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Abstract
HIF-1α represents the oxygen-regulated sub-unit of the transcription factor HIF-1, which regulates the transcription of numerous genes involved in cellular response to hypoxia and oxidative stress. It is shown here that nitric oxide (NO) induces HIF-1α stabilization in human endothelial cells from umbilical cords (HUVECs) under normoxic conditions. HIF-1α protein was increased ∼ 36-fold after incubation with 500 μM DETA-NO, which releases a steady state NO concentration of roughly one thousandth of the initial concentration of the donor. Loading of the cells with vitamin C counteracted NO-induced HIF-1α accumulation. Based on the observations that oxidative and nitrosative stress can influence the activity of the proteasomal system, which is responsible for the non-lysosomal degradation of proteins, among them HIF-1α, it was investigated whether NO-induced stabilization of HIF-1α might be due to reduced 20S proteasomal activity. This hypothesis could not be proved, because NO concentrations to inhibit 20S proteasomal activity were about one order of magnitude higher than that to inhibit HIF-1α degradation.
Declaration of interest: Markus K. Muellner was supported by the Kamillo Eisner-Stiftung. Sabine M. Schreier was supported by the OeNB Jubiläumsfonds (10537). The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
This paper was first published online on Early Online on April 14 2010.