Descamps L, Dehouck M P, Torpier G, Cecchelli R
Institut National de la Santé et de la Recherche Médicale U325-Service d'Etude et de Recherche sur les Lipoprotéines et l'Athérosclérose, Institut Pasteur, Lille, France.
Am J Physiol. 1996 Apr;270(4 Pt 2):H1149-58. doi: 10.1152/ajpheart.1996.270.4.H1149.
A cell culture model of the blood-brain barrier consisting of a coculture of bovine brain capillary endothelial cells (BBCECs) and astrocytes has been used to examine the mechanism of iron transport to the brain. Binding experiments showed that BBCECs express 35,000 high-affinity (concn at 50% receptor saturation = 11.3 +/- 2.1 nM) transferin (Tf) receptors per cell. In contrast to apo-transferrin (apoTf) we observed a specific transport of holo-transferrin (holoTf) across BBCECs. This transport was inhibited completely at low temperature. Moreover, the anti-Tf receptor antibody (OX-26) competitively inhibited holoTf uptake by BBCECs. Pulse-chase experiments demonstrated that only 10% of Tf was recycled to the luminal side of the cells, whereas the majority of Tf was transcytosed to the abluminal side; double-labeling experiments clearly demonstrated that iron crosses BBCECs bound to Tf. No intraendothelial degradation of Tf was observed, suggesting that the intraendothelial pathway through BBCECs bypasses the lysosomal compartment. These results clearly show that the iron-Tf complex is transcytosed across brain capillary endothelial cells by a receptor-mediated pathway without any degradation.
一种由牛脑毛细血管内皮细胞（BBCECs）和星形胶质细胞共培养组成的血脑屏障细胞培养模型已被用于研究铁转运至脑的机制。结合实验表明，BBCECs每个细胞表达35,000个高亲和力（50%受体饱和时的浓度 = 11.3 +/- 2.1 nM）转铁蛋白（Tf）受体。与脱铁转铁蛋白（apoTf）不同，我们观察到全铁转铁蛋白（holoTf）可特异性地穿过BBCECs。这种转运在低温下完全被抑制。此外，抗Tf受体抗体（OX - 26）竞争性抑制BBCECs对holoTf的摄取。脉冲追踪实验表明，只有10%的Tf被循环至细胞的管腔侧，而大多数Tf被跨细胞转运至管腔外侧；双重标记实验清楚地表明，铁与Tf结合后穿过BBCECs。未观察到内皮细胞内Tf的降解，这表明通过BBCECs的内皮细胞内途径绕过了溶酶体区室。这些结果清楚地表明，铁 - Tf复合物通过受体介导的途径跨细胞转运穿过脑毛细血管内皮细胞，且没有任何降解。
