Nrf2 Mediates the Induction of Ferritin H in Response to Xenobiotics and Cancer Chemopreventive Dithiolethiones

E Christine Pietsch,Jefferson Y Chan,Frank M Torti,Suzy V Torti

doi:10.1074/jbc.m210664200

Abstract

Ferritin is a ubiquitous intracellular iron storage protein that consists of 24 subunits of the H and L type. The ability to sequester iron from participation in oxygen free radical formation is consistent with a cytoprotective role for ferritin. Here we demonstrate that ferritins H and L are induced in cells treated with beta-napthoflavone (beta-NF) and chemopreventive dithiolethiones. Induction of ferritin H by beta-NF and the dithiolethiones oltipraz and 1,2-dithiole-3-thione (D3T) occurs via a transcriptional mechanism that is mediated by the ferritin H electrophile/antioxidant-responsive element (EpRE/ARE). The murine ferritin H gene contains five potential xenobiotic-responsive element (XRE) sequences in its 5'-promoter region. However, deletion analysis demonstrates that these XRE sequences are not functional in inducing ferritin H in response to beta-NF. Electrophoretic mobility shift assays demonstrate that the ferritin H EpRE/ARE binds Nrf2. Transfection of chimeric ferritin H reporter genes with Nrf2 expression vectors and Nrf2 dominant-negative mutants indicate that Nrf2 functions at the EpRE/ARE to mediate transcriptional activation of ferritin H. Induction of ferritin H and L was not seen in Nrf2 knockout cells, demonstrating that this transcription factor is required for the induction of ferritin in response to polycyclic aromatic xenobiotics and chemopreventive agents. Nrf2 may also play a role in basal transcription of both ferritin H and L. These results provide a mechanistic link between regulation of the iron storage protein ferritin and the cancer chemopreventive response.

Highlights

Ferritin is a 480-kDa intracellular protein that can store up to 4500 atoms of iron [1]
Several laboratories have demonstrated that ferritin H and L are induced in response to oxidants and pro-oxidant xenobiotics [7,8,9,10,11], and a transcriptional mechanism has been implicated [9]
In this report we demonstrate that ferritin H and L mRNA are induced by ␤-NF and by chemopreventive dithiolethiones in fibroblasts and hepatic cells

Summary

Introduction

Ferritin is a 480-kDa intracellular protein that can store up to 4500 atoms of iron [1]. Nrf2 Mediates Transcription of Ferritin H at the EpRE/ ARE—To demonstrate that Nrf2 mediates transcriptional activation of ferritin H via an EpRE/ARE-dependent mechanism, we transiently cotransfected a Nrf2 dominant negative mutant expression plasmid and the 75bpEpREFH-Luc reporter gene construct into Hepa1– 6 cells.

Results

Conclusion