Plasma fibrin clot proteomics in patients with acute pulmonary embolism: Association with clot properties
Graphical abstract
Introduction
Prothrombotic fibrin clot properties, including reduced clot porosity and susceptibility to lysis, are known to be associated with venous and arterial thrombotic events. Fibrin clot properties can be assessed using several methods, including clot permeability, compaction, and turbidity to determine clot absorbance and clot lysis time [1]. Clots generated from the plasma of patients who were evaluated 7 months after a diagnosis of venous thromboembolism (VTE) (34% of these patients had pulmonary embolism [PE]) were characterized by lower clot permeability, lower compaction, higher maximum absorbance, and prolonged clot lysis time than VTE-free relatives and controls [2]. Reduced clot permeability and prolonged clot lysis time have been shown to be good predictors of recurrent deep vein thrombosis (DVT) and PE [[3], [4], [5]]. However, clot structure and function, including clot formation, lysis, and viscoelastic properties assessed in vitro, differed patients with acute DVT from those with PE [2,6]. Analysis of thrombotic material removed from pulmonary arteries of acute PE patients showed that fibrin is the main component of the thrombus [7,8]. When plasma clot lysability in the presence of tissue plasminogen activator is assessed, the impact of fibrinogen concentration is negligible. The key contributors to clot lysis time variation in venous thrombosis patients include plasminogen activator inhibitor 1 (PAI-1), thrombin activatable fibrinolysis inhibitor (TAFI), prothrombin, and α2-antiplasmin levels [9]. Although there have been multiple studies on plasma fibrin clot properties in acute PE [[4], [5], [6]], a comparison between plasma clot composition of acute PE patients and those of healthy subjects has not been investigated. In healthy subjects, the quantitative protein composition of fibrin clots generated from plasma has been reported to associate with clot permeability and lysis time, the two key measures of clot structure and function [10]. Using conventional biochemical assays, it has been shown that in acute PE patients, plasma levels of factor XIIIa (FXIIIa) and soluble thrombomodulin were lower, whereas plasma levels of von Willebrand Factor (vWF) antigen and fibrinogen were higher when compared with results after 7 months follow-up [11]. Using a mass spectrometer (MS)-based high-throughput approach, as many as 476 proteins incorporated into plasma clots can be quantified in a single MS run [12].
To the best of our knowledge, there have been no reports on proteomic analyses comparing the clot composition between acute PE patients and healthy subjects. Therefore, we investigated whether clot-bound protein content could be associated with prothrombotic or unfavorable clot characteristics, as evidenced by low plasma clot permeability and prolonged clot lysis time among acute PE patients.
Section snippets
Study design
We evaluated 20 patients admitted due to acute PE and 20 sex-matched apparently healthy controls. The diagnosis of PE was based on the presence of typical symptoms and positive results of high resolution spiral computed tomography, according to current guidelines [13]. The diagnosis of lower or upper limb DVT required a positive finding on color duplex sonography. An iliac/caval DVT was defined as abnormal duplex flow patterns typical of thrombosis or an intraluminal filling defect on contrast
Acute PE vs. healthy control subjects
The baseline characteristics of acute PE patients and healthy controls are presented in Table 1. None of the PE patients or controls declared current smoking. Healthy subjects were medication-free. Prior to study enrolment, medications used by acute PE patients were angiotensin converting enzyme inhibitor (n = 9, 45%), β-blocker (n = 8, 40%), aspirin (n = 7, 35%), statin (n = 6, 20%), proton pump inhibitor (n = 5, 25%), angiotensin receptor blocker (n = 1, 5%), and calcium channel blocker
Discussion
Our study is the first to show that in acute PE patients, the proteome of fibrin clots differs largely from healthy controls. Moreover, we have observed that fibrin clot protein composition is associated with clot permeability as reflected by Ks, a key measure of fibrin network density. In acute PE, this parameter correlated with coagulation factor IX and V, carboxypeptidase B2 (TAFI), complement C1s, C7, C8 α chain, and apolipoprotein A-I, which suggests the impact of proteins unrelated to the
Conclusions
Our study is the first to demonstrate differences between the protein composition of fibrin clots generated from plasma of acute PE patients and healthy controls, suggesting that clot properties might be modulated by diverse proteins, including complement components and apolipoproteins. We have extended our previous observations [10] on the relationship between fibrin clot protein content and fibrin clot properties in the apparently healthy subjects, by showing that in acute PE, decreased clot
Sources of funding
This work was supported by the Polish National Science Centre (UMO-2015/B/NZ5/02215 to A.U.).
Disclosures
None.
Acknowledgements
None.
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