RGD-ligand mimetic antagonists of integrin αIIbβ3 paradoxically enhance GPVI-induced human platelet activation
RGD-ligand mimetic antagonists of integrin αIIbβ3 paradoxically enhance GPVI-induced human platelet activation
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DOI：
10.1111/j.1538-7836.2009.03719.x
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发表时间：
2010-03-01
影响因子：
10.4
通讯作者：
Poole, A. W.
中科院分区：
文献类型：
--
作者：
Jones, M. L.;Harper, M. T.;Poole, A. W.
背景：整合素α(IIb)β(3)是血小板聚集的主要介质，因此已成为抗血栓治疗的重要靶点。α(IIb)β(3)的拮抗剂，如阿昔单抗、替罗非班和依替菲替丁，用于急性冠脉综合征的治疗。然而，除了有效地阻断整合素外，结合还可以诱导整合素的构象变化，还可以诱导整合素聚集。因此，RGD配体模拟物的这一类效应可能是先前报道的矛盾的血小板激活和血栓形成的基础。目的：研究血小板内信号转导通路和功能反应的成分可能是导致这一反常的血小板激活现象的基础。方法：我们通过免疫印迹法检测洛曲非班和其他α(IIb)β(3)拮抗剂(包括临床用药替罗非班)对血小板关键信号蛋白酪氨酸磷酸化的影响，以及对血小板胞浆钙反应、磷脂酰丝氨酸暴露(促凝血活性)和致密颗粒释放等功能输出的影响。结果：在所有病例中，α(IIb)β(3)拮抗剂没有单独作用，但这些整合素拮抗剂确实显著增强了糖蛋白VI(GPVI)相关的FCR伽马链磷酸化，激活了Src家族激酶和Syk激酶。这与致密颗粒分泌增加、胞浆钙反应和血小板表面磷脂酰丝氨酸暴露有关。P2Y(12)拮抗剂可抑制增强的磷脂酰丝氨酸暴露和致密颗粒分泌，但不能抑制胞浆钙反应。结论：这些数据提供了α(IIb)β(3)抑制剂增强血小板活性的机制，但也揭示了从整合素到GPVI信号的潜在重要信号通路。
Background: The integrin alpha(IIb)beta(3) is the major mediator of platelet aggregation and has, therefore, become an important target of antithrombotic therapy. Antagonists of alpha(IIb)beta(3), for example abciximab, tirofiban and eptifibatide, are used in the treatment of acute coronary syndromes. However, in addition to effective blockade of the integrin, binding of can induce conformational changes in the integrin and can also induce integrin clustering. This class effect of RGD-ligand mimetics might, therefore, underlie paradoxical platelet activation and thrombosis previously reported. Objectives: To examine the components of signaling pathways and functional responses in platelets that may underlie this phenomenon of paradoxical platelet activation. Methods: We assessed the effect of lotrafiban, and other alpha(IIb)beta(3) antagonists including the clinically used drug tirofiban, on tyrosine phosphorylation of key signaling proteins in platelets by immunoblotting and also platelet functional outputs such as cytosolic calcium responses, phosphatidylserine exposure (pro-coagulant activity) and dense granule release. Results: In all cases, no effect of alpha(IIb)beta(3) antagonists were observed on their own, but these integrin antagonists did lead to a marked potentiation of glycoprotein VI (GPVI)-associated FcR gamma-chain phosphorylation, activation of Src family kinases and Syk kinase. This correlated with increased dense granule secretion, cytosolic calcium response and exposure of phosphatidylserine on the platelet surface. P2Y(12) antagonism abolished the potentiated phosphatidylserine exposure and dense granule secretion but not the cytosolic calcium response. Conclusions: These data provide a mechanism for enhancement of platelet activity by alpha(IIb)beta(3) inhibitors, but also reveal a potentially important signaling pathway operating from the integrin to GPVI signaling.