Mechanisms of adenine nucleotide depletion from endothelial cells exposed to reactive oxygen metabolites

• Published in: Free radical biology & medicine Vol. 14; no. 2; pp. 177 - 183
• Main Authors: Aalto, T.Kristiina, Raivio, Kari O.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.02.1993; Elsevier Science
• Subjects: 5'-Nucleotidase - antagonists & inhibitors; Adenine Nucleotides - metabolism; Adenosine Deaminase Inhibitors; Adenosine Triphosphate - metabolism; Biological and medical sciences; Cell metabolism, cell oxidation; Cell physiology; Endothelial cells; Endothelium, Vascular - drug effects; Endothelium, Vascular - metabolism; Free radicals; Fundamental and applied biological sciences. Psychology; Humans; Hydrogen Peroxide - pharmacology; Hypoxanthine; Hypoxanthines - metabolism; Inosine - metabolism; Molecular and cellular biology; Nucleotide depletion; Reactive oxygen metabolites; Reactive Oxygen Species - pharmacology; Superoxides - metabolism; Superoxides - pharmacology; Umbilical Veins; Uric Acid - metabolism; Xanthine oxidase; Xanthine Oxidase - metabolism; Hx; APCP; Free radicals; Nucleotide depletion; DCF; XO; Xanthine oxidase; STI; Reactive oxygen metabolites; Endothelial cells; Human; Endothelial cell; Oxygen; Depletion; Enzyme; Metabolite; Nucleotide; Adenine nucleotide; Free radical
• DOI: 10.1016/0891-5849(93)90008-I
• ISSN: 0891-5849

When human umbilical vein endothelial cells were prelabeled wtih [ 14]-adenine and then exposed to xanthine oxidase (40 mU/ml) and hypoxanthine (100 μM) for 4h, cellular adenine nucleotides were depleted (18 ± 3% of total radioactivity vs. 61 ± 10% in controls), nucleotides appeared in the culture medium (8 ± 3% vs. 4 ± 3%) together with the catabolic products inosine, hypoxanthine, and uric acid (74 ± 4% vs. 35 ± 11%). In the presence of H 2O 2 (100 μM) for 30 min, cellular nucleotides were depleted (46 ± 25%) and catabolic products appeared in the medium (40 ± 26%), but radioactive nucleotides in the medium were unaltered. In the presence of an inhibitor of ecto-5′-nucleotidase [α,β-methylene-adenosine 5′-diphosphate (ADP), 0.5 mM], exposure to xanthine oxidase and hypoxanthine resulted in the appearancer of three times more nucleotides in the culture medium than in the absence of the inhibitor, but there was no change in medium nucleotides after H 2O 2 exposure. In the presence of an inhibitor of adenosine deaminase (2-deoxycoformycin, 2 μM), both exposures caused an accumulation of adenosine in the medium calculated to represent a minimum of 25% of nucleotide catabolism. We conclude that exposure to both a superoxide-generating system (hypoxanthine plus xanthine oxidase) and H 2O 2 induce catabolism of adenine nucleotides, which mainly takes place through adenosine 5′-monophosphate (AMP) deaminase. However, superoxide but not H 2O 2 also causes membrane damage and leakage of nucleotides into the medium.