摘要:

Third-generation oral contraceptives (OC) have been associated with an increased risk of venous thrombosis compared with second-generation OC. To find an explanation for this increased risk, the effect of a second- and third-generation OC and of the progestagens used in these pills on several fibrinolytic parameters was studied in the absence or presence of the factor V Leiden mutation. In a single-center, double-blind trial, 51 women without and 35 women with the factor V Leiden mutation were randomized to either a second-generation (30 μg ethinylestradiol/150 μg levonorgestrel) or a third-generation (30 μg ethinylestradiol/150 μg desogestrel) oral contraceptive. After two menstrual cycles of use and a wash-out period of two cycles, the participants received the corresponding progestagen-only preparation containing 150 μg levonorgestrel or 150 μg desogestrel. D-Dimers, thrombin-activatable fibrinolysis inhibitor (TAFI) and the clot lysis time in the absence (LYSmin) or the presence (LYSplus) of a blocking anti-factor XI antibody were determined in plasmas of the participating women, and the mean difference in changes between the OC were calculated. Both combined OC induced increased plasma levels of D-dimers and TAFI, and induced a prolongation of LYSplus, whereas LYSmin hardly changed. Virtually no changes in fibrinolytic parameters were observed for the progestagen-only preparations. No differential effects between levonorgestrel- and desogestrel-containing OC were found in women without factor V Leiden. Women with the mutation on levonorgestrel-containing OC showed an increased LYSplus compared with desogestrel containing OC (3.9; 95% confidence interval, 0.1–7.7). When using progestagen-only preparations, no differential effect on the fibrinolytic parameters were found, except for non-carriers on levonorgestrel who showed a reduced LYSmin compared with non-carriers on desogestrel (−4.0; 95% confidence interval, −7.8 to −0.2). In conclusion, the effect of oral contraceptives on fibrinolytic parameters is largely independent of the type of progestagen. The increased fibrinolytic activity during OC use appears to be induced by the estrogen component and may be counteracted by increased TAFI activation. This may result in an enhanced downregulation of fibrinolysis.

ISSN:0957-5235    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The urokinase-type plasminogen activator receptor (uPAR) is a multifunctional molecule involved in migration and adhesion of leukocytes to sites of inflammation. Based on our hypothesis that a chemoattractant can stimulate uPAR expression by its target cell, thereby promoting cell migration, we employed three chemokines [monocyte chemotactic protein (MCP)-1, MCP-2 and MCP-3] as chemoattractants, and examined their effect on uPAR expression in a human monocyte-like cell line, U937. Northern blot analysis demonstrated that all three chemokines tested increased the level of uPAR mRNA in time-dependent and dose-dependent manners. Among them, MCP-3 exhibited the most potent effect. Scatchard analysis showed that incubation with MCP-3 (1 × 10−8mol/l) for 16 h resulted in a significant increase in the number of uPAR from (6.8 ± 0.3) × 103to (10.3 ± 1.6) × 103/cell, and in a slight increase in the equilibrium dissociation constant,Kd. The effect of anti-uPAR antibodies on MCP-3-induced U937 cell migration across an endothelial cell monolayer and a type I collagen layer was assessed by means of the modified Boyden chamber assay. Although MCP-3 caused a three-fold increase in migration, incubation with an antibody to uPAR markedly abrogated the induced cell migration. These results support our hypothesis and suggest that up-regulation of uPAR in target cells might be an important and common feature of chemoattractants.

ISSN:0957-5235    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Platelet microparticles (PMP) are submicroscopic membrane vesicles released by platelets during activation. Flow cytometry is the most widely used method for quantifying PMP, but the optimization of the technical method has not yet been fully evaluated. This study was designed to assess the pre-analytical variables including blood sampling conditions, and to evaluate the analytical variations including effect of the platelet-specific antibodies and quantitative beads, precision, linearity and accuracy in comparison with β-thromboglobulin, which is one of the platelet activation markers. Numbers of PMP collected into citrate–theophylline–adenosine-dipyridamole (CTAD) tubes were increased with time, but to a lesser extent than when collected into sodium citrate tubes. The precision of the PMP assay was relatively high. Excellent linear correlation was observed for dilution linearity. Regarding the platelet-specific antibodies used, anti-CD41a-labeled samples resulted in higher PMP levels than those labeled with anti-CD61 and anti-CD42a. There was no significant difference of PMP counts according to the quantitative beads. The PMP assay is well correlated with β-thromboglobulin levels. Our findings suggest that blood samples for the PMP assay should be collected in a CTAD tube and delayed measurement is not allowed to avoid artefactual platelet activation. The PMP assay can be used successfully as a useful marker of the detection ofin vivoplatelet activation, provided that pre-analytical and technical points are optimally taken into consideration.

ISSN:0957-5235    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

High cholesterol is a well-established risk factor of myocardial infarction (MI). Since monocytes play a pivotal role in the development of atherosclerosis, one might anticipate that their functional properties are very important in relation to MI. In the present study, we have explored how the lipopolysaccharide (LPS)-induced reactivity of monocytes in whole bloodin vitrorelates to the serum lipid profile of healthy subjects with a history of MI or cancer in their close family. Twenty of the 54 subjects (of the total 266 test subjects) in the MI families had moderately high cholesterol (7.1–10.2 mmol/l), whereas 34 had normal cholesterol. Nineteen of the normocholesterol individuals had hyperactive monocytes (high responders), whereas 15 had monocytes responding normally. Two of the 20 subjects in the high cholesterol group had hyperactive monocytes. LPS-induced tissue factor, tumour necrosis factor-α and interleukin-6 were on the average three to four times higher in the normocholesterol group compared with the moderately hypercholesterol group, and hence no positive correlation was found between hyperactive monocytes and cholesterol. The 42 subjects in the families with cancer had normal cholesterol, and two of these subjects had very high LPS-induced tissue factor, tumour necrosis factor-α and interleukin-6, whereas eight of the 170 subjects without MI or cancer in their family were high responders. This further substantiates the notion that moderately high cholesterol is not associated with enhanced monocyte activation in whole blood. Hyperactive peripheral blood monocytes are suggested to be associated with a significant risk factor in developing coronary heart disease.

ISSN:0957-5235    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

At sites of blood vessel injury, platelets adhere to exposed vessel components, such as collagen, or immobilized fibrinogen derived from plasma or activated platelets. The divalent cations Mg2+and Ca2+are essential for platelet adhesion and activation, but Mg2+can also inhibit platelet activation. The present study evaluates, by an enzymatic method, the effects of various divalent cations on the adhesion of isolated human platelets to collagen, fibrinogen, albumin or plasticin vitro. By enzyme-linked immunosorbent assay, platelet surface expression of P-selectin was measured to estimate the state of activation on adherence. Mg2+increased platelet adhesion exclusively to collagen and fibrinogen at physiologically relevant concentrations. At higher concentrations, the adhesion declined. Ca2+induced a weak adhesion only to fibrinogen at physiological doses and a peak of increased adhesion to all protein-coated surfaces at 10 mmol/l. Mn2+elicited dose-dependent adhesion only to collagen and fibrinogen. Zn2+, Ni2+and Cu2+increased the adhesion of platelets independently of the surface. Ca2+dose-dependently inhibited adhesion elicited by Mg2+to collagen and fibrinogen. No other combination of divalent cations elicited such an effect. Mg2+-dependent platelet adhesion to collagen and Ca2+-dependent adhesion to fibrinogen increased P-selectin expression. Thus, the present study shows that the outcome of the platelet adhesion depends on the surface and the access of divalent cations, which co-ordinate the intensity of platelet adhesion and P-selectin surface expression.

ISSN:0957-5235    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The pathophysiology of primary pulmonary hypertension (PPH) remains poorly understood. Vascular wall remodeling and endothelial dysfunction reflected by modifications in plasma fibrinolytic proteins and von Willebrand factor have been well documented in PPH. We hypothesize that endothelial mediators, produced in excess in PPH patients, may stimulate migrating mononuclear cells and thereby modulate alveolar macrophage function; in particular, the plasminogen activation system. Components of the fibrinolytic system were therefore studied in plasma, blood monocytes and alveolar macrophages obtained from bronchoalveolar lavage in 10 patients with PPH and in four controls. Compared with controls, PPH patients had elevated plasma levels of tissue-type plasminogen activator (15.6 ± 9.9 versus 5.5 ± 3 ng/ml) and plasminogen activator inhibitor-1 (27.8 ± 23 versus 16.4 ± 12 ng/ml). In contrast, binding and activation of plasminogen by single-chain urokinase-type plasminogen activator (scu-PA) at the surface of blood monocytes and alveolar macrophages were not different from those of control values. Dissociation constants (Kd) for binding of scu-PA and plasminogen to alveolar macrophages were similar in both PPH (4.7 ± 1.5 and 0.88 ± 0.3 μmol/l, respectively) and control (6.7 ± 0.1 and 1.02 ± 0.12 μmol/l, respectively) groups. These results indicate that in PPH patients the fibrinolytic activity of alveolar macrophages is normal, whereas endothelial fibrinolytic proteins are abnormally elevated in plasma.

ISSN:0957-5235    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Mild hyperhomocysteinemia is associated with homozygosity for the thermolabile variant of 5,10-methylenetetrahydrofolate reductase (MTHFR) and could increase the risk of venous thromboembolic disease (VTD). Recently, the second A1298C mutation of the MTHFR gene was described. The present study aimed to analyze both mutations of the MTHFR gene and plasma homocysteine levels in subjects with VTD. The study groups comprised 146 patients with VTD and 100 healthy subjects. There were no statistical differences in carrier frequency and allelic frequency for both A1298C and C677T mutations, nor were there any differences encountered between subjects with VTD and controls in either plasma homocysteine levels or according to C677T or A1298C genotypes of MTHFR. In our VTD patients and controls, neither MTHFR 677CT/1298CC nor MTHFR 677TT/1298CC combined genotypes were observed; double heterozygotes (A1298C/C677T) were represented only in 11% of VTD patients, and in 15% of the controls. In conclusion, the polymorphisms C677T and A1298C of MTHFR and fasting plasma homocysteine levels do not seem to be significant risk factors for venous thromboembolic disease.

ISSN:0957-5235    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

The recently reported plasmatic, Factor Seven Activating Protease (FSAP), has also been found to be a potent activator of pro-urokinase [single-chain plasminogen activator, urinary type (scuPA)]. An initial epidemiological study surprisingly showed that plasmas of 5–10% of healthy blood donors had an impaired potential to activate scuPA. Analysis of the respective genomic DNAs revealed one particular single nucleotide polymorphism of FSAP resulting in an identical amino acid exchange (G511E), which correlates with the reduced activities. The corresponding mutation was namedFSAP Marburg I. Thrombelastographies of wild-type and mutant plasmas were performed, facilitating the auto-activation of the intrinsic FSAP pro-enzymes by addition of dextran sulfate (DXS) and accelerated clot lysis by addition of scuPA. On these conditions, tissue-factor-induced coagulation revealed that clot lysis was significantly delayed in theMarburg Imutant plasmas as compared with wild-type plasmas. Furthermore, in the presence of DXS and scuPA, a FSAP-deficient plasma revealed significantly prolonged plasma clot lysis times, whereas the addition of purified FSAP pro-enzyme plus scuPA reversed this effect. These results support the hypothesis that FSAP contributes to the scuPA-dependent plasma fibrinolytic potential, which can be impaired in plasmas containing theFSAP Marburg Ipolymorphism, for instance.

ISSN:0957-5235    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Steroid hormones may profoundly influence hemostasis; for example, as discussed for hormone replacement therapy, pregnancy and, being less obvious, for the ovarian cycle. We investigated primary hemostasis parameters using a platelet function analyzer (PFA-100TM) during the follicular and luteal phases in 18 healthy young women without oral contraceptives. During the follicular phase, the mean closure time (CT) was 164.7 ± 56.7 s, and it decreased to 130.2 ± 30.6 s in collagen/epinephrine cartridges in the luteal phase (P= 0.0095). No significant difference could be found for CT values in collagen/adenosine diphosphate cartridges during the follicular phase as compared with the luteal phase (97.2 ± 24.2 s versus 89.6 ± 18.4 s,P= 0.174). Negative correlations between the CT values in collagen/epinephrine cartridges and von Willebrand factor from both phases of the cycle were found (follicular phase:r= −0.53; luteal phase:r= −0.54). Fibrinogen and fibrinogen degradation products were significantly increased in the luteal phase (2.49 ± 0.62 g/l versus 2.05 ± 0.59 g/l and 0.12 ± 014 versus 0.04 ± 0.04,P= 0.02 for both parameters) as compared with the follicular phase. No significant differences could be detected for plasminogen, plasmin–antiplasmin complex, prothrombin fragment 1 + 2 and D-dimer between the groups. This study indicates that platelet function is periodically altered during the ovarian cycle due to the influence of progesterone and estrogen on von Willebrand factor concentrations.

ISSN:0957-5235    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Oncostatin M (OSM) is a cytokine of the interleukin-6 (IL-6) family secreted by activated monocytes, and is expressed in atherosclerotic plaque. Smooth muscle cells (SMC), by expressing tissue factor (TF) and tissue factor pathway inhibitor (TFPI) can contribute to the thrombogenicity of atherosclerotic plaque. Consequently, the aim of this study was to evaluate the effects of OSM on the procoagulant activity of SMC. We observed that OSM induced in a concentration-dependent manner a potent procoagulant activity (PCA) that was related in part to an increased synthesis of TF, both at the cell membrane and in SMC lysates. The increased expression of TF on SMC membrane induced by OSM was sustained and was still observed 24 h after stimulation by OSM. IL-6 and leukaemia inhibitory factor (LIF), two OSM-related cytokines, did not significantly modify TF expression at the surface of SMC. In addition to its effects on TF, OSM decreased the secretion of TFPI in the supernatants of SMC, as well as in the lysates, but was devoid of effect on TFPI bound at the membrane of SMC. IL-6 and LIF reduced also TFPI secretion, which could explain why the PCA of SMC lysates treated by IL-6 or LIF was increased, despite an absence of effect on TF expression. In conclusion, these data support the hypothesis that by increasing the PCA of SMC, OSM might be involved in the thrombotic complications associated with plaque rupture.

ISSN:0957-5235    

出版商:OVID    

年代:2002

数据来源: OVID