Environmentally relevant concentrations of the flame retardant BDE-209 in sediment cause minimal effects on Zebrafish embryos.
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ABSTRACT: Polychlorinated diphenyl ethers are lipophilic, persistent, and bioaccumulable compounds widely used as flame-retardants. These are chemicals of increasing environmental concern due to their lipophilic, persistent, and bioaccumulable characteristics. The objective of this study was to analyze the potential bioavailability and bioaccumulation of BDE-209 as a source of toxicity. Zebrafish embryos were exposed for 8 days to sediments spiked with an environmentally relevant concentration of BDE-209. We analyzed gene expression changes, thyroid function, and several markers for neurotoxicity. Results of this research highlight the need to consider the capability of BDE-209 to be bioavailable and bioaccumulate, indicating the potential hazardous effects.
Project description:Polychlorinated diphenyl ethers are lipophilic, persistent, and bioaccumulable compounds widely used as flame-retardants. These are chemicals of increasing environmental concern due to their lipophilic, persistent, and bioaccumulable characteristics. The objective of this study was to analyze the potential bioavailability and bioaccumulation of BDE-209 as a source of toxicity. Zebrafish embryos were exposed for 8 days to sediments spiked with an environmentally relevant concentration of BDE-209. We analyzed gene expression changes, thyroid function, and several markers for neurotoxicity. Results of this research highlight the need to consider the capability of BDE-209 to be bioavailable and bioaccumulate, indicating the potential hazardous effects. Total RNA was isolated using RNeasy kits (Qiagen, Valencia, CA, USA). The RNA quality was assessed with an Agilent 2100 Bioanalyzer (Agilent, Wilmington, DE, USA) and quantity was determined using a NanodropM-BM-. ND-1000 spectrophotometer. Total RNA was stored at -80oC until analyzed with oligonucleotide microarrays. Zebrafish 44,000 gene arrays (Agilent Single Color 19161, Platform number GPL6457) were purchased from Agilent (Sta. Clara, CA, USA). The Agilent one-color microarray hybridization protocol (One-Color Microarray-Based Gene Expression Analysis, version 5.7, Agilent Technologies, Palo Alto, CA) was used for microarray hybridizations following the manufacturerM-bM-^@M-^Ys protocol and recommendations. Four controls and four treated samples were analyzed, each sample consisting of a pool of embryos. One ug of total RNA was used for all hybridizations. cDNA synthesis, cRNA labeling, amplification and hybridization were performed following the manufacturerM-bM-^@M-^Ys kits and protocols (Quick Amp Labeling kit; Agilent, Palo Alto, CA). An Axon GenePixM-BM-. 4000B Microarray Scanner (Molecular Devices Inc., Sunnyvale, CA) was used to scan microarray images at 5 M-NM-<m resolution. Data were resolved from microarray images using Agilent Feature Extraction software and analyzed using GeneSpring (Agilent Technologies, Palo Alto, CA).
Project description:Polybrominated diphenyl ethers (PBDEs) are persistent organic chemicals implied as flame re-tardants. Humans are mainly exposed to BDE-47, -99 and -209 congeners by diet. PBDEs are metabolic disruptors with liver as main target organ. To investigate their mode of action at a human relevant concentration, we exposed HepG2 cells to these congeners and their mixture at 1 nM for 72h, analyzing their transcriptomic and proteomic profiles. KEGG pathways and GSEA Hallmarks enrichment analyses evidenced that BDE-47 disrupted the glucose metabolism and Hypoxia pathway; all the congeners and the MIX affected lipid metabolism and signaling Hallmarks regulating metabolism as mTORC1 and PI3K/AKT/MTOR. These results were confirmed by glucose secretion depletion and increased lipid accumulation, especially in BDE-47 and -209 treated cells. These congeners also affected the EGFR/MAPK signaling; further, BDE-47 enriched the Estrogen pathway. Interestingly, BDE-209 and the MIX increased ERα gene expression, whereas all the congeners and the MIX induced ERβ and PPARγ. We also found that PBDEs modulated several lncRNAs and that HNRNAP1 represented a central hub in all the four interaction networks. Overall, despite the low concentration used, the PBDEs investigated affected glucose and lipid metabolism with different underlying modes of action, as highlighted by the integrated omics analysis. These results may support the mechanism-based risk assessment of these compounds in relation to liver metabolism disruption.
Project description:Advanced paternal age at fertilization has been suggested to be a risk factor for neurodevelopmental, psychiatric and other disorders in offspring. One emerging hypothesis suggests that altered offspring phenotype is linked with age-related accumulation of epigenetic changes in the sperm of fathers. Given that paternal age is increasing in the developed world, understanding aging-related epigenetic changes in sperm is needed as well as environmental factors that modify such changes. In this study, we characterize age-dependent changes in sperm DNA methylation profiles between young pubertal (postnatal day (PNDs) 65) and mature (PND120) Wistar rats. We also analyze these changes in rats exposed perinatally to 0.2 mg/kg of ubiquitous environmental xenobiotic 2,2’,4,4’-tetrabromodiphenyl ether (BDE-47). Reduced representation bisulfite sequencing (RRBS) libraries were prepared from caudal epididymal sperm DNA and differentially methylated regions (DMRs; ≥ 10x coverage depth, ≥ 3 CpGs per cluster, ≥ 5% methylation change, q < 0.05) were identified via MethPipe package. We identified 21 and 9 exposure-related DMRs in sperm collected on PND65 and PND120, respectively. Two DMRs overlapped between the two time-points. This is the first study to demonstrate that environmentally-relevant perinatal exposure to PBDE results in long-lasting changes in sperm DNA methylation. In control animals, 5,319 age-dependent DMRs were identified, with 99.3% DMRs hypermethylated in mature animals compared to young pubertal rats. These age-related DMRs were enriched for functional categories essential for embryonic development, such as pattern specification, forebrain and sensory organ development, and the Wnt pathway. In BDE-47 exposed rats, sperm DNA methylation was higher in young pubertal and lower in mature animals when compared to controls, which resulted in a significant attenuation in the number of age-dependent DMRs (N = 189) identified in the exposed group. In conclusion, our results indicate that the natural aging process has profound effects on sperm methylation levels and this effect may be modified by environmental exposures. Moreover, our results further support the role of sperm DNA methylation as a likely mechanism by which advanced paternal age is associated with adverse offspring health and development.
Project description:For the majority of lipophilic compounds adipose tissue is traditionally considered as storage depot and only rarely as a target organ. Meanwhile, abnormalities in adipose tissue physiology induced by chemical exposures may contribute to the current epidemic of obesity and metabolic diseases. Polybrominated diphenyl ethers (PBDEs) is a group of lipophilic flame retardants found in majority of human samples in North America. Their ability to alter physiology of adipose tissue is unknown. We exposed pregnant mice to 0.2 mg/kg body weight/day of BDE-47 perinatally. Transcriptomic changes in gonadal adipose tissue were analyzed in male offspring using RNA-seq approach with subsequent bioinformatic analysis. Genes of coagulation and complement cascade, de novo lipogenesis, and xenobiotic metabolism were altered in expression in response to BDE-47 exposure. The affected molecular network included the following hubs: PPARα, HNF1A and HNF4. These findings suggest that adipose tissue should be considered a target tissue for BDE-47, in addition to its role as a storage depot. This study also builds a background for a targeted search of sensitive phenotypic endpoints of BDE-47 exposure, including lipid profile parameters and coagulation factors in circulation. Additional studies are needed to investigate the role of PBDEs as an obesogen.
Project description:Flame retardants are detected globally in the environment, and pose great risks to human health. The potential effects of these chemicals on the development of nervous system have raise public concerns. In this study, to explore the toxicity profiles of these chemicals in the early developmental stage of human nervous system, we induced neural ectoderm from human embryonic stem cells in the presence of individual or mixture of BDE-47, BDE-209, TBBPA, TBBPS, TCBPA. By analyzing the whole transcriptional changes in the samples treated with 1 μΜ of each chemical, we identified a set of neural development relative biological processes that response to these chemicals. Genes involved in the GO terms relative to neural development were further confirmed by qRT-PCR assay, with samples treated with various concentrations (10 nM, 100 nM, 1 μΜ, 5 μΜ) of these chemicals. We found out that axon guidance and synaptogenesis may be the major target of these chemicals. In addition, these flame retardants may dysregulate the WNT and AHR signaling pathways. BDE-209 showed similar toxicity with BDE-47, whereas TBBPS and TCBPA may not be safe alternatives to TBBPA.
Project description:Polybrominated diphenyl ether BDE-47 (2,2',4,4'-tetrabromodiphenyl ether) is a thyroid hormone disruptor in mice; hepatic induction of various metabolic enzymes and transporters has been suggested as the mechanism for this disruption. Utilizing Car (-/-) and Pxr (-/-) mice as well as human primary hepatocytes, here we have demonstrated that BDE-47 activated both mouse and human nuclear receptor constitutive activated/androstane receptor (CAR). In mouse livers, CAR, not PXR, was responsible for Cyp2b10 mRNA induction by BDE-47. In human primary hepatocytes, BDE-47 was able to induce translocation of YFP-tagged human CAR from the cytoplasm to the nucleus andCYP2B6 and CYP3A4 mRNAs expressions. BDE-47 activated human CAR in a manner akin to the human CAR ligand CITCO (6-(4-Chlorophenyl)imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime) in luciferase-reporter assays using Huh-7 cells. In contrast, mouse CAR was not potently activated by BDE-47 in the same reporter assays. Furthermore, human pregnane X receptor (PXR) was effectively activated by BDE-47 while mouse PXR was weakly activated in luciferase-reporter assays. Our results indicate that BDE-47 induces CYP genes through activation of human CAR in addition to the previously identified pathway through human PXR.
Project description:Transcriptomic analysis of HepG2 cells treated with BDE-47, BDE-99, BDE-209 and their ternary mixture at 1nM as a dietary relevant concentration
Project description:Recent studies suggest that exposure to endocrine-disrupting compounds (EDCs) may play a role in the development of obesity. EDCs such as the flame retardant 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) have been shown to enhance adipocyte differentiation in the murine 3T3-L1 model. The mechanisms by which EDCs direct preadipocytes to form adipocytes are poorly understood. Here, we examined transcriptional and epigenetic mechanisms underlying the induction of in vitro adipocyte differentiation by BDE-47. Quantitative high content microscopy revealed concentration-dependent enhanced adipocyte differentiation following exposure to BDE-47 or the antidiabetic drug troglitazone (TROG). BDE-47 modestly activated the key adipogenic transcription factor peroxisome proliferator-activated receptor gamma (PPAR?) in COS7 cells, transiently transfected with a GAL4 reporter construct. Increased gene expression was observed for Ppar?2, leptin (Lep), and glucose-6-phophatase catalytic subunit (G6pc) in differentiated 3T3-L1 cells after BDE-47 exposure compared to TROG. Methylation-sensitive high resolution melting (MS-HRM) revealed significant demethylation of three CpG sites in the Ppar?2 promoter after exposure to both BDE-47 and TROG in differentiated 3T3-L1 cells. This study shows the potential of BDE-47 to induce adipocyte differentiation through various mechanisms that include Ppar?2 gene induction and promoter demethylation accompanied by activation of PPAR?, and possible disruption of glucose homeostasis and IGF1 signaling.