Fujii S, Sawa H, Saffitz J E, Lucore C L, Sobel B E
Cardiovascular Division, Washington University School of Medicine, St. Louis, MO 63110.
Circulation. 1992 Dec;86(6):2000-10. doi: 10.1161/01.cir.86.6.2000.
We have shown previously that products from activated platelets can augment synthesis of plasminogen activator inhibitor type 1 (PAI-1) in cultured endothelial and hepatoma (Hep G2) cells in vitro and increase plasma PAI-1 activity in vivo in rabbits. Accordingly, the effects of activation of platelets associated with thrombosis and thrombolysis in vivo on plasma PAI-1 activity and expression of the PAI-1 gene in endothelium, liver, and other organs were characterized.
Endothelial injury giving rise to platelet-rich thrombi was induced with electrical stimulation in carotid arteries in rabbits. Clot lysis and recanalization were induced subsequently with intravenous tissue-type plasminogen activator (t-PA) and verified with Doppler flow probes. Plasma PAI-1 activity (mean +/- SD) increased from 6 +/- 2 arbitrary units (AU)/ml to 129 +/- 48 AU/ml (n = 15) within several hours after recanalization. When t-PA had failed to induce recanalization, the increase was much less (from 7 +/- 2 to 42 +/- 23 AU/ml, n = 11). To define mechanisms responsible for these changes, PAI-1 messenger RNA (mRNA) was evaluated by Northern blot analysis and localized in tissues by in situ hybridization. Strong and consistent induction of PAI-1 mRNA was evident in aorta, heart, and liver of animals subjected to thrombosis (twofold to threefold increases compared with values in controls), particularly in those in which thrombolysis had been induced (fourfold to sixfold). After thrombolysis, an intense, PAI-1 mRNA-specific signal was detected in endothelium of aorta, liver, and heart, with less intense signals in endothelium of lung, adrenals, and kidneys.
The increases in plasma PAI-1 activity follow a preceding increase in endothelial cell expression of the PAI-1 gene as reflected by PAI-1 mRNA levels. Thus, increased synthesis of endothelial cell PAI-1 after thrombosis and thrombolysis may attenuate endogenous fibrinolysis early after coronary thrombolysis, thereby potentiating early, thrombotic reocclusion.
我们之前已经表明，活化血小板的产物能够在体外增强培养的内皮细胞和肝癌（Hep G2）细胞中1型纤溶酶原激活物抑制剂（PAI-1）的合成，并在体内增加兔血浆PAI-1活性。因此，我们对体内与血栓形成和溶栓相关的血小板活化对血浆PAI-1活性以及PAI-1基因在血管内皮、肝脏和其他器官中的表达的影响进行了研究。
通过电刺激诱导兔颈动脉内皮损伤，形成富含血小板的血栓。随后静脉注射组织型纤溶酶原激活剂（t-PA）诱导血栓溶解和再通，并使用多普勒血流探头进行验证。再通后数小时内，血浆PAI-1活性（平均值±标准差）从6±2任意单位（AU）/ml增加到129±48 AU/ml（n = 15）。当t-PA未能诱导再通时，活性增加幅度小得多（从7±2增加到42±23 AU/ml，n = 11）。为了确定导致这些变化的机制，通过Northern印迹分析评估PAI-1信使核糖核酸（mRNA），并通过原位杂交在组织中定位。在发生血栓形成的动物的主动脉、心脏和肝脏中，PAI-1 mRNA出现强烈且一致的诱导（与对照组相比增加了两倍至三倍），特别是在那些诱导了溶栓的动物中（增加了四倍至六倍）。溶栓后，在主动脉、肝脏和心脏的内皮中检测到强烈的、PAI-1 mRNA特异性信号，而在肺、肾上腺和肾脏的内皮中信号较弱。
血浆PAI-1活性的增加先于PAI-1基因在内皮细胞中的表达增加，这可通过PAI-1 mRNA水平反映出来。因此，血栓形成和溶栓后内皮细胞PAI-1合成增加可能会在冠状动脉溶栓后早期减弱内源性纤维蛋白溶解，从而增强早期血栓再闭塞。
