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Research Project: Reducing Impacts of Disease on Salmonid Aquaculture Production

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Title: Effects of cortisol and lipopolysaccharide on expression of select growth-, stress- and immune-related genes in rainbow trout liver

Author
item Shepherd, Brian
item Spear, Allyn
item Philip, Anju - University Of Calgary
item Leaman, Douglas - University Of Toledo
item Stepien, Carol - University Of Toledo
item Sepulveda-villet, O - Water Institute
item Palmquist, Debra
item Vijayan, Mathalakath - University Of Calgary

Submitted to: Fish and Shellfish Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2018
Publication Date: 1/30/2018
Publication URL: http://handle.nal.usda.gov/10113/5914808
Citation: Shepherd, B.S., Spear, A., Philip, A.M., Leaman, D.W., Stepien, C.A., Sepulveda-Villet, O.J., Palmquist, D.E., Vijayan, M.M. 2018. Effects of cortisol and lipopolysaccharide on expression of select growth-, stress- and immune-related genes in rainbow trout liver. Fish and Shellfish Immunology. 74:410-418. doi: 10.1016/j.fsi.2018.01.003.
DOI: https://doi.org/10.1016/j.fsi.2018.01.003

Interpretive Summary: Many studies have shown that stress-induced levels of the hormone cortisol negatively influence growth and immunity in finfish. Despite this knowledge, few studies have assessed the direct effects of cortisol on the liver in the immune response in rainbow trout. Our goal was to determine how cortisol and lipopolysaccharide (outer surface membrane of pathogenic bacteria) affect immune function in the rainbow trout liver. Results of the study showed that the liver is an important immune organ in rainbow trout, and that cortisol suppresses the liver immune response and reduces expression of two antimicrobial peptides. We believe this is the first report of a suppressive effect of cortisol on antimicrobial peptides in the rainbow trout liver, which further underscores that acute stress negatively influences immunity in rainbow trout.

Technical Abstract: Many studies have shown that stress-induced cortisol levels negatively influence growth and immunity in finfish. Despite this knowledge, few studies have assessed the direct effects of cortisol on liver immune function in finfish. Using real-time PCR, the expression of three cortisol-responsive genes (GR: glucocorticoid receptor, IGF-1: insulin-like growth factor-I and SOCS-1: suppressor of cytokine signaling-I), genes involved with innate and adaptive immunity (IL-1': interleukin-1 beta, IgM: immunoglobin-M and Lyz: lysozyme), and liver-specific antimicrobial peptides (hepcidin and LEAP-2A: liver-expressed antimicrobial peptide-2A) were studied in vitro using rainbow trout liver slices. The abundance of GR, SOCS-1 and IGF-1 mRNAs were suppressed by cortisol treatment and elevated by LPS treatment. Abundance of IL-1' mRNA was upregulated by LPS and suppressed by cortisol treatment in time-dependent manner. While abundance of IgM mRNA was suppressed by cortisol treatment and stimulated by LPS, there were no effects of cortisol or LPS on abundance of Lyz mRNA. Abundance of hepcidin and LEAP-2A mRNA levels were suppressed by cortisol treatment and stimulated by LPS. These results demonstrate that cortisol directly suppresses abundance of GR, IGF-1, IL-1', IgM, hepcidin, LEAP-2A and SOCS-1 mRNA transcripts in the rainbow trout liver. We report for the first time, a suppressive effect of cortisol (within 8 h of treatment) on hepcidin and LEAP-2A mRNAs in rainbow trout liver, which suggests that acute stress may negatively affect liver immune function in rainbow trout.