Background—Platelet/endothelium interaction plays an important role in the pathophysiology of inflammation and atherosclerosis. The role of platelets for monocyte chemotactic protein-1 (MCP-1) secretion and surface expression of intercellular adhesion molecule-1 (ICAM-1) on endothelial cells has been assessed.

Methods and Results—Monolayers of human umbilical vein endothelial cells were incubated with nonstimulated or ADP-activated platelets for 6 hours, and secretion of MCP-1 and surface expression of ICAM-1 were determined by ELISA and flow cytometry, respectively. In the presence of ADP-activated platelets, both MCP-1 secretion and ICAM-1 surface expression were significantly increased compared with nonstimulated platelets (P<0.02). Activation of the transcription factor nuclear factor-κB (NF-κB) determined by electrophoretic mobility shift assay and κB-dependent transcriptional activity was enhanced in the presence of activated platelets. In addition, ADP-activated platelets induced MCP-1 and ICAM-1 promoter–dependent transcription. Liposomal transfection of a double-stranded κB phosphorothioate oligonucleotide, but not of the mutated form, inhibited MCP-1 secretion and surface expression of ICAM-1 on activated endothelium (P<0.05).

Conclusions—The present study indicates that activated platelets modulate chemotactic (MCP-1) and adhesive (ICAM-1) properties of endothelial cells via an NF-κB–dependent mechanism. Platelet-induced activation of the NF-κB system might contribute to early inflammatory events in atherogenesis.