Stage-Related Neurotoxicity of BPA in the Development of Zebrafish Embryos

UPLC-QqQMS based targeted metabolomics reveal combination impact on metabolism caused by bisphenol AF and fructose combined exposure in male mice

Bisphenol AF (BPAF), a fluorinated alternative to the plasticizer bisphenol A (BPA), is found in both the environment and the human body. Fructose is one of the sweeteners that has been widely used in recent years. Prior research has verified that the combined exposure to fructose and BPA considerably worsened the impact on glycolipid metabolism. However, it is currently unclear whether BPAF have a combination effect on health with fructose. Serum glucose and insulin, liver biochemistry, histology of the liver and adipose tissue, serum profiles of amino acids, vitamins, bile acids, steroid hormones, catecholamines, and adipocytokines like leptin, omentin-1, adiponectin, asprosin, and adipocyte fatty acid binding protein (A-FABP) of male mice were all investigated in this study following a week of combined exposure to two doses of BPAF (lower dose: 0.25, and higher dose: 25 μg/kg daily). The results showed that simultaneous exposure to lower doses of BPAF and fructose considerably increased blood insulin and liver coefficient, total bilirubin, direct bilirubin, and glucose while significantly decreasing body weight, food intake, liver creatinine, and serum leptin, asprosin, and A-FABP. According to histology analysis, adipocyte enlargement may result from lower dose BPAF and fructose combined exposure, while bile duct dilatation may result from both lower and higher doses of BPAF combined with fructose. Concurrently, the combination of lower doses of BPAF and fructose increased the release of adrenocortical hormones and catecholamines, worsened metabolic disorders in amino acids such as histidine, arginine and proline, branched chain amino acid (isoleucine), and aromatic amino acids (tryptophan and phenylalanine), and aggravated the depletion of vitamin B12 and A. Interestingly, following the combined exposure to BPAF and fructose, bile acids including taurocholic acid, deoxycholic acid, cholic acid, and taurine ursodeoxycholic acid rose in a dose-dependent manner. According to these results, exposure to fructose and BPAF together may have a more detrimental effect on metabolism than either substance alone. Further research should be conducted to verify the impact of joint exposure to BPAF and fructose on human.

Comparative toxicological assessment of 2 bisphenols using a systems approach: evaluation of the behavioral and transcriptomic responses of Danio rerio to bisphenol A and tetrabromobisphenol A

The zebrafish (Danio rerio) is becoming a critical component of new approach methods (NAMs) in chemical risk assessment. As a whole organism in vitro NAM, the zebrafish model offers significant advantages over individual cell-line testing, including toxicokinetic and toxicodynamic competencies. A transcriptomic approach not only allows for insight into mechanism of action for both apical endpoints and unobservable adverse outcomes, but also changes in gene expression induced by lower, environmentally relevant concentrations. In this study, we used a larval zebrafish model to assess the behavioral and transcriptomic alterations caused by subphenotypic concentrations of 2 chemicals with the same structural backbone, the endocrine-disrupting chemicals bisphenol A and tetrabromobisphenol A. Following assessment of behavioral toxicity, we used a transcriptomic approach to identify molecular pathways associated with previously described phenotypes. We also determined the transcriptomic point of departure for each chemical by modeling gene expression changes as continuous systems which allows for the identification of a single concentration at which toxic effects can be predicted. This can then be investigated with confirmatory cell-based testing in an integrated approach to testing and assessment to determine risk to human health and the environment with greater confidence. This paper demonstrates the impact of using a multi-faceted approach for evaluating the physiological and neurotoxic effects of exposure to structurally related chemicals. By comparing phenotypic effects with transcriptomic outcomes, we were able to differentiate, characterize, and rank the toxicities of related bisphenols, which demonstrates methodological advantages unique to the larval zebrafish NAM.

Non-negligible Toxicity to Fish in the Early Life Stages Triggered by Aqueous Leachate of Takeaway Plastic Containers

Ordering takeout is a growing social phenomenon and may raise public health concerns. However, the associated health risk of compounds leaching from plastic packaging is unknown due to the lack of chemical and toxicity data. In this study, 20 chemical candidates were tentatively identified in the environmentally relevant leachate from plastic containers through the nontargeted chemical analysis. Three main components with high responses and/or predicted toxicity were further verified and quantified, namely, 3,5-di-tert-butyl-4-hydroxycinnamic acid (BHC), 2,4-di-tert-butylphenol (2,4-DTBP), and 9-octadecenamide (oleamide). The toxicity to zebrafish larvae of BHC, a degradation product of a widely used antioxidant Irganox 1010, was quite similar to that of the whole plastic leachate. In the same manner, RNA-seq-based ingenuity analysis showed that the affected canonical pathways of zebrafish larvae were quite comparable between BHC and the whole plastic leachate, i.e., highly relevant to neurological disease, metabolic disease, and even behavioral disorder. Longer-term exposure (35 days) did not cause any effect on adult zebrafish but led to decreased hatching rate and obvious neurotoxicity in zebrafish offspring. Collectively, this study strongly suggests that plastic containers can leach out a suite of compounds causing non-negligible impacts on the early stages of fish via direct or parental exposure.

Synthetic azo-dye, Tartrazine induces neurodevelopmental toxicity via mitochondria-mediated apoptosis in zebrafish embryos

Tartrazine (TZ), or E 102 or C Yellow, is a commonly used azo dye in the food and dyeing industries. Its excessive usage beyond permissible levels threatens human health and the aquatic environment. While previous studies have reported adverse effects such as mutagenicity, carcinogenicity, and reproductive toxicity. Our study aimed to comprehensively evaluate the developmental neurotoxicity of TZ exposure via biochemical and behavioral examinations and explored the underlying mechanism via gene expression analyses. TZ at an environmentally relevant concentration (50 mg/L) significantly induces oxidative stress, altered antioxidant (SOD, CAT and GSH) response, triggered cellular damage (MDA and LDH), and induced neuro-biochemical changes (AChE and NO). Gene expression analyses revealed broad disruptions in genes associated with antioxidant defense (sod1, cat, and gstp1), mitochondrial dysfunction (mfn2, opa1, and fis1),evoked inflammatory response (nfkb, tnfa, and il1b), apoptosis activation (bcl2, bax, and p53), and neural development (bdnf, mbp, and syn2a). Behavioral analysis indicated altered thigmotaxis, touch response, and locomotion depending on the concentration of TZ exposure. Remarkably, the observed effective concentrations were consistent with the permitted levels in food products, highlighting the neurodevelopmental effects of TZ at environmentally relevant concentrations. These findings provide valuable insights into the underlying molecular mechanisms, particularly the role of mitochondria-mediated apoptosis, contributing to TZ-induced neurodevelopmental disorders in vivo.

Developmental Exposure to Kynurenine Affects Zebrafish and Rat Behavior

Proper nutrition and supplementation during pregnancy and breastfeeding are crucial for the development of offspring. Kynurenine (KYN) is the central metabolite of the kynurenine pathway and a direct precursor of other metabolites that possess immunoprotective or neuroactive properties, with the ultimate effect on fetal neurodevelopment. To date, no studies have evaluated the effects of KYN on early embryonic development. Thus, the aim of our study was to determine the effect of incubation of larvae with KYN in different developmental periods on the behavior of 5-day-old zebrafish. Additionally, the effects exerted by KYN administered on embryonic days 1-7 (ED 1-7) on the behavior of adult offspring of rats were elucidated. Our study revealed that the incubation with KYN induced changes in zebrafish behavior, especially when zebrafish embryos or larvae were incubated with KYN from 1 to 72 h post-fertilization (hpf) and from 49 to 72 hpf. KYN administered early during pregnancy induced subtle differences in the neurobehavioral development of adult offspring. Further research is required to understand the mechanism of these changes. The larval zebrafish model can be useful for studying disturbances in early brain development processes and their late behavioral consequences. The zebrafish-medium system may be applicable in monitoring drug metabolism in zebrafish.

Deacetyl epoxyazadiradione ameliorates BPA-induced neurotoxicity by mitigating ROS and inflammatory markers in N9 cells and zebrafish larvae

Bisphenol A (BPA) leaches from plastic products have become a major inevitable concern among the research society. Human exposure to BPA leads to deleterious effects on multiple organs by the induced hyper inflammatory and oxidative stress responses. Due to the compromised antioxidant mechanism, the brain environment was highly susceptible and required special concern to ameliorate the effects of BPA. Hence, this study investigates the potential of neem-derived semi natural deacetyl epoxyazadiradione (DEA) against the oxidative stress and inflammatory response induced by BPA exposure in N9 cells and zebrafish larvae. The results from the in vitro analyses showed a decrease in cell viability in the MTT assay and a decline in mitochondrial damage in BPA-exposed N9 cells. Further in vivo, results revealed that pre-treatment of DEA to zebrafish larvae has significantly reduced the level of superoxide anion and increased the production of antioxidant enzymes such as SOD, CAT, GST, GPx and GR. We also found a significant decrease in the production of nitric oxide (p < 0.0001) and iNOS gene expression at 150 μM concentration. Further, DEA pre-treatment improved the behaviour of zebrafish larvae by ameliorating the production of the AChE enzyme. In conclusion, DEA protected zebrafish larvae from BPA toxicity by ameliorating oxidative stress and inflammatory responses.

Preliminary study on the role of aryl hydrocarbon receptor in the neurotoxicity of three typical bisphenol compounds (BPA, BPS and TBBPA) at environmentally relevant concentrations to adult zebrafish (Danio rerio)

Objective

This study was aimed to explore the role of AhR in the neurotoxicity of adult zebrafish induced by three typical bisphenol compounds (BPA, BPS, TBBPA) at environmentally relevant doses.

Methods

The adult zebrafish were randomly divided into solvent control group (DMSO) and AhR inhibitor CH223191 (CH) group (0.05 μmol/L), bisphenol exposure groups (10, 100, 1000 nmol/L) and combined exposure groups (0.05 μmol/L CH and 1000 nmol/L bisphenol compounds). Each tank contained 8 fish (4 male and 4 female), and two parallel tanks were set synchronously. After 30 days of exposure, zebrafish were put on ice plate for anesthesia, weighed and measured for body length, and dissected for brain tissue. The gene expression was detected by RT-qPCR, and the activities of antioxidant enzymes were detected by commercial kits. SPSS 26.0 was used to analyze the data. Additionally, GO, KEGG and principal component analysis (PCA) were carried out.

Results

Compared with the solvent control group, there were no significant differences in body weight and length among the exposed groups. In general, exposure to bisphenol compounds could affect the expression of Ahr2 and AhR target genes (cyp1a1, cyp1a2, and cyp1c1), key genes of neural function (elavl3, gfap, mbp, syn2a, gap43, Zn5, shha, and ache), oxidative stress related genes (nrf2, gpx1a, gstp1/gstp1.2, gstp2/gstp1.1, sod1, sod2, and cat), and the activities of antioxidant enzymes (SOD, CAT and GSH-Px/GPX) in zebrafish brain tissue to some extent. Compared with the groups exposed to bisphenols alone, CH could antagonize the above interference effects caused by bisphenols to some extent. Therefore, the toxic effects of BPA, BPS and TBBPA might be produced through similar mechanisms.

Conclusion

Environmentally related doses of bisphenols (BPA, BPS, TBBPA) could disturb the expression of key molecules of oxidative stress and neural function through activating the AhR signaling pathway, and ultimately lead to neurotoxicity.