Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.21.68 (tissue plasminogen activator)
11,311 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We examined vascular endothelial cell markers, thrombomodulin (TM), plasminogen activator inhibitor-I (PAI-I), tissue plasminogen activator (t-PA), and von Willebrand factor, in 80 patients with disseminated intravascular coagulation (DIC). The levels of thrombin-antithrombin III complex (TAT), plasmin-alpha 2 plasmin inhibitor complex (PIC) and FDP-D-dimer were significantly increased both before and after the onset of DIC, but were not correlated with organ failure or prognosis. However, the PIC/TAT ratio was lower in patients with poor prognosis than in those with good prognosis, and it was also lower in those with organ failure than in those without. Plasma TM, PAI-I, and t-PA levels were increased in DIC patients with organ failure or poor outcome, but were not significantly increased before the onset of DIC. We consider that the prognosis of patients with DIC might be related to organ failure or endothelial cell damage and that plasma levels of TM, PAI-I, and t-PA might be useful in the detection of these disorders and in assessing prognosis. A hypofibrinolytic state might enhance organ failure in patients with DIC.
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PMID:Increased vascular endothelial cell markers in patients with disseminated intravascular coagulation. 826 24

The mechanism of functioning of protein C can briefly be presented as follows. Thrombin and factor Xa formed in the blood via coagulation, interact with endothelial thrombomodulin and thereby activate protein C circulating in the blood. The activated protein C inhibits factors V and VIII and, in so doing, blocks the further production of thrombin. In this way protein C intermediates the loop of the negative feedback and prevents excessive thrombin generation. Besides, activated protein C enhances fibrinolysis, causing the release of the tissue plasminogen activator. Activated protein C is inhibited by a heparin-dependent inhibitor and alpha 1-antitrypsin and is then excreted from the organism. Congenital deficiency of protein C gives rise to thromboses; thrombotic diseases of various etiology are accompanied by protein C decline in the blood. Injection of exogenous protein C into the blood increases the anticoagulant activity of the blood and produces an antithrombotic effect.
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PMID:[Protein C: mechanisms of activation and anticoagulant effect]. 836 8

In Vienna, Austria, health workers took blood samples from 16 healthy, nonsmoking 19-35 year old women before and after they began using a combined oral contraceptive (OC) (Gynovin) (30 mcg ethinyl estradiol and 75 mcg gestodene) to assess the OC's effects on blood coagulation and fibrinolysis and the effect of the estrogen component on endothelial cells. Fibrinogen levels increased significantly after OC use (283 mg/dl vs. 342 mg/dl after the 1st treatment cycle; p .005). These levels remained significantly higher (326 mg/dl and 339 mg/dl after the 2nd and 3rd treatment cycles; p .005 and .05, respectively). Thrombin antithrombin III complex (TAT) and prothrombin fragment F1+2 levels increased just minimally during OC treatment. Levels of fibrin split-product D-dimer, plasma tissue plasminogen activator (t-PA) activity, and plasmin-antiplasmin (PAP) complexes were significantly higher during all OC treatment cycles than they were before treatment. Active plasminogen activator inhibitor (PAI-1) antigen, t-PA, and urokinase plasminogen activator antigen levels fell significantly after OC treatment and remained low during OC treatment. Experiments with the culture of human umbilical vein endothelial cells showed that ethinyl estradiol did not significantly affect the tissue factor content or surface thrombomodulin activity of these endothelial cells (i.e., hemostatic regulatory activities). It also did not change the secretion of the fibrinolytic components t-PA and PAI-1. None of the women developed thrombosis. Even though these findings did not clearly show OC-induced hemostatic activation in this relatively small group of women, clinical researchers should still determine activation markers to monitor the activation state of blood coagulation in certain OC users, such as obese women and those who smoke cigarettes.
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PMID:Studies on oral contraceptive-induced changes in blood coagulation and fibrinolysis and the estrogen effect on endothelial cells. 839 73

Thrombomodulin (TM) is a very efficient natural anti-thrombin glycoprotein expressed on the endothelial cell surface. Circulating soluble thrombomodulin is also detected by enzyme immunoassay in plasma and represents some fragments of membrane TM with various molecular weight. Plasma TM (TMp) levels are elevated in diseases associated with endothelium damage. We have explored TMp in patients with atheromatous disease and compared its level with others endothelial cell markers, particularly those who indicate cell activation, as tissue-type plasminogen activator (t-PA), inhibitor of plasminogen activator (PAI-1) and prostacyclin (PG12). Thirty seven patients with documented atheromatous artery disease were included in this study. They were not diabetics and their hepatic and renal functions were normal. Mean age was 71 +/- years. Routine serum parameters were checked out as well as others more specific for endothelium activation (TMp, PG12, PAI-1, t-PA) measured by enzyme immunoassay. Patients were classified according to three localizations of atheromatous involvement: - 15 patients with peripheral occlusive arteriopathy disease (POAD) - 6 with coronary artery disease (CAD); and 16 with polyvascular involvement (POLY). They were compared with 21 controls without any vascular lesions (mean age: 43 +/- 13 years). In controls TMp was 36 +/- 8 ng/ml without significant change according with age and sex. In patients whatever the localization of atheroma, TMp was found significantly higher: POAD = 51.3 +/- 19.7 ng/ml (p = 0.003); CAD = 49.2 +/- 15.4 ng/ml (p = 0.008); POLY = 49.6 +/- 17.2 ng/ml (p = 0.003). A positive correlation was pointed out in all patients between TMp and t-PA (p = 0.047), TMp and PG12 (p = 0.008). A positive correlation between TMp and t-PA (p = 0.034) was found only in the subgroup with POAD. In this study, there was no correlation between TMp and the following parameters: leucocytes, haemoglobin, cholesterol, HDL, LDL-cholesterol, Lp(a), fibrinogen.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Evidence of elevated soluble plasma thrombomodulin in atherosclerosis]. 839 2

Normal blood fluidity and perpetuation of the non-thrombogenic state are primarily maintained by the anticoagulant and fibrinolytic systems of vascular endothelial cells involving heparin-like molecule, thrombomodulin, prostacyclin, and the receptor for tissue plasminogen activator. Atherosclerosis perturbes these activities, resulting in arterial thrombosis. On the other hand, recent experimental evidence suggests that the disordered thromboregulation often promotes atherosclerosis. Several known risk factors for development of atherosclerosis, including homocysteine and lipoprotein (a) perturb anticoagulant and fibrinolytic systems of vascular endothelial cells at an early stage of atherogenesis.
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PMID:[Coagulation and fibrinolytic systems and atherogenesis]. 841 63

Endothelial damage is a major factor in the pathogenesis of vascular diseases, but routine investigations of vascular lesions are hampered due to endothelial cell characteristics such as limited accessibility, intrinsic immunological and functional heterogeneity as well as the lack of specific markers. The most frequently used markers are soluble substances, found in plasma, such as the von Willebrand factor, thrombomodulin, tissue plasminogen activator and its inhibitor, or soluble adhesion molecules. Their easy evaluation in semi-routine tests gives access to a global exploration of functional alterations and of abnormal states of endothelial activation. Immunohistological techniques using monoclonal antibodies allow to study the expression of membrane antigens and permit direct and specific investigation of activation states of endothelium. However, the invasive and traumatic characteristics of sampling procedure considerably limit the utilization of immunohistological techniques for clinical applications. Detection in the peripheral blood of endothelial cells detached from vessels could be a good marker for desquamative lesions. From a simple blood sample, it is now possible, using specific immunodetection techniques to isolate circulating endothelial cells present in low numbers in various pathologies associated with vascular injury. Although significant modifications of these markers have been found associated with endothelial alterations, prospective clinical studies are still necessary to demonstrate their clinical relevance in vascular diseases.
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PMID:[Measurement of biological parameters of endothelial origin: value in human pathology]. 857 78

Growing evidence suggests that moderately elevated levels of homocysteine are associated not only with arterial thrombosis and atherosclerosis but also with venous thrombosis as well. We have reviewed recent studies that indicate that homocysteine inhibits several different anticoagulant mechanisms that are mediated by the vascular endothelium. The protein C enzyme system appears to be one of the most important anticoagulant pathways in the blood. Homocysteine inhibits the expression and activity of endothelial cell surface thrombomodulin, the thrombin cofactor responsible for protein C activation. Homocysteine inhibits the antithrombin III binding activity of endothelial heparan sulfate proteoglycan, thereby suppressing the anticoagulant effect of antithrombin III. Homocysteine also inhibits the ecto-ADPase activity of human umbilical vein endothelial cells (HUVECS). Because ADP is a potent platelet aggregatory agent, this action of homocysteine is prothrombotic. Homocysteine also interferes with the fibrinolytic properties of the endothelial surface because it inhibits the binding of tissue plasminogen activator. Homocysteine stimulates HUVEC tissue factor activity. We have found that lipoprotein(a) [Lp(a)] also stimulates HUVEC tissue factor activity. The combination of Lp(a) plus homocysteine induced more tissue factor activity than either agent alone. These disruptions in several different vessel wall-related anticoagulant functions provide plausable mechanisms for the occurrence of thrombosis in hyperhomocysteinemia.
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PMID:Homocysteine and hemostasis: pathogenic mechanisms predisposing to thrombosis. 864 72

TAFI (thrombin-activatable fibrinolysis inhibitor) is a recently discovered plasma protein that can be activated by thrombin-catalyzed proteolysis to a carboxypeptidase B-like enzyme that inhibits fibrinolysis. This work shows that the thrombin-thrombomodulin complex, rather than free thrombin, is the most likely physiologic activator. Thrombomodulin increases the catalytic efficiency of the reaction by a factor of 1250, an effect expressed almost exclusively through an increase in kcat. The kinetics of the reaction conform to a model whereby thrombin can interact with either TAFI (Km = 1.0 microM) or thrombomodulin (Kd = 8.6 nM), and either binary complex so formed can then interact with the third component to form the ternary thrombin-thrombomodulin-TAFI complex from which activated TAFI is produced with kcat = 1.2 s-1. This work also shows that activated TAFI down-regulates tPA-induced fibrinolysis half-maximally at a concentration of 1.0 nM in a system of purified components. This concentration of TAFI is about 2% of the level of the zymogen in plasma, which indicates that ample activated TAFI could be generated to very significantly modulate fibrinolysis in vivo. Therefore, TAFI in vitro and possibly in vivo defines an explicit molecular connection between the coagulation and fibrinolytic cascades, such that expression of activity in the former down-regulates the activity of the latter.
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PMID:TAFI, or plasma procarboxypeptidase B, couples the coagulation and fibrinolytic cascades through the thrombin-thrombomodulin complex. 866 47

The effects of hyperthermal stress on the coagulation and fibrinolytic systems were examined in five healthy subjects who took a 3-min 47 degrees C hot-spring bath. After a 3-min 47 degrees C bath, the sublingual temperature was transiently increased about 1.8 degrees C, returning to the baseline level within 60 min. The plasma level of plasminogen activator inhibitor-1 antigen (PAI-1) was transiently increased 15 min after the start of bathing and returned to the pre-bathing level 360 min later. The plasma levels of tissue plasminogen activator antigen, alpha 2 plasmin inhibitor activity, plasmin-antiplasmin complex, thrombin-antithrombin III complex, and thrombomodulin antigen were not influenced by the bath. The in vivo result correlated well with the in vitro result that PAI-1 was released from cultured endothelial cells by heating. These findings suggest that the increase in plasma PAI-1 level may be due to the direct hyperthermal action of the very hot hot-spring bath on the endothelial cells and that acute hyperthermal stress may decrease the fibrinolytic capacity, leading to the occurrence of thrombotic events.
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PMID:Effects of hyperthermal stress on the fibrinolytic system. 867 6

Markers of endothelial cell activation were measured in 28 patients presenting with various forms of limited or focal type cutaneous vasculitis. Plasma levels of tissue plasminogen activator antigen (t-PA:Ag), plasminogen activator inhibitor type 1 antigen (PAI-1:Ag) and PAI-1 activity, fibrin plate, von Willebrand factor antigen (vWF:Ag), tissue factor (TF) and soluble thrombomodulin (sTM) were measured. In comparison with the control group (n = 20) there was a significant increase in t-PA:Ag, vWF:Ag and TF (P < 0.05, Mann-Whitney U-test) in the cutaneous vasculitis group. This study confirms that measurable degrees of endothelial activation occur in cutaneous vasculitis. Cutaneous vasculitis includes a diverse group of clinical conditions, which are associated with inflammatory changes in cutaneous blood vessels with local fibrin deposition. The aetiology and pathogenesis of the majority of these entities remain unknown. Causative mediators are thought to include immune complexes, anti-endothelial cell antibodies, cytotoxic lymphocytes and viruses. Histologically, immune complexes and complement are frequently detected on the vessel wall, and serologically anti-endothelial antibodies are often detected in patients with vasculitis and in systemic lupus erythematosus (SLE) which correlate with the severity of cutaneous vasculitis, arthritis and nephritis. Lymphocyte-mediated toxicity to endothelial cells has been reported in a small number of patients with giant cell arteritis and Takayasu's arteritis. The vascular endothelium plays a central part in the control of haemostasis. Under physiological conditions endothelial cells present an anticoagulant surface to blood constituents, partially due to surface expression of heparan sulphate and thrombomodulin (TM). Heparan sulphate binds antithrombin III (ATIII), thereby accelerating inactivation of intrinsic coagulation enzymes. Thrombomodulin is an endothelial cell surface glycoprotein which promotes anticoagulation by forming a complex with thrombin which then activates protein C. Activated protein C together with a cofactor, protein S, inactivates FVa and FVIIIa. von Willebrand factor (vWF) is synthesized by endothelial cells, stored in Weibel-Palade bodies and released into the circulation upon endothelial stimulation. vWF mediates the binding of platelets to the subendothelium and is the carrier molecule for FVIIIC. The endothelium controls fibrinolysis by producing t-PA and its inhibitor PAI-1. Inflammatory cytokines such as interleukin-1 (IL-1) and tumour necrosis factor (TNF) activate endothelial cells, causing a shift from an antithrombotic to prothrombotic state, including expression of tissue factor, increased synthesis of PAI-1 and decreased expression of TM. Fibrin deposition and intravascular thrombosis are seen in cutaneous vasculitis syndromes, suggesting local endothelial cell activation. The aim of this pilot study was to assess whether perturbation of the endothelium in cutaneous vasculitis could be detected in the patients' plasma samples. If so, further studies to assess any correlation in levels of these markers with disease activity might prove useful in the future.
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PMID:Endothelial cell activation in cutaneous vasculitis. 868 65


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