1. The hypoxia-inducible factor-2alpha is stabilized by oxidative stress involving NOX4.
- Author
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Diebold I, Flügel D, Becht S, Belaiba RS, Bonello S, Hess J, Kietzmann T, and Görlach A
- Subjects
- Animals, Ascorbic Acid metabolism, Ascorbic Acid pharmacology, Basic Helix-Loop-Helix Transcription Factors genetics, Blotting, Western, Cell Line, Tumor, Cell Proliferation drug effects, Cells, Cultured, Humans, Hydrogen Peroxide pharmacology, Iron metabolism, NADPH Oxidase 4, NADPH Oxidases genetics, Oxidative Stress drug effects, Oxidative Stress genetics, Rats, Reactive Oxygen Species metabolism, Thrombin pharmacology, Von Hippel-Lindau Tumor Suppressor Protein genetics, Von Hippel-Lindau Tumor Suppressor Protein metabolism, Basic Helix-Loop-Helix Transcription Factors metabolism, NADPH Oxidases metabolism, Oxidative Stress physiology
- Abstract
The hypoxia-inducible factor-2alpha (HIF-2alpha) contributes to the vascular response to hypoxia. Hypoxia inhibits prolyl hydroxylation of the N-terminal transactivation domain (N-TAD), thus preventing binding of the von Hippel-Lindau protein (pVHL) and proteasomal degradation; additionally, hypoxia inhibits asparagyl hydroxylation of the C-TAD, thus diminishing cofactor recruitment. Reactive oxygen species (ROS) derived from NADPH oxidases (NOXs) have been shown to control vascular functions and to promote vascular remodeling. However, whether HIF-2alpha, ROS, and NOXs are linked under such nonhypoxic conditions is unclear. We found that activation of NOX4 by thrombin or H(2)O(2) increased HIF-2alpha protein because of decreased pVHL binding in pulmonary artery smooth muscle cells (PASMCs). Thrombin, H(2)O(2), and NOX4 overexpression increased HIF-2alpha N-TAD and C-TAD activity, which was prevented by ascorbate treatment or mutation of the hydroxylation sites in the TADs. HIF-2alpha also mediated induction of plasminogen activator inhibitor-1 and the proliferative response to thrombin, H(2)O(2), or NOX4 overexpression. Thus, ROS derived from NOX4 in response to thrombin stabilize HIF-2alpha by preventing hydroxylation of the N- and C-TAD, thus allowing formation of transcriptionally active HIF-2alpha, which promotes PASMC proliferation. Together, these findings present the first evidence that HIF-2alpha is critically involved in the ROS-regulated vascular remodeling processes.
- Published
- 2010
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