title: Localization of organic cation/carnitine transporter (OCTN2) in cells forming the blood-brain barrier.
abstract: Carnitine beta-hydroxy-gamma-(trimethylammonio)butyrate - a compound necessary in the peripheral tissues for a transfer of fatty acids for their oxidation within the cell, accumulates in the brain despite low beta-oxidation in this organ. In order to enter the brain, carnitine has to cross the blood-brain barrier formed by capillary endothelial cells which are in close interaction with astrocytes. Previous studies, demonstrating expression of mRNA coding two carnitine transporters - organic cation/carnitine transporter 2 (OCTN2) and B(0,+) in endothelial cells, did not give any information on carnitine transporters polarity in endothelium. Therefore more detailed experiments were performed on expression and localization of a high affinity carnitine transporter OCTN2 in an in vitro model of the blood-brain barrier by real-time PCR, western blot analysis, and immunocytochemistry. The amount of mRNA was comparable in endothelial cells and kidney, when referred to house-keeping genes, it was, however, significantly lower in astrocytes. Polarity of OCTN2 localization was further studied in an in vitro model of the blood-brain barrier with use of anti-OCTN2 antibodies. Z-axis analysis of the confocal microscope pictures of endothelial cells, with anti-P-glycoprotein antibodies as the marker of apical membrane, showed OCTN2 localization at the basolateral membrane and in the cytoplasmic region in the vicinity of nuclei. Localization of OCTN2 suggest that carnitine can be also transported from the brain, playing an important role in removal of certain acyl esters.
authors.affiliation: Nencki Institute of Experimental Biology, Warszawa, Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Miecz
authors.forename: Elzbieta
authors.initials: E
authors.lastname: Januszewicz
authors.forename: Magdalena
authors.initials: M
authors.lastname: Czeredys
authors.forename: Barry T
authors.initials: BT
authors.lastname: Hinton
authors.forename: Vincent
authors.initials: V
authors.lastname: Berezowski
authors.forename: Roméo
authors.initials: R
authors.lastname: Cecchelli
authors.forename: Katarzyna A
authors.initials: KA
authors.lastname: Nałecz
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism* / Q000648:ultrastructure; D001812:Blood-Brain Barrier / Q000166:cytology* / Q000502:physiology*; D001921:Brain; D002478:Cells, Cultured; D015870:Gene Expression / Q000502:physiology; D027701:Organic Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000074058:Solute Carrier Family 22 Member 5; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D027701:Organic Cation Transport Proteins; D012333:RNA, Messenger; C115441:Slc22a5 protein, rat; D000074058:Solute Carrier Family 22 Member 5