Different effects of bisphenol a and its halogenated derivatives on the reproduction and development of Oryzias melastigma under environmentally relevant doses

Differential developmental effects and its potential mechanism of long-term exposure to TBBPA in two generations of marine medaka (Oryzias melastigma) during early life stages

Tetrabromobisphenol A (TBBPA), a most widely used brominated flame retardant, has been detected in worldwide aquatic environments. However, the effects and mechanisms of TBBPA at environmentally realistic levels have not been well characterized in aquatic organisms. This study aims to investigate the impact of TBBPA on developmental toxicity and endocrine system in two generations of marine medaka (Oryzias melastigma) during early life stages. The results revealed that the embryos under exposure to environmentally relevant concentrations of TBBPA (0, 5, 50, and 500 μg/L) resulted in accelerated hatching and growth development in F0 generation. Conversely, delayed hatching, decreased hatch rate, and growth inhibition were observed in the F1 generation. Moreover, TBBPA disrupted the levels of THs (thyroid hormones), GH (growth hormone), and IGF (insulin growth factor). The gene transcriptional profiling implies modified gene expressions in the HPT axis, GH/IGF axis, and endoplasmic reticulum stress. The molecular docking analysis confirmed the binding affinity of TBBPA to key endocrine-related proteins, which partially elucidates the mechanism of endocrine disruption and developmental abnormalities. Endoplasmic reticulum stress may explain the developmental differences between the two generations. This was the first study to explore the multigenerational developmental toxicity of TBBPA to marine fish, which is essential for ecological risk assessment of this emerging pollutant.

Bisphenol analogs exposure in 4-year-old children and their intelligence quotient at 6 years: A prospective cohort study

Prenatal exposure to bisphenol A (BPA) has been shown to impact offspring cognition, behavior, and intelligence. However, whether co-exposure to bisphenol analogs (BPs) during childhood affects children's intelligence remains unclear. We included 465 mother-child pairs from the Shanghai Minhang Birth Cohort Study to examine the impact of children's exposure to BPs at 4 years of age on the intelligence quotient (IQ) measured at 6 years. BPs concentrations were measured in single-spot urine samples collected from 4-year-old children. The Wechsler Intelligence Scale for Children was used to evaluate IQ at 6 years. Multiple linear regression models were used to examine the associations between BPs and IQ. Bayesian Kernel Machine Regression (BKMR) models were used to evaluate the joint and single-exposure effects of BPs mixture. In girls, exposure to bisphenol F (BPF) was inversely associated with Full-Scale IQ (FSIQ) and Perceptual Reasoning Index (PRI) (βFSIQ = -5.46, 95 % confidence interval [CI]: -9.97, -0.94; βPRI = -5.14, 95 % CI: -9.95, -0.32). By BKMR, BPF contributed the most to the joint effect of BPs in girls. The association remained robust after adjusting for maternal IQ. In boys, exposure to tetrachlorobisphenol A seemed to be associated with an increase in FSIQ and PRI; however, the number of exposed boys was small. Our study suggests that BPs exposure at 4 years of age may be associated with a lower IQ at 6 years in girls. BPF may not be a safe substitute for BPA. Further epidemiological studies are required to confirm these findings.

Protective effect of a novel furan hybrid chalcone against bisphenol A-induced craniofacial developmental toxicity in zebrafish embryos

Bisphenol A (BPA), a pervasive endocrine disruptor, is known to cause significant developmental toxicity, particularly affecting craniofacial structures through oxidative stress and apoptosis. A novel furan hybrid chalcone derivative, 3-(2-hydroxy-5-nitrophenyl)-1-(5-methylfuran-2-yl)prop-2-en-1-one (DK04), specifically with a hydroxyl group for its antioxidant properties and a nitro group for enhanced electron-withdrawing ability, was evaluated for its potential to mitigate these toxic effects. Zebrafish embryos were exposed to BPA and co-treated with various concentrations of DK04. Our results demonstrated that DK04 significantly reduced reactive oxygen species (ROS) generation and lipid peroxidation, increased antioxidant enzyme activities (SOD and CAT), and restored the balance between pro-apoptotic (p53) and anti-apoptotic (bcl2) genes. Furthermore, DK04 treatment improved bone mineralization and chondrogenesis by reversing BPA-induced disruptions in osteogenic markers (runx2, sox9a, bmp6, and mmp13a). The locomotion impairments observed in BPA-exposed embryos were also ameliorated by DK04, indicating its potential neuroprotective effects. These findings suggest that DK04 offers a multifaceted approach to counteract BPA toxicity, making it a promising candidate for therapeutic intervention. This research underscores the importance of developing prophylactic compounds to safeguard health against environmental toxicants like BPA. Future studies should focus on long-term safety and efficacy in mammalian models and explore synergistic effects with other protective agents to broaden the applications of DK04 and contribute to public health benefits.

Bisphenol A impairs oocyte maturation by dysfunction of cumulus cells

Bisphenol A (BPA) is a well-known environmental endocrine disruptor that has detrimental effects on reproduction. This study aimed to investigate whether BPA exposure could disrupt the function of cumulus cells and influence oocyte maturation and development. Porcine oocytes at the germinal vesicle stage were exposed to BPA for 44 h. The results revealed that BPA exposure led to dysfunction in cumulus cells by inhibiting meiotic division, inducing endoplasmic reticulum stress, and disrupting steroid synthesis. Furthermore, BPA exposure significantly increased reactive oxygen species and caused abnormal distribution of mitochondria in the oocytes. Notably, matured oocytes in the MII stage from the BPA-exposed groups showed significantly reduced development to the blastocyst stage, along with increased autophagy and apoptosis. These findings suggest that cumulus-oocyte complexes are sensitive to BPA exposure during the germinal vesicle stage, and the toxic effects of BPA on cumulus cells can severely inhibit oocyte and parthenogenetic embryos development.

The Chinese medaka (Oryzias sinensis) dmrt1 gene converts females to males in medaka (Oryzias latipes)

BACKGROUND

Chinese medaka (Oryzias sinensis) is widely distributed in freshwater rivers in China. Similar to the medaka (Oryzias latipes), Chinese medaka has the characteristics of small size, rapid reproductive cycle, and strong adaptability, which makes it suitable as a model organism for studies in basic biology and environmental toxicology. Chinese medaka exhibits distinct sexual dimorphism. However, due to the lack of complete genomic information, the regulation of sex determination and differentiation-related genes in Chinese medaka remains unclear.

METHODS

Chinese medaka dmrt1 (Osdmrt1) was cloned by PCR, and transgenic individuals of medaka [Tg(CMV:Osdmrt1)] overexpressing Osdmrt1 were generated to investigate the role of Osdmrt1 in sex determination. Western blot was used to validate the integration of the Osdmrt1 into the medaka genome. Tissue sectioning and HE staining were used to identify Tg(CMV:Osdmrt1) physiological gender and phenotype. qRT-PCR was used to analyze the expression of gonad-specific genes.

RESULTS

Osdmrt1 was cloned and identified, and it shared similar evolutionary relationships with medaka dmrt1. Tg(CMV:Osdmrt1) exhibited partial sex reversal from female to male in the F2 generation, with genetically female individuals developing testes and producing functional sperm. Additionally, the secondary sexual characteristics of the transgenic females also changed to males.

CONCLUSION

The Chinese medaka dmrt1 gene could convert females to males in medaka.

GENERAL SIGNIFICANCE

These results not only elucidate the function of Chinese medaka dmrt1, but also accumulate knowledge for studying the function of economically important fish genes in model fish by transgenic technology.

A prioritization strategy for functional alternatives to bisphenol A in food contact materials

The use of bisphenol A (BPA), a substance of very high concern, is proposed to be banned in food contact materials (FCMs) in the European Union. To prevent regrettable substitution of BPA by alternatives with similar or unknown hazardous properties, it is of importance to gain the relevant toxicological information on potential BPA alternative substances and monitor them adequately. We created an inventory of over 300 substances mentioned as potential BPA alternatives in regulatory reports and scientific literature. This study presents a prioritization strategy to identify substances that may be used as an alternative to BPA in FCMs. We prioritized 20 potential BPA alternatives of which 10 are less familiar. We subsequently reviewed the available information on the 10 prioritized less familiar substances regarding hazard profiles and migration potential obtained from scientific literature and in silico screening tools to identify a possible risk of the substances. Major data gaps regarding the hazard profiles of the prioritized substances exist, although the scarce available data give some indications on the possible hazard for some of the substances (like bisphenol TMC, 4,4-dihydroxybenzophenone, and tetrachlorobisphenol A). In addition, very little is known about the actual use and exposure to these substances. More toxicological research and monitoring of these substances in FCMs are, therefore, required to avoid regrettable substitution of BPA in FCM.

Molecular insights into the effects of tetrachlorobisphenol A on puberty initiation in Wistar rats

Tetrachlorobisphenol A (TCBPA) is the chlorinated derivative of bisphenol A (BPA). Several studies have found that BPA adversely affects the reproductive activity largely through binding to estrogen receptors and the critical period of BPA exposure advances the vaginal opening time in the female offspring via the kisspeptin/G protein-coupled receptor 54 (KGG) system. However, whether TCBPA can affect puberty initiation via KGG and the roles of estrogen receptors in this process remain unknown. Therefore, this study investigated the influence of TCBPA on the onset time of puberty in Wistar rats and the related molecular mechanisms by combing in vitro GT1-7 cells and molecular docking. In female Wistar rats, TCBPA at ≥100 mg/kg bw/day (49.2 μmol/L in rat body) markedly advanced vaginal opening time and increased serum levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and gonadotropin-releasing hormone (GnRH). It also increased the relative gene expression of LH receptor (LHR), GnRH1, and FSH receptor (FSHR) in hypothalamic-pituitary-gonadal (HPG) axis tissues. In GT1-7 cells, TCBPA increased genes and proteins associated with KGG pathway and activated the extracellular-regulated protein kinase 1/2 (Erk1/2) and phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) pathways via G protein-coupled estrogen membrane receptor 1 (GPER1) and estrogen receptor alpha (ERα). Docking analyses supported its interactions with GPER1 and ERα, and treatment with specific inhibitors of ERα- and GPER1-modulated PI3K/Akt and Erk1/2 signaling suppressed its effects. Taken together, TCBPA-induced advancement of puberty initiation in Wistar rats thus results primarily from increased LH, GnRH, and FSH secretion together with GnRH1, FSHR, and LHR upregulation driven by ERα- and GPER1-modulated Erk1/2 and PI3K/Akt signaling. Our results provide new molecular insights into the reproductive toxicity of EDCs.

Bisphenol A contamination in Hilsa shad and assessment of potential health hazard: A pioneering investigation in the national river Ganga, India

The anadromous Hilsa, often known as the "Queen of Fishes" (Tenualosa ilisha), is the most valuable fishery in the Ganga-Hooghly delta estuary. Although BPA exposure has been shown to be harmful to aquatic organisms, no research has looked at the effects of BPA on the commercially valuable Hilsa shad of river Ganga. To close this information vacuum, we examined BPA levels in Hilsa fish from the Ganga estuary. Liver, muscle, kidney, and gonads were all positive for BPA among the Hilsa fish of all ages. Liver BPA levels were highest in adult males (272.16 ± 0.38 ng/g-dw), and lowest in juveniles (5.46 ± 0.06 ng/g-dw). BPA concentrations in the Hilsa shad muscle were highest in reproductively mature females (196.23 ± 0.41 ng/g-dw). The study also discovered a correlation between fish development and BPA exposure, with higher levels of BPA being identified in adult Hilsa species. This is the first study to look at the impact of BPA pollution on aquatic ecosystems and fisheries, and it showed that Hilsa shad is contaminated with BPA and poses health hazards to human beings. The results, which demonstrate BPA contamination, are useful for protecting Hilsa in the river Ganga.

Bisphenol A decreases the developmental toxicity and histopathological alterations caused by polystyrene nanoplastics in developing marine medaka Oryzias melastigma

Nanoplastics (NPs) are emerging pollutants posing risks to marine biota and human health due to their small size and high bioavailability. However, there are still knowledge gaps regarding effects of co-existing pollutants on NPs toxicity to marine organisms at their respective environmentally relevant concentrations. Herein we investigated developmental toxicity and histopathological alterations caused by co-exposure of polystyrene nanoplastics (PS-NPs) and bisphenol A (BPA) to marine medaka, Oryzias melastigma. Embryos at 6 h post-fertilization were exposed to 50-nm PS-NPs (55 μg/L) or BPA (100 μg/L) or co-exposed to a combination of both. Results showed that PS-NPs exhibited decreased embryonic heart rate, larval body length, and embryonic survival as well as larval deformities such as hemorrhaging and craniofacial abnormality. When co-exposed, BPA mitigated all the adverse developmental effects caused by PS-NPs. PS-NPs also led to an increase in histopathological condition index of liver with early inflammatory responses, while co-exposure of BPA with PS-NPs did not. Our data suggest that the toxicity reduction of PS-NPs in the presence of BPA might result from the decreased bioaccumulation of PS-NPs caused by the interaction between BPA and PS-NPs. This study unveiled the impact of BPA on the toxicity of nanoplastics in marine fish during early developmental stages and highlight the need of more research on the long-term effects of complex mixtures in the marine environment by applying omics approaches to better understand the toxicity mechanism.

Proliferation toxicity and mechanism of novel mixed bromine/chlorine transformation products of tetrabromobisphenol A on human embryonic stem cell

Mixed bromine/chlorine transformation products of tetrabromobisphenol A (Cl_yBr_xBPAs) are mixed halogenated-type compounds recently identified in electronic waste dismantling sites. There are a lack of toxicity data on these compounds. To study their development toxicity, the proliferation toxicity was investigated using human embryonic stem cells (hESC) exposed to the lowest effective dose of two Cl_yBr_xBPA analogues (2-chloro-2',6-dibromobisphenol A and 2,2'-dichloro-6-monobromobisphenol A). For comparison, tetrabromobisphenol A, 2,2',6-tribromobisphenol A, and bisphenol A were also assessed. It was observed that Cl_yBr_xBPAs inhibited hESCs proliferation in a concentration-dependent manner. The cell bioaccumulation efficiency of Cl_yBr_xBPAs was higher than that of tetrabromobisphenol A. Also, Cl_yBr_xBPAs were more toxic than tetrabromobisphenol A, with 2,2'-dichloro-6-monobromobisphenol A exhibiting the most potent toxicity. Furthermore, flow cytometry and oxidative stress results showed that increased reactive oxygen species raised the degree of apoptosis and reduced DNA synthesis. Metabolomics analysis on the effect of Cl_yBr_xBPAs on metabolic pathway alteration showed that Cl_yBr_xBPAs mainly interfered with four metabolic pathways related to amino acid metabolism and biosynthesis. These results provide an initial perspective on the proliferation toxicity of Cl_yBr_xBPAs, indicating development toxicity in children.

Eucalyptol antagonized the apoptosis and immune dysfunction of grass carp hepatocytes induced by tetrabromobisphenol A by regulating ROS/ASK1/JNK pathway

Tetrabromobisphenol A (TBBPA) is a common environmental pollutant which has multi-organ toxicity to mammals. Eucalyptol (EUC) has super antioxidant biological activity. However, in this experimental study, we probed into the mechanism of toxic of TBBPA exposure on Grass carp hepatocytes (L8824 cells) and the antagonistic impact of EUC on TBBPA. We treated L8824 cells with 8 μg/ml TBBPA and/or 20 μM EUC for 24 h in this test research. The experiment results suggested that TBBPA exposure induced elevated levels of reactive oxygen species (ROS), led to oxidative stress, decreased SOD and CAT activities, decreased GSH and T-AOC contents, exacerbated MDA accumulation, activated ASK1/JNK signaling pathway, and further increased the contents of mitochondrial dependent apoptosis pathway related indicators (Cyt-C, Bax, Caspase 9, Caspase 3), while Bcl-2 expression decreased. In addition, TBBPA exposure induced increased expression of TNF-α, IL-6, IL-1β, and decreased expression of IL-2, IFN-γ, Hepcidin, β-defensin, LEAP2. The oxidative stress level, ASK1/JNK signal pathway expression level, apoptosis ratio and cellular immune function of cells exposed to EUC alone did not change significantly. Combined exposure of TBBPA and EUC significantly reduced the proportion of apoptosis and restored cellular immune function. Therefore, these results suggest that EUC can effectively antagonize TBBPA-induced apoptosis and immune dysfunction of L8824 cells by regulating ROS/ASK1/JNK signaling pathway.

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.

Toxicity and Estrogenicity of Bisphenol TMC in Oryzias melastigma via In Vivo and In Silico Studies

Bisphenol 4-[1-(4-hydroxyphenyl)-3,3,5-trimethylcyclohexyl] phenol (BPTMC), as a substitute for bisphenol A, has been detected in environments. However, the ecotoxicological data of BPTMC are extremely scarce. Here, the lethality, developmental toxicity, locomotor behavior, and estrogenic activity of BPTMC at different concentrations (0.25-2000 μg/L) in marine medaka (Oryzias melastigma) embryos were examined. In addition, the in silico binding potentials of O. melastigma estrogen receptors (omEsrs) with BPTMC were assessed by docking study. Low-concentration BPTMC exposure (including an environmentally relevant concentration, 0.25 μg/L) resulted in stimulating effects, including hatching rate, heart rate, malformation rate, and swimming velocity. However, elevated concentrations of BPTMC led to an inflammatory response, changed heart rate and swimming velocity in the embryos and larvae. In the meantime, BPTMC (including 0.25 μg/L) altered the concentrations of estrogen receptor, vitellogenin, and endogenous 17 β-estradiol as well as the transcriptional levels of estrogen-responsive genes in the embryos or/and larvae. Furthermore, elaborate tertiary structures of omEsrs were built by ab initio modeling, and BPTMC exerted potent binding potential with three omEsrs with -47.23, -49.23, and -50.30 kJ/mol for Esr1, Esr2a, and Esr2b, respectively. This work suggests that BPTMC has potent toxicity and estrogenic effects in O. melastigma.

TET1 involved in bisphenol A induced TM3 Leydig cell toxicity by regulating Cav3.3 hydroxymethylation

Bisphenol A (BPA), an important environmental pollutant, is known to damage reproductive development. However, the underlying epigenetic mechanism in Leydig cells during BPA exposure has not been explored in detail. In this study, TM3 Leydig cells were treated with BPA (0, 20, 40 and 80 μM) for 72 h. The differentially expressed TET1 cell model was constructed to explore the mechanism of BPA-induced cytotoxicity. Results showed that BPA exposure significantly inhibited cell viability and increased apoptosis of TM3 Leydig cells. Meanwhile, the mRNA of TET1, Cav3.2 and Cav3.3 decreased significantly with the increase of BPA exposure. Importantly, TET1 significantly promoted proliferation of TM3 Leydig cells and inhibited apoptosis. Differentially expressed TET1 significantly affected BPA-induced toxicity in TM3 Leydig cells. Notably, TET1 elevated the mRNA levels of Cav3.2 and Cav3.3. MeDIP and hMeDIP confirmed that TET1 regulated the expression of Cav3.3 through DNA hydroxymethylation. Our study firstly presented that TET1 participated in BPA-induced toxicity in TM3 Leydig cells through regulating Cav3.3 hydroxymethylation modification. These findings suggest that TET1 acts as a potential epigenetic marker for reproductive toxicity induced by BPA exposure and may provide a new direction for the research on male reproductive damage.

Anthropogenic impact on the reproductive health of two wild Patagonian fish species with differing reproductive strategies

A particularly concerning outcome of environmental pollution is the disturbance of reproductive processes. However, studies on the impacts of pollution on the reproductive health of fish inhabiting South American environments are limited. We studied the impact of anthropogenic pollution on the reproductive health of two sympatric Patagonian marine fish species with different reproductive strategies: the live-bearing rockfish Sebastes oculatus and the egg-laying Brazilian sandperch Pinguipes brasilianus. Our findings reveal that both species presented some degree of reproductive disturbance when inhabiting an affected site, but the specific alterations differed depending on the species, sex, and season. During the reproductive season, 17β-estradiol levels were elevated in females of both species living in polluted areas, while no differences in androgen levels were observed in either species or season. The gonadosomatic index (GSI) was affected in both sexes of S. oculatus during the non-reproductive season, while the gonadal stages were mainly affected in both sexes of P. brasilianus. No signs of intersex condition were observed. Our results highlight the importance of including diverse reproductive parameters to better understand anthropogenic effects on wild animals. Long-term studies including other fish species and including offspring (to evaluate possible transgenerational effects) will be necessary to determine the consequences of the documented reproductive alterations, particularly whether fish species inhabiting Patagonian marine reef areas will be able to reproductively adapt to increasing marine anthropogenic disturbances.

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.

Tetrachlorobisphenol A mediates reproductive toxicity in Caenorhabditis elegans via DNA damage-induced apoptosis

Tetrachlorobisphenol A (TCBPA), an alternative to tetrabromobisphenol A (TBBPA), is ubiquitous in the environment and could potentially impact the reproductive system of organisms. However, the mechanisms underlying TCBPA-mediated reproductive effects remain unclear. Herein, we exposed Caenorhabditis elegans (C. elegans, L4 larvae) to TCBPA at environmentally relevant doses (0-100 μg/L) for 24 h. Exposure to TCBPA at concentrations of 1-100 μg/L impaired fertility of C. elegans, as indicated by brood size. After staining, the number of germline cells decreased in a dose-dependent manner, whereas germline cell corpses increased in exposed nematodes (10-100 μg/L TCBPA). Moreover, the expression of genes related to the germline apoptosis pathway was regulated following exposure to 100 μg/L TCBPA, indicating the potential role of DNA damage in TCBPA-induced apoptosis. Apoptosis was nearly abolished in ced-4 and ced-3 mutants and blocked in hus-1, egl-1, cep-1, and ced-9 mutants. Numerous foci were detected in TCBPA (100 μg/L)-exposed hus-1::GFP strains. These results indicate that TCBPA induces hus-1-mediated DNA damage and further causes apoptosis via a cep-1-dependent pathway. Our data provide evidence that TCBPA causes reproductive toxicity via DNA damage-induced apoptosis.

Hormetic dose responses induced by organic flame retardants in aquatic animals: Occurrence and quantification

The organic flame retardants (OFRs) have attracted global concerns due to their potential toxicity and ubiquitous presence in the aquatic environment. Hormesis refers to a biphasic dose response, characterized by low-dose stimulation and high-dose inhibition. The present study provided substantial evidence for the widespread occurrence of OFRs-induced hormesis in aquatic animals, including 202 hormetic dose response relationships. The maximum stimulatory response (MAX) was commonly lower than 160% of the control response, with a combined value of 134%. Furthermore, the magnitude of MAX varied significantly among multiple factors and their interactions, such as chemical types and taxonomic groups. Moreover, the distance from the dose of MAX to the no-observed-adverse-effect-level (NOAEL) (NOAEL: MAX) was typically below 10-fold (median = 6-fold), while the width of the hormetic zone (from the lowest dose inducing hormesis to the NOAEL) was approximately 20-fold. Collectively, the quantitative features of OFRs-induced hormesis in aquatic animals were in accordance with the broader hormetic literature. In addition, the implications of hormetic dose response model for the risk assessment of OFRs were discussed. This study offered a novel insight for understanding the biological effects of low-to-high doses of OFRs on aquatic animals and assessing the potential risks of OFRs in the aquatic environment.

Norethindrone alters growth, sex differentiation and gene expression in marine medaka (Oryzias melastigma)

Norethindrone (NET) is a widely used synthetic progestin, which appears in water environments and threatens aquatic organisms. In this study, marine medaka (Oryzias melastigma) larvae were exposed to 7.6 and 80.1 ng/L NET for 190 days. The effects of NET on growth, sex differentiation, gonad histology and transcriptional expression profiles of hypothalamic-pituitary-gonadal (HPG) axis-related genes were determined. The results showed that exposure to 80.1 ng/L NET caused an all-male marine medaka population and significantly decreased the growth of males. Exposure to 7.6 ng/L NET increased the ratio of males/females in the marine medaka population, decreased the growth of males and delayed the ovary maturation in females. However, the sperm maturation was accelerated by 7.6 or 80.1 ng/L NET. In females, the transcription levels of cytochrome P450 aromatase (cyp19a1a) and progesterone receptor (pgr) in ovaries, glucocorticoid receptor (gr) and vitellogenin (vtg) in livers were suppressed after exposure to 7.6 ng/L NET, which may cause delayed ovary maturation. In males, NET significantly decreased the transcription levels of follicle stimulating hormone β (fshβ) and Luteinizing hormone β (lhβ)in the brain, Estrogen receptor β (erβ)，gr and pgr in the liver, and vitellogenin receptor (vtgr) in the testes, while NET of 80.1 ng/L led to a significant up-regulation of steroidogenic acute regulatory protein (star) in the testes of males. These results showed that NET could influence growth, sex differentiation and gonadal maturation and significantly alter the transcriptional expression levels of HPG axis-related genes.

Bisphenol-A alters hematopoiesis through EGFR/ERK signaling to induce myeloblastic condition in zebrafish model

Experimental evidence from the etiology of cancer studies suggests that a correlation between Bisphenol-A (BPA) exposure and alterations in hematopoiesis leads to blood cancer. In our study zebrafish were used to assess the lethality, developmental effect, embryonic apoptosis and changes in transcription factor of hematopoiesis through EGFR/ERK signaling pathways in response to BPA. The in silico interaction of EGFR and BPA was analysed by molecular dynamic simulation. According to our results, BPA induced a significant lethal effect in hatching retardation, reduction in heart rate and teratogenic effects on zebrafish embryos and larvae at three different concentrations 100, 500 and 2500 μg/L. The mortality of adult zebrafish exposed to the acute toxicity of BPA from 5 to 30 mg/L concentrations was determined for 96 h. The peripheral blood cells and vital organs such as kidney, liver and spleen from BPA exposed fish showed predominantly abnormal myeloid blast cells along with severe morphological changes in erythrocytes at sublethal concentration 245 μg/L. The BPA showed the highest binding affinity to zebrafish EGFR with a docking score of -7.5 kcal/mol with an RMSD of 3.0 nm during MD simulation. We found that EGFR/ERK overexpression leads to induce hematopoietic cell proliferation and impaired differentiation, which enhances the myeloid repopulating activity and the accumulation of immature myeloblast cells. BPA also caused a corresponding increase in expression of hematopoietic transcription factor c-MYB and RUNX-1 leading to polychromasia, poikilocytosis, acanthocytes and anisocytosis and promoted myeloblastosis by inhibiting GATA-1 expression. These morphological changes often resulted in the prior condition of acute myeloid leukemia (AML). Comprehensively, our data suggest that BPA can trigger the malignancy of AML cells by alteration of respective hematopoietic transcription factors via EGFR/ERK signaling in the zebrafish model.

Insight into the mechanism of tetrachlorobisphenol A (TCBPA)-induced proliferation of breast cancer cells by GPER-mediated signaling pathways

Tetrachlorobisphenol A (TCBPA), a chlorinated derivative of bisphenol A, is an endocrine disruptor based on interaction with nuclear estrogen receptor alpha (ERα). However, there is only limited data on the mechanisms through which TCBPA-associated estrogenic activity is related to the membrane G protein-coupled estrogen receptor (GPER) pathway. In this study, three human breast cancer cell lines-MCF-7, SKBR3, and MDA-MB-231 cells were used to evaluate whether, as well as how, TCBPA at concentration range of 0.001-50 μM affect cell proliferation. The role of GPER signaling in TCBPA-induced cell proliferation was studied by analyzing the protein expression and mRNA levels of relevant signal targets. The results showed that low concentrations of TCBPA significantly induced the proliferation of MCF-7, SKBR3, and MDA-MB-231 cells, with MCF-7 cells being the most sensitive to TCBPA exposure. Low-concentration TCBPA also upregulated the expression of GPER, CyclinD1, c-Myc, and c-Fos proteins, as well as increased the phosphorylation of extracellular signal-regulated-kinase 1/2 (Erk1/2) and protein kinase B (Akt). Additionally, the mRNA levels of genes associated with estrogen signaling pathways also increased upon exposure to TCBPA. However, the phosphorylation of Erk1/2 and Akt decreased when the cells were treated with GPER inhibitor G15 and phosphatidylinositide 3-kinase (PI3K) inhibitor wortmannin (WM) prior to TCBPA exposure. Besides, the increased proliferation of breast cancer cells induced by TCBPA were also inhibited. In ERα-positive MCF-7 cells, TCBPA also upregulated ERα expression, and ERα was found to interact with GPER-mediated signaling. The results indicate that GPER activates the PI3K/Akt and Erk1/2 signal cascades to drive the cell proliferation observed for low concentrations of TCBPA. The presented results suggest a new mechanism by which TCBPA exerts estrogenic action in breast cancer cells, namely, GPER signaling in an ERα-independent manner, and also highlights the potential risks to human health of the usage of TCBPA.

Environmental behavior and potential driving force of bisphenol A in the Elbe River: A long-term trend study

As an endocrine disruptor, a deep understanding of the environmental behavior and potential driving force of bisphenol A (BPA) is helpful for developing a mitigation strategy and reducing the exposure risk to the public. Based on long-term monitoring data from 2004 to 2016, this study systematically evaluated the long-term trend, periodic characteristics, and potential risks of BPA in the Elbe River in the state of Saxony, Germany. Multiple advanced statistical approaches were employed for data mining. Pettitt's test was used to determine the main change points of BPA that occurred from 2008 to 2011. The Mann-Kendall test showed a decreasing trend in BPA concentrations (slope: -0.087 to -0.112, P < 0.05) over the past 13 years, particularly in the wet seasons (slope: -0.730 to -0.038, P < 0.05). Wavelet analysis revealed similar periodicities of BPA among stations (which experienced 4-5 oscillations in the first major period). The ARIMA model forecasted the mean BPA concentration as ranging from 9 to 41 ng L^-1 in the subsequent 3 months, which was similar to that in the last 3 months (20-42 ng L^-1). Besides, the highest hazard quotients (>0.3) were documented for Chironomus riparius, Oryzias latipes, Potamopyrgus antipodarum, and Hydra vulgar, which indicates that BPA may threaten their growth and development. The hazard index values for non-cancer risk of BPA no greater than 6.47 × 10^-9 (HQ far below 1), which suggests that BPA did not pose a significant threat to human health. Because BPA pollution is closely related to industrial activities, a long-term decline in BPA concentrations could be attributed to the reduced number of factories, limited discharge, and improved decontamination efficiency. However, the minimal change in the BPA concentration in the near future could reflect periodic fluctuations.

TBBPA, TBBPS, and TCBPA disrupt hESC hepatic differentiation and promote the proliferation of differentiated cells partly via up-regulation of the FGF10 signaling pathway

Halogenated flame retardants (HFRs), including Tetrabromobisphenol A (TBBPA), Tetrabromobisphenol S (TBBPS), and Tetrachlorobisphenol A (TCBPA), are widely applied in the manufacturing industry to improve fire safety and can be detected in pregnant women's serum at nanomolar levels. Thus, it is necessary to pay attention to the three HFR potential development toxicity, which has not been conclusively addressed yet. The liver is the main organ that detoxifies our body; TBBPA exposure may lead to increased liver weight in rodents. Therefore, in this study, we assessed the developmental hepatic toxicity of the three HFRs with a human embryonic stem cell hepatic differentiation-based system and transcriptomics analyses. We mostly evaluated lineage fate alterations and demonstrated the three HFRs may have common disruptive effects on hepatic differentiation, with TCBPA being significantly more potent. More specifically, the three HFRs up-regulated genes related to cell cycle and FGF10 signaling, at late stages of the hepatic differentiation. This indicates the three chemicals promoted hepatoblast proliferation likely via up-regulating the FGF10 cascade. At the same time, we also presented a powerful way to combine in vitro differentiation and in silico transcriptomic analyses, to efficiently evaluate hazardous materials' adverse effects on lineage fate decisions during early development.

Developmental neurotoxicity of low concentrations of bisphenol A and S exposure in zebrafish

The vulnerability to environmental insults is heightened at early stages of development. However, the neurotoxic potential of bisphenol A (BPA) and bisphenol S (BPS) at developmental windows remains unclear. To investigate the mechanisms mediating the developmental neurotoxicity, zebrafish embryos were treated with 0.01, 0.03, 0.01, 0.3, 1 μM BPA/BPS. Also, we used Tg(HuC:GFP) zebrafish to investigate whether BPA/BPS could induce neuron development. The reduction in body length, and increased heart rate were significant in 0.3 and 1 μM BPA/BPS groups. The green fluorescence protein (GFP) intensity increased at 72 hpf and 120 hpf in Tg(HuC:GFP) larvae which was consistent with the increased mRNA expression of elval3 following BPS treatments, an indication of the plausible effect of BPS on embryonic neuron development. Additionally, BPA/BPS treatments elicited hyperactivity and reduced static time in zebrafish larvae, suggesting behavioral alterations. Moreover, qRT-PCR results showed that BPA and BPS could interfere with the normal expression of development-related genes vegfa, wnt8a, and mstn1 at the developmental stages. The expression of neurodevelopment-related genes (ngn1, elavl3, gfap, α1-tubulin, mbp, and gap43) were significantly upregulated in BPA and BPS treatments, except for the remarkable downregulation of mbp and gfap elicited by BPA at 48 (0.03 μM) and 120 hpf (0.3 μM) respectively; ngn1 at 48 hpf for 0.1 μM BPS. Overall, our results highlighted that embryonic exposure to low concentrations of BPA/BPS could be deleterious to the central nervous system development and elicit behavioral abnormalities in zebrafish at developmental stages.

Protecting Group-Controlled Remote Regioselective Electrophilic Aromatic Halogenation Reactions

Being able to utilize a protecting group to influence remote regiocontrol offers a simple alternative approach to direct late-stage functionalization of complex organic molecules. However, protecting groups that have the ability to influence reaction regioselectivity remote to their local chemical environment are not widely reported in the literature. Herein, we report the development of remote regioselective electrophilic aromatic substitution (S_EAr) reactions that are enabled via the application of the tetrafluoropyridyl (TFP) phenol-protecting group. We demonstrate that through sequential reactions and protection/deprotection of the TFP group, substitution patterns that do not conform to classical S_EAr regioselectivity rules can be readily accessed.

Assessment of the Effects of Bisphenol A on Dopamine Synthesis and Blood Vessels in the Goldfish Brain

Bisphenol A (BPA) is an abundant contaminant found in aquatic environments. While a large number of toxicological studies have investigated the effects of BPA, the potential effects of BPA exposure on fish brain have rarely been studied. To understand how BPA impacts goldfish brains, we performed a transcriptome analysis of goldfish brains that had been exposed to 50 μg L⁻¹ and 0 μg L⁻¹ BPA for 30 days. In the analysis of unigene expression profiles, 327 unigenes were found to be upregulated and 153 unigenes were found to be downregulated in the BPA exposure group compared to the control group. Dopaminergic signaling pathway-related genes were significantly downregulated in the BPA exposure group. Furthermore, we found that serum dopamine concentrations decreased and TUNEL (terminal deoxynucleotidyl transferase 2-deoxyuridine, 5-triphosphate nick end labeling) staining was present in dopamine neurons enriched regions in the brain after BPA exposure, suggesting that BPA may disrupt dopaminergic processes. A KEGG analysis revealed that genes involved in the fluid shear stress and atherosclerosis pathway were highly significantly enriched. In addition, the qRT-PCR results for fluid shear stress and atherosclerosis pathway-related genes and the vascular histology of the brain showed that BPA exposure could damage blood vessels and induce brain atherosclerosis. The results of this work provide insights into the biological effects of BPA on dopamine synthesis and blood vessels in goldfish brain and could lay a foundation for future BPA neurotoxicity studies.

The mechanisms underlying the developmental effects of bisphenol F on zebrafish

With the increasing use of bisphenol F (BPF) as BPA alternative, BPF are widely distributed in multiple environment media. Our previous study demonstrated that BPF possess equivalent toxicity towards zebrafish as BPA, while its toxic mechanism remains largely unknown. To investigate the mechanisms mediating the developmental effects of BPF, zebrafish embryos were exposed to 0.0005, 0.5, and 5.0 mg/L BPF. Morphological examination indicated that BPF exposure led to depigmentation, decreased heart rate, inhibited spontaneous movement, hatch inhibition, and spinal deformation. Motor neuron-green fluorescence zebrafish assay indicated that exposure to 0.5 or 5.0 mg/L BPF affected embryonic motor neuron development, which is consistent with the spinal defect and spontaneous movement inhibition. Transcriptomic analysis showed that genes associated with the observed symptoms, including neuron development (ngln2a, socs3a, fosb), cardiac development (klf2a), and spinal deformation (ngs, col8a1a, egr2a), were down-regulated after exposure to either 0.0005 (environmental relevant concentration) or 0.5 mg/L BPF. This partially explained the mechanisms underlying the effects of BPF. In conclusion, BPF had the potential to affect zebrafish development even at environmental level through down-regulating associated genes.

In Vitro Effects of Bisphenol A and Tetrabromobisphenol A on Cell Viability and Reproduction-Related Gene Expression in Pituitaries from Sexually Maturing Atlantic Cod (Gadus morhua L.)

Bisphenol A (BPA) and tetrabromobisphenol A (TBBPA) are widely used industrial chemicals, ubiquitously present in the environment. While BPA is a well-known endocrine disruptor and able to affect all levels of the teleost reproductive axis, information regarding TBBPA on this subject is very limited. Using primary cultures from Atlantic cod (Gadus morhua), the present study was aimed at investigating potential direct effects of acute (72 h) BPA and TBBPA exposure on cell viability and the expression of reproductive-relevant genes in the pituitary. The results revealed that both bisphenols stimulate cell viability in terms of metabolic activity and membrane integrity at environmentally relevant concentrations. BPA had no direct effects on gonadotropin gene expression, but enhanced the expression of gonadotropin-releasing hormone (GnRH) receptor 2a, the main gonadotropin modulator in Atlantic cod. In contrast, TBBPA increased gonadotropin transcript levels but had no effect on GnRH receptor mRNA. In conclusion, both anthropogenic compounds display endocrine disruptive properties and are able to directly interfere with gene expression related to reproductive function in cod pituitary cells at environmentally relevant concentrations in vitro.

Effects of a chronic exposure to different water temperatures and/or to an environmental cadmium concentration on the reproduction of the threespine stickleback (Gasterosteus aculeatus)

Knowledge about combined effects of chemicals and temperature on reproductive capacity of fish are rare in literature, especially when it comes to the effects of chronic low-dose chemical exposure combined to the thermal stress. The aim of the study was to evaluate the single and combined effects of temperature (16, 18, 21 °C) and an environmentally relevant concentration of waterborne cadmium (1 µg L^-1, nominal concentration) on the reproductive outputs of threespine stickleback (Gasterosteus aculeatus), and their consequences on offspring survival parameters. The high temperature (21 °C) was the only factor that affected parental parameters (gonadosomatic index "GSI", and vitellogenin "VTG" particularly). On females, 21 °C had a stimulating effect on gonadal development evaluated by an early increase, followed by a sharp decrease of GSI, probably indicating gonadal atresia. Promoting effect of temperature was corroborated by an early production of VTG. In vitro fertilization assays showed interesting results, particularly cadmium effects. As it was supposed, high temperature had a negative impact on offspring parameters (significant decrease in survival and an increase of unhatched embryos). Parental exposure to the very low concentration of cadmium had also negative consequences on mortality rate (significant increase) and hatching rate (significant decrease). Our results indicate that in a global warming context, high temperature and its combination with contaminant may impact reproductive capacity of G. aculeatus, by decreasing parental investment (low eggs and/or sperm quality).

Toxic effects of bisphenol A on goldfish gonad development and the possible pathway of BPA disturbance in female and male fish reproduction

Bisphenol A (BPA) is an abundant endocrine-disrupting compound that is found in the aquatic environment and has adverse effects on fish reproduction; however, the exact pathway of these impacts is unclear. In this study, the different effects of BPA on ovarian and testis development in goldfish (Carassius auratus) and the different mechanisms underlying these effects were investigated. The gonadosomatic index (GSI) and gonadal histology demonstrated that BPA diminished ovarian maturation in goldfish, which recovered after BPA treatment withdrawal. In males, BPA disrupted testis maturation, but this disruption could not be recovered after BPA treatment withdrawal. The hypothalamic-pituitary-gonad (HPG) axis-related genes sgnrh, fshβ and lhβ were significantly decreased in BPA-treated female fish, while no changes in sex steroid hormone levels and no TUNEL and PCNA staining were found in the ovary, suggesting that BPA may reduce ovarian maturation through the HPG axis. In male fish, TUNEL staining was found in 1 μg L^-1 BPA-exposed germ cells and 50 and 500 μg L^-1 BPA-exposed Leydig cells. Decreases in 11-KT levels were also found in 50 and 500 μg L^-1 BPA-exposed fish, but BPA did not affect genes associated with the HPG axes. This result shows that BPA disrupts testis maturation through apoptosis of germ cells and Leydig cells, thus inducing decreases in 11-KT levels that disrupt spermatogenesis. Collectively, our findings provide insights into the molecular and cellular mechanisms underlying BPA disturbance of goldfish reproduction.

Diets contaminated with Bisphenol A and Di-isononyl phtalate modify skeletal muscle composition: A new target for environmental pollutant action

In the last years, an increasing number of studies reported that food pollution represents a significant route of exposure to environmental toxicants, able to cause mild to severe food illnesses and health problems, including hormonal and metabolic diseases. Pollutants can accumulate in organisms and biomagnify along the food web, finally targeting top consumers causing health and economic problems. In this study, adults of gilthead sea bream, Sparus aurata, were fed with diets contaminated with Bisphenol A (BPA) (4 and 4000 μg BPA kg^-1 bw day^-1) and Di-isononyl phthalate (DiNP) (15 and 1500 μg DiNP kg^-1 bw day^-1), to evaluate the effects of the contamination on the muscle macromolecular composition and alterations of its texture. The analysis conducted in the muscle using infrared microspectroscopy, molecular biology and biochemical assays, showed, in fish fed BPA contaminated diets, a decrease of unsaturated lipids and an increase of triglycerides and saturated alkyl chains. Conversely, in fish fed DiNP, a decrease of lipid content, caused by a reduction of both saturated and unsaturated chains and triglycerides was measured. Protein content was decreased by both xenobiotics evidencing a novel macromolecular target affected by these environmental contaminants. In addition, in all treated groups, proteins resulted more phosphorylated than in controls. Calpain and cathepsin levels, orchestrating protein turnover, were deregulated by both xenobiotics, evidencing alterations of muscle composition and texture. In conclusion, the results obtained suggest the ability of BPA and DiNP to modify the muscle macromolecular building, advising this tissue as a target of Endocrine-Disrupting Chemicals (EDCs) and providing a set of biomarkers as possible monitoring endpoints to develop novel OEDC test guidelines.

Brominated Flame Retardants, Microplastics, and Biocides in the Marine Environment: Recent Updates of Occurrence, Analysis, and Impacts

Emerging contaminants (ECs) may pose adverse effects on the marine ecosystem and human health. Based on the analysis of publications filed in recent years, this paper provides a comprehensive overview on three prominent groups of ECs, i.e., brominated flame retardants, microplastics, and biocides. It includes detailed discussions on: (1) the occurrence of ECs in seawater, sediment, and biota; (2) analytical detection and monitoring approaches for these target ECs; and (3) the biological impacts of the ECs on humans and other trophic levels. This review provides a summary of recent advances in the field and remaining knowledge gaps to address, to enable the assessment of risk and support the development of regulations and mitigation technologies for the control of ECs in the marine environment.

Development of ELISAs for the detection of vitellogenin in three marine fish from coastal areas of China

Estrogenic pollution has aroused great concern for its adverse effects on marine organisms. This study aimed to establish biomarker-based methods for detecting environmental estrogens using vitellogenin (Vtg) of teleost fishes inhabiting coastal areas of China. Firstly, Vtgs in marbled flounder (Pseudopleuronectes yokohamae), black rockfish (Sebastes schlegelii) and fat greenling (Hexagrammos otakii) were purified, characterized and used to prepare antibodies. Then, Vtg ELISA for each species was developed using purified Vtg and its antibody. Marbled flounder Vtg ELISA had a working range of 3.9-500 ng/mL and a detection limit of 2.1 ng/mL, and black rockfish Vtg ELISA had strong cross-reactivity with marbled flounder Vtg. Furthermore, Vtg induction in male marbled flounder exposed to pentadecafluorooctanoic acid (PFOA) was measured by developed ELISA. Plasma Vtg concentrations were significantly increased with PFOA concentrations in seawater and fish muscle. Therefore, Vtg ELISAs for these species might be useful tools for monitoring marine environmental estrogens.

Endocrine disruptors in soil: Effects of bisphenol A on gene expression of the earthworm Eisenia fetida

Xenobiotics such as bisphenol A (BPA), are present in biosolids, which are applied as organic fertilizers in agricultural fields. Their effects on soil life have been poorly assessed, and this is particularly important in the case of earthworms, which represent the main animal biomass in this medium. In the present work we study the impacts of BPA on gene expression of Eisenia fetida, a widely used ecotoxicological model. Chronic soil tests and acute contact tests were performed, and gene expression was analyzed in total tissue and in masculine reproductive organs of the earthworms. The genes studied in this research played a role in endocrine pathways, detoxification mechanisms, stress response, epigenetics, and genotoxicity. Most of the genes were identified for the first time, providing potentially useful biomarkers for future assessments. For chronic exposures, no changes were detected in whole-body tissue; however, masculine reproductive organs showed changes in the expression of genes related to endocrine function (EcR, MAPR, AdipoR), epigenetic mechanisms (DNMTs), genotoxicity (PARP1), and stress responses (HSC70 4). For acute exposures, the expression of one epigenetic-related gene was altered for both whole-body tissues and male reproductive organs (Piwi2). Further changes were detected for whole-body tissues involved in detoxification (Metallothionein), stress (HSC70 4), and genotoxicity (PARP1) mechanisms. Acute exposure effects were also tested in whole-body tissues of juveniles, showing changes in the expression of Metallothionein and Piwi2. The molecular changes found in the analyzed earthworms indicate that exposure to BPA may have negative implications in their populations. Particularly interesting are the alterations related to epigenetic mechanisms, which suggest that future generations may be impacted. This study is the first to evaluate the molecular effects of BPA on soil organisms, and further assays will be necessary to better characterize the true environmental repercussions.

CAPSULE

Levels of gene expression in total-body tissues and masculine reproductive organs were analyzed in earthworms after exposure to bisphenol A and we observed associated changes in detoxification, endocrine, epigenetic, genotoxic and stress pathways.

Bisphenol risk in fish exposed to a contamination gradient: Triggering of spatial avoidance

Bisphenol A (BPA) is an emerging contaminant widely used in various industrial products. Sublethal toxicity of BPA on aquatic organisms is expected to occur at a concentration of around 500 μg L^-1, which is much higher than environmentally realistic concentrations found in water bodies (up to 0.41 μg L^-1). However, there is no information concerning how a BPA contamination gradient could affect the spatial displacement of organisms. We hypothesized that fish might be able to detect an environmentally realistic BPA contamination gradient and avoid potential toxic effects due to continuous exposure. Therefore, the objectives of this work were: (i) to determine if BPA could trigger an avoidance response in the freshwater fish Poecilia reticulata; (ii) to assess whether BPA-driven avoidance occurs at environmentally relevant concentrations; and (iii) to estimate the population immediate decline (PID) at the local scale, considering avoidance and mortality as endpoints. Avoidance experiments were performed in a seven-compartment non-forced exposure system, in which a BPA contamination gradient was simulated. The results indicated that BPA triggered avoidance in P. reticulata. In a traditional forced acute toxicity test, lethal effects in 50% of the population occurred at a BPA concentration of 1660 μg L^-1, while in the non-forced system with a BPA concentration gradient, avoidance of 50% of the population occurred at a concentration four orders of magnitude lower (0.20 μg L^-1). At environmentally relevant BPA concentrations, PID was mainly determined by the avoidance response. Avoidance in P. reticulata populations is expected to occur at BPA concentrations below those that cause sublethal effects on fish and are considered safe by international agencies (≤1 μg L^-1). The approach used in the present study represents a valuable tool for use in environmental risk assessment strategies, providing a novel and ecologically relevant response that is complementary to traditional ecotoxicological tests.

Developmental Effects and Estrogenicity of Bisphenol A Alternatives in a Zebrafish Embryo Model

In order to understand the negative effects of bisphenol A (BPA) alternatives comprehensively, zebrafish embryos were used to assess the lethality, developmental effects, and estrogenic activity of bisphenol analogues. The in silico estrogenic activities of bisphenol analogues were assayed by binding simulation. According to our results, the lethality of bisphenol analogues decreased in order of bisphenol AF (BPAF) > BPA > bisphenol F (BPF) > bisphenol S (BPS). BPAF and BPF induced significant effects on zebrafish embryos, including decreased heart rate, hatching inhibition, and teratogenic effects. The binding potentials of bisphenol analogues toward zebrafish ERs (zfERS) decreased in the following order: BPAF > BPA > BPF > BPS. Among the three subtypes of zfERs, zfERβ2 showed the highest binding activity toward the bisphenols, followed by zfERα and zfERβ1. In vivo estrogenic activity tests showed that BPAF, BPA, and BPF significantly enhanced the protein levels of ERα along with the mRNA levels of esr1, esr2a, esr2b, and vtg1 in zebrafish embryos. Esr2b showed the strongest response to BPAF and BPA exposure among the three esrs. In contrast, BPS did not significantly regulate ER protein level or ER transcription. In conclusion, BPAF showed the highest lethality, developmental effects, and estrogenic activity (both in silico and in vivo) followed by BPA and BPF. BPS showed the weakest toxicity and estrogenic activity. zfERβ2 might act as the main target among the three ER subtypes of zebrafish after exposure to BPAF and BPA.