Maternal bisphenol-A levels at delivery: a looming problem?

Maternal bisphenol a exposure promotes the development of experimental asthma in mouse pups

BACKGROUND

We recently reported that various environmental estrogens induce mast cell degranulation and enhance IgE-mediated release of allergic mediators in vitro.

OBJECTIVES

We hypothesized that environmental estrogens would enhance allergic sensitization as well as bronchial inflammation and responsiveness. To test this hypothesis, we exposed fetal and neonatal mice to the common environmental estrogen bisphenol A (BPA) via maternal loading and assessed the pups' response to allergic sensitization and bronchial challenge.

METHODS

Female BALB/c mice received 10 microg/mL BPA in their drinking water from 1 week before impregnation to the end of the study. Neonatal mice were given a single 5 microg intraperitoneal dose of ovalbumin (OVA) with aluminum hydroxide on postnatal day 4 and 3% OVA by nebulization for 10 min on days 13, 14, and 15. Forty-eight hours after the last nebulization, we assessed serum IgE antibodies to OVA by enzyme-linked immunosorbent assay (ELISA) and airway inflammation and hyperresponsiveness by enumerating eosinophils in bronchoalveolar lavage fluid, whole-body barometric plethysmography, and a forced oscillation technique.

RESULTS

Neonates from BPA-exposed mothers responded to this "suboptimal" sensitization with higher serum IgE anti-OVA concentrations compared with those from unexposed mothers (p < 0.05), and eosinophilic inflammation in their airways was significantly greater. Airway responsiveness of the OVA-sensitized neonates from BPA-treated mothers was enhanced compared with those from unexposed mothers (p < 0.05).

CONCLUSIONS

Perinatal exposure to BPA enhances allergic sensitization and bronchial inflammation and responsiveness in a susceptible animal model of asthma.

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.

Prenatal bisphenol A exposure and early childhood behavior

BACKGROUND

Prenatal exposure to bisphenol A (BPA) increases offspring aggression and diminishes differences in sexually dimorphic behaviors in rodents.

OBJECTIVE

We examined the association between prenatal BPA exposure and behavior in 2-year-old children.

METHODS

We used data from 249 mothers and their children in Cincinnati, Ohio (USA). Maternal urine was collected around 16 and 26 weeks of gestation and at birth. BPA concentrations were quantified using high-performance liquid chromatography-isotope-dilution tandem mass spectrometry. Child behavior was assessed at 2 years of age using the second edition of the Behavioral Assessment System for Children (BASC-2). The association between prenatal BPA concentrations and BASC-2 scores was analyzed using linear regression.

RESULTS

Median BPA concentrations were 1.8 (16 weeks), 1.7 (26 weeks), and 1.3 (birth) ng/mL. Mean (+/- SD) BASC-2 externalizing and internalizing scores were 47.6 +/- 7.8 and 44.8 +/- 7.0, respectively. After adjustment for confounders, log(10)-transformed mean prenatal BPA concentrations were associated with externalizing scores, but only among females [beta = 6.0; 95% confidence interval (CI), 0.1-12.0]. Compared with 26-week and birth concentrations, BPA concentrations collected around 16 weeks were more strongly associated with externalizing scores among all children (beta = 2.9; 95% CI, 0.2-5.7), and this association was stronger in females than in males. Among all children, measurements collected at <or= 16 weeks showed a stronger association (beta = 5.1; 95% CI, 1.5-8.6) with externalizing scores than did measurements taken at 17-21 weeks (beta = 0.6; 95% CI, -2.9 to 4.1).

CONCLUSIONS

These results suggest that prenatal BPA exposure may be associated with externalizing behaviors in 2-year-old children, especially among female children.

Alterations in male infant behaviors towards its mother by prenatal exposure to bisphenol A in cynomolgus monkeys (Macaca fascicularis) during early suckling period

Bisphenol A (BPA) is an environmental chemical with physiological potencies that cause adverse effects, even at environmentally relevant exposures, on the basis of a number of studies in experimental rodents. Thus, there is an increasing concern about environmental exposure of humans to BPA. In the present study, we used experimentally controlled cynomolgus monkeys (Macaca fascicularis) to assess the influence of prenatal exposure to BPA (10 microg/(kg day)) via subcutaneously implanted pumps and examined social behaviors between infants and their mothers during the suckling period. Mother-infant interactions in cynomolgus monkeys had behavioral sexual dimorphism associated with sex of infant from early suckling period. Prenatal exposure to BPA altered the behaviors of male infants significantly; BPA-exposed male infants behaved as female infants. And it also affected some of female infant behaviors. Consequently, gestational BPA exposure altered some behaviors of their mothers, mainly in male-nursing mothers. These results suggest that BPA exposure affects behavioral sexual differentiation in male monkeys, which promotes the understanding of risk of BPA exposure in human.

Bisphenol A levels in blood depend on age and exposure

We present two approaches to estimate blood concentrations of Bisphenol A (BPA). Simple kinetic principles were applied to calculate steady state plasma concentrations. A physiologically based model was used to simulate the blood concentration time profile in several age groups exploring the influence of not yet fully developed metabolic capacity on the blood concentrations in the newborn. Both approaches gave concordant results and are in excellent agreement with experimental results [Völkel, W., Colnot, T., Csanady, G.A., Filser, J.G., Dekant, W., 2002. Metabolism and kinetics of bisphenol A in humans at low doses following oral administration. Chem. Res. Toxicol. 15, 1281-1287]. The predictions also agree with published results obtained with a different physiologically based model. According to model simulations, BPA is present in the blood of the normal population at concentrations several orders of magnitude lower than most measurements reported in the literature. At the same external exposure level, the newborn is predicted to have 3 times greater blood concentration than the adult. This is due to the not yet fully developed glucuronidation activity in the newborn, not fully compensated by the unimpaired sulfation pathway. For the highest measured external BPA exposure, the predicted blood concentrations of 2.6 pg/ml (steady state concentration) and 8.2 pg/ml (peak concentration) in the adult are lower than the in vitro concentrations at which inhibiting adiponectin release from human adipocytes and stimulation of beta-cell production and secretion were observed.

Neonatal bisphenol-a exposure alters rat reproductive development and ovarian morphology without impairing activation of gonadotropin-releasing hormone neurons

Developmental exposure to endocrine-disrupting compounds is hypothesized to adversely affect female reproductive physiology by interfering with the organization of the hypothalamic-pituitary-gonadal axis. Here, we compared the effects of neonatal exposure to two environmentally relevant doses of the plastics component bisphenol-A (BPA; 50 microg/kg and 50 mg/kg) with the ESR1 (formerly known as ERalpha)-selective agonist 4,4',4''-(4-propyl-[(1)H]pyrazole-1,3,5-triyl)trisphenol (PPT; 1 mg/kg) on the development of the female rat hypothalamus and ovary. An oil vehicle and estradiol benzoate (EB; 25 microg) were used as negative and positive controls. Exposure to EB, PPT, or the low dose of BPA advanced pubertal onset. A total of 67% of females exposed to the high BPA dose were acyclic by 15 wk after vaginal opening compared with 14% of those exposed to the low BPA dose, all of the EB- and PPT-treated females, and none of the control animals. Ovaries from the EB-treated females were undersized and showed no evidence of folliculogenesis, whereas ovaries from the PPT-treated females were characterized by large antral-like follicles, which did not appear to support ovulation. Severity of deficits within the BPA-treated groups increased with dose and included large antral-like follicles and lower numbers of corpora lutea. Sexual receptivity, examined after ovariectomy and hormone replacement, was normal in all groups except those neonatally exposed to EB. FOS induction in hypothalamic gonadotropic (GnRH) neurons after hormone priming was impaired in the EB- and PPT-treated groups but neither of the BPA-treated groups. Our data suggest that BPA disrupts ovarian development but not the ability of GnRH neurons to respond to steroid-positive feedback.

Prenatal exposure to bisphenol a at environmentally relevant doses adversely affects the murine female reproductive tract later in life

BACKGROUND

Exposure to endocrine-disrupting chemicals during critical developmental periods causes adverse consequences later in life; an example is prenatal exposure to the pharmaceutical diethylstilbestrol (DES). Bisphenol A (BPA), an environmental estrogen used in the synthesis of plastics, is of concern because its chemical structure resembles that of DES, and it is a "high-volume production" chemical with widespread human exposure.

OBJECTIVES

In this study we investigated whether prenatal BPA causes long-term adverse effects in female reproductive tissues in an experimental animal model previously shown useful in studying effects of prenatal DES.

METHODS

Timed pregnant CD-1 mice were treated on days 9-16 of gestation with BPA (0.1, 1, 10, 100, or 1,000 mug/kg/day). After delivery, pups were held for 18 months; reproductive tissues were then evaluated.

RESULTS

Ovarian cysts were significantly increased in the 1-mug/kg BPA group; ovarian cyst-adenomas were seen in the other three BPA-treated groups but not in corn-oil controls. We observed increased progressive proliferative lesions of the oviduct after BPA treatment, similar to those described in response to DES. Further, although not statistically different from the controls, prominent mesonephric (Wolffian) remnants and squamous metaplasia of the uterus, as well as vaginal adenosis, were present in BPA-treated mice, similar to lesions reported following DES treatment. More severe pathologies observed in some BPA-treated animals included atypical hyperplasia and stromal polyps of the uterus; sarcoma of the uterine cervix; and mammary adenocarcinoma. We did not observe these lesions in controls.

CONCLUSIONS

These data suggest that BPA causes long-term adverse reproductive and carcinogenic effects if exposure occurs during critical periods of differentiation.

Developmental programming: prenatal androgen excess disrupts ovarian steroid receptor balance

Steroid hormones play an important role in reproduction and the receptors through which they signal change in a developmental time, follicle stage, and cell-specific manner. Disruption in steroid receptor expression affects follicle formation and differentiation. In this study, using prenatal testosterone (T) and dihydrotestosterone (DHT)-treated female sheep as model systems, we tested the hypothesis that prenatal androgen excess disrupts the developmental ontogeny of ovarian steroid receptor protein expression. Pregnant Suffolk ewes were injected twice weekly with T propionate or DHT propionate (a non-aromatizable androgen) in cottonseed oil from days 30 to 90 of gestation. Changes in ovarian estrogen receptors (ER; ESR1, ESR2), androgen receptor (AR) and progesterone receptor (PGR) proteins were determined at fetal (days 90 and 140), postpubertal (10 months), and adult (21 months; only prenatal T-treated sheep studied) ages by immunohistochemistry. Prenatal T and DHT treatment induced selective increase in AR but not ER or PGR expression in the stroma and granulosa cells of fetal days 90 and 140 ovaries. An increase in ESR1 and decrease in ESR2 immunostaining coupled with increased AR expression were evident in granulosa cells of antral follicles of 10- and 21-month-old prenatal T but not DHT-treated females (analyzed only at 10 months). These findings provide evidence that an early increase in ovarian AR is the first step in the altered ovarian developmental trajectory of prenatal T-treated females, and manifestations of postnatal ovarian dysfunction are likely facilitated via altered equilibrium of antral follicular granulosa cell ER/AR protein expression.

Potencies of bisphenol A on the neuronal differentiation and hippocampal neurogenesis

Endocrine-disrupting chemicals (EDC) produce adverse effects on reproductive and immune function or neurological behavior, and may also induce cancer. The environmental EDC bisphenol A (BPA) is widely used in the manufacture of plastics and epoxy resins. BPA affects reproductive organ growth and development, but the potential adverse effects of BPA on neuronal development are not fully understood. Here, BPA concentration-dependently decreased proliferation of murine-derived multipotent neural progenitor cells (NPC), and high concentrations produced cytotoxicity. In contrast, low concentrations of BPA, which possess estrogenic activity, stimulated NPC differentiation into a neuronal phenotype. BPA treatment did not affect neonatal brain development in F1 mice. However, BPA treatment (20 mg/kg) accelerated formation of the dentate gyrus in postnatal day 1 mice. Prenatal and postnatal BPA treatment did not affect adult hippocampal neurogenesis in the dentate gyrus in 8-wk-old mice. Data indicate that BPA stimulates neuronal differentiation and might disrupt neonatal brain development.