On the mechanism of oleate transport across human brain microvessel endothelial cells

The blood-brain barrier formed by the brain capillary endothelial cells provides a protective barrier between the systemic blood and the extracellular environment of the CNS. As most fatty acids in the brain enter from the blood, we examined the mechanism of oleate (C18:1) transport across primary human brain microvessel endothelial cells (HBMEC). The permeability of [1-14C]oleate was determined using confluent cells grown on Transwell inserts in both the absence or presence of bovine serum albumin in the basolateral media, and following inhibition of various fatty acid transporters. The passage of [1-14C]oleate across confluent HBMEC monolayers was significantly enhanced when fatty acid free albumin was present in the basolateral media. The presence of the non-specific fatty acid uptake inhibitor phloretin significantly decreased [1-14C]oleate uptake by HBMEC and the subsequent release of [1-14C]oleate into the basolateral medium. Knockdown of fatty acid transport protein-1 or fatty acid translocase/CD36 significantly decreased [1-14C]oleate transport across the HBMEC monolayer from either apical as well as basolateral sides. The findings indicate that a fatty acid acceptor is a requirement for oleate transport across HBMEC monolayers. In addition, transport of oleate across HBMEC is, in part, a transcellular process mediated by fatty acid transport proteins.