Acute von Willebrand Factor Secretion from the Endothelium In Vivo: Assessment through Plasma Propeptide (vWf:AgII) Levels

Von Willebrand Factor in Health and Disease

Abstract—

Von Willebrand factor (vWF), the key component of hemostasis, is synthesized in endothelial cells and megakaryocytes and released into the blood as high molecular weight multimeric glycoproteins weighing up to 20 million Daltons. Blood plasma metalloprotease ADAMTS13 cleaves ultra-large vWF multimers to smaller multimeric and oligomeric molecules. The vWF molecules attach to the sites of damage at the surface of arterioles and capillaries and unfold under conditions of shear stress. On the unfolded vWF molecule, the regions interacting with receptors on the platelet membrane are exposed. After binding to the vWF filaments, platelets are activated; platelets circulating in the vessels are additionally attached to them, leading to thrombus formation, blocking of microvessels, and cessation of bleeding. This review describes the history of the discovery of vWF, presents data on the mechanisms of vWF secretion and its structure, and characterizes the processes of vWF metabolism in the body under normal and pathological conditions.

Endothelial Markers: Thrombomodulin and Von Willebrand Factor and Risk of Kidney Thrombosis After Transplantation

OBJECTIVE

Endothelial disturbance is well known as one of the causes of thrombosis. This study measured von Willebrand factor (vWF) and soluble thrombomodulin (sTM) in renal vein blood to evaluate for the risk of thrombosis after kidney transplantation.

METHODS

A cross-sectional study that included 61 consecutive recipients of kidney transplant. The sTM and activity of vWF were evaluated in blood of the renal vein at the time of reperfusion.

RESULTS

The renal vein blood had higher values of vWF activity and sTM concentration than the peripheral blood. In the first minutes of reperfusion, the concentration of thrombomodulin was the highest but activity of vWF was the lowest. As the reperfusion continued, thrombomodulin gradually decreased, but vWF increased. The strong correlations of TMs and vWF with warm ischemia were observed (r = 0.5577 and r = 0.3429, respectively). Thrombosis was found in about 10% of all recipients. However, other complications, such as delayed graft function or ureter necrosis, were associated with high values of vWF and sTM. They were correlated with increased sTM concentration and activity of vWF (P < .006 and P < .05, respectively). This was confirmed by analysis of the receiver operator characteristic curve. The area under the curve values for TMs and vWF were 0.762 and 0.602, respectively (P < .0001 and P < .015, respectively). The cutoff points for sTM and vWF were 14.89 ng/mL and 129.89%, respectively. Positive prediction value sTM and vWF were 76% and 66% and negative prediction value 69% and 59%, respectively.

CONCLUSIONS

The endothelium of a transplanted kidney could be involved in the pathogenesis of renal thrombosis. Endothelial protection during harvesting can greatly contribute to the improvement of transplantation outcomes. The renal pool of sTM and vWF could be a useful marker of the risk of renal thrombosis.

Impact of Von Willebrand Factor on Bacterial Pathogenesis

Von Willebrand factor (VWF) is a mechano-sensitive protein with crucial functions in normal hemostasis, which are strongly dependant on the shear-stress mediated defolding and multimerization of VWF in the blood stream. Apart from bleeding disorders, higher plasma levels of VWF are often associated with a higher risk of cardiovascular diseases. Herein, the disease symptoms are attributed to the inflammatory response of the activated endothelium and share high similarities to the reaction of the host vasculature to systemic infections caused by pathogenic bacteria such as Staphylococcus aureus and Streptococcus pneumoniae. The bacteria recruit circulating VWF, and by binding to immobilized VWF on activated endothelial cells in blood flow, they interfere with the physiological functions of VWF, including platelet recruitment and coagulation. Several bacterial VWF binding proteins have been identified and further characterized by biochemical analyses. Moreover, the development of a combination of sophisticated cell culture systems simulating shear stress levels of the blood flow with microscopic visualization also provided valuable insights into the interaction mechanism between bacteria and VWF-strings. In vivo studies using mouse models of bacterial infection and zebrafish larvae provided evidence that the interaction between bacteria and VWF promotes bacterial attachment, coagulation, and thrombus formation, and thereby contributes to the pathophysiology of severe infectious diseases such as infective endocarditis and bacterial sepsis. This mini-review summarizes the current knowledge of the interaction between bacteria and the mechano-responsive VWF, and corresponding pathophysiological disease symptoms.

Physiological Roles of the von Willebrand Factor-Factor VIII Interaction

Von Willebrand factor (VWF) and coagulation factor VIII (FVIII) circulate as a complex in plasma and have a major role in the hemostatic system. VWF has a dual role in hemostasis. It promotes platelet adhesion by anchoring the platelets to the subendothelial matrix of damaged vessels and it protects FVIII from proteolytic degradation. Moreover, VWF is an acute phase protein that has multiple roles in vascular inflammation and is massively secreted from Weibel-Palade bodies upon endothelial cell activation. Activated FVIII on the other hand, together with coagulation factor IX forms the tenase complex, an essential feature of the propagation phase of coagulation on the surface of activated platelets. VWF deficiency, either quantitative or qualitative, results in von Willebrand disease (VWD), the most common bleeding disorder. The deficiency of FVIII is responsible for Hemophilia A, an X-linked bleeding disorder. Here, we provide an overview on the role of the VWF-FVIII interaction in vascular physiology.

von Willebrand factor propeptide to antigen ratio identifies platelet activation and reduced von Willebrand factor survival phenotype in mice

Essentials Reduced survival of von Willebrand factor (VWF) in plasma causes type 1C von Willebrand disease. Blood was collected from mouse strains by various methods and VWF propeptide and antigen assayed. VWF propeptide to antigen ratio identifies a reduced VWF survival phenotype in mice. This ratio validates the acceptability of murine blood samples for coagulation studies.

SUMMARY

Background Reduced plasma survival of von Willebrand factor (VWF) is characteristic of patients with type 1C von Willebrand disease (VWD). These subjects can be identified by an increased steady-state ratio of plasma VWF propeptide (VWFpp) to VWF antigen (VWF:Ag). A similar phenotype occurs in mice with the Mvwf1 allele. Objectives To (i) determine if the VWFpp/VWF:Ag ratio can be used to identify a 'type 1C' phenotype in mice, (ii) determine the most reliable method for murine blood sampling, and (iii) identify the source of VWF released during problematic blood collection. Methods 'Platelet-VWF' and 'endothelial-VWF' mice were generated by bone marrow transplantation between C57BL/6J and VWF-/- mice. Several blood sampling methods were used and murine VWFpp and VWF:Ag levels determined. Plasma and platelet VWF:Ag and VWFpp, VWF multimers and VWF half-life were examined in mouse strains with and without Mvwf1. Results A single retro-orbital bleed and vena cava collection were found to be the optimal methods of blood collection. Problematic collection resulted in release of VWF from platelets and endothelium. The VWFpp/VWF:Ag ratio identified strains of mice with reduced VWF survival. Conclusion Assay of murine VWFpp and VWF:Ag has utility in determining the acceptability of murine blood samples for coagulation testing and in identification of a reduced VWF survival phenotype in mice.

von Willebrand factor and inflammation

Von Willebrand factor (VWF) is a plasma glycoprotein best known for its crucial hemostatic role in serving as a molecular bridge linking platelets to subendothelial components following vascular injury. In addition, VWF functions as chaperone for coagulation factor VIII. In pathological settings, VWF is recognized as a risk factor for both arterial and venous thrombosis, as well as a molecular player that directly promotes the thrombotic process. Recent years have seen the emergence of the concept of immuno-thrombosis by which inflammatory cells participate in thrombotic processes. In return, reports about the involvement of hemostatic proteins or cells (such as platelets) in inflammatory responses have become increasingly common, emphasizing the intricate link between hemostasis and inflammation. However, evidence of a link between VWF and inflammation arose much earlier than these recent developments. At first, VWF was considered only as a marker of inflammation in various pathologies, due to its acute release by the activated endothelium. Later on, a more complex role of VWF in inflammation was uncovered, owing to its capacity to direct the biogenesis of specific endothelial organelles, the Weibel-Palade bodies that contain known inflammation players such as P-selectin. Finally, a more direct link between VWF and inflammation has become apparent with the discovery that VWF is able to recruit leukocytes, either via direct leukocyte binding or by recruiting platelets which in turn will attract leukocytes. This review will focus on these different aspects of the connection between VWF and inflammation, with particular emphasis on VWF-leukocyte interactions.

Increased Von Willebrand factor, decreased ADAMTS13 and thrombocytopenia in melioidosis

BACKGROUND

Melioidosis, caused by bioterror treat agent Burkholderia pseudomallei, is an important cause of community-acquired Gram-negative sepsis in Southeast Asia and Northern Australia. New insights into the pathogenesis of melioidosis may help improve treatment and decrease mortality rates from this dreadful disease. We hypothesized that changes in Von Willebrand factor (VWF) function should occur in melioidosis, based on the presence of endothelial stimulation by endotoxin, pro-inflammatory cytokines and thrombin in melioidosis, and investigated whether this impacted on outcome.

METHODS/PRINCIPAL FINDINGS

We recruited 52 controls and 34 culture-confirmed melioidosis patients at Sappasithiprasong Hospital in Ubon Ratchathani, Thailand. All subjects were diabetic. Platelet counts in melioidosis patients were lower compared to controls (p = 0.0001) and correlated with mortality (p = 0.02). VWF antigen levels were higher in patients (geometric mean, 478 U/dl) compared to controls (166 U/dL, p<0.0001). The high levels of VWF in melioidosis appeared to be due to increased endothelial stimulation (VWF propeptide levels were elevated, p<0.0001) and reduced clearance (ADAMTS13 reduction, p<0.0001). However, VWF antigen levels did not correlate with platelet counts implying that thrombocytopenia in acute melioidosis has an alternative cause.

CONCLUSIONS/SIGNIFICANCE

Thrombocytopenia is a key feature of melioidosis and is correlated with mortality. Additionally, excess VWF and ADAMTS13 deficiency are features of acute melioidosis, but are not the primary drivers of thrombocytopenia in melioidosis. Further studies on the role of thrombocytopenia in B. pseudomallei infection are needed.

Platelets and von Willebrand factor in atherogenesis

The role of platelet adhesion, activation, and aggregation in acute atherothrombotic events such as myocardial infarction and stroke is well established. There is increasing evidence that platelet-endothelial interactions also contribute to early atherosclerotic plaque initiation and growth. Through these interactions, platelet-derived factors can contribute to the proinflammatory and mitogenic status of resident mural cells. Among the many putative mechanisms for platelet-endothelial interactions, increased endothelial-associated von Willebrand factor, particularly in a multimerized form, which interacts with platelet glycoproteins and integrins, is a major factor and represents a therapeutic target in early atherogenesis.

The association of low complement with disease activity in systemic sclerosis: a prospective cohort study

Background

In some rheumatic diseases such as systemic lupus erythematosus (SLE), low serum complement (‘hypocomplementaemia’) is a feature of active disease. However, the role of hypocomplementaemia in systemic sclerosis (SSc) is unknown. We sought to determine the frequency, clinical associations and relationship to disease activity of hypocomplementaemia in SSc.

Methods

The study included 1140 patients fulfilling the 2013 American College of Rheumatology criteria for SSc. Demographic, serological and clinical data, obtained prospectively through annual review, were analysed using univariable methods. Linear and logistic regression, together with generalised estimating equations, were used to determine the independent correlates of hypocomplementaemia ever, and at each visit, respectively.

Results

At least one episode of hypocomplementaemia (low C3 and/or low C4) occurred in 24.1 % of patients over 1893 visits; these patients were more likely to be seropositive for anti-ribonucleoprotein (OR = 3.8, p = 0.002), anti-Ro (OR = 2.2, p = 0.002), anti-Smith (OR = 6.3, p = 0.035) and anti-phospholipid antibodies (OR = 1.4, p = 0.021) and were more likely to display features of overlap connective tissue disease, in particular polymyositis (OR = 16.0, p = 0.012). However, no association was found between hypocomplementaemia and either the European Scleroderma Study Group disease activity score or any of its component variables (including erythrocyte sedimentation rate) in univariate analysis. Among patients with SSc overlap disease features, those who were hypocomplementaemic were more likely to have digital ulcers (OR = 1.6, p = 0.034), tendon friction rubs (OR = 2.4, p = 0.037), forced vital capacity <80 % predicted (OR = 2.9, p = 0.008) and lower body mass index (BMI) (OR for BMI = 0.9, p < 0.0005) at that visit, all of which are features associated with SSc disease activity and/or severity.

Conclusions

While hypocomplementaemia is not associated with disease activity in patients with non-overlap SSc, it is associated with some features of increased SSc disease activity in patients with overlap disease features.

Retrospectively gated MRI for in vivo assessment of endothelium-dependent vasodilatation and endothelial permeability in murine models of endothelial dysfunction

Endothelial dysfunction is linked to impaired endothelial-dependent vasodilatation and permeability changes. Here, we quantify both of these phenomena associated with endothelial dysfunction by MRI in vivo in mice. Endothelial function was evaluated in the brachiocephalic artery (BCA) and left carotid artery (LCA) in ApoE/LDLR(-/-) and high-fat diet (HFD)-fed mice as compared with control mice (C57BL/6J). The 3D IntraGate® FLASH sequence was used for evaluation of changes in vessels' cross-sectional area (CSA) and volume following acetylcholine (Ach) administration. Evaluation of endothelial permeability after administration of contrast agent (Galbumin, BioPAL) was based on the variable flip angle method for the assessment of parameters based on the relaxation time (T1 ) value. In order to confirm the involvement of nitric oxide (NO) in response to Ach, L-NAME-treated mice were also analyzed. To confirm that endothelial permeability changes accompany the impairment of Ach-dependent vasodilatation, permeability changes were analyzed in isolated, perfused carotid artery. In C57BL/6J mice, Ach-induced vasodilatation led to an approximately 25% increase in CSA in both vessels, which was temporarily dissociated from the effect of Ach on heart rate. In ApoE/LDLR(-/-) or HFD-fed mice Ach induced a paradoxical vasoconstriction that amounted to approximately 30% and 50% decreases in CSA of BCA and LCA respectively. In ApoE/LDLR(-/-) and HFD-fed mice endothelial permeability in BCA was also increased (fall in T1 by about 25%). In L-NAME-treated mice Ach-induced vasodilatation in BCA was lost. In isolated, perfused artery from ApoE/LDLR(-/-) mice endothelial permeability was increased. MRI-based assessment of endothelium-dependent vasodilatation induced by Ach and endothelial permeability using a retrospectively self-gated 3D gradient-echo sequence (IntraGate® FLASH) enables the reliable detection of systemic endothelial dysfunction in mice and provides an important tool for the experimental pharmacology of the endothelium in murine models of diseases in vivo. Copyright © 2016 John Wiley & Sons, Ltd.

von Willebrand factor propeptide: biology and clinical utility

von Willebrand factor (VWF) is a large multimeric glycoprotein that mediates the attachment of platelets to damaged endothelium and also serves as the carrier protein for coagulation factor VIII (FVIII), protecting it from proteolytic degradation. Quantitative or qualitative defects in VWF result in von Willebrand disease (VWD), a common inherited bleeding disorder. VWF is synthesized with a very large propeptide (VWFpp) that is critical for intracellular processing of VWF. VWFpp actively participates in the process of VWF multimerization and is essential for trafficking of VWF to the regulated storage pathway. Mutations identified within VWFpp in VWD patients are associated with altered VWF structure and function. The assay of plasma VWFpp has clinical utility in assessing acute and chronic vascular perturbation associated with diseases such as thrombotic thrombocytopenic purpura, sepsis, and diabetes among others. VWFpp assay also has clear utility in the diagnosis of VWD subtypes, particularly in discriminating true type 3 subjects from type 1C (reduced plasma survival of VWF), which is clinically important and has implications for therapeutic treatment.

Circulating endothelial mediators in human pancreatitis-associated lung injury

OBJECTIVES

To investigate the role of endothelial cell mediators, E-selectin (ES), intercellular adhesion molecule-1 (ICAM-1), tissue factor (TF), and von Willebrand factor (vWF), in the early phase of severe acute pancreatitis (SAP) complicated with respiratory failure [pancreatitis-associated lung injury (PALI)].

PATIENTS AND METHODS

This study included 30 patients with SAP and 39 patients with PALI. Blood samples were taken from SAP and PALI patients on presenting to the hospital (day 1), and days 2, 3, 5, and 10. The relationship between blood concentrations of the studied endothelial mediators and lung function tests was analyzed.

RESULTS

PALI patients had significantly higher ES, ICAM-1, TF, and vWF blood levels than those with SAP as early as at admission and throughout the period studied. We found the highest concentration of ES on the second day, ICAM-1 and TF at admission, and vWF level on the fifth day. There were adverse correlations between ES, ICAM-1, TF, vWF concentrations, and the index of oxygenation--PaO2/FiO2 ratio (Rs=-0.385, Rs=-0.523, Rs=-0.505, Rs=-0.408, P<0.001, respectively). The most accurate prediction of PALI was provided by ICAM-1 and TF levels on the day of admission [areas under curve (AUCs): ES, 0.704; ICAM-1, 0.787; TF, 0.757; and vWF, 0.686].

CONCLUSION

Endothelium-related mediators ES, ICAM-1, TF, and vWF appear to participate in pancreatitis-associated lung injury. In SAP, the measurement of endothelial mediator levels (especially ICAM-1 and TF) may be used as an early prognostic indicator that would predict the development of respiratory failure and to monitor the severity of lung dysfunction.

VWF excess and ADAMTS13 deficiency: a unifying pathomechanism linking inflammation to thrombosis in DIC, malaria, and TTP

Absent or severely diminished activity of ADAMTS13 (A Disintegrin And Metalloprotease with a ThromboSpondin type 1 motif, member 13) resulting in the intravascular persistence and accumulation of highly thrombogenic ultra large von Willebrand factor (UL-VWF) multimers is the pathophysiological mechanism underlying thrombotic thrombocytopenic purpura. Reduced VWF-cleaving protease levels, however, are not uniquely restricted to primary thrombotic microangiopathy (TMA), e. g. thrombotic thrombocytopenic purpura, but also occur in other life-threatening thrombocytopenic conditions: severely decreased ADAMTS13 activity is seen in severe sepsis, disseminated intravascular coagulation (DIC) and complicated malarial infection. The clinical relevance of these secondary thrombotic microangiopathies is increasingly recognised, but its therapeutic implications have not yet been determined. The presence of a secondary TMA in certain diseases may define patient groups which possibly could benefit from ADAMTS13 replacement or a VWF-targeting therapy. This short-review focuses on the role of UL-VWF multimers in secondary TMA and discusses the potential of investigational therapies as candidates for the treatment of TTP. In conclusion, prospective clinical trials on the effectiveness of protease replacementin vivo seem reasonable. Carefully selected patients with secondary TMA may benefit from therapies primarily intended for the use in patients with TTP.

Evaluation of von Willebrand factor and von Willebrand factor propeptide in models of vascular endothelial cell activation, perturbation, and/or injury

Pharmacologically, vasoactive agents targeting endothelial and/or smooth muscle cells (SMC) are known to cause acute drug-induced vascular injury (DIVI) and the resulting pathology is due to endothelial cell (EC) perturbation, activation, and/or injury. Alteration in EC structure and/or function may be a critical event in vascular injury and, therefore, evaluation of the circulatory kinetic profile and secretory pattern of EC-specific proteins such as VWF and VWFpp could serve as acute vascular injury biomarkers. In rat and dog models of DIVI, this profile was determined using pharmacologically diverse agents associated with functional stimulation/perturbation (DDAVP), pathological activation (lipopolysaccharide [LPS]/endotoxin), and structural damage (fenoldopam [FD], dopamine [DA], and potassium channel opener (PCO) ZD6169). In rats, FD caused moderate DIVI and time-related increase in plasma VWF levels ∼33% while in control rats VWF increased ∼5%. In dogs, VWF levels transiently increased ∼30% when there was morphologic evidence of DIVI by DA or ZD6169. However, in dogs, VWFpp increased >60-fold (LPS) and >6-fold (DDAVP), respectively. This was in comparison to smaller dynamic 1.38-fold (LPS) and 0.54-fold (DDAVP) increases seen in plasma VWF. Furthermore, DA was associated with a dose-dependent increase in plasma VWFpp. In summary, VWF and VWFpp can discriminate between physiological and pathological perturbation, activation, and injury to ECs.

VWF propeptide and ratios between VWF, VWF propeptide, and FVIII in the characterization of type 1 von Willebrand disease

During posttranslational modifications of von Willebrand factor (VWF), the VWF propeptide (VWFpp) is cleaved. The ratio between VWFpp and VWF antigen (VWF:Ag) and the ratio between factor VIII (FVIII:C) and VWF:Ag may be used to assess synthesis and clearance of VWF. We analyzed the contribution of VWFpp and ratios of VWFpp/VWF:Ag and FVIII:C/VWF:Ag in the pathophysiological characterization of type 1 von Willebrand disease (VWD) in the Molecular and Clinical Markers for the Diagnosis and Management of Type 1 VWD (MCMDM-1VWD) study. The VWFpp/VWF:Ag and FVIII:C/VWF:Ag ratios were increased among patients compared with unaffected family members and healthy controls. The VWFpp/VWF:Ag ratio was higher in individuals heterozygous for missense mutations than in those heterozygous for null alleles. In contrast, the FVIII:C/VWF:Ag ratio was highest among heterozygotes for VWF null alleles. The ratios of VWFpp/VWF:Ag and FVIII:C/VWF:Ag indicate that the pathophysiological mechanisms of type 1 VWD include reduced production and accelerated clearance of VWF, but that often a combination of both mechanisms is implicated.

Elevated plasma von Willebrand factor and propeptide levels in Malawian children with malaria

Background

In spite of the significant mortality associated with Plasmodium falciparum infection, the mechanisms underlying severe disease remain poorly understood. We have previously shown evidence of endothelial activation in Ghanaian children with malaria, indicated by elevated plasma levels of both von Willebrand factor (VWF) and its propeptide. In the current prospective study of children in Malawi with retinopathy confirmed cerebral malaria, we compared these markers with uncomplicated malaria, non malarial febrile illness and controls.

Methods and Findings

Children with cerebral malaria, mild malaria and controls without malaria were recruited into the study. All comatose patients were examined by direct and indirect ophthalmoscopy. Plasma VWF and propeptide levels were measured by ELISA. Median VWF and propeptide levels were significantly higher in patients with uncomplicated malaria than in children with non-malarial febrile illness of comparable severity, in whom levels were higher than in non-febrile controls. Median concentrations of both markers were higher in cerebral malaria than in uncomplicated malaria, and were similar in patients with and without retinopathy. Levels of both VWF and propeptide fell significantly 48 hours after commencing therapy and were normal one month later.

Conclusions

In children with malaria plasma VWF and propeptide levels are markedly elevated in both cerebral and mild paediatric malaria, with levels matching disease severity, and these normalize upon recovery. High levels of both markers also occur in retinopathy-negative ‘cerebral malaria’ cases, many of whom are thought to be suffering from diseases other than malaria, indicating that further studies of these markers will be required to determine their sensitivity and specificity.

Animal models of DIC and their relevance to human DIC: a systematic review

Disseminated intravascular coagulation (DIC) is a severe clinical condition with activation of coagulation and fibrinolysis. Its diagnosis is based on the International Society of Thrombosis and Haemostasis (ISTH) scoring system of DIC. Animal models of DIC, used to investigate pathophysiology and evaluate treatments, have not been developed in a standardized way, which impedes comparison between models and translation to the human setting. In the current review of animal models of DIC an overview of species, inducers, and dosing regimens is provided. Diagnostic approaches are compared in the light of the ISTH score and treatments tested in animal models of DIC are summarized. Systematic analysis revealed that the rat is by far the preferred species amongst animal models of DIC and lipopolysaccharides (LPS) the preferred inducer of DIC. An overview of the reporting of ISTH DIC score parameters elucidated that only about 25% of the studies measure all of the four parameters necessary for the implementation the ISTH scoring system. Furthermore, most therapeutic interventions tested in animal models of DIC are administered prophylactically, which may be irrelevant to the clinical setting and could explain why compounds effective in preclinical animal models often fail in clinical trials. It is concluded that Implementation of a scoring system in animal models of DIC may increase the ability to compare DIC amongst animal models and improve the translational aspect of treatment effect.

Functional variation in the arginine vasopressin 2 receptor as a modifier of human plasma von Willebrand factor levels

SUMMARY OBJECTIVES

Stimulation of arginine vasopressin 2 receptor (V2R) with arginine vasopressin (AVP) results in a rise in von Willebrand factor (VWF) and factor VIII plasma levels. We hypothesized that gain-of-function variations in the V2R gene (AVPR2) would lead to higher plasma levels of VWF and FVIII.

METHODS AND RESULTS

We genotyped the control populations of two population-based studies for four AVPR2 variations: a-245c, G12E, L309L, and S331S. Rare alleles of a-245c, G12E, and S331S, which were in linkage disequilibrium, were associated with higher VWF propeptide, VWF and FVIII levels. The functionality of the G12E variant was studied in stably transfected MDCKII cells, expressing constructs of either 12G-V2R or 12E-V2R. Both V2R variants were fully glycosylated and expressed on the basolateral membrane. The binding affinity of V2R for AVP was increased three-fold in 12E-V2R-green fluorescent protein (GFP) cells, which is in accordance with increased levels of VWF propeptide associated with the 12E variant. The dissociation constant (K(D)) was 4.5 nm [95% confidence interval (CI) 3.6-5.4] for 12E-V2R-GFP and 16.5 nm (95% CI 10.1-22.9) for 12G-V2R-GFP. AVP-induced cAMP generation was enhanced in 12E-V2R-GFP cells.

CONCLUSIONS

The 12E-V2R variant has increased binding affinity for AVP, resulting in increased signal transduction, and is associated with increased levels of VWF propeptide, VWF, and FVIII.

von Willebrand factor and its propeptide: the influence of secretion and clearance on protein levels and the risk of venous thrombosis

BACKGROUND AND OBJECTIVES

Elevated levels of factor (F)VIII are associated with an increased risk of thrombosis. FVIII levels are determined mainly by von Willebrand factor (VWF). We have investigated the contribution of secretion and clearance rates to the elevated VWF antigen (VWF:Ag) and to the risk of thrombosis. VWF is secreted in equimolar amounts with its propeptide, which has a shorter half-life. VWF propeptide can be used as a measure of VWF secretion and allows estimation of the VWF half-life.

METHODS AND RESULTS

We have measured VWF propeptide, VWF:Ag, FVIII:Ag and FVIII activity (FVIII:C) in the Leiden Thrombophilia Study. In controls, high VWF propeptide was associated with high VWF:Ag, FVIII:Ag and FVIII:C. In contrast to mature VWF:Ag, VWF propeptide was not influenced by blood groups. Using an ELISA-based assay we have shown that VWF propeptide lacks ABO antigens. Levels were higher in men and increased with age. A long VWF half-life was also associated with high VWF:Ag, FVIII:Ag and FVIII:C. The VWF half-life was influenced by blood group (10 h in O vs. 12 h in non-O individuals), but not by sex, and only slightly by age. VWF propeptide was higher in thrombosis patients than in controls. The VWF half-life was similar in patients and controls (11.4 and 11.1 h, respectively).

CONCLUSIONS

Both secretion and clearance rates are important determinants of VWF and FVIII levels. However, mainly high VWF and FVIII levels caused by increased secretion seem to be associated with thrombosis. ABO blood group influences the clearance rates of VWF rather than VWF secretion rates.

von Willebrand factor propeptide in malaria: evidence of acute endothelial cell activation

The pathogenicity of Plasmodium falciparum is thought to relate to the unique ability of infected erythrocytes to adhere to and subsequently activate the vascular endothelium. To study the state of endothelial activation during falciparum malaria, we measured plasma levels of both von Willebrand factor (VWF) and its propeptide, indices of chronic and acute endothelial cell perturbation, respectively. Results were correlated with clinical and biochemical markers of disease severity, including plasma lactate. Our data show that acute endothelial cell activation is a hallmark of malaria in children, indicated by a significant rise in VWF and VWF propeptide. The highest VWF and propeptide levels were seen in cerebral and non-cerebral severe malaria, and associations found between VWF propeptide level and lactate (P < 0.001). Mean VWF propeptide levels (nmol/l) were in cerebral malaria 33.4, non-cerebral severe malaria 26.3, mild malaria 22.1, non-malaria febrile illness 10.2, and controls 10.1. Differences between patient and control groups were highly significant (P < 0.005). Follow-up of 26 cerebral malaria cases showed that levels of VWF propeptide, but not VWF fell by 24 h, following the clinical course of disease and recovery. These novel findings potentially implicate acute, regulated exocytosis of endothelial cell Weibel-Palade bodies in the pathogenesis of Plasmodium falciparum malaria.

Biomarkers and mechanisms of drug-induced vascular injury in non-rodents

In preclinical safety studies, drug-induced vascular injury can negatively impact candidate-drug selection because there are no obvious diagnostic markers for monitoring this pathology preclinically or clinically. Furthermore, our current understanding of the pathogenesis of this lesion is limited. While vasodilatation and increased shear stress appear to play a role, the exact mechanism(s) of injury to the primary target cells, smooth muscle (SMC) and endothelial cell (EC), are unknown. Evaluation of potential novel markers for clinical monitoring with a mechanistic underpinning would add value in risk assessment and risk management. This mini review focuses on the efforts and progress to identify diagnostic markers as well as understanding the mechanism of action in nonrodent drug-induced vascular injury.

Candidate-based proteomics in the search for biomarkers of cardiovascular disease

The key concept of proteomics (looking at many proteins at once) opens new avenues in the search for clinically useful biomarkers of disease, treatment response and ageing. As the number of proteins that can be detected in plasma or serum (the primary clinical diagnostic samples) increases towards 1000, a paradoxical decline has occurred in the number of new protein markers approved for diagnostic use in clinical laboratories. This review explores the limitations of current proteomics protein discovery platforms, and proposes an alternative approach, applicable to a range of biological/physiological problems, in which quantitative mass spectrometric methods developed for analytical chemistry are employed to measure limited sets of candidate markers in large sets of clinical samples. A set of 177 candidate biomarker proteins with reported associations to cardiovascular disease and stroke are presented as a starting point for such a 'directed proteomics' approach.

Endothelial cell activation in thrombotic thrombocytopenic purpura (TTP): a prospective analysis

It is generally assumed that endothelial cell injury is the primary event in the pathogenesis of thrombotic thrombocytopenic purpura (TTP). In this study, we have determined the extent of vascular perturbation during acute episodes of the disease. We performed a prospective, serial study of nine patients with relapsing TTP during hospitalization and treatment, and assessed the degree of endothelial cell involvement at admission, exacerbation and remission by measurement of von Willebrand factor (VWF) and VWF-propeptide levels. Measurement of both VWF and its propeptide enabled discrimination between acute and chronic perturbation of the endothelium. Elevated levels of both VWF and propeptide were found at admission. These levels decreased immediately upon plasma exchange therapy. However, plasma VWF and propeptide concentrations did not change, even at the time of acute exacerbation. These observations suggest that endothelial cell activation is not the primary event leading to TTP. Vascular perturbation seems to be a consequence, rather than a cause, of the disease.

Reassessment of von Willebrand factor (VWF), VWF propeptide, factor VIII:C and plasminogen activator inhibitors 1 and 2 during normal pregnancy

The use of von Willebrand factor [VWF antigen (WF:Ag)] measurement as a marker of endothelial cell activation for monitoring hypertensive pregnancies is limited by the poor definition of reference values. We reassessed these reference values using different assays, and those of the propeptide (VWF:Ag II) and factor VIII coagulant activity (factor VIII:C), in a large population of normal pregnancies, at 3-week intervals of gestational age. Plasminogen activator inhibitors (PAI-1 and PAI-2) were measured in parallel. Blood was collected at single time points between 12 weeks and delivery in 306 women undergoing normal singleton pregnancy. For clinical purposes, the VWF:Ag reference values were assay independent and the influence of ABO blood group on VWF:Ag or factor VIII:c was found to be limited during the third trimester. VWF:Ag II was not influenced by the ABO blood group. The ratio, VWF:Ag/factor VIII:C was close to 1.0 throughout pregnancy. In contrast, VWF:Ag II increased more slowly than VWF:Ag and the ratio of VWF:Ag II to VWF:Ag in plasma decreased from 1.00 to 0.5 at term. PAI-1 and PAI-2 increased with gestational age, but PAI-2 decreased during the last 2 weeks, indicating physiological placental regression at the very end of pregnancy.

von Willebrand factor and its propeptide in children with diabetes. Relation between endothelial dysfunction and microalbuminuria

It has been shown that patients with insulin-dependent diabetes mellitus have elevated von Willebrand factor (vWF) plasma concentrations. Plasma fibrinogen, vWF, and its propeptide concentrations have been evaluated in 102 children with insulin-dependent diabetes mellitus to determine whether an increase of vWF and its propeptide levels precedes and may predict the development of persistent microalbuminuria. The patients have been divided into two groups according to the presence or absence of microalbuminuria at the end of follow-up. They have been followed up for at least 8 y. Control group consisted of 80 age- and sex-matched healthy volunteers. At the beginning of the study there was no significant difference in fibrinogen, vWF, and its propeptide levels between patients and control subjects. During the follow-up, a significant increase of plasma vWF and its propeptide has been observed in the group of patients who later developed microalbuminuria but not in those who remained normoalbuminuric. This increase started 3 y and become statistically significant (p < 0.01) 2 y before the onset of microalbuminuria, persisting until the end of the study. During the entire follow-up plasma values of fibrinogen persisted in the normal range. In conclusion, an increase in plasma concentration of vWF and its propeptide precedes microalbuminuria and, therefore, can be useful to identify children with insulin-dependent diabetes mellitus at risk to develop incipient nephropathy later in life.

Changes in von Willebrand factor-cleaving protease (ADAMTS13) activity after infusion of desmopressin

von Willebrand factor-cleaving protease (ADAMTS13) cleaves von Willebrand factor (VWF) and regulates its physiologic function. To investigate the relation between ADAMTS13 activity and VWF, we compared ADAMTS13 activity with the VWF-related parameters VWF antigen (VWF:Ag), VWF collagen-binding activity (VWF:CBA), VWF-propeptide, proVWF, and VWF multimeric composition in 10 healthy volunteers and 3 patients with type 1 von Willebrand disease before and after infusing 0.3 microg/kg desmopressin. The VWF-related parameters in the volunteers increased 60 minutes after start of infusion by 3.7-fold for VWF:Ag, 7.2-fold for propeptide, and 2.2-fold for VWF:CBA. Unusually large VWF multimers and traces of proVWF appeared. The ADAMTS13 activity decreased to about half the initial value. After 24 hours values returned to baseline. Patients with type 1 von Willebrand disease showed similar results. We conclude that the inverse correlation between ADAMTS13 and VWF-related parameters suggests a consumption of ADAMTS13 after the desmopressin-induced release of higher multimers of VWF.

Endothelial function in patients with hyperthyroidism before and after treatment with propranolol and thiamazol

Hyperthyroidism is associated with a higher incidence of arterial thromboembolism; increasing age, atrial fibrillation, and mitral valve abnormalities are risk factors. However, the contribution of endogenous coagulation parameters is unclear. Because thyroid hormone influences receptor and transcription factors, it can be expected that it will influence proteins involved in coagulation processes synthetised in many cells. Fourteen hyperthyroid patients were studied untreated, after 1 week of treatment with propranolol, and after therapeutic treatment with thiamazol. Fourteen matched controls were used for comparison. On each occasion, endothelial marker proteins, coagulation/fibrinolysis factors, and inflammatory (liver) markers were measured. Excess thyroid hormone was associated with elevated levels of most endothelium-associated proteins. In addition, plasma fibronectin and fibrinogen were increased, while plasminogen was decreased. No evidence was found that hyperthyroidism was associated with coagulation/fibrinolysis activation, or with increased levels of the inflammation markers interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) or C-reactive protein (CRP). Propranolol treatment only lowered the von Willebrand factor propeptide, and slightly increased plasminogen. Treatment with thiamazol returned all parameters to normal. Hyperthyroidism increased the plasma levels of most endothelial marker proteins, and of some liver-synthetized proteins. No evidence for coagulation/fibrinolysis activation was found. However, it appears that endothelial activation, which is indicative of a procoagulant state, is present in hyperthyroidism. This may explain the association between hyperthyroidism and thromboembolism especially if other risk factors are present. von Willebrand factor II (vWF:Ag-II) levels may be suitable markers to evaluate acute changes in endothelial function because this parameter responds more rapidly to changes in endothelial function than other factors.

Evaluation of plasma von Willebrand factor as a biomarker for acute arterial damage in rats

Plasma von Willebrand factor (vWF) was evaluated as a potential biomarker of acute arterial damage in rats after a vasotoxic dose of the dopaminergic vasodilator, fenoldopam (FP). Male Sprague-Dawley rats were given FP or isotonic saline by subcutaneous injection, and plasma vWF was measured at 2, 6, and 24 hours after challenge. Mean plasma vWF values increased in FP-treated rats compared to controls at 2 hours (167 vs 122%; p < 0.05) and 6 hours postdose (172 vs 130%; p < 0.01) but were comparable to control values after 24 hours. Mesenteric arterial lesions were observed microscopically in all FP-treated rats 24 hours postdose but were not present in rats at 1, 2, 4, 6, or 8 hours after FP challenge. Further, plasma vWF concentrations increased in saline-treated rats after only the minimal perturbation of repeated venipuncture. These results indicate an early, minimal, and transient release of vWF that precedes the onset of morphologically evident vascular damage. The minimal increases in plasma vWF concentrations were of limited predictive value, may be more reflective of an acute-phase reactant response, and were not considered a reliable biomarker of acute FP-induced arterial damage in the rat.

Vasopressin-induced von Willebrand factor secretion from endothelial cells involves V2 receptors and cAMP

Vasopressin and its analogue 1-deamino-8-D-arginine vasopressin (DDAVP) are known to raise plasma von Willebrand factor (vWF) levels. DDAVP is used as a hemostatic agent for the treatment of von Willebrand's disease. However, its cellular mechanisms of action have not been elucidated. DDAVP, a specific agonist for the vasopressin V2 receptor (V2R), exerts its antidiuretic effect via a rise in cAMP in kidney collecting ducts. We tested the hypothesis that DDAVP induces vWF secretion by binding to V2R and activating cAMP-mediated signaling in endothelial cells. vWF secretion from human umbilical vein endothelial cells (HUVECs) can be mediated by cAMP, but DDAVP is ineffective, presumably due to the absence of V2R. We report that DDAVP stimulates vWF secretion in a cAMP-dependent manner in HUVECs after transfection of the V2R. In addition, vasopressin and DDAVP induce vWF secretion in human lung microvascular endothelial cells (HMVEC-L). These cells (but not HUVECs) express endogenous V2R, as shown by RT-PCR. Vasopressin-induced vWF secretion is mimicked by DDAVP and inhibited by the selective V2R antagonist SR121463B. It is mediated by cAMP, since it is inhibited by the protein kinase A inhibitor Rp-8CPT-cAMPS. These results indicate that vasopressin induces cAMP-mediated vWF secretion by a direct effect on endothelial cells. They also demonstrate functional expression of V2R in endothelial cells, and provide a cellular mechanism for the hemostatic effects of DDAVP.

Regulated von Willebrand factor (vWf) secretion is restored by pro-vWf expression in a transfectable endothelial cell line

Von Willebrand factor (vWf) is a glycoprotein involved in primary hemostasis and synthesized in endothelial cells (EC). vWf is stored in secretory granules specific for EC called Weibel-Palade bodies (WPb). Studies on the molecular mechanisms of vWf storage and acute release are hampered by the limitations of the available endothelial cell culture models. We created a suitable model by stable transfection of the vWf-negative ECV304 endothelial cell line with pro-vWf cDNA. Pro-vWf was normally cleaved to mature vWf and stored in WPb. Acute vWf release occurred in response to the calcium ionophore A23187. Thus, vWf expression is sufficient to restore functional secretory granules in ECV304 cells. We used this model to study the role of WPb in the storage of tissue-type plasminogen activator (t-PA), a key fibrinolytic enzyme that is acutely released by EC, but whose intracellular storage compartment is still a matter of debate. We observed that restoration of WPb in ECV304 cells results in the targeting of t-PA to these storage granules.

Evidence for Extracellular Processing of Pro-von Willebrand Factor After Infusion in Animals With and Without Severe von Willebrand Disease

Although proteolytic processing of pro-von Willebrand factor (pro-vWF) resulting in free propeptide and mature vWF is known to be initiated intracellularly, vWF released from endothelial cells may contain a high proportion of incompletely processed pro-vWF. Because pro-vWF is only rarely detectable in normal human plasma, we investigated whether extracellular processing of pro-vWF is possible. A recombinant preparation (rpvWF) containing both pro-vWF and mature vWF subunits was infused into 2 pigs and 1 dog with severe von Willebrand disease, 2 mice with a targeted disruption of the vWF gene, and 2 healthy baboons. Total vWF antigen (vWF:Ag), free propeptide, and pro-vWF were measured using enzyme-linked immunosorbent assay techniques in blood samples drawn before and after infusion. vWF:Ag increased promptly. No pro-vWF could be detected when the first postinfusion sample was drawn after 30 minutes (pigs) or 60 minutes (mice), but pro-vWF was detectable for short periods when postinfusion samples were drawn after 15 minutes (dog) or 5 minutes (baboons). In contrast, free propeptide was increased at the first timepoint measured, suggesting that it was generated from the pro-vWF in the rpvWF preparation. vWF multimers were analyzed in the rpvWF preparation and in plasma samples drawn before and after infusion of rpvWF using ultra-high resolution 3% agarose gels to allow separation of homo- and hetero-forms of the vWF polymers. Within 30 minutes after infusion in the pigs, 1 hour in the dog and the mice, and within 2 hours in the baboons, the multimer pattern had changed to that typically seen in mature vWF. These data indicate that propeptide cleavage from unprocessed vWF can occur extracellularly in the circulation. The enzyme or enzymes responsible for this cleavage in plasma remain to be identified.

Evidence for Extracellular Processing of Pro-von Willebrand Factor After Infusion in Animals With and Without Severe von Willebrand Disease

Although proteolytic processing of pro-von Willebrand factor (pro-vWF) resulting in free propeptide and mature vWF is known to be initiated intracellularly, vWF released from endothelial cells may contain a high proportion of incompletely processed pro-vWF. Because pro-vWF is only rarely detectable in normal human plasma, we investigated whether extracellular processing of pro-vWF is possible. A recombinant preparation (rpvWF) containing both pro-vWF and mature vWF subunits was infused into 2 pigs and 1 dog with severe von Willebrand disease, 2 mice with a targeted disruption of the vWF gene, and 2 healthy baboons. Total vWF antigen (vWF:Ag), free propeptide, and pro-vWF were measured using enzyme-linked immunosorbent assay techniques in blood samples drawn before and after infusion. vWF:Ag increased promptly. No pro-vWF could be detected when the first postinfusion sample was drawn after 30 minutes (pigs) or 60 minutes (mice), but pro-vWF was detectable for short periods when postinfusion samples were drawn after 15 minutes (dog) or 5 minutes (baboons). In contrast, free propeptide was increased at the first timepoint measured, suggesting that it was generated from the pro-vWF in the rpvWF preparation. vWF multimers were analyzed in the rpvWF preparation and in plasma samples drawn before and after infusion of rpvWF using ultra-high resolution 3% agarose gels to allow separation of homo- and hetero-forms of the vWF polymers. Within 30 minutes after infusion in the pigs, 1 hour in the dog and the mice, and within 2 hours in the baboons, the multimer pattern had changed to that typically seen in mature vWF. These data indicate that propeptide cleavage from unprocessed vWF can occur extracellularly in the circulation. The enzyme or enzymes responsible for this cleavage in plasma remain to be identified.

Storage of tissue-type plasminogen activator in Weibel-Palade bodies of human endothelial cells

Tissue-type plasminogen activator (t-PA) is acutely released by endothelial cells. Although its endothelial storage compartment is still not well defined, t-PA release is often accompanied by release of von Willebrand factor (vWf), a protein stored in Weibel-Palade bodies. We investigated, therefore, whether t-PA is stored in these secretory organelles. Under basal culture conditions, a minority of human umbilical vein endothelial cells (HUVEC) exhibited immunofluorescent staining for t-PA, which was observed only in Weibel-Palade bodies. To increase t-PA expression, HUVEC were infected with a t-PA recombinant adenovirus (AdCMVt-PA). Overexpressed t-PA was detected in Weibel-Palade bodies and acutely released together with endogenous vWf by thrombin or calcium ionophore stimulation. In contrast, plasminogen activator inhibitor type 1 and urokinase were not detected in Weibel-Palade bodies after adenovirus-mediated overexpression. Infection of HUVEC with proinsulin recombinant adenovirus resulted in the storage of insulin in Weibel-Palade bodies, indicating that these organelles can also store nonendothelial proteins that show regulated secretion. Infection of AtT-20 pituitary cells, a cell type with regulated secretion, with AdCMVt-PA resulted in the localization of t-PA in adrenocorticotropic hormone-containing granules, indicating that t-PA can be diverted to secretory granules independently of vWf. Coinfection of AtT-20 cells with AdCMVt-PA and proinsulin recombinant adenovirus resulted in the colocalization of t-PA and insulin in the same granules. Taken together, these results suggest that HUVEC have protein sorting mechanisms similar to those of other regulated secretory cells. Although the results did not exclude an alternative storage site for t-PA in HUVEC, they established that t-PA can be stored in Weibel-Palade bodies. This finding may explain the acute coordinate secretion of t-PA and vWf.

von Willebrand Factor Propeptide in Vascular Disorders: A Tool to Distinguish Between Acute and Chronic Endothelial Cell Perturbation

Before de novo synthesized von Willebrand factor (vWF) leaves the endothelial cell, it undergoes endoproteolytic cleavage of its propeptide (vW antigen II). The processed vWF and propeptide are either released constitutively or, following activation of the endothelium, released through the regulated pathway. In a recent study (Borchiellini et al, Blood 88:2951, 1996), we showed that the half-life of mature vWF and of its propeptide differ fourfold to fivefold. We postulated that the molar ratio of the propeptide to mature vWF could serve as a tool to assess the extent of endothelial cell activation under physiologic and clinical conditions. To test this hypothesis, we measured mature vWF and propeptide in patients with documented acute and chronic vascular disease, including patients with thrombotic thrombocytopenic purpura (TTP), acute septicemia, and diabetes mellitus. These data were compared with experimental conditions in healthy subjects in which perturbation of the endothelium was simulated by physical exercise or by administration of 1-deamino-8-D-arginine vasopressin (DDAVP) or endotoxin. In all individuals of the latter study group, both vWF and propeptide levels were elevated during the acute phase of the experimentally induced vascular perturbation; at later time points after stimulation, only vWF levels remained elevated. In patients with sepsis and TTP, both vWF and propeptide were elevated several-fold. Thus, this pattern can readily be explained in terms of acute perturbation of the endothelium. In contrast, in patients with diabetes mellitus propeptide levels were only slightly elevated, whereas vWF levels were elevated twofold to threefold. This pattern is a typical feature of chronic, low-grade activation of the endothelium. These observations support our hypothesis that measurement of both propeptide and vWF levels allows to discriminate between chronic and acute phases of endothelial cell activation in vivo. Measurement of only vWF is less indicative in this respect.

Long-term effects of combined hormone replacement therapy on markers of endothelial function and inflammatory activity in healthy postmenopausal women

OBJECTIVE

To study the effects of combined hormone replacement therapy on markers of endothelial function and inflammatory activity.

DESIGN

Prospective, randomized, controlled study.

SETTING

Academic hospital.

PATIENT(S)

Healthy postmenopausal women with an intact uterus.

INTERVENTION(S)

For the first 12 months, the hormone replacement therapy group (n = 14) received oral E2, 1 mg daily, sequentially combined with 5 or 10 mg of dydrogesterone. Thereafter, they received oral E2, 2 mg daily, sequentially combined with 10 mg of dydrogesterone. The control group (n = 13) received no treatment. Data were collected at baseline and at 3, 12, and 15 months.

MAIN OUTCOME MEASURE(S)

Parameters of endothelial function and inflammatory activity.

RESULT(S)

During 12 months of follow-up, we observed decreases of 15% in plasma levels of endothelin-l, of 21% in soluble thrombomodulin, of 14% in von Willebrand factor, and of 12% in clottable fibrinogen in the hormone replacement therapy group compared with the control group. There was a 5% decrease in soluble E-selectin tevels. All significant changes were observed by 3 months and sustained after 15 months. Brachial artery flow-mediated vasodilatation and C-reactive protein levels did not change significantly.

CONCLUSION(S)

Long-term combined hormone replacement therapy with E2 and dydrogesterone in healthy women was associated with sustained improvement in some aspects of endothelial function and in clottable fibrinogen levels.

Early increase of von Willebrand factor predicts adverse outcome in unstable coronary artery disease: beneficial effects of enoxaparin. French Investigators of the ESSENCE Trial

BACKGROUND

The pathogenesis of unstable angina and non-Q-wave myocardial infarction is still poorly understood, and early evaluation of prognosis remains difficult. We therefore studied the predictive value of 5 biological indicators of inflammation, thrombogenesis, vasoconstriction, and myocardial necrosis, and we examined the effects of enoxaparin and unfractionated heparin on these markers after 48 hours of treatment.

METHODS AND RESULTS

Sixty-eight patients with unstable angina or non-Q-wave myocardial infarction randomized in the international ESSENCE trial participated in this French substudy. C-reactive protein, fibrinogen, von Willebrand factor antigen, endothelin-1 and troponin I were measured on admission and 48 hours later. The composite end point of death, myocardial infarction, recurrent angina, or revascularization was significantly lower at 14 and 30 days of follow-up in patients allocated to enoxaparin compared with unfractionated heparin. All acute-phase reactant proteins were elevated on admission and increased further at 48 hours. Multivariate analysis demonstrated that the rise of von Willebrand factor over 48 hours was a significant and independent predictor of the composite end point at both 14 days and 30 days. Moreover the early increase of von Willebrand factor was more frequent and more severe with unfractionated heparin than with enoxaparin (mean change was +8.7+/-8.8% with enoxaparin versus +93.9+/-11.7% with unfractionated heparin, P<0.0001). The other clinical and biological variables did not predict outcome.

CONCLUSIONS

In patients with unstable angina or non-Q-wave myocardial infarction, the acute-phase proteins increase over the first 2 days despite medical treatment. The early rise of von Willebrand factor is an independent predictor of adverse clinical outcome at 14 days and at 30 days. Enoxaparin provides protection as evidenced by the reduced release of von Willebrand factor, which represents a favorable prognostic finding.