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-κB

Abstract

In the present studies, we examined the effect of flavonoids on the endothelial cell expression of adhesion molecules, an early step in inflammation and atherogenesis. Addition of tumor necrosis factor-α (TNF) 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 flavonoid, 2-(3-amino-phenyl)-8-methoxy-chromene-4-one (PD 098063), markedly inhibited TNF-induced VCAM-1 cell-surface expression in a concentration-dependent fashion with half-maximal inhibition at 19 μmol/L but had no effect on ICAM-1 expression. Another structurally distinct flavonoid, 2-phenyl-chromene-4-one, similarly selectively decreased VCAM-1 expression. The inhibition in cell-surface expression of VCAM-1 by PD 098063 correlated with decreases in steady-state mRNA levels, but there was no effect on ICAM-1 mRNA levels. The decrease in VCAM-1 mRNA levels was not due to changes in mRNA stability but rather resulted from a reduction in the rate of transcription of the gene. However, electrophoretic mobility shift assays using nuclear extracts from TNF-induced HAECs treated with PD 098063 failed to show a decrease in the activation of NF-κB, indicating that inhibition of activation of this transcription factor may not be its mode of action. Similarly, PD 098063 did not affect chloramphenicol acetyltransferase reporter gene activity in TNF-inducible minimal VCAM-1 promoter constructs containing two NF-κB sites, suggesting that the compound does not affect the transactivation driven by these sites. We conclude that this compound selectively blocks agonist-induced VCAM-1 protein and gene expression in HAECs by NF-κB-independent mechanicm(s).