Impaired fibrinolysis and risk of thromboembolism

Intermittent pneumatic compression and deep vein thrombosis prevention in postoperative patients

High incidence of venous thromboembolism (VTE) makes prophylaxis, screening and treatment extremely important. Both pharmacological and mechanical techniques can be used to reduce the risk of deep vein thrombosis (DVT). Mechanical methods have been studied much less intensively than pharmacological options. The principal mechanical methods of prophylaxis are graduated compression stockings and intemittent pneumatic compression devices. We conducted a meta-analysis of all randomized controlled trials to determine the effectiveness of intermittent pneumatic compression (IPC) devices in the preventon of DVT in post-surgical patients. The results of this analysis indicate that IPC devices reduced the risk of DVT by 60% when compared with patients with no mechanical or pharmacological prophylaxis. Contemporary randomized trials should be undertaken to test the utility of IPC in medcal patients as well as combined pharmacological plus IPC prophylaxis in both medical patients.

Coagulation and Fibrinolysis in Preeclampsia and Neonates

Coagulation and fibrinolysis were determined in 67 Indonesian women admitted to the University Hospitals for delivery in Medan. They were diagnosed to be at term gestation (mean 39.3 ± 1.1 weeks) with moderate and severe preeclampsia (n=32) and in labor, and 8 had preterm labor (gestation mean 33.5 ± 2.6 weeks). Twenty-seven normal pregnant women in labor (gestation mean 39.7 ± 1.0 weeks) served as controls. Cord blood from 23 neonates from normal pregnancy and 31 neonates from preeclampsia was also evaluated. Preeclamptic women in labor showed further enhanced coagulation activation (F1+2) with raised urokinase-like plasminogen activator (u-PA) activity and reduced plasminogen activator inhibitor-2 (PAI-2) levels. In preterm preeclampsia, significantly reduced antithrombin III (ATIII) and PAI-2 levels with further elevated tissue-type PA (t-PA) antigen and plasminogen activator inhibitor-1 (PAI-1) antigen were seen compared to normal pregnancy. These would suggest a state of enhanced thrombin generation with elevated fibrinolytic/inhibitor proteins in preterm preeclampsia. The reduced PAI-2 levels seen in preeclampsia have been suggested to be associated with reduced placental function. Neonates born to mothers of either normal pregnancy or preeclampsia at term showed similar hemostatic changes with reduced fibrinogen, ATIII, t-PA, u-PA antigen, PAI-1 levels, and coagulation activation compared to their respective maternal plasma levels. No significant differences in hemostatic parameters studied between the neonates of both cohorts were seen, and this would suggest that the neonates were protected from the adverse effects of preeclampsia and their hemostatic system was physiologically balanced.

Impact of fibrate therapy on plasma plasminogen activator inhibitor-1: a systematic review and meta-analysis of randomized controlled trials

OBJECTIVE

The aim of this systematic review was to perform a meta-analysis of randomized controlled trials (RCTs) examining the efficacy of fibrate therapy in reducing plasma concentration or activity of plasminogen activator inhibitor 1 (PAI-1).

METHODS

Scopus and MEDLINE databases were searched (up to October 15, 2014) to identify RCTs investigating whether fibrates lower plasma PAI-1 concentration or activity. A random-effects model and the generic inverse variance method were used for quantitative data synthesis. Sensitivity analyses were conducted using the one-study remove approach. Random-effects meta-regression was performed to assess the impact of potential moderators on the estimated effect sizes.

RESULTS

A total of 14 RCTs examining the effects of gemfibrozil (6 trials), bezafibrate (4 trials), and fenofibrate (5 trials) were included. Meta-analysis suggested that fibrate therapy did not significantly reduce plasma PAI-1 concentration (weighed mean difference [WMD]: -11.39 ng/mL, 95% CI: -26.64, 3.85, p=0.143) or activity (WMD: 2.02 U/mL, 95% CI: -0.87, 4.90, p=0.170). These results remained unchanged after subgroup analysis according to duration of treatment (<12 and ≥12 weeks) and type of fibrate administered (fenofibrate, bezafibrate or gemfibrozil). The estimated effects of fibrate therapy on plasma concentration and activity of PAI-1 were independent of treatment duration and changes in plasma triglyceride levels in the meta-regression analysis.

CONCLUSION

This meta-analysis of RCTs suggested that fibrate therapy does not reduce plasma concentration or activity of PAI-I. The putative benefits of fibrate therapy in patients with cardiovascular disease appear to be exerted via mechanisms independent of effects on PAI-1.

Prevalence of asymptomatic lower limb venous thrombosis in infertile women with thrombophilic disorders

OBJECTIVE

We sought to assess the prevalence of asymptomatic venous thrombosis in infertile women with thrombophilic disorders (TDs).

METHODS AND RESULTS

A total of 73 infertile women with TDs underwent duplex ultrasound scan to evaluate superficial and deep venous circulation of lower limbs. A control group of 35 infertile women without TDs was included. A single TD was found in 13 (17.8%) subjects, and 40 (54.8%) women presented a combined defect (more than three alterations). No residual mural thrombosis (RT) was noted in any deep veins. We found RT in 48 (65.8%) patients of TD group, while no RT was found in the control group (p < 0.0001). None of the clinical and prothrombotic factors were predictors of RT (all p > 0.20), and frequency of TD did not correlate with multi-vessel RT (p = 0.252).

CONCLUSIONS

No signs of deep vein thrombosis but high prevalence of superficial RT is present in infertile women with TDs. Further studies are needed to assess the prognostic value of our findings.

Plasminogen activator inhibitor-1 gene: selection of tagging single nucleotide polymorphisms and association with coronary heart disease

OBJECTIVE

To explore the effect of plasminogen activator inhibitor-1 (PAI-1) gene variations on the risk of coronary heart disease (CHD) in Chinese Han population.

METHODS AND RESULTS

We screened all exons and the promoter region of PAI-1 gene in 48 patients and identified 17 polymorphisms. Five tagging single nucleotide polymorphisms were selected and genotyped in 816 patients with CHD and 937 controls. In the total sample, no main effects of the loci or haplotypes reached statistical significance after adjusting environmental covariates. However, a strongly significant gene-smoking interaction was observed. Among nonsmokers, 2 polymorphisms located at promoter region (rs2227631 and rs1799889) showed significant association with CHD. The cases had higher frequency of rs2227631 A allele and rs1799889 4G allele than the controls (0.42 versus 0.33, P=0.001; 0.60 versus 0.52, P=0.002). Haplotype analyses confirmed the effects of the PAI-1 gene-smoking interaction on CHD risk. Compared with the most common haplotype G-5G-A-A-T (35.1%), the haplotype A-4G-A-A-C (32.7%) significantly increased the risk of CHD with adjusted odds ratio of 1.51 (95% CI, 1.12 to 2.05; P=0.008) in nonsmokers.

CONCLUSIONS

This study identified a significant interaction between PAI-1 gene and smoking status. Both single locus and haplotype analyses indicated that rs2227631 A allele and rs1799889 4G allele increased the risk of CHD among nonsmokers in Chinese.

Plasminogen activator inhibitor-1 4G/5G polymorphism in Turkish children with cerebral infarct and effect on factor V 1691 A mutation

The thrombotic risk of carrying plasminogen activator inhibitor-1-675 4G allele was found to be controversial in previous studies. The aim of this study was to evaluate the possible effect of plasminogen activator inhibitor-1 4G/5G polymorphism in the pathogenesis of childhood stroke. The case-control study included 43 patients with cerebral infarct who were below the age of 18 years (range, 10 months to 18 years) and 113 healthy unrelated individuals without family histories of thrombosis. Plasminogen activator inhibitor-1 4G/5G polymorphism was analyzed according to a previously described method. There was no statistically significant difference in patient and control groups for the distribution of plasminogen activator inhibitor-1 4G/5G polymorphism (P = .75) (allele frequency 4G controls: 0.50; patients: 0.53). However, there was a significant difference for the factor V (FV) 1691 A mutation for both groups (P = .0007).

Job strain and risk indicators for cardiovascular disease in young female nurses

This study examined the possible effects of job demands, decision latitude, and job-related social support on risk indicators for cardiovascular disease (CVD) in 165 female nurses. Job strain was measured with the Job Content Questionnaire; CVD risk was measured with insulin, total cholesterol, triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), fibrinogen, tissue-type plasminogen activator (tPA) antigen, tPA activity, plasminogen activator inhibitor-1 antigen, and blood pressure. Multivariate analysis of covariance and regression analyses revealed no effects of either job strain or social support on these risk indicators. All risk indicators deteriorated with age and body mass index. Oral contraceptive use improved fibrinolytic potential and increased HDL-C but had adverse effects on TG levels. Results suggest that in healthy young women job strain is not associated with an unfavorable metabolic or fibrinolytic risk profile.

Effect of plasminogen activator inhibitor-1 4G/5G polymorphism in Turkish deep vein thrombotic patients with and without FV1691 G-A

A decreased fibrinolytic activity due to increased levels of plasminogen activator inhibitor-1 has been shown in deep vein thrombosis patients. Elevated plasma plasminogen activator inhibitor-1 levels are associated with the 4G allele of a 4G/5G polymorphism located in the promoter region of the plasminogen activator inhibitor-1 gene. Because there is no existing data in the Turkish population, we aimed to study these mutations in patients with deep vein thrombosis (n = 136) and normal controls (n = 113), consecutively selected among unrelated healthy subjects without personal and familial history of atherothrombosis from Ankara, Turkey. DNA was extracted by conventional methods, and polymerase chain reaction of the plasminogen activator inhibitor-1 4G/5G polymorphism was performed according to a previously described method. Genotype distributions of FV 1691G-A and plasminogen activator inhibitor-1 4G/5G are as follows: plasminogen activator inhibitor-1 4G (patients) 0.562, plasminogen activator inhibitor-1 4G (controls) 0.50 (p = 0.6); FV1691A (patients) 0.147, FV1691A (controls) 0.035 (p = 0.005). Our data indicated that plasminogen activator inhibitor-1 4G/5G does not have an effect on the thrombotic risk. Carrying the 4G allele either in heterozygous or homozygous state increases the risk in the presence of FV1691A (odds ratio: 9.8 and 6.9, confidence interval 95% 2.9-32.7 and 1.3-35.8). FV1691A is an independent risk factor for thrombosis (odds ratio: 5.5, confidence interval: 95% 2.5-12.1). We concluded that coexistence of FV1691A and plasminogen activator inhibitor-1 4G allele leads to an increased risk for thrombosis leading a further evidence to another prothrombotic factor that may be necessary for the development of a manifest thrombotic event.

Work stress and metabolic and hemostatic risk factors

OBJECTIVE

A high level of work stress has been associated with cardiovascular disease. However, the pathophysiological mechanisms underlying this association remain unclear. This study examined the effect of work stress on a cluster of metabolic and hemostatic risk factors.

METHODS

Blood was collected three times, on the first, third, and fifth day of a work week, from 124 middle-aged, white-collar workers. Metabolic measures were insulin, glucose, triglycerides, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and total cholesterol. Hemostatic measures were fibrinogen, tissue-type plasminogen activator activity, tissue-type plasminogen activator antigen, and type 1 plasminogen activator inhibitor antigen. Chronic work stress was defined according to Siegrist's model as 1) a combination of high effort and low reward at work (effort-reward imbalance) or 2) high overcommitment (an exhaustive work-related coping style).

RESULTS

Overcommitment, but not imbalance or the imbalance-overcommitment interaction, was associated with an impaired fibrinolytic system, as reflected in decreased tissue-type plasminogen activator activity levels and increased type 1 plasminogen activator inhibitor antigen levels on all three measurement occasions. After controlling for body mass index, total cholesterol, triglycerides, high-density lipoprotein/low-density lipoprotein cholesterol ratio, glucose, and insulin, the relation between overcom-mitment and the fibrinolytic factors was attenuated but remained significant.

CONCLUSIONS

The results suggest that individuals with an exhaustive coping style at work have an impaired fibrinolytic capacity that is possibly due to the effects of chronic stress on insulin resistance.

Effects of native, triglyceride-enriched, and oxidatively modified LDL on plasminogen activator inhibitor-1 expression in human endothelial cells

Whereas VLDL has consistently been shown to induce a concentration-dependent increase in the expression of plasminogen activator inhibitor-1 (PAI-1) in human umbilical vein endothelial cells (HUVECs) and liver cells, variable effects have been reported for native and oxidatively modified LDL. In the present study, activation of PAI-1 protein and mRNA expression by native LDL (nLDL), UV-oxidized LDL (uvLDL), and triglyceride (TG)-enriched LDL was studied in HUVECs by using different incubation times and a wide range of lipoprotein concentrations. No significant increase of PAI-1 protein expression was observed after 4 hours of incubation with nLDL or uvLDL. However, PAI-1 protein secretion from HUVECs was markedly enhanced after 18 hours of incubation with uvLDL (200% increase at 10 microg/mL). Stimulation of PAI-1 protein expression in HUVECs by nLDL was seen, however, after increasing the TG content of the LDL particle. LDL enriched in phospholipid had no effect on PAI-1 secretion. PAI-1 mRNA levels on northern blot increased in parallel with the activation of PAI-1 protein expression by native and modified forms of LDL. Low concentrations of TG-enriched LDL (10 microg/mL) and higher concentrations of nLDL and uvLDL (100 microg/mL) were found to increase the binding of a VLDL-inducible transcription factor to the PAI-1 promoter. These results indicate that the TG content of the LDL particle influences PAI-1 expression in endothelial cells. Low concentrations of uvLDL enhanced PAI-1 protein and mRNA expression in the HUVECs after an 18-hour incubation but did not influence the VLDL-inducible transcription factor. This suggests that low levels of oxidized LDL increase PAI-1 expression by a different mechanism than VLDL and TG-enriched LDL.

PPARgamma activation in human endothelial cells increases plasminogen activator inhibitor type-1 expression: PPARgamma as a potential mediator in vascular disease

Plasminogen activator inhibitor type-1 (PAI-1) is a major physiological inhibitor of fibrinolysis, with its plasma levels correlating with the risk for myocardial infarction and venous thrombosis. The regulation of PAI-1 transcription by endothelial cells (ECs), a major source of PAI-1, remains incompletely understood. Adipocytes also produce PAI-1, suggesting possible common regulatory pathways between adipocytes and ECs. Peroxisomal proliferator-activated receptor-gamma (PPAR)gamma is a ligand-activated transcription factor that regulates gene expression in response to various mediators such as 15-deoxy-Delta12, 14-prostaglandin J2 (15d-PGJ2) and oxidized linoleic acid (9- and 13-HODE). The present study tested the hypotheses that human ECs express PPARgamma and that this transcriptional activator regulates PAI-1 expression in this cell type. We found that human ECs contain both PPARgamma mRNA and protein. Immunohistochemistry of human carotid arteries also revealed the presence of PPARgamma in ECs. Bovine ECs transfected with a PPAR response element (PPRE)-luciferase construct responded to stimulation by the PPARgamma agonist 15d-PGJ2 in a concentration-dependent manner, suggesting a functional PPARgamma in ECs. Treatment of human ECs with 15d-PGJ2, 9(S)-HODE, or 13(S)-HODE augmented PAI-1 mRNA and protein expression, whereas multiple PPARalpha activators did not change PAI-1 levels. Introduction of increasing amounts of a PPARgamma expression construct in human fibroblasts enhanced PAI-1 secretion from these cells in proportion to the amount of transfected DNA. Thus, ECs express functionally active PPARgamma that regulates PAI-1 expression in ECs. Our results establish a role for PPARgamma in the regulation of EC gene expression, with important implications for the clinical links between obesity and atherosclerosis.

Determinants of plasma levels of plasminogen activator inhibitor-1 : A study of normotensive twins

We investigated whether plasma levels of the plasminogen activator inhibitor type 1 antigen (PAI-1:Ag) are genetically determined in monozygotic (MZ) and dizygotic (DZ) twins. Twenty-five pairs of healthy twins underwent measurements of PAI-1:Ag and other variables, including body mass index, mean blood pressure, plasma renin activity, insulin, and glucose. To ascertain the zygosity of twins, highly discriminating micro- and minisatellite systems with variable numbers of tandem repeats were analyzed by PCR amplification followed by polyacrylamide gel electrophoresis. Subjects were also genotyped for the 4G/5G polymorphism by PCR. Estimates of genetic variance and heritability were obtained for PAI-1:Ag, and for body mass index, mean blood pressure, plasma renin activity, glucose, and insulin by jointly examining data in a path analysis with TWINAN90. Results showed that 12 pairs of twins were MZ and 13 were DZ. All tests of genetic variance [within pair (WP): F=6.24, P=0.002; among component (AC): F=2.62, P=0.04; average absolute difference t test=3. 00, P=0.004] showed significant genetic variance of PAI-1:Ag, but not of the other variables. Three tests of heritability (WP=0.837, P=0.002; AC=1.791, P<0.05; intraclass correlation: 1.180, P=0.001) consistently showed significant PAI-1:Ag heritability. Additive genetic influences (A), dominance genetic effect (D), and random environmental influences (E) accounted for 0.714, 0.154, and 0.132 of PAI-1:Ag variance, respectively. No effect of different 4G/5G genotypes was found. Thus, these results show significant genetic variance and heritability of PAI-1:Ag and suggest that A is more important than both D and E in determining PAI-1:Ag variance.

Tissue plasminogen activator (tPA) antigen in plasma: correlation with different tPA/inhibitor complexes

In many studies, tPA antigen has been a strong predictor of myocardial infarction. However, only a few percent of the total tPA antigen present in plasma samples taken at rest constitutes active tPA. The rest is enzymatically inactive and consists of a heterogeneous mixture of tPA in complex with inhibitors such as PAI-1, antiplasmin and C1 inhibitor. In the present study we developed specific two-site ELISA methods for determining the individual protease/inhibitor complexes constituting tPA antigen. We subsequently measured the concentrations of the different complexes in plasma samples taken from 30 healthy individuals. The results show that the concentration of the complex between tPA and PAI-1 in plasma correlated strongly with that of tPA antigen in plasma, as measured with a commercially available kit. Also the correlation between tPA/PAI-1 complex levels in plasma and the PAI-1 activity concentration was significant. However, no significant correlations were found between tPA antigen concentration and tPA/C1 inhibitor or tPA/antiplasmin concentrations in plasma.

Concentration of endogenous tPA antigen in coronary artery disease: relation to thrombotic events, aspirin treatment, hyperlipidemia, and multivessel disease

Tissue plasminogen activator (tPA) is the major plasminogen activator responsible for dissolving blood clots found in blood vessels. However, elevated concentrations of tPA antigen were found to be related to adverse events in patients with coronary artery disease (CAD). Considerable controversy about the significance of these results exists. The goal of this cross-sectional study was to identify independent determinants for tPA antigen concentrations in patients with CAD, to possibly clarify the above paradoxical relationship. The baseline tPA antigen concentrations of 366 patients with angiographic evidence of coronary sclerosis were determined. Univariate analysis showed that age (P=0.013), angiographic extent of disease (P<0.001), presence of angina at rest (P<0.001), diabetes mellitus (P=0.004), hypercholesterolemia (P=0. 045), hypertriglyceridemia (P=0.015), and chronic intake of nitrates (P<0.001) were significantly and positively related to tPA antigen concentration, while the chronic intake of aspirin was inversely related to tPA antigen (P<0.001). In addition, plasminogen activator inhibitor type 1 (PAI-1) activity was found to be significantly and positively associated with tPA antigen concentration (P<0.001). A multivariate analysis identified chronic low-dose aspirin therapy (P<0.001), PAI-1 activity (P<0.001), hypertriglyceridemia (P=0.005), the type of angina (P=0.026), multivessel disease (P=0.041), and hypercholesterolemia (P=0.043) as significant and independent determinants of tPA antigen. While hypertriglyceridemia and hypercholesterolemia both are related to the underlying disease, the type of angina and the number of involved vessels are linked to the severity and extent of disease, and all of them are indicators of a prothrombotic state found during the progression of CAD. In contrary, low-dose aspirin rather would decrease the likelihood of thrombotic events. The relation of tPA antigen to PAI-1 activity furthermore underlines the relation between tPA antigen concentration and a prothrombotic state. Therefore, the positive or-in case of aspirin therapy-negative correlation of these parameters with tPA antigen concentration would indicate that thrombus formation and simultaneous endothelial cell activation might be major determinants for tPA antigen concentration in CAD.

Influence of glycation on LDL-induced generation of fibrinolytic regulators in vascular endothelial cells

Hyperglycemia and dyslipidemia are two biochemical markers of diabetes mellitus. Increased incidence of cardiovascular disease and impaired fibrinolytic activity have been found in diabetic subjects. Previous studies have demonstrated that low density lipoproteins (LDLs) stimulate the production of plasminogen activator inhibitor-1 (PAI-1) and reduce the generation of tissue plasminogen activator (tPA) in vascular endothelial cells (ECs). The present study investigated the effect of glycated LDL on the production of PAI-1 and tPA in cultured human umbilical vein ECs (HUVECs). Glycation increased the abundance of glucitollysine and conjugated dienes in LDL and amplified the overproduction of PAI-1 and the reduction in tPA generation from HUVECs induced by LDL. The steady-state levels of PAI-1 mRNA in glycated LDL-treated ECs were significantly higher than those in native LDL-treated cells. Actinomycin D blocked the increase in PAI-1 generation induced by glycated LDL. Glycated LDL did not significantly reduce the levels of tPA mRNA but attenuated de novo synthesis of tPA in ECs. Treatment with 25 mmol/L aminoguanidine, an antioxidant and inhibitor of the formation of advanced glycation end products, during glycation normalized glycated LDL-induced generation of PAI-1 and tPA in ECs. The results of the present study indicate that glycation enhances the production of PAI-1 and attenuates tPA synthesis in ECs induced by LDL, which may contribute to the increased incidence of cardiovascular complications in diabetes. Formation of advanced glycation end products or peroxidation may be involved in glycated LDL-induced alterations in the generation of fibrinolytic regulators from ECs.

Very-low-density lipoprotein response element in the promoter region of the human plasminogen activator inhibitor-1 gene implicated in the impaired fibrinolysis of hypertriglyceridemia

Hypertriglyceridemia and impaired fibrinolytic function are linked to coronary heart disease and other atherothrombotic disorders. Triglyceride-rich lipoproteins may attenuate fibrinolysis by increasing the plasma levels of plasminogen activator inhibitor-1 (PAI-1). Furthermore, a common 4/5 guanosine (4G/5G) polymorphism in the promoter region of the PAI-1 gene has been indicated to influence plasma PAI-1 activity and to be involved in an allele-specific response to triglycerides. Herein we show by transfection assays that VLDLs induce transcription of the human PAI-1 promoter in endothelial cells. A VLDL response element (VLDLRE) is located to residues -672 to -657 in the promoter region by electromobility shift assay, methylation interference, and DNase I footprinting, and its activity is shown to be influenced by the common 4G/5G polymorphism located adjacent to and upstream of the binding site of a VLDL-inducible transcription factor. These findings may provide a molecular explanation to the link between VLDL and PAI-1 activity elevation in plasma and to the interaction between the 4G/5G polymorphism and plasma triglycerides.

The fibrinolytic effects of intermittent pneumatic compression: mechanism of enhanced fibrinolysis

BACKGROUND AND OBJECTIVES

Intermittent pneumatic compression (IPC) is an effective form of deep vein thrombosis prophylaxis for general surgery patients. The antithrombotic effect of IPC is thought to be the result of increased venous velocity and stimulation of endogenous fibrinolysis. However, the mechanism of enhanced fibrinolytic activity and the relative effects on normal and postthrombotic veins have not been defined. The purposes of this study are 1) to quantify changes in fibrinolytic activity with IPC; 2) to study the mechanism of fibrinolytic enhancement with IPC; and 3) to evaluate whether postthrombotic patients have the same capacity for fibrinolytic enhancement with IPC as do normal subjects.

METHODS

Twelve volunteers (6 normal and 6 postthrombotic) had 5 IPC devices applied for 120 minutes in random fashion, 1 per week x 5 weeks. The devices included single-chamber, sequential, foot, calf, and long-leg compression. Subjects had an indwelling antecubital venous cannula placed for blood drawn at baseline, 60, 120, and 180 minutes after IPC devices were applied. Global fibrinolytic activity (euglobulin fraction, fibrin plate assay), tissue plasminogen activator (tPA) antigen (Ag) and activity (Act), plasminogen activator inhibitor-1 (PAI-1) Ag and Act, alpha-2-antiplasmin-plasmin complexes, and von Willebrand factor (vWF) antigen were assayed.

RESULTS

A striking elevation in fibrinolytic activity was noted at 180 minutes with all devices in normal subjects and postthrombotic patients (p = 0.01-0.0001); however, baseline and stimulated fibrinolytic activity was attenuated in postthrombotic patients (<0.03). The tPA-Act increased only in normal subjects (3.8 +/- 1.9%) (p = 0.057), despite a decrease in plasma tPA-Ag, which was observed in both normal subjects (-12.4 +/- 3.8%) (p = 0.009) and patients (-17.2 +/- 3.1%) (p = 0.001). PAI-1-Ag decreased in both normal subjects (-13.4 +/- 3.8%) (p = 0.007) and patients (-12.0 +/- 3.1%) (p = 0.013) with a marked reduction in PAI-1-Act in both normal subjects (p = 0.003) and patients (p = 0.004). There were no changes in vWF, and alpha-2-antiplasmin-plasmin complexes increased only in postthrombotic patients (p = 0.021).

CONCLUSIONS

Stimulation of endogenous fibrinolytic activity occurs after IPC, both in normal subjects and postthrombotic patients; however, baseline and overall fibrinolytic response in postthrombotic patients is reduced. The mechanism of increased fibrinolytic activity is likely because of a reduction in PAI-1, with a resulting increase of tPA activity.

Fibrinolytic function after dietary supplementation with omega3 polyunsaturated fatty acids

Hypertension is associated with derangements in glucose and lipid metabolism. Increased levels of plasminogen activator inhibitor type 1 (PAI-1) are thought to potentiate the development of coronary events in this condition. Fish oil (omega3 polyunsaturated fatty acids [PUFAs]) have lipid-lowering effects, but the cardioprotective potential has been questioned because fish oil has been found to increase PAI-1 activity. This study was performed to determine the effects of omega3 PUFAs on the fibrinolytic function in hypertension. Seventy-eight persons with untreated hypertension were included in a 16-week, double-blind, randomized, controlled intervention study with 4 g/d of eicosapentaenoic and docosahexaenoic acids or corn oil placebo. Plasma PAI-1 activity, tissue plasminogen activator (tPA) activity, levels of fibrinogen and factor VII(c), and platelet count were measured before and after intervention (mean+/-SE). PAI-1 activity changed similarly in the fish oil and corn oil groups (1.8+/-1.0 U/mL versus 3.5+/-1.2 U/mL, P=.25), as did tPA (-0.02+/-0.02 IU/mL versus -0.13+/-0.03 IU/mL, P=.28), levels of factor VII(c) (6+/-5% versus 5+/-4%, P>.3), and platelet count (2+/-7x10(9)/L versus 3+/-5x10(9)/L, P>.3). None of these variables changed from pretreatment levels during fish oil intake. Fibrinogen levels increased significantly both during fish oil (0.6+/-0.1 g/L, P=.0001) and corn oil (0.4+/-0.1 g/L, P=.002) intake. There was no between-group difference (P>.3). In conclusion, a daily intake of 4 g omega3 PUFAs does not affect PAI-1 and tPA activity in persons with hypertension. A modest increase in fibrinogen levels was observed after both fish oil and corn oil intake.

Gender differences in the relationships between plasma plasminogen activator inhibitor-1 activity and factors linked to the insulin resistance syndrome in essential hypertension

Impaired fibrinolysis due to elevated levels of plasma plasminogen activator inhibitor type 1 (PAI-1) is a risk factor for thromboembolic disease. Hypertension, obesity, derangements in lipid and glucose homeostasis, and elevated levels of PAI-1 are features of the insulin resistance syndrome. The interrelationships between PAI-1 and the metabolic disturbances seen in this condition are unsettled. We investigated the associations between PAI-1 activity and components of the insulin resistance syndrome in 53 men and 31 women with untreated hypertension. In men, PAI-1 activity correlated significantly with plasma glucose (r = .41, P = .002), insulin sensitivity (r = -.35, P = .01), and insulin-induced suppression of nonesterified fatty acid (NEFA) (r = -.43, P = .007). Plasma glucose and NEFA suppression were independently associated with PAI-1 activity in a multivariate analysis. In women, PAI-1 activity correlated with body mass index (r = .62, P = .0005), waist-to-hip ratio (r = .75, P = .0001), plasma glucose (r = .50, P = .007), insulin (r = .49, P = .009), proinsulin (r = .57, P = .002), C-peptide (r = .60, P = .0009), insulin sensitivity (r = -.74, P = .0001), NEFA suppression (r = -.64, P = .003), and triglycerides (r = .58, P = .001). In multivariate analyses, insulin sensitivity and NEFA suppression were independently associated with PAI-1 if waist-to-hip ratio was not included in the model. After introduction of waist-to-hip ratio into the model, waist-to-hip ratio was the only independent predictor of PAI-1 activity. We conclude that in women, waist-to-hip ratio, body mass index, and insulin-induced NEFA suppression are determinants for PAI-1 activity. In men, insulin-induced NEFA suppression and plasma glucose are independently associated with PAI-1 activity.

Molecular Pathogenesis of Type I Congenital Plasminogen Deficiency: Expression of Recombinant Human Mutant Plasminogens in Mammalian Cells

We previously reported the genetic abnormality in a Japanese family with type I congenital plasminogen deficiency caused by a Ser572 to Pro572 mutation. To characterize the molecular pathogenesis of the disease in this family, we expressed recombinant human wild-type and mutant (rS572P) plasminogens in COS-1 cells. Activation-resistant wild-type and mutant plasminogen stable transfectants in CHO-K1 cells also were established. Transient transfection and metabolic labeling experiments followed by immunoprecipitation analysis showed that the mutant plasminogen was secreted from COS-1 cells in reduced amounts, compared with the wild type. Endo H digestion of the wild-type and mutant plasminogen showed no shift in their migrations on sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, indicating that both contain complex type oligosaccharide structures and could therefore be secreted. Furthermore, the secretion of activation-resistant mutant plasminogen was significantly reduced. Pulse-chase experiments and Northern blot analysis showed that the impaired secretion of the mutant plasminogen was the consequence of the accumulation of the mutant protein inside the cells but not of reduced plasminogen mRNA. Immunocytochemical staining of stable transfectants also revealed that CHO-K1 cells expressing the activation-resistant mutant plasminogen stained mainly in the perinuclear area, suggesting delayed processing of the mutant protein in the intracellular transport pathway. We conclude that the impaired secretion of mutant plasminogen, due to intracellular accumulation, is the molecular pathogenesis of type I congenital plasminogen deficiency caused by a Ser572 to Pro572 mutation.

Molecular Pathogenesis of Type I Congenital Plasminogen Deficiency: Expression of Recombinant Human Mutant Plasminogens in Mammalian Cells

We previously reported the genetic abnormality in a Japanese family with type I congenital plasminogen deficiency caused by a Ser572 to Pro572 mutation. To characterize the molecular pathogenesis of the disease in this family, we expressed recombinant human wild-type and mutant (rS572P) plasminogens in COS-1 cells. Activation-resistant wild-type and mutant plasminogen stable transfectants in CHO-K1 cells also were established. Transient transfection and metabolic labeling experiments followed by immunoprecipitation analysis showed that the mutant plasminogen was secreted from COS-1 cells in reduced amounts, compared with the wild type. Endo H digestion of the wild-type and mutant plasminogen showed no shift in their migrations on sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, indicating that both contain complex type oligosaccharide structures and could therefore be secreted. Furthermore, the secretion of activation-resistant mutant plasminogen was significantly reduced. Pulse-chase experiments and Northern blot analysis showed that the impaired secretion of the mutant plasminogen was the consequence of the accumulation of the mutant protein inside the cells but not of reduced plasminogen mRNA. Immunocytochemical staining of stable transfectants also revealed that CHO-K1 cells expressing the activation-resistant mutant plasminogen stained mainly in the perinuclear area, suggesting delayed processing of the mutant protein in the intracellular transport pathway. We conclude that the impaired secretion of mutant plasminogen, due to intracellular accumulation, is the molecular pathogenesis of type I congenital plasminogen deficiency caused by a Ser572 to Pro572 mutation.

Hemodynamic and fibrinolytic consequences of intermittent pneumatic compression: preliminary results

OBJECTIVE

To elucidate the time course and magnitude of hemodynamic and fibrinolytic changes associated with sequential gradient intermittent pneumatic compression (SGIPC).

DESIGN

Two-phase, intervention and response investigation in normal volunteers.

MATERIALS AND METHODS

Subjects were assigned to control (phase I) or compression (phase II) groups. Serial blood samples were obtained via femoral venous catheters for tissue plasminogen activator (tPA), plasminogen activator inhibitor (PAI-1), tPA-PAI-1 complex (tPA-PAI), and euglobulin lysis time (ELT) from all subjects and for fibrin degradation products (FbDP) and fibrinogen degradation products (FgDP) from phase II subjects. Duplex venous scanning was carried out on phase II subjects before and during SGIPC.

RESULTS

Catheter placement caused elevations in PAI-1 and tPA-PAI, which stabilized within 4 hours of catheter insertion. In phase II, SGIPC induced significant increases in FbDP, FgDP, and tPA-PAI and decreases in ELT and PAI-1, all of which quickly reverted to baseline on termination of compression. Femoral venous blood flow increased by more than 100% with SGIPC.

CONCLUSIONS

Sequential gradient intermittent pneumatic compression induces prompt, but short-lived, alterations in both fibrinolytic and hemodynamic function. Noncontinuous SGIPC may result in suboptimal thromboembolic prophylaxis.

Decreased fibrinolytic stimulation by a short-term venous occlusion test in patients with cerebrovascular disease

The aim of the present study was to determine whether patients with previous cerebrovascular disease have abnormalities in hemostatic functions stimulated by a 5-min venous-occlusion-test. Twenty-two patients with brain ischaemia 3-6 months previously were compared to a control group of twenty patients with non-vascular neurological diseases. Cases showed less increase in tissue plasminogen activator and fibrin degradation products than controls. There were no differences in baseline and stimulated levels of plasminogen activator inhibitor, fibrinogen degradation products, thrombin-antithrombin complex or global lysis assay (Fibriscreen). Since patients with acute cerebrovascular disease were not included, the present findings may represent either preexisting or longterm reactive fibrinolytic deficiencies, possibly predisposing to further thrombotic disease.

Fibrinolysis and atherosclerosis

The link between impaired fibrinolytic function and CHD has been reinforced considerably in the past couple of years. This has been achieved by a combination of epidemiological, clinical, cell biological and molecular biological studies. The molecular mechanisms for the identified associations between more established risk factors for atherosclerotic disease and impaired fibrinolytic function now need to be disentangled to promote the design of specific drugs that may pave the way for intervention. The possibility that some of the observed relations are epiphenomena should also not be disregarded. The concept of genotype-specific differences in the susceptibility of the individual to common metabolic disturbances needs to be examined in greater detail. Basic research on the role of fibrinolysis in atherosclerosis and its thrombotic complications should be given high priority, because the modulation of fibrinolytic function is likely to become an important approach to prevention.

Allele-specific increase in basal transcription of the plasminogen-activator inhibitor 1 gene is associated with myocardial infarction

Increased plasminogen-activator inhibitor 1 (PAI-1) activity is a common finding in patients with coronary heart disease. Here we provide evidence for an independent, etiological role of PAI-1 in myocardial infarction. The 4G allele of a recently described common 4/5-guanine-tract (4G/5G) polymorphism in the PAI-1 promoter is associated with higher plasma PAI-1 activity. The prevalence of the 4G allele is significantly higher in patients with myocardial infarction before the age of 45 than in population-based controls (allele frequencies of 0.63 vs. 0.53). Both alleles bind a transcriptional activator, whereas the 5G allele also binds a repressor protein to an overlapping binding site. In the absence of bound repressor, the basal level of PAI-1 transcription is increased.

Abnormalities in the fibrinolytic system of the vascular wall associated with atherosclerosis

In summary, studies of the expression of fibrinolytic genes in the vessel wall suggest an active, ongoing proteolytic process, the activity of which is dependent on the relative amounts of tPA, uPA, and PAI-1 secreted and locally deposited. Disturbances in the balance of pro- and antifibrinolytic activity in atherosclerotic vessels have considerable potential for influencing both intra- and extravascular fibrinolytic events and may be causally related to the development of vascular disease.

A cross-sectional study of endogenous tissue plasminogen activator, total cholesterol, HDL cholesterol, and apolipoproteins A-I, A-II, and B-100

Elevated levels of endogenous tissue-type plasminogen activator (t-PA) appear to be a marker for preclinical atherosclerosis. At present, however, data describing potential relations between plasma t-PA level and established lipid risk factors for coronary atherosclerosis are sparse. To explore these potential relations, we measured plasma levels of t-PA antigen (t-PA:ag) in 633 apparently healthy men in the Physicians' Health Study as well as total cholesterol, high-density lipoprotein (HDL) cholesterol, HDL2 cholesterol, HDL3 cholesterol, and apolipoproteins A-I, A-II, and B-100. Overall, plasma t-PA:ag levels were inversely correlated with HDL cholesterol (r = -.1616, P < .0005), HDL2 cholesterol (r = -.1632, P < .0005), and HDL3 cholesterol (r = -.0927, P = .019). In stratified analyses, the inverse association between t-PA:ag and HDL cholesterol was present among frequent (P trend = .002) and infrequent (P trend = .004) consumers of alcohol as well as among the subgroups of frequent exercisers (P trend < .001), men in the lower half of body mass index (P trend = .001), and nonsmokers (P trend < .001). In contrast, there was no association between t-PA:ag and total cholesterol (r = .0219, P = .58), whereas relations of t-PA:ag with apolipoproteins A-I, A-II, and B-100 were minimal and of borderline significance. These data indicate that plasma levels of endogenous t-PA:ag are inversely related to HDL cholesterol as well as HDL2 and HDL3 cholesterol.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between plasma plasminogen activator inhibitor-1 activity and VLDL triglyceride concentration, insulin levels and insulin sensitivity: studies in randomly selected normo- and hypertriglyceridaemic men

Impaired fibrinolytic function secondary to elevated plasma plasminogen activator inhibitor-1 activity, hypertriglyceridaemia and hyperinsulinaemia are frequent findings in patients with coronary heart disease. It has been debated whether VLDL or insulin is the major regulator of plasma plasminogen activator inhibitor-1 activity. This study examines the relationships between plasma plasminogen activator inhibitor-1 activity and VLDL triglyceride concentration, fasting and post-oral glucose load insulin levels and insulin sensitivity, as estimated by the minimal model method. Subjects studied were randomly selected hypertriglyceridaemic (n = 65) and age-matched normotriglyceridaemic (n = 61) men, aged 40-50 years, recruited in a population survey. Plasma plasminogen activator inhibitor-1 activity was higher in the hypertriglyceridaemic than in the normotriglyceridaemic group (21 +/- 14 vs 10 +/- 8 mU/l; p < 0.01). The hypertriglyceridaemic group had higher serum insulin, basal as well as 2 h after intake of the oral glucose load, and a lower insulin sensitivity index. In univariate analysis, plasma plasminogen activator inhibitor-1 activity correlated positively with VLDL triglycerides in both the hyper- and normotriglyceridaemic groups (r = 0.43 r = 0.60, respectively) and negatively with the insulin sensitivity index (r = -0.35 r = -0.44, respectively). In multivariate analysis, VLDL triglyceride levels were found to be independently related to plasma plasminogen activator inhibitor-1 activity in both groups, whereas insulin sensitivity/serum insulin levels were not. An unexpected finding was that the serum activity of the enzyme gamma glutamyl transpeptidase appeared to influence the relationships for plasma plasminogen activator inhibitor-1 in the hypertriglyceridaemic group.(ABSTRACT TRUNCATED AT 250 WORDS)

Transferable lipids in oxidized low-density lipoprotein stimulate plasminogen activator inhibitor-1 and inhibit tissue-type plasminogen activator release from endothelial cells

Decreased fibrinolytic activity has been reported in atherosclerotic cardiovascular diseases. To determine whether oxidized low-density lipoprotein (Ox-LDL), which accumulates in atherosclerotic arteries, modulates the endothelial fibrinolytic system, cultures of human umbilical vein endothelial cells were incubated with low-density lipoproteins or lipids, and levels of plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (t-PA) antigens in the conditioned medium were measured by enzyme-linked immunosorbent assay. Ox-LDL (30 micrograms protein/mL) and its extracted lipid (50 micrograms cholesterol/mL) stimulated PAI-1 release by 42 +/- 3% and 29 +/- 3% of control cultures, respectively, whereas Ox-LDL and its lipid inhibited t-PA release by 42 +/- 4% and 53 +/- 3% of control cultures, respectively. Native LDL and its lipid were inactive on their release. Ox-LDL depleted of hydrophilic lipids, which was prepared by the incubation with defatted albumin (an acceptor for hydrophilic lipids), lost both the stimulatory action on PAI-1 and the inhibitory action on t-PA. The extracted lipid from the incubated albumin, which has been found to accept the hydrophilic lipids from Ox-LDL, gained the stimulatory action on PAI-1 and the inhibitory action on t-PA. Ox-LDL depleted of lysophosphatidylcholine (LPC), which was prepared by the incubation with phospholipase B, lost the stimulatory effect on PAI-1, whereas the inhibitory effect on t-PA remained present in the Ox-LDL depleted of LPC. The incubation with synthetic palmitoyl LPC (10 microM) stimulated PAI-1 release by 85 +/- 7% of control.(ABSTRACT TRUNCATED AT 250 WORDS)

Triazolobenzodiazepines: a new class of stimulators of tissue-type plasminogen activator synthesis in human endothelial cells

In our search for compounds that can stimulate endogenous fibrinolysis, we have found that certain triazolobenzodiazepines enhance the production of tissue-type plasminogen activator (t-PA) by vascular endothelial cells maintained in vitro, with no or even a lowering effect on plasminogen activator inhibitor type-1 (PAI-1) production. The most active compounds tested, U-34599, U-46195 and U-51477, were studied in more detail and showed a time- and dose-dependent increase in the production of t-PA by human umbilical vein endothelial cells. At optimal stimulatory concentrations (about 10 microM), the three compounds stimulated t-PA expression about 2-fold after 24 hr and maximally about 4-fold after 48 hr of incubation; this maximal increase in t-PA synthesis was sustained at prolonged incubations of 72 or 96 hr. The triazolobenzodiazepine effects on t-PA production were accompanied by parallel increases in t-PA mRNA levels, without marked changes in PAI-1 or glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA concentrations. Numerous analogues of the three lead compounds were then tested to determine the relationship between benzodiazepine structure and the ability to stimulate t-PA production. No positive correlation was found between the ability of the various triazolobenzodiazepines to stimulate t-PA production and their affinity for the benzodiazepine receptor. In agreement with this, no specific binding of [3H]flunitrazepam, a specific ligand for benzodiazepine receptors, to endothelial cell membrane preparations was observed. Thus, it is unlikely that the triazolobenzodiazepines act through central-type benzodiazepine receptors to stimulate t-PA production. Similarly, no evidence was found for the presence of peripheral-type benzodiazepine receptors on endothelial cell membranes. The ability of the benzodiazepines to stimulate t-PA production, however, appeared to be related to their platelet-activating factor (PAF) antagonist activity. Despite this finding, several non-benzodiazepine PAF antagonists did not stimulate t-PA production. While the precise mechanism of action is not yet clear, selected benzodiazepine analogues possessing PAF antagonist activity stimulate the production of t-PA by endothelial cells in vitro.

Endogenous tissue-type plasminogen activator and risk of myocardial infarction

Endogenous tissue-type plasminogen activator (tPA) has been hypothesised to be a marker of baseline fibrinolytic capacity. We therefore tested whether tPA antigen is associated with the occurrence of future myocardial infarction (MI) among apparently healthy individuals. tPA antigen concentrations were measured at baseline in plasma samples from 231 apparently healthy men from the Physicians' Health Study cohort who later developed MI, and in an equal number of controls matched for age and smoking habit who remained free of reported cardiovascular disease during a follow-up of 60.2 months. In crude matched-pair analyses, baseline concentrations of tPA antigen were higher in cases than controls (p = 0.03) and strongly associated with risk of future MI. Specifically, the relative risks of developing a first MI from lowest (referent) to highest quintiles of tPA antigen were 1.00, 1.27, 1.75, 1.88, and 2.81 (p for trend 0.0008, 95% CI for the relative risk in the fifth as compared with first quintile 1.47 to 5.37, p = 0.002). Analyses which adjusted for risk factors that affect progression of atherosclerosis, particularly HDL-cholesterol, abolished the statistical significance of this association, a finding which suggests that elevations of tPA antigen are a result rather than a cause of atherosclerotic coronary disease. These prospective data suggest that endogenous tPA concentrations increase as a consequence of important preclinical atherosclerosis and therefore may be a marker for risk of future MI.