Inhibition of P-glycoprotein pumps by PEO-PPO amphiphiles: branched versus linear derivatives.
Inhibition of the activity of efflux transporters may relevantly improve the chemotherapy of cancer and infectious diseases.


OBJECTIVE
To explore the ability of poloxamines (Tetronic(®), X-shaped structure with a central ethylendiamine group and four branches of poly[ethylene oxide]-poly[propylene oxide] [PEO-PPO]) to inhibit the activity of P-glycoprotein (P-gp) on Caco-2 cell monolayers and to elucidate the incidence of the molecular architecture of PEO-PPO block copolymers on the intracellular accumulation of a relevant substrate, doxorubicin, by comparison with poloxamers (Pluronic(®), linear triblock copolymers), well-known inhibitors of this efflux transporter.


METHODS
Both pristine and N-methylated poloxamines displaying a wide range of molecular weights and EO/PO ratios were tested regarding cytocompatibility and accumulation of doxorubicin in Caco-2 monolayers. Verapamil was used as a control.


RESULTS
The most active anti-P-gp poloxamines (which enhanced two- to three-fold doxorubicin accumulation compared with verapamil) resulted to be pristine medium-to-high hydrophobic T304, T904, T1301, T901 and T150R1. A notable dependence of the anti-P-gp activity on the copolymer concentration was found. A joint diagram of the inhibitory activity of poloxamers and poloxamines as a function of the effective length of the PPO block is proposed.


CONCLUSIONS
The anti-P-gp activity is maxima for block copolymers possessing a low-to-medium hydrophilic-lipophilic balance and an 'effective number' of PO units ranging from 30 to 50.
Departamento de Farmacia y Tecnología Farmacéutica, Universidad de Santiago de Compostela, 15782-Santiago de Compostela, Spain.
Carmen
C
Alvarez-Lorenzo
Ana
A
Rey-Rico
Jose
J
Brea
Maria Isabel
MI
Loza
Angel
A
Concheiro
Alejandro
A
Sosnik
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000187:drug effects*; D018938:Caco-2 Cells; D002470:Cell Survival / Q000187:drug effects; D004317:Doxorubicin / Q000378:metabolism*; D004852:Epoxy Compounds / Q000737:chemistry*; D006801:Humans; D018613:Microscopy, Confocal; D020442:Poloxamer / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry* / Q000494:pharmacology*; D013329:Structure-Activity Relationship
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D004852:Epoxy Compounds; D011108:Polymers; D020442:Poloxamer; D011092:Polyethylene Glycols; D004317:Doxorubicin; C009068:propylene oxide