title: Endocytosis and transcytosis of an immunoliposome-based brain drug delivery system.
abstract: Immunoliposomes conjugated with the OX26 monoclonal antibody to the rat transferrin receptor can be used for brain delivery of small molecules. In the present study the uptake of OX26-immunoliposomes by target cells as well as their transcytosis across the blood-brain barrier was investigated. Microscopy of RG2 rat glioma cells incubated with fluorescence labeled OX26-immunoliposomes revealed intracellular co-localization of liposomal cargo, the liposomal membrane bilayer and the OX26 monoclonal antibody. The distinct particulate staining pattern was indicative for accumulation of OX26-immunoliposomes within endosomal or lysosomal compartments. Prolonged incubations demonstrated endosomal release of the liposomal cargo propidium iodide to the cytoplasm. A maximum of 50% of propidium iodide was released from the endosomal compartment after 24 hours of incubation. Transcytosis was studied using an in vitro model of the blood-brain barrier consisting of immortalized RBE4 rat brain endothelial cells. OX26-immunoliposomes did permeate across the RBE4 cell monolayer and showed a permeability coefficient of P(app) = 1.6 x 10(-5) ml/s. Transport was inhibited at low temperature, by competition with free OX26 or by exchanging the OX26 monoclonal antibody for an unspecific isotype antibody. Transcytosis of OX26-immunolipsomes was confirmed in vivo by the brain perfusion and capillary depletion technique. OX26-immunoliposomes were detected within the post-vascular compartment of brain parenchyma (PS product = 2.4 microl/g/min.) and were not associated with the brain microvasculature.
authors.affiliation: Dept. of Research and Clinical Pharmacology, University Hospital, CH-4031 Basel, Switzerland.
authors.forename: A
authors.initials: A
authors.lastname: Cerletti
authors.forename: J
authors.initials: J
authors.lastname: Drewe
authors.forename: G
authors.initials: G
authors.lastname: Fricker
authors.forename: A N
authors.initials: AN
authors.lastname: Eberle
authors.forename: J
authors.initials: J
authors.lastname: Huwyler
mesh_terms: D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000493:pharmacokinetics*; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics*; D001812:Blood-Brain Barrier / Q000502:physiology; D001921:Brain / Q000378:metabolism*; D002478:Cells, Cultured; D003630:Daunorubicin / Q000493:pharmacokinetics*; D016503:Drug Delivery Systems / Q000379:methods*; D004705:Endocytosis / Q000502:physiology; D011992:Endosomes / Q000378:metabolism*; D008081:Liposomes; D051381:Rats; D011990:Receptors, Transferrin / Q000378:metabolism*; D014407:Tumor Cells, Cultured
chemical_list: D000903:Antibiotics, Antineoplastic; D000911:Antibodies, Monoclonal; D008081:Liposomes; D011990:Receptors, Transferrin; D003630:Daunorubicin