Endothelial IKKβ signaling is required for monocyte adhesion under laminar flow conditions

Endothelial activation induces expression of pro-inflammatory molecules that are thought to play an important role in atherogenesis through enhanced vascular monocyte recruitment. Many pro-inflammatory endothelial signals are transcriptionally regulated by members of the NF-κB family. The serine-threonine kinase, IKKβ, can mediate NF-κB activation although several alternative pathways exist. To test whether IKKβ is necessary for cytokine activation of human vascular endothelium and endothelial recruitment of human monocytes under laminar flow, we constructed a recombinant adenoviral vector carrying a dominant negative mutant of IKKβ (Ad.dnIKKβ) to transduce human umbilical vein endothelial cells (HUVEC) in vitro. We found that dnIKKβ expression effectively blocked NF-κB activation as assessed by nuclear translocation of NF-κB, IκB degradation, and NF-κB dependent reporter expression, without affecting activation of the other relevant signaling pathways, SAPK/JNK and p38. Furthermore, overexpression of dnIKKβ in TNF-α-stimulated HUVEC blocked induction of the surface adhesion molecules E-selectin, ICAM-1, and VCAM-1. Under simulated physiologic flow conditions, both firm adhesion and rolling of human peripheral monocytes on dnIKKβ-transduced endothelial monolayers were markedly inhibited. We conclude that IKKβ is necessary for the cytokine-induced inflammatory phenotype of human endothelium and endothelial recruitment of human monocytes under flow.