Lipopolysaccharide-induced interleukin-8 gene expression in human granulocytes: transcriptional inhibition by interferon-gamma.
We recently showed that lipopolysaccharide (LPS) is a potent inducer of interleukin-8 (IL-8) expression in human polymorphonuclear leucocytes (PMN), at the level of both mRNA and protein, and that interferon-gamma (IFN gamma) inhibits IL-8 mRNA accumulation in stimulated PMN. To further define the molecular basis of the regulation of IL-8 gene expression in PMN, we investigated the effects of LPS and IFN gamma at both the transcriptional and post-transcriptional levels. As determined by Northern blot analysis, new protein synthesis was not required for the induction of IL-8 mRNA expression by LPS. Neither did the half-life of IL-8 mRNA in LPS-treated PMN differ from that observed in untreated cells. However, nuclear run-on analysis revealed that LPS increased the transcription of the IL-8 and IL-1 beta genes and that, in LPS-activated cells, IFN gamma markedly inhibited the rate of IL-8 gene transcription, but not that of IL-1 beta. IFN gamma did not affect IL-8 mRNA stability in LPS-treated PMN, indicating that the cytokine does not regulate LPS-induced IL-8 gene expression through post-transcriptional events. These results provide the first evidence that human granulocytes can actively transcribe the IL-8 gene, and that transcriptional inhibition is the mechanism by which IFN gamma inhibits IL-8 gene expression in PMN.
Cassatella
M A
MA
Department of General Pathology, University of Verona, Italy.
Gasperini
S
S
Calzetti
F
F
McDonald
P P
PP
Trinchieri
G
G
D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects*; D006098:Granulocytes / Q000187:drug effects / Q000276:immunology*; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology*; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000097:blood; D008070:Lipopolysaccharides / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000097:blood; D011994:Recombinant Proteins; D014158:Transcription, Genetic / Q000187:drug effects*
D016209:Interleukin-8; D008070:Lipopolysaccharides; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D011994:Recombinant Proteins; D007371:Interferon-gamma; D003513:Cycloheximide