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Dunboyne, Ireland

Pacitti D.,University of Aberdeen | Pacitti D.,University of British Columbia | Lawan M.M.,University of Aberdeen | Sweetman J.,Alltech Biosciences Center | And 3 more authors.
PLoS ONE | Year: 2015

Background: Selenium (Se) is an essential oligonutrient, as a component of several Se-containing proteins (selenoproteins), which exert important biological functions within an organism. In livestock, Se-enriched products have been proposed as dietary supplements to be included into functional feeds for animal preventive health care. To this end, it is important to understand the optimal range of concentrations for supplementation and how long it takes to be assimilated into the organism. Methods: In this study, rainbow trout (Oncorhynchus mykiss) were fed a control diet containing 0.9 g Kg-1 Se or the same diet supplemented with a Se-Yeast product (Sel-Plex) to achieve Se concentrations ranging from 1.5-8.9 g Kg-1 for a period of ten weeks. Fish were sampled every two weeks for analysis. The kinetics of Se bioaccumulation and the effects on fish selenoprotein expression was determined in different tissues combining chemical and bimolecular techniques. Results: The Sel-Plex enriched diets did not have any effect on survival and growth performance. The highest Se levels were found in liver and kidney followed by muscle and blood cells. Analysis of the Se concentration factor showed that liver is able to initially regulate the amount of Se accumulated. However, with higher dietary Se level (4.8 and 8.9 g Kg-1) and longer times of exposure (10 weeks), regulation is ineffective and the Se tissue concentration increases. The expression of the selected trout selenoprotein transcripts showed an inverse correlation with Sel-Plex augmentation in most cases. In liver, kidney and blood cells the highest up-regulation of the trout selenoprotein genes was seen mostly in the group fed the diet enriched with the lowest concentration of Sel-Plex (0.5 g Kg-1) for 10 weeks. Conclusion: Sel-Plex may represent an excellent Se supplement to deliver a high level of Se without provoking harm to the fish and to guarantee the maximal absorption of the element. According to our results, a dietary supplementation of Sel-Plex between 0.5 and 4 g Kg-1 may allow maximal benefits, whereas 8 g Kg-1 may be excessive for the purpose of supplementation. © 2015 Pacitti et al. Source

Pacitti D.,University of Aberdeen | Wang T.,University of Aberdeen | Page M.M.,University of Aberdeen | Martin S.A.M.,University of Aberdeen | And 3 more authors.
Aquatic Toxicology | Year: 2013

Selenium (Se) is an oligonutrient with both essential biological functions and recognized harmful effects. As the selenocysteine (SeCys) amino acid, selenium is integrated in several Se-containing proteins (selenoproteins), many of which are fundamental for cell homeostasis. Nevertheless, selenium may exert toxic effects at levels marginally above those required, mainly through the generation of reactive oxygen species (ROS). The selenium chemical speciation can strongly affect the bioavailability of this metal and its impact on metabolism, dictating the levels that can be beneficial or detrimental towards an organism.Glutathione peroxidase (GPxs) is the largest and the most studied selenoprotein family. Cytosolic glutathione peroxidase (cGPx, GPx1) and phospholipid hydroperoxide glutathione peroxidase (PHGPx, GPx4) are widely distributed throughout tissues, and play a pivotal role in regulating the oxidative status in the cell. In this study we have cloned GPx1 and GPx4 genes in rainbow trout (Oncorhynchus mykiss). The constitutive mRNA expression of these GPx genes was examined in 18 trout tissues and their responsiveness to Se availability was analysed using a rainbow trout liver cell line (RTL). An inorganic (sodium selenite, Na2SeO3) and organic (selenocysteine, Cys-Se-Se-Cys) selenocompound have been used as Se sources. GPx1 activity was also tested to verify the impact of transcript changes on the enzymatic function of these molecules. To understand if the results obtained from the transcript expression analysis were due to Se bioavailability or generation of ROS, the cytoxicity of the two selenocompounds was tested by measuring the impact of Se on cell membrane integrity. Lastly, Se availability was quantified by mass spectrophotometry to determine the amount of Se in the cell culture media, the Se background due to the foetal calf serum supplement and the contribution from the two selenocompounds used in the treatments.Three isoforms of genes for both GPx1 (GPx1a, 1b1 and 1b2) and GPx4 (GPx4a1, a2 and b) have been identified. The discovery of a third gene encoding for GPx1 and GPx4 hints that salmonids may have the biggest selenoproteome amongst all vertebrates. Transcripts of GPx4 genes were more highly expressed in most tissues examined in vivo (except blood, head kidney and spleen), whereas those of the GPx1 genes were more responsive to selenium exposure in vitro, especially to the organic form. Interestingly, GPx1a was the most sensitive to selenium availability in non stressful conditions, whereas GPx1b1 and GPx1b2 were highly induced by exposure to selenium levels that had some toxic effects on the cells. Although the different concentrations tested of the two selenocompounds modulate GPx1 transcript expression to various degrees, no significant change of GPx1 enzymatic activity was detectable. Our results lead us to conclude that trout GPx1 transcripts expression level may represent a sensitive biomarker for selenium intake, helping to evaluate if selenium concentration and chemical speciation impact on cell homeostasis. © 2012 Elsevier B.V. Source

Pacitti D.,University of Aberdeen | Pacitti D.,University of British Columbia | Lawan M.M.,University of Aberdeen | Feldmann J.,University of Aberdeen | And 4 more authors.
BMC Genomics | Year: 2016

Background: Selenium (Se) is required for the synthesis of proteins (selenoproteins) with essential biological functions. Selenoproteins have a crucial role in the maintenance of cellular redox homeostasis in nearly all tissues, and are also involved in thyroid hormone metabolism, inflammation and immunity. Several immune processes rely on Se status and can be compromised if this element is present below the required level. Previous work has supported the notion that when Se is delivered at levels above those deemed to be the minimal required but below toxic concentrations it can have a boosting effect on the organism's immune response. Based on this concept Se-enriched supplements may represent a valuable resource for functional feeds in animal farming, including aquaculture. Results: In this study we tested the effects of Se supplemented as Sel-Plex during an immune challenge induced by polyinosinic:polycytidylic acid (poly(I:C)), a pathogen-associated molecular pattern (PAMP) that mimics viral infection. Trout were fed two diets enriched with 1 or 4mg Se Kg-1 of feed (dry weight) by Sel-Plex addition and a commercial formulation as control. The whole trout transcriptomic response was investigated by microarray and gene ontology analysis, the latter carried out to highlight the biological processes that were influenced by Sel-Plex supplementation in the head kidney (HK) and liver, the main immune and metabolic organs in fish. Overall, Sel-Plex enrichement up to 4mg Se Kg-1 induced an important response in the trout HK, eliciting an up-regulation of several genes involved in pathways connected with hematopoiesis and immunity. In contrast, a more constrained response was seen in the liver, with lipid metabolism being the main pathway altered by Se supplementation. Upon stimulation with poly(I:C), supplementation of 4mg Se Kg-1 increased the expression of principal mediators of the antiviral defences, especially IFN-γ, and down-stream molecules involved in the cell-mediated immune response. Conclusions: Supplementation of diets with 4mg Se Kg-1 using Sel-Plex remarkably improved the fish response to viral PAMP stimulation. Sel-Plex, being a highly bioavailable supplement of organic Se, might represent a suitable option for supplementation of fish feeds, to achieve the final aim of improving fish fitness and resistance against immune challenges. © 2016 Pacitti et al. Source

Pacitti D.,University of Aberdeen | Wang T.,University of Aberdeen | Martin S.A.M.,University of Aberdeen | Sweetman J.,Alltech Biosciences Center | Secombes C.J.,University of Aberdeen
Developmental and Comparative Immunology | Year: 2014

Production of reactive oxygen species (ROS) is the first biological response during a disease outbreak and after injury. ROS are highly reactive molecules that can either endanger cell homeostasis or mediate cell signaling in several physiological pathways, including the immune response. Thioredoxin (Trx) and thioredoxin reductase (TrxR) are the essential components of the thioredoxin system, one of the main intracellular redox systems and are therefore important regulators of ROS accumulation. Through the regulation of the intracellular redox milieu, the thioredoxin system plays a key role within the immune system, linking immunology and free radical science. In this study we have firstly identified TrxRs in fish and used this new sequence information to reevaluate the evolution of the thioredoxin system within the vertebrate lineage. We next measured the expression of rainbow trout (Oncorhynchus mykiss) Trx and TrxR transcripts during infection in vivo and in vitro after stimulation of a macrophage cell line and primary macrophage cultures with pathogen associated molecular patterns (PAMPs). Our results showed that both Trx and TrxR were induced during infection at the transcriptional level, confirming their likely involvement in the innate immune response of fish. Since TrxRs are selenium-containing proteins (selenoproteins), we also measured the modulation of their expression upon organic and inorganic selenium exposure in vitro. TrxR was found to be responsive to selenium exposure in vitro, suggesting that it may represent a key mediator in the selenium modulation of innate immunity. In conclusion, our study highlights the need to investigate the involvement of the cell antioxidant pathways, especially the thioredoxin system, within the immune system of vertebrate species. © 2013 Elsevier Ltd. Source

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