Long-Term Effects of Fetal Exposure to Low Doses of the Xenoestrogen Bisphenol-A in the Female Mouse Genital Tract1

The Effects of Short- and Long-Term Ingestion of Plastic Toxin Bisphenol A on Gastrointestinal Transit Time in Rats

Introduction Exposure to bisphenol A (BPA), a toxic chemical released from plastic, affects various body functions, including reproduction, metabolism, and development. The most common route of exposure to BPA is oral, and the gastrointestinal (GI) tract is, therefore, the first body system to be exposed to BPA. BPA has been well-documented to impair gut contractility in rats, in vitro. It may therefore be hypothesized that BPA may adversely affect GI motility and hence slow down the movement of food, resulting in the increased transit of food bolus in the GI tract. There are no reports so far on the effects of BPA on GI transit time. Objectives The present study was undertaken to examine the impact of exposure to BPA by a single oral dose (termed as short-term ingestion of BPA) and chronic (28-day) oral dose (termed as long-term ingestion of BPA) on the transit time of food bolus in the gut of adult male albino rats. Methods and materials The study was conducted in the Department of Physiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi, Uttar Pradesh, India. In one set of experiments, each animal was fed a food pellet, once (short-term ingestion) containing BPA (2 µg/kg and 50 µg/kg in different groups), and in another set of experiments, each animal was fed a food pellet containing BPA (50 µg/kg/day) for 28 consecutive days (long-term ingestion). Control rats in both sets were fed food pellets without BPA. Subsequently, the gastric transit index (GTI), ileocecal transit index (ICTI), and colonic transit time (CTT) were determined by the standard charcoal marker method. Results One-time ingestion of a food pellet containing BPA caused a significant (p < 0.05) drop in the GTI and ICTI and an increase in the CTT with both doses of BPA (2 and 50 µg/kg). Similarly, after chronic (28-day), oral BPA exposure, a significant decrease in the GTI and ICTT and an increase in CTT were observed. Conclusion Both short-term (one-time) and long-term (28-day) oral exposure to BPA-containing food harmed GI transit. Slow GI transit may lead to metabolic disorders and GI motility disorders, such as constipation.

Evaluating endocrine disrupting chemicals: A perspective on the novel assessments in CLARITY-BPA

BACKGROUND

The Consortium Linking Academic and Regulatory Insights on Bisphenol A Toxicity (CLARITY-BPA) was a collaborative research effort to better link academic research with governmental guideline studies. This review explores the secondary goal of CLARITY-BPA: to identify endpoints or technologies from CLARITY-BPA and prior/concurrent literature from these laboratories that may enhance the capacity of rodent toxicity studies to detect endocrine disrupting chemicals (EDCs).

METHODS

A systematic literature search was conducted with search terms for BPA and the CLARITY-BPA participants. Relevant studies employed a laboratory rodent model and reported results on 1 of the 10 organs/organ systems evaluated in CLARITY-BPA (brain and behavior, cardiac, immune, mammary gland, ovary, penile function, prostate gland and urethra, testis and epididymis, thyroid hormone and metabolism, and uterus). Study design and findings were summarized, and a risk-of-bias assessment was conducted.

RESULTS

Several endpoints and methods were identified as potentially helpful to detect effects of EDCs. For example, molecular and quantitative morphological approaches were sensitive in detecting alterations in early postnatal development of the brain, ovary, and mammary glands. Hormone challenge studies mimicking human aging reported increased susceptibility of the prostate to disease following developmental BPA exposure. Statistical analyses for nonmonotonic dose responses, and computational approaches assessing multiple treatment-related outcomes concurrently in linked hormone-sensitive organ systems, reported effects at low BPA doses.

CONCLUSIONS

This review provided an opportunity to evaluate the unique insights provided by nontraditional assessments in CLARITY-BPA to identify technologies and endpoints to enhance detection of EDCs in future studies.

Validation of a new Custom Polyclonal Progesterone Receptor Antibody for Immunohistochemistry in the Female Mouse Brain

Immunohistochemical visualization of progesterone receptor (PR)-expressing cells in the brain is a powerful technique to investigate the role of progesterone in the neuroendocrine regulation of fertility. A major obstacle to the immunohistochemical visualization of progesterone-sensitive cells in the rodent brain has been the discontinuation of the commercially produced A0098 rabbit polyclonal PR antibody by DAKO. To address the unavailability of this widely used PR antibody, we optimized and evaluated 4 alternative commercial PR antibodies and found that each lacked the specificity and/or sensitivity to immunohistochemically label PR-expressing cells in paraformaldehyde-fixed female mouse brain sections. As a result, we developed and validated a new custom RC269 PR antibody, directed against the same 533-547 amino acid sequence of the human PR as the discontinued A0098 DAKO PR antibody. Immunohistochemical application of the RC269 PR antibody on paraformaldehyde-fixed mouse brain sections resulted in nuclear PR labeling that was highly distinguishable from background, specific to its antigen, highly regulated by estradiol, matched the known distribution of PR protein expression in the female mouse hypothalamus, and nearly identical to that of the discontinued A0098 DAKO PR antibody. In summary, the RC269 PR antibody is a specific and sensitive antibody to immunohistochemically visualize PR-expressing cells in the mouse brain.

NTS, NTSR1 and ERs in the Pituitary-Gonadal Axis of Cycling and Postnatal Female Rats after BPA Treatment

The neuropeptide neurotensin (NTS) is involved in regulating the reproductive axis and is expressed at each level of this axis (hypothalamus-pituitary-gonads). This dependence on estrogen levels has been widely demonstrated in the hypothalamus and pituitary. We focused on confirming the relationship of NTS with estrogens and the gonadal axis, using a particularly important environmental estrogenic molecule, bisphenol-A (BPA). Based on the experimental models or in vitro cell studies, it has been shown that BPA can negatively affect reproductive function. We studied for the first time the action of an exogenous estrogenic substance on the expression of NTS and estrogen receptors in the pituitary-gonadal axis during prolonged in vivo exposure. The exposure to BPA at 0.5 and 2 mg/kg body weight per day during gestation and lactation was monitored through indirect immunohistochemical procedures applied to the pituitary and ovary sections. Our results demonstrate that BPA induces alterations in the reproductive axis of the offspring, mainly after the first postnatal week. The rat pups exposed to BPA exhibited accelerated sexual maturation to puberty. There was no effect on the number of rats born per litter, although the fewer primordial follicles suggest a shorter fertile life.

Protective Role of Kelulut Honey against Toxicity Effects of Polystyrene Microplastics on Morphology, Hormones, and Sex Steroid Receptor Expression in the Uterus of Rats

BACKGROUND

Microplastics (MPs) are an emerging global pollutant. Previous studies have revealed that chronic exposure to MPs can affect animal and human reproductive health, particularly by impairing the reproductive system's normal functions, which may increase the risk of infertility in both males and females. Kelulut honey (KH), an excellent source of antioxidants, has been used to counteract the disruptive effects of Polystyrene microplastics (PS-MPs) in the rat uterus. Thus, this study aimed to investigate the potential protective effects of Kelulut honey against PS-MPs-induced uterine toxicity in pubertal rats.

METHODS

Prepubertal female Sprague Dawley rats were divided into four groups (n = 8): (i) normal control group (NC: treated with deionized water), MPs-exposed group (M: exposed to PS-MPs at 2.5 mg/kg), (iii) Kelulut honey group (DM: pretreated with 1200 mg/kg of KH 30 minutes before they were administered with PS-MPs at 2.5 mg/kg), and (iv) Kelulut honey control group (DC: only treated with KH at 2.5 mg/kg). The rats were treated orally once daily for six consecutive weeks.

RESULTS

Uterine abnormalities in PS-MPs-exposed rats were significantly improved after concurrent treatment with Kelulut honey. Morphology improvement was observed and luminal epithelial cells seemed thicker with more goblet cells, glandular cells had a more regular and circular shape, stromal cell increased in size, interstitial gaps between stromal cells expanded, and the myometrium layer was thicker. Kelulut honey treatment also effectively normalized the suppressive effect of PS-MPs on the expression and distribution of sex steroid receptors (ERα and ERβ), as well as the level of serum gonadotropin (LH and FSH) and sex steroid (estradiol and progesterone) hormones.

CONCLUSION

Kelulut honey can protect the female reproductive system against the disruptive effects of PS-MPs. The phytochemical properties of Kelulut honey might be responsible for these beneficial benefits. However, future studies are warranted to identify the mechanisms involved.

Chemical Effects on Breast Development, Function, and Cancer Risk: Existing Knowledge and New Opportunities

Population studies show worrisome trends towards earlier breast development, difficulty in breastfeeding, and increasing rates of breast cancer in young women. Multiple epidemiological studies have linked these outcomes with chemical exposures, and experimental studies have shown that many of these chemicals generate similar effects in rodents, often by disrupting hormonal regulation. These endocrine-disrupting chemicals (EDCs) can alter the progression of mammary gland (MG) development, impair the ability to nourish offspring via lactation, increase mammary tissue density, and increase the propensity to develop cancer. However, current toxicological approaches to measuring the effects of chemical exposures on the MG are often inadequate to detect these effects, impairing our ability to identify exposures harmful to the breast and limiting opportunities for prevention. This paper describes key adverse outcomes for the MG, including impaired lactation, altered pubertal development, altered morphology (such as increased mammographic density), and cancer. It also summarizes evidence from humans and rodent models for exposures associated with these effects. We also review current toxicological practices for evaluating MG effects, highlight limitations of current methods, summarize debates related to how effects are interpreted in risk assessment, and make recommendations to strengthen assessment approaches. Increasing the rigor of MG assessment would improve our ability to identify chemicals of concern, regulate those chemicals based on their effects, and prevent exposures and associated adverse health effects.

Evaluation of the Toxicity of Bisphenol A in Reproduction and Its Effect on Fertility and Embryonic Development in the Zebrafish (Danio rerio)

Bisphenol A (BPA) is a chemical substance commonly used in the manufacture of plastic products. Its inhalation or ingestion from particles in suspension, water, and/or polluted foods can trigger toxic effects related to endocrine disruption, resulting in hormonal, reproduction, and immunological alterations in humans and animals. The zebrafish (Danio rerio) is an ideal experimental model frequently used in toxicity studies. In order to assess the toxic effects of BPA on reproduction and embryonic development in one generation after parental exposure to it, a total of 80 zebrafish, males and females, divided into four groups in duplicate (n = 20) were exposed to BPA concentrations of 500, 50, and 5 µg L^-1, along with a control group. The fish were kept in reproduction aquariums for 21 days. The embryos obtained in the crosses were incubated in a BPA-free medium and observed for signs of embryotoxicity. A histopathological study (under optical and electron microscopes) was performed of adult fish gonads. The embryos of reproducers exposed to BPA were those most frequently presenting signs of embryotoxicity, such as mortality and cardiac and musculoskeletal malformations. In the histopathological studies of adult individuals, alterations were found in ovocyte maturation and in spermatazoid formation in the groups exposed to the chemical. Those alterations were directly related to BPA action, affecting fertility in both sexes, as well as the viability of their offspring, proportionally to the BPA levels to which they were exposed, so that our results provide more information by associating toxic effects on the offspring and on the next generation.

Toxicity testing and endocrine disrupting chemicals

Regulatory agencies around the world depend on standardized testing approaches to evaluate environmental chemicals for endocrine disrupting properties. The US Environmental Protection Agency (EPA) has developed a two-tiered testing approach within its Endocrine Disruptor Screening Program (EDSP). The eleven Tier 1 and three Tier 2 EDSP assays can be used to identify chemicals that act as agonists or antagonists of estrogen receptor, androgen receptor, or thyroid hormone receptor, or chemicals that interfere with steroidogenesis. Additional assays have been developed in the context of Tox21, and others have been validated by the OECD. In spite of the availability of validated toxicity tests, problems have been identified with the approaches and methods used to identify endocrine disrupting chemicals (EDCs). This chapter will provide an overview of several of these issues including: (1) The way an EDC is defined by an agency impacts whether a specific test can be used to determine if a chemical is an EDC. This is especially important when considering which assays examine outcomes that are considered "adverse effects." (2) Some assumptions about the validated studies used to identify EDCs may not be true (e.g., their reproducibility has been questioned). (3) Many of the validated assays are less sensitive than other methods that have not yet been validated. Ultimately, these and other problems contribute to the current landscape, where testing approaches have failed to protect the public from known EDCs. The chapter concludes with a review of approaches that have been taken to improve current guideline studies.

Protective role of Mas Cotek (Ficus deltoidea) against the toxic effects of bisphenol A on morphology and sex steroid receptor expression in the rat uterus

BACKGROUND

Numerous scientific studies have found that young women are at a high risk of reproductive infertility due to their routine exposure to numerous bisphenol A (BPA) products. This risk is highly associated with the production of reactive oxygen species from BPA products. Ficus deltoidea, which has strong antioxidant properties, was selected as a potential protective agent to counter the detrimental effects of BPA in the rat uterus.

METHODS

Female Sprague-Dawley rats were allocated into four groups (n = 8) as follows: (i) the Normal Control group (NC), (ii) the BPA-exposed group (PC), (iii) the group concurrently treated with BPA and F. deltoidea (FC) and (iv) the group treated with F. deltoidea alone (F).

RESULTS

After 6 weeks of concurrent treatment with F. deltoidea, uterine abnormalities in the BPA-exposed rats showed a significant improvement. Specifically, the size of stromal cells increased; interstitial spaces between stromal cells expanded; the histology of the glandular epithelium and the myometrium appeared normal and mitotic figures were present. The suppressive effects of BPA on the expression levels of sex steroid receptors (ERα and ERβ) and the immunity gene C3 were significantly normalised by F. deltoidea treatment. The role of F. deltoidea as an antioxidant agent was proven by the significant reduction in malondialdehyde level in BPA-exposed rats. Moreover, in BPA-exposed rats, concurrent treatment with F. deltoidea could normalise the level of the gonadotropin hormone, which could be associated with an increase in the percentage of rats with a normal oestrous cycle.

CONCLUSION

F. deltoidea has the potential to counter the toxic effects of BPA on the female reproductive system. These protective effects might be due to the phytochemical properties of F. deltoidea. Therefore, future study is warranted to identify the bioactive components that contribute to the protective effects of F. deltoidea.

Molecular mechanisms of mammary gland remodeling: A review of the homeostatic versus bisphenol a disrupted microenvironment

Mammary gland (MG) undergoes critical points of structural changes throughout a woman's life. During the perinatal and pubertal stages, MG develops through growth and differentiation to establish a pre-mature feature. If pregnancy and lactation occur, the epithelial compartment branches and differentiates to create a specialized structure for milk secretion and nurturing of the newborn. However, the ultimate MG modification consists of a regression process aiming to reestablish the smaller and less energy demanding structure until another production cycle happens. The unraveling of these fascinating physiologic cycles has helped the scientific community elucidate aspects of molecular regulation of proliferative and apoptotic events and remodeling of the stromal compartment. However, greater understanding of the hormonal pathways involved in MG developmental stages led to concern that endocrine disruptors such as bisphenol A (BPA), may influence these specific development/involution stages, called "windows of susceptibility". Since it is used in the manufacture of polycarbonate plastics and epoxy resins, BPA is a ubiquitous chemical present in human everyday life, exerting an estrogenic effect. Thus, descriptions of its deleterious effects on the MG, especially in terms of serum hormone concentrations, hormonal receptor expression, molecular pathways, and epigenetic alterations, have been widely published. Therefore, allied to a didactic description of the main physiological mechanisms involved in different critical points of MG development, the current review provides a summary of key mechanisms by which the endocrine disruptor BPA impacts MG homeostasis at different windows of susceptibility, causing short- and long-term effects.

Bisphenol A decreases expression of Insulin-like factor 3 and induces histopathological changes in the Testes of Rats

Bisphenol A (BPA) is a chemical agent known to have detrimental reproductive and developmental effects. The tissue-specific impacts of BPA exposures and target tissues sensitiveness to BPA are still unclear. The aim of this study was to determine the short- and long-term dose-dependent toxic effects of BPA on rat testes. Forty-eight Wistar albino male rats were divided into four groups each containing 12 rats. To induce toxicity, BPA was administered orally at three different dosages (50, 100, and 200 mg/kg) for 14 and 28 days, respectively. Testis tissues were examined using light and electron microscopy, immunohistochemistry, and biochemical methods. Serum testosterone (T) and luteinizing hormone (LH) levels were measured. Additionally, insulin-like factor 3 (INSL3) as a marker of Leydig cell function was evaluated immunohistochemically. Groups administered high doses of BPA showed severe degenerations such as testicular atrophy, spermatogenic arrest, and interstitial edema in testis. Also, a significant decrease in INSL3 immunoreactivity and serum LH and T levels was found. The results indicated that both increased exposure time and dosage of BPA caused more serious detrimental effects on testes in the rat. Decreased INSL3 and T levels was evidence of Leydig cell function impairment due to BPA.

Bisphenol A induces hepatic triglyceride level in adult male rare minnow Gobiocypris rarus

Bisphenol A (BPA), an endocrine disruptor, exist in almost all waters. In the present study, we expose adult male Gobiocypris rarus rare minnow to 15 μg/L BPA to study the effect BPA on fish hepatic lipid metabolism. Following 1, 3 and 5 weeks exposure, the liver tissue of rare minnow was separated. The change of the hepatic morphology, hepatosomatic index, lipid composition and expression of lipid metabolism related genes were analyzed through paraffin section, oil red O staining, lipidomic analysis, and quantitative real-time PCR. BPA can cause significant hepatic lipid deposition in male rare minnow, leading to an increase in triglyceride (TG) level (1.84-22.87-fold), but it is also accompanied by a decrease in diglyceride level (1.67-4.78-fold). The expression of lipid metabolism related genes showed that BPA exposure can up-regulate TG synthesis related genes expression, and down-regulate TG degradation genes expression. Expression of TG transport related genes were also disrupted by BPA. It suggests that BPA can up-regulate rare minnow hepatic TG level through multi-path, and ultimately lead to lipid accumulation in the liver. The results of the present study enrich the mechanisms of environmental endocrine disruptors affecting lipid accumulation in fish.

From Wingspread to CLARITY: a personal trajectory

In the three decades since endocrine disruption was conceptualized at the Wingspread Conference, we have witnessed the growth of this multidisciplinary field and the accumulation of evidence showing the deleterious health effects of endocrine-disrupting chemicals. It is only within the past decade that, albeit slowly, some changes regarding regulatory measures have taken place. In this Perspective, we address some historical points regarding the advent of the endocrine disruption field and the conceptual changes that endocrine disruption brought about. We also provide our personal recollection of the events triggered by our serendipitous discovery of oestrogenic activity in plastic, a founder event in the field of endocrine disruption. This recollection ends with the CLARITY study as an example of a discordance between 'science for its own sake' and 'regulatory science' and leads us to offer a perspective that could be summarized by the motto attributed to Ludwig Boltzmann: "Nothing is more practical than a good theory".

The phthalate DEHP modulates the estrogen receptors α and β increasing lactotroph cell population in female pituitary glands

Humans are exposed to numerous endocrine disruptors on a daily basis, which may interfere with endogenous estrogens, with Di-(2-ethylhexyl) phthalate (DEHP) being one of the most employed. The anterior pituitary gland is a target of 17β-estradiol (E2) through the specific estrogen receptors (ERs) α and β, whose expression levels fluctuate in the gland under different contexts, and the ERα/β index is responsible for the final E2 effect. The aim of the present study was to evaluate in vivo and in vitro the DEHP effects on ERα and β expression in the pituitary cell population, and also its impact on lactotroph and somatotroph cell growth. Our results revealed that perinatal exposure to DEHP altered the ERα and β expression pattern in pituitary glands from prepubertal and adult female rats and increased the percentage of lactotroph cells in adulthood. In the in vitro system, DEHP down-regulated ERα and β expression, and as a result increased the ERα/β ratio and decreased the percentages of lactotrophs and somatotrophs expressing ERα and β. In addition, DEHP increased the S + G2M phases, Ki67 index and cyclin D1 in vitro, leading to a rise in the lactotroph and somatotroph cell populations. These results showed that DEHP modified the pituitary ERα and β expression in lactotrophs and somatotrophs from female rats and had an impact on the pituitary cell growth. These changes in ER expression may be a mechanism underlying DEHP exposure in the pituitary gland, leading to cell growth deregulation.

Canned food intake and urinary bisphenol a concentrations: a randomized crossover intervention study

Bisphenol A (BPA) is an endocrine disruptor. To evaluate the effect of canned food consumption on internal BPA dose, urinary BPA concentrations were measured before and after intake of canned foods. This study applied a randomized crossover design, recruited 20 healthy volunteers, and divided them into two groups. One group consumed canned food; the other group consumed fresh food. After a 1-day washout, the dietary interventions were reversed. In each period, urine samples were collected immediately before meals and then 2 h, 4 h, and 6 h after meals. A mixed-effects model was used to assess BPA changes over time. Our results showed urinary BPA concentrations increased after consumption of canned food. Specifically, urinary BPA concentrations significantly differed between consumption of canned food and fresh food at 2 h, 4 h, and 6 h after intake (p values of 0.001, < 0.001, and < 0.001, respectively). Mean BPA concentrations at 2 h, 4 h, and 6 h after meals were 152%, 206%, and 79% higher, respectively, than mean BPA concentrations before meals. Urine concentration profiles of canned food intake showed that peaks were at 4 h, the increase diminished at 6 h, and returned to baseline levels at 24 h after intake. Therefore, dietary intervention and a 1-day washout period are effective for limiting internal BPA burden. This study provides convincing evidence of a human exposure route to BPA and a basis for designing interventions to mitigate exposure.

N-acetylcysteine alleviated bisphenol A-induced testicular DNA hypermethylation of rare minnow (Gobiocypris rarus) by increasing cysteine contents

Ubiquitous BPA exposure resulted in DNA methylation errors and oxidative stress. Numerous studies have demonstrated that oxidative stress can lead to changes in DNA methylation levels and supplementation with antioxidants, including N-acetylcysteine (NAC), was able to restore these changes. Our previous study supposed that BPA-induced de novo synthesis of glutathione (GSH) promoted DNA methylation process in Gobiocypris rarus testes. To validate this conjecture and explore the protective effects of NAC on BPA toxicity, the present study was carried out. Adult male G. rarus was treated with 225 μg L^-1 BPA and/or NAC for 7 days. The sperm motility and DNA integrity of G. rarus were determined. Meanwhile, the levels of 5-methylcytosine (5mC), GSH, hydrogen peroxide (H₂O₂), DNA methyltransferase proteins (DNMTs), γ-glutamyl cysteine synthetase (GCS), S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), homocysteine (HCY), nicotinamide adenine dinucleotide phosphate (NADPH) and cysteine in the testes were detected. Furthermore, the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) were measured. Results indicated that NAC addition resulted in increase of cysteine contents and partially inhibited the BPA-induced DNA hypermethylation of G. rarus testes. In addition, the changes in DNA methylation levels in the testes after BPA and/or NAC treatment might be controlled by DNA methylation process that mediated by DNMTs. Moreover, BPA exposure caused oxidative stress in the testes and the elimination of H₂O₂ might be mainly accomplished by CAT while it changed to mainly through GPx after NAC supplement. Finally, the positive response of testicular antioxidant enzyme system and the antioxidant activity of NAC itself protected sperm motility and DNA integrity from oxidative damage in each group.

Once Resin Composites and Dental Sealants Release Bisphenol-A, How Might This Affect Our Clinical Management?-A Systematic Review

(1) Background: Bisphenol A (BPA) based dental resins are commonly used in preventive and reparative dentistry. Since some monomers may remain unpolymerized in the application of dental resin, they dissolve in the saliva. (2) Methods: The literature search was carried out in Pubmed, Cochrane and Embase databases. Randomized controlled trials, cohort studies and case-control studies that evaluated BPA levels in human urine, saliva and/or blood were included. (3) Results: The initial search had 5111 results. A total of 20 studies were included in the systematic review. Most studies showed an increase of the levels of bisphenol A 1 h after treatments with composite resins and dental sealants. One week after treatments the levels were decreased. (4) Conclusions: Some clinical precautions should be taken to decrease the release of BPA, namely the use of rubber dam, the immediate polishing of all resins used, or the use of glycerin gel to avoid non-polymerization of the last resin layer, and mouthwash after treatment. Another preventive measure in addition to the above-mentioned is the use of the smallest possible number of restorations or sealants, a maximum of four per appointment. These measures are even more important in children, adolescents and pregnant women.

Chronic Exposure of Mice to Bisphenol-A Alters Uterine Fibroblast Growth Factor Signaling and Leads to Aberrant Epithelial Proliferation

Uterine epithelial proliferation is regulated in a paracrine manner by a complex interplay between estrogen (E) and progesterone (P) signaling, in which E stimulates proliferation and P inhibits it. Perturbation of steroid hormone signaling within the uterine milieu could contribute to the development of endometrial hyperplasia and cancer. It is well established that bisphenol-A (BPA) is an endocrine-disrupting chemical with weak estrogenic effects, although little is known about how it affects steroid hormone signaling in the adult uterus. Because BPA acts as a weak E, we hypothesized that chronic exposure to BPA would create an imbalance between E and P signaling and cause changes in the uterus, such as aberrant epithelial proliferation. Indeed, exposure to an environmentally relevant dose of BPA had a uterotrophic affect. BPA-treated mice showed increased proliferation, notably in the glandular epithelium, which are sites of origin for endometrial hyperplasia and cancer. Increased proliferation appeared to be mediated through a similar mechanism as E-induced proliferation, via activation of the fibroblast growth factor receptor pathway and phosphorylation of the ERK1/2 mitogen-activated protein kinases in the epithelium. Interestingly, BPA reduced expression of heart and neural crest derivatives expressed 2 (HAND2), a known mediator of the antiproliferative effects of P. BPA also increased methylation of a CpG island in the Hand2 gene promoter, suggesting that BPA may promote epithelial proliferation through epigenetic silencing of antiproliferative factors like HAND2. Collectively, these findings establish that chronic exposure to BPA impairs steroid hormone signaling in the mouse uterus, and may contribute to the pathogenesis of uterine hyperplasia and cancer.

Effects of effluent organic matters on endocrine disrupting chemical removal by ultrafiltration and ozonation in synthetic secondary effluent

Endocrine disrupting chemicals (EDCs) in the secondary effluent discharged from wastewater treatment plants are of great concern when water reuse is intended. Ozonation and ultrafiltration (UF) are powerful technologies reported to eliminate EDCs. Due to the importance of effluent organic matters (EfOMs) in secondary effluent, the effects of three kinds of EfOM on the treatment of five EDCs using ozonation and UF were investigated. The three kinds of EfOM studied were humic acid sodium salt (NaAH), bovine serum albumin (BSA) and sodium alginate (NaAg); and the five EDCs were estrone, 17β-estradiol, estriol, 17α-ethynyl estradiol and bisphenol A. The results showed that EfOM accelerated the decay rate of ozone and inhibited the degradation efficiency of EDCs by ozonation in the order NaAH>BSA>NaAg. The ultraviolet absorbance at 280nm (UVA₂₈₀) has potential for use as a surrogate indicator to assess EDC removal via ozonation without conducting difficult EDC analyses. When the decline in UVA₂₈₀ exceeded 18%, the five EDCs had been completely removed. The UF behavior of NaAH, BSA and NaAg was found to follow the cake filtration law. The fouling potential of EfOM followed the order NaAg>NaAH>BSA; while EfOM on the membrane surface enhanced EDC removal in the order NaAH>BSA>NaAg. The mean retention rate of the membrane was increased by 24%, 10% and 8%, respectively. The properties of EDCs and EfOM cakes both influenced the EDC removal rates due to adsorption, size exclusion and charge attraction.

Water and soil pollution as determinant of water and food quality/contamination and its impact on female fertility

A mounting body of the literature suggests that environmental chemicals found in food and water could affect female reproduction. Many worldwide daily-used products have been shown to contain chemicals that could incur adverse reproductive outcomes in the perinatal/neonatal periods, childhood, adolescence, and even adulthood. The potential impact of Bisphenol A (BPA), Phthalates and Perfluoroalkyl substances (PFAS) on female reproduction, in particular on puberty, PCOS pathogenesis, infertility, ovarian function, endometriosis, and recurrent pregnancy loss, in both humans and animals, will be discussed in this report in order to provide greater clinician and public awareness about the potential consequences of these chemicals. The effects of these substances could interfere with hormone biosynthesis/action and could potentially be transmitted to further generations. Thus proper education about these chemicals can help individuals decide to limit exposure, ultimately alleviating the risk on future generations.

The Case for BPA as an Obesogen: Contributors to the Controversy

Since the inception of the term endocrine disruptor, the idea that the environment is an important determinant of phenotype has motivated researchers to explore the effect of low dose exposure to BPA during organogenesis. The syndrome observed was complex, affecting various endpoints such as reproduction and reproductive tissues, behavior, mammary gland development and carcinogenesis, glucose homeostasis, and obesity. This constellation of impacted endpoints suggests the possibility of complex interactions among the multiple effects of early BPA exposure. One key finding of our rodent studies was alterations of energy and amino-acid metabolism that were detected soon after birth and continued to be present at all time points examined through 6 months of age. The classical manifestations of obesity and associated elements of metabolic disease took a longer time to become apparent. Here we examine the validity of the often-mentioned lack of reproducibility of obesogenic effects of BPA, starting from the known environmental causes of variation, which are diverse and range from the theoretical like the individuation process and the non-monotonicity of the dose-response curve, to the very pragmatic like housing, feed, and time and route of exposure. We then explore environmental conditions that may hinder reproducibility and discuss the effect of confounding factors such as BPA-induced hyperactivity. In spite of all the potential sources of variation, we find that some obesogenic or metabolic effects of BPA are reproducibly observed when study conditions are analogous. We recommend that study authors describe details of their study conditions including the environment, husbandry, and feed. Finally, we show that when experimental conditions are strictly maintained, reproducibility, and stability of the obese phenotype is consistently observed.

1,25-Dihydroxyvitamin D3 modulates the effects of sublethal BPA on mitochondrial function via activating PI3K-Akt pathway and 17β-estradiol secretion in rat granulosa cells

Bisphenol A (BPA), an endocrine-disrupting chemical, is capable of producing reproductive toxicity. BPA results in mitochondrial DNA (mtDNA) deletion and mitochondrial dysfunction; however, the effect of BPA on the mitochondria of ovarian granulosa cells is not clear. Further, 1,25-dihydroxyvitamin D₃ (1,25D₃) may play a role in reproduction, because its receptor, VDR, contributes to the inhibition of oxidative stress and predominantly exists in the nuclei of granulosa cells. Hence, the role of 1,25D₃ in BPA-mediated effects on mitochondrial function was examined in this study. Primary rat granulosa cells treated with BPA, 1,25D₃, or both were subjected to molecular/biochemical assays to measure cell survival, mtDNA content, mtDNA deletion, superoxide dismutase activity, levels of proteins related to mitochondrial biogenesis, and mitochondrial function. We found that cell viability was dose-dependently reduced and reactive oxygen species (ROS) levels were increased by BPA treatment. BPA administration elevated Mn-superoxide dismutase (MnSOD) expression but negatively regulated total SOD activity. 1,25D₃ treatment alone increased 17β-estradiol secretion, ATP production, and cellular oxygen consumption. In cells treated with both agents, 1,25D₃ enhanced BPA-induced MnSOD protein upregulation and blocked the BPA-mediated decline in total SOD activity. Furthermore, 1,25D₃ attenuated BPA-mediated mtDNA deletion but showed no effect on BPA-induced increases in mtDNA content. Although BPA had no influence on the levels of peroxisome proliferator-activated receptor-γ coactivator-1 α, nuclear respiratory factor-1, mitochondrial transcription factor A, or cytochrome c oxidase subunit IV, 1,25D₃ plus BPA markedly increased mitochondrial biogenesis-related protein expression via the PI3K-Akt pathway. Moreover, BPA-mediated negative regulation of cytochrome c oxidase subunit I levels and 17β-estradiol secretion was attenuated by 1,25D₃ pre-treatment. Our results suggest that 1,25D₃ attenuates BPA-induced decreases in 17β-estradiol and that treatment with 1,25D₃ plus BPA regulates granulosa cell mitochondria by elevating mitochondrial biogenesis-related protein levels.

Evaluation of Prenatal Exposure to Bisphenol Analogues on Development and Long-Term Health of the Mammary Gland in Female Mice

BACKGROUND

Continued efforts to phase out bisphenol A (BPA) from consumer products have been met with the challenges of finding safer alternatives.

OBJECTIVES

This study aimed to determine whether early-life exposure to BPA and its related analogues, bisphenol AF (BPAF) and bisphenol S (BPS), could affect female pubertal mammary gland development and long-term mammary health in mice.

METHODS

Timed pregnant CD-1 mice were exposed to vehicle, BPA (0.5, 5, 50 mg/kg), BPAF (0.05, 0.5, 5 mg/kg), or BPS (0.05, 0.5, 5 mg/kg) via oral gavage between gestation days 10–17. Mammary glands were collected from resulting female offspring at postnatal day (PND) 20, 28, 35, and 56, and at 3, 8, and 14 months for whole mount, histopathological evaluation, and quantitative real-time polymerase chain reaction (qPCR); serum steroid concentrations were also measured at these time points.

RESULTS

In the bisphenol-exposed mice, accelerated mammary gland development was evident during early puberty and persisted into adulthood. By late adulthood, mammary glands from bisphenol-exposed female offspring exhibited adverse morphology in comparison with controls; most prominent were undifferentiated duct ends, significantly more lobuloalveolar hyperplasia and perivascular inflammation, and various tumors, including adenocarcinomas. Effects were especially prominent in the BPAF 5 mg/kg and BPS 0.5 mg/kg groups. Serum steroid concentrations and mammary mRNA levels of Esr1, Pgr, Ar, and Gper1 were similar to controls.

CONCLUSIONS

These data demonstrate that prenatal exposure of mice to BPAF or BPS induced precocious development of the mammary gland, and that siblings were significantly more susceptible to spontaneous preneoplastic epithelial lesions and inflammation, with an incidence greater than that observed in vehicle- and BPA-exposed animals. https://doi.org/10.1289/EHP3189.

Bisphenol A concentrations in human urine, human intakes across six continents, and annual trends of average intakes in adult and child populations worldwide: A thorough literature review

Bisphenol A (BPA) is an important industrial raw material that is widely applied in daily products. BPA is also an endocrine-disrupting chemical that may adversely affect humans. This review thoroughly collected data on BPA concentration in human urine and determined main influencing factors. The average BPA intake of humans across six continents or the average value worldwide was calculated based on a simple model. Results showed that the average BPA intake was ranked from high to low as follows: Oceania, Asia, Europe, and North America in the child population and Oceania, Europe, Asia, and North America in the adult population. The annual trend of the average BPA intake was similar between the adult and child populations. The BPA intake in the two populations evidently decreased from 2000 to 2008 and then slightly increased from 2008 to 2011. The BPA intake in the child population started to decrease again from 2011, whereas the corresponding intake in the adult population continued to increase. The distinct difference likely contributed to the wide prohibition of the use of BPA in food-related products for children in many countries since 2009; the bans effectively decreased the total BPA exposure in the child population.

Perinatal BPA exposure and reproductive axis function in CD-1 mice

Perinatal Bisphenol-A (BPA) exposure reduces fertility and fecundity in mice. This study examined effects of early BPA exposure on activation of gonadotropin releasing hormone (GnRH) neurons in conjunction with a steroid-induced luteinizing hormone (LH) surge, characterized patterns of estrous cyclicity and fertility over time, and assessed the ovarian follicular reserve to further explore factors responsible for the reduced fertility we previously described in this model. The percent activated GnRH neurons was reduced in BPA-exposed females at 3-6 months, and periods of persistent proestrus were increased. These data suggest that perinatal exposure to BPA reduces GnRH neuronal activation required for the generation of the LH surge and estrous cyclicity. Assessments of anti-Müllerian hormone (AMH) levels failed to suggest a decline in the follicular reserve at the BPA exposure levels examined.

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.

Water contamination by endocrine disruptors: Impacts, microbiological aspects and trends for environmental protection

Hormone active agents constitute a dangerous class of pollutants. Among them, those agents that mimic the action of estrogens on target cells and are part of the group of endocrine-disruptor compounds (EDCs) are termed estrogenic EDCs, the main focus of this review. Exposure to these compounds causes a number of negative effects, including breast cancer, infertility and animal hermaphroditism. However, especially in underdeveloped countries, limited efforts have been made to warn people about this serious issue, explain the methods of minimizing exposure, and develop feasible and efficient mitigation strategies at different levels and in various environments. For instance, the use of bioremediation processes capable of transforming EDCs into environmentally friendly compounds has been little explored. A wide diversity of estrogen-degrading microorganisms could be used to develop such technologies, which include bioremediation processes for EDCs that could be implemented in biological filters for the post-treatment of wastewater effluent. This review describes problems associated with EDCs, primarily estrogenic EDCs, including exposure as well as the present status of understanding and the effects of natural and synthetic hormones and estrogenic EDCs on living organisms. We also describe potential biotechnological strategies for EDC biodegradation, and suggest novel treatment approaches for minimizing the persistence of EDCs in the environment.

Comparative effects of Bisphenol S and Bisphenol A on the development of female reproductive system in rats; a neonatal exposure study

Bisphenol A (BPA) has been well documented for its endocrine disrupting potential however, very little is known about endocrine disrupting abilities of bisphenol S (BPS). The present study aimed to compare the endocrine disrupting potentials of BPS with BPA, using female rats as an experimental animal model. On postnatal day 1 (PND 1) female pups born were randomly assigned to seven different treatments. Control group received subcutaneous injection of castor oil (50 μL) from PND 1 to PND 10. Three groups of female pups were injected subcutaneously with different concentrations (0.5, 5 and 50 mg/kg in 50 μL castor oil) of BPS, while remaining three groups were treated with 0.5, 5 and 50 mg/kg BPA. Highest doses treatments of both compounds resulted in delayed puberty onset and altered estrous cyclicity. Final body weight was significantly high in the highest dose treated groups of both BPS and BPA. Gonadosomatic index, absolute and relative weight of uteri was significantly reduced in BPS (5 and 50 mg/kg) and BPA (5 and 50 mg/kg) treated groups than control. Plasma concentrations of testosterone and estradiol were significantly increased, while plasma progesterone, Luteinizing hormone (LH) and Follicle stimulating hormone (FSH) concentrations were significantly reduced in highest doses treated groups. Dose dependent increase in the number of cystic follicles in the ovaries was evident along with an increase in the number of atratic follicles. The results suggest that neonatal exposure to higher concentrations of BPS can lead to BPA like structural and endocrine alterations in female rats.

Environmentally relevant levels of bisphenol A affect uterine decidualization and embryo implantation through the estrogen receptor/serum and glucocorticoid-regulated kinase 1/epithelial sodium ion channel α-subunit pathway in a mouse model

OBJECTIVE

To investigate whether bisphenol A (BPA) exposure is associated with uterine decidualization and embryo implantation failure in mice.

DESIGN

Experimental animal study and in vitro study.

SETTING

University-based infertility center.

ANIMAL(S)

ICR mice.

INTERVENTION(S)

Mice treated with different doses of BPA; Ishikawa cells cultured in medium of different concentrations of BPA.

MAIN OUTCOME MEASURE(S)

Embryo implantation sites, uterine weight, quantitative real-time reverse transcriptase-polymerase chain reaction, Western blot analysis, hematoxylin and eosin staining, and immunohistochemical, cell proliferation, and statistical analyses.

RESULT(S)

In the experiment of mouse model, administration of 1-100 μg/kg/day of BPA by gavage led to reduction of the number of embryo implantation sites in a dose-dependent manner; 100 μg/kg/day of BPA statistically significantly reduced the number of implantation sites compared with the control group. The uterine weight change (the wet weight of the decidualized uterine horn divided by the wet weight of the undecidualized uterine horn of the mouse) in groups exposed to BPA (100-10,000 μg/kg/day) were statistically significantly lower compared with the control group. Immunohistochemical analysis demonstrated that administration of 100, 1,000, or 10,000 μg/kg/day of BPA by gavage statistically significantly down-regulated the expression of epithelial Na⁺ channel α-subunit (ENaCα) in the luminal epithelial cells and desmin in decidual cells of the oil-induced decidualized uterine horns. Administration of 100 μg/kg/day BPA on embryo days 0.5-3.5 by gavage statistically significantly decreased the level of uterine serum and glucocorticoid-regulated kinase 1 (SGK1) protein expression on embryo days 4 and 6. After treatment with 0.001, 0.01, 0.1, or 1.0 μg/mL of BPA for 48 hours, the SGK1, ENaCα, and phospho-SGK1 protein expression of Ishikawa cells was down-regulated, and the effect of BPA on SGK1 could be abrogated by fulvestrant.

CONCLUSION(S)

Our study provides the first indication that BPA exposure at levels as low as 100 μg/kg/day can impair embryo implantation in mice and BPA can affect decidualization of the uterus in mouse model. Our results suggest that BPA can down-regulate SGK1 and ENaCα protein expression through estrogen receptors in Ishikawa cells.

Adult exposure to bisphenol A in rare minnow Gobiocypris rarus reduces sperm quality with disruption of testicular aquaporins

Bisphenol A (BPA) is an endocrine disrupter which has adverse effects on male reproduction. Aquaporins (AQPs), well known water-selective channels, play important roles in spermatogenesis and sperm functions. However, whether AQPs participate in the process that BPA induces abnormal sperms has not been investigated to date. In the present study, adult male rare minnows Gobiocypris rarus were exposed to environmentally relevant concentrations BPA (15 and 225 μg/L) for 1, 2 and 3 weeks. Results showed that BPA exposure disrupted sperm motility, increased the percentage of abnormal sperm cells, and decreased sperm tolerance to hypotonic solution and sperm fertilization capacity. Meanwhile, protein levels of AQPs were up-regulated, and their distribution in the testis was abnormal following BPA exposure. The following chromatin immune coprecipitation showed that BPA could regulate aqp3 and 8 expression through the ERE in their 5'-flanking region. The present study demonstrated that BPA could decrease the sperm quality in rare minnow, and AQP3 and 8 might play significant roles in this process.

Effects of Exposure to the Endocrine-Disrupting Chemical Bisphenol A During Critical Windows of Murine Pituitary Development

Critical windows of development are often more sensitive to endocrine disruption. The murine pituitary gland has two critical windows of development: embryonic gland establishment and neonatal hormone cell expansion. During embryonic development, one environmentally ubiquitous endocrine-disrupting chemical, bisphenol A (BPA), has been shown to alter pituitary development by increasing proliferation and gonadotrope number in females but not males. However, the effects of exposure during the neonatal period have not been examined. Therefore, we dosed pups from postnatal day (PND)0 to PND7 with 0.05, 0.5, and 50 μg/kg/d BPA, environmentally relevant doses, or 50 μg/kg/d estradiol (E2). Mice were collected after dosing at PND7 and at 5 weeks. Dosing mice neonatally with BPA caused sex-specific gene expression changes distinct from those observed with embryonic exposure. At PND7, pituitary Pit1 messenger RNA (mRNA) expression was decreased with BPA 0.05 and 0.5 μg/kg/d in males only. Expression of Pomc mRNA was decreased at 0.5 μg/kg/d BPA in males and at 0.5 and 50 μg/kg/d BPA in females. Similarly, E2 decreased Pomc mRNA in both males and females. However, no noticeable corresponding changes were found in protein expression. Both E2 and BPA suppressed Pomc mRNA in pituitary organ cultures; this repression appeared to be mediated by estrogen receptor-α and estrogen receptor-β in females and G protein-coupled estrogen receptor in males, as determined by estrogen receptor subtype-selective agonists. These data demonstrated that BPA exposure during neonatal pituitary development has unique sex-specific effects on gene expression and that Pomc repression in males and females can occur through different mechanisms.

Endocrine disruptors and the tumor microenvironment: A new paradigm in breast cancer biology

Breast cancer is one of the most frequently diagnosed malignancies in women and is characterized by predominantly estrogen dependent growth. Endocrine disruptors (EDCs) have estrogenic properties which have been shown to increase breast cancer risk. While the direct effects of EDCs on breast cancer cell biology and tumor progression have been well studied, the roles for EDCs on tumor microenvironment composition, signaling and structure are incompletely defined. Estrogen targeting of tumor stromal cells can drive paracrine signaling to breast cancer cells regulating tumorigenesis and progression. Additionally, estrogen and estrogen receptor signaling has been shown to alter breast architecture and extracellular matrix component synthesis. Unsurprisingly, EDCs have been shown to induce structural changes in the mammary gland as well as increased collagen fibers in the tissue stroma. Previous work demonstrates that human mesenchymal stem cells (hMSC) are essential components of the tumor microenvironment and are direct targets of both estrogens and EDCs. Furthermore, estrogen-stem cell cross talk has been implicated in breast cancer progression and results in increased tumor cell proliferation, angiogenesis and invasion. This review aims to dissect the possible relationship and mechanisms between EDCs, the tumor microenvironment, and breast cancer progression.

Possible effects of melatonin against rat uterus exposure to bisphenol A during neonatal period

The aim of this study was to investigate the possible effects of melatonin on rat uterine tissue against exposure with bisphenol A (BPA) in the neonatal period. Twenty-four female rats were divided into four groups, (n=6) per group. Group I was used as a control (sesame oil + ethanol), group II was injected daily with (100 mg/kg) BPA by subcutaneously (sc) daily postnatal days (PND 0-10), group III was injected daily with (10 mg/kg) melatonin by sc for 10 days (PND 20-30), and group IV was injected daily with (100 mg/kg) BPA (PND 0-10) and (10 mg/kg) melatonin (PND 20-30). All rats were sacrificed in the same day of metestrus cycle, approximately PND 70. Histological analyses, immunostaining of B cell lymphoma 2 (Bcl-2), and cytochrome c and TUNEL assays were performed. According to our results, neonatal exposure to BPA accelerates onset of puberty, causes degenerative and morphometric changes on rat uterus, and increases apoptotic reaction rates. The immunoreactivity of Bcl-2 was decreased after BPA administration. In addition, immunoreactivity of Bcl-2 showed an increase after melatonin treatment. However, cytochrome c immunoreactivity was decreased after melatonin administration. Our results suggest that melatonin may have positive effects against BPA-induced degenerative changes on rat uterus.

The effects of in utero bisphenol A exposure on ovarian follicle numbers and steroidogenesis in the F1 and F2 generations of mice

Bisphenol A (BPA) is a commonly used plasticizer. Previous studies show that in utero exposure to BPA affects reproductive outcomes in the F1-F3 generations of mice. However, its multigenerational effects on ovarian histology and steroidogenesis over the reproductive lifespan are unknown. Thus, we tested the hypothesis that BPA has multigenerational effects on follicle numbers and steroidogenesis. Mice were exposed in utero to vehicle control or BPA (0.5, 20, and 50μg/kg/day). Ovaries were collected for histological and gene expression analyses and sera were collected for hormone assays. In utero BPA exposure decreased preantral follicle numbers, cytochrome P450 aromatase mRNA levels, and estradiol levels in the F1 generation, whereas it decreased testosterone levels and altered steroidogenic acute regulatory protein, cytochrome P450 cholesterol side-chain cleavage, 3β-hydroxysteroid dehydrogenase 1, and cytochrome P450 aromatase mRNA levels in the F2 generation. These data suggest that BPA has multigenerational effects on the ovary in mice.

Shipbuilding Docks as Experimental Systems for Realistic Assessments of Anthropogenic Stressors on Marine Organisms

Empirical investigations of the impacts of anthropogenic stressors on marine organisms are typically performed under controlled laboratory conditions, onshore mesocosms, or via offshore experiments with realistic (but uncontrolled) environmental variation. These approaches have merits, but onshore setups are generally small sized and fail to recreate natural stressor fields, whereas offshore studies are often compromised by confounding factors. We suggest the use of flooded shipbuilding docks to allow studying realistic exposure to stressors and their impacts on the intra- and interspecific responses of animals. Shipbuilding docks permit the careful study of groups of known animals, including the evaluation of their behavioral interactions, while enabling full control of the stressor and many environmental conditions. We propose that this approach could be used for assessing the impacts of prominent anthropogenic stressors, including chemicals, ocean warming, and sound. Results from shipbuilding-dock studies could allow improved parameterization of predictive models relating to the environmental risks and population consequences of anthropogenic stressors.

The “Low Dose” Hypothesis: Validity and Implications for Human Risk

In the late 1990s, a “low dose” hypothesis was proposed based on studies that purported to show that hormonally active environmental agents were causing a variety of effects, mainly reproductive and developmental, at “low doses.” The supporters of this hypothesis claim that traditional “high-dose” toxicity studies are not adequate to assess adverse effects from these hormonally active agents in that they do not detect effects that are occurring at “low doses.” In addition, it is claimed that these “low dose” effects are occurring at levels comparable to those to which humans are being exposed. These claims have been controversial and expert panels evaluated the evidence behind them in the early 2000s. Although these panels generally concluded that such “low dose” effects were not conclusively established, proponents of the “low dose” hypothesis assert that a large number of more recent studies now provide clear support for their hypothesis. This review carefully examines both recent and older studies that have been cited to support the “low dose” hypothesis, including their relevance for the human population. These include in vivo and in vitro laboratory studies as well as a very limited number of epidemiological investigations. Based on the evidence, it is concluded that these “low dose” effects have yet to be established, that the studies purported to support these cannot be validly extrapolated to humans, and the doses at which the studies have been performed are significantly higher than the levels to which humans are exposed.

Linking the Epigenome with Exposure Effects and Susceptibility: The Epigenetic Seed and Soil Model

The epigenome is a dynamic mediator of gene expression that shapes the way that cells, tissues, and organisms respond to their environment. Initial studies in the emerging field of "toxicoepigenetics" have described either the impact of an environmental exposure on the epigenome or the association of epigenetic signatures with the onset or progression of disease; however, the majority of these pioneering studies examined the relationship between discrete epigenetic modifications and the effects of a single environmental factor. Although these data provide critical blocks with which we construct our understanding of the role of the epigenome in susceptibility and disease, they are akin to individual letters in a complex alphabet that is used to compose the language of the epigenome. Advancing the use of epigenetic data to gain a more comprehensive understanding of the mechanisms underlying exposure effects, identify susceptible populations, and inform the next generation risk assessment depends on our ability to integrate these data in a way that accounts for their cumulative impact on gene regulation. Here we will review current examples demonstrating associations between the epigenetic impacts of intrinsic factors, such as such as age, genetics, and sex, and environmental exposures shape the epigenome and susceptibility to exposure effects and disease. We will also demonstrate how the "epigenetic seed and soil" model can be used as a conceptual framework to explain how epigenetic states are shaped by the cumulative impacts of intrinsic and extrinsic factors and how these in turn determine how an individual responds to subsequent exposure to environmental stressors.

Bisphenol A induces spermatocyte apoptosis in rare minnow Gobiocypris rarus

Bisphenol A (BPA) is an endocrine disruptor, and could induce germ cells apoptosis in the testis of mammals. But whether it could affect fish in the same mechanism has not' been studied till now. In the present study, to investigate the influence of BPA on testis germ cells in fish, adult male rare minnow Gobiocypris rarus were exposed to 225μgL(-1) (0.99μM) BPA for 1, 3 and 9 weeks. Through TdT-mediated dUTP nick end labeling (TUNEL) and transmission electron microscope (TEM) analysis, we found that the amount of apoptotic spermatocytes significantly increased in a time dependent manner following BPA exposure. Western Blot results showed that the ratio of Bcl2/Bax, the important apoptosis regulators in intrinsic mitochondrial apoptotic pathway, was significantly decreased. qPCR showed that mRNA expression of several genes in mitochondrial apoptotic pathway including bcl2, bax, casp9, cytc and mcl1b were significantly changed following BPA exposure. In addition, mRNA expression of meiosis regulation genes (kpna7 and wee2), and genes involved in both apoptosis and meiosis (birc5, ccna1, and gsa1a) were also affected by BPA. Taken together, the present study demonstrated that BPA could induce spermatocytes apoptosis in rare minnow testis, and the apoptosis was probably under regulation of intrinsic mitochondrial apoptotic pathway. Moreover, the spermatocyte apoptosis was likely initiated by BPA induced meiosis arrest.

From BPA to its analogues: Is it a safe journey?

Bisphenol-A (BPA) is one of the most abundant synthetic chemicals in the world due to its uses in plastics. Its widespread exposure vis-a-vis low dose effects led to a reduction in its safety dose and imposition of ban on its use in infant feeding bottles. This restriction paved the way for the gradual market entry of its analogues. However, their structural similarity to BPA has put them under surveillance for endocrine disrupting potential. The application of these analogues is increasing and so are the studies reporting their toxicity. This review highlights the reasons which led to the ban of BPA and also reports the exposure and toxicological data available on its analogues. Hence, this compilation is expected to answer in a better way whether the replacement of BPA by these analogues is safer or more harmful?

The plasticizer bisphenol A affects somatic and sexual development, but differently in pipid, hylid and bufonid anurans

Due to their terrestrial habitats and aquatic reproduction, many amphibians are both very vulnerable and highly suitable bioindicators. The plasticizer bisphenol A (BPA) is one of the most produced chemical substances worldwide, and knowledge on its impacts on humans and animals is mounting. BPA is used for the industrial production of polycarbonate plastics and epoxy resins and found in a multitude of consumer products. Studies on BPA have involved mammals, fish and the fully aquatic anuran model Xenopus laevis. However, our knowledge about the sexual development of non-model, often semi-terrestrial anuran amphibians remains poor. Using a recently developed experimental design, we simultaneously applied BPA to two non-model species (Hyla arborea, Hylidae; Bufo viridis, Bufonidae) and the model X. laevis (Pipidae), compared their genetic and phenotypic sex for detection of sex reversals, and studied sexual development, focusing on anatomical and histological features of gonads. We compared three concentrations of BPA (0.023, 2.28 and 228 μg/L) to control groups in a high-standard flow-through-system, and tested whether conclusions, drawn from the model species, can be extrapolated to non-model anurans. In contrast to previous studies on fish and Xenopus, often involving dosages much higher than most environmental pollution data, we show that BPA causes neither the development of mixed sex nor of sex-reversed individuals (few, seemingly BPA-independent sex reversals) in all focal species. However, environmentally relevant concentrations, as low as 0.023 μg/L, were sufficient to provoke species-specific anatomically and histologically detectable impairments of gonads, and affected morphological traits of metamorphs. As the intensity of these effects differed between the three species, our data imply that BPA diversely affects amphibians with different evolutionary history, sex determination systems and larval ecologies. These results highlight the role of amphibians as a sensitive group that is responsive to environmental pollution.

Bisphenol A (BPA) Exposure In Utero Leads to Immunoregulatory Cytokine Dysregulation in the Mouse Mammary Gland: A Potential Mechanism Programming Breast Cancer Risk

Bisphenol-A (BPA) is a ubiquitous estrogen-like endocrine disrupting compound (EDC). BPA exposure in utero has been linked to breast cancer and abnormal mammary gland development in mice. The recent rise in incidence of human breast cancer and decreased age of first detection suggests a possible environmental etiology. We hypothesized that developmental programming of carcinogenesis may involve an aberrant immune response. Both innate and adaptive immunity play a role in tumor suppression through cytolytic CD8, NK, and Th1 T-cells. We hypothesized that BPA exposure in utero would lead to dysregulation of both innate and adaptive immunity in the mammary gland. CD1 mice were exposed to BPA in utero during gestation (days 9-21) via osmotic minipump. At 6 weeks, the female offspring were ovariectomized and estradiol was given at 8 weeks. RNA and protein were extracted from the posterior mammary glands, and the mRNA and protein levels were measured by PCR array, qRT-PCR, and western blot. In mouse mammary tissue, BPA exposure in utero significantly decreased the expression of members of the chemokine CXC family (Cxcl2, Cxcl4, Cxcl14, and Ccl20), interleukin 1 (Il1) gene family (Il1β and Il1rn), interleukin 2 gene family (Il7 receptor), and interferon gene family (interferon regulatory factor 9 (Irf9), as well as immune response gene 1 (Irg1). Additionally, BPA exposure in utero decreased Esr1 receptor gene expression and increased Esr2 receptor gene expression. In utero exposure of BPA resulted in significant changes to inflammatory modulators within mammary tissue. We suggest that dysregulation of inflammatory cytokines, both pro-inflammatory and anti-inflammatory, leads to a microenvironment that may promote disordered cell growth through inhibition of the immune response that targets cancer cells.

Preferential epigenetic programming of estrogen response after in utero xenoestrogen (bisphenol-A) exposure

Bisphenol-A (BPA) is an environmentally ubiquitous estrogen-like endocrine-disrupting compound. Exposure to BPA in utero has been linked to female reproductive disorders, including endometrial hyperplasia and breast cancer. Estrogens are an etiological factor in many of these conditions. We sought to determine whether in utero exposure to BPA altered the global CpG methylation pattern of the uterine genome, subsequent gene expression, and estrogen response. Pregnant mice were exposed to an environmentally relevant dose of BPA or DMSO control. Uterine DNA and RNA were examined by using methylated DNA immunoprecipitation methylation microarray, expression microarray, and quantitative PCR. In utero BPA exposure altered the global CpG methylation profile of the uterine genome and subsequent gene expression. The effect on gene expression was not apparent until sexual maturation, which suggested that estrogen response was the primary alteration. Indeed, prenatal BPA exposure preferentially altered adult estrogen-responsive gene expression. Changes in estrogen response were accompanied by altered methylation that preferentially affected estrogen receptor-α (ERα)-binding genes. The majority of genes that demonstrated both altered expression and ERα binding had decreased methylation. BPA selectively altered the normal developmental programming of estrogen-responsive genes via modification of the genes that bind ERα. Gene-environment interactions driven by early life xenoestrogen exposure likely contributes to increased risk of estrogen-related disease in adults.-Jorgensen, E. M., Alderman, M. H., III, Taylor, H. S. Preferential epigenetic programming of estrogen response after in utero xenoestrogen (bisphenol-A) exposure.

Possible relationship between endocrine disrupting chemicals and hormone dependent gynecologic cancers

The effects of the natural and synthetic estrogens have been studied for a long time but the data regarding estrogen related chemicals (endocrine disrupting chemicals, EDCs) and their effects on reproductive system are scarce. EDCs are hormone like agents that are readily present in the environment, which may alter the endocrine system of humans and animals. Approximately 800 chemicals are known or suspected to have the potential to function as EDC. Potential role of EDCs on reproductive disease has gained attention in medical literature in recent years. We hypothesize that exposure to low doses of EDCs in a chronic manner could cause hormone dependent genital cancers including ovarian and endometrial cancer. Long term exposure to low concentrations of EDCs may exert potentiation effect with each other and even with endogenous estrogens and could inhibit enzymes responsible for estrogen metabolism. Exposure time to these EDCs is essential as we have seen from Diethylstilbestrol experience. Dose-response curves of EDCs are also unpredictable. Hence mode of action of EDCs are more complex than previously thought. In the light of these controversies lower doses of EDCs in long term exposure is not harmless. Possibility of this relationship and this hypothesis merit further investigation especially through in vivo studies that could better show the realistic environmental exposure. With the confirmation of our hypothesis, possible EDCs could be identified and eliminated from general use as a public health measure.

Effects of Endocrine-disrupting Chemicals on Female Reproductive Health

Endocrine-disrupting chemicals (EDCs) are increasingly prevalent in the environment and the evidence demonstrates that they affect reproductive health, has been accumulating for the last few decades. In this review of recent literature, we present evidence of the effects of estrogen-mimicking EDCs on female reproductive health especially the ovaries and uteri. As representative EDCs, data from studies with a pharmaceutical estrogen, diethylstilbestrol (DES), an organochlorine pesticide methoxychlor (MXC), a phytoestrogen (genistein), and a chemical used in plastics, bisphenol a (BPA) have been presented. We also discuss the effects of a commonly found plasticizer in the environment, a phthalate (DEHP), even though it is not a typical estrogenic EDC. Collectively, these studies show that exposures during fetal and neonatal periods cause developmental reprogramming leading to adult reproductive disease. Puberty, estrous cyclicity, ovarian follicular development, and uterine functions are all affected by exposure to these EDCs. Evidence that epigenetic modifications are involved in the progression to adult disease is also presented.

Tualang Honey Protects against BPA-Induced Morphological Abnormalities and Disruption of ERα, ERβ, and C3 mRNA and Protein Expressions in the Uterus of Rats

Bisphenol A (BPA) is an endocrine disrupting chemical (EDC) that can disrupt the normal functions of the reproductive system. The objective of the study is to investigate the potential protective effects of Tualang honey against BPA-induced uterine toxicity in pubertal rats. The rats were administered with BPA by oral gavage over a period of six weeks. Uterine toxicity in BPA-exposed rats was determined by the degree of the morphological abnormalities, increased lipid peroxidation, and dysregulated expression and distribution of ERα, ERβ, and C3 as compared to the control rats. Concurrent treatment of rats with BPA and Tualang honey significantly improved the uterine morphological abnormalities, reduced lipid peroxidation, and normalized ERα, ERβ, and C3 expressions and distribution. There were no abnormal changes observed in rats treated with Tualang honey alone, comparable with the control rats. In conclusion, Tualang honey has potential roles in protecting the uterus from BPA-induced toxicity, possibly accounted for by its phytochemical properties.

The Role of Hox Genes in Female Reproductive Tract Development, Adult Function, and Fertility

HOX genes convey positional identity that leads to the proper partitioning and adult identity of the female reproductive track. Abnormalities in reproductive tract development can be caused by HOX gene mutations or altered HOX gene expression. Diethylstilbestrol (DES) and other endocrine disruptors cause Müllerian defects by changing HOX gene expression. HOX genes are also essential regulators of adult endometrial development. Regulated HOXA10 and HOXA11 expression is necessary for endometrial receptivity; decreased HOXA10 or HOXA11 expression leads to decreased implantation rates. Alternation of HOXA10 and HOXA11 expression has been identified as a mechanism of the decreased implantation associated with endometriosis, polycystic ovarian syndrome, leiomyoma, polyps, adenomyosis, and hydrosalpinx. Alteration of HOX gene expression causes both uterine developmental abnormalities and impaired adult endometrial development that prevent implantation and lead to female infertility.