Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Myocardial ischemia inhibits endothelium-dependent relaxation stimulated by the coagulant peptide, thrombin. To investigate whether activation of endogenous thrombin contributed to this reduction in relaxant sensitivity, the effects of pretreatment of dogs with the coumarin anticoagulant, brodifacoum, were studied. Experiments were performed in both normal coronary vasculature and coronary vasculature exposed to 90 min of myocardial ischemia, with or without 60 min of subsequent reperfusion. Ischemia was induced in the left anterior descending artery (LAD); nonischemic vessels from the left circumflex (LCX) artery of the same animals were used as control. Thrombin caused dose-dependent relaxation in isolated LCX preconstricted with prostaglandin F2 alpha (Emax of 89.1 +/- 2.33%). Relaxation was reduced by 90 min of ischemia (Emax of 27.5 +/- 8.0%; p less than 0.05), and further reduced after subsequent reperfusion (Emax of 8.7 +/- 8.7%). However, maximum relaxations to acetylcholine, calcimycin, and isoproterenol were unchanged after ischemia (Emax greater than 90% in all groups). Brodifacoum had no effect on thrombin-induced relaxation in control vessels (Emax of 83.0 +/- 3.5%), or on relaxation in response to acetylcholine, calcimycin, or isoproterenol (Emax greater than 90%). In contrast, brodifacoum markedly reduced thrombin-induced relaxation after ischemia (Emax of 3.3 +/- 3.3%; p less than 0.05) yet significantly preserved the relaxant response to thrombin after ischemia and reperfusion (Emax of 36.6 +/- 4.3%). Infusion of the thrombin inhibitor, D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone (PPACK), during ischemia and reperfusion also preserved in part the relaxant response induced by thrombin (Emax of 30.0 +/- 5.1%; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of thrombin-induced endothelium-dependent relaxation after coronary ischemia in the dog: possible role of the coagulation cascade. 171 94

Thrombin has been suggested as one of the main pharmacologic targets in unstable coronary syndromes. Electrocardiographic signs of ischemia during continuous monitoring convey prognostic information in these patients. This study assessed the anti-ischemic and clinical effects of the novel low-molecular weight thrombin inhibitor inogatran in patients with unstable angina and non-Q-wave infarction without persistent ST-segment elevation on hospital admission. Within 24 hours of the last episode of chest pain, 324 patients were randomized to 72 hours of treatment with inogatran or heparin. Continuous ST-segment analysis with computerized vectorcardiography was used to monitor ischemia for 24 hours. The occurrence of cardiac events during the first 7 days were studied and compared with ischemic episodes during the initial 24 hours. The heparin-treated patients had less episodes of ischemia (ST vector magnitude [ST-VM]: 1 +/- 2.6 vs 2 +/- 4.5, p < 0.001 and ST change vector magnitude [STC-VM]: 3 +/- 4.7 vs 6 +/- 7.6, p < 0.001) than the patients receiving inogatran. This was paralleled by a lower incidence of the combined end point of death, nonfatal infarction, refractory or recurrent angina during the first 7 days for the heparin-treated patients (35%) compared with the inogatran-treated patients (50%) (p < 0.05). Patients who had episodes of ischemia in spite of anti-ischemic therapy were at increased risk of all events studied. Heparin is more effective than inogatran in suppressing myocardial ischemia and clinical events at short-term follow-up. Continuous ST-segment monitoring with vectorcardiography identifies nonresponders who are at an increased level of risk.
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PMID:Heparin is more effective than inogatran, a low-molecular weight thrombin inhibitor in suppressing ischemia and recurrent angina in unstable coronary disease. Thrombin Inhibition in Myocardial Ischemia (TRIM) Study Group. 957 50

Thrombolytic therapy has become a standard treatment for selected patients with acute myocardial infarction (MI). Various thrombolytic agents have been shown to decrease mortality. However, current thrombolytic agents still suffer significant shortcomings, such as a low optimal reperfusion rate delayed reperfusion. and incomplete myocardial perfusion. Furthermore, cyclic flow variations and reocclu.sions remain a significant cause of late morbidity and mortality. In thrombolysis with tissue plasminogen activator (t-PA), heparin seems to play an important role. However, it has several features that suggest that it may not be the optimal adjunct to thrombolytics, including weak and indirect action on thrombin, little access to clot-bound thrombin, inhibition by acute-phase plasma proteins, and its direct stimulation of platelet aggregation. Argatroban (NOVASTAN(R)), a small-molecule, synthetic, direct thrombin inhibitor, has several potential advantages over heparin, and prior studies suggest superior thrombin inhibition with favorable pharmacokinetic and pharmacodynamic properties warranting further investigation The Myocardial Infarction using NOVASTAN (R) and t-PA (MINT) study is a phase II, single-blind, angiographic trial directly comparing heparin versus two doses of argatroban in 120 patients with ST-elevation MI who present within 6 hours of symptom onset. The primary objective of the MINT trial is to assess the TIMI grade 3 flow and TIMI Frame Count at 90 minutes after the initiation of t-PA. This trial will also evaluate the safety of the combination of t-PA, argatroban, and aspirin. The incidence of clinical or silent ischemia, will be monitored. All patients will be followed up to 30 days for the composite endpoint of death, nonfatal recurrent myocardial infarction, coronary artery bypass surgery, PTCA, recurrent ischemia, and shock/new-onset heart failure.
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PMID:A Randomized, Blinded Study of Two Doses of Novastan(R) (Brand of Argatroban) Versus Heparin as Adjunctive Therapy to Recombinant Tissue Plasminogen Activator (Accelerated Administration) in Acute Myocardial Infarction: Rationale and Design of the Myocardial Infarction using Novastan(R) and T-PA (MINT) Study. 1060 50

We investigated whether anticoagulant therapy with heparin or a selective thrombin inhibitor, argatroban, may ameliorate the postischemic cerebral circulation and attenuate mortality after 10 min of forebrain ischemia. Postischemic subcutaneous injection of argatroban (5 mg/kg) significantly attenuated mortality (9.1%) compared with non-treatment (45.5%) during 14 days' observation period. This effect coincided with: (1) increased cortical CBF after reperfusion; (2) attenuation of brain edema; and (3) less severe cell damages in the cerebral cortex. In contrast, nine of the 22 gerbils treated with heparin (830 IU/kg) were found dead on the next day due to massive bleeding in the surgical wound and 13 bleeding-avoided gerbils did not show significant amelioration in mortality (30.8%). These findings suggest that argatroban is an effective anticoagulant for prevention of cell damage after a relatively long forebrain ischemia.
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PMID:Argatroban, a thrombin inhibitor, decreased mortality after 10 min of forebrain ischemia in the gerbil. 1067 29

We have considered the extracellular serine protease thrombin and its receptor as endogenous mediators of neuronal protection against brain ischemia. Exposure of gerbils to prior mild ischemic insults, here two relatively short-lasting occlusions (2 min) of both common carotid arteries applied at 1-day intervals 2 days before a severe occlusion (6 min), caused a robust ischemic tolerance of hippocampal CA1 neurons. This resistance was impaired if the specific thrombin inhibitor hirudin was injected intracerebroventricularly before each short-lasting insult. Thus, efficient native neuroprotective mechanisms exist and endogenous thrombin seems to be involved therein. In vitro experiments using organotypic slice cultures of rat hippocampus revealed that thrombin can have protective but also deleterious effects on hippocampal CA1 neurons. Low concentrations of thrombin (50 pM, 0.01 unit/ml) or of a synthetic thrombin receptor agonist (10 microM) induced significant neuroprotection against experimental ischemia. In contrast, 50 nM (10 units/ml) thrombin decreased further the reduced neuronal survival that follows the deprivation of oxygen and glucose, and 500 nM even caused neuronal cell death by itself. Degenerative thrombin actions also might be relevant in vivo, because hirudin increased the number of surviving neurons when applied before a 6-min occlusion. Among the thrombin concentrations tested, 50 pM induced intracellular Ca(2+) spikes in fura-2-loaded CA1 neurons whereas higher concentrations caused a sustained Ca(2+) elevation. Thus, distinct Ca(2+) signals may define whether or not thrombin initiates protection. Taken together, in vivo and in vitro data suggest that thrombin can determine neuronal cell death or survival after brain ischemia.
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PMID:The protease thrombin is an endogenous mediator of hippocampal neuroprotection against ischemia at low concentrations but causes degeneration at high concentrations. 1068 55

Little is known about interactions between endogenous anti-inflammatory paradigms and microvascular thrombosis in lung ischemia/reperfusion (I/R) injury. Interleukin (IL)-10 suppresses macrophage activation and down-regulates proinflammatory cytokine production, but there are no available data to suggest a link between IL-10, thrombosis, and fibrinolysis in the setting of I/R. We hypothesized that hypoxia/ischemia triggers IL-10 production, to dampen proinflammatory cytokine and adhesion receptor cascades and to restore vascular patency by fibrinolytic potentiation. Studies were performed in a mouse lung I/R model. IL-10 mRNA levels in lung were increased 43-fold over base line by 1 h of ischemia/2 h of reperfusion, with a corresponding increase in plasma IL-10. Expression was prominently localized in bronchial epithelial cells and mononuclear phagocytes. To study the link between IL-10 and fibrinolysis in vivo, the induction of plasminogen activator inhibitor-1 (PAI-1) was evaluated. Northern analysis demonstrated exaggerated pulmonary PAI-1 expression in IL-10 (-/-) mice after I/R, with a corresponding increase in plasma PAI/tissue-type plasminogen activator activity. In vivo, IL-10 (-/-) mice showed poor postischemic lung function and survival after I/R compared with IL-10 (+/+) mice. Despite a decrease in infiltration of mononuclear phagocytes in I/R lungs of IL-10 (-/-) mice, an increased intravascular pulmonary fibrin deposition was observed by immunohistochemistry and Western blotting, along with increased IL-1 expression. Recombinant IL-10 given to IL-10 (-/-) mice normalized the PAI/tissue-type plasminogen activator ratio, reduced pulmonary vascular fibrin deposition, and rescued mice from lung injury. Since recombinant hirudin (direct thrombin inhibitor) also sufficed to rescue IL-10 (-/-) mice, these data suggest a preeminent role for microvascular thrombosis in I/R lung injury. Ischemia-driven IL-10 expression confers postischemic pulmonary protection by augmenting endogenous fibrinolytic mechanisms.
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PMID:Potentiation of endogenous fibrinolysis and rescue from lung ischemia/reperfusion injury in interleukin (IL)-10-reconstituted IL-10 null mice. 1080 8

Our previous studies have shown that prior intracerebral infusion of a low dose of thrombin (thrombin preconditioning; TPC) reduces the brain edema that follows a subsequent intracerebral infusion of a high dose of thrombin or an intracerebral hemorrhage. In vitro studies have also demonstrated that low concentrations of thrombin protect neurons and astrocytes from hypoglycemia and oxidative stress-induced damage. This study, therefore, examines the hypothesis that TPC would offer protection from ischemic brain damage in vivo. This was a blinded design study. The rat brain was preconditioned with 1 U thrombin by direct infusion into the left caudate nucleus. Seven days after thrombin pretreatment, permanent middle cerebral artery occlusion (MCAO) was induced. Twenty-four hours post-ischemia, neurological deficit was evaluated and infarction volume, brain water and ion contents were measured. Compared to saline-treated rats, thrombin pretreatment significantly attenuated brain infarction in cortex (90+/-33 vs. 273+/-22 mm(3); P<0.05) and basal ganglia (56+/-17 vs. 119+/-12 mm(3); P<0.05) that followed 24 h of permanent MCAO. TPC also reduced the brain edema in cortex and basal ganglia by 50 and 53% (P<0.05). Neurological deficit was improved in thrombin pretreatment group (P<0.05). These effects of TPC were, in part, prevented by co-injection of hirudin, a thrombin inhibitor, indicating that the protection was indeed thrombin mediated. Cerebral TPC significantly reduces ischemic brain damage, perhaps by activation of the thrombin receptor. This finding provides a new mechanism by which to study ischemic tolerance.
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PMID:The effects of thrombin preconditioning on focal cerebral ischemia in rats. 1083 11

The pathophysiologic role of thrombin in the development of lung injury after the normothermic cardiopulumonary bypass (CPB) was studied in the rabbit model. A control group (group D) was subjected to the pericardiotomy without institution of CPB. Group A rabbits (n = 6) underwent left heart bypass (80 ml/kg/min) for 60 minutes without occlusion of the systemic or pulmonary artery and a succeeding reduced flow (20-30 ml/kg/min) for another 30 minutes, group B rabbits (n = 6) underwent complete CPB (80 ml/kg/min) for 60 minutes in the working mode with occlusion of the pulmonary arterial trunk and a succeeding reduced flow without occlusion of the pulmonary artery for another 30 minutes, group C rabbits (n = 6) underwent the same CPB technique as group B in conjunction with continuous intravenous infusion of argatroban (60 micrograms/kg/min), the specific thrombin inhibitor. In this group, infusion of argatroban was initiated 60 minutes prior to institution of CPB and terminated at the end of the experiment. We sacrificed rabbits four hours after the experiment began, and assessed not only morphometrically thrombus formation, leukocytic infiltration and luminal narrowing of small-sized pulmonary arteries but also immunohistochemically the expression of tissue factor (TF) and IL-1 beta, and physico-functionally respiratory index (RI) and pulmonary vascular resistance (PVR). Rabbits in group A showed multiple occurrence of lung thrombi, luminal narrowing of small arteries, and mild infiltration of macrophages and neutrophils positive for TF, and, in addition, their RI and PVR became mildly worse. In group B, all these morphological and physico-functional parameters became much worse than those observed in group A rabbits (p < .01). In contrast, argatroban treatment could significantly improve these parameters (p < .01). The expression of TF and IL-1 beta, however, was not significantly different in group A, B and C. These findings indicate that thrombin function intimately participates in the development of pulmonary ischemia-reperfusion injury during CPB. In addition, the anti-thrombin treatment would be an effective therapeutical tool for the prevention of not only activation of extrinsic coagulation pathway but also its sequential inflammatory and circulatory disturbance in ischemia-reperfusion injury of lung during CPB.
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PMID:[Specific inhibition of thrombin activity during cardiopulmonary bypass reduces ischemia-reperfusion injury of the lung]. 1124 85

Acute coronary syndromes encompass a spectrum of conditions, including myocardial infarction and unstable angina. These syndromes are related to the formation and disruption of atherosclerotic plaque. Rupture of plaque leads to thrombin generation, fibrin deposition, and platelet aggregation, ultimately resulting in restriction of blood flow and ischemia of cardiac tissue. Percutaneous coronary intervention (PCI), including angioplasty and coronary stent placement, has been developed to open occluded arteries. The frequency with which these procedures are performed speaks to their largely successful outcomes. However, the mechanical manipulations of PCI result in additional plaque rupture and damage to the vessel wall, exposing subendothelial components to blood and resulting in the initiation of the clotting cascade and in platelet activation. Left unchecked, these intertwined processes lead to formation of arterial thrombi at the site of endothelial damage, and potentially to abrupt vessel closure or embolization of thrombi into the distal microcirculation. Thrombin plays a central role in thrombus formation and platelet activation, and its inhibition significantly reduces thrombus-related sequelae. Current antithrombotic strategies during PCI are based on the traditional indirect thrombin inhibitor heparin. Heparin has several limitations in efficacy and safety, due in part to its indirect mechanism of action. Bivalirudin, a direct thrombin inhibitor, offers significant improvement over heparin in the clinical outcomes and risks associated with PCI.
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PMID:The role of thrombin inhibition during percutaneous coronary intervention. 1206 71

We investigated whether or not a combination of the selective thrombin inhibitor, argatroban, and the free radical scavenger, edaravone (MCI-186), ameliorates postischemic hypoperfusion and decreases mortality after 15 min of forebrain ischemia in the gerbil. Argatroban or edaravone alone significantly increased postischemic cerebral blood flow and attenuated brain edema after reperfusion. However, only the combination increased the survival ratio (P<0.05 by Mantel-Cox) and protected the damage of neuronal cells. The present study indicates that anticoagulants and free radical scavengers reciprocally function to inhibit the progression of ischemic cell damage and that a combination of these types of drugs will help to improve the outcomes after cerebral ischemia.
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PMID:Combined argatroban and edaravone caused additive neuroprotection against 15 min of forebrain ischemia in gerbils. 1207 43


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