Neurointermediate Pituitary Lobe Cells Synthesize and Release Interleukin-6 in Vitro: Effects of Lipopolysaccharide and Interleukin- 1-beta

Spangelo, B. L. and Deholl, P. D. and Kalabay, László and Bond, B. R. and Arnaud, P. (1994) Neurointermediate Pituitary Lobe Cells Synthesize and Release Interleukin-6 in Vitro: Effects of Lipopolysaccharide and Interleukin- 1-beta. ENDOCRINOLOGY, 135 (2). pp. 556-563. ISSN 0013-7227

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The cytokine interleukin-6 (IL-6) is produced by a variety of cells, including macrophages, T-cells, and B-cells. Recent studies have confirmed a neuroendocrine role for IL-6 in the regulation of anterior pituitary (AP) hormone release. Because the neurointermediate pituitary lobe (NIL) may modulate AP hormone release, we investigated the production of IL-6 by NIL cells in, vitro. NIL tissue removed from pituitary glands of male Long-Evans rats was enzymatically and mechanically dispersed, and the cells were subsequently cultured in 96-well tissue culture plates for 4-6 days in 10% serum-containing RPMI-1640. Test incubations were performed in serum-free RPMI-1640, and IL-6 concentrations were determined using the 7TD1 cell bioassay. Preliminary studies revealed a cell-dependent release of IL-6: increasing the number of NIL cells per well from 6.25 to 50 x 10(3) revealed detectable basal release of IL-6 between 25-50 x 10(3) cells/well. The endotoxin lipopolysaccharide (LPS; 100 ng/ml) and IL-1 beta (100 ng/ml) stimulated IL-6 release at 25 and 50 x 10(3) cells/well. Subsequent studies used a cell density of 50 x 10(3) cells/well and demonstrated time-dependent 3- to 6-fold inductions of IL-6 release by 100 ng/ml IL-1 beta and LPS. Concentration-response studies revealed maximal stimulation of IL-6 release by 1 ng/ml and a minimally effective concentration of 1 pg/ml for both IL-1 beta and LPS. Treatment of NIL cells with 1-10 mM (Bu)(2)cAMP increased IL-6 release by 7- to 14-fold. Endotoxin and IL-1 beta also enhanced the accumulation of IL-6 messenger RNA in these cells. Vasopressin and oxytocin (1 mu M) inhibited LPS and IL-1 beta stimulation of IL-6 release from NIL cells, but did not inhibit IL-6 release from AP cells. Immunofluorescent dual labeling of NIL cells for flow cytometry revealed that greater than 95% of the cells did not stain for CD11b/c (common epitope found on monocytes, granulocytes, and macrophages) or CD45 (leukocyte common antigen). These results demonstrate for the first time the synthesis and release of IL-6 from cultured NIL cells. Agents that enhance IL-6 release [LPS, IL-1 beta, and (Bu)(2)cAMP] from other cell types also increase IL-6 release from NIL cells. Vasopressin and oxytocin inhibition of IL-6 release suggests a role for these neuropeptides in feedback inhibition in vivo. Finally, the release of IL-6 is unlikely to be due to leukocytes in the NIL cultures, but is probably caused by either pituicytes (modified astroglial cells in the neural lobe) or melanotrophs of the intermediate lobe.

Item Type: Article
Subjects: R Medicine / orvostudomány > RC Internal medicine / belgyógyászat
Depositing User: MTMT SWORD
Date Deposited: 08 Jun 2020 13:06
Last Modified: 08 Jun 2020 13:06

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