Interleukin-1 stimulates interleukin-6 release from rat anterior pituitary cells in vitro.
We have reported previously that anterior pituitary cells released interleukin-6 (IL-6) and that this release was stimulated by lipopolysaccharide (LPS), phorbol myristate acetate (PMA), or agents that increased intracellular cAMP concentrations. We now report that IL-1 stimulates IL-6 release from anterior pituitary cells in vitro. IL-1 alpha and IL-1 beta (0.04-25 ng/ml) significantly increased IL-6 release 3- to 4-fold in a concentration-related manner during 6-h incubations; however, there was no change in extracellular or intracellular cAMP concentrations. IL-1 alpha and IL-1 beta (10 ng/ml), vasoactive intestinal peptide (VIP, 500 nM), prostaglandin E2 (PGE2, 1 microM), and LPS (1 ng/ml) stimulated IL-6 release to a similar degree. In the presence of VIP and PGE2, IL-1 alpha and IL-1 beta increased IL-6 release without any apparent further change in extracellular or intracellular cAMP. Conversely, LPS did not increase cAMP concentrations, and IL-1 did not significantly increase IL-6 release in the presence of LPS. The preexposure of anterior pituitary cells to 1 microM PMA caused the apparent down-regulation of protein kinase C activity because 100 nM PMA was no longer effective to stimulate IL-6 release; however, the ability of IL-1 alpha, IL-1 beta, PGE2, or LPS to stimulate IL-6 release was not altered. In addition, IL-1 alpha and IL-1 beta stimulated IL-6 release in the presence of maximally stimulative concentrations of PMA. The synthetic glucocorticoid dexamethasone (10 nM) significantly inhibited IL-6 release induced by IL-1 alpha, IL-1 beta, or LPS. The separation of anterior pituitary cells on unit gravity BSA gradients generated fractions of IL-6-producing cells that were inducible by LPS and IL-1 beta and separate from the PRL-, ACTH-, GH-, or LH-producing cell fractions. These data suggest that IL-1 stimulates IL-6 release from a subpopulation of anterior pituitary cells via a glucocorticoid-sensitive and non-cAMP-mediated pathway that is different from those pathways used by VIP, PGE2, and PMA.
Spangelo
B L
BL
Department of Medicine, University of Virginia Health Sciences Center, Charlottesville 22908.
Judd
A M
AM
Isakson
P C
PC
MacLeod
R M
RM
D000818:Animals; D002469:Cell Separation / Q000379:methods; D003907:Dexamethasone / Q000494:pharmacology; D015232:Dinoprostone / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology
D007375:Interleukin-1; D015850:Interleukin-6; D008070:Lipopolysaccharides; D014660:Vasoactive Intestinal Peptide; D003907:Dexamethasone; D015232:Dinoprostone; D013755:Tetradecanoylphorbol Acetate