title: Transcriptional changes in Atlantic salmon (Salmo salar) after embryonic exposure to road salt.
abstract: Road salt is extensively used as a deicing chemical in road maintenance during winter and has in certain areas of the world led to density stratifications in lakes and ponds, and adversely impacted aquatic organisms in the recipients of the road run-off. Aquatic vertebrates such as fish have been particularly sensitive during fertilisation, as the fertilisation of eggs involves rapid uptake of the surrounding water, reduction in egg swelling and in ovo exposure to high road salt concentrations. The present study aimed to identify the persistent molecular changes occurring in Atlantic salmon (Salmo salar) eggs after 24h exposure to high concentrations (5000 mg/L) of road salt at fertilisation. The global transcriptional changes were monitored by a 60k salmonid microarray at the eyed egg stage (cleavage stage, 255 degree days after fertilisation) and identified a high number of transcripts being differentially regulated. Functional enrichment, pathway and gene-gene interaction analysis identified that the differentially expressed genes (DEGs) were mainly associated with toxiciologically relevant processes involved in osmoregulation, ionregulation, oxidative stress, metabolism (energy turnover), renal function and developmental in the embryos. Quantitative rtPCR analysis of selected biomarkers, identified by global transcriptomics, were monitored in the eggs for an extended range of road salt concentrations (0, 50, 100, 500 and 5000 mg/L) and revealed a positive concentration-dependent increase in cypa14, a gene involved in lipid turnover and renal function, and nav1, a gene involved in neuraxonal development. Biomarkers for osmoregulatory responses such as atp1a2, the gene encoding the main sodium/potassium ATP-fueled transporter for chloride ions, and txdc9, a gene involved in regulation of cell redox homeostasis (oxidative stress), displayed apparent concentration-dependency with exposure, although large variance in the control group precluded robust statistical discrimination between the groups. A No Transcriptional Effect Level (NOTEL) of 50mg/L road salt was found to be several orders of magnitude lower than the adverse effects documented in developing fish embryos elsewhere, albeit at concentrations realistic in lotic systems receiving run-off from road salt. It remains to be determined whether these transcriptional changes may cause adverse effects in fish at ecologically relevant exposure concentrations of road salt.
authors.affiliation: Norwegian Institute for Water Research (NIVA), Gaustadalléen 21, N-0349 Oslo, Norway; Norwegian University of Life Sciences (NMBU), Faculty of Environmental Science & Technology, Dept. for Environmental Sciences, P.O. Box 5003, N-1432 Ås, Norway; Norwegian University of Life Sciences (NMBU), Centre for Environmental Radioactivity (CERAD CoE), Isotope Laboratory, P.O. Box 5003, N-1432 Ås, Norway. Electronic address: ket@niva.no.
authors.forename: Knut Erik
authors.initials: KE
authors.lastname: Tollefsen
authors.affiliation: Norwegian Institute for Water Research (NIVA), Gaustadalléen 21, N-0349 Oslo, Norway; Norwegian University of Life Sciences (NMBU), Centre for Environmental Radioactivity (CERAD CoE), Isotope Laboratory, P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: You
authors.initials: Y
authors.lastname: Song
authors.affiliation: Norwegian University of Life Sciences (NMBU), Faculty of Environmental Science & Technology, Dept. for Environmental Sciences, P.O. Box 5003, N-1432 Ås, Norway; Norwegian University of Life Sciences (NMBU), Centre for Environmental Radioactivity (CERAD CoE), Isotope Laboratory, P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: Merethe
authors.initials: M
authors.lastname: Kleiven
authors.affiliation: Norwegian University of Life Sciences (NMBU), Faculty of Environmental Science & Technology, Dept. for Environmental Sciences, P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: Urma
authors.initials: U
authors.lastname: Mahrosh
authors.affiliation: Norwegian University of Life Sciences (NMBU), Faculty of Environmental Science & Technology, Dept. for Environmental Sciences, P.O. Box 5003, N-1432 Ås, Norway; Norwegian Public Roads Administration, Environmental Assessment Section, P.O. Box 8142 Dep, N-0033 Oslo, Norway.
authors.forename: Sondre
authors.initials: S
authors.lastname: Meland
authors.affiliation: Norwegian University of Life Sciences (NMBU), Faculty of Environmental Science & Technology, Dept. for Environmental Sciences, P.O. Box 5003, N-1432 Ås, Norway; Norwegian University of Life Sciences (NMBU), Centre for Environmental Radioactivity (CERAD CoE), Isotope Laboratory, P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: Bjørn Olav
authors.initials: BO
authors.lastname: Rosseland
authors.affiliation: Norwegian University of Life Sciences (NMBU), Faculty of Environmental Science & Technology, Dept. for Environmental Sciences, P.O. Box 5003, N-1432 Ås, Norway; Norwegian University of Life Sciences (NMBU), Centre for Environmental Radioactivity (CERAD CoE), Isotope Laboratory, P.O. Box 5003, N-1432 Ås, Norway.
authors.forename: Hans-Christian
authors.initials: HC
authors.lastname: Teien
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D047108:Embryonic Development / Q000187:drug effects* / Q000235:genetics; D004734:Energy Metabolism / Q000187:drug effects / Q000235:genetics; D005306:Fertilization; D020869:Gene Expression Profiling; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics; D020317:Salmo salar / Q000196:embryology* / Q000378:metabolism; D012965:Sodium Chloride / Q000633:toxicity*; D059467:Transcriptome / Q000187:drug effects*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D015415:Biomarkers; D014874:Water Pollutants, Chemical; D012965:Sodium Chloride
keywords: Atlantic salmon; Development; Ionregulation; Metabolism; Osmoregulation; Oxidative stress; Renal function; Road salt; Transcriptional effects