Tran N D, Schreiber S S, Fisher M
Department of Neurology, University of Southern California School of Medicine, Los Angeles, USA.
J Cereb Blood Flow Metab. 1998 Dec;18(12):1316-24. doi: 10.1097/00004647-199812000-00006.
Expression of tissue plasminogen activator (tPA) substantially determines endothelial-dependent fibrinolysis. We used a blood-brain barrier (BBB) model to analyze regulation of brain capillary endothelial tPA and its inhibitor, plasminogen activator inhibitor-1 (PAI-1). This model consists of coculture of murine astrocytes with bovine brain capillary endothelial cells grown as capillary-like structures (CS); after 1 week, astrocytes become extensively associated with CS, and the BBB-associated enzyme gamma-glutamyl transpeptidase is present. We measured tPA and PAI-1 mRNA and tPA activity in this model. Reverse transcription-polymerase chain reaction (RT-PCR) studies showed similar tPA and PAI-1 mRNA levels after 1 day mono-culture (endothelial cells only) versus astrocyte-endothelial coculture preparations. After 7 days (i.e., when elements of the BBB are present), astrocyte-endothelial cocultures (compared with endothelial mono-cultures) showed a 50.7%+/-27.1% (mean +/- SD) reduction in tPA mRNA (P < 0.03) and a 183.3%+/-86.9% increase in PAI-1 mRNA expression (P < 0.02). Moreover, 7-day cocultures demonstrated reduced tPA activity compared with mono-cultures (14.6+/-2.9 IU/mL versus 30.2+/-7.7 IU/mL, P < 0.01); 1-day cocultures and mono-cultures had similar tPA activity. These findings demonstrate that astrocytes regulate brain capillary endothelial expression of tPA when elements of the BBB phenotype are present in this model. These data suggest an important role for astrocytes in the regulation of brain capillary endothelial fibrinolysis.
组织型纤溶酶原激活物（tPA）的表达在很大程度上决定了内皮依赖性纤维蛋白溶解。我们使用血脑屏障（BBB）模型来分析脑毛细血管内皮tPA及其抑制剂纤溶酶原激活物抑制剂-1（PAI-1）的调控情况。该模型由小鼠星形胶质细胞与以毛细血管样结构（CS）生长的牛脑毛细血管内皮细胞共培养组成；1周后，星形胶质细胞与CS广泛关联，且存在与BBB相关的酶γ-谷氨酰转肽酶。我们在该模型中测量了tPA和PAI-1 mRNA以及tPA活性。逆转录-聚合酶链反应（RT-PCR）研究表明，1天单培养（仅内皮细胞）与星形胶质细胞-内皮共培养制剂相比，tPA和PAI-1 mRNA水平相似。7天后（即BBB成分出现时），星形胶质细胞-内皮共培养物（与内皮单培养物相比）显示tPA mRNA降低了50.7%±27.1%（平均值±标准差）（P<0.03），PAI-1 mRNA表达增加了183.3%±86.9%（P<0.02）。此外，与单培养物相比，7天共培养物的tPA活性降低（14.6±2.9 IU/mL对30.2±7.7 IU/mL，P<0.01）；1天共培养物和单培养物的tPA活性相似。这些发现表明，当该模型中出现BBB表型成分时，星形胶质细胞可调节脑毛细血管内皮tPA的表达。这些数据表明星形胶质细胞在调节脑毛细血管内皮纤维蛋白溶解中起重要作用。
