Granulocyte-macrophage colony-stimulating factor increases 5-lipoxygenase gene transcription and protein expression in human neutrophils.
The complex process of neutrophil activation and accumulation is orchestrated by a cascade of cytokines and bioactive lipids produced at the site of inflammation. Neutrophils are a rich source of the potent inflammatory lipid leukotriene B4(LTB4). Granulocyte-macrophage colony-stimulating factor (GM-CSF) can activate neutrophils for an exponential increase in LTB4 production in response to a number of subsequent stimuli. In this report, we examined the temporal regulation, by GM-CSF, of the gene and protein expression of 5-lipoxygenase (5-LOX), a key enzyme of the LTB4 production pathway. Human neutrophils were exposed to 10 ng/mL of GM-CSF for various periods of time and 5-LOX mRNA was measured by Northern blot analysis. We observed no change in 5-LOX mRNA at early time points (0.25 to 3 hours); however, by 18 hours we observed a significant augmentation of 5-LOX-specific message (4.3 +/- 1.7-fold increase; n = 6). Nuclear transcription assays indicated that the rate of 5-LOX gene transcription was augmented threefold in neutrophils incubated with GM-CSF, whereas the half-life of the message was not markedly changed. Parallel experiments indicated that the levels of 5-LOX protein were also increased by GM-CSF. The augmentation was observed within 30 minutes after stimulation and was maximal (5.23 +/- 2.6; n = 4) at 18 hours. Incubation of GM-CSF-stimulated neutrophils with protein synthesis inhibitors resulted in a time-dependent impairment of their ability to produce LTB4, with no inhibition seen during the first hours, a 75% decrease seen by 12 hours, and greater than 95% inhibition seen at 18 hours. Collectively, our data imply that GM-CSF can regulate LTB4 production by two distinct mechanisms: a short-term increase that is not related to increased 5-LOX mRNA expression and is independent of protein synthesis, and a sustained increase in LTB4 production that is associated with the transcriptional activation of the 5-LOX gene, increase in 5-LOX mRNA levels, and dependence on protein synthesis. Such transcriptional modulation of 5-LOX enzyme expression may provide new approaches for therapeutic intervention in protracted inflammatory conditions.
Stanková
J
J
Immunology Division, Faculty of Medicine, University of Sherbrooke, Quebec, Canada.
Rola-Pleszczynski
M
M
Dubois
C M
CM
D001094:Arachidonate 5-Lipoxygenase / Q000096:biosynthesis* / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D009504:Neutrophils / Q000187:drug effects / Q000201:enzymology*; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic / Q000187:drug effects
D012333:RNA, Messenger; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D001094:Arachidonate 5-Lipoxygenase