Roles of Coagulation Proteases and PARs (Protease-Activated Receptors) in Mouse Models of Inflammatory Diseases

Abstract

Activation of the blood coagulation cascade leads to fibrin deposition and platelet activation that are required for hemostasis. However, aberrant activation of coagulation can lead to thrombosis. Thrombi can cause tissue ischemia, and fibrin degradation products and activated platelets can enhance inflammation. In addition, coagulation proteases activate cells by cleavage of PARs (protease-activated receptors), including PAR1 and PAR2. Direct oral anticoagulants have recently been developed to specifically inhibit the coagulation proteases FXa (factor Xa) and thrombin. Administration of these inhibitors to wild-type mice can be used to determine the roles of FXa and thrombin in different inflammatory diseases. These results can be compared with the phenotypes of mice with deficiencies of either Par1 (F2r) or Par2 (F2rl1). However, inhibition of coagulation proteases will have effects beyond reducing PAR signaling, and a deficiency of PARs will abolish signaling from all proteases that activate these receptors. We will summarize studies that examine the roles of coagulation proteases, particularly FXa and thrombin, and PARs in different mouse models of inflammatory disease. Targeting FXa and thrombin or PARs may reduce inflammatory diseases in humans.

Keywords: anticoagulants; blood coagulation; inflammation; models, animal; thrombin.

Figure 1. Roles of coagulation proteases and downstream pathways in inflammatory diseases

Activation of the coagulation cascade leads to cleavage of fibrinogen into fibrin and platelet activation that can contribute to thrombosis Platelet activation and fibrin degradation products can also enhance inflammation. Additionally, coagulation proteases can activate cells via various PARs that can increase the expression of inflammatory mediators.