Enhanced Disrupting Effect of Benzophenone-1 Chlorination Byproducts to the Androgen Receptor: Cell-Based Assays and Gaussian Accelerated Molecular Dynamics Simulations.

Benzophenone-1 (BP-1), one of the commonly used ultraviolet filters, has caused increasing public concern due to frequently detected residues in environmental and recreational waters. Its susceptibility to residual chlorine and the potential to subsequently trigger endocrine disruption remain unknown. We herein investigated the chlorination of BP-1 in swimming pool water and evaluated the endocrine disruption toward the human androgen receptor (AR). The structures of monochlorinated (P1) and dichlorinated (P2) products were separated and characterized by mass spectrometry and 1H-1H NMR correlation spectroscopy. P1 and P2 exhibited significantly higher antiandrogenic activity in yeast two-hybrid assays (EC50, 6.13 µM and 9.30 µM) than did BP-1 (12.89 µM). Our 350 ns Gaussian accelerated molecular dynamics simulations showed the protein dynamics in a long-time scale equilibrium, and further energy calculations revealed that although increased hydrophobic interactions are primarily responsible for enhanced binding affinities between chlorinated products and the AR ligand binding domain, the second chloride in P2 still hinders the complex motion because of the solvation penalty. The mixture of BP-1-P1-P2 elicited additive antiandrogenic activity, well fitted by the concentration addition model. P1 and P2 at 1 µM consequently downregulated the mRNA expression of AR-regulated genes, NKX3.1 and KLK3, by 1.7-9.1-fold in androgen-activated LNCaP cells. Because chlorination of BP-1 occurs naturally by residual chlorine in aquatic environments, our results regarding enhanced antiandrogenic activity and disturbed AR signaling provided evidence linking the use of personal care products with potential health risks.

Human exposure to synthetic endocrine disrupting chemicals (S-EDCs) is generally negligible as compared to natural compounds with higher or comparable endocrine activity. How to evaluate the risk of the S-EDCs?

Theoretically, both synthetic endocrine-disrupting chemicals (S-EDCs) and natural (exogenous and endogenous) endocrine-disrupting chemicals (N-EDCs) can interact with endocrine receptors and disturb hormonal balance. However, compared to endogenous hormones, S-EDCs are only weak partial agonists with receptor affinities several orders of magnitude lower than S-EDCs. Thus, to elicit observable effects, S-EDCs require considerably higher concentrations to attain sufficient receptor occupancy or to displace natural hormones and other endogenous ligands. Significant exposures to exogenous N-EDCs may result from ingestion of foods such as soy-based diets, green tea, and sweet mustard. While their potencies are lower as compared to natural endogenous hormones, they usually are considerably more potent than S-EDCs. Effects of exogenous N-EDCs on the endocrine system were observed at high dietary intakes. A causal relation between their mechanism of action and these effects is established and biologically plausible. In contrast, the assumption that the much lower human exposures to S-EDCs may induce observable endocrine effects is not plausible. Hence, it is not surprising that epidemiological studies searching for an association between S-EDC exposure and health effects have failed. Regarding testing for potential endocrine effects, a scientifically justified screen should use in vitro tests to compare potencies of S-EDCs with those of reference N-EDCs. When the potency of the S-EDC is similar or smaller than that of the N-EDC, further testing in laboratory animals and regulatory consequences are not warranted.

Human exposure to synthetic endocrine disrupting chemicals (S-EDCs) is generally negligible as compared to natural compounds with higher or comparable endocrine activity: how to evaluate the risk of the S-EDCs?

Theoretically, both synthetic endocrine disrupting chemicals (S-EDCs) and natural (exogenous and endogenous) endocrine disrupting chemicals (N-EDCs) can interact with endocrine receptors and disturb hormonal balance. However, compared to endogenous hormones, S-EDCs are only weak partial agonists with receptor affinities several orders of magnitude lower. Thus, to elicit observable effects, S-EDCs require considerably higher concentrations to attain sufficient receptor occupancy or to displace natural hormones and other endogenous ligands. Significant exposures to exogenous N-EDCs may result from ingestion of foods such as soy-based diets, green tea and sweet mustard. While their potencies are lower as compared to natural endogenous hormones, they usually are considerably more potent than S-EDCs. Effects of exogenous N-EDCs on the endocrine system were observed at high dietary intakes. A causal relation between their mechanism of action and these effects is established and biologically plausible. In contrast, the assumption that the much lower human exposures to S-EDCs may induce observable endocrine effects is not plausible. Hence, it is not surprising that epidemiological studies searching for an association between S-EDC exposure and health effects have failed. Regarding testing for potential endocrine effects, a scientifically justified screen should use in vitro tests to compare potencies of S-EDCs with those of reference N-EDCs. When the potency of the S-EDC is similar or smaller than that of the N-EDC, further testing in laboratory animals and regulatory consequences are not warranted.

Revisión de los modelos computacionales que relacionan la estructura química con la disrupción del sistema endocrino / Protection against endocrine disruption through quantitative structure-activity relationship modelling

El término interruptor endocrino define una amplia y diversa clase de sustancias de origen natural o antropogénico con la capacidad de interferir con alguna función del sistema endocrino y provocar efectos adversos en un organismo o su descendencia. La disrupción endocrina se asocia con cáncer, obesidad, diabetes, disfunción reproductiva e inmunológica. Constituye una forma específica de toxicidad cuyas regulaciones y legislación actualmente carecen de consenso. Los métodos computacionales, y particularmente los estudios quimioinformáticos como las relaciones cuantitativas estructura-actividad (QSAR), son herramientas valiosas de investigación que han ocupado gradualmente un importante espacio en los estudios toxicológicos. Esta revisión propone un análisis del más reciente estado del arte relativo a la modelación QSAR de la disrupción endocrina. Los casos de estudio seleccionados se centran en tres mecanismos importantes que representan la biosíntesis, el transporte y la interacción con los receptores hormonales mediados por la capacidad inhibitoria de la enzima aromatasa, y los efectos sobre la proteína transportadora de transtiretina y el receptor de andrógenos, respectivamente. Estas herramientas predictivas pueden ayudar a priorizar sustancias como posibles alteradores endocrinos y, por lo tanto, son contribuciones importantes que garantizan el ahorro de tiempo, materiales y recursos humanos

The endocrine disruptors are defined as a broad and diverse class of substances of natural or anthropogenic origin with the ability to interfere with some function of the endocrine system and, in doing so, cause adverse effects on an organism or its descendants. Endocrine disruption, associated with pathologies such as cancer, obesity, diabetes, and reproductive and immunological dysfunction, constitutes a specific form of toxicity whose regulation and legislation currently lack consensus. Computational methods, and within them chemoinformatic studies such as the prediction of quantitative structure-activity relationships (QSAR), are valuable research tools that have gradually occupied an important space in toxicological studies. This review proposes an analysis of the most recent state of the art related to QSAR modelling in the context of endocrine disruption. For this, case studies reported on three important hormonal mechanisms were selected, which represent synthesis, transport, and interaction with receptors. The summarized QSARs modelled the inhibitory capacity of the aromatase enzyme and the effects on the transthyretin transporter protein and the androgen receptor. These predictive tools can assist in prioritizing substances as potential endocrine disruptors and are therefore important contributions that guarantee the saving of time, material, and human resources

Synthesis of defined endocrine-disrupting nonylphenol isomers for biological and environmental studies.

Nonylphenols are very important environmentally relevant substances in the focus of the world-wide endocrine disrupter research for over 25 years. Thus, they are among the 10 priority hazardous substances of the new European Union Water Framework Directive. They consist of a very complex mixture of isomers representing therefore a multi-component problem like dioxins or PCBs. As estrogenic effect and degradation behavior in the environment of individual 4-nonylphenols are heavily dependent on the structure and bulkiness of the side chain, it is absolutely necessary to consider the nonylphenol problem from an isomer-specific viewpoint. Therefore a range of 28 differently branched nonylphenol isomers were synthesized for biological and environmental studies. Nonylphenols with a quaternary alpha-carbon, like 4-(1,1,3,4-tetramethylpentyl)phenol (4-NP(95)) and 4-(1-ethyl-1,3,3-trimethylbutyl)phenol (4-NP(170)), were obtained by Friedel-Crafts alkylation of anisole with tertiary nonyl bromides and demethylation with BI(3). Nonylphenols with a tertiary alpha-carbon, such as 4-(1,2-dimethylheptyl)phenol (4-NP(10)) and 4-(1,2,4-trimethylhexyl)phenol (4-NP(41)), were accessible via coupling of p-methoxyphenylmagnesium bromide with ketones. Nonylphenols bearing a quaternary beta-carbon, like 4-(2,2-dimethylheptyl)phenol (4-NP(15)) and 4-(1,2,2-trimethylhexyl)phenol (4-NP(39)), were synthesized starting from 4'-methoxyisobutyrophenone. The compounds were characterized by GC-MS and NMR-spectroscopy. The individual isomers were designated according to the Juelich Nomenclature.

Analysis of natural and synthetic estrogenic endocrine disruptors in environmental waters using online preconcentration coupled with LC-APPI-MS/MS.

This paper describes a fully automated online method for solid-phase extraction coupled with liquid chromatography and tandem mass spectrometry using atmospheric pressure ionization (LC-LC-APPI-MS/MS) to simultaneously detect selected dissolved natural and synthetic hormones at concentrations as low as 5 ng/L from aqueous matrices. The method shows excellent performance for the direct analysis of water and wastewater with respect to calibration curve linearity, analytic specificity, sensitivity, and carryover, as well as overall method accuracy and precision. With a runtime of 15 min, a minimum of 200 samples were analyzed using a single online solid-phase extraction (SPE) column without noticeable differences in system performance. Because of the ruggedness and simplicity of this system, generic methods can be easily developed and applied for the high-throughput analysis of a wide variety of compounds without the need to resort to laborious offline SPE sample preparation.

Syntheses and estrogenic activity of 4-nonylphenol isomers.

Eight branched 4-nonylphenol (NP) isomers, which were identified from commercially available NP reagent, 4-(1-ethyl-1,4-dimethylpentyl)phenol (NP-C), 4-(1,1-dimethyl-3-ethylpentyl)phenol (NP-D), 4-(1,3-dimethyl-1-ethylpentyl)phenol (NP-E(G)), diastereomeric mixture), 4-(1,1,4-trimethylhexyl)phenol (NP-F), 4-(1-methyl-1-n-propylpentyl)phenol (NP-H), 4-(1,1-dimethyl-2-ethylpentyl)phenol (NP-I), 4-(1,1,2-trimethylhexyl)phenol (NP-M), and 4-(1-ethyl-1-methylhexyl)phenol (NP-N), were synthesized by two different synthetic methods starting from 4-benzyloxyacetophenone or phenol. The chemical structures of the synthesized compounds were confirmed by MS and NMR spectroscopy. The estrogenic activities of these synthetic NP isomers were tested and exhibited different activities on the recombinant yeast screen system. NP-I was found to exhibit three times greater estrogenic activity than the commercial NP mixture.

Seguridad farmacológica y ambiental: disrupción endocrina / Drug and environmental safety: hyroid endocrine disruption

La exposición humana a compuestos químicos que interfieren con la homeostasis hormonal es bien conocida, a pesar de que la evidencia sea muy desigual para los distintos sistemas hormonales. Mientras que la disrupción endocrina de los esteroides (estrógenos y andrógenos) ha merecido gran atención, la de la homeostasis de las hormonas tiroideas está mal entendida, si se exceptúa lo que se refiere a la captación de yodo. La lista de disruptores endocrinos que interfieren con la síntesis, la circulación, la unión a receptores específicos, el metabolismo y la degradación de las hormonas tiroideas crece día a día. A los bifenilospoliclorados (PCB), las dioxinas y los furanos, se unen ahora los compuestos bromados retardadores de la llama, los bisfenoles y losftalatos. Cambios sutiles en las concentraciones de las hormonas tiroideas pueden ocasionar efectos adversos en períodos esenciales del desarrollo, de tal manera que se empieza a ver los efectos de tal exposición ahora, una vez que los mecanismos que ligan hormonastiroideas y neurodesarrollo son cada vez más evidentes ( AU)

Human exposure to environmental chemicals that disrupt endocrine homeostasis has been related to several hormone systems. Sex hormones (estrogen sand androgens) have received special attention, but thyroid hormone disruption is not so well known except in the special case of iodine intake deficiency. The list of chemicals that alter synthesis, circulation, binding to specific receptors, metabolism and degradation of thyroid hormones increases daily. Brominated flameretardants, bisphenols and phthalates are now included alongside polychlorinated biphenyls (PCBs), dioxins and furans. Subtle changes in circulating thyroid hormones may have undesirable effects during development. As our understanding of the role of thyroid hormones in neurodevelopment improves, exposure to environmental thyroid disruptors becomes a matter of increasing concern (AU)