title: Xanthine oxidase mediates hypoxia-inducible factor-2α degradation by intermittent hypoxia.
abstract: 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.
authors.affiliation: Institute for Integrative Physiology and Center for Systems Biology of O2 Sensing, Biological Sciences Division, University of Chicago, Chicago, Illinois, United States of America.
authors.forename: Jayasri
authors.initials: J
authors.lastname: Nanduri
authors.forename: Damodara Reddy
authors.initials: DR
authors.lastname: Vaddi
authors.forename: Shakil A
authors.initials: SA
authors.lastname: Khan
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
authors.forename: Vladislav
authors.initials: V
authors.lastname: Makerenko
authors.forename: Nanduri R
authors.initials: NR
authors.lastname: Prabhakar
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D015687:Cell Hypoxia / Q000502:physiology*; D015151:Immunoblotting; D008297:Male; D016716:PC12 Cells; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D014969:Xanthine Oxidase / Q000378:metabolism*; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D017382:Reactive Oxygen Species; D014969:Xanthine Oxidase; D000099162:Endothelial PAS Domain-Containing Protein 1