title: Valproic acid-induced gene expression through production of reactive oxygen species.
abstract: Valproic acid (VPA) is a widely used anticonvulsive agent that has profound antiproliferative effects in many cell types, as well as inductive effects on a number of genes. The mechanism of its gene-inducing effect has been reported to involve transcription factors, Sp1 and activator protein-1. Using two well-characterized antioxidant response element (ARE)-driven gene promoters, i.e., mouse heme oxygenase-1 and human NAD(P)H:quinone oxidoreductase 1 genes as tools to monitor the transcriptional response to VPA, we show here that VPA-induced gene transcription was abrogated by antioxidants. With the human Galpha(i2) gene promoter, which was previously used to establish the involvement of Sp1 in the transcriptional action of VPA, we found that VPA-induced gene transcription was also blocked by antioxidants. Mutation of the ARE (5'-TGACtggGC-3') in this promoter abrogated the transcriptional response to VPA. With such mutants, the NADPH oxidase inhibitor, diphenyleneiodonium, had no effect on VPA-induced transcription. In gel mobility shift assays, VPA-induced binding of nuclear proteins to a DNA probe containing the relevant ARE sequence in the Galpha(i2) gene promoter was decreased in nuclear extracts from cells pretreated with antioxidants. Chromatin immunoprecipitation assays showed that the prototype redox-sensitive transcription factors, Nrf2, small Maf protein(s), and c-Fos, were recruited to this promoter in VPA-treated cells. Overall, this study reveals that the mechanism of the transcriptional response to VPA includes VPA-induced production of reactive oxygen species which induce the activation of redox-sensitive transcription factors that interact with the ARE.
authors.affiliation: Department of Biomedical Sciences, Meharry Medical College, 1005 Dr. David B. Todd Jr. Boulevard, Nashville, TN 37208, USA.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Kawai
authors.forename: Ifeanyi J
authors.initials: IJ
authors.lastname: Arinze
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D004347:Drug Interactions; D051960:GTP-Binding Protein alpha Subunit, Gi2 / Q000096:biosynthesis / Q000235:genetics; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D020014:K562 Cells; D011401:Promoter Regions, Genetic / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism*; D020218:Response Elements; D014158:Transcription, Genetic / Q000187:drug effects*; D014635:Valproic Acid / Q000037:antagonists & inhibitors / Q000494:pharmacology*
chemical_list: D000975:Antioxidants; D056572:Histone Deacetylase Inhibitors; D017382:Reactive Oxygen Species; D014635:Valproic Acid; D051960:GTP-Binding Protein alpha Subunit, Gi2