Activation of Hsp90-eNOS and increased NO generation attenuate respiration of hypoxia-treated endothelial cells

• Published in: American Journal of Physiology: Cell Physiology 2008-11, Vol.295 (5), p.C1281-C1291
• Main Authors: Presley, Tennille, Vedam, Kaushik, Velayutham, Murugesan, Zweier, Jay L, Ilangovan, Govindasamy
• Format: Article
• Language: English
• Subjects: Adaptation, Physiological; Animals; Cattle; Cell Hypoxia; Cell Respiration; Cells; Cells, Cultured; Cellular and Mitochondrial Metabolism; Electron Spin Resonance Spectroscopy; Endothelial Cells - drug effects; Endothelial Cells - enzymology; Enzyme Inhibitors - pharmacology; HSP90 Heat-Shock Proteins - antagonists & inhibitors; HSP90 Heat-Shock Proteins - metabolism; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit - metabolism; Nitric oxide; Nitric Oxide - metabolism; Nitric Oxide Synthase Type III - antagonists & inhibitors; Nitric Oxide Synthase Type III - metabolism; Oxygen Consumption; Phosphatidylinositol 3-Kinases - antagonists & inhibitors; Phosphatidylinositol 3-Kinases - metabolism; Protein Binding; Protein Stability; Proteins; Signal transduction; Time Factors; Up-Regulation
• ISSN: 0363-6143; 1522-1563
• DOI: 10.1152/ajpcell.00550.2007

1 The Center for Biomedical EPR Spectroscopy and Imaging, 2 Biophysics Program, and 3 The Division of Cardiovascular Medicine, Department of Internal Medicine, Davis Heart and Lung Research Institute and The Ohio State University, Columbus, Ohio Submitted 19 November 2007 ; accepted in final form 3 September 2008 Hypoxia induces various adoptive signaling in cells that can cause several physiological changes. In the present work, we have observed that exposure of bovine aortic endothelial cells (BAECs) to extreme hypoxia (1–5% O 2 ) attenuates cellular respiration by a mechanism involving heat shock protein 90 (Hsp90) and endothelial nitric oxide (NO) synthase (eNOS), so that the cells are conditioned to consume less oxygen and survive in prolonged hypoxic conditions. BAECs, exposed to 1% O 2 , showed a reduced respiration compared with 21% O 2 -maintained cells. Western blot analysis showed an increase in the association of Hsp90-eNOS and enhanced NO generation on hypoxia exposure, whereas there was no significant accumulation of hypoxia-inducible factor-1 (HIF-1 ). The addition of inhibitors of Hsp90, phosphatidylinositol 3-kinase, and NOS significantly alleviated this hypoxia-induced attenuation of respiration. Thus we conclude that hypoxia-induced excess NO and its derivatives such as ONOO – cause inhibition of the electron transport chain and attenuate O 2 demand, leading to cell survival at extreme hypoxia. More importantly, such an attenuation is found to be independent of HIF-1 , which is otherwise thought to be the key regulator of respiration in hypoxia-exposed cells, through a nonphosphorylative glycolytic pathway. The present mechanistic insight will be helpful to understand the difference in the magnitude of endothelial dysfunction. oxygen; electron paramagnetic resonance oximetry; heat shock protein 90; endothelial nitric oxide synthase Address for reprint requests and other correspondence: G. Ilangovan, Rm. 392, Biomedical Research Tower, Ohio State Univ., 420 West 12th Ave., Columbus, OH 43210 (e-mail: govindasamy.ilangovan{at}osumc.edu )