Upregulation of heme oxygenase-1 by Epigallocatechin-3-gallate via the phosphatidylinositol 3-kinase/Akt and ERK pathways

Life Sci. 2006 May 15;78(25):2889-97. doi: 10.1016/j.lfs.2005.11.013. Epub 2005 Dec 27.


Heme oxygenase-1 (HO-1) is a cytoprotective enzyme activated by various phytochemicals and we examined the ability of Epigallocatechin-3-gallate (EGCG), the major constituent of green tea, to upregulate HO-1 expression in endothelial cells (ECs). We demonstrate that EGCG induces HO-1 expression in a concentration- and time-dependent manner. Furthermore, EGCG-mediated HO-1 induction was abrogated in the presence of actinomycin D and cycloheximide, indicating that this upregulation of HO-1 occurred at the transcriptional level. EGCG also upregulates Nrf2 levels in nuclear extracts and increases ARE-luciferase activity. Furthermore, EGCG is the most potent inducer of HO-1 expression of the different green tea constituents that we analyzed, but had no detectable cytotoxic effects over the 25-100 microM dosage range. The inhibition of intracellular ROS production by N-acetylcysteine (NAC), glutathione (GSH), superoxide dismutase (SOD), catalase and the mitochondrial complex I inhibitor, rotenone, results in a decrease in EGCG-dependent HO-1 expression. In addition, we determined that tyrosine kinase is involved in EGCG induction of HO-1 as this is abrogated by genistein. ECs treated with EGCG exhibit activation of Akt and ERK1/2. In addition, pharmacological inhibitors of phosphatidylinositol 3-kinase and MEK1/2, which are upstream of Akt and ERK1/2, respectively, attenuate EGCG-induced HO-1 expression. On the other hand, pretreatment of these cells with EGCG exerts significant cytoprotective effects against H2O2, suggesting that the induction of HO-1 is an important component in the protection against oxidative stress. Hence, EGCG is a novel phytochemical inducer of HO-1 expression and we further identify the principal underlying mechanisms involved in this process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antioxidants / pharmacology*
  • Catechin / analogs & derivatives*
  • Catechin / pharmacology
  • Cattle
  • Cell Survival / drug effects
  • Cells, Cultured
  • Dose-Response Relationship, Drug
  • Endothelial Cells / drug effects
  • Endothelial Cells / enzymology
  • Endothelial Cells / metabolism
  • Enzyme Inhibitors / pharmacology
  • Extracellular Signal-Regulated MAP Kinases / antagonists & inhibitors
  • Extracellular Signal-Regulated MAP Kinases / physiology*
  • Heme Oxygenase-1 / biosynthesis*
  • Oxidative Stress / drug effects
  • Phosphatidylinositol 3-Kinases / physiology*
  • Phosphoinositide-3 Kinase Inhibitors
  • Signal Transduction / drug effects*
  • Up-Regulation


  • Antioxidants
  • Enzyme Inhibitors
  • Phosphoinositide-3 Kinase Inhibitors
  • Catechin
  • epigallocatechin gallate
  • Heme Oxygenase-1
  • Extracellular Signal-Regulated MAP Kinases