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.     

Susceptibility of male reproductive system to bisphenol A,an endocrine disruptor: Updates from epidemiological and experimental evidence

Bisphenol A (BPA) is an omnipresent environmental pollutant. Despite being restrictions in-force for its utilization, it is widely being used in the production of polycarbonate plastics and epoxy resins. Direct, low-dose, and long-term exposure to BPA is expected when they are used in the packaging of food products and are used as containers for food consumption. Occupationally, workers are typically exposed to BPA at higher levels and for longer periods during the manufacturing process. BPA is a known endocrine disruptor chemical (EDC), that causes male infertility, which has a negative impact on human life from emotional, physical, and societal standpoints. To minimize the use of BPA in numerous consumer products, efforts and regulations are being made. Despite legislative limits in numerous nations, BPA is still found in consumer products. This paper examines BPA's overall male reproductive toxicity, including its impact on the hypothalamic-pituitary-testicular (HPT) axis, hormonal homeostasis, testicular steroidogenesis, sperm parameters, reproductive organs, and antioxidant defense system. Furthermore, this paper highlighted the role of non-monotonic dose–response (NMDR) in BPA exposure, which will help to improve the overall understanding of the harmful effects of BPA on the male reproductive system.     

Bisphenol A: an endocrine disruptor with widespread exposure and multiple effects

Bisphenol A (BPA) is one of the highest volume chemicals produced worldwide. This compound is a building block of polycarbonate plastics often used for food and beverage storage, and BPA is also a component of epoxy resins that are used to line food and beverage containers. Studies have shown that BPA can leach from these and other products in contact with food and drink, and as a result, routine ingestion of BPA is presumed. This compound is also found in an enormous number of other products that we come into contact with daily, and therefore it is not surprising that it has been detected in the majority of individuals examined. BPA is a known endocrine disruptor. Although initially considered to be a weak environmental estrogen, more recent studies have demonstrated that BPA may be similar in potency to estradiol in stimulating some cellular responses. Moreover, emerging evidence suggests that BPA may influence multiple endocrine-related pathways. Studies in rodents have identified adverse effects of BPA at levels at or below the current acceptable daily intake level for this compound. The various reported adverse effects of BPA are reviewed, and potential mechanisms of BPA action are discussed. Much more investigation is needed to understand the potential adverse health effects of BPA exposure in humans and to understand the multiple pathways through which it may act. Although many questions remain to be answered, it is becoming increasingly apparent that exposure to BPA is ubiquitous and that the effects of this endocrine disruptor are complex and wide-ranging.     

Bisphenol a exposure causes meiotic aneuploidy in the female mouse

BACKGROUND: There is increasing concern that exposure to man-made substances that mimic endogenous hormones may adversely affect mammalian reproduction. Although a variety of reproductive complications have been ascribed to compounds with androgenic or estrogenic properties, little attention has been directed at the potential consequences of such exposures to the genetic quality of the gamete. RESULTS: A sudden, spontaneous increase in meiotic disturbances, including aneuploidy, in studies of oocytes from control female mice in our laboratory coincided with the accidental exposure of our animals to an environmental source of bisphenol A (BPA). BPA is an estrogenic compound widely used in the production of polycarbonate plastics and epoxy resins. We identified damaged caging material as the source of the exposure, as we were able to recapitulate the meiotic abnormalities by intentionally damaging cages and water bottles. In subsequent studies of female mice, we administered daily oral doses of BPA to directly test the hypothesis that low levels of BPA disrupt female meiosis. Our results demonstrated that the meiotic effects were dose dependent and could be induced by environmentally relevant doses of BPA. CONCLUSIONS: Both the initial inadvertent exposure and subsequent experimental studies suggest that BPA is a potent meiotic aneugen. Specifically, in the female mouse, short-term, low-dose exposure during the final stages of oocyte growth is sufficient to elicit detectable meiotic effects. These results provide the first unequivocal link between mammalian meiotic aneuploidy and an accidental environmental exposure and suggest that the oocyte and its meiotic spindle will provide a sensitive assay system for the study of reproductive toxins.     

Transgenerational effects of prenatal bisphenol A on social recognition

Bisphenol A (BPA) is a man-made endocrine disrupting compound used to manufacture polycarbonate plastics. It is found in plastic bottles, canned food linings, thermal receipts and other commonly used items. Over 93% of people have detectable BPA levels in their urine. Epidemiological studies report correlations between BPA levels during pregnancy and activity, anxiety, and depression in children. We fed female mice control or BPA-containing diets that produced plasma BPA concentrations similar to concentrations in humans. Females were mated and at birth, pups were fostered to control dams to limit BPA exposure to gestation in the first generation. Sibling pairs were bred to the third generation with no further BPA exposure. First (F1) and third (F3) generation juveniles were tested for social recognition and in the open field. Adult F3 mice were tested for olfactory discrimination. In both generations, BPA exposed juvenile mice displayed higher levels of investigation than controls in a social recognition task. In F3 BPA exposed mice, dishabituation to a novel female was impaired. In the open field, no differences were noted in F1 mice, while in F3, BPA lineage mice were more active than controls. No impairments were detected in F3 mice, all were able to discriminate different male urine pools and urine from water. No sex differences were found in any task. These results demonstrate that BPA exposure during gestation has long lasting, transgenerational effects on social recognition and activity in mice. These findings show that BPA exposure has transgenerational actions on behavior and have implications for human neurodevelopmental behavioral disorders.     

Developmental exposure to bisphenol a modulates innate but not adaptive immune responses to influenza A virus infection

Bisphenol A (BPA) is used in numerous products, such as plastic bottles and food containers, from which it frequently leaches out and is consumed by humans. There is a growing public concern that BPA exposure may pose a significant threat to human health. Moreover, due to the widespread and constant nature of BPA exposure, not only adults but fetuses and neonates are also exposed to BPA. There is mounting evidence that developmental exposures to chemicals from our environment, including BPA, contribute to diseases late in life; yet, studies of how early life exposures specifically alter the immune system are limited. Herein we report an examination of how maternal exposure to a low, environmentally relevant dose of BPA affects the immune response to infection with influenza A virus. We exposed female mice during pregnancy and through lactation to the oral reference dose for BPA listed by the US Environmental Protection Agency, and comprehensively examined immune parameters directly linked to disease outcomes in adult offspring following infection with influenza A virus. We found that developmental exposure to BPA did not compromise disease-specific adaptive immunity against virus infection, or reduce the host's ability to clear the virus from the infected lung. However, maternal exposure to BPA transiently reduced the extent of infection-associated pulmonary inflammation and anti-viral gene expression in lung tissue. From these observations, we conclude that maternal exposure to BPA slightly modulates innate immunity in adult offspring, but does not impair the anti-viral adaptive immune response, which is critical for virus clearance and survival following influenza virus infection.     

Weight of the Evidence Evaluation of Low-Dose Reproductive and Developmental Effects of Bisphenol A

A panel convened by the Harvard Center for Risk Analysis (HCRA) evaluated the weight of evidence for potential developmental and reproductive toxicity of bisphenol A (BPA, CASRN 80-05-7) in animals at doses well below the Lowest Observed Adverse Effect Level (LOAEL) of 50 mg/kg-day previously identified by the U.S. Environmental Protection Agency (US EPA) and even US EPA's reference dose (RfD) of 0.05 mg/kg-day. The effects are hypothesized to occur through an endocrine-modulating mode of action, specifically through estrogen receptors. The panel focused on potential male reproductive effects but also examined other endpoints possibly associated with hormone-like effects. The review considered studies published through April 2002. A formal deliberation framework focused on consistency, generalizability, and biological plausibility. The panel found no consistent affirmative evidence of low-dose BPA effects for any endpoint. Inconsistent responses across rodent species and strains made generalizability of low-dose BPA effects questionable. Lack of adverse effects in two multiple-generation reproductive and developmental studies casts doubt on suggestions of significant physiological or functional impairment. The panel was concerned about generalization of non-oral administration results to oral exposures. Differences in the pattern of BPA responses compared to estradiol or diethylstilbestrol (DES) cast doubt on estrogenicity as a low-dose mechanism of action for BPA. Finally, there is indirect evidence that humans may be less sensitive to possible estrogenic effects from BPA exposure due to pharmacodynamic factors. The panel recommended replication of existing studies under carefully controlled conditions and further study of BPA's pharmacokinetics and pharmacodynamics. The study was funded by a grant from the American Plastics Council.     

Developmental exposure to low-dose estrogenic endocrine disruptors alters sex differences in exploration and emotional responses in mice

Estrogenic endocrine disruptors (EEDs) are naturally occurring or man-made compounds present in the environment that are able to bind to estrogen receptors and interfere with normal cellular development in target organs and tissues. There is mounting evidence that EEDs can interfere with the processes of sexual differentiation of brain and behavior in different animal models. We investigated the effects of maternal exposure to EEDs, at concentrations within the range of human exposure and not patently teratogenic, on behavioral responses of male and female house mice (Mus musculus domesticus) before and after puberty. Pregnant dams were trained to spontaneously drink daily doses of corn oil with or without the estrogenic plastic derivative, bisphenol A (BPA 10 microg/kg), or the estrogenic insecticide methoxychlor (MXC 20 microg/kg) from gestation day 11 to postpartum day 8. Their male and female offspring were examined at different ages to examine several components of explorative and emotional behaviors in 3 experimental paradigms: a novelty test before puberty and, as adults, a free-exploratory open-field test and the elevated plus maze test. The main results are sex differences in control mice on a number of behavioral responses at both ages and in all experimental paradigms, while perinatal exposure to BPA or MXC decreased or eliminated such sex differences. The present findings are evidence of long-term consequences of developmental exposure to BPA and MXC on neurobehavioral development and suggest a differential effect of low-dose exposure to these estrogenic chemicals in males and females.     

Bisphenol a binds to the local anesthetic receptor site to block the human cardiac sodium channel

Bisphenol A (BPA) has attracted considerable public attention as it leaches from plastic used in food containers, is detectable in human fluids and recent epidemiologic studies link BPA exposure with diseases including cardiovascular disorders. As heart-toxicity may derive from modified cardiac electrophysiology, we investigated the interaction between BPA and hNav1.5, the predominant voltage-gated sodium channel subtype expressed in the human heart. Electrophysiology studies of heterologously-expressed hNav1.5 determined that BPA blocks the channel with a K(d) of 25.4±1.3 μM. By comparing the effects of BPA and the local anesthetic mexiletine on wild type hNav1.5 and the F1760A mutant, we demonstrate that both compounds share an overlapping binding site. With a key binding determinant thus identified, an homology model of hNav1.5 was generated based on the recently-reported crystal structure of the bacterial voltage-gated sodium channel NavAb. Docking predictions position both ligands in a cavity delimited by F1760 and contiguous with the DIII-IV pore fenestration. Steered molecular dynamics simulations used to assess routes of ligand ingress indicate that the DIII-IV pore fenestration is a viable access pathway. Therefore BPA block of the human heart sodium channel involves the local anesthetic receptor and both BPA and mexiletine may enter the closed-state pore via membrane-located side fenestrations.     

Bisphenol A induces permanent squamous change in mouse prostatic epithelium

Bisphenol A (BPA) is a monomer of plastic products widely used in daily life, and has weak estrogenic activity. In this study, male BALB/c mice were treated with BPA and diethylstilbestrol (DES) in adult and fetal periods to investigate whether BPA could affect prostatic epithelial differentiation. Eight-to 9-week-old mice treated for 3 weeks with subcutaneous implants of 0.2-200 mg BPA pellets induced the expression of cytokeratin 10 (CK10) in prostatic basal epithelial cells in a dose-dependent manner. Utilizing organ culture of adult prostate, 1 nM and 1 microM BPA also induced CK10 expression and squamous metaplasia with multilayering of basal epithelial cells, respectively. Fetal exposure to low-dose BPA (20 microg/kg/day) from gestation day (GD) 13 to GD18 induced permanent CK10 expression in basal cells of the adult prostate similar to DES (0.2 microg/kg/day). These results indicate that in mouse, BPA can directly elicit CK10 expression in prostatic epithelium, and that this change can be elicited by doses as low as 20 microg/kg/day. We speculate that low-dose BPA during fetal life may also induce permanent squamous change in human prostate.     

基于氧化应激与细胞凋亡探究双酚A慢性暴露致小鼠肾毒性作用机制

双酚A (bisphenol A, BPA)被广泛应用于生产环氧树脂和聚碳酸酯塑料等制品,在强酸、强碱或高温条件下,BPA被释放出来,然后渗入环境中。在大多数生物液体中都检测到了不同浓度的BPA,BPA的存在已被证明与许多慢性疾病密切相关,包括慢性肾病(chronic kidney disease,CKD)。然而,关于BPA的有害作用及其对CKD的不良影响知之甚少。为了探讨BPA对动物肾毒性的作用机制,本研究通过向饮水中加入0.01、0.1和1 mg/L的BPA,暴露于雌性小鼠4周后,交配和怀孕的雌性小鼠持续接触BPA,直到断奶;F1代3周龄雄性仔鼠继续口服相同剂量的BPA,持续10周。结果表明,0.1mg/L和1mg/LBPA处理组小鼠的肾脏损伤严重,血清中肾脏功能指标尿素氮(urea nitrogen,UN)、肌酐(creatinine,CR)和尿酸(uric acid,UA)的含量均发生显著升高(P<0.05);肾脏组织形态结构被损害;肾脏抗氧化相关基因在mRNA和蛋白水平上的表达显著降低(P<0.05),包括谷胱甘肽硫转移酶(glutathione-S-transf...     

What is an endocrine disruptor?

Endocrine disrupting chemicals (EDCs) and potential EDCs are mostly man-made found in various materials. By interfering with the body's endocrine system, endocrine disruptors produce adverse developmental, reproductive, neurological, and immune effects in humans, abnormal growth patterns and neurodevelopmental delays in children. Thus, diethylstilbestrol (DES) a non-steroidal estrogen, which is regarded as a proof of concept, induces clear cell carcinoma among young women. EDCS may be found in plastic bottles and metal food cans (BPA), medical devices (phthalates), detergents, flame retardants (polybrominated diphenyl ethers), food (BPA), toys (phthalates), cosmetics and drugs (parabens), and pesticides (alkyl phenols such as nonylphenol). The deleterious effects of endocrine disruptors constitute a real public health issue. However concerning the mechanisms of action of EDCs, many questions remain unanswered and need further investigations.     

The naringenin-induced proapoptotic effect in breast cancer cell lines holds out against a high bisphenol a background

Fruit and vegetable consumption has generally been associated with the prevention or suppression of cancer. However, food could contain a multitude of chemicals (e.g., bisphenol A; BPA) that could synergize or antagonize the effects of diet-derived compounds. Remarkably, food containers (e.g., water and infant bottles) are the largest source of exposure to BPA for human beings. Here, the effects of the coexposure of naringenin (Nar, 1.0 × 10(-9) M to 1.0 × 10(-4) M) and BPA (1.0 × 10(-5) M) in estrogen-dependent breast cancer cell lines expressing (i.e., MCF-7 and T47D) or not expressing (i.e., MDA-MB-231) estrogen receptor α (ERα) are reported. Although both Nar and BPA bind to ERα, they induce opposite effects on breast cancer cell growth. BPA induces cell proliferation, whereas Nar only decreases the number of ERα-positive cells (i.e., MCF-7 and T47D). Notably, even in the presence of BPA, Nar impairs breast cancer cell proliferation by activating caspase-3. The molecular pathways involved require p38 activation, whereas, the BPA-induced AKT activation is completely prevented by the Nar treatment. As a whole, Nar maintains its proapoptotic effects even in the presence of the food contaminant BPA, thus, enlarging the chemopreventive potential of this flavanone.     

Bisphenol-A Can Inhibit the Enzymatic Activity of Human Superoxide Dismutase

Bisphenol-A (BPA), a synthetic xenoestrogen, is currently being used to produce a wide variety of consumer products. Humans as well as animals are exposed to this ubiquitous compound through ingestion, inhalation, and dermal exposure. The effect of this compound on superoxide dismutase (SOD), an antioxidant enzyme, isolated from human blood was studied using an enzyme inhibition assay. The mode of interaction of BPA on SOD was investigated using modeling and docking studies. Purified human SOD from erythrocytes was used to study the enzyme inhibition assay of BPA. Molecular level interactions of BPA on SOD were also analyzed by modeling and docking studies. Our study demonstrates that BPA has an inhibitory effect on SOD. The docking results showed that it could bind to the active site residues of SOD and could interfere with the catalytic activity of the enzyme. Our study reveals for the first time that BPA can directly inhibit the enzymatic activity of human SOD and thus impairs the free radical scavenging mechanism.     

Migration of phthalates from plastic products to model solutions

The aim of this investigation was to determine the level and rate of migration of phthalates, compounds used as plastic softeners, from various plastic products into model solutions and to assess the possible adverse effects of the phthalate amounts released on human health, thus to contribute to harmonization of the opinions on the maximal allowed human exposure to these compounds through environmental factors. Nine specimens of plastic toys, 16 specimens of plastic food containers and 10 specimens of other plastic consumer goods were analyzed. The specimens of plastic products were submitted to 10-day action of model solutions. Three model solutions were used: distilled water, 10% ethyl alcohol, and 3% acetic acid. Identification and quantification of the phthalates released were performed by the method of gas chromatography on days 1, 5 and 10 of exposure, at a detection limit of 0.005 microgram/kg. On day 10, the highest level of released phthalates (54.5 mg/kg) was measured in distilled water, followed by 44.4 mg/kg in 3% acetic acid and 32.3 mg/kg in 10% ethyl alcohol. According to plastic product categories, the highest pooled level of phthalates released to all three solutions was recorded for plastic toys (66.2 mg/kg), followed by food containers (37.6 mg/kg) and other consumer goods (27.4 mg/kg). According to plastic product categories, toys showed the most rapid phthalate release, with 65.4% (43.3 of 66.2 mg/kg) of the pooled level of phthalates released to all three solutions recorded on day 1. As indicated by the study results, the levels of phthalates released would not present a hazard for human health, not even over a prolonged period of time. However, data on the highest and fastest pooled phthalate release from plastic toys, and this especially to distilled water simulating salivary action, point to the need of continuous evaluation and amendments of the legislation on phthalates in consumer goods.     

The industrial chemical bisphenol A (BPA) interferes with proliferative activity and development of steroidogenic capacity in rat Leydig cells

The presence of bisphenol A (BPA) in consumer products has raised concerns about potential adverse effects on reproductive health. Testicular Leydig cells are the predominant source of the male sex steroid hormone testosterone, which supports the male phenotype. The present report describes the effects of developmental exposure of male rats to BPA by gavage of pregnant and lactating Long-Evans dams at 2.5 and 25 μg/kg body weight from Gestational Day 12 to Day 21 postpartum. This exposure paradigm stimulated Leydig cell division in the prepubertal period and increased Leydig cell numbers in the testes of adult male rats at 90 days. Observations from in vitro experiments confirmed that BPA acts directly as a mitogen in Leydig cells. However, BPA-induced proliferative activity in vivo is possibly mediated by several factors, such as 1) protein kinases (e.g., mitogen-activated protein kinases or MAPK), 2) growth factor receptors (e.g., insulin-like growth factor 1 receptor-beta and epidermal growth factor receptors), and 3) the Sertoli cell-secreted anti-Mullerian hormone (also called Mullerian inhibiting substance). On the other hand, BPA suppressed protein expression of the luteinizing hormone receptor (LHCGR) and the 17beta-hydroxysteroid dehydrogenase enzyme (HSD17B3), thereby decreasing androgen secretion by Leydig cells. We interpret these findings to mean that the likely impact of deficits in androgen secretion on serum androgen levels following developmental exposure to BPA is alleviated by increased Leydig cell numbers. Nevertheless, the present results reinforce the view that BPA causes biological effects at environmentally relevant exposure levels and its presence in consumer products potentially has implication for public health.     

Assessment of human contamination of estrogenic endocrine-disrupting chemicals and their risk for human reproduction

There is broad human exposure to estrogenic endocrine-disrupting chemicals (EDCs), but the data sets that exist are primarily for various environmental media such as food and water rather than the most relevant internal exposure. We have detected various kind of EDC contamination in humans including dioxin and bisphenol A (BPA) widely used for the production of plastic products. BPA was present in serum and follicular fluid at approximately 1–2 ng/ml, as well as in fetal serum and full-term amniotic fluid, confirming passage through the placenta. An approximately five-fold higher concentration, 8.3 ± 8.7 ng/ml, was revealed in amniotic fluid at 15–18 weeks of gestation, compared to other fluids showing increased exposure at the critical developmental period in humans. Interestingly, serum BPA concentrations were significantly higher in normal men and in women with polycystic ovary syndrome (PCOS) compared with normal women possibly due to differences in the androgen-related metabolism of BPA. These findings may provide some insight into the metabolism of EDCs in human and the pathophysiology of endocrine disorders such as PCOS. Dioxin contamination in relationship to development of endometriosis is also discussed.     

Endocrine disrupting chemicals and disease susceptibility

Environmental chemicals have significant impacts on biological systems. Chemical exposures during early stages of development can disrupt normal patterns of development and thus dramatically alter disease susceptibility later in life. Endocrine disrupting chemicals (EDCs) interfere with the body's endocrine system and produce adverse developmental, reproductive, neurological, cardiovascular, metabolic and immune effects in humans. A wide range of substances, both natural and man-made, are thought to cause endocrine disruption, including pharmaceuticals, dioxin and dioxin-like compounds, polychlorinated biphenyls, DDT and other pesticides, and components of plastics such as bisphenol A (BPA) and phthalates. EDCs are found in many everyday products--including plastic bottles, metal food cans, detergents, flame retardants, food additives, toys, cosmetics, and pesticides. EDCs interfere with the synthesis, secretion, transport, activity, or elimination of natural hormones. This interference can block or mimic hormone action, causing a wide range of effects. This review focuses on the mechanisms and modes of action by which EDCs alter hormone signaling. It also includes brief overviews of select disease endpoints associated with endocrine disruption.     

Application of a novel mass spectrometric (MS) method to examine exposure to Bisphenol-A and common substitutes in a maternal fetal cohort

The use of Bisphenol A (BPA) has widely been replaced in consumer products by analogs BPB, BPE, BPF, BPS, and BPAF. Recent studies have linked these substitutes to similar adverse health outcomes as BPA, including disruption of endocrine pathways in animal and human studies. We designed a novel MS method, developed specifically for this study, to capture the most relevant BPA alternatives, BPB, BPE, BPF, BPS, BPAF and 4-NP in human blood and urine to quantify potential in utero exposures. To our knowledge, this is the first study to explore in utero exposure to these BPA analogs and the first U.S. study to test for BPA in maternal/fetal pairs. The method was run on 30 paired maternal urine and fetal cord blood samples from mothers undergoing elective Caesarean sections. 90% of mothers and 77% of babies tested positive for at least one BP analog. 83% of mothers tested positive for BPAF, 60% for BPS, 57% for BPB, 17% for BPF and 7% for BPA. 57% of babies tested positive for BPAF and 50% for BPF. BPA and BPB were detected in one cord blood sample each. BPS was not detected in cord blood. BPE was not detected in any fetal cord blood or maternal urine samples. These findings demonstrate the pervasiveness of some BP analogs in pregnant women and their babies at birth.