title: Hypoxia-inducible factor 1 mediates increased expression of NADPH oxidase-2 in response to intermittent hypoxia.
abstract: Sleep-disordered breathing with recurrent apnea is associated with intermittent hypoxia (IH). Cardiovascular morbidities caused by IH are triggered by increased generation of reactive oxygen species (ROS) by pro-oxidant enzymes, especially NADPH oxidase-2 (Nox2). Previous studies showed that (i) IH activates hypoxia-inducible factor 1 (HIF-1) in a ROS-dependent manner and (ii) HIF-1 is required for IH-induced ROS generation, indicating the existence of a feed-forward mechanism. In the present study, using multiple pharmacological and genetic approaches, we investigated whether IH-induced expression of Nox2 is mediated by HIF-1 in the central and peripheral nervous system of mice as well as in cultured cells. IH increased Nox2 mRNA, protein, and enzyme activity in PC12 pheochromocytoma cells as well as in wild-type mouse embryonic fibroblasts (MEFs). This effect was abolished or attenuated by blocking HIF-1 activity through RNA interference or pharmacologic inhibition (digoxin or YC-1) or by genetic knockout of HIF-1α in MEFs. Increasing HIF-1α expression by treating PC 12 cells with the iron chelator deferoxamine for 20 h or by transfecting them with HIF-1alpha expression vector increased Nox2 expression and enzyme activity. Exposure of wild-type mice to IH (8 h/day for 10 days) up-regulated Nox2 mRNA expression in brain cortex, brain stem, and carotid body but not in cerebellum. IH did not induce Nox2 expression in cortex, brainstem, carotid body, or cerebellum of Hif1a(+/-) mice, which do not manifest increased ROS or cardiovascular morbidities in response to IH. These results establish a pathogenic mechanism linking HIF-1, ROS generation, and cardiovascular pathology in response to IH.
authors.affiliation: Institute for Integrative Physiology and The Center for Systems Biology of O2 Sensing, Biological Science Division, University of Chicago, Illinois 60637, USA.
authors.forename: Guoxiang
authors.initials: G
authors.lastname: Yuan
authors.forename: Shakil A
authors.initials: SA
authors.lastname: Khan
authors.forename: Weibo
authors.initials: W
authors.lastname: Luo
authors.forename: Jayasri
authors.initials: J
authors.lastname: Nanduri
authors.forename: Gregg L
authors.initials: GL
authors.lastname: Semenza
authors.forename: Nanduri R
authors.initials: NR
authors.lastname: Prabhakar
mesh_terms: D000818:Animals; D002344:Carotid Body / Q000187:drug effects / Q000378:metabolism; D002490:Central Nervous System / Q000187:drug effects / Q000201:enzymology; D003676:Deferoxamine / Q000494:pharmacology; D004077:Digoxin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005663:Furans / Q000494:pharmacology; D005786:Gene Expression Regulation; D000860:Hypoxia / Q000235:genetics / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D007191:Indazoles / Q000494:pharmacology; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D051379:Mice; D008807:Mice, Inbred BALB C; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics*; D016716:PC12 Cells; D017933:Peripheral Nervous System / Q000187:drug effects / Q000201:enzymology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D017262:Siderophores / Q000494:pharmacology; D012891:Sleep Apnea Syndromes / Q000235:genetics / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D005663:Furans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007191:Indazoles; D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; D017262:Siderophores; C090937:3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole; D004077:Digoxin; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D003676:Deferoxamine