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Mol Biol Cell. 2010 Sep 15;21(18):3247-57. doi: 10.1091/mbc.E10-01-0025. Epub 2010 Jul 21.

Hypoxia-inducible factor-1 activation in nonhypoxic conditions: the essential role of mitochondrial-derived reactive oxygen species.

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  • 1Centre de recherche du CHUQ, L'Hôtel-Dieu de Québec, Department of Molecular Biology, Medical Biochemistry and Pathology, Université Laval, Québec, QC, G1R 2J6, Canada.

Abstract

Hypoxia-inducible factor-1 (HIF-1) is a key transcription factor for responses to low oxygen. Different nonhypoxic stimuli, including hormones and growth factors, are also important HIF-1 activators in the vasculature. Angiotensin II (Ang II), the main effecter hormone in the renin-angiotensin system, is a potent HIF-1 activator in vascular smooth muscle cells (VSMCs). HIF-1 activation by Ang II involves intricate mechanisms of HIF-1α transcription, translation, and protein stabilization. Additionally, the generation of reactive oxygen species (ROS) is essential for HIF-1 activation during Ang II treatment. However, the role of the different VSMC ROS generators in HIF-1 activation by Ang II remains unclear. This work aims at elucidating this question. Surprisingly, repression of NADPH oxidase-generated ROS, using Vas2870, a specific inhibitor or a p22(phox) siRNA had no significant effect on HIF-1 accumulation by Ang II. In contrast, repression of mitochondrial-generated ROS, by complex III inhibition, by Rieske Fe-S protein siRNA, or by the mitochondrial-targeted antioxidant SkQ1, strikingly blocked HIF-1 accumulation. Furthermore, inhibition of mitochondrial-generated ROS abolished HIF-1α protein stability, HIF-1-dependent transcription and VSMC migration by Ang II. A large number of studies implicate NADPH oxidase-generated ROS in Ang II-mediated signaling pathways in VSMCs. However, our work points to mitochondrial-generated ROS as essential intermediates for HIF-1 activation in nonhypoxic conditions.

PMID:
20660157
[PubMed - indexed for MEDLINE]
PMCID:
PMC2938389
Free PMC Article
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