Dataset Information

Abiotic Methylation of Tetrabromobisphenol A (TBBPA) with the Occurrence of Methyl Iodide in Aqueous Environments.

ABSTRACT: Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant in the world. Its biotic methylation products, tetrabromobisphenol A mono- and dimethyl ether (TBBPA MME and TBBPA DME, respectively), are frequently detected in the environment, but the importance of abiotic methylation reactions of TBBPA in the environment is not known. In this study, the methylation of TBBPA mediated by methyl iodide (CH3I), a ubiquitous compound in aqueous environments, was investigated in simulated waters in the laboratory. It was found that abiotic methylation occurred under both light and dark conditions and was strongly affected by the pH, temperature, and natural organic matter concentration of the water. Abiotic methylation was further verified in natural river water, and the yield of TBBPA MME mediated abiotically by CH3I was much greater than that of biotic methylation. According to our calculations and by comparison of the activation energies (E a) for the abiotic methylation of TBBPA and the other four typical phenolic contaminants and/or metabolites (bisphenol A, triclosan, 5-OH-BDE-47, and 4'-OH-CB-61) mediated by CH3I, those phenolic compounds all show great methylation potentials. The results indicate a new abiotic pathway for generating TBBPA MME and TBBPA DME from TBBPA, and they also confirm the potentials for abiotic methylation of other phenolic contaminants in aqueous environments.

SUBMITTER: Hou X

PROVIDER: S-EPMC7643859 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Abiotic Methylation of Tetrabromobisphenol A (TBBPA) with the Occurrence of Methyl Iodide in Aqueous Environments.

Hou Xingwang X Kong Wenqian W Wang Xiaoyun X Liu Yanwei Y Chen Weifang W Liu Jiyan J Schnoor Jerald L JL Jiang Guibin G

Environmental science & technology letters 20190805 9

Tetrabromobisphenol A (TBBPA) is the most widely used brominated flame retardant in the world. Its biotic methylation products, tetrabromobisphenol A mono- and dimethyl ether (TBBPA MME and TBBPA DME, respectively), are frequently detected in the environment, but the importance of abiotic methylation reactions of TBBPA in the environment is not known. In this study, the methylation of TBBPA mediated by methyl iodide (CH<sub>3</sub>I), a ubiquitous compound in aqueous environments, was investigat ...[more]

PMID: 33163543

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Project description:3,3’,5.5’-Tetrabromobisphenol A (TBBPA) is a widely used brominated flame-retardant utilized in the production of electronic devices and plastic paints. The objective of this study is to use zebrafish as a model and determine the effects of TBBPA exposure on early embryogenesis. We initiated TBBPA exposures (0, 10, 20 and 40μM) at 0.75 h post fertilization (hpf) and monitored early developmental events such as cleavage, blastula and epiboly that encompass maternal-to-zygotic transition (MZT) and zygotic genome activation (ZGA). Our data revealed that TBBPA exposures induced onset of developmental delays by 3 hpf (blastula). By 5.5 hpf (epiboly), TBBPA-exposed (10-20 μM) embryos showed concentration-dependent developmental lag by up to 3 stages or 100% mortality at 40 μM. Interestingly, while continued 0.75- 48 hpf TBBPA exposures (10 μM) led to severely deformed embryos, replacing exposure solution with chemical-free media at 6 hpf mitigated this effect, with 100% normal embryos at 48 hpf. To examine the genetic basis of TBBPA-induced delays, we conducted mRNA-sequencing on embryos exposed to 0 or 40 μM TBBPA from 0.75 hpf to 2, 3.5 or 4.5 hpf. Read count data showed that while TBBPA exposures had no overall impacts on maternal or maternal-zygotic genes, collective read counts for zygotically activated genes were lower in TBBPA treatment at 4.5 hpf compared to time-matched controls, suggesting that TBBPA delays ZGA. Gene ontology assessments for both time- and stage-matched differentially expressed genes revealed TBBPA-induced inhibition of chromatin assembly- a process regulated by histone modifications. Since acetylation is the primary histone modification system operant during early ZGA, we hypothesized that TBBPA inhibits histone acetylation, resulting in lack of open chromatin within promoters of zygotic genes and delaying ZGA. Therefore, we co-exposed embryos to 20 μM TBBPA and 100 μM N-(4-Chloro-3-(trifluoromethyl)phenyl)-2-ethoxybenzamide (CTB) -a histone acetyltransferase activator that promotes histone acetylation- and showed that TBBPA-CTB co-exposures from 0.75- 3 hpf significantly reversed TBBPA-only developmental delays, suggesting that TBBPA-induced phenotypes are indeed driven by repression of histone acetylation. Collectively, our work demonstrates that TBBPA disrupts ZGA and early developmental morphology, potentially by inhibiting histone acetylation. Future studies will focus on mechanisms of TBBPA-induced chromatin modifications.

Dataset Information

Abiotic Methylation of Tetrabromobisphenol A (TBBPA) with the Occurrence of Methyl Iodide in Aqueous Environments.

Publications

Abiotic Methylation of Tetrabromobisphenol A (TBBPA) with the Occurrence of Methyl Iodide in Aqueous Environments.

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