Recombinant interleukin-1 beta activates the hypothalamic-pituitary-interrenal axis in rainbow trout, Oncorhynchus mykiss

Abstract

The present study provides the first direct evidence that implicates fish cytokines as the effector molecules by which the immune system signals the neuroendocrine system and activates the hypothalamic-pituitary-interrenal stress axis. I.p. injections of trout recombinant interleukin-1 (rIL-1 ) or E. coli lipopolysaccharide (LPS), at concentrations known to induce immune/inflammatory responses in vivo (0·1-0·6 nmol/kg and 1·3 mg/kg respectively), significantly elevated plasma cortisol levels in a dose-and/or time-dependent manner. However, in contrast to general stress responses in fish, under the conditions employed in this study, no specific treatment effects on plasma glucose levels could be demonstrated. The trout IL-1 peptides (P1 and P3), which are homologous to receptor-binding sequences of human IL-1 , failed to influence the prevailing cortisol concentration even though an equivalent dose has been found to have immunostimulatory properties in vivo. Blockade of endogenous ACTH release by administration of the synthetic glucocorticoid dexamethasone prevented the rIL-1 /LPS-mediated elevation of plasma cortisol, suggesting that IL-1 and LPS modulate cortisol secretion via effects at the level of the hypothalamic-pituitary axis. These data indicate that, with respect to IL-1 , cytokine signalling between the immune and neuroendocrine systems in mammals appears to be conserved in lower vertebrates.

Stress-induced regulation of steroidogenic acute regulatory protein expression in head kidney of Gilthead seabream (Sparus aurata)

“…When we injected seabream with 8 mg/kg i.p. of bacterial endotoxin to induce infection, it provoked a marked rise in plasma cortisol levels similar to those previously described (Balm et al 1995, Holland et al 2002 and to the results previously reported (Acerete et al 2007). This produced a cortisol peak after 6 h (threefold the controls) and a progressive decrease in cortisol until 72 h, which are similar to the results reported in rats (Grinevich et al 2001) where a single LPS injection stimulated plasma cortisol levels.…”

The effect of allostatic load on hypothalamic–pituitary–interrenal (HPI) axis before and after secondary vaccination in Atlantic salmon postsmolts (Salmo salar L.)

“…ACTH secretion seems also to be some control of IL-6 as high IL-6 levels have shown correlated with higher ACTH and cortisol levels (Zarkovic et al 2008). In fish, several studies have shown a similar bi-directional communication between HPI-Axis and cytokines (Tort 2011). Holland et al (2002 showed that recombinant IL-1injection raises cortisol levels, and injection of lipopolysaccharide (LPS) raised plasma cortisol in yellow perch (Haukenes and Barton 2004) and promoted StAR HK expression in gilt-head bream (Castillo et al 2008).…”

Ghrelin stimulates phagocytosis and superoxide production in fish leukocytes

“…Administration of homologous interleukin (IL)-1 activates the hypothalamo-pituitary-interrenal axis in rainbow trout (Holland et al 2002). In man, ghrelin inhibits expression of IL-1 , IL-6, and tumor necrosis factor (TNF)-in T cells and monocytes, suggesting that ghrelin modulates cell-to-cell interaction in leukocytes during inflammatory processes (Dixit et al 2004).…”