Studies on the Functionality of Newly Synthesized Fibrinogen after Treatment of Acute Myocardial Infarction with Streptokinase, Increase in the Rate of Fibrinopeptide Release

In 15 patients with acute myocardial infarction who received 1,500,000 U of streptokinase, the gradual appearance of newly synthesized fibrinogen and the fibrinopeptide release during the first 35 h after SK treatment were evaluated. At 5 h the fibrinogen circulating in plasma was observed as the high molecular weight fraction (HMW-Fg). The concentration of HMW-Fg increased continuously, and at 20 h reached values higher than those obtained from normal plasma. HMW-Fg represented about 95% of the total fibrinogen during the first 35 h. The degree of phosphorylation of patient fibrinogen increased from 30% before treatment to 65% during the first 5 h, and then slowly declined to 50% at 35 h.

The early rates of fibrinopeptide A (FPA) and phosphorylated fibrinopeptide A (FPAp) release are higher in patient fibrinogen than in isolated normal HMW-Fg and normal fibrinogen after thrombin addition. The early rate of fibrinopeptide B (FPB) release is the same for the three fibrinogen groups. However, the late rate of FPB release is higher in patient fibrinogen than in normal HMW-Fg and normal fibrinogen. Therefore, the newly synthesized fibrinogen clots faster than fibrinogen in the normal steady state.

In two of the 15 patients who had occluded coronary arteries after SK treatment the HMW-Fg and FPAp levels increased as compared with the 13 patients who had patent coronary arteries.

These results provide some support for the idea that an increased synthesis of fibrinogen in circulation may result in a procoagulant tendency. If this is so, the HMW-Fg and FPAp content may serve as a risk index for thrombosis.

Effect of Aspirin on Platelet Phospholipids

It was observed that the acetylsalicylic acid “in vitro” (final concentration 10−4 M) as well as “in vivo” (1 g of aspirin) caused a platelet phospholipids variation which basically consisted of:

1. A diminution of the phospholipids/proteins rate of 22%.

2. A reduction of sphingomyelin “in vivo” of 27.66% and “in vitro” of 16.82%.

3. An increase in phosphatidyl choline “in vivo” of 12.24% and “in vitro” 10.28%.

The possible effects that these changes might have on the platelet function are evaluated.

Changes in Human Amniotic Fluid Fibrinolytic Inhibitor Levels during Pregnancy

The amniotic fluid (AF) when incubated with the patient’s own plasma diminishes the lytic activity of the plasma. It is suggested that this inhibition is due to the presence of fibrinolytic inhibitors in the AF. The inhibitors rate increases as pregnancy advances. Evaluating these inhibitors in a group of 65 women before and after the 38th week of pregnancy, a higher rate of fibrinolytic inhibitors is found after the 38th week. The said differences are statistically significant. For the moment it does not seem that the increasing of the inhibitors in the last part of pregnancy might be used as a fetal maturity test.

Interaction of Plasma Kallikrein with Protein C Inhibitor in Purified Mixtures and in Plasma

The interaction between plasma kallikrein (KK) and protein C inhibitor (PCI) and the influence of KK on the complex formation between activated protein C (APC) and PCI was studied in purified systems as well as in plasma in order to assess the significance of these reactions in the plasma milieu. PCI complexed to KK (KK: PCI) or to APC (APC: PCI) was measured by sandwich ELISA’s using antibodies directed against each protein in the complexes. The formation of KK: PCI complexes assayed by this method paralleled the inhibition of KK amidolytic activity by PCI in purified system. Incubation of normal plasma (NHP) at 4 °C, which can induce prekallikrein activation due to cold activation, resulted in PCI inactivation and appearance of KK: PCI complexes. PCI activity fell to 35% of the NHp and 1.2 μ/ml of KK: PCI complex was formed. However, incubation of NHP at room temperature or of prekallikrein deficient plasma at 4 °C did not result in significant decrease of PCI activity. Thus the PCI inactivation was associated with prekallikrein activation and complexation to PCI following cold activation. Incubation of exogenous purified KK with NHP resulted in PCI inactivation and complexation with KK in a temperaturedependent manner. Addition of 2.8 μ/ml KK to plasma at 4 °C resulted in the inactivation of 55% of plasma PCI and the formation of 0.9 μ/ml KK: PCI which represents 21% of the KK added, whereas at 37 °C PCI was inactivated to 30% and only 0.30 μg/ml KK: PCI complexes were measured. These results indicate that PCI is a major KK inhibitor at 4 °C. At 37 °C, PCI accounted for aborfi 7% of the inhibition of the KK added. In separate experiments, following addition of 2.5 μg/ml APC to NHR more than 1 μg/ml of APC: PCI complex was formed in 3 h. When NHP was prior incubated with KK, PCI activity decreased to 10% of that of the normal plasma. Subsequent addition of APC to the plasma treated with KK resulted in formation of only 35 μg/ml of APC: PCI complex compared to 1,350 μg/ml when plasma was not previously incubated with KK. These results indicate that PCI could play a physiological role in the inhibition of plasma KK, and that, in turn, plasma KK can either complex to or inactivate plasma PCI. Thus, KK could modulate the PCI inhibition of APC in plasma.

Fibrinogen Valencia A New Case of Congenital Dysfibrinogenemia

A new case of dysfibrinogenemia is described, the proband had low fibrinogen level and a moderate hyperfibrinolysis. Attention is drawn to the florid hemorrhagic picture and its early presentation.

The family history showed a moderate hyperfibrinolysis.

It appeared that the cause of the dysfibrinogenemia was due to a deficient polymerization of the α chains of the fibrinogen.

It is not yet known if this is caused by a defective liberation of fibrinopeptides. Due to the peculiar characteristic of this case and in accordance with the international norms, we propose to call this dysfibrinogenemia “Fibrinogen Valencia.”

Contribution of Platelets to Increased Plasminogen Activator Inhibitor Type 1 in Severe Preeclampsia

Plasminogen activator inhibitor activity and antigen were evaluated in plasma, serum and platelet lysate in patients with severe preeclampsia (n = 12), and in normal pregnant women (n = 21). Other parameters, including β-thromboglobulin and platelet count, were also evaluated. A significant increase (p <0.05) in β-thromboglobulin was observed in platelet poor plasma of preeclamptic women when compared with that of normal pregnant women, and the platelet count was lower in the preeclamptic group than in the normal pregnant group. A significant increase in plasminogen activator inhibitor activity and antigen was observed in platelet poor plasma of the preeclamptic group as compared with normal pregnant women, whereas platelet lysate from preeclamptic women showed a significant decrease in both plasminogen activator inhibitor activity and antigen as compared with that of normal pregnant women. No correlation between β-thromboglobulin and plasminogen activator inhibitor type 1 antigen in platelet poor plasma was observed, but a significant inverse correlation (r = −0.78, p <0.05) between β-thromboglobulin in platelet poor plasma and plasminogen activator inhibitor-1 antigen in platelet lysate was obtained in preeclamptic patients. However, in platelet poor plasmas obtained from normal platelet rich plasmas activated with thrombin (0.1 IU/ml, 37° C, 1 min), an increase of about 300 ng/ ml in β-thromboglobulin was observed while the increase in plasminogen activator inhibitor was only 4 ng/ml. It is concluded that the contribution of platelet plasminogen activator inhibitor-1 to the increase in plasma plasminogen activator inhibitor-1 levels in preeclamptic patients is negligible but the possibility that intravascular platelet activation indirectly contributes “in vivo” to the increase in plasma plasminogen activator inhibitor-1 levels in severe preeclampsia patients cannot be ruled out.

Protein C Inhibitor and Other Components of the Protein C Pathway in Patients with Acute Deep Vein Thrombosis during Heparin Treatment

The protein C inhibitor (PCI) concentration and other parameters of the protein C pathway were studied in 19 patients with symptomatic acute deep vein thrombosis before and during the first 5 days of heparin treatment. The mean levels of PCI antigen and activity decreased rapidly and significantly during the first day of heparin therapy from 83 and 81% to 60 and 59% of the pooled normal human plasma (p <0.01), respectively, and to 56 and 54% after 5 days of treatment (p <0.01). In contrast, antithrom-bin III decreased progressively 25% during 5 days of heparin treatment. Protein C antigen and activity and total protein S remained unchanged during heparin treatment. Free protein S was decreased before heparin treatment (83%, p <0.05) and increased to normal values after 5 days of treatment. C4b-binding protein was significantly increased before and during heparin treatment (p <0.01). Activated protein C (APC) complexed to its two major plasma inhibitors, PCI and α1-antitrypsin (α1AT) were measured by specific ELISA’s. Before treatment, 18 of the 19 patients studied had increased levels of APC: α1AT complexes with a mean value of 27 ± 22 ng/ml (range, 6−86 ng/ml) compared to normal values (8 ± 2 ng/ml) and 12 of the patients also had detectable APC:PCI complex levels with a mean value of 11 ±17 ng/ml (range, 5−68 ng/ml). Both APC:inhibitor complexes decreased significantly during heparin treatment.

Low Level of Circulating Activated Protein C Is a Risk Factor for Venous Thromboembolism

The levels of circulating activated protein C (APC) reflect in vivo protein C activation. The aim of this study was to determine whether a low APC level is an independent risk factor for venous thromboembolism (VTE). We measured APC in 160 patients with a history of VTE and without recognized thrombophilic defects, and in 199 healthy individuals. The mean (±SD) APC level was lower in patients (0.99 ± 0.44 ng/ml) than in controls (1.19 ± 0.41 ng/ml) (p <0.0001), and showed a different distribution in the two groups. Thirty-eight patients (23.7%) had APC levels below the 5th percentile of the control group (<0.69 ng/ml) and 57 patients (35.6%) had APC levels below the 10th percentile (<0.77 ng/ml). APC levels <0.69 ng/ml increased the risk of a single or recurrent episode of VTE 4.2-fold (95% confidence interval, 2.0-9.0) or 6.9-fold (2.6-17.9), respectively, and APC levels <0.77 ng/ml increased these risks 3.4-fold (1.9-6.2) or 5.1-fold (2.3-11.2), respectively, compared with controls. Familial studies revealed that in some cases the low APC phenotype seems to be hereditary. We conclude that a low level of circulating APC in individuals without any of the most recognized thrombophilic defects is a prevalent, independent risk factor for VTE, and that it predisposes to recurrent VTE.

Plasma PAI-1 Levels in Obese Children – Effect of Weight Loss and Influence of PAI-1 Promoter 4G/5G Genotype

An association between an increase in plasminogen activator inhibitor type 1 (PAI-1) and obesity, and also between elevated levels of PAI-1 and the presence of PAI-1 promoter 4G allele has been described in adults and can contribute to increased risk of cardiovascular disease. It has also been suggested that in adults a decrease in adiposity has beneficial effects on the haemostatic system. However, less information is available regarding adiposity and fibrinolysis in children. The aim of the present study is to evaluate the effect of weight loss and the influence of the PAI-1 promoter 4G/5G genotype on the fibrinolytic system and lipid parameters in obese children. The clinical groups included 102 obese children and 105 controls of similar age and sex distribution. A significant decrease in fibrinolytic activity due to a significant increase in PAI-1 antigen and activity levels was observed in the obese children in comparison with the control group. In obese children, no significant differences in PAI-1 levels between the PAI-1 4G/5G genotypes were obtained. A significant correlation was observed between PAI-1 antigenic and functional levels and body mass index (BMI), as well as between PAI-1 levels and both triglyceride and insulin levels. No correlation between PAI-1 levels and either cholesterol or glucose levels was observed.

After a three-month period of treatment to reduce weight, an increase in fibrinolytic activity due to a decrease in PAI-1 levels was observed in the obese children who had reduced their BMI in comparison with the group of obese children who did not show a decrease in their BMI. No significant differences between the two groups with respect to the variations in tissue type plasminogen activator and fibrinogen levels were obtained after three months of intervention to reduce weight. A significant correlation was observed between variations in BMI and variations in PAI-1 levels, and a significant inverse correlation was also observed between previous PAI-1 levels and variation in PAI-1 levels. Therefore, the largest decrease in PAI-1 levels was observed in the obese children with the highest previous PAI-1 levels.

In conclusion, a decrease in BMI in obese children shows a favourable effect on the fibrinolytic system due to a decrease in PAI-1 levels. However, no influence of 4G/5G genotype on PAI-1 levels was observed.

Plasminogen Activator Inhibitor-1 (PAI-1) Promoter 4G/5G Genotype and Increased PAI-1 Circulating Levels in Postmenopausal Women with Coronary Artery Disease

Increased circulating levels of type 1 plasminogen activator inhibitor (PAI-1) have been associated with coronary artery disease (CAD). However, genetic and environmental determinants of PAI-1 expression are only partially understood. The levels of PAI-1 have been found to relate to 4/5 guanosine (4G/5G) polymorphism in the promoter region of the PAI-1 gene. The 4G allele in this polymorphism has been associated with higher levels of plasma PAI-1 activity, but despite the strong correlation between PAI-1 activity and antigen, no association has been found between PAI-1 antigen levels and the PAI-1 promoter 4G/5G genotype. The aim of the present study was to analyze the influence of the PAI-1 promoter 4G/5G genotype on PAI-1 levels in post-menopause women with coronary disease in comparison with healthy women in pre and postmenopausal status, and the influence of this genotype on variations in PAI-1 levels after hormone replacement therapy (HRT). No differences between 4G/5G allele distribution in the groups studied were observed. The group of postmenopausal women with CAD showed significantly increased PAI-1 antigen and activity levels in comparison with the control groups, and the levels of PAI-1 correlated with the 4G/5G genotype. A multivariate analysis revealed that in the CAD group there was a high correlation between 4G allele dosage and PAI-1 antigen levels, which were also influenced by the triglyceride levels but not by estrogen or glucose levels. After hormone replacement therapy the decrease in PAI-1 levels was correlated with the 4G allele dosage. We conclude that in the group of postmenopausal women with CAD the influence of the PAI-1 promoter 4G/5G genotype on PAI-1 levels is more evident than in the control groups, and that the decrease in PAI-1 levels after HRT in CAD women correlates with the 4G allele dosage.

Elevated High Molecular Weight Fibrinogen in Plasma Is Predictive of Coronary Ischemic Events after Acute Myocardial Infarction

This study investigates the association between the concentration and function of plasma fibrinogen molecules measured at the time of hospital admission in patients with acute myocardial infarction (AMI), with reference to the risk of new coronary ischemic events during a three-day follow-up period of. Before starting fibrinolytic and anticoagulant treatment plasma fibrinogen, high molecular weight fibrinogen (HMW-fibrinogen), fibrin formation rate (FbFR) and phosphorous content in fibrinogen were determined in 90 AMI patients. During a three-day follow-up period 12 patients suffered new ischemic events. The 12 patients with coronary ischemia had higher concentrations of plasma fibrinogen (312 ± 23 vs. 270 ± 73 mg/dl, p <0.05) and HMW-fibrinogen (246 ± 35 vs. 189 ± 23 mg/dl, p <0.001) and a higher FbFR (65 ± 30 vs. 40 ± 25, p <0.001) than patients without these events. No association was found between the phosphorous content in fibrinogen and new coronary ischemic events. We conclude that after myocardial infarction an elevated plasma level of HMW-fibrinogen and a high FbFR value at the time of hospital admission are associated with new coronary ischemic events during a three-day follow-up period.

Prothrombin G20210A mutation and oral contraceptive use increase upper-extremity deep vein thrombotic risk

The role played by a hypercoagulable state, either inherited or acquired, in the pathogenesis of upper-extremity deep vein thrombosis (UEDVT) remains a question of debate. We performed a case-control study including 79 patients with a first objectively confirmed episode of UEDVT, 31 secondary and 48 primary, and 165 healthy controls. Nine patients (11.4%) with UEDVT were carriers of the prothrombin G20210A mutation vs. six (3.7%) in controls; P = 0.025, OR: 3.39 (95% CI 1.16 to 9.88). No statistical difference was observed between cases and controls for the factor V Leiden mutation, AT, protein C or protein S deficiency and anticardiolipin antibodies (ACAs). Thirteen (35.1%) UEDVT patients were oral contraceptive (OC) users vs. 12 (16%) controls; P = 0.020, OR: 2.89 (95% CI 1.16-7.21). When secondary UEDVT patients were compared with controls, no differences were observed in any of the risk factors analysed. On the other hand, when primary UEDVT was considered, six (12.5%) patients were carriers of the prothrombin G20210A mutation vs. six (3.7%) controls; P = 0.031, OR: 3.76 (95% CI 1.15-12.26). Regarding ACAs, a borderline statistical significance was observed when primary UEDVT was compared with controls, P = 0.048; OR: 4.88 (95% CI 1.05-22.61). In primary UEDVT, 52% of the fertile women were OC users vs. 16% of controls; P = 0.001, OR:5.78 (95% CI 2.13-15.67). When the interaction of both factors, i.e. prothrombin G20210A mutation and OC intake, were considered, the risk increased markedly, indicating a synergistic effect as observed with other thrombotic locations. In patients with primary UEDVT screening for antithrombin, protein C and protein S deficiency and APC resistance would not be justified, although it might be reasonable to determine the carrier status of the prothrombin G20210A mutation only in OC users.

Hereditary Homozygous Heparin Cofactor II Deficiency and the Risk of Developing Venous Thrombosis

Heparin cofactor II (HCII) is a specific inhibitor of thrombin in the presence of heparin or dermatan sulphate. Although there have been reports on families in which a heterozygous HCII deficiency is associated with thromboembolic events, several epidemiological studies revealed that heterozygous HCII deficiency is as prevalent among healthy subjects as it is among patients with deep venous thrombosis (DVT). It is therefore not yet clear whether HCII is or is not a thrombotic risk factor.

We analyze and describe in an extended family the biochemical and genetic thrombophilic risk factors and evaluate the potential thrombotic risk involved in homozygous and heterozygous HCII deficiency, either alone or associated with other thrombotic or circumstantial risk factors. The propositus has had three episodes of DVT and a pulmonary embolism. During the first episode of DVT the patient was diagnosed as having AT deficiency. Later, a functional and antigenic HCII deficiency, compatible with the homozygous form, was detected. The family study shows that both the propositus and her sister have homozygous HCII deficiency and that 12 of the 27 family members have heterozygous HCII deficiency.

This is possibly the first case report on a homozygous phenotype for the HCII deficiency with, in addition, partial AT deficiency. The propositus has suffered several thrombotic events, unlike the other 12 family members with heterozygous HCII deficiency and her sister, who is also homozygous for this disorder. We suggest that HCII deficiency may play a limited in vivo role as a thrombotic risk factor unless associated with AT deficiency or another congenital thrombotic risk factor.

Lipoprotein(a) Levels and Isoforms and Fibrinolytic Activity in Postmenopause – Influence of Hormone Replacement Therapy

Epidemiological studies suggest that hormone replacement therapy (HRT) decreases the risk of cardiovascular disease in postmenopausal women via several mechanisms, including modifications in the fibrinolytic system and lipoprotein(a) [Lp(a)] levels. The aim of this study was to examine the influence of the levels and isoforms of Lp(a) on fibrinolytic activity in 91 postmenopausal women in comparison with premenopause and analyze the effect of HRT on those parameters. In postmenopause, an increase in plasma Lp(a) and plasminogen activator inhibitor-1 (PAI-1) levels was found. A significant inverse correlation was observed between Lp(a) or PAI-1 levels and plasmin generation. Plasma samples with low molecular weight (MW) apo(a) isoforms showed higher plasmin inhibition than plasmas with high MW apo(a) isoforms and similar levels of total Lp(a) and PAI-1. HRT induced a significant decrease in Lp(a) and PAI-1 levels and an increase in estradiol levels, as well as an increase in fibrinolytic activity. A significant correlation was found between the percentages of variation in Lp(a) levels and in plasmin generation and between the percentages of variation in PAI-1 levels and in the euglobulin lysis time under HRT. In conclusion, the increase in fibrinolytic activity observed in women under HRT could be explained by two independent mechanisms: (a) the decrease in PAI-1 and (b) the decrease in the inhibition of plasmin generation due to the decrease in Lp(a) levels.

Influence of Lipoprotein (a) Levels and Isoforms on Fibrinolytic Activity – Study in Families with High Lipoprotein (a) Levels

Increased levels of lipoprotein (a) [Lp(a)] have been considered an independent risk factor for cardiovascular disease, but the mechanism behind this relationship is not completely understood. A high concentration of Lp(a) may interfere with fibrinolysis because of the structural similarity between apo(a) and plasminogen. The aim of the present study was to examine the influence of apo(a) levels and isoforms on fibrinolytic activity in 82 subjects from 24 families in which the Lp(a) levels were ≥30 mg/dl in at least one child and one parent. Several fibrinolytic parameters, including plasmin generation by fibrin-bound tissue plasminogen activator, the lipid profile and apo(a) isoforms were studied. Subjects with high circulating Lp(a) levels (n = 44) had significantly reduced plasmin generation compared with their relatives with normal Lp(a) levels (n = 38). A significant inverse correlation between Lp(a) levels and plasmin generation was observed. The individuals with a combination of high levels of plasma Lp(a) and a major apo(a) isoform ≤580 kD molecular weight show the lowest fibrinolytic activity. A high correlation was found between the levels of apo(a) isoforms in children and the levels of the corresponding parental apo(a) iso-forms. We conclude that the antifibrinolytic effect of Lp(a) in subjects with two apo(a) isoforms may depend not only on the total plasma level of Lp(a) but also on the relative concentration of the small apo(a) isoform.

Abnormal Expression of Type 1 Plasminogen Activator Inhibitor and Tissue Factor in Severe Preeclampsia

Preeclampsia is a multisystemic obstetric disease of unknown etiology that is commonly associated with fibrin deposition, occlusive lesions in placental vasculature, and intrauterine fetal growth retardation. We previously reported that type 1 plasminogen activator inhibitor (PAI-1) levels are significantly increased in plasma and placenta from pregnant women with preeclampsia compared to normal pregnant women. In the present report we localize the expression of placental PAI-1 in greater detail and compare it with that of tissue factor (TF), a procoagulant molecule, and vitronectin (Vn), a PAI-1 cofactor. We also examine the expression of two cytokines, tumor necrosis factor α (TNFα) and interleukin-1 (IL-1), in order to begin to define the underlying mechanisms responsible for the elevated levels of PAI-1 and fibrin deposits observed in placenta from preeclampsia. We demonstrate a significant increase in PAI-1, TF and TNFα antigen and PAI-1 and TF mRNA in placentas from preeclamptic patients. PAI-1 mRNA was increased not only in syncytiotrophoblast and infarction areas, but also in fibroblasts and in some endothelial cells of fetal vessels in placentas from preeclamptic patients. However, there was no colocalization between PAI-1, TF, Vn and TNFα in placental villi. The elevated TNFα in the placenta may induce PAI-1 and TF, and thus promote the thrombotic alterations associated with preeclampsia.