Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0151744 (myocardial ischemia)
 31,282 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of this study was to assess the anti-platelet properties of endocardial endothelial cells (EECs) by measuring platelet aggregation after a brief incubation with cultured EECs. EECs were isolated from the right ventricles of porcine hearts and coronary artery endothelial cells (C-ECs) were also isolated from the same animals. After brief incubations (2-min) of platelet suspensions with cultured EEC and CEC monolayers, platelet aggregation in response to thrombin and 6-keto-PGF1 alpha (a stable metabolite of PGI2) content of platelet suspensions were measured. Platelet aggregation was significantly inhibited by a brief incubation of platelet suspensions with EEC and C-ECs monolayers. Pretreatment of EECs and C-ECs with indomethacin (5 x 10(-5) M) restored platelet activity, but pretreatment with N omega-nitro-L-arginine methyl ester (L-NAME, 5 x 10(-5) M) or hemoglobin (1 x 10(-6) M) did not. Platelet/EEC interactions multiplicatively increased the 6-keto-PGF1 alpha content of platelet suspensions and the 6-keto-PGF1 alpha content of platelet suspensions after incubations with EECs correlated significantly with the inhibition of platelet aggregation. Both the anti-aggregation properties and 6-keto-PGF1 alpha production were significantly greater in EECs than in C-ECs. A brief incubation (2-min) with PDGF (10 ng/ml) or TGF-beta (1 and 10 ng/ml) stimulated 6-keto-PGF1 alpha production in EECs but not in C-ECs, although these growth factors stimulated 6-keto-PGF1 alpha production in C-ECs after a longer incubation time (30 or 60 min). In this study, after a brief incubation (2-min) with platelet suspensions, EECs inhibited platelet aggregation mainly through the release of PGI2 but not EDRF. As this anti-aggregation property was significantly greater in EECs than in C-ECs, it is suggested that endocardial endothelial PGI2 may inhibit both intracardiac and intracoronary artery thrombus formation, contributing to the prevention of myocardial ischemia.
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PMID:Antithrombotic effects of endocardial endothelial cells-comparison with coronary artery endothelial cells. 924 71

The initial step in atherosclerosis is the rapid targeting of monocytes to the sites of inflammation and endothelial injury. Serum levels of intercellular adhesion molecule-1 were found to be increased in ischaemic heart disease patients and polymorphisms in the E-selectin gene were associated with accelerated atherosclerosis in young (age < 40 years) patients, further suggesting a role of inflammation in atherosclerosis. Cholesterol loading in macrophages was found to induce interleukin-8 expression, suggesting an association between foam cell formation and beta 2-integrin-dependent adhesion of leukocytes. Enhanced endothelium-platelet interaction induced by hypercholesterolaemia is mediated by von Willebrand factor, whereas platelet adhesion to subendothelial matrix is mediated by fibulin-fibrinogen complexes. Activated platelets mediate the homing of leukocytes by interaction with the subendothelial matrix under shear stresses that do not allow neutrophil adhesion. They may also contribute to the oxidative modification of LDL, provide a source of lipids for foam cell generation and contribute to smooth muscle cell proliferation. Oxidized LDL induces tissue factor in macrophages that also provide sites for fibrin polymerization and decreases the anticoagulant activity of endothelium by interfering with thrombomodulin expression and inactivating tissue factor pathway inhibitor. Intravascular fibrinolysis induced by tissue-type plasminogen activator or urokinase may contribute to the initiation of atherosclerosis by inducing P-selectin and platelet activating factor as well as to plaque rupture, either directly or indirectly, by activating metalloproteinases. Plasminogen activator inhibitor-1 inhibits smooth muscle cell migration and, in the presence of vitronectin, promotes the clearance of thrombin by LDL receptor-related protein at sites of endothelial injury.
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PMID:Thrombosis and atherosclerosis. 933 57

Activation of phospholipase A2 (PLA2) and accumulation of lysophosphatidylcholine contribute importantly to arrhythmogenesis during acute myocardial ischemia. We examined thrombin stimulation of PLA2 activity in isolated ventricular myocytes. Basal and thrombin-stimulated cardiac myocyte PLA2 activity demonstrated a distinct preference for sn-1 ether-linked phospholipids with arachidonate esterified at the sn-2 position. The majority of PLA2 activity was calcium independent and membrane associated. Thrombin stimulation of membrane-associated PLA2 occurs in a time- and concentration-dependent fashion. An increase in PLA2 activity was also observed using the synthetic peptide SFLLRNPNDKYEPF (the tethered ligand generated by thrombin cleavage of its receptor). Bromoenol lactone, a selective inhibitor of calcium-independent PLA2, completely blocked thrombin-stimulated increases in PLA2 activity and arachidonic acid release. No significant inhibition of thrombin-induced PLA2 was observed following pretreatment with mepacrine or dibucaine. These data confirm the presence of high-affinity thrombin receptors on isolated cardiac myocytes and demonstrate the specific activation of a unique membrane-associated, calcium-independent PLA2 following thrombin receptor ligation.
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PMID:Thrombin activates a membrane-associated calcium-independent PLA2 in ventricular myocytes. 948 35

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

In recent years, relevant changes have occurred in the knowledge of the cellular mechanisms regulating platelet aggregation and adhesion to the endothelial surface. In particular, major aspects of the interactions between platelets and endothelial cells and neutrophils have been clarified. These interactions involve not only thrombosis-promoting or thrombosis-inhibiting properties but also several aspects of the regulation of vascular function. A new concept has progressively emerged showing thrombosis as a multicellular event in which cell-to cell interactions between platelets, neutrophils, and endothelium regulate the size of a growing thrombus. In brief, there is consistent evidence showing that two vasodilating mediators produced by endothelial cells and neutrophils (nitric oxide and prostacyclin) have antiaggregating platelet effects. Platelet activation is particularly relevant in myocardial ischemia, and several pharmacological strategies have been devised to prevent intravascular platelet activation. Aspirin remains a keystone of these preventive and damage-limiting strategies. Current knowledge maintains that low doses of aspirin decrease in vivo platelet aggregation by a selective inhibitory effect on thromboxane A2 production by platelets with maintenance of prostacyclin production by the endothelium. We have recently focussed our research on the basis that the antiaggregating effect of aspirin could be explained not only by the above-mentioned effects on thromboxane A2 synthesis, but also through its action on neutrophils. Our in vitro and ex vivo studies have demonstrated that neutrophils enhance the antiaggregating effects of acetylsalicilic acid on platelets. We have shown that acetylsalicilic acid stimulates nitric oxide production on neutrophils inhibiting the aggregating effects of thrombin, ADP or epinephrine on platelets. the role of the neutrophils in ischemic events enhancing the tissue damage through the release of several proteases, reactive oxygen species and tumor necrosis factor-alpha has been extensively demonstrated. In an experimental model of acute ischemia/reperfusion in rabbits, we have shown that acetylsalicilic acid is able to enhance the nitric oxide production by neutrophils providing a potential mechanism for the beneficial action of aspirin in the myocardial infarction. Further research is needed to assess the mechanisms of the action of aspirin during the thrombotic phenomena and its effects on the different types of cells that compound the microvascular environment.
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PMID:[Thrombosis and coronary disease: neutrophils, nitric oxide and aspirin]. 957 62

Antiphospholipid antibodies (aPL) have been found to be associated with arterial and venous thrombosis. Percutaneous transluminal coronary angioplasty (PTCA) is an established therapy for ischaemic heart disease (IHD), which is still affected by restenosis at a rate of 20-30%. This study was aimed at investigating the possible role of aPL in restenosis after PTCA. In sixty consecutive IHD patients, aPL (lupus anticoagulant -LA- and anticardiolipin antibodies -aCL) and markers of haemostatic activation were investigated before PTCA, and patients were followed up for restenosis. No infections, autoimmune disease or treatment by drugs that may alter aPL levels occurred in any of the patients. aPL were found in 15/60 patients: aCL in 7/60, LA in 5/60 and aCL and LA in 3/60. No statistically significant difference was found between aPL negative and aPL positive patients in pre PTCA plasma levels of prothrombin activation fragment (F1+2) 1.4 nmol/l (0.3-5.71) vs 1.4 nmol/l (0.9-4.0), thrombin-antithrombin complex (TAT) 4.0 microg/l (1.1-34.2) vs 5.2 microg/l (2.1-60.0), D-dimer (DD) 25 ng/ml (2-515) vs 44 ng/ml (2-160) or plasminogen activator inhibitor activity (PAI) 4.8 IU/ml (2.5-36.4) vs 4.4 IU/ml (2.5-13.4). Restenosis was observed in 13/60 patients (7/45-15% - aPL negative and 6/15-40% - aPL positive patients) who underwent angiographic tests after PTCA because of recurring angina or positive exercise test. Restenosis occurred after 2.2 months (0.5-3) in aPL positive patients and after 3.5 months (1-12.8) in aPL negative. These results suggest that 1) restenosis with recurrent ischaemia occurs more frequently in aPL positive than in aPL negative patients, 2) in aPL positive patients restenosis occurs earlier, and 3) the presence of aPL is not associated with hypercoagulability.
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PMID:Antiphospholipid antibodies: a new risk factor for restenosis after percutaneous transluminal coronary angioplasty? 960 31

Several prospective studies have demonstrated that high plasma fibrinogen levels are associated with an increased risk of ischemic heart disease. Since in most patients an increased thrombin generation has been reported, we investigated whether the control of thrombin generation could affect plasma fibrinogen levels. Forty male outpatients (20 asymptomatic with previous myocardial infarction and 20 with stable effort angina) were enrolled in a randomized medium-term (6 months) cross-over study. Clottable fibrinogen, according to Clauss, prothrombin fragment 1 + 2, thrombin-antithrombin complex, and fibrinopeptide A were evaluated in relation to treatment with low-dose heparin. After a 15-day wash-out period, during which patients had been treated only with nitrates if needed, patients were allocated to two sequential periods of treatment with standard heparin (12,500 U, subcutaneously daily) plus antianginal treatment or antianginal treatment alone, separated by a second 15-day wash-out period. At the end of the treatment period with low-dose heparin significant decreases in the plasma fibrinogen (2.5 +/- 0.6 g/l vs. 3.3 +/- 0.5 g/l, P < 0.001), prothrombin fragment 1 + 2 (1.4 +/- 0.5 nmol/l vs. 1.9 +/- 0.7 nmol/l, P < 0.001), thrombinantithrombin (4.5 +/- 2.4 ng/ml vs. 9.7 +/- 3.6 ng/ml, P < 0.001), and fibrinopeptide A (2.1 +/- 1.1 ng/ml vs. 3.5 +/- 2.1 ng/ml, P < 0.001) were observed compared with the period without heparin. The present results indicate that low-dose heparin can effectively control the increased abnormal thrombin generation and elevated fibrinogen levels in patients with ischemic heart disease, possibly decreasing the risk of cardiovascular death.
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PMID:Effect of low-dose heparin on fibrinogen levels in patients with chronic ischemic heart disease. 980 27

Generalized atherosclerosis and coronary artery disease (CAD) are associated with endothelial dysfunction and during acute myocardial ischemia platelet activation has been reported. Activated platelets exert activated fibrinogen receptors (GP IIb/IIIa) and express CD 62p being regarded as reliable marker for platelet activation. Patients with angiographically proven CAD performed a bicycle exercise test until the onset of angina or ST-segment depression. We studied the ischemia-induced alterations in fibrinogen binding to activated platelet GP IIb/IIIa receptors and CD 62p expression. Therefore, the basal fibrinogen binding to GP IIb/IIIa and CD 62p expression and the thrombin-concentration for half-maximal platelet activation before and after exercise testing were determined. Additionally, inhibition of thrombin-induced platelet activation by increasing concentrations of the prostacyclin-analog iloprost and the NO-donor SIN-1 was examined. In patients with CAD, a significantly reduced basal activation and a highly significant reduction in sensitivity towards thrombin was measured. The thrombin-induced expression of GP IIb/IIIa and CD 62p was significantly diminished in patients with CAD after physical exercise and their platelets were significantly more sensitive towards the inhibitory effects of iloprost and SIN-1. These data demonstrate a significant reduction in platelet activation in response to physical exercise in patients with CAD and advanced atherosclerosis. Despite exercise induced myocardial ischemia as evidenced by angina and ECG-changes, the platelets are not generally activated, as it could be expected. Thus, patients with myocardial ischemia experienced a reduced platelet activity and enhanced sensitivity towards prostacyclin (PGI2) and nitric oxide, probably due to an augmented release of endogenous platelet inhibitory mediators.
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PMID:Increased platelet sensitivity toward platelet inhibitors during physical exercise in patients with coronary artery disease. 995 Feb 58

The cardiac sarcolemmal Na+/H+ exchanger extrudes intracellular H+ in exchange for Na+, in an electroneutral process. Of the 6 mammalian exchanger isoforms identified to date, the Na+/H+ exchanger (NHE)-1 is believed to be the molecular homolog of the sarcolemmal Na+/H+ exchanger. The exchanger is activated primarily by a reduction in intracellular pH (intracellular acidosis), although such activation is subject to modulation by a variety of endogenous mediators (e.g., catecholamines, thrombin, endothelin) through receptor-mediated mechanisms. A large body of preclinical evidence now suggests that inhibition of the sarcolemmal Na+/H+ exchanger attenuates many of the unfavorable consequences of acute myocardial ischemia and reperfusion. Much of this evidence has been obtained with recently developed potent, selective inhibitors of the exchanger, such as HOE-642 (cariporide) and its structurally related congener HOE-694, in studies using both in vitro and in vivo models of ischemia and reperfusion in a variety of species. The data from these studies indicate that Na+/H+ exchange inhibition leads to a decreased susceptibility to severe ventricular arrhythmia, attenuates contractile dysfunction, and limits tissue necrosis (i.e., decreases infarct size) during myocardial ischemia and reperfusion. Such protection is likely to arise, at least in part, from attenuation of "Ca2+ overload," which has been linked causally with all of these pothologic phenomena. The consistent and marked cardioprotective benefit that has been observed with cariporide and related compounds in preclinical studies suggests that Na+/H+ exchange inhibition may represent a novel and effective approach to the treatment of acute myocardial ischemia in humans.
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PMID:Rational basis for use of sodium-hydrogen exchange inhibitors in myocardial ischemia. 1048 75

Background: Myocardial ischemia at rest is typically associated with atherosclerotic coronary artery disease, atherommous plaque rupture, and intracoronary thrombosis. In areas of advanced disease and vascular injury, the extent of thrombus is influenced largely by a delicate balance of procoagulant factors, favoring thrombus initiation, growth, and development, and anticoagulant factors, attempting to limit potentially flow-limiting coronary thrombosis. Thrombin, a 308 amino acid serine pretense, is considered the most patent procoagulant factor in the setting of acute vessel wall injury, playing an essential role in the conversion of fibrinogen to fibrin, accelerating the prothrombinase complex, activating platelets, and stabilizing fibrin polymers. The purpose of this study was to determine the relationship between electrocardiographic abnormalities and markers of thrombin activity and generation among patients with unstable angina and non-Q.wave myocardial infarction. Mehtods and Results: In a study of 36 patients (59.1+/- 11.0 years) with myocardial ischemia at rest participating in the Thrombolysis in Myocardial Ischemia (TIMI) IIIB trial, thrombin activity in plasma, as determined by fibrinopeptide A (FPA), prothrombin fragment 1.2 (F 1.2), and thrombin-antithrombin III complexes (TAT) concentrations, were found to be increased significantly when compared with healthy volunteers (p < 0.004). Thrombin generation was also increased modestly compared with age-matched patients with stable coronary artery disease undergoing elective cardiac catheterization. Given that,he surface 12-lead electrocardiogram (ECG) is frequently abnormal in patients with ischemic chest pain at rest and represents a readily available, first-line diagnostic test for assessing disease activity and treatment response, we investigated whether ECG abnormalities and thrombin activity/generation in plasma were correlated. Twenty-six patients (72%) had ECG changes compatible with myocardial ischemia at the time of study entry, including 18 (50%) with newly inverted T waves (or pseudonormalization), 14 (39%) with reversible ST-segment depression, and 4 (11%) with transient (<30 minutes) ST-segment elevation. Within the predefined ECG groups there were no differences in plasma thrombin activity between patients with and those without confirmed abnormalities. Similarly, there were no differences in either plasma thrombin activity or generation between the predefined ECG groups. Conclusion: Although ECG abnormalities supporting the presence of myocardial ischemia occur commonly in patients with chest pain at rest, they do not correlate closely with markers of thrombin activity and generation in plasma. The diagnostic and prognostic capabilities of these diagnostic tools, considered either alone or together, require further investigation.
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PMID:Surface 12-Lead Electrocardiographic Findings and Plasma Markers of Thrombin Activity and Generation in Patients with Myocardial Ischemia at Rest. 1060 19


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