Blood-brain Barrier Transport Of Drugs Research Articles

Fatty Acid–Binding Protein 5 Mediates the Uptake of Fatty Acids, but not Drugs, Into Human Brain Endothelial Cells

The purpose of this study was to examine the involvement of fatty acid–binding protein 5 (FABP5), a lipid-binding protein expressed at the blood-brain barrier (BBB), in fatty acid and drug uptake into human brain endothelial cells. Following transfection with siRNA against hFABP5, human brain endothelial cell (hCMEC/D3) uptake of lipophilic ligands with varying affinity to FABP5 was assessed with intracellular concentrations quantified by liquid scintillation counting, HPLC, or LCMS/MS. The in situ BBB transport of [3H]-diazepam was also assessed in wild type and FABP5-deficient mice. hFABP5 siRNA reduced FABP5 expression in hCMEC/D3 cells by 39.9 ± 3.8% (mRNA) and 38.8 ± 6.6% (protein; mean ± SEM), leading to a reduction in uptake of [14C]-lauric acid, [3H]-oleic acid, and [14C]-stearic acid by 37.5 ± 8.8%, 41.7 ± 11.6%, and 50.7 ± 13.6%, respectively, over 1 min. No significant changes in [14C]-diazepam, pioglitazone, and troglitazone uptake were detected following FABP5 knockdown in hCMEC/D3 cells. Similarly, no difference in BBB transport of [3H]-diazepam was observed between wild type and FABP5-deficient mice. Therefore, although FABP5 facilitates brain endothelial cell uptake of fatty acids, it has limited effects on brain endothelial cell uptake and BBB transport of drugs with lower affinity for FABP5.

Blood-Brain Barrier Transport of Drugs for the Treatment of Brain Diseases

The central nervous system is a sanctuary protected by barriers that regulate brain homeostasis and control the transport of endogenous compounds into the brain. The blood-brain barrier, formed by endothelial cells of the brain capillaries, restricts access to brain cells allowing entry only to amino acids, glucose and hormones needed for normal brain cell function and metabolism. This very tight regulation of brain cell access is essential for the survival of neurons which do not have a significant capacity to regenerate, but also prevents therapeutic compounds, small and large, from reaching the brain. As a result, various strategies are being developed to enhance access of drugs to the brain parenchyma at therapeutically meaningful concentrations to effectively manage disease.

Interaction of Poly(butylcyanoacrylate) Nanoparticles with the Blood-Brain Barrier in vivo and in vitro

Poly(butylcyanoacrylate) nanoparticles were produced by emulsion polymerisation and used either uncoated or overcoated with polysorbate 80 (Tween® 80). [3H]-dalargin bound to nanoparticles overcoated with polysorbate 80 or in the form of saline solution was injected into mice and the brain concentrations of radioactivity determined. Statistically significant, three-fold higher brain concentrations with the nanoparticle preparations were obtained after 45 minutes, the time of greatest pharmacological response assessed as analgesia in previous experiments. In addition the brain inulin spaces in rats and the uptake of fluoresceine isothiocyanate labelled nanoparticles in immortalised rat cerebral endothelial cells, (RBE4) were measured. The inulin spaces after i.v. injection of polysorbate 80-coated nanoparticles were significantly increased by 1% compared to controls. This is interpreted as indicating that there is no large scale opening of the tight junctions of the brain endothelium by the polysorbate 80-coated nanoparticles. In in vitro experiments endocytic uptake of fluorescent nanoparticles by RBE4 cells was only observed after polysorbate 80-overcoating, not with uncoated particles. These results further support the hypothesis that the mechanism of blood-brain barrier transport of drugs by polysorbate 80-coated nanoparticles is one of endocytosis followed by possible transcytosis. The experiments were conducted in several laboratories as part of an EEC/INTAS collaborative program. For various procedural and regulatory reasons this necessitated the use of both rats and mice as experimental animals. The brain endothelial cell line used for the in vitro studies is the rat RBE4.

Drug transport across the blood-brain barrier. II. Experimental techniques to study drug transport.

This is part II of a review on the transport of drugs across the blood-brain barrier. In this part, the emphasis is on the various experimental techniques that can be used to characterize the blood-brain barrier transport of drugs. Generally speaking, three approaches can be distinguished: in vitro techniques using isolated brain capillaries, cerebrovascular endothelial cells in primary culture or endothelium-derived cell lines; in vivo techniques (both single-passage and multi-passage techniques) and in situ perfusion techniques. Each of these techniques has specific advantages and disadvantages associated with it. Therefore, in many instances, a combination of different approaches is needed to study the fundamental aspects of drug transport across the blood-brain barrier.