Bioconcentration and developmental neurotoxicity of novelbrominatedflame retardants, hexabromobenzene andpentabromobenzene in zebrafish


Theflame retardants hexabromobenzene (HBB) and pentabromobenzene (PBB) have been extensivelyused and become ubiquitous pollutants in the aquatic environment and biota, but their potential toxiceffects on wildlife remained unknown. In this study, by using zebrafish (Danio rerio) as a model, thebioconcentration and developmental neurotoxicity were investigated. Zebrafish embryos were exposedto HBB and PBB (0, 30, 100 and 300mg/L) from 2 until 144 h post-fertilization (hpf). Chemical analysisshowed bioconcentrations of both chemicals, while HBB is readily metabolized to PBB in zebrafish larvae.Embryonic exposure to both chemicals did not cause developmental toxicity, but induced locomotorbehavioral anomalies in larvae. Molecular docking results indicated that both chemicals could bind tozebrafish acetylcholinesterase (AChE). Furthermore, HBB and PBB significantly inhibited AChE activities,accompanied by increased contents of acetylcholine and decreased choline in larvae. Downregulation ofthe genes associated with central nervous system (CNS) development (e.g.,mbp,a1-tubulin,gfap,shha)aswell as the corresponding proteins (e.g., Mbp,a1-Tubulin) was observed, but gap-43 was upregulated atboth gene and protein levels. Together, our results indicate that both HBB and PBB exhibit developmentalneurotoxicity by affecting various parameters related to CNS development and indications for futuretoxicological research and risk assessment of the novel brominatedflame retardants.


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