Enhancement of transport of D-melphalan analogue by conjugation with L-glutamate across bovine brain microvessel endothelial cell monolayers.
In this paper, the L-glutamate (L-Glu) transport system was targeted to improve the delivery of a model compound, p-di(hydroxyethyl)-amino-D-phenylalanine (D-MOD), through the blood-brain barrier (BBB) in vitro cell culture model. D-MOD is an analogue of an antitumor agent D-melphalan. To target the L-Glu transport system, D-MOD was conjugated to L-Glu to give D-MOD-L-Glu conjugate. D-MOD and D-MOD-L-Glu transport properties were evaluated using the bovine brain microvessel endothelial cell (BBMEC) monolayers. The results suggest that D-MOD-L-Glu conjugate permeates through the BBMEC monolayers more readily than the parent D-MOD. The improvement of transport may be due to the recognition of D-MOD-L-Glu by the L-Glu transport system. The transport mechanism was evaluated using several different experiments including: (a) concentration-dependent studies; (b) temperature-dependent studies; (c) substrate inhibition studies; and (d) metabolic inhibitor studies. The D-MOD-L-Glu transport was inhibited by the change of temperature from 37 degrees C to 4 degrees C. At higher concentrations, the transport of D-MOD-L-Glu reached plateau due to saturation. Furthermore, some amino acids (i.e., L-Glu, L-Asp, D-Asp, and L-Gln) inhibited the transport of D-MOD-L-Glu; presumably the conjugate was competing with these amino acids for the same transport system. Metabolic inhibitors (i.e., 2,4-dinitrophenol and sodium azide) suppressed the transport of the conjugate. However, the conjugate was not transported by monocarboxylic acid, dipeptide and neutral amino acid transporters. In conclusion, the L-Glu transport system can be utilized to facilitate a non-permeable drug across the BBB by conjugating the drug with L-Glu amino acid.
Department of Pharmaceutical Chemistry, University of Kansas, Lawrence, KS 66047, USA.
T
T
Sakaeda
T J
TJ
Siahaan
K L
KL
Audus
V J
VJ
Stella
D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000493:pharmacokinetics*; D001812:Blood-Brain Barrier / Q000187:drug effects*; D002199:Capillary Permeability / Q000187:drug effects*; D002417:Cattle; D004730:Endothelium, Vascular / Q000378:metabolism; D018698:Glutamic Acid / Q000493:pharmacokinetics*; D008558:Melphalan / Q000031:analogs & derivatives / Q000493:pharmacokinetics*
D018906:Antineoplastic Agents, Alkylating; D018698:Glutamic Acid; D008558:Melphalan