Impact of environmental chemicals on the thyroid hormone function in pituitary rat GH3 cells

Thyroid and neurobehavioral effects of DiNP on GH3 cells and larval zebrafish (Danio rerio)

Diisononyl phthalate (DiNP) has been used to replace bis(2-ethylhexyl) phthalate (DEHP) and is frequently found in the environment and humans. DiNP is reported for its anti-androgenic activity; however, little is known about its effects on thyroid function and neurodevelopment. In the present study, the thyroid disruption and neurobehavioral alteration potential of DiNP and its major metabolites were assessed in a rat pituitary carcinoma cell line (GH3) and embryo-larval zebrafish (Danio rerio). In GH3 cells, exposure to DiNP and its metabolites not only increased proliferation but also induced transcriptional changes in several target genes, which were different from those observed with DEHP exposure. In larval fish, a 5-day exposure to DiNP caused significant increases in thyroid hormone levels, following a similar pattern to that reported for DEHP exposure. Following exposure to DiNP, the activity of the larval fish decreased, and neurodevelopment-related genes, such as c-fos, elavl3, and mbp, were down-regulated. These changes are generally similar to those observed for DEHP. Up-regulation of gap43 and down-regulation of elavl3 gene, which are important for both thyroid hormone production and neurodevelopment, respectively, support the potential for both thyroid and behavioral disruption of DiNP. Overall, these results emphasize the need to consider the adverse thyroid and neurodevelopmental effects in developing regulations for DEHP-replacing phthalates.

In vitro and in vivo investigation of a thyroid hormone system-specific interaction with triazoles

Alterations in thyroid hormones (TH) and thyroid-stimulating hormone levels are frequently found following exposure to chemicals of concern. Dysregulation of TH levels can severely perturb physiological growth, metabolism, differentiation, homeostasis in the adult and developmental processes in utero. A frequently identified mode of action for this interaction is the induction of hepatic detoxification mechanisms (e.g. SULTs and UGTs), which lead to TH conjugation and elimination and therefore interfere with hormonal homeostasis, fulfilling the endocrine disruptors (EDs) definition. A short-term study in rats with dietary exposure to cyproconazole, epoxiconazole and prochloraz was conducted and hepatocyte hypertrophy, hepatic UGT activity and Phase 1/2 gene expression inductions were observed together with changes in TH levels and thyroid follicular hypertrophy and hyperplasia. To test for specific interaction with the thyroid hormone system, in vitro assays were conducted covering thyroidal I-uptake (NIS), TH transmembranal transport via MCT8 and thyroid peroxidase (TPO) function. Assays for iodothyronine deiodinases (DIO1-DIO3) and iodotyrosine deiodinase (DEHAL1) were included, and from the animal experiment, Dio1 and Dehal1 activities were measured in kidney and liver as relevant local indicators and endpoints. The fungicides did not affect any TH-specific KEs, in vitro and in vivo, thereby suggesting hepatic conjugation as the dominant MoA.

Bisphenol analogues induce thyroid dysfunction via the disruption of the thyroid hormone synthesis pathway

Bisphenol analogues are widely used in industrial and daily-use consumer products having imperfect thyroid hormones (THs) structures. Widespread exposure interferes with thyroid-related health outcomes in human. The mechanisms of disruption on TH synthesis and subsequent thyroid dysfunction by different bisphenol analogues remain unclear. Here, we evaluated bisphenol-induced thyroid endocrine disruption in C57BL/6 mice at doses of 0.002, 0.02, 2, and 20 mg/kg body weight/day (BW/d) for five consecutive weeks. Administration of 20 mg/kg BW/d bisphenol S (BPS) and 2 mg/kg BW/d tetrabromobisphenol S (TBBPS) significantly increased serum thyrotropin (TSH) levels to 1.21-fold and 1.20-fold of control group, respectively, indicating that bisphenols induced thyroid dysfunction in mice. Height of the thyroid follicle epithelium significantly increased to 1.27-, 1.24-, 1.26-, and 1.36-fold compared to control group with BPA, BPS, TBBPA, and TBBPS at 20 mg/kg BW/d, respectively, indicating impairment of the thyroid gland structure, and TBBPS showed potent effect. Exposure to bisphenol analogues of 0.02 mg/kg BW/d downregulated the protein expression levels of thyrotropin receptor, the sodium/iodide symporter, thyroperoxidase. The TH-dependent effects were further determined using the T-Screen assay at 10-11 M to 10-5 M concentrations. Bisphenol analogues significantly decreased TH-dependent GH3 cell proliferation, indicating the antagonistic activity of bisphenol analogues. The gene responsible for THs synthesis of thyrotropin releasing hormone receptor and TSH were upregulated, but downregulation of thyroid receptor β was observed. Our results suggest that bisphenol analogues distinctly induce thyroid dysfunction via TH synthesis, implying adverse effect of bisphenol analogues on TH homeostasis and subsequent physiological processes.

Exposure to persistent organic pollutants in Danish pregnant women: Hormone levels and fetal growth indices

This study examines possible associations of maternal Persistent Organic Pollutants (POP) exposure during pregnancy, maternal hormone levels and fetal growth indices (FGI). During 1st trimester, we measured maternal thyroids, androgens and estrogens, lipophilic POP and perfluorinated-alkyl-acid (PFAA) levels in serum from nulliparous women. Adjusted multivariate-linear regression models assessed associations between exposure and outcomes. Maternal characteristics and POP exposures associated with maternal hormone levels. Lipophilic POP elicited inverse association with androgen and estrogen levels but no strong association with thyroids. Higher level of PFAA was associated with higher thyroid and androgen levels. The PFAA did not associate with estrogens. Higher thyroid-peroxidase-antibody (TPO-Ab) and estradiol level associated with higher birth weight and length in sons. For daughters, the TPO-Ab associations were the opposite being inversely associated with birth weight and length, and higher TPO-Ab and estradiol associated with lower gestational age. Mediation analyses suggested that TPO-Ab mediates the association of PFAA with FGI.

The effects of bisphenols on the cardiovascular system ex vivo and in vivo

The human population is regularly exposed to bisphenols. The first compound of this class, bisphenol A, is burdened by numerous reports of its potential toxicity and has been hence replaced by its analogues, so-called next generation bisphenols. Their widespread use has made them pervasive throughout the environment. These endocrine disrupting chemicals can affect the cardiovascular system, and hence the aim of this study was to test 14 bisphenols (A, AF, AP, B, BP, C, E, F, G, M, P, PH, S and Z), and compare their effects in vitro (human and rat cell lines), ex vivo (isolated rat aorta) and in vivo (Wistar Han rats, acutely or chronically exposed to low environmental and high toxic doses). The majority of the tested bisphenols relaxed rat aorta, but their potency varied markedly. The most potent compound, bisphenol AF, had an EC₅₀ of 57 μM. The mechanism of action was likely based on the inhibition of calcium influx via L-type calcium channels. The cytotoxicity of bisphenols towards 4 human and rat cell lines (H9c2, A-10, MCF7/S0.5 and MCF7/182R-6) showed variable potencies ranging from units of micromolar to millimolar concentrations. Based on these data, an effect on arterial blood pressure and possible cardiotoxicity was expected. Contrarily, the in vivo acute effects of three doses (0.005, 0.05 and 2.5 mg/kg) of bisphenol AF and 3 other analogues (A, S and F) on the cardiovascular system were rather biologically negligible. The most potent bisphenol, AF, was also administered chronically at a dose of 2.5 mg/kg for 4 weeks to rats, but had no impact on arterial blood pressure. Our results showed that bisphenols can relax vascular smooth muscles, but the effective concentrations are too high to produce clear cardiovascular effects in relation to common biological exposure as was confirmed with the most potent bisphenol AF.

Breast adipose metabolites mediates the association of tetrabromobisphenol a with breast cancer: A case-control study in Chinese population

Studies exploring the association of tetrabromobisphenol A (TBBPA) with breast cancer and related mechanisms are limited. To investigate the relationship between TBBPA levels in breast adipose and breast cancer, we carried out case-control research. As well as further examine the mediating role of adipose metabolites between TBBPA and breast cancer using the metabolomics approach. In this study, the concentration of TBBPA was determined utilizing ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) after a solid phase extraction (SPE) pretreatment. High-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) was employed to analyze adipose metabolomics. Evaluation of metabolites linked to TBBPA exposure and breast cancer was performed utilizing mediation analysis. With an estimated OR (95%CI) of 1.153 (1.023, 1.299), TBBPA was firmly linked with breast cancer. We also used propensity score matching analysis and sensitivity analysis to reduce the effect of confounding factors on the results. Metabolomics of adipose suggested significant perturbation in the linoleic acid metabolism pathway. In addition, for PC (16:0/16:0) as phospholipids, a mediation effect on the associations of TBBPA exposure with breast cancer risks was observed (estimated mediation percentage: 56.58%). Understanding the relationship between TBBPA exposure and the risk of breast cancer may be facilitated by the findings, which point to potential mediation metabolites.

Widening the Lens on Prothioconazole and Its Metabolite Prothioconazole-Desthio: Aryl Hydrocarbon Receptor-Mediated Reproductive Disorders through in Vivo, in Vitro, and in Silico Studies

Reproductive disorders are a serious public health problem worldwide. Epidemiological data suggest that exposure to environmental pollutants is associated with the onset of reproductive disorders. However, the effects in reproductive health and exact mechanism of action of representative agricultural compounds prothioconazole (PTC) and its metabolite prothioconazole-desthio (dPTC) on mammals remain unclear. Here, we studied the physiological effects of the exposure to environmentally relevant doses of PTC and dPTC in mice reproductive systems. Combining in vivo, in vitro, and in silico studies, we observed that PTC and dPTC disrupt reproductive health by inducing metabolic perturbation, induction of apoptosis, and inflammation in gonadal tissue, which are achieved via activation of the aryl hydrocarbon receptor (AhR). Convincingly, the addition of alternate-day injections of CH223191 (an AhR inhibitor) to the 30-day exposure regimen ameliorated ovarian tissue damage, as evidenced by decreased TUNEL-positive cells and partially restored the inflammation and apoptotic factor levels. This study comprehensively reports the toxic effects of low-dose PTC and dPTC in the reproductive system in vivo and identifies AhR as a potential therapeutic target for the amelioration of reproductive disorders caused by similar endocrine-disrupting chemicals.

Vascular Response of Tetrabromobisphenol a in Rat Aorta: Calcium Channels Inhibition and Potassium Channels Activation

Tetrabromobisphenol A (TBBPA) is a flame retardant widely used to reduce flammability. It is an endocrine disruptor, and due to constant human exposure, some concerns have been raised regarding its impact on human health. Studies showed that TBBPA affects oxidative stress, cell proliferation and intracellular calcium levels. However, the vascular consequences of TBBPA exposure are still relatively unexplored. Hence, this work aimed to analyse TBBPA effects on rat aortic smooth muscle and its action mechanisms. Through an ex vivo approach, Wistar rat aortas were used in an organ bath to evaluate the vascular effect of TBBPA (0.01-100 μM). Additionally, TBBPA's mode of action was studied through calcium and potassium channel inhibitors. Resorting to in vitro studies, A7r5 cells were used to analyse L-Type voltage-gated calcium channel (VGCC) activity through the whole-cell configuration of the patch clamp technique, and the mRNA expression of proteins and ion channels involved in vascular contractility. The results showed vasorelaxation of rat aorta induced by TBBPA exposure, involving the inactivation of L-Type VGCC and activation of potassium channels, and the modulation of mRNA expression of L-type calcium and large-conductance calcium 1.1 and the BK_Ca 1.1 α- and β₁ -subunit channels, soluble guanylyl cyclase and protein Kinase G.

The effects of bisphenols on the cardiovascular system

Bisphenols, endocrine disrupting chemicals, have frequently been used for producing food packaging materials. The best-known member, bisphenol A (BPA), has been linked to impaired foetal development in animals. Possible negative effects of BPA on human health have resulted in the production of novel, so-called next-generation (NextGen) bisphenols whose effects on humans are much less explored or even missing. This review aimed to summarise and critically assess the main findings and shortages in current bisphenol research in relation to their potential impact on the cardiovascular system in real biological exposure. Because of the common presence of bisphenols in daily use products, humans are clearly exposed to these compounds. Most data are available on BPA, where total serum levels (i.e. included conjugated metabolite) can reach up to ∼430 nM, while free bisphenol levels have been reported up to ∼80 nM. Limited data are available for other bisphenols, but maximal serum levels of bisphenol S have been reported (680 nM). Such levels seem to be negligible, although in vitro studies have showed effects on ion channels, and thyroid, oestrogenic and androgenic receptors in low micromolar concentrations. Ex vivo studies suggest vasodilatory effects of bisphenols. This stays in clear contrast to the elevation of arterial blood pressure documented in vivo and in observatory cross-sectional human studies. Bisphenols are also claimed to have a negative effect on lipidic spectrum and coronary artery disease. Regardless, the reported data are generally inconsistent and unsatisfactory. Hence novel well-designed studies, testing in particular NextGen bisphenols, are needed.

Health toxicity effects of brominated flame retardants: From environmental to human exposure

Hexabromocyclododecane (HBCD) and Tetrabromobisphenol A (TBBP-A) are brominated flame retardants widely used in variety of industrial and consumer products (e.g., automobiles, electronics, furniture, textiles and plastics) to reduce flammability. HBCD and TBBPA can also contaminate the environment, mainly water, dust, air and soil, from which human exposure occurs. This constant exposure has raised some concerns against human health. These compounds can act as endocrine disruptors, a property that gives them the ability to interfere with hormonal function and quantity, when HBCD and TBBPA bind target tissues in the body. Studies in human and animals suggest a correlation between HBCD and TBBPA exposure and adverse health outcomes, namely thyroid disorders, neurobehavior and development disorders, reproductive health, immunological, oncological and cardiovascular diseases. However, in humans these effects are still poorly understood, once only a few data evaluated the human health effects. Thus, the purpose of this review is to present the toxicity effects of HBCD and TBBPA and how these compounds affect the environment and health, resorting to data and knowledge of 255 published papers from 1979 to 2020.

Endocrine disruptors also function as nervous disruptors and can be renamed endocrine and nervous disruptors (ENDs)

Endocrine disruption (ED) and endocrine disruptors (EDs) emerged as scientific concepts in 1995, after numerous chemical pollutants were found to be responsible for reproductive dysfunction. The World Health Organization established in the United Nations Environment Programme a list of materials, plasticizers, pesticides, and various pollutants synthesized from petrochemistry that impact not only reproduction, but also hormonal functions, directly or indirectly. Cells communicate via either chemical or electrical signals transmitted within the endocrine or nervous systems. To investigate whether hormone disruptors may also interfere directly or indirectly with the development or functioning of the nervous system through either a neuroendocrine or a more general mechanism, we examined the scientific literature to ascertain the effects of EDs on the nervous system, specifically in the categories of neurotoxicity, cognition, and behaviour. To date, we demonstrated that all of the 177 EDs identified internationally by WHO are known to have an impact on the nervous system. Furthermore, the precise mechanisms underlying this neurodisruption have also been established. It was previously believed that EDs primarily function via the thyroid. However, this study presents substantial evidence that approximately 80 % of EDs operate via other mechanisms. It thus outlines a novel concept: EDs are also neurodisruptors (NDs) and can be collectively termed endocrine and nervous disruptors (ENDs). Most of ENDs are derived from petroleum residues, and their various mechanisms of action are similar to those of "spam" in electronic communications technologies. Therefore, ENDs can be considered as an instance of spam in a biological context.

Organophosphate pesticide exposure, hormone levels, and interaction with PON1 polymorphisms in male adolescents

OBJECTIVE

To examine the association between urinary metabolites of organophosphate (OP) pesticides and serum concentrations of thyroid and reproductive hormones in male adolescents and to assess the potential effect of interactions between OP pesticides and paraoxonase 1 (PON1) polymorphisms on hormone levels.

METHODS

Study subjects (N = 117) were male 16- to 17-year-olds from the Environment and Childhood (INMA)-Granada cohort in Spain. Concentrations of 3,5,6-trichloro-2-pyridinol (TCPy), a metabolite of chlorpyrifos/chlorpyrifos-methyl, 2-isopropyl-6-methyl-4-pyrimidinol (IMPy), a metabolite of diazinon, and diethylthiophosphate (DETP) and diethyldithiophosphate (DEDTP), non-specific metabolites of OP pesticides, were measured in a spot urine sample from each subject and adjusted for creatinine. Levels of reproductive hormones (total testosterone [TT], estradiol [E₂], dehydroepiandrosterone sulfate [DHEAS], sex hormone binding globulin [SHBG], luteinizing hormone [LH], follicle stimulating hormone [FSH], anti-Müllerian hormone [AMH], insulin growth factor 1 [IGF-1], and prolactin), thyroid hormones (free thyroxine [FT4], total triiodothyronine [TT3], and thyroid stimulating hormone [TSH]), and PON1 Q192R and L55M polymorphisms were determined in blood drawn during the same clinical visit.

RESULTS

Multiple linear regression models showed that detectable levels of TCPy were associated with an increase in DHEAS and decreases in E₂, FSH, and AMH; detectable IMPy with increases in E₂, DHEAS, FSH, AMH, and prolactin and decreases in SHBG and LH; and detectable DETP with marginally-significant increases in TT and TT3 and decreases in FSH, AMH, and prolactin. The effect of IMPy and DETP on DHEAS and TT levels, respectively, was higher in subjects that carried the PON1 55MM genotype, while the effect of TCPy, IMPy, and DETP on thyroid hormone levels was higher in PON1 192QR/RR or 55MM genotype carriers.

CONCLUSIONS

In male adolescents, non-occupational exposure to OP pesticides was associated with several changes in reproductive and thyroid hormone levels, and the magnitude of some associations was greater in adolescents genetically more susceptible to OP pesticide exposure who carry the PON1 55MM genotype.

Endocrine disrupting chemical Bisphenol A and its potential effects on female health

BACKGROUND AND AIM

A large number of chemical compounds with endocrine-disrupting activity have been documented. These chemicals are ubiquitous and widely used in many products of our daily lives. Bisphenol A (BPA) is among the most common Endocrine Disrupting Chemical (EDC) that has been used for many years in the manufacture of polycarbonate plastics and epoxy resins. There is growing evidence that exposure to these EDCs poses a possible health risk. This review focuses on the effect of EDCs, in particular, BPA on female reproduction and Polycystic Ovary Syndrome (PCOS), which is the most prevalent endocrine disorder of reproductively aged women.

METHODS

A relevant literature survey was conducted with Google scholar and Pubmed using several appropriate keywords to select the most relevant studies evaluating the role of endocrine disrupting-chemicals in female reproduction.

RESULTS

The female menstrual cycle and fertility are very sensitive to hormonal imbalance and alteration in endocrine function during critical times and different stages of lifecycle owing to EDC exposure results in many abnormalities like menstrual irregularities, impaired fertility, PCOS, and Endometriosis among others. BPA is the most extensively studied EDC worldwide and has been strongly associated with female reproductive health.

CONCLUSION

EDCs lead to deleterious effects on human health including reproductive health which are of global concern. Exposure to EDCs in early life can elicit disease in adult life and maybe even transgenerational. There is an immediate need to minimize the ill effect of EDCs which can be tackled through the collection of more data to clarify the clinical implications of EDCs.

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.

A comprehensive review on chlorpyrifos toxicity with special reference to endocrine disruption: Evidence of mechanisms, exposures and mitigation strategies

Chlorpyrifos (CPF) is a broad-spectrum chlorinated organophosphate (OP) pesticide used for the control of a variety of insects and pathogens in crops, fruits, vegetables, as well as households, and various other locations. The toxicity of CPF has been associated with neurological dysfunctions, endocrine disruption, and cardiovascular diseases (CVDs). It can also induce developmental and behavioral anomalies, hematological malignancies, genotoxicity, histopathological aberrations, immunotoxicity, and oxidative stress as evidenced by animal modeling. Moreover, eye irritation and dermatological defects are also reported due to CPF toxicity. The mechanism of action of CPF involves blocking the active sites of the enzyme, acetylcholinesterase (AChE), thereby producing adverse nervous system effects. Although CPF has low persistence in the body, its active metabolites, 3,5,6-trichloro-2-pyridinol (TCP), and chlorpyrifos-oxon (CPO) are comparatively more persistent, albeit equally toxic, and thus produce serious health complications. The present review has been compiled taking into account the work related to CPF toxicity and provides a brief compilation of CPF-induced defects in animals and humans, emphasizing the abnormalities leading to endocrine disruption, neurotoxicity, reproductive carcinogenesis, and disruptive mammary gland functionality. Moreover, the clinical signs and symptoms associated with the CPF exposure along with the possible pharmacological treatment are reported in this treatise. Additionally, the effect of food processing methods in reducing CPF residues from different agricultural commodities and dietary interventions to curtail the toxicity of CPF has also been discussed.

Thyroid disrupting effects of perfluoroundecanoic acid and perfluorotridecanoic acid in zebrafish (Danio rerio) and rat pituitary (GH3) cell line

Due to global restriction on perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), the use of long-chain perfluoroalkyl substances (PFASs, C > 8) and their environmental occurrences have increased. PFOS and PFOA have been known for thyroid disruption, however, knowledge is still limited on thyroid disrupting effects of long-chain PFASs (C > 10). In this study, two long-chain perfluorinated carboxylic acids (PFCAs), i.e., perfluoroundecanoic acid (PFUnDA) and perfluorotridecanoic acid (PFTrDA), were chosen and investigated for thyroid disrupting effects, using zebrafish embryo/larvae and rat pituitary cell line (GH3). For comparison, PFOA was also added as a test chemical and also investigated for its thyroid disruption potential. Following a 5 d exposure to PFTrDA, zebrafish larvae showed upregulation of the genes responsible for thyroid hormone synthesis (tshβ, nkx2.1, nis, tpo, mct8) and (de)activation (dio1, dio2). In contrast, both PFUnDA and PFOA induced no regulatory changes except for upregulation of a thyroid metabolism related gene (ugt1ab). Morphological changes such as decreased eyeball size, increased yolk sac size, or deflated swim bladder, occurred following exposure to PFUnDA, PFTrDA, and PFOA. In GH3 cells, exposure to PFUnDA and PFTrDA upregulated Tshβ gene, suggesting that these PFCAs increase thyroid hormone synthesis through stimulation by Tsh. In summary, both long-chain PFCAs could cause transcriptional changes of thyroid regulating genes that may lead to increased malformation of the zebrafish larvae, but the pathway of thyroid disruption appears to be different by the chain length. Confirmation and validation in adult fish following long term exposure are warranted.

Cytotoxic and estrogenic activity of chlorpyrifos and its metabolite 3,5,6-trichloro-2-pyridinol. Study of marine yeasts as potential toxicity indicators

Chlorpyrifos (CP) is one of the organophosphate insecticides most used worldwide today. Although the main target organ for CP is the nervous system triggering predominantly neurotoxic effects, it has suggested other mechanisms of action as cytotoxicity and endocrine disruption. The risk posed by the pesticide metabolites on non-target organisms is increasingly recognized by regulatory agencies and natural resource managers. In the present study, cytotoxicity and estrogenic activity of CP, and its principal metabolite 3,5,6-trichloro-2-pyridinol (TCP) have been evaluated by in vitro assays, using two mammalian cell lines (HEK293 and N2a), and a recombinant yeast. Results indicate that TCP is more toxic than CP for the two cell lines assayed, being N2a cells more sensitive to both compounds. Both compounds show a similar estrogenic activity being between 2500 and 3000 times less estrogenic than 17β-estradiol. In order to find new toxicity measurement models, yeasts isolated from marine sediments containing CP residues have been tested against CP and TCP by cell viability assay. Of the 12 yeast strains tested, 6 of them showed certain sensitivity, and a concentration-dependent response to the tested compounds, so they could be considered as future models for toxicity tests, although further investigations and proves are necessary.

Exposure to Perflouroalkyl acids and foetal and maternal thyroid status: a review

BACKGROUND

Exposure to perfluorinated-alkyl-acids (PFAAs) is ubiquitous. PFAAs are hormone-disrupting compounds that are strongly suspected to affect mother-child-health such as fetal growth. Thyroid disruption is a plausible mechanism of action. We aim to summarize the epidemiological evidence for the relation between prenatal and postnatal exposure to PFAAs and disruption of thyroid homeostasis in mothers and/or infants.

METHOD

Fifteen original publications on PFAAs concentrations and thyroid hormones (TH) in pregnant women and/or infants were found upon a literature search in the PubMed database. Information on exposure to seven PFAAs congeners [Perfluorooctane sulfonate (PFOS), Perfluorooctanoate (PFOA), Perfluorohexane sulfonate (PFHxS), Perfluorononanoic acid (PFNA), Perfluorodecanoic acid (PFDA), Perfluoroundecanoic acid (PFUnA), and Perfluorododecanoic acid (PFDoA)] and thyroid stimulating hormone (TSH), free and total thyroxine (FT4 and TT4), free and total triiodothyronine (FT3 and TT3), T3RU (Free triiodothyronine resin uptake) and FT4-index (FT4I) levels were recorded. We evaluated sampling of maternal TH by trimester, and infant TH by sex stratification. Reported associations between mother or infant PFAAs and TH were not uniformly assessed in the selected studies.

RESULTS

Ten out of the fifteen studies examined maternal PFAAs concentration and TSH level. Seven studies showed significant associations between TSH and exposure to six PFAAs congeners, most of them were positive. Maternal T4 and T3 were investigated in nine studies and five studies found inverse associations between exposure to six PFAAs congeners and TH (TT3, TT4, FT3, FT4 and FT4I) levels. Eight of the fifteen studies investigated PFAAs concentrations and infant TSH. Infant TSH level was significantly affected in four studies, positively in three studies. Nine studies investigated infant T4 and T3 and seven studies found significant associations with PFAAs exposure. However, both inverse and positive significant associations with infant TH were found eliciting no clear direction.

CONCLUSION

Results indicate a mainly positive relationship between maternal PFAAs concentrations and TSH levels, and suggestion of an inverse association with T4 and/or T3 levels. Associations of infant TH with PFAAs concentration were less consistent.

TDCPP mimics thyroid hormones associated with the activation of integrin αvβ3 and ERK1/2

Tri(1,3-dichloropropyl) phosphate (TDCPP) potentially damages the thyroid system in humans and animals. However, knowledge of its toxic effects and underlying mechanisms is limited. The present study was conducted to determine the thyroid hormone-disrupting effects of TDCPP and its major metabolite, bis(1,3-dichloro-2-propyl) phosphate (BDCPP) in rat pituitary cell lines (GH3). TDCPP and BDCPP, that mimic the thyroid hormone (TH), promoted GH3 cell proliferation and modulated the progression of the cell cycle at 20 and 200 μmol/L, respectively. Similar to T3, TDCPP and BDCPP also significantly upregulated c-fos and downregulated Tshβ gene expression. Although the binding affinity of these chemicals for thyroid receptor β (TRβ) was not measured, significant competition between these chemicals to bind to the membrane thyroid hormone receptor (integrin α_vβ₃) was found, suggesting that TDCPP and BDCPP were strongly bound to integrin α_vβ₃. Results from a molecular docking analysis provided further evidence of strong binding affinities of TDCPP and BDCPP for integrin α_vβ₃, and the ligand binding site of Arg-Gly-Asp (RGD) was identified. Real-time PCR also supported the supposition that, after binding to integrin α_vβ₃, TDCPP and BDCPP may induce the activation of the extracellular signal-regulated protein kinase (ERK1/2) signal transduction pathway. Taken together, our data suggest that TDCPP and BDCPP have the ability to mimic THs and that the underlying mechanism might be associated with their interactions with integrin α_vβ₃ and the activation of the ERK1/2 pathway, providing new insight into the mechanism of TDCPP- and BDCPP-induced cytotoxicity.

Evaluation and mechanistic study of chlordecone-induced thyroid disruption: Based on in vivo, in vitro and in silico assays

The present study aimed to evaluate the thyroid-disrupting potency of chlordecone, and reveal the underlying mechanism. In the in vivo assays, rare minnow embryos were exposed to 0, 0.01, 0.1, 1 and 10 μg·L^-1 chlordecone until sexually mature. The results showed decreased T4 but increased T3 concentrations in plasma, upregulated mRNA levels of thyrotropin-releasing hormone receptor (trhr) and sodium-iodide symporter (nis) in the brain, and transthyretin (ttr), thyroid hormone receptor α (trα) and deiodinase enzymes (dio1 and dio2) in the liver of adult fish. In the in vitro assays, single chlordecone treatments promoted growth hormone (GH) and prolactin (PRL) secretion in GH3 cells. Transcription of thyroid receptor (trβ) was inhibited, but this is not likely responsible for chlordecone-induced GH secretion and altered transcription. When co-treated with T3, chlordecone acted independently of the effect of T3 on GH secretion; chlordecone-induced GH/PRL secretion and mRNA expression were further promoted when co-treated with E2, but inhibited when co-treated with ICI, indicating an important role for estrogen receptors (ERs) in chlordecone-induced changes in GH3 cells. Furthermore, in silico prediction suggested no stable interactions between chlordecone and thyroid hormone-related proteins, as well as a regulatory role for ERs in thyroid systems. Overall, our results indicated that chlordecone may have adverse effects on thyroid systems upon long-term exposure. However, rather of TRs, ERs may be responsible for thyroid disruption following chlordecone exposure.

Environmental exposure to nonylphenol and cancer progression Risk-A systematic review

Environmental exposure to nonylphenol (NP) can adversely affect human and wildlife health. A systematic review was conducted to evaluate the relationship between environmental NP exposure and cancer progression risk. Literature surveys were conducted within several international databases using appropriate keywords. A comprehensive search yielded 58 eligible studies involving a wide range of adverse effects, exposure assessment methods, study designs, and experimental models. Most studies reported that NP strongly induced breast cancer progression in intended experiments. Positive associations between NP exposure and ovarian, uterine, pituitary, and testicular cancers were also reported. Although some studies reported no relation between environmental NP exposure and tumour and/or cancer progression, NP (a known endocrine disrupting chemical) induced action mechanisms in multiple experimental models and may interfere with/hyper-activate oestrogen signalling. Secretion of oestrogen and development of reproductive tissues like breasts, uteruses, and ovaries showed strong associations with possible neoplasia (i.e., uncontrolled development of tumours and/or malignant cancers). Findings of this study are important for informing policymakers to pass legislation limiting the use of environmental contaminants such as NP before all adverse effects of exposure have been determined.

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.

Multiple pesticides in mothers' hair samples and children's measurements at birth: Results from the French national birth cohort (ELFE)

BACKGROUND

A growing body of studies now suggests that the general population is continuously and ubiquitously exposed to numerous pesticides. However, studies investigating the possible role of environmental exposure to pesticides on fetal growth have focused on a limited set of substances, despite the hundreds of modern pesticides currently available.

AIM

To explore the relation between maternal hair concentrations of 64 pesticides and metabolites and their newborns' measurements at birth, with data from the ELFE French nationwide birth cohort.

METHODS

We measured 64 compounds (10-100% detection) in bundles of hair 9 cm long collected at birth from 311 women who gave birth in France in 2011. We assessed their associations with birth weight, length, and head circumference, adjusted for potential confounders, and used elastic net regularization to simultaneously select the strongest predictors of measurements at birth. Selected variables were multiply imputed for missing values, and unpenalized estimators were assessed by standard linear regression.

RESULTS

We observed statistically significant associations between maternal hair concentrations of seven pesticides or pesticide metabolites and birth measurements (weight: fipronil sulfone; length: TCPy, bitertanol, DEP, and isoproturon; head circumference: tebuconazole and prochloraz). Analyses restricted to boys identified 12 additional compounds: 8 independently associated with birth weight (3Me4NP, DCPMU, DMST, fipronil, mecoprop, propoxur, fenhexamid, and thiabendazole), 2 with birth length (dieldrin and β-endosulfan), and 6 with head circumference (β-endosulfan, β-HCH, fenuron, DCPMU, propoxur, and thiabendazole).

CONCLUSION

Our results suggest that prenatal exposure to 19 pesticides or metabolites from various chemical families may influence measurements at birth. As with any exploratory research findings, results should be interpreted cautiously, until they are replicated or verified by further epidemiological or mechanistic studies.

A comparison of endocrine disruption potential of nonylphenol ethoxylate, vanillin ethoxylate, 4-n-nonylphenol and vanillin in vitro

The widely used surfactant nonylphenol ethoxylate (NPEO) and its raw material 4-n-nonylphenol (4-n-NP), as well as its degradation products, are recognized as endocrine disrupting chemicals. The USA Environmental Protection Agency (EPA) released an assessment that looked for safe alternatives to NPEO. Vanillin ethoxylate (VAEO) is a novel substitute for NPEO and is quite similar to NPEO in structure; there is a risk that it has similar endocrine disrupting effects to NPEO. However, their effects on various nuclear hormone receptors have not been thoroughly examined. In this study, the effects of NPEO, VAEO, 4-n-NP and Vanillin on the estrogen receptor α (ERα), androgen receptor (AR), thyroid hormone receptor (TR), retinoic X receptor β (RXRβ) and estrogen-related receptor γ (ERRγ) were determined and compared using a battery of recombined yeast strains expressing β-galactosidase. The results showed that NPEO and 4-n-NP acted as significant antagonists of ER, AR, TR and ERRγ. In addition, 4-n-NP also had antagonistic activity toward RXRβ. Moreover, VAEO was shown to be a very weak antagonist of TR and ERRγ, and Vanillin had no interaction with any nuclear receptors. For the first time, it was found that NPEO had AR, TR and ERRγ antagonistic effects and that 4-n-NP was an antagonist of RXRβ. The in vitro data indicated that NPEO, 4-n-NP and VAEO have the potential to act as endocrine disruptors involving more than one nuclear hormone receptor, but VAEO has much lower endocrine disrupting potential than NPEO. Thus, it is critical to find safe substitutes for NPEO and a substitute of NPEO with structural analogues should be carried out with caution. Furthermore, to look for preferable alternatives for NPEO, more in vivo and in vitro studies of the alternatives concerning endocrine disruption are needed, especially in vitro studies need to involve various target points, not only focus on their effects on ER but also take other nuclear hormone receptor pathways into consideration.

Comparative Analyses of the 12 Most Abundant PCB Congeners Detected in Human Maternal Serum for Activity at the Thyroid Hormone Receptor and Ryanodine Receptor

Polychlorinated biphenyls (PCBs) pose significant risk to the developing human brain; however, mechanisms of PCB developmental neurotoxicity (DNT) remain controversial. Two widely posited mechanisms are tested here using PCBs identified in pregnant women in the MARBLES cohort who are at increased risk for having a child with a neurodevelopmental disorder (NDD). As determined by gas chromatography-triple quadruple mass spectrometry, the mean PCB level in maternal serum was 2.22 ng/mL. The 12 most abundant PCBs were tested singly and as a mixture mimicking the congener profile in maternal serum for activity at the thyroid hormone receptor (THR) and ryanodine receptor (RyR). Neither the mixture nor the individual congeners (2 fM to 2 μM) exhibited agonistic or antagonistic activity in a THR reporter cell line. However, as determined by equilibrium binding of [3H]ryanodine to RyR1-enriched microsomes, the mixture and the individual congeners (50 nM to 50 μM) increased RyR activity by 2.4-19.2-fold. 4-Hydroxy (OH) and 4-sulfate metabolites of PCBs 11 and 52 had no TH activity; but 4-OH PCB 52 had higher potency than the parent congener toward RyR. These data support evidence implicating RyRs as targets in environmentally triggered NDDs and suggest that PCB effects on the THR are not a predominant mechanism driving PCB DNT. These findings provide scientific rationale regarding a point of departure for quantitative risk assessment of PCB DNT, and identify in vitro assays for screening other environmental pollutants for DNT potential.

Changes in the Hypothalamic-Pituitary-Gonadal Axis in Adult Male Rats Poisoned with Proteus and Biscaya Insecticides

BACKGROUND

Insecticides may have negative effects on reproductive organs. Given the interaction between leptin and the hypothalamic-pituitary-gonadal (HPG) axis, we sought to investigate the changes in leptin and the HPG axis in adult male rats poisoned with Proteus and Biscaya insecticides.

METHODS

Our experimental subjects were 110 adult male Wistar rats (80-90 days of age; average weight=200-210 g). They were randomly split into 11 groups of 10 rats: control, sham, and 9 experimental groups namely treatment with 2.75, 5.5, and 11 mg/kg/BW of Proteus, treatment with 1.5, 3, and 6 mg/kg/BW of Biscaya, treatment with 2.75 mg/kg/BW of Proteus+1.5 mg/kg/BW of Biscaya, treatment with 5.5 mg/kg/BW of Proteus+3 mg/kg/BW of Biscaya, and treatment with 11 mg/kg/BW of Proteus+6 mg/kg/BW of Biscaya. Intraperitoneal injections were performed over a 14-day period. For bloodletting at the end of the experiment, blood samples were withdrawn from the rats in order to investigate the serum concentration of luteinizing hormone (LH), follicle-stimulating hormone (FSH), gonadotropin- releasing hormone (GnRH), testosterone, and leptin. The data were analyzed using SPSS, version 16, via ANOVA and the Duncan test. A P value equal to or less than 0.05 was considered statistically significant.

RESULTS

Our comparisons between the experimental groups (average and maximum compound concentrations of Proteus and Biscaya) and the control group showed a significant decrease in the mean serum levels of FSH (P=0.001), LH (P=0.001), GnRH (P=0.001), testosterone (P=0.005), and leptin (P=0.001) in all the experimental groups in a dose-dependent manner.

CONCLUSION

Proteus and Biscaya decreased GnRH, LH, FSH, and testosterone by reducing the serum level of leptin in the hypothalamus in a dose-dependent manner.

Autism spectrum disorders, endocrine disrupting compounds, and heavy metals in amniotic fluid: a case-control study

Background

Evidence has indicated that some non-inherited factors such as exposure to environmental pollutants are associated with neurodevelopment disorders like autism spectrum disorder (ASD). Studies report that endocrine disrupting compounds (EDCs), including polychlorinated biphenyls, organochlorine pesticides, perfluoroalkyl substances (PFAS), and some metals, have adverse effects on the fetal neurodevelopment. The aim of this study was to measure the amniotic fluid (AF) levels of EDCs and metals as well as the receptor transactivities induced by AF and investigate the possible link between prenatal exposure to EDCs and heavy metals and ASD risk.

Methods

In this case-control study, we included AF samples of 75 ASD cases and 135 frequency-matched controls and measured the levels of the endogenous sex hormones, PFAS, and elements including heavy metals. The combined effect of endogenous hormones and EDCs on the receptor of estrogen (ER), androgen (AR), aryl hydrocarbon (AhR), and thyroid hormone-like activity were also determined and expressed as receptor ligand equivalents. We assessed the associations of AF levels of chemicals, sex hormones, and receptor activities with ASD risk using unconditional logistical regression analyses. To control for multiple comparisons, the false discovery rate (FDR) was used and q values less than 0.25 were designated as statistical significance.

Results

PFAS and metals were detectable in AF samples. The ASD cases had significantly lower AF levels of PFAS than controls, and the adjusted odds ratio (OR) was 0.410 (95% CI 0.174, 0.967; p = 0.042; FDR q _value = 0.437) for perfluorooctane sulfonate (PFOS). The principal component, including PFAS congeners, copper, iron, and estrogenic activity, was significantly inversely associated with ASD risk (adjusted OR = 0.100; 95% CI 0.016, 0.630; p = 0.014; FDR q _value = 0.098).Testosterone level in AF weakly associated with ASD risk (adjusted OR = 1.002; 95% CI 1.000, 1.004; p = 0.05). However, after multiple comparison correction, the association was not significant (FDR q _value = 0.437). No significant associations between AF-induced receptor transactivities and ASD risk were observed. The adjusted OR was 2.176 (95%CI 0.115, 41.153) for the ratio of the combined androgenic activity to combined estrogenic activity.

Conclusions

The presence of PFAS and heavy metals in AF indicates that they can cross the placenta. The inverse association between levels of PFAS congeners in AF and ASD risk might relate to the weak estrogenic activities and anti-androgenic activities of PFAS.The observed tendency of positive association between the ratio of combined androgenic effect to the combined estrogenic effect and ASD risk needs further studies to explore whether EDCs together with endogenous hormones play a role in the development of ASD.

Effects of bisphenol analogs on thyroid endocrine system and possible interaction with 17β-estradiol using GH3 cells

This study was conducted using a rat pituitary (GH3) cell line to understand the effects of bisphenol analogs (BPs) on the thyroid endocrine system, in the presence of 17β-estradiol (E2). In the first series of experiments, changes in cell proliferation were examined after exposure to each of ten BPs, in the absence or presence of a median effective concentration (6.4 × 10-10 M) of triiodothyronine (T3). All tested BPs significantly increased cell proliferation, suggesting thyroid hormone (TH) agonistic effects of BPs. BPs did not potentiate the T3-induced cell proliferation at 48 h exposure, while several tested BPs including BPA, BPAF, BPB, BPF, BPS, and BPZ elicited a potentiating effect on the T3-induced cell proliferation at 96 h exposure. These results indicate that TH-antagonistic effects of BPs depend on the tested dose and exposure time. In the second set of experiments, one of the most potent BPs, i.e., BPAF, was selected, and its possible interaction with E2 on the thyroid endocrine system was evaluated. Co-exposure of GH3 cells to 10-12 M E2 showed an additive-like effect. The extent of increase in cell proliferation was more pronounced with a combination of BPAF and E2 than with that of BPA and E2. Significant down-regulation of Trα, Trβ, and Dio2 genes and up-regulation of the Tshβ gene were observed in GH3 cells following co-exposure to BPAF and E2. Our results showed that some BP analogs might influence the thyroid endocrine system, and such perturbation appeared to be enhanced in the presence of E2.

Bisphenol A: Food Exposure and Impact on Human Health

Bisphenol A (BPA) is an industrial compound used extensively to produce synthetic polymers, such as epoxy resins, which are incorporated into the inner coating of metal cans, and also to manufacture polycarbonates with applications in bottles, including bottles of water. Several studies have reported on the transfer of this compound to food. Regarding human exposure to BPA, food intake can be considered the most serious among all the routes, not only because it potentially reaches more people in different age groups (including infants, an especially vulnerable group), but also because it inadvertently occurs over long time periods. BPA is considered an endocrine disruptor and several studies have proposed a relationship between exposure to BPA and the appearance of adverse health effects, such as cancer, infertility, diabetes, and obesity, among others. In 2015 however, the European Food Safety Authority concluded in its last scientific opinion that this compound does not pose any risk to the exposed population's health. Therefore, the EU regards BPA as an authorized product to be used as food contact material. Although BPA intake through food is apparently below the set limits, research into BPA and its potential negative effects is still ongoing. This review contains the most recent in vitro and in vivo studies on BPA toxicity and its harmful effects on health, and it intends to address human exposure to BPA, namely through dietary exposure and its impact on human health.

Chlorinated Polyfluoroalkylether Sulfonates Exhibit Similar Binding Potency and Activity to Thyroid Hormone Transport Proteins and Nuclear Receptors as Perfluorooctanesulfonate

Chlorinated polyfluoroalkylether sulfonates (Cl-PFAESs) have been used as perfluorooctanesulfonate (PFOS) alternatives in the chrome plating industry for years. Although Cl-PFAESs have become ubiquitous environmental contaminants, knowledge on their toxicological mechanism remains very limited. We compared potential thyroid hormone (TH) disruption effects of Cl-PFAESs and PFOS via the mechanisms of competitive binding to TH transport proteins and activation of TH receptors (TRs). Fluorescence binding assays revealed that 6:2 Cl-PFAES, 8:2 Cl-PFAES and F-53B (a mixture of 6:2 and 8:2 Cl-PFAES) all interacted with a TH transport protein transthyretin (TTR), with 6:2 Cl-PFAES showing the highest affinity. It was also found that the chemicals interacted with TRs, with the affinity following the order of 6:2 Cl-PFAES > PFOS > 8:2 Cl-PFAES. In reporter gene assays the chemicals exhibited agonistic activity toward TRs, with the potency of 6:2 Cl-PFAES comparable to that of PFOS. The chemicals also promoted GH3 cell proliferation, with 6:2 Cl-PFAES displaying the highest potency. Molecular docking and molecular dynamic simulation revealed that both Cl-PFAESs fit into the ligand binding pockets of TTR and TRs with the binding modes similar to PFOS. Collectively, our results demonstrate that Cl-PFAESs might cause TH disruption effects through competitive binding to transport proteins and activation of TRs.

Thyroid Hormone-Disrupting Potentials of Major Benzophenones in Two Cell Lines (GH3 and FRTL-5) and Embryo-Larval Zebrafish

Benzophenones (BPs) have been widely used in personal care products (PCPs) such as UV protectants. Sex endocrine-disrupting effects have been documented for some BPs, but, significant knowledge gaps are present for their thyroid-disrupting effects. To investigate the thyroid-disrupting potential of BPs, a rat pituitary (GH3) and thyroid follicle (FRTL-5) cell line were employed on six BPs, i.e., benzophenone (BP), benzophenone-1 (BP-1), benzophenone-2 (BP-2), benzophenone-3 (BP-3), benzophenone-4 (BP-4), and benzophenone-8 (BP-8). Subsequently, zebrafish ( Danio rerio) embryo exposure was conducted for three potent BPs that were identified based on the transcriptional changes observed in the cells. In GH3 cells, all BPs except BP-4 down-regulated the Tshβ, Trhr, and Trβ genes. In addition, some BPs significantly up-regulated the Nis and Tg genes while down-regulating the Tpo gene in FRTL-5 cells. In zebrafish embryo assay conducted for BP-1, BP-3, and BP-8, significant decreases in whole-body T4 and T3 level were observed at 6 day postfertilization (dpf). The up-regulation of the dio1 and ugt1ab genes in the fish suggests that decreased thyroid hormones are caused by changing metabolism of the hormones. Our results show that these frequently used BPs can alter thyroid hormone balances by influencing the central regulation and metabolism of the hormones.

Editor's Highlight: Structure-Based Investigation on the Binding and Activation of Typical Pesticides With Thyroid Receptor

A broad range of pesticides have been reported to interfere with the normal function of the thyroid endocrine system. However, the precise mechanism(s) of action has not yet been thoroughly elucidated. In this study, 21 pesticides were assessed for their binding interactions and the potential to disrupt thyroid homeostasis. In the GH3 luciferase reporter gene assays, 5 of the pesticides tested had agonistic effects in the order of procymidone > imidacloprid > mancozeb > fluroxypyr > atrazine. 11 pesticides inhibited luciferase activity of T3 to varying degrees, demonstrating their antagonistic activity. And there are 4 pesticides showed mixed effects when treated with different concentrations. Surface plasmon resonance (SPR) biosensor technique was used to directly measure the binding interactions of these pesticides to the human thyroid hormone receptor (hTR). 13 pesticides were observed to bind directly with TR, with a KD ranging from 4.80E-08 M to 9.44E-07 M. The association and disassociation of the hTR/pesticide complex revealed 2 distinctive binding modes between the agonists and antagonists. At the same time, a different binding mode was displayed by the pesticides showed mix agonist and antagonist activity. In addition, the molecular docking simulation analyses indicated that the interaction energy calculated by CDOCKER for the agonists and antagonists correlated well with the KD values measured by the surface plasmon resonance assay. These results help to explain the differences of the TR activities of these tested pesticides.

Thyroid Function Disruptors: from nature to chemicals

The modern concept of thyroid disruptors includes man-made chemicals and bioactive compounds from food that interfere with any aspect of the hypothalamus-pituitary-thyroid axis, thyroid hormone biosynthesis and secretion, blood and transmembrane transport, metabolism and local action of thyroid hormones. This review highlights relevant disruptors that effect populations through their diet: directly from food itself (fish oil and polyunsaturated fatty acids, pepper, coffee, cinnamon and resveratrol/grapes), through vegetable cultivation (pesticides) and from containers for food storage and cooking (bisphenol A, phthalates and polybrominated diphenyl ethers). Due to the vital role of thyroid hormones during every stage of life, we review effects from the gestational period through to adulthood, including evidence from in vitro studies, rodent models, human trials and epidemiological studies.

Bisphenol A alternatives bisphenol S and bisphenol F interfere with thyroid hormone signaling pathway in vitro and in vivo

The wide use of the alternatives to bisphenol A (BPA) has raised concerns about their potential toxicities. Considering the disrupting activity of BPA on thyroid hormone (TH) signaling, we investigated whether bisphenol S (BPS) and bisphenol F (BPF), two leading alternatives, could interfere with TH signaling pathway using a series of assays in vitro and in vivo. In the fluorescence competitive binding assay, we found BPS and BPF, like BPA, bound to TH receptors (TRα and TRβ), with the binding potencies an order of magnitude lower than BPA (BPA > BPF > BPS). Molecular docking data also show their binding potencies to TRs. In the coactivator recruitment assay, BPS and BPF recruited coactivator to TRβ but not TRα, with weaker potencies than BPA. Correspondingly, agonistic actions of the three bisphenols in the absence or presence of T3 were observed in the TR-mediated reporter gene transcription assay. Also, all the three bisphenols induced TH-dependent GH3 cell proliferation, whereas BPA and BPF inhibited T3 induction in the presence of T3. As for in vivo assay, the three bisphenols like T3 induced TH-response gene transcription in Pelophylax nigromaculatus tadpoles, but in the presence of T3 altered T3-induced gene transcription in a biphasic concentration-response manner. These results for the first time demonstrate that BPS and BPF, like BPA, have potential to interfere with TH signaling pathway, i.e., they generally activate TH signaling in the absence of T3, but in the presence of TH, display agonistic or/and antagonistic actions under certain condition. Our study highlights the potential risks of BPS and BPF as BPA alternatives.

Contamination trends and factors affecting the transfer of hexabromocyclododecane diastereomers, tetrabromobisphenol A, and 2,4,6-tribromophenol to breast milk in Japan

This study investigated contamination trends and factors affecting the levels of brominated flame retardants (BFRs), including hexabromocyclododecane (HBCD) diastereomers, tetrabromobisphenol A (TBBP-A), and 2,4,6-tribromophenol (2,4,6-TBP), in breast milk in Japan. Breast milk samples (n = 64) were collected from mothers living in six prefectures in Japan. The mean concentrations were 2.2, 0.19, 0.29, 3.0, and 0.59 ng/g lipid weight for α-HBCD, β-HBCD, γ-HBCD, TBBP-A, and 2,4,6-TBP, respectively. Based on the previous studies, the levels of ΣHBCD in Japanese women's milk appear to be increasing, and the levels of TBBP-A are higher than those in other Asian countries. Although ΣHBCD were not correlated to phenolic BFRs, the concentration of β-HBCD was significantly correlated to the concentrations of TBBP-A (r = 0.440, p < 0.01) and 2,4,6-TBP (r = 0.320, p < 0.01). The concentration of γ-HBCD increased significantly with maternal age (r = 0.378, p < 0.01), but the concentrations of the other analytes were not dependent on age. The concentration of α-HBCD was higher in primiparae than in multiparae (p < 0.05), while TBBP-A was higher in multiparae. No significant correlation was found between the phenolic BFR levels in milk and mothers' age, working place, and drinking/smoking habits. These results suggest that exposure to α- and γ-HBCD diastereomers could be affected by maternal age and parity, respectively, because of their different kinetics and sources. Therefore, these factors should be considered when conducting infant risk assessments.

Thyroid-disrupting chemicals and brain development: an update

This review covers recent findings on the main categories of thyroid hormone-disrupting chemicals and their effects on brain development. We draw mostly on epidemiological and experimental data published in the last decade. For each chemical class considered, we deal with not only the thyroid hormone-disrupting effects but also briefly mention the main mechanisms by which the same chemicals could modify estrogen and/or androgen signalling, thereby exacerbating adverse effects on endocrine-dependent developmental programmes. Further, we emphasize recent data showing how maternal thyroid hormone signalling during early pregnancy affects not only offspring IQ, but also neurodevelopmental disease risk. These recent findings add to established knowledge on the crucial importance of iodine and thyroid hormone for optimal brain development. We propose that prenatal exposure to mixtures of thyroid hormone-disrupting chemicals provides a plausible biological mechanism contributing to current increases in the incidence of neurodevelopmental disease and IQ loss.

The Roles of Three Types of Knowledge and Perceived Uncertainty in Explaining Risk Perception, Acceptability, and Self-Protective Response-A Case Study on Endocrine Disrupting Surfactants

The ubiquitous surfactants nonylphenol (NP) and its ethoxylates (NPEOs), which are known as endocrine disrupters, have appeared in the lists of restricted chemical substances, monitoring programs, and environmental quality standards of many countries due to their adverse effects. Recent studies have reported alarming levels of NP, as the final metabolite of NPEOs, in Vietnamese urban waters, whilst response to this issue is negligible. With the aim of addressing how the public perceives and expects to avoid the risk of endocrine disrupting surfactants (EDSs), the study tested the hypothesized roles of specific knowledge, general knowledge, and perceived uncertainty using structural equation modelling. The findings revealed that different types of knowledge played certain roles in explaining risk perception, risk acceptability, and self-protective response, which are distinguished by experience amongst the public. Evidence of the mediating role that perceived uncertainty may play in the decrease of risk perception and the increase of risk unacceptance has been provided. The insights gained from the study may help answer why the public are in favor of taking non-diet-related self-protective measures rather than changing their dietary habits, which illustrates a comparison with the basis of health belief model. The needs for building cognitive capacity amongst the public, particularly pregnant women and young mothers, and risk communication concerning endocrine disrupting contamination linked to reproductive health are highlighted.

Differential neurotoxic effects of in utero and lactational exposure to hydroxylated polychlorinated biphenyl (OH-PCB 106) on spontaneous locomotor activity and motor coordination in young adult male mice

We investigated whether in utero or lactational exposure to 4-hydroxy-2',3,3',4',5'-pentachlorobiphenyl (OH-PCB 106) affects spontaneous locomotor activity and motor coordination in young adult male mice. For in utero exposure, pregnant C57BL/6J mice received 0.05 or 0.5 mg/kg body weight of OH-PCB 106 or corn oil vehicle via gavage every second day from gestational day 10 to 18. For lactational exposure, the different groups of dams received 0.05 or 0.5 mg/kg body weight of OH-PCB 106 or corn oil vehicle via gavage every second day from postpartum day 3 to 13. At 6-7 weeks of age, the spontaneous locomotor activities of male offspring were evaluated for a 24-hr continuous session in a home cage and in an open field for 30-min. Motor coordination function on an accelerating rotarod was also measured. Mice exposed prenatally to OH-PCB 106 showed increased spontaneous locomotor activities during the dark phase in the home cage and during the first 10-min in the open field compared with control mice. Mice exposed lactationally to OH-PCB 106, however, did not show a time-dependent decrease in locomotor activity in the open field. Instead, their locomotor activity increased significantly during the second 10-min block. In addition, mice exposed lactationally to OH-PCB 106 displayed impairments in motor coordination in the rotarod test. These results suggest that perinatal exposure to OH-PCB 106 affects motor behaviors in young adult male mice. Depending on the period of exposure, OH-PCB 106 may have different effects on neurobehavioral development.

Increased risk for hypothyroidism after anticholinesterase pesticide poisoning: a nationwide population-based study

PURPOSE

Previous animal studies have reported that acute anticholinesterase pesticide (organophosphate and carbamate) poisoning may affect thyroid hormones. However, there is no human study investigating the association between hypothyroidism and anticholinesterase pesticide poisoning, and therefore, we conducted a retrospective nationwide population-based cohort study to delineate this issue.

METHODS

We identified 10,372 anticholinesterase pesticide poisoning subjects and matched 31,116 non-anticholinesterase pesticide poisoning subjects between 2003 and 2012 from the Nationwide Poisoning Database and the Longitudinal Health Insurance Database 2000, respectively, in a 1:3 ratio by index date, age, and sex for this study. We compared the cumulative incidence of hypothyroidism between the two cohorts by following up until 2013. Independent predictors for hypothyroidism were also investigated.

RESULTS

In total, 75 (0.72%) anticholinesterase pesticide poisoning subjects and 184 (0.59%) non-anticholinesterase pesticide poisoning subjects were diagnosed with hypothyroidism during the follow-up. Cox proportional hazard regression analysis showed that anticholinesterase pesticide poisoning subjects had higher risk for hypothyroidism than did non-anticholinesterase pesticide poisoning subjects (adjusted hazard ratio: 1.47, 95% confidence interval: 1.11-1.95) after adjusting for age, sex, hypertension, malignancy, liver disease, renal disease, atrial fibrillation or flutter, thyroiditis, goiter, other endocrine disorders, and mental disorder. Stratified analysis showed that anticholinesterase pesticide poisoning subjects had higher risk for hypothyroidism than did non-anticholinesterase pesticide poisoning subjects in terms of the age subgroup of 40-64 years, female sex, past history of goiter, follow-up of <1 month, and anticholinesterase pesticide poisoning subjects without atropine treatment (incidence rate ratio [IRR]: 1.66, 95% confidence interval: 1.20-2.30). Female sex, malignancy, renal disease, thyroiditis, goiter, mental disorder, and anticholinesterase pesticide poisoning without atropine treatment were independent predictors for hypothyroidism.

CONCLUSIONS

Anticholinesterase pesticide poisoning is associated with increased risk for hypothyroidism. Early evaluation of thyroid function in anticholinesterase pesticide poisoning subjects is suggested, especially in subjects without atropine treatment, aged 40-64 years, female sex, and past history of goiter.

Estrogenic Endocrine Disrupting Chemicals Influencing NRF1 Regulated Gene Networks in the Development of Complex Human Brain Diseases

During the development of an individual from a single cell to prenatal stages to adolescence to adulthood and through the complete life span, humans are exposed to countless environmental and stochastic factors, including estrogenic endocrine disrupting chemicals. Brain cells and neural circuits are likely to be influenced by estrogenic endocrine disruptors (EEDs) because they strongly dependent on estrogens. In this review, we discuss both environmental, epidemiological, and experimental evidence on brain health with exposure to oral contraceptives, hormonal therapy, and EEDs such as bisphenol-A (BPA), polychlorinated biphenyls (PCBs), phthalates, and metalloestrogens, such as, arsenic, cadmium, and manganese. Also we discuss the brain health effects associated from exposure to EEDs including the promotion of neurodegeneration, protection against neurodegeneration, and involvement in various neurological deficits; changes in rearing behavior, locomotion, anxiety, learning difficulties, memory issues, and neuronal abnormalities. The effects of EEDs on the brain are varied during the entire life span and far-reaching with many different mechanisms. To understand endocrine disrupting chemicals mechanisms, we use bioinformatics, molecular, and epidemiologic approaches. Through those approaches, we learn how the effects of EEDs on the brain go beyond known mechanism to disrupt the circulatory and neural estrogen function and estrogen-mediated signaling. Effects on EEDs-modified estrogen and nuclear respiratory factor 1 (NRF1) signaling genes with exposure to natural estrogen, pharmacological estrogen-ethinyl estradiol, PCBs, phthalates, BPA, and metalloestrogens are presented here. Bioinformatics analysis of gene-EEDs interactions and brain disease associations identified hundreds of genes that were altered by exposure to estrogen, phthalate, PCBs, BPA or metalloestrogens. Many genes modified by EEDs are common targets of both 17 β-estradiol (E2) and NRF1. Some of these genes are involved with brain diseases, such as Alzheimer's Disease (AD), Parkinson's Disease, Huntington's Disease, Amyotrophic Lateral Sclerosis, Autism Spectrum Disorder, and Brain Neoplasms. For example, the search of enriched pathways showed that top ten E2 interacting genes in AD-APOE, APP, ATP5A1, CALM1, CASP3, GSK3B, IL1B, MAPT, PSEN2 and TNF-underlie the enrichment of the Kyoto Encyclopedia of Genes and Genomes (KEGG) AD pathway. With AD, the six E2-responsive genes are NRF1 target genes: APBB2, DPYSL2, EIF2S1, ENO1, MAPT, and PAXIP1. These genes are also responsive to the following EEDs: ethinyl estradiol (APBB2, DPYSL2, EIF2S1, ENO1, MAPT, and PAXIP1), BPA (APBB2, EIF2S1, ENO1, MAPT, and PAXIP1), dibutyl phthalate (DPYSL2, EIF2S1, and ENO1), diethylhexyl phthalate (DPYSL2 and MAPT). To validate findings from Comparative Toxicogenomics Database (CTD) curated data, we used Bayesian network (BN) analysis on microarray data of AD patients. We observed that both gender and NRF1 were associated with AD. The female NRF1 gene network is completely different from male human AD patients. AD-associated NRF1 target genes-APLP1, APP, GRIN1, GRIN2B, MAPT, PSEN2, PEN2, and IDE-are also regulated by E2. NRF1 regulates targets genes with diverse functions, including cell growth, apoptosis/autophagy, mitochondrial biogenesis, genomic instability, neurogenesis, neuroplasticity, synaptogenesis, and senescence. By activating or repressing the genes involved in cell proliferation, growth suppression, DNA damage/repair, apoptosis/autophagy, angiogenesis, estrogen signaling, neurogenesis, synaptogenesis, and senescence, and inducing a wide range of DNA damage, genomic instability and DNA methylation and transcriptional repression, NRF1 may act as a major regulator of EEDs-induced brain health deficits. In summary, estrogenic endocrine disrupting chemicals-modified genes in brain health deficits are part of both estrogen and NRF1 signaling pathways. Our findings suggest that in addition to estrogen signaling, EEDs influencing NRF1 regulated communities of genes across genomic and epigenomic multiple networks may contribute in the development of complex chronic human brain health disorders.

Influence of Temperature on the Thyroidogenic Effects of Diuron and Its Metabolite 3,4-DCA in Tadpoles of the American Bullfrog (Lithobates catesbeianus)

Temperature is a key variable affecting the timing of amphibian metamorphosis from tadpoles to tetrapods, through the production and subsequent function of thyroid hormones (TH). Thyroid function can be impaired by environmental contaminants as well as temperature. Tadpoles can experience large temperature fluctuations in their habitats and many species are distributed in areas that may be impacted by agriculture. Diuron is a widely used herbicide detected in freshwater ecosystems and may impact endocrine function in aquatic organisms. We evaluated the influence of temperature (28 and 34 °C) on the action of diuron and its metabolite 3,4-dichloroaniline (3,4-DCA) on thyroid function and metamorphosis in tadpoles of Lithobates catesbeianus. Exposure to both compounds induced more pronounced changes in gene expression and plasma 3,3',5-triiodothyronine (T₃) concentrations in tadpoles treated at higher temperature. T₃ concentrations were increased in tadpoles exposed to 200 ng/L of diuron at 34 °C and an acceleration of metamorphosis was observed for the same group. Transcriptomic responses included alteration of thyroid hormone induced bZip protein (thibz), deiodinases (dio2, dio3), thyroid receptors (trα, trβ) and Krüppel-like factor 9 (klf9), suggesting regulation by temperature on TH-gene expression. These results suggest that environmental temperature should be considered in risk assessments of environmental contaminants for amphibian species.

Identification of Thyroid Hormone Disruptors among HO-PBDEs: In Vitro Investigations and Coregulator Involved Simulations

Some hydroxylated polybrominated diphenyl ethers (HO-PBDEs), that have been widely detected in the environment and tissues of humans and wildlife, bind to thyroid hormone (TH) receptor (TR) and can disrupt functioning of systems modulated by the TR. However, mechanisms of TH disrupting effects are still equivocal. Here, disruption of functions of TH modulated pathways by HO-PBDEs was evaluated by assays of competitive binding, coactivator recruitment, and proliferation of GH3 cells. In silico simulations considering effects of coregulators were carried out to investigate molecular mechanisms and to predict potencies for disrupting functions of the TH. Some HO-PBDEs were able to bind to TR with moderate affinities but were not agonists. In GH3 proliferation assays, 13 out of 16 HO-PBDEs were antagonists for the TH. In silico simulations of molecular dynamics revealed that coregulators were essential for identification of TH disruptors. Among HO-PBDEs, binding of passive antagonists induced repositioning of H12, blocking AF-2 (transactivation function 2) and preventing recruitment of the coactivator. Binding of active antagonists exposed the coregulator binding site, which tended to bind to the corepressor rather than the coactivator. By considering both passive and active antagonisms, anti-TH potencies of HO-PBDEs could be predicted from free energy of binding.

Thyroid Hormone Disruption by Water-Accommodated Fractions of Crude Oil and Sediments Affected by the Hebei Spirit Oil Spill in Zebrafish and GH3 Cells

A crude oil and the coastal sediments that were affected by the Hebei Spirit Oil Spill (HSOS) of Taean, Korea were investigated for thyroid hormone disruption potentials. Water-accommodated fractions (WAFs) of Iranian Heavy crude oil, the major oil type of HSOS, and the porewater or leachate of sediment samples collected along the coast line of Taean were tested for thyroid disruption using developing zebrafish and/or rat pituitary GH3 cells. Major polycyclic aromatic hydrocarbons (PAHs) and their alkylated forms were also measured from the test samples. In zebrafish larvae, significant decreases in whole-body thyroxine (T4) and triiodothyronine (T3) levels, along with transcriptional changes of thyroid regulating genes, were observed following 5 day exposure to WAFs. In GH3 cells, transcriptions of thyroid regulating genes were influenced following the exposure to the sediment samples, but the pattern of the regulatory change was different from those observed from the WAFs. Composition of PAHs and their alkylated homologues in the WAFs could partly explain this difference. Our results clearly demonstrate that WAFs of crude oil can disrupt thyroid function of larval zebrafish. Sediment samples also showed thyroid disrupting potentials in the GH3 cell, even several years after the oil spill. Long-term ecosystem consequences of thyroid hormone disruption due to oil spill deserve further investigation.

Exposure to non-persistent pesticides and thyroid function: A systematic review of epidemiological evidence

Numerous pesticides are recognized for their endocrine-disrupting properties. Non-persistent pesticides such as organophosphates, dithiocarbamates and pyrethroids may interfere with thyroid function as suggested by animal studies. However, the influence of chronic exposure to these compounds on thyroidal functions in humans remains to be determined. The present study aimed to review epidemiological evidence for an association between exposure to non-persistent pesticides and circulating levels of thyroid hormones (thyroxin [T4] and triiodothyronine [T3]) and thyroid-stimulating hormone (TSH). A systematic review was conducted using MEDLINE, SCOPUS and Virtual Health Library (BVS) databases. Articles were limited to original studies and reports published in English, Portuguese or Spanish. Nineteen epidemiological studies were identified, 17 of which were cross-sectional, 14 were of occupationally exposed workers and 11 used exposure biomarkers. Fungicides and organophosphates (OP) insecticides were the most studied pesticides. Although methodological heterogeneity between studies was noted, particularly regarding study design, exposure assessment, and control of confounding, most of them showed associations with changes in T3 and T4, and/or TSH levels, while results from a few of these are consistent with experimental data supporting the findings that non-persistent pesticide exposure exerts hypothyroid-like effects. However, reporting quality was moderate to poor in 50% of the studies, particularly regarding method of selection of participants and discussion of external validity. Overall, current knowledge regarding the impact of non-persistent pesticides on human thyroid function is still limited. Given the widespread use of pesticides, future research should assess effects of exposure to currently-used pesticides in cohort studies combining comprehensive questionnaire-based assessment and biomarkers. Investigators need to pay particular attention to exposure during critical windows of brain development and exposure in agricultural populations.

Estrone sulfate and dehydroepiandrosterone sulfate: Transactivation of the estrogen and androgen receptor

Dehydroepiandrosterone sulfate (DHEAS) and estrone sulfate (E1S) are two of the most abundant steroids in the human circulation. The enzyme steroid sulfatase (STS) cleaves the sulfate group of DHEAS and E1S leading to biosynthesis of endogenous hormones such as testosterone and estrone. In the current study we aimed at determining the effect of E1S and DHEAS on estrogen receptor (ER) and androgen receptor (AR) transactivation. Using luciferase reporter gene assays, the ER and AR transactivities of E1S and DHEAS were determined by direct cell exposure; as well as upon extraction from human serum using a method to extract perfluorinated alkyl acids (PFAAs). By direct cell exposure, both E1S and DHEAS transactivated the ER and the AR in dose-dependent manners. The DHEAS-induced AR transactivity could be abolished by the STS inhibitor STX64. Immunoassay analysis confirmed the presence of E1S and DHEAS in the serum PFAA extracts with mean recoveries below 2.5%. For the PFAA extracts of human male and female serum, only the AR was significantly transactivated. The AR transactivity of the sulfated steroids in the extracts was abolished by STX64 to obtain the net PFAA induced xenohormone transactivity, but further cleanup might be needed at high concentrations of E1S.

A comparative assessment of human exposure to tetrabromobisphenol A and eight bisphenols including bisphenol A via indoor dust ingestion in twelve countries

Tetrabromobisphenol A (TBBPA) and eight bisphenol analogues (BPs) including bisphenol A (BPA) were determined in 388 indoor (including homes and microenvironments) dust samples collected from 12 countries (China, Colombia, Greece, India, Japan, Kuwait, Pakistan, Romania, Saudi Arabia, South Korea, U.S., and Vietnam). The concentrations of TBBPA and sum of eight bisphenols (ƩBPs) in dust samples ranged from <1 to 3600 and from 13 to 110,000 ng/g, respectively. The highest TBBPA concentrations in house dust were found in samples from Japan (median: 140 ng/g), followed by South Korea (84 ng/g) and China (23 ng/g). The highest ∑BPs concentrations were found in Greece (median: 3900 ng/g), Japan (2600 ng/g) and the U.S. (2200 ng/g). Significant variations in BPA concentrations were found in dust samples collected from various microenvironments in offices and homes. Concentrations of TBBPA in house dust were significantly correlated with BPA and ∑BPs. Among the nine target chemicals analyzed, BPA was the predominant compound in dust from all countries. The proportion of TBBPA in sum concentrations of nine phenolic compounds analyzed in this study was the highest in dust samples from China (27%) and the lowest in Greece (0.41%). The median estimated daily intake (EDI) of ∑BPs through dust ingestion was the highest in Greece (1.6-17 ng/kg bw/day), Japan (1.3-16) and the U.S. (0.89-9.6) for various age groups. Nevertheless, in comparison with the reported BPA exposure doses through diet, dust ingestion accounted for less than 10% of the total exposure doses in China and the U.S. For TBBPA, the EDI for infants and toddlers ranged from 0.01 to 3.4 ng/kg bw/day, and dust ingestion is an important pathway for exposure accounting for 3.8-35% (median) of exposure doses in China.