Organophosphate esters cause thyroid dysfunction via multiple signaling pathways in zebrafish brain

Zhenfei Yan; Chenglian Feng; Xiaowei Jin; Fangkun Wang; Cong Liu; Na Li; Yu Qiao; Yingchen Bai; Fengchang Wu; John P Giesy

doi:10.1016/j.ese.2022.100198

Organophosphate esters cause thyroid dysfunction via multiple signaling pathways in zebrafish brain

Environ Sci Ecotechnol. 2022 Jun 6:12:100198. doi: 10.1016/j.ese.2022.100198. eCollection 2022 Oct.

Authors

Zhenfei Yan^{1

2}, Chenglian Feng¹, Xiaowei Jin³, Fangkun Wang⁴, Cong Liu⁴, Na Li⁵, Yu Qiao¹, Yingchen Bai¹, Fengchang Wu^{1

2}, John P Giesy^{6

7

8}

Affiliations

¹ State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
² College of Environment, Hohai University, Nanjing, 210098, China.
³ China National Environmental Monitoring Centre, Beijing, 100012, China.
⁴ Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Shandong Agricultural University, Taian, 271018, China.
⁵ Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
⁶ Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, SK, Canada.
⁷ Toxicology Centre, University of Saskatchewan, Saskatoon, SK, Canada.
⁸ Department of Environmental Sciences, Baylor University, Waco, TX, USA.

Abstract

Organophosphate esters (OPEs) are widespread in various environmental media, and can disrupt thyroid endocrine signaling pathways. Mechanisms by which OPEs disrupt thyroid hormone (TH) signal transduction are not fully understood. Here, we present in vivo-in vitro-in silico evidence establishing OPEs as environmental THs competitively entering the brain to inhibit growth of zebrafish via multiple signaling pathways. OPEs can bind to transthyretin (TTR) and thyroxine-binding globulin, thereby affecting the transport of TH in the blood, and to the brain by TTR through the blood-brain barrier. When GH3 cells were exposed to OPEs, cell proliferation was significantly inhibited given that OPEs are competitive inhibitors of TH. Cresyl diphenyl phosphate was shown to be an effective antagonist of TH. Chronic exposure to OPEs significantly inhibited the growth of zebrafish by interfering with thyroperoxidase and thyroglobulin to inhibit TH synthesis. Based on comparisons of modulations of gene expression with the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes databases, signaling pathways related to thyroid endocrine functions, such as receptor-ligand binding and regulation of hormone levels, were identified as being affected by exposure to OPEs. Effects were also associated with the biosynthesis and metabolism of lipids, and neuroactive ligand-receptor interactions. These findings provide a comprehensive understanding of the mechanisms by which OPEs disrupt thyroid pathways in zebrafish.

Keywords: AChE, acetylcholinesterase; ANOVA, analysis of variance; BCF, bioconcentration factor; BFR, brominated flame retardant; CD-FBS, charcoal-dextran-treated fetal bovine serum; CDP, cresyl diphenyl phosphate; Competitive inhibition assay; DEG, differentially expressed gene; DKA, β-diketone antibiotic; DMSO, dimethyl sulfoxide; EAS, estrogen; FBS, fetal bovine serum; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GO, Gene Ontology; HPLC-MS/MS, high-performance liquid chromatograph interfaced with a mass spectrometer; HPT, hypothalamic–pituitary–thyroid; HS, horse serum; KEGG, Kyoto Encyclopedia of Genes and Genomes; MAPK, mitogen-activated protein kinase; Molecular docking simulation; NIS, Na+/I− symporter; OD490, optical density; OPE, organophosphate ester; OPFR, organophosphate flame retardant; Organophosphate ester; P/S, penicillin–streptomycin; PBDE, polybrominated diphenyl ether; PBS, phosphate-buffered saline; RIC20/50, concentration inhibiting 20%/50%; T4, thyroxin; TBG, thyroxine-binding globulin; TCIPP, tris(2-chloroisopropyl) phosphate; TDCIPP, tris(1,3-dichloro-2-propyl) phosphate (TDCIPP); TDCIPP-d15, tris(1,3-dichloroisopropyl) phosphate-D15; TG, thyroglobulin; TH, thyroid hormone; THR, thyroid hormone receptor; TIPP, tris(isopropyl) phosphate; TPHP, triphenyl phosphate; TPO, thyroperoxidase; TRβ, thyroid hormone receptor β; TTR, transthyretin; Thyroid endocrine function; Transcriptome sequencing; androgen, and steroidogenesis; cga, glycoprotein hormone; qRT-PCR, quantitative real-time PCR; tshβa, thyroid-stimulating hormone beta subunit a.