title: Relationship between the structure of amphiphilic copolymers and their ability to disturb lipid bilayers.
abstract: Nonionic amphiphiles and particularly block copolymers of ethylene oxide and propylene oxide (Pluronics) cause pronounced chemosensitization of tumor cells that exhibit multiple resistance to antineoplastic drugs. This effect is due to inhibition of P-glycoprotein (P-gp) responsible for drug efflux. It was suggested that the inhibition of P-gp might be due to changes in its lipid surrounding. Indeed, high dependence of P-gp activity on the membrane microviscosity was demonstrated [Regev et al. (1999) Eur. J. Biochem. 259, 18-24], suggesting that the ability of Pluronics to affect the P-gp activity is mediated by their effect on the membrane structure. We have found recently that adsorption of Pluronics on lipid bilayers induced considerable disturbance of the lipid packing [Krylova et al. (2003) Chemistry 9, 3930-3936]. In the present paper, we studied 19 amphiphilic copolymers, including newly synthesized hyperbranched polyglycerols, Pluronic and Brij surfactants, for their ability to accelerate flip-flop and permeation of antitumor drug doxorubicin (DOX) in liposomes. It was found that not only bulk hydrophobicity but also the chemical microstructure of the copolymer determines its membrane disturbing ability. Copolymers containing polypropylene oxide caused higher acceleration of flip-flop and DOX permeation than polysurfactants containing aliphatic chains. The effects of copolymers containing hyperbranched polyglycerol "corona" were more pronounced, as compared to the copolymers with linear poly(ethylene oxide) chains, indicating that a bulky hydrophilic block induces additional disturbances in the lipid bilayer. A good correlation between the copolymer flippase activity and a linear combination of copolymer bulk hydrophobicity and the van der Waals volume of its hydrophobic block was found. The relationship between the structure of a copolymer and its ability to disturb lipid membranes presented in this paper may be useful for the design of novel amphiphilic copolymers capable of affecting the activity of membrane transporters in living cells.
authors.affiliation: Chemistry Department, Lomonosov Moscow State University, Vorobiovy Gory, 119899 Moscow, Russia.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Demina
authors.forename: Irina
authors.initials: I
authors.lastname: Grozdova
authors.forename: Oxana
authors.initials: O
authors.lastname: Krylova
authors.forename: Artem
authors.initials: A
authors.lastname: Zhirnov
authors.forename: Vladislav
authors.initials: V
authors.lastname: Istratov
authors.forename: Holger
authors.initials: H
authors.lastname: Frey
authors.forename: Holger
authors.initials: H
authors.lastname: Kautz
authors.forename: Nikolay
authors.initials: N
authors.lastname: Melik-Nubarov
mesh_terms: D000327:Adsorption; D000818:Animals; D002417:Cattle; D004317:Doxorubicin / Q000737:chemistry; D004852:Epoxy Compounds / Q000737:chemistry*; D005027:Ethylene Oxide / Q000737:chemistry*; D005609:Free Radicals / Q000737:chemistry; D005990:Glycerol / Q000138:chemical synthesis / Q000737:chemistry; D006586:Hexanes / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes; D008567:Membranes, Artificial; D010539:Permeability; D010713:Phosphatidylcholines / Q000737:chemistry; D020442:Poloxamer / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry; D013329:Structure-Activity Relationship; D014867:Water / Q000737:chemistry
chemical_list: D004852:Epoxy Compounds; D005609:Free Radicals; D006586:Hexanes; D008051:Lipid Bilayers; D008081:Liposomes; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D011108:Polymers; D014867:Water; D020442:Poloxamer; C043941:polyglycerol; C026385:n-hexane; D011092:Polyethylene Glycols; D004317:Doxorubicin; D005027:Ethylene Oxide; D005990:Glycerol; C009068:propylene oxide