Justo Aznar

Erythrocyte Promotion of Platelet Reactivity Decreases the Effectiveness of Aspirin as an Antithrombotic Therapeutic Modality The Effect of Low-Dose Aspirin Is Less Than Optimal in Patients With Vascular Disease Due to Prothrombotic Effects of Erythrocytes on Platelet Reactivity

BACKGROUND Aspirin (acetylsalicylic acid, ASA) is widely used for secondary prevention of ischemic vascular events, although its protection only occurs in 25% of patients. We previously demonstrated that platelet reactivity is enhanced by a prothrombotic effect of erythrocytes in a thromboxane-independent manner. This diminishes the antithrombotic therapeutic potential of ASA. Recent data from our laboratory indicate that the prothrombotic effect of erythrocytes also contains an ASA-sensitive component. In accordance with this observation, intermittent treatment with high-dose ASA reduced the prothrombotic effects of erythrocytes ex vivo in healthy volunteers. In the present study, the effects of platelet-erythrocyte interactions were evaluated ex vivo in 82 patients with vascular disease: 62 patients with ischemic heart disease treated with 200 mg ASA/d and 20 patients with ischemic stroke treated with 300 mg ASA/d. METHODS AND RESULTS Platelet activation (release reaction) and platelet recruitment (fluid-phase proaggregatory activity of cell-free releasates from activated platelets) were assessed after collagen stimulation (1 microg/mL) of platelets, platelet-erythrocyte mixtures, or whole blood. Platelet thromboxane A2 synthesis was inhibited by >94% by ASA administration in all patients. Importantly, platelet recruitment followed one of three distinct patterns. In group A (n=32; 39%), platelet recruitment was blocked by ASA both in the presence and absence of erythrocytes. In group B (n=37; 45%), recruitment was abolished when platelets were evaluated alone but continued in the presence of erythrocytes, indicating a suboptimal effect of ASA on erythrocytes of this patient group. In group C (n= 13; 16%), detectable recruitment in stimulated platelets alone persisted and was markedly enhanced by the presence of erythrocytes. CONCLUSIONS In two thirds of a group of patients with vascular disease, 200 to 300 mg ASA was insufficient to block platelet reactivity in the presence of erythrocytes despite abolishing thromboxane A2 synthesis. Platelet activation in the presence of erythrocytes can induce the release reaction and generate biologically active products that recruit additional platelets into a developing thrombus. Insufficient blockade of this proaggregatory property of erythrocytes can lead to development of additional ischemic complications.

Functionally active protein C inhibitor/plasminogen activator inhibitor-3 (PCI/PAI-3) is secreted in seminal vesicles, occurs at high concentrations in human seminal plasma and complexes with prostate-specific antigen

Protein C inhibitor (PCI) is a heparin-dependent serpin present in a native form in plasma at concentrations of 5 micrograms/mL. In vitro, PCI inhibits activated protein C (APC), thrombin, plasma kallikrein (KK) and urokinase-(uPA) and tissue-type plasminogen activator (tPA), and we have shown in vivo inhibition of APC, uPA and KK by PCI. In order to further characterize the physiological role of PCI, we have measured the level of PCI in several biological fluids. PCI antigen was assayed by ELISA and PCI activity was measured by its capability to form complexes with APC in the presence of heparin. Seminal plasma from voluntary donors had PCI levels (160 +/- 20 micrograms/mL, mean +/- SD) about 30 or 40 times higher than those found in blood plasma. Patients under a fertilization program had significantly reduced PCI seminal levels (110 +/- 35 micrograms/mL). Seminal plasma PCI retained about 45% of its activity immediately after ejaculation, and the activity rapidly decreased following incubation of seminal plasma at 37 degrees C, in parallel with the appearance of complexes of PCI with prostate-specific antigen (PSA). PCI was present in seminal vesicle secretion, obtained by autopsy, at concentration similar to that observed in semen, was mostly active and was not inactivated by incubation of secretion at 37 degrees C. The mean functional and antigen levels of PCI in urine from normal donors were 0.58 and 0.25 micrograms/mL, respectively, whereas in saliva these levels were 20 and 0.8 ng/mL, respectively. Amniotic fluid contained PCI antigen levels of 2.1 +/- 0.2 microgram/mL. These results show that PCI is secreted in the seminal vesicles in a functional form, and suggest that PSA, a major secretory component of the prostate, is responsible for its inactivation. They also suggest a physiological role of PCI in reproduction, and show that PCI is present in various biological fluids.

PAI-1 promoter 4G/5G genotype as an additional risk factor for venous thrombosis in subjects with genetic thrombophilic defects

Impaired fibrinolysis as a result of increased plasminogen activator inhibitor‐1 (PAI‐1) levels in plasma is a common finding in patients with deep vein thrombosis (DVT). A 4G/5G polymorphism in the promoter region of the PAI‐1 gene has been reported to influence the levels of PAI‐1. The 4G allele was found to be associated with higher plasma PAI‐1 activity (act), but contradictory results on the incidence of the 4G allele in DVT patients have been reported. The aim of this study was to analyse whether the PAI‐1 promoter 4G/5G genotype increases the risk of venous thrombosis in subjects with thrombophilic defects, and to determine the distribution of the PAI‐1 4G/5G genotype and its relation to plasma PAI‐1 levels in 190 unrelated patients with DVT in comparison with a control group of 152 healthy subjects. No differences between the 4G/5G allele distribution in the DVT group (0·43/0·57) and in the control group (0·42/0·58) were observed. However, the presence of the 4G allele significantly increased the risk of thrombosis in patients with other thrombophilic defects. Significantly higher PAI‐1 levels were observed in DVT patients than in the controls. Our results also showed significant differences in the plasma levels of PAI‐1 antigen (ag) and PAI‐1 act among the 4G/5G genotypes in DVT patients. A multivariate analysis revealed that, in the DVT group, PAI‐1 ag levels were influenced by the 4G allele dosage, triglyceride levels and body mass index (BMI). The influence of the 4G allele dosage on PAI‐1 levels was independent of the triglyceride levels and BMI. In the control group, no significant correlation between PAI‐1 levels and 4G allele dosage was observed. In conclusion, the PAI‐1 promoter polymorphism was found to have an influence on PAI‐1 levels in DVT patients and on the risk of venous thrombosis in subjects with other genetic thrombophilic defects.

Hyperlipidaemia and venous thromboembolism in patients lacking thrombophilic risk factors

Summary. To ascertain the potential contribution of serum lipids to the development of deep vein thrombosis (DVT), a case–control study was conducted in 143 DVT patients lacking thrombophilic risk factors and in 194 age‐ and sex‐matched controls. DVT patients showed significantly higher body mass indices (BMI), and triglyceride levels than did controls (P < 0·001 and P = 0·045 respectively). Using multivariate analysis, BMI was the only variable which remained statistically different, thus the risk of DVT was associated with obesity (odds ratio = 2·49). These results were confirmed when additional control for fibrinogen and plasminogen activator inhibitor type 1 (PAI‐1) was carried out in a subgroup of cases and controls. When idiopathic (n = 39) and secondary (n = 104) patients with DVT were compared, the former showed a higher mean age, a higher proportion of men, and higher cholesterol levels. Age, sex and total cholesterol were statistically different by multivariate analysis. After age was dichotomized as ≥ 50 years and cholesterol ≥ 5·69 mmol/l, all three variables constituted independent risk factors for idiopathic DVT, with odds ratios of 2·73 for ages ≥ 50 years; 3·72 for men and 2·67 for cholesterolaemia ≥ 5·69 mmol/l. Obesity thus constitutes an independent risk factor for DVT, possibly in part mediated through triglyceride, fibrinogen and PAI‐1 effects on haemostasis. In addition, cholesterolaemia levels of ≥ 5·69 mmol/l constitute an independent risk factor for idiopathic DVT.

Thrombin‐activatable fibrinolysis inhibitor in young patients with myocardial infarction and its relationship with the fibrinolytic function and the protein C system

Summary. Thrombin‐activatable fibrinolysis inhibitor (TAFI) is a fibrinolytic inhibitor. Studies in coronary artery disease have reported increased TAFI activity (TAFI Act) and low TAFI antigen (TAFI Ag) levels. This controversy might be explained by the polymorphisms of its gene. Only the Thr325Ile polymorphism modulates both TAFI Ag and Act levels in vitro. This study assessed TAFI Ag and Act levels, TAFI Thr325Ile polymorphism, the fibrinolytic and protein C systems and some prothrombotic mutations in a young patient group (n = 127, aged < 51 years, with myocardial infarction) and a control group (n = 99) with similar characteristics. Patients exhibited hypofibrinolysis and higher plasminogen activator inhibitor‐1 (PAI‐1) levels. Although TAFI Ag was lower, TAFI Act level was significantly higher in patients and positively correlated with PAI‐1, protein C inhibitor and the euglobulin lysis time. No differences between groups were found according to the Thr325Ile polymorphism. Irrespective of the genotype, patients had higher TAFI Act levels. The Ile‐325 variant exhibited lower TAFI Ag levels. We suggest that the hypofibrinolysis observed in these patients results from an increase in both PAI‐1 and TAFI Act, which is not related to the Thr325Ile polymorphism. Patients have high TAFI Act with low TAFI Ag levels, probably because of an increased stability of TAFI related to a fibrinolytic hypofunction.

The effect of estrogen replacement therapy with or without progestogen on the fibrinolytic system and coagulation inhibitors in postmenopausal status.

OBJECTIVE The aim of this study was to analyze several fibrinolytic components and coagulation inhibitors in postmenopausal women and had to evaluate the effect of hormone replacement therapy. STUDY DESIGN Several hemostatic parameters were evaluated in 75 postmenopausal women before and after 3 to 4 and 12 months of hormone therapy. RESULTS An increase in plasma fibrinolytic activity primarily related to a significant increase in tissue-type plasminogen activator and a decrease in plasminogen activator inhibitor type 1 was observed in women receiving hormone replacement therapy. A significant decrease in protein S and lipoprotein(a) was detected under therapy. No modifications in tissue-type plasminogen activator/plasminogen activator inhibitor-1 and activated protein C/alpha 1-antitrypsin complexes, urokinase activity, plasminogen, and antithrombin III were detected. CONCLUSIONS The increase in fibrinolytic activity and the decrease in lipoprotein(a) levels observed in women receiving hormone replacement therapy could help decrease the risk of coronary disease associated with the postmenopausal state.

Factor V Leiden and prothrombin G20210A mutations in young adults with cryptogenic ischemic stroke.

The association between factor V Leiden (FVL) and prothrombin G20210A (PT 20210) mutations and ischemic stroke remains controversial, particularly in young adults with cryptogenic stroke. Prevalence of FVL (4.1%) and PT 20210 (8.2%) mutations was assessed in 49 patients under 50 years with cryptogenic stroke and compared with controls. Odd ratio (OR) for cryptogenic stroke was 2.62 (95% CI, 0.49-13.95) for FVL and 3.75 (95% CI, 1.05-13.34) for PT 20210 and 3.28 (95% CI, 1,17-9.20) for some recognized genetic thrombophilic defect. Moreover, the OR for cryptogenic stroke in young women using oral contraceptives (OC) was 3.59 (95% CI, 1.28-10.5). When some genetic thrombophilic defect was associated with OC, the OR was much higher (OR: 14.27; 95% CI, 0.66-309.99). Our results suggest that in the Mediterranean populations the PT 20210 mutation, but not FV Leiden, is a risk factor for cryptogenic stroke in young adults. OC use is also a significant risk factor for cryptogenic stroke, which is increased in women with some genetic thrombotic risk factor.

REDUCED FIBRINOLYTIC ACTIVITY IN CORONARY HEART DISEASE IN BASAL CONDITIONS AND AFTER EXERCISE

Fibrinolysis may be impaired in coronary heart disease patients. 20 coronary heart disease patients and 10 control subjects were examined for tissue-plasminogen activator activity, tissue-plasminogen activator antigen, fast tissue-plasminogen activator inhibitor and other fibrinolytic and haemostatic parameters including antigenic and functional protein C. Both patient and control groups were similar in age and smoking habits. All of these patients had a myocardial infarction between 1-3 months before this study. Assays were evaluated before and after an exercise test. Prothrombin time, activated partial thromboplastin time, protein C, plasminogen, alpha 2-antiplasmin, fibrinogen/fibrin degradation products and contact-activated fibrinolysis were similar before and after exercise in both groups. Fibrinolytic activity assayed by the euglobulin lysis time and fibrin-plate lysis methods was decreased in the patient group as compared with the control group but the difference was not significant. In basal conditions, tissue-plasminogen activator activity was defective in 50% of the coronary heart disease patients (p less than 0.01) and after exercise this percentage rose to 77% (p less than 0.01). However, tissue-plasminogen activator antigen in the coronary heart disease group was similar to that of the control group, both before and after exercise. The activity of the tissue-plasminogen activator inhibitor was persistently increased in coronary heart disease though this increase was not statistically significant. It is concluded that in coronary heart disease patients there is a defective fibrinolytic activity probably due to an increase in tissue-plasminogen activator inhibitor.

Physiological coagulation inhibitors (protein S, protein C and antithrombin III) in severe preeclamptic states and in users of oral contraceptives

Protein C, protein S and antithrombin III were evaluated in normal pregnancy, severe preeclampsia and chronic hypertension with superimposed severe preeclampsia. The same study was performed on a group of 10 normal women using oral contraceptives. In normal pregnancy a significant decrease in the level of free and total PS was observed in the 2nd trimester of pregnancy and was sustained throughout the remaining months. No significant changes in the levels of protein C and antithrombin III were observed during normal pregnancy. In preeclamptic states a significant decrease in protein C was observed. It was more evident in severe preeclampsia when compared with the normal pregnancy group at similar gestational age. No statistically significant differences in protein S were found when the normal and pathological groups were compared. Antithrombin III decreased only slightly in the severe preeclamptic group. The decrease in protein C and antithrombin III levels in severe preeclampsia could be related with the microthrombotic state that these patients may present. However, the role played by protein S, which decreases during normal pregnancy and in preeclampsia, is not clear. A decrease in the level of total protein S was observed in the group of women using oral contraceptives. No significant changes in protein C and antithrombin III levels were observed in this group.

Fibrinolytic parameters in normotensive pregnancy with intrauterine fetal growth retardation and in severe preeclampsia

In pregnancy a decrease in fibrinolytic activity, which is due to an increase in plasminogen activator inhibitor activity and plasminogen activator inhibitor type 1 and type 2, has been described. Because the placenta is a source of both type 1 and type 2 plasminogen activator inhibitor, we have studied them and other fibrinolytic parameters in a group of normotensive pregnant women with intrauterine fetal growth retardation and in two groups of women with preeclampsia, with or without intrauterine growth retardation. A significant increase in plasminogen activator inhibitor type 1 antigen and plasminogen activator inhibitor activity was observed in preeclampsia, with or without intrauterine growth retardation, but not in normotensive pregnancy with intrauterine growth retardation, when compared with normal pregnancy. Plasminogen activator inhibitor type 2 antigen levels showed a significant decrease in both groups of pregnant women (normotensive or preeclamptic) with intrauterine growth retardation when compared with pregnancies without intrauterine growth retardation. A significant correlation between plasminogen activator inhibitor type 2 levels and fetal weight has been observed in the clinical groups.