Estrogenic effect of a series of bisphenol analogues on gene and protein expression in MCF-7 breast cancer cells

Lignin-derivable alternatives to bisphenol A with potentially undetectable estrogenic activity and minimal developmental toxicity

Lignin-derivable bisguaiacols/bissyringols are viable alternatives to commercial bisphenols; however, many bisguaiacols/bissyringols (e.g., bisguaiacol F [BGF]) have unsubstituted bridging carbons between the aromatic rings, making them more structurally similar to bisphenol F (BPF) than bisphenol A (BPA) - both of which are suspected endocrine disruptors. Herein, we investigated the estrogenic activity (EA) and developmental toxicity of dimethyl-substituted bridging carbon-based lignin-derivable bisphenols (bisguaiacol A [BGA] and bissyringol A [BSA]). Notably, BSA showed undetectable EA at seven test concentrations (from 10-12 M to 10-6 M) in the MCF-7 cell proliferation assay, whereas BPA had detectable EA at five concentrations (from 10-10 M to 10-6 M). In silico results indicated that BSA had the lowest binding affinity with estrogen receptors. Moreover, in vivo chicken embryonic assay results revealed that lignin-derivable monomers had minimal developmental toxicity vs. BPA at environmentally relevant test concentrations (8.7-116 μg/kg). Additionally, all lignin-derivable compounds showed significantly lower expression fold changes (from ∼1.81 to ∼4.41) in chicken fetal liver tests for an estrogen-response gene (apolipoprotein II) in comparison to BPA (fold change of ∼11.51), which was indicative of significantly reduced estrogenic response. Altogether, the methoxy substituents on lignin-derivable bisphenols appeared to be a positive factor in reducing the EA of BPA alternatives.

The internal exposure of bisphenol analogues in South China adults and the associated health risks

Bisphenol A (BPA) is widely applied in industrial products and household products, leading to ubiquitous occurrences in environmental and biological samples. However, knowledge on human internal exposure to bisphenol analogues remains limited. Our study determined nine bisphenol analogues in urine samples collected from 1168 South China adults. BPA and bisphenol F (BPF) exhibited the highest detection frequencies in urine, i.e., 99.4% and 74.6%, respectively. BPA dominated over other analogues, with a median concentration of 1.74 μg/L, while BPF had a median concentration of 0.08 μg/L. Significant positive correlation was observed between urinary BPA and BPF (r = 0.201, p < 0.01), indicating similar exposure sources or pathways of these two chemicals. Urinary BPA concentrations were significantly correlated with age, marital status, drinking status and history of hyperlipidemia (p < 0.05). The median estimated daily intake (EDI) of Σ₃BPs (the sum concentrations of BPA, BPF and BPAF) was determined to be 53.6 ng/kg-bw/day for adults. The EDIs were much lower than the temporary tolerable reference dose of BPA recommended by the European Food Safety Authority, indicating the bisphenol analogues presented no obvious health risks to South China adults.

Bisphenol A Analogues Suppress Spheroid Attachment on Human Endometrial Epithelial Cells through Modulation of Steroid Hormone Receptors Signaling Pathway

Bisphenol A (BPA) is a well-known endocrine disruptor, widely used in various consumer products and ubiquitously found in air, water, food, dust, and sewage leachates. Recently, several countries have restricted the use of BPA and replaced them with bisphenol S (BPS) and bisphenol F (BPF), which have a similar chemical structure to BPA. Compared to BPA, both BPS and BPF have weaker estrogenic effects, but their effects on human reproductive function including endometrial receptivity and embryo implantation still remain largely unknown. We used an in vitro spheroid (blastocyst surrogate) co-culture assay to investigate the effects of BPA, BPS, and BPF on spheroid attachment on human endometrial epithelial cells, and further delineated their role on steroid hormone receptor expression. We also used transcriptomics to investigate the effects of BPA, BPS, and BPF on the transcriptome of human endometrial cells. We found that bisphenol treatment in human endometrial Ishikawa cells altered estrogen receptor alpha (ERα) signaling and upregulated progesterone receptors (PR). Bisphenols suppressed spheroid attachment onto Ishikawa cells, which was reversed by the downregulation of PR through PR siRNA. Overall, we found that bisphenol compounds can affect human endometrial epithelial cell receptivity through the modulation of steroid hormone receptor function leading to impaired embryo implantation.

An overview of the literature on emerging pollutants: Chlorinated derivatives of Bisphenol A (ClxBPA)

CONTEXT

Bisphenol A (BPA) is a ubiquitous contaminant with endocrine-disrupting effects in mammals. During chlorination treatment of drinking water, aqueous BPA can react with chlorine to form chlorinated derivatives of BPA (mono, di, tri and tetra-chlorinated derivatives) or Cl_xBPA.

OBJECTIVE

The aim of this study is to summarize and present the state of knowledge on human toxicological risk assessment of Cl_xBPA.

MATERIALS AND METHODS

A search on Cl_xBPA in the PubMed database was performed based on studies published between 2002 and 2021. Forty-nine studies on chlorinated derivatives of BPA were found. Available information on their sources and levels of exposure, their effects, their possible mechanisms of action and their toxicokinetics data was extracted and presented.

RESULTS

Cl_xBPA have been essentially detected in environmental aqueous media. There is evidence in toxicological and epidemiological studies that Cl_xBPA also have endocrine-disrupting capabilities. These emerging pollutants have been found in human urine, serum, breast milk, adipose and placental tissue and can constitute a risk to human health. However, in vitro and in vivo toxicokinetic data on Cl_xBPA are scarce and do not allow characterization of the disposition kinetics of these compounds.

CONCLUSION

More research to assess their health risks, specifically in vulnerable populations, is needed. Some water chlorination processes are particularly hazardous, and it is important to evaluate their chlorination by-products from a public health perspective.

Discovery of New Protein Targets of BPA Analogs and Derivatives Associated with Noncommunicable Diseases: A Virtual High-Throughput Screening

BACKGROUND

Bisphenol A analogs and derivatives (BPs) have emerged as new contaminants with little or no information about their toxicity. These have been found in numerous everyday products, from thermal paper receipts to plastic containers, and measured in human samples.

OBJECTIVES

The objectives of this research were to identify in silico new protein targets of BPs associated with seven noncommunicable diseases (NCDs), and to study their protein-ligand interactions using computer-aided tools.

METHODS

Fifty BPs were identified by a literature search and submitted to a virtual high-throughput screening (vHTS) with 328 proteins associated with NCDs. Protein-protein interactions between predicted targets were examined using STRING, and the protocol was validated in terms of binding site recognition and correlation between in silico affinities and in vitro data.

RESULTS

According to the vHTS, several BPs may target proteins associated with NCDs, some of them with stronger affinities than bisphenol A (BPA). The best affinity score (the highest in silico affinity absolute value) was obtained after docking 4,4'-bis(N-carbamoyl-4-methylbenzensulfonamide)diphenylmethane (BTUM) on estradiol 17-beta-dehydrogenase 1 (-13.7 kcal/mol). However, other molecules, such as bisphenol A bis(diphenyl phosphate) (BDP), bisphenol PH (BPPH), and Pergafast 201 also exhibited great affinities (top 10 affinity scores for each disease) with proteins related to NCDs.

DISCUSSION

Molecules such as BTUM, BDP, BPPH, and Pergafast 201 could be targeting key signaling pathways related to NCDs. These BPs should be prioritized for in vitro and in vivo toxicity testing and to further assess their possible role in the development of these diseases. https://doi.org/10.1289/EHP7466.

Presence of Parabens and Bisphenols in Food Commonly Consumed in Spain

Given the widespread use of bisphenols and parabens in consumer products, the assessment of their intake is crucial and represents the first step towards the assessment of the potential risks that these compounds may pose to human health. In the present study, a total of 98 samples of food items commonly consumed by the Spanish population were collected from different national supermarkets and grocery stores for the determination of parabens and bisphenols. Our analysis demonstrated that 56 of the 98 food samples contained detectable levels of parabens with limits of quantification (LOQ) between 0.4 and 0.9 ng g-1. The total concentration of parabens (sum of four parabens: ∑parabens) ranged from below the LOQ to 281.7 ng g-1, with a mean value of 73.86 ng g-1. A total of 52% of the samples showed detectable concentrations of bisphenols. Bisphenol A (BPA) was the most frequently detected bisphenol in the food samples analysed, followed by bisphenol S (BPS) and bisphenol E (BPE). Bisphenol AF (BPAF), bisphenol B (BPB) and bisphenol P (BPP) were not found in any of the analysed samples. LOQ for these bisphenols were between 0.4 and 4.0 ng g-1.

Bisphenol B Exposure Disrupts Mouse Oocyte Meiotic Maturation in vitro Through Affecting Spindle Assembly and Chromosome Alignment

Bisphenol B (BPB), a substitute of bisphenol A (BPA), is widely used in the polycarbonate plastic and resins production. However, BPB proved to be not a safe alternative to BPA, and as an endocrine disruptor, it can harm the health of humans and animals. In the present study, we explored the effects of BPB on mouse oocyte meiotic maturation in vitro. We found that 150 μM of BPB significantly compromised the first polar body extrusion (PBE) and disrupted the cell cycle progression with meiotic arrest. The spindle assembly and chromosome alignment were disordered after BPB exposure, which was further demonstrated by the aberrant localization of p-MAPK. Also, BPB exposure increased the acetylation levels of α-tubulin. As a result, the spindle assemble checkpoint (SAC) was continuously provoked, contributing to meiotic arrest. We further demonstrated that BPB severely induced DNA damage, but the ROS and ATP production were not altered. Furthermore, the epigenetic modifications were changed after BPB exposure, as indicated by increased K3K9me3 and H3K27me3 levels. Besides, the pattern of estrogen receptor α (ERα) dynamics was disrupted with a mass gathering on the spindle in BPB-exposed oocytes. Our collective results indicated that exposure to BPB compromised meiotic maturation and damaged oocyte quality by affecting spindle assembly and chromosome alignment, acetylation of α-tubulin, DNA damage, epigenetic modifications, and ERα dynamics in mouse oocytes.

Simultaneous determination of bisphenol A and its chlorinated derivatives in human plasma: Development, validation and application of a UHPLC-MS/MS method

Bisphenol A (BPA) is a well-known ubiquitous chemical found in polycarbonate, polysulfone and epoxy resins, used in mass production for many consumer products. BPA exhibits endocrine disruptor properties that can potentially induce adverse health effects. In aquatic environments, it can react with chlorine to produce chlorinated derivatives (ClxBPAs). ClxBPAs exhibit oestrogenic activity 10 to 105 times higher than BPA itself. Assessing human exposure to endocrine disrupting chemicals is mandatory to assess health risk. Blood, as well as urine matrix, are commonly used to perform human biomonitoring. We therefore developed, fully validated and applied a method based on Ultra High Performance Liquid Chromatography couples to a Triple Quad Mass Spectrometer to determine BPA, monochlorobisphenol A (MCBPA), dichlorobisphenol A (DCBPA), trichlorobisphenol A (TCBPA) and tetrachlorobisphenol A (TTCBPA) in human blood plasma. The European Medicines Agency guidelines for bioanalytical method validation have been applied. Precision and trueness of the method were <15% at medium and high levels of quality control and <20% at the limits of quantification (LOQs). The LOQs were settled at 0.1 ng/mL for BPA, 0.02 ng/mL for TTCBPA and 0.005 ng/mL for MCBPA, DCBPA, and TCBPA. The analytical method was applied to ten patients suffering from end stage renal disease. BPA was quantified in all ten patients while MCBPA, DCBPA and TTCBPA were determined in three and TCBPA in four. In conclusion, we have successfully developed a highly sensitive method to determine BPA and ClxBPAs in human plasma. Thanks to this method, for the first time, we could demonstrate ClxBPAs occurrence in human blood.

Determination of Endocrine Disruption Potential of Bisphenol A Alternatives in Food Contact Materials Using In Vitro Assays: State of the Art and Future Challenges

Alternatives to bisphenol A (BPA) are developed for food contact materials as a result of increasing evidence of exposure-correlated harmful effects of BPA. In vitro assays provide the fast, affordable, and mechanism insightful ways to screen endocrine disruption (ED), which is a major concern of new BPA alternatives. In this review, we summarize the safety and regulation information on the alternatives to BPA, review the state of the art of in vitro assays for ED evaluation, highlight their advantages and limitations, and discuss the challenges and future research needs. Our review shows that ligand binding, reporter gene, cell proliferation, and steroidogenesis are four commonly used in vitro assays to determine the ED at the response of receptor, gene transcription, and whole cell level. Major challenges are found from in vitro-in vivo translation and identification of ED chemicals in polymers. More studies on these areas are needed in the future.

Occurrence and distribution of parabens and bisphenols in sediment from northern Chinese coastal areas

Despite high production and usage of parabens and bisphenols, little is known about their spatiotemporal distribution in the marine environment. In this study, we determined the concentrations of several parabens and their metabolites as well as bisphenol analogues in sediment collected from coastal areas of northern China. All sediment samples, including surface sediment and sediment cores, contained at least one of the parabens analyzed, and the total concentrations of parabens (ΣPBs; sum of six parabens) ranged from 1.37 to 24.2 ng/g dw (geometric mean: 3.30-6.09 g/g dw), which was comparable to or slightly higher than those found for the total concentrations of five detectable bisphenols (ΣBPAs; geometric mean: 2.18-4.61 ng/g dw). 4-hydroxybenzoic acid, a common metabolite of parabens, was found in all samples at concentrations in the range of 6.85-437 ng/g dw, which was one order of magnitude lower than those found for benzoic acid. Methyl-, ethyl-, and propyl-parabens were the predominant paraben analogues, collectively accounting for >88% of ΣPBs. Bisphenol A and bisphenol F were the two major bisphenols, collectively accounting for >86% of ΣBPAs. We also examined vertical profiles in concentrations of target analytes in sediment cores. The sediment core from the Shandong Peninsula showed a gradual increase in the concentrations of several parent and metabolic parabens as well as bisphenols during the past decade. Relatively higher concentrations of parabens and bisphenols were found in sediment cores collected from industrialized areas. Significant positive correlations were found among the concentrations of parabens in sediment, which suggested the existence of similar sources for these compounds. Overall, our findings suggest that the Bohai Sea coast is moderately contaminated with parabens and bisphenols in comparison to other coastal areas in China or elsewhere.

Evidence for Bisphenol B Endocrine Properties: Scientific and Regulatory Perspectives

BACKGROUND

The substitution of bisphenol A (BPA) by bisphenol B (BPB), a very close structural analog, stresses the need to assess its potential endocrine properties.

OBJECTIVE

This analysis aimed to investigate whether BPB has endocrine disruptive properties in humans and in wildlife as defined by the World Health Organization (WHO) definition used in the regulatory field, that is, a) adverse effects, b) endocrine activity, and c) plausible mechanistic links between the observed endocrine activity and adverse effects.

METHODS

We conducted a systematic review to identify BPB adverse effects and endocrine activities by focusing on animal models and in vitro mechanistic studies. The results were grouped by modality (estrogenic, androgenic, thyroid hormone, steroidogenesis-related, or other endocrine activities). After critical analysis of results, lines of evidence were built using a weight-of-evidence approach to establish a biologically plausible link. In addition, the ratio of BPA to BPB potency was reported from studies investigating both bisphenols.

RESULTS

Among the 36 articles included in the analysis, 3 subchronic studies consistently reported effects of BPB on reproductive function. In rats, the 28-d and 48-week studies showed alteration of spermatogenesis associated with a lower height of the seminiferous tubules, the alteration of several sperm parameters, and a weight loss for the testis, epididymis, and seminal vesicles. In zebrafish, the results of a 21-d reproductive study demonstrated that exposed fish had a lower egg production and a lower hatching rate and viability. The in vitro and in vivo mechanistic data consistently demonstrated BPB's capacity to decrease testosterone production and to exert an estrogenic-like activity similar to or greater than BPA's, both pathways being potentially responsible for spermatogenesis impairment in rats and fish.

CONCLUSION

The available in vivo, ex vivo, and in vitro data, although limited, coherently indicates that BPB meets the WHO definition of an endocrine disrupting chemical currently used in a regulatory context. https://doi.org/10.1289/EHP5200.

Bisphenol A Analogues in Food and Their Hormonal and Obesogenic Effects: A Review

Bisphenol A (BPA) is the most well-known compound from the bisphenol family. As BPA has recently come under pressure, it is being replaced by compounds very similar in structure, but data on the occurrence of these BPA analogues in food and human matrices are limited. The main objective of this work was to investigate human exposure to BPA and analogues and the associated health effects. We performed a literature review of the available research made in humans, in in vivo and in vitro tests. The findings support the idea that exposure to BPA analogues may have an impact on human health, especially in terms of obesity and other adverse health effects in children.

Overexposure to Bisphenol A and Its Chlorinated Derivatives of Patients with End-Stage Renal Disease during Online Hemodiafiltration

The health safety conditions governing the practice of online hemodiafiltration (OL-HDF) do not yet incorporate the risks related to the presence of endocrine disruptors such as bisphenol A (BPA). The aim of this study was to assess, for the first time, the exposure to BPA but also to its chlorinated derivatives (ClxBPA) (100 times more estrogenic than BPA) during OL-HDF. We demonstrated that BPA is transmitted by the different medical devices used in OL-HDF: ultrafilters, dialysis concentrate cartridges (and not only dialyzers, as previously described). Moreover, BPA has been found in dialysis water as well as in ultrapure dialysate and replacement fluid due to contamination of water coming from municipal network. Indeed, due to contaminations provided by both ultrafilters and water, high levels of BPA were determined in the infused replacement fluid (1033 ng.L⁻¹) from the beginning of the session. Thus, our results demonstrate that dialysis water must be considered as an important exposure source to endocrine disruptors, especially since other micropollutants such as ClxBPA have also been detected in dialysis fluids. While assessment of the impact of this exposure remains to be done, these new findings should be taken into account to assess exposure risks in end-stage renal disease patients.

Dynamics of microbial community in the bioreactor for bisphenol S removal

Bisphenol S is one of the alternative substitutes of Bisphenol A, a chemical widely recognized as an endocrine disrupting compound. In the past few years, a variety of studies on degradation of BPA demonstrated that microorganisms play important roles in the degradation process. However, the fate of BPS during wastewater treatment processes and the composition of microorganisms that functionalize BPS degradation remain to be explored. In this study, three bioreactors, R-BPS (amended with Bisphenol S), R-BPSHA (amended with Bisphenol S and humic acid) and Con (control bioreactor), were set up to investigate the fate of BPS and the microbial compositions and dynamics in the bioreactors, especially for the microorganisms associated with BPS removal. Results showed that a complete removal was achieved within 24 days. The addition of humic acid accelerated the elimination of BPS in both effluent and sludge. The results of 16S rRNA gene ampilicon sequencing revealed that the most abundant bacteria in all samples were affiliated to Proteobacteria, Bacteroidetes, Acidobacteria and Chloroflexi. Seven major genera were likely associated with BPS removal, including Pseudomonas, Azospira, Hydrogenophaga, Devosia, Delftia, Acidovorax and Rhodobacter. Among them, humic acid increased relative abundance of some bacteria, such as Pseudomonas, Hydrogenophaga and Acidovorax. These findings would give valuable information on the microbial community composition associated with BPS removal, providing biological background for bioremediation of BPS-contaminated environment.

Species-specific accumulation and temporal trends of bisphenols and benzophenones in mollusks from the Chinese Bohai Sea during 2006-2015

Information on the occurrence and bioaccumulation of bisphenols and benzophenones in coastal marine invertebrates is limited. In this study, concentrations of eight bisphenol and five benzophenone analogues were determined in 186 mollusks collected from coastal areas of the Chinese Bohai Sea during the period 2006-2015. Total concentrations of bisphenols and benzophenones were in range of not detected (nd)-58 (geometric mean: 13.0 ng/g) and nd-59.1 (2.06 ng/g) on a dry-weight basis, respectively. BPA and BPF were the major bisphenols, collectively accounting for >90% of the total concentrations. BP-3 was the predominant benzophenone, representing 74% of the total concentrations. The mollusk species, Meretrix meretrix, accumulated high concentrations of both bisphenols and benzophenones. A steady increase in bisphenol concentrations in mollusks was observed in recent years, whereas no obvious temporal trend was found for benzophenones. The estimated daily intakes of bisphenols through consumption of mollusks were lower than the current reference dose. This study establishes a baseline concentration for bisphenols and benzophenones in mollusks in Chinese coastal waters.

Mass flows and removal of eight bisphenol analogs, bisphenol A diglycidyl ether and its derivatives in two wastewater treatment plants in New York State, USA

Despite high production and usage of bisphenols including bisphenol A (BPA) as well as bisphenol A diglycidyl ether and its derivatives (BADGEs), little is known about the occurrence and fate of these substances in wastewater treatment plants (WWTPs) in the U.S. In this study, we investigated the occurrence, removal, mass flows, and fate of eight bisphenol analogues and six BADGEs based on the concentrations measured in influent, primary effluent, final effluent, and sludge from two WWTPs (WWTP_A and WWTP_B) in the Albany area of New York State, USA. BPA, bisphenol F, bisphenol S, and BADGE·2H₂O were the predominant compounds found in influents of both WWTPs, at respective geometric mean (GM) concentrations of 90.0, 90.2, 31.2, and 6.48 ng/L in WWTP_A, and 53.3, <MLOQ, 27.6, 2.25 ng/L in WWTP_B. Incomplete removal of these compounds was observed in both WWTPs with the highest removal rate (52%) was found for BPA after the secondary treatment in WWTP_A. The fraction of BPA sorbed to suspended particulate matter (SPM) was 6.83%. Mean daily mass loadings of total bisphenols and BADGEs ranged from 9.2 [∑(BADGEs) in WWTP_B] to 226 mg/d/1000 inhabitants [∑(BPs) in WWTP_A]. The environmental emission rates of total bisphenols and BADGEs through effluent discharges from WWTPs ranged from 13.7 [∑(BADGEs) in WWTP_B] to 246 mg/d/1000 inhabitants [∑(BPs) in WWTP_A]. Overall, bisphenols and BADGEs were not removed completely by activated sludge treatment. Furthermore, formation of bisphenols from the degradation of microplastics or other precursors such as alkylated bisphenols, in WWTPs is suggested.

Comparative study on ferrate oxidation of BPS and BPAF: Kinetics, reaction mechanism, and the improvement on their biodegradability

Bisphenol S (BPS) and bisphenol AF (BPAF) were increasingly consumed and these compounds are resistant to environmental degradation. Herein, ferrate oxidation of BPS and BPAF was investigated, and biodegradability of the oxidation products was examined. The second-order reaction rate constants of ferrate with BPS and BPAF were 1.3 × 10³ M^-1s^-1 and 3 × 10² M^-1s^-1, respectively, at pH 7.0, 25 °C. In the oxidation process, some BPS molecules dimerized, while other BPS molecules were oxidized through oxygen-transfer process, leading to the formation of hydroxylation products and benzene-ring cleavage products. The dominant reaction of BPAF with ferrate was oxygen-transfer process, and BPAF was degraded into lower molecular weight products. The variation of assimilable organic carbon (AOC) suggested that the biodegradability of BPAF and BPS was largely improved after ferrate oxidation. Compared with the BPS oxidation products, the BPAF oxidation products were easier to be bio-consumed. Pure culture test showed that BPAF inhibited the growth of Escherichia coli, while ferrate oxidation completely eliminated this toxic effect. Co-existing humic acid (HA, 1 mg C/L to 5 mg C/L) decreased the removal of BPS and BPAF with ferrate. Compared with BPAF, more oxidation intermediates formed in the ferrate oxidation of BPS may be reduced by HA to the parent molecular. Thus, the inhibition effect of HA on the ferrate oxidation of BPS was more obvious than that on BPAF.

Binary Mixtures of Selected Bisphenols in the Environment: Their Toxicity in Relationship to Individual Constituents

Bisphenol A (BPA) is one of the most popular and commonly used plasticizer in the industry. Over the past decade, new chemicals that belong to the bisphenol group have increasingly been used in industrial applications as alternatives to BPA. Nevertheless, information on the combined effects of bisphenol (BP) analogues is insufficient. Therefore, our current study aimed to find the biological response modulations induced by the binary mixtures of BP compounds. We determined the toxicity levels in Microtox and XenoScreen YES/YAS assays for several BP analogs alone, and for their binary mixtures. The results obtained constituted the database for chemometric intelligent data analysis to evaluate the possible interactions occurring in the mixtures. Several chemometric/biophysical models have been used (concentration addition—CA, independent action—IA and polynomial regression calculations) to realize this aim. The best fitting was found for the IA model and even in this description strong evidence for synergistic behaviors (modes of action) of some bisphenol analogue mixtures was demonstrated. Bisphenols A, S, F and FL were proven to be of significant endocrine threat (with respect to XenoScreen YES/YAS assay); thus, their presence in mixtures (including presence in tissues of living organisms) should be most strictly monitored and reported.

Chlorinated and brominated bisphenol A derivatives: Synthesis, characterization and determination in water samples

Bisphenol A (BPA) has been used in the plastics industry for several decades. During the treatment of drinking water with chlorine reagent, the formation of chlorinated derivatives of BPA (ClxBPA) but also bromoBPA and bromochloroBPA is to be expected. Some of these compounds are considered to have an estrogenic effect and could induce major risks for human health by targeting different organs and systems in the body. In this paper, we describe the synthesis of chloro- and bromobisphenol A (ClxBPA, BrxBPA, BrxClxBPA)and their analytical characterization. These derivatives could be used as analytical standards in LC-MS/MS or evaluated in in vitro biological tests for their potential as endocrine disruptors. In this study, we evaluated the presence of BPA, ClxBPA in a pilot study from water samples. Range values found for BPA, ClxBPA were respectively 2.8-4169.3 ng/L and 0.8-11.3 ng/L.

Occurrence, endocrine-related bioeffects and fate of bisphenol A chemical degradation intermediates and impurities: A review

In recent decades, increasing attention has been directed toward the effects of bisphenol A (BPA) as an environmental pollutant, primarily due to its demonstrated endocrine-disruptive effects. A growing body of evidence indicates that many BPA derivatives also exhibit endocrine activity and other adverse biological properties. A review of the published literature was performed to identify BPA degradation intermediates resulting from chemical degradation processes of BPA, as well as BPA's associated co-pollutants. Products of biological metabolism were not included in this study. Seventy-nine chemicals were identified. Of these chemicals, a subset - those containing two 6-membered aromatic rings connected by a central ring-linking carbon - was identified, and a further literature review was conducted to identify demonstrated biological effects associated with the chemicals in this subset. The objectives of this review were to assess the potential risks to human and environmental health associated with BPA derivatives, characterize our current understanding of BPA's degradation intermediates and co-pollutants, and aid in the identification of compounds of interest that have received insufficient scrutiny.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Determination of trace levels of eleven bisphenol A analogues in human blood serum by high performance liquid chromatography-tandem mass spectrometry

Chemicals showing structural or functional similarity to bisphenol A (BPA), commonly called BPA analogues, have recently drawn scientific attention due to their common industrial and commercial application as a substitute for BPA. In the European Union, the use of BPA has been severely restricted by law due to its endocrine disrupting properties. Unfortunately, it seems that all BPA analogues show comparable biological activity, including hormonal disruption, toxicity and genotoxicity. Until now, the knowledge about human exposure to BPA analogues is scarce, mainly due to the lack of the data concerning their occurrence in human derived biological samples. This study presents the development of an analytical method for determination of trace levels of eleven BPA analogues in human blood serum samples. The method involves fast and simple liquid-liquid extraction, using low sample and solvent volumes. Chromatographic separation of analytes was optimized using one-factor-at-a-time approach (mobile phase composition, gradient shape, chromatographic column selection, separation temperature, etc.). The method allows for effective separation of the analytes, even in the case of configurational isomers (bisphenol M and bisphenol P). The calibration curves for all analytes were linear in the range tested. The limits of detection and quantitation were in the range of 0.0079÷0.039ng/mL and 0.024÷0.12ng/mL respectively. Compound-dependent recovery values were in the rage of 88÷138%. Matrix effects were mitigated with the help of matrix-matched calibration curves prepared for every batch of samples. Results obtained after the analysis of 245 real human blood serum samples indicate that human beings are exposed to different BPA analogues, that are present in the environment and in common, daily use products.

Estrogen receptor-based fluorescence polarization assay for bisphenol analogues and molecular modeling study of their complexation mechanism

A fluorescence polarization (FP) assay based on estrogen receptor was developed for the determination of bisphenol compounds (BPs). The human estrogen receptor α ligand binding domain (hERα-LBD) and coumestrol were employed as recognition element and fluorescent probe, respectively. Competitive displacement of tracer from receptor suggested that BPs exhibited dose-dependent binding to hERα-LBD. In order to elucidate the structural basis for the interaction between BPs and hERα-LBD, molecular dynamics simulations were performed to explore their complexation mechanism. The docked bisphenol compounds adopted agonist/antagonist conformations with varying positions and orientations in the hydrophobic binding pocket, depending on their structural characteristics of bridging moieties. Interestingly, the calculated binding energies were generally correlated with the experimentally measured affinities, indicating a potential advantage of the molecular modeling approach in predicting the binding potencies of putative ligands. Considering that the real samples may contain more than one BP, the established FP assay can potentially be used as a pre-screening method to determine the total amounts of bisphenol compounds.

Immunotoxicity of bisphenol S and F are similar to that of bisphenol A during zebrafish early development

Bisphenol S (BPS) and bisphenol F (BPF) have been increasingly used as alternatives to bisphenol A (BPA) owing to health concerns. The present study aims to evaluate the impact of these two BPA analogs on oxidative stress and the immune system during zebrafish embryonic and larval development. Environmentally relevant levels of BPS and BPF exposure could increase reactive oxygen species (ROS) content, nitric oxide (NO) content, nitric oxide synthase (NOS) activity, and the expression of immunity-related genes in concentration dependent manners during the early developmental stages in zebrafish. At a concentration of 100 μg/L, BPS and BPF showed similar effects on the immune toxicity of zebrafish as that of BPA. Moreover, BPS and BPF induced both erα and nf-κb expression, and antagonists of estrogen receptor and NF-κB blocked the effects on immunity-related gene expression, providing evidence that the two pathways mediate the actions of BPS and BPF on fish immune response and functions. Thus we conclude that the presence of BPS and BPF in the environment, similar to BPA, may also pose risks to ecosystem and human health and cannot be widely used without limitations and precautions.

Extranuclear-initiated estrogenic actions of endocrine disrupting chemicals: Is there toxicology beyond paracelsus?

Endocrine Disrupting Chemicals (EDCs), including bisphenol-A (BPA) do not act as traditional toxic chemicals inducing massive cell damage or death in an unspecific manner. EDCs can work upon binding to hormone receptors, acting as agonists, antagonists or modulators. Bisphenol-A displays estrogenic activity and, for many years it has been classified as a weak estrogen, based on the classic transcriptional action of estrogen receptors serving as transcription factors. However, during the last two decades our knowledge about estrogen signaling has advanced considerably. It is now accepted that estrogen receptors ERα and ERβ activate signaling pathways outside the nucleus which may or may not involve transcription. In addition, a new membrane estrogen receptor, GPER, has been proposed. Pharmacological and molecular evidence, along with results obtained in genetically modified mice, demonstrated that BPA, and its substitute BPS, are potent estrogens acting at nanomolar concentrations via extranuclear ERα, ERβ, and GPER. The different signaling pathways activated by BPA and BPS explain the well-known estrogenic effects of low doses of EDCs as well as non-monotonic dose-response relationships. These signaling pathways may help to explain the actions of EDCs with estrogenic activity in the etiology of different pathologies, including type-2 diabetes and obesity.

ERE-dependent transcription and cell proliferation: Independency of these two processes mediated by the introduction of a sulfone function into the weak estrogen estrothiazine

The synthetic coumestrol derivative 6,12-dihydro-3-methoxy-1-benzopyrano[3,4-b][1,4]benzothiazin-6-one (estrothiazine, ESTZ) has been identified as a weak estrogen receptor α (ERα) ligand unable to compete with tritiated estradiol. The biological activity of this compound, supported by a methoxy group in position 3, seems mainly to result from its capacity to activate ERα dimerization without any participation of coactivators. In support of this view and referring to conventional estrogens, an ESTZ metabolism study conducted with hepatic human microsomes failed to provide any argument in favour of an estrogenic activity dependent on a metabolic conversion of the compound into hydroxylated metabolites with strong receptor activation ability. Interestingly, we failed to detect any oxidation of the sulfur atom of the compound. In the light of pharmacological literature data concerning sulfonylation, we assessed ERα-mediated activities generated by two sulfonylated ESTZ derivatives in which the methoxy group that plays a key role in its mechanism of action was maintained or removed. Sulfonylated ESTZ, even in its demethoxylated form, induced ERE-mediated transcriptions in MCF-7 breast cancer cells, without affecting the ERα turnover rate. In contrast to ESTZ, this compound failed to enhance the proliferation of ERα-positive breast cancer cells, suggesting that its sulfone function confers upon the receptor a capacity to elicit some of the known characteristics associated with estrogenic responses. Moreover, we demonstrated that this sulfone may contribute to ERα dimerization without any requirement of the methoxy group. Nevertheless, it seems to cooperate with this group, as reflected by a weak ability of the sulfonylated form of ESTZ to compete with tritiated estradiol for ERα-binding. Assessment of the docking of this compound within the ligand-binding domain of the receptor by molecular dynamics provided an explanation for this observation since the sulfone is engulfed in a small hydrophobic pocket involving the residues Leu-346, Leu-349, Ala-350 and Leu-384, also known to recruit coactivators. This work not only reports the sulfone functional group as a pharmacophore for estrogenic activity, but also opens new perspectives for the development of estrogenic molecules with therapeutic purpose and devoid of proliferative side effects.

State of the evidence 2017: an update on the connection between breast cancer and the environment

BACKGROUND

In this review, we examine the continually expanding and increasingly compelling data linking radiation and various chemicals in our environment to the current high incidence of breast cancer. Singly and in combination, these toxicants may have contributed significantly to the increasing rates of breast cancer observed over the past several decades. Exposures early in development from gestation through adolescence and early adulthood are particularly of concern as they re-shape the program of genetic, epigenetic and physiological processes in the developing mammary system, leading to an increased risk for developing breast cancer. In the 8 years since we last published a comprehensive review of the relevant literature, hundreds of new papers have appeared supporting this link, and in this update, the evidence on this topic is more extensive and of better quality than that previously available.

CONCLUSION

Increasing evidence from epidemiological studies, as well as a better understanding of mechanisms linking toxicants with development of breast cancer, all reinforce the conclusion that exposures to these substances - many of which are found in common, everyday products and byproducts - may lead to increased risk of developing breast cancer. Moving forward, attention to methodological limitations, especially in relevant epidemiological and animal models, will need to be addressed to allow clearer and more direct connections to be evaluated.

Characterizing properties of non-estrogenic substituted bisphenol analogs using high throughput microscopy and image analysis

Animal studies have linked the estrogenic properties of bisphenol A (BPA) to adverse effects on the endocrine system. Because of concerns for similar effects in humans, there is a desire to replace BPA in consumer products, and a search for BPA replacements that lack endocrine-disrupting bioactivity is ongoing. We used multiple cell-based models, including an established multi-parametric, high throughput microscopy-based platform that incorporates engineered HeLa cell lines with visible ERα- or ERβ-regulated transcription loci, to discriminate the estrogen-like and androgen-like properties of previously uncharacterized substituted bisphenol derivatives and hydroquinone. As expected, BPA induced 70–80% of the estrogen-like activity via ERα and ERβ compared to E2 in the HeLa prolactin array cell line. 2,2’ BPA, Bisguaiacol F, CHDM 4-hydroxybuyl acrylate, hydroquinone, and TM modified variants of BPF showed very limited estrogen-like or androgen-like activity (< 10% of that observed with the control compounds). Interestingly, TM-BFP and CHDM 4-hydroxybuyl acrylate, but not their derivatives, demonstrated evidence of anti-estrogenic and anti-androgenic activity. Our findings indicate that Bisguaiacol F, TM-BFP-ER and TM-BPF-DGE demonstrate low potential for affecting estrogenic or androgenic endocrine activity. This suggest that the tested compounds could be suitable commercially viable alternatives to BPA.

Adsorptive removal of bisphenol A (BPA) from aqueous solution: A review

Endocrine-disrupting compounds (EDCs) are an important class of emerging contaminants that have been detected (and are still being detected) in aquatic environments such as surface waters, groundwater, wastewater, runoff, and landfill leachates. Bisphenol A (BPA) is a known endocrine disruptor that is acutely toxic to the living organisms. BPA has been widely used in the manufacture of sunscreen lotions, nail polish, body wash/lotions, bar soaps, shampoo, conditioners, shaving creams, and face lotions/cleanser, besides its other industrial applications. In the present review, an overview of the recent research studies dealing with the BPA removal from water by adsorption method is presented. We have reviewed various conventional and non-conventional adsorbents which have been used for BPA removal from water. It is evident from the literature reviewed that modified adsorbents and composite materials have shown promising results for BPA removal from water. Literature has been extensively discussed in terms of adsorption capacities, fitted isotherm and kinetic models and thermodynamic aspects.

Predicting anti-androgenic activity of bisphenols using molecular docking and quantitative structure-activity relationships

Both in vivo and in vitro assay indicated that bisphenols can inhibit the androgen receptor. However, the underlying antagonistic mechanism is unclear. In this study, molecular docking was employed to probe the interaction mechanism between bisphenols and human androgen receptor (hAR). The binding pattern of ligands in hAR crystal structures was also analyzed. Results show that hydrogen bonding and hydrophobic interactions are the dominant interactions between the ligands and hAR. The critical amino acid residues involved in forming hydrogen bonding between bisphenols and hAR is Asn 705 and Gln 711. Furthermore, appropriate molecular structural descriptors were selected to characterize the non-bonded interactions. Stepwise multiple linear regressions (MLR) analysis was employed to develop quantitative structure-activity relationship (QSAR) models for predicting the anti-androgenic activity of bisphenols. Based on the QSAR development and validation guideline issued by OECD, the goodness-of-fit, robustness and predictive ability of constructed QSAR model were assessed. The model application domain was characterized by the Euclidean distance and Williams plot. The mechanisms of the constructed model were also interpreted based on the selected molecular descriptors i.e. the number of hydroxyl groups (nROH), the most positive values of the molecular surface potential (Vs,max) and the lowest unoccupied molecular orbital energy (ELUMO). Finally, based on the model developed, the data gap for other twenty-six bisphenols on their anti-androgenic activity was filled. The predicted results indicated that the anti-androgenic activity of seven bisphenols was higher than that of bisphenol A.

Determination of endocrine-disrupting chemicals in human milk by dispersive liquid–liquid microextraction

Aim: Human populations are widely exposed to numerous so-called endocrine-disrupting chemicals, exogenous compounds able to interfere with the endocrine system. This exposure has been associated with several health disorders. New analytical procedures are needed for biomonitoring these xenobiotics in human matrices. A quick and inexpensive methodological procedure, based on sample treatment by dispersive liquid–liquid microextraction, is proposed for the determination of bisphenols, parabens and benzophenones in samples. Results: LOQs ranged from 0.4 to 0.7 ng ml-1 and RSDs from 4.3 to 14.8%. Conclusion: This methodology was satisfactorily applied in the simultaneous determination of a wide range of endocrine-disrupting chemicals in human milk samples and is suitable for application in biomonitoring studies.

Comparative study of the interactions between bisphenol analogues and serum albumins by electrospray mass spectrometry and fluorescence spectroscopy

RATIONALE

Bisphenol A and its alternatives are widely used in common consumer products and are known as environmental endocrine disrupting chemicals. Five bisphenol analogues, namely, tetrabromobisphenol A (TBBPA), tetrachlorobisphenol A (TCBPA), 4,4'-sulfonyldiphenol (BPS), bisphenol A (BPA) and 4,4'-hexafluoroisopropylidenediphenol (BPAF), were selected to study their interactions with serum albumins, aiming at a better understanding of the toxicological mechanisms of bisphenol compounds.

METHODS

The interactions between human and bovine serum albumins (HSA and BSA) with these five compounds were investigated by electrospray ionization mass spectrometry (ESI-MS). Fluorescence spectroscopy and molecular docking confirmed the ESI-MS observations and provided complementary information with respect to thermodynamic properties and binding modes.

RESULTS

TBBPA showed the highest binding ability with HSA and BSA, followed by TBBPA and BPS, whereas BPA and BPAF exhibited little or no binding with these serum albumins. The calculated thermodynamic parameters suggested that hydrogen bonds and electrostatic forces played important roles for these interactions. Binding energies of TBBPA, TCBPA, and BPS calculated by molecular docking were -35.18, -34.39, and -25.89 kJ mol(-1) , respectively, in good agreement with ESI-MS measurements.

CONCLUSIONS

The results of this study showed that halogenated substituents on the phenolic rings of bisphenol could enhance the binding ability with serum albumins. This work could provide useful information for further research on the relationship between molecular structures and toxicities of bisphenols. Copyright © 2016 John Wiley & Sons, Ltd.

Occurrence and estrogenic potency of eight bisphenol analogs in sewage sludge from the U.S. EPA targeted national sewage sludge survey

As health concerns over bisphenol A (BPA) in consumer products are mounting, this weak estrogen mimicking compound is gradually being replaced with structural analogs, whose environmental occurrence and estrogen risks are not well understood yet. We used high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) to determine the concentrations of eight bisphenol analogs in 76 sewage sludge samples collected by the U.S. Environmental Protection Agency (EPA) in 2006/2007 from 74 wastewater treatment plants (WWTPs) in 35 states. Bisphenols were detected at the following concentration ranges (ng/g dry weight) and detection frequencies: BPA (6.5-4700; 100%); bisphenol S (BPS; <1.79-1480; 84%); bisphenol F (BPF; <1.79-242; 68%); bisphenol AF (BPAF; <1.79-72.2; 46%); bisphenol P (BPP; <1.79-6.42; <5%), bisphenol B (BPB; <1.79-5.60; <5%), and bisphenol Z (BPZ; <1.79--66.7; <5%). Bisphenol AP (BPAP) was not detected in any of the samples (<1.79 ng/g dw). Concentrations of BPA in sewage sludge were an order of magnitude higher than those reported in China but similar to those in Germany. The calculated 17β-estradiol equivalents (E2EQ) of bisphenols present in sludge samples were 7.74 (0.26-90.5) pg/g dw, which were three orders of magnitude lower than the estrogenic activity contributed by natural estrogens present in the sludge. The calculated mass loading of bisphenols through the disposal of sludge and wastewater was <0.02% of the total U.S. production. As the usage of BPA is expected to decline further, environmental emissions of BPS, BPF, and BPAF are likely to increase in the future. This study establishes baseline levels and estrogenic activity of diverse bisphenol analogs in sewage sludge.

Biomonitoring of human exposures to chlorinated derivatives and structural analogs of bisphenol A

The high reactivity of bisphenol A (BPA) with disinfectant chlorine is evident in the instantaneous formation of chlorinated BPA derivatives (ClxBPA) in various environmental media that show increased estrogen-activity when compared with that of BPA. The documented health risks associated with BPA exposures have led to the gradual market entry of BPA structural analogs, such as bisphenol S (BPS), bisphenol F (BPF), bisphenol B (BPB), etc. A suite of exposure sources to ClxBPA and BPA analogs in the domestic environment is anticipated to drive the nature and range of halogenated BPA derivatives that can form when residual BPA comes in contact with disinfectant in tap water and/or consumer products. The primary objective of this review was to survey all available studies reporting biomonitoring protocols of ClxBPA and structural BPA analogs (BPS, BPF, BPB, etc.) in human matrices. Focus was paid on describing the analytical methodologies practiced for the analysis of ClxBPA and BPA analogs using hyphenated chromatography and mass spectrometry techniques, because current methodologies for human matrices are complex. During the last decade, an increasing number of ecotoxicological, cell-culture and animal-based and human studies dealing with ClxBPA exposure sources and routes of exposure, metabolism and toxicity have been published. Up to date findings indicated the association of ClxBPA with metabolic conditions, such as obesity, lipid accumulation, and type 2 diabetes mellitus, particularly in in-vitro and in-vivo studies. We critically discuss the limitations, research needs and future opportunities linked with the inclusion of ClxBPA and BPA analogs into exposure assessment protocols of relevant epidemiological studies.

Preimplantation Exposure to Bisphenol A and Triclosan May Lead to Implantation Failure in Humans

Endocrine disrupting chemicals (EDCs) are chemicals that have the capacity to interfere with normal endocrine systems. Two EDCs, bisphenol A (BPA) and triclosan (TCS), are mass-produced and widespread. They both have estrogenic properties and similar chemical structures and pharmacokinetic features and have been detected in human fluids and tissues. Clinical evidence has suggested a positive association between BPA exposure and implantation failure in IVF patients. Studies in mouse models have suggested that preimplantation exposure to BPA and TCS can lead to implantation failure. This paper reviews the relationship between preimplantation exposure to BPA and TCS and implantation failure and discusses the remaining problems and possible solutions.

Genome-wide gene expression profiling of low-dose, long-term exposure of human osteosarcoma cells to bisphenol A and its analogs bisphenols AF and S

The bisphenols AF (BPAF) and S (BPS) are structural analogs of the endocrine disruptor bisphenol A (BPA), and are used in common products as a replacement for BPA. To elucidate genome-wide gene expression responses, estrogen-dependent osteosarcoma cells were cultured with 10 nM BPA, BPAF, or BPS, for 8 h and 3 months. Genome-wide gene expression was analyzed using the Illumina Expression BeadChip. Three months exposure had significant effects on gene expression, particularly for BPS, followed by BPAF and BPA, according to the number of differentially expressed genes (1980, 778, 60, respectively), the magnitude of changes in gene expression, and the number of enriched biological processes (800, 415, 33, respectively) and pathways (77, 52, 6, respectively). 'Embryonic skeletal system development' was the most enriched bone-related process, which was affected only by BPAF and BPS. Interestingly, all three bisphenols showed highest down-regulation of genes related to the cardiovascular system (e.g., NPPB, NPR3, TXNIP). BPA only and BPA/BPAF/BPS also affected genes related to the immune system and fetal development, respectively. For BPAF and BPS, the 'isoprenoid biosynthetic process' was enriched (up-regulated genes: HMGCS1, PDSS1, ACAT2, RCE1, DHDDS). Compared to BPA, BPAF and BPS had more effects on gene expression after long-term exposure. These findings stress the need for careful toxicological characterization of BPA analogs in the future.

Preliminary evidence of the association between monochlorinated bisphenol A exposure and type II diabetes mellitus: A pilot study

Evidence for the association of bisphenol A (BPA) with type II diabetes mellitus (T2DM) has been inconsistent in human studies. In-vitro and animal studies indicate that chlorinated BPA derivatives aggravate BPA health effects via higher estrogenic activity and alteration of membrane-initiating signaling pathways. We evaluated the association between urinary monochlorinated BPA (mono-ClBPA) concentrations and the incidence of T2DM. In our cross-sectional study, we identified 20 adult participants (≥18 yr) who reported having T2DM (doctor-diagnosed) and 131 adults with normal health. First morning void urine samples were analyzed for total BPA and mono-ClBPA. Detection limits of the analytical method were 95 ng L(-1) for BPA and 32 ng L(-1) for mono-ClBPA. Multivariable logistic regression analyses and additive Bayesian network modeling were performed. After adjusting for age, gender, BMI, urinary total BPA and other confounders, the odds of having T2DM was 3.29 times higher (95% confidence interval, CI: 1.10, 11.4; P < 0.05) per unit increase in log-transformed and creatinine-adjusted urinary mono-ClBPA levels (n = 151); this relation did not hold for total BPA. The globally optimum Bayesian model corroborated the results of the logistic regression by expressing mono-ClBPA in the pathway of T2DM, and not for total BPA. An age-matched sensitivity analysis confirmed the increase in OR of T2DM by 3.04 times (95% CI: 1.10, 11.0; P < 0.05) per unit increase in log-transformed and creatinine-adjusted urinary mono-ClBPA concentration (n = 68). The urinary monochlorinated BPA derivative was significantly associated with T2DM, whereas the parent compound (total BPA) was not. Caution should be applied in interpreting these findings, as this is the first study to report this association and the sample size of participants with T2DM is small. Additional research with a larger sample size coupled with relevant toxicological studies is warranted.

Estrogenic and androgenic activities of TBBA and TBMEPH, metabolites of novel brominated flame retardants, and selected bisphenols, using the XenoScreen XL YES/YAS assay

The present study investigated and compared the estrogenic and androgenic activities of the three different classes of environmental pollutants and their metabolites using the XenoScreen XL YES/YAS assay, which has advantages compared with the original YES/YAS protocol. Contrary to the parent brominated flame retardants TBB and TBPH, which demonstrated no or very weak (anti)estrogenic or (anti)androgenic activities, their metabolites, TBBA and TBMEPH, exhibited anti-estrogenic (IC50 for TBBA=31.75 μM and IC50 for TBMEPH=0.265 μM) and anti-androgenic (IC50 for TBBA=73.95 μM and IC50 for TBMEPH=2.92 μM) activities. These results reveal that metabolism can enhance the anti-estrogenic and anti-androgenic effects of these two novel brominated flame retardants. Based on the activities of BPAF, BPF, BPA and MBP, we can conclude that the XenoScreen XL YES/YAS assay gives comparable results to the (anti)estrogenic or (anti)androgenic assays that are reported in the literature. For BPA, it was confirmed previously that the metabolite formed after an ipso-reaction (hydroxycumyl alcohol) exhibited higher estrogenic activity compared with the parent BPA, but this was not confirmed for BPAF and BPF ipso-metabolites, which were not active in the XenoScreen YES/YAS assay. Among the substituted BPA analogues, bis-GMA exhibited weak anti-estrogenic activity, BADGE demonstrated weak anti-estrogenic and anti-androgenic activities (IC50=13.73 μM), and the hydrolysed product BADGE·2H2O demonstrated no (anti)estrogenic or (anti)androgenic activities.

Defining estrogenic mechanisms of bisphenol A analogs through high throughput microscopy-based contextual assays

Environmental exposures to chemically heterogeneous endocrine-disrupting chemicals (EDCs) mimic or interfere with hormone actions and negatively affect human health. Despite public interest and the prevalence of EDCs in the environment, methods to mechanistically classify these diverse chemicals in a high throughput (HT) manner have not been actively explored. Here, we describe the use of multiparametric, HT microscopy-based platforms to examine how a prototypical EDC, bisphenol A (BPA), and 18 poorly studied BPA analogs (BPXs), affect estrogen receptor (ER). We show that short exposure to BPA and most BPXs induces ERα and/or ERβ loading to DNA changing target gene transcription. Many BPXs exhibit higher affinity for ERβ and act as ERβ antagonists, while they act largely as agonists or mixed agonists and antagonists on ERα. Finally, despite binding to ERs, some BPXs exhibit lower levels of activity. Our comprehensive view of BPXs activities allows their classification and the evaluation of potential harmful effects. The strategy described here used on a large-scale basis likely offers a faster, more cost-effective way to identify safer BPA alternatives.

Structure-activity relationships of bisphenol A analogs at estrogen receptors (ERs): discovery of an ERα-selective antagonist

Our multi-template approach for drug discovery, focusing on protein targets with similar fold structures, has yielded lead compounds for various targets. We have also shown that a diphenylmethane skeleton can serve as a surrogate for a steroid skeleton. Here, on the basis of those ideas, we hypothesized that the diphenylmethane derivative bisphenol A (BPA) would bind to the ligand-binding domain of estrogen receptors (ERs) in a similar manner to estradiol and act as a steroid surrogate. To test this idea, we synthesized a series of BPA analogs and evaluated their structure-activity relationships, focusing on agonistic/antagonistic activities at ERs and ERα/ERβ subtype selectivity. Among the compounds examined, 18 was found to be a potent ERα-antagonist with high selectivity over ERβ and androgen receptor under our assay conditions. A computational docking study suggested that 18 would bind to the antagonistic conformation of ERα. ERα-selective antagonists, such as 18, are candidate agents for treatment of breast cancer.

In vitro study on the agonistic and antagonistic activities of bisphenol-S and other bisphenol-A congeners and derivatives via nuclear receptors

Bisphenols are a group of chemicals structurally similar to bisphenol-A (BPA) in current use as the primary raw material in the production of polycarbonate and epoxy resins. Some bisphenols are intended to replace BPA in several industrial applications. This is the case of bisphenol-S (BPS), which has an excellent stability at high temperature and resistance to sunlight. Studies on the endocrine properties of BPS have focused on its interaction with human estrogen receptor alpha (hERα), but information on its interaction with other nuclear receptors is scarce. The aim of this study was to investigate interactions of BPS, BPF, BPA and its halogenated derivatives, tetrachlorobisphenol A (TCBPA), and tetrabromobisphenol A (TBBPA), with human estrogen receptors (hERα and hERβ), androgen receptor (hAR), and pregnane X receptor (hPXR), using a panel of in vitro bioassays based on competitive binding to nuclear receptors (NRs), reporter gene expression, and cell proliferation assessment. BPS, BPF, and BPA efficiently activated both ERs, while TCBPA behaved as weak hERα agonist. Unlike BPF and BPA, BPS was more active in the hERβ versus hERα assay. BPF and BPA were full hAR antagonists (BPA>BPF), whereas BPA and BPS were weak hAR agonists. Only BPA, TCBPA, and TBBPA, were hPXR agonists (TCBPA>TBBPA>BPA). These findings provide evidence that BPA congeners and derivatives disrupt multiple NRs and may therefore interfere with the endocrine system. Hence, further research is needed to evaluate the potential endocrine-disrupting activity of putative BPA substitutes.

Assessment of the estrogenicity of the diet of a healthy female Spanish population based on its isoflavone content

Phytoestrogens are natural components of plants consumed by humans. The hormonal activity of these substances has long been known. Various in vitro tests have demonstrated the agonistic or antagonistic estrogenic activity of some phytoestrogens. The objective of this study was to estimate the supply of isoflavones in the diet of a healthy adult female population and to assess its estrogenic effect. The diet was assessed by questionnaire and the estrogenicity of the estimated isoflavone content was tested by E-screen, finding a mean total estrogenic capacity of 0.129 × 10⁻¹⁰ eq.E₂ (12.9 pmol day⁻¹), corresponding to a daily isoflavone intake of 265.8 μg day⁻¹. This study offers a preliminary insight into the phytoestrogen content of the diet of a healthy active population of Spanish women. The effects of this additional hormonal burden are highly controversial, and this approach to estimating dietary phytoestrogen intake of specific populations may help to elucidate its implications for human health.

Distribution and preliminary exposure assessment of bisphenol AF (BPAF) in various environmental matrices around a manufacturing plant in China

Increasing attention has been paid to bisphenol A and bisphenol (BP) analogues due to high production volumes, wide usage and potential adverse effects. Bisphenol AF (BPAF) is considered a new bisphenol analogue which is used as raw material in plastic industry, but little is known about its occurrence in the environment and the potential associated risk. In this work, BPAF levels and environmental distribution were reported in samples collected around a manufacturing plant and a preliminary exposure risk assessment to local residents was conducted. BPAF was detected in most of the samples, with levels in river ranging between <LOD to 1.53 × 10⁴ ng/L, sediments (0.520-2.00 × 10³ ng/g dry weight, dw), soils (<LOD to 331 ng/g dw) and indoor dusts (7.82-739 ng/g dw) and well water (<LOD to 300 ng/L). Exponential declining trends were observed for BPAF levels with increasing distance from the manufacturing plant. Based on the quantitative data and quantitative structure-property relationship (QSPR) model deduction, BPAF was predicted to mainly retain in sediment and soil after released into the ambient environment and organic carbon was the domain factor during the process. The preliminary BPAF exposure assessment based on the CSOIL model suggested that children could have higher intake of BPAF than adults through inhalation of soils, dermal exposure by soils contact and bathing with well water.