Signaling pathways involved in IL-8-dependent activation of adhesion through Mac-1.
In human neutrophils, IL-8 induces chemotaxis, the respiratory burst, and granule release, and enhances cellular adhesion, a beta(2) integrin-dependent event. IL-8 stimulates neutrophil adhesion to purified fibrinogen in a Mac-1-dependent manner. Mitogen-activated protein kinase (MAPK) activation was detected in human neutrophil lysates after treatment with IL-8 and PMA, but not the activating mAb CBR LFA 1/2. IL-8-stimulated neutrophil adhesion to fibrinogen was blocked 50% by the MAPK/extracellular signal-related kinase-activating enzyme inhibitor PD098059. Adhesion was blocked approximately 75% by inhibition of the phosphatidylinositol-3 kinase (PI3K) pathway with LY294002, supporting that activation of both MAPK and PI3K may play a role in IL-8-dependent inside-out signals that activate Mac-1. Activation of MAPK was inhibited in IL-8-stimulated cells in the presence of PI3K inhibitors LY294002 or wortmannin, supporting a model in which PI3K is upstream of MAPK. IL-8-stimulated neutrophil adhesion was inhibited 50% by bisindolylmaleimide-I, implicating protein kinase C (PKC) in the intracellular signaling from the IL-8R to Mac-1. A 74-kDa molecular mass species was detected by an activation-specific Ab to PKC when cells were stimulated with PMA or IL-8, but not a beta(2)-activating Ab. Inhibition of either MAPK or PKC resulted in partial inhibition of IL-8-stimulated polymorphonuclear neutrophil adhesion, and treatment with both inhibitors simultaneously completely abolished IL-8-stimulated adhesion to ligand. Inhibition of PI3K blocked MAPK activation, but not PKC activation, suggesting a branch point that precedes PI3K activation. These data suggest that both MAPK and PKC are activated in response to IL-8 stimulation, and that these may represent independent pathways for beta(2) integrin activation in neutrophils.
Takami
Mimi
M
Division of Gastroenterology, Department of Internal Medicine, University of Michigan Medical Center and Department of Veterans Affairs Medical Center, Ann Arbor, MI 48109, USA.
Terry
Valeri
V
Petruzzelli
Lilli
L
D002448:Cell Adhesion; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005340:Fibrinogen / Q000378:metabolism; D006801:Humans; D016209:Interleukin-8 / Q000494:pharmacology*; D007700:Kinetics; D020935:MAP Kinase Signaling System; D016177:Macrophage-1 Antigen / Q000502:physiology*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D009504:Neutrophils / Q000187:drug effects / Q000276:immunology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins / Q000032:analysis; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D015398:Signal Transduction
D004791:Enzyme Inhibitors; D005340:Fibrinogen; D016209:Interleukin-8; D016177:Macrophage-1 Antigen; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010750:Phosphoproteins; D011493:Protein Kinase C