Hypoxia inducible factor 1 (HIF-1) regulates the transcription of
vascular endothelial growth factor (
VEGF), which plays important roles in angiogenesis. We investigated the redox effect of
glutathione (GSH) on the hypoxic induction of HIF-1 in a human
oral squamous cell carcinoma (HSC-2) cell line. The maximal induction of HIF-1 in HSC-2 cells was observed 30 h after
hypoxia, and
VEGF mRNA was expressed after 36 h under
hypoxia. GSH ethyl
ester (GSHee, a membrane permeable analog of GSH) and
N-acetyl-L-cysteine (NAC, a membrane permeable precursor of GSH) reduced HIF-1 binding activity in a dose-dependent manner. Further, HIF-1 dependent promoter activity was similarly reduced by GSHee and NAC. However,
ebselen, which increases
glutathione peroxidase activity and oxidizes GSH, negated the effect of GSHee on HIF-1 dependent promoter activity. The inhibitory effect of GSHee and NAC on HIF-1 binding activity was reversed by bis (2-chlorethyl)-nitrosourea, an
oxidized glutathione (
GSSG)
reductase inhibitor which increases the concentration of
GSSG.
GSSG methyl
ester (GSSGme), a membrane permeable analog of
GSSG, enhanced HIF-1 dependent promoter activity and exhibited a bell-shaped concentration-dependant activity curve. The increasing effect of GSSGme on HIF-1 induction was also observed under chemically-induced
hypoxia obtained using
cobalt chloride. These results suggest that changes in the intracellular
GSSG/GSH ratio may regulate HIF-1 induction during
hypoxia.