Thrombin-induced platelet endostatin release is blocked by a proteinase activated receptor-4 (PAR4) antagonist
Thrombin-induced platelet endostatin release is blocked by a proteinase activated receptor-4 (PAR4) antagonist
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DOI：
10.1038/sj.bjp.0704312
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发表时间：
2001-10-01
影响因子：
7.3
通讯作者：
Wallace, JL
中科院分区：
文献类型：
--
作者：
Ma, L;Hollenberg, MD;Wallace, JL
内皮抑素是一种有效的内源性血管生成抑制剂，最近被证明储存在血小板中，并响应于凝血酶而不是ADP释放。在本研究中，我们已经测试了假设，凝血酶诱导内皮抑制素释放大鼠血小板是通过蛋白酶激活受体4（PAR 4）介导的。免疫沉淀和蛋白质印迹证实，内皮抑素是包含在大鼠血小板。凝血酶（0.5-1.0 U ml（-1））或特异性PAR 4激动剂（AYPGKF-NH 2; AY-NH 2; 15-50 μ M）可引起内皮抑制素的聚集和释放。低于诱导聚集所需剂量的凝血酶可诱导内皮抑制素的显著释放。腺苷二磷酸（ADP）清除剂腺苷三磷酸双磷酸酶抑制凝血酶诱导的血小板聚集，但不释放内皮抑素。相反，选择性PAR 4拮抗剂（trans-cinnamoyl-YPGKF-NH 2; tcY-NH 2）阻止由凝血酶或AY-NH 2诱导的内皮抑制素释放和聚集。我们的结论是，凝血酶诱导的内皮抑制素释放大鼠血小板PAR 4介导的ADP-独立的机制，可以发生独立的血小板聚集。
Endostatin is a potent endogenous inhibitor of angiogenesis that was recently shown to be stored in platelets and released in response to thrombin, but not ADP. In the present study, we have tested the hypothesis that thrombin-induced endostatin release from rat platelets is mediated via proteinase-activated receptor-4 (PAR4). Immunoprecipitation and Western blotting confirmed that endostatin is contained within rat platelets. Aggregation and release of endostatin could be elicited by thrombin (0.5-1.0 U ml(-1)) or by specific PAR4 agonist (AYPGKF-NH2; AY-NH2; 15-50 muM). Significant release of endostatin could be induced by a dose of thrombin below that necessary for induction of aggregation. An adenosine diphosphate (ADP) scavenger, apyrase, inhibited the platelet aggregation induced by thrombin, but not the release of endostatin. In contrast, a selective PAR4 antagonist (trans-cinnamoyl-YPGKF-NH2; tcY-NH2) prevented endostatin release and aggregation induced by thrombin or by AY-NH2. We conclude that thrombin-induced endostatin release from rat platelets is PAR4-mediated via an ADP-independent mechanism that can occur independently of platelet aggregation.