Abstract
Teleost innate immune system is a most developed and powerful system in which fish highly rely throughout their lives. Conditions in aquaculture farms are particularly prone to disease, thus, health and welfare ensuring strategies are an urgent call to which nutrition is gradually becoming a most regarded achievement tool. This study intended to evaluate different amino acids’ effect on immune-related mechanisms as well as their potential as enhancers of European seabass, Dicentrarchus labrax, leucocyte functioning. To achieve these goals, primary cultures of head-kidney leucocytes were established and kept in amino acid (glutamine, arginine, tryptophan or methionine) supplemented culture media in two doses. The effects of amino acids treatments were then evaluated after stimulation with either Vibrio anguillarum or Vibrio anguillarum lipopolysaccharides by measuring nitric oxide production, extracellular respiratory burst, ATP and arginase activities, and expression of immune-related genes. Glutamine, arginine and tryptophan showed to be particularly relevant regarding cell energy dynamics; arginine and tryptophan supplementation also resulted in down-regulation of important immune-related genes. Immune responses in cells treated with methionine were generally enhanced but further studies, particularly those of enzymes activity, are essential to complement gene expression results and to better understand this nutrient’s immune role in fish.
Highlights
In spite of being among the oldest vertebrates, teleosts are able to mount both innate and adaptive immune responses
HKL were exposed to amino acids (AA) treatments by supplementing Leibovitz L-15 culture medium with each AA to the following final concentrations: L-glutamine (G1, 4.1 mM or G2, 5.1 mM), L-arginine (A1, 5.7 mM or A2, 7.2 mM), L-tryptophan (T1, 0.2 mM or T2, 0.25 mM) and L-methionine (M1, 1 mM or M2, 1.25 mM)
A complete description of results can be found as Supplementary Table S1, and Fig. 1 provides a selected subset of most relevant results, regarding the effects of AA surplus on nitric oxide (NO) production
Summary
In spite of being among the oldest vertebrates, teleosts are able to mount both innate and adaptive immune responses. Regardless of organism phylogeny, innate immune mechanisms are orchestrated by a great variety of cells and effector intermediates that are absent in specific immune responses[3]. Arginine is precursor of nitric oxide, a potent bactericidal agent of the pro-inflammatory phase It can be converted in ornithine which, in turn, is the starting point for polyamine biosynthesis, essential players during cell proliferation. Primary leucocyte cultures are useful tools in functional studies as they allow to evaluate responses under well controlled conditions and without the interference of external and unpredictable factors It allows the evaluation of important cellular responses to bacteria or bacterial antigens and the assessment of signalling pathways eventually affected by treatments
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