Title:
Activation of factor VII-activating protease in human inflammation: a sensor for cell death

Authors and Source:
Stephan F, Hazelzet JA, Bulder I, Boermeester MA, van Till JO, van der Poll T, Wuillemin WA, Aarden LA, Zeerleder S.
Crit Care. 2011 Apr 5;15(2):R110. [Epub ahead of print]

FSAP was observed prominently in alveolar epithelial cells as well as microvascular endothelial cells of the lung parenchyma and was markedly increased at the early phase of bleomycin-induced pulmonary fibrosis, but decreased at the late stage, particularly during the pulmonary fibrosis.

The authors demonstrate that epithelial cells in lungs represent a source of FSAP at the early stage in acutely injured lung. Moreover, FSAP had an inhibitory effect on PDGF-stimulated proliferation and migration of human pulmonary fibroblasts in vitro.

Taken together FSAP may modulate inflammation and exert a beneficial effect on acute respiratory distress syndrome (ARDS).

Title:
Changes in factor VII-activating protease in a bleomycin-induced lung injury rat model and its influence on human pulmonary fibroblasts in vitro.

Authors and Source:
Mu E et al., Int J Mol Med. 2010 Oct;26(4):549-55.

The authors have developed an ELISA using antibodies specific for the FSAP Marburg I variant, which accurately detects the Marburg I SNP.

ELISA results were correlated with FSAP genotypes from 523 blood donors measured using PCR. Diagnostic sensitivity and specificity of the assay for determination of the genotype were 100% (95% confidence interval wCIx: 93.36–100) and 99.79% (95% CI: 98.80–99.96), respectively.

This ELISA will significantly simplify FSAP Marburg I testing, particularly in large cohorts.

Title:
Qualitative detection of the Marburg I alloenzyme of factor VII-activating protease by an immunoassay and its comparison to PCR testing

Authors and Source:
Schwartz H et al. Clin Chem Lab Med 2010;48(12):1745–1749

 The findings indicate that HABP2, although primarily localized in the plasma, is upregulated in the lung endothelium with LPS-induced ALI and in cultured human pulmonary ECs. The enzymatic activity of HABP2 is differentially regulated by HA, with HMW-HA inhibiting HABP2 protease activity and LMW-HA binding to the PABD of HABP2 and stimulating activity. Activated HABP2 induces protease-activated receptor signaling in ECs, which leads to activation of the actin regulatory molecules RhoA and ROCK and endothelial barrier disruption. The barrier-disruptive role of HABP2 is further confirmed by vascular silencing of HABP2 expression, which attenuated the vascular leakiness observed in LPS- and ventilator-induced lung injury.

Title:
Hyaluronic Acid Binding Protein 2 Is a Novel Regulator of Vascular Integrity

Authors and Source:
Mambetsariev N et al. Arterioscler Thromb Vasc Biol. 2010 Mar;30(3):483-490.

Plasma FSAP antigen and activity level was significantly higher in late pregnancy than in non-pregnant women. FSAP levels 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.

The authors conclude that hormonal status critically influences the expression of FSAP in pregnancy and in women using OCs. Hormonal influences could be observed in monocytes in vivo and ex-vivo but not in hepatocytes indicating cell-specific regulation.

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

Authors and Source:
Parahuleva MS et al. Thromb Res. 2010 Apr 8. [Epub ahead of print]

The authors explored the potential influence of various hormone therapy regimens on plasma measures of FSAP antigen and activity in postmenopausal women (n= 139) treated for 1 year with different hormone therapy formulations or no hormone therapy.

In conclusion, hormone therapy increases FSAP antigen levels and the scu-PA activating properties of FSAP, suggesting that FSAP may contribute to the CVD-protective effect of hormone therapy observed in younger, postmenopausal women.

Title:
Hormone therapy affects plasma measures of factor VII-activating protease in younger postmenopausal women

Authors and Source:
Sidelmann JJ et al. Climacteric. 2010 Mar 12. [Epub ahead of print]

FSAP was found to activate pro-uPA to uPA but, over time, to decrease the activity of uPA in cultured EC and VSMC. Protein levels of uPA were reduced and the enzymatic activity of FSAP was required for this. In contrast, an increase in the gelatinase activity (MMP-2 and -9) was observed, without changes in the levels of individual proteins. FSAP caused this through a non-proteolytic mechanism. However, there was no regulation of the mRNA levels for uPA, tPA, MMP-2 and -9. Also the levels of the gelatinase inhibitors, i.e. the tissue inhibitors of matrix metalloproteinases (TIMPs), were not affected. In a similar manner as in vitro, FSAP reduced uPA activity and increased gelatinase activity in vessel walls in the mouse vascular injury model.

Title:
Factor Seven activating protease (FSAP); A key regulator of pericellular proteolysis.

Authors and Source:
J Daniel, O Uslu, K Hersemeyer, O Rannou, L Muhl, KT Preissner, D Sedding, SM Kanse
Poster presentation ISTH 2009: AS-TH-058

In the recFSAP, the natural activation site (R313-I314) was replaced by a cleavage site for the bacterial protease thermolysin, which prevented the problem of autoactivation and autodegradation observed in natural FSAP. This allowed to otain purified intact FSAP.

Thermolysin activated recFSAP displayed the same affinity for chromogenic peptide substrates as pdFSAP and retained its capability to activate pro-uPA. recFSAP interacted with negatively charged surfaces but did not have FVII-cleaving activity, even in the presence of calcium-ions and lipid vesicles of varying composition. Only On membranes of 100% cardiolipin FVII cleavage did occur, but this resulted in transient activation and rapid degradation.

While recFSAP indeed activates pro-uPA, it does not activate FVII. Whether or not the effect of cardiolipin, which is an intracellular lipid, has any physiological significance remains to be explored.

Title:
Factor VII-activating protease (FSAP): Does it activate Factor VII?

Authors and Source:
F Stavenuiter, E Sellink, HJM Brinkman, AB Meijer, K Mertens
Poster presentation ISTH 2009: OC-WE-084  

The authors compared FSAP activation in the presence of apoptotic vs. non-apoptotic cells. FSAP in plasma was found to be activated upon incubation with apoptotic cells as evidenced by appearance of two-chain FSAP on western blots. No FSAP activation was observed upon incubation of plasma with living cells. FSAP activation by apoptotic cells was also indicated by complex formation of FSAP with C1Inh and AP, whereas no such complexes could be detected after incubation with living cells.

Moreover, the authors asked, whether a similar mechanism can also be expected in vivo and they analysed plasmas from cases of sepsis, during which the formation of apoptotic cells is a hallmark-They found elevated levels of FSAP/C1Inh complexes in plasma of baboons with lethal sepsis and in plasmas from 8 out of 16 patients suffering from severe sepsis.

In conclusion the authors demonstrate that FSAP is activated upon contact with apoptotic cells and forms complexes with C1Inh and AP. They sugest, that determination of complexes between FSAP and C1Inh or AP in plasma is  a tool to study FSAP activation in vivo.

Title:
Factor VII-activating protease is activated in sepsis

Authors and Source:
S Zeerleder, I Bulder, F Stephan, M de Kruif, J Hoogerwerf, T van der Poll, L Aarden
ISTH 2009: PP-TH-153  

pro-uPA was found to be cleaved much more efficiently and at lower concentrations than FVII, indicating a preference of FSAP for the fibrinolytic system. Purified FSAP -MI activated FVII much less effficient than FSAP-wt. This was confirmed with FSAP from plasma of 5 individuals homozygous for the FSAP -MI allele. Pro-uPA was only weakly processed by FSAP from homozygous Marburg I carriers.

However, the central finding was on Factor VIII (FVIII) processing: FSAP-wt caused inactivation of FVIII, whereas FSAP-MI caused activation.

The authors conclude that the hypothesis of a haemostatic imbalance and increased athero-thrombotic risk in Marburg I-carriers due to reduced uPA but unchanged FVII activation capacity needs a revision and should take into consideration circulating FVIII levels.

Title:
The Marburg I polymorphism (G534E) of Factor VII activating protease (FSAP) prevents FVII activation, but contributes to thromboembolic risk due to FVIII activation.

Authors and Source:
M Etscheid, L Muhl, D Pons, KT Preissner, W Ruf, W Jukema, SM Kanse
Poster presentation ISTH 2009: OC-TH-110