Mechanism of pluronic effect on P-glycoprotein efflux system in blood-brain barrier: Contributions of energy depletion and membrane fluidization

Elena V. Batrakova, Shu Li, Sergey V. Vinogradov, Valery Yu Alakhov, Donald W. Miller, Alexander V. Kabanov

Research output: Contribution to journalArticle

243 Citations (Scopus)

Abstract

Pluronic block copolymer, P85, inhibits the P-glycoprotein (Pgp) drug efflux system and increases the permeability of a broad spectrum of drugs in the blood-brain barrier (BBB). This study examines the mechanisms by which P85 inhibits Pgp using bovine brain microvessel endothelial cells (BBMEC) as an in vitro model of the BBB. The hypothesis was that simultaneous alterations in intracellular ATP levels and membrane fluidization in BBMEC monolayers by P85 results in inhibition of the drug efflux system. The methods included the use of 1) standard Pgp substrate rhodamine 123 to assay the Pgp efflux system in BBMEC, 2) luciferin/luciferase assay for ATP intracellular levels, and 3) 1,6-diphenyl-1,3,5-hexatriene for membrane microviscosity. Using 3H-labeled P85 and fluoresceinlabeled P85 for confocal microscopy, this study suggests that P85 accumulates in the cells and intracellular organelles such as the mitochondria where it can interfere with metabolic processes. Following exposure of BBMEC to P85, the ATP levels were depleted, and microviscosity of the cell membranes was decreased. Furthermore, P85 treatment decreased Pgp ATPase activity in membranes expressing human Pgp. A combination of experiments examining the kinetics, concentration dependence, and directionality of P85 effects on Pgp-mediated efflux in BBMEC monolayers suggests that both energy depletion (decreasing ATP pool available for Pgp) and membrane fluidization (inhibiting Pgp ATPase activity) are critical factors contributing to the activity of the block copolymer in the BBB.

Original languageEnglish (US)
Pages (from-to)483-493
Number of pages11
JournalJournal of Pharmacology and Experimental Therapeutics
Volume299
Issue number2
StatePublished - Oct 30 2001

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Poloxamer
P-Glycoprotein
Blood-Brain Barrier
Microvessels
Membranes
Endothelial Cells
Adenosine Triphosphate
Brain
Adenosine Triphosphatases
Pharmaceutical Preparations
Diphenylhexatriene
Rhodamine 123
Luciferases
Confocal Microscopy
Organelles
Permeability
Mitochondria
Cell Membrane

ASJC Scopus subject areas

  • Molecular Medicine
  • Pharmacology

Cite this

Mechanism of pluronic effect on P-glycoprotein efflux system in blood-brain barrier : Contributions of energy depletion and membrane fluidization. / Batrakova, Elena V.; Li, Shu; Vinogradov, Sergey V.; Alakhov, Valery Yu; Miller, Donald W.; Kabanov, Alexander V.

In: Journal of Pharmacology and Experimental Therapeutics, Vol. 299, No. 2, 30.10.2001, p. 483-493.

Research output: Contribution to journalArticle

Batrakova, Elena V. ; Li, Shu ; Vinogradov, Sergey V. ; Alakhov, Valery Yu ; Miller, Donald W. ; Kabanov, Alexander V. / Mechanism of pluronic effect on P-glycoprotein efflux system in blood-brain barrier : Contributions of energy depletion and membrane fluidization. In: Journal of Pharmacology and Experimental Therapeutics. 2001 ; Vol. 299, No. 2. pp. 483-493.
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