title: Insights in the chemical components of liposomes responsible for P-glycoprotein inhibition.
abstract: In this work we investigated how the surface charge and the presence of polyethylene glycol (PEG) on liposome carriers affect the delivery of the encapsulated doxorubicin in P-glycoprotein (Pgp)-overexpressing cells. We found that neutral net charge was critical to favour the liposome uptake and decrease the Vmax of doxorubicin efflux. PEG-coating was necessary to increase the Km of doxorubicin for Pgp. In particular the PEGylated phospholipid present in neutral liposomes, i.e. PEGylated distearoyl-phosphatidylethanolamine (DSPE-PEG), was a Pgp allosteric inhibitor, increased doxorubicin Km and inhibited Pgp ATPase activity. Site-directed mutagenesis experiments suggested that the domain centred around glycine 185 of Pgp was necessary for these inhibitory properties of DSPE-PEG and PEGylated neutral liposomes. We conclude that both surface charge and PEGylation must be considered to optimize the doxorubicin delivery within chemoresistant cells. DSPE-PEG-enriched particles may represent promising tools for therapeutic and diagnostic applications in tissues with high levels of Pgp.
  
  
  BACKGROUND
  These authors investigated how surface charge and PEGylation of liposome carriers affect the delivery of encapsulated doxorubicin to Pgp-overexpressing cells, concluding that both factors need to be considered in order to optimize doxorubicin delivery to chemoresistant cells.
authors.affiliation: Department of Oncology, Università di Torino, via Santena 5/bis, 10126 Torino, Italy.
authors.forename: Joanna
authors.initials: J
authors.lastname: Kopecka
authors.affiliation: Department of Oncology, Università di Torino, via Santena 5/bis, 10126 Torino, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Salzano
authors.affiliation: Department of Oncology, Università di Torino, via Santena 5/bis, 10126 Torino, Italy.
authors.forename: Ivana
authors.initials: I
authors.lastname: Campia
authors.affiliation: Department of Pharmacy, Università degli Studi di Napoli Federico II, Via D. Montesano 49, 80131 Napoli, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Lusa
authors.affiliation: Department of Oncology, Università di Torino, via Santena 5/bis, 10126 Torino, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Ghigo
authors.affiliation: Department of Pharmacy, Università degli Studi di Napoli Federico II, Via D. Montesano 49, 80131 Napoli, Italy. Electronic address: gderosa@unina.it.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: De Rosa
authors.affiliation: Department of Oncology, Università di Torino, via Santena 5/bis, 10126 Torino, Italy. Electronic address: chiara.riganti@unito.it.
authors.forename: Chiara
authors.initials: C
authors.lastname: Riganti
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000037:antagonists & inhibitors; D000251:Adenosine Triphosphatases / Q000378:metabolism; D004317:Doxorubicin / Q000008:administration & dosage* / Q000737:chemistry; D016503:Drug Delivery Systems; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D006801:Humans; D008081:Liposomes / Q000008:administration & dosage* / Q000737:chemistry; D009369:Neoplasms / Q000188:drug therapy*; D011092:Polyethylene Glycols / Q000008:administration & dosage / Q000737:chemistry; D013499:Surface Properties
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D008081:Liposomes; D011092:Polyethylene Glycols; D004317:Doxorubicin; D000251:Adenosine Triphosphatases
keywords: 1,2-dioleoyloxy-3-trimethylammoniumpropanchloride; 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-glycerol; 1,2-dipalmitoyl-sn-glycero-3-phosphocholine; BCRP; Chemoresistance; DOTAP; DPPC; DPPG; DSPE-PEG; Doxorubicin; Liposome; MRPs; P-glycoprotein; PEG; PEGylated distearoyl-phosphatidylethanolamine; Pgp; Polyethylene glycol; breast cancer resistance protein; multidrug-resistance related proteins; polyethylene glycol