Plasma α-MSH and acetylated β-endorphin levels following stress vary according to CRH sensitivity of the pituitary melanotropes in common carp, Cyprinus carpio

Burg, Erwin H. van den; Metz, Juriaan R.; Spanings, F.A.T.; Bonga, S.E. Wendelaar; Flik, G.

doi:10.1016/j.ygcen.2004.11.010

Cited by 21 publications

(7 citation statements)

References 42 publications

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“…30G0 . 11 nM (nZ19), which values are, again, within the range measured in unstressed carp (van den Burg et al 2003, 2005a, Metz et al 2005. In hyperthyroid carp, basal a-MSH levels had increased by 30% (P!0 .…”

Section: Plasma Hormone Levelssupporting

confidence: 75%

Experimental hyperthyroidism and central mediators of stress axis and thyroid axis activity in common carp (Cyprinus carpio L.)

Geven¹,

Verkaar²,

Flik³

et al. 2006

Journal of Molecular Endocrinology

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The effect of experimental hyperthyroidism, realized by T 4 injection, on central mediators of the hypothalamo-pituitaryinterrenal axis (HPI-axis) in common carp (Cyprinus carpio L.) was studied. Our results show that hyperthyroidism evokes a marked 3 . 2-fold reduction in basal plasma cortisol levels. Corticotropin-releasing hormone-binding protein (CRH-BP) mRNA levels in the hypothalamus, measured by real-time quantitative PCR, were significantly elevated by 40%, but CRH, urotensin-I, prepro-TRH, prohormone convertase-1 (PC1), and POMC mRNA levels were unchanged. In the pituitary pars distalis, PC1, CRH receptor-1, and POMC mRNA levels were unaffected, as was ACTH content. Plasma a-MSH concentrations were significantly elevated by 30% in hyperthyroid fish, and this was reflected in PC1 and POMC mRNA levels in pituitary pars intermedia that were increased 1 . 5-and 2 . 4-fold respectively. The a-MSH content of the pars intermedia was unchanged. Hyperthyroidism has profound effects on the basal levels of a central mediator, i.e., CRH-BP, of HPI-axis function in unstressed carp in vivo, and we conclude that HPI-and hypothalamo-pituitary-thyroidaxis functions are strongly interrelated. We suggest that the changes in plasma cortisol, thyroid hormone, and a-MSH levels reflect their concerted actions on energy metabolism.

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Section: Plasma Hormone Levelssupporting

confidence: 75%

Experimental hyperthyroidism and central mediators of stress axis and thyroid axis activity in common carp (Cyprinus carpio L.)

Geven¹,

Verkaar²,

Flik³

et al. 2006

Journal of Molecular Endocrinology

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“…Strikingly, N-Ac b-endorphin release was more profoundly stimulated than a-MSH release. Although these peptides are derived from the same precursor, there is evidence that their release is not tightly coupled and differential release occurs in carp (Van den Burg et al 2005). It must be noted though that we here present only a single experiment due to limited availability of recombinant carp IL-1b.…”

Section: Discussionmentioning

confidence: 97%

“…RIAs for a-MSH, N-Ac b-endorphin and cortisol a-MSH, N-Ac b-endorphin were measured by RIA with antibodies against synthetic human mono-Ac a-MSH (Van Zoest et al 1989) and salmon N-Ac b-endorphin (Takahashi et al 1984) respectively, according to the method described earlier (Van den Burg et al 2005). Cortisol was measured using the manufacturer's protocol of a commercially available kit (Campro Scientific, Veenendaal, The Netherlands).…”

Section: In Vitro Superfusionmentioning

confidence: 99%

Central and peripheral interleukin-1β and interleukin-1 receptor I expression and their role in the acute stress response of common carp, Cyprinus carpio L.

Metz¹,

Huising²,

Leon³

et al. 2006

Journal of Endocrinology

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In fish, the hypothalamus-pituitary-interrenal axis (HPIaxis), the equivalent of the hypothalamus-pituitary-adrenal axis (HPA-axis) in mammals, is activated during stress and leads to production and release of cortisol by the interregnal cells in the head kidney. In mammals, the cytokine interleukin-1b (IL-1b) takes a key position in the innate immune and inflammatory responses and influences the HPA-axis. In fish, studies that address the effects of cytokines on HPI-axis activation are limited. We quantitatively assessed expression of IL-1b and its receptor, IL-1RI (the latter was cloned and sequenced), in an acute restraint stress paradigm in common carp, Cyprinus carpio. We also considered expression of the pituitary hormones prolactin (PRL) and GH that have been shown to be structurally related to cytokines and have immunomodulatory actions. Pituitary PRL expression increased fourfold during stress; GH mRNA levels were unaffected. Following restraint, hypothalamic IL-1b expression was upregulated; in head kidney and pituitary pars intermedia, IL-1RI expression significantly increased. We suggest that during acute stress IL-1b signalling in the HPI-axis becomes more sensitive, since both ligand and receptor expressions are enhanced. In vitro, recombinant carp IL-1b stimulates release of a-MSH and N-Ac b-endorphin from the pituitary gland. This observation concurs with increased in vivo plasma levels of a-MSH and N-Ac b-endorphin following restraint. Our findings combined lead us to conclude that IL-1b affects the activity of the HPI-axis and, in turn, expression profiles of genes encoding IL-1b and its receptor are modified during acute stress. Our study provides convincing evidence for bi-directional communication of the HPI-axis and the immune system in fish.

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“…Apparently, a differential regulation of processing and release of these peptides, that reside in a 1:1 ratio in the precursor POMC, is part of the complex pituitary response to hypothalamic stress signals (Van den Burg et al, 2005a). Acetylated endorphin has been assigned a potentiating role in corticotropic actions of MSH in the Mozambique tilapia (Balm et al 1995).…”

Section: Some Functional Anatomy Of the Endocrine Stress Axis In Adulmentioning

confidence: 99%

CRF and stress in fish

Flik¹,

Klaren²,

Burg³

et al. 2006

General and Comparative Endocrinology

228

140

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The endocrine stress response is pivotal in vertebrate physiology. The stress hormone cortisol-the end product of the endocrine stress axis-(re-)directs energy flows for optimal performance under conditions where homeostasis may be or become at risk. Key players in the continuous adaptation process are corticotropin-releasing factor (CRF) from the hypothalamic nucleus preopticus (NPO), pituitary adrenocorticotropic hormone (ACTH) and cortisol produced by the interrenal cells in the headkidney (adrenal equivalent of fish). CRF is a member of a large family of related peptides that signals through CRF-receptor subtypes specific for central and peripheral actions of the peptide. CRF is "chaperoned" by a unique and phylogenetically very well-conserved binding protein (CRFBP); the functions of the CRFBP can only be speculated on so far, but its mRNA and protein abundance are important indicators of the central CRF-system activity, and indeed its mRNA levels are altered by restraint stress. Moreover, the unique structure and size of the CRFBP provide good tools in phylogenetic studies, that date the CRF-system to at least one billion years old. Pro-opiomelanocortin is produced and processed to ACTH and endorphin in the hypothalamic NPO and pituitary pars distalis ACTH-cells, to MSH and acetylated endorphins in the pituitary pars intermedia MSH-cells. ACTH is the prime corticotrope in acute stress conditions. In carp, MSH, considered a mild corticotrope in chronic stress responses in other fish, lacks corticotropic effects (in line with the absence of the melanocortin-5 receptor in headkidney); yet, an unknown corticotropic signal substance in the pars intermedia of carp awaits elucidation. Interesting observations were made on the CRF control of pituitary cells. CRF stimulates ACTH-cells, but only when these cells experience a mild dopaminergic block. Endorphin, produced in the NPO and transported via axons to the pituitary gland in vivo, reverses the stimulatory CRF action on MSH-cells to a differential inhibition of N-acetyl beta-endorphin release in vitro (MSH release is not affected). We speculate that the consistently observed elevation of plasma MSH during chronic stress may exert central actions related to feeding and leptin regulated processes. A BOLD-fMRI study revealed the functional anatomy of the stress response at work in a paradigm, where carp were exposed to a sudden water temperature drop. In carp (and other fish), the endocrine stress axis is already operational in very early life stages, viz., around hatching and comprises hypothalamic, pituitary, and interrenal signaling to adjust the physiology of the hatchling to its dynamically changing environment. Understanding of stress during early life stages is critical as the consequent rises in cortisol may have long lasting effects on survival and fish quality.

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Plasma α-MSH and acetylated β-endorphin levels following stress vary according to CRH sensitivity of the pituitary melanotropes in common carp, Cyprinus carpio

Cited by 21 publications

References 42 publications

Experimental hyperthyroidism and central mediators of stress axis and thyroid axis activity in common carp (Cyprinus carpio L.)

Experimental hyperthyroidism and central mediators of stress axis and thyroid axis activity in common carp (Cyprinus carpio L.)

Central and peripheral interleukin-1β and interleukin-1 receptor I expression and their role in the acute stress response of common carp, Cyprinus carpio L.

CRF and stress in fish

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