Factor Seven Activating Protease Research Articles

Circulating Factor Seven Activating Protease (FSAP) in the Hyperacute Phase of Stroke

Background. Factor VII activating protease (FSAP) is a circulating serine protease that could be involved in the pathophysiology of stroke. We analyzed the temporal changes in FSAP antigen and FSAP activity after acute cerebral ischemia (ACI) and tested if FSAP could be used to differentiate between stroke subtypes in the hyperacute phase (<4.5 hours after symptom onset). Methods. Of the 118 suspected stroke patients enrolled, 76 had ACI; of which 20 suffered from large vessel occlusion (LVO), 19 had intracerebral hemorrhage (ICH), and 23 had stroke mimics. Median time from symptom onset to the two plasma sample collections, <4.5 hours, were 66 and 107 minutes for the entire study population. Additional samples were collected up to 90 days post stroke in a subset of ACI patients ( n = 19 ). FSAP antigen, FSAP activity, FSAP-α2-antiplasmin-complex (FSAP-AP complex), and nucleosomes were measured by activity assays or ELISA. Results. ACI patients treated with tissue plasminogen activator (tPA) had elevated FSAP activity < 4.5 hours ( p = 0.016 ) that subsequently normalized after 6 hours. FSAP-AP complex levels decreased significantly from <4.5 hours ( p = 0.015 ) to 6 hours after symptom onset. tPA did not increase FSAP activity significantly in plasma in vitro. FSAP antigen significantly decreased < 4.5 hours after symptom onset in LVO ( p = 0.008 ) and ICH ( p = 0.017 ) patients. FSAP could not differentiate ACI from ICH or strokes (ACI and ICH) from stroke mimics. FSAP did not correlate with stroke severity. Conclusion. LVO and ICH seem to influence FSAP levels in the hyperacute phase of stroke, but FSAP does not differentiate between stroke subtypes in a hyperacute setting.

Extracellular histones promote fibrinolysis by single-chain urokinase-type plasminogen activator in a factor seven activating protease-dependent way

IntroductionExtracellular histones inhibit tissue plasminogen activator (t-PA)-mediated fibrinolysis by modifying fibrin structure and rheological properties. However, other plasminogen activators involved in intravascular and extravascular fibrinolysis have not been considered yet. ObjectivesWe investigated the effect of histones on fibrinolysis driven by different plasminogen activators. MethodsClot lysis induced by t-PA, urokinase (u-PA) and its single chain precursor (scu-PA) was evaluated by turbidimetry. Conversion of scu-PA to u-PA and activation of factor seven activating protease (FSAP) were assessed by fluorogenic and chromogenic assays, respectively. ResultsHistones delayed t-PA- and u-PA-mediated fibrinolysis but strongly accelerated scu-PA-driven clot lysis through the enhancement of scu-PA to u-PA conversion. This effect required a plasma factor identified as FSAP by the following findings: 1) histones enhanced neither scu-PA activation nor scu-PA-mediated clot lysis under purified conditions; 2) in plasma, the enhancement of fibrinolytic activity by histones was abolished by a neutralizing anti-FSAP antibody; and 3) histones promoted the activation of plasma FSAP. The effect of the natural mixture of histones on scu-PA-driven fibrinolysis was differentially recapitulated by the individual recombinant histones, H4 displaying the strongest activity. When complexed to DNA, histones still accelerated scu-PA-mediated fibrinolysis but with a lesser efficiency due to a reduced FSAP activation. Finally, preincubation of histones with heparin or activated protein C, two known inhibitors of histones, further amplified histone-mediated boost of scu-PA-driven fibrinolysis. ConclusionsEnhancement of FSAP-mediated scu-PA activity by histones may play yet unforeseen roles in intravascular fibrinolysis and contribute to extravascular proteolysis and tissue damage.

Factor seven activating protease (FSAP) predicts response to intravenous thrombolysis in acute ischemic stroke.

Prediction of recanalization after intravenous thrombolysis could be important to direct secondary reperfusion techniques. Factor seven activating protease (FSAP) has been described to have a relevant pathophysiological role in stroke. The aim is to determine whether plasma FSAP levels are associated with recanalization after tissue plasminogen activator in acute stroke. FSAP antigen, activity, and FSAP-inhibitor complexes were measured in 120 acute stroke patients admitted to Hospital Vall d'Hebron with arterial occlusions, before intravenous thrombolysis. Recanalization was assessed by transcranial Doppler 2 h after thrombolysis. Predictors of recanalization were determined by logistic regression analysis and the additional predictive value of FSAP over them was determined by integrated discrimination improvement index. Complete recanalization was achieved in 31 patients. FSAP antigen levels were lower in patients achieving recanalization (8.2 (6.3-11.7) µg/mL vs. 9.8 (7.6-12.8) µg/mL; p = 0.046). After adjustment by age, sex, and National Institutes of Health Stroke Scale, Oxfordshire Community Stroke Project (odds ratio = 0.33 (0.13-0.82), p = 0.017) and FSAP antigen (odds ratio = 3.22 (1.22-8.47), p = 0.018) were independently associated with recanalization, and the addition of FSAP improved the model discrimination (integrated discrimination improvement = 5.5% (1.4-9.7), p = 0.009). Our study showed that lower FSAP antigen plasma levels were associated with a higher chance of arterial recanalization after tissue plasminogen activator treatment, suggesting an involvement of FSAP in tissue plasminogen activator-induced clot lysis. FSAP antigen determination might be useful in predicting tissue plasminogen activator response in stroke patients.

Association of circulating factor seven activating protease (FSAP) and of oral Omega-3 fatty acids supplements with clinical outcome in patients with atrial fibrillation: the OMEGA-AF study

Factor VII Activating Protease (FSAP) activates factor VII (FVII) as well as pro-urokinase (uPA). Our goal was to evaluate the relation between plasma levels of FSAP and clinical instability in atrial fibrillation (AF) and possible effects of oral omega-3 fatty acids (FA) supplements. 101 patients with persistent AF were analyzed in the OMEGA-AF Study. Plasma FSAP levels were measured at baseline and after 12weeks of treatment with omega-3 FA. The median FSAP antigen concentration, in contrast to FSAP activity, was higher in patients with persistent AF. The maintenance of SR after successful cardioversion (CV) did not lead to a normalization of FSAP concentration. Supplementation with omega-3 FA but not placebo significantly reduced elevated FSAP concentration. Furthermore, elevated FSAP levels did not indicate a significantly increased risk of recurrence of AF after electrical CV or cardiovascular clinical events during 1year of follow-up. Plasma FSAP concentration was increased in patients with AF and may be involved in the pathogenesis of this condition. The possible effects of omega-3 FA on clinical AF potential could be linked with modulation of circulating FSAP levels.

Factor seven activating protease (FSAP) expression in human placenta and its role in trophoblast migration

Factor seven activating protease (FSAP) is a plasma serine protease known to play a critical role in hemostasis and remodeling processes: FSAP levels increase markedly during normal pregnancy. In order to define the role of FSAP in vascular pathophysiology in pregnant women and particularly in the placenta, we performed this study (i) to evaluate the FSAP expression in human placenta and (ii) to identify the role of FSAP in human trophoblast migration. FSAP expression in placental tissues was analyzed by using immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR). To determine whether FSAP plays any role in trophoblast migration, we used human trophoblast cells in transwell migration assays. Immunohistochemistry showed that FSAP protein was expressed by syncytiotrophoblast and in the cytoplasma of invasive extravillous trophoblasts (EVT) within the maternal decidua (DC) in implantation sites of human first trimester placenta. Furthermore, FSAP mRNA and protein decreased with gestational age (p<0.05, 1st vs 3rd trimester). FSAP (10μg/ml) had a significant stimulatory effect on the migration of human trophoblast cells. This effect was abolished by addition of aprotinin to block the enzymatic activity of FSAP. The high expression level of FSAP in the placenta supports a relevant role of this protease in trophoblast migration and vascular remodeling, identifies a new concept of coagulation/fibrinolysis at the feto-maternal interface and may be essential for the maintenance of pregnancy.

Factor seven activating protease (FSAP): does it activate factor VII?

Factor seven activating protease (FSAP) was initially reported as an activator of single-chain urokinase-type plasminogen activator (scuPA) and factor VII (FVII). Subsequently, numerous additional substrates have been identified, and multiple other biological effects have been reported. Due to the apparent lack of specificity, the physiological role of FSAP has become increasingly unclear. Rigorous studies have been limited by the difficulty of obtaining intact FSAP from blood or recombinant sources. Our aim was to produce intact recombinant human FSAP, and to assess its role as a trigger of coagulation and fibrinolysis. Expression of wild-type FSAP in various mammalian cells invariably resulted in the accumulation of degraded FSAP due to autoactivation and degradation. To overcome this problem, we constructed a variant in which Arg(313) at the natural activation site was replaced by Gln, creating a cleavage site for the bacterial protease thermolysin. HEK293 cells produced FSAP(R313Q) in its intact form. Thermolysin-activated FSAP displayed the same reactivity toward the substrate S-2288 as plasma-derived FSAP, and retained its ability to activate scuPA. Polyphosphate and heparin increased V(max) by 2-3-fold, without affecting K(m) (62 nm) of scuPA activation. Surprisingly, FVII activation by activated FSAP proved negligible, even in the presence of calcium ions, phospholipid vesicles and recombinant soluble tissue factor. On membranes of 100% cardiolipin FVII cleavage did occur, but this resulted in transient activation and rapid degradation. While FSAP indeed activates scuPA, FVII appears remarkably resistant to activation. Therefore, reappraisal of the putative role of FSAP in hemostasis seems appropriate.

Factor seven‐activating protease: does it do what it says on the tin?

<i>See also</i> Stavenuiter F, Dienava‐Verdoold I, Boon‐Spijker MG, Brinkman HJM, Meijer AB, Mertens K. Factor seven activating protease (FSAP): does it activate factor VII? This issue, pp 859–66.

Factor Seven Activating Protease Activity Levels in Women With Recurrent Pregnancy Loss

This study was designed to analyze the changes in circulating factor seven activating protease (FSAP) levels in association with the thrombophilic state of 40 women with recurrent pregnancy loss (RPL). All women were trying to conceive and were prospectively followed up until the achievement of spontaneous pregnancy. The results obtained showed that plasma FSAP activity levels were higher in RPL than in fertile women (P < .001) and represented an adverse predictor of pregnancy at multivariate analysis (P = .002). In 7 consenting RPL women, FSAP activity levels increased continuously during pregnancy until the third trimester, remained elevated immediately after delivery, and declined 6-week postpartum, although at levels that were still above the range of control women. These results suggest that FSAP activity levels might provide useful information during pregnancy progression in at-risk women, possibly acting as a predictive factor for adverse pregnancy outcome in RPL even in the absence of other well recognized thrombophilic conditions.

Factor Seven Activating Protease (FSAP) levels during normal pregnancy and in women using oral contraceptives

Introduction Factor seven activating protease (FSAP) is a plasma serine protease involved in haemostasis and remodeling processes. We have investigated whether pregnancy or the use of oral contraceptives (OCs) influences circulating FSAP levels. The effect of female sex hormones on FSAP expression in cultured cells was also determined. Materials and Methods FSAP levels and activity was measured in plasma samples obtained at different gestation stages from healthy pregnant women (n = 101), from non-pregnant women, pre-menopausal women who currently use OCs (n = 48), and non-pregnant women who did not use OCs (n = 69). Results In late pregnancy the plasma FSAP antigen (median 2.28 PEU/ml [range 1.11 to 2.62 PEU/ml]; p < 0.001 vs control group) and activity (median 2.98 PEU/ml [range 1.05 to 4.24 PEU/ml]; p < 0.001 vs control group) was significantly higher compared with levels in non-pregnant women and remained elevated after delivery. Plasma FSAP levels in women using OCs was also significantly elevated compared to the control group. Ex vivo experiments demonstrated enhanced FSAP expression in monocytes isolated from women using OCs. In vitro experiments showed that FSAP mRNA levels were strongly induced by estradiol in monocytes but not in hepatocytes. Conclusions Increased levels of circulating FSAP in pregnancy and in women using OCs indicate that hormonal status critically influences FSAP expression. Hormonal influences could be observed in monocytes in vivo and ex-vivo but not in hepatocytes indicating cell-specific regulation. Future studies designed to investigate the role of FSAP in haemostasis and remodeling processes should consider the role of female sex hormones on FSAP expression.

Factor Seven Activating Protease (FSAP) expression in human monocytes and accumulation in unstable coronary atherosclerotic plaques

ObjectiveThe Factor Seven Activating Protease (FSAP) is known to influence fibrinolysis and to play a critical role in the inhibition of vascular smooth muscle cell (VSMC) proliferation and migration as well as neointima formation. In order to define the role of FSAP in vascular pathophysiology we have investigated the expression of FSAP protein and mRNA in human vascular cells and coronary atherosclerotic plaques with defined clinical features. Methods and resultsDirectional coronary atherectomy (DCA) specimens from 40 lesions were analyzed for FSAP antigen and mRNA expression. Higher level of FSAP mRNA (p<0.001) as well as FSAP immunostaining (p<0.005) was observed in patients with acute coronary syndromes compared to patients with stable angina pectoris. FSAP antigen was found to be focally accumulated in hypocellular and lipid-rich areas within the necrotic core of atherosclerotic plaques. FSAP was also co-localized with CD11b/CD68 expressing cells in macrophage-rich shoulder regions of the plaques. Monocyte-derived macrophages expressed FSAP in vitro and this was further induced by pro-inflammatory mediators. ConclusionsFSAP accumulation in coronary atherosclerotic lesions is due to either local synthesis by monocytes/macrophages, or uptake from the plasma due to plaque hemorrhage. The higher expression of FSAP in unstable plaques suggests that it may destabilise plaque through reducing VSMC proliferation/migration and altering the hemostatic balance.

The frequent Marburg I polymorphism impairs the pro-urokinase activating potency of the factor VII activating protease (FSAP).

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

Factor VII activating protease (FSAP): a novel protease in hemostasis.

Recently a novel serine protease in human plasma was described and was named PHBP, PHBSP or factor seven activating protease (FSAP), respectively, the latter according to the finding that it can support coagulation by factor VII activation. Later on FSAP was identified as a potent activator of single chain plasminogen activators, in particular of prourokinase, as well. The physiological role of FSAP is still speculative, but recent studies suggest a contribution to hemostasis. Due to its affinity to glycosaminoglycans a role in cell-associated or extracellular proteolytic events is also likely. The impact of a very recently uncovered frequent polymorphism impairing the prourokinase activation potential of FSAP needs to be investigated in more detail.