Potential physiological effects of pharmaceutical compounds in Atlantic salmon (Salmo salar) implied by transcriptomic analysis
Background, aim, and scope
Pharmaceuticals are emerging pollutants widely used in everyday urban activities which can be detected in surface, ground, and drinking waters. Their presence is derived from consumption of medicines, disposal of expired medications, release of treated and untreated urban effluents, and from the pharmaceutical industry. Their growing use has become an alarming environmental problem which potentially will become dangerous in the future. However, there is still a lack of knowledge about long-term effects in non-target organisms as well as for human health. Toxicity testing has indicated a relatively low acute toxicity to fish species, but no information is available on possible sublethal effects. This study provides data on the physiological pathways involved in the exposure of Atlantic salmon as representative test species to three pharmaceutical compounds found in ground, surface, and drinking waters based on the evaluation of the xenobiotic-induced impairment resulting in the activation and silencing of specific genes.
Materials and methods
Individuals of Atlantic salmon (Salmo salar) parr were exposed during 5 days to environmentally relevant concentrations of three representative pharmaceutical compounds with high consumption rates: the analgesic acetaminophen (54.77 ± 34.67 µg L−1), the anticonvulsant carbamazepine (7.85 ± 0.13 µg L−1), and the beta-blocker atenolol (11.08 ± 7.98 µg L−1). Five immature males were selected for transcriptome analysis in brain tissues by means of a 17k salmon cDNA microarray. For this purpose, mRNA was isolated and reverse-transcribed into cDNA which was labeled with fluorescent dyes and hybridized against a common pool to the arrays. Lists of significantly up- and down-regulated candidate genes were submitted to KEGG (Kyoto Encyclopedia of Genes and Genomes) in order to analyze for induced pathways and to evaluate the usefulness of this method in cases of not completely annotated test organisms.
Exposure during 5 days to environmentally relevant concentrations of the selected pharmaceutical compounds acetaminophen, carbamazepine, and atenolol produced differences in the expression of 659, 700, and 480 candidate genes, respectively. KEGG annotation numbers (KO annotations) were obtained for between 26.57% and 33.33% of these differently expressed genes per treatment in comparison to non-exposure conditions. Pathways that showed to be induced did not always follow previously reported targets or metabolic routes for the employed treatments; however, several other pathways have been found (four or more features) to be significantly induced.
Energy-related pathways have been altered under exposure in all the selected treatments, indicating a possible energy budget leakage due to additional processes resulting from the exposure to environmental contaminants. Observed induction of pathways may indicate additional processes involved in the mode of action of the selected pharmaceuticals which may not have been detected with conventional methods like quantitative PCR in which only suspected features are analyzed punctually for effects. The employment of novel high-throughput screening techniques in combination with global pathway analysis methods, even if the organism is not completely annotated, allows the examination of a much broader range of candidates for potential effects of exposure at the gene level.
The continuously growing number of annotations of representative species relevant for environmental quality testing is facilitating pathway analysis processes for not completely annotated organisms. KEGG has shown to be a useful tool for the analysis of induced pathways from data generated by microarray techniques with the selected pharmaceutical contaminants acetaminophen, carbamazepine, and atenolol, but further studies have to be carried out in order to determine if a similar expression pattern in terms of fold change quantity and pathways is observed after long-term exposure. Together with the information obtained in this study, it will then be possible to evaluate the potential risk that the continuous release of these compounds may have on the environment and ecosystem functioning.
KeywordsAcetaminophen Atenolol Atlantic salmon Carbamazepine cDNA microarray KEGG pathway analysis Pharmaceuticals Sublethal effects Transcriptomics
- Agon P, Goethals P, Van Haver D, Kaufman JM (1991) Permeability of the blood–brain barrier for atenolol studied by positron emission tomography. J Pharm Pharmacol 43(8):597–600Google Scholar
- Ahlborn GJ, Nelson GM, Ward WO, Knapp G, Allen JW, Ouyang M, Roop BC, Chen Y, O'Brien T, Kitchin KT, Delker DA (2008) Dose response evaluation of gene expression profiles in the skin of K6/ODC mice exposed to sodium arsenite. Toxicol Appl Pharmacol 227:400–416Google Scholar
- Barthel A, Schmoll D, Kruger KD, Bahrenberg G, Walther R, Roth RA, Joost HG (2001) Differential regulation of endogenous glucose-6-phosphatase and phosphoenolpyruvate carboxykinase gene expression by the forkhead transcription factor FKHR in H4IIE-hepatoma cells. Biochem Biophys Res Commun 285:897–902CrossRefGoogle Scholar
- Cummings AJ, King ML, Martin BK (1967) A kinetic study of drug elimination: the excretion of paracetamol and its metabolites in man. Br J Pharmacol 29:150–157Google Scholar
- ECETOC Workshop Report No. 11 (2007) Workshop on the application of ‘Omic’ technologies in toxicology and ecotoxicology: case studies and risk assessment 6–7 December 2007, Malaga. European Centre for Ecotoxicology and Toxicology of ChemicalsGoogle Scholar
- Jollow DJ, Mitchell JR, Potter WZ, Davis DC, Gillette JR, Brodie BB (1973) Acetaminophen-induced hepatic necrosis: II Role of covalent binding in vivo. J Pharmacol Exp Ther 187:195–202Google Scholar
- Kanehisa M, Araki M, Goto S, Hattori M, Hirakawa M, Itoh M, Katayama T, Kawashima S, Okuda S, Tokimatsu T, Yamanishi Y (2008) KEGG for linking genomes to life and the environment. Nucleic Acids Res, 36, database issue D480–D484 (doi:10.1093/nar/gkm882).
- Kitamura T, Kitamura Y, Kuroda S, Hino Y, Ando M, Kotani K, Konishi H, Matsuzaki H, Kikkawa U, Ogawa W, Kasuga M (1999) Insulin-induced phosphorylation and activation of cyclic nucleotide phosphodiesterase 3B by the serine-threonine kinase Akt. Mol Cell Biol 19:6286–6296Google Scholar
- OECD Guideline for Testing of Chemicals 203: Fish, Acute Toxicity Test (Updated Guideline, adopted 17th July 1992) and 204 Fish, Prolonged Toxicity Test: 14-Day Study (Original Guideline, adopted 4th April 1984)Google Scholar
- Schmoll D, Walker KS, Alessi DR, Grempler R, Burchell A, Guo S, Walther R, Unterman TG (2000) Regulation of glucose-6-phosphatase gene expression by protein kinase B alpha and the forkhead transcription factor FKHR. Evidence for insulin response unit-dependent effects of insulin on promotor activity. J Biol Chem 275:36324–36333CrossRefGoogle Scholar
- Taggart JB, Bron JE, Martin SAM, Seear PJ, Høyheim B, Talbot R, Carmichael SN, Villeneuve LAN, Sweeney GE, Houlihan DF, Secombes CJ, Tocher DR, Teale AJ (2008) A description of the origins, design and performance of the TRAITS–SGP Atlantic salmon Salmo salar L. cDNA microarray. J Fish Biol 72:2071–2094CrossRefGoogle Scholar