Department of Studies in Biochemistry, University of Mysore, Manasagangothri, Mysuru, Karnataka, India.
Vijayashree Diagnostics, Specialized Coagulation Lab, Bengaluru, Karnataka, India.
J Cell Biochem. 2021 Aug;122(8):870-881. doi: 10.1002/jcb.29917. Epub 2021 Mar 21.
Hemostasis is a proteolytically regulated process that requires activation of platelets and the blood coagulation cascade upon vascular injury. Activated platelets create a thrombogenic environment and amplify the coagulation process. Plant latex proteases (PLPs) have been used as therapeutic components to treat various ailments by folk healers. One of the main applications of plant latices is to stop bleeding from minor injuries and to enhance wound healing activity. Although many studies have reported the pro-coagulant activities of PLPs, an in-depth investigation is required to understand the mechanism of action of PLPs on platelets. Here, the effect of PLPs on platelet aggregation was studied systematically to validate the observed pharmacological effect by folk healers. Among 29 latices from the Ficus genus tested, Ficus drupacea exhibited potent pro-coagulant and thrombin-like activity. Drupin, a thrombin-like cysteine protease responsible for platelet aggregation was purified from F. drupacea latex. Drupin exhibits pro-coagulant activity and reduces the bleeding time in mice tail. It induces platelet aggregation by activating mitogen-activated protein kinases and the nuclear factor-κB and PI3K/Akt signalling cascade, which, in turn, phosphorylats, cytosolic phospholipase A leading to the release of thromboxane A from the granules to activate the nearby platelets to aggregate. Furthermore, we investigated the involvement of protease-activated receptors in drupin-induced platelet aggregation using specific protease activated receptor 1 (PAR1) and PAR4 receptor antagonists. The results confirmed that the drupin-induced platelet aggregation was mediated by both PAR1 and PAR4, synergistically. Overall, drupin reduces the bleeding time by exerting pro-coagulant activity and induces platelet aggregation by activating the intracellular signalling cascade.
止血是一个蛋白水解调控的过程，需要在血管损伤时激活血小板和血液凝血级联反应。激活的血小板会产生血栓形成环境并放大凝血过程。植物乳胶蛋白酶（PLP）已被用作治疗成分，由民间治疗师治疗各种疾病。植物乳胶的主要应用之一是止血轻微损伤并增强伤口愈合活性。尽管许多研究报告了 PLP 的促凝活性，但需要深入研究以了解 PLP 对血小板的作用机制。在这里，系统研究了 PLP 对血小板聚集的影响，以验证民间治疗师观察到的药理作用。在测试的 29 种榕属植物乳胶中，榕属 Ficus drupacea 表现出强大的促凝和类凝血酶活性。Drupin，一种负责血小板聚集的类凝血酶半胱氨酸蛋白酶，从 F. drupacea 乳胶中纯化出来。Drupin 表现出促凝活性，并缩短小鼠尾巴的出血时间。它通过激活丝裂原活化蛋白激酶和核因子-κB 和 PI3K/Akt 信号级联诱导血小板聚集，这反过来又使细胞质磷脂酶 A 磷酸化，导致血栓素 A 从颗粒中释放出来，激活附近的血小板聚集。此外，我们使用特异性蛋白酶激活受体 1（PAR1）和 PAR4 受体拮抗剂研究了 drupin 诱导的血小板聚集中蛋白酶激活受体的参与。结果证实，drupin 诱导的血小板聚集是由 PAR1 和 PAR4 共同介导的，具有协同作用。总体而言，drupin 通过发挥促凝活性来缩短出血时间，并通过激活细胞内信号级联诱导血小板聚集。
