Transport of amentoflavone across the blood-brain barrier in vitro.
The biflavone amentoflavone is an ingredient of Hypericum perforatum L. (Clusiaceae), a plant which is widely used for the treatment of mild to moderate depression. Amentoflavone inhibits the binding of flumazenil to the benzodiazepine binding site of the GABA A -receptor (IC(50) = 14.9 nM). Since it has to pass the blood-brain barrier (BBB) before reaching this receptor, the penetration of [(3)H]-amentoflavone through BBB was studied in an in vitro model consisting of primary cell cultures of porcine brain capillary endothelial cells (BCEC). Concentration-dependent uptake (37-2000 nM) was neither saturable nor temperature-sensitive indicating passive diffusion as the major uptake mechanism. This finding was confirmed by transport experiments through BCEC monolayers (> 2 % of applied dose was transported after 30 min). Co-administration of Hypericum extract increased amentoflavone transport significantly (amentoflavone alone: permeability coefficient P(app) = 4.59.10(-6) cm/s; co-administrated sucrose: P(app) = 3.22.10(-6)cm/s; amentoflavone together with hypericum: P(app) = 6.74.10(-6)cm/s, co-administrated sucrose P(app) = 5.49.10(-6)cm/s) indicating that Hypericum constituents enhance amentoflavone transport possibly by modulating paracellular permeability. Experiments with the P-glycoprotein (P-gp) overexpressing cell line P388-MDR showed that amentoflavone uptake was significantly enhanced by addition of the P-gp inhibitor verapamil, suggesting a P-gp mediated back-transport out of the cells. In conclusion, our findings show, that amentoflavone is able to pass the blood-brain barrier in vitro by passive diffusion.
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000818:Animals; D044946:Biflavonoids; D001692:Biological Transport / Q000187:drug effects; D001812:Blood-Brain Barrier / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects; D005419:Flavonoids / Q000494:pharmacology*; D020902:Hypericum; D010936:Plant Extracts / Q000494:pharmacology; D013552:Swine; D014316:Tritium / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D044946:Biflavonoids; D005419:Flavonoids; D010936:Plant Extracts; D014316:Tritium; C011164:amentoflavone; D014700:Verapamil