sq-29548 and Thrombosis

N-aralkylpyroglutamides of substituted bispidine were prepared and evaluated for their ability to inhibit collagen induced platelet aggregation, both in vivo and in vitro. Some compounds showed high anti-platelet efficacy (in vitro) of which six inhibited both collagen as well as U46619 induced platelet aggregation with concentration dependent anti-platelet efficacy through dual mechanism. In particular, the compound 4j offered significant protection against collagen epinephrine induced pulmonary thromboembolism as well as ferric chloride induced arterial thrombosis, without affecting bleeding tendency in mice. Therefore, the present study suggests that the compound 4j displays a remarkable antithrombotic efficacy much better than aspirin and clopidogrel.

Topics: Animals; Blood Coagulation; Blood Platelets; Bridged Bicyclo Compounds, Heterocyclic; Hemorrhage; Humans; Mice; Platelet Adhesiveness; Platelet Aggregation; Platelet Aggregation Inhibitors; Pulmonary Embolism; Pyrrolidonecarboxylic Acid; Thrombosis

TRA-418, a compound with both thromboxane A2 receptor (TP receptor) antagonistic and prostacyclin receptor (IP receptor) agonistic activities, was synthesised in our laboratory as a new antithrombotic agent. In this study, we examined the effects of TRA-418 on platelet-leukocyte interactions in human whole blood. Platelet-leukocyte interactions were induced by U-46619 in the presence of epinephrine (U-46619 + epinephrine) or with thrombin receptor agonist peptide 1-6 (TRAP). Platelet-leukocyte interactions were assessed by flow cytometry, with examination of both platelet-neutrophil and platelet-monocyte complexes. In a control experiment, the TP receptor antagonist SQ-29548 significantly inhibited the induction of platelet-leukocyte complexes by the combination of U-46619 and epinephrine, but not TRAP-induced formation of platelet-leukocyte complexes. Conversely, the IP receptor agonist beraprost sodium inhibited platelet-leukocyte complex formation induced by both methods, although the IC50 values of beraprost sodium for U-46619 + epinephrine were at least 10-fold greater than for TRAP. Under such conditions, TRA-418 inhibited both U-46619 + epinephrine-induced and TRAP-induced platelet-leukocyte complex formation in a concentration-dependent manner, in a similar range. These results suggest that TRA-418 exerts its inhibitory effects on platelet-leukocyte interactions by acting as a TP receptor antagonist as well as an IP receptor agonist in an additive or synergistic manner. These inhibitory effects of TRA-418 on formation of platelet-leukocyte complexes suggest the compound is beneficial effects as an antithrombotic agent.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Blood Platelets; Bridged Bicyclo Compounds, Heterocyclic; Cell Communication; Cell Separation; Cells, Cultured; Epinephrine; Epoprostenol; Fatty Acids, Unsaturated; Flow Cytometry; Humans; Hydrazines; Leukocytes; Oxazines; Peptide Fragments; Platelet Activation; Receptors, Epoprostenol; Receptors, Thromboxane A2, Prostaglandin H2; Thrombosis

Previous studies using washed platelets demonstrated that certain flavonoids inhibit platelet function through several mechanisms including blockade of TxA(2) receptors (TPs). We aimed to analyze the binding capacity of flavonoids to TPs in platelet rich plasma (PRP), investigated their effect in flowing blood, and evaluated the ability of apigenin to improve the efficacy of aspirin in the inhibition of platelet aggregation. The binding of flavonoids to TPs in PRP was explored using binding assays and the TP antagonist [ (3)H]SQ29548. Effects of flavonoids on platelet adhesion were assessed using arterial subendothelium with annular plate perfusion chambers, and global evaluation of apigenin on high-shear-dependent platelet function was determined by the PFA-100. To evaluate the ability of apigenin to potentiate the effect of aspirin, arachidonic acid-induced platelet aggregation was measured prior to and after consumption of subaggregatory doses of aspirin in the presence or absence of apigenin. Binding assays revealed that apigenin was an efficient competitor of [ (3)H]SQ29548 binding to PRP ( K i = 155.3 +/- 65.4 microM), and perfusion studies showed that apigenin, genistein, and catechin significantly diminished thrombus formation when compared to control (26.2 +/- 3.8, 33.1 +/- 5.2, and 26.2 +/- 5.2 vs 76.6 +/- 2.6%, respectively; p < 0.05). Apigenin, similarly to the TP antagonist SQ29548, significantly prolonged collagen epinephrine-induced PFA-100 closure time in comparison to the control and, when added to platelets that had been exposed in vivo to aspirin, potentiated its inhibitory effect on platelet aggregation. The inhibitory effect of some flavonoids in the presence of plasma, particularly apigenin, might in part rely on TxA(2) receptor antagonism. There is a clear increase in the ex vivo antiplatelet effect of aspirin in the presence of apigenin, which encourages the idea of the combined use of aspirin and certain flavonoids in patients in which aspirin fails to properly suppress the TxA(2) pathway.

Topics: Apigenin; Arachidonic Acid; Aspirin; Blood Platelets; Bridged Bicyclo Compounds, Heterocyclic; Drug Synergism; Endothelium; Fatty Acids, Unsaturated; Humans; Hydrazines; Platelet Adhesiveness; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet-Rich Plasma; Receptors, Thromboxane A2, Prostaglandin H2; Thrombosis

Topics: Animals; Blood Pressure; Bridged Bicyclo Compounds, Heterocyclic; Death, Sudden; Drug Synergism; Fatty Acids, Unsaturated; Hydrazines; Imidazoles; Indomethacin; Isoquinolines; Male; Pyridines; Rabbits; Tetrahydroisoquinolines; Thrombin; Thrombosis; Thromboxane A2; Thromboxane-A Synthase

We studied the effects of thromboxane-receptor antagonism and thromboxane synthetase inhibition in a thrombotic model of sudden death in mice. Intravenous injection of arachidonic acid (AA; 80 mg/kg) or the prostaglandin-endoperoxide analog U-46,619 (2.3 mg/kg) results in sudden death in approximately 90% of the animals. Pretreatment with the thromboxane receptor antagonist SQ-29,548 (0.3-10 mg/kg) protects dose-dependently against AA and U-46,619-induced sudden death. In contrast, CGS-13,080, a thromboxane synthetase inhibitor, shows a dose-dependent beneficial effect in AA-induced sudden death only. Although PTA2 has partial thromboxane agonistic properties in the rabbit, it protected the mice against AA-induced sudden death, thus demonstrating TxA2 antagonistic properties in this species. These data emphasize the importance of thromboxane A2 as a major mediator of arachidonic acid-induced sudden death and the effectiveness of thromboxane-receptor antagonists in endoperoxide-induced sudden death.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Animals; Arachidonic Acid; Arachidonic Acids; Bicyclic Monoterpenes; Bridged Bicyclo Compounds, Heterocyclic; Death, Sudden; Fatty Acids, Unsaturated; Fibrinolytic Agents; Hydrazines; Imidazoles; Injections, Intravenous; Male; Mice; Platelet Aggregation; Prostaglandin Endoperoxides, Synthetic; Pyridines; Receptors, Cell Surface; Receptors, Prostaglandin; Receptors, Thromboxane; Thrombosis; Thromboxane A2; Thromboxane-A Synthase