Prenatal and lactational exposure to low-doses of bisphenol A alters adult mice behavior

Effects of perinatal bisphenol A exposure during early development on radial arm maze behavior in adult male and female rats

Previous work has shown that exposure to bisphenol A (BPA) can affect anxiety behavior. However, no studies have examined whether administration of this endocrine disruptor during the perinatal period has the potential to induce alterations in cognitive behavior in both adult males and females as assessed in an appetitive task. The goal of the current study was to determine whether exposure to different doses of BPA during early development alters performance on the 17-arm radial maze in adulthood in Long-Evans rats. Oral administration of corn oil (vehicle), 4 μg/kg, 40 μg/kg, or 400 μg/kg BPA to the dams occurred daily throughout pregnancy, and the pups received direct oral administration of BPA between postnatal days 1-9. Blood was collected from offspring at weaning age to determine levels of several hormones (thyroxine, thyroid stimulating hormone, follicle stimulating hormone, luteinizing hormone). One male and one female from each litter were evaluated on the 17-arm radial maze, a working/reference memory task, in adulthood. Results indicated that after exposure to BPA at both 4 and 400 μg/kg/day, rats of both sexes had decreased levels of FSH at weaning. There were no significant effects of BPA on performance on the radial arm maze in males or females. In conclusion, exposure to BPA during early development had modest effects on circulating hormones but did not affect performance on a spatial learning and memory task.

A multi-generational study on low-dose BPA exposure in Wistar rats: effects on maternal behavior, flavor intake and development

Bisphenol A (BPA) is a common endocrine disruptor found as an environmental and food contaminant. It exerts both developmental and behavioral effects, mainly when exposure occurs in early life. The aim of this study was to determine the multi-generational effects of chronic, human-relevant low-dose exposure to BPA on development, maternal behavior and flavor preference in Wistar rats. BPA was orally administered at a daily dose of 5 μg/kg body weight to F0 pregnant dams from the first day of gestation (GD 1) until the last day of lactation (LD 21), and then to F1 offspring from weaning (PND 21) to adulthood (PND 100). F2 offspring were not exposed. Development and clinical signs of toxicity were assessed daily. Maternal behavior was evaluated by observing nursing and pup-caring actions, as well as "non-maternal" behaviors in F0 and F1 dams from parturition until LD 8. The flavor preferences of F1 and F2 offspring were evaluated based on the intake of sweet, salt and fat solutions using the two-bottle choice test on PND 21-34 and PND 86-99. BPA exposure: 1) decreased maternal behavior in F1 dams, 2) caused developmental defects in both F1 and F2 offspring, with a noticeable decrease in anogenital distance in male rats, and 3) did not affect flavored solution intake in F1, but induced changes in sweet preference in F2 juveniles and in salt and fat solution intakes in F2 adults, and 4) induced a body weight increase in the F2 generation only, whereas food intake and water consumption did not change. Taken as a whole, our findings showed that both gestational (F0) and lifelong (F1) exposures to a human-relevant dose of BPA could induce multi-generational effects on both development and behavior. These results suggest possible selective neuroendocrine defects and/or epigenetic changes caused by BPA exposure.

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.

Maternal bisphenol a exposure during pregnancy and its association with adipokines in Mexican-American children

Bisphenol A (BPA) is a high volume production chemical that has been detected in 93% of the United States population. It is thought to have endocrine disrupting activity but human data are limited. In this study, we examined whether prenatal or concurrent urinary BPA concentrations are associated with key metabolism-related hormones, adiponectin and leptin (adipokines), in 9-year-old children. For this analysis, we used 188 mother-child pairs from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) prospective study. BPA was measured in urinary spot samples during early (12.6 ± 3.9 weeks gestation) and late (26.3 ± 2.5 weeks gestation) pregnancy and in 9-year-old children. We found that BPA concentrations during late pregnancy were associated with increased plasma leptin in boys (β = 0.06, P = 0.01), controlling for maternal prepregnancy body mass index (BMI), pregnancy soda consumption, and smoking, years in US prior to pregnancy, maternal education, household poverty status, child BMI and child soda, fast food and sweet snack consumption at 9 years. Additionally, we found that BPA concentrations during early pregnancy are directly associated with plasma adiponectin levels in girls (β = 3.71, P = 0.03). However, we did not find any significant relationships between concurrent BPA concentrations and 9-year child adiponectin or leptin. Overall, our data suggest that prenatal BPA concentrations may influence adipokine levels in 9-year-old children.

Social behavior is perturbed in mice after exposure to bisphenol A: a novel assessment employing an IntelliCage

In order to investigate whether or not prenatal and lactational exposure to bisphenol A (BPA) affects social behavior in mice, pregnant mice were exposed to 500 μg/kg of BPA daily from embryonic day 0 (E0) until postnatal day 21 (P21). The behavior of offspring was monitored at 11-13 and 13-15 weeks of age using an automated behavior assessment system (IntelliCage). Groups of eight mice were tasked with a nose poke, which enabled the mice to open a door to drink bottled water at the corner of their cage. BPA-exposed females visited the corner without drinking behavior during the light cycle less frequently than control female mice did. BPA-exposed males stayed at the corner for longer periods of time and showed a significantly stronger bias in the visit with drinking. In addition, the BPA-exposed males showed a shorter time interval before they visited the corner after preceding animals had visited it, compared with the control males. These findings suggest that prenatal and lactational BPA exposure might affect murine motivational behavior in a social setting differently in males and females.

Sex-specific effects of bisphenol-A on memory and synaptic structural modification in hippocampus of adult mice

Humans are routinely exposed to low levels of bisphenol A (BPA), a synthetic xenoestrogen widely used in the production of polycarbonate plastics. The effects of long-term exposure to BPA on memory and modification of synaptic structure in hippocampus of adult mice were investigated in the present study. The adult mice were exposed to BPA (0.4, 4, and 40 mg/kg/day) or arachis oil for 12 weeks. In open field test, BPA at 0.4, 4, or 40 mg/kg/day increased the frequency of rearing and time in the central area of the males, while BPA at 0.4 mg/kg/day reduced the frequency of rearing in the females. Exposure to BPA (0.4 or 40 mg/kg/day) extended the average escape pathlength to the hidden platform in Morris water maze task and shortened the step-down latency 24 h after footshock of the males, but no changes were found in the females for these measures. Meanwhile, BPA induced a reduced numeric synaptic density and a negative effect on the structural parameters of synaptic interface, including an enlarged synaptic cleft and the reduced length of active zone and PSD thickness, in the hippocampus of the male mice. Western blot analyses further indicated that BPA down-regulated expressions of synaptic proteins (synapsin I and PSD-95) and synaptic NMDA receptor subunit NR1 and AMPA receptor subunit GluR1 in the hippocampus of the males. These results suggest that long-term exposure to low levels of BPA in adulthood sex-specifically impaired spatial and passive avoidance memory of mice. These effects may be associated with the higher susceptibility of the hippocampal synaptic plasticity processes, such as remodeling of spinal synapses and the expressions of synaptic proteins (e.g. synapsin I and PSD-95) and NMDA and AMPA receptors, to BPA in the adult male mice.

The effects of bisphenol A on emotional behavior depend upon the timing of exposure, age and gender in mice

Experimental evidence suggests that endocrine-disrupting chemicals (EDCs) can permanently disrupt the development of sexually dimorphic behaviors and the structure of sexually dimorphic areas of the brain. EDC exposure has different effects depending on diverse factors, such as the timing and dose of the exposure, the maternal environment and the individual's age and sex. Among EDCs, bisphenol A (BPA) is one of the most studied because of its extensive use, which ranges from dentistry to food/drink packaging. In the present study, we aimed to investigate the behavioral effects of developmental exposure to a low dose of BPA with respect to the timing of the exposure, maternal environment, sex and age at testing. Starting from the last week of pregnancy to the first postpartum week, dams spontaneously drank either corn oil (control group) or a solution containing BPA (10 μg/kg bw/day). At birth, the litters were cross-fostered to different dams to differentiate among the effects of pre- and postnatal exposure. Pre- and postnatally exposed offspring underwent three diverse experimental paradigms for anxiety-related behaviors: as juveniles, a novelty test and at adulthood, both the free exploratory open field and elevated plus maze tests. At both testing ages, pre- and postnatally exposed females showed evidence of increased anxiety and were less prone to explore a novel environment relative to the control females, showing a behavioral profile more similar to control males than females. In this study, the direction of the behavioral changes was affected similarly by the pre- and postnatal exposures, resulting in a disruption of these sexually dimorphic behaviors, although with a greater effect associated with postnatal exposure primarily in females. Our findings indicate that non-reproductive, sexually dimorphic behaviors are sensitive to endocrine disruption during critical developmental periods-particularly the highly critical early neonatal stage. Combined with previous research, our study provides further evidence of the potential risks that even low doses of EDCs may pose to humans, with fetuses and infants being highly vulnerable.

Bisphenol A delays the perinatal chloride shift in cortical neurons by epigenetic effects on the Kcc2 promoter

Bisphenol A (BPA) is a ubiquitous compound that is emerging as a possible toxicant during embryonic development. BPA has been shown to epigenetically affect the developing nervous system, but the molecular mechanisms are not clear. Here we demonstrate that BPA exposure in culture led to delay in the perinatal chloride shift caused by significant decrease in potassium chloride cotransporter 2 (Kcc2) mRNA expression in developing rat, mouse, and human cortical neurons. Neuronal chloride increased correspondingly. Treatment with epigenetic compounds decitabine and trichostatin A rescued the BPA effects as did knockdown of histone deacetylase 1 and combined knockdown histone deacetylase 1 and 2. Furthermore, BPA evoked increase in tangential interneuron migration and increased chloride in migrating neurons. Interestingly, BPA exerted its effect in a sexually dimorphic manner, with a more accentuated effect in females than males. By chromatin immunoprecipitation, we found a significant increase in binding of methyl-CpG binding protein 2 to the "cytosine-phosphate-guanine shores" of the Kcc2 promoter, and decrease in binding of acetylated histone H3K9 surrounding the transcriptional start site. Methyl-CpG binding protein 2-expressing neurons were more abundant resulting from BPA exposure. The sexually dimorphic effect of BPA on Kcc2 expression was also demonstrated in cortical neurons cultured from the offspring of BPA-fed mouse dams. In these neurons and in cortical slices, decitabine was found to rescue the effect of BPA on Kcc2 expression. Overall, our results indicate that BPA can disrupt Kcc2 gene expression through epigenetic mechanisms. Beyond increase in basic understanding, our findings have relevance for identifying unique neurodevelopmental toxicity mechanisms of BPA, which could possibly play a role in pathogenesis of human neurodevelopmental disorders.

Effects of developmental bisphenol A exposure on reproductive-related behaviors in California mice (Peromyscus californicus): a monogamous animal model

Bisphenol A (BPA), a pervasive, endocrine disrupting compound (EDC), acts as a mixed agonist-antagonist with respect to estrogens and other steroid hormones. We hypothesized that sexually selected traits would be particularly sensitive to EDC. Consistent with this concept, developmental exposure of males from the polygynous deer mouse, Peromyscus maniculatus, to BPA resulted in compromised spatial navigational ability and exploratory behaviors, while there was little effect on females. Here, we have examined a related, monogamous species, the California mouse (Peromyscus californicus), where we predicted that males would be less sensitive to BPA in terms of navigational and exploratory behaviors, while displaying other traits related to interactions with females and territorial marking that might be vulnerable to disruption. As in the deer mouse experiments, females were fed either a phytoestrogen-free CTL diet through pregnancy and lactation or the same diet supplemented with BPA (50 mg/kg feed weight) or ethinyl estradiol (EE) (0.1 part per billion) to provide a "pure" estrogen control. After weaning, pups were maintained on CTL diet until they had reached sexual maturity, at which time behaviors were evaluated. In addition, territorial marking was assessed in BPA-exposed males housed alone and when a control male was visible in the testing arena. In contrast to deer mice, BPA and EE exposure had no effect on spatial navigational skills in either male or female California mice. While CTL females exhibited greater exploratory behavior than CTL males, BPA exposure abolished this sex difference. BPA-exposed males, however, engaged in less territorial marking when CTL males were present. These studies demonstrate that developmental BPA exposure can disrupt adult behaviors in a sex- and species-dependent manner and are consistent with the hypothesis that sexually selected traits are particularly vulnerable to endocrine disruption and should be a consideration in risk assessment studies.

Gestational and lactational exposure to bisphenol-A affects anxiety- and depression-like behaviors in mice

Bisphenol-A (BPA), an environmental endocrine disruptor, has attracted attention because of its adverse effects on the brain and behavioral development. Previous evidence indicates that perinatal exposure to low levels of BPA affects anxiety-like and cognitive behaviors in adult rodents. The present study aims to investigate the changes of anxiety- and depression-like behaviors of perinatally exposed mice in adulthood following the gestational (gestation days 7 to 20) or lactational (postnatal days 1 to 14) exposure to BPA (0.4 or 4 mg/kg/d). The results indicated that both gestational and lactational exposures to BPA increased anxiety and depression-like behavior in mice of both sexes. The females with gestational exposure exhibited an increased anxiety-like state in the four models tested, including the open field, dark-light transition task, mirrored maze, and elevated plus maze tasks. Furthermore, the females with lactational exposure and the males with gestational exposure exhibited an anxiogenic-like behavior in two models, whereas the males with lactational exposure exhibited an anxiogenic-like behavior only in the elevated plus maze test. The results of the forced swim task showed that gestational exposure markedly increased the immobile time in both sexes, and the same effect was induced by lactational exposure only with 4 mg/kg/d BPA. Furthermore, western blot analyses showed that both gestational and lactational exposures inhibited the expression of the AMPA receptor subunit GluR1 in the hippocampus and amygdala in mice of both sexes, whereas the level of the NMDA receptor subunit NR1 was increased in the amygdala following gestational exposure but was reduced in the hippocampus of the females with lactational exposure. These results suggest that both gestational and lactational exposures to BPA increased anxiety- and depression-like behaviors of adult mice of both sexes. In addition gestational exposure exhibited a stronger effect on anxiety-like state in females. The altered levels of AMPA and NMDA receptors in the hippocampus and amygdala may be associated with BPA-induced behavioral changes.

Developmental neurotoxicity: some old and new issues

The developing central nervous system is often more vulnerable to injury than the adult one. Of the almost 200 chemicals known to be neurotoxic, many are developmental neurotoxicants. Exposure to these compounds in utero or during childhood can contribute to a variety of neurodevelopmental and neurological disorders. Two established developmental neurotoxicants, methylmercury and lead, and two classes of chemicals, the polybrominated diphenyl ether flame retardants and the organophosphorus insecticides, which are emerging as potential developmental neurotoxicants, are discussed in this paper. Developmental neurotoxicants may also cause silent damage, which would manifest itself only as the individual ages, and may contribute to neurodegenerative diseases such as Parkinson's or Alzheimer's diseases. Guidelines for developmental neurotoxicity testing have been implemented, but there is still room for their improvement and for searching and validating alternative testing approaches.

Bisphenol A, an endocrine-disrupting chemical, and brain development

Bisphenol A (BPA) is an endocrine-disrupting chemical, widely used in various industries and the field of dentistry. The consequent increase in BPA exposure among humans has led us to some concerns regarding the potential deleterious effects on reproduction and brain development. The emphasis of this review is on the effects of prenatal and lactational exposure to low doses of BPA on brain development in mice. We demonstrated that prenatal exposure to BPA affected fetal murine neocortical development by accelerating neuronal differentiation/migration during the early embryonic stage, which was associated with up- and down-regulation of the genes critical for brain development, including the basic helix-loop-helix transcription factors. In the adult mice brains, both abnormal neocortical architecture and abnormal corticothalamic projections persisted in the group exposed to the BPA. Functionally, BPA exposure disturbed murine behavior, accompanied with a disrupted neurotransmitter system, including monoamines, in the postnatal development period and in adult mice. We also demonstrated that epigenetic alterations in promoter-associated CpG islands might underlie some of the effects on brain development after exposure to BPA.

Neurodevelopmental low-dose bisphenol A exposure leads to early life-stage hyperactivity and learning deficits in adult zebrafish

Developmental bisphenol A (BPA) exposure has been implicated in adverse behavior and learning deficits. The mode of action underlying these effects is unclear. The objectives of this study were to identify whether low-dose, developmental BPA exposure affects larval zebrafish locomotor behavior and whether learning deficits occur in adults exposed during development. Two control compounds, 17β-estradiol (an estrogen receptor ligand) and GSK4716 (a synthetic estrogen-related receptor gamma ligand), were included. Larval toxicity assays were used to determine appropriate BPA, 17β-estradiol, and GSK4716 concentrations for behavior testing. BPA tissue uptake was analyzed using HPLC and lower doses were extrapolated using a linear regression analysis. Larval behavior tests were conducted using a ViewPoint Zebrabox. Adult learning tests were conducted using a custom-built T-maze. BPA exposure to <30μM was non-teratogenic. Neurodevelopmental BPA exposure to 0.01, 0.1, or 1μM led to larval hyperactivity or learning deficits in adult zebrafish. Exposure to 0.1μM 17β-estradiol or GSK4716 also led to larval hyperactivity. This study demonstrates the efficacy of using the zebrafish model for studying the neurobehavioral effects of low-dose developmental BPA exposure.

Hybrid cyst: case reports and review of 15 cases in Japan

Hybrid cyst is a rare cystic lesion that includes more than two components of the pilosebaceous units. To clarify the clinical and pathological features of hybrid cysts, we report two cases and review 15 cases of hybrid cyst in Japan. On the whole, the age range was 12-73 years with a 2.95:1 female predominance and predilection for the scalp and face (46.7%). Most of the tumours presented as a solitary lesion and the size range was 2-45 mm. The most frequent histological type was the combination of infundibular and trichilemmal cysts (60.0%). Studying the clinicopathological features of hybrid cysts helps us in understanding the pathogenesis of diseases arising from pilosebaceous units.