Aprotinin Inhibits Thrombin Generation by Inhibition of the Intrinsic Pathway, but is not a Direct Thrombin Inhibitor

Abstract

Background Aprotinin is a broad-acting serine protease inhibitor that has been clinically used to prevent blood loss during major surgical procedures including cardiac surgery and liver transplantation. The prohemostatic properties of aprotinin likely are related to its antifibrinolytic effects, but other mechanisms including preservation of platelet function have been proposed. Aim Here we assessed effects of aprotinin on various hemostatic pathways in vitro, and compared effects to tranexamic acid(TXA), which is an antifibrinolytic but not a serine protease inhibitor. Methods We used plasma-based clot lysis assays, clotting assays in whole blood, plasma, and using purified proteins, and platelet activation assays to which aprotinin or TXA were added in pharmacological concentrations. Results Aprotinin and TXA dose-dependently inhibited fibrinolysis in plasma. Aprotinin inhibited clot formation and thrombin generation initiated via the intrinsic pathway, but had no effect on reactions initiated by tissue factor. However, in the presence of thrombomodulin, aprotinin enhanced thrombin generation in reactions started by tissue factor. TXA had no effect on coagulation. Aprotinin did not inhibit thrombin, only weakly inhibited the TF-VIIa complex and had no effect on platelet activation and aggregation by various agonists including thrombin. Aprotinin and TXA inhibited plasmin-induced platelet activation. Conclusion Pharmacologically relevant concentrations of aprotinin inhibit coagulation initiated via the intrinsic pathway. The antifibrinolytic activity of aprotinin likely explains the prohemostatic effects of aprotinin during surgical procedures. The anticoagulant properties may be beneficial during surgical procedures in which pathological activation of the intrinsic pathway, for example by extracorporeal circuits, occurs.

Snake Venom Hydrogels as a Rapid Hemostatic Agent for Uncontrolled Bleeding

“…A similar trend was observed across aprotinin and tranexamic acid treatment in terms of clot parameters, but clot initiation was significantly delayed in the presence of aprotinin, which is attributed to its inhibition of the clotting pathway. [ 39 ]…”

“…A similar trend was observed across aprotinin and tranexamic acid treatment in terms of clot parameters, but clot initiation was significantly delayed in the presence of aprotinin, which is attributed to its inhibition of the clotting pathway. [39] The blood clot breakdown (fibrinolysis) kinetics under the hyperfibrinolytic condition (presence of tPA), was then evaluated in the presence and absence of these antifibrinolytics. In the absence of antifibrinolytics the calcium only control, PICP1 and PicEcarin treated samples underwent 43.5% ± 0.8%, 20.3% ± 1.7%, and 37.5% ± 6.1% clot breakdown, respectively after 60 min, indicating PIC hydrogel is mediating some protection of the blood clots to fibrinolytic activity (Figure 5D).…”

Oral delivery of glutathione: antioxidant function, barriers and strategies

“…Aprotinin (a small protein with a molecular weight of 6500 Da) is a competitive enzyme inhibitor of several serine proteases, such as trypsin and chymotrypsin [108]. It has been used as an enzyme inhibitor in various studies investigating protein and peptide drug absorption across Citric acid Insulin [96,97] Cyclodextrins Limaprost [98] Glycerides DuP 532 [99] Lauroyl carnitine chloride Insulin [100] Sodium lauryl sulfate (SLS/sodium dodecyl sulfate) Cefazolin [101] Sodium N-[8-(2-hydroxybenzoyl) aminocaprylate] Semaglutide [102] the intestinal membrane.…”

A Microfluidics-Assisted Double-Barreled Nanobioconjugate Synthesis Introducing Aprotinin as a New Moonlight Nanocarrier Protein: Tested toward Physiologically Relevant 3D-Spheroid Models

“…14 Consequently, blocking these proteolytic enzyme cascades can be a promising strategy to suppress the metastatic and invasive nature of tumor cells to distant sites, hence offering a promising approach for cancer therapy. 19 Aprotinin, a nonspecific serine protease inhibitor 20 with antifibrinolytic and anti-inflammatory properties, 21 has only been shown to suppress the release of proinflammatory cytokines 22 and decrease the ability of leukocytes to pass through the vascular wall 21 for alternative cancer treatment. 23 However, the limited number of in vitro and in vivo studies on the antitumor effects of aprotinin have produced varying results, depending on the type of cancer model investigated.…”

“…Aprotinin, a nonspecific serine protease inhibitor with antifibrinolytic and anti-inflammatory properties, has only been shown to suppress the release of proinflammatory cytokines and decrease the ability of leukocytes to pass through the vascular wall for alternative cancer treatment . However, the limited number of in vitro and in vivo studies on the antitumor effects of aprotinin have produced varying results, depending on the type of cancer model investigated.…”