Caffeic acid phenethyl ester-mediated Nrf2 activation and IkappaB kinase inhibition are involved in NFkappaB inhibitory effect: structural analysis for NFkappaB inhibition

Eur J Pharmacol. 2010 Sep 15;643(1):21-8. doi: 10.1016/j.ejphar.2010.06.016. Epub 2010 Jun 20.


Caffeic acid phenethyl ester (CAPE) is an active component of propolis from honeybee. We investigated potential molecular mechanisms underlying CAPE-mediated nuclear factor kappa beta (NFkappaB) inhibition and analyzed structure of CAPE for its biological effect. CAPE attenuated expression of NFkappaB dependent luciferase stimulated with TNF-alpha or LPS and suppressed LPS-mediated induction of iNOS, a target gene product of NFkappaB. In HCT116 cells, CAPE interfered with TNF-alpha dependent IkappaBalpha degradation and subsequent nuclear accumulation of p65, which occurred by direct inhibition of inhibitory protein kappaB kinase (IKK). CAPE increased the expression of Nrf2-dependent luciferase and heme oxygenase-1, a target gene of Nrf2, and elevated the nuclear level of Nrf2 protein, indicating that CAPE activated the Nrf2 pathway. In HCT116 cells with stable expression of Nrf2 shRNA, CAPE elicited a reduced inhibitory effect on TNF-alpha-activated NFsmall ka, CyrillicB compared to scramble RNA expressing control cells. On the other hand, the NFkappaB inhibitory effect of CAPE was diminished by removal or modification of the Michael reaction acceptor, catechol or phenethyl moiety in CAPE. These data suggest that CAPE inhibits TNF-alpha-dependent NFkappaB activation via direct inhibition of IKK as well as activation of Nrf2 pathway, in which the functional groups in CAPE may be involved.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-Inflammatory Agents, Non-Steroidal / chemistry
  • Anti-Inflammatory Agents, Non-Steroidal / pharmacology*
  • Caffeic Acids / chemistry
  • Caffeic Acids / pharmacology*
  • Cell Culture Techniques
  • Cell Line, Tumor
  • Cell Nucleus / drug effects
  • Cell Nucleus / enzymology
  • Cell Nucleus / metabolism
  • Cytosol / drug effects
  • Cytosol / enzymology
  • Cytosol / metabolism
  • Genes, Reporter
  • Humans
  • I-kappa B Kinase / antagonists & inhibitors*
  • Immunoblotting
  • Lipopolysaccharides / pharmacology
  • Luciferases / genetics
  • Macrophages / drug effects
  • Macrophages / enzymology
  • Macrophages / metabolism
  • Mice
  • Molecular Structure
  • NF-E2-Related Factor 2 / antagonists & inhibitors
  • NF-E2-Related Factor 2 / genetics
  • NF-E2-Related Factor 2 / metabolism*
  • NF-kappa B / antagonists & inhibitors*
  • Phenylethyl Alcohol / analogs & derivatives*
  • Phenylethyl Alcohol / chemistry
  • Phenylethyl Alcohol / pharmacology
  • Plasmids
  • Recombinant Proteins / pharmacology
  • Reverse Transcriptase Polymerase Chain Reaction
  • Structure-Activity Relationship
  • Transfection
  • Tumor Necrosis Factor-alpha / pharmacology


  • Anti-Inflammatory Agents, Non-Steroidal
  • Caffeic Acids
  • Lipopolysaccharides
  • NF-E2-Related Factor 2
  • NF-kappa B
  • NFE2L2 protein, human
  • Recombinant Proteins
  • Tumor Necrosis Factor-alpha
  • Luciferases
  • I-kappa B Kinase
  • caffeic acid phenethyl ester
  • Phenylethyl Alcohol