Signaling Pathways Involved in IL-8-Dependent Activation of Adhesion Through Mac-1

Abstract

In human neutrophils, IL-8 induces chemotaxis, the respiratory burst, and granule release, and enhances cellular adhesion, a β2 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 ∼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 β2-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 β2 integrin activation in neutrophils.

The immune system and cardiac repair

“…IL-8 induces the neutrophil respiratory burst and granule release, and enhances cellular adhesion, a β2 integrin-dependent event. IL-8-induced β2 integrin activation may be mediated through Mitogen-activated protein kinase (MAPK) and Protein Kinase C (PKC) signaling [104]. It appears that neutrophils may need to sample immobilized IL-8 molecules presented by the vessel wall before forming a sufficient number of high avidity β2 integrin bonds for firm adhesion [105].…”

“…It appears that neutrophils may need to sample immobilized IL-8 molecules presented by the vessel wall before forming a sufficient number of high avidity β2 integrin bonds for firm adhesion [105]. In addition, IL-8 may also have effects beyond its neutrophil chemotactic properties [104]. IL-8 neutralization significantly reduces the degree of necrosis in a rabbit model of myocardial ischemia-reperfusion injury without affecting neutrophil infiltration [106].…”

Granulocyte-Macrophage Colony-Stimulating Factor Is a Chemoattractant Cytokine for Human Neutrophils: Involvement of the Ribosomal p70 S6 Kinase Signaling Pathway

“…This could be potentially important, considering the evidence suggesting that the signaling pathways governing locomotion vary depending on the stimulus. Previous studies (53)(54)(55)(56)(57) showed that FMLP and C5a activate chemotaxis through p38 MAPK , while IL-8 uses the PI3K pathway. IL-8 activates ERK2 (p42 MAPK ), but this is apparently unrelated to its effect on chemotaxis.…”

G31P, an Antagonist against CXC Chemokine Receptors 1 and 2, Inhibits Growth of Human Prostate Cancer Cells in Nude Mice

“…PC-3 cells were grown and treated with or without G31P (up to 100 ng/ml) in a serum-free medium for 24 h. Then, the cells were seeded at 3 × 10 5 cells/well in the pre-coated plates, incubated for 1 h at 37°C, and gently washed three times with PBS. The remaining adhered cells were enumerated using the same cell counting reagent as above, and the absorbance rate at 450 nm was determined with a 96-well plate reader (Takami et al 2002).…”