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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Several lipid-related reactions involving coagulation and fibrinolytic mechanisms have been described. Many of these reactions have been related to the development of atherosclerosis and thromboembolism. In this article, I review the antiphospholipid antibody syndrome, the tissue factor pathway inhibitor, the involvement of fatty acids in fibrinolysis, and the Lp(a) lipoprotein.
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PMID:Lipid-related clotting reactions of clinical significance. 145 82

Recent advances in determining anti-thrombogenic functions of vascular endothelial cells are reviewed. The following anticoagulant and fibrinolytic systems of endothelial cells are physiologically important; (1) Endothelial cell-derived metabolites including prostacyclin and nitric oxide (NO) support platelet inactivity. (2) Antithrombin III and tissue factor pathway inhibitor (TFPI) bound to heparin-like proteoglycans on endothelial cell membrane inhibit activated serine protease coagulation factors such as thrombin, factor Xa and factor VIIa-tissue factor complex. (3) Thrombomodulin converts thrombin from procoagulant into anticoagulant. Thrombin associated to thrombomodulin on endothelial cells activates protein C. Activated protein C in concert with protein S bound to endothelial cell membrane inactivates factors Va and VIIIa. (4) A receptor for both tissue plasminogen activator and plasminogen on endothelial cells provides an efficient plasmin generating system. Perturbation of these anti-thrombogenic systems of endothelial cells is caused by endotoxin (LPS), cytokines such as interleukin-1 and tumor necrosis factor (TNF), and risk factors for atherogenesis including lipoprotein(a) and homocysteine may result in arterial or venous thrombosis with subsequent development of atherosclerosis.
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PMID:[Anticoagulant and fibrinolytic systems of the injured vascular endothelial cells]. 817 40

There is compelling experimental evidence that tissue factor pathway inhibitor (TFPI) exerts important role(s) as a natural anticoagulant. Immunodepletion of TFPI lowers the treshold by which tissue factor (TF) can induce disseminated intravascular coagulation. Conversely, infusion of recombinant TFPI protects against thrombosis and disseminated intravascular coagulation in numerous experimental models. Since TFPI mutants associated with thrombosis have not yet been identified, a definite role of TFPI in coagulation is yet to be assigned. Current research on TFPI is mainly focused on the cell biology of TFPI, on the contribution of TFPI to the anticoagulant action of heparins, and on the role of lipoprotein-associated TFPI. TFPI is produced constitutively in endothelial cells, and is to a great extent bound to its surface. The binding molecule(s) have not yet been characterized, but TFPI is rapidly released by heparin and other negatively charged ions. In other cell lines degradation of TFPI is mediated by the low density lipoprotein receptor-related protein, which may be important for its clearance. In plasma, TFPI contributes strongly to the postheparin anticoagulant effect seen in dilute prothrombin time assays. The effect is probably mediated by redistribution of TFPI. Moreover, in the presence of heparin, antithrombin and TFPI cooperate to inhibit activation of coagulation. Antithrombin abrogates activation of factor VII bound to TF, whereas TFPI inhibits factor VIIa/TF complexes formed. The role of lipoprotein associated TFPI is still essentially unknown, but may play an important role in atherosclerosis.
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PMID:Tissue factor pathway inhibitor (TFPI)--an update. 897 19

We describe recent information on the atherothrombotic processes leading to the acute coronary syndromes (ACS) in humans. Then, we outline the mechanism of action and impact of lipid-lowering therapy in stabilization and secondary prevention of such processes. We start with (1) definitions of atherosclerotic lesions. In the progression of coronary atherosclerosis, eight morphologically different lesions are defined (Type I to VI) in various phases of disease. (2) Then we discuss vulnerable lipid-rich plaques and ACS. The type IV and Va lesions tend to be relatively small in size, but soft or vulnerable to disruption (with subsequent thrombosis) because of high lipid content (cholesterol esters rather than free cholesterol monohydrate crystals). The above process represents a "passive" phenomenon of plaque disruption. In addition to this "passive" phenomenon, an "active," macrophage-dependent, phenomenon of plaque disruption is evolving. (3) We then show the role of thrombosis in ACS. Monocytes/macrophages in lipid-rich plaques may play a detrimental role after plaque disruption, promoting thrombin generation and thrombosis through the tissue factor pathway, which can be prevented by tissue factor pathway inhibitor. Such thrombotic phenomena are critical in the development of ACS. (4) Finally, we discuss the effect of lipid-modifying strategies on the vulnerable lipid-rich plaques. When high LDL-cholesterol is reduced therapeutically, efflux from the plaques of the liquid or sterified cholesterol, and also its hydrolysis into cholesterol crystals depositing in the vessel wall, predominate over the influx of LDL-cholesterol. Consequently, there is a decrease in the softness of the plaque and so, presumably in the "passive" phenomenon of plaque disruption. When low HDL-cholesterol is increased experimentally, there is a partial decrease in the number and activity of the macrophages and so, presumably in the "active" phenomenon of plaque disruption.
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PMID:Human lesion studies. 918 99

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

Tissue factor pathway inhibitor (TFPI) is a potent inhibitor of tissue factor (TF) -initiated coagulation and may play a role in regulating coagulation in atherosclerotic plaques. The expression of TFPI protein and mRNA was examined by immunohistology and in situ hybridization in normal human and rabbit arteries, in human carotid arteries with advanced atherosclerosis, and in atherosclerotic aortas from cholesterol-fed rabbits. In normal human and rabbit arteries, TFPI protein and mRNA were detected in the adventitial layer but were undetectable in the luminal endothelium. In the medial smooth muscle layer of rabbits, weak expression of TFPI mRNA, but not protein, was detected; in that of humans, neither TFPI mRNA nor protein was detectable. In atherosclerotic arteries, TFPI protein and mRNA were detected in three of six internal carotid plaques from patients undergoing endarterectomy, and mRNA alone was detected in one further specimen. TFPI protein was found in areas of the plaque where TF was abundant and colocalized with macrophages, suggesting that these cells are responsible for TFPI synthesis. TFPI protein and mRNA were also detected in fatty-streak lesions in 18 of 19 rabbits fed a high-cholesterol diet for periods between 4 and 16 weeks. In these macrophage-rich lesions, expression of TFPI protein and mRNA was most intense at the base of the plaques. These studies suggest that TFPI is expressed in the adventitial layer of large arteries and that in atherosclerotic vessels, TFPI is expressed by macrophages in focal areas throughout the plaque. Local production of TFPI may regulate procoagulant activity and thrombotic events within atherosclerotic plaques.
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PMID:Tissue factor pathway inhibitor expression in atherosclerosis. 935 63

Thrombotic complications are frequently associated with atherosclerosis. Lysophosphatidylcholine (LPC), a component accumulated in oxidatively modified LDL (ox-LDL), is known to play a crucial role in the initiation and progression of atherosclerotic vascular lesions. Since a vascular anticoagulant, tissue factor pathway inhibitor (TFPI), has the function of regulating the initial reaction of tissue factor (TF)-induced coagulation, we investigated the effect of LPC on TFPI synthesis in cultured human umbilical vein endothelial cells (HUVEC). The treatment of HUVEC with LPC for 24 h decreased TFPI antigen levels in both the culture medium and the cell lysate in a dose-dependent manner. Northern blot analysis revealed that LPC caused a time-dependent decrease in the TFPI mRNA levels. The levels of TFPI antigen and mRNA were decreased to 72% and 38%, respectively, by the incubation with 50 microM LPC for 24 h. The down-regulation by LPC of TFPI mRNA expression was not observed in the presence of cycloheximide, suggesting that protein synthesis was involved in the suppression of TFPI mRNA expression. The TFPI mRNA levels in actinomycin D-treated cells were relatively stable, indicating that the down-regulation of TFPI mRNA by LPC would be partly explained by the enhanced mRNA destabilization. In contrast to the significant down-regulatory effects of LPC on TFPI expression, LPC did not induce TF mRNA expression in HUVEC. These results indicate that LPC accumulated in the atherosclerotic vascular wall would suppress endothelial TFPI synthesis, reducing the antithrombotic property of endothelial cells.
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PMID:Lysophosphatidylcholine decreases the synthesis of tissue factor pathway inhibitor in human umbilical vein endothelial cells. 945 50

Atherosclerotic plaque rupture and erosions precipitate thrombus formation and may lead to an acute ischemic syndrome. Lipids and lipoproteins modulate the expression and/or function of thrombotic, fibrinolytic and rheologic factors, and thereby influence hemostasis and potential tissue damage resulting from vascular injury. Triglyceride-enriched lipoproteins are accompanied by elevations in factor VII clotting activity, plasminogen activator inhibitor (PAI-1) and viscosity of blood and plasma. Low density lipoprotein (LDL) promotes platelet activation and tissue factor expression and LDL levels correlate with levels of vitamin K dependent coagulation factors and fibrinogen. Conversely, LDL inhibits tissue factor pathway inhibitor (TFPI) which limits activation of the extrinsic coagulation pathway. High density lipoprotein (HDL) has anti-atherothrombotic properties that result from inhibition of platelet and erythrocyte aggregation, reduced blood viscosity and suppression of tissue factor activity and PAI-1 activity and antigen levels. The effects of lipids and lipoproteins on hemostasis and rheology may have important implications for the clinical sequelae following plaque disruption and erosion.
Atherosclerosis 1998 Oct
PMID:Effects of lipids and lipoproteins on thrombosis and rheology. 986 70

The primary cause of cardiac morbidity and mortality in developed countries is ischemic (coronary) heart disease. The incidence of this disease is virtually all due to atherosclerosis, and ischemic heart disease is also the most prevalent disease in the industrialized world, causing over 40% of all deaths in the United States and Western Europe. In Japan, the incidence of ischemic heart disease due to coronary atherosclerosis is gradually increasing as well. Compared with the classical nomenclature of atherosclerosis; that is, fatty streak, fibrous plaque and complicated lesions, the term Stary's classification has been universally accepted because it reflects the more recently acquired knowledge about the morphological and biochemical details of the processes in coronary atherosclerosis, which have been obtained by new strategies such as angioscopy, intravascular ultrasound and molecular biological methods. The term Stary's classification has been applied for the coronary atherosclerosis of patients with acute coronary syndrome at the National Cardiovascular Center, for the analysis of predisposing atherosclerosis of these patients. The recent findings regarding acute coronary syndrome resulting from a rupture of coronary atherosclerotic plaques indicate that this syndrome is probably the most important mechanism underlying the sudden onset. It has been found that the risk of plaque rupture may depend more on plaque composition than on plaque size. Plaques rich in soft extracellular lipids and macrophages are possibly more vulnerable to plaque rupture. Two of the goals of the present review are to clarify how plaque disruption occurs and to elucidate the relationship between plaque disruption and coronary risk factors in elderly Japanese patients with acute coronary syndrome. Coronary stents have been shown to be efficacious in the treatment of acute and threatened closure complicating percutaneous transluminal coronary angioplasty (PTCA) and have produced encouraging initial results in the prevention of restenosis. In the autopsy study of restenosis after PTCA, it was observed that dense caps of collagen fibers in the adventitia in the vicinity of the disrupted internal elastic laminae were present in all of the remodeling lesions. It is suggested that remodeling, which resulted in adventitial scarring, is one of the major causative factors of restenosis after PTCA. The long-term success of stenting, however, remains limited by the occurrence of late in-stent restenosis, with an incidence of 20-42% depending on the stent design and the patient population studied. Another aim of the present review is to describe the pathological mechanism of restenosis after PTCA and/or stent replacement and, consequently, the vascular remodeling that occurs around adventitial tissue after PTCA and intimal hyperplasia that is chronically irritated by a foreign body granulomatous reaction after stenting. Finally, the results of the investigation of the effect of a tissue factor pathway inhibitor on the prevention of interventional restenosis is described.
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PMID:Coronary atherosclerosis and interventions: pathological sequences and restenosis. 1036 46

The procoagulant activity of tissue factor is regulated by circulating inhibitors such as tissue factor pathway inhibitor (TFPI) and LDL. These 2 inhibitors also readily associate making the distinction between their activities difficult. We have examined the relative contributions of intact and C-terminal truncated TFPI and ApoB100. By following the inhibitory potential of the preparations, over a period of 120 minutes, it was demonstrated that TFPI and LDL-resembling particles inhibited tissue factor at different rates. TFPI was found to be a short, fast-acting inhibitor, whereas the action of LDL-resembling particles was more prolonged but slower. The oxidation of LDL has been closely associated with the development of cardiovascular disease, including atherosclerosis and thrombosis. Positively charged amino acids, particularly lysine residues, are prone to alterations via the formation of adducts by lipid peroxidation products. These residues are important in the inhibition of tissue factor activity by ApoB100. They also play an important role in the inhibitory Kunitz domains of TFPI. We have shown that the decline in the ability of LDL to inhibit tissue factor was as a result of modifications in LDL arising from oxidation. By examining the effects of oxidation on full-length and C-terminal truncated TFPI bound to LDL-resembling particles, we found that TFPI is only affected when in close association with ApoB100. C-terminal truncated TFPI was not affected significantly by oxidation. Finally, chemical modification of lysine and arginine residues reduced the overall inhibition of tissue factor by TFPI. We propose that TFPI and LDL act separately to inhibit tissue factor in vivo. However, the oxidation of LDL can alter both the endogenous activity of ApoB100 and reduce that of closely associated TFPI, compromising normal hemostasis.
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PMID:Comparison of the inhibitory effects of ApoB100 and tissue factor pathway inhibitor on tissue factor and the influence of lipoprotein oxidation. 1039 99


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