Effects of a novel Mac-1 inhibitor, NPC 15669, on hemostatic parameters during preconditioned myocardial infarction

NPC 15669, a member of the leumedins family, inhibits leukocyte adhesion to the endothelium by blockage of upregulation of a member of β2 integrin family Mac1 (CD11b/CD18). Inhibition of neutrophil-endothelial interactions may alter the course of myocardial reperfusion injury. However, the effects of NPC 15669 supplementation on the hemostatic profile during ischemia- reperfusion are unknown. The aim of the present study was to define changes in the certain hemostatic factors in the natural course of preconditioned myocardial infarction. Twelve consecutive Yorkshire swine underwent myocardial stunning (8 min. left anterior descending artery occlusion followed by 90 min. of reperfusion) and then preconditioned myocardial infarction (50 min. occlusion followed by 3 hours of reperfusion) experiments. NPC 15669 (10 mg/kg loading dose followed by constant infusion at 6 mg·kg^-1·h^-1) was administered in 6 animals; another 6 swine received saline and served as controls. Blood samples were obtained at baseline, twice during occlusion; and three times during reperfusion. The levels of antithrombin-III, Protein C, total Protein S, fibronectin, endothelin-1, as well as the stable metabolites of thromboxane (TxB₂) and prostacyclin (6-keto-PGF(1a)), were determined. NPC 15669 treatment was associated with diminished endothelin-1, TxB₂ levels and increased fibronectin, 6-keto-PGF(1a), Protein C and total Protein S concentrations in the setting of preconditioned myocardial infarction. There were no changes in the plasma concentrations of antithrombin-III in NPC 15669 group when compared with controls. The increase in Protein C, total Protein S, and 6- keto-PGF(1a) (favoring antithrombosis), and decrease in endothelin-1 and TxB₂ levels (favoring vasodilatation), following NPC 15669 may explain the reduction in infarct size previously reported with this agent.