Xanthine oxidase mediates hypoxia-inducible factor-2α degradation by intermittent hypoxia

• Published in: PloS one 2013-10, Vol.8 (10), p.e75838-e75838
• Main Authors: Nanduri, Jayasri, Vaddi, Damodara Reddy, Khan, Shakil A, Wang, Ning, Makerenko, Vladislav, Prabhakar, Nanduri R
• Format: Article
• Language: English
• Subjects: Activation; Adrenal medulla; Allopurinol; Animals; Apnea; Basic Helix-Loop-Helix Transcription Factors - metabolism; Biology; Biotechnology; Breathing; C-Terminus; Calpain; Cell culture; Cell Hypoxia - physiology; Degradation; Enzymes; Experiments; Hypertension; Hypoxia; Hypoxia-inducible factors; Immunoblotting; Inflammation; Ischemia; Male; N-Terminus; Oxidative stress; Oxygen; PC12 Cells; Pharmacology; Pheochromocytoma cells; Physiology; Proteins; Proteolysis; Rats; Rats, Sprague-Dawley; Reactive oxygen species; Reactive Oxygen Species - metabolism; Rodents; Signal transduction; Signaling; Sleep; Sleep disorders; Xanthine; Xanthine dehydrogenase; Xanthine oxidase; Xanthine Oxidase - metabolism
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0075838

Sleep-disordered breathing with recurrent apnea produces chronic intermittent hypoxia (IH). We previously reported that IH leads to down-regulation of HIF-2α protein via a calpain-dependent signaling pathway resulting in oxidative stress. In the present study, we delineated the signaling pathways associated with calpain-dependent HIF-2α degradation in cell cultures and rats subjected to chronic IH. Reactive oxygen species (ROS) scavengers prevented HIF-2α degradation by IH and ROS mimetic decreased HIF-2α protein levels in rat pheochromocytoma PC12 cell cultures, suggesting that ROS mediate IH-induced HIF-2α degradation. IH activated xanthine oxidase (XO) by increased proteolytic conversion of xanthine dehydrogenase to XO. ROS generated by XO activated calpains, which contributed to HIF-2α degradation by IH. Calpain-induced HIF-2α degradation involves C-terminus but not the N-terminus of the HIF-2α protein. Pharmacological blockade as well as genetic knock down of XO prevented IH induced calpain activation and HIF-2α degradation in PC12 cells. Systemic administration of allopurinol to rats prevented IH-induced hypertension, oxidative stress and XO activation in adrenal medulla. These results demonstrate that ROS generated by XO activation mediates IH-induced HIF-2α degradation via activation of calpains.