Unraveling molecular targets of bisphenol A and S in the thyroid gland

Bisphenol S dysregulates thyroid hormone homeostasis; Testicular survival, redox and metabolic status: Ameliorative actions of melatonin

Bisphenol S (BPS) is an incipient threat for reproductive health augmenting societal burden of infertility worldwide. In the present study, we investigated the mechanism of BPS induced testicular dysfunctions and protective actions of melatonin in mice. BPS (150 mg/kg BW) treatment reduced serum T3/T4, testosterone and elevated insulin levels along with adverse effect on thyroid and testicular histoarchitecture. Further, BPS treatment compromised sperm quality, reduced mRNA expression of steroidogenic (StAR/CYP11A1) markers, elevated oxidative load and disrupts metabolic status. However, melatonin (5 mg/kg BW) administration to BPS treated mice showed improved hormonal/histological parameters, enhanced thyroid hormone (TR-α/Dio-2)/melatonin (MT-1) receptor expressions. Further, melatonin treatment modulated the expression of testicular survival/redox (SIRT1/PGC-1α/FOXO-1, Nrf2/HO-1, p-JAK2/p-STAT3), proliferative (PCNA) and metabolic (IR/pAKT/GLUT-1) markers. Furthermore, melatonin treatment enhanced testicular antioxidant status and reduced caspase-3 expression. In conclusion, our results showed that BPS induces endocrine/oxidative and metabolic anomalies while melatonin improved male reproductive health.

Mediterranean Diet and Thyroid: An Interesting Alliance

The Mediterranean diet, recognized as being cultural heritage by UNESCO, is mostly plant-based and includes a high consumption of whole-grain, fruit, and vegetables with a moderate consumption of alcohol during meals. Thus, it provides a small amount of saturated fatty acids and a high quantity of antioxidants and fiber. For this reason, it has been considered to have an important role in preventing cardiovascular diseases, chronic kidney diseases, type 2 diabetes mellitus, and cancer, but its relationship with thyroid function and diseases is still under debate. The aim of this review was to search for the possible correlation between the Mediterranean diet and thyroid function, and to critically evaluate the pathophysiological link between selected food intake and thyroid disorders.

Estrogenic activity of lignin-derivable alternatives to bisphenol A assessed via molecular docking simulations

Lignin-derivable bisphenols are potential alternatives to bisphenol A (BPA), a suspected endocrine disruptor; however, a greater understanding of structure-activity relationships (SARs) associated with such lignin-derivable building blocks is necessary to move replacement efforts forward. This study focuses on the prediction of bisphenol estrogenic activity (EA) to inform the design of potentially safer BPA alternatives. To achieve this goal, the binding affinities to estrogen receptor alpha (ERα) of lignin-derivable bisphenols were calculated via molecular docking simulations and correlated to median effective concentration (EC50) values using an empirical correlation curve created from known EC50 values and binding affinities of commercial (bis)phenols. Based on the correlation curve, lignin-derivable bisphenols with binding affinities weaker than ∼-6.0 kcal mol-1 were expected to exhibit no EA, and further analysis suggested that having two methoxy groups on an aromatic ring of the bio-derivable bisphenol was largely responsible for the reduction in binding to ERα. Such dimethoxy aromatics are readily sourced from the depolymerization of hardwood biomass. Additionally, bulkier substituents on the bridging carbon of lignin-bisphenols, like diethyl or dimethoxy, were shown to weaken binding to ERα. And, as the bio-derivable aromatics maintain major structural similarities to BPA, the resultant polymeric materials should possess comparable/equivalent thermal (e.g., glass transition temperatures, thermal decomposition temperatures) and mechanical (e.g., tensile strength, modulus) properties to those of polymers derived from BPA. Hence, the SARs established in this work can facilitate the development of sustainable polymers that maintain the performance of existing BPA-based materials while simultaneously reducing estrogenic potential.

Long-term exposure to low doses of bisphenol S has hypoglycaemic effect in adult male mice by promoting insulin sensitivity and repressing gluconeogenesis

Bisphenol S (BPS), an industrial chemical that is a structural analogue of bisphenol A, has been widely reported to be involved in various biological processes. Epidemiological studies have demonstrated that exposure to BPS is associated with dysglycaemia-related health outcomes. The role of BPS in glucose metabolism, however, remains controversial. In this study, we aimed to investigate the effects of chronic exposure to environmentally relevant concentrations of BPS on glucose metabolism in different nutritionally conditioned mice. Our results revealed that 1-month exposure to a BPS dosage of 100 μg/kg bw slightly increased the insulin sensitivity of normal diet-fed mice, and that this effect was enhanced after 3-month exposure. It was also found that BPS exposure attenuated insulin resistance and reduced gluconeogenesis in high-fat diet-fed mice. Consequently, the concentrations of hepatic metabolites related to glucose metabolism were altered in both groups of mice. Moreover, thyroid hormone signalling was disrupted after BPS administration in both groups of mice. Taken together, our results demonstrated that chronic exposure to environmentally relevant concentrations of BPS exerted an unexpected hypoglycaemic effect in mice of different nutritional statuses, and that this was partly attributable to disrupted thyroid hormone signalling.

Bisphenol S is a haemodialysis-associated xenobiotic that is less toxic than bisphenol A

BACKGROUND

Bisphenol S (BPS) is a structural analogue of bisphenol A (BPA) that is found in the environment. BPS may accumulate in anuric patients due to decreased urinary excretion. The toxicity and health effects of BPS are poorly characterized.

METHODS

A cross-over study was performed using polynephron (PN) or polysulphone (PS) dialysers for a short (1 week each, 14 patients) or long (3 months each, 20 patients) period on each dialyser. Plasma BPA, BPS and hippuric acid were assessed by SRM mass spectrometry (SRM-MS). The biological significance of the BPS concentrations found was explored in cultured kidney tubular cells.

RESULTS

In haemodiafiltration (HDF) patients, plasma BPS was 10-fold higher than in healthy subjects (0.53 ± 0.52 versus 0.05 ± 0.01 ng/mL; P = 0.0015), while BPA levels were 35-fold higher (13.23 ± 14.65 versus 0.37 ± 0.12 ng/mL; P = 0.007). Plasma hippuric acid decreased after an HDF session, while BPS and BPA did not. After 3 months of HDF with the same membranes, the BPS concentration was 1.01 ± 0.87 ng/mL for PN users and 0.62 ± 0.21 ng/mL for PS users (P non-statistically significant). In vitro, BPS and BPA leaked from dialysers containing them. In cultured tubular cells, no biological impact (cytotoxicity, inflammatory and oxidative stress gene expression) was observed for BPS up to 200 µM, while BPA was toxic at concentrations ≥100 µM.

CONCLUSIONS

BPS may be released from dialysis membranes, and dialysis patients display high BPS concentrations. However, BPS concentrations are lower than BPA concentrations and no BPS toxicity was observed at concentrations found in patient plasma.

Dietary Intake of Endocrine Disrupting Substances Presents in Environment and Their Impact on Thyroid Function

According to the available data, environmental pollution is a serious problem all over the world. Between 2015 and 2016, pollution was responsible for approximately nine million deaths worldwide. They also include endocrine disrupting chemicals (EDCs) that can interfere with the functioning of the thyroid gland. They are characterized by high persistence in the environment. These substances can enter the body through the gastrointestinal tract, respiratory system, as well as contact with the skin and overcome the placental barrier. EDC can be found in food, water, and personal care products. They can get into food from the environment and as a result of their migration to food products and cosmetics from packaging. EDCs can disrupt the functioning of the thyroid gland through a number of mechanisms, including disrupting the activation of thyroid receptors and the expression of genes that are related to the metabolism, synthesis, and transport of thyroid hormones (HT). There is a need to strengthen the food safety policy that aimed at the use of appropriate materials in direct contact with food. At the same time, an important action is to reduce the production of all waste and, when possible, use biodegradable packaging, which may contribute to the improvement of the quality of the entire ecosystem and the health of food, thus reducing the risk of developing thyroid diseases.

Crosstalk of cholinergic pathway on thyroid disrupting effects of the insecticide chlorpyrifos in zebrafish (Danio rerio)

Chlorpyrifos is a widely used organophosphate insecticide and ubiquitously detected in the environment. However, little attention has been paid to its endocrine disrupting effect to non-target organisms. In the present study, zebrafish was exposed to 13 and 65 μg/L of chlorpyrifos for 7 and 10 days to determine the induced neurotoxicity and the alteration of thyroid metabolism. The 120 h LC₅₀ and LC₁₀ of chlorpyrifos was estimated as 1.35 mg/L and 0.62 mg/L based on the acute embryo toxicity assay, respectively. The acetylcholinesterase (AChE) inhibitory was detected by 13 μg/L chlorpyrifos and could be reversed by the co-exposure of 100 and 1000 μg/L anticholinergic agent atropine. For thyroid hormone level, 13 and 65 μg/L of chlorpyrifos induced increased free T₃ levels in 10 dpf (days post-fertilization). The expression of thyroid related genes in 7 and 10 dpf exposed zebrafish were measured by the quantitative Real-Time PCR (qRT-PCR) assay. The mRNA expression of tshba, thrb, crhb, ttr, tpo, ugt1ab and slc5a5 had significant change. However, the alterations of thyroid hormone and mRNA expression could be partly rescued by the addition of atropine. The molecular docking of chlorpyrifos and T₃ to the thyroid receptor β in zebrafish using homology modelling and CDOCKER procedures shown weaker binding ability of chlorpyrifos compared to T₃. Therefore, we concluded that the disturbance of thyroid signaling in zebrafish might arise from the developmental neurotoxicity induced by chlorpyrifos.

The Putative Adverse Effects of Bisphenol A on Autoimmune Diseases

Bisphenol A (BPA) is a monomer that is widely used in the manufacture of polycarbonate plastics including storage plastics and baby bottles, and is considered one of the most widely used synthetic compounds in the manufacturing industry. Exposure to BPA mainly occurs after oral ingestion and results from leaks into food and water from plastic containers and according to epidemiological data exposure is widespread and estimated to occur in 90% of individuals. BPA exertspleiotropiceffects and demonstrates estrogen like effects, thus considered an endocrine disrupting chemical. Growing body of evidence highlight the role of BPA in modulating immune responses and signaling pathways resulting in a proinflammatory response by enhancing the differential polarization of immune cells and cytokine production profile to one that is consistent with proinflammation. Indeed, epidemiological studies have uncovered associations between several autoimmune diseases and BPA exposure. Data from animal models provided consistent evidence highlighting the role of BPA in the pathogenesis, exacerbation and perpetuation of various autoimmune phenomena including neuroinflammation in the context of multiple sclerosis, colitis in inflammatory bowel disease, nephritis in systemic lupus erythematosus, and insulitis in type 1 diabetes mellitus. Given the wide spread of BPA use and its effects in immune systemdysregulation, a call for careful assessment of patients' risks and for public health measures are needed to limit exposure and subsequent deleterious effects. The purpose of this paper is to explore the autoimmune triggering mechanisms and present the current literature supporting the role of BPA in the pathogenesis of autoimmune diseases.

A comprehensive review of the neurobehavioral effects of bisphenol S and the mechanisms of action: New insights from in vitro and in vivo models

The normal brain development and function are delicately driven by an ever-changing milieu of steroid hormones arising from fetal, placental, and maternal origins. This reliance on the neuroendocrine system sets the stage for the exquisite sensitivity of the central nervous system to the adverse effects of endocrine-disrupting chemicals (EDCs). Bisphenol A (BPA) is one of the most common EDCs which has been a particular focus of environmental concern for decades due to its widespread nature and formidable threat to human and animal health. The heightened regulatory actions and the scientific and public concern over the adverse health effects of BPA have led to its replacement with a suite of structurally similar but less known alternative chemicals. Bisphenol S (BPS) is the main substitute for BPA that is increasingly being used in a wide array of consumer and industrial products. Although it was considered to be a safe BPA alternative, mounting evidence points to the deleterious effects of BPS on a wide range of neuroendocrine functions in animals. In addition to its reproductive toxicity, recent experimental efforts indicate that BPS has a considerable potential to induce neurotoxicity and behavioral dysfunction. This review analyzes the current state of knowledge regarding the neurobehavioral effects of BPS and discusses its potential mode of actions on several aspects of the neuroendocrine system. We summarize the role of certain hormones and their signaling pathways in the regulation of brain and behavior and discuss how BPS induces neurotoxicity through interactions with these pathways. Finally, we review potential links between BPS exposure and aberrant neurobehavioral functions in animals and identify key knowledge gaps and hypotheses for future research.

Effects of bisphenol A and S on blood coagulation: in vivo, in vitro and in silico approaches in toxicodynamic

Bisphenol A (BPA) is a well-known endocrine disruptor with several effects on mammalian systems and has been linked to diseases, such as cancer. Bisphenol S (BPS) emerged as a likely alternative to BPA in industrial production. Despite being well studied and exhibiting BPA-like toxic capacity, many effects are still being elucidated. The blood coagulation system is well controlled in an effort to minimize blood loss. To our knowledge, no study reported actions of bisphenols in this system. The aim of this work was to evaluate the effects of bisphenols on blood coagulation. Zebrafish were used to measure bleeding time. To assess possible mechanisms, platelet-rich plasma was incubated with both bisphenols in the presence of arachidonic acid. Prothrombin time (PT) and activated partial thromboplastin time (APTT) assays were performed in the presence of BPA and BPS. Alignment of human factor VII sequence was compared to zebrafish and docking simulations performed with FVIIa and bisphenols. An extended time was observed in BPA-treated but not BPS-treated animals in bleeding time; in PT, bisphenols showed no effect. APTT was increased in the highest concentration of bisphenols, with no effects in platelet aggregation, indicating interference with factor VII. Protein alignment showed that both proteins have well conserved residues, as those being required for interaction of FVIIa-BPA and FVIIa-BPS complexes, as shown in molecular docking. Taken together, these data show BPA and BPS as capable of interfering with the coagulation process via FVIIa.

Bisphenols as Environmental Triggers of Thyroid Dysfunction: Clues and Evidence

Bisphenols (BPs), and especially bisphenol A (BPA), are known endocrine disruptors (EDCs), capable of interfering with estrogen and androgen activities, as well as being suspected of other health outcomes. Given the crucial role of thyroid hormones and the increasing incidence of thyroid carcinoma in the last few decades, this review analyzes the effects of BPS on the thyroid, considering original research in vitro, in vivo, and in humans published from January 2000 to October 2019. Both in vitro and in vivo studies reported the ability of BPs to disrupt thyroid function through multiple mechanisms. The antagonism with thyroid receptors (TRs), which affects TR-mediated transcriptional activity, the direct action of BPs on gene expression at the thyroid and the pituitary level, the competitive binding with thyroid transport proteins, and the induction of toxicity in several cell lines are likely the main mechanisms leading to thyroid dysfunction. In humans, results are more contradictory, though some evidence suggests the potential of BPs in increasing the risk of thyroid nodules. A standardized methodology in toxicological studies and prospective epidemiological studies with individual exposure assessments are warranted to evaluate the pathophysiology resulting in the damage and to establish the temporal relationship between markers of exposure and long-term effects.

Bisphenols and Thyroid Hormone

In recent decades, attention has been directed toward the effects of bisphenol A (BPA) on human health. BPA has estrogenic activity and is regarded as a representative endocrine disruptor. In addition, mounting evidence indicates that BPA can disrupt thyroid hormone and its action. This review examined human epidemiological studies to investigate the association between BPA exposure and thyroid hormone levels, and analyzed in vivo and in vitro experiments to identify the causal relationship and its mechanism of action. BPA is involved in thyroid hormone action not only as a thyroid hormone receptor antagonist, but also through several other mechanisms. Since the use of bisphenols other than BPA has recently increased, we also reviewed the effects of other bisphenols on thyroid hormone action.

Assessment of the endocrine-disrupting effects of organophosphorus pesticide triazophos and its metabolites on endocrine hormones biosynthesis, transport and receptor binding in silico

Triazophos (TAP) was a widely used organophosphorus insecticide in developing countries. TAP could produce specific metabolites triazophos-oxon (TAPO) and 1-phenyl-3-hydroxy-1,2,4-triazole (PHT) and non-specific metabolites diethylthiophosphate (DETP) and diethylphosphate (DEP). The objective of this study involved computational approaches to discover potential mechanisms of molecular interaction of TAP and its major metabolites with endocrine hormone-related proteins using molecular docking in silico. We found that TAP, TAPO and DEP showed high binding affinity with more proteins and enzymes than PHT and DETP. TAP might interfere with the endocrine function of the adrenal gland, and TAP might also bind strongly with glucocorticoid receptors and thyroid hormone receptors. TAPO might disrupt the normal binding of androgen receptor, estrogen receptor, progesterone receptor and adrenergic receptor to their natural hormone ligands. DEP might affect biosynthesis of steroid hormones and thyroid hormones. Meanwhile, DEP might disrupt the binding and transport of thyroid hormones in the blood and the normal binding of thyroid hormones to their receptors. These results suggested that TAP and DEP might have endocrine disrupting activities and were potential endocrine disrupting chemicals. Our results provided further reference for the comprehensive evaluation of toxicity of organophosphorus chemicals and their metabolites.

Thyroid endocrine disruption effects of perfluoroalkyl phosphinic acids on zebrafish at early development

Perfluoroalkyl phosphinic acids (PFPiAs, including 6:6, 6:8 and 8:8 PFPiAs) are one kind of emerging perfluoroalkyl substances and usually used as leveling and wetting agents in household cleaning products and pesticide formulations. In this study, zebrafish embryos (6 h post-fertilization [hpf]) were exposed to 6:6, 6:8 and 8:8 PFPiAs individually (0.5, 5 and 50 nM) for 168 hpf. 8:8 PFPiA at 5 and 50 nM reduced the body length, while all treatments of 6:8 and 8:8 PFPiA depressed the heartbeat of the zebrafish larvae. 8:8 PFPiA at 50 nM distinctly enhanced the thyroxine (T4) and triiodothyronine (T3) contents. In a negative feedback mechanism, the three PFPiAs remarkably suppressed the genes responsible for THs regulation (corticotropin-releasing hormone, crh; thyroid stimulating hormone, tshβ), and 8:8 PFPiA displayed the strongest effect. In addition, 8:8 PFPiA significantly promoted the gene expressions corresponding to THs transport, metabolism and action (transthyretin, ttr; uridine diphosphate glucuronosyltransferase, ugt1ab; deiodinases, dio1 and dio2; thyroid hormone receptors, trα and trβ). As a result, 8:8 PFPiA displayed the strongest thyroid endocrine disrupting effect and significantly affected the growth of zebrafish larvae among the three PFPiAs in the present study.

A scoping review of the health and toxicological activity of bisphenol A (BPA) structural analogues and functional alternatives

Recent studies report widespread usage or exposure to a variety of chemicals with structural or functional similarity to bisphenol A (BPA), referred to as BPA analogues or derivatives. These have been detected in foodstuffs, house dust, environmental samples, human urine or blood, and consumer products. Compared to BPA, relatively little is known about potential toxicity of these compounds. This scoping review aimed to summarize the human, animal, and mechanistic toxicity data for 24 BPA analogues of emerging interest to research and regulatory communities. PubMed was searched from March 1, 2015 to January 5, 2019 and combined with the results obtained from literature searches conducted through March 23, 2015, in The National Toxicology Program's Research Report 4 (NTP RR-04), "Biological Activity of Bisphenol A (BPA) Structural Analogues and Functional Alternatives". Study details are presented in interactive displays using Tableau Public. In total, 5748 records were screened for inclusion. One hundred sixty seven studies were included from NTP RR-04 and 175 studies were included from the updated literature search through January 2019. In total, there are 22, 117, and 221 human epidemiological, experimental animal, or in vitro studies included. The most frequently studied BPA analogues are bisphenol S (BPS), bisphenol F (4,4-BPF), and bisphenol AF (BPAF). Notable changes in the literature since 2015 include the growing body of human epidemiological studies and in vivo studies conducted in zebrafish. Numerous new endpoints were also evaluated across all three evidence streams including diabetes, obesity, and oxidative stress. However, few studies have addressed endpoints such as neurodevelopmental outcomes or impacts on the developing mammary or prostate glands, which are known to be susceptible to disruption by BPA. Further, there remains a critical need for better exposure information in order to prioritize experimental studies. Moving forward, researchers should also ensure that full dose responses are performed for all main effects in order to support hazard and risk characterization efforts. The evidence gathered here suggests that hazard and risk characterizations should expand beyond BPA in order to consider BPA structural and functional analogues.

Multiplex Analysis Platform for Endocrine Disruption Prediction Using Zebrafish

Small fish are an excellent experimental model to screen endocrine-disrupting compounds, but current fish-based assays to detect endocrine disruption have not been standardized yet, meaning that there is not consensus on endpoints and biomarkers to be measured. Moreover, exposure conditions may vary depending on the species used as the experimental model and the endocrine pathway evaluated. At present, a battery of a wide range of assays is usually needed for the complete assessment of endocrine activities. With the aim of providing a simple, robust, and fast assay to assess endocrine-disrupting potencies for the three major endocrine axes, i.e., estrogens, androgens, and thyroid, we propose the use of a panel of eight gene expression biomarkers in zebrafish larvae. This includes brain aromatase (cyp19a1b) and vitellogenin 1 (vtg1) for estrogens, cytosolic sulfotransferase 2 family 2 (sult2st3) and cytochrome P450 2k22 (cyp2k22) for androgens, and thyroid peroxidase (tpo), transthyretin (ttr), thyroid receptor α (trα), and iodothyronine deiodinase 2 (dio2) for thyroid metabolism. All of them were selected according to their responses after exposure to the natural ligands 17β-estradiol, testosterone, and 3,3',5-triiodo-L-thyronine (T3), respectively, and subsequently validated using compounds reported as endocrine disruptors in previous studies. Cross-talk effects were also evaluated for all compounds.