Endothelial IKK beta signaling is required for monocyte adhesion under laminar flow conditions.

Abstract

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- kappa B family. The serine-threonine kinase, IKK beta, can mediate NF- kappa B activation although several alternative pathways exist. To test whether IKK beta 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 IKK beta (Ad.dnIKK beta) to transduce human umbilical vein endothelial cells (HUVEC) in vitro. We found that dnIKK beta expression effectively blocked NF-kappa B activation as assessed by nuclear translocation of NF-kappa B, I kappa B degradation, and NF-kappa B dependent reporter expression, without affecting activation of the other relevant signaling pathways, SAPK/JNK and p38. Furthermore, overexpression of dnIKK beta in TNF-alpha-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 dnIKK beta-transduced endothelial monolayers were markedly inhibited. We conclude that IKK beta is necessary for the cytokine-induced inflammatory phenotype of human endothelium and endothelial recruitment of human monocytes under flow.