Fluid shear stress activation of IκB kinase is integrin-dependent

Vascular endothelial cells (ECs), forming a boundary between the circulating blood and the vessel wall, are constantly subjected to fluid shear stress due to blood flow. The aim of this study was to determine the role of the recently identified I kappa B kinases (IKKs) in shear stress activation of NF-kappa B and to elucidate the upstream signaling mechanism that mediates IKK activation. Our results demonstrate that IKKs in ECs are activated by shear stress in a rapid and transient manner. This IKK activation is followed by I kappa B degradation and NF-kappa B translocation into the nucleus. Transfection of plasmids encoding catalytic inactive mutants of IKKs, i.e. hemagglutinin (HA)-IKK alpha(K44M) and HA-IKK beta(K44A), inhibits shear stress-induced NF-kappa B translocation, In addition, constructs encoding antisense IKKs, i.e. HA-IKK alpha(AS) and HA-IKK beta(AS), attenuate shear stress induction of a promoter driven by the kappa B enhancer element. Preincubation of the EC monolayer with a monoclonal anti-alpha(v)beta(3) integrin antibody (clone LM609) attenuates shear stress induction of IKK. Inhibition of tyrosine kinases by genistein causes a similar down-regulating effect. These results suggest that the integrin-mediated signaling pathway regulates NP-kappa B through IKKs in ECs in response to shear stress.