Transient Platelet Interaction Induces MCP-1 Production by Endothelial Cells via IκB Kinase Complex Activation

Activated platelets alter endothelial chemotactic and adhesive properties. Transient interaction of α-thrombin-activated platelets with endothelial cells is sufficient to induce secretion of the NF-KB-regulated chemokine MCP-1. To evaluate upstream signaling events in platelet-induced NF-KB activation, we compared the effect of platelets, IL-1β or TNF-a on IKB kinase (IKK) complex activation and IKB phosphorylation/proteolysis. Kinase assays demonstrated that platelets induced a slow increase in IKK activity over 30 min, which was similar, but not identical, to IL-1β, whereas TNF-a elicited a rapid induction of IKK. Differential effects were also found on IκB-α/∈ degradation, while IKK levels were unaffected. Furthermore, overexpression of kinase-inactive IKK-β K A , as well as NIK K A , inhibited platelet- or IL-1β-induced κB-, MCP-1- or VCAM-1-dependent transcription. Using adeno-associated virus particles for cell transduction, we found that IKK-β K A substantially reduced stimulus-induced MCP-1 secretion. Platelet-induced signaling and resulting endothelial gene expression may play a role in early atherogenesis as well as plaque progression/destabilization.