Mechanism of heme oxygenase-1 gene activation by cadmium in MCF-7 mammary epithelial cells: Role of p38 kinase and Nrf2 transcription factor

Jawed Alam, Claire Wicks, Daniel Stewart, Pengfei Gong, Cheri Touchard, Sherrie Otterbein, Augustine M.K. Choi, Matthew E. Burow, Jen Sie Tou

Research output: Contribution to journalArticle

349 Scopus citations

Abstract

The mouse heine oxygenase-1 (HO-1) gene, ho-1 contains two inducible enhancers, E1 and E2. Of several cell lines tested, induction of an E1/luciferase fusion construct, pE1-luc, by CdCl2 is most pronounced in MCF-7 cells. In these cells, E1, but not E2, is necessary and sufficient for ho-1 gene activation. Exposure of MCF-7 cells to 10 μM CdCl2 stimulates phosphorylation of ERK, JNK, and p38 mitogen-activated protein kinases, implicating one or more of these signaling pathways in ho-1 gene induction. SB203580, an inhibitor of p38, diminishes cadmium-stimulated pE1-luc expression and HO-1 mRNA levels by up to 70-80%. PD098059, an ERK pathway inhibitor, does not affect HO-1 mRNA induction at the highest concentration (40 μM) tested. Similarly, co-expression of a dominant-negative mutant of p38vα, but not of ERK1, ERK2, JNK1, or JNK2, reduces basal and cadmium-induced pE1-luc activity. E1 contains binding sites for the activator protein-1 (Fos/Jun), Cap'n'Collar/basic leucine zipper (CNC-bZIP), and CCAAT/enhancer-binding protein (C/EBP) families of transcription factors. A dominant-negative mutant of Nrf2 (a CNC-bZIP member), but not of c-Jun or C/EBPβ, inhibits pE1-luc activation by cadmium. Induction of the endogenous ho-1 gene is also inhibited by the Nrf2 mutant. Mutations of E1 that inhibit cadmium inducibility also suppress the trans-activation and DNA binding activities of Nrf2, and SB203580, but not PD098059, attenuates Nrf2-mediated trans-activation of pE1-luc. Taken together, these results indicate that cadmium induces ho-1 gene expression via sequential activation of the p38 kinase pathway and Nrf2.

Original languageEnglish (US)
Pages (from-to)27694-27702
Number of pages9
JournalJournal of Biological Chemistry
Volume275
Issue number36
DOIs
StatePublished - Sep 8 2000

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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