SELECTIVE-INHIBITION OF TUMOR NECROSIS FACTOR-INDUCED VASCULAR CELL-ADHESION MOLECULE-1 GENE-EXPRESSION BY A NOVEL FLAVONOID - LACK OF EFFECT ON TRANSCRIPTION FACTOR NF-KAPPA-B

In the present studies, we examined the effect of flavonoids on the en dothelial cell expression of adhesion molecules, an early step in infl ammation and atherogenesis. Addition of tumor necrosis factor-alpha (T NF) to human aortic endothelial cells (HAECs) led to the induction of vascular cell adhesion molecule-1 (VCAM-1) expression and enhancement in expression of intercellular adhesion molecule-1 (ICAM-1). A flavono id, 2-(3-amino-phenyl)-8-methoxy-chromene-4-one (PD 098063), markedly inhibited TNF-induced VCAM-1 cell-surface expression in a concentratio n;dependent fashion with half-maximal inhibition at 19 mu mol/L but ha d no effect on ICAM-1 expression. Another structurally distinct flavon oid, 2-phenyl-chromene-4-one, similarly selectively decreased VCAM-1 e xpression. The inhibition in cell-surface expression of VCAM-1 by PD 0 98063 correlated with decreases in steady-state mRNA levels, but there was no effect on ICAM-1 mRNA levels. The decrease in VCAM-1 mRNA leve ls was not due to changes in mRNA stability but rather resulted from a reduction in the rate of transcription of the gene. However, electrop horetic mobility shift assays using nuclear extracts from TNF-induced HAECs treated with PD 098063 failed to show a decrease in the activati on of NF-kappa B, indicating that inhibition of activation of this tra nscription factor may not be its mode of action. Similarly, PD 098063 did not affect chloramphenicol acetyltransferase reporter gene activit y in TNF-inducible minimal VCAM-1 promoter constructs containing two N F-kappa B sites, suggesting that the compound does not affect the tran sactivation driven by these sites. We conclude that this compound sele ctively blocks agonist-induced VCAM-1 protein and gene expression in H AECs by NF-kappa B-independent mechanism(s).