CORTISOL MODIFY THE TRANSCRIPTOMIC RESPONSE TO Piscirickettsia salmonis INFECTION IN RAINBOW TROUT Oncorhynchus mykiss MYOTUBES

Stress and diseases are two of the main factors that affect Chilean aquaculture, generating important economic losses. Under stressful conditions, the immune response of the fish is affected, favoring the appearing of bacterial diseases  such  as Piscirickettsiosis, generated by the  intracellular  bacteria Piscirickettsia salmonis . Despite that skeletal muscle is the main product in aquaculture, little information exist respect on how this tissue response against the infection with this pathogen and how an increase in cortisol levels (main hormone associated with stress response) affects the response on myotubes during the infection with  P.salmonis.

To answer this interrogates, we develop an in vitro experiment using Rainbow trout myotubes . Four experimental groups  were used as follow: (i) untreated cell or control (CTRL); (ii) P. salmonis ATCC LF-89 (MOI 50) -infected cells for 8 hours (INF); (iii)  100 ng/ml  cortisol-treated cells for  3 hours  (CORT) and (iv )  pre-treated cells with cortisol and then infected by P. salmonis (CORT+INF).  After treatments, we collected RNA samples,  performed RNA-seq analysis with Illumina Hiseq ,  and  then  analyzed  by  CLC Genomic Workbench platform.

The RNA-seq analysis showed several differentials expressed genes among the groups (Table 1).  A higher transcriptional response was observed across the groups associated with cortisol pre-treatment. Interestingly , we observed that  cortisol impacts o n the transcriptional capacity of myotube to response to P.salmonis , modulating processes associated to immune response and apoptosis .  This results evidence that myotube-pathogen interaction could be modulated by cortisol, information that should be considered to understand the effect of stress in bacterial infections in muscle of salmonids species. Funding:  CONICYT FONDECYT 1171307 , CONICYT FONDECYT 11713 18  and CONICYT/FONDAP 15110027.