title: Acute exposure to synthetic pyrethroids causes bioconcentration and disruption of the hypothalamus-pituitary-thyroid axis in zebrafish embryos.
abstract: Synthetic pyrethroids (SPs) have the potential to disrupt the thyroid endocrine system in mammals; however, little is known of the effects of SPs and underlying mechanisms in fish. In the current study, embryonic zebrafish were exposed to various concentrations (1, 3 and 10 μg/L) of bifenthrin (BF) or λ-cyhalothrin (λ-CH) until 72 h post fertilization, and body condition, bioaccumulation, thyroid hormone levels and transcription of related genes along the hypothalamus-pituitary-thyroid (HPT) axis examined. Body weight was significantly decreased in the λ-CH exposure groups, but not the BF exposure groups. BF and λ-CH markedly accumulated in the larvae, with concentrations ranging from 90.7 to 596.8 ng/g. In both exposure groups, alterations were observed in thyroxine (T4) and triiodothyronine (T3) levels. In addition, the majority of the HPT axis-related genes examined, including CRH, TSHβ, TTR, UGT1ab, Pax8, Dio2 and TRα, were significantly upregulated in the presence of BF. Compared to BF, λ-CH induced different transcriptional regulation patterns of the tested genes, in particular, significant stimulation of TTR, Pax8, Dio2 and TRα levels along with concomitant downregulation of Dio1. Molecular docking analyses revealed that at the atomic level, BF binds to thyroid hormone receptor (TRα) protein more potently than λ-CH, consequently affecting HPT axis signal transduction. In vitro and in silico experiments disclosed that during the early stages of zebrafish development, BF and λ-CH have the potential to disrupt thyroid endocrine system.
authors.affiliation: Research Institute of Poyang Lake, Jiangxi Academy of Sciences, Nanchang 330029, China; Institute of Environmental Science, College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032, China.
authors.forename: Wenqing
authors.initials: W
authors.lastname: Tu
authors.affiliation: Institute of Environmental Science, College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032, China. Electronic address: chaoxu@zjut.edu.cn.
authors.forename: Chao
authors.initials: C
authors.lastname: Xu
authors.affiliation: Institute of Environmental Science, College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Lu
authors.affiliation: Institute of Environmental Science, College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032, China.
authors.forename: Chunmian
authors.initials: C
authors.lastname: Lin
authors.affiliation: Research Institute of Poyang Lake, Jiangxi Academy of Sciences, Nanchang 330029, China.
authors.forename: Yongming
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Institute of Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China.
authors.forename: Weiping
authors.initials: W
authors.lastname: Liu
mesh_terms: D000818:Animals; D004625:Embryo, Nonmammalian / Q000187:drug effects*; D052244:Endocrine Disruptors / Q000633:toxicity*; D004703:Endocrine System / Q000187:drug effects*; D011722:Pyrethrins / Q000633:toxicity*; D023382:Toxicity Tests, Acute; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015027:Zebrafish
chemical_list: D052244:Endocrine Disruptors; D011722:Pyrethrins; D014874:Water Pollutants, Chemical
keywords: Bioconcentration; HTP axis; Pyrethroid insecticides; Zebrafish embryos