Role of platelets and serine proteinases in coupling of blood coagulation and inflammation

In addition to having a key role in thrombogenesis, platelets are actively involved in acute and chronic inflammation: they induce the release of proinflammatory mediators, expose adhesion molecules, and recruit leukocytes. The inflammation-induced expression of tissue factor by endothelium and monocytes leads to production of hemostatic serine proteinases, which can regulate both blood coagulation and the inflammatory response of the body. Serine proteinases activate blood and connective tissue cells and regulate blood coagulation, inflammation, tissue repair, atherogenesis, etc. This review considers new functions of platelets in thrombogenesis and inflammation, stabilization of platelet-platelet and platelet-leukocyte aggregations, receptor functions of tissue factor, proinflammatory properties of hemostatic serine proteinases mediated by proteinase-activated receptors (PAR), activation of transcriptional factors (NFkappaB and other), and anti-inflammatory and cytoprotective properties of the anticoagulant proteinase (activated protein Q mediated through binding of the endothelial protein C receptor (EPCR) and cleavage of PAR1.