA) is classified as an EDC with xenoestrogenic activity with potentially adverse effects in reproduction. Currently, a significant knowledge gap remains regarding the complete spectrum of BPA-induced effects on the human placenta. As such, the present study examined the effects of physiologically relevant doses of BPA in vitro. Methods: qRT-PCR, Western blotting, immunofluorescence, ELISA, microarray analyses, and bioinformatics have been employed to study the effects of BPA using nonsyncytialised (non-ST) and syncytialised (ST) BeWo cells. Results: Treatment with 3 nM BPA led to an increase in cell number and altered the phosphorylation status of p38, an effect mediated primarily via the membrane-bound estrogen receptor (GPR30). Nonbiased microarray analysis identified 1195 and 477 genes that were differentially regulated in non-ST BeWo cells, whereas in ST BeWo cells, 309 and 158 genes had altered expression when treated with 3 and 10 nM, respectively. Enriched pathway analyses in non-ST BeWo identified a leptin and insulin overlap (3 nM), methylation pathways (10 nM), and differentiation of white and brown adipocytes (common). In the ST model, most significantly enriched were the nuclear factor erythroid 2-related factor 2 (NRF2) pathway (3 nM) and mir-124 predicted interactions with cell cycle and differentiation (10 nM). Conclusion: Collectively, our data offer a new insight regarding BPA effects at the placental level, and provide a potential link with metabolic changes that can have an impact on the developing fetus.

Impact of prenatal exposure to bisphenol A on pregnant rats: Fetal bone development and immunohistochemistry implications

BACKGROUND:

Bisphenol A (BPA) is one of the most commonly produced chemicals in the world. BPA is used in products such as food packaging, personal care products, detergents, and plastic bottles. This study was conducted to determine the effect of BPA on fetal bone development.

MATERIAL AND METHODS:

In this study, 16 pregnant female Sprague-Dawley rats were used. The rats were divided into four groups: the control group and 0.5 mg/kg/day, 5 mg/kg/day, and 50 mg/kg/day dose BPA groups. The skeletal system development of fetuses was examined with double skeletal and immunohistochemistry (IHC) staining (tartrate resistant acid phosphatase (TRAP) and the alkaline phosphatase (AP) expressions) methods.

RESULTS:

The highest ossification rates in the humerus, radius, and ulna were detected as 41.05%, 39.25%, and 37.26% in the control group, respectively. The highest ossification rates in the femur, tibia, and fibula were detected as 23.04%, 30.73%, and 32.78% in the control group, respectively. Statistically significant differences were found between control and experimental groups in the TRAP and AP expression of the femur by IHC staining ( p < 0.001).

CONCLUSION:

Exposure to BPA during pregnancy adversely affected ossification and bone growth. A dose-dependent decrease was observed in the rate of ossification.

Lycopene: Hepatoprotective and Antioxidant Effects toward Bisphenol A-Induced Toxicity in Female Wistar Rats

Bisphenol A (BPA)—an endocrine disruptor xenoestrogen—is widely spread in the environment. Lycopene (LYC) is an antioxidant phytochemical carotenoid. The hereby study was designed to verify the deleterious effect of BPA on cyclic female rats' hepatic tissue as well as evaluation of the effect of LYC toward BPA hepatic perturbation. Twenty-eight female Wistar rats were allocated equally into four groups: control group, LYC group (10 mg/kg B.wt), BPA group (10 mg/kg B.wt), and BPA + LYC group (the same doses as former groups). The treatments were given daily via gavage to the rats for 30 days. The rats in BPA displayed high activities of serum liver enzymes with low levels of total proteins (TP) and albumin. Moreover, BPA induced hepatic oxidative stress via depletion of antioxidant enzymes concomitant with augmentation of lipid peroxidation, increased comet tail DNA %, and overexpression of caspase-3. Meanwhile, LYC administration reduced the cytotoxic effects of BPA on hepatic tissue, through improving the liver function biomarkers and oxidant-antioxidant state as well as DNA damage around the control values. These findings were confirmed by hepatic histopathological examination. Finally, LYC credited to have a noticeable protective effect versus BPA provoked oxidative injury and apoptosis of the liver tissue.

Bisphenol A Affects on the Functional Properties and Proteome of Testicular Germ Cells and Spermatogonial Stem Cells in vitro Culture Model

The endocrine disruptor bisphenol A (BPA) is well known for its adverse effect on male fertility. Growing evidence suggests that BPA may interact with testicular germ cells and cause infertility as a result of its estrogenic activity. Objective of current in vitro study was to investigate the proliferation, survivability and stemness properties of mouse testicular germ cells exposed to BPA, and to evaluate possible expression of cellular proteome. Our results showed that germ cell viability and proliferation were not affected by low concentrations (0.01, 0.1, 1, and 10 µM) although significant reduction observed at 100 µM BPA. Germ cell self-renewal and differentiation related marker proteins expression found unchanged at those concentrations. When BPA-exposed germ cells were transplanted into recipient testes, we observed fewer colonies at higher concentrations (10 and 100 µM). Additionally, a significant frequency of recombination failure during meiosis was observed in 10 µM BPA-exposed germ cell transplanted recipient. Moreover, experiment on continuous BPA-exposed and 100 µM BPA-recovered germ cells suggested that spermatogonial stem cells are more potential to survive in adverse environment. Finally, scrutinizing differentially expressed cellular proteins resulted from our proteomic analysis, we conclude that BPA exposure might be associated with several health risks and infertility.

Effect of Bisphenol-A (BPA) on insulin signal transduction and GLUT4 translocation in gastrocnemius muscle of adult male albino rat

Environmental estrogens bind to estrogen receptors, mimic estrogenic actions, and have adverse effects on human health like Bisphenol - A (BPA) which is used as a monomer in the production of polycarbonate plastics (PC) and epoxy resins which are used in variety of canned foods. Skeletal muscle plays an essential role in maintaining systemic glucose metabolism. In the present study, we investigated the possible effects of BPA on insulin signalling molecules and GLUT4 translocation in the gastrocnemius muscle of adult male rat. Rats were divided into four groups - Group I: Control (vehicle-corn oil treated), Group II, III and IV were administered with BPA (10, 100 and 400mg/kg b.wt/day, respectively) through oral gavage. Fasting blood glucose level of BPA treated groups showed a significant increase, oral glucose tolerance and insulin tolerance were also impaired in these animals. BPA significantly decreased the protein levels of insulin signalling molecules like IR, IRS-1, Akt, AS160 and its phosphorylated forms and blunts GLUT4 translocation by altering the levels of v- and t- SNARE proteins that assist the translocation process, thereby decreasing glucose uptake and oxidation in the gastrocnemius muscle. These results suggest that BPA has detrimental effects on insulin signalling molecules and GLUT4 translocation in the gastrocnemius muscle and thus impairs glucose homeostasis.

Effects of Low-Dose Developmental Bisphenol A Exposure on Metabolic Parameters and Gene Expression in Male and Female Fischer 344 Rat Offspring

BACKGROUND

Bisphenol A (BPA) is an endocrine-disrupting chemical that may contribute to development of obesity and metabolic disorders. Humans are constantly exposed to low concentrations of BPA, and studies support that the developmental period is particularly sensitive.

OBJECTIVES

The aim was to investigate the effects of low-dose developmental BPA exposure on metabolic parameters in male and female Fischer 344 (F344) rat offspring.

METHODS

Pregnant F344 rats were exposed to BPA via their drinking water, corresponding to 0.5 μg/kg BW/d (BPA0.5; n=21) or 50 μg/kg BW/d (BPA50; n=16), from gestational day (GD) 3.5 until postnatal day (PND) 22, and controls were given vehicle (n=26). Body weight (BW), adipose tissue, liver (weight, histology, and gene expression), heart weight, and lipid profile were investigated in the 5-wk-old offspring.

RESULTS

Males and females exhibited differential susceptibility to the different doses of BPA. Developmental BPA exposure increased plasma triglyceride levels (0.81±0.10 mmol/L compared with 0.57±0.03 mmol/L, females BPA50 p=0.04; 0.81±0.05 mmol/L compared with 0.61±0.04 mmol/L, males BPA0.5 p=0.005) in F344 rat offspring compared with controls. BPA exposure also increased adipocyte cell density by 122% in inguinal white adipose tissue (iWAT) of female offspring exposed to BPA0.5 compared with controls (68.2±4.4 number of adipocytes/HPF compared with 55.9±1.5 number of adipocytes/HPF; p=0.03) and by 123% in BPA0.5 females compared with BPA50 animals (68.2±4.4 number of adipocytes/high power field (HPF) compared with 55.3±2.9 number of adipocytes/HPF; p=0.04). In iWAT of male offspring, adipocyte cell density was increased by 129% in BPA50-exposed animals compared with BPA0.5-exposed animals (69.9±5.1 number of adipocytes/HPF compared with 54.0±3.4 number of adipocytes/HPF; p=0.03). Furthermore, the expression of genes involved in lipid and adipocyte homeostasis was significantly different between exposed animals and controls depending on the tissue, dose, and sex.

CONCLUSIONS

Developmental exposure to 0.5 μg/kg BW/d of BPA, which is 8-10 times lower than the current preliminary EFSA (European Food Safety Authority) tolerable daily intake (TDI) of 4 μg/kg BW/d and is within the range of environmentally relevant levels, was associated with sex-specific differences in the expression of genes in adipose tissue plasma triglyceride levels in males and adipocyte cell density in females when F344 rat offspring of dams exposed to BPA at 0.5 μg/kg BW/d were compared with the offspring of unexposed controls. https://doi.org/10.1289/EHP505.

Inhalation Toxicity of Bisphenol A and Its Effect on Estrous Cycle, Spatial Learning, and Memory in Rats upon Whole-Body Exposure

Bisphenol A (BPA) is a monomer used in a polymerization reaction in the production of polycarbonate plastics. It has been used in many consumer products, including plastics, polyvinyl chloride, food packaging, dental sealants, and thermal receipts. However, there is little information available on the inhalation toxicity of BPA. Therefore, the aim of this study was to determine its inhalation toxicity and effects on the estrous cycle, spatial learning, and memory. Sprague-Dawley rats were exposed to 0, 10, 30, and 90 mg/m³ BPA, 6 hr/day, 5 days/week for 8 weeks via whole-body inhalation. Mortality, clinical signs, body weight, hematology, serum chemistry, estrous cycle parameters, performance in the Morris water maze test, and organ weights, as well as gross and histopathological findings, were compared between the control and BPA exposure groups. Statistically significant changes were observed in serum chemistry and organ weights upon exposure to BPA. However, there was no BPA-related toxic effect on the body weight, food consumption, hematology, serum chemistry, organ weights, estrous cycle, performance in the Morris water maze test, or gross or histopathological lesions in any male or female rats in the BPA exposure groups. In conclusion, the results of this study suggested that the no observable adverse effect level (NOAEL) for BPA in rats is above 90 mg/m³/6 hr/day, 5 days/week upon 8-week exposure. Furthermore, BPA did not affect the estrous cycle, spatial learning, or memory in rats.

Folic Acid and Grape Seed Extract Prevent Azathioprine-induced Fetal Malformations and Renal Toxicity in Rats

Azathioprine (AZA) is an important drug commonly used in the therapy of the autoimmune system disorders. It induces many hazard effects that restrict its use. The present study was designed to investigate the influence of AZA on the fetal development and renal function and its co-administration with either folic acid (FA) or grape seed extract (GSE). The effects of administration of GSE or FA on AZA toxicity by gavage simultaneously for 4 weeks were studied by determining the changes in kidney histology, the glutathione level (GSH), and lipid per oxidation content as malondialdehyde in the kidney tissue. Additionally, their effects on the fetal development were investigated. Azathioprine induced a renal damage as indicated from the pronounced changes in histological structure, a significant increase in serum urea and creatinine, and malondialdehyde content in the kidney tissue. Meanwhile, the GSH activity was significantly decreased. Co-treatment with GSE significantly minimized the previously mentioned hazard effects of AZA by ameliorating the antioxidant activity. At this point, FA induced a nonsignificant protective activity. The results also revealed that administration of FA or GSE at 6th to 15th day of gestation did not altered fetal development. While, AZA administration clearly disturbed fetal development as indicated from a significant decrease in fetal weights. Furthermore, co-administration of both drugs significantly minimized similarly the hazards of AZA on the fetal development. It may be concluded that GSE and FA are a useful remedies. Maternal administrations of either both are protective agents against AZA-induced fetal malformations. Grape seed extract was more active than FA in potentiating the antioxidative defenses for controlling AZA-induced oxidative renal damages. Copyright © 2016 John Wiley & Sons, Ltd.

Maternal urinary bisphenol A levels and infant low birth weight: A nested case-control study of the Health Baby Cohort in China

BACKGROUND

Exposure to bisphenol A (BPA), a known endocrine disruptor, has been demonstrated to affect fetal development in animal studies, but findings in human studies have been inconsistent.

OBJECTIVES

We investigated whether maternal exposure to BPA during pregnancy is associated with an increased risk of infant low birth weight (LBW).

METHODS

A total 452 mother-infant pairs (113 LBW cases and 339 matched controls) were selected from the participants enrolled in the prospective Health Baby Cohort (HBC) in Wuhan city, China, during 2012-2014. BPA concentrations were measured in maternal urine samples collected at delivery, and the information of birth outcomes was retrieved from the medical records. A conditional logistic regression was used to evaluate the relationship between urinary BPA levels and LBW.

RESULTS

Mothers with LBW infants had significantly higher urinary BPA levels (median: 4.70μg/L) than the control mothers (median: 2.25μg/L) (p<0.05). Increased risk of LBW was associated with higher maternal urinary levels of BPA [adjusted odds ratio (OR)=3.13 for the medium tertile, 95% confidence interval (CI): 1.21, 8.08; adjusted OR=2.49 for the highest tertile, 95% CI: 0.98, 6.36]. The association was more pronounced among female infants than among male infants, with a statistical evidence of heterogeneity in risk (p=0.03).

CONCLUSIONS

Prenatal exposure to higher levels of BPA may potentially increase the risk of delivering LBW infants, especially for female infants. This is the first case-control study to examine the association in China.

Endocrine Disruptors: Improving Regulatory Science Policy

Law and science combine in the estimation of risks from endocrine disruptors (EDs) and actions for their regulation. For both, dose–response models are the causal link between exposure and probability (or percentage change) of adverse response. The evidence that leads to either regulations or judicial decrees is affected by uncertainty and limited knowledge, raising difficult policy issues that we enumerate and discuss. In the United States, some courts have dealt with EDs, but causation based on animal studies has been a stumbling block for plaintiffs seeking compensation, principally because those courts opt for epidemiological evidence. The European Union (EU) has several regulatory tools and ongoing research on the risks associated with bisphenol A, under the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Regulation and other regulations or directives. The integration of a vast (in kind and in scope) number of research papers into a statement of causation for either policy or to satisfy legal requirements, in both the United States and the EU, relies on experts. We outline the discursive dilemma and issues that may affect consensus-based results and a Bayesian causal approach that accounts for the evolution of information, yielding both value of information and flexibility associated with public choices.

Bisphenol A and congenital developmental defects in humans

Over 50% of the causes of fetal malformations in humans are still unknown. Recent evidence suggests the relationship between environmental exposure to endocrine disruptors and fetal malformations. Our study aims to establish the role of Bisphenol A (BPA), if any, in altering human reproduction. We enrolled 151 pregnant women who were divided into two groups: case group (CS, n=101), women with established diagnosis of developmental defect, and control group (CL, n=50), pregnant women with normally developed fetus. Total, free and conjugated BPA were measured in their blood using GC-MS with isotopic dilution. The results show a correlation between environmental exposure to BPA and the genesis of fetal malformations. Conjugated BPA, which was higher in the CL, casts light on the hypothesis that a reduced ability to metabolize the chemical in the mother can concur to the occurrence of malformation. In a more detailed manner, in case of chromosomal malformations, the average value of free BPA appears to be nearly three times greater than that of the controls. Similarly, in case of central and peripheral nervous system non-chromosomal malformations, the value of free BPA is nearly two times greater than that of the controls.

Increase in the expression of inducible nitric oxide synthase on exposure to bisphenol A: a possible cause for decline in steroidogenesis in male mice

Bisphenol A (BPA) is a well-known plasticizer and xenoestrogen that is responsible for many acquired reproductive difficulties, especially in men. Despite the prevalence of BPA in society, the mechanism behind reproductive deficits remains elusive. The present study investigates the mode of BPA's action by evaluating its effect on the expression of inducible nitric oxide synthase (iNOS) and steriodogenic acute regulatoryprotein (StAR) in male mice testis. Swiss albino mice were treated with a range BPA concentrations of 0.5, 50 and 100μg/kg body weight/day intraperitoneally for 60 days. Several markers of oxidative stress and male fertility were investigated. Nitrite levels, malondialdehyde levels and testicular injury scores were elevated whereas the sperm count, serum testosterone levels and catalase activity were reduced in the BPA groups. Mechanistically, an increase in iNOS expression was observed in the testis whereas the expression of the StAR was down regulated in the BPA treated mouse. These results suggest that BPA induces oxidative stress by altering the expression of iNOS, which consequently leads to the down regulation of StAR expression in the testis of male mouse.

Analysis of Differentially Regulated Proteins in TM4 Cells Treated with Bisphenol A

BPA, bisphenol A, a monomer of epoxy resins and polycarbonate plastic, is used in many consumer products including the plastic linings of cans for food and babies' bottles. BPA has been reported to cause reproductive toxicity and affects cells in rats and mice at high doses. In this study, the effect of BPA on protein expression in TM4 cells (a mouse Sertoli cell line) known to play an essential role in Spermatogenesis was investigated by two-dimensional electrophoresis (2-DE). After 16 h exposure to 50, 100, 150, 200, and 250 microM of BPA, the viability of TM4 cells decreased to about 90, 85, 78, 55, and 30% of control respectively. Approximately 800 protein spots in TM4 cells were analyzed by 2-DE with pH 4-7 linear immobilized pH gradient (IPG) Dry Strip, and 11 proteins which showed significantly different expression levels were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). Among these, HSP 27 and placental calcium binding protein may be proteins differentially expressed by BPA exposure.

Estrogenic endocrine-disrupting chemicals: molecular mechanisms of actions on putative human diseases

Endocrine-disrupting chemicals (EDC), including phthalates, bisphenol A (BPA), phytoestrogens such as genistein and daidzein, dichlorodiphenyltrichloroethane (DDT), and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), are associated with a variety of adverse health effects in organisms or progeny by altering the endocrine system. Environmental estrogens, including BPA, phthalates, and phytoestrogens, are the most extensively studied and are considered to mimic the actions of endogenous estrogen, 17β-estradiol (E2). Diverse modes of action of estrogen and estrogen receptors (ERα and ERβ) have been described, but the mode of action of estrogenic EDC is postulated to be more complex and needs to be more clearly elucidated. This review examines the adverse effects of estrogenic EDC on male or female reproductive systems and molecular mechanisms underlying EDC effects that modulate ER-mediated signaling. Mechanisms of action for estrogenic EDC may involve both ER-dependent and ER-independent pathways. Recent findings from systems toxicology of examining estrogenic EDC are also discussed.

Establishment of the korean tolerable daily intake of bisphenol a based on risk assessments by an expert committee

Recently, reproductive and neurobehavioral effects of bisphenol A (BPA) have been documented, and thus a review was requested for BPA management direction by the government. Therefore, this study was performed to establish a Korean tolerable daily intake (TDI) for BPA. An expert committee, consisting of specialists in fields such as toxicology, medicine, pharmacology, and statistics, was asked to evaluate BPA health based guidance values (HbGVs) . Although many toxicological studies were reviewed to select a point of departure (POD) for TDI, rat and mouse reproductive studies by Tyl et al. (2002, 2006) , which were performed according to GLP standards and OECD guidelines, were selected. This POD was the lowest value determined from the most sensitive toxicological test. The POD, a NOAEL of 5 mg/kg bw/day, was selected based on its systemic toxicity as critical effects. An uncertainty factor of 100 including interspecies and intraspecies differences was applied to calculate the TDI. According to the evaluation results, a TDI of BPA for Korean was suggested at 0.05 mg/kg bw/day. In addition, the BPA exposure level based on food consumption by the Korean population was estimated as 1.509 μg/kg bw/day, and the HI was evaluated at 0.03 when the TDI of 0.05 mg/kg bw/day was applied. This HI value of 0.03 indicated that hazardous effects would not be expected from BPA oral exposures. Although highly uncertain, further studies on low dose neurobehavioral effects of BPA should be performed. In addition, it is recommended that the 'as low as reasonably achievable' (ALARA) principle be applied for BPA exposure from food packaging materials in newborn infants and children.

Metabolic disruption in male mice due to fetal exposure to low but not high doses of bisphenol A (BPA): evidence for effects on body weight, food intake, adipocytes, leptin, adiponectin, insulin and glucose regulation

Exposure to bisphenol A (BPA) is implicated in many aspects of metabolic disease in humans and experimental animals. We fed pregnant CD-1 mice BPA at doses ranging from 5 to 50,000μg/kg/day, spanning 10-fold below the reference dose to 10-fold above the currently predicted no adverse effect level (NOAEL). At BPA doses below the NOAEL that resulted in average unconjugated BPA between 2 and 200pg/ml in fetal serum (AUC0-24h), we observed significant effects in adult male offspring: an age-related change in food intake, an increase in body weight and liver weight, abdominal adipocyte mass, number and volume, and in serum leptin and insulin, but a decrease in serum adiponectin and in glucose tolerance. For most of these outcomes non-monotonic dose-response relationships were observed; the highest BPA dose did not produce a significant effect for any outcome. A 0.1-μg/kg/day dose of DES resulted in some but not all low-dose BPA outcomes.

Testing the efficacy of quercetin in mitigating bisphenol A toxicity in liver and kidney of mice

Quercetin (3,5,7,3',4'-pentahydroxy flavone) is a potent antioxidant found in various fruits and vegetables. The present investigation was an attempt to evaluate the mitigatory effect of quercetin on the damage caused by bisphenol A (BPA; 2,2-bis (4-hydroxyphenyl) propane), a well-known xenoestrogen, on liver and kidney of mice. Swiss strain adult male albino mice were orally administered with 120 and 240 mg/kg body weight (bw)/day BPA with or without quercetin (60 mg/kg bw/day) for 30 days. On the completion of the treatment period, animals were killed; organs were isolated and used for the study. Results revealed that oral administration of BPA for 30 days caused significant and dose-dependent decrease in body weight. Absolute and relative organ weights, total lipid and cholesterol contents were significantly increased in liver and kidney of mice when compared with vehicle control. BPA treatment also caused, when compared with vehicle control, a statistically significant reductions in the activities of catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase and glutathione-S-transferase as well as in glutathione and total ascorbic acid contents; however, significant increase was found in malondialdehyde (MDA) levels. Histopathological studies revealed hepatocellular necrosis, cytoplasmic vacuolization and decrease in hepatocellular compactness in liver as well as distortion of the tubules, increased vacuolization, necrosis and disorganization of glomerulus in the kidney of BPA-treated mice. All these effects were dose-dependent. Co-treatment with quercetin (60 mg/kg bw) and BPA (low dose and high dose) alleviates the changes in body weight, as well as absolute and relative organ weights of mice. It also ameliorates the oxidative stress created by BPA by lowering MDA levels and by increasing enzymatic and nonenzymatic antioxidants as well as it brings back the normal histoarchitecture of liver and kidney of mice. The present results revealed that graded doses of BPA caused oxidative damage in liver and kidney of mice, which is mitigated by quercetin.

Bisphenol A in dental sealants and its estrogen like effect

Bisphenol A or BPA-based epoxy resins are widely used in the manufacture of commercial products, including dental resins, polycarbonate plastics, and the inner coating of food cans. BPA is a precursor to the resin monomer Bis-GMA. During the manufacturing process of Bis-GMA dental sealants, Bisphenol A (BPA) might be present as an impurity or as a degradation product of Bis-DMA through esterases present in saliva. Leaching of these monomers from resins can occur during the initial setting period and in conjunction with fluid sorption and desorption over time and this chemical leach from dental sealants may be bioactive. Researchers found an estrogenic effect with BPA, Bis-DMA, and Bis-GMA because BPA lacks structural specificity as a natural ligand to the estrogen receptor. It generated considerable concern regarding the safety of dental resin materials. This review focuses on the BPA in dental sealants and its estrogen-like effect.

Bisphenol A: developmental toxicity from early prenatal exposure

Bisphenol A (BPA) exposure has been documented in pregnant women, but consequences for development are not yet widely studied in human populations. This review presents research on the consequences for offspring of BPA exposure during pregnancy. Extensive work in laboratory rodents has evaluated survival and growth of the conceptus, interference with embryonic programs of development, morphological sex differentiation, sex differentiation of the brain and behavior, immune responsiveness, and mechanism of action. Sensitive measures include RAR, aryl hydrocarbon receptor, and Hox A10 gene expression, anogenital distance, sex differentiation of affective and exploratory behavior, and immune hyperresponsiveness. Many BPA effects are reported at low doses (10-50 µg/kg d range) by the oral route of administration. At high doses (>500,000 µg/kg d) fetal viability is compromised. Much of the work has centered around the implications of the estrogenic actions of this agent. Some work related to thyroid mechanism of action has also been explored. BPA research has actively integrated current knowledge of developmental biology, concepts of endocrine disruption, and toxicological research to provide a basis for human health risk assessment.

Effects of perinatal administration of Bisphenol A on the neuronal nitric oxide synthase expressing system in the hypothalamus and limbic system of CD1 mice

Bisphenol A (BPA) is a well-known plastic-derived pollutant that can bind to oestrogen receptors and is considered an endocrine-disrupting chemical. Its impact on different behaviours in rodents has been largely investigated, however, only a few data are available on its effects upon neural circuits. In the present study, we investigated the long-term effects of early exposure of mice of both sexes to BPA on the nitrinergic system, one of the neural systems involved in the control of sexual behaviour and under the control of gonadal hormones. Mice of both sexes were exposed for eight prenatal and eight postnatal days to BPA that was administered to the mothers. The maternally-exposed mice were sacrificed at the age of 2 months and their brains were sectioned and immunohistochemically treated for the detection of neuronal nitric oxide synthase (nNOS). Significant effects of BPA exposure were detected for the number of immunoreactive cells in the medial preoptic nucleus and in the ventromedial subdivision of the bed nucleus of the stria terminalis, in a sex-oriented and dose-dependent way. These results indicate that BPA has a powerful effect on specific portions of the nNOS-immunoreactive system belonging to the accessory olfactory system that are particularly important for the control of sexual behaviour. In addition, they confirm that perinatal exposure to endocrine-disrupting chemicals, in particular to BPA, may have a high impact on the organisation of specific neural pathways that can later affect complex behaviours and functions.

Dietary exposure to low doses of bisphenol A: effects on reproduction and development in two generations of C57BL/6J mice

The present study was conducted to examine the effects of low-dose exposure to bisphenol A on reproduction and development in two generations of mice. Pregnant female C57BL/6J mice (F(0)) were fed a diet containing low doses of bisphenol A (0, 0.33, 3.3, or 33 ppm) from gestational day 6 through postnatal day 22, and the weanlings (F(1) and F(2)) from each F(0) and F(1) dam group, respectively, were also fed these same concentrations of bisphenol A ad libitum until sacrifice. There were no treatment-related changes in body weight, body weight gain, food consumption, gestation length, or the number of live births on postnatal day 1 in F(0) dams between the control group and bisphenol A groups. Sex ratio and viability were similar in all F(1) pups. No treatment-related changes were observed in body weight, food consumption, developmental parameters, anogenital distance, or weight of any of the organs (liver, kidney, heart, spleen, thymus, testis, ovary, or uterus) in F(1) and F(2) adults in either sex. The epididymis weight was slightly higher with 0.33 and 3.3 ppm in F(1) males, but this slight increase was neither dose dependent nor seen across generations. There were no treatment-related effects of bisphenol A on cauda epididymal sperm count or sperm motility in F(1) or F(2) males. These findings indicate that dietary exposure to bisphenol A between 0.33 and 33 ppm does not adversely affect reproduction or development as assessed in two generations of mice.

Assessment of bisphenol A exposure in Korean pregnant women by physiologically based pharmacokinetic modeling

The objective of this study was to predict the exposure to bisphenol A (BPA) after oral intake in human blood and tissues using physiologically based pharmacokinetic (PBPK) modeling. A refined PBPK model was developed taking into account of glucuronidation, biliary excretion, and slow absorption of BPA in order to describe the second peak of BPA observed following oral intake. This developed model adequately described the second peak and BPA concentrations in blood and various tissues in rats after oral administration. A prospective validation study in rats additionally supported the proposed model. For extrapolation to humans, a daily oral BPA dose of 0.237 mg/70 kg/d or 0.0034 mg/kg/d was predicted to achieve an average steady-state blood concentration of 0.0055 ng/ml (median blood BPA concentration in Korean pregnant women). This dose was lower than the reference dose (RfD, 0.016 mg/kg/d) and the tolerable daily intake established by the European Commission (10 μg/kg/d). Data indicate that enterohepatic recirculation may be toxicologically important as this pathway may increase exposure and terminal half-life of BPA in humans.

Bisphenol-A and disparities in birth outcomes: a review and directions for future research

Racial disparities in pregnancy outcome in the United States are significant, persistent and costly, but the causes are poorly understood. We propose that disproportionate exposure of African-American women to environmental endocrine disrupting compounds (EDCs) may contribute to birth outcome disparities. Marked racial segregation, as well as health behaviors associated with poverty could result in differences in exposure to particular EDCs. One EDC that has aroused concern in recent years is bisphenol-A (BPA), a widely used industrial plasticizer with known estrogenic properties. Published studies indicate that excessive BPA exposure is associated with reduced fetal survival, as well as reductions in maternal weight and fetal body weight. Related findings include adverse effects of BPA exposure on ovarian function, mammary gland development, earlier age of puberty onset and some metabolic parameters. However, these findings are largely limited to experimental animal studies, and need to be validated in human populations. Our review supports the need to move beyond the currently dominant toxicological approach to examining the effects of BPA exposure, and rely more on observational human studies and epidemiological methods. Many of the risk factors for racial disparities in pregnancy outcome are global or difficult to modify, but exposure to BPA is a potentially malleable risk factor. If BPA contributes to racial disparities in pregnancy outcome, there are important implications for prevention. It is our hope that this review will stimulate further research in this important and neglected area.