Cytokine-specific activation of distinct mitogen-activated protein kinase subtype cascades in human neutrophils stimulated by granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, and tumornecrosis factor-alpha

To clarify the differences of the signaling pathways used by granulocyte co lony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor-a (TNF), we investigated activat ion of mitogen-activated protein kinase (MAPK) subtype cascades in human ne utrophils stimulated by these cytokines, G-CSF exclusively tyrosine-phospho rylated extracellular signal-regulated kinase (ERK), GM-CSF tyrosine-phosph orylated ERK strongly and p38 MAPK weakly, whereas TNF tyrosinephosphorylat ed p38 MAPK strongly and ERK weakly. Consistent with these findings, MEK, a n upstream kinase of ERK, was phosphorylated by G-CSF, GM-CSF, and TNF, whe reas MKK3/MKK6, an upstream kinase of p38 MAPK, was phosphorylated by GM-CS F and TNF, but not by G-CSF. The potency of these cytokines to phosphorylat e ERK and MEK was GM-CSF > G-CSF > TNF, whereas that to phosphorylate p38 M APK and MKK3/MKK6 was TNF > GM-CSF. C-Jun amino-terminal kinase (JNK) was n ot tyrosine-phosphorylated by any cytokine despite the existence of JNK pro teins in human neutrophils, whereas it was tyrosine-phosphorylated by TNF i n undifferentiated and all-trans retinoic acid-differentiated HL-60 cells. Increased phosphorylation of ERK or p38 MAPK was detected within 1 to 5 min utes after stimulation with each cytokine and was dependent on the concentr ations of cytokines used. MEK inhibitor (PD98059) reduced tyrosine phosphor ylation of ERK, but not p38 MAPK, induced by G-CSF, GM-CSF, or TNF, GM-CSF- or TNF-induced superoxide (O-2(-)) release was inhibited by p38 MAPK inhib itor (SB203580) in a dose-dependent manner, suggesting the possible involve ment of p38 MAPK in GM-CSF- or TNF- induced O-2(-) release. The results ind icate that G-CSF, GMCSF, and TNF activate the overlapping but distinct MAPK subtype cascades in human neutrophils and suggest that the differential ac tivation of ERK and p38 MAPK cascades may explain the differences of the ef fects of these cytokines on human neutrophil functions. (C) 1999 by The Ame rican Society of Hematology.