Microparticle-linked tissue factor activity and increased thrombin activity play a potential role in fibrinolysis failure in ST-segment elevation myocardial infarction.

Fibrinolysis for acute ST-segment elevation MI achieves early recanalisation of the infarct artery in approximately 60% of cases. The aim of the study was to determine whether failure to achieve recanalisation was associated with differences in haemostasis biomarkers compared to patients with successful fibrinolysis. Fourty-three patients were prospectively enrolled in a case-control study.

Leukocyte activation: the link between inflammation and coagulation during heatstroke. A study of patients during the 2003 heat wave in Paris.

Objective: The mechanisms linking severe inflammation and coagulation during heatstroke are poorly understood. Here, we examined the roles of the tissue factor pathway, leukocyte activation, and mediators of innate immunity in patients admitted to an intensive care unit for heatstroke during an intense heat wave in Paris.

Design: Retrospective observational study.

Hypercoagulability after partial liver resection.

One concern of living donor liver transplantation remains the risk of morbidity and/or mortality for the donors, including the risk of postoperative thrombosis. We studied the coagulation changes after partial liver resection in l2 living donors and eight patients with non-malignant hepatic tumors (controls) and searched for potential predictive markers of thrombotic complications. Thrombosis (pulmonary embolism and portal vein thrombosis) developed in two donors and two controls.

Prothrombotic markers and early spontaneous recanalization in ST-segment elevation myocardial infarction.

We tested the hypothesis that selected prothrombotic biomarkers might be associated with early spontaneous coronary recanalization in patients with ST-segment elevation acute myocardial infarction (STEMI). We prospectively enrolled 123 patients with STEMI including 53 patients with spontaneous coronary recanalization (cases) and 70 patients with persistent occlusion (controls) at the time of emergent coronary angiography and before angioplasty. All had received aspirin and heparin.

Renewal of mural thrombus releases plasma markers and is involved in aortic abdominal aneurysm evolution.

Human abdominal aortic aneurysm (AAA) expansion has been linked to the presence of a mural thrombus. Here we explored the mechanism of the continual luminal renewal of this thrombus and its ability to release biological markers potentially detectable in plasma. We also explored the ability of platelet inhibition to pacify the thrombus and to limit aneurysm progression in an experimental model.

Prothrombin Saint-Denis: a natural variant with a point mutation resulting in Asp to Glu substitution at position 552 in prothrombin.

A new prothrombin variant, with a point mutation at nucleotide 20 029 resulting in Asp 552 to Glu substitution (prothrombin numbering), has been identified in a male newborn. Plasma prothrombin level was <3%, 16% and 60% when measured by clotting, chromogenic and immunological assays respectively. The substitution did not affect the rate of prothrombin conversion to thrombin but altered thrombin activity.

A new plastic collection tube made of polyethylene terephtalate is suitable for monitoring traditional anticoagulant therapy (oral anticoagulant, unfractionated heparin, and low molecular weight heparin).

To improve the safety of blood collection, plastic tubes have been developed but various interactions with the coagulation system and/or antithrombotic drugs were reported with the first generation of such tubes. The aim of this multicentre study was to compare hemostasis test results measured in evacuated plastic tubes made of polyethylene terephtalate (VenoSafe, Terumo Europe) and in siliconized glass tubes containing the same citrate concentration (0.129 M).

Association of the -92C/G and 807C/T polymorphisms of the alpha2 subunit gene with human platelets alpha2beta1 receptor density.

Objective: Platelet adhesion to the subendothelial tissue via the collagen receptor alpha2beta1 is a crucial event in vascular biology. Although evidence has been provided that the number of platelets alpha2beta1 copies is genetically determined, the molecular change primary responsible has not been yet elucidated. The aim of our present study was to investigate the effect of combined polymorphisms within both regulatory (-52C/T and -92C/G) and coding regions (807C/T and 1648A/G) of the alpha2 subunit gene on human platelets alpha2beta1 receptor density and/or susceptibility to coronary artery disease (CAD).

Enhanced shear-induced platelet aggregation in patients who experience subacute stent thrombosis: a case-control study.

Objectives: The goal of this study was to identify differences in shear-induced platelet aggregation (SIPA) between patients who did or did not experience subacute stent thrombosis (SAT).

Background: Despite dual antiplatelet therapy, SAT after coronary stenting occurs in approximately 1% of patients. There is no accepted platelet function test to identify patients at risk.

A paradoxical pro-apoptotic effect of thrombin on smooth muscle cells.

Whereas thrombin (below 10 nM) is a potent mitogen, recent studies report that exposure to higher doses of thrombin could lead to apoptosis of neurons and tumor cells. Our results show that prolonged exposure (> or = 24 h) to thrombin (50-100 nM) exerts a pro-apoptotic effect on cultured vascular smooth muscle cells (VSMCs). This phenomenon depends on thrombin serine-protease activity but is independent of PAR-1 and -4 activation and subsequent signaling.

Protease nexin-1: a cellular serpin down-regulated by thrombin in rat aortic smooth muscle cells.

Protease nexin-1 (PN-1), a potent inhibitor of serine proteases, is present in vascular cells and forms complexes with thrombin, plasminogen activators, and plasmin. We examined the effect of thrombin on PN-1 expression by rat aortic smooth muscle cells (RASMCs). PN-1 expression was determined by measuring protein and mRNA levels, using respectively immunoblotting and semi-quantitative reverse transcriptase polymerase chain reaction (PCR).

Protease nexin-1 inhibits plasminogen activation-induced apoptosis of adherent cells.

Degradation of adhesive glycoproteins by plasmin is implicated in cell migration. In this study, we further explored the role of plasminogen activation in cell adhesion and survival and show that uncontrolled plasminogen activation at the cell surface may induce cell detachment and apoptosis. We hypothesized that this process could be prevented in adherent cells by expression of protease nexin-1, a potent serpin able to inhibit thrombin, plasmin, and plasminogen activators.

Glycoprotein Ib-mediated platelet activation. A signalling pathway triggered by thrombin.

Platelet activation by thrombin plays a major role in the development of haemostasis and thrombosis. Thrombin activates human platelets by cleaving the N-terminal region of G-protein-coupled protease-activated receptors (PARs). On the other hand, the platelet membrane glycoprotein GPIb acts as a thrombin-binding site and promotes platelet activation by low thrombin concentrations.

The serpin protease-nexin 1 is present in rat aortic smooth muscle cells and is upregulated in L-NAME hypertensive rats.

Objective: Protease-nexin 1 (PN-1) belongs to the serpin superfamily and behaves as a specific thrombin inhibitor in the pericellular environment. Little is known about PN-1 expression and its regulation in the vascular system. In this study, we examined the expression of functionally active PN-1 in vitro in rat aortic smooth muscle cells and in vivo in rat arterial media and its regulation in hypertensive rats.

Hemostasis imbalance in experimental hypertension.

Background: The rat model of chronic intoxication by N(G) -nitro-L-arginine methyl ester (L-NAME) induces severe systemic arterial hypertension and progressive ischemic lesions in the central nervous system and kidneys. We investigated the possible molecular basis of these thrombotic events.

Methods And Results: Administration of L-NAME increased plasma markers of thrombin generation, thrombin-antithrombin complexes, and soluble glycoprotein V, measured by specific ELISA.

Plasma matrix metalloproteinase-9 as a marker of blood stasis in varicose veins.

Background: Possible intermediate circulating markers linking blood stasis to vein remodeling were explored in patients with varicose veins in the lower limbs.

Methods And Results: Blood was sampled at rest (supine position) and after a stasis of 30 minutes both in the varicose vein (limbs hanging down) and in the brachial vein (arm hanging down) as a paired control. Several endothelial and leukocyte markers were measured in plasma with the use of ELISA kits.

Red blood cells from patients with homozygous sickle cell disease provide a catalytic surface for factor Va inactivation by activated protein C.

The structure of red blood cell (RBC) membranes in homozygous sickle cell disease (SCD) is significantly disturbed, with an increased exposure of aminophospholipids (phosphatidylserine and phosphatidylethanolamine) at the outer surface, responsible for a procoagulant activity of SS RBCs. Aminophospholipids are known not only to promote procoagulant reactions, but also to support inhibition of blood coagulation by the protein C system. The aim of the present study was to examine whether SS RBCs could serve as a catalytic surface for the inactivation of factor Va by activated protein C (APC).