Toxicological effect of single contaminants and contaminant mixtures associated with plant ingredients in novel salmon feeds

Abstract

Increasing use of plant feed ingredients may introduce contaminants not previously associated with farming of salmonids, such as pesticides and PAHs from environmental sources or from thermal processing of oil seeds. To screen for interaction effects of contaminants newly introduced in salmon feeds, Atlantic salmon primary hepatocytes were used. The xCELLigence cytotoxicity system was used to select optimal dosages of the PAHs benzo(a)pyrene and phenanthrene, the pesticides chlorpyrifos and endosulfan, and combinations of these. NMR and MS metabolic profiling and microarray transcriptomic profiling was used to identify novel biomarkers. Lipidomic and transcriptomic profiling suggested perturbation of lipid metabolism, as well as endocrine disruption. The pesticides gave the strongest responses, despite having less effect on cell viability than the PAHs. Only weak molecular responses were detected in PAH-exposed hepatocytes. Chlorpyrifos suppressed the synthesis of unsaturated fatty acids. Endosulfan affected steroid hormone synthesis, while benzo(a)pyrene disturbed vitamin D3 metabolism. The primary mixture effect was additive, although at high concentrations the pesticides acted in a synergistic fashion to decrease cell viability and down-regulate CYP3A and FABP4 transcription. This work highlights the usefulness of 'omics techniques and multivariate data analysis to investigate interactions within mixtures of contaminants with different modes of action.

Modifying Effects of Vitamin E on Chlorpyrifos Toxicity in Atlantic Salmon

“…Freshly isolated primary hepatocytes were used as a model, and cells were either kept as control or treated with 100 μM alpha tocopherol, 100 μM chlorpyrifos or a combination of vitamin E and chlorpyrifos for 48 hours. Previous experiments have shown the chosen chlorpyrifos concentration to be non-cytotoxic to Atlantic salmon hepatocytes, but still high enough to induce marked transcriptional responses [22]. Similar experiments have been conducted with vitamin E, providing the rationale for using the selected concentration of alpha tocopherol in the current study (unpublished data).…”

“…Furthermore, decreased levels of these metabolites may be indicative of conversion to lipid peroxidation products such as 13-HODE and 9-HODE that can be indicative of increased oxidative stress and are peroxisome proliferator-activated receptor (PPAR) ligands associated with inflammatory hyperalgesia. 13-HODE and 9-HODE are oxidative metabolites of the essential fatty acid linoleic acid [35] and these were the only lipid metabolism biochemicals that showed a significant interaction effect for chlorpyrifos and vitamin E. In a previous study in which Atlantic salmon hepatocytes were exposed to chlorpyrifos [22], several putatively annotated eicosanoids in different lipid metabolism pathways were affected by the exposure. We were however not able to reproduce the effect on these metabolites in the current experiment, although the suggested overall effect on lipid metabolism was the same.…”

Comprehensive overview of feed‐to‐fillet transfer of new and traditional contaminants in Atlantic salmon and gilthead sea bream fed plant‐based diets

“…The current stagnation of fish meal and fish oil production from wild fisheries limits further growth of aquaculture unless effective alternative ingredients are found (Tacon & Metian, 2015). Indeed, important progress has been made in this way and the use of plant products has been a common practice for years in salmonids and marine fish to reduce the reliance of European aquaculture on marine fishery resources (Bell & Waagbø, 2008;Benedito-Palos, Saera-Vila, Calduch-Giner, Kaushik, & Pérez-Sánchez, 2007;Benedito-Palos et al, 2008;Izquierdo et al, 2003;Jennings et al, 2016;Nasopoulou & Zabetakis, 2012;Sitjà-Bobadilla et al, 2005;Søfteland et al, 2014;Torstensen et al, 2008;Waagbø et al, 2013). Hence, in 1990, 90% of the feed ingredients used for farming the Norwegian salmon were of marine origin whereas marine ingredients constituted only around 30% of total in 2013 (Ytrestoyl, Aas, & Asgard, 2015).…”

Omega-3 and alpha-tocopherol provide more protection against contaminants in novel feeds for Atlantic salmon ( Salmo salar L.) than omega-6 and gamma tocopherol

“…Residue levels of pesticides like endosulfan and chlorpyrifos have been reported in products from plants such as soya or maize [33] , [49] which are commonly used as ingredients in salmon feeds [4] . Both PAH and pesticides have been shown in several in vitro and in vivo experiments to cause lipid and endocrine disturbances and to induce cytochrome P450 enzymes in teleost fish [43] , [53] , [68] , [79] , [100] , [102] . PAHs are genotoxic [16] , [86] , [35] and exposure has been suggested to cause vitamin D signalling disruption [79] as well as an effect on cell membrane integrity [65] , [70] .…”