Modulation of gene expression by cancer chemopreventive dithiolethiones through the Keap1-Nrf2 pathway. Identification of novel gene clusters for cell survival.
Enzyme inducers such as 3H-1,2-dithiole-3-thione (D3T) enhance the detoxication of environmental carcinogens and protect against neoplasia. The putative molecular sensor for inducers is Keap1, a sulfhydryl-rich protein that sequesters the transcription factor Nrf2 in the cytoplasm. Expression of these detoxication enzymes is blunted in nrf2-deficient mice; moreover, these mice are more sensitive to carcinogenesis, and the protective actions of dithiolethiones are lost with nrf2 disruption. Hepatic gene expression profiles were examined by oligonucleotide microarray analysis in vehicle- or D3T-treated wild-type mice as well as in nrf2 single and keap1-nrf2 double knockout mice to identify those genes regulated by the Keap1-Nrf2 pathway. Transcript levels of 292 genes were elevated in wild-type mice 24 h after treatment with D3T; 79% of these genes were induced in wild-type, but not nrf2-deficient mice. These nrf2-dependent, D3T-inducible genes included known detoxication and antioxidative enzymes. Unexpected clusters included genes for chaperones, protein trafficking, ubiquitin/26 S proteasome subunits, and signaling molecules. Gene expression patterns in keap1-nrf2 double knockout mice were similar to those in nrf2-single knockout mice. D3T also led to nrf2-dependent repression of 31 genes at 24 h; principally genes related to cholesterol/lipid biosynthesis. Collectively, D3T increases the expression of genes through the Keap1-Nrf2 signaling pathway that directly detoxify toxins and generate essential cofactors such as glutathione and reducing equivalents. Induction of nrf2-dependent genes involved in the recognition and repair/removal of damaged proteins expands the role of this pathway beyond primary control of electrophilic and oxidative stresses into secondary protective actions that enhance cell survival.
Kwak
Mi-Kyoung
MK
Department of Environmental Health Sciences, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland 21205, USA.
Wakabayashi
Nobunao
N
Itoh
Ken
K
Motohashi
Hozumi
H
Yamamoto
Masayuki
M
Kensler
Thomas W
TW
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D016588:Anticarcinogenic Agents / Q000494:pharmacology*; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D002470:Cell Survival / Q000235:genetics*; D003598:Cytoskeletal Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D000072019:Kelch-Like ECH-Associated Protein 1; D051379:Mice; D018345:Mice, Knockout; D005810:Multigene Family; D051267:NF-E2-Related Factor 2; D020411:Oligonucleotide Array Sequence Analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013438:Sulfhydryl Compounds / Q000494:pharmacology*; D015534:Trans-Activators / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; D016588:Anticarcinogenic Agents; D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; C117301:Keap1 protein, mouse; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D013438:Sulfhydryl Compounds; D015534:Trans-Activators