Bacterial lipopolysaccharide (LPS) modulates corticotropin-releasing hormone (CRH) content and release in the brain of juvenile and adult tilapia (Oreochromis mossambicus; Teleostei)

Abstract

SUMMARY Although immune endocrine interactions in teleost fish have been shown to involve adrenocorticotropin hormone (ACTH) and cortisol, the involvement of corticotropin-releasing hormone (CRH) has not been demonstrated. The present study investigates whether treatment with bacterial endotoxin(lipopolysaccharide, LPS) modulates brain CRH contents or in vitroCRH release in tilapia (Oreochromis mossambicus). 10 days LPS(Escherichia coli) exposure of juvenile tilapia (4.5 weeks post hatch) via the ambient water increased brain CRH and α-MSH content,whereas cortisol contents were not increased. This indicates that the elevation of brain CRH levels were not secondary to activation of HPI-axis. Adult tilapia were treated for 6 days with LPS (intraperitoneally) and were sampled before and after 24 h of confinement. Overall LPS pre-treatment modified the reaction of tilapia to the additional stressor of 24 h confinement, as interactions between LPS treatment and confinement were observed at the level of the hypothalamus (diencephalic CRH content), the pituitary (CRH and α-MSH content) and in plasma glucose levels. In vitro, LPS pre-treatment abolished CRH release from telencephalic tissues induced by norepinephrine, one of the CRH secretagogues released during stress in vivo. This effect might be a mechanism of action through which LPS in vivo abolished the up-regulation of telencephalic CRH induced by confinement stress. Our results provide evidence that the role of CRH in immune–endocrine interactions is a phylogenetically old mechanism, and we here demonstrate that LPS molecules are able to locally modulate CRH release in the central nervous system.

Fantastically plastic: fish larvae equipped for a new world

“…Cortisol is suggested to control chloride cell function immediately after hatching of carp and may have major consequences for further development. This is corroborated by evidence in tilapia, where freshwater adaption increased the cortisol response of larvae by over five times relative to saltwater adapted larvae/juveniles but did not affect the CRF and ACTH levels (Pepels & Balm ). These authors further suggest that the early cortisol response in tilapia is regulated independently from CRF and ACTH.…”

“…In zebrafish embryos, physical stress raised cortisol at 97 hpf or about 40 h post‐hatch (Alsop & Vijayan ). In mouthbrooding tilapia Orechromis mossambicus larvae, a similar pattern is observed: already at 2 dph, a marker for corticotrophin‐releasing factor is found in the preoptic nucleus and two hypothalamic nuclei as well as in the neural part of the pituitary, while the endocrine cells of the pars distalis and intermedia contain POMC‐derived peptides, and all life stages were able to rapidly increase their response to handling (Pepels & Balm ). It seems that even fish eggs are capable of responding to the stress of their environment, with all that entails.…”

Sequences, expression patterns and regulation of the corticotropin-releasing factor system in a teleost

“…CRF, CRFBP, and both CRF receptor types are expressed in the brain and pituitary in A. burtoni and in the other teleosts (Olivereau and Olivereau, 1988;Arai et al, 2001;Pepels et al, 2002;Pepels and Balm, 2004;Alderman and Bernier, 2007;Alderman et al, 2008) suggesting that CRF acts in the central nervous system along with its role in the HPI axis. The present of CRFBP and both types of CRF-Rs, not CRF mRNA in the pituitary gland implicates that the outside CRF neurons, possibly in the hypothalamus innervate the pituitary via CRF receptors and the ligands are regulated by CRFBP.…”

Environmentally relevant concentrations of citalopram partially inhibit feeding in the three-spine stickleback (Gasterosteus aculeatus)

“…In rodents (Boisvert et al, 2011) andfish (De Pedro N et al, 1998;Ortega et al, 2013), the effect of serotonin on feeding and satiety is at least in part mediated by the Corticotropin Releasing Hormone (CR) system. CRH is also known as the Corticotropin Releasing Factor (CRF) In tilapia (Oreochromis mossambicus ), in vitro stimulation of telencephalic tissue by serotonin causes CRH release (Pepels, 2004). In goldfish (Carassius auratus ) and rainbow trout (Oncorhynchus mykiss) (De Pedro N et al, 1998;Ortega et al, 2013) the Corticotropin Releasing Factor (CRF) receptor antagonist α-helical CRF(9-41) partially blocks the inhibitory effect of serotonin on feeding.…”