Figure 12

Concerted transport at blood-brain and blood-CSF barriers: Cerebral capillaries and choroid plexuses transport different materials [16, 17, 27, 34]. Although there is transport overlap, the BBB largely supplies brain with glucose, amino acids, free fatty acids (FFA) and peptides, whereas BCSFB furnishes the CSF-brain nexus with vitamins, growth factors and proteins such as transthyretin. CNS fluid balance results from regulated water transport across AQP4 at BBB and AQP1 in BCSFB. The reabsorptive transporters LRP-1 and P-glycoprotein (Pgp) are expressed differentially in BBB [225, 229] and BCSFB [291]. Both interfaces have to be analyzed to characterize phenomena such as Aβ deposition in interstitium. To understand brain fluid composition and barrier interaction pathophysiologically, it is advantageous to analyze BBB and BCSFB concurrently.