Abstract
Although inflammatory pathways have been linked with various chronic diseases including cancer, identification of an agent that can suppress these pathways has therapeutic potential. Herein we describe the identification of a novel compound bharangin, a diterpenoid quinonemethide that can suppress pro-inflammatory pathways specifically. We found that bharangin suppresses nuclear factor (NF)-κB activation induced by pro-inflammatory cytokine, tumor promoter, cigarette smoke, and endotoxin. Inhibition of NF-κB activation was mediated through the suppression of phosphorylation and degradation of inhibitor of nuclear factor-κB (IκBα); inhibition of IκBα kinase activation; and suppression of p65 nuclear translocation, and phosphorylation. The diterpenoid inhibited binding of p65 to DNA. A reducing agent reversed the inhibitory effect, and mutation of the Cys38 of p65 to serine abrogated the effect of bharangin on p65-DNA binding. Molecular docking revealed strong interaction of the ligand with the p65 via two hydrogen bonds one with Lys37 (2.204 Å) and another with Cys38 (2.023 Å). The inhibitory effect of bharangin on NF-κB activation was specific, inasmuch as binding of activator protein-1 and octameric transcription factor 1 to DNA was not affected. Suppression of NF-κB activation by this diterpenoid caused the down-regulation of the expression of proteins involved in tumor cell survival, proliferation, invasion, and angiogenesis, leading to potentiation of apoptosis, suppression of proliferation, and invasion of tumor cells. Furthermore, the genetic deletion of p65 and mutation of p65Cys38 residue to Ser abolished the affect of bharangin. Overall, our results demonstrate that bharangin specifically inhibits the NF-κB activation pathway by modifying p65 and inhibiting IκBα kinase activation and potentiates apoptosis in tumor cells.
Footnotes
This research was supported by the National Institutes of Health National Cancer Institute [Grant P01-CA124787-01A2]; and a grant from the M.D. Anderson Cancer Center for Targeted Therapy. B.B.A. is the Ransom Horne, Jr., Professor of Cancer Research.
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.111.073122.
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ABBREVIATIONS:
- NF-κB
- nuclear factor-κB
- IκBα
- inhibitor of nuclear factor-κBα
- IKK
- IκB kinase
- TNF
- tumor necrosis factor
- FBS
- fetal bovine serum
- MEF
- mouse embryonic fibroblast
- EMSA
- electrophoretic mobility shift assay
- AP-1
- activator protein-1
- Oct-1
- octameric transcription factor 1
- TAK1
- TGF-β-activated kinase 1
- TNFR
- tumor necrosis factor receptor
- TRADD
- TNFR-associated death domain
- TRAF
- TNFR-associated factor
- NIK
- NF-κB-inducing kinase
- TAB1
- TAK-1 binding protein-1
- SEAP
- secretory alkaline phosphatase
- PS
- phosphatidylserine
- DTT
- dithiothreitol
- CSC
- cigarette smoke condensate
- OA
- okadaic acid
- PMA
- phorbol 12-myristate 13-acetate
- LPS
- lipopolysaccharide
- PI3K
- phosphatidylinositol 3-kinase
- PDK1
- phosphoinositide-dependent protein kinase-1
- mTOR
- mammalian target of rapamycin
- AKT
- AKT8 virus oncogene cellular homolog
- MSK
- mitogen- and stress activated protein kinase
- ICAM
- intercellular adhesion molecule
- COX
- cyclooxygenase
- MMP
- matrix metalloproteinase
- VEGF
- vascular endothelial growth factor
- PARP
- poly (ADP-ribose) polymerase
- ROS
- reactive oxygen species
- Bcl-2
- B-cell lymphoma-2
- Bcl-xL
- B cell lymphoma extra large
- c-Myc
- cellular-myelocytomatosis.
- Received April 20, 2011.
- Accepted July 27, 2011.
- Copyright © 2011 The American Society for Pharmacology and Experimental Therapeutics
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