Suppression of tumor necrosis factor-activated nuclear transcription factor-κB, activator protein-1, c-Jun N-terminal kinase, and apoptosis by β-lapachone

Abstract

β-Lapachone, the product of a tree from South America, is known to exhibit various pharmacologic properties, the mechanisms of which are poorly understood. In the present report, we examined the effect of β-lapachone on the tumor necrosis factor (TNF)-induced activation of the nuclear transcription factors NF-κB and activator protein-1 (AP-1) in human myeloid U937 cells. TNF-induced NF-κB activation, p65 translocation, IκBα degradation, and NF-κB-dependent reporter gene expression were inhibited in cells pretreated with β-lapachone. Direct treatment of the p50-p65 heterodimer of NF-κB with β-lapachone had no effect on its ability to bind to the DNA. Besides myeloid cells, β-lapachone was also inhibitory in T-cells and epithelial cells. β-Lapachone also suppressed the activation of NF-κB by lipopolysaccharide, okadaic acid, and ceramide but had no significant effect on activation by H 2O 2 or phorbol myristate acetate, indicating that its action is selective. β-Lapachone also abolished TNF-induced activation of AP-1, c-Jun N-terminal kinase, and mitogen-activated protein kinase kinase (MAPKK or MEK). TNF-induced cytotoxicity and activation of caspase-3 were also abolished by β-lapachone. Because reducing agents (dithiothreitol and N-acetylcysteine) reversed the effect of β-lapachone, it suggests the role of a critical sulfhydryl group. Overall, our results identify NF-κB, AP-1, and apoptosis as novel targets for β-lapachone, and this may explain some of its pharmacologic effects.