title: Alterations in gene expression levels provide early indicators of chemical stress during Xenopus laevis embryo development: A case study with perfluorooctane sulfonate (PFOS).
abstract: In the present study, Xenopus laevis embryos were exposed to a range of perfluorooctane sulfonate (PFOS) concentrations (0, 0.5, 6, 12, 24, 48 and 96mg/L) for 96h in laboratorial conditions to establish toxicity along with possible gene expression changes. Mortality and deformities were monitored daily and head-tail length was measured at the end of the assay as an indicator of growth. At 24 and 96h post-exposure (hpe), the mRNA expression levels of the genetic markers involved in general stress responses (hsp70, hsp47, crh-a and ucn1), oxidative stress (cat.2 and sod), lipid metabolism (ppard) and apoptosis (tp53 and bax) were analyzed by RT-qPCR. Malformations were significantly higher in the embryos exposed to the highest PFOS concentration (41.8% to 56.4%) compared to controls (5.5%) at 48, 72 and 96hpe. Growth inhibition was observed in the embryos exposed to PFOS concentrations≥48mg/L. At 24 hpe, a statistically significant up-regulation of genes hsp70, hsp47, ppard, tp53 and bax in relation to controls was found. Similar responses were found for genes hsp70, hsp47, crh-a, ucn1, sod and ppard at 96 hpe. Alterations in the mRNA expression levels indicated both a stress response to PFOS exposure during X. laevis embryo development, and alterations in the regulation of oxidative stress, apoptosis, and differentiation. These molecular alterations were detected at an earlier exposure time or at lower concentrations than those producing developmental toxicity. Therefore, these sensitive warning signals could be used together with other biomarkers to supplement alternative methods (i.e. the frog embryo test) for developmental toxicity safety evaluations, and as tools in amphibian risk assessments for PFOS and its potential substitutes.
authors.affiliation: INIA-National Institute for Agricultural and Food Research and Technology, Laboratory for Ecotoxicology, Department of Environment, A-6, Km. 7.5, E-28040 Madrid, Spain. Electronic address: san-segundo.laura@inia.es.
authors.forename: Laura
authors.initials: L
authors.lastname: San-Segundo
authors.affiliation: CIIMAR/CIMAR-Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal. Electronic address: lguimaraes@ciimar.up.pt.
authors.forename: Laura
authors.initials: L
authors.lastname: Guimarães
authors.affiliation: INIA-National Institute for Agricultural and Food Research and Technology, Laboratory for Ecotoxicology, Department of Environment, A-6, Km. 7.5, E-28040 Madrid, Spain. Electronic address: torija@inia.es.
authors.forename: Carlos
authors.initials: C
authors.lastname: Fernández Torija
authors.affiliation: INIA-National Institute for Agricultural and Food Research and Technology, Laboratory for Ecotoxicology, Department of Environment, A-6, Km. 7.5, E-28040 Madrid, Spain. Electronic address: embeltran@inia.es.
authors.forename: Eulalia M
authors.initials: EM
authors.lastname: Beltrán
authors.affiliation: CIIMAR/CIMAR-Interdisciplinary Centre of Marine and Environmental Research, University of Porto, Rua dos Bragas 289, 4050-123 Porto, Portugal; ICBAS-Institute of Biomedical Sciences of Abel Salazar, University of Porto, Department of Populations Study, Laboratory of Ecotoxicology, Rua de Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal. Electronic address: lguilher@icbas.up.pt.
authors.forename: Lúcia
authors.initials: L
authors.lastname: Guilhermino
authors.affiliation: INIA-National Institute for Agricultural and Food Research and Technology, Laboratory for Ecotoxicology, Department of Environment, A-6, Km. 7.5, E-28040 Madrid, Spain. Electronic address: pablos@inia.es.
authors.forename: María Victoria
authors.initials: MV
authors.lastname: Pablos
mesh_terms: D017738:Alkanesulfonic Acids / Q000633:toxicity*; D000818:Animals; D047108:Embryonic Development / Q000187:drug effects*; D004785:Environmental Pollutants / Q000633:toxicity*; D005466:Fluorocarbons / Q000633:toxicity*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects*; D050356:Lipid Metabolism / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects*; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D015854:Up-Regulation; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics
chemical_list: D017738:Alkanesulfonic Acids; D004785:Environmental Pollutants; D005466:Fluorocarbons; D012333:RNA, Messenger; C076994:perfluorooctane sulfonic acid
keywords: Embryotoxicity; Gene expression; Perfluorooctane sulfonate; Stress response genes; Xenopus laevis