MECHANISMS OF SICKLE ERYTHROCYTE/ENDOTHELIAL ADHESION

镰状细胞病的特点是间歇性的，局部的 微血管闭塞危象 血红蛋白-S脱氧导致 形态学镰状化和刚性红细胞的形成， 阻塞毛细血管并阻碍随后的红细胞通过。 血红蛋白聚合动力学是这样的， 红细胞在形态学改变之前穿过微循环 镰刀形。 然而，延迟的微血管通过将增加 毛细血管内镰状化、微血管闭塞和疼痛的可能性 危机 我们假设红细胞粘附于血管壁， 微循环中的内皮细胞延迟红细胞通过 足以引发或传播镰状细胞血管闭塞。 红细胞/内皮细胞粘附可能与复杂的变化有关 在红细胞表面、内皮和血管环境中。 在体外，镰状红细胞粘附定量相关， 镰状细胞病的临床严重程度。 此外，急性期 反应物，如纤维蛋白原和高分子量vWF多聚体， 以及活化血小板释放的因子， 细胞粘附 此外，与大血管和微血管的粘连 内皮细胞在质和量上是不同的。 我们提出 研究粘附静脉，动脉， 微血管内皮在危机和无症状期， 为了鉴定血浆成分和细胞粘附分子， 促进镰状红细胞与培养内皮细胞的粘附。 是 还建议研究内皮细胞刺激的作用， 这可能是由于凝血、感染或 镰刀病人怀孕。 内皮细胞激活会导致 调节细胞粘附分子的表达和/或分泌 粘附蛋白 在拟议的实验中，动态体外 粘附测定，其结合了存在于细胞中的流体剪切力， 将利用体内毛细血管后小静脉。 利用这个系统，我们 将（i）表征镰状红细胞粘附的差异 微血管和脐静脉的内皮细胞， 激动剂和拮抗剂对粘附的影响，（ii）确定 镰状红细胞粘附内皮细胞的变异性 危机期间的患者对患者和个体患者， （iii）确定血浆因子，包括可溶性 从激活的血小板中释放的因子， 红细胞粘附，和（iv）对比激动剂的作用， 可能刺激内皮细胞，如凝血酶，内毒素， 纤溶酶、纤维蛋白原和TNF对粘附蛋白分泌、细胞 粘附分子表达和粘附。

Sickle cell disease is characterized by intermittent, localized microvascular occlusive crises. Hemoglobin-S deoxygenation leads to morphologic sickling and the formation of rigid erythrocytes which occlude capillaries and obstruct passage of subsequent red cells. Hemoglobin polymerization kinetics are such that the majority of erythrocytes traverse the microcirculation prior to morphologic sickling. However, delayed microvascular transit will increase the likelihood of intracapillary sickling, microvascular occlusion, and pain crisis. We hypothesize that erythrocyte adherence to vascular endothelium in the microcirculation delays erythrocyte transit sufficiently to initiate or propagate sickle cell vaso-occlusion. Erythrocyte/endothelial adherence is likely related to complex changes in the erythrocyte surface, the endothelium, and the vascular milieu. In vitro, sickle red cell adherence quantitatively correlates with the clinical severity of sickle cell disease. Furthermore, acute phase reactants, such as fibrinogen and high molecular weight vWF multimers as well as factors released from activated platelets, promote sickle red cell adherence. In addition, adhesion to large vessel and microvascular endothelium is qualitatively and quantitatively different. We propose to investigate the mechanism of adherence to venous, arterial, and microvascular endothelium during crisis and asymptomatic periods in order to identify plasma components and cell adhesion molecules which promote sickle erythrocyte adherence to cultured endothelium. It is also proposed to investigate the role of endothelial cell stimulation which may occur as a result of activation of coagulation, infection, or pregnancy in sickle patients. Endothelial cell activation would lead to modulation of cell adhesion molecule expression and/or secretion of adhesive proteins. In the proposed experiments, a dynamic in vitro adherence assay which incorporates the fluid shear forces present in the post-capillary venules in vivo will be utilized. Using this system, we will (i) characterize the difference in adhesion of sickle erythrocytes to endothelial cells from microvessels and umbilical vein by determining the effects of agonists and antagonists on adherence, (ii) determine the variability in sickle red cell adherence to endothelial cells from patient to patient and for individual patients during crisis and asymptomatic periods, (iii) identify plasma factors, including soluble factors released from activated platelets, which promote sickle erythrocyte adherence, and (iv) contrast the effects of agonists which presumably stimulate endothelial cells, such as thrombin, endotoxin, plasmin, fibrin(ogen), and TNF on adhesive protein secretion, cell adhesion molecule expression, and adherence.