Selective inhibition of inhibitory kappa B kinase-β abrogates induction of nitric oxide synthase in lipopolysaccharide-stimulated rat aortic smooth muscle cells

1 In this study, we utilised a number of adenoviral constructs in order to examine the role of intermediates of the NF-kB pathway in the regulation of inducible nitric oxide synthase ( iNOS) induction in rat aortic smooth muscle cells ( RASMCs). 2 Lipopolysaccharide (LPS) stimulated a significant increase in iNOS induction and NF-kappa B DNA binding. These parameters were substantially reduced by overexpression of a wild-type I kappa-B alpha adenoviral construct ( Ad. Ik-B alpha), confirming a role for NF-kappa B in iNOS induction. 3 Infection with a dominant-negative IKK alpha adenoviral construct (Ad.IKK alpha(+/-)) did not significantly affect iNOS induction, NF-kappa B DNA binding or Ik-Ba loss. Infection of RASMCs with adenovirus encoding a dominant-negative IKK beta (Ad.IKK beta(+/-)) essentially abolished iNOS induction and activation of the NF-kB pathway. 4 Pretreatment of RASMCs with a novel specific inhibitor of IKK beta, SC-514, significantly reduced iNOS induction, NF-kB DNA binding and I-kappa B alpha loss in a concentration-dependent manner. 5 In both RASMCs and human umbilical vein endothelial cells ( HUVECs), infection with Ad.IKK beta(+/-) also inhibited COX- 2 expression in response to LPS. However, Ad.IKK alpha(+/-) was again without effect. 6 These data suggest that IKKb plays a predominant, selective role in the regulation of NF-kappa B dependent induction of iNOS in RASMCs.