title: iNOS expression inhibits hypoxia-inducible factor-1 activity.
abstract: Hypoxia-inducible factor-1 (HIF-1) activates genes important in vascular function such as vascular endothelial growth factor (VEGF), erythropoietin (EPO), and inducible nitric oxide synthase (iNOS). iNOS catalyzes the synthesis of nitric oxide (NO), a free radical gas that mediates a number of cellular processes, including regulation of gene expression, vasodilatation, and neurotransmission. Here we demonstrate that iNOS expression inhibits HIF-1 activity under hypoxia in C6 glioma cells transfected with an iNOS gene and a VEGF promoter-driven luciferase gene. HIF-1 induction of VEGF-luciferase activity in C6 cell is also inhibited by sodium nitroprusside (SNP). Furthermore, pretreatment of C6 cells with N-acetyl-l-cysteine (NAC), an antioxidant, nullified the inhibitory effect of iNOS on HIF-1 binding. These results demonstrate that NO generated by iNOS expression inhibits HIF-1 activity in hypoxic C6 cells and suggest a negative feedback loop in the HIF-1 --> iNOS cascade.
authors: Department of Medicine, Tao-Yuan Armed Forces General Hospital, Taiwan.
authors: J H
authors: JH
authors: Yin
authors: D I
authors: DI
authors: Yang
authors: G
authors: G
authors: Ku
authors: C Y
authors: CY
authors: Hsu
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D014157:Transcription Factors
chemical_list: D017931:DNA Primers; D004268:DNA-Binding Proteins; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D009687:Nuclear Proteins; D014157:Transcription Factors; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D000111:Acetylcysteine