THE NATURAL PRODUCT HYMENIALDISINE INHIBITS INTERLEUKIN-8 PRODUCTION IN U937 CELLS BY INHIBITION OF NUCLEAR FACTOR-KAPPA-B

The nuclear factor-kappa B (NF-kappa B) family of transcription factor s have been implicated in the inducible expression of genes involved i n inflammatory and immune responses. As such, a specific inhibitor of NF-kappa B would be a useful therapeutic agent in a variety of inflamm atory disorders. The marine natural product hymenialdisine was evaluat ed as an inhibitor of NF-kappa B in U937 cells. U937 cells were transf ected with either a luciferase reporter plasmid containing the human i mmunodeficiency virus long terminal repeat or the interleukin-8 (IL-8) core promoter, both of which are activated by NF-kappa B. Hymenialdis ine caused a concentration-dependent decrease in luciferase production from both reporters when the cells were stimulated with tumor necrosi s factor-alpha, lipopolysaccharide or phorbol myristate acetate. An el ectrophoretic mobility shift assay confirmed its activity by inhibitin g DNA binding of NF-kappa B. Hymenialdisine was shown to be a selectiv e inhibitor of NF-kappa B in that it had no effect on the binding of o ther transcription factors to their DNA concensus motifs; these includ ed activator protein-1, CCAAT/enhancer binding protein and Sp1. Functi onal studies showed hymenialdisine to be an inhibitor of IL-8 producti on and IL-8 mRNA formation in the U937 cell. Investigation into the me chanism of action of hymenialdisine showed that it was not due to inhi bition of protein kinase C because the selective protein kinase G inhi bitor RO 32-0432 was inactive against tumor necrosis factor-alpha-stim ulated luciferase and IL-8 production. The compound also had no effect on I kappa B beta or I kappa B beta phosphorylation and degradation. Thus, hymenialdisine is a potent inhibitor of NF-kappa B and IL-8 prod uction in U937 cells.