Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei 110, Taiwan.
Department of Ecology and Environmental Sciences, Pondicherry University, Puducherry 605014, India.
Life Sci. 2023 Aug 1;326:121791. doi: 10.1016/j.lfs.2023.121791. Epub 2023 May 19.
Platelet activation plays a central role in arterial thrombosis. Platelets are activated by adhesive proteins (i.e., collagen) or soluble agonists (i.e., thrombin), the respective receptor-specific signaling cause inside-out signaling, leading to the binding of fibrinogen to integrin αβ. This binding triggers outside-in signaling, resulting in platelet aggregation. Garcinol, a polyisoprenylated benzophenone, is extracted from the fruit rind of Garcinia indica. Although garcinol exhibits considerable bioactivities, few studies have investigated the effect of garcinol on platelet activation.
Aggregometry, immunoblotting, flow cytometer, confocal microscopic analysis, fibrin clot retraction, animal studies such as fluorescein-induced platelet plug formation in mesenteric microvessels, acute pulmonary thromboembolism, and tail bleeding time were performed in this study.
This study indicates that garcinol inhibited platelet aggregation stimulated by collagen, thrombin, arachidonic acid, and U46619. Garcinol reduced integrin αβ inside-out signaling, including ATP release; cytosolic Ca mobilization; P-selectin expression; and Syk, PLCγ2/PKC, PI3K/Akt/GSK3β, MAPKs, and NF-κB activation stimulated by collagen. Garcinol directly inhibited integrin αβ activation by interfering with FITC-PAC-1 and FITC-triflavin by collagen. Additionally, garcinol affected integrin αβ-mediated outside-in signaling, such as decreasing platelet adhesion and the single-platelet spreading area; suppressing integrin β, Src, FAK, and Syk phosphorylation on immobilized fibrinogen; and inhibiting thrombin-stimulated fibrin clot retraction. Garcinol substantially reduced mortality caused by pulmonary thromboembolism and prolonged the occlusion time of thrombotic platelet plug formation without extending bleeding time in mice.
This study identified that garcinol, a novel antithrombotic agent, acts as a naturally occurring integrin αβ inhibitor.
血小板激活在动脉血栓形成中起着核心作用。血小板可被黏附蛋白（如胶原）或可溶性激动剂（如凝血酶）激活，相应的受体特异性信号转导导致内向外信号转导，导致纤维蛋白原与整合素 αβ 结合。这种结合触发外向信号转导，导致血小板聚集。鞣花酸是一种多异戊二烯基二苯甲酮，从 Garcinia indica 的果皮中提取。尽管鞣花酸表现出相当大的生物活性，但很少有研究调查鞣花酸对血小板激活的影响。
在这项研究中进行了聚集测定、免疫印迹、流式细胞仪、共聚焦显微镜分析、纤维蛋白凝块回缩、动物研究，如在肠系膜微血管中荧光素诱导的血小板栓形成、急性肺血栓栓塞和尾部出血时间。
本研究表明，鞣花酸抑制了由胶原、凝血酶、花生四烯酸和 U46619 刺激的血小板聚集。鞣花酸减少整合素 αβ 内向外信号转导，包括 ATP 释放；胞质 Ca 动员；P-选择素表达；以及由胶原刺激的 Syk、PLCγ2/PKC、PI3K/Akt/GSK3β、MAPKs 和 NF-κB 激活。鞣花酸通过干扰胶原与 FITC-PAC-1 和 FITC-triflavin 的结合，直接抑制整合素 αβ 的激活。此外，鞣花酸影响整合素 αβ 介导的外向信号转导，如减少血小板黏附和单个血小板铺展面积；抑制固定化纤维蛋白原上整合素 β、Src、FAK 和 Syk 的磷酸化；并抑制凝血酶刺激的纤维蛋白凝块回缩。鞣花酸显著降低了肺血栓栓塞引起的死亡率，并延长了血栓性血小板栓形成的闭塞时间，而不延长小鼠的出血时间。
本研究确定了鞣花酸，一种新型抗血栓形成药物，作为一种天然存在的整合素 αβ 抑制剂。
