Structure-internalization relationship for adsorptive-mediated endocytosis of basic peptides at the blood-brain barrier.
For the purpose of the brain delivery of peptides, the structural specificity of adsorptive-mediated endocytosis at the blood-brain barrier was studied by measuring transport of a newly synthesized basic peptide 001-C8, H-MeTyr-Arg-MeArg-D-Leu-NH(CH2)aNH2, using primary cultured bovine brain capillary endothelial cells. The apparent uptake of [125I]001-C8 increased time-dependently and reached a steady-state at 60 min. The steady-state uptake of [125I]001-C8 was temperature and concentration dependent and was significantly decreased in the presence of dansylcadaverine, protamine or poly-L-lysine. Uptakes of peptides modified by 1,8-octanediamine, 1,5-pentanediamine, 1,2-ethanediamine or ethylamide and peptides with a free carboxyl terminal were significantly higher than, and similar to, that of [3H]PEG900, respectively. The half-saturation constants and the maximal uptake capacities of these peptides were in the ranges of 0.2 to 134 microM and 1.1 to 408 pmol/mg protein, respectively. These values were correlated with the basicity of the molecules. In conclusion, not the number of constituent amino acids of peptides, but rather the C-terminal structure and the basicity of the molecules are the most important determinants for the uptake by the adsorptive-mediated endocytosis system at the blood brain barrier.
Tamai
I
I
Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Kanazawa University, Japan.
Sai
Y
Y
Kobayashi
H
H
Kamata
M
M
Wakamiya
T
T
Tsuji
A
A
D000327:Adsorption; D000818:Animals; D001812:Blood-Brain Barrier; D002196:Capillaries / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D004705:Endocytosis; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D009842:Oligopeptides / Q000493:pharmacokinetics*; D013329:Structure-Activity Relationship
D009842:Oligopeptides