Nievelstein P F, Sixma J J
Department of Hematology, University Hospital Utrecht, The Netherlands.
Blood. 1988 Jul;72(1):82-8.
Previous studies have indicated that activated blood platelets interact with fibronectin through binding of fibronectin to the glycoprotein IIb-IIIa complex (GPIIb-IIIa). The cell attachment site of fibronectin with its crucial arg-gly-asp(-ser) [RGD(S)]sequence is involved in these bindings. We studied the importance of these interactions for the fibronectin dependence of platelet adhesion under flow conditions. An RGDS-containing hexapeptide (GRGDSP) was compared with a nonreactive control peptide (GRGESP). The GRGDSP-peptide inhibited thrombin-induced aggregation and adhesion under static conditions at 0.1 mmol/L. This concentration had no effect on platelet adhesion to nonfibrillar collagen type I in flow. GRGDSP at 1 mmol/L had a significant inhibitory effect at 1,500 s-1, but not at the lower shear rates of 800 and 300 s-1 where platelet adhesion is also fibronectin dependent. On the matrix of cultured human umbilical vein endothelial cells, 1 mmol/L GRGDSP had no effect on platelet adhesion. The relation between GPIIb-IIIa and fibronectin dependence was investigated with platelets of a patient with Glanzmann's thrombasthenia and monoclonal antibodies to GPIIb-IIIa using endothelial cell matrix (ECM) as a surface. Platelets of normal controls or a patient with Glanzmann's thrombasthenia showed a similar inhibition of adhesion in the presence of fibronectin-free plasma after the ECMs had been preincubated with antifibronectin F(ab')2 fragments. Incubation of platelets with anti-GPIIb-IIIa showed inhibition of platelet adhesion at high shear rates. Dependence on fibronectin for platelet adhesion was still observed even though separate experiments had shown that these anti-GPIIb-IIIa antibodies could block binding of radiolabeled fibronectin to thrombin-activated platelets. These data suggest the existence of another binding system for the interaction of platelets with fibronectin that may only appear when fibronectin is present on a surface.
以往研究表明，活化的血小板通过纤连蛋白与糖蛋白IIb-IIIa复合物（GPIIb-IIIa）的结合而与纤连蛋白相互作用。纤连蛋白带有关键的精氨酸-甘氨酸-天冬氨酸（-丝氨酸）[RGD(S)]序列的细胞附着位点参与了这些结合。我们研究了这些相互作用对于流动条件下血小板黏附的纤连蛋白依赖性的重要性。将含RGDS的六肽（GRGDSP）与无反应性的对照肽（GRGESP）进行比较。GRGDSP肽在0.1 mmol/L时可抑制静态条件下凝血酶诱导的聚集和黏附。该浓度对流动状态下血小板与I型非纤维状胶原的黏附无影响。1 mmol/L的GRGDSP在剪切速率为1500 s-1时有显著抑制作用，但在800和300 s-1的较低剪切速率下无此作用，而在较低剪切速率下血小板黏附也依赖纤连蛋白。在培养的人脐静脉内皮细胞基质上，1 mmol/L的GRGDSP对血小板黏附无影响。利用内皮细胞基质（ECM）作为表面，用针对GPIIb-IIIa的单克隆抗体对一名Glanzmann血小板无力症患者的血小板进行研究，探讨了GPIIb-IIIa与纤连蛋白依赖性之间的关系。在用抗纤连蛋白F(ab')2片段预孵育ECM后，正常对照者或Glanzmann血小板无力症患者的血小板在无纤连蛋白血浆存在时表现出相似的黏附抑制。用抗GPIIb-IIIa孵育血小板在高剪切速率下显示出对血小板黏附的抑制作用。尽管单独实验表明这些抗GPIIb-IIIa抗体可阻断放射性标记的纤连蛋白与凝血酶激活的血小板的结合，但仍观察到血小板黏附对纤连蛋白的依赖性。这些数据表明存在另一种血小板与纤连蛋白相互作用的结合系统，该系统可能仅在表面存在纤连蛋白时才出现。
