Unravelling sex-specific BPA toxicokinetics in children using a pediatric PBPK model

Bisphenol A (BPA) is a widely known endocrine disruptor (ED) found in many children's products such as toys, feeding utensils, and teething rings. Recent epidemiology association studies have shown postnatal BPA exposure resulted in developing various diseases such as diabetes, obesity, and neurodegeneration, etc., later in their lives. However, little is known about its sex-specific metabolism and consequently internal exposure. The aim of this study was to develop a sex-specific pediatric physiologically based pharmacokinetic model (PBPK) for BPA to compare their toxicokinetic differences. First, the published adult PBPK model was re-validated, and then this model was extended by interpolation to incorporate pediatric sex specific physiological and biochemical parameters. We used both the classical body weight and ontogeny-based scaling approach to interpolate the metabolic process. Then, the pharmacokinetic attributes of the models using the two-scaling approach mentioned above were compared with adult model. Further, a sex-specific PBPK model with an ontogeny scaling approach was preferred to evaluate the pharmacokinetic differences. Moreover, this model was used to reconstruct the BPA exposure from two cohorts (Helix and PBAT Cohort) from 7 EU countries. The half-life of BPA was found to be almost the same in boys and girls at the same exposure levels. Our model estimated BPA children's exposure to be about 1500 times higher than the tolerable daily intake (TDI) recently set by European Food Safety Authority (EFSA) i.e., 0.04 ng/kg BW/day. The model demonstrated feasibility of extending the adult PBPK to sex-specific pediatric, thus investigate a gender-specific health risk assessment.

Evaluation of acetamiprid and azoxystrobin residues and their hormonal disrupting effects on male rats using liquid chromatography-tandem mass spectrometry

Endocrine-disrupting compounds as pesticides affect the hormonal balance, and this can result in several diseases. Therefore, the analysis of representative hormones with acetamiprid (AC) and azoxystrobin (AZ) was a good strategy for the investigation of the endocrine-disrupting activity of pesticides. Hence, a sensitive and rapid analytical method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed. The method was validated for the analysis of AC, AZ, estriol, estrone, progesterone, and testosterone in the serum, testis, and liver of rats. The correlation between the residues of pesticides and the disturbance of the endocrine system was evaluated. The different mass parameters, mobile phase types, analytical columns, injection volumes, and extraction solvents were compared to get the lowest limit of detection of the studied compounds. The detection limits of AC, AZ, estriol, estrone, progesterone, and testosterone were 0.05, 0.05, 1.0, 10, and 1.0 ng/ml, respectively. The method developed was applied to evaluate the changes in these hormones induced by the duration of exposure to AC and AZ in rat testis and serum. The hormones level in rat serum and testis had a significant decrease as they were oral gavage treated with different high concentrations of studied pesticides. Both pesticides were distributed in the body of rats by the multi-compartment model (liver, testis, and serum).

The adsorption, kinetics, and interaction mechanisms of various types of estrogen on electrospun polymeric nanofiber membranes

This study focuses on the adsorption kinetics of four highly potent sex hormones (estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (EE2), and estriol (E3)), present in water reservoirs, which are considered a major cause of fish feminization, low sperm count in males, breast and ovarian cancer in females induced by hormonal imbalance. Herein, electrospun polymeric nanostructures were produced from cellulose acetate, polyamide, polyethersulfone, polyurethanes (918 and elastollan), and polyacrylonitrile (PAN) to simultaneously adsorbing these estrogenic hormones in a single step process and to compare their performance. These nanofibers possessed an average fiber diameter in the range 174-330 nm and their specific surface area ranged between 10.2 and 20.9 m²g^-1. The adsorption-desorption process was investigated in four cycles to determine the effective reusability of the adsorption systems. A one-step high-performance liquid chromatography technique was developed to detect and quantify concurrently each hormone present in the solution. Experimental data were obtained to determine the adsorption kinetics by applying pseudo-first-order, pseudo-second-order and intraparticle diffusion models. Findings showed that E1, E2 and EE2 best fitted pseudo-second-order kinetics, while E3 followed pseudo-first-order kinetics. It was found that polyurethane Elastollan nanofibers had maximum adsorption capacities of 0.801, 0.590, 0.736 and 0.382 mg g^-1for E1, E2, EE2 and E3, respectively. In addition, the results revealed that polyurethane Elastollan nanofibers had the highest percentage efficiency of estrogens removal at ∼58.9% due to its strong hydrogen bonding with estrogenic hormones, while the least removal efficiency for PAN at ∼35.1%. Consecutive adsorption-desorption cycles demonstrated that polyurethane maintained the best efficiency, even after being repeatedly used four times compared to the other polymers. Overall, the findings indicate that all the studied nanostructures have the potential to be effective adsorbents for concurrently eradicating such estrogens from the environment.

Endocrine disruption caused by the aquatic exposure to aluminum and manganese in Astyanax altiparanae (Teleostei: Characidae) females during the final ovarian maturation

Aluminum (Al) and manganese (Mn) can be toxic to aquatic biota and cause endocrine disruption in fish, affecting reproduction. This study evaluates the physiological responses of the ray-finned teleost fish Astyanax altiparanae vitellogenic females after acute exposure (96 h) to Al and Mn (alone and combined) in acid pH followed by the same period of exposure to metal-free water in neutral pH. The aim of this second period of exposure was to assess the recovery capacity from the toxic effects these metals. Five experimental groups were established: a control in neutral pH (Ctrl), and acidic pH (Ac), aluminum (Al), manganese (Mn), and Al + Mn groups, maintaining the acidic pH in the groups to which metals were added. The following biological parameters were evaluated: metal tissue concentration, relative fecundity (RF: absolute fecundity/body mass). Plasma levels of cortisol (proxy for stress) and 17α hydroxyprogesterone (17α-OHP), and gene expression of pituitary lhβ mRNA (proxies for final maturation) were measured to evaluate endocrine disruption. In the synchronic exposure, the presence of Mn potentiated the accumulation of Al in gills. The females from acidic pH and Al groups showed a reduced RF. Exposure to Al and Mn triggered an endocrine disruption response, evidenced by a decrease in the plasma concentration of 17α-OHP and cortisol. Despite this anti-steroidogenic effect, no changes occurred in the pituitary gene expression of lhβ. The endocrine changes and the metal accumulation were temporary, while the impacts on RF under the experimental conditions suggest permanent impairment in the reproduction of this species.

Human-relevant concentrations of the antifungal drug clotrimazole disrupt maternal and fetal steroid hormone profiles in rats

Clotrimazole is a non-prescription and broad-spectrum antifungal drug sold under brand names such as Canesten® and Lotrimin®. It is used to treat different types of fungal infections, from oral thrush to athlete's foot and vaginal mycosis. The level of exposure to clotrimazole is uncertain, as the exact usage amongst self-medicating patients is unclear. Recent studies have raised potential concern about the unsupervised use of clotrimazole during pregnancy, especially since it is a potent inhibitor of CYP enzymes of the steroidogenesis pathway. To address some of these concerns, we have assessed the effects of intrauterine exposure to clotrimazole on developing rat fetuses. By exposing pregnant rats to clotrimazole 25 or 75 mg/kg bw/day during gestation days 7-21, we obtained internal fetal concentrations close to those observed in humans. These in vivo data are in strong agreement with our physiologically-based pharmacokinetic (PBK)-modelled levels. At these doses, we observed no obvious morphological changes to the reproductive system, nor shorter male anogenital distance; a well-established morphometric marker for anti-androgenic effects in male offspring. However, steroid hormone profiles were significantly affected in both maternal and fetal plasma, in particular pronounced suppression of estrogens was seen. In fetal testes, marked up-concentration of hydroxyprogesterone was observed, which indicates a specific action on steroidogenesis. Since systemic clotrimazole is rapidly metabolized in humans, relevant exposure levels may not in itself cause adverse changes to the reproductive systems. Its capacity to significantly alter steroid hormone concentrations, however, suggests that clotrimazole should be used with caution during pregnancy.

Epigenetic Modifications Associated with Exposure to Endocrine Disrupting Chemicals in Patients with Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) remains a significant clinical and public health issue due to its increasing prevalence and the possibility for numerous short- and long-term complications. The growing incidence of GDM seems to coincide with the widespread use of endocrine disrupting chemicals (EDCs). The extensive production and common use of these substances in everyday life has resulted in constant exposure to harmful substances from the environment. That may result in epigenetic changes, which may manifest themselves also after many years and be passed on to future generations. It is important to consider the possible link between environmental exposure to endocrine disrupting chemicals (EDCs) during pregnancy, epigenetic mechanisms and an increased risk for developing gestational diabetes mellitus (GDM). This manuscript attempts to summarize data on epigenetic changes in pregnant women suffering from gestational diabetes in association with EDCs. There is a chance that epigenetic marks may serve as a tool for diagnostic, prognostic, and therapeutic measures.

Toward a better understanding of the effects of endocrine disrupting compounds on health: Human-relevant case studies from sheep models

There are many challenges to overcome in order to properly understand both the exposure to, and effects of, endocrine disruptors (EDs). This is particularly true with respect to fetal life where ED exposures are a major issue requiring toxicokinetic studies of materno-fetal exchange and identification of pathophysiological consequences. The sheep, a large, monotocous, species, is very suitable for in utero fetal catheterization allowing a modelling approach predictive of human fetal exposure. Predicting adverse effects of EDs on human health is frequently impeded by the wide interspecies differences in the regulation of endocrine functions and their effects on biological processes. Because of its similarity to humans as regards gestational and thyroid physiologies and brain ontogeny, the sheep constitutes a highly appropriate model to move one step further on thyroid disruptor hazard assessment. As a grazing animal, the sheep has also proven to be useful in the evaluation of the consequences of chronic environmental exposure to "real-life" complex mixtures at different stages of the reproductive life cycle.

Critical Review of Read-Across Potential in Testing for Endocrine-Related Effects in Vertebrate Ecological Receptors

Recent regulatory testing programs have been designed to evaluate whether a chemical has the potential to interact with the endocrine system and could cause adverse effects. Some endocrine pathways are highly conserved among vertebrates, providing a potential to extrapolate data generated for one vertebrate taxonomic group to others (i.e., biological read-across). To assess the potential for biological read-across, we reviewed tools and approaches that support species extrapolation for fish, amphibians, birds, and reptiles. For each of the estrogen, androgen, thyroid, and steroidogenesis (EATS) pathways, we considered the pathway conservation across species and the responses of endocrine-sensitive endpoints. The available data show a high degree of confidence in the conservation of the hypothalamus-pituitary-gonadal axis between fish and mammals and the hypothalamus-pituitary-thyroid axis between amphibians and mammals. Comparatively, there is less empirical evidence for the conservation of other EATS pathways between other taxonomic groups, but this may be due to limited data. Although more information on sensitive pathways and endpoints would be useful, current developments in the use of molecular target sequencing similarity tools and thoughtful application of the adverse outcome pathway concept show promise for further advancement of read-across approaches for testing EATS pathways in vertebrate ecological receptors. Environ Toxicol Chem 2020;39:739-753. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Computational evaluation of interactions between organophosphate esters and nuclear hormone receptors

Organophosphate esters (OPEs) have gained considerable interest from many environmental chemists and toxicologists due to their frequent detection in the environment and potential adverse effects on health. Nuclear hormone receptors (NHRs) were found to mediate many of their adverse effects. However, our knowledge regarding the direct binding and interaction between OPEs and NHRs is limited. In this study, Endocrine Disruptome, an online computational tool based on the technique of inverse docking, was used to calculate the binding affinity score of 25 individual OPEs with 12 different human NHRs. Results showed that 20% of potential binding interactions between the OPEs and NHRs had medium-to-high probabilities. The accuracy, sensitivity and specificity of the predictions were 78.8, 60.0 and 80.9%, respectively. OPEs with a benzene ring were more active than those without, among which, tri-o-tolyl phosphate and tri-m-tolyl phosphate displayed the highest activities, suggesting that they might pose the greatest potential risks for interference with endocrine functions. In addition, the antagonistic conformations of androgen receptor and estrogen receptor β were found to be the two most vulnerable NHR conformations. Our findings can further the understanding about the health risk(s) of OPEs.

Development and evaluation of a harmonized whole body physiologically based pharmacokinetic (PBPK) model for flutamide in rats and its extrapolation to humans

By their definition, inadvertent exposure to endocrine disrupting compounds (EDCs) intervenes with the endocrine signalling system, even at low dose. On the one hand, some EDCs are used as important pharmaceutical drugs that one would not want to dismiss. On the other hand, these pharmaceutical drugs are having off-target effects and increasingly significant exposure to the general population with unwanted health implications. Flutamide, one of the top pharmaceutical products marketed all over the world for the treatment of prostate cancer, is also a pollutant. Its therapeutic action mainly depends on targeting the androgen receptors and inhibiting the androgen action that is essential for growth and survival of prostate tissue. Currently flutamide is of concern with respect to its categorization as an endocrine disruptor. In this work we have developed a physiologically based pharmacokinetic (PBPK) model of flutamide that could serve as a standard tool for its human risk assessment. First we built the model for rat (where many parameters have been measured). The rat PBPK model was extrapolated to human where the re-parameterization involved human-specific physiology, metabolic kinetics derived from in-vitro studies, and the partition coefficient same as the rat model. We have harmonized the model by integrating different sets of in-vitro, in-vivo and physiological data into a PBPK model. Then the model was used to simulate different exposure scenarios and the results were compared against the observed data. Both uncertainty and sensitivity analysis was done. Since this new whole-body PBPK model can predict flutamide concentrations not only in plasma but also in various organs, the model may have clinical applications in efficacy and safety assessment of flutamide. The model can also be used for reverse dosimetry in the context of interpreting the available biomonitoring data to estimate the degree to which the population is currently being exposed, and a tool for the pharmaceutical companies to validate the estimated Permitted Daily Exposure (PDE) for flutamide.

The challenging use and interpretation of blood biomarkers of exposure related to lipophilic endocrine disrupting chemicals in environmental health studies

The use of exposure biomarkers has been growing during the last decades, being considered the 'gold-standard' approach for individual exposure assessment to environmental chemicals. However, lipophilic endocrine disrupting chemicals (LEDC) have specific physicochemical and biological properties implying particular analytical challenges and interpretative caveats. The epidemiological literature is therefore afflicted by methodological inconsistencies and results divergences, in part due to recognised sources of exposure measurement error and misinterpretation of results. The aim of the present review is to identify external and endogenous sources of variability and uncertainty associated with the LEDC blood biomarkers in epidemiological studies. The dynamic nature of blood and an overview of the known mechanisms of transport, storage and partition of LEDCs in the organism are first described. The external sources of variability and uncertainty introduced at pre-analytical and analytical level are subsequently presented. Subsequently, we present some specific cases where the dynamics of lipids and LEDCs may be substantially modified and thus, the interpretation of biomarkers can be particularly challenging. The environmental obesogens as source of biomarkers variability is also discussed in the light of the most recent findings. Finally, different modelling approaches (statistical and pharmacokinetic models) proposed to improve the use and interpretation of biomarkers are appraised.

The Effect of Dissolved Organic Matter (DOM) on the Release and Distribution of Endocrine-Disrupting Chemicals (Edcs) from Sediment under Hydrodynamic Forces, A Case Study of Bisphenol A (BPA) and Nonylphenol (NP)

Endocrine-disrupting chemicals (EDCs) that exist in the aquatic system bring severe environmental risks. In this study, we investigate the dissolved organic matter (DOM) effect on the release and distribution of EDCs under varied hydrodynamic conditions. A water chamber mesocosm was designed to simulate the hydrodynamic forces in a shallow lake. The contents of bisphenol A (BPA) and nonylphenol (NP) in colloid-bound and soluble phases were measured under four increasing hydrodynamic intensities that were 5%, 20%, 50%, and 80% of the critical shear stress. The total BPA and NP contents in overlying water grew linearly with the hydrodynamic intensity (R² = 0.997 and 0.987), from 108.28 to 415.92 ng/L of BPA and 87.73 to 255.52 ng/L of NP. The exponential relationships of EDC content and hydrodynamic intensity in soluble phase (R² = 0.985 of BPA and 0.987 of NP) and colloid phase (R² = 0.992 of BPA and 0.995 of NP) were also detected. The DOM concentrations in colloid-bound phase (cDOM) and in soluble phase (sDOM) were measured and the linear relationships with BPA content (R² = 0.967 of cDOM and 0.989 of sDOM) and NP content (R² = 0.978 of cDOM and 0.965 of sDOM) were detected. We analyzed the ratio (αDOM) of sDOM and cDOM that grew logarithmically with the hydrodynamic intensity (R² = 0.999). Moreover, the ratio (αEDCs) of BPA and NP contents in soluble and colloid-bound phases varied differently with αDOM. The results suggested that BPA tended to be in the soluble phase and NP tended to be in the colloid-bound phase due to the increasing value of αDOM.

Bisphenol S instead of Bisphenol A: Toxicokinetic investigations in the ovine materno-feto-placental unit

Bisphenol S (BPS) is widely used as a substitute for Bisphenol A in consumer products. Despite its potential endocrine-disrupting effects and widespread exposure, toxicokinetic data, particularly during the critical period of pregnancy, are not available for BPS. The objectives of our study were to evaluate the mechanisms determining fetal exposure to BPS and to BPS glucuronide (BPSG) and to compare them with those prevailing for BPA. The disposition of BPS and BPSG was evaluated in the materno-fetal unit of the catheterized pregnant ewe model, following intravenous administrations of BPS and BPSG to mothers and their fetuses. In a second experiment, the rate of BPS accumulation in the fetal compartment was determined under steady-state conditions after repeated intravenous BPS administrations to the mother. In the maternal compartment, BPS was mainly metabolized into BPSG and totally eliminated in urine. Only 0.40% of the maternal dose was transferred to the fetus. However, once in the fetal compartment, 26% of the fetal dose was rapidly eliminated through placental transfer, while 46% of BPS was metabolized into BPSG which remained trapped in the fetal compartment. Thus, the elimination of BPSG from the fetal compartment required its back-conversion into bioactive BPS, leading to an 87% enhancement of the fetal BPS exposure. Our findings demonstrate that, despite the low materno-fetal placental transfer of BPS, this substitute for BPA is able to accumulate in the fetal compartment after repeated maternal exposure, leading to chronic fetal exposure to BPS in a range of concentrations similar to those of BPA.

Verifying community-wide exposure to endocrine disruptors in personal care products - In quest for metabolic biomarkers of exposure via in vitro studies and wastewater-based epidemiology

This study aimed to identify human specific metabolites of selected known or suspected endocrine disruptors (EDCs), mainly UV filters, used in personal care and consumer products whose metabolism has hardly been explored and to select suitable candidate biomarkers for human exposure studies using wastewater based epidemiology (WBE). The analysis of metabolic biomarkers of target chemicals is crucial in order to distinguish between internal and external exposure, since many sources contribute to chemicals being discharged into wastewater. This was achieved through the employment of a new analytical framework for verification of biomarkers of exposure to chemicals combining human biomonitoring and water fingerprinting. Eight EDCs with unknown metabolic pathways (benzophenone-1 (BP-1); benzophenone-2 (BP-2); 4,4'-dihydroxybenzophenone (4,4'-DHBP); 4-benzylphenol (4-BenzPh); homosalate (HO); octocrylene (OC); 3-benzylidene camphor (3-BC), and two EDCs with known metabolism (bisphenol A (BPA) and benzophenone-3 (BP-3)) were tested. The biotransformation observed consisted mainly of phase I processes such as hydrolysis and hydroxylation together with phase II conjugation reactions such as sulphation and glucuronidation. Only two chemicals (BP-1, BP-3) were identified in urine and three chemicals (BPA, BP-1, BP-3) in wastewater. Five newly discovered metabolites (HO-Met1, OC-Met1, 4-BenzPh-Met4, 4-BenzPh-Met5 and 4-BenzPh-Met6) and one previously known metabolite (BPA-Met3) were detected in tested urine/wastewater samples from five WWTPs serving large communities ranging between 17 and 100 thousand inhabitants. The presence of metabolic biotransformation products of OC, 4-BenzPh, BPA and HO in wastewater provides evidence for internal exposure of studied populations to these chemicals.

Alterations of cytochrome P450 and the occurrence of persistent organic pollutants in tilapia caged in the reservoirs of the Iguaçu River

Environmental chemicals originating from human activities, such as persistent organic pollutants (POPs), may interfere with the endocrine system of aquatic organisms. The effect of these chemicals on biota and human populations is of high public concern but remains poorly understood, especially in aquatic environments of South America. The aim of this study was to investigate the bioavailability of POPs and the related effects in caged male tilapia (Oreochromis niloticus) in four cascading reservoirs of the Iguaçu River, Southern Brazil. POPs including organochlorine pesticides (OCPs), polychlorinated biphenyl (PCBs), and polybrominated diphenyl ethers (PBDEs) were determined in the reservoir water and tissue samples of tilapia after two months of exposure. The PCB levels in water (14.7 ng L^-1) were 14 times higher than the limits permitted by the Brazilian legislation in the Salto Santiago (SS) reservoir. Similarly, concentrations of aldrin and its metabolites (6.05 ng L^-1) detected in the water sample of the Salto Osório (SO) reservoir were also above the permitted limits. RT-qPCR analysis revealed different transcript levels of cytochrome P450 enzymes (CYP1A and CYP3A) in the liver among the four groups, with induced activity in tilapia from the SS reservoir. Quantification of the CYP3A mRNA expression and catalytic activity showed higher values for fish caged at the SS reservoir. The fish from this site also had a higher number of eosinophils observed in the testes. Although overt measurements of endocrine disruption were not observed in caged fish, alteration of CYP enzymes with co-occurrence of organochlorine contaminants in water may suggest bioavailability of contaminants from agricultural sources to biota. Additional studies with feral or caged animals for a longer duration may be necessary to evaluate the risks of the waterways to humans and wildlife.

Physiologically Based Pharmacokinetic (PBPK) Modeling of the Bisphenols BPA, BPS, BPF, and BPAF with New Experimental Metabolic Parameters: Comparing the Pharmacokinetic Behavior of BPA with Its Substitutes

BACKGROUND

The endocrine disrupting chemical bisphenol A (BPA) has been facing stricter regulations in recent years. BPA analogs, such as the bisphenols S, F, and AF (BPS, BPF, and BPAF) are increasingly used as replacement chemicals, although they were found to exert estrogenic effects similar to those of BPA. Research has shown that only the parent compounds have affinity to the estrogen receptors, suggesting that the pharmacokinetic behavior of bisphenols (BPs) can influence their potency.

OBJECTIVES

Our goal was to compare the pharmacokinetic behaviors of BPA, BPS, BPF, and BPAF for different age groups after environmentally relevant external exposures by taking into account substance-specific metabolism kinetics and partitioning behavior. This comparison allowed us to investigate the consequences of replacing BPA with other BPs.

METHODS

We readjusted a physiologically based pharmacokinetic (PBPK) model for peroral exposure to BPA and extended it to include dermal exposure. We experimentally assessed hepatic and intestinal glucuronidation kinetics of BPS, BPF, and BPAF to parametrize the model for these BPs and calibrated the BPS model with a biomonitoring study. We used the PBPK models to compare resulting internal exposures and focused on females of childbearing age in a two-dimensional Monte Carlo uncertainty analysis.

RESULTS

Within environmentally relevant concentration ranges, BPAF and BPS were glucuronized at highest and lowest rates, respectively, in the intestine and the liver. The predominant routes of BPS and BPAF exposure were peroral and dermal exposure, respectively. The calibration of the BPS model with measured concentrations showed that enterohepatic recirculation may be important. Assuming equal external exposures, BPS exposure led to the highest internal concentrations of unconjugated BPs.

CONCLUSIONS

Our data suggest that the replacement of BPA with structural analogs may not lower the risk for endocrine disruption. Exposure to both BPS and BPAF might be more critical than BPA exposure, if their respective estrogenic potencies are taken into account. https://doi.org/10.1289/EHP2739.

In silico binding of 4,4'-bisphenols predicts in vitro estrogenic and antiandrogenic activity

Bisphenols, anthropogenic pollutants, leach from consumer products and have potential to be ingested and are excreted in waste. The endocrine disrupting effects of highly manufactured bisphenols (BPA, BPS, and BPF) are known, however the activities of others are not. Here, the estrogenic and androgenic activities of a series of 4,4'-bisphenols that vary at the inter-connecting bisphenol bridge were determined (BPA, BPB, BPBP, BPC2, BPE, BPF, BPS, and BPZ) and compared to in silico binding to estrogen receptor-alpha and the androgen receptor. Bioassay results showed the order of estrogenicity (BPC2 (strongest) > BPBP > BPB > BPZ > BPE > BPF > BPA > BPS, r²  = 0.995) and anti-androgenicity (BPC2 (strongest) > BPE, BPB, BPA, BPF, and BPS, r²  = 0.996) correlated to nuclear receptor binding affinities. Like testosterone and the anti-androgen hydroxyflutamide, bisphenol fit in the ligand-binding domain through hydrogen-bonding at residues Thr877 and Asn705, but also interacted at either Cys784/Ser778 or Gln711 through the other phenol ring. This suggests the 4,4'-bisphenols, like hydroxyflutamide, are androgen receptor antagonists. Hydrogen-bond trends between ERα and the 4,4'-bisphenols were limited to residue Glu353, which interacted with the -OH of one phenol and the -OH of the A ring of 17β-estradiol; hydrogen-bonding varied at the -OH of ring D of 17β-estradiol and the second phenol -OH group. While both estrogen and androgen bioassays correlated to in silico results, conservation of hydrogen-bonding residues in the androgen receptor provides a convincing picture of direct antagonist binding by 4,4'-bisphenols.

Exposure to bisphenols and parabens during pregnancy and relations to steroid changes

BACKGROUND

The harmful effects of endocrine disrupting compounds (EDCs) on human health are generally well-known, and exposure during fetal development may have lasting effects. Fetal exposure to bisphenol A (BPA) has been recently relatively well-studied; however, less is known about alternatives such as bisphenol S (BPS), bisphenol F (BPF) and bisphenol AF (BPAF), which have started to appear in consumer products. Parabens are another widespread group of EDCs, with confirmed transplacental passage. The usage of many cosmetic, pharmaceutical and consumer products during the pregnancy that may contain parabens and bisphenols has led to the need for investigation.

OBJECTIVES

To shed more light into the transplacental transport of BPA, its alternatives, and parabens, and to study their relation to fetal steroidogenesis.

METHODS

BPA, BPS, BPF, BPAF, methylparaben, ethylparaben, propylparaben, butylparaben, benzylparaben and 15 steroids including estrogens, corticoids, androgens and immunomodulatory ones were determined in 27 maternal (37th week of pregnancy) and cord plasma samples using liquid chromatography - tandem mass spectrometry methods.

RESULTS

In cord blood, significantly higher BPA levels (p=0.0455) were observed compared to maternal plasma. The results from multiple regression models showed that in cord blood, methylparaben (β=-0.027, p=0.027), propylparaben (β=-0.025, p=0.03) and the sum of all measured parabens (β=-0.037, p=0.015) were inversely associated with testosterone levels.

CONCLUSION

To the best of our knowledge, this is the first study reporting the simultaneous detection of BPA, alternative bisphenols, parabens and steroids in maternal and cord plasma. Our study confirmed the transplacental transport of BPA, with likely accumulation in the fetal compartment. The negative association of cord blood parabens and testosterone levels points to possible risks with respect to importance of testosterone for prenatal male development.

Nitrate induces a type 1 diabetic profile in alligator hatchlings

Type 1 diabetes (T1D) is a chronic autoimmune disease that affects 1 in 300 children by age 18. T1D is caused by inflammation-induced loss of insulin-producing pancreatic beta cells, leading to high blood glucose and a host of downstream complications. Although multiple genes are associated with T1D risk, only 5% of genetically susceptible individuals actually develop clinical disease. Moreover, a growing number of T1D cases occur in geographic clusters and among children with low risk genotypes. These observations suggest that environmental factors contribute to T1D etiology. One potential factor, supported primarily by epidemiological studies, is the presence of nitrate and nitrite in drinking water. To test this hypothesis, female hatchling alligators were exposed to environmentally relevant concentrations of nitrate in their tank water (reference, 10mg/L, or 100mg/L NO₃-N) from hatch through 5 weeks or 5 months of age. At each time point, endpoints related to T1D were investigated: plasma levels of glucose, triglycerides, testosterone, estradiol, and thyroxine; pancreas, fat body, and thyroid weights; weight gain or loss; presence of immune cells in the pancreas; and pancreatic beta cell number, assessed by antibody staining of nkx6.1 protein. Internal dosing of nitrate was confirmed by measuring plasma and urine nitrate levels and whole blood methemoglobin. Cluster analysis indicated that high nitrate exposure (most animals exposed to 100mg/L NO3-N and one alligator exposed to 10mg/L NO3-N) induced a profile of endpoints consistent with early T1D that could be detected after 5 weeks and was more strongly present after 5 months. Our study supports epidemiological data correlating elevated nitrate with T1D onset in humans, and highlights nitrate as a possible environmental contributor to the etiology of T1D, possibly through its role as a nitric oxide precursor.

Prenatal exposure estimation of BPA and DEHP using integrated external and internal dosimetry: A case study

Prenatal exposure to Endocrine disruptors (EDs), such as Bisphenol A (BPA) and di (2-ethylhexyl) phthalate (DEHP), has been associated with obesity and diabetes diseases in childhood, as well as reproductive, behavioral and neurodevelopment problems. The aim of this study was to estimate the prenatal exposure to BPA and DEHP through food consumption for pregnant women living in Tarragona County (Spain). Probabilistic calculations of prenatal exposure were estimated by integrated external and internal dosimetry modelling, physiologically based pharmacokinetic (PBPK) model, using a Monte-Carlo simulation. Physical characteristic data from the cohort, along with food intake information from the questionnaires (concentrations of BPA and DEHP in different food categories and the range of the different food ratios), were used to estimate the value of the total dietary intake for the Tarragona pregnancy cohort. The major contributors to the total dietary intake of BPA were canned fruits and vegetables, followed by canned meat and meat products. In turn, milk and dairy products, followed by ready to eat food (including canned dinners), were the most important contributors to the total dietary intake of DEHP. Despite the dietary variations among the participants, the intakes of both chemicals were considerably lower than their respective current tolerable daily intake (TDI) values established by the European Food Safety Authority (EFSA). Internal dosimetry estimates suggest that the plasma concentrations of free BPA and the most important DEHP metabolite, mono (2-ethylhexyl) phthalate (MEHP), in pregnant women were characterized by transient peaks (associated with meals) and short half-lives (< 2h). In contrast, fetal exposure was characterized by a low and sustained basal BPA and MEHP concentration due to a lack of metabolic activity in the fetus. Therefore, EDs may have a greater effect on developing organs in young children or in the unborn child.

Distribution of Non-Persistent Endocrine Disruptors in Two Different Regions of the Human Brain

Non-persistent endocrine disrupting chemicals (npEDCs) can affect multiple organs and systems in the body. Whether npEDCs can accumulate in the human brain is largely unknown. The major aim of this pilot study was to examine the presence of environmental phenols and parabens in two distinct brain regions: the hypothalamus and white-matter tissue. In addition, a potential association between these npEDCs concentrations and obesity was investigated. Post-mortem brain material was obtained from 24 individuals, made up of 12 obese and 12 normal-weight subjects (defined as body mass index (BMI) > 30 and BMI < 25 kg/m², respectively). Nine phenols and seven parabens were measured by isotope dilution TurboFlow-LC-MS/MS. In the hypothalamus, seven suspect npEDCs (bisphenol A, triclosan, triclocarban and methyl-, ethyl-, n-propyl-, and benzyl paraben) were detected, while five npEDCs (bisphenol A, benzophenone-3, triclocarban, methyl-, and n-propyl paraben) were found in the white-matter brain tissue. We observed higher levels of methylparaben (MeP) in the hypothalamic tissue of obese subjects as compared to controls (p = 0.008). Our findings indicate that some suspected npEDCs are able to cross the blood-brain barrier. Whether the presence of npEDCs can adversely affect brain function and to which extent the detected concentrations are physiologically relevant needs to be further investigated.

Prolonged Exposure to Bisphenol A from Single Dermal Contact Events

Bisphenol A (BPA) is an endocrine disruptor frequently detected in human biofluids. Dermal absorption of BPA from thermal paper receipts occurs but BPA pharmacokinetics following dermal exposure is not understood. To compare the pharmacokinetics of dermal and dietary BPA exposure, six male participants handled simulated receipts containing relevant levels of BPA (isotope-labeled BPA-d₁₆) for 5 min, followed by hand-washing 2 h later. Urine (0-48 h) and serum (0-7.5 h) were monitored for free and total BPA-d₁₆. One week later, participants returned for a dietary administration with monitoring as above. One participant repeated the dermal administration with extended monitoring of urine (9 days) and serum (2 days). After dietary exposure, urine total BPA-d₁₆ peaked within 5 h and quickly cleared within 24 h. After dermal exposure, cumulative excretion increased linearly for 2 days, and half the participants still had detectable urinary total BPA-d₁₆ after 1 week. The participant repeating the dermal exposure had detectable BPA-d₁₆ in urine for 9 days, showed linear cumulative excretion over 5 days, and had detectable free BPA-d₁₆ in serum. Proportions of free BPA-d₁₆ in urine following dermal exposure (0.71%-8.3% of total BPA-d₁₆) were generally higher than following the dietary exposure (0.29%-1.4%). Compared to dietary BPA exposure, dermal absorption of BPA leads to prolonged exposure and may lead to higher proportions of unconjugated BPA in systemic circulation.

[Toxicological characteristics of Ochratoxin A and its impact on male reproduction]

Ochratoxin A (OTA) is found not only nephrotoxic, teratogenic, neurotoxic, and immunotoxic, but also reprotoxic for human and animals. In the recent decade, more attention has been paid to the impact of OTA on human reproduction and the studies of its underlying mechanisms. Many studies show that OTA affects the function of the reproductive system by acting as an endocrine disrupter and, as a testicular toxin, decreases sperm quality and even induces testis cancer. This review summarizes the toxicological characteristics and toxicokinetic process of OTA as well as recent progress in the studies of various toxic effects of OTA and their underlying mechanisms, hoping to call the attention from more people to the toxicity of OTA to male reproductive health.

Chronic exposures to fungicide pyrimethanil: multi-organ effects on Italian tree frog (Hyla intermedia)

Amphibian habitats are easily contaminated by several pollutants, and in agricultural landscapes the likely exposure scenario is represented by pesticides. Many of these substances are known or suspected to act as endocrine disrupting chemicals (EDCs). The goal of the present study was to assess the effects of pyrimethanil, a common-used but also overlooked fungicide, on liver, kidney and gonadal differentiation of Hyla intermedia. Through a multi-organ evaluation, we demonstrated that a long term exposure to two environmentally relevant concentrations of pyrimethanil (5 and 50 µg/L) elicits a range of toxic responses. First we showed that pyrimethanil induces underdevelopment of ovaries and interferes with normal sexual differentiation, thus revealing the endocrine disruption potential of this fungicide. Moreover we revealed that all considered organs are seriously affected by this fungicide and both necrosis and apoptosis contribute to the histological response. This is the first report on the effects of pyrimethanil on gonads, liver and kidney histology of a non-model species and it demonstrates that the hazardous properties of this fungicide can result from several pathological processes affecting different key compartments of amphibian.

Accumulation of endocrine disrupting chemicals in the liver of Diplodus sargus sargus in Torre Guaceto Natural Reserve

Studies on the quality of marine environments in Italy have traditionally favoured heavily impacted areas, such as harbours and industrial areas, while there are few investigations aimed at the evaluation of the presence of organic pollutants in the areas of marine reserve. The aim of this study was to determine endocrine-disrupting compounds (EDCs) in the liver of white seabreams (Diplodus sargus sargus) from the Natural Reserve of Torre Guaceto, Italy. Among EDCs, alkyl-phenols 2,6-DTBP, 2,4-DTBP, OP, and BPA were identified and quantified. The mean concentration of 2,6-DTBP, 2,4-DTBP, OP, and BPA were 2.2, 2.0, 1.2 and 3.6ng/g of liver, respectively, confirming the occurrence and transfer of these organic pollutants in the food web of marine organisms in marine reserves.

Biomarker response and hypothalamus-pituitary-interrenal axis functioning in Arctic charr from Bjørnøya (74°30' N), Norway, with high levels of organohalogenated compounds

The populations of Arctic charr (Salvelinus alpinus) residing in Lake Ellasjøen at Bjørnøya Island in the Norwegian Arctic (74° 30'N, 19° 00'E) possess substantially higher levels of organohalogenated compounds (strongly dominated by polychlorinated biphenyls, PCBs) than conspecifics residing in other, proximate lakes on the island. In the present study we sampled large (<400g), immature charr from Lake Ellasjøen (high PCB levels) and Lake Laksvatn (reference lake, low PCB levels) by hook and line for an immediate blood sampling, and blood and tissue sampling after a 1h confinement stressor. This was done in order to investigate possible effects of pollutants on an acute stress performance in a high-latitude fish species by comparing muscle PCB levels, hepatic cytochrome P4501A (CYP1A) biomarker activation and functioning of the hypothalamus-pituitary-interrenal (HPI) axis between these two populations of Arctic charr. As expected sum PCB muscle levels were 8-fold higher on a wet weigh basis, and 19-fold higher on a lipid weight basis, in charr from Ellasjøen than in charr from Laksvatn. This was accompanied by a 3.5-fold higher liver cyp1a mRNA abundance in the Ellasjøen charr compared to Laksvatn charr. Brain transcript levels encoding glucocorticoid receptor 1 and 2 (GR2) and corticotropin-releasing factor, and pituitary transcript levels encoding GR2 and proopiomelanocortin A1 and A2 were higher in Ellasjøen charr than in Laksvatn charr, while interrenal transcript levels encoding melanocortin 2 receptor and steroidogenic acute regulatory protein were lower. There were no differences in plasma cortisol concentration between the two charr populations immediately after capture and one hour after confinement. The strong biomarker response to OHCs and altered mRNA abundances of key genes related to HPI axis functioning in the Ellasjøen charr suggest endocrine disruptive effects of OHCs in this charr population. Possible ecological implications are not known, but it cannot be excluded that a slower growth rate in Ellasjøen charr compared to Laksvatn charr due to an increased metabolic demand associated with the activation of xenobiotic defense and detoxification systems may have contributed to the lower body mass of Ellasjøen charr compared to Laksvatn charr.

Human exposure to endocrine disrupting chemicals: effects on the male and female reproductive systems

Endocrine disrupting chemicals (EDCs) comprise a group of chemical compounds that have been examined extensively due to the potential harmful effects in the health of human populations. During the past decades, particular focus has been given to the harmful effects of EDCs to the reproductive system. The estimation of human exposure to EDCs can be broadly categorized into occupational and environmental exposure, and has been a major challenge due to the structural diversity of the chemicals that are derived by many different sources at doses below the limit of detection used by conventional methodologies. Animal and in vitro studies have supported the conclusion that endocrine disrupting chemicals affect the hormone dependent pathways responsible for male and female gonadal development, either through direct interaction with hormone receptors or via epigenetic and cell-cycle regulatory modes of action. In human populations, the majority of the studies point towards an association between exposure to EDCs and male and/or female reproduction system disorders, such as infertility, endometriosis, breast cancer, testicular cancer, poor sperm quality and/or function. Despite promising discoveries, a causal relationship between the reproductive disorders and exposure to specific toxicants is yet to be established, due to the complexity of the clinical protocols used, the degree of occupational or environmental exposure, the determination of the variables measured and the sample size of the subjects examined. Future studies should focus on a uniform system of examining human populations with regard to the exposure to specific EDCs and the direct effect on the reproductive system.

Review on crosstalk and common mechanisms of endocrine disruptors: Scaffolding to improve PBPK/PD model of EDC mixture

Endocrine disruptor compounds (EDCs) are environment chemicals that cause harmful effects through multiple mechanisms, interfering with hormone system resulting in alteration of homeostasis, reproduction and developmental effect. Many of these EDCs have concurrent exposure with crosstalk and common mechanisms which may lead to dynamic interactions. To carry out risk assessment of EDCs' mixture, it is important to know the detailed toxic pathway, crosstalk of receptor and other factors like critical window of exposure. In this review, we summarize the major mechanism of actions of EDCs with the different/same target organs interfering with the same/different class of hormone by altering their synthesis, metabolism, binding and cellular action. To show the impact of EDCs on life stage development, a case study on female fertility affecting germ cell is illustrated. Based on this summarized discussion, major groups of EDCs are classified based on their target organ, mode of action and potential risk. Finally, a conceptual model of pharmacodynamic interaction is proposed to integrate the crosstalk and common mechanisms that modulate estrogen into the predictive mixture dosimetry model with dynamic interaction of mixture. This review will provide new insight for EDCs' risk assessment and can be used to develop next generation PBPK/PD models for EDCs' mixture analysis.

To Cull or Not To Cull? Considerations for Studies of Endocrine-Disrupting Chemicals

The power of animal models is derived from the ability to control experimental variables so that observed effects may be unequivocally attributed to the factor that was changed. One variable that is difficult to control in animal experiments is the number and composition of offspring in a litter. To account for this variability, artificial equalization of the number of offspring in a litter (culling) is often used. The rationale for culling, however, has always been controversial. The Developmental Origins of Health and Disease concept provides a new context to evaluate the pros and cons of culling in laboratory animal studies, especially in the context of endocrine-disrupting chemicals. Emerging evidence indicates that culling, especially of large litters, can drastically change the feeding status of a pup, which can result in compensatory growth with long-term consequences for the animal, including increased risk of cardio-metabolic diseases. Similarly, culling of litters to intentionally bias sex ratios can alter the animal's behavior and physiology, with effects observed on a wide range of outcomes. Thus, in an attempt to control for variability in developmental rates, culling introduces an uncontrolled or confounding variable, which itself may affect a broad spectrum of health-related consequences. Variabilities in culling protocols could be responsible for differences in responses to endocrine-disrupting chemicals reported across studies. Because litter sex composition and size are vectors that can influence both prenatal and postnatal growth, they are essential considerations for the interpretation of results from laboratory animal studies.

The Effect of Exposure to Persistent Organic Pollutants on Metabolic Health among KOREAN Children during a 1-Year Follow-Up

Previous evidence suggests the potential for adverse effects of persistent organic pollutants (POPs) on metabolic health even at low-dose exposure levels common among the general population, but there is less evidence of these associations among children. Therefore, as part of a prospective cohort study, 214 children were measured for POPs exposure. After the 1-year follow-up, we assessed the effect of circulating POPs exposure among 158 children aged 7-9 years (at baseline) on the change of metabolic components of metabolic syndrome using multiple regression analysis. In addition, we calculated the continuous metabolic syndrome (cMetS) score and assessed the variation among individuals by POPs exposure. The concentrations of marker polychlorinated biphenyls (PCBs) were significantly associated with increased change in diastolic blood pressure (BP) and triglyceride levels during a 1-year follow-up, after controlling for sex, age, household income, and change in body mass index. Total PCBs also showed a marginal association with increasing cMetS score from the baseline. Of the metabolic components, change in diastolic BP over time showed a notable association with specific PCBs, but no association with organochlorine pesticides. Here, we found that low-dose exposures to PCBs among children in the general population could negatively influence metabolic health, particularly diastolic BP. Increased disease sensitivity during childhood can continue to adulthood, thus, these results support the need for continuous assessment of the health impact of POPs.

Co-Formulants in Glyphosate-Based Herbicides Disrupt Aromatase Activity in Human Cells below Toxic Levels

Pesticide formulations contain declared active ingredients and co-formulants presented as inert and confidential compounds. We tested the endocrine disruption of co-formulants in six glyphosate-based herbicides (GBH), the most used pesticides worldwide. All co-formulants and formulations were comparably cytotoxic well below the agricultural dilution of 1% (18-2000 times for co-formulants, 8-141 times for formulations), and not the declared active ingredient glyphosate (G) alone. The endocrine-disrupting effects of all these compounds were measured on aromatase activity, a key enzyme in the balance of sex hormones, below the toxicity threshold. Aromatase activity was decreased both by the co-formulants alone (polyethoxylated tallow amine-POEA and alkyl polyglucoside-APG) and by the formulations, from concentrations 800 times lower than the agricultural dilutions; while G exerted an effect only at 1/3 of the agricultural dilution. It was demonstrated for the first time that endocrine disruption by GBH could not only be due to the declared active ingredient but also to co-formulants. These results could explain numerous in vivo results with GBHs not seen with G alone; moreover, they challenge the relevance of the acceptable daily intake (ADI) value for GBHs exposures, currently calculated from toxicity tests of the declared active ingredient alone.

Enhanced Bioconcentration of Bisphenol A in the Presence of Nano-TiO2 Can Lead to Adverse Reproductive Outcomes in Zebrafish

Titanium dioxide nanoparticles (n-TiO2) and bisphenol A (BPA) are widespread environmental contaminants in the aquatic environment. We hypothesized that n-TiO2 may adsorb BPA, and thus modify its bioavailability and toxicity to aquatic organisms. In this study, the bioavailability and toxicity of BPA (0, 2, 20, 200 μg/L) was investigated in the presence of n-TiO2 (100 μg/L). The n-TiO2 sorbed BPA and the resulting nanoparticles were taken up by zebrafish, where they translocated to the liver, brain, and gonad tissues. Increased tissue burdens of both BPA and n-TiO2 were observed following coexposure, and they also caused a reduction in plasma concentrations of estradiol (E2), testosterone (T), follicle-stimulating hormone (FSH), and luteinizing hormone (LH). Plasma vitellogenin (VTG) concentrations were significantly increased in males and females upon exposure to BPA. Histological examination of the ovary and testes did not show obvious morphological alterations; however, inhibition of egg production was noted in the presence of n-TiO2. The results indicated that n-TiO2 acts as a carrier of BPA and enhances its bioconcentration in zebrafish, leading to endocrine disruption and impairment of reproduction.

Endocrine-Disrupting Effects of Pesticides through Interference with Human Glucocorticoid Receptor

Many pesticides have been identified as endocrine-disrupting chemicals (EDCs) due to their ability to bind sex-steroid hormone receptors. However, little attention has been paid to the ability of pesticides to interfere with other steroid hormone receptors such as glucocorticoid receptor (GR) that plays a critical role in metabolic, endocrine, immune, and nervous systems. In this study, the glucocorticoidic and antiglucocorticoidic effects of 34 pesticides on human GR were investigated using luciferase reporter gene assay. Surprisingly, none of the test chemicals showed GR agonistic activity, but 12 chemicals exhibited apparent antagonistic effects. Bifenthrin, λ-cyhalothrin, cypermethrin, resmethrin, o,p'-DDT, p,p'-DDT, methoxychlor, ethiofencarb, and tolylfluanid showed remarkable GR antagonistic properties with RIC20 values lower than 10(-6) M. The disruption of glucocorticoid-responsive genes in H4IIE and J774A.1 cells was further evaluated on these 12 GR antagonists. In H4IIEcells, four organochlorine insecticides, bifenthrin, and 3-PBA decreased cortisol-induced PEPCK gene expression, while o,p'-DDT and methoxychlor inhibited cortisol-stimulated Arg and TAT gene expression. Cypermethrin and tolyfluanid attenuated cortisol-induced TAT expression. In J774A.1 cells, λ-cyhalothrin, resmethrin, 3-PBA, o,p'-DDT, p,p'-DDT, p,p'-DDE, methoxychlor- and tolylfluanid-reduced cortisol-stimulated GILZ expression. Furthermore, molecular docking simulation indicated that different interactions may stabilize the binding between molecules and GR. Our findings suggest that comprehensive screening and evaluation of GR antagonists and agonists should be considered to better understand the health and ecological risks of man-made chemicals such as pesticides.

Sorption and toxicity reduction of pharmaceutically active compounds and endocrine disrupting chemicals in the presence of colloidal humic acid

This study investigated the toxicity changes and sorption of pharmaceuticals and endocrine disrupters in the presence of humic acid (HA). For the sorption experiment, a dead end filtration (DEF) system was used to separate bound and free-form target compounds. An algae growth inhibition test and E-screen assay were conducted to estimate the toxic effect of pharmaceutically active compounds (PhACs) and endocrine disrupting chemicals (EDCs), respectively. The permeate concentration was confirmed using liquid chromatography-mass spectrometry. In the sorption test, we observed significant sorption of PhACs and EDCs on colloidal HA, except for sulfamethoxazole (SMX). The values of log KCOC derived from DEF determinations ranged from 4.40 to 5.03. The removal efficiency varied with the HA concentration and the target chemical properties. Tetracycline and 4-octylphenol showed the highest sorption or removal efficiency (≈50%), even at 5 mg C/L HA. The algal growth inhibition of PhACs and the estrogenic effects of EDCs were significantly decreased in proportion to HA concentrations, except for SMX. In addition, the chemical analysis results showed a positive relationship with the bioassay results. Consequently, the sorption of PhACs and EDCs onto colloidal HA should be emphasized in natural environments because it significantly reduces bioavailable concentrations and toxicity to aquatic organisms.

17α-Ethinylestradiol (EE2) effect on global gene expression in primary rainbow trout (Oncorhynchus mykiss) hepatocytes

The potential impact of endocrine disrupting chemicals (EDCs) in the aquatic environment has driven the development of screening assays to evaluate the estrogenic properties of chemicals and their effects on aquatic organisms such as fish. However, obtaining full concentration-response relationships in animal (in vivo) exposure studies are laborious, costly and unethical, hence a need for developing feasible alternative (non-animal) methods. Use of in vitro bioassays such as primary fish hepatocytes, which retain many of the native properties of the liver, has been proposed for in vitro screening of estrogen receptor (ER) agonists and antagonists. The aim of present study was to characterize the molecular mode of action (MoA) of the ER agonist 17α-ethinylestradiol (EE2) in primary rainbow trout (Oncorhynchus mykiss) hepatocytes. A custom designed salmonid 60,000-feature (60k) oligonucleotide microarray was used to characterize the potential MoAs after 48h exposure to EE2. The microarray analysis revealed several concentration-dependent gene expression alterations including classical estrogen sensitive biomarker gene expression (e.g. estrogen receptor α, vitellogenin, zona radiata). Gene Ontology (GO) analysis displayed transcriptional changes suggesting interference of cellular growth, fatty acid and lipid metabolism potentially mediated through the estrogen receptor (ER), which were proposed to be associated with modulation of genes involved in endocrine function and reproduction. Pathway analysis supported the identified GOs and revealed modulation of additional genes associated with apoptosis and cholesterol biosynthesis. Differentially expressed genes (DEGs) related to impaired lipid metabolism (e.g. peroxisome proliferator-activated receptor α and γ), growth (e.g. insulin growth factor protein 1), phase I and II biotransformation (e.g. cytochrome P450 1A, sulfotransferase, UDP-glucuronosyltransferase and glutathione S-transferase) provided additional insight into the MoA of EE2 in primary fish hepatocytes. Results from the present study suggest that biotransformation, estrogen receptor-mediated responses, lipid homeostasis, growth and cancer/apoptosis in primary fish hepatocytes may be altered after short-term exposure to ER-agonists such as EE2. In many cases the observed changes were similar to those reported for estrogen-exposed fish in vivo. In conclusion, global transcriptional analysis demonstrated that EE2 affected a number of toxicologically relevant pathways associated with an estrogenic MoA in the rainbow trout hepatocytes.

Physiological Responses in Chinese Rare Minnow Larvae Following Exposure to Low-Dose Tributyltin

In the present study, the antioxidant response and acetylcholinesterase (AChE) activity were measured in Chinese rare minnow larvae (Gobiocypris rarus) after exposure to tributyltin (TBT) (0, 100, 400 and 800 ngL(-1)) for 7 days, as well as the expression of a series of genes, including cr, aptase and prl genes involved in the ion-regulatory process and igfbp3 and gh related to growth rate. Results shows that oxidative stress was generated in fish exposed to TBT, as evidenced by elevated malondialdehyde levels and the inhibition of antioxidant parameters. The activity of acetylcholinesterase (AChE) was also inhibited in fish under higher TBT stress. Moreover, genes involved in ion regulation and growth were affected, based on the regulated transcription of the cr, atpase, gh, prl and igfbp3 genes in the treated groups. The observed effects of TBT upon antioxidant responses and altered expression of genes provides insight into the use of these molecular biomarkers in evaluating mechanisms of TBT toxicity in fish.

A review on endocrine disruptors and their possible impacts on human health

Endocrine disruption is a named field of research which has been very active for over 10 years, although the effects of endocrine disruptors in wildlife have been studied mainly in vast since the 1940s. A large number of chemicals have been identified as endocrine disruptors and humans can be exposed to them either due to their occupations or through dietary and environmental exposure (water, soil and air). Endocrine disrupting chemicals are compounds that alter the normal functioning of the endocrine system of both humans and wildlife. In order to understand the vulnerability and risk factors of people due to endocrine disruptors as well as the remedies for these, methods need to be developed in order to predict effects on populations and communities from the knowledge of effects on individuals. For several years there have been a growing interest on the mechanism and effect of endocrine disruptors and their relation with environment and human health effect. This paper, based on extensive literature survey, briefly studies the progress mainly in human to provide information concerning causative substances, mechanism of action, ubiquity of effects and important issues related to endocrine disruptors. It also reviews the current knowledge of the potential impacts of endocrine disruptors on human health so that the effects can be known and remedies applied for the problem as soon as possible.

Bioconcentration and transfer of the organophorous flame retardant 1,3-dichloro-2-propyl phosphate causes thyroid endocrine disruption and developmental neurotoxicity in zebrafish larvae

Organophosphate flame retardants are emerging environmental contaminants, although knowledge of their health risks is limited. Here, thyroid hormone homeostasis and neuronal development was studied in the progeny of adult zebrafish exposed to tris(1,3-dichloro-2-propyl) phosphate (TDCPP). Adult zebrafish were exposed to TDCPP (0, 4, 20, and 100 μg/L) for 3 months. Increased generation of reactive oxygen species and reduced survival rates was observed in exposed F1 larvae. We also observed a significant decrease in plasma thyroxine and 3,5,3'-triiodothyronine levels in F0 females and F1 eggs/larvae. The mRNA and protein expression of factors associated with neuronal development (e.g., α1-tubulin, myelin basic protein, and synapsin IIa) were significantly downregulated in exposed F1 larvae, as was the level of the neurotransmitters dopamine, serotonin, gamma amino butyric acid, and histamine. Larval locomotion was significantly decreased in exposed fish, but there was no effect on acetylcholinesterase activity. Bioconcentration of TDCPP was observed in F0 fish. TDCPP was also detected in F1 eggs following parental exposure, indicating maternal transfer of this compound. This study uniquely shows that TDCPP can be transferred to the offspring of exposed adults, causing thyroid endocrine disruption and developmental neurotoxicity.

Bioaccumulation, biotransformation, and toxicity of BDE-47, 6-OH-BDE-47, and 6-MeO-BDE-47 in early life-stages of zebrafish (Danio rerio)

2,2',4,4'-Tetrabromodiphenyl ether (BDE-47), 6-hydroxy-tetrabromodiphenyl ether (6-OH-BDE-47), and 6-methoxy-tetrabromodiphenyl ether (6-MeO-BDE-47) are the most detected congeners of polybrominated diphenyl ethers (PBDEs), OH-BDEs, and MeO-BDEs, respectively, in aquatic organisms. Although it has been demonstrated that BDE-47 can interfere with certain endocrine functions that are mediated through several nuclear hormone receptors (NRs), most of these findings were from mammalian cell lines exposed in vitro. In the present study, embryos and larvae of zebrafish were exposed to BDE-47, 6-OH-BDE-47, and 6-MeO-BDE-47 to compare their accumulation, biotransformation, and bioconcentration factors (BCF) from 4 to 120 hpf. In addition, effects on expression of genes associated with eight different pathways regulated by NRs were investigated at 120 hpf. 6-MeO-BDE-47 was most bioaccumulated and 6-OH-BDE-47, which was the most potent BDE, was least bioaccumulated. Moreover, the amount of 6-MeO-BDE-47, but not BDE-47, transformed to 6-OH-BDE-47 increased in a time-dependent manner, approximately 0.01%, 0.04%, and 0.08% at 48, 96, and 120 hpf, respectively. Expression of genes regulated by the aryl hydrocarbon receptor (AhR), estrogen receptor (ER), and mineralocorticoid receptor (MR) was affected in larvae exposed to 6-OH-BDE-47, whereas genes regulated by AhR, ER, and the glucocorticoid receptor (GR) were altered in larvae exposed to BDE-47. The greatest effect on expression of genes was observed in larvae exposed to 6-MeO-BDE-47. Specifically, 6-MeO-BDE-47 affected the expression of genes regulated by AhR, ER, AR, GR, and thyroid hormone receptor alpha (TRα). These pathways were mostly down-regulated at 2.5 μM. Taken together, these results demonstrate the importance of usage of an internal dose to assess the toxic effects of PBDEs. BDE-47 and its analogs elicited distinct effects on expression of genes of different hormone receptor-mediated pathways, which have expanded the knowledge of different mechanisms of endocrine disrupting effects in aquatic vertebrates. Because some of these homologues are natural products, assessments of risks of anthropogenic PBDE need to be made against the background of concentrations from naturally occurring products. Even though PBDEs are being phased out as flame retardants, the natural products remain.

Triclosan exhibits a tendency to accumulate in the epididymis and shows sperm toxicity in male Sprague-Dawley rats

Triclosan (TCS) is considered a potent endocrine disruptor that causes reproductive toxicity in non-mammals, but it is still unclear exactly whether TCS has adverse effects on the sperm or reproductive organs in mammals. In this study, we aimed to evaluate the distribution status of TCS in male reproductive organs of rats, and seek the correlation with the TCS-induced sperm toxicity or reproductive organ damage. Male rats were intragastrically administered with TCS at a dose of 50 mg/kg, the kinetics of TCS in the plasma and reproductive organs were investigated. TCS in testes and prostates both showed a lower-level distribution compared to that in the plasma, which indicates it has no tendency to accumulate in those organs. However, TCS in the epididymides showed a longer elimination half-life (t1/2 z), a longer the mean retention time (MRT), and a lower clearance (CLZ /F) compared with those in the plasma. Besides, the ratios of mean area under the concentration-time curve (AUC)(0-96 h(epididymides/plasma)) and AUC(0-∞(epididymides/plasma)) were 1.13 and 1.51, respectively. These kinetic parameters suggest TCS has an accumulation tendency in the epididymides. Based on this, we investigated the TCS-induced sperm toxicity and histopathological changes of reproductive organs in rats. TCS was given intragastrically at doses of 10, 50, and 200 mg/kg for 8 weeks. Rats treated with the high dose (200 mg/kg) of TCS showed a significant decrease in daily sperm production (DSP), changes in sperm morphology and epididymal histopathology. Considering the histopathological change in the epididymides, TCS may induce the epididymal damage due to the epididymal accumulation of that.

Bisphenol-A: epigenetic reprogramming and effects on reproduction and behavior

Bisphenol A (BPA) is a synthetic compound used in the production of many polycarbonate plastics and epoxy resins. It is one of the most widely produced chemicals in the world today and is found in most canned goods, plastics, and even household dust. Exposure to BPA is almost universal: most people have measurable amounts of BPA in both urine and serum. BPA is similar in structure to estradiol and can bind to multiple targets both inside and outside the nucleus, in effect acting as an endocrine disruptor. Research on BPA exposure has accelerated in the past decade with findings suggesting that perinatal exposure to BPA can negatively impact both male and female reproduction, create alterations in behavior, and act as a carcinogen. BPA can have both short term and long term effects with the latter typically occurring through epigenetic mechanisms such as DNA methylation. This review will draw on both human and animal studies in an attempt to synthesize the literature and examine the effects of BPA exposure on reproduction, behavior, and carcinogenesis with a focus on the potential epigenetic mechanisms by which it acts.

Should oral gavage be abandoned in toxicity testing of endocrine disruptors?

For decades, hazard assessments for environmental chemicals have used intra-gastric gavage to assess the effects of 'oral' exposures. It is now widely used--and in some cases required--by US federal agencies to assess potential toxicity of endocrine disrupting chemicals (EDCs). In this review we enumerate several reasons why gavage is not appropriate for the assessment of EDCs using bisphenol A (BPA) as a main example. First, whereas human dietary exposures interact with the oral mucosa, gavage exposures avoid these interactions, leading to dramatic differences in absorption, bioavailability and metabolism with implications for toxicokinetic assumptions and models. Additionally, there are well acknowledged complications associated with gavage, such as perforation of the esophagus that diminish its value in toxicological experiments. Finally, the gavage protocol itself can induce stress responses by the endocrine system and confound the assessment of EDCs. These serious flaws have not been taken into account in interpreting results of EDC research. We propose the exploration of alternatives to mimic human exposures when there are multiple exposure routes/sources and when exposures are chronic. We conclude that gavage may be preferred over other routes for some environmental chemicals in some circumstances, but it does not appropriately model human dietary exposures for many chemicals. Because it avoids exposure pathways, is stressful, and thus interferes with endocrine responses, gavage should be abandoned as the default route of administration for hazard assessments of EDCs.

In vitro evidence for endocrine-disrupting chemical (EDC)'s inhibition of drug metabolism

BACKGROUND

Humans can be frequently exposed to Bisphenol A (BPA) via multiple sources, and babies are considered to be the most sensitive group to exposure of BPA.

AIMS

To investigate the inhibition potential of BPA towards human liver microsomes (HLMs)-catalyzed zidovudine (AZT) glucuronidation.

MATERIALS AND METHODS

In vitro HLMs incubation system was used to investigate the inhibition potential of BPA towards AZT glucuronidation. Both Dixon and Lineweaver-Burk plots were employed to determine the inhibition kinetic type, and nonlinear repression was utilized to calculate the inhibition kinetic parameters (Ki).

RESULTS

Concentration-dependent inhibition of BPA towards AZT glucuronidation was observed. Both Dixon and Lineweaver-Burk plots showed that BPA exerted competitive inhibition towards the glucuronidation of AZT, and nonlinear repression with competitive equation was used to calculate the Ki value to be 3.2 µM.

CONCLUSION

Potential BPA-AZT interaction might occur when the patients administered with AZT is also exposed to BPA.

Effect of long-term dietary lead exposure on some maturation and reproductive parameters of a female Prussian carp (Carassius gibelio B.)

Lead is reported to be an endocrine disruptor. In the current study, we exposed female Prussian carp to artificial feed, supplemented with five doses of dietary Pb (0, 1 (control), 8, 13, 24, and 49 mg/kg) over either a 24-month period or a 12-month period, followed by further 12 months where the fish were fed the control diet. Periodically, oocyte maturation, gonadosomatic index (GSI), ability to secret luteinizing hormone (LH) as well as gonad Pb concentrations were measured. It was found that the reproductive system of the female Prussian carp is not indifferent to chronic exposure to lead. The negative effect was manifested by a decrease in the GSI after 12 months despite the fact that a higher proportion of oocytes at more advanced maturity stages were concurrently observed. After 12 months of exposure, the effect on LH secretion varied according to the dose. In the group exposed to the lowest dose (8 mg/kg), LH decreased spontaneously, and in the groups exposed to the highest two doses (24 and 48 mg/kg), a significantly higher LHRH-A-stimulated LH secretion was observed. After 24 months of lead exposure, the effects on oocyte maturation and size and on GSI values were not pronounced. Analysis of the effect of lead exposure on LH secretion showed that the relationships were similar to those observed after 12 months but nonsignificant. During chronic a 24-month period exposure to Pb, Prussian carp female appears to acclimate to Pb doses used in the experiment. After 12 months of exposure and 12 months of depuration, the levels of spontaneous and stimulated LH secretion observed in all the groups were similar to the control, which is evidence that depuration eliminates the previously observed effects of exposure to lead. Lead is easily accumulated in the ovary, reaching a fivefold higher level (0.8 mg/kg tissue) compared to the control(0.15 mg/kg tissue), but after discontinuation of exposure, this organ is quickly depurated. The results indicate that environmental Pb can be a potent endocrine disruptor affecting ovarian steroidogenesis, gametogenesis, and ovulation, which may lead to adverse impacts on fish reproduction and population density and that female Prussian carp become resistant to the negative effects of lead with advancing age, and their organs cope by reaching a state of homeostasis.

Biotransformation of bisphenol AF to its major glucuronide metabolite reduces estrogenic activity

Bisphenol AF (BPAF), an endocrine disrupting chemical, can induce estrogenic activity through binding to estrogen receptor (ER). However, the metabolism of BPAF in vivo and the estrogenic activity of its metabolites remain unknown. In the present study, we identified four metabolites including BPAF diglucuronide, BPAF glucuronide (BPAF-G), BPAF glucuronide dehydrated and BPAF sulfate in the urine of Sprague-Dawley (SD) rats. BPAF-G was further characterized by nuclear magnetic resonance (NMR). After treatment with a single dose of BPAF, BPAF was metabolized rapidly to BPAF-G, as detected in the plasma of SD rats. Biotransformation of BPAF to BPAF-G was confirmed with human liver microsomes (HLM), and V_max of glucuronidation for HLM was 11.6 nmol/min/mg. We also found that BPAF glucuronidation could be mediated through several human recombinant UDP-glucuronosyltransferases (UGTs) including UGT1A1, UGT1A3, UGT1A8, UGT1A9, UGT2B4, UGT2B7, UGT2B15 and UGT2B17, among which UGT2B7 showed the highest efficiency of glucuronidation. To explain the biological function of BPAF biotransformation, the estrogenic activities of BPAF and BPAF-G were evaluated in ER-positive breast cancer T47D and MCF7 cells. BPAF significantly stimulates ER-regulated gene expression and cell proliferation at the dose of 100 nM and 1 μM in breast cancer cells. However, BPAF-G did not show any induction of estrogenic activity at the same dosages, implying that formation of BPAF-G is a potential host defense mechanism against BPAF. Based on our study, biotransformation of BPAF to BPAF-G can eliminate BPAF-induced estrogenic activity, which is therefore considered as reducing the potential threat to human beings.

Removal of a combination of endocrine disruptors from aqueous systems by seedlings of radish and ryegrass

Endocrine disruptors (EDs) are widespread in the environment, especially aquatic systems, and cause dangerous effects on wildlife and humans. This work was aimed to assess the capacity of radish (Raphanus sativus L.) and ryegrass (Lolium perenne L.) seedlings to tolerate and remove two combinations of EDs containing bisphenol A (BPA), 17alpha-ethynilestradiol (EE2), and linuron from four aqueous media: distilled water, a solution of natural organic matter (NOM), a lake water and a river water. Seeds of the two species were germinated in each contaminated medium and, at the end of germination, the seedling growth was evaluated by biometric measurements and residual EDs were quantified by chromatographic analysis. Biometric measurements revealed that the phytotoxicity of the two combinations of EDs depended on the medium used. Radish showed a discrete tolerance in distilled water and lake water but was inhibited in the solution of NOM and river water. Ryegrass was negatively affected mainly in river water. The concentration of each ED appeared significantly reduced in all media in the presence of seedlings of both species, but not in the blanks without plants. In 5 days, radish removed up to 88% of BPA, 100% of EE2 and 42% of linuron, and in 6 days ryegrass removed up to 92% of BPA, 74% of EE2 and 16% of linuron. The considerable removal capacity of radish and ryegrass in all media tested encourages the use of phytoremediation to remove EDs from waters.

Fetal origin of endocrine dysfunction in the adult: the phthalate model

Di-(2-ethylhexyl) phthalate (DEHP) is a plasticizer with endocrine disrupting properties that is found ubiquitously in the environment as well as in human amniotic fluid, umbilical cord blood, human milk, semen, and saliva. It is used in the industry to add flexibility to polyvinyl chloride-derived plastics and its wide spread use and presence has resulted in constant human exposure through fetal development and postnatal life. Epidemiological studies have suggested an association between phthalate exposures and human reproductive effects in infant and adult populations. The effects of fetal exposure to phthalates on the male reproductive system were unequivocally shown on animal models, principally rodents, in which short term deleterious reproductive effects are well established. By contrast, information on the long term effects of DEHP in utero exposure on gonadal function are scarce, while its potential effects on other organs are just starting to emerge. The present review focuses on these novel findings, which suggest that DEHP exerts more complex and broader disruptive effects on the endocrine system and metabolism than previously thought. This article is part of a Special Issue entitled "CSR 2013".

Effect of bisphenol A on rat metabolic profiling studied by using capillary electrophoresis time-of-flight mass spectrometry

Bisphenol A (BPA), a chemical widely used in the manufacture of polycarbonate plastics, has raised considerable concern in recent decades because of its hormone-like properties. Whether BPA exposure is a health risk remains controversial in many countries. A metabolomics study based on capillary electrophoresis time-of-flight mass spectrometry (CE-TOF/MS) was performed to study the urine metabolic profiles of Sprague-Dawley rats fed with four dose levels of BPA (0, 1, 10, and 100 μg/kg body weight) for 45 days. Multivariate pattern recognition directly reflected the metabolic perturbations caused by BPA. On the basis of univariate analysis, 42 metabolites including amino acids, polyamines, nucleosides, organic acids, carbohydrates, pterins, polyphenols, and sugar phosphates were found as the most significantly differential metabolites. The marked perturbations were related with valine, leucine and isoleucine biosynthesis, D-glutamine and D-glutamate metabolism, etc. Significant alterations of neurotransmitters (glutamate, gamma-aminobutyric acid, and noradrenaline) and neurotransmitter-related metabolites (tyrosine, histamine, valine, and taurine) suggested that the toxic effects of small-dose BPA (below 50 mg/kg/day) may contribute to its interactions with the neuromediating system. Our study demonstrated that metabolomics may offer more specific insights into the molecular changes underlying the physiological effects of BPA.

Exposure levels of environmental endocrine disruptors in mother-newborn pairs in China and their placental transfer characteristics

There is a growing concern about the potential health effects of exposure to various environmental chemicals during pregnancy and infancy. The placenta is expected to be an effective barrier protecting the developing embryo against some endocrine disruptors (EDs) circulating in maternal blood. The current study was designed to assess in utero exposure levels of non-persistent organic pollutants (non-POPs) and persistent organic pollutants (POPs) in Chinese newborns and potential role of placenta barrier against fetal exposure to these commonly-used environmental endocrine disruptors. A total of 230 newborn-mother pairs were enrolled during 2010–2011, 201 pairs of which were recruited from Shanghai, and the other 29 pairs came from Wenzhou. Maternal blood, cord blood, and meconium specimens were collected in the subject population from Shanghai and analyzed for non-POPs, including mono-2-ethylhexyl phthalate (MEHP), octylphenol (OP) and 4-nonylphenol (4-NP). A total of 19 polybrominated diphenyl ethers (PBDEs) congeners, which belong to POPs, were detected in maternal and cord blood specimens from the other 29 pairs. Fetal-maternal ratios (F-M ratios) and regression coefficients were presented to assess potential function of placenta on barricading the mother/fetal transfer of these EDs. Concentrations of the detected non-POPs in cord blood samples were approximately 20% lower than those in maternal blood, and regression coefficients of which were all over 0.80. In contrast, PBDEs levels in cord blood samples were significantly higher than those in maternal blood. MEHP levels in meconium were much higher than those in cord blood samples, and highly correlated. Therefore, observations demonstrated that the placental barrier slightly decreased the fetal exposure to most non-POPs, while PBDEs seemed to be totally transferred across the placenta and finally reached the fetus. For in utero exposure assessment of Di-2-ethylhexyl phthalate (DEHP), MEHP level in meconium may be a useful biomarker.