iNOS Expression Inhibits Hypoxia-Inducible Factor-1 Activity

• Published in: Biochemical and biophysical research communications 2000-12, Vol.279 (1), p.30-34
• Main Authors: Yin, Jiu-Haw, Yang, Ding-I, Ku, Grace, Hsu, Chung Y.
• Format: Article
• Language: English
• Subjects: Acetylcysteine - pharmacology; Base Sequence; Cell Line; DNA Primers; DNA-Binding Proteins - antagonists & inhibitors; DNA-Binding Proteins - metabolism; glioma; HIF-1; hypoxia; Hypoxia-Inducible Factor 1; Hypoxia-Inducible Factor 1, alpha Subunit; iNOS; luciferase; NAC; Nitric Oxide Synthase - genetics; Nitric Oxide Synthase - metabolism; Nitric Oxide Synthase Type II; Nuclear Proteins - antagonists & inhibitors; Nuclear Proteins - metabolism; SNP; Transcription Factors
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.2000.3896

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.