Soluble E-selectin acts in synergy with platelet-activating factor to activate neutrophil beta 2-integrins. Role of tyrosine kinases and Ca2+ mobilization.
Selectins play a critical role in neutrophil recruitment to sites of inflammation, in tethering and rolling of neutrophils on vascular endothelium, as well as triggering beta(2)-integrin-mediated adhesion. We have previously demonstrated potential pro-inflammatory effects of soluble E-selectin upon neutrophil effector functions, using a soluble recombinant molecule (E-zz), which increased beta(2)-integrin-mediated adhesion, decreased beta(2)-integrin-dependent migration, and triggered reactive oxygen species generation and release. In this study, we have examined the intracellular signals following neutrophil activation by soluble E-selectin. We show that exposure of neutrophils to E-selectin and platelet-activating factor (PAF) in combination induced a synergistic effect upon beta(2)-integrin-mediated adhesion. Although soluble E-selectin did not induce Ca(2+) mobilization in neutrophils by itself, elevation of intracellular Ca(2+) was specifically prolonged in response to PAF but not leukotriene B(4) or N-formyl-Met-Leu-Phe. The prolonged Ca(2+) mobilization observed in the presence of E-selectin was dependent on Ca(2+) influx from intracellular stores rather than influx of extracellular Ca(2+) through SKF 96365-sensitive channels. The specific alteration of Ca(2+) mobilization reported here appears not to have a role in the synergistic effects of E-selectin and PAF upon neutrophil O(2) release but may be involved in augmentation of beta(2)-integrin-mediated adhesion.
Ruchaud-Sparagano
M H
MH
Rayne Laboratory, Respiratory Medicine Unit, University of Edinburgh Medical School, Edinburgh EH8 9AG, United Kingdom. mhs@srv1.med.ed.ac.uk
Walker
T R
TR
Rossi
A G
AG
Haslett
C
C
Dransfield
I
I
D018821:CD18 Antigens / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002448:Cell Adhesion / Q000187:drug effects / Q000235:genetics; D019040:E-Selectin / Q000235:genetics / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D018375:Neutrophil Activation / Q000187:drug effects*; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D010972:Platelet Activating Factor / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects; D013481:Superoxides / Q000378:metabolism
D018821:CD18 Antigens; D019040:E-Selectin; D010972:Platelet Activating Factor; D013481:Superoxides; D019000:Phosphotyrosine; D002118:Calcium