Computational insights into the molecular interactions of environmental xenoestrogens 4-tert-octylphenol, 4-nonylphenol, bisphenol A (BPA), and BPA metabolite, 4-methyl-2, 4-bis (4-hydroxyphenyl) pent-1-ene (MBP) with human sex hormone-binding globulin

Computational study on the endocrine-disrupting metabolic activation of Benzophenone-3 catalyzed by cytochrome P450 1A1: A QM/MM approach

Predicting the metabolic activation mechanism and potential hazardous metabolites of environmental endocrine-disruptors is a challenging and significant task in risk assessment. Here the metabolic activation mechanism of benzophenone-3 catalyzed by P450 1A1 was investigated by using Molecular Dynamics, Quantum Mechanics/Molecular Mechanics and Density Functional Theory approaches. Two elementary reactions involved in the metabolic activation of BP-3 with P450 1A1: electrophilic addition and hydrogen abstraction reactions were both discussed. Further conversion reactions of epoxidation products, ketone products and the formaldehyde formation reaction were investigated in the non-enzymatic environment based on previous experimental reports. Binding affinities analysis of benzophenone-3 and its metabolites to sex hormone binding globulin indirectly demonstrates that they all exhibit endocrine-disrupting property. Toxic analysis shows that the eco-toxicity and bioaccumulation values of the benzophenone-3 metabolites are much lower than those of benzophenone-3. However, the metabolites are found to have skin-sensitization effects. The present study provides a deep insight into the biotransformation process of benzophenone-3 catalyzed by P450 1A1 and alerts us to pay attention to the adverse effects of benzophenone-3 and its metabolites in human livers.

Bisphenol A Exposure Interferes with Reproductive Hormones and Decreases Sperm Counts: A Systematic Review and Meta-Analysis of Epidemiological Studies

Bisphenol A (BPA), an acknowledged endocrine disrupter, is easily exposed to humans via food packaging and container. However, a consensus has not been reached on the extent to which BPA exposure affects the reproductive system. We therefore conducted this systematic review and meta-analysis to elucidate the relationship between BPA exposure and male reproduction-related indicators. Up to October 2023, a comprehensive search was carried out in the PubMed, Embase, Cochrane and Web of Science, and 18 studies were ultimately included. β coefficients from multivariate linear regression analyses were pooled using a random effects model. The results showed that the urinary BPA concentration was negatively correlated with the sperm concentration (β coefficient = -0.03; 95% CI: -0.06 to -0.01; I2 = 0.0%, p = 0.003) and total sperm count (β coefficient = -0.05; 95% CI: -0.08 to -0.02; I2 = 0.0%, p < 0.001). In addition, BPA concentrations were associated with increased sex hormone-binding globulin (SHBG) levels, increased estradiol (E2) levels, and reduced biologically active androgen levels. However, the relationship between an increased risk of below-reference sperm quality and BPA exposure was not robust. This systematic review revealed that BPA exposure disrupts reproductive hormones, reduces sperm counts and may ultimately adversely affect male reproduction.

Fabrication of molecularly imprinted resin via controlled polymerization applied in the enrichment of bisphenol A for plastic products

The addition of bisphenol A has been frequently used in industrial manufacturing because it imparts plastic products with characteristics such as transparency, durability, and excellent impact resistance. However, its widespread use raises concerns about potential leakage into the surrounding environment, which poses a significant risk to human health. In this study, molecularly imprinted polymers with specific recognition of bisphenol A were synthesized through surface-initiated atom transfer radical polymerization using poly(glycidyl methacrylate-co-ethylene glycol dimethacrylate) as the substrate, bisphenol A as the template molecule, 4-vinylpyridine as the monomer, and ethylene glycol dimethacrylate as the cross-linker. The bisphenol A adsorption capacity was experimentally investigated, and the kinetic analysis of the molecularly imprinted polymers produced an adsorption equilibrium time of 25 min, which is consistent with the pseudo-second-order kinetic model. The results of the static adsorption experiments exhibited consistency with the Langmuir adsorption model, revealing a maximum adsorption capacity of 387.2 μmol/g. The analysis of molecularly imprinted polymers-enriched actual samples using high-performance liquid chromatography demonstrated excellent selectivity for bisphenol A, with a linear range showing 93.4%-99.7% recovery and 1.1%-6.4% relative standard deviation, demonstrating its high potential for practical bisphenol A detection and enrichment applications.

Importance of relative binding of bisphenol A and bisphenol S to plasma proteins for predicting their in vivo potencies

Many studies suggest that the potential impact of bisphenol S (BPS) as an endocrine disruptor is comparable to that of bisphenol A (BPA). However, in vitro-to-in vivo and from animal to human extrapolations require knowledge of the plasma free fraction of the active endocrine compounds. The present study aimed to characterise BPA and BPS binding to plasma proteins both in humans and different animal species. The plasma protein binding of BPA and BPS was assessed by equilibrium dialysis in plasma from adult female mice, rats, monkeys, early and late pregnant women as well as paired cord blood, early and late pregnant sheep and foetal sheep. The fraction of free BPA was independent of plasma concentrations and ranged between 4% and 7% in adults. This fraction was 2 to 3.5 times lower than that of BPS in all species except sheep, ranging from 3% to 20%. Plasma binding of BPA and BPS was not affected by the stage of pregnancy, BPA and BPS free fractions representing about 4% and 9% during early and late human pregnancy, respectively. These fractions were lower than the free fractions of BPA (7%) and BPS (12%) in cord blood. Our results suggest that similarly to BPA, BPS is extensively bound to proteins, mainly albumin. The higher fraction of free BPS compared to BPA may have implications for human exposure assessment since BPS free plasma concentrations are expected to be 2 to 3.5 times higher than that of BPA for similar plasma concentration.

System-wide health risk prediction for 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene(MBP), a major active metabolite of environmental pollutant and food contaminant - Bisphenol A

Human exposure to plastic contaminated foods and environmental micro/nano plastic derived chemicals necessitates system-wide health risk assessment. Hence, current study intend to explore the mode of action (MoA) based adverse outcome pathways of 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), the major active metabolite of bisphenol A (BPA). The computational study employed broad range of target prediction, systems biology tools and molecular docking protocols. Further, validation of MBP targets was done using protein-ligand fluorescence quenching assay, endothelial cell culture and chicken embryo vascular angiogenesis models. Interestingly, the current results illustrate that various physiological signaling pathways (MAPK and VEGF related angiogenesis signaling) and disease progression pathways (hypertension, cancer and endocrine disorders) were enriched as potential targets of MBP. Further, docking studies highlights the possible binding mechanism of MBP with important targets including endothelial nitric oxide synthase (eNOS) and serum albumin (BSA). In addition, the validation studies on MBP-BSA interaction (fluorescence quenching), eNOS derived nitric oxide (NOx) generation in endothelial cells and chicken embryo angiogenesis support the system-wide impacts of MBP with highlights on cardiovascular pathogenesis. Thus, the current observation provides novel insights into the system wide impacts of MBP for the futuristic health risk assessment of plastic derived chemicals.

Mechanism of 17β-estradiol degradation by Rhodococcus equi via the 4,5-seco pathway and its key genes

Steroid estrogens have been detected in oceans, rivers, lakes, groundwaters, soils, and even urban water supply systems, thereby inevitably imposing serious impacts on human health and ecological safety. Indeed, many estrogen-degrading bacterial strains and degradation pathways have been reported, with the 4,5-seco pathway being particularly important. However, few studies have evaluated the use of the 4,5-seco pathway by actinomycetes to degrade 17β-estradiol (E2). In this study, 5 genes involved in E2 degradation were identified in the Rhodococcus equi DSSKP-R-001 (R-001) genome and then heterologously expressed to confirm their functions. The transformation of E2 with hsd17b14 reached 63.7% within 30 h, resulting in transformation into estrone (E1). Furthermore, we found that At1g12200-encoded flavin-binding monooxygenase (FMO_At1g12200) can transform E1 at a rate of 51.6% within 30 h and can transform E1 into 4-hydroxyestrone (4-OH E1). In addition, catA and hsaC genes were identified to further transform 4-OH E1 at a rate of 97-99%, and this reaction was accomplished by C-C cleavage at the C4 position of the A ring of 4-OH E1. This study represents the first report on the roles of these genes in estrogen degradation and provides new insights into the mechanisms of microbial estrogen metabolism and a better understanding of E2 degradation via the 4,5-seco pathway by actinomycetes.

Testicular toxicity of bisphenol compounds: Homeostasis disruption of cholesterol/testosterone via PPARα activation

The widespread application of bisphenols (BPs) has made them ubiquitous in the environment. Although the side effects of bisphenol A (BPA) substitutes have received increasing attention, studies on their reproductive toxicity remain lacking. In this research, the effects of BPA and its substitutes, including bisphenol S (BPS), bisphenol F (BPF), and bisphenol AF (BPAF), on the male reproductive system were evaluated. Results proved that these BPs disturbed germ cell proliferation, induced germ cell apoptosis, and perturbed sperm physiologies and spermatogenesis, which resulted from the disruption of testosterone (T) biosynthesis in Leydig cells (LCs). Importantly, in vitro and in vivo studies indicated that the exhausted cholesterol in LCs accounted for the reduced T production. Furthermore, the knockdown of peroxisome proliferator-activated receptor alpha (PPARα) remarkably ameliorated the downregulation of cholesterogenesis-related genes (i.e., Hmgcs1, Hmgcr, and Srebf2), indicating that PPARα played a critical role in BPs-induced testicular dysfunction. Overall, our studies indicated that BPS, BPF, and BPAF could induce testicular toxic effects similar to that of BPA, which were associated with the PPARα pathway.

Iridoid glycoside Aucubin protects against nonylphenol-induced testicular damage in male rats via modulation of steroidogenic and apoptotic signaling

Aucubin (AU) is one of the widespread compounds belonging to the group of iridoid glycosides, which possesses numerous beneficial properties. Nonylphenol (NP), is a synthetic environmental toxicant that has the potential to cause male infertility through excessive production of reactive oxygen species. In the current study, the remedial potential of Aucubin was assessed against NP-generated testicular damage in male rats. Animals were distributed into four groups and treated for 56 days in this study. Control-group (0.1% DMSO + food), NP group (100 µg/kg), NP + AU group (100 µg/kg + 5 mg/kg) and AU group (5 mg/kg). NP exposure significantly (p < 0.05) reduced the activity of antioxidant enzymes i.e., glutathione reductase, catalase (CAT), superoxide dismutase, glutathione peroxidase (GPx), and total protein content (TPC), whereas the level of reactive oxygen species (ROS) and thiobarbituric acid reactive substances (TBARS) was enhanced substantially (p < 0.05). Treatment with AU substantially (p < 0.05) recovered activities of antioxidant enzymes, TPC, ROS, and TBARS levels. Moreover, decrease in the levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), plasma testosterone, sperm count, motility, sperm membrane integrity, and the number of spermatocytes of different stages along with the level of steroidogenic enzymes i.e., 17β-hydroxysteroid dehydrogenase (17β-HSD), 3β-hydroxysteroid dehydrogenase (3β-HSD), and B-cell lymphoma 2 (Bcl-2) by NP administration were recovered to control values by AU treatment. However, AU mitigated the sperm abnormalities (head/midpiece/tail), the number of dead sperms, and proapoptotic proteins i.e., Bcl-2 associated X protein (Bax), caspase-9, and caspase-3 that were increased by NP. Besides, AU treatment recovered the NP-induced potential histopathological alterations in the testicular tissues such as the height of epithelium, seminiferous tubules diameter as well as the height of tunica propria. Overall, NP-induced toxicity was effectively recuperated by the AU administration. These results indicate that AU might be considered as a potential protective agent against testicular damage. The observed protection may be due to its antioxidant, anti-apoptotic, anti-inflammatory and androgenic potential.

Endocrine-disrupting metabolic activation of 2-nitrofluorene catalyzed by human cytochrome P450 1A1: A QM/MM approach

Nitropolycyclic aromatic hydrocarbons (NPAHs) present one of the most important airborne pollutants. Recent studies have shown that one of the most abundant NPAHs, 2-Nitrofluorene (NF), was supposed to be converted to endocrine-disrupting metabolites by cytochrome P450 1A1 (CYP1A1) in human cells. However, the mechanism is still largely unexplored. Here the metabolic activation and transformation mechanism of NF catalyzed by CYP1A1 were systematically studied with the aid of Molecular Dynamics, Density Functional Theory and Quantum Mechanics/Molecular Mechanics techniques. We evidence that CYP1A1 can activate NF through two elementary processes: (i) electrophilic addition (12.4 kcal·mol-1) or hydrogen abstraction (38.2 kcal·mol-1) and (ii) epoxidation (5.9 and 8.7 kcal·mol-1) or NIH shift (12.5 and 14.9 kcal·mol-1) or proton shuttle (12.1 kcal·mol-1). Electrophilic addition was found to be the rate-determining step while epoxidation rather than NIH shift or proton shuttle is the more feasible pathway after electrophilic addition. Metabolites 6,7-epoxide-2-nitrofluorene and 7,8-epoxide-2-nitrofluorene were identified as the major epoxidation products. Epoxides are unstable and easy to react with hydrated hydrogen ions and hydroxyls to produce endocrine disrupter 7-hydroxy-2-nitrofluorene. Toxic analysis shows that some of the metabolites are more toxic to model aquatic organisms (e.g. Green algea) than NF. Binding affinity analysis to human sex hormone binding globulin reveals that NF metabolites all have endocrine-disrupting potential. This study provides a comprehensive understanding on the biotransformation process of NF and may aid future studies on various NPAHs activation catalyzed by human P450 enzyme.

Growth and gonadal development retardations after long-term exposure to estradiol in little yellow croaker, Larimichthys polyactis

Endocrine disrupting chemicals (EDCs) including 17β-estradiol (E2) are widely distributed in the aquatic environment and are known to negatively affect the reproductive system of many animals, including fish. EDCs leading to feminization, altered sex ratio and reduced fecundity, it is possibly posing potential risks to the ecosystems. To investigate the potentially toxic effects of E2 exposure on little yellow croaker (Larimichthys polyactis, L. poliactis) who have a unique gonadal development pattern that males undergo a hermaphroditic stage. An experiment was set up where L. poliactis were maintained in tanks and exposed to E2 concentrations of 10 μg/L or no E2 exposure (the ethanol and control groups) from 30 to 90 days post-hatching (dph). After exposure, the E2 withdrawal and continual cultured to 150 and 365 dph. The morphological and histological analyses were used to compare the changes in the fish body and gonad under E2 exposure. The results showed that E2 exposure caused three major phenotypes at 30 and 60 days after treatment (dat), including ovary, ovotestis and gonadal development retardation compared with the control groups. The average ratio of these three phenotypes is 60.6%, 11.97% and 27.43%, respectively. The body length and weight of E2 exposure groups were repressed during the E2 exposure period, while it can recover after E2 withdrawal. However, the gonadal development (Gonadosomatic Index) of E2 exposure groups testis were retarded at 60 dat and doesn't recover until 365 dph. The sex determination/differentiation-related genes erα, erβI, erβII, fshβ and cyp11b2 were significantly decreased in E2-exposure male fish. This research highlights the E2 leads to feminization, disrupts testis maturation and spermatogenesis, this effect persisted into the stage of sexual maturity. Collectively, our findings provide insights into the molecular mechanisms underlying E2 disturbance of a marine economic fish reproduction.

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

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

Key proteins of proteome underlying sperm malformation of rats exposed to low fenvalerate doses are highly related to P53

Fenvalerate (Fen) is an endocrine disruptor, capable of interfering with the activity of estrogen and androgen. Our objective was to explore the molecular mechanisms of Fen on sperm in vivo. Adult male Sprague-Dawley rats were orally exposed to 0, 0.00625, 0.125, 2.5, 30 mg/kg/day Fen for 8 weeks. Sperm morphology, differential proteomics of sperm and testes, bioinformatic analysis, western blotting (WB), and RT-PCR were used to explore the mechanism of Fen on sperm. Data showed that low Fen doses significantly induced sperm malformations. In sperm proteomics, 47 differentially expressed (DE) proteins were enriched in biological processes (BPs) related to energy metabolism, response to estrogen, spermatogenesis; and enriched in cellular components (CCs) relating to energy-metabolism, sperm fibrous sheath and their outer dense fibers. In testicular proteomics, 56 DE proteins were highly associated with mRNA splicing, energy metabolism; and enriched in CCs relating to vesicles, myelin sheath, microtubules, mitochondria. WB showed that the expression of selected proteins was identical to their tendency in 2D gels. Literature indicates that key DE proteins in proteomic profiles (such as Trap1, Hnrnpa2b1, Hnrnpk, Hspa8, and Gapdh) are involved in P53-related processes or morphogenesis or spermatogenesis. Also, P53 mRNA and protein levels were significantly increased by Fen; bioinformatic re-analysis showed that 88.5% DE proteins and P53 formed a complex interacting network, and the key DE proteins were coenriched with P53-related BPs. Results indicate that key DE proteins of proteome underlying sperm malformations of rats exposed to low Fen doses are highly related to P53.

The Influence of Environmental Factors on Ovarian Function, Follicular Genesis, and Oocyte Quality

Endocrine-disrupting chemicals (EDCs) exist ubiquitously in the environment. Epidemiological data suggest that the increasing prevalence of infertility may be related to the numerous chemicals. Exposure to EDCs may have significant adverse impacts on the reproductive system including fertility, ovarian reserve, and sex steroid hormone levels. This chapter covers the common exposure ways, the origins of EDCs, and their effects on ovarian function, follicular genesis, and oocyte quality. Furthermore, we will review the origin and the physiology of ovarian development, as well as explore the mechanisms in which EDCs act on the ovary from human and animal data. And then, we will focus on the bisphenol A (BPA), which has been shown to reduce fertility and ovarian reserve, as well as disrupt steroidogenesis in animal and human models. Finally, we will discuss the future direction of prevention and solution methods.

Environmental Distribution of Personal Care Products and Their Effects on Human Health

Personal care products (PCPs) are generally used for personal hygiene, cleaning, grooming, and beautification. These include hair and skin care products, baby care products, UV blocking creams, facial cleansers, insect repellents, perfumes, fragrances, soap, detergents, shampoos, conditioners, toothpaste, etc., thus exposing humans easily. Personal preferences related to PCPs usage frequency are highly variable and depend on socioeconomic status and lifestyle factors. The increasing availability and diversity of PCPs from the retailer outlets consequently result in higher loading of PCPs into wastewater systems and, therefore, the environment. These compounds persistently and continuously release biologically active and inactive ingredients in the atmosphere, biosphere, geosphere, and demonstrating adverse effects on human, wild, and marine life. Advanced techniques such as granular activated carbon filtration and algae-based system may help biotransformation and remove PCP contaminants from water with improved efficiency. Additionally, harmony among PCPs related regulations of different countries may encourage standard checks to control their manufacturing, sale, and distribution across the borders to ensure consumers' safety. Furthermore, all intended ingredients, their concentrations, and instructions for frequency of use as per age groups may be clearly labeled on packages of PCPs. In conclusion, the emerging environmental contaminants of PCPs and their association with the growing risks of negative effects on human health and globally on the environment emphasize the chemical-free simple lifestyle.

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.

Seasonal distribution, risks, and sources of endocrine disrupting chemicals in coastal waters: Will these emerging contaminants pose potential risks in marine environment at continental-scale?

Coastal waters are the critical ecologically fragile regions under the influence of the fastest economic developing pace and the extensive anthropogenic activities in coastal zone. Little information on the seasonal distribution, risks, and sources of endocrine disrupting chemicals (EDCs) which are emerging contaminants to pose potential risks at very low concentrations in coastal waters at continental-scale is available. This study investigated the coastline-based distribution, risks, and sources of target EDCs in coastal water of China. EDCs in coastal waters of China showed significant spatio-temporal variation with phenolic compounds serving as predominant EDCs. Bisphenol A (BPA) was detected in all water samples with average concentration of 449.2/186.3 ng/L in winter/summer while estrone was the main steroidal estrogen with the average concentration of 87.2/2.7 ng/L in winter/summer. EDCs in coastal waters of South China Sea Area showed higher concentrations. EDCs in coastal waters exerted high ecological risks and estrone/BPA averagely accounted for over 61%/71% of total risk quotient in winter/summer. Average estradiol equivalent concentration of all target EDCs reached 68.87/1.76 ng/L in winter/summer. EDCs in coastal waters did not pose potential non-cancer health risks for humans. The positive matrix factorization (PMF) model was firstly used to identify and quantify possible sources of EDCs. The PMF analysis showed that wastewater and sewage might be the main source for EDCs in coastal waters. EDCs in coastal waters showed high estradiol equivalent concentration and ecological risks at continental-scale, highlighting that EDCs contamination has become a crucial stress affecting the sustainable development of coastal regions.

Molecular interactions of thyroxine binding globulin and thyroid hormone receptor with estrogenic compounds 4-nonylphenol, 4-tert-octylphenol and bisphenol A metabolite (MBP)

AIM

Endocrine disruption due to environmental chemical contaminants is a global human health issue. The aim of present study was to investigate the structural binding aspects of possible interference of commonly detected environmental contaminants on thyroid function.

MATERIAL AND METHODS

Three compounds, 4-tert-octylphenol (4-tert-OP), 4-nonylphenol (4-NP), and 4-methyl-2,4-bis(4-hydroxypentyl)pent-1-ene (MBP) were subjected to induced fit docking (IFD) against thyroxine binding globulin (TBG) and thyroid hormone receptor (THR). Structural analysis included molecular interactions of the amino acid residues and binding energy estimation between the ligands and the target proteins.

KEY RESULTS

All the ligands were successfully placed in the ligand binding pocket of TBG and THR using induced fit docking (IFD). The IFD results revealed high percentage of commonality in interacting amino acid residues between the aforementioned compounds and the native ligand for both TBG and THR. The results of our study further revealed that all the compounds have the potential to interfere with thyroid transport and signaling. However, MBP showed higher binding affinity for both TBG and THR, suggesting higher thyroid disruptive potential as compared to 4-t-OP and 4-NP. Furthermore, our results also suggest that the reported disruptive effects of BPA could actually be exerted through its metabolite; MBP.

SIGNIFICANCE

This work implies that all the three compounds 4-NP, 4-t-OP and especially MBP have the potential to interfere with thyroid hormone transport and signaling. This potentially leads to disruption of thyroid hormone function.

Inhibition of pancreatic lipase by environmental xenoestrogens

Environmental xenoestrogens are the most accessible endocrine disrupting chemicals that have been reported with harmful effects on human health. Although the influences of xenoestrogens on the endocrine system have been extensively studied, it remains unclear whether these xenoestrogens can affect the digestive system in mammals. This study aimed to investigate the inhibitory effects and the underlying mechanism of six non-steroidal synthetic estrogens (including hexestrol, diethylstilbestrol, dienestrol, bisphenol A, bisphenol AF and bisphenol Z) on pancreatic lipase (PL), a key digestive enzyme responsible for lipid digestion and absorption in mammals. The results clearly demonstrated that hexestrol, diethylstilbestrol and dienestrol exhibited strong inhibition on PL, with the IC₅₀ values of less than 1.0 μM. Further investigations elucidated that these three synthetic estrogens functioned as mixed inhibitors of PL, with the K_i values of less than 1 μM. Moreover, molecular dynamics simulations showed that diethylstilbestrol and its analogues might block the binding of substrate on PL via occupying the portal to the active site of PL and thereby inhibit the hydrolytic activity of this key enzyme. Collectively, these results suggested that diethylstilbestrol and its analogues were potent PL inhibitors, which might play a profound role in lipid absorption and weight gain in mammals.

Experimental Approaches for Characterizing the Endocrine-Disrupting Effects of Environmental Chemicals in Fish

Increasing industrial and agricultural activities have led to a disturbing increase of pollutant discharges into the environment. Most of these pollutants can induce short-term, sustained or delayed impacts on developmental, physiological, and behavioral processes that are often regulated by the endocrine system in vertebrates, including fish, thus they are termed endocrine-disrupting chemicals (EDCs). Physiological impacts resulting from the exposure of these vertebrates to EDCs include abnormalities in growth and reproductive development, as many of the prevalent chemicals are capable of binding the receptors to sex steroid hormones. The approaches employed to investigate the action and impact of EDCs is largely dependent on the specific life history and habitat of each species, and the type of chemical that organisms are exposed to. Aquatic vertebrates, such as fish, are among the first organisms to be affected by waterborne EDCs, an attribute that has justified their wide-spread use as sentinel species. Many fish species are exposed to these chemicals in the wild, for either short or prolonged periods as larvae, adults, or both, thus, studies are typically designed to focus on either acute or chronic exposure at distinct developmental stages. The aim of this review is to provide an overview of the approaches and experimental methods commonly used to characterize the effects of some of the environmentally prevalent and emerging EDCs, including 17 α-ethinylestradiol, nonylphenol, BPA, phthalates, and arsenic; and the pervasive and potential carriers of EDCs, microplastics, on reproduction and growth. In vivo and in vitro studies are designed and employed to elucidate the direct effects of EDCs at the organismal and cellular levels, respectively. In silico approaches, on the other hand, comprise computational methods that have been more recently applied with the potential to replace extensive in vitro screening of EDCs. These approaches are discussed in light of model species, age and duration of EDC exposure.

Molecular interactions between sex hormone-binding globulin and nonsteroidal ligands that enhance androgen activity

Sex hormone-binding globulin (SHBG) determines the equilibrium between free and protein-bound androgens and estrogens in the blood and regulates their access to target tissues. Using crystallographic approaches and radiolabeled competitive binding-capacity assays, we report here how two nonsteroidal compounds bind to human SHBG, and how they influence androgen activity in cell culture. We found that one of these compounds, (-)3,4-divanillyltetrahydrofuran (DVT), present in stinging nettle root extracts and used as a nutraceutical, binds SHBG with relatively low affinity. By contrast, a synthetic compound, 3-(1H-imidazol-1-ylmethyl)-2phenyl-1H-indole (IPI), bound SHBG with an affinity similar to that of testosterone and estradiol. Crystal structures of SHBG in complex with DVT or IPI at 1.71-1.80 Å resolutions revealed their unique orientations in the SHBG ligand-binding pocket and suggested opportunities for the design of other nonsteroidal ligands of SHBG. As observed for estradiol but not testosterone, IPI binding to SHBG was reduced by ∼20-fold in the presence of zinc, whereas DVT binding was almost completely lost. Estradiol-dependent fibulin-2 interactions with SHBG similarly occurred for IPI-bound SHBG, but not with DVT-bound SHBG. Both DVT and IPI increased the activity of testosterone in a cell culture androgen reporter system by competitively displacing testosterone from SHBG. These findings indicate how nonsteroidal ligands of SHBG maybe designed to modulate the bioavailability of sex steroids.

Removal of an Ethoxylated Alkylphenol by Adsorption on Zeolites and Photocatalysis with TiO2/Ag

Two advanced removal methods (adsorption and photocatalysis) were compared for the elimination of an ethoxylated alkylphenol (nonylphenol polyethylene glycol, NPEG). For the adsorption process, zeolites were used in their natural state, and the process was characterized by DRX (X-ray diffraction) and SEM–EDS (Scanning electron microscopy). The analysis of the results of the adsorption kinetics was carried out using different isotherms to interpret the removal capacity of zeolites. The Temkin kinetic model better predicted the experimental data and was satisfactorily adjusted to models of pseudo-second order (PSO). On the other hand, for photocatalysis, nano-particles of Ag (silver) were deposited on titanium oxide (TiO2) Degussa-P25 by photo-deposition, and the catalyst was characterized by diffuse reflectance and SEM–EDS. The data obtained using the two removal techniques were analyzed by UV–Vis (ultraviolet-visible spectrophotometry) and total organic carbon (TOC). The kinetic data were compared. The photocatalytic process showed the highest efficiency in the removal of NPEG, corresponding to >80%, while the efficiency of the adsorption process was <60%. This was attributed to the recalcitrant and surfactant nature of NPEG.

Protonation state effects of estrogen receptor α on the recognition mechanisms by perfluorooctanoic acid and perfluorooctane sulfonate: A computational study

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have been reported to cause adverse health effects on wildlife as well as humans. Numerous studies demonstrated that PFOA and PFOS could interfere with the transcriptional activation of estrogen receptor α (ERα) by mimicking the function of endogenous ligand, whereas some reports suggested that the two compounds present non-estrogenic activities. These conflicting results bring a confusion to understand their molecular mechanism on the ERα-mediated signaling pathway. To address this issue, we performed the molecular docking and molecular dynamics simulations to elaborate the structural characteristics for the binding of PFOA and PFOS to ERα. Our results indicated that the two opposite binding orientations were modulated by the protonation states of key residue His524. In sub-acidic condition, PFOA and PFOS prefer to form the H-bonding interactions with the protonated His524, whereas Arg394 provided the H-bonding interactions for stable binding in sub-alkaline condition. Conformational analyses implied that the diverse binding modes were closely related to the conformational propensity of ERα for subsequent coactivator recruitment and transcription activation. Generally, our findings provide a flexible strategy to assess the pH impacts of microenvironment on the toxicities of perfluoroalkyl acids by their interactions with proteins.

4-tert-octylphenol injures motility and viability of human sperm by affecting cAMP-PKA/PKC-tyrosine phosphorylation signals

4-tert-octylphenol (4t-OP) is a well-known xenoestrogen. Our objective was to explore the effects and molecular mechanisms of 4t-OP on human sperm. Sperm samples were exposed to 0, 0.1, or 0.3 mM 4t-OP for two hours. Results showed that both sperm viability and motility were significantly injured by 0.3 mM 4t-OP. We applied comparative proteomics to explore the molecular targets affected by 4t-OP. 81 differentially expressed (DE) proteins were identified. Bioinformatic analysis showed that these proteins were highly associated with motility and apoptosis, and were mostly enriched in cAMP-PKA/PKC-phosphorylation-associated pathway. We further verified that 0.1 mM and 0.3 mM 4t-OP significantly decreased cAMP activity of sperm. Expression of RACK1 and PRDX6 were detected by western blot (WB) to verify their tendencies in gels; antiapoptotic factor BCL2 was also detected by WB. The data indicated that 4-tert-octylphenol injures the motility and viability of human sperm probably by affecting cAMP-PKA/PKC-tyrosine phosphorylation signals.

Water contamination by endocrine disruptors: Impacts, microbiological aspects and trends for environmental protection

Hormone active agents constitute a dangerous class of pollutants. Among them, those agents that mimic the action of estrogens on target cells and are part of the group of endocrine-disruptor compounds (EDCs) are termed estrogenic EDCs, the main focus of this review. Exposure to these compounds causes a number of negative effects, including breast cancer, infertility and animal hermaphroditism. However, especially in underdeveloped countries, limited efforts have been made to warn people about this serious issue, explain the methods of minimizing exposure, and develop feasible and efficient mitigation strategies at different levels and in various environments. For instance, the use of bioremediation processes capable of transforming EDCs into environmentally friendly compounds has been little explored. A wide diversity of estrogen-degrading microorganisms could be used to develop such technologies, which include bioremediation processes for EDCs that could be implemented in biological filters for the post-treatment of wastewater effluent. This review describes problems associated with EDCs, primarily estrogenic EDCs, including exposure as well as the present status of understanding and the effects of natural and synthetic hormones and estrogenic EDCs on living organisms. We also describe potential biotechnological strategies for EDC biodegradation, and suggest novel treatment approaches for minimizing the persistence of EDCs in the environment.

Adverse effects of chronic exposure to nonylphenol on non-alcoholic fatty liver disease in male rats

Endocrine-disrupting chemical (EDC) has been thought to play a role in non-alcoholic fatty liver disease (NAFLD). However, the toxic effects of Nonylphenol (NP), an EDC, on non-alcoholic fatty liver disease have never been elaborated. This study aimed to investigate whether exposure to NP could induce NAFDL, a promoting effect of high-sucrose-high-fat diet (HSHFD) on the adverse effects caused by NP was evaluated. Fourth eight male rats were assigned to four groups and each group was treated with a specific testing sample: normal-diet (ND) control group (C-ND); normal diet plus NP (180mg/kg/day) group (NP-ND); high-sucrose-high-fat-diet control group (C-HSHFD); HSHFD plus NP (180mg/kg/day) group (NP-HSHFD). At the age of 80 day, sonogram presents diffusely increased hepatic echogenicity in the NP-HSHFD group. The oblique diameter of liver in the NP-HSHFD group was significantly bigger than that in both the C-ND and NP-ND groups. At the age of 90 day, exposure to NP-HSHFD and NP-ND caused a significant increase in NP concentration in liver as compared to the C-ND group. The rats in the groups treated with NP+ND, HSHFD and NP+HSHFD produced significant increases in the body weight, fat weight and FMI, respectively, when compared to the C-ND group. The liver weight and hepatosomatic indexes (HIS) of rats in the NP-HSHFD group are higher than those in the C-HSHFD group. Exposure to NP-HSHFD induced the increases in plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), cholesterol (TC), triglyceride (TG) and low density lipoprotein (LDL) as compared to the C-ND group. Morphological examination of liver tissue from rats exposed to NP+HSHFD shown steatosis with marked accumulation of lipid droplets, hepatocellular ballooning degeneration and inflammatory cell infiltration. Chronic exposure to NP might induce NAFLD in male rats. The high-sucrose-high-fat diet accelerates and exacerbates the development of NAFLD caused by NP exposure.