Microparticles from various cells are generated during inflammation. Platelet-derived microparticles (PMPs) harbor receptors that are not genuinely expressed by neutrophils. We tested whether or not functional glycoprotein IIb/IIIa (GPIIb/IIIa) receptors can be acquired by neutrophils via PMPs and whether these receptors participate in pro-inflammatory signaling. Surface expression was analyzed by flow cytometry and confocal microscopy. NF-κB activation was analyzed by Western blot experiments, electrophoretic mobility shift assays, and reverse transcription-PCR. Cell adhesion and spreading were estimated by myeloperoxidase assay and light microscopy. We found that PMPs transfer GPIIb/IIIa receptors to isolated and whole blood neutrophils via PMPs. We used specific antibodies in granulocyte macrophage colony-stimulating factor-treated neutrophils and observed that acquired GPIIb/IIIa receptors co-localized with β2-integrins and cooperated in NF-κB activation. We show that Src and Syk non-receptor tyrosine kinases, as well as the actin cytoskeleton, control NF-κB activation. In contrast to NF-κB, acquisition of GPIIb/IIIa receptors was not necessary to induce adhesion to fibronectin or phosphatidylinositol 3-kinase/Akt signaling. When granulocyte macrophage colony-stimulating factor-stimulated neutrophils were incubated on fibronectin, strong NF-κB activation was observed, but only after loading with PMPs. Blocking either β2-integrins or GPIIb/IIIa receptors abrogated this effect. Therapeutic GPIIb/IIIa inhibitors were similarly effective. The compounds also inhibited NF-κB-dependent tumor necrosis factor-α mRNA up-regulation. The data implicate GPIIb/IIIa receptors as new therapeutic targets in neutrophil-induced inflammation.
Granulocyte-macrophage colony-stimulating factor is a stimulant of platelet-activating factor and superoxide anion generation by human neutrophils.
