Thyroid Disruption by Bisphenol S Analogues via Thyroid Hormone Receptor β: in Vitro, in Vivo, and Molecular Dynamics Simulation Study

Distribution, transformation, and toxic effects of the flame retardant tetrabromobisphenol S and its derivatives in the environment: A review

As widely used alternative brominated flame retardants, tetrabromobisphenol S (TBBPS) and its derivatives have attracted increasing amounts of attention in the field of environmental science. Previous studies have shown that TBBPS and its derivatives easily accumulate in environmental media and may cause risks to environmental safety and human health. Therefore, to explore the environmental behaviours of TBBPS and its derivatives, in this paper, we summarized relevant research on the distribution of these compounds in water, the atmosphere, soil and food/biota, as well as their transformation mechanisms (biological and nonbiological) and toxic effects. The summary results show that TBBPS and its derivatives have been detected in water, the atmosphere, soil, and food/biota globally, making them a ubiquitous pollutant. These compounds may be subject to adsorption, photolysis or biological degradation after being released into the environment, which in turn increases their ecological risk. TBBPS and its derivatives can cause a series of toxic effects, such as neurotoxicity, hepatotoxicity, cytotoxicity, thyrotoxicity, genotoxicity and phytotoxicity, to cells or living organisms in in vitro and in vivo exposure. Toxicological studies suggest that TBBPS as an alternative to TBBPA is not entirely environmentally friendly. Finally, we propose future directions for research on TBBPS and its derivatives, including the application of new technologies in studies on the migration, transformation, toxicology and human exposure risk assessment of TBBPS and its derivatives in the environment. This review provides useful information for obtaining a better understanding of the behaviour and potential toxic effects of TBBPS and its derivatives in the environment.

Update of the scientific opinion on tetrabromobisphenol A (TBBPA) and its derivatives in food

The European Commission asked EFSA to update its 2011 risk assessment on tetrabromobisphenol A (TBBPA) and five derivatives in food. Neurotoxicity and carcinogenicity were considered as the critical effects of TBBPA in rodent studies. The available evidence indicates that the carcinogenicity of TBBPA occurs via non-genotoxic mechanisms. Taking into account the new data, the CONTAM Panel considered it appropriate to set a tolerable daily intake (TDI). Based on decreased interest in social interaction in male mice, a lowest observed adverse effect level (LOAEL) of 0.2 mg/kg body weight (bw) per day was identified and selected as the reference point for the risk characterisation. Applying the default uncertainty factor of 100 for inter- and intraspecies variability, and a factor of 3 to extrapolate from the LOAEL to NOAEL, a TDI for TBBPA of 0.7 μg/kg bw per day was established. Around 2100 analytical results for TBBPA in food were used to estimate dietary exposure for the European population. The most important contributors to the chronic dietary LB exposure to TBBPA were fish and seafood, meat and meat products and milk and dairy products. The exposure estimates to TBBPA were all below the TDI, including those estimated for breastfed and formula-fed infants. Accounting for the uncertainties affecting the assessment, the CONTAM Panel concluded with 90%-95% certainty that the current dietary exposure to TBBPA does not raise a health concern for any of the population groups considered. There were insufficient data on the toxicity of any of the TBBPA derivatives to derive reference points, or to allow a comparison with TBBPA that would support assignment to an assessment group for the purposes of combined risk assessment.

Evaluation of thyroid-disrupting effects of bisphenol F and bisphenol S on zebrafish (Danio rerio) using anti-transthyretin monoclonal antibody-based immunoassays

The thyroid disrupting chemicals (TDCs) have raised great concerns due to their adverse impacts on thyroid hormones (THs). In this study, we investigated the thyroid-disrupting effects of bisphenol F (BPF) and bisphenol S (BPS), two major BPA substitutes, on adult zebrafish (Danio rerio). Firstly, anti-transthyretin (TTR) monoclonal antibody (anti-TTR mAb) was prepared and used to establish an indirect ELISA, which had a working range of 15.6∼1000 ng/mL of a detection limit of 6.1 ng/mL. The immunoassays based on anti-TTR mAb showed that exposure to BPF (10 and 100 μg/L) and BPS (100 μg/L) significantly elevated the levels of TTR protein in the plasma, liver, and brain tissues. Moreover, immunofluorescence showed that 100 μg/L BPF and BPS induced the production of TTR protein in liver and brain tissues. In addition, BPF and BPS increased THs levels and damaged thyroid tissue structure in adult female zebrafish. Especially, 100 μg/L BPF significantly increased T4 and T3 levels by 2.05 and 1.14 times, and induced pathological changes of thyroid follicles. The changes in the expression levels of genes involved in the hypothalamus-pituitary-thyroid (HPT) axis further illustrated that BPF and BPS had significant adverse effects on THs homeostasis and thyroid function in zebrafish. Therefore, TTR immunoassays could be used for the evaluation of thyroid-disrupting effects in fish and BPF exhibited greater disruption than BPS.

Estrogenic disruption effects and formation mechanisms of transformation products during photolysis of preservative parabens

The ubiquitous presence of emerging contaminants (ECs) in the environment and their associated adverse effects has raised concerns about their potential risks. The increased toxicity observed during the environmental transformation of ECs is often linked to the formation of their transformation products (TPs). However, comprehension of their formation mechanisms and contribution to the increased toxicity remains an unresolved challenge. To address this gap, by combining quantum chemical and molecular simulations with photochemical experiments in water, this study investigated the formation of TPs and their molecular interactions related to estrogenic effect using the photochemical degradation of benzylparaben (BZP) preservative as a representative example. A non-targeted analysis was carried out and three previously unknown TPs were identified during the transformation of BZP. Noteworthy, two of these novel TPs, namely oligomers BZP-o-phenol and BZP-m-phenol, exhibited higher estrogenic activities compared to the parent BZP. Their IC50 values of 0.26 and 0.50 μM, respectively, were found to be lower than that of the parent BZP (6.42 μM). The binding free energies (ΔGbind) of BZP-o-phenol and BZP-m-phenol (-29.71 to -23.28 kcal·mol-1) were lower than that of the parent BZP (-20.86 kcal·mol-1), confirming their stronger binding affinities toward the estrogen receptor (ER) α-ligand binding domain. Subsequent analysis unveiled that these hydrophobic residues contributed most favorably to ER binding, with van der Waals interactions playing a significant role. In-depth examination of the formation mechanisms indicated that these toxic TPs primarily originated from the successive cleavage of ester bonds (OCH2C6H5 and COO group), followed by their combination with BZP*. This study provides valuable insight into the mechanisms underlying the formation of toxic TPs and their binding interactions causing the endocrine-disrupting effects. It offers a crucial framework for elucidating the toxicological patterns of ECs with similar structures.

Occurrence and exposure evaluation of bisphenol A and its analogues in indoor and outdoor dust from China

Bisphenol A (BPA) and its analogues have been proved to be harmful to human reproduction, endocrine and nervous system. But information on the occurrence and human exposure to bisphenol compounds (BPs) in dust (especially outdoor dust) is limited. In this study, 14 BPs were determined in 174 indoor dust samples and 202 outdoor dust samples from Chinese mainland, Hong Kong, Macau and Taiwan. BPA, BPS, BPAF, BPF, BPAP and BPE were widely detected with detection frequencies of 98.94 %, 98.67 %, 97.87 %, 95.21 %, 87.23 % and 71.54 %, respectively. The median total concentrations of the most detected six BPs in the dust were in the order of south urban indoors (556 ng/g) > south rural outdoors (438 ng/g) > south urban outdoors (432 ng/g) > south rural outdoors (418 ng/g) > north rural indoors (412 ng/g) > north urban outdoors (341 ng/g) > north urban indoors (311 ng/g) > north rural outdoors (246 ng/g). The amounts of garbage incineration, plastic output and recycled paper may have influence on the BPs levels. Some BPs (BPAF, BPAP, BPF and BPS) in the indoor and outdoor samples were significantly positively correlated. In addition, the BPs in the indoor dust from different indoor micro environments in Chengdu were investigated. BPA (median concentration: 571.2 ng/g) and BPF (median concentration: 114.3 ng/g) were the two primary BPs, accounting for 78.1 % of the median total concentrations of the investigated BPs. High concentration of BPA appeared in printing workshops and offices, while high concentration of BPAP, BPC, BPE and BPF appeared in electronic repair shops. Occupational exposure to BPs deserves attention in the future. ΣBPs exposure risk for children and adults in the urban areas of southern China was the highest. To our knowledge, this is the first report in China to study BPs in outdoor dust sample.

Effects and mechanisms of bisphenols exposure on neurodegenerative diseases risk: A systemic review

Environmental bisphenols (BPs) pose a global threat to human health because of their extensive use as additives in plastic products. BP residues are increasing in various environmental media (i.e., water, soil, and indoor dust) and biological and human samples (i.e., serum and brain). Both epidemiological and animal studies have determined an association between exposure to BPs and an increased risk of neurodegenerative diseases (e.g., Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis), including cognitive abnormalities and behavioral disturbances. Hence, understanding the biological responses to different BPs is essential for prevention, and treatment. This study provides an overview of the underlying pathogenic molecular mechanisms as a valuable basis for understanding neurodegenerative disease responses to BPs, including accumulation of misfolded proteins, reduction of tyrosine hydroxylase and dopamine, abnormal hormone signaling, neuronal death, oxidative stress, calcium homeostasis, and inflammation. These findings provide new insights into the neurotoxic potential of BPs and ultimately contribute to a comprehensive health risk evaluation.

Bisphenols and brominated bisphenols induced endothelial dysfunction via its disruption of endothelial nitric oxide synthase

Emerging literatures have concentrated on the association between cardiovascular diseases risk of typical endocrine disruptor bisphenols, which also put forward the further studies need respect to the potential mechanism. Herein, we investigated the endothelial dysfunction effects of bisphenols and brominated bisphenols involved in aortic pathological structure, endothelial nitric oxide synthase (eNOS) protein phosphorylation, synthase activity and nitric oxide (NO) production in human umbilical vein endothelial cells (HUVECs) and C57BL/6 mice. Bisphenol A (BPA) and bisphenol S (BPS) increased NO production by 85.7% and 68.8% at 10-6 M level in vitro and 74.3%, 41.5% in vivo, respectively, while tetrabromobisphenol S (TBBPS) significantly inhibited NO by 55.7% at 10-6 M in vitro and 28.9% in vivo at dose of 20 mg/kg BW/d. Aortic transcriptome profiling revealed that the process of 'regulation of NO mediated signal transduction' was commonly induced. The mRNA and protein expression of phosphorylated eNOS at Ser1177 were promoted by BPA and BPS but decreased by TBBPA and TBBPS in HUVECs. Phosphorylation and enzymatic activity of eNOS were significantly increased by 43.4% and 13.8% with the treatment of BPA and BPS at 10-7 M, but decreased by 16.9% after exposure to TBBPS at 10-6 M in vitro. Moreover, only TBBPS was observed to increase aorta thickness significantly in mice and induce endothelial dysfunction. Our work suggests that bisphenols and brominated bisphenols may exert adverse outcome on vascular health differently in vitro and in vivo, and emphasizes areas of public health concern similar endocrine disruptors vulnerable on the vascular endothelial function.

Screening of the Antagonistic Activity of Potential Bisphenol A Alternatives toward the Androgen Receptor Using Machine Learning and Molecular Dynamics Simulation

Over the past few decades, extensive research has indicated that exposure to bisphenol A (BPA) increases the health risks in humans. Toxicological studies have demonstrated that BPA can bind to the androgen receptor (AR), resulting in endocrine-disrupting effects. In recent investigations, many alternatives to BPA have been detected in various environmental media as major pollutants. However, related experimental evaluations of BPA alternatives have not been systematically implemented for the assessment of chemical safety and the effects of structural characteristics on the antagonistic activity of the AR. To promote the green development of BPA alternatives, high-throughput toxicological screening is fundamental for prioritizing chemical tests. Therefore, we proposed a hybrid deep learning architecture that combines molecular descriptors and molecular graphs to predict AR antagonistic activity. Compared to previous models, this hybrid architecture can extract substantial chemical information from various molecular representations to improve the model's generalization ability for BPA alternatives. Our predictions suggest that lignin-derivable bisguaiacols, as alternatives to BPA, are likely to be nonantagonist for AR compared to bisphenol analogues. Additionally, molecular dynamics (MD) simulations identified the dihydrotestosterone-bound pocket, rather than the surface, as the major binding site of bisphenol analogues. The conformational changes of key helix H12 from an agonistic to an antagonistic conformation can be evaluated qualitatively by accelerated MD simulations to explain the underlying mechanism. Overall, our computational study is helpful for toxicological screening of BPA alternatives and the design of environmentally friendly BPA alternatives.

Halogenation of common phenolic household and personal care product ingredients enhances their AhR-modulating capacity

The Aryl Hydrocarbon Receptor (AhR), a ligand-activated transcription factor, orchestrates responses to numerous structurally diverse endogenous and exogenous ligands. In addition to binding various xenobiotics, AhR also recognizes endocrine disruptors, particularly those featuring chlorinated or brominated aromatic structures. There is limited data available on the impact of common household and personal care product ingredients let alone their halogenated transformation products. Herein we bridge this knowledge gap by preparing a library of chlorinated and brominated parabens, bisphenols, UV filters, and nonylphenols. An evaluation of total of 125 compounds for agonistic and antagonistic activity on AhR unveiled a low micromolar agonist, Cl2BPAF with an EC50 of 13 μM. Moreover, our study identified several AhR antagonists, with BrBzP emerging as the most potent with an IC50 of 8.9 μM. To further investigate the functional implications of these compounds, we subjected the most potent agonist and antagonist to a functional assay involving cytokine secretion from peripheral blood mononuclear cells and compared their activity with the commercially available AhR agonist and antagonist. Cl2BPAF exhibited an overall immunosuppressive effect by reducing the secretion of proinflammatory cytokines, including IL-6, IFN-γ, and TNF-α, while BrBzP displayed opposite effects, leading to an increase of those cytokines. Notably, the immunomodulatory effects of Cl2BPAF surpassed those of ITE, a bona fide AhR agonist, while the impact of BrBzP exceeded that of CH223191, a bona fide AhR antagonist. In summary, our study underscores the potential influence of halogenated transformation products on the AhR pathway and, consequently, their role in shaping the immune responses.

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

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

Effects of Prenatal Exposure to Bisphenol A Substitutes, Bisphenol S and Bisphenol F, on Offspring's Health: Evidence from Epidemiological and Experimental Studies

Pregnancy and lactation are critical periods for human well-being and are sensitive windows for pollutant exposure. Bisphenol A (BPA) is well demonstrated as a toxicant and has been replaced in the plastic industry with other bisphenol analogs that share similarities in structure and characteristics, most commonly Bisphenol S (BPS) and Bisphenol F (BPF). Maternal exposure to BPS or BPF can result in their accumulation in the fetal compartment, leading to chronic exposure and potentially limiting normal fetal growth and development. This review summarizes considerable findings of epidemiological or experimental studies reporting associations between BPS or BPF and impaired fetal growth and development. Briefly, the available findings indicate that exposure to the two bisphenol analogs during pregnancy and lactation can result in multiple disturbances in the offspring, including fetal growth restrictions, neurological dysfunctions, and metabolic disorders with the potential to persist throughout childhood. The occurrence of premature births may also be attributed to exposure to the two bisphenols. The possible mechanisms of actions by which the two bisphenols can induce such effects can be attributed to a complex of interactions between the physiological mechanisms, including impaired placental functioning and development, dysregulation of gene expression, altered hormonal balance, and disturbances in immune responses as well as induced inflammations and oxidative stress. In conclusion, the available evidence suggests that BPS and BPF have a toxic potential in a compartment level to BPA. Future research is needed to provide more intensive information; long-term studies and epidemiological research, including a wide scale of populations with different settings, are recommended. Public awareness regarding the safety of BPA-free products should also be enhanced, with particular emphasis on educating individuals responsible for the well-being of children.

Mechanism of thyroid hormone and its structurally similar contaminant bisphenol S exposure on retinoid metabolism in zebrafish larval eyes

The photoreceptor necessitates the retinoids metabolism processes in visual cycle pathway to regenerate visual pigments and sustain vision. Bisphenol S (BPS), with similar structure of thyroid hormone (TH), was reported to impair the light-sensing function of zebrafish larvae via disturbing TH-thyroid hormone receptor β (TRβ) signaling pathway. However, it remains unknown whether TRβ could modulate the toxicity of BPS on retinoid metabolism in visual cycle. This study showed that BPS diminished the optokinetic response of zebrafish larvae and had a stimulative effect on all-trans-retinoic acid (atRA) metabolism, like exogenous T3 exposure. By modulating CYP26A1 and TRβ expression, it was found that CYP26A1 played a crucial role in catalyzing oxidative metabolism of atRA and retinoids regeneration in visual cycle, and TRβ mediated cyp26a1 expression in zebrafish eyes. Similar with 10 nM T3 treatment, cyp26a1 expression could be induced by BPS in the presence of TRβ. Further, in CYP26A1 and TRβ- deficient eyes, 100 μg/L BPS could no longer promote atRA metabolism, or decrease the all-trans-retinol and 11-cis retinal contents in visual cycle, demonstrating that BPS exposure disturbed CYP26A1-mediated visual retinoids metabolism via TRβ. Overall, this study highlights the role of TRβ in mediating the retinoids homeostasis disruption caused by BPS, and provides new clues for exploring molecular targets of visual toxicity under pollutants stress.

Cross-species applicability of an adverse outcome pathway network for thyroid hormone system disruption

Thyroid hormone system disrupting compounds are considered potential threats for human and environmental health. Multiple adverse outcome pathways (AOPs) for thyroid hormone system disruption (THSD) are being developed in different taxa. Combining these AOPs results in a cross-species AOP network for THSD which may provide an evidence-based foundation for extrapolating THSD data across vertebrate species and bridging the gap between human and environmental health. This review aimed to advance the description of the taxonomic domain of applicability (tDOA) in the network to improve its utility for cross-species extrapolation. We focused on the molecular initiating events (MIEs) and adverse outcomes (AOs) and evaluated both their plausible domain of applicability (taxa they are likely applicable to) and empirical domain of applicability (where evidence for applicability to various taxa exists) in a THSD context. The evaluation showed that all MIEs in the AOP network are applicable to mammals. With some exceptions, there was evidence of structural conservation across vertebrate taxa and especially for fish and amphibians, and to a lesser extent for birds, empirical evidence was found. Current evidence supports the applicability of impaired neurodevelopment, neurosensory development (eg, vision) and reproduction across vertebrate taxa. The results of this tDOA evaluation are summarized in a conceptual AOP network that helps prioritize (parts of) AOPs for a more detailed evaluation. In conclusion, this review advances the tDOA description of an existing THSD AOP network and serves as a catalog summarizing plausible and empirical evidence on which future cross-species AOP development and tDOA assessment could build.

Angiogenic Activity and Mechanism for Bisphenols on Endothelial Cell and Mouse: Evidence of a Structural-Selective Effect

Increased epidemiological evidence indicates the association of bisphenol exposure with human vascular disorders, while the underlying mechanism has not been clarified. Here, we sought to unveil the potential angiogenic effect and the underlying mechanism of bisphenols with different structural features using endothelial cells treated with an environmentally relevant concentration of bisphenols (range: 1 nM to 10 μM) and a C57BL/6 mouse model fed with doses of 0.002, 0.02, 2, and 20 mg/kg BW/day for 5 weeks. Bisphenol A (BPA) and bisphenol S (BPS) at a 1 nM level significantly increased tube formation by 45.1 and 30.2% and induced the microvessel sprouting, while tube length and microvessel sprouting were significantly inhibited by 37.2 and 55.7% after exposure to tetrabromobisphenol S (TBBPS) at 1 μM, respectively. Mechanistically, TBBPA and TBBPS significantly inhibited the interaction between phosphatidylinositol 3-kinase (PI3K) and thyroid receptor (TR), while BPA and BPS favored the interaction between PI3K and estrogen receptor (ER), resulting in abnormal PI3K signaling with consequent distinct angiogenic activity. BPA- and BPS-induced pro-angiogenic effects and TBBPS showed anti-angiogenic effects due to their distinct disruption on the TR/ER-PI3K pathway. Our work provided new evidence and mechanistic insight on the angiogenic activity of bisphenols and expanded the scope of endocrine disruptors with interference in vascular homeostasis.

Trimester-specific associations of maternal exposure to bisphenols with neonatal thyroid stimulating hormone levels: A birth cohort study

BACKGROUND

Growing evidence suggests that exposure to bisphenol A (BPA) during pregnancy could interfere with neonatal thyroid function. Bisphenol F (BPF) and bisphenol S (BPS) are increasingly used as the substitutes of BPA. However, little is known about the effects of maternal exposure to BPS and BPF on neonatal thyroid function. The current study was aimed to investigate the trimester-specific associations of maternal exposure to BPA, BPS, and BPF with neonatal thyroid stimulating hormone (TSH) levels.

METHODS

Between November 2013 and March 2015, a total of 904 mother-newborn pairs were recruited from the Wuhan Healthy Baby Cohort Study, providing maternal urine samples in the first, second, and third trimesters for bisphenol exposure assessment, and neonatal heel prick blood samples for TSH measurement. Multiple informant model and quantile g-computation were used to evaluate the trimester-specific associations of bisphenols individually and mixture with TSH, respectively.

RESULTS

Each doubling concentration increase of maternal urinary BPA in the first trimester was significantly related to a 3.64 % (95% CI: 0.84 %, 6.51 %) increment in neonatal TSH. Each doubling concentration increase of BPS in the first, second and third trimesters were associated with 5.81 % (95 % CI: 2.27 %, 9.46 %), 5.70 % (95 % CI: 1.99 %, 9.55 %), 4.36 % (95 % CI: 0.75 %, 8.11 %) higher neonatal blood TSH, respectively. No significant association between trimester-specific BPF concentration and TSH was observed. The relationships between exposures to BPA/BPS and neonatal TSH were more evident in female infants. Quantile g-computation indicated that maternal co-exposure to bisphenols in the first trimester was significantly associated with neonatal TSH levels in a non-linear fashion.

CONCLUSION

Maternal exposure to BPA and BPS were positively associated with neonatal TSH levels. The results indicated the endocrine disrupting effect of prenatal exposure to BPS and BPA, which should be of particular concern.

Regioselective oxidation of heterocyclic aromatic hydrocarbons catalyzed by cytochrome P450: A case study of carbazole

Recently there are increasing interests in accurately evaluating the health effects of heterocyclic PAHs. However, the activation mechanism and possible metabolites of heterocyclic PAHs catalyzed by human CYP1A1 is still elusive to a great extent. Here, leveraged to high level QM/MM calculations, the corresponding activation pathways of a representative heterocyclic PAHs, carbazole, were systematically explored. The first stage is electrophilic addition or hydrogen abstraction from N-H group. Electrophilic addition was evidenced to be more feasible and regioselectivity at C3 and C4 sites were identified. Correlations between energy barriers and key structural/electrostatic parameters reveal that O-Cα distance and Fe-O-Cα angle are the main origin for the catalytic regioselectivity. Electrophilic addition was determined as the rate-determining step and the subsequent possible reactions include epoxidation, NIH shift (the hydrogen migration from the site of hydroxylation to the adjacent carbon) and proton shuttle. The corresponding products are epoxides, ketones and hydroxylated carbazoles, respectively. The main metabolites (hydroxylated carbazoles) are estimated to be more toxic than carbazole. The regioselectivity of carbazole activated by CYP1A1 is different from the environmental processes (gas and aqueous phase). Collectively, these results will inform the in-depth understanding the metabolic processes of heterocyclic PAHs and aid the accurate evaluation of their health effects.

Enantioselectivity and origin of enhanced efficiency in polyethylene terephthalate hydrolases catalyzed depolymerization

Biotechnology is one of the most promising strategies to resolve the global crisis of plastic pollution. A clear understanding of the core enzyme mechanisms in the biotransformation process is critical for rational enzyme engineering and for practical, industrial-scale applications. Herein, we systematically examined and evidenced a largely unexplored piece in the depolymerization mechanism catalyzed by polyethylene terephthalate (PET) hydrolases: their enantioselectivity. We found that all the short-lived tetrahedron intermediates (IM3 and IM8) possess S-type chirality in six representative PET hydrolases. For instance, the binding percentage ratio of pro-S:pro-R is 57:21 in FAST-PETase, while pro-S binding leads to a much lower average energy barrier (5.2 kcal/mol) than pro-R binding (33.1 kcal/mol). Key structural features (e.g. the angle for Ser@H1-His@N1-PET@O2 and distance for His@N1-PET@O2) that significantly modulate the enantioselectivity were identified. The origin of the energy landscape variation between wild-type IsPETase and mutant FAST-PETase was also unveiled via analysis of key features, the distortion/interaction energy, and non-covalent bond interactions. This study supplies the missing piece in the mechanism for depolymerization catalyzed by PET hydrolases, and will aid in the rational design of enzymes for industrial recycling of PET plastic waste.

Rational Supramolecular Strategy via Halogen Bonding for Effective Halogen Recognition in Molecular Imprinting

Halogen bonding is a highly directional interaction and a potential tool in functional material design through self-assembly. Herein, we describe two fundamental supramolecular strategies to synthesize molecularly imprinted polymers (MIPs) with halogen bonding-based molecular recognition sites. In the first method, the size of the σ-hole was increased by aromatic fluorine substitution of the template molecule, enhancing the halogen bonding in the supramolecule. The second method involved sandwiching hydrogen atoms of a template molecule between iodo substituents, which suppressed competing hydrogen bonding and enabled multiple recognition patterns, improving the selectivity. The interaction mode between the functional monomer and the templates was elucidated by ¹H NMR, ¹³C NMR, X-ray absorption spectroscopy, and computational simulation. Finally, we succeeded in the effective chromatographic separation of diiodobenzene isomers on the uniformly sized MIPs prepared by multi-step swelling and polymerization. The MIPs selectively recognized halogenated thyroid hormones via halogen bonding and could be applied to screening endocrine disruptors.

Zebrafish (Danio rerio) TRβ- and TTR-based electrochemical biosensors: Construction and application for the evaluation of thyroid-disrupting activity of bisphenols

Thyroid-disrupting chemicals (TDCs) have received increasing concerns because of their negative health impacts on both wildlife and humans. This study aimed to develop in vitro screening assays for TDCs based on thyroid hormone receptor β (TRβ) and transthyretin (TTR) proteins. Firstly, the recombinant ligand-binding domain of TRβ (TRβ-LBD) and TTR proteins of zebrafish were produced by eukaryotic expression system and then used as bio-recognition components to construct electrochemical biosensors. In the biosensors, the supported bilayer lipid membrane (s-BLM) was used as a matrix to immobilize proteins, and gold nanoflowers (AuNFs) were used to improve the sensitivity by increasing electroactive surface area. Under the optimizing conditions, the zfTRβ-LBD/AuNFs/s-BLM/GCE biosensor had a detection range of 0.23 nM-1.92 μM and a detection limit of 0.07 nM for triiodothyronine (T₃), while the zfTTR/AuNFs/s-BLM/GCE biosensor had a detection range of 0.46 nM-3.84 μM, with a detection limit of 0.13 nM. Based on the constructed biosensors, the order of T₃ equivalent concentrations of bisphenols was BPA ≈ BPS > BPF > BPAF ≈ BPAP > BPZ, which was similar to the results of recombinant TRβ two-hybrid yeast assay. Furthermore, the reliability of the biosensors was validated by molecular docking, in which BPA and BPS showed higher binding affinity to zfTRβ-LBD. Therefore, this study provided a valuable tool for efficiently screening TDCs.

Can animals tune tissue mechanics in response to changing environments caused by anthropogenic impacts?

Anthropogenic climate change and pollution are impacting environments across the globe. This Review summarises the potential impact of such anthropogenic effects on animal tissue mechanics, given the consequences for animal locomotor performance and behaviour. More specifically, in light of current literature, this Review focuses on evaluating the acute and chronic effects of temperature on the mechanical function of muscle tissues. For ectotherms, maximal muscle performance typically occurs at temperatures approximating the natural environment of the species. However, species vary in their ability to acclimate to chronic changes in temperature, which is likely to have longer-term effects on species range. Some species undergo periods of dormancy to avoid extreme temperature or drought. Whilst the skeletal muscle of such species generally appears to be adapted to minimise muscle atrophy and maintain performance for emergence from dormancy, the increased occurrence of extreme climatic conditions may reduce the survival of individuals in such environments. This Review also considers the likely impact of anthropogenic pollutants, such as hormones and heavy metals, on animal tissue mechanics, noting the relative paucity of literature directly investigating this key area. Future work needs to determine the direct effects of anthropogenic environmental changes on animal tissues and related changes in locomotor performance and behaviour, including accounting for currently unknown interactions between environmental factors, e.g. temperature and pollutants.

Bisphenol S reduces locomotor performance and modifies muscle protein levels but not mitochondrial bioenergetics in adult zebrafish

Human activity has now introduced novel chemicals into most aquatic ecosystems. Endocrine-disrupting compounds originating from plastic pollution and manufacture can have pronounced biological effects by disrupting hormone-mediated processes. Bisphenol A (BPA) is one of the most commonly produced endocrine-disrupting compounds, which interferes with signalling by a broad range of hormones. In recognition of its potentially harmful effects, BPA is being replaced by substitutes such as bisphenol S (BPS). However, toxicological studies revealed that BPS too can bind to hormone receptors and disrupt signalling, particularly of thyroid hormone. The aim of this study was to test whether BPS exposure impacts locomotor performance and muscle function in zebrafish (Danio rerio). Locomotor performance depends on thyroid hormone signalling, and it is closely related to fitness so that its disruption can have negative ecological and evolutionary consequences. BPS exposure of 15 μg l^-1 [∼60 nM] and 30 μg l^-1 (but not 60 μg l^-1) decreased sustained swimming performance (U_crit), but not sprint speed. In a fully factorial design, we show that living in flowing water increased U_crit compared to a still water control, and that BPS reduced U_crit under both conditions but did not eliminate the training effect. In a second factorial experiment, we show that BPS did not affect mitochondrial bioenergetics in skeletal muscle (state 3 and 4 rates, respiratory control ratios, ROS production), but that induced hypothyroidism decreased state 3 and 4 rates of respiration. However, both hypothyroidism and BPS exposure decreased activity of AMP-activated protein kinase (pAMPK:total AMPK) but increased protein levels of myocyte enhancer factor 2, and slow and fast myosin heavy chains. Our data indicate that BPS is not a safe alternative for BPA and that exposure to BPS can have ecological consequences, which are likely to be at least partly mediated via thyroid hormone disruption.

Broadening the lens on bisphenols in coastal waters: Occurrence, partitioning, and input fluxes of multiple novel bisphenol S derivatives along with BPA and BPA analogues in the Pearl River Delta, China

Bisphenol S derivatives (BDs) are being widely used as novel substitutes for BPA and BPA analogues (BPAs), causing pollution in various environmental compartments. However, the occurrence and fate of BDs in coastal waters are currently unknown. To broaden the lens on bisphenols in coastal waters, this study measured a broad suite of 23 bisphenols, including 12 BDs along with BPA and 10 BPAs, in water, suspended particulate matter (SPM), and sediment from eight major outlets of the Pearl River Delta, China (PRD). In addition to BPA and BPAs, all the 12 BDs were detected in the collected samples. The total concentration of 12 BDs ranged from 1.2 to 25 ng/L (median of 4.3 ng/L) in water samples, 0.80-13 ng/g dw (median of 3.0 ng/g dw) in SPM samples and 0.48-3.7 ng/g dw (median of 0.64 ng/g dw) in sediment samples. For most individual BDs, they had comparable concentrations to individual BPAs. In addition, logK_d values of the frequently detected bisphenols, including BPA, BPS, BPF, 4-((4-Isopropoxyphenyl)sulfonyl)phenol (BPSIP), 2,4-bis(phenylsulfonyl)phenol (DBSP), and other 9 bisphenols, were significantly correlated with their logK_ow values (R² = 0.38, p < 0.05), indicating that the partitioning of bisphenols between the aqueous and SPM phases were strongly influenced by hydrophobic interaction. Based on bisphenols' concentrations in water from the eight outlets of PRD, the estimated input fluxes of novel BDs (1900 kg/y) were found to be even higher than that of BPAs (550 kg/y). This indicates that the riverine input of BDs into the coastal environment is gradually increasing, which should be taken seriously in the future.

In silico profiling of endocrine-disrupting potential of bisphenol analogues and their halogenated transformation products

Due to its endocrine-disrupting properties, bisphenol A (BPA) is being phased out from plastics, thermal paper and epoxy resins, and its replacements are being introduced into the market. Bisphenols are released into the environment, where they can undergo halogenation. Unlike BPA, the endocrine-disrupting potential of BPA analogues and their halogenated transformation products has not been extensively studied. The aim of this study was to evaluate the endocrine-disrupting potential of 18 BPA analogues and their halogenated derivatives by calculating affinities for 14 human nuclear receptors utilizing the Endocrine Disruptome and VirtualToxLab™ in silico tools. Our simulations identified AR, ERs, and GR as the most favorable targets of bisphenols and their derivatives. Several BPA analogues displayed a higher predicted potential for endocrine disruption than BPA. Our models highlighted BPZ and BPPH as the most hazardous in terms of predicted endocrine activities. Halogenation, in general, was predicted to increase the binding affinity of bisphenols for AR, ERβ, MR, GR, PPARγ, and TRβ. Notably, mono- or 2,2'-di-halogenated bisphenols exhibited the highest potential for endocrine disruption. In vitro corroboration of the obtained results should be the next milestone in evaluating the safety of BPA substitutes and their halogenated transformation products.

Potential Disrupting Effects of Wastewater-Derived Disinfection Byproducts on Chinese Rare Minnow (Gobiocypris rarus) Transthyretin: An In Vitro and In Silico Study

The available information about whether wastewater-derived disinfection byproducts (DBPs) could elicit potential endocrine-related detrimental effects on aquatic organisms was scarce. Herein, the potential disrupting effects and underlying binding mechanism of 14 wastewater-derived aliphatic and aromatic DBPs and 12 other substances on Chinese rare minnow (Gobiocypris rarus) transthyretin (CrmTTR) were tested and revealed by in vitro and in silico methods. The amino acid sequences of CrmTTR were determined, and the recombinant CrmTTR with a molecular mass of 66.3 kDa was expressed and purified. In vitro assay results indicated that eight selected aromatic DBPs exhibited detectable CrmTTR disrupting ability. Meanwhile, six aliphatic DBPs were not CrmTTR binders. Molecular modeling results implied that hydrophobic hydrogen bonds and/or ionic pair interactions were non-negligible. Four binary classification models with high classification performance were constructed. A significant positive linear relationship was observed for the binding affinity data from CrmTTR and human TTR (n = 18, r = 0.922, p < 0.0001). However, the binding affinity for 13 out of 18 tested compounds with CrmTTR was higher than that with human TTR. All the results highlighted that some wastewater-derived DBPs may be potential disruptors on the aquatic organism endocrine system, and interspecies variation should not be neglected in future determination of the potential endocrine disrupting effects of wastewater-derived DBPs.

Bisphenol S disrupts opsins gene expression and impairs the light-sensing function via antagonizing TH-TRβ signaling pathway in zebrafish larvae

Bisphenol S (BPS) is extensively used in "bisphenol A-free" products such as baby bottles. Although the visual toxicity of BPS has been reported, the underlying mechanism was largely unknown. In the present study, zebrafish were exposed to 0, 4 and 400 nM BPS from 2 h post-fertilization (hpf) to 120 hpf to further explore the thyroid disruption mechanism underlying the BPS induced impairment of visual function. The results showed that BPS decreased T3 levels in larval eyes, induced retinal expression of thyroid hormone receptor β (TRβ), and thereby down-regulated the expression of TH-mediated opsin genes (opn1lw1, opn1lw2, opn1mw1, opn1mw2, opn1mw3, and opn1sw2) and impaired subsequent phototransduction pathways, leading to decreased visually mediated phototactic response and body color adaptation but stimulated visual motor response (VMR). Combining exposure of exogenous T3 or 1-850 (antagonist for TRβ) with BPS could partly compensate the inhibited expression of opsin genes (opn1mw2, opn1lw1, and opn1lw2) and alleviate the hyperactivity of larval VMR caused by BPS alone, suggesting that BPS disrupted the opsins expression and also light-sensing function via antagonizing TH-TRβ signaling pathway. This study underlined the importance of TH signaling in regulating the proper vision and proposed a novel mechanism for the visual toxicity of BPS.

Bisphenols induce cardiotoxicity in zebrafish embryos: Role of the thyroid hormone receptor pathway

Bisphenols are frequently found in the environment and have been of emerging concern because of their adverse effects on aquatic animals and humans. In this study, we demonstrated that bisphenol A, S, and F (BPA, BPS, BPF) at environmental concentrations induced cardiotoxicity in zebrafish embryos. BPA decreased heart rate at 96 hpf (hours post fertilization) and increased the distance between the sinus venosus (SV) and bulbus arteriosus (BA), in zebrafish. BPF promoted heart pumping and stroke volume, shortened the SV-BAdistance, and increased body weight. Furthermore, we found that BPA increased the expression of the dio3b, thrβ, and myh7 genes but decreased the transcription of dio2. In contrast, BPF downregulated the expression of myh7 but upregulated that of thrβ. Molecular docking results showed that both BPA and BPF are predicted to bind tightly to the active pockets of zebrafish THRβ with affinities of -4.7 and -4.77 kcal/mol, respectively. However, BPS did not significantly affect dio3b, thrβ, and myh7 transcription and had a higher affinity for zebrafish THRβ (-2.13 kcal/mol). These findings suggest that although BPA, BPS, and BPF have similar structures, they may induce cardiotoxicity through different molecular mechanisms involving thyroid hormone systems. This investigation provides novel insights into the potential mechanism of cardiotoxicity from the perspective of thyroid disruption and offer a cautionary role for the use of BPA substitution.

Endocrine disruptors and endometriosis

Endometriosis is a hormone-dependent inflammatory gynecological disease of reproductive-age women. It is clinically and pathologically characterized by the presence of functional endometrium as heterogeneous lesions outside the uterine cavity. The two major symptoms are chronic pelvic pain and infertility, which profoundly affect women's reproductive health and quality of life. This significant individual and public health concerns underscore the importance of understanding the pathogenesis of endometriosis. The environmental endocrine-disrupting chemicals (EDCs) are exogenous agents that interfere with the synthesis, secretion, transport, signaling, or metabolism of hormones responsible for homeostasis, reproduction, and developmental processes. Endometriosis has been potentially linked to exposure to EDCs. In this review, based on the robust literature search, we have selected four endocrine disruptors (i) polychlorinated biphenyls (PCB)s (ii) dioxins (TCDD) (iii) bisphenol A (BPA) and its analogs and (iv) phthalates to elucidate their critical role in the etiopathogenesis of endometriosis. The epidemiological and experimental data discussed in this review indicate that these four EDCs activate multiple intracellular signaling pathways associated with proinflammation, estrogen, progesterone, prostaglandins, cell survival, apoptosis, migration, invasion, and growth of endometriosis. The available information strongly indicates that environmental exposure to EDCs such as PCBs, dioxins, BPA, and phthalates individually or collectively contribute to the pathophysiology of endometriosis. Further understanding of the molecular mechanisms of how these EDCs establish endometriosis and therapeutic strategies to mitigate the effects of these EDCs in the pathogenesis of endometriosis are timely needed. Moreover, understanding the interactive roles of these EDCs in the pathogenesis of endometriosis will help regulate the exposure to these EDCs in reproductive age women.

Associations of bisphenol exposure with thyroid hormones in pregnant women: a prospective birth cohort study in China

Bisphenols are endocrine disruptor chemicals that disrupt thyroid hormone homeostasis. However, evidence on the effects of bisphenol mixtures on thyroid hormones are insufficient. Therefore, the present study aimed to explore the effects of bisphenol substitutes and bisphenol mixtures on thyroid hormones during pregnancy. The study was conducted among 446 pregnant women in the Guangxi Zhuang Birth Cohort (GZBC), China. In multiple linear regressions, compared with the low-exposure group, bisphenol S (BPS) concentrations in the middle-exposure group led to a 10.90% (95% CI: - 18.16%, - 2.99%) decrease in triiodothyronine (T3) levels in the first trimester; tetrabromobisphenol A (TBBPA) levels in the middle-exposure group led to an 8.26% (95% CI: - 15.82%, - 0.01%) decrease in T3 levels in the first trimester; bisphenol B (BPB) levels in the middle-exposure group led to higher free thyroxine (FT4) levels (9.84%; 95% CI: 1.73%, 18.60%) in the second trimester; bisphenol F (BPF) in the middle-exposure group led to higher FT4 levels (8.59%, 95% CI: 0.53%, 17.31%) in the second trimester; and TBBPA levels in the high-exposure group led to a 9.39% (95% CI: 1.46%, 17.93%) increase in FT4 levels in the second trimester. The Bayesian kernel machine regression (BKMR) and restricted cubic spline (RCS) models showed a U-shaped dose-response relationship between bisphenol A (BPA) and free triiodothyronine (FT3) (p < 0.01) as well as BPS and FT4 (p < 0.05). Nonlinear relationships were also observed between the bisphenol mixture and FT3. Overall, maternal bisphenol exposure affected thyroid hormone levels during pregnancy. This study provides evidence that BPB, BPF, BPS, and TBBPA are unsafe substitutes for BPA, as well as the overall effect of bisphenols on adverse health in human beings.

Bisphenol S induced dysregulations in liver; iron regulatory genes and inflammatory mediators in male Wistar rats

Bisphenol S (BPS), an analog of bisphenol A (BPA), has been frequently detected in consumer products, food wrappers, plastics, and thermal papers. Since the liver is a hub of metabolic and detoxification pathways, thus intimately related to BPS presence in the environment and body. The current study was designed to investigate the effects of BPS administration in an animal model. Twenty-five male Wistar rats weighing 175 ± 25 g were randomly divided into control and treated groups. The control group was further divided into group I (no treatment) and group II (corn oil), whereas the treatment group was divided into D-I (40 mg/kg/day), D-II (200 mg/kg/day), and D-III (400 mg/kg/day) groups, getting oral doses of BPS for 15 days. Data analysis showed a significant statistical increase in hepatic enzymes ALT (33.4%), AST (25.4%), and ALP (529.6%) in the D-III group along with the development of hypercholesterolemia and hypertriglyceridemia in all BPS groups. Aberrant mRNA expressions of some key hepatic iron regulatory genes and inflammatory mediators were evident through qRT-PCR. Bisphenol S caused congestion of central vein from mild to moderate in hepatic sections. In conclusion, our investigation insinuates BPS intoxication potential and therefore may not be a safe alternative to BPA.

The adverse effects of fluxapyroxad on the neurodevelopment of zebrafish embryos

Fluxapyroxad (Flu), one of the succinate dehydrogenase-inhibited (SDHI) fungicides, has been extensively used in crop fungal disease control. Despite its increasing use in modern agriculture and long-term retention in the environment, the potentially toxic effects of Flu in vivo, especially on neurodevelopment, remain under-evaluated. In this study, zebrafish embryos were exposed to Flu at concentrations of 0.5, 0.75, and 1 mg/L for 96 h to evaluate the neurotoxicity of Flu. The results showed that Flu caused concentration-dependent malformations, including shorter body length, smaller head and eyes, and yolk sac edema. After exposure to Flu, larval zebrafish exhibited severe motor aberrations. Flu at a concentration of 1 mg/L significantly decreased dopamine level and notably altered acetylcholinesterase (AChE) activity and acetylcholine (ACh) content. Abnormal central nervous system (CNS) neurogenesis and disordered motor neuron development were observed in Tg (HUC-GFP) and Tg (hb9-GFP) zebrafish in Flu-treated groups. The expression of key genes involved in neurotransmission and neurodevelopment further proved that Flu impaired the zebrafish nervous system. This work contributes to our understanding of the neurotoxic effects and mechanisms induced by Flu in zebrafish and may help us take precautions against the neurotoxicity of Flu.

Identification of molecular initiating events and key events leading to endocrine disrupting effects of PFOA: Integrated molecular dynamic, transcriptomic, and proteomic analyses

Perfluorooctanoic acid (PFOA) can rapidly activate signaling pathways independent of nuclear hormone receptors through membrane receptor regulation, which leads to endocrine disrupting effects. In the present work, the molecular initiating event (MIE) and the key events (KEs) which cause the endocrine disrupting effects of PFOA have been explored and determined based on molecular dynamics simulation (MD), fluorescence analysis, transcriptomics, and proteomics. MD modeling and fluorescence analysis proved that, on binding to the G protein-coupled estrogen receptor-1 (GPER), PFOA could induce a conformational change in the receptor, turning it into an active state. The results also indicated that the binding to GPER was the MIE that led to the adverse outcome (AO) of PFOA. In addition, the downstream signal transduction pathways of GPER, as regulated by PFOA, were further investigated through genomics and proteomics to identify the KEs leading to thr endocrine disrupting effects. Two pathways (Endocrine resistance, ERP and Estrogen signaling pathway, ESP) containing GPER were regulated by different concentration of PFOA and identified as the KEs. The knowledge of MIE, KEs, and AO of PFOA is necessary to understand the links between PFOA and the possible pathways that lead to its negative effects.

Tox21-Based Comparative Analyses for the Identification of Potential Toxic Effects of Environmental Pollutants

Chemical pollution has become a prominent environmental problem. In recent years, quantitative high-throughput screening (qHTS) assays have been developed for the fast assessment of chemicals' toxic effects. Toxicology in the 21st Century (Tox21) is a well-known and continuously developing qHTS project. Recent reports utilizing Tox21 data have mainly focused on setting up mathematical models for in vivo toxicity predictions, with less attention to intuitive qHTS data visualization. In this study, we attempted to reveal and summarize the toxic effects of environmental pollutants by analyzing and visualizing Tox21 qHTS data. Via PubMed text mining, toxicity/structure clustering, and manual classification, we detected a total of 158 chemicals of environmental concern (COECs) from the Tox21 library that we classified into 13 COEC groups based on structure and activity similarities. By visualizing these COEC groups' bioactivities, we demonstrated that COECs frequently displayed androgen and progesterone antagonistic effects, xenobiotic receptor agonistic roles, and mitochondrial toxicity. We also revealed many other potential targets of the 13 COEC groups, which were not well illustrated yet, and that current Tox21 assays may not correctly classify known teratogens. In conclusion, we provide a feasible method to intuitively understand qHTS data.

Development of human retinal organoid models for bisphenol toxicity assessment

Bisphenols, including Bisphenol A (BPA), Tetrabromobisphenol A (TBBPA), and Tetrabromobisphenol S (TBBPS), have been widely applied in the production of polycarbonate plastics and epoxy resins and have been detected in the environment worldwide. The frequent detection of bisphenols in maternal and fetal samples has raised concerns about their toxic effects on human embryonic development, especially on the development of the central nervous system. However, the effect of bisphenols on human retinal development is still unknown. In this study, to evaluate the toxicity of bisphenols on early retinal development, human embryonic stem cells were induced to differentiate into retinal organoids that responded to BPA, TBBPA, and TBBPS, at human exposure relevant concentrations. The global gene expression of retinal organoids was analyzed by RNA sequencing (RNA-seq). A set of retinal development-related biological processes, including neuron differentiation, phototransduction, axon guidance, and retina layer formation, were identified in retinal organoids corresponding to different developmental stages. The RNA-seq data also showed that BPA, TBBPA, and TBBPS influenced retinal development by interfering with the Cytokine-cytokine receptor interaction pathway. HSPA6, HIF1A-AS3, CDC20B, IL19, OAS1, HSPA7, and RN7SK were dysregulated by these chemicals. Additionally, BPA, TBBPA, and TBBPS exhibited different toxic effects on neural retina development, with TBBPA appearing to exert more toxicity than BPA and TBBPS. Furthermore, three bisphenols exhibited different effects at different stages of neural retina development. The sensitivity of retinal development to bisphenols depends on their developmental stage. This study provides new insights into the deep dissection of retinotoxicity after prenatal bisphenol exposure.

Interactive effects of anthropogenic environmental drivers on endocrine responses in wildlife

Anthropogenic activity has created unique environmental drivers, which may interact to produce unexpected effects. My aim was to conduct a systematic review of the interactive effects of anthropogenic drivers on endocrine responses in non-human animals. The interaction between temperature and light can disrupt reproduction and growth by impacting gonadotropins, thyroid hormones, melatonin, and growth hormone. Temperature and endocrine disrupting compounds (EDCs) interact to modify reproduction with differential effects across generations. The combined effects of light and EDCs can be anxiogenic, so that light-at-night could increase anxiety in wildlife. Light and noise increase glucocorticoid release by themselves, and together can modify interactions between individuals and their environment. The literature detailing interactions between drivers is relatively sparse and there is a need to extend research to a broader range of taxa and interactions. I suggest that incorporating endocrine responses into Adverse Outcome Pathways would be beneficial to improve predictions of environmental effects.

Exposure to amitriptyline induces persistent gut damages and dysbiosis of the gut microbiota in zebrafish (Danio rerio)

Amitriptyline (AMI), the most commonly prescribed tricyclic antidepressant, is widely detected in water environments. Exposure to AMI may lead to diverse adverse effects on aquatic organisms, but little is known about the effect of short-term exposure to AMI on the gut microbiota of aquatic organisms and their recovery characteristics. In the present study, adult zebrafish (Danio rerio) were exposed to AMI (0, 2.5, 10, and 40 μg/L) for seven days, and then allowed to recover in AMI-free culture water for 21 days. The exposure caused gut damages in all the AMI treated groups of zebrafish, which became more severe after recovery compared to the control group. AMI exposure also disturbed the microbiota of zebrafish guts and rearing water even after the 21-day recovery period. Furthermore, AMI exposure affected microbes involved in the substance and energy metabolic functions in zebrafish guts and tended to increase the abundance of microbial genera associated with opportunistic pathogens. In addition, the microbial predicted metabolic functions in AMI-exposed guts of zebrafish were significantly altered after the 21-day recovery period, explaining the persistent effects of short-term exposure to AMI. The results of this study suggest that acute exposure to AMI may have persistent impacts on the gut histomorphology and the gut microbiota in aquatic organisms.

Promotion of Bladder Cancer Cell Metastasis by 2-Mercaptobenzothiazole via Its Activation of Aryl Hydrocarbon Receptor Transcription: Molecular Dynamics Simulations, Cell-Based Assays, and Machine Learning-Driven Prediction

2-Mercaptobenzothiazole (MBT) is an industrial chemical widely used for rubber products, corrosion inhibitors, and polymer materials with multiple environmental and exposure pathways. A growing body of evidence suggests its potential bladder cancer (BC) risk as a public health concern; however, the molecular mechanism remains poorly understood. Herein, we demonstrate the activation of the aryl hydrocarbon receptor (AhR) by MBT and reveal key events in carcinogenesis associated with BC. MBT alters conformational changes of AhR ligand binding domain (LBD) as revealed by 500 ns molecular dynamics simulations and activates AhR transcription with upregulation of AhR-target genes CYP1A1 and CYP1B1 to approximately 1.5-fold. MBT upregulates the expression of MMP1, the cancer cell metastasis biomarker, to 3.2-fold and promotes BC cell invasion through an AhR-mediated manner. MBT is further revealed to induce differentially expressed genes (DEGs) most enriched in cancer pathways by transcriptome profiling. The exposure of MBT at environmentally relevant concentrations induces BC risk via AhR signaling disruption, transcriptome aberration, and malignant cell metastasis. A machine learning-based model with an AUC value of 0.881 is constructed to successfully predict 31 MBT analogues. Overall, we provide molecular insight into the BC risk of MBT and develop an effective tool for rapid screening of AhR agonists.

Development, Validation, and Application of a Human Reproductive Toxicity Prediction Model Based on Adverse Outcome Pathway

A growing number of environmental contaminants have been proved to have reproductive toxicity to males and females. However, the unclear toxicological mechanism of reproductive toxicants limits the development of virtual screening methods. By consolidating androgen (AR)-/estrogen receptors (ERs)-mediated adverse outcome pathways (AOPs) with more than 8000 chemical substances, we uncovered relationships between chemical features, a series of pathway-related effects, and reproductive apical outcomes─changes in sex organ weights. An AOP-based computational model named RepTox was developed and evaluated to predict and characterize chemicals' reproductive toxicity for males and females. Results showed that RepTox has three outstanding advantages. (I) Compared with the traditional models (37 and 81% accuracy, respectively), AOP significantly improved the predictive robustness of RepTox (96.3% accuracy). (II) Compared with the application domain (AD) of models based on small in vivo datasets, AOP expanded the ADs of RepTox by 1.65-fold for male and 3.77-fold for female, respectively. (III) RepTox implied that hydrophobicity, cyclopentanol substructure, and several topological indices (e.g., hydrogen-bond acceptors) were important, unbiased features associated with reproductive toxicants. Finally, RepTox was applied to the inventory of existing chemical substances of China and identified 2100 and 7281 potential toxicants to the male and female reproductive systems, respectively.

Halogenated ingredients of household and personal care products as emerging endocrine disruptors

The everyday use of household and personal care products (HPCPs) generates an enormous amount of chemicals, of which several groups warrant additional attention, including: (i) parabens, which are widely used as preservatives; (ii) bisphenols, which are used in the manufacture of plastics; (iii) UV filters, which are essential components of many cosmetic products; and (iv) alkylphenol ethoxylates, which are used extensively as non-ionic surfactants. These chemicals are released continuously into the environment, thus contaminating soil, water, plants and animals. Wastewater treatment and water disinfection procedures can convert these chemicals into halogenated transformation products, which end up in the environment and pose a potential threat to humans and wildlife. Indeed, while certain parent HPCP ingredients have been confirmed as endocrine disruptors, less is known about the endocrine activities of their halogenated derivatives. The aim of this review is first to examine the sources and occurrence of halogenated transformation products in the environment, and second to compare their endocrine-disrupting properties to those of their parent compounds (i.e., parabens, bisphenols, UV filters, alkylphenol ethoxylates). Albeit previous reports have focused individually on selected classes of such substances, none have considered the problem of their halogenated transformation products. This review therefore summarizes the available research on these halogenated compounds, highlights the potential exposure pathways, and underlines the existing knowledge gaps within their toxicological profiles.

Impacts of cetylpyridinium chloride on the behavior and brain neurotransmitter levels of juvenile and adult zebrafish (Danio rerio)

Cetylpyridinium chloride (CPC) is a cationic surfactant that has been widely used as an antibacterial ingredient in pharmaceutical and personal care products. Due to its high residue in surface waters, there is increasing concern over the potential risk of CPC to aquatic ecosystems. However, knowledge of its impacts on fish is still limited. Therefore, this study exposed juvenile and adult zebrafish to CPC (0, 10, and 40 μg/L) for four days. Subsequently, changes in their behavioral traits and brain levels of several neurotransmitters were investigated. The behavioral assay showed that CPC exposure significantly decreased the locomotor activity and social interaction of zebrafish at both life stages, and juveniles were more sensitive to CPC exposure than adults. In the control groups, the brain neurotransmitters concentrations increased with age in zebrafish. However, CPC exposure tended to increase the brain neurotransmitter levels of juveniles but decreased their levels in adults. Correlation analysis revealed that the brain monoamine neurotransmitters and their turnover might play important roles in the life stage-dependent behavioral response to CPC. In particular, the DOPAC/DA ratio was significantly associated with CPC-induced hypoactivity and reduced social interactions in juveniles but not adults. Our findings demonstrated that CPC exposure could cause abnormal behavior in juvenile and adult zebrafish and disturb their brain neurotransmitters, even at environmentally relevant concentrations, and thus highlighted the necessity for further assessing its potential risks to aquatic ecosystems.

Origin of metabolites diversity and selectivity of P450 catalyzed benzo[a]pyrene metabolic activation

Polycyclic Aromatic Hydrocarbon (PAHs) presents one of the most abundant class of environmental pollutants. Recent study shows a lab-synthesized PAHs derivative, helicenium, can selectively kill cancer cells rather than normal cells, calling for the in-depth understanding of the metabolic process. However, the origin of metabolites diversity and selectivity of P450 catalyzed PAHs metabolic activation is still unclear to a great extent. Here we systematically investigated P450 enzymes catalyzed activation mechanism of a representative PAHs, benzo[a]pyrene (BaP), and found the corresponding activation process mainly involves two elementary steps: electrophilic addition and epoxidation. Electrophilic addition step is evidenced to be rate determining step. Two representative binding modes of BaP with P450 were found, which enables the electrophilic addition of Heme (FeO) to almost all the carbons of BaP. This electrophilic addition was proposed to be accelerated by the P450 enzyme environment when compared with the gas phase and water solvent. To dig deeper on the origin of metabolites diversity, we built several linear regression models to explore the structural-energy relationships. The selectivity was eventually attributed to the integrated effects of structural (e.g. O-C distance and O-C-Fe angle) and electrostatic parameters (e.g. charge of C and O) from both BaP and P450.

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.

Research Progress of the Endocrine-Disrupting Effects of Disinfection Byproducts

Since 1974, more than 800 disinfection byproducts (DBPs) have been identified from disinfected drinking water, swimming pool water, wastewaters, etc. Some DBPs are recognized as contaminants of high environmental concern because they may induce many detrimental health (e.g., cancer, cytotoxicity, and genotoxicity) and/or ecological (e.g., acute toxicity and development toxicity on alga, crustacean, and fish) effects. However, the information on whether DBPs may elicit potential endocrine-disrupting effects in human and wildlife is scarce. It is the major objective of this paper to summarize the reported potential endocrine-disrupting effects of the identified DBPs in the view of adverse outcome pathways (AOPs). In this regard, we introduce the potential molecular initiating events (MIEs), key events (KEs), and adverse outcomes (AOs) associated with exposure to specific DBPs. The present evidence indicates that the endocrine system of organism can be perturbed by certain DBPs through some MIEs, including hormone receptor-mediated mechanisms and non-receptor-mediated mechanisms (e.g., hormone transport protein). Lastly, the gaps in our knowledge of the endocrine-disrupting effects of DBPs are highlighted, and critical directions for future studies are proposed.

Bisphenol A Analogs Induce Cellular Dysfunction in Human Trophoblast Cells in a Thyroid Hormone Receptor-Dependent Manner: In Silico and In Vitro Analyses

Bisphenol A (BPA) and its analogs are frequently detected in human daily necessities and environmental media. Placental thyroid hormone plays an important role in fetal development. Herein, we followed the adverse outcome pathway (AOP) to explore the toxic mechanisms of BPA and its analogs toward placental thyroid hormone receptor (TR). First, the TOX21 database was used, and the interactions between BPA analogs and the ligand-binding domains (LBDs) of two subtypes of TR (TRα and TRβ) were subjected to in silico screening using molecular docking (MD) and molecular dynamics simulation (MDS). Fluorescence spectra and circular dichroism (CD) showed that BPA and its analogs interfere with TRs as a molecular initiation event (MIE), including static fluorescence quenching and secondary structural content changes in TR-LBDs. Key events (KEs) of the AOP, including the toxicity induced in placental chorionic trophoblast cells (HTR-8/SVneo) by an inverted U-shaped dose effect and changes in ROS levels, were tested in vitro. BPA, BPB, and BPAF significantly changed the expression level of TRβ, and only BPAF significantly downregulated the expression level of TRα. In conclusion, our study contributes to the health risk assessment of BPA and its analogs regarding placental adverse outcomes (AOs).

Thyroid endocrine disruption and hepatotoxicity induced by bisphenol AF: Integrated zebrafish embryotoxicity test and deep learning

Bisphenol AF (BPAF) is an emerging contaminant prevalent in the environment as one of main substitutes of bisphenol A (BPA). It was found that BPAF exhibited estrogenic effects in zebrafish larvae in our previous study, while little is known about its effects on the thyroid and liver. A 7 d zebrafish embryotoxicity test was conducted to study the potential thyroid disruption and hepatotoxicity of BPAF. BPAF decreased levels of thyroid hormones and deiodinases but increased expressions of transthyretin at 12.5 and 125 μg/L after 7 d exposure, indicating that both the metabolism and transport of thyroid hormones were perturbed. The thyroid hormone receptor (TR) levels decreased significantly upon exposure to ≥12.5 μg/L BPAF, implying that BPAF acts as a TR antagonist, which coincided well with the prediction from the Direct Message Passing Neural Network. The liver impairment (mainly cell necrosis of hepatocytes) and apoptosis were triggered by 125 μg/L and ≥12.5 μg/L BPAF respectively, accompanied by the increased activities of caspase 3 and caspase 9. Thus BPAF might not be a safe alternative to BPA given the thyroid and liver toxicity. DMPNN appears useful to screen for thyroid disrupting activity from molecular structures.

Accurate calculation of absolute free energy of binding for SHP2 allosteric inhibitors using free energy perturbation

Accurate prediction of binding affinity is a primary objective in structure-based drug discovery. A free energy perturbation (FEP) method based on molecular dynamics simulation shows great promise for protein-ligand binding affinity predictions. However, accurate calculation of binding affinity for allosteric inhibitors remains unknown and elusive, which hampers the discovery of allosteric inhibitors. Allosteric inhibitors exhibit several significant advantages over orthosteric inhibitors including higher specificity and lower side effects. Allosteric inhibitors against SHP2 are thought to be beneficial not only for diseases related to metabolism, but also for cancer, which make SHP2 a potential drug target. However, high structural sensitivity makes structural optimization of SHP2 allosteric inhibitors face challenges. Herein, we calculated the absolute binding free energy of SHP2 allosteric inhibitors using the FEP method by employing different λ-windows/simulation time sampling strategies. A simulation run with 32 λ-windows/64 ps sampling strategy delivered an excellent correlation (r = 0.96) and an unprecedented low mean absolute error of 0.5 kcal mol^-1 between predicted binding free energies and experimental ones, outperforming the MM/PBSA method. Our study demonstrates the possibility to accurately calculate the absolute binding free energy of allosteric inhibitors using FEP, which offers exciting prospects for the discovery of more effective allosteric inhibitors.

Overlooked environmental risks deriving from aqueous transformation of bisphenol alternatives: Integration of chemical and toxicological insights

Owing to the widespread prevalence and ecotoxicity of bisphenol alternatives such as bisphenol S, bisphenol F, and bisphenol AF, the past decade has witnessed the publication of a remarkable number of studies related to their transformation and remediation in natural waters. However, the reactivity, removal efficiency, transformation products (TPs), and mechanisms of such emerging pollutants by different treatment processes have not been well elucidated. Particularly, the transformation-driven environmental risks have been mostly overlooked. Therefore, we present a review to address these issues from chemical and toxicological viewpoints. Four degradation systems can be largely classified as catalytic persulfate (PS) oxidation, non-catalytic oxidation, photolysis and photocatalysis, and biodegradation. It was found that bisphenol alternatives possess distinct reactivities with different oxidizing species, with the highest performance for hydroxyl radicals. All systems exhibit superior elimination efficiency for these compounds. The inadequate mineralization suggests the formation of recalcitrant TPs, from which the overall reaction pathways are proposed. The combined experimental and in silico analysis indicates that many TPs have developmental toxicity, endocrine-disrupting effects, and genotoxicity. Notably, catalytic PS systems and non-catalytic oxidation result in the formation of coupling products as well as halogenated TPs with higher acute and chronic toxicity and lower biodegradability than the parent compounds. In contrast, photolysis and photocatalysis generate hydroxylated and bond-cleavage TPs with less toxicity. Overall, this review highlights the secondary environmental risks from the transformation of bisphenol alternatives by conventional and emerging treatment processes. Finally, future perspectives are recommended to address the knowledge gaps of these contaminants in aquatic ecosystems.

Impacts of Cetylpyridinium Chloride on the Survival, Development, Behavior, and Oxidative Stress of Early-Life-Stage Zebrafish (Danio rerio)

Cetylpyridinium chloride (CPC) is a widely used surfactant that has been detected in various water ecosystems. However, knowledge on the toxicity of CPC to fish remains scarce. Here, we examined the survival, development, behavior, and oxidative stress in the early life stages of zebrafish exposed to CPC (0, 4, 40, 400, and 1200 μg/L) until 120 h post-fertilization (hpf). Results showed that CPC induced significant mortality at 400 and 1200 μg/L, with a 120 h-EC₅₀ value of 175.9 μg/L. CPC significantly decreased the heart rate of embryos (48 hpf; 4–400 μg/L) and larvae (72 hpf; 40 and 400 μg/L). At 120 hpf, CPC exhibited a dual effect on the locomotion activity (decreased at 400 μg/L and increased at 4 and 40 μg/L) and elevated the reactive oxygen species, superoxide dismutase, and glutathione levels in zebrafish larvae at 400 µg/L. In addition, a correlation analysis revealed that CPC-induced oxidative stress might play a critical role in mediating the cardiac and behavioral toxicity of CPC to zebrafish larvae. Our findings suggest that CPC may disturb the fish’s development, behavior, and oxidative status at environmentally relevant concentrations, which should not be ignored when assessing its potential risks to aquatic ecosystems.

Developmental exposure to the A6-pesticide causes changes in tyrosine hydroxylase gene expression, neurochemistry, and locomotors behavior in larval zebrafish

In recent years, the increase in the synthesis of biopesticides for alternative agricultural uses has necessitated the study of their impacts. Among these compounds, several of them are known to exert endocrine-disrupting effects causing deregulation of a variety of physiological functions affecting cell signaling pathways involved in neural cell differentiation leading to developmental neurotoxicity. In this current paper, we thus determined the impact of the biopesticide A6 on zebrafish larvae, which is structurally linked to estrogenic endocrine disruptors. The objective of this study was to define the toxicity of A6, the mechanisms responsible, and to evaluate its effects on the locomotors activity at nanomolar concentrations (0, 0.5, 5, and 50 nM). We show through its blue fluorescence properties that A6 accumulates in different parts of the body as intestine, adipose tissue, muscle, yolk sac and head. We display also that A6 disrupt the development and affects the function of the central nervous system, especially the expression of tyrosine hydroxylase (TH) in dopaminergic neurons. We studied whether A6 disturbs the target genes expression and recorded that it downregulated genes embroiled in TH expression, suggesting that A6's neurotoxic effect may be the result of its binding propinquity to the estrogen receptor.

Developmental toxicity of bromoacetamide via the thyroid hormone receptors-mediated disruption of thyroid hormone homeostasis in zebrafish embryos

Bromoacetamide (BAcAm) is a nitrogenous disinfection by-product. We previously found that BAcAm induced developmental toxicity in zebrafish embryos, but the underlying mechanisms remain to be elucidated. Since thyroid hormones (THs) homeostasis is crucial to development, we hypothesized that disruption of THs homeostasis may play a role in the developmental toxicity of BAcAm. In this study, we found BAcAm exposure significantly increased mortality and malformation rate, decreased hatching rate and body length, inhibited the locomotor capacity in zebrafish embryos. BAcAm elevated TSH, T₃ and T₄ levels, down-regulated T₃/T₄ ratios, and up-regulated mRNA expression changes of THs related genes (trh, tsh, tg, nis, tpo, dio1, dio2, ugt1ab，klf9 and rho), but down-regulated mRNA expression changes of TH receptors (tr α and tr β). Up-regulated tr α and tr β mRNAs by rescue treatment confirmed that both tr α and tr β were involved in the developmental toxicity of BAcAm. In conclusion, our study indicates disruption of THs homeostasis via the thyroid hormone receptors was responsible for the developmental toxicity of BAcAm.

Comparative chronic toxicities of PFOS and its novel alternatives on the immune system associated with intestinal microbiota dysbiosis in adult zebrafish

6:2 Chlorinated polyfluorinated ether sulfonate (F-53B) and sodium p-perfluorous nonenoxybenzene sulfonate (OBS) are widely used as perfluorooctane sulfonate (PFOS) alternatives in the Chinese market. Here, adult zebrafish were chronically exposed to 1 μM PFOS, F-53B, and OBS for 21 days to investigate the comparative immunotoxicity of these three per- and polyfluoroalkyl substances (PFAS). PFOS induced more severe oxidative stress in the liver than F-53B and OBS, and these three PFAS induced similar anti-inflammatory effects by repressing the expression of pro-inflammatory cytokines. The intestinal microbiota analysis showed that the relative abundance of Plesiomonas, Aeromonas, Cetobacterium, Shewanella, and Vibrio changed with the same trend in the three PFAS treatment groups. Furthermore, the PFAS increased the expression of hepcidin, muc, the immune-related genes mpo and saa, and decreased the expression of the tight junction-related gene occ in the intestine; moreover, villus height of the intestine was reduced after PFAS exposure, which indicated the functional disruption of the intestine. In particular, the significant correlation between the changed intestinal microbiota and liver and intestinal indicators also suggested the interaction between the immune system and intestinal microbiota. Taken together, our results indicate that exposure to PFOS and its alternatives F-53B and OBS can induce hepatic immunotoxicity associated with intestinal microbiota dysbiosis in adult zebrafish.