piperidines and Carotid-Artery-Thrombosis

Thrombosis and neointima formation limit the efficacy of coronary angioplasty. Factor Xa inhibitors and GPIIb/IIIa antagonists have shown to be effective on acute thrombosis and late neointima formation, however, their combined effects remain to be elucidated. Vascular injury was induced by FeCl(3) in the carotid artery in mice. For thrombosis studies, the test drug was orally administered 1 hour before vascular injury. For neointima studies, the test drug was orally administered 1 hour before and twice daily for 1 week after vascular injury, and then histological analysis was performed 3 weeks after vascular injury. YM466 inhibited thrombotic occlusion at 30 mg/kg with prolongation of prothrombin time (PT), and tail transection bleeding time (BT) was affected at 100 mg/kg. YM466 also inhibited neointima formation at 10 mg/kg. YM128 inhibited thrombotic occlusion and neointima formation at 10 and 30 mg/kg, respectively, with inhibition of platelet aggregation and prolongation of BT. In contrast, the combination of 10 mg/kg YM466 and 3 mg/kg YM128 inhibited thrombotic occlusion and neointima formation without affecting PT, platelet aggregation and BT. Concomitant inhibition of factor Xa and GPIIb/IIIa may provide a safer and more effective therapeutic regimen for treatment of coronary angioplasty.

Topics: Angioplasty; Animals; Bleeding Time; Blood Coagulation; Blood Platelets; Carotid Arteries; Carotid Artery Thrombosis; Chlorides; Dose-Response Relationship, Drug; Drug Synergism; Factor Xa; Factor Xa Inhibitors; Ferric Compounds; Mice; Mice, Inbred ICR; Naphthalenes; Piperazines; Piperidines; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIIb-IIIa Complex; Prothrombin Time; Thrombosis; Time Factors

The interaction of fibrinolytic components with platelets or coagulation factors after endothelial injury, was investigated in mouse deficient in tissue type plasminogen activator (tPA -/-), or urokinase (uPA -/-) and in their wild type control (tPA +/+, uPA +/+). A thrombus was induced in the murine carotid artery using the photochemical reaction. Blood flow was continuously monitored and the time needed before the vessel became completely obstructed was within 11 min in all types of mice. When GR144053, a platelet glycoprotein IIb/IIIa antagonist, or argatroban, a thrombin inhibitor, was applied, the time required to occlusion was prolonged in a dose-dependent manner in all types of mice. However, when GR144053 was injected in tPA -/- mice, the most significant changes were observed: that is the estimated ED50 was 14.8 times higher than the one in tPA +/+ mice. On the other hand, when argatroban was injected in tPA -/- mice, the estimated ED50 was not changed. Platelet aggregation, haemostasis tests and bleeding times were not significantly different among the different types of mice. In conclusion, the antithrombotic effect of platelet inhibition by a GPIIb/IIIa antagonist, is severely affected by the absence or presence of tPA-production. Thus, the lack of tPA significantly reduces the antithrombotic efficacy.

Topics: Animals; Arginine; Bleeding Time; Carotid Artery Thrombosis; Dose-Response Relationship, Drug; Fibrinolytic Agents; Mice; Mice, Knockout; Pipecolic Acids; Piperazines; Piperidines; Platelet Glycoprotein GPIIb-IIIa Complex; Sulfonamides; Thrombin; Thrombolytic Therapy; Tissue Plasminogen Activator; Urokinase-Type Plasminogen Activator

We examined the antithrombotic activity of a novel synthetic inhibitor of factor Xa, YM-60828, in an electrically-induced carotid artery thrombosis model in rats. In the first experiment, the antithrombotic activity of YM-60828 after i.v. infusion was compared with those of heparin, darteparin and argatroban. Test drug was administered by i.v. infusion from 30 min before electrical stimulation to the end of the experiment. YM-60828 at 1 mg/kg/h significantly improved patency status, prolonged the time to occlusive thrombus formation and duration of patency. Heparin at 300 U/kg/h also improved these parameters, but were accompanied by a marked increase in systemic coagulation time. In the second experiment, the antithrombotic activity of YM-60828 after oral administration was compared with those of ticlopidine, cilostazol, aspirin, beraprost, ethyl icosapentate and warfarin. Test drug was orally administered to fasted rats 60 min before electrical stimulation. YM-60828 at 30 mg/kg p.o., but not ticlopidine, cilostazol, aspirin, beraprost, ethyl icosapentate or warfarin, significantly reduced the incidence of occlusion and improved carotid arterial patency. These results suggest that YM-60828 may be a promising antithrombotic agent for the treatment and prevention of arterial thrombosis which can be given by oral as well as intravenous administration.

Topics: Administration, Oral; Animals; Anticoagulants; Antithrombin III; Arginine; Carotid Artery Thrombosis; Disease Models, Animal; Factor Xa Inhibitors; Heparin; Infusions, Intravenous; Naphthalenes; Pipecolic Acids; Piperidines; Rats; Sulfonamides

We examined the adjunctive effect of a novel factor Xa inhibitor, YM-60828, on vessel patency and blood loss from the operation site after successful thrombolysis with a modified tissue-type plasminogen activator (moPA) in an electrically-induced carotid artery thrombosis model in rats. Five minutes after the induction of occlusive thrombus, a test drug (YM-60828, argatroban, heparin or saline) was administered by i.v. bolus injection followed by continuous infusion. Thrombolysis was induced with moPA by i.v. bolus injection at a dose of 650,000 IU/ kg. YM-60828 at 1 mg/kg i.v. followed by 3 mg/kg/h significantly prevented reocclusion, increased the duration of patency, and improved vessel patency after successful thrombolysis without any significant increase in blood loss from the operation site. Argatroban at 1 mg/kg i.v. followed by 3 mg/kg/h and heparin at 300 U/kg i.v. followed by 150 U/kg/h also significantly improved these parameters, but were accompanied by a significant increase in blood loss. These results suggest that the factor Xa inhibitor YM-60828 may be a potent and useful adjunctive agent with a lower risk of bleeding complications than argatroban and heparin in thrombolytic therapy.

Topics: Animals; Anticoagulants; Arginine; Blood Loss, Surgical; Carotid Arteries; Carotid Artery Thrombosis; Drug Evaluation, Preclinical; Hemorrhage; Heparin; Male; Naphthalenes; Pipecolic Acids; Piperidines; Rats; Recurrence; Reperfusion; Serine Proteinase Inhibitors; Sulfonamides; Thrombolytic Therapy; Time Factors; Tissue Plasminogen Activator

The antithrombotic effects of a novel factor Xa inhibitor, YM-60828 ([N-[4-[(1-acetimidoyl-4-piperidyl)oxy]phenyl]-N-[(7-amidino-2-nap hthyl)methyl]sulfamoyl]acetic acid dihydrochloride), in three thrombosis models in guinea pigs were studied in comparison with its effect on bleeding time. The antithrombotic effects of YM-60828 were most pronounced in the venous thrombosis and the arterio-venous shunt models but YM-60828 showed 10-fold weaker effects in the carotid thrombosis model. However, YM-60828 prolonged bleeding time at a much higher dose than that required in all thrombosis models. In conclusion, YM-60828 exerted its antithrombotic effects without prolonging bleeding time in all thrombosis models and may be of clinical value not only in venous thrombosis but also in arterial thrombosis.

Topics: Animals; Antithrombin III; Arteriovenous Shunt, Surgical; Bleeding Time; Carotid Artery Thrombosis; Carotid Artery, Internal; Disease Models, Animal; Factor Xa Inhibitors; Fibrinolytic Agents; Guinea Pigs; Male; Naphthalenes; Piperidines; Thrombophlebitis; Thrombosis

The antithrombotic effect of GR144053, which inhibits platelet aggregation by binding to the fibrinogen receptor (glycoprotein IIb/IIIa), was investigated in vitro and in vivo by using hamsters. This compound inhibited the platelet aggregation induced by adenosine diphosphate (ADP; 2.5 microM) with a mean inhibitory concentration (IC50) value of 2.2 +/- 0.4 x 10(-5) M. Vascular injury was inflicted in one carotid artery by using a modified catheter to produce endothelial denudation. In the control group, arterial blood flow was interrupted 4.4 +/- 2.3 min (n = 12) after the injury. When GR144053 continuously infused intravenously at doses of 0 (saline) 0.1, 0.3, and 1.0 mg/kg/h (n = 8, each), the time that elapsed before the vessel became completely obstructed was prolonged in a dose-dependent manner. In separate experiments, reperfusion could be obtained by continuous infusion of tissue-type plasminogen activator (tPA; 0.52 mg/kg) starting 30 min after the initiation of thrombus formation. When GR144053 (0.3 and 1.0 mg/kg/h) was infused in addition to tPA, the incidence of reperfusion and the later patency of the reperfused artery were much improved as compared with tPA alone. The bleeding time at the end of tPA infusion was significantly prolonged in the presence of the highest dose of GR144053. Next, neointima formation was evaluated 2 weeks after the vascular injury. When GR144053 (0.3 mg/kg/h) was continuously infused i.v. by an implanted osmotic pump for 14 days, the neointimal area was significantly reduced. In separate hamsters, the proliferating index of smooth muscle cells (SMCs) by using bromodeoxyuridine (BrdU) was investigated, and treatment with both tPA and GR144053 significantly decreased the SMC proliferation index in vivo. However, in the in vitro experiments using a hamster SMC line, GR144053 did not have an inhibitory effect on SMC proliferation. These findings suggest that GR144053 inhibits platelet activation on the injured artery and improves vascular patency after thrombolysis with tPA, which furthermore results in suppression of neointima formation.

Topics: Animals; Bleeding Time; Carotid Artery Thrombosis; Cell Division; Cricetinae; Disease Models, Animal; Drug Interactions; Fibrinogen; Fibrinolytic Agents; Male; Muscle, Smooth; Peptides; Piperazines; Piperidines; Platelet Aggregation Inhibitors; Platelet Glycoprotein GPIIb-IIIa Complex; Thrombolytic Therapy; Tissue Plasminogen Activator; Vascular Patency

The relation between the antithrombotic effect in vivo, and the inhibition constant (Ki) and the association rate constant (k(on)) in vitro was investigated for eight different thrombin inhibitors. The carotid arteries of anaesthetized rats were exposed to FeCl3 for 1 h, and the thrombus size was determined from the amount of incorporated 125I-fibrinogen. The thrombin inhibitors were given intravenously, and complete concentration- and/or dose-response curves were constructed. Despite a 50,000-fold difference between the Ki-values comparable plasma concentrations of hirudin and melagatran were needed (0.14 and 0.12 micromol l(-1), respectively) to obtain a 50% antithrombotic effect (IC50) in vivo. In contrast, there was a comparable in vitro (Ki-value) and in vivo (IC50) potency ratio for melagatran and inogatran, respectively. These results can be explained by the concentration of thrombin in the thrombus and improved inhibition by the low-molecular-weight compounds. For all eight thrombin inhibitors tested, there was an inverse relationship between k(on)-values in vitro and the slope of the dose response curves in vivo. Inhibitors with k(on)-values of < 1 x 10(7) M(-1) s(-1) gave steep dose response curves with a Hill coefficient > 1. The association time for inhibition of thrombin for slow-binding inhibitors will be too long to give effective antithrombotic effects at low plasma concentrations, but at increasing concentrations the association time will decrease, resulting in a steeper dose-response curve and thereby a more narrow therapeutic interval.

Topics: Amino Acid Chloromethyl Ketones; Animals; Anticoagulants; Arginine; Azetidines; Benzylamines; Carotid Artery Thrombosis; Dose-Response Relationship, Drug; Fibrinolytic Agents; Glycine; Hemodynamics; Heparin; Hirudin Therapy; Hirudins; Kinetics; Male; Oligopeptides; Partial Thromboplastin Time; Peptide Fragments; Pipecolic Acids; Piperidines; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Sulfonamides; Thrombin; Thrombin Time

Specific thrombin inhibitors are considered to be more potent antithrombotics than heparin. However, the relation between the systemic anticoagulation generated by thrombin inhibitors and their antithrombotic effect is not well defined. In a guinea pig carotid thrombosis model, the activated clotting time (ACT), the activated partial thromboplastin time (aPTT), and thrombin-generation tests were evaluated for their ability to predict the arterial antithrombotic effect of direct thrombin inhibitors such as hirudin and Ro 46-6240 compared with heparin.. Thrombosis of the carotid artery was induced by subendothelial damage in guinea pigs, and the subsequent cyclic flow variations were monitored. The effects of pretreatment with intravenous heparin, hirudin, and Ro 46-6240 were tested. After doubling the baseline aPTT, 1 IU.kg-1.min-1 heparin was inactive, whereas either hirudin or Ro 46-6240 (30 micrograms.kg-1.min-1) prevented thrombus formation by 80%. Heparin (10 IU.kg-1.min-1) induced the same antithrombotic effect but with indefinite aPTT prolongation. However, for similar prolongation of the ACT, the three compounds had equivalent antithrombotic effects. Thrombin generation was predictive of the antithrombotic effect of the thrombin inhibitors but not of heparin.. The arterial antithrombotic effect of direct thrombin inhibitors, when compared with those of heparin, should be evaluated by the ACT and not the aPTT or thrombin-generation assays. For a "therapeutic" aPTT prolongation, thrombin inhibitors induce higher systemic anticoagulation than does heparin and thus might unduly have higher bleeding liability.

Topics: Animals; Antithrombins; Carotid Artery Thrombosis; Guinea Pigs; Heparin; Hirudin Therapy; Humans; In Vitro Techniques; Male; Naphthalenes; Partial Thromboplastin Time; Piperidines; Predictive Value of Tests; Rabbits; Whole Blood Coagulation Time

We have characterised the Ca2+ channel blocking properties of a new non-peptide Ca2+ channel antagonist, SB 201823-A, in cultures of rat sensory neurones. The IC50 for SB 201823-A against total Ca2+ current in sensory neurones was 4.9 microM. SB 201823-A showed little selectivity for sub-types of neuronal Ca2+ channel but was selective for Ca2+ channels over Na+ and K+ channels. Efficacy against other types of cation channel such as agonist gated channels was not assessed. SB 201823-A was neuroprotective in vivo when administered post-ischaemia in one focal and one global model of neuronal ischaemia. In the rat photothrombotic focal lesion model, SB 201823-A administered i.p. 10 min post-ischaemia resulted in a dramatic reduction in lesion volume. In the gerbil bilateral carotid artery occlusion global model, SB 201823-A dosed i.p. 30 min post-occlusion resulted in both histological and functional improvements when compared to vehicle treated animals. These data suggest that such novel neuronal Ca2+ channel antagonists may have potential in ameliorating both the pathological and functional consequences of stroke in man.

Topics: Animals; Brain Ischemia; Calcium Channel Blockers; Carotid Artery Thrombosis; Electrophysiology; Ganglia, Spinal; Gerbillinae; Neurons, Afferent; Piperidines; Potassium; Rats; Sodium Channels; Synaptosomes