Down-regulation of endothelial TLR4 signalling after apo A-I gene transfer contributes to improved survival in an experimental model of lipopolysaccharide-induced inflammation
During the inflammatory response, endothelial cells (EC) transiently upregulate a set of genes encoding, among others, cell adhesion molecules and chemotactic cytokines that together mediate the interaction of the endothelium with cells of the immune system. Gene upregulation is mediated predominantly at the transcriptional level and in many cases involves the transcription factor nuclear factor (NF) kappa B. We have tested the concept of inhibiting the inflammatory response by overexpression of a specific inhibitor of NF-kappaB, I kappa B alpha. A recombinant adenovirus expressing I kappa B alpha was constructed (rAd.I kappa B alpha) and used to infect EC of human and porcine origin. Ectopic expression of IkappaBalpha resulted in marked, and in some cases complete, reduction of the expression of several markers of EC activation, including vascular cell adhesion molecule 1, interleukins 1, 6, 8, and tissue factor. Overexpressed I kappa B alpha inhibited NF-kappa B specifically since (a) in electrophoretic mobility shift assay, NF-kappa B but not AP-1 binding activity was inhibited, and (b) von Willebrand factor and prostacyclin secretion that occur independently of NF-kappa B, remained unaffected. Functional studies of leukocyte adhesion demonstrated strong inhibition of HL-60 adhesion to I kappa B alpha-expressing EC. These findings suggest that NF-kappa B could be an attractive target for therapeutic intervention in a variety of inflammatory diseases, including xenograft rejection.