thromboxane-b2 and defibrotide

Defibrotide is a polynucleotide extracted from mammalian lung, which shows antithrombotic and anti-ischaemic activity in animals, probably related to stimulation of fibrinolysis and/or enhancement of prostacyclin production. The effect of a single infusion of defibrotide on fibrinolysis and the levels of certain prostanoids in man has been investigated in a cross-over double-blind placebo-controlled study. Evaluation of changes in fibrinolysis was difficult because of the spontaneous activation observed after placebo. However, the fast-acting plasminogen activator inhibitor was decreased only at end of the defibrotide infusion, suggesting a moderate profibrinolytic effect superimposed on the spontaneous activation. There was a marked and prolonged elevation of the plasma level of 6-keto-PGF1 alpha, the stable metabolite of prostacyclin. In collagen stimulated whole blood, both 6-keto-PGF1 alpha and prostaglandin E2 production were also greatly increased, with no consistent indication of inhibition of thromboxane B2. It is suggested that defibrotide stimulates prostacyclin and prostaglandin E2 production by leucocytes or via platelet/leukocyte interactions. The effects observed here should be useful in guiding subsequent clinical trials.

Topics: 6-Ketoprostaglandin F1 alpha; Dinoprostone; Double-Blind Method; Female; Fibrinolysis; Fibrinolytic Agents; Humans; Infusions, Intravenous; Male; Polydeoxyribonucleotides; Random Allocation; Thromboxane B2

Nitric oxide (NO) and cyclooxygenase-derived prostaglandins, such as prostacyclin (PGI2), are involved in vascular homeostasis. To better understand the reciprocal role of both NO and PGI2 on myocardial infarction in the rat, we have investigated the cardioprotective effect of nitro-naproxen, isosorbide dinitrate (ISDN), L-arginine, defibrotide and naproxen. In this study, male Wistar rats were treated orally once a day for 5 consecutive days with the compounds under investigation and then, under anesthesia, the animals were subjected to acute myocardial ischemia (30 min) and reperfusion (120 min). Systemic blood pressure, left ventricular pressure and related parameters of cardiac mechanics were recorded. Ventricular arrhythmias and infarct size of the left ventricular wall were also evaluated. Furthermore, cardiac myeloperoxidase (MPO) and plasma creatine phosphokinase (CPK) activities were determined. Defibrotide, nitro-naproxen, ISDN and L-arginine all provided a cardioprotection characterized by significant prevention of arrhythmias with high survival rate of the rats. Infarct size restriction was paralleled by reduction of both cardiac MPO and plasma CK. Cardioprotection of nitro-naproxen, ISDN and L-arginine involve nitrites/nitrates and PGI2-increased in the circulation associated to a reduction of thromboxane B2 (TXB2) in the blood. Defibrotide displays a cardioprotection by increasing PGI2 release and by reducing TXB2 in the blood. Naproxen was devoid a lower protecting activity on myocardial infarction, and PGI2 inhibition may have played a critical role in this context. The results suggested that the increase of both NO and PGI2 brings about a cascade of integrated cellular and molecular events which are of paramount importance in prevention of myocardial ischemic insult.

Topics: Animals; Arginine; Arrhythmias, Cardiac; Cardiotonic Agents; Creatine Kinase; Epoprostenol; Isosorbide Dinitrate; Male; Myocardial Infarction; Myocardial Reperfusion; Myocardium; Naproxen; Nitric Oxide; Peroxidase; Polydeoxyribonucleotides; Random Allocation; Rats; Rats, Wistar; Thromboxane B2

Defibrotide is a polydeoxyribonucleotide-derived anti-ischemic drug with multiple sites of action involving both plasmatic and cellular targets. This agent has been demonstrated to produce profibrinolytic, cytoprotective, and vaso-facilatory actions. Since monocytes are increased in the mediation of some of the pathophysiologic responses seen in ischemic disorders, the functional properties of these cells were investigated in experimental conditions to evaluate their behavior during resting and stimulated states. Defibrotide was supplemented in these systems to determine its modulatory action. In this investigation Defibrotide was found to decrease the PAI-1 levels and may indicate that this may be the mechanism for its profibrinolytic actions. Defibrotide was also found to reduce the procoagulant activity of monocytes in these experimental settings. Both PAI and procoagulant factors play an important role in the pathophysiology of inflammation, DIC, and ischemia. Defibrotide induced reduction of these two factors represents the mechanism whereby this agent produces its therapeutic action.

Topics: Blood Coagulation Factors; Cytokines; Fibrinolytic Agents; Hemostasis; Humans; Ischemia; Monocytes; Plasminogen Activator Inhibitor 2; Polydeoxyribonucleotides; Thromboxane B2

Defibrotide is a polydeoxyribonucleotide with antithrombotic effects in experimental animal models. Most of the actions of this drug have been observed in in vivo test models but no effects have been reported in in vitro systems. In this paper we demonstrate that defibrotide interferes with polymorphonuclear leukocyte-induced human platelet activation in vitro. This effect was not related to any direct interaction with polymorphonuclear leukocytes or platelets, but was due to the inhibition of cathepsin G, the main biochemical mediator of this cell-cell cooperation. Since cathepsin G not only induces platelet activation but also affects some endothelial cell functions, the anticathepsin G activity of defibrotide could help to explain the antithrombotic effect of this drug.

Topics: Catalysis; Cathepsin G; Cathepsins; Fibrinolytic Agents; Humans; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Platelet Activation; Polydeoxyribonucleotides; Serine Endopeptidases; Serotonin; Thrombin; Thromboxane B2

Prostacyclin (PGI2) improves regional contractility of postischemically dysfunctional ("stunned") myocardium. We determined whether defibrotide, a fraction of mammalian DNA known to stimulate endogenous formation of PGI2, also improves contractile recovery of stunned myocardium. Anesthetized, open-chest minipigs were subjected to coronary occlusion of 5 min (left anterior descending branch, LAD) followed by 120 min of reperfusion. The animals were treated with defibrotide (32 mg x kg-1 x h-1, intravenously, i.v.) or vehicle throughout the experimental period. Defibrotide improved regional contractility in the ischemic reperfused area from 30 (vehicle) to 78% of the preischemic control without altering the contractility of nonischemic myocardium. Transcardiac PGI2 formation, determined from the difference between coronary venous and arterial plasma concentrations, was elevated from 437 (preischemic control) to 869 pmol x l-1 in defibrotide-treated animals, but was unchanged in the vehicle-treated and a sham-operated group. Thromboxane A2 (TXA2) release was not modified. Defibrotide reduced ischemia-induced formation of platelet aggregates but did not affect the activity of polymorphonuclear neutrophil granulocytes. The data demonstrate an improvement of contractile recovery from stunning by defibrotide that may be related to an inhibition of ischemia-induced platelet activation and (or) membrane protection owing to enhanced transcardiac formation of PGI2.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Blood Platelets; Coronary Vessels; Epoprostenol; Female; Fibrinolytic Agents; Heart; Hemodynamics; Male; Myocardial Contraction; Myocardial Infarction; Myocardial Reperfusion; Neutrophils; Platelet Count; Polydeoxyribonucleotides; Stimulation, Chemical; Swine; Swine, Miniature; Thromboxane B2; Time Factors

Topics: 6-Ketoprostaglandin F1 alpha; Angiography; Arteriosclerosis; Cyclic AMP; Female; Fibrinolytic Agents; Humans; Male; Middle Aged; Physical Exertion; Polydeoxyribonucleotides; Thromboangiitis Obliterans; Thromboxane B2

Patients were treated with defibrotide (3 X 200 mg/day) for 7 days. Plasma PGI2 and TXB2 levels were measured by RIA using EDTA-aspisol as anticoagulant and cyclooxygenase inhibitor. Isolated platelet c-AMP levels were also determined by RIA, using EDTA-dipyridamole as anticoagulant and phosphodiesterase inhibitor. Blood PGI2 levels were found to increase significantly upon treatment while the increase in TXB2 levels was not significant. Blood PGI2/TXB2 ratio increased 51%, 30 min after intravenous injection and it remained 28% higher during therapy than the predrug blood level. Significantly higher platelet c-AMP levels were also obtained after the injection of drug (0.02 less than p less than 0.05).

Topics: 6-Ketoprostaglandin F1 alpha; Arteriosclerosis; Blood Platelets; Cyclic AMP; Fibrinolytic Agents; Humans; Malondialdehyde; Platelet Aggregation; Polydeoxyribonucleotides; Prostaglandins; Thromboxane B2; Time Factors