PROTEASOME INHIBITORS BLOCK VCAM-1 AND ICAM1 GENE-EXPRESSION IN ENDOTHELIAL-CELLS WITHOUT AFFECTING NUCLEAR TRANSLOCATION OF NUCLEAR FACTOR-KAPPA-B

Endothelial cells play a major role in recruiting leukocytes to sites of inflammation. This is accomplished, at least in part, by up-regulat ion of cell surface adhesion molecules, including VCAM-1 and ICAM-1, i n response to cytokines. In this report, we investigated the role of t he proteasome complex in mediating the interleukin (IL)-1 beta inducti on of VCAM-1 and ICAM-1 gene expression in human endothelial cells. We present evidence that a proteasome inhibitor, n-tosyl-Lys-chloromethy lketone and n-tosyl-Phe-chloromethylketone, blocked IL-1 beta inductio n of VCAM-1 and ICAM-1 promoter-driven reporter gene expression in sta bly transfected endothelial cells. These inhibitors also blocked cytok ine induced cell surface expression of VCAM-1 and ICAM-1 by human umbi lical vein endothelial cells. As expected, the protease inhibitors blo cked the activation of nuclear factor (NF)-kappa B in response to IL-1 beta-induced nuclear translocation of NF-kappa B. The effects of norL EU were specific because it did not inhibit the IL-1 beta induction of plasminogen activator inhibitor type 1 gene expression. This study de monstrates that inhibition of the proteolytic activity of the proteaso me blocks IL-1 beta induction of VCAM-1 and ICAM-1 gene expression in human endothelial cells.