IL-1 beta production in cultured human monocytes is regulated at multiple levels.
Cultured human monocytes and tissue macrophages exhibit a marked decrease in LPS-stimulated IL-1 production. Preincubation of monocytes in 100 U/ml IFN-gamma or in 0.25 microgram/ml cycloheximide (Cx) leads to a partial maintenance of the ability to produce IL-1 in response to subsequent stimulation with LPS, whereas preincubation in both reagents leads to a near complete maintenance of this response. These studies were performed to determine the mechanisms of these alterations in regulation of IL-1 production in cultured monocytes. In comparison to LPS-induced fresh monocytes, cells preincubated in medium for 1 day, then stimulated for 24 h with 100 ng/ml LPS, exhibited a 50% or more decrease in steady-state IL-1 beta mRNA levels. This reduction was accompanied by a four- to fivefold decrease in relative transcriptional rate, as determined by the nuclear run-on technique. The medium-aged cells also displayed greatly decreased IL-1 beta production with deficient secretion. Monocytes preincubated in IFN-gamma for 1 day before LPS stimulation exhibited a variable maintenance in IL-1 beta production, secondary both to prolonged duration of transcription and to increased IL-1 beta mRNA stability. Monocytes were preincubated for 1 day in Cx alone or in both IFN-gamma and cycloheximide, then these substances were washed out before a subsequent 24-h culture in LPS. Cx preincubation led to increases in both the peak and duration of transcription as well as to enhanced secretion of IL-1 beta protein. Monocytes preincubated in both IFN-gamma and Cx exhibited increased IL-1 beta mRNA levels due to both enhanced transcription and mRNA stability; more IL-1 beta protein secretion also was present in these cells. In summary, IFN-gamma and Cx may maintain LPS-induced IL-1 beta production in cultured human monocytes through multiple mechanisms. These alterations in regulation of IL-1 beta production during monocyte differentiation may be relevant to tissue macrophages where impaired IL-1 production may be present.
Arend
W P
WP
Division of Rheumatology, University of Colorado Health Sciences Center, Denver 80262.
Gordon
D F
DF
Wood
W M
WM
Janson
R W
RW
Joslin
F G
FG
Jameel
S
S
D001798:Blood Proteins / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics; D015152:Blotting, Northern; D002474:Cell-Free System; D002478:Cells, Cultured; D006801:Humans; D007375:Interleukin-1 / Q000032:analysis / Q000096:biosynthesis* / Q000235:genetics; D009000:Monocytes / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012313:RNA / Q000302:isolation & purification; D012333:RNA, Messenger / Q000378:metabolism; D014158:Transcription, Genetic
D001798:Blood Proteins; D007375:Interleukin-1; D012333:RNA, Messenger; D012313:RNA