Molecular mechanisms of selenium-Induced spinal deformities in fish.
Selenium toxicity to oviparous vertebrates is often attributed to selenomethionine (SeMet), which can biomagnify through maternal transfer. Although oxidative stress is implicated in SeMet toxicity, knowledge gaps remain in how SeMet causes characteristic spinal deformities. In the present study, we use the Japanese medaka (Oryzias latipes) model to investigate the role of oxidative stress, cell death, and the unfolded protein response (UPR) on skeletal gene expression and SeMet toxicity, linking localization of cellular effects to observed abnormalities. Medaka embryos were treated with 2.5μM or 5μM SeMet for 24h at stage 25 (48h post fertilization). Post treatment, embryos were separated into normal, deformed (mild, moderate or severe), or dead categories. Dichlorofluorescein staining demonstrated oxidative stress in tails of embryos with observable spinal malformations. Furthermore, acridine orange staining for apoptosis identified significantly more dead cells in tails of treated embryos. Gene expression studies for the UPR suggest a potential role for CHOP (c/ebp homologous protein) induced apoptosis deformed embryos after 5μM SeMet, accompanied by a significant decrease in PDIA4 (protein disulfide isomerase A4) and no change in Dnajb9 (ER DNA J Domain-Containing Protein 4). This expression was distinct from the UPR induced by well-studied ER stress inducer, tunicamycin, which robustly activated CHOP, PDIA4 and Dnajb9. Finally, SeMet treatment significantly decreased transcripts of cartilage development, Sox9 (SRY box 9), while increasing Runx2 in deformed embryos, without altering Twist or Collagen 2a1. Results suggest that oxidative stress, the UPR and cell death play key roles in SeMet induced deformities and altered skeletal development factors.
Environmental Toxicology Program and Department of Environmental Sciences, University of California-Riverside, Riverside, CA, United States. Electronic address: akups001@ucr.edu.
Allison
A
Kupsco
Environmental Toxicology Program and Department of Environmental Sciences, University of California-Riverside, Riverside, CA, United States.
Daniel
D
Schlenk
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001842:Bone and Bones / Q000002:abnormalities / Q000187:drug effects; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000187:drug effects / Q000502:physiology; D005260:Female; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D009990:Oryzias / Q000254:growth & development / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D019704:Protein Disulfide-Isomerases / Q000235:genetics / Q000378:metabolism; D012643:Selenium / Q000633:toxicity*; D012645:Selenomethionine / Q000378:metabolism; D056811:Unfolded Protein Response / Q000187:drug effects; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D050659:Core Binding Factor Alpha 1 Subunit; D029941:Fish Proteins; D018832:Molecular Chaperones; D014874:Water Pollutants, Chemical; D012645:Selenomethionine; D019704:Protein Disulfide-Isomerases; D012643:Selenium
Apoptosis; Japanese medaka; Oxidative stress; Selenomethionine; Skeletogenesis; Unfolded protein response