关键词: 蜱, 凝血, 凝血酶抑制剂, Xa因子抑制剂, 血小板聚集抑制剂

Abstract: Ticks are zoonotic ectoparasites transmitting pathogens to hosts via biting and feeding on hosts, which are associated with various diseases. Coagulation reaction is an important physiological process and plays critical roles in physiological hemostasis in humans and animals. During the long time of biting and feeding processes on hosts, ticks can secrete a variety of anticoagulants to inhibit coagulation reactions, which would guarantee the ticks to have blood meals for a long time. To date, the major tickderived anticoagulants which have been identified and recognized according to their functions include protease inhibitors, fibrin(ogen)olytic agents, platelet aggregation inhibitors, and vasoactive proteins. These anticoagulants can act on the intrinsic pathway, extrinsic pathway, and key steps in the common pathway of the coagulation cascade, promote fibrinolysis, and inhibit platelet activation, thereby inhibiting the coagulation response in the host blood vessels. Protease inhibitors mainly inhibit the activities of thrombin and factor Xa in the common pathway of coagulation cascade. Fibrin(ogen)olytic agents cause the hydrolysis of fibrinogen and delay the formation of fibrin clots. Platelet aggregation inhibitors can suppress platelet aggregation by degrading platelet aggregation agonists and binding thromboxane A2 (TXA2) and αIIBβ3 integrin on platelet surface. Vasoactive proteins inhibit host vasoconstriction, and wound healing and angiogenesis. In addition, there are some other protein molecules secreted by ticks that pose anticoagulation effects through different pathways. In this article, we summarized the anticoagulant proteins and small molecules found in ticks so far and their anticoagulant mechanisms, which will promote understanding of the mechanism and physiological significance of anticoagulation process in hosts triggered by ticks, and will provide important reference for developing new tickderived anticoagulant drugs and new antithrombotic therapies.

Key words:  Tick, coagulation, thrombin inhibitors, factor Xa inhibitors, platelet aggregation inhibitors