Direct treatment of mouse or human blood with soluble 5'-nucleotidase inhibits platelet aggregation.
OBJECTIVE
Adenosine signaling is known to inhibit platelet aggregation. Extracellular adenosine mainly stems from enzymatic phosphohydrolysis of precursor nucleotides via ecto-5'-nucleotidase. Previous studies suggest that soluble 5'-nucleotidase (5'-NT) derived from Crotalus atrox venom may be clinically beneficial in vascular leakage, myocardial, renal, and intestinal ischemia, or acute lung injury. However, the effects of 5'-NT treatment on platelet aggregation remain unknown. We examined the direct effects of 5'-NT treatment on platelet aggregation in vivo and ex vivo using a whole blood aggregation method.


RESULTS
Platelet aggregation in whole human blood was completely inhibited by 5'-NT. When 5'-[alphabeta-methylene] diphosphate (APCP), a specific 5'-ecto-nucleotidase inhibitor, was added together with 5'-NT, APCP fully restored collagen- or ADP-induced aggregation. Adenosine levels in whole blood were significantly increased after 5'-NT treatment compared to controls and inhibition of platelet aggregation by 5'-NT was completely reversed by pretreatment with the nonspecific adenosine receptor antagonist 8-(p-sulfophenyl)theophylline hydrate (8-SPT), suggesting that 5'-NT inhibits aggregation via increased adenosine signaling. Administration of 5'-NT to mice in vivo abolished ADP- and collagen-induced platelet aggregation and increased adenosine concentrations and tail bleeding time.


CONCLUSIONS
5'-NT treatment inhibits platelet aggregation via generation of increased levels of extracellular adenosine and subsequent adenosine receptor signaling.
Department of Anesthesiology and Intensive Care Medicine, University of Tübingen, Germany.
Melanie L
ML
Hart
David
D
Köhler
Tobias
T
Eckle
Doris
D
Kloor
Gregory L
GL
Stahl
Holger K
HK
Eltzschig
D015720:5'-Nucleotidase / Q000737:chemistry / Q000494:pharmacology*; D000241:Adenosine / Q000378:metabolism; D000818:Animals; D003435:Crotalid Venoms / Q000737:chemistry; D006801:Humans; D051379:Mice; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D018047:Receptors, Purinergic P1 / Q000378:metabolism; D014914:Whole Blood Coagulation Time
D003435:Crotalid Venoms; D010975:Platelet Aggregation Inhibitors; D018047:Receptors, Purinergic P1; D015720:5'-Nucleotidase; D000241:Adenosine