fibrin and Arteriosclerosis

A traditional perspective of arterial thrombosis begins with vessel wall injury and exposure of subendothelial proteins, including collagen and tissue factor, to circulating cellular and non-cellular components. Adhesion and activation of platelets, mediated by their interaction with von Willebrand protein and collagen, respectively, coupled with tissue factor-mediated activation of coagulation proteins, results in thrombin generation and fibrin formation. While this time-honored paradigm remains firm and soundly based, emerging evidence suggests that arterial thrombosis is much more complex and dynamic than originally believed. Several novel triggers, templates and facilitators, such as cell-free nucleic acids, histones, DNA-histone complexes, polyphosphates, and microvesicles have recently been identified and require inclusion in the expanding universe of thrombosis as a dominant phenotype of human disease. Because these mediators appear to have modest if any effect on physiologic hemostasis, they likely represent acquired and disease or condition-dependent processes that are highly attractive targets for pharmacologic intervention.

Topics: Animals; Arteriosclerosis; Collagen; Fibrin; Hemostasis; Humans; Platelet Adhesiveness; Thrombin; Thrombosis

Topics: Arteriosclerosis; Catheterization; Coronary Thrombosis; Diagnosis, Differential; Fibrin; Fibrinolytic Agents; Humans; Platelet Activation; Platelet Aggregation Inhibitors; Prognosis; Stents; Thrombolytic Therapy; Tissue Plasminogen Activator

Hemostatic factors play a crucial role in generating thrombotic plugs at sites of vascular damage (atherothrombosis). However, whether hemostatic factors contribute directly or indirectly to the pathogenesis of atherosclerosis remains uncertain. Autopsy studies have revealed that intimal thickening represents the first stage of atherosclerosis and that lipid-rich plaque arises from such lesions. Several factors contribute to the start of intimal thickening. Platelets release several growth factors and bioactive agents that play a central role in development of not only thrombus but also of intimal thickening. We have been investigating which coagulation factors simultaneously, or subsequently with platelet aggregation, participate in thrombus formation. Tissue factor (TF) is an essential initiator of blood coagulation that is expressed in various stages of atherosclerotic lesions in humans and other animals. Factors including thrombin and fibrin, which are downstream of the coagulation cascade activated by TF, also contribute to atherosclerosis. TF is involved in cell migration, embryogenesis and angiogenesis. Thus TF, in addition to factors downstream of the coagulation cascade and the protease-activated receptor 2 activation system, would be a multifactorial regulator of atherogenesis.

Topics: Arteriosclerosis; Blood Coagulation; Fibrin; Humans; Receptor, PAR-2; Thrombin; Thromboplastin

Atherothrombotic disease is a multifactorial disorder that develops secondary to a complex gene-environment interaction. The formation of an obstructive thrombus represents the final stage of the atherothrombotic process, and understanding the mechanisms involved in clot formation is essential in order to develop new preventive and therapeutic strategies aimed at decreasing mortality and morbidity from the disease. Studies have demonstrated an important correlation between final clot structure and predisposition to atherothrombotic disease. Both genetic and environmental factors contribute to the final ultrastructure of the clot, which, in turn, influences an individual's risk of the disease. This paper reviews the factors involved in determining clot structure. The role of commonly used therapeutic agents in modulating clot structure will also be discussed.

Topics: Arteriosclerosis; Blood Coagulation Factors; Disease Susceptibility; Fibrin; Humans; Molecular Structure; Thrombosis

The formation of a fibrin clot is one of the key events in atherothrombotic vascular disease. The structure of the fibrin clot and the genetic and environmental factors that modify it have effects on its biological function. Alterations in fibrin structure and function have implications for the clinical presentation of vascular disease. This review briefly describes the key features involved in the formation of a fibrin clot, its typical structure, and function. This is followed by a review of the current literature on genetic and environmental influences on fibrin structure/function and the relationship to clinical disease. The formation of a fibrin clot is one of the key events in atherothrombotic vascular disease. This review discusses how genetic and environmental factors alter fibrin structure and function and the implications this has for the clinical presentation of vascular disease.

Topics: Afibrinogenemia; Arteriosclerosis; Blood Coagulation; Diabetes Mellitus; Factor XIII; Fibrin; Fibrinogen; Fibrinolysis; Glycosylation; Humans; Hyperhomocysteinemia; Life Style; Lipoproteins; Polymorphism, Genetic; Protein Conformation; RNA Splicing; Structure-Activity Relationship; Thrombosis

The transmembrane glycoprotein tissue factor (TF) is the initiator of the coagulation cascade in vivo. When TF is exposed to blood, it forms a high-affinity complex with the coagulation factors factor VII/activated factor VIIa (FVII/VIIa), activating factor IX and factor X, and ultimately leading to the formation of an insoluble fibrin clot. TF plays an essential role in hemostasis by restraining hemorrhage after vessel wall injury. An overview of biological and physiological aspects of TF, covering aspects consequential for thrombosis and hemostasis such as TF cell biology and biochemistry, blood-borne (circulating) TF, TF associated with microparticles, TF encryption-decryption, and regulation of TF activity and expression is presented. However, the emerging role of TF in the pathogenesis of diseases such as sepsis, atherosclerosis, certain cancers and diseases characterized by pathological fibrin deposition such as disseminated intravascular coagulation and thrombosis, has directed attention to the development of novel inhibitors of tissue factor for use as antithrombotic drugs. The main advantage of inhibitors of the TF*FVIIa pathway is that such inhibitors have the potential of inhibiting the coagulation cascade at its earliest stage. Thus, such therapeutics exert minimal disturbance of systemic hemostasis since they act locally at the site of vascular injury.

Topics: Animals; Arteriosclerosis; Blood Coagulation; Blood Coagulation Disorders; Blood Coagulation Factors; Blood Vessels; Disseminated Intravascular Coagulation; Fibrin; Gene Expression Regulation; Humans; Neoplasms; Sepsis; Thromboplastin; Thrombosis

Fibrinogen is a protein synthesised by the liver. It is converted by thrombin to an insoluble fibrin network to induce, together with platelet aggregates, haemostasis in response to rupture of endothelium. This change includes several steps and implied factor XIII. Molecular properties of fibrin are responsible for its important role in hemostasis which goes beyond the one of a simple final inert product of coagulation. In fact, fibrin regulates thrombin and factor XIII activities and its own destruction also called fibrinolysis. The multiple domains of fibrinogen and fibrin confer a role not only in haemostasis but also in wound healing, cellular migration and proliferation, due to interactions with endothelial cells, leukocytes and components of the extracellular matrix. Fibrin must be removed once its haemostatic role has been reached. The fibrinolytic process takes place in the vessel lumen. It is strongly regulated by the plasma concentration of an inhibitor called plasminogen activator inhibitor-1 (PAI-1) which synthesis strongly increases in obese insulin resistant and diabetic patients. Data from animal models show that increased PAI-1 production represents a prothrombotic state. Fibrinolysis plays also a role in tissue remodeling (vascular wall, placenta, adipose tissue....) by degrading the extracellular matrix, by activating growth factors or modifying cellular adhesion and migration properties. It has been proposed that PAI-1 in excess could be directly responsible for the development of atherothrombosis in insulin resistant subjects. Moreover recent results from transgenic mice indicate that PAI-1 in excess interferes also with weight gain. These data point out the importance of the haemostatic system in the extra vascular phenomenon of tissue remodeling.

Topics: Animals; Arteriosclerosis; Carboxypeptidase B2; Cell Movement; Diabetes Mellitus; Disease Models, Animal; Endothelial Cells; Factor XIII; Fibrin; Fibrinogen; Fibrinolysis; Hemostasis; Humans; Insulin Resistance; Metalloproteases; Mice; Mice, Transgenic; Plasminogen Activator Inhibitor 1; Risk Factors; Thrombin; Thrombosis; Wound Healing

The Grützbalg analogy has obviously held up and been greatly extended by current work implicating specific molecules in inflammation and proteolysis. Still, Virchow's explanation is only partly able to account for the chronic outcome of this disease. Many of the open questions center on fibrin. For example, we do not know why fibrin forms in Virmani's eroded lesions. If the source of tissue factor in erosion is Nemerson's "stealth" particles, we may also need to rethink the source of tissue factor in plaque rupture. At the other extreme, as we all know, atherosclerotic vascular disease is a chronic disease. While multiple episodes of plaque rupture are likely to be important in this chronic process, the critical events here--scarring, narrowing of the lumen--remain largely unexplained. The data reviewed here suggest that intramural coagulation could be a critical process underlying these chronic changes.

Topics: Animals; Arteriosclerosis; Blood Coagulation; Disease Progression; Fibrin; Humans; Models, Biological; Thrombosis

The transition of fibrinogen to fibrin and to their degradation products within the arterial wall has been reported to be accompanied by atherosclerotic progression. A major step in the pathogenesis of atherosclerosis is the vectorial migration of vascular smooth muscle cells (SMCs) from the arterial media through the internal elastic lamina into the intima and their subsequent proliferation in the intima. I have been studying the effects of fibrinogen, fibrin and their degradation products on the behaviour, particularly migration, of SMCs. Fibrinogen/fibrin stimulates the adhesion and migration of SMCs and their effects are mediated by both the RGD-containing region of the alpha chain of fibrinogen/fibrin and integrin alpha v beta 3 on the cell surface. SMCs migrate into fibrin gel even with no other chemotactic stimuli. SMCs displayed two-fold increase in migration into crosslinked fibrin gels compared to non-crosslinked gels, suggesting the importance of fibrin crosslinking by factor XIIIa on its three-dimensional structure for the migration of SMCs. Fibrin gels prepared with batroxobin, which cleaves only fibrinopeptide A, with ACTE, which cleaves only fibrinopeptide B, and with protamine sulfate, which cleaves nothing, but forms a fibrin-like gel, induce migration of SMCs in a manner similar to the gel prepared with thrombin, suggesting that the cleavage of fibrinopeptides is not involved in the migration of SMCs. Both anti-fibrinogen fragment D and E antibodies inhibit the migration of SMCs into fibrin gel, suggesting that both D and E regions of fibrin are involved in the migration of SMCs into fibrin gel. The migration of SMCs into fibrin gel also depends on the RGD-containing region and integrin alpha v beta 3. Both fibrinogen fragments D and E inhibit the migration of SMCs into fibrin gels, suggesting that these fragments may be involved in the regulation of SMC migration into fibrin gel as the result of fibrinolysis. Although subcultured SMCs usually show a synthetic phenotype, the behaviour of contractile SMCs may be crucial for the subsequent migration of the cells. We employed an in vitro assay system to evaluate the effects of fibrin gels on the migration of SMCs from explants taken from rabbit aorta. alpha v beta 3 integrin and the RGD-containing region are involved in the migration of SMCs into the fibrin gels. SMCs which migrated from the explants showed positive staining with monoclonal antibodies against SMC myosin heavy chain isoforms

Topics: Animals; Arteriosclerosis; Cell Movement; Disease Progression; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Muscle, Smooth, Vascular; Rabbits

Topics: Arteriosclerosis; Biomarkers; Cardiovascular Diseases; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Humans; Risk Factors; Thrombin

We have tried to offer a unifying hypothesis tying vessel wall narrowing in atherosclerotic plaques to plaque rupture and healing (Fig. 7). This hypothesis is supported by evidence that smooth muscle cells are capable of interacting with a fibrin clot, specifically contracting a fibrin clot, and that inhibition of coagulation prevents narrowing of injured vessels. This work also presents alpha 5 beta 1 and a bridge protein, fibronectin, as possible targets to be used in pharmaceutical intervention to inhibit atherosclerosis progression.

Topics: Animals; Arteriosclerosis; Blood Vessels; Cell Adhesion; Collagen; Disintegrins; Fibrin; Fibronectins; Humans; Integrins; Muscle, Smooth, Vascular; Peptides; Receptors, Fibronectin; Wound Healing

Sudden extreme physical stress is associated with an increased risk of myocardial infarction mainly in people with preexisting atherosclerosis. In this study we compared the effect of submaximal exercise on coagulation and fibrinolysis in patients with peripheral arterial occlusive disease (PAOD) with that in healthy control subjects. Fifteen PAOD) patients with intermittent claudication and 15 healthy control subjects, matched for age, sex, medication use, smoking habit, and conditioning, were studied. Thrombin-antithrombin III complex (TAT), D-dimer, tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI)-1 antigens (Ag), t-PA activity, and plasmin-alpha2-antiplasmin complex (PAP), as well as plasma catecholamines, were measured before and after a treadmill exercise test. At rest, fibrinogen (3.3+/-0.5 versus 2.9+/-0.5 g/L [mean+/-SD]; P<.05), D-dimer (392+/-128 versus 271+/-113 ng/mL; P<.05), t-PA Ag (9.1+/-5.1 versus 5.5+/-1.2 ng/mL; P<.02), and PAI-1 Ag (14.9+/-7.1 versus 7.6+/-3.8 ng/mL; P<.002) levels in plasma were markedly higher in the patient group than in the control group. In patients but not in control subjects, exercise of similar intensity elevated circulating concentrations of TAT (from 3.43+/-1.45 to 4.83+/-2.27 ng/mL; P<.05). Exercise caused a parallel increase in D-dimer, t-PA Ag, t-PA activity, PAP, and catecholamines in both groups, whereas PAI-1 Ag remained stable. Plasma lactic acid was significantly higher in patients after exercise and was associated with lower-limb ischemia. Compared with healthy control subjects, patients with PAOD showed higher t-PA Ag, PAI-1 Ag, and D-dimer levels both at rest and after exercise. Notably, submaximal exercise on a treadmill enhanced thrombin formation in patients with PAOD but not in the control subjects. Sudden catecholamine release and local ischemia during exercise may accelerate the preexisting prothrombotic potential of the atherosclerotic vessel wall.

Topics: Adult; Aged; alpha-2-Antiplasmin; Antigens; Antithrombin III; Arteriosclerosis; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolysin; Humans; Male; Middle Aged; Peptide Hydrolases; Physical Exertion; Plasminogen Activator Inhibitor 1; Reference Values; Thrombin; Tissue Plasminogen Activator

Tissue factor (TF) protein was overexpressed by macrophages and smooth muscle cells (SMCs) and deposited in the extracellular matrix of atherosclerotic intimas, probably resulting in enhanced procoagulant activity and the intimate participation in either thrombus formation or intimal fibrin deposition after the exposure of flowing blood and permeated fibrinogen to TF in atherosclerotic lesions. On the other hand, APO(a) was localized both in the stroma and within some macrophages. Fibrin deposition, which was more frequently detected in the matrix of advanced lesions than in that of early lesions, occasionally colocated with cell- and matrix-associated TF and APO(a) deposited in the matrix. These findings further support the hypothesis that the coagulation and fibrinolysis systems can play an essential role in the initiation and progression of atherosclerosis through fibrin deposition both in atherosclerotic plaques and on the arterial surface by neointimal hypercoagulability and a hypofibrinolytic state, which can also participate in SMC proliferation due to the decreased activation of TGF-beta by embedded and deposited APO(a). The clinical implications of these phenomena may thus contribute to future investigations in the prevention and treatment of atherosclerotic diseases.

Topics: Animals; Arteriosclerosis; Fibrin; Fibrinolysis; Humans; Lipoprotein(a); Thromboplastin

Topics: Arteriosclerosis; Cardiovascular Diseases; Diabetes Mellitus; Diabetic Angiopathies; Fibrin; Fibrinogen; Fibrinolysis; Humans; Plasminogen Activator Inhibitor 1; Risk Factors

Raised plasma fibrinogen levels and markers of fibrin turnover or endothelial disturbance are associated with cardiovascular disease.. This is a critical review of the English language literature relating to fibrinogen, fibrin degradation products and endothelial products in peripheral arterial disease and revascularization surgery.. Altered levels of plasma fibrinogen and endothelial products are associated with atherosclerosis and some studies have shown an association with poor outcome following revascularization surgery. Randomized clinical trials of therapies that modify thrombotic pathways in patients undergoing surgery for peripheral arterial occlusive disease are therefore required.

Topics: Arteriosclerosis; Biomarkers; Blood Vessel Prosthesis; Fibrin; Fibrinogen; Humans; Peripheral Vascular Diseases; Plasminogen Inactivators; Thrombosis; von Willebrand Factor

Topics: Adult; Arteriosclerosis; Blood Coagulation; Blood Platelets; Fibrin; Hemostasis; Humans; Male; Middle Aged; Risk Factors; Thrombin; Thrombosis; von Willebrand Factor

Topics: Arteriosclerosis; Carotid Artery Diseases; Coronary Disease; Endothelium, Vascular; Fibrin; Humans; In Vitro Techniques; Lipoprotein(a); Monocyte Chemoattractant Proteins; Risk Factors; Transforming Growth Factor beta

Topics: Arteriosclerosis; Blood Coagulation; Blood Platelets; Cell Division; Endothelium, Vascular; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Humans; Lipoprotein(a); Macrophages; Muscle, Smooth; Platelet-Derived Growth Factor; Risk Factors; Thrombosis

Topics: Arteriosclerosis; Blood Coagulation; Fibrin; Fibrinogen; Fibrinolysis; Humans; Risk Factors; Thrombosis

Virtually all plasma proteins, including fibrinogen, low density lipoprotein and lipoprotein(a), are present in normal arterial intima and in atherosclerotic lesions, and their concentrations are related to plasma concentrations. Fibrin is also a significant component of many lesions, particularly early proliferative (gelatinous) lesions, where it may be muscle cells migrate and proliferate, bind thrombin, and are a source of fibrin degradation products (FDPs), which are mitogenic. Very recent studies suggest that free a-thrombin may be present in lesions despite an apparent excess of antithrombin III, so this may promote fibrin formation within the lesion. Furthermore, fibrinolysis and FDP generation may be mediated by catheptic enzymes in addition to plasmin.

Topics: Arteriosclerosis; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Lipoproteins; Muscle, Smooth, Vascular; Tunica Intima

Inhibition of thrombosis is proving to be an important treatment goal in many clinical situations, including coronary thrombolysis, angioplasty, and unstable angina. Heparin is a potent inhibitor of thrombin and thrombin generation, but its ability to accelerate thrombolysis, prevent acute reocclusion after vascular injury in angioplasty, and prevent myocardial infarction in unstable angina is relatively limited, possibly because clot-bound thrombin plays an important role in these clinical situations. Thus, when thrombin binds to fibrin, it remains enzymatically active and relatively impervious to inactivation by heparin or other fluid-phase inhibitors. However, direct thrombin inhibitors--such as D-Phe-L-Pro-L-Arg-CH2Cl (PPACK), hirudin, hirugen, and hirulog--inhibit free and clot-bound thrombin with equal efficacy, presumably because their sites of interaction are not masked when thrombin binds to fibrin. Advanced clinical trials suggest that the direct thrombin inhibitors and 7E3, an inhibitor of platelet glycoprotein IIb/IIIa, will soon be incorporated into the armamentarium against arterial thrombosis.

Topics: Angioplasty, Balloon, Coronary; Animals; Arteriosclerosis; Blood Coagulation; Fibrin; Heparin; Humans; Rupture, Spontaneous; Thrombin; Thrombolytic Therapy

Lipoprotein(a) [Lp(a)] is an atherogenic lipoprotein however the mechanisms by which Lp(a) promote the atherosclerotic process are not clear. The apolipoprotein(a) portion of Lp(a) shares partial homology with plasminogen, a finding that has stimulated numerous studies. Lp(a) binds to fibrin and the affinity between fibrin surfaces and Lp(a) appears to be related to the state of oxidation of the lipoprotein particle. Lp(a) also effects fibrin-dependent plasminogen activation. Recent findings suggest that dependent plasminogen activation. Recent findings suggest that depending upon the in vitro conditions, Lp(a) either promotes or inhibits plasmin formation. Lp(a) also inhibits cell-surface dependent plasmin generation that is associated with an inhibition of transforming growth factor-beta (TGF-beta) production in cell coculture systems. Lp(a) stimulates smooth muscle cell migration and proliferation as a secondary response to this decrease in TGF-beta concentration. Studies in transgenic mice containing the human apolipoprotein(a) gene, document that both plasmin and TGF-beta formation in the media of the aorta is markedly decreased in the presence of apo(a). Thus the atherogenicity of Lp(a) may be mediated, in part, through its modulation of plasmin and TGF-beta production in the blood vessel wall.

Topics: Adult; Animals; Arteriosclerosis; Cell Division; Child; Fibrin; Fibrinolysin; Haplorhini; Humans; Kringles; Lipoprotein(a); Mice; Mice, Transgenic; Muscle, Smooth, Vascular; Plasminogen; Transforming Growth Factor beta

Topics: Animals; Aorta; Arteries; Arteriosclerosis; Carotid Arteries; Cytokines; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Life Style; Rabbits

Topics: Animals; Arteriosclerosis; Blood Coagulation; Fibrin; Fibrinogen; Fibrinolysis; Hemostasis; Humans; Plasminogen; Risk Factors

The relationship between lipoprotein (a) (Lp(a)) and atherosclerosis has been appreciated for a number of years. Only in recent years, however, has the structural relationship of Lp(a) to plasminogen resulted in studies of the effect of this lipoprotein on fibrinolysis. Lp(a) inhibits activation of plasminogen by tissue-type (t-PA) and urinary-type (u-PA) plasminogen activators. These inhibitory reactions are surface-dependent. When Lp(a) binds to fibrin, fibrinogen, heparin or cells it blocks activation of plasminogen by t-PA. u-PA-mediated activation of plasminogen is blocked on surfaces including heparin and chondroitin sulfate. Lp(a) also favors inhibition of plasmin by alpha 2-antiplasmin (alpha 2-AP). The ability of Lp(a) to compete with plasmin for fibrin binding displaces plasmin into solution where alpha 2-AP rapidly inhibits this proteinase. These effects are all antifibrinolytic. Lp(a) also exhibits one profibrinolytic effect, since it blocks inhibition of t-PA by plasminogen activator type 1 in the presence of fibrinogen or heparin. Thus, Lp(a) modulates most of the reactions involved in plasmin generation and inhibition. Its overall effect will depend primarily on the concentrations of Lp(a), PAI-1 and t-PA in vivo.

Topics: alpha-2-Antiplasmin; Arteriosclerosis; Fibrin; Fibrinolysin; Fibrinolysis; Humans; Lipoprotein(a); Tissue Plasminogen Activator; Urokinase-Type Plasminogen Activator

A review of 117 research publications describes a deficiency in fatty acid transport into intracellular oxidative energy metabolism which causes increased fibrinogen synthesis and turnover into fibrin. The increased production of fibrin, coupled with depressed activation of plasminogen, increases the fibrin/plasmin ratio causing thrombosis-induced atherogenesis. This discovery unifies the two schools of atherogenesis based on blood lipid or fibrin deposition theories.

Topics: Animals; Arteriosclerosis; Energy Metabolism; Fatty Acids, Nonesterified; Fibrin; Fibrinogen; Fibrinolysin; Humans; Models, Biological; Vascular Diseases

Topics: Animals; Arteries; Arteriosclerosis; Blood Coagulation; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinolysis; Humans; Tissue Distribution

Topics: Adult; Arteries; Arteriosclerosis; Fibrin; Fibrin Fibrinogen Degradation Products; Humans; Myocardial Ischemia; Reference Values; Thrombosis

Topics: Animals; Arteriosclerosis; Fibrin; Fibrinolysin; Humans; Lipoprotein(a); Models, Cardiovascular; Sulfhydryl Compounds; Thrombosis

Atherosclerosis is probably caused by multiple interacting factors such as disturbed lipid metabolism; endothelial cell damage, leading to platelet aggregation and monocyte invasion with the release of mitogenic factors; and disorders of fibrin balance, leading to persisting fibrin deposits. Deficient fibrinolysis may (1) predispose to fibrin deposition and contribute to the pathogenesis of atherosclerosis and (2) contribute to occlusive thrombus formation on fissured plaque, provoking atherothrombosis. Prospective epidemiologic studies have so far not provided definitive evidence that deficient fibrinolysis constitutes a significant risk factor for the development of atherosclerosis. Two recent findings, however, strongly suggest a contribution: (1) Increased lipoprotein(a) levels that reduce tissue-type plasminogen activator (t-PA)-mediated clot lysis are a clear risk factor for atherosclerosis; and (2) increased plasminogen activator inhibitor-1 (PAI-1) levels in patients with disturbed glucose tolerance predispose to an accelerated development of atherosclerotic disease. However, deficient fibrinolysis constitutes a risk factor for the development of thrombotic complications (acute myocardial infarction) in patients with coronary artery disease. The potential role of deficient fibrinolysis in the pathogenesis of atherosclerosis and of atherothrombosis suggests that drugs normalizing deficient endogenous fibrinolysis by either reducing PAI-1 synthesis or by stimulating endogenous t-PA synthesis may be of clinical value. Although regulation of the gene expression of PAI-1 and t-PA is presently under active investigation, no potent specific and safe agents to downregulate PAI-1 or to upregulate t-PA have as yet been identified. Retinoic acid appears to be a specific inducer of t-PA synthesis in human endothelial cells in culture and may constitute a model for the development of drugs that stimulate endogenous t-PA synthesis.

Topics: Arteriosclerosis; Blood Coagulation; Fibrin; Fibrinolysis; Humans; Lipoprotein(a); Plasminogen Activator Inhibitor 1; Thrombosis

Fibrin is a major component of many atherosclerotic plaques. Within the intima there is continuous formation of fibrin, and continuous fibrinolysis. In aortic lesions, a lipoprotein bound to fibrin can be released by incubation with plasmin. Most of this lipoprotein is accounted for by Lp(a). The atherogenicity of Lp(a) may be more associated with lipid deposition than with inhibition of fibrinolysis. Fibrin degradation products may be chemotactic to monocyte-macrophages and stimulate smooth muscle cell proliferation.

Topics: Antigens; Aorta; Aortic Diseases; Arteriosclerosis; Binding Sites; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Lipoprotein(a); Lipoproteins

Topics: Arteriosclerosis; Endothelium, Vascular; Fibrin; Fibrinolysis; Humans; Lipoprotein(a); Lipoproteins; Plasminogen Inactivators; Receptors, Cell Surface; Receptors, Urokinase Plasminogen Activator; Thrombosis; Tissue Plasminogen Activator

Topics: Animals; Antibodies, Monoclonal; Antibody Specificity; Arteriosclerosis; Dogs; Enzyme-Linked Immunosorbent Assay; Epitopes; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinolysis; Fibrinopeptide A; Humans; Kidney Diseases; Neoplasms; Pregnancy; Pregnancy Complications; Radioimmunodetection; Thrombosis

Fibrin is a major component of atherosclerotic plaques, and there may also be situations in which intravascular fibrin is formed in contact with the endothelium. The studies to be presented describe the distribution of fibrinogen/fibrin I, fibrin II, and fragments D and D-dimer in normal vessels and atherosclerotic plaques of increasing severity and also describe some functional effects of fibrin on normal endothelium. Immunohistochemical studies using three specific monoclonal antibodies with the avidin-biotin complex immunoperoxidase technique demonstrated that little fibrinogen/fibrin I or fibrin II and no D/D-dimer were detected in normal aortas. In early lesions and in fibrous plaques, fibrinogen/fibrin I and fibrin II were distributed in long threads and around vessel wall cells. D/D-dimer was not seen in early lesions. In advanced plaques all three molecular forms were detected in areas of loose connective tissue, in thrombi, and around cholesterol crystals. Thus increased fibrin formation and degradation may be associated with progression of atherosclerotic disease. Additionally, the presence of fibrin II around vessel wall cells suggests that these cells may be involved in the fbgn to fibrin transition within the vessel wall. The second aspect of the work to be presented concerns effects of fibrin on vascular endothelium. Fibrin formed on the surface of cultured human umbilical vein endothelial cells stimulated production of prostacyclin and tissue plasminogen activator by the cells in a time- and dose-dependent manner. Stimulation of prostacyclin was completely inhibited by indomethacin and partially inhibited by actinomycin D, cycloheximide, and trifluoperazine, while stimulation of t-PA synthesis was completely inhibited by actinomycin D and cycloheximide and partially inhibited by cytochalasin D, vinblastine, and trifluoperazine.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arteriosclerosis; Blood Platelets; Blood Vessels; Endothelium, Vascular; Fibrin; Fibrinogen; Humans; Muscle, Smooth, Vascular

Topics: Arteriosclerosis; Fibrin; Fibrinolysis; Humans; Hyperinsulinism; Insulin Resistance; Plasminogen Inactivators; Thrombosis; Tissue Plasminogen Activator

This review addresses the question of the involvement of fibrin in the development of atherosclerotic plaques. Numerous studies in the older literature demonstrated the presence of fibrinogen and/or fibrin in plaques, but the techniques that were available (mainly immunochemistry and immunohistochemistry with polyclonal antifibrinogen antibodies) did not clearly distinguish fibrinogen from fibrin or fibrinogen/fibrin degradation products. Some of these studies suggested that the fibrinogen-related protein within lesions resulted from incorporation of thrombi into lesions, while other studies suggested that fibrinogen itself entered the vessel wall. Newer studies by the authors and collaborators used specific antibodies for various fibrinopeptides to quantitate fibrinogen, fibrin I, fibrin II, and fragment X in thrombi and different histologic types of plaques. These studies showed that normal aortas contained fibrinogen and that fatty and fibrous plaques contained fibrinogen, fibrin I, and fibrin II, while complicated plaques contained fibrin II and fragment X, indicating a progression from fibrinogen to fibrin and fibrinogen/fibrin degradation products in parallel with increasing severity of the lesions. Later studies by the authors and collaborators used a sensitive immunohistochemical technique with monoclonal antibodies to demonstrate the distribution of fibrinogen-related antigens. Patterns suggesting incorporation of thrombi were seen, as were patterns suggesting formation of fibrin in association with arterial wall monocyte/macrophages and smooth muscle cells. The data from these various studies suggest the possibility that fibrin formation occurs within the arterial wall and contributes to plaque formation.

Topics: Antigens; Arteriosclerosis; Endothelium, Vascular; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Immunochemistry; Immunohistochemistry; Thrombosis

In this article we have reviewed the evidence that implicates the organization and incorporation of mural thrombi as a significant component of atherosclerotic plaque growth in man. It has been emphasized that there is little or no evidence for a pathogenic role for thrombosis in plaque initiation or for the development of fatty streaks. We have suggested that the rapidly progressive category of atherosclerosis in man, as described by DeBakey, may well reflect a heightened propensity for mural or occlusive thrombosis in these patients. A broad spectrum of experimental studies examining the role of thrombosis in atherogenesis has been critically reviewed. These studies have established that experimental thrombi can become transformed into arterial fibrofatty plaques having many of the morphologic features of atherosclerosis. We have provided evidence, however, that the evolution of thrombi to fibrofatty lesions is dependent on the initial composition of the thrombi and that thrombi with a paucity of platelets and consisting predominantly of fibrin result only in fibrous intimal thickenings. The presence of hypercholesterolemia has been shown to influence the transformation of experimental thrombi. In particular, it slows the rate of thrombolysis, enhances the lipid content of the fibrofatty plaques, increases the numbers of macrophage-derived foam cells, and the frequency and extent of lesion calcification. Detailed lipid compositional studies of organizing thrombi in normolipidemic animals have shown that their lipid composition does not evolve toward the profile characteristic of atherosclerotic lesions and that the macrophage uptake of interstitial lipoproteins is probably a necessary component for the full biochemical development of the lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Arteriosclerosis; Endothelium, Vascular; Fibrin; Humans; Lipids; Risk Factors; Thrombosis

Topics: Arteriosclerosis; Fibrin; Fibrinolysis; Humans; Thrombosis; Tissue Plasminogen Activator

Many human atherosclerotic lesions, showing no evidence of fissure or ulceration, contain a large amount of fibrin which may be in the form of mural thrombus on the intact surface of the plaque, in layers within the fibrous cap, in the lipid-rich centre, or diffusely distributed throughout the plaque. Small mural thrombi are invaded by SMCs and collagen is deposited in patterns closely resembling the early proliferative gelatinous lesions. In experimental animals, thrombi are converted into lesions with all the characteristics of fibrous plaques, and in saphenous-vein bypass grafts, fibrin deposition is the main cause of wall thickening and occlusion. There seems little doubt that fibrin deposition can both initiate atherogenesis and contribute to the growth of plaques. Epidemiological studies indicate that increased levels of fibrinogen and clotting activity are associated with accelerated atherosclerosis, and although blood fibrinolytic activity has given inconsistent results, in arterial intima both fibrinolytic activity and plasminogen concentration are decreased in cardiovascular disease. Fibrin may stimulate cell proliferation by providing a scaffold along which cells migrate, and by binding fibronectin, which stimulates cell migration and adhesion. Fibrin degradation products, which are present in the intima, may stimulate mitogenesis and collagen synthesis, attract leukocytes, and alter endothelial permeability and vascular tone. In the advanced plaque fibrin may be involved in the tight binding of LDL and accumulation of lipid. Thus there is extensive evidence that enhanced blood coagulation is a risk factor not only for thrombotic occlusion, but also for atherogenesis. Enhanced blood coagulation frequently coexists with hyperlipidaemia and, together, these may have a synergistic effect on atherogenesis.

Topics: Animals; Arteriosclerosis; Coronary Disease; Disease Models, Animal; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Hemostasis; Humans; Lipoproteins, LDL; Muscle, Smooth, Vascular; Risk; Thrombosis

Topics: Arteries; Arteriosclerosis; Cytoskeleton; Fibrin; Golgi Apparatus; Humans; Hypertension; Microtubule-Associated Proteins; Muscle, Smooth, Vascular

The existence of a system in the human body capable of inducing the dissolution of endogenous pathologically formed thrombi was appreciated in ancient times. Considered in detail in this article are the data that have elucidated the physiologic regulation of which plasmin formation is dependent on, the plasma concentration of plasminogen, availability of activators of plasminogen in the plasma and surrounding tissue environment, the concentration of naturally present inhibitors, and the existence of fibrin in the circulation. Important in this rapidly progressive scientific discipline is consideration of the factors which control the synthesis of the components of this proteolytic enzyme system. Recently abundant information has indicated that this plasminogen-plasmin proteolytic enzyme system can be utilized therapeutically. Knowledge of the mechanisms of this system has permitted identification of agents that can be exogenously administered to releave thrombotic obstruction to blood flow in the venous (pulmonary emboli, deep vein thrombosis) and arterial (peripheral and central vessels) circulatory systems. Particularly important is the demonstration that thrombolytic agents can directly attack and alleviate the immediate cause of acute myocardial infarction. As a result of the innovations in the present decade, it is evident that the plasminogen system can be advantageously employed to reverse the pathologic effects of all thrombotic diseases.

Topics: alpha 1-Antitrypsin; alpha-2-Antiplasmin; alpha-Macroglobulins; Antifibrinolytic Agents; Antithrombin III; Arterial Occlusive Diseases; Arteriosclerosis; Complement C1 Inactivator Proteins; Disseminated Intravascular Coagulation; Fibrin; Fibrinogen; Fibrinolysin; Fibrinolysis; Fibrinolytic Agents; Humans; Kidney Diseases; Liver Diseases; Myocardial Infarction; Neoplasms; Plasminogen; Pulmonary Embolism; Thrombophlebitis

Topics: Animals; Arteriosclerosis; Cell Adhesion; Cell Membrane; Cell Transformation, Neoplastic; Cell Transformation, Viral; Cells, Cultured; Collagen; Endocytosis; Endothelium; Extracellular Matrix; Fibrin; Fibronectins; Growth Substances; Humans; Laminin; Lipid Bilayers; Lipoproteins; Lymphocytes; Membrane Proteins; Neoplasm Metastasis; Neoplasms; Oncogenes; Plasminogen Activators; Proteoglycans; Receptors, Cell Surface; Surface Properties

Topics: Adhesiveness; Animals; Arteriosclerosis; Basement Membrane; Blood Coagulation; Blood Vessel Prosthesis; Blood Viscosity; Capillaries; Capillary Permeability; Decompression Sickness; Endothelium; Fibrin; Fibrinogen; Fibrinolysin; Fibrinolysis; Gels; Homeostasis; Humans; Hydrogen-Ion Concentration; Neoplasms; Polysaccharides; Protein Conformation; Protein Precursors; Rheology

Topics: Adolescent; Adult; Aged; Animals; Antithrombin III; Arteriosclerosis; Bleeding Time; Blood Vessels; Cats; Child; Dietary Fats; Dogs; Eicosapentaenoic Acid; Epoprostenol; Fatty Acids, Unsaturated; Female; Fibrin; Fish Oils; Humans; Inuit; Lipoproteins; Male; Middle Aged; Platelet Aggregation; Rats; Thrombosis; Thromboxanes

Ultrastructural study of the placental bed spiral arteries confirms that non-villous cytotrophoblast is involved in the development of the physiological changes occurring in these vessels during normal pregnancy. The changes observed in the myometrial segments of the spiral arteries before the time of arrival of endovascular trophoblast but after the invasion of the myometrium by migrating interstitial trophoblast, are characterised by widening of the lumen, oedema of the intima, disruption of the elastica and widening of the intercellular spaces of the media. This vascular distension could facilitate the subsequent retrograde migration of endovascular trophoblast. The fetal cells migrate in the vessel lumen and infiltrate the subendothelial space causing further disruption of the arterial intima and media. The altered intima is subsequently recovered by the endothelium. In this way, the cytotrophoblast is incorporated into the wall of the placental bed spiral arteries which are converted from small muscular arteries into distended hyalinized tubes. In pregnancies complicated by preeclampsia and in some pregnancies complicated by fetal growth retardation, these physiological changes are largely restricted to the decidual segments leaving the myometrial segments unaffected. The lesion of acute atherosis is characterised by thickening of the intima and necrosis of the media. The intimal thickening is due to deposition of fibrin and other plasma constituents and migration into the intima of macrophages and myointimal cells which accumulate fat in their cytoplasm to become foam cells. Clinical and experimental studies indicate that these lesions can be initiated by several factors which cause endothelial injury.

Topics: Arteries; Arteriosclerosis; Endothelium; Female; Fetal Growth Retardation; Fibrin; Humans; Microscopy, Electron; Placenta; Pre-Eclampsia; Pregnancy; Pregnancy Complications, Cardiovascular; Trophoblasts; Uterus

Topics: Arachidonic Acids; Arteriosclerosis; Aspirin; Blood Platelets; Calcium; Coronary Disease; Cyclic AMP; Diabetes Mellitus; Dietary Fats; Female; Fibrin; Humans; Myeloproliferative Disorders; Nephrotic Syndrome; Oxygenases; Platelet Adhesiveness; Platelet Aggregation; Pre-Eclampsia; Pregnancy; Prostaglandins; Thrombosis

Topics: Adsorption; Arteriosclerosis; Biological Transport; Blood Flow Velocity; Blood Platelets; Blood Proteins; Elasticity; Erythrocytes; Fats; Fibrin; Fibrinogen; Glass; Hemostasis; Platelet Adhesiveness

Topics: Ancrod; Animals; Arteriosclerosis; Blood Viscosity; Disease Models, Animal; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Intermittent Claudication; Thrombophlebitis; Vascular Diseases

Topics: Animals; Antigens; Arteriosclerosis; Binding Sites, Antibody; Blood Platelets; Disease Models, Animal; Endothelium; Fibrin; Humans; Hyperplasia; Microscopy, Electron, Scanning; Muscle, Smooth; Thrombosis

Topics: Animals; Arteriosclerosis; Blood Platelets; Blood Vessels; Calcium; Cell Division; Cell Membrane Permeability; Collagen; Disease Models, Animal; Elastin; Endothelium; Fibrin; Glycosaminoglycans; Histocytochemistry; Humans; Lipid Metabolism; Microscopy, Electron; Necrosis; Platelet Adhesiveness

Topics: Animals; Arteries; Arteriosclerosis; Endothelium; Fibrin; Humans; Lipid Metabolism; Thrombosis

Topics: Arteriosclerosis; Aspirin; Blood Platelets; Blood Protein Disorders; Cell Survival; Coronary Disease; Endothelium; Fibrin; Humans; Lipid Metabolism; Lipoproteins; Phagocytosis; Platelet Adhesiveness; Prostaglandins; Pyrazoles; Pyrimidines; Thrombosis

Topics: Adenosine Diphosphate; Animals; Anti-Inflammatory Agents; Arteriosclerosis; Blood Coagulation; Blood Platelets; Blood Proteins; Blood Vessels; Collagen; Disseminated Intravascular Coagulation; Fibrin; Fibrinogen; Glass; Graft Rejection; Hemostasis; Humans; Ischemia; Kidney Transplantation; Platelet Adhesiveness; Platelet Aggregation; Thrombosis; Transplantation, Homologous

Topics: Adenosine Diphosphate; Arteriosclerosis; Basement Membrane; Blood Coagulation; Blood Coagulation Factors; Blood Flow Velocity; Blood Platelets; Collagen; Fibrin; Fibrinolysis; Humans; Platelet Adhesiveness; Thrombophlebitis; Thrombosis

Topics: Arteriosclerosis; Blood Platelets; Capillaries; Femoral Vein; Fibrin; Fibrinolysis; Humans; Mesenteric Veins; Shwartzman Phenomenon; Thrombosis

Topics: Animals; Aorta; Arteriosclerosis; Blood Platelets; Calcinosis; Child; Cholesterol; Collateral Circulation; Coronary Disease; Coronary Vessels; Erythrocytes; Female; Fibrin; Fibroblasts; Glycosaminoglycans; Hemorrhage; Histocytochemistry; Humans; Lipids; Macrophages; Male; Middle Aged; Muscle, Smooth; Necrosis; Rabbits; Rupture; Thrombosis

Topics: Adolescent; Albumins; Aorta; Aorta, Thoracic; Arteriosclerosis; Cell Membrane; Coronary Vessels; Culture Techniques; Cytoplasm; Extracellular Space; Female; Fibrin; Fibroblasts; Fluorescent Antibody Technique; Humans; Infant; Lipids; Lipoproteins; Male; Microscopy, Electron; Muscle, Smooth; Ribosomes; Thrombosis

Topics: Adenosine Diphosphate; Animals; Antigen-Antibody Complex; Arteriosclerosis; Blood Coagulation; Blood Coagulation Disorders; Blood Flow Velocity; Blood Platelets; Cell Membrane; Collagen; Coronary Disease; Cytoplasmic Granules; Factor VII; Factor XII; Fibrin; Fibrinolysis; Humans; Microscopy, Electron; Microtubules; Platelet Adhesiveness; Rabbits; Serotonin; Thrombosis

Topics: Aorta; Arteries; Arteriosclerosis; Blood Circulation; Blood Proteins; Collagen; Coronary Vessels; Elasticity; Fibrin; Fibrinogen; Glycosaminoglycans; Humans; Lipid Metabolism; Muscle, Smooth; Plasma; Thrombosis

Topics: Animals; Aorta; Arteriosclerosis; Blood Vessels; Cholesterol; Cholestyramine Resin; Coronary Vessels; Epithelial Cells; Fibrin; Humans; Lipid Metabolism; Microscopy, Electron; Rabbits; Swine

Topics: Animals; Aorta; Arteriosclerosis; Blood Coagulation; Blood Coagulation Disorders; Blood Vessels; Endocrine Glands; Fibrin; Fibrinogen; Fibrinolysis; Hemorrhage; Heparin; Heparin Antagonists; Hepatitis; Humans; Lipid Metabolism; Lipoprotein Lipase; Liver; Liver Cirrhosis; Stress, Physiological; Thrombin; Thrombosis; Triglycerides

Topics: Animals; Arteries; Arteriosclerosis; Basement Membrane; Birds; Blood Platelets; Blood Vessel Prosthesis; Capillary Permeability; Cell Membrane; Cytoplasm; Fibrin; Fibrinolysis; Humans; Lipid Metabolism; Lymphatic System; Macrophages; Mammals; Microscopy; Microscopy, Electron; Muscle, Smooth; Phagocytosis; Regeneration; Thrombosis; Vasa Vasorum

Acute mental stress may contribute to atherosclerosis by affecting inflammation and coagulation; however, the crosstalk between inflammation and coagulation during stress has not been studied. In the present study, we investigated the association of plasma fibrinogen, plasma IL-6 (interleukin-6) and free salivary cortisol with the procoagulant marker D-dimer reflecting fibrin formation both over a 2-h period and in response to acute mental stress. Twenty-one male volunteers (mean age, 47+/-8 years) underwent the Trier Social Stress Test combining a 3-min preparation phase, a 5-min job interview and 5-min mental arithmetic test before an audience. IL-6, fibrinogen, D-dimer and cortisol were measured immediately before and after stress, and after 45 min and 105 min of recovery from stress. Two distinct areas under the curve were computed to obtain integrated measures of total protein activity over the entire 2-h period and of stress reactivity of proteins. IL-6 (P < 0.001), fibrinogen (P = 0.001), D-dimer (P = 0.021) and cortisol (P < 0.001) had all significantly changed across the four time points assessed, as determined by ANOVA. For the entire 2-h period, total fibrinogen activity (R2 = 0.33, P = 0.007) and total cortisol activity (DeltaR2 = 0.17, P = 0.034) explained 50% of the variance in total D-dimer activity. Stress-induced changes in fibrinogen (R2 = 0.47, P = 0.001) and IL-6 (DeltaR2 = 0.18, P = 0.008) together explained 65% of the variance in D-dimer reactivity to stress. Total fibrin formation was independently predicted by fibrinogen and hypothalamo-pituitary-adrenal activity. Pro-inflammatory and procoagulant changes with stress were associated. Aside from fibrinogen reactivity, IL-6 reactivity was an independent predictor of stress-induced fibrin formation.

Topics: Adult; Analysis of Variance; Area Under Curve; Arteriosclerosis; Biomarkers; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Hydrocortisone; Interleukin-6; Male; Middle Aged; Psychological Tests; Saliva; Stress, Psychological

Topics: Adult; Aged; Arteriosclerosis; Arthritis, Rheumatoid; Blood Coagulation; Clinical Trials as Topic; Ethylestrenol; Female; Fibrin; Fibrinogen; Fibrinolysis; Humans; Male; Middle Aged; Phenformin; Placebos; Time Factors; Vascular Diseases

To investigate the effect of fibrinogen (Fg), fibrin (Fb) and fibrin (ogen) degradation products (FDPs) on tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) expressions of human umbilical vein endothelial cells (HUVECs) in coculture system.. Fg, Fb and FDPs at various concentrations (0, 0.5, 1.5, 3.0, 4.5 and 6.0 g/L) were added to the transwell coculture system of HUVECs and smooth muscle cells (SMCs) for 24 hours. The expressions of tPA and PAI-1 at mRNA level were examined by RT-PCR and tPA and PAI-1 protein and activity were detected by ELISA and substrate chromogenic assays.. tPA expression was not affected by Fg. Fg at concentrations between 3.0 - 4.5 g/L significantly enhanced the mRNA expression, protein content and activity of PAI-1, while expression of PAI-1 was significantly inhibited by Fg at concentration of 6.0 g/L. Fb at concentrations between 3.0 - 4.5 g/L significantly up-regulated mRNA expression, increased protein content and down-regulated activity of tPA. Fb (1.5 - 4.5 g/L) also enhanced the mRNA expression, increased protein content and activity of PAI-1. FDPs at concentrations 3.0 - 6.0 g/L down-regulated the expression of tPA and FDPs at concentrations 1.5 - 6.0 g/L significantly enhanced PAI-1 mRNA expression.. Fg, Fb and FDPs play important roles in the pathogenesis of atherosclerosis by modulating the expression of tPA and PAI-1 of endothelial and SMCs.

Topics: Animals; Arteriosclerosis; Cells, Cultured; Coculture Techniques; Endothelial Cells; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Plasminogen Activator Inhibitor 1; Rabbits; RNA, Messenger; Tissue Plasminogen Activator

MRI would be a valuable noninvasive diagnostic tool to study plaque-associated thrombi. We defined the imaging characteristics of these thrombi, composed primarily of platelets and fibrin, and distinguished them clearly from the vessel lumen and underlying atherosclerotic plaque in an animal model of plaque rupture.. After triggering plaque rupture in New Zealand White male rabbits, segments of infrarenal aorta containing either red or white thrombi were fixed in formalin. Compared with postmortem red cell-rich thrombi, atherothrombi yielded complex magnetic resonance images with intermediate signal intensity in standard T1- and T2-weighted imaging sequences and were often difficult to distinguish from the aortic wall. Diffusion-weighted imaging sequences revealed restricted diffusion of the atherothrombus relative to the vessel wall and provided excellent contrast. The apparent diffusion coefficient of the thrombus is 1.0x10(-3) mm2/s, compared with 1.5x10(-3) mm2/s in tissue. Similar results were obtained using purified aggregated platelets.. We present the first detailed description of the MRI appearance of plaque rupture-associated thrombosis in histologically validated platelet-rich thrombi. Diffusion-weighted imaging provided the best distinction between thrombus and vessel wall and has potential application for the noninvasive in vivo detection of atherothrombosis.

Topics: Animals; Aorta, Abdominal; Aortic Rupture; Arteriosclerosis; Blood Platelets; Fibrin; Magnetic Resonance Imaging; Male; Rabbits; Thrombosis

A cross sectional and prospective analysis of 3,745 British women aged 60-79 years at baseline was undertaken. Among these women there were 570 prevalent cases of coronary heart disease (CHD) and 151 new cases among 12,641 person-years of follow up of women who were free of CHD at baseline. Both fibrinogen and CRP were associated with indicators of socioeconomic position in childhood and adulthood and there was a cumulative effect of socioeconomic position from across the life course. The age-adjusted odds ratio (95% confidence interval) of prevalent CHD for a 1 unit (1 g/L) increase in fibrinogen was 1.29 (1.12, 1.49); with full adjustment for all potential confounding factors this attenuated to 1.09 (0.93, 1.28). The hazards ratio for incident CHD among those free of disease at baseline was 1.28 (1.00, 1.64); with full adjustment for all potential confounding factors this attenuated to 1.09 (0.84, 1.44). Similar effects of adjustment for confounding factors were seen for the associations between CRP and both prevalent and incident CHD. By contrast, the strong positive association between smoking (an established causal risk factor for CHD) and CHD was not attenuated by adjustment for life course socioeconomic position or other risk factors. We conclude that fibrinogen and CRP predict CHD but may not be causally related to it.

Topics: Age Factors; Aged; Arteriosclerosis; C-Reactive Protein; Confounding Factors, Epidemiologic; Coronary Artery Disease; Coronary Disease; Female; Fibrin; Fibrinogen; Humans; Inflammation; Middle Aged; Models, Statistical; Odds Ratio; Prospective Studies; Risk Factors; Social Class

Plaque rupture with subsequent thrombosis is recognized as the underlying pathophysiology of most acute coronary syndromes and stroke. Thus, direct thrombus visualization may be beneficial for both diagnosis and guidance of therapy. We sought to test the feasibility of direct imaging of acute and subacute thrombosis using MRI together with a novel fibrin-binding gadolinium-labeled peptide, EP-1873, in an experimental animal model of plaque rupture and thrombosis.. Fifteen male New Zealand White rabbits (weight, approximately 3.5 kg) were made atherosclerotic by feeding a high-cholesterol diet after endothelial aortic injury. Plaque rupture was then induced with the use of Russell's viper venom (RVV) and histamine. Subsequently, MRI of the subrenal aorta was performed before RVV, after RVV, and after EP-1873. Histology was performed on regions suggested by MRI to contain thrombus. Nine rabbits (60%) developed plaque rupture and thrombus, including 25 thrombi visually apparent on MRI as "hot spots" after injection of EP-1873. Histological correlation confirmed all 25 thrombi (100%), with no thrombi seen in the other regions of the aorta. In the remaining 6 rabbits (control) without plaque rupture, no thrombus was observed on the MR images or on histology.. We demonstrate the feasibility of in vivo "molecular" MRI for the detection of acute and subacute thrombosis using a novel fibrin-binding MRI contrast agent in an animal model of atherosclerosis and acute/subacute thrombosis. Potential clinical applications include thrombus detection in acute coronary syndromes and stroke.

Topics: Acute Disease; Animals; Arteriosclerosis; Binding, Competitive; Contrast Media; Fibrin; Gadolinium DTPA; Magnetic Resonance Imaging; Male; Peptides; Rabbits; Thrombosis; Time Factors

The mechanisms of thrombosis on plaque erosion are poorly understood. We examined the potential role of endothelial apoptosis in endothelial erosion and vessel thrombosis.. Segments of New Zealand White rabbit femoral arteries were temporarily isolated in vivo. One artery was incubated with staurosporin for 30 minutes, whereas the contralateral artery was incubated with saline and served as control. Three days later, thrombosis was evaluated angiographically and histologically. TUNEL score in the endothelial layer was significantly increased in staurosporin-treated arteries compared with controls (2.43+/-0.30 versus 0.93+/-0.44, respectively; P=0.001). Large areas of endothelial denudation were detectable in staurosporin-treated vessels, whereas endothelium integrity was almost preserved in the saline group. Vessel thrombosis occurred in 58% of staurosporin-treated arteries (7 of 12) but in only 8% of saline-treated segments (P<0.01). Immunoreactivities for tissue factor, platelets, and fibrin were detectable within the thrombus. Addition of ZVAD-fmk (0.1 mmol/L) significantly reduced the occurrence of thrombosis (1 of 7 arteries or 14%, P=0.04). These results were confirmed in balloon-injured atheromatous arteries.. In vivo induction of endothelial apoptosis leads to both vessel thrombosis and endothelial denudation. Endothelial apoptosis may be a critical step in the transition from a stable endothelialized plaque to plaque erosion and thrombosis.

Topics: Amino Acid Chloromethyl Ketones; Animals; Apoptosis; Arteriosclerosis; Catheterization; Cysteine Proteinase Inhibitors; Endothelial Cells; Endothelium, Vascular; Femoral Artery; Fibrin; In Situ Nick-End Labeling; Platelet Count; Rabbits; Staurosporine; Thromboplastin; Thrombosis; Tunica Intima

Unstable atherosclerotic plaques exhibit microdeposits of fibrin that may indicate the potential for a future rupture. However, current methods for evaluating the stage of an atherosclerotic lesion only involve characterizing the level of vessel stenosis, without delineating which lesions are beginning to rupture. Previous work has shown that fibrin-targeted, liquid perfluorocarbon nanoparticles, which carry a high payload of gadolinium, have a high sensitivity and specificity for detecting fibrin with clinical (1)H MRI. In this work, the perfluorocarbon content of the targeted nanoparticles is exploited for the purposes of (19)F imaging and spectroscopy to demonstrate a method for quantifiable molecular imaging of fibrin in vitro at 4.7 T. Additionally, the quantity of bound nanoparticles formulated with different perfluorocarbon species was calculated using spectroscopy. Results indicate that the high degree of nanoparticle binding to fibrin clots and the lack of background (19)F signal allow accurate quantification using spectroscopy at 4.7 T, as corroborated with proton relaxation rate measurements at 1.5 T and trace element (gadolinium) analysis. Finally, the extension of these techniques to a clinically relevant application, the evaluation of the fibrin burden within an ex vivo human carotid endarterectomy sample, demonstrates the potential use of these particles for uniquely identifying unstable atherosclerotic lesions in vivo.

Topics: Arteriosclerosis; Biotinylation; Carotid Artery Diseases; Contrast Media; Emulsions; Endarterectomy, Carotid; Fibrin; Fluorine; Gadolinium DTPA; Humans; Immunohistochemistry; Magnetic Resonance Imaging; Nanostructures; Particle Size; Sensitivity and Specificity

The clustering of impaired glucose metabolism, elevated triglycerides, low HDL cholesterol, and abdominal obesity is known as the metabolic syndrome. Individuals with this syndrome suffer an excess of cardiovascular disease (CVD) for reasons that are unclear.. We randomly sampled 1276 adults of South Asian, Chinese, European, and Native Indian ancestry from 4 communities in Canada. Participants provided fasting blood samples for glucose, lipids, and fibrinolytic measurements; had an oral glucose tolerance test; and underwent a B-mode carotid ultrasound examination. CVD was determined by history and ECG. The prevalence of the metabolic syndrome was 25.8% (95% CI, 23.5 to 28.2) and varied substantially by ethnic group: 41.6% among Native Indians, 25.9% among South Asians, and 22.0% among Europeans, compared with 11.0% among the Chinese (overall, P=0.0001). People with the metabolic syndrome had more atherosclerosis (maximum intimal medial thickness, 0.78+/-0.18 versus 0.74+/-0.18 mm; P=0.0005), CVD (17.2% versus 7.0%; P=0.0001), and elevated plasminogen activator inhibitor-1 (24.2 versus 14.6 U/mL; P=0.001) compared with levels among people without the metabolic syndrome. For the same amount of atherosclerosis, people with the metabolic syndrome had a greater prevalence of CVD, even among nondiabetic individuals. This difference in CVD prevalence among the groups was attenuated after adjustment for plasminogen activator inhibitor-1 levels, suggesting that fibrinolytic dysfunction mediates the increased risk of CVD in individuals with the metabolic syndrome.. CVD among people with the metabolic syndrome is explained by their excess of atherosclerosis and impaired fibrinolysis. Interventions to prevent atherosclerosis progression and improve fibrinolytic function require evaluation in this high-risk group.

Topics: Adult; Arteriosclerosis; Asia; Asian People; Blood Glucose; Canada; Cardiovascular Diseases; Carotid Arteries; Comorbidity; Electrocardiography; Europe; Female; Fibrin; Fibrinolysis; Glucose Tolerance Test; Humans; Indians, North American; Lipids; Male; Metabolic Syndrome; Middle Aged; Prevalence; Risk Assessment; Risk Factors; Ultrasonography; White People

More than 70% of circulating homocysteine is disulfide-bonded to protein, but little is known about the specific proteins that bind homocysteine and their function as a consequence of homocysteine binding.. When human plasma was incubated with [(35)S]L-homocysteine, most of the homocysteine bound to albumin. However, additional homocysteine-binding proteins were detected, and 1 of them comigrated with fibronectin. Treatment with 2-mercaptoethanol removed the bound homocysteine, demonstrating the involvement of disulfide bonding. In contrast, [35S]L-cysteine did not bind to fibronectin. Purified fibronectin bound approximately 5 homocysteine molecules per fibronectin dimer. SDS-PAGE of a limited trypsin digestion of homocysteinylated fibronectin showed that several tryptic fragments contained [35S]homocysteine. Sequence analysis demonstrated that the fragments containing bound homocysteine had localized mainly to the C-terminal region, within and adjacent to the fibrin-binding domain. Homocysteinylation of fibronectin significantly inhibited its capacity to bind fibrin by 62% (P<0.005). In contrast, neither the binding of fibronectin to gelatin nor its capacity to serve as an attachment factor for aortic smooth muscle cells was affected.. These results suggest that homocysteine may alter normal thrombosis and delay or interfere with wound healing by impairing the interaction of fibronectin with fibrin.

Topics: Arteriosclerosis; Binding, Competitive; Fibrin; Fibronectins; Gelatin; Homocysteine; Humans; In Vitro Techniques; Muscle, Smooth, Vascular; Thrombosis

Three-month studies of stent-delivered brachytherapy in the rabbit model show reduced neointimal growth. However, intimal healing is delayed, raising the possibility that intimal inhibition is merely delayed rather than prevented. The purpose of this study was to explore the long-term histological changes after placement of beta-emitting radioactive stents in normal rabbit iliac arteries.. Three-millimeter beta-emitting (32)P stents (6, 24, and 48 microCi) were placed in normal rabbit iliac arteries with nonradioactive stents as controls. Animals were euthanatized at 6 and 12 months, and histological assessment, morphometry, and analysis of endothelialization were performed. Morphometric measurements demonstrated a >50% reduction in intimal growth and percent lumen stenosis within 24- and 48-microCi stents versus control nonradioactive stents at both 6 and 12 months. However, the 24- and 48-microCi stents also showed delayed healing of the intimal surface, characterized by persistent fibrin thrombus with nonconfluent areas of matrix, incomplete endothelialization, and increased intimal cellular proliferation. Stent edge stenosis was present at 12 months in the 24- and 48-microCi stent groups, characterized by both intimal thickening and negative arterial remodeling.. Inhibition of intimal growth is maintained 6 and 12 months after (32)P beta-emitting stent placement. However, delayed arterial healing, incomplete endothelialization, and edge effects are present.

Topics: Animals; Arteriosclerosis; Cell Division; Endothelium, Vascular; Fibrin; Iliac Artery; Male; Microscopy, Electron, Scanning; Phosphorus Radioisotopes; Rabbits; Stents; Time Factors; Tunica Intima

Thrombin has been proposed to play a key role in the development of atherosclerosis, both by promoting fibrin deposition into the atherosclerotic vessel wall and also by signalling through thrombin receptors. Unfortunately, mice homozygous for a deletion of the prothrombin gene (FII) die in utero, making a direct assessment of the role of thrombin during atherogenesis difficult. We have assessed the contribution of thrombin-dependent processes to vascular lipid lesion formation in the atherosclerosis-prone apolipoprotein E (ApoE)-deficient mice by inhibiting thrombin generation with warfarin. ApoE-/- mice were treated with warfarin at a dose that increased the prothrombin time (PT) more than 10-fold (250-375 microg/kg body weight/day) for 12 weeks from the age of 12 weeks onwards. The extent and composition of the vascular lipid lesions that developed were assessed using oil red O to measure neutral lipid in the vessel wall and quantitative immunofluoresence to measure fibrin(ogen) levels as well as macrophage and smooth muscle cell numbers. Mice treated with warfarin developed lesions both in the aortic sinus and the descending aorta to the same degree as mice receiving no treatment (28,351+/-350 microm2/mouse treated with warfarin versus 27,952+/-750 micro2/control mouse; P = .86). However, the amount of fibrin(ogen) deposited in the vessel wall was decreased by more than 60% (34+/-11 arbitrary units in warfarin treated mice versus 92+/-11 arbitrary units in control mice; P < .01). Staining of macrophage and for smooth muscle cell markers was unaltered by treatment with warfarin. We conclude that suppressing thrombin generation does not alter the development of vascular lipid lesions in mice with a severe disorder of lipid metabolism, despite a marked reduction in fibrin(ogen) deposition.

Topics: Animals; Anticoagulants; Aorta; Apolipoproteins E; Arteriosclerosis; Depression, Chemical; Disease Models, Animal; Fibrin; Macrophages; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle, Smooth, Vascular; Prothrombin Time; Thrombin; Warfarin

Molecular imaging of thrombus within fissures of vulnerable atherosclerotic plaques requires sensitive detection of a robust thrombus-specific contrast agent. In this study, we report the development and characterization of a novel ligand-targeted paramagnetic molecular imaging agent with high avidity for fibrin and the potential to sensitively detect active vulnerable plaques.. The nanoparticles were formulated with 2.5 to 50 mol% Gd-DTPA-BOA, which corresponds to >50 000 Gd(3+) atoms/particle. Paramagnetic nanoparticles were characterized in vitro and evaluated in vivo. In contradistinction to traditional blood-pool agents, T1 relaxation rate as a function of paramagnetic nanoparticle number was increased monotonically with Gd-DTPA concentration from 0.18 mL. s(-1). pmol(-1) (10% Gd-DTPA nanoparticles) to 0.54 mL. s(-1). pmol(-1) for the 40 mol% Gd-DTPA formulations. Fibrin clots targeted in vitro with paramagnetic nanoparticles presented a highly detectable, homogeneous T1-weighted contrast enhancement that improved with increasing gadolinium level (0, 2.5, and 20 mol% Gd). Higher-resolution scans and scanning electron microscopy revealed that the nanoparticles were present as a thin layer over the clot surface. In vivo contrast enhancement under open-circulation conditions was assessed in dogs. The contrast-to-noise ratio between the targeted clot (20 mol% Gd-DTPA nanoparticles) and blood was approximately 118+/-21, and that between the targeted clot and the control clot was 131+/-37.. These results suggest that molecular imaging of fibrin-targeted paramagnetic nanoparticles can provide sensitive detection and localization of fibrin and may allow early, direct identification of vulnerable plaques, leading to early therapeutic decisions.

Topics: Animals; Arteriosclerosis; Biotinylation; Contrast Media; Dogs; Fibrin; Fluorocarbons; Humans; Image Enhancement; Jugular Veins; Magnetic Resonance Imaging; Microscopy, Electron, Scanning; Particle Size; Thrombosis; Venous Thrombosis

Previously, we demonstrated that amorphous calcium phosphate (ACP), chemical precursor to apatite, strongly interacted with fibrin and facilitated binding of matrix metalloproteinase (MMP)-9, a type IV collagenase. Plasmin-dependent fibrinolysis resulted in coordinate MMP-9 activation. Here we report on the effect(s) of ACP on fibrin degradation and binding of endogenous plasma proteases. Electrophoresis (8.5% SDS-PAGE) revealed that fibrin formed in the presence of ACP demonstrated characteristic gamma-gamma dimers (90-kDa) and beta-monomers (55-kDa), but resisted spontaneous fibrinolysis (72 h, 37 degrees C) or degradation by plasminogen activators (uPA, tPA). Casein zymography revealed an ACP-dependent decrease in fibrin binding of a low molecular weight (Mw) protease triplet (47-, 43-, 42-kDa) and increased fibrin binding of two high Mw proteases (94- and 84-kDa). The low Mw triplet also possessed gelatinolytic activity, but was not an MMP since 1,10-phenanthroline was ineffective as an inhibitor. Fibrin-binding proteases were inhibited to some degree by the serine protease inhibitor aprotinin. Competition/dissociation experiments with epsilon-aminocaproic acid revealed that the low Mw triplet lacked kringle regions whereas the 94- and 84-kDa proteases were tentatively identified and glu-/lys-plasmin(ogen)s. The triplet may, however, represent one or more kringle deficient mini-plasminogen(s), since electrophoretic mobility and substrate specificity was similar to elastase-generated mini-plasminogen. To explore these findings in a clinically relevant setting, a series of plasma samples was collected from a patient with unstable angina prior to, during, and post coronary artery bypass graft (CABG) surgery. Fibrin formed from plasma collected during and immediately post CABG was associated with increased fibrinolytic capacity and enhanced binding of a) MMP-9, b) the low Mw protease triplet (described above), and c) PA (as putative 110-kDa tPA:PAI-1 complex). The relevance of these findings to pathologic calcification of atherosclerotic plaques is discussed.

Topics: Aged; Aged, 80 and over; Arteriosclerosis; Calcium Phosphates; Caseins; Coronary Artery Bypass; Endopeptidases; Fibrin; Fibrinolysis; Gelatin; Humans; Male; Plasminogen Activators; Protein Binding

Impaired fibrinolysis has been linked to atherosclerosis in a number of experimental and clinical studies. Plasminogen activator inhibitor type 1 (PAI-1) is the primary inhibitor of plasminogen activation and has been proposed to promote atherosclerosis by facilitating fibrin deposition within developing lesions. We examined the contribution of PAI-1 to disease progression in 2 established mouse models of atherosclerosis. Mice lacking apolipoprotein E (apoE-/-) and mice lacking the low density lipoprotein receptor (LDLR-/-) were crossbred with transgenic mice overexpressing PAI-1 (resulting in PAI-1 Tg(+)/apoE-/- and PAI-1 Tg(+)/LDLR-/-, respectively) or were crossbred with mice completely deficient in PAI-1 gene expression (resulting in PAI-1-/-/apoE-/- and PAI-1-/-/LDLR-/-, respectively). All animals were placed on a western diet (21% fat and 0.15% cholesterol) at 4 weeks of age and analyzed for the extent of atherosclerosis after an additional 6, 15, or 30 weeks. Intimal and medial areas were determined by computer-assisted morphometric analysis of standardized microscopic sections from the base of the aorta. Atherosclerotic lesions were also characterized by histochemical analyses with the use of markers for smooth muscle cells, macrophages, and fibrin deposition. Typical atherosclerotic lesions were observed in all experimental animals, with greater severity at the later time points and generally more extensive lesions in apoE-/- than in comparable LDLR-/- mice. No significant differences in lesion size or histological appearance were observed among PAI-1-/-, PAI-1 Tg(+), or PAI-1 wild-type mice at any of the time points on either the apoE-/- or LDLR-/- genetic background. We conclude that genetic modification of PAI-1 expression does not significantly alter the progression of atherosclerosis in either of these well-established mouse models. These results suggest that fibrinolytic balance (as well as the potential contribution of PAI-1 to the regulation of cell migration) plays only a limited role in the pathogenesis of the simple atherosclerotic lesions observed in the mouse.

Topics: Animals; Apolipoproteins E; Arteriosclerosis; Endothelium, Vascular; Fibrin; Fibrinolysis; Genotype; Male; Mice; Mice, Knockout; Plasminogen Activator Inhibitor 1; Receptors, LDL; Tunica Intima

Dissolution of the fibrin blood clot is regulated in large part by plasminogen activator inhibitor-1 (PAI-1). Elevated levels of plasma PAI-1 may be an important risk factor for atherosclerotic vascular disease and are associated with premature myocardial infarction. The role of the endogenous plasminogen activation system in limiting thrombus formation following atherosclerotic plaque disruption is unknown. This study found that genetic deficiency for PAI-1, the primary physiologic regulator of tissue-type plasminogen activator (tPA), prolonged the time to occlusive thrombosis following photochemical injury to carotid atherosclerotic plaque in apolipoprotein E-deficient (apoE(-/-)) mice. However, anatomic analysis revealed a striking difference in the extent of atherosclerosis at the carotid artery bifurcation between apoE(-/-) mice and mice doubly deficient for apoE and PAI-1 (PAI-1(-/-)/apoE(-/-)). Consistent with a previous report, PAI-1(+/+)/apoE(-/-)and PAI-1(-/-)/apoE(-/-) mice developed similar atherosclerosis in the aortic arch. The marked protection from atherosclerosis progression at the carotid bifurcation conferred by PAI-1 deficiency suggests a critical role for PAI-1 in the pathogenesis of atherosclerosis at sites of turbulent flow, potentially through the inhibition of fibrin clearance. Consistent with this hypothesis, intense fibrinogen/fibrin staining was observed in atherosclerotic lesions at the carotid bifurcation compared to the aortic arch. These observations identify significant differences in the pathogenesis of atherosclerosis at varying sites in the vascular tree and suggest a previously unappreciated role for the plasminogen activation system in atherosclerosis progression at sites of turbulent flow. (Blood. 2000;96:4212-4215)

Topics: Animals; Aorta, Thoracic; Aortic Diseases; Apolipoproteins E; Arteriosclerosis; Carotid Artery Diseases; Carotid Artery Injuries; Carotid Artery, Common; Carotid Stenosis; Disease Progression; Fibrin; Fibrinogen; Hemorheology; Male; Mice; Mice, Knockout; Photochemistry; Plasminogen; Plasminogen Activator Inhibitor 1

Structure and content of atherosclerotic plaque varies between patients and may be indicative of their risk for embolisation. This study aimed to construct parametric images of B-scan texture and assess their potential for predicting plaque morphology. Sequential transverse in vitro scans of 10 carotid plaques, excised during endarterectomy, were compared with macrohistology maps of plaque content. Multidiscriminant analysis combined the output of 157 statistical and textural algorithms into five separate texture classes, displayed as ultrasound (US) texture classification images (UTCI). Visual comparison between corresponding UTCI and histology maps found the five texture classes matched with the location of fibrin, elastin, calcium, haemorrhage or lipid. However, histology preparation removes calcium and lipid and, so, can affect the structural integrity of atherosclerotic plaques. Soft tissue regions smaller than the UTCI kernel, (0.87 mm x 0.85 mm x 3.9 mm), such as blood clots, are also difficult to detect by UTCI. These factors demonstrate limitations in the use of histology as a "gold standard" for US tissue characterisation.

Topics: Arteriosclerosis; Calcium; Carotid Arteries; Carotid Stenosis; Elastin; Endarterectomy, Carotid; Fibrin; Hemorrhage; Humans; Image Processing, Computer-Assisted; In Vitro Techniques; Lipids; Ultrasonography

Fibrin or a fibrinous exudate can facilitate angiogenesis in many pathological conditions. In vitro, the outgrowth of capillary-like structures in fibrin can be mimicked by exposing human microvascular endothelial cells (hMVECs) to an angiogenic growth factor and tumor necrosis factor (TNF)-alpha. Urokinase-type plasminogen activator (u-PA) and plasmin activities are required for this angiogenic process. This study focuses on the role and localization of the u-PA receptor (u-PAR) in newly formed microvascular structures. The u-PAR-blocking monoclonal antibody (MAb) H-2 completely inhibited the formation of capillary-like tubular structures induced by exposure of hMVECs to basic fibroblast growth factor and TNF-alpha. This was accompanied by a several-fold increase in u-PA accumulation in the conditioned medium. The effect of MAb H-2 was not caused by blocking cellular activation by u-PA/u-PAR interaction, as the amino-terminal fragment (ATF) of u-PA, which also activates u-PAR, prevented tube formation. In addition, the inhibition by MAb H-2 was not due to an effect of the antibody on u-PAR-vitronectin binding. These data show that inhibition of tube formation can be caused not only by inhibition of u-PA or plasmin activities but also by unavailability of the u-PAR for cell-bound proteolysis. Immunohistochemical analysis showed that in in vitro angiogenesis u-PAR and u-PA were localized on the invading, tube-forming hMVECs and not on the endothelial cells that are located on top of the fibrin matrix. u-PAR and u-PA were also prominently expressed on endothelial cells of neovessels present in an atherosclerotic plaque. These data may give more insight into the role of u-PAR in repair-associated angiogenesis.

Topics: Antibodies, Monoclonal; Arteriosclerosis; Carrier Proteins; Cells, Cultured; Cytokines; Dose-Response Relationship, Drug; Endothelium, Vascular; Fibrin; Glutathione Transferase; Humans; Immunohistochemistry; Neovascularization, Physiologic; Plasminogen Activators; Receptors, Cell Surface; Receptors, Urokinase Plasminogen Activator; Recombinant Fusion Proteins; Urokinase-Type Plasminogen Activator; Vitronectin

A critical role of the coagulation system in the development of atherosclerosis has been frequently postulated based on a variety of indirect observations, including the expression of procoagulants and fibrinolytic factors within atherosclerotic vessels, the presence of substantial amounts of fibrin(ogen) and fibrin degradation products within intimal lesions, the cellular infiltration and assimilation of mural thrombi into developing plaques, and the identification of high plasma fibrinogen (Fib) levels as an independent risk factor for the development of ischemic heart disease. To directly examine the role of fibrin(ogen) in atherogenesis, Fib-deficient mice were crossed to atherosclerosis-prone apolipoprotein E (apo E)-deficient mice. Both apo E-/- and apo E-/-/Fib-/- mice developed lesions throughout the entire aortic tree, ranging in appearance from simple fatty streaks to complex fibrous plaques. Furthermore, remarkably little difference in lesion size and complexity was observed within the aortae of age- and gender-matched apo E-/- and apo E-/-/Fib-/- mice. These results indicate that the contribution of fibrin(ogen) to intimal mass and local cell adhesion, migration, and proliferation is not strictly required for the development of advanced atherosclerotic disease in mice with a severe defect in lipid metabolism.

Topics: Afibrinogenemia; Alleles; Animals; Aorta; Apolipoproteins E; Arteriosclerosis; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Immunohistochemistry; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Muscle, Smooth; Polymerase Chain Reaction

During the development of atherosclerotic lesions, lipoprotein(a) [Lp(a)], a highly atherogenic lipoprotein, accumulates within fibrin clots attached to blood vessel walls. As Lp(a) accumulates within the fibrin clot with time, fatty streaks are formed that develop into occlusive atherosclerotic plaques. It is not understood, however, which mechanisms are involved in the binding of Lp(a) to fibrin and, hence, the stable incorporation of Lp(a) into the fibrin clot. The results of the present study demonstrate that factor XIIIa, a transglutaminase that catalyzes the formation of amide bonds between endo-gamma-glutaminyl and endo-epsilon-lysyl residues of proteins, is capable of cross-linking Lp(a) to fibrinogen, the soluble precursor of fibrin. Biochemical assays were conducted to demonstrate that factor XIIIa cross-links Lp(a) with fibrinogen in a time- and concentration-dependent manner. Additionally, immunohistochemical studies revealed that factor XIII protein expression colocalizes with Lp(a) expression in human atherosclerotic plaques. It is proposed that factor XIIIa-mediated cross-linking of Lp(a) to fibrin effectively increases the local concentration of Lp(a) within a fibrin clot. The accumulation of Lp(a) within the blood vessel promotes an antifibrinolytic environment, foam cell formation, the generation of a fatty streak, and an increase in smooth muscle cell content, all of which may contribute to the pathogenesis of atherosclerosis.

Topics: Arteriosclerosis; Blotting, Western; Cross-Linking Reagents; Enzyme-Linked Immunosorbent Assay; Fibrin; Fibrinogen; Humans; In Vitro Techniques; Lipoprotein(a); Transglutaminases

The acute platelet response and chronic smooth muscle cell (SMC) proliferation following aortic injury in apolipoprotein E-deficient mice was investigated. The purpose of this study was to evaluate whether thrombus formation would occur following plaque injury, to determine the type of thrombus that developed, and to evaluate SMC proliferation. Aortic injury was performed by squeezing the aorta between forceps. The response to injury reflects the findings primarily associated with plaque disruption. An attempt was made to exclude the use of injured vascular segments that showed marked injury to the media to minimize the effects that medial SMCs may have in thrombus formation. Acute and chronic experiments following injury were terminated at 30 min and at 2 weeks, respectively. Injury in normal and heterozygous mice and nonplaque injury in apolipoprotein E-deficient mice were accompanied by endothelial denudation. In apolipoprotein E-deficient mice, plaque injury, which released plaque contents, foam cells and fragments of foam cells, was followed by thrombus formation that contained degranulating platelets mixed with fibrin. Large platelet-fibrin aggregates were in close contact with disrupted plaques and were mixed with foam cell debris. In addition, small thrombi were in nonplaque areas following plaque disruptions. These thrombi were not associated with injury to the media and most likely represent a heightened thrombogenicity associated with plaque disruption. At 2 weeks following injury, a thickened neointima was present in both wild type and mutant mice. Lipid filled cells were seen only in the media but not in the intima of apo E -/- vessels at 2 weeks. The results suggest that plaque injury in homozygous apolipoprotein E-deficient mice promotes platelet-fibrin thrombus formation and that these thrombi are primarily associated with disrupted plaque contents. The results also suggest that the platelet response and SMC proliferation induced by aortic injury are not altered by hyperlipidemia caused by apolipoprotein E deficiency.

Topics: Animals; Aorta, Abdominal; Aortic Diseases; Apolipoproteins E; Arteriosclerosis; Blood Platelets; Cell Division; Disease Models, Animal; Endothelium, Vascular; Female; Fibrin; Genotype; Male; Mice; Mice, Inbred C57BL; Muscle, Smooth, Vascular; Thrombosis

Fibrinogen has been recognised in recent years as an independent risk factor in athero/thrombogenesis. However, the mechanism by which elevated fibrinogen translates into higher incidence of atherosclerosis is not known. One possible mechanism may be through the modification of fibrin. While it is already known that fibrin network is altered in disease states like peripheral vascular disease, diabetes, hypercholesterolaemia and myocardial infarction, the influence of altered fibrin network structure on growth and function of endothelial cells (EC) and fibroblasts (FB) requires investigation. Fibrin network structure in plasma clots was modified by changing pH and characterised using established biophysical methods. PGI(2), von Willebrand Factor (vWF), t-PA and PAI-1 were measured to evaluate changes in cell function induced by modified fibrin structure. In general, networks composed of thin fibres induced growth over their entire layer. Networks composed of thick fibres and open matrix promoted infiltration of cells into gel matrix and growth of macrovascular structures. Furthermore, thin fibres promoted a more prothrombotic environment as observed from changes in cell biochemical function. Fibrin, whilst initially acting as a scaffolding for cellular and biochemical processes, may also alter cell function and determine the progress of atherosclerosis.

Topics: Arteriosclerosis; Cell Division; Cells, Cultured; Endothelium, Vascular; Epoprostenol; Fibrin; Fibroblasts; Humans; Hydrogen-Ion Concentration; Microscopy, Phase-Contrast; Plasminogen Activator Inhibitor 1; Risk Factors; Tissue Plasminogen Activator; von Willebrand Factor

Lipoprotein(a) contributes to the development of atherosclerosis through the binding of its plasminogen-like apolipoprotein(a) component to fibrin and other plasminogen substrates. Apolipoprotein(a) contains a major lysine binding site in one of its kringle domains. Destruction of this site by mutagenesis greatly reduces the binding of apolipoprotein(a) to lysine and fibrin. Transgenic mice expressing this mutant form of apolipoprotein(a) as well as mice expressing wild-type apolipoprotein(a) have been created in an inbred mouse strain. The wild-type apolipoprotein(a) transgenic mice have a fivefold increase in the development of lipid lesions, as well as a large increase in the focal deposition of apolipoprotein(a) in the aorta, compared with the lysine binding site mutant strain and to nontransgenic littermates. The results demonstrate the key role of this lysine binding site in the pathogenic activity of apolipoprotein(a) in a murine model system.

Topics: Animals; Aorta; Arteriosclerosis; Binding Sites; Fibrin; Lipoprotein(a); Lysine; Mice; Mice, Transgenic; Mutagenesis, Site-Directed

We examined the immunohistochemical distribution of tissue factor (TF), apolipoprotein (a) (apo(a)) in atherosclerotic intimas of human thoracic aortas obtained from 51 autopsies in order to analyze the mechanism of fibrinogen-fibrin transition as a part of thrombogenic properties of atherosclerotic intimas. TF was overexpressed mainly by macrophages in both fatty streaks and more advanced lesions, while it was also scatteringly deposited in the matrix of advanced lesions, especially in the atheromatous gruel. TF-positive macrophages were frequently intermingled at the base of fibrin thrombi formed on the eroded intimas. On the other hand, apo(a) was localized in the stroma and within some macrophages, and also in the mural thrombi. Fibrinogen and fibrin were more frequently detected in the matrix of advanced lesions than in that of early lesions. Fibrin was occasionally co-located with cell- and matrix-associated TF and apo(a) deposited in matrix. These findings suggest that the overexpressed TF in the atherosclerotic intima plays a critical role in the initiation of fibrin formation. This could result from either fibrinogen permeating into the intima or from rupture of the fibrous cap overlying atheromas. Apo(a) deposited in the atherosclerotic intima may also participate in the persistent deposition of fibrin.

Topics: Adult; Aged; Aged, 80 and over; Aorta, Thoracic; Apolipoproteins; Apoprotein(a); Arteriosclerosis; Female; Fibrin; Fibrinogen; Humans; Immunohistochemistry; Lipoprotein(a); Male; Middle Aged; Thromboplastin

Atherosclerotic plaque rupture may trigger the formation of mural thrombus. This thrombus formation is apparently affected by very high and complex shear conditions introduced by the luminal narrowing (stenosis) of the atheroma. To study the impact of such blood flow behaviour on thrombus formation we employed a model system where collagen-induced thrombogenesis is studied at the apex of well-defined eccentric stenoses. Thrombus formation in non-anticoagulated human blood drawn directly from an antecubital vein over the collagen coated stenosis apex for periods of 0.5, 1, 3 or 5 min was quantified by morphometry. The stenoses reduced the cross-sectional area of the blood flow channel by 60, 80 and 89%, which corresponded to apex wall shear rates of 2600, 10,500 and 32,000 s-1, respectively. Platelet-collagen adhesion decreased by increasing shear at the stenosis apex. The corresponding adhesion rates were highest at 1 min, then they gradually decreased upon prolongation of the perfusion time. The platelet thrombus volume increased in concert with increasing shear rate up to 10,500 s-1, whereas, at 32,000 s-1, the volume wa decreased. The corresponding growth rates and rates of thrombus occlusion at the apex levelled off at 3 min. Significant fibrin deposition was not observed before 3 min, and was most pronounced at 10,500 and 32,000 s-1. The plasma levels of fibrinopeptide A and beta-thromboglobulin increased in concert with increasing shear and perfusion time, particularly at the two highest shear conditions. Thus, hallmarks of thrombus formation at these stenoses with increasing shear are decreased platelet-collagen adhesion, and increased platelet-platelet interaction and fibrin deposition. A fibrin tail downstream to the collagen-attached platelet thrombus is regularly observed when thrombus occlusion exceeds 40%. However, the reduced thrombus growth at the most occlusive stenosis (89%) is presumably due to the high shear stresses which may reduce the rate of platelet incorporation into the thrombus and/or tear off thrombus fragments.

Topics: Analysis of Variance; Arteriosclerosis; beta-Thromboglobulin; Case-Control Studies; Collagen; Constriction, Pathologic; Fibrin; Fibrinopeptide A; Humans; Kinetics; Platelet Adhesiveness; Regional Blood Flow; Stress, Mechanical; Thrombosis

The plasminogen activator (PA) system may participate in the pathogenesis of atherosclerosis by modulating the turnover of intimal fibrin and extracellular matrix deposits and by contributing to intimal cell migration. We present an analysis of tissue-type PA (tPA) and urokinase-type PA (uPA) expression at three levels: mRNA by in situ hybridization, antigen by immunohistochemistry, and enzymatic activity by histoenzymology and zymography. For PA colocalization with cellular or matrix components, we used double immunofluorescence labeling in conjunction with confocal microscopy. In normal arteries, tPA antigen and mRNA were detected in endothelial cells and smooth muscle cells (SMCs). In atherosclerotic arteries, tPA antigen and mRNA were increased in intimal SMCs and in macrophage-derived foam cells of fibro-fatty lesions. Part of the tPA was detected in the extracellular space and colocalized with fibrin deposits. uPA antigen and mRNA were detected in association with the intimal macrophages and SMCs. A particularly high uPA expression was noted on macrophages localized on the rims of the necrotic core. Moreover, using a novel histoenzymological assay as well as classic zymography, we revealed uPA-dependent lytic activity in the advanced lesions, whereas in normal arteries, only tPA-dependent activity was detected, mainly over the vasa vasorum. Also, strong tPA and uPA staining was detected in neomicrovessels of the plaques, suggesting that PAs may play a role in plaque angiogenesis. Our results suggest a local dynamic process of PA-dependent proteolysis in lesion areas that is associated with macrophages and SMCs. A better comprehension of these proteolytic mechanisms in advanced atherosclerotic plaques may provide the basis for therapeutic approaches for plaque stabilization.

Topics: Aorta; Arteriosclerosis; Endothelium, Vascular; Extracellular Space; Fibrin; Fluorescent Antibody Technique; Gene Expression; Humans; Immunohistochemistry; In Situ Hybridization; Macrophages; Microscopy, Confocal; Muscle, Smooth, Vascular; RNA, Messenger; Tissue Plasminogen Activator; Urokinase-Type Plasminogen Activator

TF protein was overexpressed by macrophages and smooth muscle cells and deposited in the extracellular matrix of atheroclerotic intimas. TF activity was also enhanced in the atherosclerotic intima, probably resulting in either thrombus formation or intimal fibrin deposition after the exposure of flowing blood and imbibed fibrinogen to TF in atherosclerotic lesions. These findings further support the hypothesis that the coagulation and fibrinolysis systems can play an essential role in the initiation and progression of atherosclerosis, and the clinical implications of this phenomenon may thus contribute to future investigations in the prevention and treatment of atherosclerotic diseases.

Topics: Adult; Aged; Animals; Aorta; Apolipoproteins A; Arteriosclerosis; Enzyme Activation; Factor X; Fibrin; Fibrinogen; Humans; Immunohistochemistry; Middle Aged; Rabbits; Thromboplastin

D-dimer, plasminogen activator inhibitor (PAI-1) activity at rest and after exercise, and tissue plasminogen activator (t-PA) activity after exercise were measured in venous blood in 88 patients with atherosclerotic lesions of various degrees. According to clinical symptoms, coronary angiography (CAG), ultrasound Doppler signal and duplex and colour Doppler scanning of carotid arteries and their branches, subclavian, vertebral and peripheral arteries of the lower limbs, patients were divided into four groups. Group 1, 16 men without CAG and ultrasound signs of atherosclerotic lesions; group 2, 27 patients with CAG-confirmed coronary artery disease; group 3, 18 patients with peripheral artery occlusive disease; group 4, 27 patients with coexistence of two or more regions of atherosclerotic lesions. D-dimer was the highest in patients with the most extensive atherosclerosis: 432 +/- 164 ng.ml-1 in group 3, 429 +/- 98 ng.ml-1 in group 4 vs 163 +/- 25 ng.ml-1 in group 1, P < 0.05. There were correlations (P < 0.05) between: age and D-dimer (r = 0.29); D-dimer and t-PA (r = 0.34); D-dimer and PAI-1, r = -0.29. Patients were also analysed according to D-dimer level. In patients with the highest level of D-dimer, the lowest level of PAI-1 activity and the highest level of t-PA activity after exercise were observed. The low PAI-1 activity is probably the result of an increased release of t-PA in these patients.

Topics: Adult; Age Factors; Aged; Arteriosclerosis; Body Mass Index; Enzyme-Linked Immunosorbent Assay; Exercise; Fibrin; Fibrinolysis; Humans; Male; Middle Aged; Plasminogen Activator Inhibitor 1; Tissue Plasminogen Activator

Patients with peripheral arterial disease have a high risk of death from cardiovascular events. As defective fibrinolysis associated with leg atherosclerosis has been suggested as a predisposing factor, we sought a relation among decreased fibrinolysis, the presence of leg atherosclerosis and the incidence of thrombotic events in a case-control study nested in the PLAT. Fifty-eight patients with coronary and/or cerebral atherothrombotic disease, free of leg atherosclerosis at Doppler examination, were compared with 50 atherosclerotic patients with leg involvement. High D-dimer (153.0 vs 81.3 ng/ml, p < 0.001) and tPA antigen before venous stasis (14.4 vs 11.8 ng/ml, p < 0.03), and low tPA antigen (6.7 vs 15.6 ng/ml, p < 0.01) and fibrinolytic activity released after venous stasis (fibrinolytic capacity: 113.2 vs 281.4 mm2, p < 0.001) were found in patients with leg atherosclerosis. D-dimer and fibrinolytic capacity, in addition to age, were selected by stepwise discriminant analysis as characterizing patients with leg atherosclerosis. Moreover, higher D-dimer and tPA inhibitor characterized patients with leg atherosclerosis who subsequently experienced thrombotic events. These findings constitute evidence of high fibrin turnover and impaired fibrinolytic potential in patients with leg atherosclerosis. Thus impaired fibrinolysis may contribute to the prothrombotic state in these patients.

Topics: Aged; Arteriosclerosis; Blood Glucose; Blood Pressure; Blood Proteins; Case-Control Studies; Disease Susceptibility; Fibrin; Fibrinolysis; Humans; Leg; Lipids; Male; Middle Aged; Peripheral Vascular Diseases; Prospective Studies; Risk Factors; Smoking; Thrombophlebitis

The activation of the complement system has been implicated as an important mechanism in the progression of atherosclerosis. The relationship between fibrin gel characteristics and complement activation has, however, not been investigated. Zymosan-treated plasma with 87% complement activation as measured by C3a production using radioimmunoassay was found to induce changes in biophysical characteristics of fibrin network developed in both plasma and purified fibrinogen solution. Using already established methods to measure fibre thickness (mu T), permeability (T) and compaction, it was found that these networks are made of thinner fibres with increased tensile strength arranged into a matrix which renders the networks less permeable. Such networks are resistant to streptokinase-induced lysis. Fibrin networks with thin fibres in turn induced 3.7 times higher production of C3a than unmodified networks. These observations suggest the existence of positive feedback; complement activation induces major alterations in fibrin structure which in turn can induce further activation of the complement system. The detailed mechanism underlying this interrelationship is not clear at present, but this positive feedback system may play an important role in establishing a fibrin infrastructure ultimately responsible for the progression of atherosclerosis.

Topics: Arteriosclerosis; Complement Activation; Complement C3a; Disease Progression; Feedback; Fibrin; Fibrinolysis; Gels; Humans; Hydrogen-Ion Concentration; Microscopy, Electron, Scanning

Soluble fibrin/fibrinogen-related antigens and insoluble fibrin are present in virtually all samples of human aortic intima. Components of the soluble fraction were identified by SDS-PAGE and immunoblotting with specific antisera. The fibrinogen was characterized by increased proportions of low molecular mass (Mr) species (300 and 280 kD), the FDP by fragments DY and DD derived from crosslinked fibrin, and by fragment E that lacked fibrinopeptide A (FPA). Experiments suggest that fibrin is formed in situ, and free thrombin was present in all 10 samples analysed for prothrombin-related antigen (PtRA). Fibrin-derived fragment E is mitogenic, so fibrin degradation may provide continuing stimulation of smooth muscle cell (SMC) proliferation.

Topics: Aorta; Aortic Diseases; Arteriosclerosis; Electrophoresis, Polyacrylamide Gel; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinopeptide A; Humans; Muscle, Smooth, Vascular

Topics: Afibrinogenemia; Arteriosclerosis; Fibrin; Fibrinogens, Abnormal; Gels; Heparin; Humans; Image Processing, Computer-Assisted; Microscopy, Confocal; Thromboembolism; Thrombosis

The blood coagulation cascade was reported to be activated in patients with arteriosclerotic disease of the lower limbs (peripheral arterial disease, PAD). There is more thrombin and fibrin formation compared with healthy control subjects. In many studies, however, the presence of arteriosclerotic disease had not been thoroughly ruled out in the control group. Therefore, markers of the activation of the blood coagulation cascade were measured in patients with PAD and in a carefully defined control group, both groups being subjected to an exercise test.. Twenty-two patients with angiographically documented PAD of grade II (Fontaine classification) and 13 control subjects in whom the presence of arteriosclerotic lesions was ruled out by noninvasive means in the carotid arteries, abdominal aorta, leg arteries, and coronary arteries took part in the study. Before and immediately after a treadmill stress test, the concentrations of prothrombin fragment F1 + 2 (F1 + 2), thrombin-antithrombin III complexes (TAT), fibrinopeptide A (FPA; this peptide was measured in spot urine also), and D-dimers were measured. Before exercise, the concentrations of F1 + 2 (1.0 +/- 0.6 versus 0.7 +/- 0.3 nmol/L), TAT (2.9 +/- 2.1 versus 1.9 +/- 0.8 micrograms/L), and D-dimers (318.2 +/- 270.1 versus 150.0 +/- 91.4 micrograms/L) were significantly higher in the patients with PAD compared with the healthy control subjects. FPA concentrations in plasma (1.9 +/- 1.0 versus 1.4 +/- 0.6 micrograms/L) and spot urine were not different, however. F1 + 2, FPA, and D-dimer concentrations correlated with the severity of the PAD as assessed by the ankle systolic blood pressure index (ABPI). The symptom-limited stress test did not lead to further activation of the blood coagulation cascade. However, concentrations of F1 + 2 (P < .001) and TAT (P < .01) after exercise correlated with the presence of ischemic changes in the stress-test ECG.. There is evidence of enhanced thrombin formation in patients with PAD compared with an age- and sex-matched control group without clinical and sonographic evidence of arteriosclerosis. The thrombin formed, however, appears to be almost completely neutralized by antithrombin III. No direct evidence of fibrin formation was obtained, since the FPA concentrations were not different. In the patients with PAD, the higher concentrations of D-dimers are indicative of in vivo fibrinolysis. Thus, some fibrin formation must be postulated to occur in patients with arteriosclerosis.

Topics: Aged; Aged, 80 and over; Arteriosclerosis; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Fibrinopeptide A; Humans; Leg; Male; Middle Aged; Partial Thromboplastin Time; Peptide Fragments; Prothrombin

Molecular assembly of plasminogen and tissue-type plasminogen activator (t-PA) at the surface of fibrin results in the generation of fibrin-bound plasmin and thereby in the dissolution of a clot. This mechanism is triggered by specific interactions of intra-chain surface lysine residues in fibrin with the kringle domains of plasminogen, and is further amplified via the interaction of plasminogen kringles with the carboxy-terminal lysine residues of fibrin that are exposed by plasmin cleavage. By virtue of its marked homology with plasminogen, apo(a), the specific apolipoprotein component of Lp(a), may bind to the lysine sites available for plasminogen on the surface of fibrin and thereby interfere with the fibrinolytic process. A sensitive solid-phase fibrin system, which allows the study of plasminogen activation at the plasma fibrin interface and makes feasible the analysis of products bound to fibrin, has been used to investigate the effects of Lp(a) on the binding of plasminogen and its activation by fibrin-bound t-PA. Plasma samples from human subjects with high levels of Lp(a) were studied. We have established that Lp(a) binds to the fibrin surface and thereby competes with plasminogen (Ki = 44 nM) so as to inhibit its activation. We have further shown that Lp(a) blocks specifically carboxy-terminal lysine residues on the surface of fibrin. To further explore the role of apo(a) on the Lp(a) fibrin interactions, we have performed ligand-binding studies using a recombinant form of apo(a) that contains 17 kringle 4-like units. We have shown that recombinant apo(a) binds specifically to fibrin (Kd = 26 +/- 8 nM, Bmax = 26 +/- 2 fmol/well) and that this binding increases upon treatment of the fibrin surface with plasmin (Kd = 8 +/- 4 nM, Bmax = 115 +/- 14 fmol/well). Altogether, our results indicate clearly that binding of native Lp(a) through this mechanism may impair clot lysis and may favor the accumulation of cholesterol in thrombi at sites of vascular injury.

Topics: Apolipoproteins; Apoprotein(a); Arteriosclerosis; Binding, Competitive; Fibrin; Fibrinolysis; Humans; In Vitro Techniques; Kinetics; Kringles; Lipoprotein(a); Peptide Fragments; Plasminogen; Protein Binding; Recombinant Proteins; Thrombosis; Tissue Plasminogen Activator

Immunohistochemical studies of human atherosclerotic lesions have demonstrated the occurrence of fibrin deposition and its degradation in the arterial wall. We studied fibrinogen, the generation of thrombin, and the degradation of fibrin in 40 patients with stable peripheral arterial occlusive disease of varying severity, as assessed by the ankle/brachial pressure index and duplex ultrasonography and/or angiography. Circulating fibrinogen (functional and immunological), fibrinopeptide A, thrombin-antithrombin III complex, and D-dimer were measured. The severity of atherosclerosis was associated with both fibrinogen (both functional and immunological) and D-dimer (r = .57, P < .0002, and r = .57, P < .0001, respectively). Fibrinogen and D-dimer showed a significant positive correlation (r = .50, P < .001). Generation of thrombin was detected in 24 patients (60%) by fibrinopeptide A and levels of thrombin-antithrombin III complex. As a sign of coagulation activation and fibrinolysis, we found that thrombin-antithrombin III complex and the degradation of cross-linked fibrin were progressively associated with the extent of vascular disease. The plasmin-mediated fibrin breakdown contributed to increased levels of circulating fibrinogen, an established risk factor for thrombotic complications. The significant correlations between fibrinogen/D-dimer and the severity of atherosclerosis support previous pathological studies and imply that local degradation of cross-linked fibrin is involved in the progression of atherosclerosis.

Topics: Adult; Aged; Aged, 80 and over; Antithrombin III; Arteriosclerosis; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibrinolysis; Fibrinopeptide A; Humans; Male; Middle Aged; Peptide Hydrolases; Peripheral Vascular Diseases; Radiography; Ultrasonography

To test the affinity of a new F(ab')2 monoclonal antibody (TRF1) against human fragment D dimer of cross-linked fibrin for atherosclerotic plaques free of detectable thrombi, 6 atherosclerotic segments of carotid and femoral artery, and as a control 5 segments of atherosclerosis-free internal mammary artery, were drawn from 11 male patients undergoing bypass surgery. All segments were carefully washed in order to remove possible endoluminal thrombi, and cut to obtain pairs of intimal fragments of similar weight, containing either plaques (n = 16), or fatty streaks (n = 12), or normal endothelium (n = 20). Each fragment underwent a direct binding test to TRF1, or to a non-specific antibody, both labeled with 125I. The activity in each fragment was measured after 3 h of incubation at 37 degrees C, and after washing the fragments every hour for 3 h. TRF1 binding (as percentage of initial activity) was significantly higher (P < 0.001) in atherosclerotic than in normal fragments (26% +/- 11.5%, vs. 9.2% +/- 3.9% in fatty streaks, and 1.9% +/- 0.6% in normal endothelium), and indirect immunofluorescence confirmed TRF1 uptake within the plaque wall. By contrast, the non-specific antibody did not show any significant binding. These preliminary results demonstrate the high specific affinity of TRF1 for atherosclerotic plaques, probably due to the hemorheologic phenomena that activate platelets and provoke the formation of fragment D dimers of cross-linked fibrin on the plaque surface.

Topics: Arteriosclerosis; Carotid Arteries; Femoral Artery; Fibrin; Fluorescent Antibody Technique; Humans; In Vitro Techniques; Iodine Radioisotopes; Male; Middle Aged; Radionuclide Imaging

A case-control comparison within the framework of the prospective, multidisciplinary PLAT Study was performed to assess whether altered baseline fibrinolytic variables were associated with an elevated risk of ischemic thrombotic events in patients with documented coronary, cerebral, and/or peripheral atherosclerotic disease. Fibrinogen, D-dimer, tissue plasminogen activator (t-PA) antigen, and fibrinolytic activity before and after venous stasis (delta = difference between the two values), t-PA inhibitor, and lipid levels in 60 atherosclerotic patients with a thrombotic event during the first year of follow-up were compared with those in 94 atherosclerotic patients without such events, who were matched for age, sex, and diagnosis at enrollment. Events were associated with a higher release of delta t-PA antigen (P = .047), higher D-dimer (P = .024), and higher t-PA inhibitor (P = .001) levels. delta Fibrinolytic activity was correlated inversely with t-PA inhibitor (P < .01) and triglycerides (P < .05). D-Dimer was also correlated with systolic blood pressure (P < .01). Atherosclerotic patients at higher risk of thrombotic ischemic events are characterized by increased fibrin turnover and impaired fibrinolytic activity due to high t-PA inhibitor levels. This hemostatic disequilibrium may participate with conventional risk factors such as elevated triglyceride levels and systolic blood pressure in the multifactorial mechanism of ischemic sequelae in patients with preexisting vascular atherothrombotic disease.

Topics: Aged; Arteriosclerosis; Case-Control Studies; Female; Fibrin; Fibrinolysis; Forecasting; Humans; Ischemia; Male; Middle Aged; Plasminogen Activator Inhibitor 1; Risk Factors

Several epidemiological and clinical studies performed in subjects with risk factors for atherosclerotic cardiovascular events, have shown changes in plasma levels and/or activities of coagulation factors that could suggest a prothrombotic state. We studied the behaviour of the fibrinogen polymerization curve (FPC), a spectrophotometric technique evaluating the kinetics of fibrinogen transformation into fibrin, in 68 subjects with and without hypercholesterolemia. Significant differences were found between FPCs of subjects with serum cholesterol > 240 mg/dl and < or = 240 mg/dl respectively. In fact, FPCs of the first group showed high reaction velocity rate, short latency time and higher optical density rate, final readings; besides, the behaviour of FPCs was not correlated to plasma fibrinogen concentrations. Therefore, FPC could be a useful test to identify a thrombophilic condition in hypercholesterolemic patients.

Topics: Adult; Arteriosclerosis; Female; Fibrin; Fibrinogen; Humans; Hypercholesterolemia; Male; Middle Aged; Risk Factors; Veins

In this report, we review recent findings concerning the identification of mechanisms that may modulate the role of lipoprotein(a), or Lp(a), in thrombosis and atherogenesis. Lp(a) binds to surface-immobilized plasmin-modified fibrin, thus providing a mechanism for incorporating Lp(a) into the vessel wall. We found that homocysteine and other sulfhydryl-containing amino acids markedly increase the binding of Lp(a) to plasmin-modified fibrin. Our results suggest that homocysteine alters the structure of Lp(a) to expose lysine-binding sites on the apolipoprotein(a) portion of the molecule, and thus provide a potential biochemical link between thrombosis and atherogenesis. We also found that transglutaminases catalyze the incorporation of primary amines into Lp(a). Studies in cell culture systems have found that Lp(a) stimulates endothelial cells to synthesize and release plasminogen activator inhibitor-1. Further, Lp(a) inhibits the activation of transforming growth factor-beta in a coculture of bovine endothelial and smooth muscle cells.

Topics: Amino Acids, Sulfur; Arteriosclerosis; Endothelium, Vascular; Fibrin; Humans; Lipoprotein(a); Thrombosis; Transglutaminases

Diabetic patients are prone to develop vascular complications. Increased procoagulatory factors and a reduced fibrinolytic potential are considered as thrombogenic risk factors, although controversy remains. In epidemiological and dietary intervention studies fish or fish oil, rich in the two n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have demonstrated a potential to reduce cardiovascular disease. We compared the plasmatic coagulatory and fibrinolytic profile of 13 near normoglycaemic type I diabetics almost free of cardiovascular disease with healthy volunteers, matched for age and sex. Except for fibrinogen levels and tPA activity being elevated and soluble fibrin and fibrinopeptide A being reduced, no differences could be discerned between type I diabetics and controls in all investigated plasmatic parameters. In a dietary intervention study we investigated the effects of 5.4 g EPA and 2.7 g DHA per day during and after a 4-week dietary supplementation in the diabetic patients. The factors, inhibitors and activation products of coagulation and fibrinolysis measured were at best transiently affected by the diet. Only plasminogen activator inhibitory activity in plasma significantly increased during the dietary supplementation and returned to prediet values after cessation of n-3 fatty acids. Changes in PAI activity were negatively correlated to changes in serum triglycerides. We conclude that well adjusted type I diabetics show an almost unchanged haemostatic profile compared to matched healthy controls. A dietary intervention with n-3 fatty acids in these patients does not affect the plasmatic haemostatic pattern except for an increase in PAI activity.

Topics: Adult; Arteriosclerosis; Diabetes Mellitus, Type 1; Dietary Fats, Unsaturated; Docosahexaenoic Acids; Eicosapentaenoic Acid; Female; Fibrin; Fibrinogen; Fibrinolysis; Fibrinopeptide A; Hemostasis; Humans; Male; Plasminogen Inactivators; Tissue Plasminogen Activator

Thrombotic occlusion is the major cause of myocardial infarction (MI), and fibrin accumulation appears to play a significant role in development of atherosclerotic lesions. Any factor that reduces the lysis of fibrin may thus increase the risk of MI, and it has been suggested that this accounts for the atherogenicity of the lipoprotein variant Lp(a). The characteristic feature of Lp(a) is an apoprotein which is homologous with part of the plasminogen molecule, and experiments in vitro suggest that it interferes with uptake and activation of plasminogen on cell surfaces and fibrin. The presence of Lp(a) also seemed to offer an explanation for the apparent absence of plasminogen from 70-80% of intimal samples. We have compared the levels of Lp(a) and plasminogen in normal intima and atherosclerotic lesions. In aortic intima there was no relation between Lp(a) and plasminogen, which was absent in some samples with no Lp(a), and present in others with high levels. In intravascular thrombi plasminogen was present at a rather constant concentration (16.3 +/- 4.6 micrograms/100 mg wet tissue), whereas Lp(a) varied over a 100 fold range (0-104 micrograms/100 mg). Plasminogen binds to fibrin and is activated on the fibrin clot, so levels in extracts may not fully represent Lp(a)/plasminogen interactions. After extraction the residual tissues and thrombi were treated with 1 M epsilon-aminocaproic acid (epsilon-aca) to elute lysine-bound components. Lp(a) was eluted from all but one intimal sample, confirming previous findings on its binding to fibrin in lesions, but there was no relation between the amounts of Lp(a) and plasminogen in the tissue eluates. Paradoxically, in the thrombi there was a weak positive correlation between Lp(a) and plasminogen in epsilon-aca eluates (r = 0.504, P = 0.05). These results do not support the hypothesis that Lp(a) displaces plasminogen in vivo, but the large amount of Lp(a) eluted by epsilon-aca suggests that its atherogenicity resides in preferential binding to fibrin, leading to increased lipid accumulation in lesions.

Topics: Adult; Aged; Aorta; Aortic Diseases; Arteriosclerosis; Binding, Competitive; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Humans; Lipoprotein(a); Lipoproteins; Lipoproteins, LDL; Male; Middle Aged; Myocardial Infarction; Plasminogen; Thrombosis

The lipid that accumulates in some fibrous atherosclerotic lesions appears to be derived from plasma low density lipoprotein (LDL). An early stage in lipid accumulation may be immobilization of a fraction of the LDL, and this is released by incubation with proteolytic enzymes, of which the most effective is the fibrinolytic enzyme, plasmin. We have examined the relationship between release of fibrin degradation products (FDP) and LDL in controlled plasmin incubations of 42 samples of normal intima and atherosclerotic lesions from aortas of 10 patients. In three patients (group 1) no LDL was released from any of the 11 tissue samples although they comprised lesions as well as normal intima. In 2 more patients (group 2) LDL was consistently low. However, in 5 patients (group 3) substantial amounts of LDL were released from all 21 tissue samples, and there was a significant correlation between the amounts of FDP and LDL (P less than 0.001). In spite of this correlation there were marked differences in the ratio FDP/LDL, but analysis by SDS-polyacrylamide gel electrophoresis and immuno blotting of the FDP released showed no consistent pattern related to LDL binding. Although the ratio FDP/LDL showed a 4-fold range, in 6 lesions subjected to successive 2-h incubations with plasmin the ratio within each lesion remained constant, supporting the concept that fibrin and LDL are linked.

Topics: Aged; Aged, 80 and over; Aorta; Apolipoproteins B; Arteriosclerosis; Cross-Linking Reagents; Female; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolysin; Humans; In Vitro Techniques; Lipid Metabolism; Lipoproteins, LDL; Male; Middle Aged

The extracellular lipid that accumulates in fibrous atherosclerotic lesions appears to be derived directly from plasma low density lipoprotein (LDL). One factor that may influence the lipid deposition is immobilization of part of the LDL in lesions, and an immobilized fraction can be released by incubation with the fibrinolytic enzyme, plasmin, suggesting that it is associated with fibrin. The lipoprotein variant Lp(a) is associated with increased risk of arterial disease, and its characteristic apoprotein, apo(a), is structurally related to plasminogen, suggesting that it might bind to the plasminogen binding sites on fibrin. In this study we have compared blood Lp(a) and the soluble and plasmin-releasable Lp(a) in 45 samples of normal intima and different types of lesion. Levels of soluble and plasmin-releasable Lp(a) were dependent on both blood level and type of tissue sample. Although the amount of soluble LDL was 5-20 times higher than Lp(a) in intima, the amounts released by plasmin were similar, and Lp(a) appears to account for most of the apo B-containing lipoprotein that is immobilized in lesions.

Topics: Aorta; Arteriosclerosis; Fibrin; Fibrinolysin; Humans; In Vitro Techniques; Lipid Metabolism; Lipoprotein(a); Lipoproteins; Lipoproteins, LDL; Plasminogen

The low density lipoprotein (LDL) variant, lipoprotein(a) (Lp(a)) is a risk factor for coronary heart disease, and in this study we have examined its interaction with the arterial wall. Samples of normal intima and atherosclerotic lesions were extracted with buffer containing EDTA and protease inhibitors and assayed for LDL and Lp(a) by radial immunodiffusion. The extract tissues were washed, then incubated with plasmin and the amounts of LDL and Lp(a) released into the digest were measured. Intimal Lp(a) concentrations were compared to Lp(a) in the patients' blood. Levels of both soluble and plasmin-releasable Lp(a) were related to type of intimal sample and blood Lp(a) level. In early proliferative lesions there was a significant correlation between plasmin-releasable Lp(a) and blood Lp(a) (r = 0.631, P less than 0.002). Highest levels of plasmin-releasable Lp(a) were found in more advanced lesions that had accumulated some lipid. In extracts the amounts of LDL were 5-20 fold greater than Lp(a) but in the plasmin digests Lp(a) could account for most of the apoB detected, suggesting that Lp(a) may bind to fibrin in the lesion through its plasminogen-like structures and thus contribute to lipid accumulation in fibrous plaques. Plasminogen cannot be detected by rocket immunoelectrophoresis in samples from about two-thirds of aortas, and it seemed possible that the large plasminogen-like apo(a) component of Lp(a) was interfering with intimal uptake or retention of plasminogen, or its immunoassay. However, in 28 samples of intima or thrombi from 16 patients there was no relation between amounts of Lp(a) and plasminogen.

Topics: Aorta; Arteriosclerosis; Binding Sites; Fibrin; Humans; Lipoprotein(a); Lipoproteins; Lipoproteins, LDL; Plasminogen; Protein Binding; Thrombosis

Apolipoprotein B (apo B), fibrinogen/fibrin, blood platelets, factor VIII-related antigen of the blood coagulation system, and smooth muscle cells (SMC) were identified in the intima of normal and atherosclerotic human aorta and large arteries by the indirect immunofluorescence technique. Fibrinogen/fibrin was revealed by a monoclonal antibody (monAb) against the C-terminal region of human fibrinogen A alpha-chain. Fibronectin was visualized by monAb to the cellular form and against an epitope shared by different fibronectin subunit variants. In normal intima, fatty streaks, small amounts of fibrinogen/fibrin together with large amounts of apo B were observed. Fibronectin detected by two types of monAb was not found in extracellular matrix (ECM), whereas cellular fibronectin encircled SMC. According to the data obtained, fibrinogen/fibrin accumulates in plaques as a result of intramural thrombus incorporation, blood insudation, intramural haemorrhage, and in or around cells, apparently macrophages.

Topics: Aged; Antibodies, Monoclonal; Aorta; Apolipoproteins B; Arteries; Arteriosclerosis; Blood Platelets; Female; Fibrin; Fibrinogen; Fibronectins; Fluorescent Antibody Technique; Humans; Male; Middle Aged; von Willebrand Factor

Apo B, fibrinogen/fibrin, fibronectin, thrombocytes, factor VIII of the blood coagulation and smooth muscle cells (SMC) were identified by the immunofluorescence method in the intima of aorta and big arteries under normal conditions and in atherosclerosis. Monoclonal antibodies (MCA) against C-end fragments of A alpha-fibrinogen chain were used in the study of fibrinogen/fibrin. MCA reacting with plasma fibronectin and those reacting with A-area of the polypeptide chain specific for the cell fibronectin were used for the identification of fibronectin. Small amount of fibrinogen/fibrin, no fibronectin in the extracellular matrix and the cell fibronectin around SMC were observed on the normal intima and lipid strip in spite of the presence of Apo B. The results indicate that fibrinogen/fibrin is accumulated in the plaques due to the incorporation of the wall thrombi, insudation from the blood plasma, intramural haemorrhages as well as around cells, presumably macrophages.

Topics: Adult; Antibodies, Monoclonal; Aorta; Apolipoproteins B; Arteries; Arteriosclerosis; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Fibronectins; Fluorescent Antibody Technique; Histocytochemistry; Humans; Muscle, Smooth, Vascular

1) The incidence of myocardial infarction, as well as thrombosis, has been increasing recently in the consecutive autopsy cases over 40 years old in Kyushu University, but is still less frequent than those in the autopsy cases in Boston around 1960. Increased fat intake might play a significant role in the increasing frequency of myocardial infarction in Japanese. 2) In a nationwide cooperative study of atherosclerosis in young Japanese, atherosclerotic changes were observed to begin developing in childhood. Primary prevention of atherosclerosis should be initiated in the pediatric age group. We should pay more attention to subclinical atherosclerosis. Age, serum cholesterol, and blood pressure were significantly and positively correlated with SI and AI of aortas and coronary arteries. Serum cholesterol was more strongly correlated with the extent of fatty streaks than was mean blood pressure and vice versa with that of fibrous plaques. Atherosclerosis of cerebral arteries, however, showed a significant correlation only with the factor of mean blood pressure. Therefore the susceptibility to risk factors varies with the artery in the case of early lesions of atherosclerosis in young people. More attention should be paid to the fact that atherosclerosis is a multifactoral disease. 3) Deposition of fibrinogen in the intima might precede LDL deposition and possibly play a more important role than LDL in the development of atherosclerotic lesions in the cerebral arteries, especially in their early stage. 4) The proliferation of smooth muscle cells is stimulated by fibrin and later inhibited by FDP, as produced by fibrinolytic activity of smooth muscle cells. The metabolism of fibrin in the arterial wall may be of importance in the regulation of smooth muscle cell proliferation, and the coagulation-fibrinolysis system may play a significant role in atherosclerosis with the effect of other risk factors such as cholesterol and hypertension.

Topics: Adolescent; Adult; Arteriosclerosis; Child; Child, Preschool; Female; Fibrin; Humans; Incidence; Infant; Japan; Male; Myocardial Infarction; Risk Factors

The incorporation of the stable isotope 15N in plasma proteins and blood cells after oral application of 3 g 15NH4Cl (95 At% 15N) per 70 kg body weight was followed up in 11 patients with ischemic heart disease or peripheral arteriosclerosis and in 7 healthy control subjects. Preliminary results indicate that the turnover of plasma protein, especially fibrin, is elevated in patients with arteriosclerosis. Investigations of platelets intimate a decreased turnover of platelet protein in patients with arteriosclerosis as compared to control subjects. Possible reasons for these alterations are discussed.

Topics: Arteriosclerosis; Blood Platelets; Blood Proteins; Coronary Artery Disease; Fibrin; Humans; Male; Middle Aged; Nitrogen Radioisotopes; Reference Values

The sequence of the incorporation of the stable isotope 15N in plasma protein and fibrinogen has been followed by an 15N labelling test in 11 patients with arteriosclerosis and a control group of 7 persons. The investigation showed a higher turnover of plasma protein and especially of fibrinogen in the patients with arteriosclerosis.

Topics: Arteriosclerosis; Blood Proteins; Female; Fibrin; Fibrinogen; Humans; Hypertension; Male; Middle Aged; Nitrogen; Nitrogen Radioisotopes

The migration of vascular smooth muscle cells from the media into the intima and their proliferation in the intima play an important role in the pathogenesis of atherosclerosis. We examined the effects of fibrinogen and fibrin on the migration of cultured bovine aortic smooth muscle cells using a modified Boyden chamber assay. The cells migrated to a gradient of soluble fibrinogen. Checkerboard analysis indicated that the effect was largely directional in nature (chemotaxis). The cells also migrated in a dose-dependent manner to a gradient of substrate-bound fibrinogen (haptotaxis). Fibrin, converted from substrate-bound fibrinogen by thrombin, also induced haptotaxis of smooth muscle cells. These observations suggest that, by recruiting smooth muscle cells from the media into the intima, fibrinogen and fibrin may be involved in the pathogenesis of arterial intimal thickening, atherosclerosis, and the organization of a thrombus.

Topics: Animals; Arteriosclerosis; Cattle; Cell Movement; Cells, Cultured; Chemotaxis; Fibrin; Fibrinogen; Muscle, Smooth, Vascular; Thrombosis

Experimental atherosclerosis was induced in a rabbit model by intimal damage of the infrarenal aorta followed by two months cholesterol feeding. The influence of four different antiplatelet drug regimens on acute platelet and fibrin deposition after transluminal angioplasty of the atherosclerotic abdominal aorta was then evaluated. The study group consisted of 32 New Zealand rabbits: 7 controls, 7 treated with prostacyclin (10 mg/kg/min i.v.), 5 treated with low-dose acetylsalicylic acid (2 mg/kg i.v.), 7 treated with acetyl-salicylic acid (5 mg/kg i.v.) and dipyridamole (2 mg/kg i.v.), and 6 treated with low molecular dextran (5 ml/kg). By 2 hours after angioplasty, there was a significant increase of the deposition of platelets (P less than 0.001) as well as fibrin (P less than 0.01) when comparing dilated to non-dilated segments in the control animals. There was no significant difference in the amount of platelets and fibrin deposition among the control and drug treated groups. Thus, in this animal model there appears to be no immediate benefit in using antiplatelet drugs during transluminal angioplasty. Although, this study did not address the potential long-term effects of antiplatelet drug therapy, future evaluation of the clinical benefits of these drugs in conjunction with transluminal angioplasty seems warranted.

Topics: Angioplasty, Balloon; Animals; Aorta, Abdominal; Aortic Diseases; Aortography; Arteriosclerosis; Cholesterol; Female; Fibrin; Male; Platelet Aggregation Inhibitors; Platelet Count; Rabbits; Thrombosis

Lipoprotein (a) [Lp(a)] is a plasma component whose concentration is related to the development of atherosclerosis, although the underlying mechanisms are not known. Lp(a) contains a unique structure, apolipoprotein (a), that shares partial homology with plasminogen. We now report that plasmin catalyzes the binding of Lp(a) to both immobilized fibrinogen and fibrin in a manner analogous to our previously reported studies with plasminogen. Plasmin treatment of immobilized fibrinogen induces a 3.7-fold increase in Lp(a) binding. Low density lipoprotein, molecules similar to Lp(a) but lacking apolipoprotein (a), bind poorly to immobilized fibrinogen and binding is not increased by plasmin. Trypsin but not neutrophil elastase also increases the binding of Lp(a) to fibrinogen. Lp(a) also complexes to plasmin-fibrinogen digests, and binding increases in proportion to the time of plasmin-induced fibrinogen degradation. Lp(a) binding is lysine-binding site dependent as it is inhibited by epsilon-aminocaproic acid. Lp(a) inhibits the binding of plasminogen to plasmin-modified immobilized fibrinogen, indicating that both molecules compete for similar lysine-binding sites. These findings demonstrate an affinity between Lp(a) and protease-modified fibrinogen or fibrin and thereby provide a potential mechanism to explain the association between thrombosis, coronary atherosclerosis, and increased blood concentrations of Lp(a).

Topics: Arteriosclerosis; Fibrin; Fibrinogen; Fibrinolysin; Humans; In Vitro Techniques; Lipoprotein(a); Lipoproteins; Lipoproteins, LDL; Lysine; Pancreatic Elastase; Protein Binding; Structure-Activity Relationship; Trypsin

Intravascular and endoparietal fibrin deposition are thought to be involved in atherosclerotic process, especially when fibrin is stabilized by factor XIII of coagulation system. The study carried out on a group of 50 patients with obliterative atherosclerosis of the lower limbs revealed an increased plasma fibrin stabilizing activity apparently due to an increased F.XIII level. Furthermore, alterations in coagulation and fibrinolysis indicating hypercoagulable tendency were found. It is concluded, that the observed changes may contribute to the development of atherosclerotic process.

Topics: Aged; Arteriosclerosis; Factor XIII; Fibrin; Fibronectins; Hemostasis; Humans; Middle Aged

Arterial thrombi and atherosclerotic lesions were analyzed immunochemically and examined histologically. The extent of in vivo proteolytic cleavage of the amino-terminal end of fibrinogen by thrombin and plasmin was determined and quantitated by specific radioimmunoassays. The samples were treated with cyanogen bromide (CNBr), and the total amount of fibrinogen and fibrin-derived protein was determined as NDSK, the NH2-terminal disulfide knot of fibrinogen. Thrombin-releasable fibrinopeptides A and B were used to quantitate fibrinogen and fibrin I. Previous plasmin cleavage of the B beta chain was inferred from the amount of B beta 1-42 and B beta 15-42 in undigested NDSK. The results obtained in both acute and organized thrombi indicate that approximately 60% of the total protein (as determined by amino acid analysis) was fibrinogen-derived and that 70% to 80% of the fibrinogen-derived material was fibrin II. These findings support the hypothesis that fibrin II as distinct from fibrin I is the predominant component in a thrombus. In samples from normal and atherosclerotic aortas, fibrinogen-derived protein comprised less than 10% of the total protein. Samples from grossly normal aortas contained only fibrinogen and fibrin I. Fibrinogen concentration decreased and fibrin II concentration increased with increasing severity of the lesions, suggesting that increased fibrin II formation is associated with progression of atheromas.

Topics: Aorta; Arteriosclerosis; Fibrin; Fibrinogen; Fibrinolysin; Fibrinopeptide A; Fibrinopeptide B; Humans; Thrombin; Thrombosis

We evaluated 40 consecutive carotid endarterectomy specimens for the presence of fibrin. Intraplaque hemorrhage was noted in 93% of specimens. At the plaque surface, there were two patterns of fibrin distribution. Type I, suggesting a lumen thrombus, was found in 7 specimens. Type II, suggesting an intraplaque hemorrhage at the lumen surface, was found in 15 specimens. These changes were not significantly associated with the presence of ischemic symptoms or the use of antiplatelet or anticoagulant medications. All specimens with Type I change had arteriographic evidence of at least 70% diameter stenosis. The frequent lack of fibrin at the plaque surface suggests that there may be inherent limitations of standard medical treatment for carotid artery disease.

Topics: Arteriosclerosis; Carotid Arteries; Carotid Artery Diseases; Carotid Artery Thrombosis; Endarterectomy; Female; Fibrin; Hemorrhage; Histocytochemistry; Humans; Immunoenzyme Techniques; Male; Middle Aged; Prospective Studies

In this short review I have tried to report the literature findings and describe some of our observations on fibrinolysis and atherosclerosis. Although at this time it is difficult to state that diminished FA plays a pathogenic role in atherosclerosis, it certainly seems to represent a risk factor.

Topics: alpha-2-Antiplasmin; Animals; Arteriosclerosis; Blood Coagulation Disorders; Fibrin; Fibrinolysis; Fibrinolytic Agents; Humans; Plasminogen Activators; Thromboembolism; Thrombosis

Seventy-five intimal arterial thickenings (from 58 subjects) related to pulmonary emboli were examined. Many showed residua derived from the emboli (fibrin, platelets, haemosiderin) and proliferation of elastica and smooth muscle cells. Features resembling those of atherosclerosis were the frequent presence of extracellular lipid and apolipoprotein-B containing lipoproteins (LpB) which corresponded closely in distribution; and (in about 40% of the thickenings) collections of fat-filled (foam) cells. Platelet antigens were often detected within foam cells in some cases, in company with LpB. The results indicate that at least some intimal thickenings originating from pulmonary emboli undergo transformation to atherosclerotic plaques. The role of pulmonary hypertension in the process was investigated. Mechanisms relevant to this transformation and to theories of atherogenesis are discussed.

Topics: Adolescent; Adult; Aged; Apolipoproteins B; Arteriosclerosis; Blood Platelets; Female; Fibrin; Fibrinogen; Foam Cells; Humans; Hypertension, Pulmonary; Lipid Metabolism; Lung Diseases; Male; Middle Aged; Pulmonary Embolism; Time Factors

29 autogenous vein grafts, from 26 patients with peripheral arterial disease, were studied. 4 grafts of Group I (less than 3 months duration) were patent and removed for reasons other than graft failure. These showed 'arterialisation' only; 4 grafts of Group II (duration 5-18 months) showed thrombotic occlusion; 21 grafts of Group III (duration greater than 2 years) showed impaired graft patency and lipid identifiable as apolipoprotein B-containing-lipoproteins (LpB), and fibrinogen-related antigens (FRA) were seen as intramural deposits in the thickened grafts. LpB was also seen in a perifibrous distribution on the collagen of organised thrombi. Complicated lesions in some Group III grafts showed stenosis or occlusion, ulceration, calcification or aneurysm formation. These features suggest that a process indistinguishable from 'true' atherosclerosis affects vein grafts of long duration. The ways in which such changes may: contribute to graft failure; and improve our understanding of the basic processes involved in atherogenesis, are discussed.

Topics: Adult; Aged; Apolipoproteins B; Arteries; Arteriosclerosis; Endothelium; Female; Fibrin; Graft Occlusion, Vascular; Histocytochemistry; Humans; Lipid Metabolism; Male; Middle Aged; Time Factors; Vascular Diseases; Veins

Topics: Adenosine Diphosphate; Arteriosclerosis; Blood Coagulation Factors; Blood Flow Velocity; Blood Platelets; Connective Tissue; Cyclic AMP; Endothelium; Fibrin; Humans; Ischemia; Platelet Adhesiveness; Platelet Aggregation; Rheology; Thrombosis

The toxicity of elevated levels of very low density lipoproteins (VLDL, d less than 1.006 g/ml) was investigated using porcine aortic endothelial cells in vitro. VLDL isolated from normal rat serum and added at elevated levels was as toxic as VLDL isolated from streptozotocin-induced diabetic rat serum. Injury was detected by scanning electron microscopy in 4-day-old primary cultures of endothelial cells after a 1/2-h exposure to diabetic rat serum. Bleb formation and contraction was seen first in isolated cells (1/2 h), followed by cells at the periphery of the monolayer (1 h) and finally in cells throughout the monolayer (4 h). By 10 h few cells remained attached to the dish. A similar sequence of events occurred in 1-day-old cultures after a 3-h lag period. Serum from sucrose-fed as well as aged rats was also found to be toxic to endothelial cells in vitro. Elevated levels of VLDL were responsible for the toxicities of these sera. Scanning electron microscopy of the aortas from diabetic and sucrose-fed rats revealed endothelial desquamation, platelet and leukocyte attachment, fibrin deposition and the presence of microthrombi. The common occurrence of both micro- and macrovascular disease in diabetic, sucrose-fed, and aged rats and the toxicity of their serum in vitro suggest that elevated levels of VLDL may initiate vascular disease in these models.

Topics: Aging; Animals; Arteries; Arteriosclerosis; Cells, Cultured; Diabetes Mellitus, Experimental; Endothelium; Fibrin; Lipoproteins, VLDL; Male; Microscopy, Electron, Scanning; Rats; Rats, Inbred Strains; Sucrose

Topics: Adsorption; Arteriosclerosis; Basement Membrane; Blood Coagulation; Blood Viscosity; Capillaries; Capillary Fragility; Capillary Permeability; Dextrans; Endothelium; Fibrin; Fibrinogen; Filtration; Glycosaminoglycans; Humans; Molecular Weight; Rheology

Topics: Animals; Arteries; Arteriosclerosis; Dogs; Endothelium; Fibrin; Muscle, Smooth, Vascular; Thrombosis

In a previous paper (1) the organization of an experimental arterial thrombus in rat aorta during the first six days was described. The present paper will set out the thrombus organization during the following weeks and months. Within one month, fibrin and platelets inside the thrombus disappear, and are replaced by smooth muscle cells, collagen and elastin. Elastin was deposited in two forms - granular and strand-like, according to exposure to the pulsatile blood flow. In the course of that period the thrombus surface was covered by endothelial cells. Small, non-endothelialized areas, often with adhering thrombi, were found at all time intervals. The occurrence of thrombi of various ages is suggestive of continuing rethrombosis, presumably due to a permanently disturbed haemodynamical situation.

Topics: Animals; Aorta; Arteriosclerosis; Elastin; Endothelium; Fibrin; Muscle, Smooth, Vascular; Platelet Adhesiveness; Rats; Recurrence; Thrombosis; Time Factors

Chondroitin sulphates (CSs) were isolated from the intima and the media of normal (normal CSs) and atherosclerotic (sclerotic CSs) regions of human aortas. Normal and sclerotic CSs accelerated the inactivation of thrombin by antithrombin III to an equal extent. By this mechanism, both normal and sclerotic CSs prolonged thrombus formation time in a moving stream of platelet-rich plasma and thrombin-catalysed clotting time of platelet-poor plasma. However, anticoagulant activity of sclerotic CSs in thrombin-catalysed fibrin clot formation in platelet-poor plasma was lower than that of normal CSs. The lower anticoagulant activity of sclerotic CSs was due to the greater accelerating effect on the polymerization of monomeric fibrin to form clot, which was the final distinguishable step of fibrinogen-fibrin conversion.

Topics: Adult; Anticoagulants; Aorta, Thoracic; Arteriosclerosis; Blood Coagulation; Chondroitin; Chondroitin Sulfates; Dose-Response Relationship, Drug; Fibrin; Humans; In Vitro Techniques; Time Factors

Fibrin contains a factor which promotes growth of the mesenchymal cells and such may be related tissue repair. Effects of fibrin and fibrinogen degradation products (FDP) on the growth of smooth muscle cells (SMC) of rabbit aortas in culture were investigated, in relation to atherogenesis. Fibrin, free from plasminogen enhanced the proliferation of SMC during the experimental period of 48 h. Fibrin, rich in plasminogen also stimulated the proliferation of SMC within 24 h, but inhibited it after 48 h. FDP (fragments D and E) inhibited the proliferation of SMC. SMC of rabbit aortas demonstrated plasminogen activator activity. Thrombin and urokinase exhibited no promoting effects on the growth of SMC. These results support the hypothesis that the proliferation of SMC is stimulated by fibrin and later inhibited by FDP, as produced by the fibrinolytic activity of SMC. It is proposed that the metabolism of fibrin in the arterial wall may be of importance in the regulation of SMC proliferation and that the coagulation-fibrinolysis system may play a significant role in atherogenesis.

Topics: Animals; Aorta; Arteriosclerosis; Cell Division; Cells, Cultured; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolysis; Muscle, Smooth; Rabbits; Thrombin; Urokinase-Type Plasminogen Activator

Accumulation of lipid in developing fibrous atherosclerotic plaques is associated with high concentrations of fibrin and accumulation of a tightly bound lipoprotein fraction that can be released by incubation with fibrinolytic enzymes, suggesting that fibrin may play a key role in lesion development. It is not known whether this fibrin represents incorporated mural thrombus or is produced in situ by clotting of the fibrinogen that is present in intima in high concentration. Immunoelectrophoresis was used to measure the concentrations of fibrinogen and components of the clotting system in human aortic intima and lesions, and in mural thrombi. In the lipid and fibrin rich plaque centres prothrombin concentration was almost twice that in normal intima, but concentrations of the thrombin inhibitors antithrombin III and alpha 2-macroglobulin fell, so that the molar ratios of inhibitor/prothrombin fell from 3:1 in normal intima to 1:1 in the plaque centre. In mural thrombi there was preferential sequestration of fibrinogen-like antigen and prothrombin. Distribution of factor-VIII-related antigen was highly unpredictable; in both normal intima and all types of intimal lesion substantial amounts were recovered from some samples, whereas none was recovered from others. The highest concentrations were found in samples free of endothelium from the deep layers of lesions. The results are compatible with the idea that fibrinogen may be converted to fibrin within lesions; once some fibrin has accumulated within the intima it seems to bind low-density lipoprotein and sequester fibrinogen and clotting factors, thereby producing a self-amplifying system.

Topics: Aged; Aorta; Arteriosclerosis; Blood Proteins; Factor VIII; Female; Fibrin; Fibrinogen; Hemostatics; Humans; Lipoproteins, LDL; Male; Middle Aged; Prothrombin

Topics: Arteriosclerosis; Blood Coagulation; Coronary Disease; Estrogens; Female; Fibrin; Humans; Male; Prospective Studies; Risk; Sex Factors

Topics: Animals; Anti-Inflammatory Agents; Arteriosclerosis; Aspirin; Blood Platelets; Blood Vessels; Carotid Artery Diseases; Coronary Disease; Dipyridamole; Female; Fibrin; Humans; Male; Prostaglandins; Sex Factors; Sulfinpyrazone; Thrombosis

Topics: Adolescent; Adult; Aged; Aging; Aorta, Thoracic; Arteriosclerosis; Female; Fibrin; Fibrinogen; Humans; Male; Middle Aged

For the purpose of examining the interrelation between the permeability of the plasma constituents and the site of the atherosclerosis. We have perfused the solution of a dye into human aorta and observed permeability into aortic intima with aging and into atherosclerotic plaque. In addition, the deposition of bilirubin and fibrin into atherosclerotic plaque was also investigated. When the extent of the permeability was expressed as the ratio of the depth of permeability/thickness of intima, it was found that the ratio for the thoracic aorta decreased with advancing age. Permeability of the abdominal aorta occurred to show that the value of the ratio was up to 3.0 in the subject with age from 0 to 19 years and then the ratio slightly decreased with advancing age, followed by a further one step down in the seventies. Permeability into the atheromatous plaque showed diffuse pattern in the young adult but the permeability became shallower with advancing age. Regional difference of permeability around the plaque was studied. The greatest permeability was seen on the lower side of the plaque. Bilirubin and fibrin deposition into plaque was also similar to its permeability pattern.

Topics: Adolescent; Adult; Aged; Aging; Aorta; Arteriosclerosis; Bilirubin; Capillary Permeability; Child; Child, Preschool; Fibrin; Humans; Infant; Infant, Newborn; Male; Middle Aged

It has recently been found that endothelial cells exhibit an unusual change in cellular behavior in response to contact with fibrin. The possible implications of this finding with regard to the mechanism of atherogenesis are discussed. It is proposed that mural fibrin in vivo may produce a disorganized endothelium which can act as a nidus for further fibrin deposition and platelet aggregation. In the presence of inadequate fibrinolysis, a prolonged endothelial lesion could occur which may eventually result in atheromatous plaque formation. This view of atherogenesis requires reduced fibrinolytic activity as a prerequisite for plaque formation, a requirement which is in agreement with currently known data associating atherogenic risk factors with inhibited fibrinolysis.

Topics: Animals; Aorta; Arteries; Arteriosclerosis; Cattle; Endothelium; Fibrin; Fibrinolysis; In Vitro Techniques

Topics: Aorta; Arteriosclerosis; Chondroitin Sulfates; Factor VIII; Fibrin; Glycosaminoglycans; Heparin; Humans; Polymers; Solubility; Thrombelastography; Thrombosis; Tissue Extracts; Trypsin

After a short description of the morphology and the present ideas of the function of the endo-endothelial fibrin and mucopolysaccharide film, respectively, of the vascular wall hitherto undertaken experimental investigations of this structure within the pathogenesis of the arteriosclerosis are summarized. The results of these investigations are contradictory. The difficulties of a morphological demonstration of changes of the endo-endothelial film going along with disturbances of the permeability as an early change of the arteriosclerosis are in the method of demonstration, in which case it is not sure, whether with the preparative and technical means used at present processes taking place on molecular level in the substances of the endo-endothelial film may really be comprehended.

Topics: Arteriosclerosis; Blood Vessels; Capillary Permeability; Endothelium; Fibrin; Glycosaminoglycans; Humans

Already in the early stages of atherosclerosis still before the appearance of coarsely visible changes subendothelially fibrin-like material is found in the places of predilection known, which reveals electron-microscopically the typical periodicity. Lesions of the endothelium with increase of permeability, release of coagulation factors and mitogenic substances which stimulate the proliferation of smooth muscle cells always precede. There are several mechanisms for the penetration of fibrinogen or fibrin into the vascular wall, the proportion of which changes with the progressing of the atherosclerosis. They are discussed in detail. Mechanisms of fibrinolysis, in which plasmin or activators of plasmin occupy a key position, effect against this process. By histochemical estimation of this activator the fibrinolytical potential of the vascular system can be investigated under various clinical conditions. For this a series of instances is cited.

Topics: Arteriosclerosis; Cell Division; Endothelium; Fibrin; Fibrinolysin; Fibrinolysis; Humans; Muscle, Smooth

Topics: Age Factors; Arteries; Arteriosclerosis; Cell Division; Edema; Endothelium; Fibrin; Fibrinogen; Humans; Platelet Aggregation; Pulse; Systole

Plasmatic arterionecrosis, the causative lesion of hypertensive cerebral hemorrhage, follows upon medial muscle cell necrosis. The development of medial muscle cell necrosis, the earliest cerebral arterial change seen in hypertensive rats, was inhibited when these animals were fed a cholesterol and lard-supplemented diet. Insudation of fibrin was noted in the arterial intima of hypertensive rats with bilaterally constricted renal arteries. Removal of the constriction induced a fall in the elevated blood pressure and an increase of intimal muscle cells. These were responsible for the dissolution of the deposited fibrin, leading to arteriosclerosis. These myointimal cells may originate from the endothelium. Arterial contraction caused by methoxamine hydrochloride often induced the intrusion of one medial muscle cell into another and increased endothelial permeability. 12-24 h after contraction, the arterial segments showed medial muscle cell necrosis, endothelial desquamation with platelet adhesion, and blood plasma infiltration.

Topics: Animals; Arteriosclerosis; Cerebral Arteries; Cerebral Hemorrhage; Fibrin; Humans; Hypertension; Male; Mesenteric Arteries; Methoxamine; Muscle Contraction; Muscle, Smooth; Necrosis; Rats; Renal Artery

Most plasma proteins appear to be present in intima at concentrations that are a linear function of molecular weight and concentration in the plasma. Thus low density lipoprotein (LDL) (molecular weight, 2 X 10(6)) has the greatest retention relative to its plasma concentration, whereas the relative retention of albumin is only 15% of the relative retention of LDL. This gives rise to the concept that "whole plasma" crosses endothelium, and the steady state concentrations reflect rates of egress of the macromolecules, which in turn depend on molecular sieving. Fibrinogen is a major plasma protein in intima in addition to LDL and albumin, and there are also substantial amounts of the protease inhibitors alpha2-macroglobulin and alpha1-antitrypsin. Intima also contains insoluble derivatives of plasma--extracellular cholesterol, both free and esterified, and fibrin. The balances of intact LDL/"deposited" cholesterol and of fibrinogen/fibrin are closely linked with intimal morphology. Fibrinogen and electrophoretically mobile LDL are increased about threefold in gelatinous lesions, whereas there are only slight rises in fibrin and deposited cholesterol. In the deep layers of fibrous plaques, fibrin is increased fivefold and cholesterol up to thirtyfold. In these lipid-rich layers, LDL is rapidly lost on incubation of tissue samples, but in some gelatinous lesions it first increases and only decreases on longer incubation, suggesting release of a previously immobilized lipoprotein fraction. This immobilized lipoprotein was investigated by subjecting tissue samples to immunoelectrophoresis to remove mobile LDL and tissue enzymes, followed by treatment of the tissue with enzyme and measurement of the lipoprotein released on fresh immunoelectrophoresis plates. Plasmin or a crude collagenase released large amounts of lipoprotein from samples of amorphous atheroma lipid. For all samples the amount of lipoprotein released was highly correlated with the accumulation of deposited cholesterol, suggesting that immobilization of LDL may be an intermediate step in the irreversible deposition of extracellular cholesterol. Plasmin is highly effective in releasing immobilized lipoprotein, and the concentration of immobilized lipoprotein is significantly correlated with the concentration of insoluble fibrin, suggesting that the lipoprotein may in some way be immobilized by fibrin.

Topics: Age Factors; alpha-Macroglobulins; Aorta; Arteriosclerosis; Blood Proteins; Cholesterol; Fibrin; Fibrinogen; Humans; Immunoelectrophoresis; Lipoproteins, HDL; Lipoproteins, LDL; Molecular Weight; Serum Albumin

Topics: alpha-Macroglobulins; Arteries; Arteriosclerosis; Blood Proteins; Cholesterol; Fibrin; Fibrinogen; Humans; Immunoelectrophoresis; Lipoproteins, LDL; Molecular Weight; Solubility; Transferrin

Topics: Animals; Aorta; Arteriosclerosis; Blood Platelets; Fibrin; Humans; Hypertension; Swine; Thrombosis

A large amount of plasma low density lipoprotein is present in human aortic intima, and this can be removed and measured by electrophoresis directly from the minced tissue into an antibody-containing gel. We now find that, in addition to this electrophoretically mobile lipoprotein, there is an immobilized lipoprotein fraction than can be released from lesions by incubation of the tissue sample with plasmin or other proteolytic enzymes after the mobile lipoprotein has been removed. The concentration of immobilized lipoprotein is highly correlated with the concentration of the residual cholesterol (not mobile on electrophoresis) that has accumulated in the tissue (r = 0.702; P less than 0.001). Thus, in normal intima and early gelatinous lesions it is about 15% of the concentration of mobile lipoprotein, whereas in the atheroma lipid layers of fibrous or gelatinous plaques it may be 2 or 3 times greater than the concentration of mobile lipoprotein. This suggests that immobilization of plasma lipoprotein is an intermediate step in the irreversible deposition of extracellular cholesterol in atherosclerotic lesions. Incubation with plasmin allowed maximum release of lipoprotein: plasmin = crude collagenase greater than trypsin greater than "pure" collagenase greater than chondroitinase ABC in order of their relative effectiveness. The concentration of immobilized lipoprotein was significantly correlated (r = 0.793; P less than 0.001) with the concentration in the tissue of fibrin or other insoluble derivatives of fibrinogen ("fibrin"). In aliquots of lesions incubated with varying amounts of plasmin for varying times there was a constant relation between release of lipoprotein and release of fibrin-degradation products. Together, these findings suggest that the lipoprotein is associated with insoluble "fibrin". This appears to be of considerable clinical interest, suggesting a synergism between lipoprotein and fibrinogen in the accumulation of lipid in lesions.

Topics: Adult; Aged; Aorta; Arteriosclerosis; Cholesterol; Chondroitinases and Chondroitin Lyases; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinolysin; Humans; Immunoelectrophoresis, Two-Dimensional; Lipid Mobilization; Lipoproteins, LDL; Microbial Collagenase; Middle Aged

Topics: Arteriosclerosis; Factor XIII; Fibrin; Fibrin Fibrinogen Degradation Products; Fibrinogen; Humans; Thrombin

By means of the fluometric method in 76 rabbits at definite stages of the development of experimental atherosclerosis in the aorta an increased amount of gamma-globulin and fibrin was established. An increase in the level of gamma-globulin was accompanied by fixation of beta1C-fraction of complement, which is characteristic of deposit of an immune complex. The most pronounced concentration of gamma-globulin was noted in areas of lysis and fragmentation of elastic fibres.

Topics: Animals; Aorta; Arteriosclerosis; Complement System Proteins; Fibrin; Fluorescent Antibody Technique; gamma-Globulins; Lipoproteins, LDL; Microscopy, Fluorescence; Proteins; Rabbits; Time Factors

Following the administration of cholesterol for a period of 6-7 weeks, Scanning Electron Microscopic (S.E.M.) observations revealed mono-cellular, crater-like and dome-shaped endothelial changes on top of the large intimal plaques in the rabbit aortas. Finger-like and other shaped cell protrusions were observed at the edges of these crater-like and dome-shaped endothelial changes, giving the intimal plaques a rough appearance. At other sites, normal, smooth, although irregularly arranged, endothelial cells covered the lesions. By impregnating the cell borders with silver-nitrate or silver proteinate containing perfusates, it was possible in most cases to ascertain that the lesions were derived from changes in one cell or from changes in a small collection of cells. S.E.M.-observations further revealed crater-like and dome-shaped endothelial changes to be present in large fields or as isolated cell changes in normal areas at sites where no gross lesions were observed with the light microscope. In addition large, multi-cellular, crate-like endothelial changes were observed at the edges of the large intimal plaques. At these sites several endothelial cells were lacking, leaving behind a crater in which sometimes cells and a few fibrin threads were found. Following the administration of cholesterol for periods of 4-5 and 2-3 weeks similar monocellular changes were observed, some extending over large areas, other as single cells in apparently normal surroundings. Quantitatively the number of lesions was less than when the cholesterol was administered for a longer period. Transmission electron microscopic studies revealed the presence of large amounts of membrane-bound lipid globules in the subendothelial spaces and within some endothelial cells, structures which were assumed to be cross-sections of the crater-like or dome-shaped endothelial cell protrusions, visible with the S.E.M.

Topics: Animals; Aortic Diseases; Arteriosclerosis; Cholesterol; Diet, Atherogenic; Endothelium; Female; Fibrin; Histocytochemistry; Microscopy, Electron, Scanning; Rabbits; Time Factors

Topics: Arteriosclerosis; Blood Coagulation; Blood Coagulation Factors; Fibrin; Fibrinolysis; Hemophilia A; Hemostasis; Humans; Thromboembolism; Thrombosis

A variety of blood constituents was injected into an isolated segment of rabbit aorta to determine which elements might be involved in early endothelial injury. Test materials consisted of platelet-rich plasma (PRP) alone; PRP plus adenosine diphosphate (ADP); PRP plus tendon extract; PRP plus thrombin; ultrasonicated PRP alone; platelet-poor plasma alone; and thrombin in saline. Each experimental mixture was left in the aorta for 15 minutes, followed by reflow for 20 minutes. The vessel was then fixed by glutaraldehyde perfusion. Thick sections of the entire circumference of the aorta were taken for phase contrast microscopy and representative arease were selected for electron microscopy. In control PRP alone, platelet-poor plasma alone and with PRP plus ADP there were occasional subendothelial vesicles. When PRP plus thrombin and platelet-poor plasma plus thrombin were injected separately to form a thrombus or when thrombin in saline was used, there was extensive subendothelial vesiculation with focal ulceration and adherence of thrombus to endothelium. Severe injury was associated with the presence of thrombin initiating the polymerization of fibrinogen to fibrin. Electron micrographs demonstrate the earliest lesion as a disruption of the superficial fibrilliary elastica with separation of overlying endothelium.

Topics: Adenosine Diphosphate; Animals; Aorta; Arteriosclerosis; Elastic Tissue; Endothelium; Fibrin; Fibrinogen; Male; Microscopy, Electron; Microscopy, Phase-Contrast; Platelet Aggregation; Rabbits; Sonication; Thrombin; Thrombosis; Tissue Extracts

Effects of phenformin on blood sugar, serum triglyceride, thrombin time, euglobulin clot lysis time and cardiovascular complications were studied in maturity onset diabetes and in atherosclerotic patients with or without diabetes, for a period of 14-18 months. Phenformin has shown the characteristic properties of an antifibrinopathic agent in that it prolongs thrombin time and enhances fibrinolysis. The hypoglycaemic effect of phenformin was found to be directly related to its antifibrinopathic action. Plasma lipids fell in all cases. Absence of fresh cardiovascular complications and improvement in anginal symptoms were observed. The metabolic, haematological and clinical benefits of phenformin and its limitations in maturity onset diabetes and atherosclerosis may be explained by the effects of the drug upon the thrombin-fibrinogen reaction. These results lend support to the hypothesis of a primary fibrinopathic pathogenesis in maturity onset diabetes mellitus and atherosclerosis.

Topics: Adult; Aged; Arteriosclerosis; Blood Coagulation Tests; Blood Glucose; Diabetes Mellitus; Fibrin; Fibrinolysis; Fibrinolytic Agents; Humans; In Vitro Techniques; Middle Aged; Phenformin; Triglycerides

Topics: Animals; Antigen-Antibody Reactions; Arteriosclerosis; Complement System Proteins; Fibrin; gamma-Globulins; Kidney Tubules; Lipoproteins; Rabbits; Time Factors

Topics: Animals; Antithrombins; Arteriosclerosis; Blood Cell Count; Blood Coagulation; Blood Coagulation Factors; Blood Coagulation Tests; Blood Platelets; Carnivora; Cross Reactions; Factor X; Fibrin; Fibrinogen; Haplorhini; Humans; Phosphatidylethanolamines; Prothrombin Time; Species Specificity; Thrombin; Thromboplastin; Thrombosis

Topics: Arteriosclerosis; Blood Specimen Collection; Cardiac Catheterization; Coronary Disease; Coronary Vessels; Electric Countershock; Enzyme Activation; Enzyme Repression; Fibrin; Fibrinogen; Fibrinolysin; Fibrinolysis; Heparin; Humans; Hypertension; Myocardial Infarction; Plasminogen; Radiography

Topics: Arteriosclerosis; Arteriovenous Shunt, Surgical; Blood Platelets; Endarterectomy; Femoral Artery; Fibrin; Humans; Microscopy, Electron; Saphenous Vein; Transplantation, Autologous

Topics: Animals; Arteriosclerosis; Blood Platelets; Cholesterol; Embolism; Fibrin; Humans; Leukocytes; Macrophages; Male; Microscopy, Electron; Protein Binding; Rabbits; Renal Artery; Renal Artery Obstruction; Time Factors

Topics: Adolescent; Adult; Aged; Arteriosclerosis; Blood Coagulation Disorders; Blood Coagulation Tests; Diabetes Complications; Diabetes Mellitus, Type 1; Diabetic Angiopathies; Fibrin; Fibrinogen; Half-Life; Humans; Iodine Radioisotopes; Middle Aged

Topics: Adult; Aged; Aneurysm; Aortic Aneurysm; Arteriosclerosis; Blood Cell Count; Blood Coagulation; Blood Platelets; Buttocks; Cell Survival; Chromium Radioisotopes; Chronic Disease; Disseminated Intravascular Coagulation; Female; Fibrin; Fibrinogen; Hemangioma; Humans; Iodine Radioisotopes; Middle Aged; Purpura, Thrombocytopenic; Skin Neoplasms; Syndrome; Thrombosis

Hyaline deposits in arterioles and arteries of spleen were studied immunohistochemically. Hyaline lesions in arteriosclerotic heart disease were characterized by significant deposits of IgG, IgM, beta1C-beta 1A-globulins and beta-lipoproteins. These corresponded to histochemically stained deposits of acid mucopolysaccharides and microscopic areas of musculoelastic tissue damage in the hyaline masses. While, in young adults and a few other cases of other diseases, an occasional granular to linear deposit of IgG, IgM, beta1C-beta 1A-globulin and beta-lipoprotein was noted, no localization of IgA, rabbit antihuman fibrin and rabbit antihuman fibrinogen was seen. A variety of other histochemical staining reactions were found to be negative. These findings suggest that: a) hyaline deposits in splenic arterioles and arteries occur with greater severity in patients with hypertensive and arteriosclerotic heart disease; b) a possible abnormality related to filtration defects in arteries and arterioles, resulting in the trapping of plasma proteins, appears likely; c) increased localization of acid mucopolysaccharides and destruction of musculoelastic tissue is not an uncommon feature in hyaline masses; d) fibrin is not a component of these deposits and e) further study of other organs is necesary to observe the composition of hyaline in arterioles and arteries.

Topics: Adolescent; Adult; Aged; Animals; Arteriosclerosis; Beta-Globulins; Child; Child, Preschool; Complement System Proteins; Fibrin; Fibrinogen; Fluorescent Antibody Technique; Glycosaminoglycans; Histocytochemistry; Humans; Hyalin; Hypertension; Immunoglobulin G; Immunoglobulin M; Infant; Infant, Newborn; Lipoproteins, LDL; Middle Aged; Rabbits; Splenic Artery; Vascular Diseases

Topics: Adult; Aged; Arteriosclerosis; Coronary Disease; Coronary Vessels; Fibrin; Fibrinolysis; Humans; Male; Middle Aged; Myocardial Infarction

Topics: Arteries; Arteriosclerosis; Fibrin; Thrombosis

Topics: Acute Disease; Arteriosclerosis; Blood Platelets; Cardiac Output; Coronary Disease; Death, Sudden; Erythrocytes; Fibrin; Humans; Leukocytes; Myocardial Infarction

Topics: Adult; Aged; Arteriosclerosis; Autopsy; Blood Platelets; Calcinosis; Cholesterol; Coronary Disease; Coronary Vessels; Embolism; Erythrocytes; Female; Fibrin; Heart Ventricles; Hemorrhage; Humans; Leukocytes; Male; Middle Aged; Myocardial Infarction; Myocardium; Thrombosis; Time Factors

Topics: Adult; Arteriosclerosis; Coronary Disease; Diagnosis, Differential; Fibrin; Fibrinogen; Fibrinolysis; Humans; Middle Aged; Myocardial Infarction; Prognosis; Protamines; Serum Globulins

Topics: Adult; Aged; Albumins; Arteries; Arteriosclerosis; Autopsy; Complement System Proteins; Female; Fibrin; Fluorescent Antibody Technique; gamma-Globulins; Histocytochemistry; Humans; Immunochemistry; Immunoglobulin G; Immunoglobulin M; Immunoglobulins; Lipoproteins; Macroglobulins; Male; Middle Aged; Spleen

Topics: Adolescent; Adult; Aged; Aorta; Aortic Diseases; Arteriosclerosis; Child; Child, Preschool; Fibrin; Fluorescent Antibody Technique; Humans; Infant; Middle Aged

Topics: Animals; Aorta; Arteriosclerosis; Blood Proteins; Brain; Carbon Isotopes; Diet, Atherogenic; Disease Models, Animal; Fibrin; Hyaluronoglucosaminidase; Kidney; Liver; Male; Methods; Muscles; Myocardium; Pancreas; Rats; Tendons; Time Factors; Tyrosine

Topics: Animals; Aorta; Aortic Diseases; Arteriosclerosis; Cholesterol; Diet, Atherogenic; Fibrin; Guinea Pigs; Lipoproteins; Male; Microscopy, Electron, Scanning

Topics: Adolescent; Adult; Aged; Aorta; Aortic Diseases; Arteriosclerosis; Autopsy; Child; Child, Preschool; Female; Fibrin; Histocytochemistry; Humans; India; Infant; Male; Middle Aged; Staining and Labeling

Topics: Aorta, Abdominal; Arteriosclerosis; Calcinosis; Cholesterol; Fibrin; Humans; Lipid Metabolism; Microscopy, Electron, Scanning

Topics: Adult; Arteriosclerosis; Blood Coagulation Disorders; Coronary Disease; Diffuse Cerebral Sclerosis of Schilder; Fibrin; Fibrinolysis; Genetic Diseases, Inborn; Germany, East; Humans; Intracranial Arteriosclerosis; Male; Middle Aged

Topics: Animals; Antifibrinolytic Agents; Aorta; Arteries; Arteriosclerosis; Capillary Permeability; Cholesterol; Cyclohexanecarboxylic Acids; Fibrin; Fibrinogen; Fibrinolysis; Pulmonary Artery; Rabbits; Thromboembolism

Topics: Arteriosclerosis; Arteriosclerosis Obliterans; Blood Vessels; Collagen; Connective Tissue; Diabetic Angiopathies; Elastic Tissue; Embolism; Endarteritis; Fibrin; Humans; Hyalin; Ischemia; Necrosis; Vasa Vasorum

Topics: Adult; Aged; Angina Pectoris; Aorta; Arteriosclerosis; Coronary Disease; Female; Fibrin; Fluorescent Antibody Technique; Humans; Immune Sera; Male; Microtomy; Middle Aged; Myocardial Infarction

Topics: Animals; Arteries; Arteriosclerosis; Electric Stimulation; Erythrocyte Aggregation; Fibrin; Methods; Microscopy, Electron; Rabbits; Thrombosis; Time Factors; Vascular Diseases

Topics: Aorta; Arteriosclerosis; Blood Coagulation Tests; Colonic Neoplasms; Fibrin; Fibrinogen; Fibrinolysis; Humans; Hypertension; Hypertension, Renal; Immunoassay; Kidney; Obesity; Pyelonephritis; Renal Veins; Staphylococcus

Topics: Adolescent; Adult; Age Factors; Aged; Animals; Aorta; Arteriosclerosis; Blood Coagulation; Blood Platelets; Cattle; Centrifugation; Child; Child, Preschool; Factor V; Factor VII; Female; Fibrin; Fibrinogen; Horses; Humans; Infant; Infant, Newborn; Male; Middle Aged; Prothrombin; Thromboplastin; Time Factors

Topics: Animals; Aorta, Thoracic; Arteriosclerosis; Biological Transport; Cell Membrane Permeability; Chylomicrons; Coloring Agents; Densitometry; Dogs; Fibrin; Hemodynamics; Histocytochemistry; Infusions, Parenteral; Methods; Rheology; Serum Albumin; Stress, Physiological

Topics: Arteriosclerosis; Blood Coagulation; Blood Coagulation Tests; Blood Platelets; Extracorporeal Circulation; Fibrin; Fibrinolysis; Hemorrhage; Heparin; Heparin Antagonists; Humans; Hyperlipidemias; Hypersensitivity; Natriuresis; Osteoporosis; Protamines; Prothrombin Time; Thromboembolism; Thrombophlebitis; Thromboplastin

Topics: Animals; Aorta; Arteries; Arteriosclerosis; Carotid Arteries; Cattle; Cerebral Arteries; Fibrin; Fibrinogen; Fibrinolysis; Humans; Pulmonary Artery; Thrombin

Topics: Animals; Aorta; Arteriosclerosis; Cholesterol; Fibrin; Glycine; Liver; Male; Rabbits; Wound Healing

Topics: Arteriosclerosis; Blood Coagulation Disorders; Blood Platelets; Fibrin; Humans

Topics: Arteriosclerosis; Blood Chemical Analysis; Blood Sedimentation; Coronary Disease; Female; Fibrin; Glycoproteins; Haptoglobins; Humans; Lipoproteins; Male; Myocardial Infarction

Topics: Aorta; Arteriosclerosis; Basement Membrane; Blood Proteins; Elastic Tissue; Extracellular Space; Fibrin; Histocytochemistry; Humans; Lipoproteins; Microscopy, Electron

Topics: Animals; Arteriosclerosis; Fibrin; Humans; Lipids; Rabbits; Thrombosis

Topics: Arteriosclerosis; Fibrin; Fluorescent Antibody Technique; Lipid Metabolism

Topics: Adolescent; Adult; Age Factors; Aorta; Arteriosclerosis; Biological Transport; Blood Circulation; Blood Proteins; Carotid Arteries; Child; Child, Preschool; Elastic Tissue; Female; Fibrin; Humans; Infant; Male; Middle Aged

Topics: Animals; Arteriosclerosis; Blood Platelets; Fibrin; Fibrinogen; Fluorescent Antibody Technique; Immune Sera; Rabbits; Thrombosis

Topics: Arteries; Arteriosclerosis; Diabetes Mellitus; Fibrin; Humans; Kidney; Permeability

Topics: Aging; Animals; Arteriosclerosis; Carbon Isotopes; Fibrin; Fibrinogen; Glycine; Humans; Liver; Mice; Plasma; Thrombin

Topics: Aging; Animals; Aorta; Arteriosclerosis; Cholesterol; Diet, Atherogenic; Fatty Acids; Fibrin; Fibrinolysis; Glucuronidase; Heparin; Humans; Lipid Metabolism; Liver; Liver Cirrhosis; Pituitary Hormones, Posterior; Protein Biosynthesis; Stress, Psychological; Thrombin

Topics: Aged; Arteriosclerosis; Fibrin; Fibrinolysis; Humans; Hyperthyroidism; Middle Aged; Myxedema; Thrombelastography

Topics: Adsorption; Arteriosclerosis; Calcium Phosphates; Carbon Isotopes; Charcoal; Cholesterol; Fibrin; Solutions

Topics: Animals; Arteriosclerosis; Cattle; Fibrin; Histocytochemistry; Jugular Veins; Male; Pulmonary Artery; Pulmonary Embolism; Rabbits; Thrombin

Topics: Arteriosclerosis; Atherosclerosis; Electrons; Fibrin; gamma-Globulins; Microscopy; Microscopy, Electron; Pathology

Topics: Arteriosclerosis; Fibrin; Hyalin; Hypertension; Hypertension, Renal; Kidney; Microscopy; Pathology; Rats; Research; Vascular Diseases

Topics: Aminocaproates; Animals; Aorta, Abdominal; Aorta, Thoracic; Aortic Diseases; Arteriosclerosis; Fibrin; Rabbits; Thrombin; Thrombosis

Topics: Arteriosclerosis; Atherosclerosis; Blood Coagulation; Fibrin; Humans

Topics: Animals; Antibodies; Aortic Diseases; Arteriosclerosis; Atherosclerosis; Fibrin; Fluorescent Antibody Technique; Freund's Adjuvant; Immune Sera; Immunoelectrophoresis; Rabbits; Research; Serum Albumin; Serum Globulins

Topics: Aminocaproates; Aminocaproic Acid; Animals; Arteriosclerosis; Fibrin; Fibrinolysis; Glycosuria; Hematuria; Kidney Diseases; Kidney Glomerulus; Pharmacology; Pulmonary Embolism; Rabbits; Rats; Research; Thrombin

Topics: Animals; Arteriosclerosis; Epinephrine; Fibrin; Fibrinolysis; Humans; Pathology; Pharmacology; Pulmonary Artery; Pulmonary Embolism; Rabbits; Research; Serotonin; Vascular Diseases; Vasoconstriction

Topics: Aorta; Arteriosclerosis; Atherosclerosis; Fibrin; Humans; Leukocytes; Thrombosis

Topics: Aorta; Arteries; Arteriosclerosis; Blood Coagulation; Cerebral Arteries; Coronary Vessels; Fibrin; Fibrinolysis; Glycoproteins; Humans; Metabolism; Plasma; Prothrombin Time; Thrombelastography; Thromboplastin

Topics: Arterial Pressure; Arteries; Arteriosclerosis; Carotid Arteries; Fibrin; Hypertension; Necrosis; Pathology; Rats; Renal Artery; Research

Topics: Arteries; Arteriosclerosis; Blood Proteins; Fibrin; Fibrinogen; Gold Colloid; Gold Colloid, Radioactive; Hypertension; Iodine Isotopes; Mesenteric Arteries; Morphogenesis; Pathology; Rats; Renal Artery Obstruction; Research

Topics: Aorta; Aortic Diseases; Arteriosclerosis; Fibrin; Fluorescent Antibody Technique; Humans

Topics: Arteriosclerosis; Atherosclerosis; Coronary Disease; Fibrin; Fibrinolysin; Humans; Thrombosis

Topics: Arteriosclerosis; Collagen; Diabetes Mellitus; Fibrin; Geriatrics; Humans; Hyalin; Hypertension; Hypertension, Malignant; Hypertension, Pulmonary; Mitral Valve Stenosis; Pathology; Pyelonephritis

Topics: Arteriosclerosis; Fibrin; Fluorescent Antibody Technique; Humans; Immune Sera; Lipid Metabolism; Lipoproteins; Pathology

Topics: Animals; Arteries; Arteriosclerosis; Cardiovascular System; Cats; Cattle; Dogs; Fibrin; Fibrinolysis; Guinea Pigs; Haplorhini; Horses; Rabbits; Rats; Research; Swine; Thromboplastin; Veins

Topics: Anticoagulants; Arteriosclerosis; Fibrin; Humans; Thrombosis; Warfarin

Topics: Aorta; Arteriosclerosis; Coagulants; Fibrin; Fibrinogen; Glycosaminoglycans; Hemostatics; Humans

Topics: Aorta; Arteriosclerosis; Fibrin; Tunica Intima

Topics: Arteriosclerosis; Fibrin; Fibrinolysis; Humans

Topics: Arteriosclerosis; Blood Coagulation; Fibrin; Fibrinolysis; Humans; Nitrogen

Topics: Aorta; Arteriosclerosis; Fibrin; Humans; Thrombosis

Topics: Arteriosclerosis; Coagulants; Fibrin; Fibrinogen; Hemostatics; Humans; Rheumatic Diseases; Thrombosis

Topics: Arteriosclerosis; Coronary Disease; Fats; Fibrin; Fibrinolysis; Humans; Hyperlipidemias; Thrombosis

Topics: Arteriosclerosis; Electrons; Fibrin; Microscopy; Microscopy, Electron; Plaque, Atherosclerotic