Moderation of prekallkrein–factor XII interactions in surface activation of coagulation by protein-adsorption competition

Abstract

Traditional biochemistry of contact activation of blood coagulation suggesting that anionic hydrophilic surfaces are specific activators of the cascade is inconsistent with known trends in protein adsorption. To investigate contact activation reactions, a chromogenic assay was used to measure prekallikrein (PK) hydrolysis to kallikrein (Kal) by activated factor XII (FXIIa) at test hydrophilic (clean glass) and hydrophobic (silanized glass) surfaces in the presence of bovine serum albumin (BSA). Hydrolysis of PK by FXIIa is detected after contact of the zymogen FXII with a test hydrophobic surface only if putatively-adsorbed FXIIa is competitively displaced by BSA. By contrast, FXIIa activity is detected spontaneously following FXII activation by a hydrophilic surface and requires no adsorption displacement. These results (i) show that an anionic hydrophilic surface is not a necessary cofactor for FXIIa-mediated hydrolysis of PK, (ii) indicate that PK hydrolysis does not need to occur by an activation complex assembled directly on an anionic, activating surface, (iii) confirms that contact activation of FXII (autoactivation) is not specific to anionic hydrophilic surfaces, and (iv) demonstrates that protein-adsorption competition is an essential feature that must be included in any comprehensive mechanism of surface-induced blood coagulation.

Enzymes produced by autoactivation of blood factor XII in buffer

“…Alternatively, since FXII autoactivation, and subsequent conformer formation, does not exhibit surface area dependence and is efficient even with hydrophobic surfaces, the small surface area of polystyrene test-tubes might have been sufficient to produce small quantities of FXII conformers which in turn trigger the reciprocalactivation route. This finding seems to support earlier results by Kaushik et al (citation) which indicated that prekallikrein hydrolysis is not localized to an activation complex on the procoagulant surface [24]. Either scenario is indicative of the importance of reciprocal-activation and its role as the major aFXIIa generator as shown previously [38].…”

Proteins, platelets, and blood coagulation at biomaterial interfaces

“…The principle role is inhibiting FXII contact with activating surfaces, but these proteins also displace FXIIa from an activating surface into solution where FXIIa is involved in the subsequent steps of the plasma coagulation cascade 222 . The importance of protein adsorption competition in contact activation was also observed in moderating interactions between FXII and PK, which are components of the reciprocal-activations 218 . All these observations implicate protein adsorption competition is an important mediator of contact activation and must be included in any comprehensive mechanisms of surface-induced blood coagulation.…”

“…However, experimental evidence demonstrated that hydrophobic and hydrophilic surfaces have nearly equal autoactivation properties in neat – buffer solution of FXII, i.e. contact activation of FXII is not specific to anionic hydrophilic surfaces in neat buffer 214,218 . In fact, contact activation of FXII in neat-buffer solution exhibits a parabolic profile when scaled as a function of surface energy.…”

A review of protein adsorption on bioceramics

“…Another interesting aspect of protein adsorption to bioceramics is competition adsorption between two or more proteins on the same adsorbent surface [223][224][225]. Leo Vroman firstly observed that fibrinogen preferentially adsorbed onto tantalum surfaces from blood plasma.…”