Abstract
The transcription factor NF-E2-related nuclear factor 2 (Nrf2) regulates expression of genes that protect cells from oxidative damage. Here, we characterized nitric oxide (*NO)-induced Nrf2-Kelch-like ECH-associated protein 1 (Keap1) signaling and its role in counteracting *NO-induced apoptosis of human colon cancer HCT116 cells. Nrf2 was localized in the cytoplasm in control cells; *NO triggered its rapid nuclear accumulation, transcriptional activation, and up-regulation of HO-1, NQO1, and GCL, but not GST A4 and P1 subunits. Nrf2 accumulation in the nucleus was also associated with enhanced transcription and posttranscriptional modifications. (S)-nitrosation of Keap1 may contribute to nuclear accumulation of Nrf2 by facilitating its dissociation from Keap1, thus initiating *NO-mediated Nrf2-Keap1 signaling. *NO-mediated induction of ARE-dependent genes occurred well before apoptosis, as judged by caspase 3 activation. Collectively, these results show that the Nrf2-Keap1 signaling pathway mediates protective cellular responses to mitigate *NO-induced damage and may contribute to the relative resistance of HCT116 to *NO-induced cytotoxicity.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Apoptosis / drug effects
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Blotting, Western
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Caspase 3 / metabolism
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Cell Cycle / drug effects
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Cell Nucleus / metabolism
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Cell Survival / drug effects
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Colonic Neoplasms / genetics
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Colonic Neoplasms / metabolism
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Colonic Neoplasms / pathology
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Cytoplasm / metabolism
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Flow Cytometry
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Fluorescent Antibody Technique
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Gene Expression Regulation, Neoplastic / drug effects
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HCT116 Cells
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Heme Oxygenase-1 / genetics
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Heme Oxygenase-1 / metabolism
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Humans
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Intracellular Signaling Peptides and Proteins / genetics
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Intracellular Signaling Peptides and Proteins / metabolism*
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Kelch-Like ECH-Associated Protein 1
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Microscopy, Confocal
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NAD(P)H Dehydrogenase (Quinone) / genetics
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NAD(P)H Dehydrogenase (Quinone) / metabolism
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NF-E2-Related Factor 2 / genetics
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NF-E2-Related Factor 2 / metabolism*
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Nitric Oxide / pharmacology*
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Nitrosation
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Protein Transport / drug effects
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Reverse Transcriptase Polymerase Chain Reaction
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Signal Transduction / drug effects*
Substances
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Intracellular Signaling Peptides and Proteins
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KEAP1 protein, human
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Kelch-Like ECH-Associated Protein 1
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NF-E2-Related Factor 2
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NFE2L2 protein, human
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Nitric Oxide
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HMOX1 protein, human
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Heme Oxygenase-1
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NAD(P)H Dehydrogenase (Quinone)
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NQO1 protein, human
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Caspase 3