The plant Withania somnifera Dunal (
Ashwagandha), also known as Indian ginseng, is widely used in the Ayurvedic system of medicine to treat
tumors,
inflammation,
arthritis,
asthma, and
hypertension. Chemical investigation of the roots and leaves of this plant has yielded bioactive
withanolides. Earlier studies showed that
withanolides inhibit
cyclooxygenase enzymes, lipid peroxidation, and proliferation of
tumor cells. Because several genes that regulate cellular proliferation,
carcinogenesis,
metastasis, and
inflammation are regulated by activation of
nuclear factor-kappaB (
NF-kappaB), we hypothesized that the activity of
withanolides is mediated through modulation of
NF-kappaB activation. For this report, we investigated the effect of the withanolide on
NF-kappaB and
NF-kappaB-regulated gene expression activated by various
carcinogens. We found that
withanolides suppressed
NF-kappaB activation induced by a variety of inflammatory and carcinogenic agents, including
tumor necrosis factor (TNF),
interleukin-1beta,
doxorubicin, and cigarette
smoke condensate. Suppression was not cell type specific, as both inducible and constitutive
NF-kappaB activation was blocked by
withanolides. The suppression occurred through the inhibition of inhibitory subunit of
IkappaB alpha kinase activation,
IkappaB alpha phosphorylation,
IkappaB alpha degradation, p65 phosphorylation, and subsequent p65 nuclear translocation.
NF-kappaB-dependent reporter gene expression activated by TNF,
TNF receptor (TNFR) 1, TNFR-associated death domain, TNFR-associated factor 2, and
IkappaB alpha kinase was also suppressed. Consequently, withanolide suppressed the expression of TNF-induced
NF-kappaB-regulated antiapoptotic (
inhibitor of apoptosis protein 1,
Bfl-1/A1, and FADD-like
interleukin-1beta-converting enzyme-inhibitory
protein) and metastatic (
cyclooxygenase-2 and
intercellular adhesion molecule-1) gene products, enhanced the apoptosis induced by TNF and chemotherapeutic agents, and suppressed cellular TNF-induced invasion and
receptor activator of NF-kappaB ligand-induced osteoclastogenesis. Overall, our results indicate that
withanolides inhibit activation of
NF-kappaB and
NF-kappaB-regulated gene expression, which may explain the ability of
withanolides to enhance apoptosis and inhibit invasion and osteoclastogenesis.