P-selectin antagonism with recombinant P-selectin glycoprotein ligand-1 (rPSGL-1g) inhibits circulating activated platelet binding to neutrophils induced by damaged arterial surfaces

Neutrophil P-selectin glycoprotein ligand-1 (PSGL-1) mediates the initial r olling and adhesion of neutrophils to P-selectin on activated endothelium a nd platelets. Platelet-neutrophil activation and binding occur in the blood of patients with arterial diseases, suggesting that arterial damage leads to these phenomena. We investigated the influence of endothelial surface in tegrity on circulating platelet activation and binding to neutrophils and t he mechanism involved in these interactions. Expression of P-selectin on hu man platelets and their binding to neutrophils was determined by flow cytom etry at baseline after thrombin activation and after exposure for 15 min to intact and damaged arterial surfaces in flow chambers. Expression of plate let P-selectin at baseline and after perfusion over intact endothelium aver aged 13.8 +/- 1.2 and 12.7 +/- 1.8%, respectively, and increased significan tly to 19.7 +/- 1.8% (P < 0.05) after perfusion over damaged arteries. In m ixed neutrophil/ platelet suspensions, the percentage of neutrophils that b ind platelets increased significantly also, from 10.8 +/- 1.6% at baseline to 39.7 +/- 2.9% (P < 0.05) after perfusion over damaged arteries compared with 69.7 +/- 2.5% with thrombin. This binding was completely inhibited by a recombinant soluble PSGL-1 (rPSGL-Ig) and anti-P-selectin and PSGL-1-bloc king monoclonal antibodies. The inhibitory effect of rPSGL-Ig correlated we ll with its binding to platelets (r = 0.98, P < 0.001). Circulating platele ts are activated upon contact with damaged arteries, thereby enhancing thei r adhesive interactions with neutrophils via P-selectin and PSGL-1. Inhibit ion of this binding with rPSGL-Ig may constitute a target in the treatment of inflammatory and thrombotic reactions.