A Positively Charged Surface Triggers Coagulation Activation Through Factor VII Activating Protease (FSAP)

Abstract

Contact between biomedical materials and blood often initiates undesirable pro-coagulant and pro-inflammatory processes. On negatively charged materials, blood coagulation is known to be triggered through autoactivation of Factor XII, while activation on cationic surfaces follows a distinct and so far enigmatic mechanism. Because Factor VII activating protease (FSAP) is known to be activated on positively and on negatively charged macromolecules in plasma, we have investigated its interaction with charged biomaterials and its consequences for coagulation. Several activation processes in blood and plasma were characterized after contact with material surfaces with varied charge. FSAP was found to be exclusively activated by the positively charged surfaces polyethylenimine (PEI) and poly-l-lysine (PLL), not by the negatively charged glass or self-assembled monolayer with carboxyl group termination (SAM-COOH), as well as uncharged (Teflon AF) surfaces. Whole blood incubation on PEI showed that this activation was concomitant with coagulation as determined by thrombin and fibrin formation, which was high for glass (F1+2, 138 nM) and PEI (F1+2, 44 nM) but low for Teflon AF (F1+2, 3.3 nM) and SAM COOH (F1+2, 5.8 nM). Contact phase inhibitor diminished coagulation to background levels for all surfaces except PEI (F1+2: ^PEI 43 to 25 nM; glass, 58 to 1.5 nM) indicating that coagulation activation is not dependent on FXII activation on the PEI surface. A decisive role of endogenous FSAP for coagulation however was confirmed with the use of FSAP inhibitory antibodies which showed no influence on Teflon AF, glass and SAM COOH but diminished F1+2 on PEI to less than 50%. We propose that FSAP activation could be a novel mechanism of surface-driven coagulation. An inhibition of this protease might improve hemocompatibility of cationic surfaces and therefore facilitate the application of polycationic surfaces in blood.

Fluorescent activity-based probe for the selective detection of Factor VII activating protease (FSAP) in human plasma

“…The ability to measure enzyme activity in a selective and sensitive manner is important for the delineation of protease function in vivo. Recent studies on FSAP point to a unique mechanism of activation by histones [9] and positively charged surfaces [10]. However, detection of active FSAP in situ has not yet been attempted because of the lack of appropriate tools.…”

“…Zymogen activation in whole blood or plasma is mediated by factors released from damaged cells such as histones [9] as well as by positively charged surfaces [10]. In traumatic injury or sepsis nucleosome concentrations in plasma correlate strongly with FSAP activation [11,12].…”

Blood-Contacting Biomaterials: In Vitro Evaluation of the Hemocompatibility

“…The activation of coagulation system is screened by detection of FXIIa (Basu et al, 2017 ), prothrombin fragment 1 + 2 (F1 + 2) (Maitz et al, 2017 ; Sperling et al, 2017 ), which is released during thrombin formation, free active thrombin (Müller et al, 2011 ), fibrinopeptide A (FPA) (Peckham et al, 1997 ), partial thromboplastin time (PTT), or thrombin-antithrombin III complex (TAT). Furthermore, the degradation product of fibrin, D-dimer, can be detected by ELISA to determine the activation of fibrinolysis (Sperling et al, 2017 ). Antithrombin III inhibits thrombin by forming a TAT complex.…”

Poly-dopamine, poly-levodopa, and poly-norepinephrine coatings: Comparison of physico-chemical and biological properties with focus on the application for blood-contacting devices

“…For example, hydrophobic –CH 3 surfaces induced more Fn adsorption and platelet adhesion than hydrophilic –COOH [ 36 ]. The surface charge is an important factor affecting the protein adsorption and platelet adhesion, and positively charged surfaces were reported to enhance platelet activation through factor VII activating protease [ 37 ]. Microscaled surfaces cause more protein adsorption than nano-scaled surfaces, and the amount of protein adsorption on surfaces with the same dimension is related to the effective surface area [ 38 ].…”