Gene expression in Atlantic salmon skin in response to infection with the parasitic copepod Lepeophtheirus salmonis, cortisol implant, and their combination

Abstract

BackgroundThe salmon louse is an ectoparasitic copepod that causes major economic losses in the aquaculture industry of Atlantic salmon. This host displays a high level of susceptibility to lice which can be accounted for by several factors including stress. In addition, the parasite itself acts as a potent stressor of the host, and outcomes of infection can depend on biotic and abiotic factors that stimulate production of cortisol. Consequently, examination of responses to infection with this parasite, in addition to stress hormone regulation in Atlantic salmon, is vital for better understanding of the host pathogen interaction.ResultsAtlantic salmon post smolts were organised into four experimental groups: lice + cortisol, lice + placebo, no lice + cortisol, no lice + placebo. Infection levels were equal in both treatments upon termination of the experiment. Gene expression changes in skin were assessed with 21 k oligonucleotide microarray and qPCR at the chalimus stage 18 days post infection at 9°C. The transcriptomic effects of hormone treatment were significantly greater than lice-infection induced changes. Cortisol stimulated expression of genes involved in metabolism of steroids and amino acids, chaperones, responses to oxidative stress and eicosanoid metabolism and suppressed genes related to antigen presentation, B and T cells, antiviral and inflammatory responses. Cortisol and lice equally down-regulated a large panel of motor proteins that can be important for wound contraction. Cortisol also suppressed multiple genes involved in wound healing, parts of which were activated by the parasite. Down-regulation of collagens and other structural proteins was in parallel with the induction of proteinases that degrade extracellular matrix (MMP9 and MMP13). Cortisol reduced expression of genes encoding proteins involved in formation of various tissue structures, regulators of cell differentiation and growth factors.ConclusionsThese results suggest that cortisol-induced stress does not affect the level of infection of Atlantic salmon with the parasite, however, it may retard repair of skin. The cortisol induced changes are in close concordance with the existing concept of wound healing cascade.

Cortisol treatment of prespawning female cod affects cytogenesis related factors in eggs and embryos

“…Also Li et al (2012b) recently showed that cell division is increased in rainbow trout eggs containing elevated levels of cortisol. Some of the overrepresented biological processes identified in this study have previously been related to stress, and wound healing and likewise several of these were also found to be affected in salmon skin by cortisol implants (Krasnov et al, 2012).…”

Role of Pathogen-Derived Cell Wall Carbohydrates and Prostaglandin E 2 in Immune Response and Suppression of Fish Immunity by the Oomycete Saprolegnia parasitica

“…A similar effect on the host has been observed in the case of the amoebic parasite Neoparamoeba perurans, the agent of amoebic gill disease, where the same components of the antigen presentation machinery are suppressed in infected tissues (MHC-I and -II, ␤2-microglobulin, TAPBP, and PA28␤) (28). Another pathogen with the capacity to suppress the fish immune system is the salmon louse Lepeophtheirus salmonis (29,30). In this case, the parasite saliva contains biologically active molecules, such as PGE 2 , that suppress the host immune response (31).…”

Sexual maturation and administration of 17β-estradiol and testosterone induce complex gene expression changes in skin and increase resistance of Atlantic salmon to ectoparasite salmon louse

“…Teleost skin is a dynamic organ expressing great variability in physical properties, cell types and hormonal systems involved (reviewed by Rakers et al, 2010;Esteban, 2012). A wide range of susceptibilities to L. salmonis exists among salmonids; coho and pink respond with aggressive inflammation and subsequent rejection of the parasite (Johnson and Albright, 1992;Braden et al, 2012Braden et al, , 2015Sutherland et al, 2011) while in Atlantic, sockeye and chum salmon, there is a delayed or weakened inflammatory response to infection (Skugor et al 2008;Tadiso et al, 2011;Krasnov et al 2012;Braden et al, 2012Braden et al, , 2015Sutherland et al, 2011Sutherland et al, , 2014, which permits heavier parasitic abundance. The study of Holm et al (2014) suggested that a thicker epidermis and larger mucus cell size were not associated with resistance in Atlantic salmon.…”