Abstract
Rainbow trout (Oncorhynchus mykiss) is one of the most common aquaculture fish species worldwide. Vibriosis disease outbreaks cause significant setbacks to aquaculture. The stress and immune responses are bidirectionally modulated in response to the health challenges. Therefore, an investigation into the regulatory mechanisms of the stress and immune responses in trout is invaluable for identifying potential vibriosis treatments. We investigated the transcriptional profiles of genes associated with stress and trout immune functions after Vibrio anguillarum infection. We compared the control trout (CT, 0.9% saline injection), asymptomatic trout (AT, surviving trout with minor or no symptoms after bacteria injection), and symptomatic trout (ST, moribund trout with severe symptoms after bacteria injection). Our results showed activated immunomodulatory genes in the cytokine network and downregulated glucocorticoid and mineralocorticoid receptors in both AT and ST, indicating activation of the proinflammatory cytokine cascade as a common response in AT and ST. Moreover, the AT specifically activated the complement- and TNF-associated immune defenses in response to V. anguillarum infection. However, the complement and coagulation cascades, as well as steroid hormone homeostasis in ST, were disturbed by V. anguillarum. Our studies provide new insights toward understanding regulatory mechanisms in stress and immune functions in response to diseases.
Highlights
Teleosts have to cope with various challenges, including the diversity of the potential environmental stimuli and pathogen load [1, 2]
The overall transcriptional profiles of target genes in symptomatic trout (ST) and control trout (CT) in response to V. anguillarum infection were summarized by principal component analysis (PCA) (Figure 2D)
Separated PCA vectors were present, indicating that the V. anguillarum infection resulted in different profiles of genes associated with the stress response, cytokines and cellular functions, and the complement system between ST and CT (Figure 2D)
Summary
Teleosts have to cope with various challenges, including the diversity of the potential environmental stimuli and pathogen load [1, 2]. Teleosts respond differently to stressors and the immune responses remain species-specific, environmental and aquaculture insults can trigger defensive reactions of fish, including the activation of the stress response. Activation of the GR (or MR) may serve as an early danger alarm and enable the immune system to prepare for the fight against health challenges [10, 11]. Inflammation serves as the first step of immunomodulation in response to infection or irritation [12] Proinflammatory cytokines, such as interleukin 1 (IL-1) and tumor necrosis factor a (TNFa) [5], act as an important defense mechanism against pathogens. The stress response typically regulates the immune response by suppressing the synthesis and release of proinflammatory cytokines in both mammals and teleosts [13,14,15]
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