The Direct Exposure of Cortisol Does Not Modulate the Expression of Immune-Related Genes on Tissue Explants of Mucosal Surfaces in Rainbow Trout (Oncorhynchus mykiss) Nor in Gilthead Sea Bream (Sparus aurata)

Abstract

The stress response in fish is characterized by the activation of the HPI axis resulting in the release of cortisol. Previous studies in rainbow trout (Oncorhynchus mykiss) and gilthead sea bream (Sparus aurata) have shown that an acute stressor modulates the expression of immune- and stress-related genes in mucosal-associated lymphoid tissues (MALTs), particularly in the skin (SALT), gills (GIALT), and gut (GALT). However, there are no antecedents on whether the modulation on the mucosal transcriptomic profile is coordinated through the local presence of cortisol in the mucosal tissue surface. Thus, the aim of this study was to evaluate the effect of cortisol upon the modulation of a set of immune- (il-1β, il-6, tnf-α, and cox-2) and stress-related (hsp70, gr1) genes. For this purpose, tissue explants cultures were incubated with cortisol (100 ng/100 mg tissue) for 2-, 4-, and 24 h and the gene expression profile was evaluated at each time-point by real-time PCR. No differences were found in the gene expression between cortisol-incubated tissue explants and mock-incubated tissues in any of the time-points tested for both species. These results suggest that the quick modulation of the gene expression during the first 24 h after the exposure to stressor challenge reported in previous studies, is probably coordinated and mediated through a systemic-dependent mechanism but not through a peripheral/local response on mucosal tissue surfaces.

The gene expression profile of the glucocorticoid receptor 1 (gr1) but not gr2 is modulated in mucosal tissues of gilthead sea bream (Sparus aurata) exposed to acute air-exposure stress

“…The collected supernatant was stored at -80°C. Skin tissue samples were taken from the upper lateral line area behind the dorsal fin, the left side, and avoiding muscle contamination (Vallejos-Vidal et al, 2022). Then, the body cavity was opened laterally and the anterior gut was sampled removing the feces and mucus carefully with forceps, and then rinsed once with PBS.…”

“…In other words, the cortisol detected in skin mucus would be the reflection of the high circulating concentrations at systemic (bloodstream) level (Carbajal et al, 2019). Importantly, it has been recently proposed that the cortisol secreted after an intense activation of the HPI axis but not the exogenous cortisol sensed from the environment would be responsible of the changes in the expression profile in fish mucosa (Vallejos-Vidal et al, 2022). This acquires special relevance when considering the immunoprotective and defense role of mucosa-associated tissues (Parra et al, 2015), and the repercussions of the presence of cortisol in the modulation over time of the expression of genes involved in the immune response to a given stressor stimulus.…”

Transcriptional Evaluation of Neuropeptides, Hormones, and Tissue Repair Modulators in the Skin of Gilthead Sea Bream (Sparus aurata L.) Subjected to Mechanical Damage

“…In addition, some neuropeptides can act as endogenous hormones or opioids, suppressing the sensation of pain and acting on the immune system [ 15 ]. A similar organization of the peripheral stress response is present in fish but modulated by the above-mentioned special characteristics of the mucosal surfaces of these aquatic animals [ 16 ].…”

Transcriptome and molecular regulatory mechanisms analysis of gills in the black tiger shrimp Penaeus monodon under chronic low-salinity stress

“…The stress response is a complex physiological mechanism activated by stimuli that an organism perceives as potentially threatening (Vallejos-Vidal et al, 2022). It involves the sum of continuous and coordinated activation mechanisms at different functional levels, including molecular processes that have a direct impact on gene expression and protein synthesis, and will ultimately activate responses from the cellular to the systemic and performance levels (Parra et al, 2015).…”