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

Abstract

Steroidogenic acute regulatory protein (StAR) transfers cholesterol over the inner mitochondrial membrane. In mammals, StAR controls this rate-limiting step of steroidogenesis, but its expression and regulation has not been well explored in fish. The present work investigates StAR mRNA expression in the head kidney of the gilthead seabream (Sparus aurata) under different stressors. We have cloned the StAR cDNA (1461 bp) in seabream (accession number EF640987), which has an open reading frame of 861 nucleotides encoding a polypeptide of 286 aa, and displays high sequence identity with StAR of other fish and mammalian counterparts. Seabream StAR transcripts were found to be expressed exclusively in head kidneys and gonads. In fish under acute stress (chased with a net), plasma cortisol levels peaked within 1 h, were still high after 6 h, and decreased after 16 h, although no increases in head kidney StAR expression were observed at any time post-stressor. Fish under chronic high-density stress showed cortisol levels 90-fold higher than controls and StAR mRNA levels increased threefold. Lipopolysaccharide (LPS) injection increased head kidney StAR mRNA levels after 6 h, reached a maximum at 12 h, and decreased until 72 h. When the head kidney cells were incubated in vitro and treated with ACTH or LPS, ACTH induced an increase in StAR expression as expected, but LPS induced a reduction in StAR expression. In conclusion, StAR expression in seabream head kidneys is highly regulated by different stressors.

Stress-related hormones modulate cytokine expression in the head kidney of gilthead seabream (Sparus aurata)

“…In addition, ACTH receptors have been found in mammalian leukocyte populations, where they contribute to modulate immune responses [53,54]. The ACTH concentration used in the present study (150 ng mL À1 ) has been shown to be effective in trout [55] and in seabream head kidney preparations, where ACTH exerts its effects through its specific receptor, which can be blocked using a specific antagonist, as we previously reported [44]. ACTH binds to MC2 receptors in the head kidney and increases cortisol production in steroidogenic cells, among other functions.…”

“…Thus, it is likely that in vivo immunological responses to stress are dependent on the actions of various hormones, their interactions with each other, with immunocompetent cells as well as with other endogenous factors, such as cytokines. To further study the effects of stress hormones without all these interactions, we have used an in vitro model of seabream head kidney, which has been described for different fish species and has revealed as an useful tool in which to study the ''intraadrenal'' interactions among the different cell types of the tissue with a single preparation [44,46,47]. The aim of our study was to use this model to investigate the interactions of adrenaline and cortisol (hormones related to stress and secreted in the head kidney) and the pituitary hormone ACTH on the expression of cytokines in the seabream head kidney.…”

“…Gilthead seabream head kidney cells were isolated and cultured as previously described [44]. Briefly, head kidneys were dissected from seabream killed by over anesthetization in MS-222 (Sigma, Alcobendas, Spain), and placed in PBS.…”

“…Following isolation, cells were left undisturbed for 3 h to stabilize as previously described [44,45]. After this period, head kidney preparations were incubated with medium with or without ACTH (150 ng mL À1 ), adrenaline (1 mM) or cortisol (50 and 100 ng mL À1 ) (H2882, Sigma, Alcobendas, Spain) for 1 and 2 h. In addition, in order to check the effects of the interaction of LPS and stress hormones, cells were incubated with LPS alone (L8274 Sigma, Alcobendas, Spain) (10 mg mL À1 ) or in combination with ACTH (150 ng mL À1 ), adrenaline (1 mM) or cortisol (50 ng mL À1 ) for 2 h. Cell viability was >90% after isolation, and remained at the same levels after treatments, as determined by Trypan Blue exclusion test.…”

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

“…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). Similar an injection of LPS both in sea bream and trout have shown to promote increased cortisol secretion and increased cortisol receptor expression in most tissues, 6 to 72 h after the initial injection (Acerete et al 2007).…”