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

Neurodevelopment effects of early life bisphenol-A exposure on visual memory: Insights into recovery dynamics

Bisphenol A (BPA), a ubiquitous endocrine disruptor, is implicated in the cognitive deficits observed in both children and animals. Especially, BPA-induced spatial memory deterioration during the whole development phase of rodents has been well delineated. However, whether BPA exposure on the different development phases exerts similar effects on the prefrontal cortex (PFC) dependent visual memory is still elusive. Here, we chose two exposure windows, the whole gestation and lactation phases (E0∼P21) and the whole juvenile and adolescent phases (P22∼P60), for exposing rats to BPA. The visual memory of those rats was accessed by object recognition testing in the open field after BPA exposure and a constant recovery interval. The results revealed a substantial decline of visual memory under both exposure conditions, accompanied by an increase in anxiety-like behavior in BPA-exposed rats. Notably, after a 20-day recovery period, those behavioral changes induced by BPA exposure during P22∼60, not E0∼P21, were reversed compared to the control rats. According to morphological analysis of those rats after recovery, we found that the spine density of pyramidal neurons in the PFC were significant decreased in rats with BPA exposure during E0∼P21 and there was no difference between rats with or without BPA exposure during P22∼P60. Additionally, a similar change trend in excitatory receptors expression was observed under both exposure conditions. After an additional 20 days of recovery, the behavioral changes in rats with perinatal BPA exposure reverted to the normal status. Our present findings illuminate the dynamic effects of BPA on PFC-dependent functions across two crucial early developmental stages of life.

Linking Environmental Chemicals to Neuroinflammation and Autism Spectrum Disorder: Mechanisms and Implications for Prevention

This article explores the potential link between endocrine-disrupting chemicals (EDCs), neuroinflammation, and the development of autism spectrum disorder (ASD). Neuroinflammation refers to the immune system's response to injury, infection, or disease in the central nervous system. Studies have shown that exposure to EDCs, such as bisphenol A and phthalates, can disrupt normal immune function in the brain, leading to chronic or excessive neuroinflammation. This disruption of immune function can contribute to developing neurological disorders, including ASD. Furthermore, EDCs may activate microglia, increasing pro-inflammatory cytokine production and astroglia-mediated oxidative stress, exacerbating neuroinflammation. EDCs may also modulate the epigenetic profile of cells by methyltransferase expression, thereby affecting neurodevelopment. This article also highlights the importance of reducing exposure to EDCs and advocating for policies and regulations restricting their use. Further research is needed to understand better the mechanisms underlying the link between EDCs, neuroinflammation, and ASD and to develop new treatments for ASD.

Bisphenol A Effects on Neurons' Neurochemical Character in the Urinary Bladder Intramural Ganglia of Domestic Pigs

Bisphenol A (BPA), a substance globally used to produce plastics, is part of many everyday items, including bottles, food containers, electronic elements, and others. It may penetrate the environment and living organisms, negatively affecting, among others, the nervous, immune, endocrine, and cardiovascular systems. Knowledge of the impact of BPA on the urinary bladder is extremely scarce. This study investigated the influence of two doses of BPA (0.05 mg/kg body weight (b.w.)/day and 0.5 mg/kg b.w./day) given orally for 28 days on the neurons situated in the ganglia located in the urinary bladder trigone using the typical double immunofluorescence method. In the study, an increase in the percentage of neurons containing substance P (SP), galanin (GAL), a neuronal isoform of nitric oxide synthase (nNOS-used as the marker of nitrergic neurons), and/or cocaine- and amphetamine-regulated transcript (CART) peptide was noted after BPA administration. The severity of these changes depended on the dose of BPA and the type of neuronal factors studied. The most visible changes were noted in the cases of SP- and/or GAL-positive neurons after administering a higher dose of BPA. The results have shown that oral exposure to BPA, lasting even for a short time, affects the intramural neurons in the urinary bladder wall, and changes in the neurochemical characterisation of these neurons may be the first signs of BPA-induced pathological processes in this organ.

Origin, dietary exposure, and toxicity of endocrine-disrupting food chemical contaminants: A comprehensive review

Endocrine-disrupting chemicals (EDCs) are a growing public health concern worldwide. Consumption of foodstuffs is currently thought to be one of the principal exposure routes to EDCs. However, alternative ways of human exposure are through inhalation of chemicals and dermal contact. These compounds in food products such as canned food, bottled water, dairy products, fish, meat, egg, and vegetables are a ubiquitous concern to the general population. Therefore, understanding EDCs' properties, such as origin, exposure, toxicological impact, and legal aspects are vital to control their release to the environment and food. The present paper provides an overview of the EDCs and their possible disrupting impact on the endocrine system and other organs.

Chronic exposure of bisphenol-A impairs cognitive function and disrupts hippocampal insulin signaling pathway in male mice

Bisphenol-A (BPA), a well-known estrogenic endocrine disruptor, is generally applied to turn out plastic consumer products. Available data have manifested that exposure to BPA can trigger insulin resistance. Hence, the purpose of the actual study was to consider the impacts of BPA exposure on cognitive function and insulin signaling pathway in the hippocampus of male offspring mice. For this purpose, the pregnant female mice were treated either vehicle (0.1% ethanol) or BPA (0.01, 0.1, and 1µg/mL) via drinking water from day 1 of gestation until delactation (D1-PND21, newborn exposure). Afterward, the three-week-old male offspring mice took orally with the same doses of BPA for nine weeks (PND84). The behavioral tests, blood sugar level, histological observation, transcriptome sequencing, glucose transporter 4 (GLUT4), and hippocampal insulin signaling pathway were checked for the male offspring mice at 13 weeks of age (PND91). Our data indicated that BPA exposure impaired cognitive function, disrupted the hippocampal regular cell arrangement, increased blood glucose levels, disturbed the insulin signaling pathway including phosphorylated insulin receptor substrate1 (p-IRS1), protein kinase B (p-AKT), and glycogen synthase kinase 3β (p-GSK3β). At the same time, the mRNA and protein expressions of GLUT4 were markedly down-regulated in the BPA-exposed groups. To sum up, it has been suggested from these results that BPA has detrimental effects on the insulin signaling pathway, which might subsequently be conducive to the impairment of cognitive function in the adult male offspring mice. Therefore, BPA exposure might in part be an element of risk for the long-term neurodegeneration in male offspring mice.

Does Bisphenol A Confer Risk of Neurodevelopmental Disorders? What We Have Learned from Developmental Neurotoxicity Studies in Animal Models

Substantial evidence indicates that bisphenol A (BPA), a ubiquitous environmental chemical used in the synthesis of polycarbonate plastics and epoxy resins, can impair brain development. Clinical and epidemiological studies exploring potential connections between BPA and neurodevelopmental disorders in humans have repeatedly identified correlations between early BPA exposure and developmental disorders, such as attention deficit/hyperactivity disorder and autism spectrum disorder. Investigations using invertebrate and vertebrate animal models have revealed that developmental exposure to BPA can impair multiple aspects of neuronal development, including neural stem cell proliferation and differentiation, synapse formation, and synaptic plasticity-neuronal phenotypes that are thought to underpin the fundamental changes in behavior-associated neurodevelopmental disorders. Consistent with neuronal phenotypes caused by BPA, behavioral analyses of BPA-treated animals have shown significant impacts on behavioral endophenotypes related to neurodevelopmental disorders, including altered locomotor activity, learning and memory deficits, and anxiety-like behavior. To contextualize the correlations between BPA and neurodevelopmental disorders in humans, this review summarizes the current literature on the developmental neurotoxicity of BPA in laboratory animals with an emphasis on neuronal phenotypes, molecular mechanisms, and behavioral outcomes. The collective works described here predominantly support the notion that gestational exposure to BPA should be regarded as a risk factor for neurodevelopmental disorders.

In utero exposure to endocrine-disrupting chemicals, maternal factors and alterations in the epigenetic landscape underlying later-life health effects

Widespread persistence of endocrine-disrupting chemicals (EDCs) in the environment has mandated the need to study their potential effects on an individual's long-term health after both acute and chronic exposure periods. In this review article a particular focus is given on in utero exposure to EDCs in rodent models which resulted in altered epigenetic programming and transgenerational effects in the offspring causing disrupted reproductive and metabolic phenotypes. The literature to date establishes the impact of transgenerational effects of EDCs potentially associated with epigenetic mediated mechanisms. Therefore, this review aims to provide a comprehensive overview of epigenetic programming and it's regulation in mammals, primarily focusing on the epigenetic plasticity and susceptibility to exogenous hormone active chemicals during the early developmental period. Further, we have also in depth discussed the epigenetic alterations associated with the exposure to selected EDCs such as Bisphenol A (BPA), di-2-ethylhexyl phthalate (DEHP) and vinclozlin upon in utero exposure especially in rodent models.

Converging Effects of Three Different Endocrine Disrupters on Sox and Pou Gene Expression in Developing Rat Hippocampus: Possible Role of microRNA in Sex Differences

Endocrine disrupting chemicals (EDCs) can impair hippocampus-dependent behaviors in rat offspring and in children. In search for key processes underlying this effect, we compared the transcriptomes of rat hippocampus on postnatal day 6 after gestational and lactational exposure to three different EDCs at doses known to impair development of learning and memory. Aroclor 1254, a commercial PCB mixture (5 mg/kg or 0.5 mg/kg), or bisphenol A (5 mg/kg or 0.5 mg/kg) were administered in chow, chlorpyrifos (3 mg/kg or 1 mg/kg) was injected subcutaneously. Male hippocampus exhibited a common effect of all three chemicals on genes involved in cell-autonomous processes, Sox6, Sox11, Pou2f2/Oct2, and Pou3f2/Brn2, all upregulated at the high dose. Additional genes of the Sox and Pou families were affected by only one or two of the chemicals. Real time RT PCR showed a comparable expression change for bisphenol A also at the lower dose. Female hippocampus exhibited much fewer genes with expression changes (almost none with false discovery rate <0.05), and none of the genes of the Sox and Pou families was affected. Since gene network analyses in male hippocampus suggested a link between Sox6 and miR-24, known to be repressed by activation of ER-alpha and to repress Sox6 in other tissues, this microRNA was measured. miR-24 was downregulated by all chemicals at the high dose in males. Values of Sox6 mRNA and miR-24 were inversely correlated in individual male hippocampus samples, supporting the hypothesis that the change in Sox6 expression resulted from an action of miR-24. In contrast, miR-24 levels remained unchanged in hippocampus of females. A sexually dimorphic response of miR-24 may thus be at the basis of the sex difference in Sox6 expression changes following exposure to the three chemicals. ER-alpha expression was also sex-dependent, but the expression changes did not parallel those of potential downstream genes such as Sox6. Sox6 is known to suppress differentiation of Parvalbumin (Pvalb)-expressing interneurons. Individual Sox6 levels (FPKM) were inversely correlated with levels of Pvalb, but not with markers of Sox6-independent interneuron subpopulations, Nos1 and 5HT3aR. Effects on interneuron development are further suggested, in males, by expression changes of Nrg1 and its receptor Erbb4, controlling interneuron migration. Our study disclosed new types of EDC-responsive morphogenetic genes, and illustrated the potential relevance of microRNAs in sexually dimorphic EDC actions.

Role of cerium oxide nanoparticles in improving oxidative stress and developmental delays in Drosophila melanogaster as an in-vivo model for bisphenol a toxicity

Bisphenol A (BPA) is an endocrine-disrupting chemical used commonly in the manufacture of plastic bottles, beverage cans, consumer products, and medical devices. It has a high risk of disrupting hormone-mediated processes which are critical for the growth and development of an infant. In the present study, the flies are exposed to different concentrations of BPA (0.05 and 0.5 mM), which represented the federally regulated LOAEL (50 mg/kg bw/day) and a higher dose of 1 mM, to study the change in cell death, nuclear instability oxidative stress, and behavioral anomalies leading to complex behavioral disorders like Autism. Effects of BPA doses (0.05, 0.5, 1 mM) were studied and the flies showed deficits in social interaction, locomotion, and enhanced oxidative stress that was found to be deteriorating among the flies. Automated tracking and robust MATLAB analysis of behavioral paradigms like position, movement, velocity, and courtship have given us an insight into a detrimental change in development and behavior when exposed to BPA. The flies were also co-treated with Cerium Oxide nanoparticles (CeO₂ NP), well known for its antioxidant properties due to their antioxidant enzyme biomimetic nature, resulted in low oxidative stress, genotoxicity, and an improvement in behavior. In this work, we have tested our hypothesis of oxidative stress and nuclear instability as a potent cause for improper development in Drosophila when exposed to EDCs like BPA which is a potential hazard for both health and environment and might lead to various developmental disorders in children.

Endocrine-disrupting chemicals and behaviour: A high risk to take?

Early life exposure to endocrine-disrupting chemicals (EDCs) is considered a potential risk factor for aberrant brain development and the emergence of behavioral deficits. The purpose of this review is to summarize the toxic effects of bisphenol-A (BPA) and phthalate exposure during pre-, -post- or perinatal life on different types of behaviour in male and female rodents. Despite results not being always consistent, most probably due to methodological issues, it is highly probable that early life exposure to BPA or/and phthalates, affects various aspects of behaviour in the offspring. Adverse effects include: Increased levels of anxiety, altered exploratory behaviour, reduced social interaction or increased aggression and deficits in spatial or recognition learning and memory. These effects have been observed with a wide range of doses, in some cases even below the currently employed Tolerable Daily Intake dose for either BPA or phthalates.

Changes in the Population Size of Calbindin D-28k-Immunoreactive Enteric Neurons in the Porcine Caecum under the Influence of Bisphenol A: A Preliminary Study

Calbindin D-28k (CB) is a calcium-binding protein widely distributed in living organisms that may act as a calcium buffer and sensory protein. CB is present in the enteric nervous system (ENS) situated in the gastrointestinal tract, which controls the majority of activities of the stomach and intestine. The influence of various doses of bisphenol A (BPA)—a chemical compound widely used in plastics production—on the number and distribution of CB-positive enteric neuronal cells in the porcine caecum was investigated with an immunofluorescence technique. The obtained results showed that low dosages of BPA resulted in an increase in the number of CB-positive neuronal cells in the myenteric (MP) and inner submucous (ISP) plexuses, whereas it did not alter the number of such neuronal cells in the outer submucous plexus (OSP). High dosages of BPA caused the increase in the amount of CB-positive perikarya in all the above-mentioned kinds of the caecal neuronal plexuses. These observations strongly suggest that CB in the ENS participates in the processes connected with the toxic activity of BPA. Most likely, the changes noted in this experiment result from the adaptive and protective properties of CB.

Sex-biased impact of endocrine disrupting chemicals on behavioral development and vulnerability to disease: Of mice and children

Sex is a fundamental biological characteristic that influences many aspects of an organism's phenotype, including neurobiological functions and behavior as a result of species-specific evolutionary pressures. Sex differences have strong implications for vulnerability to disease and susceptibility to environmental perturbations. Endocrine disrupting chemicals (EDCs) have the potential to interfere with sex hormones functioning and influence development in a sex specific manner. Here we present an updated descriptive review of findings from animal models and human studies regarding the current evidence for altered sex-differences in behavioral development in response to early exposure to EDCs, with a focus on bisphenol A and phthalates. Overall, we show that animal and human studies have a good degree of consistency and that there is strong evidence demonstrating that EDCs exposure during critical periods of development affect sex differences in emotional and cognitive behaviors. Results are more heterogeneous when social, sexual and parental behaviors are considered. In order to pinpoint sex differences in environmentally-driven disease vulnerabilities, researchers need to consider sex-biased developmental effects of EDCs.

Prenatal and postnatal bisphenol A exposure inhibits postnatal neurogenesis in the hippocampal dentate gyrus

Bisphenol A (BPA), an endocrine disruptor with estrogenic effects, is widely used as a raw material for manufacturing polycarbonate plastic and epoxy resins. Prenatal and postnatal exposure to BPA affects brain morphogenesis. However, the effects of prenatal and postnatal BPA exposure on postnatal neurogenesis in mice are poorly understood. In this study, we developed a mouse model of prenatal and postnatal BPA exposure and analyzed its effects on hippocampal neurogenesis. The hippocampal dentate gyrus is vulnerable to chemical exposure, as neurogenesis continues in this region even after birth. Our results showed that in mice, prenatal and postnatal BPA exposure decreased the number of type-1, 2a, 2b, and 3 neural progenitor cells, as well as in granule cells, in the hippocampal dentate gyrus on postnatal days 16 and 70. The effect of prenatal and postnatal BPA exposure on neural progenitors were affected at all differentiation stages. In addition, prenatal and postnatal BPA exposure affects the maintenance of long-term memory on postnatal day 70. Our results suggest that neurodevelopmental toxicity due to prenatal and postnatal BPA exposure might affect postnatal morphogenesis and functional development of the hippocampal dentate gyrus.

Bisphenols as a Legacy Pollutant, and Their Effects on Organ Vulnerability

Bisphenols are widely used in the synthesis of polycarbonate plastics, epoxy resins, and thermal paper, which are used in manufacturing items of daily use. Packaged foods and drinks are the main sources of exposure to bisphenols. These chemicals affect humans and animals by disrupting the estrogen, androgen, progesterone, thyroid, and aryl hydrocarbon receptor functions. Bisphenols exert numerous harmful effects because of their interaction with receptors, reactive oxygen species (ROS) formation, lipid peroxidation, mitochondrial dysfunction, and cell signal alterations. Both cohort and case-control studies have determined an association between bisphenol exposure and increased risk of cardiovascular diseases, neurological disorders, reproductive abnormalities, obesity, and diabetes. Prenatal exposure to bisphenols results in developmental disorders in animals. These chemicals also affect the immune cells and play a significant role in initiating the inflammatory response. Exposure to bisphenols exhibit age, gender, and dose-dependent effects. Even at low concentrations, bisphenols exert toxicity, and hence deserve a critical assessment of their uses. Since bisphenols have a global influence on human health, the need to discover the underlying pathways involved in all disease conditions is essential. Furthermore, it is important to promote the use of alternatives for bisphenols, thereby restricting their uses.

Gestational Exposure to Common Endocrine Disrupting Chemicals and Their Impact on Neurodevelopment and Behavior

Endocrine disrupting chemicals are common in our environment and act on hormone systems and signaling pathways to alter physiological homeostasis. Gestational exposure can disrupt developmental programs, permanently altering tissues with impacts lasting into adulthood. The brain is a critical target for developmental endocrine disruption, resulting in altered neuroendocrine control of hormonal signaling, altered neurotransmitter control of nervous system function, and fundamental changes in behaviors such as learning, memory, and social interactions. Human cohort studies reveal correlations between maternal/fetal exposure to endocrine disruptors and incidence of neurodevelopmental disorders. Here, we summarize the major literature findings of endocrine disruption of neurodevelopment and concomitant changes in behavior by four major endocrine disruptor classes:bisphenol A, polychlorinated biphenyls, organophosphates, and polybrominated diphenyl ethers. We specifically review studies of gestational and/or lactational exposure to understand the effects of early life exposure to these compounds and summarize animal studies that help explain human correlative data.

Association of exposure to Bisphenol A with obesity and cardiometabolic risk factors in children and adolescents

In this study, the association of exposure to Bisphenol A (BPA) with obesity and cardiometabolic risk factors was investigated on 132 children and adolescents aged 6-18 years living in Isfahan, Iran. Potential contributors to BPA exposure were assessed by a questionnaire. Total BPA was detected in urine samples of all participants without significant difference in boys and girls. The mean body mass index (BMI) and waist circumference (WC) increased significantly across the BPA tertiles (p for trend = < 0.001). Similar trend was documented for systolic blood pressure (SBP) and diastolic blood pressure (DBP) as well as fasting blood sugar. The risk of obesity was 12.48 times higher in participants in the third tertile of BPA than in others (95% CI: 3.36-46.39, p < 0.001). The current study showed significant association between BPA exposure with obesity and some cardiometabolic risk factors in children and adolescents, however, further longitudinal studies are necessary to evaluate the clinical effects of this finding. Abbreviations: BMI: Body Mass Index; BPA: Bisphenol A; BSTFA: N, O-Bistrifluoroacetamide; CDC: Centers for Disease Control and Prevention; CI: Circumference Interval; DBP: Diastolic Blood Pressure; DLLME: Dispersive liquid-liquid microextraction method; FBS: Fasting Blood Glucose; HDL: high-density lipoprotein cholesterol were; LDL: low-density lipoprotein cholesterol; OR: Odd Ratio; PA: Physical Activity; SBP: Systolic Blood Pressure; TC: total cholesterol; TG: triglycerides; WC: Waist Circumference.

Hormonal Imprinting: The First Cellular-level Evidence of Epigenetic Inheritance and its Present State

Hormonal imprinting takes place perinatally at the first encounter between the developing hormone receptor and its target hormone. This process is needed for the normal function of the receptor-hormone pair and its effect is life-long. However, in this critical period, when the developmental window is open, related molecules (members of the same hormone family, synthetic hormones and hormone-like molecules, endocrine disruptors) also can be bound by the receptor, causing life-long faulty imprinting. In this case, the receptors’ binding capacity changes and alterations are caused at adult age in the sexual and behavioral sphere, in the brain and bones, inclination to diseases and manifestation of diseases, etc. Hereby, faulty hormonal imprinting is the basis of metabolic and immunological imprinting as well as the developmental origin of health and disease (DOHaD). Although the perinatal period is the most critical for faulty imprinting, there are other critical periods as weaning and adolescence, when the original imprinting can be modified or new imprintings develop. Hormonal imprinting is an epigenetic process, without changing the base sequence of DNA, it is inherited in the cell line of the imprinted cells and also transgenerationally (up to 1000 generations in unicellulars and up to the 3_rd generation in mammals are justified). Considering the enormously growing number and amount of faulty imprinters (endocrine disruptors) and the hereditary character of faulty imprinting, this latter is threatening the whole human endocrine system.

Impairment of learning and memory performances induced by BPA: Evidences from the literature of a MoA mediated through an ED

Many rodent studies and a few non-human primate data report impairments of spatial and non-spatial memory induced by exposure to bisphenol A (BPA), which are associated with neural modifications, particularly in processes involved in synaptic plasticity. BPA-induced alterations involve disruption of the estrogenic pathway as established by reversal of BPA-induced effects with estrogenic receptor antagonist or by interference of BPA with administered estradiol in ovariectomized animals. Sex differences in hormonal impregnation during critical periods of development and their influence on maturation of learning and memory processes may explain the sexual dimorphism observed in BPA-induced effects in some studies. Altogether, these data highly support the plausibility that alteration of learning and memory and synaptic plasticity by BPA is essentially mediated by disturbance of the estrogenic pathways. As memory function in humans involves similar signaling pathways, this mode of action of BPA has the potential to alter human cognitive abilities.

Nitric oxide as an active substance in the enteric neurons of the porcine digestive tract in physiological conditions and under intoxication with bisphenol A (BPA)

Bisphenol A (BPA) is an organic substance, which is commonly used in the production of plastic. It is known that BPA has the negative impact on the living organism, affecting among others the reproductive organs, nervous, endocrine and immune systems. Nevertheless the knowledge about the influence of BPA on the enteric nervous system (ENS) is extremely scanty. On the other hand, nitric oxide is considered to be one of the most important neuronal factors in the ENS. The aim of the study was to investigate the influence of low and high doses of BPA on neuronal isoform nitric oxide synthase - like immunoreactive (nNOS-LI) nervous structures in the various parts of the porcine gastrointestinal (GI) tract using double immunofluorescence technique. The obtained results show that BPA affects nNOS-LI enteric neurons and nerve fibers, and the character and severity of observed changes depend on the fragment of the gastrointestinal tract, part of the ENS and dose of the toxin. It should be pointed out that even relatively low doses of BPA (0.05 mg/kg body weight/day) are not neutral for the organism and may change the number of nitrergic nervous structures in the stomach and intestine. Observed changes are probably connected with neurotoxic activity of BPA, but the exact mechanisms of them still remain unclear.

In vivo maternal and in vitro BPA exposure effects on hypothalamic neurogenesis and appetite regulators

In utero exposure to the ubiquitous plasticizer, bisphenol A (BPA) is associated with offspring obesity. As food intake/appetite is one of the critical elements contributing to obesity, we determined the effects of in vivo maternal BPA and in vitro BPA exposure on newborn hypothalamic stem cells which form the arcuate nucleus appetite center. For in vivo studies, female rats received BPA prior to and during pregnancy via drinking water, and newborn offspring primary hypothalamic neuroprogenitor (NPCs) were obtained and cultured. For in vitro BPA exposure, primary hypothalamic NPCs from healthy newborns were utilized. In both cases, we studied the effects of BPA on NPC proliferation and differentiation, including putative signal and appetite factors. Maternal BPA increased hypothalamic NPC proliferation and differentiation in newborns, in conjunction with increased neuroproliferative (Hes1) and proneurogenic (Ngn3) protein expression. With NPC differentiation, BPA exposure increased appetite peptide and reduced satiety peptide expression. In vitro BPA-treated control NPCs showed results that were consistent with in vivo data (increase appetite vs satiety peptide expression) and further showed a shift towards neuronal versus glial fate as well as an increase in the epigenetic regulator lysine-specific histone demethylase1 (LSD1). These findings emphasize the vulnerability of stem-cell populations that are involved in life-long regulation of metabolic homeostasis to epigenetically-mediated endocrine disruption by BPA during early life.

Exposure to bisphenol A affects GABAergic neuron differentiation in neurosphere cultures

Endocrine-disrupting chemicals (EDCs) influence not only endocrine functions but also neuronal development and functions. In-vivo studies have suggested the relationship of EDC-induced neurobehavioral disorders with dysfunctions of neurotransmitter mechanisms including γ-aminobutyric acid (GABA)ergic mechanisms. However, whether EDCs affect GABAergic neuron differentiation remains unclear. In the present study, we show that a representative EDC, bisphenol A (BPA), affects GABAergic neuron differentiation. Cortical neurospheres prepared from embryonic mice were exposed to BPA for 7 days, and then neuronal differentiation was induced. We found that BPA exposure resulted in a decrease in the ratio of GABAergic neurons to total neurons. However, the same exposure stimulated the differentiation of neurons expressing calbindin, a calcium-binding protein observed in a subpopulation of GABAergic neurons. These findings suggested that BPA might influence the formation of an inhibitory neuronal network in developing cerebral cortex involved in the occurrence of neurobehavioral disorders.

Possible Obesogenic Effects of Bisphenols Accumulation in the Human Brain

Evidence of bisphenols’ obesogenic effects on humans is mixed and inconsistent. We aimed to explore the presence of bisphenol A (BPA), bisphenol F (BPF) and chlorinated BPA (ClBPA), collectively called the bisphenols, in different brain regions and their association with obesity using post-mortem hypothalamic and white matter brain material from twelve pairs of obese (body mass index (BMI) >30 kg/m²) and normal-weight individuals (BMI <25 kg/m²). Mean ratios of hypothalamus:white matter for BPA, BPF and ClBPA were 1.5, 0.92, 0.95, respectively, suggesting no preferential accumulation of the bisphenols in the grey matter (hypothalamic) or white matter-enriched brain areas. We observed differences in hypothalamic concentrations among the bisphenols, with highest median level detected for ClBPA (median: 2.4 ng/g), followed by BPF (2.2 ng/g) and BPA (1.2 ng/g); similar ranking was observed for the white matter samples (median for: ClBPA-2.5 ng/g, BPF-2.3 ng/g, and BPA-1.0 ng/g). Furthermore, all bisphenol concentrations, except for white-matter BPF were associated with obesity (p < 0.05). This is the first study reporting the presence of bisphenols in two distinct regions of the human brain. Bisphenols accumulation in the white matter-enriched brain tissue could signify that they are able to cross the blood-brain barrier.

Opening the black box of endocrine disruption of brain development: Lessons from the characterization of Bisphenol A

Bisphenol A (BPA) is among the best-studied endocrine disrupting chemicals, known to act via multiple steroid hormone receptors to mediate a myriad of cellular effects. Pre-, peri-, and postnatal BPA exposure have been linked to a variety of altered behaviors in multiple model organisms, ranging from zebrafish to frogs to mammalian models. Given that BPA can cross the human placental barrier and has been found in the serum of human fetuses during gestation, BPA has been postulated to adversely affect ongoing neurodevelopment, ultimately leading to behavioral disorders later in life. Indeed, the brain has been identified as a key developmental target for BPA disruption. Despite these known associations between gestational BPA exposure and adverse developmental outcomes, as well as an extensive body of evidence existing in the literature, the mechanisms by which BPA induces its cellular- and tissue-specific effects on neurodevelopmental processes still remains poorly understood at a mechanistic level. In this review we will briefly summarize the effects of gestational BPA exposure on neural developmental mechanisms and resulting behaviors, and then present suggestions for how we might address gaps in our knowledge to develop a fuller understanding of endocrine neurodevelopmental disruption to better inform governmental policy against the use of BPA or other endocrine disruptors.

Prenatal exposure to bisphenol A and hyperactivity in children: a systematic review and meta-analysis

BACKGROUND

Attention-deficit hyperactivity disorder (ADHD) has increased in prevalence in the past decade. Studies attempting to identify a specific genetic component have not been able to account for much of the heritability of ADHD, indicating there may be gene-environment interactions underlying the disorder, including early exposure to environmental chemicals. Based on several relevant studies, we chose to examine bisphenol A (BPA) as a possible contributor to ADHD in humans. BPA is a widespread environmental chemical that has been shown to disrupt neurodevelopment in rodents and humans.

OBJECTIVES

Using the Office of Health Assessment and Translation (OHAT) framework, a systematic review and meta-analysis was designed to determine the relationship between early life exposure to BPA and hyperactivity, a key diagnostic criterion of ADHD.

DATA SOURCES

Searches of PubMed, Web of Science, and Toxline were completed for all literature to January 1, 2017.

STUDY ELIGIBILITY CRITERIA

For inclusion, the studies had to publish original data, be in the English language, include a measure of BPA exposure, and assess if BPA exposure affected hyperactive behaviors in mice, rats or humans. Exposure to BPA had to occur at <3 months of age for humans, up to postnatal day 35 for rats and up to postnatal day 40 for mice. Exposure could occur either gestationally (via maternal exposure) or directly to the offspring.

STUDY APPRAISAL AND SYNTHESIS METHODS

Studies were evaluated using the OHAT risk of bias tool. The effects in humans were assessed qualitatively. For rodents exposed to 20 μg/kg/day BPA, we evaluated the study findings in a random effects meta-analytical model.

RESULTS

A review of the literature identified 29 rodent and 3 human studies. A random effects meta-analysis showed significantly increased hyperactivity in male rodents. In humans, early BPA exposure was associated with hyperactivity in boys and girls.

LIMITATIONS, CONCLUSIONS, AND IMPLICATIONS OF KEY FINDINGS

We concluded that early life BPA exposure is a presumed human hazard for the development of hyperactivity. Possible limitations of this systematic review include deficiencies in author reporting, exclusion of some literature based on language, and insufficient similarity between human studies. SRs that result in hazard-based conclusions are the first step in assessing and mitigating risks. Given the widespread exposure of BPA and increasing diagnoses of ADHD, we recommend immediate actions to complete such risk analyses and take next steps for the protection of human health. In the meantime, precautionary measures should be taken to reduce exposure in pregnant women, infants and children. The present analysis also discusses potential mechanisms by which BPA affects hyperactivity, and the most effective avenues for future research.

SYSTEMATIC REVIEW REGISTRATION NUMBER

Not available.

The Influence of High and Low Doses of Bisphenol A (BPA) on the Enteric Nervous System of the Porcine Ileum

Bisphenol A, used in the production of plastic, is able to leach from containers into food and cause multidirectional adverse effects in living organisms, including neurodegeneration and metabolic disorders. Knowledge of the impact of BPA on enteric neurons is practically non-existent. The destination of this study was to investigate the influence of BPA at a specific dose (0.05 mg/kg body weight/day) and at a dose ten times higher (0.5 mg/kg body weight/day), given for 28 days, on the porcine ileum. The influence of BPA on enteric neuron immunoreactive to selected neuronal active substances, including substance P (SP), vasoactive intestinal polypeptide (VIP), galanin (GAL), vesicular acetylcholine transporter (VAChT—used here as a marker of cholinergic neurons), and cocaine- and amphetamine-regulated transcript peptide (CART), was studied by the double immunofluorescence method. Both doses of BPA affected the neurochemical characterization of the enteric neurons. The observed changes depended on the type of enteric plexus but were generally characterized by an increase in the number of cells immunoreactive to the particular substances. More visible fluctuations were observed after treatment with higher doses of BPA. The results confirm that even low doses of BPA may influence the neurochemical characterization of the enteric neurons and are not neutral for living organisms.

Prenatal and lactational bisphenol A exposure does not alter serotonergic neurons morphologically in the murine dorsal raphe nucleus

OBJECTIVE

There is concern that bisphenol A (BPA), an endocrine-disrupting chemical, affects brain development when exposed to a fetus and/or infant. We previously reported that increased serotonin (5-HT) and its metabolite (5-HIAA) in the dorsal raphe nucleus (DRN) in murine adult brains when they were prenatally exposed to low doses of BPA. This study investigates the morphological alteration of the dorsal raphe nucleus (DRN) in order to explain the disrupted serotonergic system after prenatal and lactational exposure to bisphenol A (BPA).

METHODS

The murine dams were orally administrated with 500μg/kg/day of BPA from embryonic day 0 to postnatal 3weeks. The DRN, the main region of serotonin production, was morphometrically analyzed at 14weeks, using immunohistochemistry and image analysis combined with 3-dimensional reconstruction.

RESULTS

No significant differences were revealed in the number of tryptophan hydroxylase 2-immunoreactive neurons in any of the DRN sub-regions or the morphometric parameters, including the whole volume, ventrodorsal, longitudinal, and wing lengths of the DRN among the BPA treatment and sex groups.

CONCLUSIONS

The murine DRN was not morphologically affected by prenatal and lactational exposure to low doses of BPA. Further studies are necessary regarding the function of serotonergic neurons and the activity of different kinds of related receptors in the brain.

Effects of bisphenol A on incidence and severity of cardiac lesions in the NCTR-Sprague-Dawley rat: A CLARITY-BPA study

The goal of this study was to determine whether bisphenol A (BPA) had adverse effects indicative of cardiac toxicity. As part of the "Consortium Linking Academic and Regulatory Insights on BPA Toxicity" (CLARITY-BPA), study dams and offspring were exposed by daily gavage to five doses of BPA ranging from 2.5 to 25000μg/kg/day, 0.05 or 0.5μg/kg/day 17α-ethinyl-estradiol (EE) or 0.3% carboxymethylcellulose vehicle. Exposure-related effects were analyzed in isolated hearts by quantitative morphometry and histopathology. No dose-related changes in body weight were detected. Across all exposure groups including vehicle controls, body weight of continuously dosed males was reduced compared to males dosed only until PND21. Heart weight was increased only in females exposed to EE, and consistent alterations in LV wall thickness were not observed. Exposure-related changes in collagen accumulation were minor and limited to highest EE exposure groups with increased collagen accumulation in PND21 males. Decreased collagen was observed in hearts of BPA or EE exposed females at PND90 and PND180. In BPA or EE treated females cardiomyopathy incidence and severity was significantly increased compared to control females at PND21 with myocardial degeneration observed in both males and females at PND21 and PND90.

Prenatal phthalate, triclosan, and bisphenol A exposures and child visual-spatial abilities

INTRODUCTION

During fetal development, sex steroids influence sexually dimorphic behaviors, such as visual-spatial abilities. Thus, endocrine disrupting chemicals that impact sex steroids during gestation may affect these behaviors.

OBJECTIVE

We investigated the relationship between prenatal urinary phthalate metabolite, triclosan, and BPA concentrations and visual-spatial abilities in a prospective cohort of 198 mother-child dyads.

METHODS

Data are from a prospective cohort in Cincinnati, OH (HOME Study). We measured nine phthalate metabolites, triclosan, and BPA in maternal urine samples collected at 16 and 26 weeks of gestation. We assessed children's visual-spatial abilities at 8 years of age using the Virtual Morris Water Maze (VMWM), a computerized version of the rodent Morris Water Maze. We quantified the covariate-adjusted change in the time or distance to complete the VMWM and time spent in the correct quadrant during a probe trial with an interquartile range increase in chemical concentrations using linear mixed models and linear regression, respectively.

RESULTS

Boys completed the VMWM faster (4.1s; 95% CI:-7.1, -1.2) and in less distance (1.4 units; 95% CI:-2.8, 0) than girls. Overall, children with higher mono-n-butyl (MnBP), mono-benzyl (MBzP), and mono-carboxypropyl phthalate concentrations completed the VMWM in less time and distance than children with lower concentrations. For example, children with higher MnBP concentrations completed the VMWM in 0.9 less distance units (95% CI:-1.8, -0.0). Child sex modified the association between MnBP and VMWM performance. In girls, higher MnBP concentrations were associated with longer time (1.7s; 95% CI: -0.7, 4.1) and shorter distance (-1.7 units; 95% CI: -2.8, -0.5), whereas in boys, it was associated with shorter time (-3.0s; 95% CI:-5.6, -0.4), but not distance (-0.1 units; 95% CI:1.4, 1.0). Other phthalate metabolites, triclosan, and BPA were not associated with VMWM performance, and sex did not consistently modify these associations.

CONCLUSIONS

In this cohort, greater prenatal urinary concentrations of some phthalate metabolites were associated with improved VMWM performance, particularly among boys. Future studies should confirm these findings and determine if phthalates affect other hormonally sensitive aspects of child neurobehavior.

The Effects of Bisphenol A Exposure at Different Developmental Time Points in an Androgen-Sensitive Neuromuscular System in Male Rats

The industrial plasticizer bisphenol A (BPA) is a ubiquitous endocrine disruptor to which the general human population is routinely exposed. Although BPA is well known as an estrogenic mimic, there have been some suggestions that this compound may also alter activity at the androgen receptor. To determine whether BPA does have antiandrogenic properties, we evaluated BPA effects in the spinal nucleus of the bulbocavernosus and dorsolateral nucleus, sexually dimorphic groups of motor neurons in the lumbar spinal cord that are critically dependent on androgens for survival and maintenance, as well as the monomorphic retrodorsolateral nucleus. In experiment 1, we administered varying concentrations of BPA to juvenile rats pre- and postnatally and examined both the number and size of motor neurons in adulthood. In experiment 2, different doses of BPA were given to adult rats for 28 days, after which the soma size of motor neurons were measured. Although no effect of BPA on neural survival or soma size was noted after perinatal BPA exposure, BPA exposure did result in a decrease in soma size in all motor neuron pools after chronic exposure in adulthood. These findings are discussed with regard to putative antiandrogenic effects of BPA; we argue that BPA is not antiandrogenic but is acting through nonandrogen receptor-dependent mechanisms.

Association of early life exposure to bisphenol A with obesity and cardiometabolic traits in childhood

BACKGROUND

Bisphenol A (BPA) is a chemical used extensively worldwide in the manufacture of plastic polymers. The environmental obesogen hypothesis suggests that early life exposure to endocrine disrupting chemicals such as BPA may increase the risk for wt gain later in childhood but few prospective epidemiological studies have investigated this relationship.

OBJECTIVES

We examined the association of early life BPA exposure with offspring obesity and cardiometabolic risk factors in 500 mother-child pairs from the RHEA pregnancy cohort in Crete, Greece.

METHODS

BPA concentrations were measured in spot urine samples collected at the 1st trimester of pregnancy) and from children at 2.5 and 4 years of age. We measured birth wt, body mass index (BMI) from 6 months to 4 years of age, waist circumference, skinfold thickness, blood pressure, serum lipids, C-reactive protein, and adipokines at 4 years of age. BMI growth trajectories from birth to 4 years were estimated by mixed effects models with fractional polynomials of age. Adjusted associations were obtained via multivariable regression analyses.

RESULTS

The prevalence of overweight/obesity was 9% at 2, 13% at 3% and 17% at 4 years of age. Geometric mean BPA concentrations were 1.2μg/g creatinine±7.9 in 1st trimester, 5.1μg/g±13.3 in 2.5 years and 1.9μg/g±4.9 in 4 years. After confounder adjustment, each 10-fold increase in BPA at 4 years was associated with a higher BMI z-score (adj. β=0.2; 95% CI: 0.01, 0.4), waist circumference (adj. β=1.2; 95% CI: 0.1, 2.2) and sum of skinfold thickness (adj. β=3.7mm; 95% CI: 0.7, 6.7) at 4 years. Prenatal BPA was negatively associated with BMI and adiposity measures in girls and positively in boys. We found no associations of early life exposure to BPA with other offspring cardiometabolic risk factors.

CONCLUSIONS

Prenatal BPA exposure was not consistently associated with offspring growth and adiposity measures but higher early childhood BPA was associated with excess child adiposity.

Impairment of object recognition memory by maternal bisphenol A exposure is associated with inhibition of Akt and ERK/CREB/BDNF pathway in the male offspring hippocampus

Bisphenol A (BPA) is a commonly used endocrine-disrupting chemical used as a component of polycarbonates plastics that has potential adverse effects on human health. Exposure to BPA during development has been implicated in memory deficits, but the mechanism of action underlying the effect is not fully understood. In this study, we investigated the effect of maternal exposure to BPA on object recognition memory and the expressions of proteins important for memory, especially focusing on the ERK/CREB/BDNF pathway. Pregnant Sprague-Dawley female rats were orally treated with either vehicle or BPA (0.05, 0.5, 5 or 50 mg/kg BW/day) during days 9-20 of gestation. Male offspring were tested on postnatal day 21 with the object recognition task. Recognition memory was assessed using the object recognition index (index=the time spent exploring the novel object/(the time spent exploring the novel object+the time spent exploring the familiar object)). In the test session performed 90 min after the training session, BPA-exposed male offspring not only spent more time in exploring the familiar object at the highest dose than the control, but also displayed a significantly decreased the object recognition index at the doses of 0.5, 5 and 50 mg/kg BW/day. During the test session performed 24h after the training session, BPA-treated males did not change the time spent exploring the familiar object, but had a decreased object recognition index at 5 and 50 mg/kg BW/day, when compared to control group. These findings indicate that object recognition memory was susceptible to maternal BPA exposure. Western blot analysis of hippocampi from BPA-treated male offspring revealed a decrease in Akt, phospho-Akt, p44/42 MAPK and phospho-p44/42 MAPK protein levels, compared to controls. In addition, BPA significantly inhibited the levels of phosphorylation of CREB and BDNF in the hippocampus. Our results show that maternal BPA exposure may full impair object recognition memory, and that impairment may be related to a decrease in Akt activation and an inhibition of the ERK/CREB/BDNF pathway in the hippocampus. This study also adds new evidence that suggests BPA has an antagonistic effect on the action of estrogen in the brain.

EDC-2: The Endocrine Society's Second Scientific Statement on Endocrine-Disrupting Chemicals

The Endocrine Society's first Scientific Statement in 2009 provided a wake-up call to the scientific community about how environmental endocrine-disrupting chemicals (EDCs) affect health and disease. Five years later, a substantially larger body of literature has solidified our understanding of plausible mechanisms underlying EDC actions and how exposures in animals and humans-especially during development-may lay the foundations for disease later in life. At this point in history, we have much stronger knowledge about how EDCs alter gene-environment interactions via physiological, cellular, molecular, and epigenetic changes, thereby producing effects in exposed individuals as well as their descendants. Causal links between exposure and manifestation of disease are substantiated by experimental animal models and are consistent with correlative epidemiological data in humans. There are several caveats because differences in how experimental animal work is conducted can lead to difficulties in drawing broad conclusions, and we must continue to be cautious about inferring causality in humans. In this second Scientific Statement, we reviewed the literature on a subset of topics for which the translational evidence is strongest: 1) obesity and diabetes; 2) female reproduction; 3) male reproduction; 4) hormone-sensitive cancers in females; 5) prostate; 6) thyroid; and 7) neurodevelopment and neuroendocrine systems. Our inclusion criteria for studies were those conducted predominantly in the past 5 years deemed to be of high quality based on appropriate negative and positive control groups or populations, adequate sample size and experimental design, and mammalian animal studies with exposure levels in a range that was relevant to humans. We also focused on studies using the developmental origins of health and disease model. No report was excluded based on a positive or negative effect of the EDC exposure. The bulk of the results across the board strengthen the evidence for endocrine health-related actions of EDCs. Based on this much more complete understanding of the endocrine principles by which EDCs act, including nonmonotonic dose-responses, low-dose effects, and developmental vulnerability, these findings can be much better translated to human health. Armed with this information, researchers, physicians, and other healthcare providers can guide regulators and policymakers as they make responsible decisions.

Alterations of neurotransmitter norepinephrine and gamma-aminobutyric acid correlate with murine behavioral perturbations related to bisphenol A exposure

AIM

Humans are commonly exposed to endocrine-disrupting chemical bisphenol A (BPA), giving rise to concern over the psychobehavioral effects of BPA. The aim of this study was to investigate the effects of prenatal and lactational BPA exposure on neurotransmitters, including norepinephrine (NE), gamma-aminobutyric acid (GABA) and glutamate (Glu), and to assess the association with behavioral phenotypes.

METHODS

C57BL/6J mice were orally administered with BPA (500 μg/bwkg/day) or vehicle daily from embryonic day 0 to postnatal week 3 (P3W), through their dams. The IntelliCage behavioral experiments were conducted from P11W to P15W. At around P14-16W, NE, GABA and Glu levels in nine brain regions were measured by high performance liquid chromatography. Furthermore, the associations between the neurotransmitter levels and the behavioral indices were statistically analyzed.

RESULTS

In females exposed to BPA, the GABA and Glu levels in almost all regions, and the NE levels in the cortex, hypothalamus and thalamus were higher than those in the controls. In males exposed to BPA, the GABA levels in the amygdala and hippocampus showed lower values, while Glu levels were higher in some regions, compared with the controls. In regard to the associations, the number of "diurnal corner visits without drinking" was correlated with the NE levels in the cortex and thalamus in females. The "nocturnal corner visit duration without drinking" was correlated with the GABA level in the hippocampus in males.

CONCLUSION

These results suggest that prenatal and lactational exposure to low doses of BPA might modulate the NE, GABA and Glu systems, resulting in behavioral alterations.

Impact of Low-Dose Oral Exposure to Bisphenol A (BPA) on Juvenile and Adult Rat Exploratory and Anxiety Behavior: A CLARITY-BPA Consortium Study

Bisphenol A (BPA) is a high volume production chemical and has been identified as an endocrine disruptor, prompting concern that developmental exposure could impact brain development and behavior. Rodent and human studies suggest that early life BPA exposure may result in an anxious, hyperactive phenotype but results are conflicting and data from studies using multiple doses below the no-observed-adverse-effect level are limited. To address this, the present studies were conducted as part of the CLARITY-BPA (Consortium Linking Academic and Regulatory Insights on BPA Toxicity) program. The impact of perinatal BPA exposure (2.5, 25, or 2500 µg/kg body weight (bw)/day) on behaviors related to anxiety and exploratory activity was assessed in juvenile (prepubertal) and adult NCTR Sprague-Dawley rats of both sexes. Ethinyl estradiol (0.5 µg/kg bw/day) was used as a reference estrogen. Exposure spanned gestation and lactation with dams gavaged from gestational day 6 until birth and then the offspring gavaged directly through weaning (n = 12/sex/group). Behavioral assessments included open field, elevated plus maze, and zero maze. Anticipated sex differences in behavior were statistically identified or suggested in most cases. No consistent effects of BPA were observed for any endpoint, in either sex, at either age compared to vehicle controls; however, significant differences between BPA-exposed and ethinyl estradiol-exposed groups were identified for some endpoints. Limitations of this study are discussed and include suboptimal statistical power and low concordance across behavioral tasks. These data do not indicate BPA-related effects on anxiety or exploratory activity in these developmentally exposed rats.

Perinatal exposure to bisphenol-A impairs spatial memory through upregulation of neurexin1 and neuroligin3 expression in male mouse brain

Bisphenol-A (BPA), a well known endocrine disruptor, impairs learning and memory in rodents. However, the underlying molecular mechanism of BPA induced impairment in learning and memory is not well known. As synaptic plasticity is the cellular basis of memory, the present study investigated the effect of perinatal exposure to BPA on the expression of synaptic proteins neurexin1 (Nrxn1) and neuroligin3 (Nlgn3), dendritic spine density and spatial memory in postnatal male mice. The pregnant mice were orally administered BPA (50 µg/kgbw/d) from gestation day (GD) 7 to postnatal day (PND) 21 and sesame oil was used as a vehicle control. In Morris water maze (MWM) test, BPA extended the escape latency time to locate the hidden platform in 8 weeks male mice. RT-PCR and Immunoblotting results showed significant upregulation of Nrxn1 and Nlgn3 expression in both cerebral cortex and hippocampus of 3 and 8 weeks male mice. This was further substantiated by in-situ hybridization and immunofluorescence techniques. BPA also significantly increased the density of dendritic spines in both regions, as analyzed by rapid Golgi staining. Thus our data suggest that perinatal exposure to BPA impairs spatial memory through upregulation of expression of synaptic proteins Nrxn1 and Nlgn3 and increased dendritic spine density in cerebral cortex and hippocampus of postnatal male mice.

Thyroid hormone signaling during early neurogenesis and its significance as a vulnerable window for endocrine disruption

The essential roles of thyroid hormone (TH) in perinatal brain development have been known for decades. More recently, many of the molecular mechanisms underlying the multiple effects of TH on proliferation, differentiation, migration, synaptogenesis and myelination in the developing nervous system have been elucidated. At the same time data from both epidemiological studies and animal models have revealed that the influence of thyroid signaling on development of the nervous system, extends to all periods of life, from early embryogenesis to neurogenesis in the adult brain. This review focuses on recent insights into the actions of TH during early neurogenesis. A key concept is that, in contrast to the previous ideas that only the unliganded receptor was implicated in these early phases, a critical role of the ligand, T3, is increasingly recognized. These findings are considered in the light of increasing knowledge of cell specific control of T3 availability as a function of deiodinase activity and transporter expression. These requirements for TH in the early stages of neurogenesis take on new relevance given the increasing epidemiological data on adverse effects of TH lack in early pregnancy on children's neurodevelopmental outcome. These ideas lead logically into a discussion on how the actions of TH during the first phases of neurogenesis can be potentially disrupted by gestational iodine lack and/or chemical pollution. This article is part of a Special Issue entitled: Nuclear receptors in animal development.

Abbreviated assessment of bisphenol A toxicology literature

Bisphenol A (BPA), synthesized in 1891, is produced in quantities of >2 million metric tons annually for polycarbonate plastics, epoxy resins and food contact applications. BPA can be a weak estrogen mimic, and is ubiquitous in humans (in 93% US population; in 96% US pregnant women). European/US food/drug agencies conclude that current BPA levels present no risk to the general population (some include infants/children); basic endocrine disruption (ED) researchers state that entire populations are at risk from these levels. The US Food and Drug Administration banned BPA in baby bottles in 2012 'not based on safety concerns'; the US Environmental Protection Agency and its UK counterpart concurred. Basic ED researchers report reproductive/developmental effects from perinatal BPA exposure in mice at very low doses, e.g. 2 ng/g body weight (0.002 mg/kg body weight), with non-monotonic dose-response (NMDR) curves, using few animals per group and few groups; contract research organizations, in good laboratory practice- and guideline-compliant large studies in rats and mice, report no low-dose effects or NMDR curves. The argument rages!

Bisphenol A and human chronic diseases: current evidences, possible mechanisms, and future perspectives

Bisphenol-A (BPA) is one of the highest volume chemicals produced worldwide, with over 6billion pounds produced and over 100t released into the atmosphere each year. Recent extensive literature has raised concerns about its possible implication in the etiology of some human chronic diseases such as diabetes, obesity, reproductive disorders, cardiovascular diseases, birth defects, chronic respiratory and kidney diseases and breast cancer. In this review, we present the highlighted evidences on the relationship between BPA exposure and human chronic diseases and we discuss its eventual mechanisms of action, especially genetic, epigenetic and endocrine disruption mechanisms with the possible involvement of oxidative stress, mitochondrial dysfunction and cell signaling.

Bisphenol A--sources, toxicity and biotransformation

Bisphenol A (BPA) is a chemical compound used in massive amounts in the production of synthetic polymers and thermal paper. In this review, the sources of BPA, which influence its occurrence in the environment and human surrounding will be presented. Data concerning BPA occurrence in food, water and indoor environments as well as its appearance in tissues and body fluids of human body will be shown. The results of in vitro and in vivo studies and the results of epidemiological surveys showing toxic, endocrine, mutagenic and cancerogenic action of BPA will also be discussed. Moreover, data suggesting that exposure of human to BPA may elevate risk of obesity, diabetes and coronary heart diseases will be presented. Finally, biotransformation of BPA in animals, plants and microorganisms (bacteria, fungi, algae), resulting in the formation of various metabolites that exhibit different from BPA toxicity will be described.