title: Activation of PKC isoform beta(I) at the blood-brain barrier rapidly decreases P-glycoprotein activity and enhances drug delivery to the brain.
abstract: P-glycoprotein is an ATP (adenosine triphosphate)-driven drug efflux transporter that is highly expressed at the blood-brain barrier (BBB) and is a major obstacle to the pharmacotherapy of central nervous system diseases, including brain tumors, neuro-AIDS, and epilepsy. Previous studies have shown that P-glycoprotein transport activity in rat brain capillaries is rapidly reduced by the proinflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha) acting through protein kinase C (PKC)-dependent signaling. In this study, we used isolated rat brain capillaries to show that the TNF-alpha-induced reduction of P-glycoprotein activity was prevented by a PKCbeta(I/II) inhibitor, LY333531, and mimicked by a PKCbeta(I/II) activator, 12-deoxyphorbol-13-phenylacetate-20-acetate (dPPA). Western blotting of brain capillary extracts with phospho-specific antibodies showed that dPPA activated PKCbeta(I), but not PKCbeta(II). Moreover, in intact rats, intracarotid infusion of dPPA potently increased brain accumulation of the P-glycoprotein substrate, [(3)H]-verapamil without compromising tight junction integrity. Thus, PKCbeta(I) activation selectively reduced P-glycoprotein activity both in vitro and in vivo. Targeting PKCbeta(I) at the BBB may prove to be an effective strategy for enhancing the delivery of small molecule therapeutics to the brain.
authors.affiliation: Laboratory of Pharmacology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Rigor
authors.forename: Brian T
authors.initials: BT
authors.lastname: Hawkins
authors.forename: David S
authors.initials: DS
authors.lastname: Miller
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism*; D000818:Animals; D001812:Blood-Brain Barrier / Q000378:metabolism*; D001921:Brain / Q000098:blood supply / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000378:metabolism; D002196:Capillaries / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D007211:Indoles / Q000378:metabolism; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008301:Maleimides / Q000378:metabolism; D004364:Pharmaceutical Preparations / Q000008:administration & dosage / Q000378:metabolism; D010703:Phorbol Esters / Q000378:metabolism; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D064546:Protein Kinase C beta; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D013395:Sucrose / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D014700:Verapamil / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002121:Calcium Channel Blockers; D007211:Indoles; D007527:Isoenzymes; D008301:Maleimides; D004364:Pharmaceutical Preparations; D010703:Phorbol Esters; D014409:Tumor Necrosis Factor-alpha; D013395:Sucrose; C029704:12-deoxyphorbolphenylacetate; C099154:ruboxistaurin; D014700:Verapamil; D011493:Protein Kinase C; D064546:Protein Kinase C beta