Isodeoxyelephantopin, a novel sesquiterpene lactone, potentiates apoptosis, inhibits invasion, and abolishes osteoclastogenesis through suppression of nuclear factor-kappaB (nf-kappaB) activation and nf-kappaB-regulated gene expression.
Sleutelwoorden
Abstract
OBJECTIVE
Deoxyelephantopin (ESD) and isodeoxyelephantopin (ESI) are two sesquiterpene lactones derived from the medicinal plant Elephantopus scaber Linn. (Asteraceae). Although they are used for the treatment of a wide variety of proinflammatory diseases, very little is known about their mechanism of action. Because most genes that control inflammation are regulated by activation of the transcription factor nuclear factor-kappaB (NF-kappaB), we postulated that ESD and ESI mediate their activities through modulation of the NF-kappaB activation pathway.
METHODS
We investigated the effect of ESI and ESD on NF-kappaB activation by electrophoretic mobility shift assay and NF-kappaB-regulated gene expression by Western blot analysis.
RESULTS
We found that ESI suppressed NF-kappaB activation induced by a wide variety of inflammatory agents, including tumor necrosis factor (TNF), interleukin-1beta, phorbol 12-myristate 13-acetate, and lipopolysaccharide. The suppression was not cell type specific, and both inducible and constitutive NF-kappaB activation was blocked. ESI did not interfere with the binding of NF-kappaB to DNA but rather inhibited IkappaBalpha kinase, IkappaBalpha phosphorylation, IkappaBalpha degradation, p65 phosphorylation, and subsequent p65 nuclear translocation. ESI also suppressed the expression of TNF-induced NF-kappaB-regulated, proliferative, antiapoptotic, and metastatic gene products. These effects correlated with enhancement of apoptosis induced by TNF and suppression of TNF-induced invasion and receptor activator of NF-kappaB ligand-induced osteoclastogenesis.
CONCLUSIONS
Our results indicate that ESI inhibits NF-kappaB activation and NF-kappaB-regulated gene expression, which may explain the ability of ESI to enhance apoptosis and inhibit invasion and osteoclastogenesis.
