The endocrine effects of dietary brominated diphenyl ether-47 exposure, measured across multiple levels of biological organization, in breeding fathead minnows

Dietary exposure to 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) induces oxidative damage promoting cell apoptosis primarily via mitochondrial pathway in the hepatopancreas of carp, Cyprinus carpio

To investigate the mechanisms of BDE-47 on hepatotoxicity in fish, this study examined the effects of dietary exposure to BDE-47 (40 and 4000 ng/g) on carp for 42 days. The results showed that BDE-47 significantly increased carp's condition factor and hepatosomatic index. Pathological results revealed unclear hepatic cord structure, hepatocytes swelling, cellular vacuolization, and inflammatory cell infiltration in the hepatopancreas of carp. Further investigation showed that ROS levels significantly increased on days 7, 14, and 42. Moreover, the activities of antioxidant enzymes SOD, GSH, CAT, and GST increased significantly from 1 to 7 days, and the transcription levels of antioxidant enzymes CAT, Cu-Zn SOD, Mn-SOD, GST, and GPX, and antioxidant pathway genes Keap1, Nrf2, and HO-1 changed significantly at multiple time-points during the 42 days. The results of apoptosis pathway genes showed that the mitochondrial pathway genes Bax, Casp3, and Casp9 were significantly upregulated and Bcl2 was significantly downregulated, while the transcription levels of FADD and PERK were significantly enhanced. These results indicate that BDE-47 induced oxidative damage in hepatopancreas, then it promoted cell apoptosis mainly through the mitochondrial pathway. This study provides a foundation for analyzing the mechanism of hepatotoxicity induced by BDE-47 on fish.

Transcriptomic response patterns of hornyhead turbot (Pleuronichthys verticalis) dosed with polychlorinated biphenyls and polybrominated diphenyl ethers

To evaluate the impact of environmental contaminants on aquatic health, extensive surveys of fish populations have been conducted using bioaccumulation as an indicator of impairment. While these studies have reported mixtures of chemicals in fish tissues, the relationship between specific contaminants and observed adverse impacts remains poorly understood. The present study aimed to characterize the toxicological responses induced by persistent organic pollutants in wild-caught hornyhead turbot (P. verticalis). To do so, hornyhead turbot were interperitoneally injected with a single dose of PCB or PBDE congeners prepared using environmentally realistic mixture proportions. After 96-hour exposure, the livers were excised and analyzed using transcriptomic approaches and analytical chemistry. Concentrations of PCBs and PBDEs measured in the livers indicated clear differences across treatments, and congener profiles closely mirrored our expectations. Distinct gene profiles were characterized for PCB and PBDE exposed fish, with significant differences observed in the expression of genes associated with immune responses, endocrine-related functions, and lipid metabolism. Our findings highlight the key role that transcriptomics can play in monitoring programs to assess chemical-induced toxicity in heterogeneous group of fish (mixed gender and life stage) as is typically found during field surveys. Altogether, the present study provides further evidence of the potential of transcriptomic tools to improve aquatic health assessment and identify causative agents.

Disruption of thyroid hormone regulated proteins and gene expression by polychlorinated biphenyls, polybrominated diphenyl ethers and new flame retardants in residents of an e-waste region

Polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and new flame retardants (NFRs) are known thyroid hormone (TH) disruptors, but their disrupting mechanisms in humans are not completely understood. In this study, we aimed to explore the disrupting mechanisms of the aforementioned chemicals via examining TH-regulated proteins and gene expression in human serum. Adult participants from an e-waste dismantling (exposed group) and a control region (control group) in South China provided blood samples for the research. Some compounds of PCBs, PBDEs, and NFRs showed strong binding affinity to the thyroid-stimulating hormone (TSH), thyroglobulin, thyroxine-binding globulin (TBG), gene expression of TH receptor α (TRα) and β, and iodothyronine deiodinase I (ID1). The highly exposed individuals had lower levels of TBG, TSH, and expression of TRα, but higher expression of ID1 than those of the control group. The disruption of TH-regulated proteins and gene expression suggested the exertion of different and, at times, even contradictory effects on TH disruption. However, no statistically significant difference was found in the TH levels between the exposed and the control group, implying that the TH disruption induced by these chemicals depends on the combined influence of multiple mechanisms. Gene expression appears to be an effective approach for investigations of TH disruption and the potential health effects.

The mechanism and conformational changes of polybrominated diphenyl ethers to TTR by fluorescence spectroscopy, molecular simulation, and quantum chemistry

Free energy contribution of amino acid LYS (B and D chains) and PDBEs was analyzed combining quantum chemistry and molecular modeling.

Dietary exposure to polybrominated diphenyl ether 47 (BDE-47) inhibits development and alters thyroid hormone-related gene expression in the brain of Xenopus laevis tadpoles

Few studies have investigated the thyroid-disrupting effects of polybrominated diphenyl ethers (PBDEs) across multiple levels of biological organization in anurans, despite their suitability for the screening of thyroid disruptors. Therefore, the present study evaluated the effects of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on development, thyroid histology and thyroid hormone-related gene expression in Xenopus laevis exposed to 0 (control), 50 (low), 500 (medium) or 5000μg BDE-47/g food (high) for 21days. Only the high dose of BDE-47 hindered growth and development; however, thyroid hormone-associated gene expression was downregulated in the brains of tadpoles regardless of dose. These results show that BDE-47 disrupts thyroid hormone signaling at the molecular and whole-organism levels and suggest that gene expression in the brain is a more sensitive endpoint than metamorphosis. Furthermore, the altered gene expression patterns among BDE-47-exposed tadpoles provide insight into the mechanisms of PBDE-induced thyroid disruption and highlight the potential for PBDEs to act as neurodevelopmental toxicants.

Early Life Stage Exposure to BDE-47 Causes Adverse Effects on Reproductive Success and Sexual Differentiation in Fathead Minnows (Pimephales promelas)

2,2',4,4'-Tetrabromodiphenyl ether (BDE-47), a compound manufactured for use as a flame retardant, is a ubiquitous environmental contaminant and suspected endocrine disruptor. Though several studies have explored the reproductive effects of BDE-47 in adult fish, there is a paucity of data regarding the reproductive effects of early life stage exposure. The goal of this study was to assess the reproductive effects of early life stage BDE-47 exposure in fathead minnows (Pimephales promelas). To achieve this, minnows were exposed to either a low (57.68 μg BDE-47/g Artemia) or high (392.59 μg BDE-47/g Artemia) dose of BDE-47 from fertilization to 34 days postfertilization (dpf) via a combination of maternal transfer and dietary exposure. Larvae were then raised on a clean diet until sexual maturity (∼184 dpf) when reproductive function was evaluated using a 21 day breeding study. Fish exposed to BDE-47 had significantly reduced clutch size and fecundity relative to controls. BDE-47 exposed groups also had female-biased sex ratios and exposed males had fewer tubercles. Overall, this study demonstrates that exposure to BDE-47 during early life stages can alter both sexual differentiation and reproductive function.