Chronic stimulation of the hypothalamus-pituitary-adrenal axis in rats by interleukin 1beta: central and peripheral mechanisms.
The authors have studied mechanisms which could be involved in the sustained activation of the hypothalamus-pituitary-adrenal (HPA) axis during continuous infusion of rats with recombinant human interleukin-1beta (IL-1beta). First, the effects of 3 days of intracerebroventricular (i.c.v.) infusion of rats with IL-1 on plasma adrenocorticotropin (ACTH) and corticosterone (B) levels were investigated. Thereafter, changes in plasma ACTH and B levels were followed in rats intraperitoneally (i.p.) infused with IL-1beta after immunoneutralization of corticotropin-releasing hormone (CRH), hypophysectomy (HPX), macrophage depletion using dichloromethylene diphosphonate (Cl2MDP)-containing liposomes, adrenalectomy (ADX) and dexamethasone (DEX) administration, respectively. Infusion of IL-1beta i.c.v., even in doses as low as 0.1 microg/day, induced significant increases in plasma ACTH and B levels. HPX and ADX rats died within 18 h after starting the IL-1beta infusion (0.5 microg/day). Immunoneutralization of CRH significantly decreased and macrophage depletion significantly increased the stimulation of the HPA axis by IL-1 (4.0 microg/day). Administration of high doses of DEX completely abolished the stimulation of the HPA axis by IL-1beta (2.0 microg/day). The present study demonstrates that lower doses of IL-1beta were able to activate the HPA axis when infused i.c.v. compared with i.p. Regarding stimulation of the HPA axis by chronic i.p. infusion of IL-1beta the present study: (1) provides evidence that the CRH system is involved; (2) provides no evidence for a direct stimulatory effect of IL-1beta on the release of B by the adrenal gland which is of sufficient magnitude to resist the stress of chronic i.p. IL-1beta infusion; (3) shows that endogenous macrophage-derived mediators, induced by i.p. IL-1beta infusion, express an overall inhibitory rather than a stimulatory effect on the activity of the HPA axis; (4) demonstrates that exogenous administration of DEX blocks the effect of IL-1beta, which fits well in the concept of an immunoregulatory feedback between IL-1beta and glucocorticoids.
van der Meer
M J
MJ
Department of Medicine, University Hospital Nijmegen, The Netherlands.
Sweep
C G
CG
Pesman
G J
GJ
Tilders
F J
FJ
Hermus
A R
AR
D000315:Adrenalectomy; D000324:Adrenocorticotropic Hormone / Q000097:blood; D000818:Animals; D000906:Antibodies / Q000276:immunology; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000276:immunology; D003907:Dexamethasone / Q000494:pharmacology; D006801:Humans; D007016:Hypophysectomy; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects*; D007274:Injections, Intraperitoneal; D007276:Injections, Intraventricular; D007375:Interleukin-1 / Q000494:pharmacology*; D008264:Macrophages / Q000276:immunology; D010913:Pituitary-Adrenal System / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000494:pharmacology; D012965:Sodium Chloride
D000906:Antibodies; D007375:Interleukin-1; D011994:Recombinant Proteins; D012965:Sodium Chloride; D003907:Dexamethasone; D000324:Adrenocorticotropic Hormone; D003346:Corticotropin-Releasing Hormone; D003345:Corticosterone