(A) Photomotor response of zebrafish larvae at 120 hpf. (B) Fluorescent microscopic images of the larvae at 120 hpf, with white arrow indicating fluorescence around the eyes. (C) Histological changes in the brain and retinal tissues of zebrafish larvae at 120 hpf. GCL, ganglion cell layer; INL, inner nuclear layer; IPL, inner plexiform layer; L, lens; ONL, outer nuclear cell; OPL, outer plexiform layer; REP, retinal pigmented epithelium.

(A) Principal coordinate analysis (PCoA) of gene expression profiles. (B) GO terms of DEGs after exposure to THM. (C) Circos diagram illustrating the interaction of traits and enriched KEGG pathways. ACT, amino acid transport; ASP, Adipocytokine signaling pathway; AT, axon terminus; ATSS, anterograde trans-synaptic signaling; BP, biological processes; CB, cell body; CC, cellular components; CR, circadian rhythm; CRoGE, circadian regulation of gene expression; CRtHS, cellular response to hormone stimulus; CST, chemical synaptic transmission; DA, distal axon; DT, dendritic tree; ERA, endopeptidase regulator activity; ErbB, ErbB signaling pathway; GPCRB, G protein-coupled receptor binding; GPM, Glycerophospholipid metabolism; HCAvPMAM, homophilic cell adhesion via plasma membrane adhesion molecules; HSV1I, Herpes simplex virus 1 infection; IF, intermediate filament; IFC, intermediate filament cytoskeleton; LAATTA, L-amino acid transmembrane transporter activity; LATFA, ligand-activated transcription factor activity; LD, Lysine degradation; LTA, lipid transporter activity; MAPK, MAPK signaling pathway; MC, myosin complex; MF, molecular functions; mTOR, mTOR signaling pathway; NCA, nuclear receptor activity; NCB, neuronal cell body; Notch, Notch signaling pathway; NPT, neuron projection terminus; NRoGE, negative regulation of endopeptidase activity; NRoHA, negative regulation of hydrolase activity; NSP, neuropeptide signaling pathway; PCL, peptide cross-linking; PGGGA, protein-glutamine gamma-glutamyltransferase activity; RMSP, hormone-mediated signaling pathway; RoEA, regulation of endopeptidase activity; RoT, regulation of transport; RoHA, regulation of hydrolase activity; RtH, response to hormone; SLM, Sphingolipid metabolism; SP, sensory perception; SS, synaptic signaling; STEIA, serine-type endopeptidase inhibitor activity; SC, somatodendritic compartment; TSS, trans-synaptic signaling.

(A) PCoA of the metabolomics. (B–D) KEGG pathways of the DEGs and DCMs based on the joint analysis of transcriptomics and metabolomics at 10, 100 ng/L, and 1000 ng/L, respectively. The significance level was verified by p < 0.05. The tail in red or blue represents more up-regulated or down-regulated DEGs and DCMs, respectively. βAM, beta-Alanine metabolism; ABCT, ABC transporters; ASaGM, alanine, aspartate, and glutamate metabolism; ASaNSM, amino sugar and nucleotide sugar metabolism; BM, butanoate metabolism; Calcium, calcium signaling pathway; CM, caffeine metabolism; GoG, glycolysis or Gluconeogenesis; NaNM, nicotinate and nicotinamide metabolism; NLRI, neuroactive ligand-receptor interaction; PMM, pyrimidine metabolism; PPP, pentose phosphate pathway; PRM, purine metabolism; TaHM, taurine and hypotaurine metabolism; TCAC, TCA cycle.

Predicted binding modes obtained from the docking simulation analysis of THM with target receptors in zebrafish. Two-dimensional views of the interaction of (A) THM-nAChR, (B) THM-GPCR, (C) THM-ARα, (D) THM-ARβ, (E) THM-GR, (F) THM-TRα, and (G) THM-TRβ. (H) Binding energies of THM with target receptors.

Proposed mechanisms for neurotoxicity induced by THM at environmentally relevant concentrations.