Atorvastatin is a powerful new synthetic 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor currently in clinical use. Its effects on plasma levels of factor VII were examined in 30 hyperlipidemic patients. After 12 weeks of atorvastatin treatment, factor VII activity (FVIIc) and factor VII antigen (FVIIag) levels had decreased by 13% (p < 0.0001) and 12% (p < 0.0001), respectively. The decreased concentrations of serum triglycerides correlated with decreases in FVIIc levels (r = 0.54, p = 0.0023) and FVIIag levels (r = 0.59, p = 0.0006) at 12 weeks of treatment with atorvastatin. No significant changes were seen in activated factor VII (FVIIa) levels. Plasma concentrations of fibrinogen were slightly, but not significantly, increased at 12 weeks. No significant changes were seen in plasminogen activator inhibitor-1 levels. The effects of atorvastatin on FVII may contribute to a decreased thrombotic potential, resulting in fewer thromboembolic events, including a reduction in coronary heart disease.

The lipolysis of triglyceride-rich lipoproteins may provide a surface that supports the activation of factor XII (FXII) with subsequent activation of factor VII (FVII). Plasma levels of activated FVII (FVIIa) but not activated FXII (FXIIa) are increased in the post-prandial state when there is a transient increase in triglyceride levels. We compared plasma levels of FXIIa antigen in control subjects (n = 33) and in patients with chronically elevated lipids (primary hyperlipidaemia, n = 49), with FVIIa and markers of thrombin generation. Results are given as median (first and third quartiles). Plasma levels of FXIIa [2.34 (1.68-3.32) ng/ml versus 1.53 (0.93-1.86) ng/ml, P = 0.0002], FVIIa [3.02 (2.15-4.64) ng/ml versus 2.20 (1.66-2.56) ng/ml, P = 0.0004], thrombin-antithrombin complexes [3.08 (2.16-5.54) microg/I versus 2.13 (1.46-2.84) microg/l, P = 0.005] and prothrombin fragment 1 + 2 (Pro F1 + 2) [1.28 (1.08-1.50) nmol/l versus 0.92 (0.65-1.08) nmol/l, P = 0.0001] were increased compared with controls irrespective of the type of hyperlipidaemia. In hyperlipdaemic subjects, levels of Pro F1 + 2 were correlated with FVIIa (r = 0.56, P = 0.0002) and FXIIa (r = 0.31, P = 0.03). These results suggest increased activation of both FVII and FXII in hyperlipidaemic subjects, which correlates with increased thrombin generation. Given the lack of correlation between levels of FXIIa and FVIIa, it remains to be established whether the increase in FXIIa is responsible for increased FVIIa activity in this subject group.

OBJECTIVE

Numerous studies have emphasized the role of triglyceride-rich lipoproteins and of Factor VII (FVII) polymorphisms in determining levels of FVII activity.

METHODS

This study was undertaken to evaluate the role of other lipid fractions and the interaction between lipids and FVII in subjects with recognised genotypes. Volunteer subjects (n=459) from 5 European countries were studied. Blood samples were drawn irrespective of the time of day or fasting status. Levels of FVII activity (FVIIc), activated FVII (FVIIa) and FVII antigen (FVIIAg) were evaluated with reference to a number of lipid parameters (HDL-, LDL- and total cholesterol, triglycerides, phospholipids, lipoprotein(a), and apoliproptein A1). The two most common FVII polymorphisms were analyzed in combination (353R/Q and 5'F7; alleles M1/M2 and A1/A2, respectively).

RESULTS

Homozygotes for the A1 and M1 alleles (M11/A11) had significantly higher FVII levels. At multiple regression analysis the strongest predictor of FVIIa and FVIIc was the concentration of phospholipids. This interaction was confined to the A11M11 genotype subjects.

CONCLUSIONS

These data indicate that lipids contribute mainly to FVIIa levels through their phospholipid content, and that the degree of this contribution is strictly dependent on FVII genotypes.

BACKGROUND

Hemostatic factors influenced by postmenopausal hormone therapy may contribute to atherosclerosis. The Estrogen in the Prevention of Atherosclerosis Trial (EPAT), a 2-year, randomized, double-blind, placebo-controlled trial, demonstrated reduced subclinical atherosclerosis progression measured by change in common carotid artery intima-media thickness (CIMT) with unopposed oral 17beta-estradiol.

OBJECTIVE

To assess the effect of postmenopausal hormone therapy on the levels of several hemostatic factors, and the relationship between these factors and the progression of subclinical atherosclerosis.

METHODS

We measured tissue plasminogen activator (t-PA) antigen, factor (F) VII, D-dimer and albumin longitudinally, and plasminogen activator inhibitor type 1 (PAI-1) and fibrinogen at trial-end, in 186 postmenopausal women.

RESULTS

Estradiol vs. placebo was associated with greater FVII and lower t-PA, albumin, PAI-1 and fibrinogen (all P < or = 0.001), with no estradiol effect on D-dimer (P = 0.42). Only mean on-trial t-PA was positively associated with the absolute level of CIMT on-trial (r = 0.29, P < 0.0001), but this was attenuated with age and body mass index adjustment. No longitudinally measured hemostatic factor was associated with CIMT progression. However, higher CIMT during the trial was significantly related to increases in t-PA.

CONCLUSIONS

These results confirm previous findings regarding estrogen's effect on hemostatic factors and show that albumin is negatively associated with estrogen therapy. These hemostatic factors did not account for the reduction of CIMT progression with 17beta-estradiol seen in EPAT. Atherosclerosis itself may affect levels of hemostatic factors (reverse causality), with subsequent involvement in atherosclerosis-associated thrombosis.

BACKGROUND

A raised plasma factor VII (FVII) level is a risk factor for coronary heart disease. DNA variants have been described to be associated with alteration in FVII levels. The prevalence of FVII polymorphisms is unknown in the Tunisian Arab population.

METHODS

In a group of 240 healthy Tunisians, we examined the relationship between levels of FVII coagulant activity (FVIIc) and two polymorphisms in the FVII gene. One polymorphism alters arginine at position 353 to glutamine (R/Q) and the other is a 10 base pair insertion (0/10 bp).

RESULTS

The FVII distribution was in accordance with the Hardy-Weinberg equilibrium. The allele frequencies of Q and 10 bp were 0.212 and 0.235, respectively. There were significant differences in these allelic frequencies between Tunisian and other populations (p<0.001). We observed lower FVIIc levels among subjects with the Q allele compared to RR subjects (RR: 98.17%, RQ/QQ: 57.41%, p<0.0001). For the 0/10 polymorphism, no statistically difference was observed.

CONCLUSIONS

The prevalence of the Q allele which was found to be associated with lower plasma FVIIc levels is high in Tunisian population. Further analyses should yield information on the protective role of carrying the Q allele for coronary heart disease.

We describe studies on variation in the genes coding for factor VII (FVII) and plasminogen activator inhibitor-1 (PAI-1) that influence levels of these proteins in the blood. For FVII, we have identified a genetic polymorphism that results in the substitution of arginine at residue 353 to glutamine. The frequency of the glutamine allele is approximately 0.1 in samples of individuals from the United Kingdom (n = 777) and the United States (n = 140) and in Afro-Caribbeans (n = 49), and is significantly higher in a sample of individuals from the Indian subcontinent (n = 53). In all samples, carriers of the glutamine allele had levels of FVII coagulant activity 20% to 25% lower than those with only the arginine allele. These differences were highly statistically significant in the United Kingdom sample. This effect was consistent in healthy men and women and in those with coronary artery disease. In individuals homozygous for the glutamine allele, both FVII coagulant activity and antigen are low, and the mechanism of the association appears likely to be due to an effect on secretion from the liver or stability in the plasma. In individuals in the general population FVII coagulant activity is positively correlated with levels of plasma triglycerides, due to the effect of such lipoproteins on activation of FVII. This relationship appears weaker in individuals carrying the glutamine allele, and since elevated FVII coagulant antibody is associated with risk of thrombosis, this is an example of how environmental factors may interact with an individual's genotype to determine his or her thrombotic risk. Roughly 20% of the general population are carriers of the glutamine allele and are likely to be genetically protected from such risk. For PAI-1, we have recently shown that variation at the PAI gene locus, detected as DNA polymorphisms, is associated with between-individual differences in levels of PAI-1. We have now detected a common sequence change in the promoter region of the gene that explains part of this effect. The sequence change is at position 675, where a fifth guanine (5G allele) has been inserted into a run of four guanines (4G allele) when compared with published sequences. In a sample of both 83 healthy individuals and 105 young patients with coronary artery disease from Sweden, the frequency of the 4G allele is roughly 0.5, and those individuals homozygous for the 4G allele have higher levels of PAI-1 than those with other genotypes (29% higher). Preliminary data show that the 5G allele binds a hepatic nuclear protein that the 4G allele does not, suggesting that the mechanism of the effect may be due to a direct effect of the sequence change on transcription of the PAI-1 gene.(ABSTRACT TRUNCATED AT 400 WORDS)

During tissue factor (TF)-induced coagulation, the factor (F)VIIa-TF complex activates factor (F)X and factor (F)IX. Through positive feedback, the generated FXa and FIXa activate FVII-TF. The first epidermal growth factor-like (EGF1) domains of FX and FIX serve as important TF-recognition motifs when FVIIa-TF activates FX or FIX. Here, we investigated the role of EGF1 domains of FXa and FIXa during the activation of FVII-TF and inhibition by tissue factor pathway inhibitor (TFPI). FXaPCEGF1 (EGF1 domain of FXa replaced with that of protein C), and FXaQ49P (EGF1 domain mutant with impaired calcium-binding), and the corresponding FIXa mutants were generated, and their abilities to activate FVII-TF were compared with the wild-type (WT) enzymes. In the absence of TF, the rates of FVII activation were similar between WT enzymes and mutant FXa and FIXa proteases. In the presence of either soluble TF (sTF) or relipidated TF, each mutant of FXa or FIXa activated FVII-TF at a slower rate than the corresponding WT enzyme. Kinetics of inhibition of the amidolytic activity of WT and the mutant FXa proteases by either two-domain or full-length TFPI were similar. However, compared with the complex of TFPI-FXaWT, the abilities of the complexes of TFPI-FXa mutants to inhibit FVIIa-TF were impaired. We conclude that the EGF1 domains of FXa and FIXa are important for the activation of FVII-TF and for the formation of FVIIa-TF-FXa-TFPI complex.

To understand the role of the factor X (fX) activation peptide (AP), a deletion mutagenesis approach was employed. Two single-chain, variant enzymes were generated in which 41 residues were deleted from the AP: fX (des-137-183) and fX(des-137-183;N191A), which lacks a carbohydrate moiety at Asn191 due to an alanine substitution. Deletion of the fX AP did not impact fXa catalytic activity. Activation of the variant zymogens, however, was altered. Neither mutant enzyme was activated by the fX coagulant protein from Russell's viper venom (RVV-X(1)). Activation by factor VIIa (fVIIa) and fVIIa in the presence of cofactor, lipidated tissue factor (TF), occurred at an accelerated rate for both variants as compared to wild-type fX (WTfX). Similar to fVII, the mutants auto-activated in a cofactor-independent manner, which was characterized by a lag period and accelerated dose-dependently by plasma fXa (kcat/Km, 0.046 +/- 0.004 micro M(-1) s(-1)). Both mutants were also found to be activated by fVIIa (0.31 +/- 0.03 micro M(-1) s(-1)), fIXa (0.30 +/- 0.03 micro M(-1) s(-1)), and thrombin (0.00078 +/- 0.00015 micro M(-1) s(-1)). In all cases, the rate of activation was faster for fX(des-137-183;N191A) as compared to fX(des-137-183). We propose that the fX AP and Asn191 carbohydrate serve primarily as negative autoregulation mechanisms to prevent spurious activation of fX and secondarily in cofactor dependence and activator specificity.

OBJECTIVE

To examine whether there is an association between bile acids and coagulation factors in children with chronic liver disease.

METHODS

Forty-five patients (age 2.8 months-18.8 years) were included in this cross-sectional observational study carried out at a single tertiary referral center. Coagulation factors, prothrombin time, albumin, and total fasting serum bile acids were analyzed. The international normalized ratio (INR) and the pediatric end-stage liver disease score were calculated.

RESULTS

The 12 patients with bile acids more than 200 μmol/l showed a significant positive correlation between bile acids and factor V (FV), FVII, and prothrombin time (r(s) = 0.80, 0.72, 0.60, P<0.05) and a significant negative correlation between bile acids and INR (r(s) = -0.58, P<0.05). Conversely, in the group with bile acids less than 200 μmol/l, there was a significant negative correlation between bile acids and FVII and FIX (r(s) = -0.41 and -0.41, P<0.05) and a positive, albeit nonsignificant, correlation between bile acids and INR. No in-vitro analytical interference between bile acids and coagulation factors was found. Patients with bile acids more than 200 μmol/l had a significantly worse outcome than patients with lower levels of bile acids.

CONCLUSIONS

A positive correlation was found between bile acids and coagulation factors in patients with bile acids more than 200 μmol/l. Coagulation factors may be questionable as prognostic markers in patients with markedly elevated bile acids.

Severe coagulant factor VII (FVII) deficiency in postpubertal dizygotic twin males results from two point mutations in the FVII gene, a promoter region T→C transition at -60 and a His-to-Arg substitution at amino acid 348; both mutations prevent persistence of plasma functional FVII. This report documents longitudinal laboratory measurements from infancy to adulthood of FVII coagulant activity (FVII:C) in the twin FVII-deficient patients; it also details specific biochemical analyses of the -60 T→C mutation. The results revealed FVII:C levels of less than 1% in infancy that remain severely decreased through puberty and into adulthood. In-vitro analyses utilizing hepatocyte nuclear factor 4α (HNF4α) co-transfection and a chromatin immunoprecipitation assay indicate that the -60 T→C mutation severely diminishes functional interaction between the FVII promoter and transcription factor HNF4α. The importance of interaction between the FVII gene and HNF4α in normal FVII expression provides an in-vivo illustration of the regulated expression of an autosomal gene encoding a coagulation protein. The constancy of FVII:C and peripubertal patient symptomatology reported here illustrates androgen-independent expression in contrast to expression with an analogous mutation in the promoter region of the gene encoding coagulation FIX.

We have recently investigated the association between the risk of developing PE and clinical, hemostatic, inflammatory and genetic parameters of 108 severe preeclamptic women. A multivariate logistic regression analysis was performed to assess what variables are independent risk factors for PE. Univariate analysis was performed including the variables in age, smoking condition, multiple pregnancy, blood group, phenotypes and alleles of IL-4, IL-5, IL-10, IL-6, IL-8, IL-12, IL-1β, IFN-γ, TNF-α, and the plasma levels of FVII, FVIIa, FVIIa-AT, FVIII, FVW, ADAMTS13, D-Di, PAI-1, ADMA. Those variables whose P<0.20 (smoking, multiple pregnancy, blood group, phenotype IL-6, IFN-γ allele, IL-10 allele and FVII) were selected to the multivariate logistic regression. In the final model, only FVII, IFN-γ allele and smoking were independently associated to severe PE (P<0.0001, P<0.0001 and P=0.008, respectively). Increased FVII plasma levels and IFN-γ "T" allele were associated to an increased probability of developing PE (OR 1.001, 95% CI [1.001-1.002], and OR 4.81 95% CI [2.42-9.60], respectively). On the other hand, smoker status was associated with a 4.72 decreased chance of PE occurrence (OR 4.72, 95% CI [1.51-14.75]). In this article we also reviewed the studies that investigate the risk of PE in pregnant women who smoked, as well as the effect of tobacco extract in cells or animal models. The hypotheses proposed to explain the biological mechanism by which smoking during pregnancy reduces the risk of PE was also discussed.

Recombinant factor VII (rFVII) is the main therapeutic choice for hemophilia patients who have developed inhibitory antibodies against conventional treatments (FVIII and FIX). Because of the post-translational modifications, rFVII needs to be produced in mammalian cell lines. In this study, for the first time, we have shown efficient rFVII production in HepG2, Sk-Hep-1, and HKB-11 cell lines. Experiments in static conditions for a period of 96 h showed that HepG2-FVII produced the highest amounts of rhFVII, with an average of 1843 ng/mL. Sk-hep-1-FVII cells reached a maximum protein production of 1432 ng/mL and HKB-11-FVII cells reached 1468 ng/mL. Sk-Hep-1-rFVII and HKB-11-rFVII were selected for the first step of scale-up. Over 10 days of spinner flask culture, HKB-11 and SK-Hep-1 cells showed a cumulative production of rFVII of 152 μg and 202.6 μg in 50 mL, respectively. Thus, these human cell lines can be used for an efficient production of recombinant FVII. With more investment in basic research, human cell lines can be optimized for the commercial production of different bio therapeutic proteins.

Vascular injury brings tissue factor (TF) into contact with blood and its natural ligands, factors VII (FVII) and VIIa (FVIIa). This results in localized FVIIa activity on TF-expressing cells, initiating coagulation, and nonhemostatic activities. Activation of transcription factors, expression of genes for inflammation, tissue remodeling, and wound healing follow, but these mechanisms for maintaining vascular integrity may lead to pathophysiologic states. Recombinant FVIIa is converted into a catalytically inert protein by reactive site residues reacting with Phe-Phe-Arg-chloromethyl ketone. Active site-inhibited FVIIa (ASIS) retains its affinity for TF and competes for FVIIa and FVII binding to TF, blocking FVIIa activity and FVII to FVIIa activation. It therefore acts as an antithrombotic agent and has been shown in previous studies on animal models of sepsis to prevent organ failure associated with fibrin deposition. Mitigation of inflammatory response and prolonged survival were remarkable and additional effects of TF blockage by ASIS not observed with inhibitors of downstream coagulation factors Xa and thrombin. This suggests that FVIIa/TF exerts a noncoagulopathic effect on cellular activities, attenuated by ASIS blocking FVIIa-induced signaling. The precise mechanism remains elusive but blockade of TF/FVIIa activity provides an attractive possibility for pharmaceutical intervention. In vitro measurements of ASIS-TF binding and FVIIa/TF inhibition are described, together with investigation of the FVIIa-induced signaling pathway and gene expression. Additionally, possible implications of ASIS blockage for hemostatic and nonhemostatic aspects of the pathophysiology associated with vascular stress and injury are discussed.

Following vessel wall injury, tissue factor (TF) is being exposed and forms complexes with the already activated FVII (FVIIa) present in the circulating blood, providing a limited amount of thrombin molecules that activate a number of coagulation proteins as well as the platelets. As a result of activation with thrombin the platelet surface exposes negatively charged phospholipids to which activated coagulation proteins bind tightly, and full thrombin generation occurs, resulting in the conversion of fibrinogen into fibrin. After the first FXa is formed, the tissue factor pathway inhibitor (TFPI) forms a complex with FXa. In the next step a quaternary complex is being formed, TF/FVIIa/FXa/TFPI, which inhibits the first step of the haemostatic pathway. Recombinant FVIIa (rFVIIa) has been developed for use as a haemostatic agent (NovoNordisk A/S, Denmark). Inactivated rFVIIa (rFVIIai) has also been prepared, and it has similar binding capacity to TF as rFVIIa but it blocks the catalytic activity of the TF complex. In various animal models rFVIIai has been demonstrated to prevent or diminish immediate thrombus formation at the site of vessel wall injury (athroplasty or other forms of mechanical injury) as well as the development of long-term intima thickening. Also, topical application of rFVIIai was found to block the formation of a thrombus. rFVIIai was shown to have an anti-inflammatory effect in lipopolysaccharide (LPS)-induced sepsis, and postischaemic reperfusion injury was found to be reduced by the administration of rFVIIai. In a limited number of patients undergoing percutaneous transluminal coronary angioplasty (PTCA), rFVIIai was observed to allow PTCA to be performed at lower doses of heparin than what has been reported previously. Recombinant TFPI has been shown to attenuate the lethal inflammatory and coagulopathic response. Furthermore, topical application of rFVIIai has been found to increase the patency rate in a model of graft surgery.

The monitoring of coagulation-inhibitor bypassing agents, including recombinant factor VIIa (rFVIIa), remains a major issue in the management of clinical hemophilia. Clotting assays using prothrombin time (PT) and measurements of factor VII (FVII) activity do not always reflect the hemostatic effects of treatment. Thrombelastography can be used to observe the global effects of treatment on the overall coagulation process and is especially useful for observing the effects of hemostatic treatment in hemophilia patients with inhibitors. Waveform analysis is another technique for evaluating global hemostatic condition where changes in light transmission during routine clotting assays, such as the activated partial thromboplastin time (aPTT), are measured. We found that waveforms differed between individual patients with severe hemophilia A (FVIII:C < 1.0 IU/dL) with levels of sensitivity at below FVIII:C 1.0 IU/dL. Clot waveforms indicated dose-dependent improvements in clot formation after the addition of rFVIIa to both FVIII-deficient and factor IX (FIX)-deficient plasma. The improvements were further enhanced in the presence of both platelets and synthetic phospholipids, and were more pronounced with FVIII-deficient plasma than with FIX-deficient plasma. It appears that clot waveform analysis provides a very useful means for monitoring hemostasis in hemophilia A patients with inhibitors.

BACKGROUND

Obesity is associated with a hypercoagulable state and increased risk for thrombotic cardiovascular events.

OBJECTIVE

Establish the onset and reversibility of the hypercoagulable state during the development and regression of nutritionally-induced obesity in mice, and its relation to transcriptional changes and clearance rates of coagulation factors as well as its relation to changes in metabolic and inflammatory parameters.

METHODS

Male C57BL/6J mice were fed a low fat (10% kcal as fat; LFD) or high fat diet (45% kcal as fat; HFD) for 2, 4, 8 or 16 weeks. To study the effects of weight loss, mice were fed the HFD for 16 weeks and switched to the LFD for 1, 2 or 4 weeks. For each time point analyses of plasma and hepatic mRNA levels of coagulation factors were performed after overnight fasting, as well as measurements of circulating metabolic and inflammatory parameters. Furthermore, in vivo clearance rates of human factor (F) VII, FVIII and FIX proteins were determined after 2 weeks of HFD-feeding.

RESULTS

HFD feeding gradually increased the body and liver weight, which was accompanied by a significant increase in plasma glucose levels from 8 weeks onwards, while insulin levels were affected after 16 weeks. Besides a transient rise in cytokine levels at 2 weeks after starting the HFD, no significant effect on inflammation markers was present. Increased plasma levels of fibrinogen, FII, FVII, FVIII, FIX, FXI and FXII were observed in mice on a HFD for 2 weeks, which in general persisted throughout the 16 weeks of HFD-feeding. Interestingly, with the exception of FXI the effects on plasma coagulation levels were not paralleled by changes in relative transcript levels in the liver, nor by decreased clearance rates. Switching from HFD to LFD reversed the HFD-induced procoagulant shift in plasma, again not coinciding with transcriptional modulation.

CONCLUSIONS

Changes in dietary fat content rapidly alter the mouse plasma coagulation profile, thereby preceding plasma metabolic changes, which cannot be explained by changes in relative expression of coagulation factors or decreased clearance rates.

Postprandial lipaemia is associated with activation of factor VII (FVII) and efflux of cholesterol from tissues to nascent plasma high density lipoproteins (HDL) containing apolipoprotein A-I (apo A-I). To determine whether FVII activation and cholesterol efflux occur together in other situations, the responses to intravenous infusion of HDL-like apo A-I/phosphatidylcholine discs were measured in 10 healthy men. Disc infusion (40 mg apo A-I/kg body weight) over 4 h was followed by increases in HDL cholesteryl ester and plasma apo A-I (p <0.0001). Significant activation of FVII was apparent during infusion in fasting subjects (p = 0.03), activated FVII averaging 123% of baseline value by 12 h (p <0.0001). Plasma thrombin-antithrombin (TAT) complex increased to 156% of baseline level by 12 h (p >0.05) but individual responses differed considerably. Peak TAT post-infusion was associated inversely with peak HDL triglyceride concentration (p = 0.004). The coagulation responses to disc-infusion may be due to transfer of phosphatidylserine to cell surfaces during cholesterol efflux.

Factor VIII/von Willebrand factor (FVIII/vWF) is a glycoprotein with a molecular weight greater than one-million daltons. Two activities are associated with this large molecule: FVIII procoagulant activity and vWF activity. Incubation of FVIII/vWF with proteolytic enzymes causes rapid inactivation of the FVIII procoagulant activity but has little effect on the vWF activity or antigenicity. In an attempt to gain insight into the structural features required for these two activities, antisera were raised in rabbits to normal, thrombin-inactivated, and plasmin-inactivated FVIII/vWF. All of these proteolytically modified forms of FVIII/vWF cross-reacted with each of the rabbit antisera; each blocked the ability of a human inhibitor to inactivate native active FVIII/vWF. Each of the antisera was a potent inhibitor of vWF activity and inactivated vWF activity at the same titer. The antisera were much less potent inhibitors of FVIII activity than of vWF activity. Antibodies to thrombin-inactivated FVIII/vWF or normal FVIII/vWF had about the same ability to inactivate FVIII procoagulant activity. Surprisingly, those to plasmin-inactivated FVIII/vWF still retained about 50% of this inhibitory capacity. A comparison of the three types of antigens by polyacrylamide gel electrophoresis in sodium dodecyl sulfate-6 M urea demonstrated that the structure of thrombin-inactivated FVIII/vWF was indistinguishable from that of normal FVIII/vWF, while plasmin-inactivated FVII/vWF was completely cleaved to lower molecular weight fragments. Some of the reported variations in the ability of rabbit antibodies to inhibit procoagulant activity may be due to partial degradation of the starting antigen. The retention by FVIII/vWF protein of its immunologic properties even after extensive proteolytic degradation suggests that under nondenaturing conditions, the conformation of the native and degraded molecules are very similar.

There is evidence that high plasma levels of factor (F) VIII, FIX, FXI and fibrinogen are independent risk factors for venous thromboembolism.

OBJECTIVE

To determine the plasma concentrations of several coagulation factors and C4b-binding protein (C4BP) in a group of patients with non-metastatic colorectal cancer in order to investigate some aspects of cancer-acquired thrombophilia.

METHODS

Plasma fibrinogen, FII, FV, FVII, FVIII, FIX, FX, FXI and FXII activity levels and C4BP concentrations were determined in 73 patients with non-metastatic colorectal cancer (48 colon and 25 rectum) and in 67 matched control subjects. No one in either group had had previous thrombotic events.

RESULTS

Mean plasma concentrations of fibrinogen (functional and antigen), FVIII, FIX, FV and C4BP were significantly higher in colorectal cancer patients than in control subjects, while FVII and FXII levels were significantly decreased. Several correlations were found between the increased coagulation factors and C4BP concentrations, while FVII was highly correlated with FXII.

CONCLUSIONS

In colorectal cancer patients high plasma fibrinogen, FVIII and FIX levels might represent further risk factors for venous thrombotic complications in the immediate post-surgery period, while decreased FVII and FXII concentrations may be an index of intravascular coagulation activation, still in a subclinical phase.

OBJECTIVE

In most countries hypersensitivity to vitamin K antagonists (VKA) is considered to be a rare congenital bleeding diathesis. It occurs in patients with FIX propeptide mutations at locus -10. We present a Swiss family with two patients who suffered major bleedings under oral anticoagulant treatment in the presence of therapeutic or subtherapeutic INR levels and abnormally prolonged aPTT. In both patients a mutation in the propeptide of FIX at locus -10 with substitution of alanine by threonine (Ala-10Thr) was found. In one patient FIX clotting activity was found to be severely reduced (2%). The observed bleeding tendency is related to this--compared to the other vitamin K dependent factors (FII, FVII, FX)--excessively and disproportionately low level of FIX. Three generations of this family were tested for propeptide mutations, which are transmitted in an X-chromosomal recessive mode of inheritance. Apart from the two symptomatic male patients we found another male with the mutation who has not been exposed to VKA, six female carriers and four potential male carriers in the fourth generation who have not been tested. A founder effect for this mutation has been previously described for cases in Switzerland and Germany.

CONCLUSIONS

FIX propeptide mutation-associated hypersensitivity to VKA is a rare occurrence in Switzerland. The severity of associated bleeding complications and the reversible nature of the bleeding diathesis may nonetheless warrant increased awareness on the part of primary care physicians in Switzerland.

Human endothelial cells (ECs) synthesize, store, and secrete von Willebrand factor multimeric strings and coagulation factor (F) VIII. It is not currently known if ECs produce other coagulation factors for active participation in coagulation. We found that 3 different types of human ECs in primary culture produce clotting factors necessary for FX activation via the intrinsic (FVIII-FIX) and extrinsic (tissue factor [TF]-FVII) coagulation pathways, as well as prothrombin. Human dermal fibroblasts were used as comparator cells. TF, FVII, FIX, FX, and prothrombin were detected in ECs, and TF, FVII, FIX, and FX were detected in fibroblasts. In addition, FVII, FIX, FX, and prothrombin were detected by fluorescent microscopy in EC cytoplasm (associated with endoplasmic reticulum and Golgi proteins). FX activation occurred on human umbilical vein EC surfaces without the addition of external coagulation proteins, proteolytic enzymes, or phospholipids. Tumour necrosis factor, which suppresses the generation of activated protein C and increases TF, augmented FX activation. Fibroblasts also produced TF, but (in contrast to ECs) were incapable of activating FX without the exogenous addition of FX and had a marked increase in FX activation following the addition of both FX and FVII. We conclude that human ECs produce their own coagulation factors that can activate cell surface FX without the addition of exogenous proteins or phospholipids.

BACKGROUND

Warfarin is routinely used in the prevention and treatment of prothrombotic events. During initiation of warfarin therapy levels of factor (F) VII and protein C decrease rapidly but prothrombin, FIX and FX decline much slower. Therefore, propagation of thrombin generation (TG) remains unaffected much longer, increasing the risk of inadequate anticoagulation. Recently, a novel agent, anti-IXa aptamer, RB006, has been developed. Therefore, we have evaluated the in vitro effects of this agent in warfarin plasma.

METHODS

The investigation consisted of two parts. First, a computer simulated time course of TG with warfarin alone and in combination with FIXa inhibition was evaluated and, second, normal volunteer, protein C deficient, FVII deficient and commercial warfarin plasmas (INR 2.1 and 3.1) were spiked with increasing concentrations of aptamer (0-24 microg/ml) and its anticoagulant effects were evaluated using prothrombin time (PT), activated partial thromboplastin time (aPTT) and TG with tissue factor and Actin as activators. Direct effects of aptamer on protein C were also evaluated.

RESULTS

Simulation of coagulation during warfarin induction showed that TG can be significantly delayed and decreased by inhibiting FIXa (i.e., with anti-FIXa aptamer). The anti-FIXa aptamer inhibited TG in all tested plasmas, but was most efficacious in warfarin and FVII deficient plasma. The aptamer itself did not inhibit protein C and had no effect on PT, but concentration-dependently increased aPTT.

CONCLUSIONS

The anti-FIXa aptamer potentiates the inhibitory effects of warfarin on TG, and may fill the need as an adjuvant agent during initiation of warfarin therapy.

Hypercoagulability is often associated with a variety of disease states, leading to cardiovascular complications. Polyethylenimine (PEI) prolonged prothrombin time, demonstrating its anticoagulant potential. In vitro, PEI at low concentration (nM) significantly blocked thrombin-catalyzed fibrin formation, accounting for its mode of anticoagulation. The uncompetitive inhibition by PEI of fibrin formation was independent of the concentration of fibrinogen (FBG), thrombin, or NaCl. PEI showed no effect on thrombin amidolytic activity, suggesting that the blockade of thrombin interaction with FBG could account for the inhibition on fibrin formation. PEI drastically depressed rabbit brain thromboplastin procoagulation monitored by a single-stage clotting assay using human plasma. In a THP-1 monocytic hypercoagulation model, a 4-h exposure to bacterial endotoxin or Ca(2+) ionophore A23187, respectively, resulted in a 5- or 10-fold enhancement in monocytic tissue factor (mTF) procoagulation. mTF hypercoagulation was offset by PEI included in the assay mixture. PEI showed the potential to arrest mTF hypercoagulation with IC(50) around 1.2 nM. Using a chromogenic assay to dissect the extrinsic pathway, we further assessed whether PEI has any effect on other clotting factors. PEI was not an inhibitor for either FVIIa or FXa, having no effect on not only the amidolytic but also their corresponding functionally catalytic activities. Although PEI upregulated TF-dependent FVII activation under the low-salt condition, the effective downstream inhibition of fibrin formation readily abolished and overrode the upstream enhancement, demonstrating the overall anticoagulation. PEI could present a new class of anticoagulant.

OBJECTIVE

An activated Factor VII (FVIIa) concentrate, prepared from human plasma on a large scale, has to date not been available for clinical use for haemophiliacs with antibodies against FVIII and FIX. In the present study, we attempted to establish a large-scale manufacturing process to obtain plasma-derived FVIIa concentrate with high recovery and safety, and to characterize its biochemical and biological properties.

METHODS

FVII was purified from human cryoprecipitate-poor plasma, by a combination of anion exchange and immunoaffinity chromatography, using Ca2+-dependent anti-FVII monoclonal antibody. To activate FVII, a FVII preparation that was nanofiltered using a Bemberg Microporous Membrane-15 nm was partially converted to FVIIa by autoactivation on an anion-exchange resin. The residual FVII in the FVII and FVIIa mixture was completely activated by further incubating the mixture in the presence of Ca2+ for 18 h at 10 degrees C, without any additional activators. For preparation of the FVIIa concentrate, after dialysis of FVIIa against 20 mm citrate, pH 6.9, containing 13 mm glycine and 240 mm NaCl, the FVIIa preparation was supplemented with 2.5% human albumin (which was first pasteurized at 60 degrees C for 10 h) and lyophilized in vials. To inactivate viruses contaminating the FVIIa concentrate, the lyophilized product was further heated at 65 degrees C for 96 h in a water bath.

RESULTS

Total recovery of FVII from 15 000 l of plasma was approximately 40%, and the FVII preparation was fully converted to FVIIa with trace amounts of degraded products (FVIIabeta and FVIIagamma). The specific activity of the FVIIa was approximately 40 U/ micro g. Furthermore, virus-spiking tests demonstrated that immunoaffinity chromatography, nanofiltration and dry-heating effectively removed and inactivated the spiked viruses in the FVIIa. These results indicated that the FVIIa concentrate had both high specific activity and safety.

CONCLUSIONS

We established a large-scale manufacturing process of human plasma-derived FVIIa concentrate with a high yield, making it possible to provide sufficient FVIIa concentrate for use in haemophiliacs with inhibitory antibodies.