Jy W, Mao W W, Horstman L, Tao J, Ahn Y S
William J. Harrington Sr., Center for Blood Diseases, Dept of Medicine, School of Medicine, University of Miami.
Blood Cells Mol Dis. 1995;21(3):217-31; discussion 231a. doi: 10.1006/bcmd.1995.0025.
The interaction of activated platelets with leukocytes are believed to play an important role in ischemic reperfusion injury and other thrombotic conditions. Upon activation, platelets shed platelet microparticles (PMP) and express activation markers CD62P expressed on activated platelets mediates adhesion of platelets to leukocytes, chiefly neutrophils, but little is known of the interaction of PMP isolated from stored platelets or thrombin activated platelets was incubated with leukocytes and binding assessed by flow cytometry. FITC-labeled alpha-CD41 was used to assess platelet material associated with WBC. Like platelets PMP bound preferentially to neutrophils rather than lymphocytes, and exhibited an absolute dependence on the presence of Ca2+. Binding was time-and concentration-dependent, reaching a plateau at 10 min at a ratio of PMP to neutrophils of 150:1. Fluorescence microscopy showed that most of the neutrophils were aggregated into clusters of 5-20 cells. Clustering of neutrophils was not observed to result form interaction with platelets. In these clusters the adherent PMP appeared to serve as bridges between the neutrophil. Addition of EGTA after brief incubation (5-10 min) released most of the bound PMP but if added after > 10 min, only approximately 60% of bound PMP were released. In contrast, nearly all bound platelets were released by EGTA at the same time of incubation. Incubation of neutrophils with PMP gave significantly higher percentage of CD41a(+)neutrophils than did platelets incubated at the same numerical ratio. PMP association with neutrophils was less markedly inhibited by alpha-CD62P (AC1.2) than platelets, but binding of both PMP and activated platelets was inhibited approximately 90% by antisialyl Lewis X. PMP binding to neutrophils induced a significant increase in both CD11b expression and phagocytic activity in a concentration-dependent manner. These findings suggest a possible role for PMP in addition to providing platelet factor 3, specifically, as an activator and mediator of neutrophils in ischemic injury, thrombosis, and inflammation.
活化血小板与白细胞之间的相互作用被认为在缺血再灌注损伤及其他血栓形成性病症中发挥重要作用。活化后，血小板会释放血小板微粒（PMP）并表达活化标志物，活化血小板上表达的CD62P介导血小板与白细胞（主要是中性粒细胞）的黏附，但对于从储存血小板或凝血酶活化血小板中分离出的PMP与白细胞相互作用的了解甚少。将PMP与白细胞一起孵育，并通过流式细胞术评估结合情况。用异硫氰酸荧光素（FITC）标记的α-CD41来评估与白细胞相关的血小板物质。与血小板一样，PMP优先与中性粒细胞而非淋巴细胞结合，并且对Ca2+的存在表现出绝对依赖性。结合呈时间和浓度依赖性，在10分钟时达到平台期，PMP与中性粒细胞的比例为150:1。荧光显微镜显示，大多数中性粒细胞聚集成5 - 20个细胞的簇。未观察到中性粒细胞的聚集是与血小板相互作用的结果。在这些簇中，黏附的PMP似乎充当了中性粒细胞之间的桥梁。短暂孵育（5 - 10分钟）后添加乙二醇双四乙酸（EGTA）可释放大部分结合的PMP，但如果在10分钟后添加，只有约60%的结合PMP被释放。相比之下，几乎所有结合的血小板在孵育的同一时间被EGTA释放。以相同数量比例孵育时，用PMP孵育中性粒细胞产生的CD41a(+)中性粒细胞百分比明显高于用血小板孵育的情况。与血小板相比，α-CD62P（AC1.2）对PMP与中性粒细胞结合的抑制作用较弱，但抗唾液酸化路易斯X对PMP和活化血小板的结合均有大约90%的抑制作用。PMP与中性粒细胞的结合以浓度依赖性方式显著增加了CD11b的表达和吞噬活性。这些发现表明，PMP除了提供血小板因子3外，可能还具有其他作用，具体而言，在缺血性损伤、血栓形成和炎症中作为中性粒细胞的激活剂和介质发挥作用。
