Transport Of Basic Peptides At The Blood-Brain Barrier

This chapter describes the use of the basic peptide transport system at the blood-brain barrier (BBB) to deliver peptides as neuro-pharmaceuticals. Many influx and efflux transport systems are expressed at the BBB, including transporter-mediated translocation systems and receptor-mediated transcytosis systems. The mechanism underlying basic peptide transport at the BBB has been suggested to be adsorptive-mediated endocytosis which is triggered after the binding of peptides to cell-surface anionic sites. The adsorptive-mediated endocytosis at the BBB has been functionally characterized as time-, temperature-, and energy-dependent. Internalization is inhibited by endocytosis inhibitors, such as phenylarsine oxide and dansylcadaverine. The chemical modification of neuropeptides to achieve high basicity can significantly enhance BBB transport via the basic peptide transport system. An increase in the basicity of a peptide may result in increased uptake by peripheral tissues in parallel with increased BBB permeability because adsorptive-mediated endocytosis operates in the peripheral tissues.