Bisphenol A-induced downregulation of murine macrophage activities in vitro and ex vivo

Adverse Effects of Bisphenol A on the Liver and Its Underlying Mechanisms: Evidence from In Vivo and In Vitro Studies

BPA is a known endocrine-disrupting agent that is capable of binding to the estrogen receptor and has exhibited adverse effects in many laboratory animal and in vitro studies. Moreover, it also been shown to have estrogenic, antiandrogenic, inflammatory, and oxidative properties. The widespread presence of BPA in the environment presents a considerable threat to humans. BPA has been shown to be leached into the human ecosystem, where it is commonly found in food products consumed by humans. Although the concentration is relatively low, its prolonged consumption may cause a variety of deleterious health effects. The liver is an important organ for metabolizing and detoxifying toxic metabolites to protect organisms from potentially toxic chemical insults. BPA that is ingested will be eliminated by the liver. However, it has also induced hepatoxicity and injury via various mechanisms. To find research demonstrating the effects of BPA on kidney, a number of databases, including Google Scholar, MEDLINE, PubMed, and the Directory of Open Access Journals, were searched. Thus, this review summarizes the research on the relationship between BPA and its effects on the liver-derived from animals and cellular studies. The underlying mechanism of liver injury caused by BPA is also elucidated.

Potential Pro-Tumorigenic Effect of Bisphenol A in Breast Cancer via Altering the Tumor Microenvironment

Simple Summary

Bisphenol A (BPA) is primarily used to produce polycarbonate plastics, such as water bottles. Exposure to BPA has been shown to increase the growth of breast cancer cells that depend on estrogen for growth due to its ability to mimic estrogen. More recent studies have suggested that BPA also affects the cellular and non-cellular components that compose tumor microenvironments (TMEs), namely the environment around a tumor, thereby potentially promoting breast cancer growth via altering the TME. The TME plays an essential role in cancer development and promotion. Therefore, it is crucial to understand the effect of BPA on breast TMEs to assess its role in the risk of breast cancer adequately. This review examines the potential effects of BPA on immune cells, fibroblasts, extracellular matrices, and adipocytes to highlight their roles in mediating the carcinogenic effect of BPA, and thereby proposes considerations for the risk assessment of BPA exposure.

Abstract

BPA, a chemical used in the preparation of polycarbonate plastics, is an endocrine disruptor. Exposure to BPA has been suggested to be a risk factor for breast cancer because of its potential to induce estrogen receptor signaling in breast cancer cells. More recently, it has been recognized that BPA also binds to the G protein-coupled estrogen receptor and other nuclear receptors, in addition to estrogen receptors, and acts on immune cells, adipocytes, and fibroblasts, potentially modulating the TME. The TME significantly impacts the behavior of cancer cells. Therefore, understanding how BPA affects stromal components in breast cancer is imperative to adequately assess the association between exposure to BPA and the risk of breast cancer. This review examines the effects of BPA on stromal components of tumors to highlight their potential role in the carcinogenic effect of BPA. As a result, I propose considerations for the risk assessment of BPA exposure and studies needed to improve understanding of the TME-mediated, breast cancer-promoting effect of BPA.

Developmental programming of macrophages by early life adversity

Macrophages are central elements of all organs, where they have a multitude of physiological and pathological functions. The first macrophages are produced during fetal development, and most adult organs retain populations of fetal-derived macrophages that self-maintain without major input of hematopoietic stem cell-derived monocytes. Their developmental origins make macrophages highly susceptible to environmental perturbations experienced in early life, in particular the fetal period. It is now well recognized that such adverse developmental conditions contribute to a wide range of diseases later in life. This chapter explores the notion that macrophages are key targets of environmental adversities during development, and mediators of their long-term impact on health and disease. We first briefly summarize our current understanding of macrophage ontogeny and their biology in tissues and consider potential mechanisms by which environmental stressors may mediate fetal programming. We then review evidence for programming of macrophages by adversities ranging from maternal immune activation and diet to environmental pollutants and toxins, which have disease relevance for different organ systems. Throughout this chapter, we contemplate appropriate experimental strategies to study macrophage programming. We conclude by discussing how our current knowledge of macrophage programming could be conceptualized, and finally highlight open questions in the field and approaches to address them.

Interplay Between Endocrine Disruptors and Immunity: Implications for Diseases of Autoreactive Etiology

The sex-bias of disease susceptibility has remained a puzzling aspect of several autoimmune conditions, including post-infection viral autoimmunity. In the last half of the twentieth century, the incidence rate of female-biased autoimmunity has steadily increased independent of medical advances. This has suggested a role for environmental factors, such as endocrine disrupting chemicals, which have been described to interfere with endocrine signaling. Endocrine involvement in the proper function of innate and adaptive immunity has also been defined, however, these two areas have rarely been reviewed in correlation. In addition, studies addressing the effects of endocrine disruptors have reported findings resulting from a broad range of exposure doses, schedules and models. This experimental heterogeneity adds confusion and may mislead the translation of findings to human health. Our work will normalize results across experiments and provide a necessary summary relevant to human exposure. Through a novel approach, we describe how different categories of ubiquitously used environmental endocrine disruptors interfere with immune relevant endocrine signaling and contribute to autoimmunity. We hope this review will guide identification of mechanisms and concentration-dependent EDC effects important not only for the sex-bias of autoimmunity, but also for other conditions of immune dysfunction, including post-infection autoreactivity such as may arise following severe acute respiratory syndrome coronavirus 2, Epstein-Barr virus, Herpes Simplex virus.

Physiological and metabolic approach of plastic additive effects: Immune cells responses

Human and wildlife are continually exposed to a wide range of compounds and substances, which reach the body through the air, water, food, or personal care products. Plasticizers are compounds added to plastics and can be released to the environment under certain conditions. Toxicological studies have concluded that plasticizers, phthalates, and bisphenols are endocrine disruptors, alter the endocrine system and functioning of the immune system and metabolic process. A functional immune response indicates favourable living conditions for an organism; conversely, a weak immune response could reveal a degraded environment that requires organisms to adapt. There is growing concern about the presence of plastic debris in the environment. In this review, the current knowledge of the action of plasticizers on leukocyte cells will be itemized. We also point out critically the role of some nuclear and membrane receptors as key players in the action of plasticizers on cells possess immune function. We discuss the role of erythrocytes within the immune responses and the alteration caused by plasticizers. Finally, we highlight data evidencing mitochondrial dysfunctions triggered by plasticizing toxic action, which can lead to immunosuppression.

Bisphenol A Exposure Changes the Transcriptomic and Proteomic Dynamics of Human Retinoblastoma Y79 Cells

Bisphenol A (BPA) is a xenoestrogen chemical commonly used to manufacture polycarbonate plastics and epoxy resin and might affect various human organs. However, the cellular effects of BPA on the eyes have not been widely investigated. This study aimed to investigate the cellular cytotoxicity by BPA exposure on human retinoblastoma cells. BPA did not show cytotoxic effects, such as apoptosis, alterations to cell viability and cell cycle regulation. Comparative analysis of the transcriptome and proteome profiles were investigated after long-term exposure of Y79 cells to low doses of BPA. Transcriptome analysis using RNA-seq revealed that mRNA expression of the post-transcriptional regulation-associated gene sets was significantly upregulated in the BPA-treated group. Cell cycle regulation-associated gene sets were significantly downregulated by exposure to BPA. Interestingly, RNA-seq analysis at the transcript level indicated that alternative splicing events, particularly retained introns, were noticeably altered by low-dose BPA treatment. Additionally, proteome profiling using MALDI-TOF-MS identified a total of nine differentially expressed proteins. These results suggest that alternative splicing events and altered gene/protein expression patterns are critical phenomena affected by long-term low-dose BPA exposure. This represents a novel marker for the detection of various diseases associated with environmental pollutants such as BPA.

Endocrine Disruptor Compounds-A Cause of Impaired Immune Tolerance Driving Inflammatory Disorders of Pregnancy?

Endocrine disrupting compounds (EDCs) are prevalent and ubiquitous in our environment and have substantial potential to compromise human and animal health. Amongst the chronic health conditions associated with EDC exposure, dysregulation of reproductive function in both females and males is prominent. Human epidemiological studies demonstrate links between EDC exposure and infertility, as well as gestational disorders including miscarriage, fetal growth restriction, preeclampsia, and preterm birth. Animal experiments show EDCs administered during gestation, or to either parent prior to conception, can interfere with gamete quality, embryo implantation, and placental and fetal development, with consequences for offspring viability and health. It has been presumed that EDCs operate principally through disrupting hormone-regulated events in reproduction and fetal development, but EDC effects on maternal immune receptivity to pregnancy are also implicated. EDCs can modulate both the innate and adaptive arms of the immune system, to alter inflammatory responses, and interfere with generation of regulatory T (Treg) cells that are critical for pregnancy tolerance. Effects of EDCs on immune cells are complex and likely exerted by both steroid hormone-dependent and hormone-independent pathways. Thus, to better understand how EDCs impact reproduction and pregnancy, it is imperative to consider how immune-mediated mechanisms are affected by EDCs. This review will describe evidence that several EDCs modify elements of the immune response relevant to pregnancy, and will discuss the potential for EDCs to disrupt immune tolerance required for robust placentation and optimal fetal development.

Prenatal exposure to bisphenol - A is associated with dysregulated perinatal innate cytokine response and elevated cord IgE level: A population-based birth cohort study

BACKGROUND

Reports on the relationship between prenatal exposure to bisphenol-A (BPA) and the development of childhood allergy have been conflicting. This study aimed to investigate the impact of prenatal BPA exposure on several objective outcomes such as cytokine profile, atopic sensitization, and infant lung function (ILF) tests in addition to clinical allergic symptoms.

METHODS

A subset of 274 children from the PATCH cohort study with available cord BPA data were followed until 3 years of age. Total and specific IgE level and Toll-like receptor (TLR) stimulated cytokine production were assessed yearly since birth. ILF such as tidal volume, Vmax_FRC, airway resistance and compliance were performed at least once before the age of 2 years. Allergic outcome was determined by questionnaires and physician's assessment.

RESULTS

There was significant association between BPA concentration and IgE level in the cord blood (p < 0.01), but the correlation was no longer significant at ages 1 through 3 years. In addition, cord BPA concentration was associated with dysregulated TLR stimulated TNF-α and IL-6 production, but the correlation was significant only at birth. No relationship was found between cord BPA concentration and ILF measurements or allergic symptoms (wheezing, rhino-conjunctivitis, or eczema) throughout early childhood.

CONCLUSION

Results showed that prenatal exposure to BPA was not associated with increased risk of childhood allergy or impaired ILF. However, with its impact on biomarkers for allergy such as alterations in perinatal cytokine profile and elevated cord IgE level, the potential role of prenatal BPA exposure on the development of allergy cannot be disregarded.

The use of patient-derived breast tissue explants to study macrophage polarization and the effects of environmental chemical exposure

Ex vivo mammary explant systems are an excellent model to study interactions between epithelium and stromal cell types because they contain physiologically relevant heterotypic interactions in the background of genetically diverse patients. The intact human mammary tissue, termed patient-derived explant (PDE), can be used to investigate cellular responses to a wide variety of external stimuli in situ. For this study, we examined the impact of cytokines or environmental chemicals on macrophage phenotypes. We demonstrate that we can polarize macrophages within human breast tissue PDEs toward M1 or M2 through the addition of interferon-γ (IFNγ) + lipopolysaccharide (LPS) or interleukin (IL)-4 + IL-13, respectively. Elevated expression levels of M(IFNγ + LPS) markers (HLADRA and CXCL10) or M(IL-4 + IL-13) markers (CD209 and CCL18) were observed in cytokine-treated tissues. We also examined the impact of the endocrine-disrupting chemical, benzophenone-3, on PDEs and measured significant, yet varying effects on macrophage polarization. Furthermore, a subset of the PDEs respond to IL-4 + IL-13 through downregulation of E-cadherin and upregulation of vimentin which is reminiscent of epithelial-to-mesenchymal transition (EMT) changes. Finally, we were able to show immortalized nonmalignant breast epithelial cells can exhibit EMT characteristics when exposed to growth factors secreted by M(IL-4 + IL-13) macrophages. Taken together, the PDE model system is an outstanding preclinical model to study early tissue-resident immune responses and effects on epithelial and stromal responses to stimuli found both endogenously in the breast and exogenously as a result of exposures.

Bisphenol A and its substitutes regulate human B cell survival via Nrf2 expression

B cells contribute to produce inflammatory cytokines and antibodies, to present autoantigens, and to interact with T cells, which lead to body defense and disease control. Nuclear factor (erythroid-derived 2)-like 2(Nrf2) is responsible for gene expression of antioxidant enzymes to protect cells from oxidative stress by reactive oxygen species(ROS) production. Bisphenol A(BPA) may not be safe due to the effect on body's physiological functions. The chemicals that substitute for BPA may still have similar effects in the body. Tritan™ copolyester is a novel plastic form using BPA substitutes, 1,4-cyclohexanedimethanol(CHDM), dimethyl terephthalate(DMT), and 2,2,4,4-tetramethyl-1,3-cyclobutanediol(TMCD). Isosorbide(ISO) was also used as a substitute for TMCD and DMT. Here, we investigated whether B cell viability is influenced by BPA and its substitutes via Nrf2 induction using WiL2-NS human B lymphoblast cells. When cytotoxicity was measured by using assays with MTT, CellTiter-Glo, trypan blue and propidium iodide, cytotoxicity by BPA was higher than that by substitutes. BPA and its substitutes showed significant cytotoxicity and ROS production, which were attenuated by the treatment with N-acetylcysteine(NAC), a ROS scavenger. In addition, BPA treatment enhanced gene expression of antioxidant enzymes, heme oxygenase(HO)-1, catalase, superoxide dismutase(SOD) 1 and 2. As H₂O₂ treatment induced cell death and Nrf2 amount in WiL2-NS cells, BPA treatment increased Nrf2. Cell death by H₂O₂ was increased in doxycycline-inducible Nrf2-knockdown(KD) cells. In Cytotoxicity by the treatment with BPA or its substitutes was also enhanced in Nrf2-KD cells but that was reduced by Nrf2 overexpression compared to control cells. Taken together, these results implicate that B cell cytotoxicity by substitutes should be lower than BPA and Nrf2 can prevent B cells from BPA- or BPA substitutes-induced cytotoxicity via ROS production. Data suggest that the comprehensive studies or evaluation could be necessary to replace BPA in manufacture by other substitutes.

Recovery From a Myocardial Infarction Is Impaired in Male C57bl/6 N Mice Acutely Exposed to the Bisphenols and Phthalates That Escape From Medical Devices Used in Cardiac Surgery

Bisphenols and phthalates leach from medical devices, and this exposure is likely to increase in postcardiac surgery patients. Previous studies suggest that such chemical exposure may impact recovery and wound healing, yet the direct effects of bisphenols and phthalates are unknown in this context. To study the direct effect of clinically based chemical exposures, we measured the metabolites representative of 6 bisphenols and 10 phthalates in men before and after cardiac surgery and then replicated this exposure in a mouse model of cardiac surgery and assessed survival, cardiac function and inflammation. Bisphenol A (BPA), di-ethyl hexyl phthalate (DEHP), butylbenzyl phthalate, di-isodecyl phthalate, and di-n-butyl phthalate metabolites were increased after surgery. DEHP exposure predominated, was positively correlated with duration on the cardiopulmonary bypass machine and exceeded its tolerable daily intake limit by 37-fold. In vivo, C57bl/6 N male mice treated with BPA+phthalates during recovery from surgery-induced myocardial infarction had reduced survival, greater cardiac dilation, reduced cardiac function and increased infiltration of neutrophils, monocytes and macrophages suggesting impaired recovery. Of interest, genetic ablation or estrogen receptor beta (ERβ) antagonism did not improve recovery and replacement of DEHP with tri-octyl trimellitate or removal of BPA from the mixture did not ameliorate these effects. To examine the direct effects on inflammation, treatment of human THP-1 macrophages with BPA and phthalates induced a dysfunctional proinflammatory macrophage phenotype with increased expression of M1-type macrophage polarization markers and MMP9 secretion, yet reduced phagocytic activity. These results suggest that chemicals escape from medical devices and may impair patient recovery.

Immune Cells in the Uterine Remodeling: Are They the Target of Endocrine Disrupting Chemicals?

Sufficient uterine remodeling is essential for fetal survival and development. Pathologies related to poor remodeling have a negative impact on maternal and fetal health even years after birth. Research of the last decades yielded excellent studies demonstrating the key role of immune cells in the remodeling processes. This review summarizes the current knowledge about the relevance of immune cells for uterine remodeling during pregnancy and further discusses immunomodulatory effects of man-made endocrine disrupting chemicals on immune cells.

Bisphenol A Promotes the Invasive and Metastatic Potential of Ductal Carcinoma In Situ and Protumorigenic Polarization of Macrophages

Increased cancer risk and immune disorders linked with exposure to environmental endocrine disruptors like bisphenol A (BPA) have been steadily reported. Nevertheless, the impacts of BPA on the breast ductal carcinoma in situ (DCIS) progression and macrophage polarization remain to be elucidated. Here, we analyzed the differentially expressed genes in BPA-exposed DCIS cells and explored BPA effects on DCIS progression and macrophage polarization in vitro and in vivo. Two hundred and ninety-one genes were differentially expressed in 10−8 M BPA-exposed DCIS cells, in which the gene ontology terms of biological processes associated with negative regulation of cell death, cell adhesion, and immune response was enriched. 10−8 M BPA promoted the proliferation and migration of DCIS cells and the migration of macrophages, and upregulated the expression of M1 (NOS2) or M2 markers (Arg-1 and CD206) in macrophages. In coculture system, the migratory capacity of both cells and the expression levels of NOS2, Arg-1, and CD206 in macrophages were significantly enhanced upon 10−8 M BPA. In a DCIS xenograft model, oral exposure to an environmentally human-relevant low dose of 2.5 µg/l BPA for 70 days via drinking water led to an approximately 2-fold promotion in the primary tumor growth rate and a significant enhancement of lymph node metastasis along with increased protumorigenic CD206+ M2 polarization of macrophages. These results demonstrate that BPA acts as an accelerator to promote DCIS progression to invasive breast cancer by affecting DCIS cell proliferation and migration as well macrophage polarization toward a protumorigenic phenotype.

Bisphenol A promotes macrophage proinflammatory subtype polarization via upregulation of IRF5 expression in vitro

Exposure to environmental endocrine-disrupting chemical Bisphenol-A (BPA) is closely associated with an imbalance of immune homeostasis, but the underlying mechanisms are not fully understood. In the present study, the effects of BPA on the polarization of mouse peritoneal macrophages were investigated in vitro. Environmentally relevant low concentrations of BPA treatment under M1 type polarization conditions increased the number of M1 subtype macrophages, the gene expression of M1 phenotypic marker CD11c and the activity and gene expression of M1 functional marker iNOS, as well as the production of pro-inflammatory cytokines. However, The same dose BPA treatment under M2 type polarization conditions reduced the number of M2 subtype macrophages, the gene expression of M2 phenotypic marker CD206 and the activity and gene expression of M2 functional marker Arg-1, along with the production of anti-inflammatory cytokines. We also identified that the expression of transcription factor IRF5 was upregulated by BPA exposure in M1 macrophages under M1 type polarization conditions. Our results demonstrate that BPA promotes macrophage polarization toward proinflammatory M1 subtype and M1 activity, associated with upregulated expression of IRF5, while BPA inhibits macrophage toward anti-inflammatory M2 subtype polarization. These findings provide new insight into the link between exposure to BPA and impairment of immune functions.

Immunomodulatory effects of synthetic endocrine disrupting chemicals on the development and functions of human immune cells

Endocrine disrupting chemicals (EDCs) are added to food, cosmetics, plastic packages, and children's toys and have thus become an integral part of the human environment. In the last decade, there has been increasing interest in the effect of EDCs on human health, including their impact on the immune system. So far, researchers have proved that EDCs (e.g. bisphenols, phthalates, triclosan, phenols, propanil, tetrachlorodibenzo-p-dioxin, diethylstilbestrol, tributyltin (TBT), and parabens) affect the development, functions, and lifespan of immune cells (e.g., monocytes, neutrophils, mast cells, eosinophils, lymphocytes, dendritic cells, and natural killers). In this review, we have summarized the current knowledge of the multivariable influence of EDCs on immune cells and underlined the novel approach to EDC studies, including dose-dependent effects and low-dose effects. We discuss critically the possible relationship between exposure to EDCs and immunity related diseases (e.g. allergy, asthma, diabetes, and lupus). Moreover, based on the literature, we construct a model of possible mechanisms of EDC action on immune cells at cellular, molecular, and epigenetic levels.

Expression of pro-inflammatory cytokines and mediators induced by Bisphenol A via ERK-NFκB and JAK1/2-STAT3 pathways in macrophages

Macrophages not only play an important role in the innate immune response but also participate in many inflammatory and infectious diseases including asthma, diabetes, obesity, cardiovascular diseases, and cancers. Bisphenol A (BPA) is the most commonly used component for plastic products. However, BPA is an endocrine disruptor for mammals and participates in several inflammatory and infectious diseases. Up until now, there are no researches demonstrated the potential role of BPA in macrophage activation and its relative mechanism. BPA promoted the generation of proinflammatory cytokines IL-1β, IL-6, and TNFα in a concentration-dependent manner (P < 0.05). BPA was identified to increase the expression of proinflammatory mediators NO and PGE2, and its upstream factors iNOS, COX2, and cPLA2 in a concentration-dependent manner (P < 0.05). Phosphorylation and nuclear translocation of NF-κB p65 were significantly induced by BPA via IκB degradation (P < 0.05). In addition, phosphorylation of ERK significantly induced by BPA at a concentration which was less than that for phosphorylation of p38 MAPK and JNK (P < 0.05). Furthermore, phosphorylation of STAT3 significantly induced by BPA at a concentration lower than that for phosphorylation of STAT1 (P < 0.05). Phosphorylation of JAK1 and JAK2 was also significantly induced by BPA in a concentration-dependent manner (P < 0.05).

Low-dose bisphenol A induces RIPK1-mediated necroptosis in SH-SY5Y cells: Effects on TNF-α and acetylcholinesterase

Bisphenol A (BPA) is an endocrine disruptor chemical, which is commonly used in everyday products. Adverse effects of its exposure are reported even at picomolar doses. Effects of picomolar and nanomolar concentrations of BPA on cytotoxicity, nitric oxide (NO) levels, acetylcholinesterase (AChE) gene expression and activity, and tumor necrosis factor-α (TNF-α) and caspase-8 levels were determined in SH-SY5Y cells. The current study reveals that low-dose BPA treatment induced cytotoxicity, NO, and caspase-8 levels in SH-SY5Y cells. We also evaluated the mechanism underlying BPA-induced cell death. Ours is the first report that receptor-interacting serine/threonine-protein kinase 1-mediated necroptosis is induced by nanomolar BPA treatment in SH-SY5Y cells. This effect is mediated by altered AChE and decreased TNF-α levels, which result in an apoptosis-necroptosis switch. Moreover, our study reveals that BPA is an activator of AChE.

From the Cover: Lifelong Exposure of C57bl/6n Male Mice to Bisphenol A or Bisphenol S Reduces Recovery From a Myocardial Infarction

Bisphenol A (BPA) leaches from plastics to contaminate foodstuffs. Analogs, such as bisphenol S (BPS), are now used increasingly in manufacturing. Greater BPA exposure has been correlated with exacerbation of cardiovascular disease, including myocardial infarction (MI). To test the hypothesis that bisphenol exposure impairs cardiac healing, we exposed C57bl/6n mice to water containing 25ng/ml BPA or BPS from conception and surgically induced an MI in adult male progeny. Increased early death and cardiac dilation, and reduced cardiac function were found post-MI in BPA- and BPS-exposed mice. Flow cytometry revealed increased monocyte and macrophage infiltration that correlated with increased chemokine C-C motif ligand-2 expression in the infarct. In vitro BPA and BPS addition increased matrix metalloproteinase-9 (MMP) protein and secreted activity in RAW264.7 macrophage cells suggesting that invivo increases in MMP2 and MMP9 in exposed infarcts were myeloid-derived. Bone marrow-derived monocytes isolated from exposed mice had greater expression of pro-inflammatory polarization markers when chemokine stimulated indicating an enhanced susceptibility to develop a pro-inflammatory monocyte population. Chronic BPA exposure of estrogen receptor beta (ERβ) deficient mice did not worsen early death, cardiac structure/function, or expression of myeloid markers after an MI. In contrast, BPS exposure of ERβ-deficient mice resulted in greater death and expression of myeloid markers. We conclude that lifelong exposure to BPA or BPS augmented the monocyte/macrophage inflammatory response and adverse remodeling from an MI thereby reducing the ability to survive and successfully recover, and that the adverse effect of BPA, but not BPS, is downstream of ERβ signaling.

CLARITY-BPA: Effects of chronic bisphenol A exposure on the immune system: Part 2 - Characterization of lymphoproliferative and immune effector responses by splenic leukocytes

Bisphenol A (BPA) is commonly used in the manufacturing of a wide range of consumer products, including polycarbonate plastics, epoxy resin that lines beverage and food cans, and some dental sealants. Consumption of food and beverages containing BPA represents the primary route of human BPA exposure, which is virtually ubiquitous. An increasing number of studies have evaluated the effects of BPA on immune responses in laboratory animals that have reported a variety of effects some of which have been contradictory. To address the divergent findings surrounding BPA exposure, a comprehensive chronic treatment study of BPA was conducted in Sprague-Dawley rats, termed the Consortium Linking Academic and Regulatory Insights on Toxicity of BPA (CLARITY-BPA). As a participant in the CLARITY-BPA project, our studies evaluated the effects of BPA on a broad range of immune function endpoints using spleen cells isolated from BPA or vehicle treated rats. This comprehensive assessment included measurements of lymphoproliferation in response to mitogenic stimuli, immunoglobulin production by B cells, and cellular activation of T cells, NK cells, monocytes, granulocytes, macrophages and dendritic cells. In total, 630 different measurements in BPA treated rats were performed of which 35 measurements were statistically different from vehicle controls. The most substantive alteration associated with BPA treatment was the augmentation of lymphoproliferation in response to pokeweed mitogen stimulations in 1 year old male rats, which was also observed in the reference estrogen ethinyl estradiol treated groups. With the exception of the aforementioned, the statistically significant changes associated with BPA treatment were mostly sporadic and not dose-dependent with only one out of five BPA dose groups showing a statistical difference. In addition, the observed BPA-associated alterations were mostly moderate in magnitude and showed no persistent trend over the one-year time period. Based on these findings, we conclude that the observed BPA-mediated changes observed in this study are unlikely to alter immune competence in adult rats.

Prenatal exposure to bisphenol-A is associated with Toll-like receptor-induced cytokine suppression in neonates

BACKGROUND

Despite widespread human exposure to biphenol A (BPA), limited studies exist on the association of BPA with adverse health outcomes in young children. This study aims to investigate the effect of prenatal exposure to BPA on toll-like receptor-induced cytokine responses in neonates and its association with infectious diseases later in life.

METHODS

Cord bloods were collected from 275 full-term neonates. Production of TNF-α, IL-6, and IL-10 were evaluated after stimulating mononuclear cells with toll-like receptor ligands (TLR1-4 and 7-8). Serum BPA concentrations were analyzed by enzyme-linked immunosorbent assay. Bacteria from nasopharyngeal specimens were identified with multiplex PCR and culture method.

RESULT

Result showed significant association between cord BPA concentration and TLR3- and TLR4-stimulated TNF-α response (P = 0.001) and that of TLR78-stimulated IL-6 response (P = 0.03). Clinical analysis did not show prenatal BPA exposure to be correlated with infection or bacterial colonization during the first year of life.

CONCLUSION

This is the first cohort study that indicated prenatal BPA exposure to play a part in TLR-related innate immune response of neonatal infants. However, despite an altered immune homeostasis, result did not show such exposure to be associated with increased risk of infection during early infancy.

Effects of Endocrine Disruptor Compounds, Alone or in Combination, on Human Macrophage-Like THP-1 Cell Response

The aim of the present study was to evaluate the immunological effects on human macrophages of four endocrine disruptor compounds (EDCs) using the differentiated human THP-1 cell line as a model. We studied first the effects of these EDCs, including Bisphenol A (BPA), di-ethylhexyl-phthalate (DEHP), dibutyl phthalate (DBP) and 4-tert-octylphenol (4-OP), either alone or in combination, on cytokine secretion, and phagocytosis. We then determined whether or not these effects were mediated by estrogen receptors via MAPK pathways. It was found that all four EDCs studied reduced strongly the phagocytosis of the differentiated THP-1 cells and that several of these EDCs disturbed also TNF-α, IL-1 β and IL-8 cytokine secretions. Furthermore, relative to control treatment, decreased ERK 1/2 phosphorylation was always associated with EDCs treatments-either alone or in certain combinations (at 0.1 μM for each condition). Lastly, as treatments by an estrogen receptor antagonist suppressed the negative effects on ERK 1/2 phosphorylation observed in cells treated either alone with BPA, DEHP, 4-OP or with the combined treatment of BPA and DEHP, we suggested that estrogen receptor-dependent pathway is involved in mediating the effects of EDCs on human immune system. Altogether, these results advocate that EDCs can disturb human immune response at very low concentrations.

Chronic Exposure to Bisphenol A Reduces Successful Cardiac Remodeling After an Experimental Myocardial Infarction in Male C57bl/6n Mice

Estrogenic compounds such as bisphenol A (BPA) leach from plastics into food and beverage containers. Increased BPA exposure has been correlated with increased cardiovascular disease. To test the hypothesis that increased BPA exposure reduces cardiovascular remodeling, we chronically exposed C57bl/6n male mice to BPA and performed a myocardial infarction (MI). We measured cardiac function, as well as myeloid and cardiac fibroblast accumulation and activity. We found increased early death as well as increased cardiac dilation and reduced cardiac function in surviving BPA-exposed mice. Matrix metalloproteinase-2 (MMP2) protein and activity were increased 1.5-fold in BPA-exposed heart. BPA-exposed mice had similar neutrophil infiltration; however, monocyte and macrophage (MΦ) infiltration into the ischemic area was 5-fold greater than VEH mice potentially due to a 2-fold increase in monocyte chemoattractant protein-1. Monocyte and MΦ exposure to BPA in vitro in primary bone marrow cultures or in isolated peritoneal MΦ increased polarization to an activated MΦ, increased MMP2 and MMP9 expression 2-fold and activity 3-fold, and increased uptake of microspheres 3-fold. Cardiac fibroblasts (CF) differentiate to α-smooth muscle actin (αSMA) expressing myofibroblasts, migrate to the ischemic area and secrete collagen to strengthen the scar. Collagen and αSMA expression were reduced 50% in BPA-exposed hearts. Chronic in vivo or continuous in vitro BPA exposure ablated transforming growth factor beta-mediated differentiation of CF, reduced αSMA expression 50% and reduced migration 40% yet increased secreted MMP2 activity 2-fold. We conclude that chronic BPA exposure reduces the ability to successfully remodel after an MI by increasing MΦ-based inflammation and reducing myofibroblast repair function.

Exposure to bisphenol A, but not phthalates, increases spontaneous diabetes type 1 development in NOD mice

Type 1 diabetes mellitus (T1DM) is an autoimmune destruction of insulin producing pancreatic beta-cells due to a genetic predisposition and can be triggered by environmental factors. We have previously shown that bisphenol A (BPA) accelerates the spontaneous development of diabetes in non-obese diabetic (NOD) mice. Here, we hypothesized that oral exposure to a mixture of the endocrine disruptors BPA and phthalates, relevant for human exposure, would accelerate diabetes development compared to BPA alone. NOD mice were exposed to BPA (1 mg/l), a mixture of phthalates (DEHP 1 mg/l, DBP 0.2 mg/l, BBP 10 mg/l and DiBP 20 mg/l) or a combination of BPA and the phthalate mixture through drinking water from conception and throughout life. Previous observations that BPA exposure increased the prevalence of diabetes and insulitis and decreased the number of tissue resident macrophages in pancreas were confirmed, and extended by demonstrating that BPA exposure also impaired the phagocytic activity of peritoneal macrophages. None of these effects were observed after phthalate exposure alone. The phthalate exposure in combination with BPA seemed to dampen the BPA effects on macrophage number and function as well as diabetes development, but not insulitis development. Exposure to BPA alone or in combination with phthalates decreased cytokine release (TNFα, IL-6, IL-10, IFNγ, IL-4) from in vitro stimulated splenocytes and lymph node cells, indicating systemic changes in immune function. In conclusion, exposure to BPA, but not to phthalates or mixed exposure to BPA and phthalates, accelerated diabetes development in NOD mice, apparently in part via systemic immune alterations including decreased macrophage function.

Epigenetic Regulation of Non-Lymphoid Cells by Bisphenol A, a Model Endocrine Disrupter: Potential Implications for Immunoregulation

Endocrine disrupting chemicals (EDC) abound in the environment since many compounds are released from chemical, agricultural, pharmaceutical, and consumer product industries. Many of the EDCs such as Bisphenol A (BPA) have estrogenic activity or interfere with endogenous sex hormones. Experimental studies have reported a positive correlation of BPA with reproductive toxicity, altered growth, and immune dysregulation. Although the precise relevance of these studies to the environmental levels is unclear, nevertheless, their potential health implications remain a concern. One possible mechanism by which BPA can alter genes is by regulating epigenetics, including microRNA, alteration of methylation, and histone acetylation. There is now wealth of information on BPA effects on non-lymphoid cells and by comparison, paucity of data on effects of BPA on the immune system. In this mini review, we will highlight the BPA regulation of estrogen receptor-mediated immune cell functions and in different inflammatory conditions. In addition, BPA-mediated epigenetic regulation of non-lymphoid cells is emphasized. We recognize that most of these studies are on non-lymphoid cells, and given that BPA also affects the immune system, it is plausible that BPA could have similar epigenetic regulation in immune cells. It is hoped that this review will stimulate studies in this area to ascertain whether or not BPA epigenetically regulates the cells of the immune system.

Modulation of cytokine expression in human macrophages by endocrine-disrupting chemical Bisphenol-A

Exposure to environmental endocrine-disrupting chemical Bisphenol-A (BPA) is often associated with dysregulated immune homeostasis, but the mechanisms remain unclear. In the present study, the effects of BPA on the cytokines responses of human macrophages were investigated. Treatment with BPA increased pro-inflammation cytokines tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production, but decreased anti-inflammation cytokines interleukin-10 (IL-10) and transforming growth factor-β (TGF-β) production in THP1 macrophages, as well as in primary human macrophages. BPA effected cytokines expression through estrogen receptor α/β (ERα/β)-dependent mechanism with the evidence of ERα/β antagonist reversed the expression of cytokines. We also identified that activation of extracellular regulated protein kinases (ERK)/nuclear factor κB (NF-κB) signal cascade marked the effects of BPA on cytokines expression. Our results indicated that BPA effected inflammatory responses of macrophages via modulating of cytokines expression, and provided a new insight into the link between exposure to BPA and human health.

The Potential Roles of Bisphenol A (BPA) Pathogenesis in Autoimmunity

Bisphenol A (BPA) is a monomer found in commonly used consumer plastic goods. Although much attention in recent years has been placed on BPA's impact as an endocrine disruptor, it also appears to activate many immune pathways involved in both autoimmune disease development and autoimmune reactivity provocation. The current scientific literature is void of research papers linking BPA directly to human or animal onset of autoimmunity. This paper explores the impact of BPA on immune reactivity and the potential roles these mechanisms may have on the development or provocation of autoimmune diseases. Potential mechanisms by which BPA may be a contributing risk factor to autoimmune disease development and progression include its impact on hyperprolactinemia, estrogenic immune signaling, cytochrome P450 enzyme disruption, immune signal transduction pathway alteration, cytokine polarization, aryl hydrocarbon activation of Th-17 receptors, molecular mimicry, macrophage activation, lipopolysaccharide activation, and immunoglobulin pathophysiology. In this paper a review of these known autoimmune triggering mechanisms will be correlated with BPA exposure, thereby suggesting that BPA has a role in the pathogenesis of autoimmunity.

Transmaternal bisphenol A exposure accelerates diabetes type 1 development in NOD mice

Diabetes mellitus type 1 is an autoimmune disease with a genetic predisposition that is triggered by environmental factors during early life. Epidemiological studies show that bisphenol A (BPA), an endocrine disruptor, has been detected in about 90% of all analyzed human urine samples. In this study, BPA was found to increase the severity of insulitis and the incidence of diabetes in female non obese diabetic (NOD) mice offspring after transmaternal exposure through the dams' drinking water (0, 0.1, 1, and 10mg/l). Both the severity of insulitis in the pancreatic islets at 11 weeks of age and the diabetes prevalence at 20 weeks were significantly increased for female offspring in the highest exposure group compared to the control group. Increased numbers of apoptotic cells, a reduction in tissue resident macrophages and an increase in regulatory T cells were observed in islets prior to insulitis development in transmaternally exposed offspring. The detectable apoptotic cells were identified as mostly glucagon producing alpha-cells but also tissue resident macrophages and beta-cells. In the local (pancreatic) lymph node neither regulatory T cell nor NKT cell populations were affected by maternal BPA exposure. Maternal BPA exposure may have induced systemic immune changes in offspring, as evidenced by alterations in LPS- and ConA-induced cytokine secretion in splenocytes. In conclusion, transmaternal BPA exposure, in utero and through lactation, accelerated the spontaneous diabetes development in NOD mice. This acceleration appeared to be related to early life modulatory effects on the immune system, resulting in adverse effects later in life.

Long-term bisphenol A exposure accelerates insulitis development in diabetes-prone NOD mice

Exposure to the endocrine disruptor (ED) bisphenol A (BPA) used in polycarbonate plastic and epoxy resins appears ubiquitous since BPA can be found in over 90% of analyzed urine samples from all age groups. There is a parallel occurrence of increased prevalence in type 1 diabetes mellitus (T1DM) and an increased exposure to EDs the last decades. T1DM is caused by insulin deficiency due to autoimmune destruction of insulin producing pancreatic beta cells and has been suggested to be induced by various environmental factors acting together with a genetic predisposition. The objective of the present study was to investigate the effect of BPA (0, 1 and 100 mg/l BPA in the drinking water) on T1DM development in nonobese diabetic (NOD) mice, spontaneously developing T1DM. Histological evaluation of pancreas from 12-weeks-old female mice revealed significantly increased insulitis in mice exposed to 1 mg/l BPA, while the insulitis was less severe at the higher BPA exposure. Serum glucose levels in the 1 mg/ml BPA group tended to be hyperglycaemic, also indicating an accelerated onset of T1DM. The high BPA exposure seemed to counteract the diabetes development in females and also in male NOD mice for both BPA concentrations. Prior to insulitis, both BPA concentrations resulted in increased apoptosis and reduced numbers of tissue resident macrophages in pancreatic islets. In conclusion, long-term BPA exposure at a dose three times higher than the tolerable daily intake of 50 µg/kg, appeared to accelerate spontaneous insulitis and diabetes development in NOD mice.

Proteomic biomarkers for prenatal bisphenol A-exposure in mouse immune organs

Many investigators have encountered difficulty in clarifying the risks of exposure to bisphenol A (BPA), an endocrine disrupting chemical in epidemiological studies or animal experiments. In the present study, we developed biomarkers of BPA-induced proteomic alterations in immune organs of mouse offspring that were prenatally exposed to BPA (15 and 300 mg/L of drinking water; they were exposed to 8.9 +/- 1.8 mg of BPA/kg/day and 171.1 +/- 16.8 mg of BPA/kg/day, respectively) that were evaluated in terms of sex, age, and BPA-exposure levels. We performed 2D-gel analyses of samples from various tissues (thymus and spleen), exposure levels, sex, and ages (3- and 7-week-old) (N = 48), and found seven proteins that were altered in a BPA dose-dependent manner. Among them, we further studiedapo-AI, DPPIII, and VAT1, which are suspected to be associated with endocrine disorders. By performing Western blots, we confirmed BPA upregulation of all three proteins. Moreover, the apo-AI mRNA levels were increased in a BPA dose-dependent manner in 3- and 7-week-old female mice. Females and young offspring were somewhat more sensitive to protein alterations than others. Our study, which is based on proteome analyses, suggests that apo-AI, DPPIII, and VAT represent protein biomarkers for BPA and provide useful mechanistic clues for BPA-induced endocrine disruption.

Derivation of a bisphenol A oral reference dose (RfD) and drinking-water equivalent concentration

Human exposure to bisphenol A (BPA) is due to that found in the diet, and BPA and its metabolites were detected at parts per billion (or less) concentrations in human urine, milk, saliva, serum, plasma, ovarian follicular fluid, and amniotic fluid. Adverse health effects in mice and rats may be induced after parenteral injection or after massive oral doses. Controlled ingestion trials in healthy adult volunteers with 5 mg d16-BPA were unable to detect parent BPA in plasma despite exquisitely sensitive (limit of detection = 6 nM) methods, but by 96 h 100% of the administered dose was recovered in urine as the glucuronide. The extensive BPA glucuronidation following ingestion is not seen after parenteral injection; only the parent BPA binds plasma proteins and estrogen receptors (ER). The hypothesis that BPA dose-response may be described by a J- or U-shape curve was not supported by toxicogenomic data collected in fetal rat testes and epididymes (after repeated parenteral exposure at 2-400,000 microg/kg-d), where a clear monotonic dose-response both in the numbers of genes and magnitude of individual gene expression was evident. There is no clear indication from available data that the BPA doses normally consumed by humans pose an increased risk for immunologic or neurologic disease. There is no evidence that BPA poses a genotoxic or carcinogenic risk and clinical evaluations of 205 men and women with high-performance liquid chromatography (HPLC)-verified serum or urinary BPA conjugates showed (1) no objective signs, (2) no changes in reproductive hormones or clinical chemistry parameters, and (3) no alterations in the number of children or sons:daughters ratio. Results of benchmark dose (BMD10 and BMDL10) calculations and no-observed-adverse-effect level (NOAEL) inspections of all available and reproducible rodent studies with oral BPA found BMD and NOAEL values all greater than the 5 mg/kg-d NOAELs from mouse and rat multigeneration reproduction toxicity studies. While allometric and physiologically based pharmacokinetic (PBPK) models were constructed for interspecies scaling of BPA and its interaction with ER, multigeneration feeding studies with BPA at doses spanning 5 orders of magnitude failed to identify signs of developmental toxicity or adverse changes in reproductive tract tissues; the 5-mg/kg-d NOAELs identified for systemic toxicity in rats and mice were less than the oral NOAELs for reproductive toxicity. Thus, it is the generalized systemic toxicity of ingested BPA rather than reproductive, immunologic, neurobehavioral, or genotoxic hazard that represents the point of departure. Using U.S. Environmental Protection Agency (EPA) uncertainty factor guidance and application of a threefold database uncertainty factor (to account for the fact that the carcinogenic potential of transplacental BPA exposure has yet to be fully defined and comprehensive neurobehavioral and immunotoxicologic evaluations of BPA by relevant routes and at relevant doses have yet to be completed) to the administered dose NOAEL results in an oral RfD of 0.016 mg/kg-d. Assuming the 70-kg adult consumes 2 L of water each day and adopting the default 20% U.S. EPA drinking water relative source contribution yields a 100 microg/L BPA total allowable concentration (TAC).

Downregulation of peritoneal macrophage activity in mice exposed to bisphenol A during pregnancy and lactation

Bisphenol A (BPA) is an environmental endocrine disrupter that is known to be transferred to the fetus via the placenta and to the neonate via milk. In this study, we investigated BPA-induced alterations of the activities of murine peritoneal macrophages in dams and 7 week old offspring of dams exposed to BPA from gestational day 7 until lactation on day 21 after delivery, i.e. 34-36 days. BPA was administered in drinking water at three doses, 15, 75, and 300 mg/L. Dams were sacrificed 21 days after delivery and offspring at the age of 7 weeks. Peritoneal macrophages were cultured in the presence of LPS or LPS plus IFN-gamma for 2 or 4 days. We found that nitric oxide (NO) production by maternal macrophages was significantly decreased in a BPA-dose dependent manner. However, while a significant reduction of NO production by macrophages in the offspring was observed at BPA concentrations of 75 mg/L and 300 mg/L in drinking water, this effect was not seen at the lowest concentration of 15 mg/L. Similar inhibition of tumor necrosis factor-alpha (TNF-alpha) production was observed with macrophages from both BPA-exposed dams and offspring. Thus, our results suggest that exposure to BPA during gestation and lactation induces downregulation of the activities of macrophages in both dams and offspring.