Consensus on the key characteristics of endocrine-disrupting chemicals as a basis for hazard identification

[Environmental endocrine disruptors and fertility]

Endocrine disruptor chemicals (EDCs) are ubiquitous contaminants in the environment, wildlife, and humans. During the last 20 years, several epidemiological, clinical and experimental studies have demonstrated the role of EDCs on the reduction of male and female fertility. The concept of foetal origins of adult disease is particularly topical in the field of reproduction. Moreover, exposure to EDCs during pregnancy has been shown to influence epigenetic programming of endocrine signalling and other important physiological pathways, and provided the basis for multi- and transgenerational transmission of adult diseases. However, the large panel of EDCs simultaneously present in the air, sol and water makes the quantification of human exposition still a challenge. Gas chromatography coupled with mass spectrometry, the measurement of total plasmatic hormonal bioactivity on stably transfected cell lines as well as the EDC analysis in hair samples are useful methods of evaluation. More recently, microRNAs analysis offers a new perspective in the comprehension of the mechanisms behind the modulation of cellular response to foetal or post-natal exposure to EDCs. They will help researchers and clinicians in identifying EDCs exposition markers and new therapeutic approaches in the future.

Phytotoxicity of the chiral herbicide dichlorprop: Cross-talk between nitric oxide, reactive oxygen species and phytohormones

Nitric oxide (NO), reactive oxygen species (ROS), and phytohormones in plants often initiate responses to sources of abiotic stress. However, we have a poor understanding of the cross-talk between NO, ROS, and phytohormones during exogenous chiral auxin-induced phytotoxicity. In this study, the toxicity of the chiral synthetic auxin herbicide dichlorprop (DCPP) to Arabidopsis thaliana, as well as the mutual regulation of NO, hydrogen peroxide (H₂O₂), superoxide anion (O₂^.-), and phytohormones at the enantiomeric level was investigated. The ROS production exhibited an enantioselective manner, further, that was positively correlated with the change of the morphological indicators. This confirmed that ROS played an important role in the enantioselective effect of DCPP. The distribution of ROS and NO was partially overlapped, indicating that the production of NO may be affected by ROS, and also related to the degree of plant damage. In terms of phytohormones, the level of salicylic acid (SA), jasmonic acid (JA), and abscisic acid (ABA) in the whole plant increased as the (R)-DCPP concentration applied increased, however, the trend has changed, when the data of leaves and roots was discussed separately. The results revealed that the redistribution of phytohormones may exist between leaves and roots, caused by the joint action of ROS and NO. The differences in the biological activity identified between the two enantiomers in this study enhance our understanding of the toxicity mechanism of exogenous auxin via their effects on phytohormones.

Background exposure to polychlorinated biphenyls and all-cause, cancer-specific, and cardiovascular-specific mortality: A systematic review and meta-analysis

BACKGROUND

Polychlorinated biphenyls (PCBs) are a large family of man-made organic, ubiquitous, and persistent contaminants with endocrine-disrupting properties. PCBs have been associated with numerous adverse health effects and were classified as carcinogenic to humans, but their long-term impact on mortality risk in the general population is unknown.

OBJECTIVE

To conduct a systematic review and meta-analysis in order to assess whether background exposure levels of PCBs increase all-cause and cancer- and cardiovascular-specific mortality risk in the general population.

METHODS

We searched the Pubmed, Web of Science, Cochrane Library, and Embase databases for eligible studies up to 1st of January, 2021. We included cohort and nested-case control studies comparing the lowest vs. the highest background exposure level of PCBs in the general population and reporting data for all-cause mortality and/or cancer-/cardiovascular-specific mortality. Studies reporting occupational and accidental exposures were excluded. Random-effects meta-analysis was used to estimate summary relative risks (SRRs) and 95% confidence intervals (CIs). Heterogeneity across studies was assessed by I2 statistics, and publication bias both graphically and using Egger's and Begg's tests. Quality of included studies was assessed using the National Toxicology Program/Office of Health Assessment and Translation (NTP/OHAT). Confidence in the body of evidence and related level of evidence were assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) based on the NTP/OHAT framework. The protocol was registered in PROSPERO (CRD42020178079).

RESULTS

The initial search led to 2,132 articles. Eight prospective cohort studies met our inclusion criteria, leading to 72,852 participants including 17,805 deaths. Overall exposure to PCBs was not statistically significantly associated with all-cause mortality (SRR = 1.13, 95% CI = 0.90-1.41, n = 7 studies, low certainty); however, dietary exposure to PCBs was associated with an increased risk of cardiovascular-specific mortality (SRR = 1.38, 95% CI = 1.14-1.66, n = 3 studies, moderate certainty), while no association was found with cancer-specific mortality (SRR = 1.07, 95% CI = 0.72-1.59, n = 5 studies, low certainty).

CONCLUSION

Our meta-analysis suggests that background exposure to PCBs is associated with an increased risk of cardiovascular-specific mortality in the general population with a "moderate" level of evidence. These findings should be interpreted with caution given the small number of studies on mortality in the general population.

Endocrine disrupting chemicals and bone

Endocrine-disrupting chemicals (EDCs) are defined as chemicals that interfere with the function of the endocrine system. EDCs exert their hormonal effects through several mechanisms; modulating hormone receptors or changing metabolism of different hormones. EDCs also influence multiple signalling pathways while effecting the hormonal systems and possess complex dose-response curves. EDCs can exert deleterious effects on bone tissue through changing bone modelling and remodelling via altering bone paracrine hormone synthesis, the release of systemic hormones, cytokines, chemokines and growth factors, and effecting stem cell fate, as well as bone marrow mesenchymal stem cell differentiation. Evidence is accumulating of the bone disrupting effect of different groups of EDCs, such as; the perfluoroalkyl substances, the phthalate esters, the bisphenol A, the organotin compounds, the alkylphenols and the dioxin and dioxin-like compounds. This review highlights the recent discoveries of the effects of commonly found environmental chemicals on bone from basic molecular findings to clinical implications.

Thyroid hormone system disrupting chemicals

The thyroid hormone system is a main target of endocrine disruptor compounds (EDC) at all levels of its intricately fine-tuned feedback regulation, synthesis, distribution, metabolism and action of the 'prohormone' thyroxine and its active metabolites. Apart from classical antithyroid effects of EDC on the gland, the majority of known and suspected effects occurs at the pre-receptor control of T3 ligand availability to T3 receptors exerting ligand modulated thyroid hormone action. Tissue-, organ- and cell-specific expression and function of thyroid hormone transporters, deiodinases, metabolizing enzymes and T3-receptor forms, all integral components of the system, may mediate adverse EDC effects. Established evidence from nutritional, pharmacological and molecular genetic studies clearly support the functional, biological, and clinical relevance of these targets. Iodine-containing thyroid hormones and the organization of this system are highly conserved during evolution from primitive aquatic life forms, amphibia, birds throughout all vertebrates including humans. Mechanistic studies from various animal experimental models strongly support cause-effect relationships upon EDC exposure, hazards and adverse effects of EDC across various species. Retrospective case-control, cohort and population studies linking EDC exposure with epidemiological data on thyroid hormone-related (dys-)functions provide clear evidence that human development, especially of the fetal and neonatal brain, growth, differentiation and metabolic processes in adult and aging humans are at risk for adverse EDC effects. Considering that more than half of the world population still lives on inadequate iodine supply, the additional ubiquitous exposure to EDC and their mixtures is an additional threat for the essential thyroid hormone system, the health of the human population and their future progenies, animal life forms and our global environment.

Human biomonitoring initiative (HBM4EU): Human biomonitoring guidance values (HBM-GVs) derived for bisphenol A

The "European Human Biomonitoring Initiative" (HBM4EU) derives human biomonitoring guidance values (HBM-GVs) for the general population (HBM-GV_GenPop) and/or for occupationally exposed adults (HBM-GV_Worker) for several priority substances and substance groups as identified by policy makers, scientists and stakeholders at EU and national level, including bisphenol A (BPA). Human exposure to BPA is widespread and of particular concern because of its known endocrine-disrupting properties. Unlike the conjugated forms of BPA circulating in the body, free BPA is known to interact with the nuclear estrogen receptors. Because free BPA is considered to be more toxicologically active than the conjugated forms (e.g. BPA-glucuronide (BPA-G) and BPA-sulfate (BPA-S)), its measurement in blood provides the superior surrogate of the biologically effective dose. However, considering the difficulty of implementing blood sampling in large HBM cohorts, as well as the current analytical capacities complying with the quality assurance (QA)/quality control (QC) schemes, total BPA in urine (i.e. the sum of free and conjugated forms of BPA measured after an hydrolysis of phase II metabolites) was retained as the relevant exposure biomarker for BPA. HBM-GV_GenPop for total BPA in urine of 230 µg/L and 135 µg/L for adults and children, respectively, were developed on the basis of toxicological data. To derive these values, the concentrations of urinary total BPA consistent with a steady-state exposure to the temporary Tolerable Daily Intake (t-TDI) of 4 µg/kg bw/day set in 2015 by the European Food Safety Authority (EFSA) were estimated. The BPA human physiologically-based pharmacokinetic (PBPK) model developed by Karrer et al. (2018) was used, assuming an oral exposure to BPA at the t-TDI level averaged over 24 h. Dermal uptake of BPA is suspected to contribute substantially to the total BPA body burden, which in comparison with the oral route, is generating a higher ratio of free BPA to total BPA in blood. Therefore, an alternative approach for calculating the HBM-GV_GenPop according to the estimated relative contributions of both the oral and dermal routes to the global BPA exposure is also discussed. Regarding BPA exposure at the workplace, the steady-state concentration of urinary total BPA was estimated after a dermal uptake of BPA that would generate the same concentration of free BPA in plasma (considered as the bioactive form) as would a 24 h-averaged intake to the European Chemicals Agency (ECHA)'s oral DNEL of 8 µg BPA/kg bw/day set for workers. The predicted concentration of urinary total BPA at steady-state is equivalent to, or exceeds the 95th percentile of total BPA in urine measured in different European HBM studies conducted in the general population. Thus, no HBM-GV_Worker was proposed, as the high background level of BPA coming from environmental exposure - mostly through food intake - is making the discrimination with the occupational exposure to BPA difficult.

Phthalates, ovarian function and fertility in adulthood

Phthalates are a family of high-production volume industrial chemicals used in the manufacture of plastics. Some phthalates are regulated as endocrine disrupting chemicals (EDCs) and reproductive toxicants based on adverse effects in the male. Potential effects in females are less understood although exposure levels can be higher in women compared to men. Here, we review the literature on the effects of phthalate exposures in adulthood on ovarian function and fertility in women. Experimental studies using cell cultures and rodents combined with human evidence from epidemiological studies suggest that phthalates pose a hazard to ovaries. Phthalates can disrupt follicle growth pattern, increase oxidative stress and cause follicle death. These effects could lead to infertility, faster depletion of ovarian reserve, and earlier reproductive senescence. However, more studies using more realistic exposure levels will be needed to properly assess the risks in women.

Perinatal exposure to endocrine disrupting chemicals and neurodevelopment: How articles of daily use influence the development of our children

Substances that interfere with the body's hormonal balance or their function are called endocrine disrupting chemicals (EDCs). Many EDCs are ubiquitous in the environment and are an unavoidable aspect of daily life, including during early embryogenesis. Developmental exposure to these chemicals is of critical relevance, as EDCs can permanently alter developmental programs, including those that pattern and wire the brain. Of emerging interest is how these chemicals may also affect the immune response, given the cross-talk between the endocrine and immune systems. As brain development is strongly dependent on hormones including thyroid, androgens, and estrogens, and can also be affected by immunomodulation, this complicated interplay may have long-lasting neurodevelopmental consequences. This review focuses on data available from human cohorts, in vivo models, and in vitro assays regarding the impact of EDCs after a gestational and/or lactational exposure, and how they may impact the immune system and/or neurodevelopment.

Key Characteristics of Cardiovascular Toxicants

BACKGROUND

The concept of chemical agents having properties that confer potential hazard called key characteristics (KCs) was first developed to identify carcinogenic hazards. Identification of KCs of cardiovascular (CV) toxicants could facilitate the systematic assessment of CV hazards and understanding of assay and data gaps associated with current approaches.

OBJECTIVES

We sought to develop a consensus-based synthesis of scientific evidence on the KCs of chemical and nonchemical agents known to cause CV toxicity along with methods to measure them.

METHODS

An expert working group was convened to discuss mechanisms associated with CV toxicity.

RESULTS

The group identified 12 KCs of CV toxicants, defined as exogenous agents that adversely interfere with function of the CV system. The KCs were organized into those primarily affecting cardiac tissue (numbers 1-4 below), the vascular system (5-7), or both (8-12), as follows: 1) impairs regulation of cardiac excitability, 2) impairs cardiac contractility and relaxation, 3) induces cardiomyocyte injury and death, 4) induces proliferation of valve stroma, 5) impacts endothelial and vascular function, 6) alters hemostasis, 7) causes dyslipidemia, 8) impairs mitochondrial function, 9) modifies autonomic nervous system activity, 10) induces oxidative stress, 11) causes inflammation, and 12) alters hormone signaling.

DISCUSSION

These 12 KCs can be used to help identify pharmaceuticals and environmental pollutants as CV toxicants, as well as to better understand the mechanistic underpinnings of their toxicity. For example, evidence exists that fine particulate matter [PM ≤2.5μm in aerodynamic diameter (PM2.5)] air pollution, arsenic, anthracycline drugs, and other exogenous chemicals possess one or more of the described KCs. In conclusion, the KCs could be used to identify potential CV toxicants and to define a set of test methods to evaluate CV toxicity in a more comprehensive and standardized manner than current approaches. https://doi.org/10.1289/EHP9321.

Endocrine disruptors and gut microbiome interactions

Anthropogenic environmental pollutants affect many physiological, biochemical, and endocrine actions as reproduction, metabolism, immunity, behavior and as such can interfere with any aspect of hormone action. Microbiota and their genes, microbiome, a large body of microorganisms, first of all bacteria and co-existing in the host´s gut, are now believed to be autonomous endocrine organ, participating at overall endocrine, neuroendocrine and immunoendocrine regulations. While an extensive literature is available on the physiological and pathological aspects of both players, information about their mutual relationships is scarce. In the review we attempted to show various examples where both, endocrine disruptors and microbiota are meeting and can act cooperatively or in opposition and to show the mechanism, if known, staying behind these actions.

Chemosensory Dysfunction Induced by Environmental Pollutants and Its Potential As a Novel Neurotoxicological Indicator: A Review

Air pollution composed of the complex interactions among particular matter, chemicals, and pathogens is an emerging and global environmental issue that closely correlates with a variety of diseases and adverse health effects, especially increasing incidences of neurodegenerative diseases. However, as one of the prevalent health outcomes of air pollution, chemosensory dysfunction has not attracted enough concern until recently. During the COVID-19 pandemic, multiple scientific studies emphasized the plausibly essential roles of the chemosensory system in the airborne transmission airway of viruses into the human body, which can also be utilized by pollutants. In this Review, in addition to summarizing current progress regarding the contributions of traditional air pollutants to chemosensory dysfunction, we highlight the roles of emerging contaminants. We not only sum up clarified mechanisms, such as inflammation and apoptosis but also discuss some not yet completely identified mechanisms, e.g., disruption of olfactory signal transduction. Although the existing evidence is not overwhelming, the chemosensory system is expected to be a useful indicator in neurotoxicology and neural diseases based on accumulating studies that continually excavate the deep link between chemosensory dysfunction and neurodegenerative diseases. Finally, we argue the importance of studies concerning chemosensory dysfunction in understanding the health effects of air pollution and provide comments for some future directions of relevant research.

Exploring the Biological Activity and Mechanism of Xenoestrogens and Phytoestrogens in Cancers: Emerging Methods and Concepts

Xenoestrogens and phytoestrogens are referred to as "foreign estrogens" that are produced outside of the human body and have been shown to exert estrogen-like activity. Xenoestrogens are synthetic industrial chemicals, whereas phytoestrogens are chemicals present in the plant. Considering that these environmental estrogen mimics potentially promote hormone-related cancers, an understanding of how they interact with estrogenic pathways in human cells is crucial to resolve their possible impacts in cancer. Here, we conducted an extensive literature evaluation on the origins of these chemicals, emerging research techniques, updated molecular mechanisms, and ongoing clinical studies of estrogen mimics in human cancers. In this review, we describe new applications of patient-derived xenograft (PDX) models and single-cell RNA sequencing (scRNA-seq) techniques in shaping the current knowledge. At the molecular and cellular levels, we provide comprehensive and up-to-date insights into the mechanism of xenoestrogens and phytoestrogens in modulating the hallmarks of cancer. At the systemic level, we bring the emerging concept of window of susceptibility (WOS) into focus. WOS is the critical timing during the female lifespan that includes the prenatal, pubertal, pregnancy, and menopausal transition periods, during which the mammary glands are more sensitive to environmental exposures. Lastly, we reviewed 18 clinical trials on the application of phytoestrogens in the prevention or treatment of different cancers, conducted from 2002 to the present, and provide evidence-based perspectives on the clinical applications of phytoestrogens in cancers. Further research with carefully thought-through concepts and advanced methods on environmental estrogens will help to improve understanding for the identification of environmental influences, as well as provide novel mechanisms to guide the development of prevention and therapeutic approaches for human cancers.

Hazard identification and early warning system based on stochastic forest algorithm in underground coal mine

Aiming at the problem of large error and long time of early warning response in the traditional system, this paper designs a hazard identification early warning system based on random forest algorithm in underground coal mine. By random classification decision forest created dangerous content in different areas of the downhole information input into the decision tree as a test sample, according to the result of the output of the leaf node determine the risk level of decision trees, and USES the high precision of decision forest classification ability the threat level assessment test sample, radically reducing hazards identification error. Then, based on the evaluation results, combined with the threshold value of warning criteria to identify the gas exceeding limit area, and determine the fire source warning level, so as to realize the hazard source identification and warning. The simulation results show that the average hazard location identification error of the system is only 4.1%, and the warning response time can be controlled within 9 s.

Endocrine disrupting potential of replacement flame retardants - Review of current knowledge for nuclear receptors associated with reproductive outcomes

BACKGROUND AND AIM

Endocrine disrupting chemicals (EDCs) constitute a major public health concern because they can induce a large spectrum of adverse effects by interfering with the hormonal system. Rapid identification of potential EDCs using in vitro screenings is therefore critical, particularly for chemicals of emerging concerns such as replacement flame retardants (FRs). The review aimed at identifying (1) data gaps and research needs regarding endocrine disrupting (ED) properties of replacement FRs and (2) potential EDCs among these emerging chemicals.

METHODS

A systematic search was performed from open literature and ToxCast/Tox21 programs, and results from in vitro tests on the activities of 52 replacement FRs towards five hormone nuclear receptors (NRs) associated with reproductive outcomes (estrogen, androgen, glucocorticoid, progesterone, and aryl hydrocarbon receptors) were compiled and organized into tables. Findings were complemented with information from structure-based in silico model predictions and in vivo information when relevant.

RESULTS

For the majority of the 52 replacement FRs, experimental in vitro data on activities towards these five NRs were either incomplete (15 FRs) or not found (24 FRs). Within the replacement FRs for which effect data were found, some appeared as candidate EDCs, such as triphenyl phosphate (TPhP) and tris(1,3-dichloropropyl)phosphate (TDCIPP). The search also revealed shared ED profiles. For example, anti-androgenic activity was reported for 19 FRs and predicted for another 21 FRs.

DISCUSSION

This comprehensive review points to critical gaps in knowledge on ED potential for many replacement FRs, including chemicals to which the general population is likely exposed. Although this review does not cover all possible characteristics of ED, it allowed the identification of potential EDCs associated with reproductive outcomes, calling for deeper evaluation and possibly future regulation of these chemicals. By identifying shared ED profiles, this work also raises concerns for mixture effects since the population is co-exposed to several FRs and other chemicals.

Environmental impact on reproductive health and risk mitigating strategies

PURPOSE OF REVIEW

The purpose of this review is to increase awareness among reproductive health professionals and trainees about the impact of environmental toxicants and climate change on women's health and mitigation strategies at the individual, professional and governmental levels.

RECENT FINDINGS

Global health indicators reveal a meteoric rise of noncommunicable diseases over the past 50 years, which threaten reproductive health directly and indirectly. Evolutionary genetic mutations as contributors are unlikely in this timeframe, and environmental causes have been invoked. Notably, the past 75 years have witnessed marked increases in industrial chemical production, and global warming has rendered a 'climate crisis' with extreme temperatures and compromised food, water, and air quality. There is now strong experimental and epidemiologic evidence for endocrine disrupting chemicals and particulate matter and chemical components of air pollution in the pathophysiology of human reproductive disorders during development and across the lifespan, especially among vulnerable populations.

SUMMARY

Environmental impacts on fertility, pregnancy outcomes, childhood neurodevelopment, and reproductive tract development are significant, not widely appreciated, and may be preventable. In light of the evidence, education and advocating economical mitigations of toxic environmental chemicals and alternative energy strategies are imperatives to assure quality reproductive health for this and future generations.

Environmental Exposure to Endocrine Disrupting Chemicals Influences Genomic Imprinting, Growth, and Metabolism

Genomic imprinting is an epigenetic mechanism that results in monoallelic, parent-of-origin-specific expression of a small number of genes. Imprinted genes play a crucial role in mammalian development as their dysregulation result in an increased risk of human diseases. DNA methylation, which undergoes dynamic changes early in development, is one of the epigenetic marks regulating imprinted gene expression patterns during early development. Thus, environmental insults, including endocrine disrupting chemicals during critical periods of fetal development, can alter DNA methylation patterns, leading to inappropriate developmental gene expression and disease risk. Here, we summarize the current literature on the impacts of in utero exposure to endocrine disrupting chemicals on genomic imprinting and metabolism in humans and rodents. We evaluate how early-life environmental exposures are a potential risk factor for adult metabolic diseases. We also introduce our mouse model of phthalate exposure. Finally, we describe the potential of genomic imprinting to serve as an environmental sensor during early development and as a novel biomarker for postnatal health outcomes.

NF-κB-An Important Player in Xenoestrogen Signaling in Immune Cells

The proper functioning of the immune system is critical for an effective defense against pathogenic factors such as bacteria and viruses. All the cellular processes taking place in an organism are strictly regulated by an intracellular network of signaling pathways. In the case of immune cells, the NF-κB pathway is considered the key signaling pathway as it regulates the expression of more than 200 genes. The transcription factor NF-κB is sensitive to exogenous factors, such as xenoestrogens (XEs), which are compounds mimicking the action of endogenous estrogens and are widely distributed in the environment. Moreover, XE-induced modulation of signaling pathways may be crucial for the proper development of the immune system. In this review, we summarize the effects of XEs on the NF-κB signaling pathway. Based on our analysis, we constructed a model of XE-induced signaling in immune cells and found that in most cases XEs activate NF-κB. Our analysis indicated that the indirect impact of XEs on NF-κB in immune cells is related to the modulation of estrogen signaling and other pathways such as MAPK and JAK/STAT. We also summarize the role of these aspects of signaling in the development and further functioning of the immune system in this paper.

Yale School of Public Health Symposium: An overview of the challenges and opportunities associated with per- and polyfluoroalkyl substances (PFAS)

On December 13, 2019, the Yale School of Public Health hosted a symposium titled "Per- and Polyfluoroalkyl Substances (PFAS): Challenges and Opportunities" in New Haven, Connecticut. The meeting focused on the current state of the science on these chemicals, highlighted the challenges unique to PFAS, and explored promising opportunities for addressing them. It brought together participants from Yale University, the National Institute of Environmental Health Sciences, the University of Massachusetts Amherst, the University of Connecticut, the Connecticut Agricultural Experiment Station, the Connecticut Departments of Public Health and Energy and Environmental Protection, and the public and private sectors. Presentations during the symposium centered around several primary themes. The first reviewed the current state of the science on the health effects associated with PFAS exposure and noted key areas that warranted future research. As research in this field relies on specialized laboratory analyses, the second theme considered commercially available methods for PFAS analysis as well as several emerging analytical approaches that support health studies and facilitate the investigation of a broader range of PFAS. Since mitigation of PFAS exposure requires prevention and cleanup of contamination, the third theme highlighted new nanotechnology-enabled PFAS remediation technologies and explored the potential of green chemistry to develop safer alternatives to PFAS. The fourth theme covered collaborative efforts to assess the vulnerability of in-state private wells and small public water supplies to PFAS contamination by adjacent landfills, and the fifth focused on strategies that promote successful community engagement. This symposium supported a unique interdisciplinary coalition established during the development of Connecticut's PFAS Action Plan, and discussions occurring throughout the symposium revealed opportunities for collaborations among Connecticut scientists, state and local officials, and community advocates. In doing so, it bolstered the State of Connecticut's efforts to implement the ambitious initiatives that its PFAS Action Plan recommends.

In vitro and in silico investigations of endocrine disruption induced by metabolites of plasticizers through glucocorticoid receptor

The endocrine disruptive capability of plasticizers to activate nuclear receptors has attracted great interest. This study is aimed to assess the potential glucocorticoid effects of metabolites of plasticizers. The effects of metabolites of plasticizers on the transcriptional activity of glucocorticoid receptor (GR) were investigated using reporter gene assays. All of them failed to exhibit agonistic/antagonistic effects on GR. However, a combination of dexamethasone and monobutyl phthalate (MBP) could synergistically activate GR. MBP combined with dexamethasone also enhanced GR nuclear translocation by Western blot, while mifepristone restrained GR cytoplasmic-to-nuclear translocation. MBP co-treated with dexamethasone resulted in synergistic induction of PEPCK and MKP-1 gene expression by real-time PCR and PEPCK protein level by Western blot. Furthermore, the carboxyl and ester groups of MBP have influences on the charge distribution of MBP, leading to change of electrostatic interactions between MBP and GR by calculations on electronic properties. Both hydrophobic and hydrogen bonding interactions play a crucial role in the stabilization between MBP and GR conducted by molecular docking and dynamics simulation. This work confirms that GR could remain stable upon binding to MBP. In conclusion, dexamethasone and MBP could synergistically activate GR, resulting in synergetic enhancement of subsequent GR-mediated endocrine disrupting effect.

Endocrine disrupting chemicals (EDCs) and the neuroendocrine system: Beyond estrogen, androgen, and thyroid

Hundreds of anthropogenic chemicals occupy our bodies, a situation that threatens the health of present and future generations. This chapter focuses on endocrine disrupting compounds (EDCs), both naturally occurring and man-made, that affect the neuroendocrine system to adversely impact health, with an emphasis on reproductive and metabolic pathways. The neuroendocrine system is highly sexually dimorphic and essential for maintaining homeostasis and appropriately responding to the environment. Comprising both neural and endocrine components, the neuroendocrine system is hormone sensitive throughout life and touches every organ system in the body. The integrative nature of the neuroendocrine system means that EDCs can have multi-system effects. Additionally, because gonadal hormones are essential for the sex-specific organization of numerous neuroendocrine pathways, endocrine disruption of this programming can lead to permanent deficits. Included in this review is a brief history of the neuroendocrine disruption field and a thorough discussion of the most common and less well understood neuroendocrine disruption modes of action. Also provided are extensive examples of how EDCs are likely contributing to neuroendocrine disorders such as obesity, and evidence that they have the potential for multi-generational effects.

An approach to classifying occupational exposures to endocrine disrupting chemicals by sex hormone function using an expert judgment process

Endocrine disrupting chemicals (EDCs) are exogenous substances that interfere with the endocrine system and cause adverse effects. We aimed to classify the effects of 24 known EDCs, prevalent in certain occupations, according to four modes of action (estrogenic, antiestrogenic, androgenic, and/or antiandrogenic). A literature search, stratified into four types of literature was conducted (namely: national and international agency reports; review articles; primary studies; ToxCast^TM). The state of the evidence of each EDC on sex hormone function was summarized and reviewed by an expert panel. For each mode of action, the experts evaluated the likelihood of endocrine disruption in five categories: "No", "Unlikely", "Possibly", "Probably", and "Yes". Seven agents were categorized as "Yes," or having strong evidence for their effects on sex hormone function (antiandrogenic: lead, arsenic, butylbenzyl phthalate, dibutyl phthalate, dicyclohexyl phthalate; estrogenic: nonylphenol, bisphenol A). Nine agents were categorized as "Probable," or having probable evidence (antiandrogenic: bis(2-ethylhexyl)phthalate, nonylphenol, toluene, bisphenol A, diisononyl phthalate; androgenic: cadmium; estrogenic: copper, cadmium and; anti-estrogenic: lead). Two agents (arsenic, polychlorinated biphenyls) had opposing conclusions supporting both "probably" estrogenic and antiestrogenic effects. This synthesis will allow researchers to evaluate the health effects of selected EDCs with an added level of precision related to the mode of action.

Application of an in Vitro Assay to Identify Chemicals That Increase Estradiol and Progesterone Synthesis and Are Potential Breast Cancer Risk Factors

BACKGROUND

Established breast cancer risk factors, such as hormone replacement therapy and reproductive history, are thought to act by increasing estrogen and progesterone (P4) activity.

OBJECTIVE

We aimed to use in vitro screening data to identify chemicals that increase the synthesis of estradiol (E2) or P4 and evaluate potential risks.

METHOD

Using data from a high-throughput (HT) in vitro steroidogenesis assay developed for the U.S. Environmental Protection Agency (EPA) ToxCast program, we identified chemicals that increased estradiol (E2-up) or progesterone (P4-up) in human H295R adrenocortical carcinoma cells. We prioritized chemicals by their activity. We compiled in vivo studies and assessments about carcinogenicity and reproductive/developmental (repro/dev) toxicity. We identified exposure sources and predicted intakes from the U.S. EPA's ExpoCast.

RESULTS

We found 296 chemicals increased E2 (182) or P4 (185), with 71 chemicals increasing both. In vivo data often showed effects consistent with this mechanism. Of the E2- and P4-up chemicals, about 30% were likely repro/dev toxicants or carcinogens, whereas only 5-13% were classified as unlikely. However, most of the chemicals had insufficient in vivo data to evaluate their effects. Of 45 chemicals associated with mammary gland effects, and also tested in the H294R assay, 29 increased E2 or P4, including the well-known mammary carcinogen 7,12-dimethylbenz(a)anthracene. E2- and P4-up chemicals include pesticides, consumer product ingredients, food additives, and drinking water contaminants.

DISCUSSION

The U.S. EPA's in vitro screening data identified several hundred chemicals that should be considered as potential risk factors for breast cancer because they increased E2 or P4 synthesis. In vitro data is a helpful addition to current toxicity assessments, which are not sensitive to mammary gland effects. Relevant effects on the mammary gland are often not noticed or are dismissed, including for 2,4-dichlorophenol and cyfluthrin. Fifty-three active E2-up and 59 active P4-up chemicals that are in consumer products, food, pesticides, or drugs have not been evaluated for carcinogenic potential and are priorities for study and exposure reduction. https://doi.org/10.1289/EHP8608.

Associations between Exposure to Organochlorine Chemicals and Endometriosis: A Systematic Review of Experimental Studies and Integration of Epidemiological Evidence

BACKGROUND

Growing epidemiological evidence suggests that organochlorine chemicals (OCCs), including 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), may play a role in the pathogenesis of endometriosis.

OBJECTIVES

We aimed to systematically review the experimental evidence (in vivo and in vitro) on the associations between exposure to OCCs and endometriosis-related end points.

METHODS

A systematic review protocol was developed following the National Toxicology Program /Office of Health Assessment and Translation (NTP/OHAT) framework and managed within a web-based interface. In vivo studies designed to evaluate the impact of OCCs on the onset or progression of endometriosis and proliferation of induced endometriotic lesions were eligible. Eligible in vitro studies included single-cell and co-culture models to evaluate the proliferation, migration, and/or invasion of endometrial cells. We applied the search strings to PubMed, Web of Science, and Scopus®. A final search was performed on 24 June 2020. Assessment of risk of bias and the level of evidence and integration of preevaluated epidemiological evidence was conducted using NTP/OHAT framework Results: Out of 812 total studies, 39 met the predetermined eligibility criteria (15 in vivo, 23 in vitro, and 1 both). Most studies (n=27) tested TCDD and other dioxin-like chemicals. In vivo evidence supported TCDD's promotion of endometriosis onset and lesion growth. In vitro evidence supported TCDD's promotion of cell migration and invasion, but there was insufficient evidence for cell proliferation. In vitro evidence further supported the roles of the aryl hydrocarbon receptor and matrix metalloproteinases in mediating steroidogenic disruption and inflammatory responses. Estrogen interactions were found across studies and end points.

CONCLUSION

Based on the integration of a high level of animal evidence with a moderate level of epidemiological evidence, we concluded that TCDD was a known hazard for endometriosis in humans and the conclusion is supported by mechanistic in vitro evidence. Nonetheless, there is need for further research to fill in our gaps in understanding of the relationship between OCCs and their mixtures and endometriosis, beyond the prototypical TCDD. https://doi.org/10.1289/EHP8421.

Effects of air pollution exposure on social behavior: a synthesis and call for research

BACKGROUND

There is a growing literature from both epidemiologic and experimental animal studies suggesting that exposure to air pollution can lead to neurodevelopmental and neuropsychiatric disorders. Here, we suggest that effects of air pollutant exposure on the brain may be even broader, with the potential to affect social decision-making in general.

METHODS

We discuss how the neurobiological substrates of social behavior are vulnerable to air pollution, then briefly present studies that examine the effects of air pollutant exposure on social behavior-related outcomes.

RESULTS

Few experimental studies have investigated the effects of air pollution on social behavior and those that have focus on standard laboratory tests in rodent model systems. Nonetheless, there is sufficient evidence to support a critical need for more research.

CONCLUSION

For future research, we suggest a comparative approach that utilizes diverse model systems to probe the effects of air pollution on a wider range of social behaviors, brain regions, and neurochemical pathways.

Reproductive Health Risks Associated with Occupational and Environmental Exposure to Pesticides

A marked reduction in fertility and an increase in adverse reproductive outcomes during the last few decades have been associated with occupational and environmental chemical exposures. Exposure to different types of pesticides may increase the risks of chronic diseases, such as diabetes, cancer, and neurodegenerative disease, but also of reduced fertility and birth defects. Both occupational and environmental exposures to pesticides are important, as many are endocrine disruptors, which means that even very low-dose exposure levels may have measurable biological effects. The aim of this review was to summarize the knowledge collected between 2000 and 2020, to highlight new findings, and to further interpret the mechanisms that may associate pesticides with infertility, abnormal sexual maturation, and pregnancy complications associated with occupational, environmental and transplacental exposures. A summary of current pesticide production and usage legislation is also included in order to elucidate the potential impact on exposure profile differences between countries, which may inform prevention measures. Recommendations for the medical surveillance of occupationally exposed populations, which should be facilitated by the biomonitoring of reduced fertility, is also discussed.

Impaired Morphogenesis and Function of Rat Adrenal Zona Glomerulosa by Developmental Low-Dose Exposure to DDT Is Associated with Altered Oct4 Expression

Dichlorodiphenyltrichloroethane (DDT) is a persistent organic pollutant and one of the most widespread endocrine disrupting chemicals. The impact of low-dose exposure to DDT on the morphogenesis of the adrenal gland is still poorly understood. The development and function of zona glomerulosa in rats has been found to be associated with changes in the expression of the transcription factor Oct4 (Octamer 4), which is the most important player in cell pluripotency. The aim of the study was to investigate the morphogenesis and function of rat adrenal zona glomerulosa in rats exposed to low doses of DDT during prenatal and postnatal development and to determine the possible role of Oct4 in DDT-mediated structural and functional changes. The DDT-exposed rats demonstrated slower development and lower functional activity of the zona glomerulosa during the pubertal period associated with higher expression of Oct4. Further, accelerated growth and restoration of hormone production was associated with, firstly, a decrease in Oct4 expressing cells and secondly, the loss of the inverse relationship between basal aldosterone levels and the number of Oct4 expressing cells. Thus, the transcriptional factor Oct4 exhibited an altered pattern of expression in the DDT-exposed rats during postnatal development. The results of the study uncover a novel putative mechanism by which low doses of DDT disrupt the development of adrenal zona glomerulosa.

Endocrine Disrupting Chemicals, Hormone Receptors, and Acne Vulgaris: A Connecting Hypothesis

The relationship between endocrine disrupting chemicals (EDCs) and the pathogenesis of acne vulgaris has yet to be explored in the literature. Acne vulgaris is a chronic inflammatory skin disease of the pilosebaceous unit. The pathogenesis of acne involves several hormonal pathways, including androgens, insulin-like growth factor 1(IGF-1), estrogens, and corticosteroids. EDCs influence these pathways primarily through two mechanisms: altering endogenous hormone levels and interfering with hormone receptor function. This review article describes the mechanistic links between EDCs and the development of acne lesions. Highlighted is the contributory role of androgen receptor ligands, such as bisphenol A (BPA) and mono-2-ethylhexyl Phthalate (MEHP), via upregulation of lipogenic genes and resultant exacerbation of cholesterol synthesis. Additionally discussed is the protective role of phytoestrogen EDCs in counteracting androgen-induced sebocyte maturation through attenuation of PPARy transcriptional activity (i.e., resveratrol) and restoration of estrogen-regulated TGF-B expression in skin cells (i.e., genistein). Examination of the relationship between EDCs and acne vulgaris may inform adjunctive avenues of treatment such as limiting environmental exposures, and increasing low-glycemic, plant-rich foods in the diet. With a better understanding of the cumulative role that EDCs play in acne, clinicians can be better equipped to treat and ultimately improve the lives of their patients.

Inappropriately sweet: Environmental endocrine-disrupting chemicals and the diabetes pandemic

Afflicting hundreds of millions of individuals globally, diabetes mellitus is a chronic disorder of energy metabolism characterized by hyperglycemia and other metabolic derangements that result in significant individual morbidity and mortality as well as substantial healthcare costs. Importantly, the impact of diabetes in the United States is not uniform across the population; rather, communities of color and those with low income are disproportionately affected. While excessive caloric intake, physical inactivity, and genetic susceptibility are undoubted contributors to diabetes risk, these factors alone fail to fully explain the rapid global rise in diabetes rates. Recently, environmental contaminants acting as endocrine-disrupting chemicals (EDCs) have been implicated in the pathogenesis of diabetes. Indeed, burgeoning data from cell-based, animal, population, and even clinical studies now indicate that a variety of structurally distinct EDCs of both natural and synthetic origin have the capacity to alter insulin secretion and action as well as global glucose homeostasis. This chapter reviews the evidence linking EDCs to diabetes risk across this spectrum of evidence. It is hoped that improving our understanding of the environmental drivers of diabetes development will illuminate novel individual-level and policy interventions to mitigate the impact of this devastating condition on vulnerable communities and the population at large.

Hypothalamic Expression of Neuropeptide Y (NPY) and Pro-OpioMelanoCortin (POMC) in Adult Male Mice Is Affected by Chronic Exposure to Endocrine Disruptors

In the arcuate nucleus, neuropeptide Y (NPY) neurons, increase food intake and decrease energy expenditure, and control the activity of pro-opiomelanocortin (POMC) neurons, that decrease food intake and increase energy expenditure. Both systems project to other hypothalamic nuclei such as the paraventricular and dorsomedial hypothalamic nuclei. Endocrine disrupting chemicals (EDCs) are environmental contaminants that alter the endocrine system causing adverse health effects in an intact organism or its progeny. We investigated the effects of long-term exposure to some EDCs on the hypothalamic NPY and POMC systems of adult male mice that had been previously demonstrated to be a target of some of these EDCs after short-term exposure. Animals were chronically fed for four months with a phytoestrogen-free diet containing two different concentrations of bisphenol A, diethylstilbestrol, tributyltin, or E₂. At the end, brains were processed for NPY and POMC immunohistochemistry and quantitatively analyzed. In the arcuate and dorsomedial nuclei, both NPY and POMC immunoreactivity showed a statistically significant decrease. In the paraventricular nucleus, only the NPY system was affected, while the POMC system was not affected. Finally, in the VMH the NPY system was affected whereas no POMC immunoreactive material was observed. These results indicate that adult exposure to different EDCs may alter the hypothalamic circuits that control food intake and energy metabolism.

The EU endocrine disruptors' regulation and the glyphosate controversy

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Endocrine disruptors are compounds that alter the functioning of the endocrine system of humans and wildlife.

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Regulation 2017/2100 and Regulation 2018/605.

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Glyphosate as Endocrine Disruptor.

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EU EDs Regulation and pesticide legislation.

Endocrine disruptors are compounds that alter the functioning of the endocrine system of humans and wildlife. A large number of chemicals have been identified as EDs and humans can be exposed to them through dietary and/or environmental exposure (air, water, soil). At international level, scientific discussion on the topic of EDs focuses on the issue of setting out the scientific criteria according to which the key properties of these substances that render them EDs are determined. Regulatory action in EU has been impacted by the aforementioned discussion and, in particular, Regulation 2017/2100 and Regulation 2018/605 have been issued. However, these scientific criteria do not constitute a complete framework for the detection of EDs and, therefore, their adoption does not entail a fully effective human health protection. Moreover, glyphosate-based herbicides (GBH), are the most widely used pesticides worldwide. The glyphosate controversy turned the spotlight on pesticide regulation in the EU. The disagreement between IARC and regulatory evaluations of EFSA/ECHA has received great attention of citizens, organizations and stakeholders, as a result of methodological differences in the evaluation of the available evidence have been identified. This paper outlines the glyphosate controversy, following an overview of the EU EDs Regulation and pesticide legislation.

Integration of data across toxicity endpoints for improved safety assessment of chemicals: the example of carcinogenicity assessment

In view of the need to enhance the assessment of consumer products called for in the EU Chemicals Strategy for Sustainability, we developed a methodology for evaluating hazard by combining information across different systemic toxicity endpoints and integrating the information with new approach methodologies. This integrates mechanistic information with a view to avoiding redundant in vivo studies, minimising reliance on apical endpoint tests and ultimately devising efficient testing strategies. Here, we present the application of our methodology to carcinogenicity assessment, mapping the available information from toxicity test methods across endpoints to the key characteristics of carcinogens. Test methods are deconstructed to allow the information they provide to be organised in a systematic way, enabling the description of the toxicity mechanisms leading to the adverse outcome. This integrated approach provides a flexible and resource-efficient means of fully exploiting test methods for which test guidelines are available to fulfil regulatory requirements for systemic toxicity assessment as well as identifying where new methods can be integrated.

Exposure to Propylparaben During Pregnancy and Lactation Induces Long-Term Alterations to the Mammary Gland in Mice

The mammary gland is a hormone sensitive organ that is susceptible to endocrine-disrupting chemicals (EDCs) during the vulnerable periods of parous reorganization (ie, pregnancy, lactation, and involution). Pregnancy is believed to have long-term protective effects against breast cancer development; however, it is unknown if EDCs can alter this effect. We examined the long-term effects of propylparaben, a common preservative used in personal care products and foods, with estrogenic properties, on the parous mouse mammary gland. Pregnant BALB/c mice were treated with 0, 20, 100, or 10 000 µg/kg/day propylparaben throughout pregnancy and lactation. Unexposed nulliparous females were also evaluated. Five weeks post-involution, mammary glands were collected and assessed for changes in histomorphology, hormone receptor expression, immune cell number, and gene expression. For several parameters of mammary gland morphology, propylparaben reduced the effects of parity. Propylparaben also increased proliferation, but not stem cell number, and induced modest alterations to expression of ERα-mediated genes. Finally, propylparaben altered the effect of parity on the number of several immune cell types in the mammary gland. These results suggest that propylparaben, at levels relevant to human exposure, can interfere with the effects of parity on the mouse mammary gland and induce long-term alterations to mammary gland structure. Future studies should address if propylparaben exposures negate the protective effects of pregnancy on mammary cancer development.

Endocrine disruptor global policy

Over the past several decades, scientific consensus has grown around the concept and evidence for human health impacts from exposure to endocrine disrupting chemicals (EDCs). A series of publications have now demonstrated considerable economic costs of EDC exposure-induced adverse health outcomes. This research has suggested economic burdens in the hundreds of billions, even considering only a small subset of EDCs and health. As of yet, regulatory efforts and policies to protect and decrease human exposure to most EDCs have been insufficient and have not kept pace with the science. Given the overwhelming scientific evidence, referenced throughout this collection, as well as the economic costs of inaction, described here, regulations are clearly needed. The EU and some other countries have taken promising steps towards protective regulation of EDCs, though the response of the US and many other countries has been limited or altogether lacking. Regulatory bodies that have and continue to apply risk-based approaches to regulating EDCs have also failed to consider the complete economic impacts of EDC-related health impacts. In this chapter, we will discuss broad strategies taken to regulate EDCs, examine the approaches currently taken to regulate EDCs in a global context (discussing the strengths and weaknesses of these regulations), discuss the economic costs of EDC exposures (detailing where consideration of health and economic costs could improve regulations), and discuss next steps and novel approaches to adapting existing regulatory frameworks to this class of chemicals.

A systematic approach to metabolic characterization of thyroid-disrupting chemicals and their in vitro biotransformants based on prediction-assisted metabolomic analysis

Thyroid-disrupting compounds (TDCs) are chemicals that modify thyroid gland function and disrupt hormonal homeostasis. Like other endocrine-disrupting chemicals (EDCs), TDCs often show altered activities following post-metabolic modification via endogenous enzymatic reaction. Hence, we developed evaluation system consisting of (1) in vitro metabolic reaction module, (2) high-resolution mass-spectrometry, and (3) human cell-based reporter gene assay. We developed the reaction module using rat S9 fraction where levothyroxine (T4) as a model compound, was subjected to phase-I or phase-I+II biotransformation. The metabolic profiles of the biotransformants were systematically configured based on in-silico prediction of potential products and experimental validation using liquid-chromatography Orbitrap mass-spectrometry. Thyroid agonistic activities of the biotransformants were evaluated by thyroid receptor-mediated stably transfected transcriptional activation assay using hTRE_HeLa cells. Indeed, we detected the increased activities following metabolic conversion of T4 in a dose-dependent manner. Note that the activity by phase-I+II reaction was much greater than by phase-I reaction (3.8-fold increase). Subsequently, we explored metabolic signatures, which potentially contributed to the hyperactivity by phase-I+II reaction. A total of 77 metabolic features were annotated based on the in-silico prediction, which included biotransformants with deiodination and conjugation. The glucuronide-conjugated form was found at the highest fold-increase (970-fold increase) whereas marginal increases were determined in the deiodinized forms (1.6-fold increase in T3 and 2.0-fold increase in rT3). Further, the systematic approach was evaluated and comparably analyzed by the metabolic profiles of bithionol, which is structurally related to T4. Our current result suggested the potential application of in vitro evaluation system to risk assessment of thyroid-disrupting activity.

Phthalates promote the invasion of hepatocellular carcinoma cells by enhancing the interaction between Pregnane X receptor and E26 transformation specific sequence 1

Phthalates (PAEs) are considered endocrine-disrupting chemicals (EDCs), a series of compounds able to disrupt the normal regulation of the human endocrine-system. In the present study, we investigated the roles of four PAEs, butyl benzyl phthalate (BBP), dibutyl phthalate (DBP), dimethyl phthalate (DMP), and diethyl phthalate (DEP), in hepatocellular carcinoma (HCC) cells. We define novel roles for the PAEs on the migration of HCC cells via their enhancing of the interaction between the pregnane X receptor (PXR) and E26 transformation specific sequence 1 (ETS-1). Our results indicate that PAEs induced the transcriptional activation of ETS-1 and PXR. PXR activated by PAEs could bind to ETS-1 directly and enhanced the activity of ETS-1, which resulted in the induction of invasion-related ETS-1 target genes. The "LXXLL" motif in the ETS-1C-terminal was essential for the interaction between PXR and ETS-1 induced by PAEs. Treatment of PAEs promoted the nuclear accumulation of ETS-1 or the recruitment of ETS-1, but not in cells expressing ETS-1 with a mutated LXXLL motif in its downstream gene promoter region, or following transfection of PXR siRNA. Treatment with the PXR antagonist ketoconazole almost completely inhibited the effects of PAEs. Moreover, PAEs enhanced the in vitro or in vivo invasion of HCC cells via PXR/ETS-1. Therefore, our results not only contribute to a better understanding of HCC, but also extended the roles of EDCs regulating human malignancies.

Identification of Potential Bisphenol A (BPA) Exposure Biomarkers in Ovarian Cancer

Endocrine-disrupting chemicals (EDCs) can exert multiple deleterious effects and have been implicated in carcinogenesis. The xenoestrogen Bisphenol A (BPA) that is found in various consumer products has been involved in the dysregulation of numerous signalling pathways. In this paper, we present the analysis of a set of 94 genes that have been shown to be dysregulated in presence of BPA in ovarian cancer cell lines since we hypothesised that these genes might be of biomarker potential. This study sought to identify biomarkers of disease and biomarkers of disease-associated exposure. In silico analyses took place using gene expression data extracted from The Cancer Genome Atlas (TCGA) and the Genotype-Tissue Expression (GTEx) databases. Differential expression was further validated at protein level using immunohistochemistry on an ovarian cancer tissue microarray. We found that 14 out of 94 genes are solely dysregulated in the presence of BPA, while the remaining 80 genes are already dysregulated (p-value < 0.05) in their expression pattern as a consequence of the disease. We also found that seven genes have prognostic power for the overall survival in OC in relation to their expression levels. Out of these seven genes, Keratin 4 (KRT4) appears to be a biomarker of exposure-associated ovarian cancer, whereas Guanylate Binding Protein 5 (GBP5), long intergenic non-protein coding RNA 707 (LINC00707) and Solute Carrier Family 4 Member 11 (SLC4A11) are biomarkers of disease. BPA can exert a plethora of effects that can be tissue- or cancer-specific. Our in silico findings generate a hypothesis around biomarkers of disease and exposure that could potentially inform regulation and policy making.

Endocrine disrupting chemicals (EDCs) and sex steroid receptors

Sex-steroid receptors (SSRs) are essential mediators of estrogen, progestin, and androgen signaling that are critical in vast aspects of human development and multi-organ homeostasis. Dysregulation of SSR function has been implicated in numerous pathologies including cancers, obesity, Type II diabetes mellitus, neuroendocrine disorders, cardiovascular disease, hyperlipidemia, male and female infertility, and other reproductive disorders. Endocrine disrupting chemicals (EDCs) modulate SSR function in a wide variety of cell and tissues. There exists strong experimental, clinical, and epidemiological evidence that engagement of EDCs with SSRs may disrupt endogenous hormone signaling leading to physiological abnormalities that may manifest in disease. In this chapter, we discuss the molecular mechanisms by which EDCs interact with estrogen, progestin, and androgen receptors and alter SSR functions in target cells. In addition, the pathological consequences of disruption of SSR action in reproductive and other organs by EDCs is described with an emphasis on underlying mechanisms of receptors dysfunction.

Glyphosate and the key characteristics of an endocrine disruptor: A review

Glyphosate is a large-spectrum herbicide that was introduced on the market in 1974. Due to its important impact on the crop industry, it has been significantly diversified and expanded being considered the most successful herbicide in history. Currently, its massive use has led to a wide environmental diffusion and its human consumption through food products has made possible to detect it in urine, serum, and breast milk samples. Nevertheless, recent studies have questioned its safety and international agencies have conflicting opinions about its effects on human health, mainly as an endocrine-disrupting chemical (EDC) and its carcinogenic capacity. Here, we conduct a comprehensive review where we describe the most important findings of the glyphosate effects in the endocrine system and asses the mechanistic evidence to classify it as an EDC. We use as guideline the ten key characteristics (KCs) of EDC proposed in the expert consensus statement published in 2020 (La Merrill et al., 2020) and discuss the scopes of some epidemiological studies for the evaluation of glyphosate as possible EDC. We conclude that glyphosate satisfies at least 8 KCs of an EDC, however, prospective cohort studies are still needed to elucidate the real effects in the human endocrine system.

Endocrine disrupting chemicals: strategies to protect present and future generations

Introduction: Endocrine-disrupting chemicals (EDCs) are chemicals that alter the actions of hormones. In the 21^st Century, numerous expert groups of clinicians, scientists, and environmental activists have called for action to protect present and future generations from the harm induced by EDC exposures. These demands for regulatory responses come because of the strong weight of the evidence from epidemiology, wildlife, and controlled laboratory studies.Areas covered: In this review, we examine the conclusions drawn by experts from different scientific and medical disciplines. We also address several areas where recent findings or work has changed the landscape of EDC work including new approaches to identify and evaluate the evidence for EDCs using a key characteristics approach, the need to expand our understanding of vulnerable periods of development, and the increasing concern that traditional methods used to evaluate toxicity of environmental chemicals are insufficient for EDCs and how collaborative science could help to address these gaps.Expert opinion: The science is clear: there is more than enough evidence to demonstrate that EDCs affect the health of humans and wildlife. Waiting to act is a decision that puts the health of current and future generations at risk.

Multi-omics phenotyping of the gut-liver axis reveals metabolic perturbations from a low-dose pesticide mixture in rats

Health effects of pesticides are not always accurately detected using the current battery of regulatory toxicity tests. We compared standard histopathology and serum biochemistry measures and multi-omics analyses in a subchronic toxicity test of a mixture of six pesticides frequently detected in foodstuffs (azoxystrobin, boscalid, chlorpyrifos, glyphosate, imidacloprid and thiabendazole) in Sprague-Dawley rats. Analysis of water and feed consumption, body weight, histopathology and serum biochemistry showed little effect. Contrastingly, serum and caecum metabolomics revealed that nicotinamide and tryptophan metabolism were affected, which suggested activation of an oxidative stress response. This was not reflected by gut microbial community composition changes evaluated by shotgun metagenomics. Transcriptomics of the liver showed that 257 genes had their expression changed. Gene functions affected included the regulation of response to steroid hormones and the activation of stress response pathways. Genome-wide DNA methylation analysis of the same liver samples showed that 4,255 CpG sites were differentially methylated. Overall, we demonstrated that in-depth molecular profiling in laboratory animals exposed to low concentrations of pesticides allows the detection of metabolic perturbations that would remain undetected by standard regulatory biochemical measures and which could thus improve the predictability of health risks from exposure to chemical pollutants.

Endocrine-Disrupting Chemicals: Introduction to the Theme

BACKGROUND

Endocrine-disrupting chemicals (EDCs) are natural or synthetic compounds deriving from different human activities and are widely spread into the environment, contributing to indoor and outdoor pollution. EDCs may be conveyed by food and water consumption and skin, airways, placental, and breastfeeding. Upon entering the circulation, they can interfere with endocrine system homeostasis by several mechanisms.

AIM

In this narrative review, the authors overviewed the leading mechanisms by which EDCs interact and disrupt the endocrine system, leading to possible human health concerns.

RESULTS

The leading mechanisms of EDCs-related toxicity have been illustrated in in vitro studies and animal models and may be summarized as follows: receptor agonism and antagonism; modulation of hormone receptor expression; interference with signal transduction in hormone-responsive cells; epigenetic modifications in hormone-producing or hormone-responsive cells; interference with hormone synthesis; interference with hormone transport across cell membranes; interference with hormone metabolism or clearance; interference with the destiny of hormone-producing or hormone-responsive cells.

DISCUSSION

Despite these well-defined mechanisms, some limitations do not allow for conclusive assumptions. Indeed, epidemiological and ecological studies are currently lacking and usually refer to a specific cluster of patients (occupational exposure). Methodological aspects could further complicate the issue since these studies could require a long time to provide useful information. The lack of a real unexposed group in environmental conditions, possible interference of EDCs mixture on biological results, and unpredictable dose-response curves for some EDCs should also be considered significant limitations.

CONCLUSION

Given these limitations, specific observational and long-term studies are needed to identify at-risk populations for adequate treatment of exposed patients and effective prevention plans against excessive exposure to EDCs.

FutureTox IV Workshop Summary: Predictive Toxicology for Healthy Children

FutureTox IV, a Society of Toxicology Contemporary Concepts in Toxicology workshop, was held in November 2018. Building upon FutureTox I, II, and III, this conference focused on the latest science and technology for in vitro profiling and in silico modeling as it relates to predictive developmental and reproductive toxicity (DART). Publicly available high-throughput screening data sets are now available for broad in vitro profiling of bioactivities across large inventories of chemicals. Coupling this vast amount of mechanistic data with a deeper understanding of molecular embryology and post-natal development lays the groundwork for using new approach methodologies (NAMs) to evaluate chemical toxicity, drug efficacy, and safety assessment for embryo-fetal development. NAM is a term recently adopted in reference to any technology, methodology, approach, or combination thereof that can be used to provide information on chemical hazard and risk assessment to avoid the use of intact animals (U.S. Environmental Protection Agency [EPA], Strategic plan to promote the development and implementation of alternative test methods within the tsca program, 2018, https://www.epa.gov/sites/production/files/2018-06/documents/epa_alt_strat_plan_6-20-18_clean_final.pdf). There are challenges to implementing NAMs to evaluate chemicals for developmental toxicity compared with adult toxicity. This forum article reviews the 2018 workshop activities, highlighting challenges and opportunities for applying NAMs for adverse pregnancy outcomes (eg, preterm labor, malformations, low birth weight) as well as disorders manifesting postnatally (eg, neurodevelopmental impairment, breast cancer, cardiovascular disease, fertility). DART is an important concern for different regulatory statutes and test guidelines. Leveraging advancements in such approaches and the accompanying efficiencies to detecting potential hazards to human development are the unifying concepts toward implementing NAMs in DART testing. Although use of NAMs for higher level regulatory decision making is still on the horizon, the conference highlighted novel testing platforms and computational models that cover multiple levels of biological organization, with the unique temporal dynamics of embryonic development, and novel approaches for estimating toxicokinetic parameters essential in supporting in vitro to in vivo extrapolation.

Alkyphenol Exposure Alters Steroidogenesis in Male Lizard Podarcis siculus

BACKGROUND

Nonylphenol (NP) and Octylphenol (OP) are persistent and non-biodegradable environmental contaminants classified as endocrine disruptor chemicals (EDCs). These compounds are widely used in several industrial applications and present estrogen-like properties, which have extensively been studied in aquatic organisms. The present study aimed to verify the interference of these compounds alone, and in mixture, on the reproductive cycle of the male terrestrial vertebrate Podarcis siculus, focusing mainly on the steroidogenesis process.

METHODS

Male lizards have been treated with different injections of both NP and OP alone and in mixture, and evaluation has been carried out using a histological approach.

RESULTS

Results obtained showed that both substances are able to alter both testis histology and localization of key steroidogenic enzymes, such as 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β- hydroxysteroid dehydrogenase (17β-HSD) and P450 aromatase. Moreover, OP exerts a preponderant effect, and the P450 aromatase represents the major target of both chemicals.

CONCLUSIONS

In conclusion, NP and OP inhibit steroidogenesis, which in turn may reduce the reproductive capacity of the specimens.

The E-Morph Assay: Identification and characterization of environmental chemicals with estrogenic activity based on quantitative changes in cell-cell contact organization of breast cancer cells

Adverse health effects that are caused by endocrine disrupting chemicals (EDCs) in the environment, food or consumer products are of high public concern. The identification and characterization of EDCs including substances with estrogenic activity still necessitates the use of animal testing as most of the approved alternative test methods only address single mechanistic events of endocrine activity. Therefore, novel human-relevant in vitro assays covering more complex functional endpoints of adversity, including hormone-related tumor formation and progression, are needed. This study describes the development and evaluation of a novel high-throughput screening-compatible assay called "E-Morph Assay". This image-based phenotypic screening assay facilitates robust predictions of the estrogenic potential of environmental chemicals using quantitative changes in the cell-cell contact morphology of human breast cancer cells as a novel functional endpoint. Based on a classification model, which was developed using six reference substances with known estrogenic activity, the E-Morph Assay correctly classified an additional set of 11 reference chemicals commonly used in OECD Test Guidelines and the U.S. EPA ToxCast program. For each of the tested substances, a relative ER bioactivity score was derived that allowed their grouping into four main categories of estrogenic activity, i.e. 'strong' (>0.9; four substances, i.e. natural hormones or pharmaceutical products), 'moderate' (0.9-0.6; six substances, i.e. phytoestrogens and Bisphenol AF), 'weak' (<0.6; three substances, i.e Bisphenol S, B, and A), and 'negative' (0.0; four substances). The E-Morph Assay considerably expands the portfolio of test methods providing the possibility to characterize the influence of environmental chemicals on estrogen-dependent tumor progression.

Antioxidative Molecules in Human Milk and Environmental Contaminants

Breastfeeding provides overall beneficial health to the mother-child dyad and is universally recognized as the preferred feeding mode for infants up to 6-months and beyond. Human milk provides immuno-protection and supplies nutrients and bioactive compounds whose concentrations vary with lactation stage. Environmental and dietary factors potentially lead to excessive chemical exposure in critical windows of development such as neonatal life, including lactation. This review discusses current knowledge on these environmental and dietary contaminants and summarizes the known effects of these chemicals in human milk, taking into account the protective presence of antioxidative molecules. Particular attention is given to short- and long-term effects of these contaminants, considering their role as endocrine disruptors and potential epigenetic modulators. Finally, we identify knowledge gaps and indicate potential future research directions.

Assessing Indoor Dust Interference with Human Nuclear Hormone Receptors in Cell-Based Luciferase Reporter Assays

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS), organophosphate esters (OPEs), and polybrominated diphenyl ethers (PBDEs) are hormone-disrupting chemicals that migrate from building materials into air and dust.

OBJECTIVES

We aimed to quantify the hormonal activities of 46 dust samples and identify chemicals driving the observed activities.

METHODS

We evaluated associations between hormonal activities of extracted dust in five cell-based luciferase reporter assays and dust concentrations of 42 measured PFAS, OPEs, and PBDEs, transformed as either raw or potency-weighted concentrations based on Tox21 high-throughput screening data.

RESULTS

All dust samples were hormonally active, showing antagonistic activity toward peroxisome proliferator-activated receptor (PPARγ2) (100%; 46 of 46 samples), thyroid hormone receptor (TRβ) (89%; 41 samples), and androgen receptor (AR) (87%; 40 samples); agonist activity on estrogen receptor (ERα) (96%; 44 samples); and binding competition with thyroxine (T4) on serum transporter transthyretin (TTR) (98%; 45 samples). Effects were observed with as little as 4μg of extracted dust. In regression models for each chemical class, interquartile range increases in potency-weighted or unknown-potency chemical concentrations were associated with higher hormonal activities of dust extracts (potency-weighted: ΣPFAS-TRβ, ↑28%, p<0.05; ΣOPEs-TRβ, ↑27%, p=0.08; ΣPBDEs-TRβ, ↑20%, p<0.05; ΣPBDEs-ERα, ↑7.7%, p=0.08; unknown-potency: ΣOPEs-TTR, ↑34%, p<0.05; ΣOPEs-AR, ↑13%, p=0.06), adjusted for chemicals with active, inactive, and unknown Tox21 designations.

DISCUSSION

All indoor dust samples exhibited hormonal activities, which were associated with PFAS, PBDE, and OPE levels. Reporter gene cell-based assays are relatively inexpensive, health-relevant evaluations of toxic loads of chemical mixtures that building occupants are exposed to. https://doi.org/10.1289/EHP8054.

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".