Burdick Monica M, Konstantopoulos Konstantinos
Dept. of Chemical and Biomolecular Engineering, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218-2694, USA.
Am J Physiol Cell Physiol. 2004 Aug;287(2):C539-47. doi: 10.1152/ajpcell.00450.2003. Epub 2004 Apr 14.
This study was undertaken to characterize the adhesion of LS174T colon adenocarcinoma cells to 4-h TNF-alpha-stimulated human umbilical vein endothelial cells (HUVECs) under flow in the presence and absence of platelets and erythrocytes. Cell binding to HUVECs was significantly enhanced by simultaneous perfusion of thrombin-activated, but not resting, platelets. This increase was achieved via a platelet bridging mechanism whereby a previously tethered LS174T cell (primary tether) captures a free-flowing cell (secondary tether) that subsequently attaches to the endothelium downstream of the already adherent cell. The total number of tumor cells tethering to HUVECs and the percentage of secondary tethers relative to the total amount of cell tethering depended on platelet concentration and wall shear stress. At 0.8 dyn/cm(2) and a platelet-to-LS174T cell ratio of 25:1, the total amount of cell tethering nearly doubled as a result of platelet-induced enhancement compared with the amount without platelet perfusion. Moreover, the percentage of secondary tethers increased from background levels (<5%) in the absence of platelets to approximately 60% at a platelet-to-LS174T cell ratio of 25:1. Platelet-mediated secondary tethering is not limited to LS174T colon carcinoma cells, as THP-1 monocytoid cells also displayed this pattern of interaction. Secondary tethering was dependent on both platelet P-selectin and alpha(IIb)beta(3)-integrin for LS174T cells and P-selectin alone for THP-1 cells. Furthermore, platelet-mediated secondary tethering of both cell types occurred in the presence of red blood cells. Altogether, these results reveal a novel role for platelets in promoting cell binding to endothelium through a secondary tethering mechanism.
本研究旨在表征在有血小板和红细胞存在及不存在的情况下，LS174T结肠腺癌细胞在流动状态下与经4小时肿瘤坏死因子-α（TNF-α）刺激的人脐静脉内皮细胞（HUVECs）的黏附情况。同时灌注凝血酶激活的血小板（而非静息血小板）可显著增强细胞与HUVECs的结合。这种增加是通过血小板桥接机制实现的，即先前拴系的LS174T细胞（初级拴系）捕获一个自由流动的细胞（次级拴系），该细胞随后附着于已黏附细胞下游的内皮细胞。拴系到HUVECs的肿瘤细胞总数以及次级拴系相对于细胞拴系总量的百分比取决于血小板浓度和壁面剪应力。在0.8达因/平方厘米及血小板与LS174T细胞比例为25:1的条件下，与无血小板灌注时相比，由于血小板诱导的增强作用，细胞拴系总量几乎增加了一倍。此外，次级拴系的百分比从无血小板时的背景水平（<5%）增加到血小板与LS174T细胞比例为25:1时的约60%。血小板介导的次级拴系不仅限于LS174T结肠癌细胞，THP-1单核细胞样细胞也表现出这种相互作用模式。对于LS174T细胞，次级拴系依赖于血小板P-选择素和α（IIb）β（3）整合素，而对于THP-1细胞则仅依赖于P-选择素。此外，两种细胞类型的血小板介导的次级拴系在有红细胞存在的情况下也会发生。总之，这些结果揭示了血小板在通过次级拴系机制促进细胞与内皮细胞结合方面的新作用。
