Characterization of a panel of monoclonal antibodies toward mouse PAI-1 that exert a significant profibrinolytic effect in vivo

Introduction

PAI-1 is the main physiological inhibitor of t-PA and u-PA. Elevated PAI-1 levels have been implicated in the pathogenesis of several thrombotic and non-thrombotic diseases. The effect of PAI-1 inhibition can be studied in mouse models, when appropriate immunological tools are available. The majority of the available monoclonal antibodies against PAI-1 have been raised against human PAI-1. Even though some of these antibodies cross-react with non-glycosylated PAI-1 from different species, these antibodies often do not cross-react sufficiently with glycosylated mouse PAI-1. Moreover, the antibodies that cross-react with glycosylated mouse PAI-1 often have decreased inhibitory properties in the presence of vitronectin. Our objective was the generation of a panel of monoclonal antibodies reacting with vitronectin-bound glycosylated mouse PAI-1.

Results

Five monoclonal antibodies revealed binding to glycosylated mouse PAI-1 and exerted a strong (i.e. 58-80% inhibition of PAI-1 activity) inhibitory effect toward mouse PAI-1. Similar inhibitory effects were seen in the presence of a 33-fold molar excess of vitronectin. The PAI-1 inhibitory potential of the antibodies in vivo was demonstrated in a thromboembolism model, in which the evaluated antibodies significantly increased the percentage of mice with normal physical activity in comparison to mice treated with negative control antibody.

Conclusions

To the best of our knowledge this is the first panel of monoclonal antibodies that can inhibit mouse PAI-1 in the presence of vitronectin and that show a profibrinolytic effect in vivo. Therefore these antibodies provide excellent immunological tools to further investigate the role of PAI-1 in mouse models.     

In vitro effects of detergent sclerosants on fibrinolytic enzymes and inhibitors

Objective

To investigate the effects of Sodium Tetradecyl Sulphate (STS) and Polidocanol (POL) on fibrinolytic mechanisms.

Materials and methods

Measurements were done with serial dilutions of sclerosants in whole blood (WB), platelet rich (PRP) and platelet poor plasma (PPP). Control experiments were done in 5% bovine serum albumin (BSA), spiked with the enzyme/inhibitor. Plasminogen was measured with a chromogenic assay. Alpha-2-antiplasmin (AP) activity, plasmin-alpha-2-antiplasmin (PAP) complexes, plasminogen activator inhibitor-1 (PAI-1) activity, tissue plasminogen activator (t-PA) total antigen, t-PA activity, t-PA/PAI-1 complexes, thrombin activatable fibrinolysis inhibitor (TAFI) antigen and activated TAFI (TAFIa) were measured by ELISA.

Results

At high concentrations (> 0.3%), STS destroyed plasminogen, PAI-1, t-PA/PAI-1 complexes and total t-PA antigen but increased t-PA activity. At low concentrations (< 0.3%), both agents reduced PAP complexes while increasing AP activity. Low concentration STS increased PAI-1 activity, t-PA/PAI-1 complexes, TAFI and TAFIa. Low concentration POL mildly increased the total t-PA antigen and TAFI.

Conclusion

At low concentrations, both agents demonstrated a prothrombotic, antifibrinolytic (increase in PAI-1, total t-PA antigen, AP, TAFI and TAFIa) activity. At high concentrations, STS demonstrated non-prothrombotic (destruction of PAI-1, t-PA/PAI-1 complexes), antifibrinolytic (destruction of plasminogen, increase in AP) activity while POL had minimal effect.     

Fibrin clot properties in women heterozygous for factor V Leiden mutation: Effects of oral contraceptives

Introduction

Oral contraceptives (OC) in the presence of factor V Leiden mutation (FVL) markedly increase the risk of venous thromboembolism (VTE). Little is known about the OC and FVL-related alterations in fibrin clot properties.

Subjects and Methods

Plasma fibrin clot permeability (K_s) and efficiency of lysis, reflected by clot lysis time (CLT) and the rate of D-dimer release from clots (D-D_rate) induced by recombinant tissue plasminogen activator (tPA) were determined in 25 women with a family history of VTE who were heterozygous for FVL [FVL(+/−) - twice, on third-generation OC and after their discontinuation. Female non-carriers of FVL, matched for demographics, using OC and after their discontinuation served as controls (n = 25). All participants had no personal history of VTE.

Results

OC discontinuation in FVL(+/−) women resulted in shortened CLT (− 9%), and increased K_s (+ 4%) and D-D_rate (+ 1.4%; all p < 0.01). Alterations in fibrin clot properties were associated with decreased prothrombin fragments 1 + 2 (F1 + 2) (− 8%), plasminogen activator inhibitor-1 (PAI-1) antigen (− 11%), and thrombin activatable fibrinolysis inhibitor (TAFI) activity (− 20%; all p < 0.01). During OC use FVL(+/−) carriers compared with non-carriers had higher platelet count, activity of PAI-1, TAFI, and tPA, as well as prolonged CLT and higher D-D_max, along with lower D-D_rate and K_s. Multiple regression analysis adjusted for fibrinogen and age, showed that PAI-1 antigen and TAFI activity independently predicted CLT in FVL(+/−) women on OC.

Conclusion

FVL(+/−) is associated with hypofibrinolysis in apparently healthy women and third-generation OC administration unfavorably alters plasma clot characteristics in female FVL(+/−) carriers with a family history of thrombotic events.     

D-dimer relates positively with increased blood pressure in black South Africans: The SABPA study

Introduction

Hypertension is highly prevalent in black South Africans in which morbidity and mortality from stroke are on the increase. Elevated blood pressure and haemostatic markers can induce changes in blood rheology and endothelial function which could result in a procoagulant state that increases the risk for cerebrovascular disease. Information about the coagulation and fibrinolytic systems of people from African descent are limited. We therefore, investigated the haemostatic profile and its relationships with blood pressure in black South Africans.

Materials and methods

We measured ambulatory blood pressure and haemostatic markers of 201 black and 208 white school teachers. The haemostatic markers included measurements representing coagulation and fibrinolysis (von Willebrand factor, fibrinogen, plasminogen activator inhibitor-1, fibrin D-dimer and clot lysis time).

Results

Black participants displayed significantly higher blood pressure, von Willebrand factor, fibrinogen, plasminogen activator inhibitor-1 and D-dimer levels and longer clot lysis times (p ≤ 0.001). Single, partial and multiple regression analyses showed that systolic (p ≤ 0.011) and diastolic blood pressure (p = 0.010) correlated positively with D-dimer in black participants, while systolic (p ≤ 0.001) and daytime diastolic blood pressure (p = 0.011) correlated negatively with clot lysis time in white participants.

Conclusion

The black population had a more prothrombotic profile, with higher levels of coagulation markers and inhibited fibrinolysis, than the white study participants. The positive association between blood pressure and elevated D-dimer in the blacks may contribute to the high prevalence of hypertension and related increased cardiovascular and cerebrovascular risk in this group.     

Increase in proinflammatory cytokines in peripheral blood without haemostatic changes after LPS inhalation

Introduction

Bronchoalveolar fibrin deposition is a characteristic of various lung disorders including acute lung injury, acute respiratory distress syndrome and sepsis. It is secondary to the activation of coagulation and inhibition of fibrinolysis in the alveolar space, and can be stimulated by lipopolysaccharide (LPS) inhalation. The aim of this study was to determine the relation between compartmental stress in the lung and systemic response after LPS inhalation by measuring haemostatic parameters.

Patients and methods

12 healthy subjects underwent a bronchial challenge test with LPS; sequential dosages were performed for 5 biological markers (Interleukin-6 (IL-6), C-Reactive Protein (CRP), Prothrombin Fragments 1 and 2 (F 1+2), cortisol and Plasminogen Activator Inhibitor 1 (PAI-1) before endotoxin inhalation and 2, 4, 6, 8 and 24 hours afterwards.

Results

IL-6 and CRP levels in the peripheral blood were higher after LPS inhalation; there was no activation of coagulation and no increase in PAI-1 level.

Conclusion

This study confirms that despite systemic release of proinflammatory cytokines, LPS inhalation does not induce systemic haemostatic response to LPS challenge.     

Haemostatic markers in patients with abdominal aortic aneurysm and the impact of aneurysm size

Introduction

Abdominal aortic aneurysm is a common condition with high mortality when rupturing. However, the condition is also associated with nonaneurysmal cardiovascular mortality. A possible contributing mechanism for the thrombosis related cardiovascular mortality is an imbalance between the activation of the coagulation system and the fibrinolytic system. The aim of the present study was to investigate haemostatic markers in patients with nonruptured abdominal aortic aneurysm with special regard to the influence of aneurysm size and smoking habits.

Methods

Seventy-eight patients with infrarenal aortic aneurysm and forty-one controls without aneurysm matched by age, gender and smoking habits were studied. Thrombin-antithrombin (TAT), prothrombin fragment 1 + 2 (F 1 + 2) - markers of thrombin generation, and von Willebrand factor antigen (vWFag) - considered as a reliable marker of endothelial dysfunction - were measured. Plasma levels of tissue plasminogen activator antigen (tPAag), and plasminogen activator inhibitor type 1 (PAI-1) were measured as markers of fibrinolytic activity. D-dimer, a marker of fibrin turnover, was also measured.

Results

There were significantly higher levels of TAT and D-dimer in patients with abdominal aortic aneurysm. The highest level of TAT and D-dimer were detected in patients with large compared to small AAA.

Conclusions

The present data indicate a state of activated coagulation in patients with abdominal aortic aneurysm which is dependent by aneurysm size. The activated coagulation in AAA patients could contribute to an increased cardiovascular risk in patients also with small AAA. The possible impact of secondary prevention apart from smoking cessation has to be further evaluated and is maybe as important as finding patients at risk of rupture.     

Haemostatic system, biochemical profiles, kynurenines and the prevalence of cardiovascular disease in peritoneally dialyzed patients

Introduction

The haemostatic and biochemical abnormalities participate in the progression of cardiovascular disease (CVD) in peritoneally dialysed (PD) patients. Recently, the role of kynurenine (KYN) pathway of tryptophan (TRP) degradation in the development of CVD has been postulated.

Materials and methods

The present study was undertaken to investigate haemostatic parameters, biochemical profiles and kynurenines in PD patients both with and without CVD compared to age- and sex-matched healthy controls.

Results

The multiple biochemical abnormalities were present in PD patients, particularly in those with CVD. Tissue factor (TF), its inhibitor (TFPI), prothrombin fragment 1 + 2 (F_1 + 2)_, urokinase-type plasminogen activator (uPA), its soluble receptor (suPAR), plasmin/antiplasmin (PAP) complexes, KYN, kynurenic (KYNA) and quinolinic (QA) acids levels were significantly higher, whereas TRP was significantly lower in the PD patients than in the controls. Tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) were higher in the patients with CVD than in the patients without CVD and controls. PD patients with CVD had higher F_1 + 2, and they had lower suPAR and KYNA levels compared with PD patients without CVD. KYNA was positively associated with TFPI, whereas its was inversely associated with F_1 + 2 both in the whole PD group and in CVD patients. Logistic regression analysis showed that low KYNA, high glucose, low HDL-cholesterol levels and the duration of dialysis treatment were independently associated with the presence of CVD in PD patients.

Conclusions

The present study suggests a relationship between kynurenine pathway of tryptophan degradation, haemostatic and biochemical disturbances and CVD prevalence in peritoneally dialyzed patients.     

Endothelial haemostatic markers in members of families with familial combined hyperlipidemia

Introduction

The aim of this study was to evaluate the plasma levels of endothelial haemostatic markers - von Willebrand factor (vWF), plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (t-PA) and soluble thrombomodulin (sTM) — in asymptomatic, nonsmoking members of families with familial combined hyperlipidemia (FCH). We investigated the association between these factors and the intima-media thickness (IMT) of the common carotid artery, selected risk factors of atherosclerosis and markers of insulin resistance.

Methods

82 members of 29 FCH families were divided into two groups: HL (probands and hyperlipidemic first-degree relatives, n = 47) and NL (normolipidemic first-degree relatives, n = 35). The control groups C-HL (n = 20) and C-NL (n = 20) consisted of sex- and age-matched healthy individuals. IMT was measured by ultrasound at a far wall of both common carotid arteries.

Results

Compared with healthy controls, hyperlipidemic subjects had significantly higher levels of vWF (146.4 ± 73.2% versus 112.2 ± 29.4%, p < 0.05), of PAI-1 (102.4[83.0-117.0] ng/ml versus 63.5[31.8-87.3] ng/ml, p < 0.01) and of t-PA (5.1[2.5-7.9] ng/ml versus 3.4[1.4-5.8] ng/ml, p < 0.05). They had increased IMT, which correlated with vWF (r = 0.29, p < 0.05). Their normolipidemic relatives had significantly higher levels of vWF (137.2 ± 42.8% versus 106.6 ± 24.0%, p < 0.01) and of PAI-1 (75.3[53.2-92.0] ng/ml versus 48.6[37.4-85.9] ng/ml, p < 0.05). Levels of vWF, PAI-l and t-PA were independently associated with several markers of insulin resistance.

Conclusions

Asymptomatic members of FCH families have increased endothelial haemostatic factors— vWF, PAI-1, t-PA, which are associated with insulin resistance. VWF correlates with morphological vascular changes, detected by the increase of IMT, presented in only hyperlipidemic subjects.     

Parameters of the thrombogram are associated with serum 25-hydroxyvitamin D levels at baseline, but not affected during supplementation with vitamin D

Introduction

In vitro studies indicate an anticoagulant effect of 1,25-dihydroxyvitamin D, and sun exposure may lower the risk of thrombotic events. Accordingly, an effect on haemostatic parameters could be expected after supplementation with vitamin D.

Materials and Methods

158 obese or overweight subjects were included in a one year intervention study with supplementation with 40.000 IU vitamin D₃ per week or placebo. All subjects were given 500 mg calcium daily. Plasminogen activator inhibitor 1 (PAI-1), tissue plasminogen activator antigen (tPA Ag), and tissue factor-induced thrombin generation over time in plasma assessed by the calibrated automated thrombogram (CAT) method as a parameter of over all thrombotic activity, were measured before and at the end of the study.

Results

Mean baseline serum 25(OH)D level was 61.8 nmol/L and increased in the vitamin D group to 145.6 nmol/L at the end of the study. At baseline there was a significant decrease in the CAT variables lag time and time to peak of the thrombogram across increasing serum 25(OH)D quartiles, whereas no significant associations between serum 25(OH)D and PAI-1 or tPA Ag were found. After one year, no significant differences were found between the vitamin D and placebo groups regarding change in any of the haemostatic parameters.

Conclusions

The association between lag time and time to peak in the CAT assay and serum 25(OH)D levels could indicate a pro-thrombotic state in subjects with high serum 25(OH)D levels, whereas the lack of effect of high dose vitamin D supplementation questions the causality of this relation.     

Effects of carvedilol or metoprolol on PAI-1, tPA-mass concentration or Von Willebrand factor in chronic heart failure - a COMET substudy

Introduction

In COMET (Carvedilol or Metoprolol European Trial), carvedilol reduced mortality compared with metoprolol in patients with chronic heart failure. We hypothesized that carvedilol might have greater effects on endothelial derived haemostatic factors than metoprolol. We aimed to study the effects of carvedilol or metoprolol on tissue plasminogen activator (tPA), its inhibitor PAI-1 and Von Willebrand factor (VWF) in patients with heart failure.

Material and Methods

We recruited 260 patients (134 on carvedilol, 126 on metoprolol), mean age 66 years and 84% of them men. Plasma mass concentrations of tPA and PAI-1and percent of VWF were measured at baseline and after one and two years of treatment.

Results

Plasma tPA, PAI-1 and VWF were similar between treatment groups at baseline and no significant differences between groups emerged after one or two years of treatment. In paired analyses in patients assigned to carvedilol, median PAI-1 level decreased from 37.2 to 32.1 µg/l at two years (p = 0.034) and of VWF decreased from baseline to one year (240 vs. 218%, p = 0.023) in patients assigned to carvedilol but were not reduced at any time in patients assigned to metoprolol. Plasma tPA increased over time in both treatment groups (p = 0.013 and 0.027 respectively).

Conclusion

We found no significant difference in the effects of carvedilol or metoprolol on tPA, PAI-1 and VWF. Comparison over time within treatment groups suggested that PAI-1 and VWF might have declined on carvedilol but not on metoprolol. Our hypothesis is not proved but this may reflect an inadequate sample size rather than lack of an effect.     

Compartment-specific expression of plasminogen activator inhibitor-1 correlates with severity/outcome of murine polymicrobial sepsis

Introduction

Plasminogen activator inhibitor type 1 (PAI-1) co-induces septic coagulopathy. We aimed to characterize spatiotemporal PAI-1 gene/protein changes occurring in acute sepsis and tested whether PAI-1 fluctuations correlate with sepsis severity and early outcome.

Materials and Methods

Female mice underwent cecal ligation and puncture (CLP) in three experiments. I: mild (23G needle) CLP to compare circulating PAI-1 to its organ gene expression within 0-24 h. II: mild or severe (17G) CLP to asses differences in PAI-1 organ-specific expression and in coagulation/fibrinolysis. III: moderate (18G) CLP to characterize circulating PAI-1 in survivors (SUR), and to retrospectively compare it to dying (DIE) mice.

Results

In mild sepsis, the trajectory of circulating PAI-1 (1089 ng/ml peak at 24 h) was identical to PAI-1 gene expression in the left cranial vena cava (LCVC; 39-fold peak at 24 h). PAI-1 expression rise was immediate (60-fold at 6 h) and sustained in the liver, but marginal in the kidney, lungs and heart. Body temperature decrease correlated with the PAI-1 expression increase in the liver (rho = − 0.79), and blood (protein, rho = − 0.53). Regardless of severity, PAI-1 gene expression remained unaltered except the LCVC where it was > 3-fold higher in 17G (vs. 23G). Severe sepsis extended activated partial thromboplastin/pro-thrombin time and increased circulating PAI-1, while antithrombin and fibrinogen decreased at 6 and/or 24 h (vs. 23G). Within 24 h of death, circulating PAI-1 in DIE was > 3-fold higher versus SUR.

Conclusions

Polymicrobial sepsis caused a gradual circulating PAI-1 release and highly variable gene expression response pattern in organs. Only circulating PAI-1 and PAI-1 expression in the LCVC correlated with response severity and/or outcome.     

Plasminogen activator inhibitor-1 (PAI-1) 4G/5G polymorphism and endometriosis. Influence of PAI-1 polymorphism on PAI-1 antigen and mRNA expression

Introduction

Endometriosis is a benign gynecologic disease with a high prevalence. It is a multifactorial and polygenic entity in which the fibrinolytic system may be implicated. The objective of this study was to evaluate the plasminogen activator inhibitor-1 (PAI-1) 4G/5G polymorphism in a group of women with and without endometriosis and to analyze the influence of this polymorphism in PAI-1 expression in endometrial tissue and peritoneal fluid.

Material and methods

In 389 women (170 patients with endometriosis and 219 controls) PAI-1 4G/5G polymorphism was determined by PCR amplification using allele-specific primers. Quantitative real-time RT-PCR assay was used to quantify PAI-1 mRNA and PAI-1 antigen (ag) levels were quantified by ELISA.

Results

The genotype and allele frequencies of PAI-1 4G/5G polymorphism did not differ significantly between patients and controls. Control women with the 4G/4G genotype had higher endometrial PAI-1ag (P = 0.026) and mRNA (P = 0.014) levels than those with the 5G/5G genotype. Control carrying the 4G/4G genotype tended to have higher peritoneal fluid PAI-1ag levels than those carrying the 5G/5G genotype. Moreover, PAI-1ag levels in peritoneal fluid were higher in patients than in controls (P = 0.003).

Conclusions

The PAI-1 genotype distribution was similar in patients and controls. PAI-1 levels in endometrial tissue and peritoneal fluid seem to be associated with PAI-1 4G/5G polymorphism in controls. The increased PAI-1ag levels observed in peritoneal fluid from patients could contribute to increase the peritoneal adhesions observed in endometriosis.     

A nationwide family study of pulmonary embolism: identification of high risk families with increased risk of hospitalized and fatal pulmonary embolism

Background

Family history is an important risk factor for deep venous thrombosis. However, few studies have determined the importance of family history of pulmonary embolism (PE).

Objective

This nationwide study aimed to determine the familial risks of fatal and hospitalized PE.

Methods

The Swedish Multi-Generation Register for subjects aged 0 to 76 years old born since 1932 were linked to the Hospital Discharge Register and Cause of Death Register for the period 1964-2008. Standardized incidence ratios (SIRs) for first hospitalization or death (without previous hospitalization for PE) with a main diagnosis of PE were calculated for individuals whose parent or siblings were hospitalized with or died from PE, compared to those whose parent or siblings were not affected by PE.

Results

A total of 20,860 individuals were hospitalized for PE and 862 died due to primary fatal PE (without previous hospitalization for PE). The familial SIR for individuals with one sibling with hospitalized PE was 2.49 (95% CI 1.62-3.83). The familial SIR for siblings with two affected probands was 114.29 (95% CI 56.57-223.95). The familial SIRs for individuals with a parent or sibling hospitalized for PE were significantly increased for fatal PE (1.76; 95% CI 1.38-2.21) and hospitalized PE (2.13; 95% CI 2.04-2.23). Spouses had low overall familial risk for PE (1.09; 95% CI, 1.03-1.14).

Conclusion

The high familial risk in multiplex sibling families suggests the existence of strong genetic risk factors for PE. Familial factors and possibly genetic factors are important risk factors for primary fatal pulmonary embolism.     

Association of tissue plasminogen activator and plasminogen activator inhibitor polymorphism with myocardial infarction: A meta-analysis

Introduction

To investigate whether t-PA Alu repeat insertion/deletion (I/D) and PAI-1 4 G/5 G genetic variations are associated with the risk of MI.

Methods

We conducted a meta-analysis to assess the association between the t-PA I/D and PAI-1 4 G/5 G polymorphisms and risk of MI. We also performed subgroup analyses based on ethnicity (Caucasian, Asian, and African), gender and age. Forty one eligible studies including 12,461 cases and 14,993 controls were identified to evaluate the impact of PAI-1 4 G/5 G polymorphism on MI. Seven studies investigated the relationship between t-PA I/D and MI.

Results

This meta-analysis revealed that the PAI-1 4 G allele (4 G/4 G and 4 G/5 G genotype) was associated with an increased risk of MI compared with the 5 G allele in the overall population (OR = 1.094, 95% CI = 1.021 - 1.172, p = 0.011). The relative risks of MI for 4 G/4 G genotype was increased when compared to 5 G/5 G genotype and 5 G allele, with odds ratio at 1.157 (95% CI 1.015 - 1.320, p = 0.029) and 1.126 (95% CI = 1.015 - 1.249, p = 0.025). However, the results show that the 4 G/5 G polymorphism risk for MI was not associated with ethnicity stratification as Caucasian, Asian or African population. No substantial differences in the genotype distributions were observed in the MI group and control group along the lines of gender and age. After multivariable analysis t-PA I/D polymorphism showed no consistent association with MI.

Conclusions

This study suggests that the 4 G/5 G polymorphism of PAI-1 may be a risk factor for MI in overall populations.     

Short-term effects of estrogen, tamoxifen and raloxifene on hemostasis: a randomized-controlled study and review of the literature

Introduction

Estrogen therapy (ET), tamoxifen and raloxifene are associated with a two- to three-fold increased risk of venous thrombosis (VT); however, the mechanisms by which each drug increases venous thrombosis propensity are not fully understood. The objectives of this investigation were to compare the effects of these three treatments on hemostasis in a head to head randomized placebo-controlled trial.

Patients/methods

Ninety-four postmenopausal women were assigned to receive oral estrogen (conjugated equine estrogen [CEE] 0.625 mg, n=23), tamoxifen 20 mg (n=24), raloxifene 60 mg (n=24) or placebo (n=23) daily for 6 months. Blood samples were analyzed for procoagulant factors (prothrombin, factors VII [fVII], VIII [fVIII], IX [fIX] and XI [fXI], D-dimer and von Willebrand factor [vWf]), anticoagulant factors (antithrombin [AT], total and free protein S, protein C and activated protein C [APC] resistance) and fibrinolytic factors (thrombin activatable fibrinolysis inhibitor [TAFI] and plasminogen activator inhibitor-1 [PAI-1]), at baseline and at 6 months of treatment.

Results

Estrogen increased factor VII and D-dimer, and decreased antithrombin, total and free protein S and PAI-1. Changes with tamoxifen were distinct from estrogen with increases in factors VIII, IX, vWf and free protein S, and decreases in AT, total protein S, protein C and plasminogen activator inhibitor-1. Raloxifene produced similar effects as tamoxifen, but did not increase factor IX or decrease protein C.

Conclusions

Estrogen, tamoxifen and raloxifene affected hemostasis favoring procoagulation and impairing anticoagulation. The biochemical effects of the selective estrogen receptor modulators (SERMs) were distinct from those of estrogen and differed only subtly from each other.     

Unfavorably altered fibrin clot properties in patients with active rheumatoid arthritis

Objective

Altered fibrin clot properties have been reported in cardiovascular diseases (CVD) and inflammatory states. Given increased prevalence of CVD in patients with rheumatoid arthritis (RA), we investigated whether fibrin characteristics are also altered in RA patients.

Patients and methods

We studied 46 consecutive RA patients versus 50 controls matched for age and gender. Ex vivo plasma clot permeability, turbidity, tissue-type plasminogen activator (tPA)-induced fibrinolysis, and scanning electron microscopy (SEM) images of clots were evaluated.

Results

Patients with RA had lower clot permeability, faster clot formation, higher maximum clot absorbancy indicating thicker fibrin fibers, maximum clot mass and prolonged fibrinolysis time than controls. Maximum rates of clot lysis were similar in both groups. SEM images showed formation of dense clots with many projections on fibrin fibers. Clot permeability inversely correlated with fibrinogen, tPA, plasminogen activator inhibitor-1 (PAI-1), CRP, platelet count, disease activity score (DAS28) and a marker of oxidative stress, 8-iso-prostaglandin F_2α (r from -0.44 to -0.79; all, p < 0.0001). Similar positive associations were found for clot lysis time (r 0.44 to 0.69; all, p < 0.01). Multiple regression analysis showed that fibrinogen was the only independent predictor of clot permeability (R² = 0.87, p < 0.0001) and lysis time (R² = 0.80, p < 0.003) in RA. Maximum D-dimer levels released from clots, maximum clot turbidity and the time of clot formation were predicted by PAI-1 (all, p < 0.05).

Conclusion

We showed unfavorably altered plasma fibrin clot structure and function in RA, which might contribute to an increased risk of thrombotic events in this disease.     

The role of thrombin receptors PAR1 and PAR4 for PAI-1 storage, synthesis and secretion by human platelets

Introduction

Arterial thrombi contain more platelets than venous thrombi and are more resistant to fibrinolysis. This resistance could partly be due to plasminogen activator inhibitor 1 (PAI-1) secreted by platelets. The aim of this study was to elucidate differences between thrombin receptors protease-activated receptor (PAR) 1 and 4 and platelet storage, secretion and synthesis of platelet PAI-1, as compared to other platelet α-granule proteins such as VEGF and endostatin.

Materials and methods

Human isolated platelets were incubated with thrombin (0.5 U/ml), PAR1-activating peptide (AP) (0.4-30 μM) or PAR4-AP (1.5-300 μM) for up to 24 hours. ELISA, western blot and fluorescence microscopy were used to measure secretion, contents and localization of PAI-1, VEGF and endostatin.

Results

Our results show that PAI-1 and VEGF might be co-localized and that endostatin does not co-localize with either PAI-1 or VEGF. PAI-1 and VEGF show a similar secretion pattern, being more sensitive to low grade PAR1 activation, but secretion was also observed with higher concentrations of PAR4-APs. PAI-1 is secreted in an active form. PAI-1 mRNA was found in platelets, and elevated levels of PAI-1 were detected after 24 hours incubation of platelets.

Conclusions

PAI-1 and VEGF, but not endostatin, might be stored in the same α-granule in human platelets. PAI-1 and VEGF also show a similar secretion pattern, being more sensitive to PAR1 than to PAR4 activation, but the secretion is not exclusively selective. Our results also show that platelet PAI-1 is increased if incubated for 24 hours, both with addition of PAR1-activating peptide and without activation, which could indicate de novo synthesis.     

TM5275 prolongs secreted tissue plasminogen activator retention and enhances fibrinolysis on vascular endothelial cells

Introduction

Elevated plasminogen activator inhibitor-1 (PAI-1) reduces fibrinolytic potential in plasma, contributing to thrombotic disease. Thus, inhibiting PAI-1 activity is clinically desirable. We recently demonstrated that tissue plasminogen activator (tPA) remains on the surface of vascular endothelial cells (VECs) after secretion in a heavy-chain dependent manner, which is essential for high fibrinolytic activity on the surface of VECs, and that PAI-1 dissociates retained tPA from the cell surface as a result of high-molecular weight complex formation. Based on the model whereby amounts of tPA and its equilibrium with PAI-1 dynamically change after exocytosis, we examined how TM5275, a newly synthesized small molecule PAI-1 inhibitor, modulated tPA retention and VEC surface-derived fibrinolytic activity using microscopic techniques.

Materials and methods

The effects of TM5275 on the kinetics of the secretion and retention of green fluorescent protein (GFP)-tagged tPA (tPA-GFP) on VECs were analyzed using total internal reflection fluorescence microscopy. The effects of TM5275 on the generation of plasmin activity were evaluated by both plasminogen accumulation and fibrin clot lysis on tPA-GFP-expressing VECs using confocal laser scanning microscopy.

Results

TM5275 at concentrations of 20 and 100 μM significantly prolonged the retention of tPA-GFP on VECs by inhibiting tPA-GFP-PAI-1 high-molecular-weight complex formation. TM5275 enhanced the time-dependent accumulation of plasminogen as well as the dissolution of fibrin clots on and around the tPA-GFP-expressing cells.

Conclusions

The profibrinolytic effects of TM5275 were clearly demonstrated by the prolongation of tPA retention and enhancement of plasmin generation on the VEC surface as a result of PAI-1 inhibition.     

Haemostatic effects of phytoestrogen genistein in postmenopausal women

Introduction

Genistein is an isoflavone phytoestrogen derived from the soybean which acts as natural selective estrogen receptor modulator. Various studies have pointed out its cardioprotective role. The aim of the study was to evaluate the haemostatic effects of genistein in postmenopausal women.

Material and methods

In this double-blind placebo-controlled trial we enrolled 104 healthy postmenopausal women with osteopenia. 53 patients (mean age 54.9 ± 4.2 yr; BMI 23.4 ± 3.2 Kg/m²) received genistein (54 mg/day) and 51 patients (mean age 55.4 ± 4.3 yr; BMI 23.6 ± 3.6 Kg/m²) received an identical placebo-tablet. Both groups received a calcium and vitamin D supplement. Plasma levels of D-dimer (DD), plasminogen activator inhibitor-1 (PAI-1) and prothrombin fragment 1 + 2 (F1 + 2) were measured at baseline and after 6 and 12 months of treatment.

Results

Baseline characteristics of the two groups were similar. Compared with placebo, genistein decreased significantly DD (p < 0.001), but did not affect PAI-1 and F 1 + 2 plasma levels.

Conclusion

The results of our study do not confirm effects of genistein on activation of the haemostatic system, but on the contrary the significant decrease of DD could indicate a possible cardioprotective role of genistein in postmenopausal women.