title: Priming of hypoxia-inducible factor by neuronal nitric oxide synthase is essential for adaptive responses to severe anemia.
abstract: Cells sense and respond to changes in oxygen concentration through gene regulatory processes that are fundamental to survival. Surprisingly, little is known about how anemia affects hypoxia signaling. Because nitric oxide synthases (NOSs) figure prominently in the cellular responses to acute hypoxia, we defined the effects of NOS deficiency in acute anemia. In contrast to endothelial NOS or inducible NOS deficiency, neuronal NOS (nNOS)(-/-) mice demonstrated increased mortality during anemia. Unlike wild-type (WT) animals, anemia did not increase cardiac output (CO) or reduce systemic vascular resistance (SVR) in nNOS(-/-) mice. At the cellular level, anemia increased expression of HIF-1α protein and HIF-responsive mRNA levels (EPO, VEGF, GLUT1, PDK1) in the brain of WT, but not nNOS(-/-) mice, despite comparable reductions in tissue PO(2). Paradoxically, nNOS(-/-) mice survived longer during hypoxia, retained the ability to regulate CO and SVR, and increased brain HIF-α protein levels and HIF-responsive mRNA transcripts. Real-time imaging of transgenic animals expressing a reporter HIF-α(ODD)-luciferase chimeric protein confirmed that nNOS was essential for anemia-mediated increases in HIF-α protein stability in vivo. S-nitrosylation effects the functional interaction between HIF and pVHL. We found that anemia led to nNOS-dependent S-nitrosylation of pVHL in vivo and, of interest, led to decreased expression of GSNO reductase. These findings identify nNOS effects on the HIF/pVHL signaling pathway as critically important in the physiological responses to anemia in vivo and provide essential mechanistic insight into the differences between anemia and hypoxia.
authors: Department of Anesthesia, St. Michael's Hospital, University of Toronto, Keenan Research Centre in the Li Ka Shing Knowledge Institute, Toronto, ON, Canada M5B 1W8.
authors: Albert K Y
authors: AK
authors: Tsui
authors: Philip A
authors: PA
authors: Marsden
authors: C David
authors: CD
authors: Mazer
authors: S Lee
authors: SL
authors: Adamson
authors: R Mark
authors: RM
authors: Henkelman
authors: J J David
authors: JJ
authors: Ho
authors: David F
authors: DF
authors: Wilson
authors: Scott P
authors: SP
authors: Heximer
authors: Kim A
authors: KA
authors: Connelly
authors: Steffen-Sebastian
authors: SS
authors: Bolz
authors: Darcy
authors: D
authors: Lidington
authors: Mostafa H
authors: MH
authors: El-Beheiry
authors: Neil D
authors: ND
authors: Dattani
authors: Kevin M
authors: KM
authors: Chen
authors: Gregory M T
authors: GM
authors: Hare
mesh_terms: D000222:Adaptation, Physiological; D000740:Anemia / Q000235:genetics / Q000503:physiopathology*; D000818:Animals; D001921:Brain / Q000098:blood supply / Q000378:metabolism; D002302:Cardiac Output; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D052248:Nitric Oxide Synthase Type I / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000097:blood; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014655:Vascular Resistance; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000378:metabolism
chemical_list: D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D052248:Nitric Oxide Synthase Type I; C496321:Nos1 protein, mouse; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D010100:Oxygen