Transport of paclitaxel (taxol) across the blood-brain barrier in vitro and in vivo

Stephan Fellner, Björn Bauer, David S. Miller, Martina Schaffrik, Martina Fankhänel, Thilo Spruß, Günther Bernhardt, Claudia Graeff, Lothar Färber, Harald Gschaidmeier, Armin Buschauer, Gert Fricker

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369 Scopus citations

Abstract

Paclitaxel concentrations in the brain are very low after intravenous injection. Since paclitaxel is excluded from some tumors by p-glycoprotein (p-gp), the same mechanism may prevent entry into the brain. In vitro, paclitaxel transport was examined in capillaries from rat brains by confocal microscopy using BODIPY Fl-paclitaxel. Western blots and immunostaining demonstrated apical expression of p-gp in isolated endothelial cells, vessels, and tissue. Secretion of BODIPY Fl-paclitaxel into capillary lumens was specific and energy-dependent. Steady state luminal fluorescence significantly exceeded cellular fluorescence and was reduced by NaCN, paclitaxel, and SDZ PSC-833 (valspodar), a p-gp blocker. Leukotriene C4 (LTC4), an Mrp2-substrate, had no effect. Luminal accumulation of NBDL-cyclosporin, a p-gp substrate, was inhibited by paclitaxel. In vivo, paclitaxel levels in the brain, liver, kidney, and plasma of nude mice were determined after intravenous injection. Co-administration of valspodar led to increased paclitaxel levels in brains compared to monotherapy. Therapeutic relevance was proven for nude mice with implanted intracerebral human U-118 MG glioblastoma. Whereas paclitaxel did not affect tumor volume, co-administration of paclitaxel (intravenous) and PSC833 (peroral) reduced tumor volume by 90%. Thus, p-gp is an important obstacle preventing paclitaxel entry into the brain, and inhibition of this transporter allows the drug to reach sensitive tumors within the CNS.

Original languageEnglish
Pages (from-to)1309-1318
Number of pages10
JournalJournal of Clinical Investigation
Volume110
Issue number9
DOIs
StatePublished - Nov 2002

ASJC Scopus subject areas

  • General Medicine

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