Cytokine regulation of the interleukin-1 receptor antagonist protein in U937 cells.
A naturally occurring receptor-level antagonist of interleukin-1 (IRAP or IL-1 ra) has recently been cloned. To determine what stimuli might regulate this inhibitor, cytokines were tested for their effects on the steady-state level of IRAP mRNA in phorbol ester-differentiated U937 cells. The cytokines tested fell into one of three groups: (a) inducers: granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-4, (b) weak inducers (< 2-fold stimulation): [IL-1 alpha, IL-1 beta, and transforming growth factor-beta (TGF-beta)] and (c) cytokines with no effect: (IL-2, platelet-derived growth factor, acidic fibroblast growth factor, basic fibroblast growth factor, epidermal growth factor, granulocyte colony-stimulating factor, IL-3, IL-5, IL-6, interferon-gamma, multi-colony stimulating factor, tumor necrosis factor-alpha and IRAP itself. One hundred U/ml of either GM-CSF or IL-4 was the dose inducing peak IRAP mRNA expression; that peak expression occurred 12 h after addition of cytokine. GM-CSF induced a 34 +/- 15-fold increase in IRAP mRNA, and IL-4 induced a 15 +/- 6-fold increase. In the same RNA samples, GM-CSF increased IL-1 beta mRNA 5.9 +/- 1.7-fold, but IL-4 decreased IL-1 beta mRNA to half that of control levels (0.45 +/- 0.17). Thus, a single stimulus (IL-4) decreased the expression of an agonist (IL-1) while it increased the expression of an antagonist (IRAP). When U937 cells were treated with both IL-4 and GM-CSF, the level of IRAP mRNA induced was additive, suggesting that the cytokines acted differently to increase IRAP mRNA levels. The level of IL-1 mRNA in cells treated with both IL-4 and GM-CSF was intermediate. Dexamethasone and cycloheximide inhibited all mRNA increases and did not reverse IL-4-induced decreases in IL-1 mRNA. These studies have identified two cytokines which induce IRAP in the monocytic cells studied, and have partially characterized the differential regulation of IL-1 and its antagonist, IRAP.
Berger
A E
AE
Cell Biology Unit, Upjohn Company, Kalamazoo, MI 49008.
Carter
D B
DB
Hankey
S O
SO
McEwan
R N
RN
D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D016207:Cytokines / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006801:Humans; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000096:biosynthesis* / Q000235:genetics; D015847:Interleukin-4 / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D012795:Sialoglycoproteins / Q000096:biosynthesis* / Q000235:genetics
D016207:Cytokines; C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D012333:RNA, Messenger; D012795:Sialoglycoproteins; D015847:Interleukin-4; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D003513:Cycloheximide