Exposure to tributyltin induces endoplasmic reticulum stress and the unfolded protein response in zebrafish.
Tributyltin (TBT) is a major marine contaminant and causes endocrine disruption, hepatotoxicity, immunotoxicity, and neurotoxicity. However, the molecular mechanisms underlying the toxicity of TBT have not been fully elucidated. We examined whether exposure to TBT induces the endoplasmic reticulum (ER) stress response in zebrafish, a model organism. Zebrafish-derived BRF41 fibroblast cells were exposed to 0.5 or 1 μM TBT for 0.5-16 h and subsequently lysed and immunoblotted to detect ER stress-related proteins. Zebrafish embryos, grown until 32 h post fertilization (hpf), were exposed to 1 μM TBT for 16 h and used in whole mount in situ hybridization and immunohistochemistry to visualize the expression of ER chaperones and an ER stress-related apoptosis factor. Exposure of the BRF41 cells to TBT caused phosphorylation of the zebrafish homolog of protein kinase RNA-activated-like ER kinase (PERK), eukaryotic translation initiation factor 2 alpha (eIF2α), and inositol-requiring enzyme 1 (IRE1), characteristic splicing of X-box binding protein 1 (XBP1) mRNA, and enhanced expression of activating transcription factor 4 (ATF4) protein. In TBT-exposed zebrafish embryos, ectopic expression of the gene encoding zebrafish homolog of the 78 kDa glucose-regulating protein (GRP78) and gene encoding CCAAT/enhancer-binding protein homologous protein (CHOP) was detected in the precursors of the neuromast, which is a sensory organ for detecting water flow and vibration. Our in vitro and in vivo studies revealed that exposure of zebrafish to TBT induces the ER stress response via activation of both the PERK-eIF2α and IRE1-XBP1 pathways of the unfolded protein response (UPR) in an organ-specific manner.
Department of Hygiene and Public Health I, School of Medicine, Tokyo Women's Medical University, 8-1 Kawadacho, Shinjuku, Tokyo 162-8666, Japan. Electronic address: komoike@research.twmu.ac.jp.
Yuta
Y
Komoike
Masato
M
Matsuoka
D000818:Animals; D002460:Cell Line; D004625:Embryo, Nonmammalian; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D005347:Fibroblasts / Q000187:drug effects; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D014220:Trialkyltin Compounds / Q000633:toxicity*; D056811:Unfolded Protein Response / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity*; D015027:Zebrafish / Q000502:physiology*; D029961:Zebrafish Proteins / Q000235:genetics
D014220:Trialkyltin Compounds; D014874:Water Pollutants, Chemical; D029961:Zebrafish Proteins; C011559:tributyltin
4,6-diamidino-2-phenylindole; ATF4; DAPI; DIG; DMSO; ER; Endoplasmic reticulum (ER) stress; FBS; IRE1; MAB; PBS; PCR; PERK; RT; SERCA; TBS; TBT; Tg; Tm; Tributyltin (TBT); Tris buffered saline; UPR; Unfolded protein response (UPR); X-box binding protein 1.; XBP1; Zebrafish; activating transcription factor 4; digoxygenin; dimethyl sulfoxide; eIF2α; endoplasmic reticulum; eukaryotic translation initiation factor 2 alpha; fetal bovine serum; hours post fertilization; hpf; inositol-requiring enzyme 1; maleic acid buffer; phosphate-buffered saline; polymerase chain reaction; protein kinase RNA-activated-like ER kinase; reverse transcription; sarcoplasmic–endoplasmic reticulum Ca(2+)-ATPase; thapsigargin; tributyltin; tunicamycin; unfolded protein response