Dipyridamole Inhibits Hydroxylamine Augmented Nitric Oxide (NO) Production by Activated Polymorphonuclear Neutrophils Through an Adenosine-Independent Mechanism

A. WYKRETOWICZ, A. FILIPIAK, A. SZCZEPANIK, H. WYSOCKI

Department of Cardiology – Intensive Therapy, University School of Medicine, Poznan, Poland

Received April 1, 2003
Accepted December 18, 2003



Summary
Polymorphonuclear neutrophils (PMN) are thought to play a role in reperfusion injury and ischemia. These effects are partly mediated by toxic oxygen species (superoxide anion, hydrogen peroxide and hydroxyl radical) acting at the level of the endothelium. It was demonstrated recently that the superoxide anion reacts with nitric oxide (NO) and that interaction leads to the generation of highly toxic peroxynitrite. Several drugs were tested so far in order to affect PMN function. It was demonstrated that dipyridamole (2,6-bis-diethanolamino-4,8-dipiperidinopyrimido-(5,4-d)-pyrimidine) can influence neutrophil function by inhibiting adenosine uptake. However, this action can not fully explain all of the observed effects of dipyridamole action on PMN metabolism. The aim of our study was to evaluate the influence of dipyridamole on nitric oxide production by activated polymorphonuclear neutrophils. Incubation of PMNs with hydroxylamine (HA) and phorbol myristate acetate (PMA) generated nitrite (36.4±4.2 nmol/h 2x106 PMN), dipyridamole at 100 μmol/l, 50 μmol/l and 10 μmol/l caused a considerable drop in nitrite production (11.8±1.8, 19.7±2.7 and 27.4±3.2 nmol/h, respectively). Neither adenosine nor the adenosine analogue could mimic the dipyridamole effect. Moreover theophylline, an adenosine inhibitor could not reverse the dipirydamole action on PMN metabolism. We also found that dipyridamole inhibited hydrogen peroxide release from neutrophils. Catalase that scavenges hydrogen peroxide also largely abolished nitric oxide release from PMN. It is evident that dipyridamole inhibits hydroxylamine-augmented nitric oxide production by activated polymorphonuclear neutrophils through an adenosine-independent mechanism.


Key words
Nitric oxide • Neutrophils • Dipyridamole • Hydrogen peroxide • Toxic oxygen species