Receptor-mediated transcytosis of lactoferrin through the blood-brain barrier
1999
Fillebeen, Carine | Descamps, Laurence | Dehouck, Marie-Pierre | Fenart, Laurence | Benaissa, Monique | Spik, Geneviève | Cecchelli, Roméo | Pierce, Annick
Lactoferrin (Lf) is an iron-binding protein involved in host defense against infection and severe inflammation; it accumulates in the brain during neurodegenerative disorders. Before determining Lf function in brain tissue, we investigated its origin and demonstrate here that it crosses the blood-brain barrier. An in vitro model of the blood-brain barrier was used to examine the mechanism of Lf transport to the brain. We report that differentiated bovine brain capillary endothelial cells exhibited specific high (K<SUB>d</SUB> = 37.5 nM; n = 90,000/cell) and low (K<SUB>d</SUB> = 2 μM; n = 900,000 sites/cell) affinity binding sites. Only the latter were present on nondifferentiated cells. The surface-bound Lf was internalized only by the differentiated cell population leading to the conclusion that Lf receptors were acquired during cell differentiation. A specific unidirectional transport then occurred via a receptor-mediated process with no apparent intraendothelial degradation. We further report that iron may cross the bovine brain capillary endothelial cells as a complex with Lf. Finally, we show that the low density lipoprotein receptor-related protein might be involved in this process because its specific antagonist, the receptor-associated protein, inhibits 70% of Lf transport.
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