Kim Jeong Ai, Tran Nam D, Wang Shur-Jen, Fisher Mark J
Department of Neurology, University of California, Irvine, College of Medicine, Irvine, CA, USA.
Thromb Res. 2003;112(3):159-65. doi: 10.1016/j.thromres.2003.10.021.
Astrocytes are known to regulate a wide variety of brain endothelial cell functions. Prior work, using a mixed species co-culture system, has shown astrocyte regulation of brain capillary endothelial expression of key hemostasis factors tissue plasminogen activator (tPA) and its inhibitor, plasminogen activator inhibitor-1 (PAI-1). The purpose of this study is to define the fibrinolytic regulatory role of human astrocytes on human brain capillary endothelial cells.
We used a blood-brain barrier model consisting of human astrocytes grown on transwell membrane inserts and co-cultured with human brain capillary endothelial cells. Following 48 h co-culture, we analyzed both endothelial mono-cultures and astrocyte-endothelial co-cultures for expression of tPA and PAI-1 mRNA, protein, and activity.
There were significant changes for both tPA and PAI-1 mRNA:tPA mRNA levels were decreased in co-cultures (55+/-16% of mono-cultures, p<0.0005) and PAI-1 mRNA levels were increased 144+/-38%, compared to mono-cultures (p<0.005). Co-cultures produced a 54% reduction in tPA protein (12.7+/-3.8 vs. 27.5+/-7.1 ng/ml, p<0.005) and a 24% increase in PAI-1 protein (117.5+/-3.2 vs. 94.9+/-5.9 ng/ml, p<0.0005). TGF-beta neutralizing antibody attenuated the observed changes in both tPA and PAI-1. These data indicate that human astrocytes regulate human brain capillary fibrinolysis in vitro by inhibiting tPA and enhancing PAI-1 expression. This regulation is mediated, in part, by transforming growth factor-beta. Our findings provide further evidence for the role of astrocytes in brain-specific hemostasis regulation.
已知星形胶质细胞可调节多种脑内皮细胞功能。先前使用混合物种共培养系统的研究表明，星形胶质细胞可调节脑毛细血管内皮细胞中关键止血因子组织型纤溶酶原激活剂（tPA）及其抑制剂纤溶酶原激活剂抑制剂-1（PAI-1）的表达。本研究的目的是确定人星形胶质细胞对人脑毛细血管内皮细胞的纤溶调节作用。
我们使用了一种血脑屏障模型，该模型由生长在Transwell膜插入物上的人星形胶质细胞与人脑毛细血管内皮细胞共培养组成。共培养48小时后，我们分析了内皮细胞单培养物和星形胶质细胞-内皮细胞共培养物中tPA和PAI-1的mRNA、蛋白质表达及活性。
tPA和PAI-1的mRNA均有显著变化：与单培养物相比，共培养物中tPA mRNA水平降低（为单培养物的55±16%，p<0.0005），PAI-1 mRNA水平升高144±38%（p<0.005）。共培养使tPA蛋白减少54%（12.7±3.8对27.5±7.1 ng/ml，p<0.005），PAI-1蛋白增加24%（117.5±3.2对94.9±5.9 ng/ml，p<0.0005）。转化生长因子-β（TGF-β）中和抗体减弱了tPA和PAI-1的上述变化。这些数据表明，人星形胶质细胞在体外通过抑制tPA和增强PAI-1表达来调节人脑毛细血管纤溶。这种调节部分由转化生长因子-β介导。我们的研究结果为星形胶质细胞在脑特异性止血调节中的作用提供了进一步证据。
