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- W2109905900 abstract "The non-ionic surfactant D-alpha-tocopheryl poly(ethylene glycol 1000) succinate (TPGS 1000) has been previously shown to increase oral bioavailability of P-glycoprotein (P-gp) substrates by modulating activity of the efflux pump. In the present thesis structure activity relationship of the interaction and possible mechanism of inhibition of the efflux transporter were investigated to optimize the TPGS structure. P-gp inhibitory activity of TPGS could be increased by modifying the length of the PEG chain with optimal inhibition being achieved at a PEG molecular weight of ~1500 Da. The inhibitory effect of TPGS on P-gp could be also increased by modifications to the hydrophobic part of the molecule, such as the exchange of the alpha-tocopherol moiety for cholesterol. The inhibitory activity of the TPGS analogues does not correlate with their physicochemical properties such as molecular weight, molecule volume, or lipophilicity. In agreement with these findings, an unspecific alteration of the P-gp membrane environment could be ruled out in electron spin resonance experiments. TPGS was shown not to be a P-gp substrate itself nor does it interact with one of the transport active drug binding sites of P-gp to competitively block drug efflux. Rather, the inhibitory effect of the TPGS analogues correlates with their inhibition of substrate induced ATPase activity, indicating that the depletion of the energy source of the efflux pump is an integral part in the inhibitory mechanism of TPGS. Fur das nicht ionische Tensid D-Alpha-tocopheryl poly(ethylene glycol 1000) succinat (TPGS 1000) wurde kurzlich gezeigt, dass es die orale Bioverfugbarkeit von Substraten des Effluxtransporters P-Glykoprotein (P-gp) durch Hemmung der Effluxpumpe steigert. In der vorliegenden Arbeit wurden die Strukturwirkungsbeziehungen der Wechselwirkung zwischen TPGS und P-gp und der Mechanismus, der der Hemmung zu Grunde liegt, untersucht, um die TPGS Struktur zu optimieren. Die P-gp Hemmung durch TPGS konnte durch Variation der PEG Kettenlange erhoht werden, wobei der optimale Hemmeffekt bei einem PEG Molekulargewicht von ungefahr 1500 Da beobachtet wurde. Des weiteren steigerten auch Modifikationen des hydrophoben Molekulteils, wie der Austausch des Alpha-Tocopherol-Restes durch Cholesterol, das Hemmpotenzial von TPGS. Die inhibitorische Wirkung der TPGS Derivate korreliert nicht mit ihren physikochemischen Eigenschaften wie Molekulargewicht, Molekulvolumen oder Lipophilie. In Ubereinstimmung mit diesen Ergebnissen konnte eine unspezifische Anderung der Membranumgebung von P-gp in Elektronenspinresonanz-Untersuchungen ausgeschlossen werden. Fur TPGS konnte gezeigt werden, dass es selbst kein Substrat von P-gp ist und nicht mit einer der transportaktiven Bindungsstellen von P-gp, im Sinne einer kompetitiven Hemmung interagiert. Vielmehr korreliert der inhibitorische Effekt mit der Hemmung der Substrat-induzierten ATPase Aktivitat, was darauf hinweist, dass diese Depletion der Energiequelle der Effluxpumpe ein essentieller Bestandteil des Hemmmechanismus von TPGS ist." @default.
- W2109905900 created "2016-06-24" @default.
- W2109905900 creator A5018845246 @default.
- W2109905900 date "2007-05-10" @default.
- W2109905900 modified "2023-09-27" @default.
- W2109905900 title "Modulation of the apical efflux transporter P-glycoprotein by Vitamin E TPGS: Structure-activity relationships and mechanism of inhibition" @default.
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