טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentNurit Vizel
SubjectModulation of Drug Transport via Membranes by Modulators in
Liposomes and Cells
DepartmentDepartment of Biology
Supervisor Professor Eytan Gera


Abstract

In this study we searched for an alternative modulation mechanism which would catalyze cytotoxic drug accumulation within cells, in a manner similar to fluidizers - which accelerate influx, into the cells. Therefore, we examined the potentially useful non-classic modulator activity of the amphipathic detergent Pluronic acid

MDR is the result of competition between passive uptake and efflux by the MDR pumps. In this study we used doxorubicin and rhodamines as indicators for the following stages of passive drug transport, rate of doxorubicin and rhodamines flip-flop across membranes was measured using fluorescence resonance energy transfer (FRET) with NBD-labeled liposomes, and rate of doxorubicin influx into liposomes was measured using trypan-blue containing liposomes.

Similar flip-flop and influx acceleration rates were observed when we compared the effect of Pluronic acid to that of two known fluidizers - benzyl alcohol and Propofol.

By measuring uptake and influx rates in resistant cells, we have demonstrated that Pluronic acid most likely acts through inhibition of the Pgp drug efflux system. This, in contrast to our early expectations that the primary effect would be observed on the plasma membrane.

According to previous reports, co-administration of Pluronic acid and doxorubicin induces drastic ATP depletion in resistant cells which affects various mechanisms of resistance. The ATP dependent luciferin-luciferase reaction was used to determine ATP levels in living cells, when the latter were exposed to Pluronic acid. In contrast to previously published studies, our assays demonstrated no ATP depletion in resistant cells.