Involvement of Nrf2, p38, B-Raf, and Nuclear Factor-κB, but Not Phosphatidylinositol 3-Kinase, in Induction of Hemeoxygenase-1 by Dietary Polyphenols

• Published in: Molecular pharmacology 2006-03, Vol.69 (3), p.1033
• Main Authors: Catherine K. Andreadi, Lynne M. Howells, Paul A. Atherfold, Margaret M. Manson
• Format: Article
• Language: English
• ISSN: 0026-895X; 1521-0111
• DOI: 10.1124/mol.105.018374

The highly inducible enzyme, hemeoxygenase-1 (HO-1), metabolizes heme, thereby protecting a variety of cells against oxidative stress and apoptosis. Up-regulation by cancer chemopreventive agents has been reported, but its regulation and function in transformed cells are unclear. We compared induction by two dietary polyphenols, curcumin and epigallocatechin-3-gallate (EGCG), with that by the endogenous substrate hemin in epithelial and endothelial cells and examined the relevance to apoptosis. Curcumin or hemin (20 μM) induced HO-1 in breast cells from 5 to 24 h. Curcumin (5-40 μM) or hemin (5-100 μM) induced HO-1 and nuclear levels of nuclear factor (erythroid-derived 2)-related factor (Nrf2) in a dose-dependent manner. EGCG had no effect in breast cells, but at 30 μM, it induced nuclear translocation of Nrf2 and HO-1 expression in B-lymphoblasts. In all cases, induction was inhibited by pretreatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor 2-(4-morpholinyl)-8-phenyl-4 H -1-benzopyran-4-one (LY294002) or the p38 inhibitor 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1 H -imidazole (SB203580). The nuclear factor-κB (NF-κB)-DNA binding inhibitor helenalin (20 μM) also prevented induction. However, wortmannin had no effect, suggesting that PI3K was not involved. Curcumin and hemin also induced nuclear Nrf2 and HO-1 effectively in wild-type mouse embryo fibroblasts (wt MEFs) and in B-Raf -/- MEFs but not in Nrf2 -/- MEFs. However, EGCG (5-20 μM) induced HO-1 only in wt MEFs. Results suggest that signaling through p38 mitogen-activated protein kinase, NF-κB, and Nrf2 as well as other unidentified molecules is involved in HO-1 induction by hemin and both polyphenols, but cell-specific factors also play a role, particularly with respect to EGCG. Induction of HO-1 by curcumin, EGCG, or low concentrations (5-10 μM) of helenalin did not protect MDA-MB468 breast cells or B-lymphoblasts from apoptosis.