A plethora of evidence supports a link between inflammation and atherogenesis. The vasoactive peptide endothelin-1 (ET-1) has both proatherogenic and proinflammatory properties. The CD40-CD154 signaling pathway exhibits a direct influence on atherogenesis. We therefore tested the hypothesis that ET-1 induces CD40 in human vascular smooth muscle cells (SMC). ET-1 concentration-dependently stimulated CD40 protein in SMC. The specific ET-A-receptor antagonist BQ-123 prevented CD40 induction demonstrating receptor specificity of the ET-1 effect. Experiments with PI-1, an inhibitor of the IκB-α-degrading proteasome complex, demonstrated involvement of the transcription factor NF-κB in ET-1-induced CD40 expression. Specific decoy oligodeoxynucleotides with the consensus binding sequence for NF-κB and AP-1 supported a NF-κB-dependent and AP-1-independent induction pathway. Functional relevance of ET-1-induced CD40 expression was demonstrated by an increase in IL-6 secretion after stimulation with CD154 of cells preactivated with ET-1. The data show a link between a proatherogenic vasoactive peptide and cellcell contact mediated inflammatory pathways and may implicate novel therapeutic options for vascular disease.