Moderate hypoxia induces xanthine oxidoreductase activity in arterial endothelial cells.
Xanthine oxidoreductase (XOR) activity has been previously noted to be responsive to changes in O2 tension. While prior studies have focused on the extremes (0-3% and 95-100%) of O2 tensions, we report the influence of 10% O2 on endothelial cell XOR, a concentration resembling modest arterial hypoxia commonly found in patients with chronic cardiopulmonary diseases. Exposure of bovine aortic endothelial cells to 10% O2 increased XOR mRNA and protein abundance by 50%. Concomitantly, there was a 3-fold increase in XOR activity, XOR-dependent reactive oxygen species production, and cellular export of active enzyme. Although increases in mRNA and immunoreactive protein levels were observed, inhibition of transcription, translation, or protein degradation did not significantly alter cellular XOR specific activity, suggesting only modest contributions to 10% O2-induced effects. Exposure to 10% O2 did not increase cellular HIF-1alpha protein levels and hypoxia mimics did not alter XOR activity. Treatment of control cells with adenosine resulted in increased XOR activity similar to hypoxia. Exposure to the adenosine receptor agonist NECA increased enzymatic activity 4-fold while 8SPT, an adenosine receptor antagonist, reduced hypoxic induction of XOR activity approximately 50%. Combined, these data reveal that moderate hypoxia significantly enhances endothelial XOR specific activity, release, and XOR-derived reactive oxygen species generation. These effects appear to be mediated in part via adenosine-dependent processes.
Kelley
Eric E
EE
Department of Anesthesiology, University of Alabama at Birmingham, AL 35233, USA. ekelly@uab.edu
Hock
Thomas
T
Khoo
Nicholas K H
NK
Richardson
Gloria R
GR
Johnson
Kamorris K
KK
Powell
Pamela C
PC
Giles
Gregory I
GI
Agarwal
Anupam
A
Lancaster
Jack R
JR
Tarpey
Margaret M
MM
D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000241:Adenosine / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000166:cytology; D002417:Cattle; D004730:Endothelium, Vascular / Q000166:cytology / Q000201:enzymology; D004790:Enzyme Induction; D000860:Hypoxia / Q000201:enzymology* / Q000503:physiopathology; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000494:pharmacology; D010100:Oxygen / Q000494:pharmacology; D058915:Purinergic P1 Receptor Antagonists; D017382:Reactive Oxygen Species / Q000378:metabolism; D014969:Xanthine Oxidase / Q000378:metabolism*
D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D058915:Purinergic P1 Receptor Antagonists; D017382:Reactive Oxygen Species; D019830:Adenosine-5'-(N-ethylcarboxamide); C010192:9-(2-hydroxy-3-nonyl)adenine; D014969:Xanthine Oxidase; D000225:Adenine; D000241:Adenosine; D010100:Oxygen