The Fibrinolytic System of the Vascular Wall

Extracellular vesicles from periodontal pathogens regulate hepatic steatosis via Toll-like receptor 2 and plasminogen activator inhibitor-1

Plasminogen activator inhibitor-1 (PAI-1) is associated with nonalcoholic fatty liver disease (NAFLD) by lipid accumulation in the liver. In this study, we showed that extracellular vesicles (EVs) from the periodontal pathogens Filifactor alocis and Porphyromonas gingivalis induced steatosis by inducing PAI-1 in the liver and serum of mice fed a low-fat diet. PAI-1 induction was not observed in TLR2-/- mice. When tested using HEK-Blue hTLR2 cells, human TLR2 reporter cells, the TLR2-activating ability of serum from NAFLD patients (n = 100) was significantly higher than that of serum from healthy subjects (n = 100). Correlation analysis confirmed that PAI-1 levels were positively correlated with the TLR2-activating ability of serum from NAFLD patients and healthy subjects. Amphiphilic molecules in EVs were involved in PAI-1 induction. Our data demonstrate that the TLR2/PAI-1 axis is important for hepatic steatosis by EVs of periodontal pathogens.

Design of Novel Thrombolytic Agents via Domain Modifications*

Generation of plasmin in the vicinity of a blood clot has proven to be an effective approach for treating thrombotic disorders, particularly myocardial infarction. Conceptually, the ideal thrombolytic agent would initiate the formation of plasmin, primarily in association with fibrin incorporated into the occlusive thrombus. Thus, thrombolytic agents that exhibit relative fibrin specificity and, thus, presumably clot selectivity (e.g., tissue plasminogen activator) were expected to have a marked clinical benefit compared to agents that do not display affinity for fibrin (e.g., streptokinase). However, results obtained recently from clinical trials indicate that these 2 agents essentially were equally effective in treating myocardial infarction. With these findings in mind, efforts are being made to develop novel thrombolytic agents that might achieve more rapid and specific thrombolysis than that achieved by presently available agents and, thus, could be administered earlier because of an improved margin of safety. The available data suggest that tissue-type PA (tPA) mutants possessing resistance to endogenous inhibitors, altered fibrin affinity, and/or slower rates of clearance may prove beneficial in this regard. In addition, adjunctive therapies (i.e., anti-platelet and anti-thrombin compounds) have been found to decrease the time necessary to achieve reperfusion and have reduced rates of reocclusion. These efforts are expected to yield therapeutic agents in the 1990s and beyond that, when administered in combination, would exhibit increased efficacy in the treatment of myocardial infarction and other thrombotic disorders.

Characteristic clinical presentation and CSF biomarker pattern in cerebral small vessel disease

To be able to live a good, independent life cognitive functions need to be intact. Dementia, stroke and neuropsychiatric disorders are the major disorders underlying disability. Stroke is usually a consequence of an underlying vessel wall disease that has lasted for a longer period. This vessel wall disease is commonly silent or without prominent symptoms. Damage to the small penetrating arterioles of the brain, arteriolosclerosis, induced by aging and hypertension, as well as other factors such as diabetes and genetic vulnerability, plays an important role in the origin of white matter changes. The pathological vascular wall process leads to lumen constriction, impaired ability to change lumen diameter according to metabolic needs and possible ischemic-hypoxic tissue damage in the vulnerable vascular architectural terminal areas of the long penetrating arteries. The arteriolosclerotic blood vessels are associated with inflammation and remodelling of the extracellular matrix. Enzymes connected to this process have also been found to be involved in demyelination and blood brain barrier opening but also in the repair process of angiogenesis and neurogenesis. Biochemical changes reflecting these processes might be early indicators of small vessel disease and hence increase the knowledge about the disease characteristic mechanisms. Moreover, monitoring disease modifying treatment effects can be an important application for small vessel disease specific biochemical markers.

Glycaemic control, smoking habits and diabetes duration affect the extrinsic fibrinolytic system in type I diabetic patients but microangiopathy does not

The fibrinolytic system was studied in 43 type I diabetic patients with long duration of the disease, with or without evidence of microangiopathy, and in 26 control subjects. There were positive and independent correlations between tissue plasminogen activator (tPA) activity after venous occlusion and HbA1c, and between triglycerides and plasminogen activator inhibitor (PAI-1) and tPA antigen concentrations before and after venous occlusion. The tPA activities both at rest and after venous occlusion were higher in the patients. There were no differences with regard to sex, hypertension or nephropathy for the levels of fibrinolytic variables in these patients. Subjects with retinopathy did not differ from those without retinopathy. Diabetes duration showed a significant negative association with tPA activity in multivariate regression analysis. Tobacco-smoking diabetics, as compared to non-smoking, had an increased tPA antigen release at venous occlusion, but also higher PAI-1 levels and reduced specific activity of the tPA protein. When assessed with the new specific assays now available, the fibrinolytic parameters appear to be specific indicators of endothelial dysfunction related to smoking and to degree of glycaemic control in type I diabetic subjects.

Selective Promotion of Plasminogen Activator Inhibitor-1 Secretion by Activation of Proteinase-Activated Receptor-1 in Cultured Human Brain Microvascular Pericytes: Comparison with Endothelial Cells

Microvessels are composed of endothelial cells that cover the luminal surface and pericytes that wrap around and along endothelial cells. In the present study, we investigated the regulation of fibrinolysis in cultured human brain microvascular pericytes and endothelial cells after exposure to thrombin. It was found that the regulation in pericytes is different from that in endothelial cells. Specifically, thrombin increases the secretion of fibrinolytic proteins (tissue- and urokinase-type plasminogen activators and plasminogen activator inhibitor-1), resulting in an enhancement of plasminogen activator activity in endothelial cells, whereas the proteinase increases the secretion of only plasminogen activator inhibitor-1 by activation of proteinase-activated receptor-1 and induces suppression of plasminogen activator activity in pericytes. The present data suggest that thrombin regulation of fibrinolytic activity in endothelial cells and pericytes may be involved in the removal of intravascular thrombi and the maintenance of hemostasis, respectively, in human brain microvessels.

Central retinal vein occlusion: review of management

Central retinal vein occlusion is usually a disease of the elderly and is often associated with systemic vascular disease, e.g., hypertension, diabetes mellitus, arteriosclerotic vascular disease. Younger patients, especially those less than 45 years of age, with retinal vein occlusion should be evaluated carefully for the possibility of an underlying thrombotic tendency. The authors describe the ocular manifestations, pathogenesis, associated conditions, patient evaluation, and treatment of patients with central retinal vein occlusion.

Intrinsic Anticoagulation: Protein C, Protein S, and Thrombomodulin

The protein C anticoagulant system provides important control over the blood coagulation cascade. Any alteration in this pathway, either hereditary, iatrogenic, or otherwise, may interfere with normal coagulation. In this review, current concepts and understanding of surface-dependent hemostatis are reviewed, effects of deficiencies in the intrinsic anticoagulant system are described, and potentially useful therapeutic strategies are proposed. The importance of protein C, protein S, and thrombomodulin in patients undergoing cardiac surgery is specifically addressed. Further work is required before complex interactions of individual components of the intrinsic anticoagulation pathway are fully understood.

Lead perturbs the regulation of spontaneous release of tissue plasminogen activator and plasminogen activator inhibitor-1 from vascular smooth muscle cells and fibroblasts in culture

To evaluate the toxicity of lead on the blood fibrinolytic system during hemostasis, human aortic smooth muscle cells and human fetal lung fibroblasts were cultured in the presence of lead chloride. Tissue plasminogen activator antigen (t-PA:Ag) and plasminogen activator inhibitor-1 antigen (PAI-1:Ag) released were determined by enzyme immunoassay. It was found that lead decreased the release of both t-PA:Ag and PAI-1:Ag from vascular smooth muscle cells. On the other hand, in fibroblasts, the release of t-PA:Ag was markedly decreased whereas that of PAI-1:Ag was markedly increased by the metal. Fibrin zymography showed that lead reduced the plasminogen activator activity in the conditioned medium of both cell types. However, lead did not cause a nonspecific cell damage and an alteration of protein synthesis when evaluated by lactate dehydrogenase leakage and [14C]leucine incorporation, respectively. Lead accumulated within either vascular smooth muscle cells or fibroblasts in a dose-dependent manner; intracellular accumulation of calcium could be increased by lead. However, the effects of lead on the release of t-PA:Ag and PAI-1:Ag were different from those of calcium ionophore A23187. It was therefore suggested that regulation of spontaneous release of fibrinolytic proteins from subendothelial cells is disturbed by lead through intracellular calcium-independent pathway.

Primary fibrinolysis during supraceliac aortic clamping

PURPOSE

An increased incidence of bleeding complications has been observed after supraceliac aortic clamping (SCC). This study was performed to identify possible hemostatic abnormalities that contribute to this problem.

METHODS

A prospective cohort study over a 3-month period was performed by comparing hemostatic parameters in 10 consecutive patients who required elective SCC with those of eight concurrent randomly selected control subjects who required infrarenal clamping (IRC) for abdominal aortic reconstruction. Measures of coagulation, fibrinolysis, platelet function, temperature, hemodilution, and hepatic function were performed at selected times before, during, and after operation.

RESULTS

Aneurysm size, fibrinogen, D-dimers, prothrombin, partial thromboplastin time, platelet counts, bleeding times, hemodilution, and temperature were comparable in both groups. Patients in the SCC group, however, consistently developed a primary fibrinolytic state within 20 minutes after supraceliac clamping, reflected by significantly decreased euglobulin clot lysis times (ECLT; p < 0.0001), elevated tissue plasminogen activator (t-PA) levels (p < 0.0006), elevated t-PA-to-plasminogen activator inhibitor-1 ratios (p < 0.0001), and reduced alpha 2-antiplasmin levels (p < 0.002). SCC produced hepatocellular injury documented by elevations in both aspartate transaminase (p < 0.0001) and lactate dehydrogenase (p < 0.009).

CONCLUSIONS

SCC rapidly induces a primary fibrinolytic state manifested by increased circulating t-PA, reduced alpha 2-antiplasmin, and increased fibrinolytic activator-to-inhibitor ratios. These effects may be a result of hepatic hypoperfusion caused by SCC leading to insufficient clearance of t-PA. Antifibrinolytic agents may be of benefit if bleeding develops after aortic procedures that require supraceliac clamping.

Effects of humic acid on the viability and coagulant properties of human umbilical vein endothelial cells

We have previously shown that humic acid (well-water humic acid, HA, and synthetic humic acid, SHA) enhances cell surface expression of tissue factor (TF). Here we report that incubation of human umbilical vein endothelial cells (HUVEC) for 2 hr with HA or SHA cause a rapid rise in TF mRNA levels, as shown by Northern blot analysis. To understand the cytotoxic and fibrinolytic effects of HA and SHA on cultured HUVEC, the cells treated with varying concentrations of HA and SHA for various periods of time. Both HA and SHA (10-200 micrograms/ml) inhibited the viability of subconfluent HUVEC, cultured in the presence or absence of 20% FBS (Fetal Bovine serum) in the culture medium, in a dose-dependent manner. Both HA and SHA induced surface changes in the HUVEC as revealed by scanning electron micrography (SEM). However, protocatechuic acid, the monomer of SHA, did not significantly inhibit cell growth, and showed a cytotoxic effect only at 200 micrograms/ml. Furthermore both HA and SHA stimulated HUVEC to produce plasminogen activator inhibitor (PAI-1) and tissue plasminogen activator (t-PA) in a dose and time dependent fashion; the amount of PAI-1 produced was found to exceed that of t-PA. The monomer of SHA did not have this stimulatory effect. These results distinctly suggest that in addition to the inhibition of viability HA is involved in TF induction and PAI-1 synthesis in HUVEC and these may be some of the plausible mechanisms underlying the thrombotic disorders in Blackfoot disease.

Sphingomyelinase and cell-permeable ceramide analogs increase the release of plasminogen activator inhibitor-1 from cultured endothelial cells

We investigated the effect of exogenous staphylococcal sphingomyelinase (SMase) on the release of tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) from cultured human umbilical vein endothelial cells (HUVEC). Addition of SMase (2 units/ml) to the culture medium induced an approx. 15-fold increase in the extracellular level of PAI-1 antigen at 3 h. No significant increase in the level of t-PA antigen was detected. Treatment of HUVEC with SMASE (2 units/ml) for 3 h resulted in a significant decrease in the cellular sphingomyelin (SM) level, accompanied by a corresponding increase in the ceramide level. Cell-permeable ceramide analogs also enhanced the release of PAI-1 from cultured HUVEC in concentration- and time-dependent manners. A 6-fold increase in PAI-1 antigen level was observed after incubation for 3 h with 10 microM N-acetylsphingosine. Similar effect was noted as early as 2 h with 10 microM N-hexyanoylsphingosine. Addition of sphingosine failed to affect the release of PAI-1 from cultured HUVEC, indicating that the effects of ceramide analogs were independent of sphingosine generation. Pretreatment with cycloheximide or actinomycin D abated the response of HUVEC to N-acetylsphingosine in the increased levels of both extracellular and intracellular PAI-1. These results suggest that ceramide, generated via "SM cycle", acts as a lipid mediator of PAI-1 release from vascular endothelial cells, and may contribute to a better understanding of the pathogenesis of the PAI-1-associated thrombotic disorders.

Distinction of endothelial cell growth and fibrinolytic activity between WKY/Izm and SHRSP/Izm in vitro

1. In the present study, endothelial cells (EC) growth and fibrinolytic activity of WKY/Izm and SHRSP/Izm were investigated in vitro. 2. EC were isolated from the thoracic aortas of WKY and SHRSP at the age of 8-9 weeks. Proliferative activities of EC were analysed with doubling time and DNA synthesis. Fibrinolytic activity was determined by tissue type plasminogen activator (tPA) and plasminogen activator inhibitor type 1 (PAI-1) activities in cultured medium. 3. SHRSP-EC growth rate was significantly greater than WKY-EC growth rate in doubling time. In the assay for DNA synthesis, 5-bromo-2'-deoxy uridine incorporation rate in SHRSP-EC was significantly increased compared with that in WKY-EC. 4. The tPA activity in cultured medium of WKY-EC was 2-fold greater than that of SHRSP-EC, while PAI-1 activities were nearly equal in them. 5. These physiological distinctions of EC of SHRSP/Izm from that of WKY/Izm with close genetic background could be contributory genetic factors to hypertension-related vascular diseases in SHRSP.

Retroviral vector-mediated transfer and expression of human tissue plasminogen activator gene in human endothelial and vascular smooth muscle cells

PURPOSE

Enhancement of the fibrinolytic activity of vascular cells by tissue plasminogen activator (tPA) gene transfer has considerable clinical potential. However, it is unknown whether greater constitutive expression of the tPA gene might increase plasminogen activator inhibitor-1 (PAI-1) secretion, which could negate expected increases in fibrinolytic activity that accompany greater tPA protein production. The objective of this investigation was to determine whether transduction of human endothelial cells (EC) and vascular smooth muscle cells (SMC) with a retroviral vector containing the human tPA gene would increase tPA production and what effect this would have on endogenous PAI-1 secretion and subsequent fibrinolytic activity.

METHODS

Cultivated human EC and SMC either were transduced with a murine leukemia retroviral vector (MFG) containing the human tPA gene and, in the case of controls, the lacZ gene, or they were exposed to media alone. On days 14 and 28 after transduction, supernatent tPA antigen and PAI-1 antigen levels were measured by ELISA, and supernatent tPA activity was quantitated with a spectrolyse tPA/PAI assay.

RESULTS

Southern and Northern blot analyses documented integration and transcription of the tPA gene in both EC and SMC. Greater tPA antigen production occurred in MFG-tPA-transduced EC and SMC compared with nontransduced or MFG-lac Z-transduced cells (p < 0.05). The tPA activity increased in transduced human saphenous vein EC (up to 5.1-fold) and human iliac artery EC (up to 4.7-fold), but no increased tPA activity occurred in transduced SMC, compared with nontransduced or MFG-lac Z-transduced cells (p < 0.05). PAI-1 antigen was unchanged in transduced SMC but decreased in MFG-tPA-transduced EC (p < 0.05). PAI-1 mRNA was unchanged in the transduced EC and SMC compared with nontransduced cells, suggesting that posttranslational events may have caused the changes in EC PAI-1.

CONCLUSIONS

This investigation demonstrated that MFG-mediated tPA gene transfer into human EC resulted in a significant increase in tPA activity. Enhancement of adult human EC fibrinolytic activity by transfer of the human tPA gene has not been previously reported and represents a necessary finding in the development of this gene therapy technology for the prevention of thrombotic complications of vascular disease.

Plasminogen activator inhibitor-1 in the pathogenesis of delayed radiation damage in rat spinal cord in vivo

The pathophysiology of radiation-induced damage to the central nervous system (CNS) is poorly understood. Preliminary data suggest that fibrinolytic inhibitors are involved in the development of necrosis. In this study, cervical spinal cord irradiation was studied in 90 rats by measuring plasminogen activator inhibitor (PAI)-1 on Days 2, 7, 30, 60, 90, 120, 130, or 145 after irradiation. Paralysis due to radiation necrosis developed in all animals kept alive for 140 to 150 days. Assay of PAI-1 was by Western blot, enzyme-linked immunosorbent assay (ELISA), and complex formation with 125I-labeled urokinase. No PAI-1 was detected in normal spinal cord tissue or in irradiated spinal cord up to Day 90. However, PAI-1 was detected at Day 120 and was marked by elevated ELISA levels at the time of paralysis. Western blot showed detectable PAI-1 (51 kD) at Day 120 and very significant levels at the time of paralysis. Complex formation with 125I-labeled urokinase was also detected at Day 120 with similar results. Immunohistochemical studies showed that PAI-1 was highly concentrated within and immediately adjacent to zones of necrosis at 145 days and was absent in normal tissue. This study adds considerable weight to the proposal that PAI-1 is closely associated with the pathogenesis of CNS radiation necrosis.

Capturing host plasmin(ogen): a common mechanism for invasive pathogens?

Plasmin is a potent enzyme that can dissolve blood clots and degrade extracellular matrix proteins. A number of pathogenic bacteria produce plasminogen activators. Many of these organisms can also bind plasmin(ogen) to surface receptors and protect the active enzyme from physiological inhibition. Cell-surface localization of plasmin may be a common mechanism used by bacteria to facilitate movement through normal tissue barriers.

Cadmium stimulation of plasminogen activator inhibitor-1 release from human vascular endothelial cells in culture

We investigated the effect of cadmium (0.5, 1.0 or 2.0 microM) on the release of plasminogen activator inhibitor-1 antigen (PAI-1:Ag) from cultured human vascular endothelial cells. It was found that cadmium at 1.0 and 2.0 microM significantly increased the PAI-1:Ag release from the cells after a 24-h incubation. However, the tissue plasminogen activator antigen (t-PA:Ag) release was not changed by the metal. Although nickel as well as cadmium increased the PAI-1:Ag release, the other heavy metals including cobalt, zinc and copper did not exhibit such a stimulatory effect. The incorporation of [3H]leucine into the acid-insoluble fraction of the cell layer was unchanged by cadmium, suggesting that the metal may stimulate the synthesis of PAI-1 without association with generalized increase in protein synthesis. Cadmium at 1.0 and 2.0 microM significantly decreased the t-PA activity in the medium. The present study showed that cadmium increases the release of PAI-I:Ag from cultured endothelial cells without non-specific stimulation of protein synthesis. The decrease in the t-PA activity suggests an implication of cadmium in vascular lesion which is mediated by anti-fibrinolytic activity.

Contribution of sinusoidal endothelial liver cells to liver fibrosis: expression of transforming growth factor-beta 1 receptors and modulation of plasmin-generating enzymes by transforming growth factor-beta 1

Transforming growth factor-beta 1 is an important cytokine in the pathophysiology of liver fibrosis, stimulating the production of extracellular matrix. Whether this cytokine can also control the degradation of matrix proteins in liver cells has not been investigated. Because plasmin is an important protease for the degradation of matrix glycoproteins, we investigated whether sinusoidal endothelial liver cells could contribute to fibrosing liver disease through the modulation of plasmin-generating enzymes in response to transforming growth factor-beta 1. Sinusoidal endothelial cells from guinea pig liver were investigated in pure monolayer culture. Using 125I-labelled transforming growth factor-beta, we demonstrated high-affinity binding sites on sinusoidal endothelial cells at a density of 9.3 x 10(2) per cell, and a dissociation constant of about 5.5 x 10(-11) mol/L. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed the known three classes of membrane receptors for transforming growth factor-beta. Using biosynthetic labeling of proteins with 35S-methionine, immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, we showed that sinusoidal endothelial cells produce and secrete plasminogen activator inhibitor type 1 from the beginning of culture. Treatment of confluent cell cultures for 24 hr with transforming growth factor-beta 1 increased synthesis and release of plasminogen activator inhibitor type 1. The response was almost maximal at a concentration of 1 ng transforming growth factor-beta/ml and paralleled the increased synthesis of fibronectin. On reverse fibrin autography we proved that transforming growth factor-beta 1 stimulated the release of functionally active plasminogen activator inhibitor type 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Production of prostacyclin and fibrinolysis modulators by endothelial cells cultured in the presence of polyethylene terephthalate

The aim of this study was the evaluation of the in vitro production of prostacyclin, and of tissue plasminogen activator (tPA) and its inhibitor, PAI-1, by human endothelial cells cultured in the presence of polyethylene terephthalate (PET). After a 48 h contact between the cells and the polymer, the concentration of 6-keto-PGF1 alpha, a stable metabolite of prostacyclin, tPA, and PAI-1, was assayed on the supernatants. Contact of the endothelial cells with PET produced a highly significant reduction of 6-keto-PGF1 alpha with respect to control cultures. Tissue plasminogen activator concentration in the supernatants of the cultures in contact with the material was similar to that observed in the controls, while PAI-1 production was significantly reduced. It can be concluded that the contact between endothelial cells and PET determines a reduction in the platelet aggregability and an increase of the fibrinolytic activity due to a decrease in PAI-1, while tPA concentration remains unchanged.

Regulation of endothelial cell protein C activation and fibrinolysis by procoagulant albumin

Endothelial cell regulation of protein C activation and fibrinolysis are important components of the hemostatic response to vascular injury or perturbation. Procoagulant albumin (P-A1), a constituent of normal human plasma has been purified and identified as an inducer of endothelial cell tissue factor activity. The purpose of the studies reported herein was to investigate the effects of P-A1 on human endothelial cell protein C activation and fibrinolysis. P-A1 suppressed protein C activation, enhanced release of plasminogen activator inhibitor-1, but had no effect on tissue-plasminogen activator release. Plasminogen activator inhibitor-1 released by P-A1 was functional as evidenced by the capacity to form a covalent complex with 125I-urokinase. Inactive albumin (isolated during the same purification procedure as P-A1, but without tissue factor-inducing activity) did not suppress protein C activation or increase plasminogen activator inhibitor-1 release. These results indicate that P-A1, a component of human plasma, can modulate multiple vascular hemostatic properties, and support the hypothesis that P-A1 is involved in normal or pathologic hemostasis.

Tissue plasminogen activator, plasminogen activator inhibitor, and other parameters of fibrinolysis in the early stages of taurocholate acute pancreatitis in rats

It is well known that fibrinolytic activity in the early stages of acute experimental pancreatitis (AEP) as assessed by euglobulin lysis time (ELT) is depressed. The aim of this study was to evaluate changes in the fibrinolytic system in the early stages of taurocholate AEP in rats. Tissue plasminogen activator (t-PA) activity, plasminogen activator inhibitor 1 (PAI-1) activity, plasminogen, alpha 1 proteinase inhibitor (alpha 1 PI), alpha 2 antiplasmin (alpha 2 AP), antithrombin III (AT III), fibrinogen, and ELT were measured 0.5, 1, 3, and 6 h after the induction of taurocholate AEP in rats, as well as in sham-operated animals and the control group, which was not submitted to any operation. T-PA activity decreased significantly after 3 and 6 h of AEP; PAI activity had a time course reverse to t-PA and was parallel to alpha 1 PI activity. ELT was slightly prolonged after 0.5, 1, and 3 h, whereas alpha 2 AP activity and plasminogen levels increased significantly; AT III activity was increased after 1 h in comparison to control group. Sham operation caused nonsignificant changes in fibrinolysis. Increase of PAI activity and decrease of t-PA could be a reasonable explanation for inhibited plasma euglobulin fibrinolytic activity noted in the early period of AEP.

N-oleoyl heparin inhibits the amidolytic activity of plasmin and urokinase

N-desulphated heparin, partially N-acylated on average with three oleoyl chains per molecule, inhibits the amidolytic activity of plasmin (IC50 16 nM) and urokinase (IC50 10mM) when assayed on N-p-tosyl-Gly-Pro-Lys-4-nitroanilide and benzoyl-Ala-Gly-Arg-4-nitroanilide substrates respectively. N-desulphated heparin is not inhibitory. This effect requires the covalent binding of oleoyl residues to heparin and it decreases with increasing concentration of Tris-HCl and non-ionic detergents.

Prothrombotic and fibrinolytic function of normal and perturbed endothelium

Endothelium mediates thrombosis and fibrinolysis in part through cell-based production and binding of coagulation factors and anticoagulant moieties. A variety of biologically active agents (homocysteine, interleukin-1, and endotoxin) and environmental factors (mechanical injury and hypoxia) can upset the homeostasis of the coagulation system leading in vitro and in vivo to abnormal propensity for thrombin formation. None of the above agents or any similar agents have been demonstrated to inhibit clotting factors or thrombosis formation. As one would expect, injury to endothelium even on a sublethal basis promotes a procoagulant response. This procoagulant response appears to be multifactorial and multiphasic. Gross injury leads to factor release by dead or dying cells with rapid promotion of thrombosis by neighboring infact cells. A more subtle prothrombotic state promulgated by viable cells appears after sublethal perturbation and is characterized by protein synthesis-dependent production of endothelial-produced clotting factors in the early stages of injury with subsequent return to normal levels of these factors by 24 hr. A second phase of abnormal levels of fibrinolysis inhibitors and possible reduction in fibrinolysis promoters appears to follow up to 48 hr after the initial injury. Thus the cell can be viewed as producing means of promoting thrombus formation followed by preventing thrombus dissolution. The data presented in this article are primarily cell culture data and are thus limited both in physiologic applicability and in ability to define over long periods the relevance of those findings to other cells in the hemostatic system. Nonetheless, in vivo data of endothelial perturbation correlate with the in vitro findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Familial clustering of defective release of t-PA

91 unrelated patients with idiopathic or familial deep vein thrombosis (DVT) and 72 (34 with DVT) relatives from 26 families were screened for hypofibrinolysis by measuring tissue plasminogen activator antigen (t-PA:Ag) after venous occlusion (VO) for 10 and 20 min and by measuring t-PA inhibitor activity (PAI) at rest. 21 healthy subjects served as controls. Defective release of t-PA:Ag was found in eight out of the 91 patients (9%). A partial family study of six of these eight patients was performed. This study included 10 family members with and 21 without DVT. A defective release of t-PA:Ag was found in 50% (5/10) of the family members with DVT, which is significantly more frequent than the 9% (8/91) prevalence in the unrelated patients (P less than 0.001). Furthermore, 24% (5/21) of asymptomatic members of these families also had defective release of t-PA:Ag. In the 18 families where the propositus had a normal level of t-PA:Ag, none of the 24 studied family members with DVT had defective release of t-PA:Ag. In contrast to the defective release of t-PA:Ag, increased basal level of PAI did not show familial clustering. In conclusion, low release of t-PA during VO shows familial clustering in a proportion of the cases.

Relationship between plasma levels of components of the fibrinolytic system and acute-phase reactants in patients with uterine malignancies

Plasma samples from 17 patients with endometrial cancer and from 52 patients with cervical carcinoma were determined with respect to their levels of components of the fibrinolytic system (tissue-type plasminogen activator antigen, urokinase-type plasminogen activator antigen, plasminogen activator inhibitor activity) and related to the observed alterations of three acute-phase reactants (C-reactive protein, coeruloplasmin, alpha-1-antitrypsin). As shown previously, uterine malignancies, especially at later stages, exhibited significant increases in plasma levels of urokinase-type plasminogen activator antigen as compared to an age-matched control group. In contrast, tissue-type plasminogen activator antigen and plasminogen activator inhibitor activity remained unchanged. Determination of the acute-phase reactants revealed significant changes in the case of C-reactive protein and coeruloplasmin in later tumour stages. However, the increase in urokinase-type plasminogen activator antigen did not correlate with the increase of either C-reactive protein or coeruloplasmin plasma level. These data indicate that the increase in plasma urokinase-type plasminogen activator antigen in patients with uterine malignancies does not follow the pattern of common acute-phase reactants, like C-reactive protein or coeruloplasmin.

Structure and expression of the human gene encoding plasminogen activator inhibitor, PAI-1

The gene (pai1) encoding human plasminogen activator inhibitor, PAI-1 was cloned from a lambda EMBL3 genomic library and was found to span approx. 12 kb and to contain eight introns. Primer extension and S1 nuclease analyses both showed the transcription start point to be located 142 nt upstream from the start codon. The 5'-flanking region was sequenced and found to contain a TATA box, but no CAAT sequence. When a fragment containing 730 nt of 5'-untranslated region was placed upstream from a promoterless cat gene, it was shown to function as a promoter when transfected into COS cells. Northern-blot analysis was consistent with low level expression of the endogenous pai1 gene in COS cells. When the pai1 gene structure was compared to those of other members of the serine-protease-inhibitor encoding gene family, little conservation of intron positions was observed.

Tissue plasminogen activator-induced secretion of type-1 plasminogen activator inhibitor in cultured human fibroblasts

Tissue plasminogen activator (t-PA) regulation of type-1 plasminogen activator inhibitor (PAI-1) secretion by WI-38 human fibroblasts was investigated utilizing a specific ELISA to measure PAI-1 antigen levels. Incubation of confluent fibroblasts with t-PA in serum-free medium resulted in a concentration and time-dependent increase in the secretion of PAI-1, with the maximum response (a two-fold increase) observed following a 4 hour incubation with 0.1 microM t-PA. This t-PA effect was reduced by cycloheximide, suggesting that the involvement of specific protein synthesis, and by inhibitors of t-PA's enzymatic activity, suggesting a requirement for a free catalytic site. The t-PA effect could not be attributed to endotoxin contamination. Increased levels in cell-associated PAI-1 were also detected following incubation of fibroblasts with t-PA. This previously undescribed effect, although seen at relatively high concentrations of t-PA, may have important biological implications.

The organization of the human-plasminogen-activator-inhibitor-1 gene. Implications on the evolution of the serine-protease inhibitor family

Plasminogen activator inhibitor 1 (PAI-1) is a member of the serine protease inhibitor super family (SERPINS) which is thought to play an integral role in the control of plasminogen activation. PAI-1 inhibits both tissue-type plasminogen activator and urokinase-type plasminogen activator and may therefore be implicated in the control of various physiological processes. We have isolated the PAI-1 gene including its 5'-flanking sequence. The gene was characterized by restriction enzyme analysis, Southern blotting and DNA sequencing of all the coding parts as well as the 5'-flanking region. The PAI-1 gene contains nine exons and eight introns distributed over approximately 12.3 kb of DNA. All exon/intron boundaries agree with the 'GT-AG' rule. To characterize the presumptive promoter region, 800 bp of the 5'-flanking region was sequenced and potential binding sites for transacting transcriptional factors were localized. The transcription initiation site was identified by S1 protection experiments and is located 25 base pairs downstream of a TATA consensus sequence. By aligning the gene structure of PAI-1 and four other SERPINS and extrapolating a general tertiary structure to these SERPINS, we find that most introns map between subdomain structures of the proteins. Evidence is presented supporting an intron loss model for the evolution of the SERPIN family.

The role of coagulation, fibrinogenolysis and fibrinolysis in the development of fluid and clotted cadaver plasma

Parameters for coagulation, fibrinogenolysis and fibrinolysis were measured in order to understand the formation of fluid or clotted cadaver plasma. All values found were distinctly elevated without significant differences between fluid and clotted material. The electrophoretic banding pattern of the fibrinogen and fibrin material also proved extensive coagulation and fibrinolysis in all cases. In vitro experiments in which similar electrophoretic banding patterns were obtained suggested that the development of fluid cadaver plasma depends on the activation of fibrinolysis prior to complete coagulation, and is enhanced by persistence of circulation as well as a physiological pH (7.4). In correspondence to post mortal time only an increase in elastase values was found.

Detection of both type 1 and type 2 plasminogen activator inhibitors in human cells

This report describes the development and use of functional immunoradiometric assays that distinguish the activity of beta-migrating endothelial-type plasminogen activator inhibitor (PAI-1) from that of placental-type plasminogen activator inhibitor (PAI-2). These assays are based upon the binding of PAI-1 and PAI-2 to immobilized single-chain tissue-type plasminogen activator (tPA) and to immobilized urokinase (UK), respectively. The extent of binding of each PAI is quantified by incubating the PAI-PA complex first with rabbit antiserum specific for the individual PAI and then with 125I-labeled goat antirabbit IgG. In control experiments, the assays were shown to be sensitive, dose-dependent over a wide range, and specific for each PAI. These assays were employed to establish the PAI profile of a variety of human cells. Neither PAI-1 nor PAI-2 could be detected in Bowes melanoma cells or in a renal adenocarcinoma cell line (ACHN), while the histiocytic lymphoma cell (U-937) produced only PAI-2. Five cell lines, including two that were previously shown to contain one or the other PAI (e.g., umbilical vein endothelial cells and a fibrosarcoma cell line, HT-1080) in fact contained both PAIs. The cells containing both PAIs were studied in more detail. In each case, SDS treatment of CM was shown to enhance PAI-1 activity (by converting the latent form of this inhibitor into its active form) and to destroy PAI-2 activity. Various compounds including interleukin 1, dexamethasone, and phorbol myristate acetate were found to selectively influence the cellular production of one PAI without concomitantly affecting the production of the other, suggesting that the synthesis of these inhibitors is not coordinately regulated.

In vitro and in vivo interactions of cells with biomaterials

The biocompatibility of materials at an implant site involves a complex interaction of cells and tissues with the biomaterial. This cell-cell and cell-polymer interaction evokes the release of mediators such as chemotactic and growth factors that elicit and sustain inflammatory responses at the implant site. In this review, we summarize the interaction of cells with biomaterials in vitro and in vivo.