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Liposomal sphingomyelin influences the cellular lipid profile of human lymphoblastic leukaemia cells without effect on P-glycoprotein activity.


Mol Pharm. 2013 Feb 4;


Authors: Zembruski NC, Nguyen CD, Theile D, Ali RM, Herzog M, Hofhaus G, Heintz U, Burhenne J, Haefeli WE, Weiss J


Abstract

Sphingomyelin (SM)/cholesterol liposomes are currently investigated as drug carriers in cancer therapy. However, no data is available on the influence of SM itself on P-glycoprotein (P-gp) mediated multidrug resistance. P-gp is at least partly located in sphingolipid-enriched lipid raft domains of the plasma membrane and its activity depends on the lipid profile of the membrane, which could be altered by therapeutical SM liposomes. Therefore, the aim of this study was to analyse the effect of liposomal SM on P-gp activity, P-gp distribution in microdomains, SM content of the membrane domains, and sensitivity of human lymphoblastic CEM cells towards cytotoxic drugs in-vitro. Assays were conducted in CEM and multidrug resistant CEM/ADR5000 cells. SM-only liposomes were prepared by a newly developed ethanol injection protocol and thoroughly characterised. Inclusion of SM into the membrane was analysed by fluorescence microscopy and flow cytometry. Influence of SM liposomes on P-gp activity was assessed by rhodamine efflux and calcein assay and sensitivity towards cytotoxic drugs was analysed by flow cytometric 7-AAD staining. Influence on P-gp distribution was analysed by western blot after density gradient centrifugation. SM 16:0, 18:0, and 24:1 were quantified by liquid chromatography coupled to tandem mass-spectrometry. P-gp was mainly located in non-raft fractions, which did not change upon liposome treatment. Liposomes increased SM 16:0 and SM 24:1 content in non-raft domains, but not in raft domains of multidrug resistant cells. SM-only liposomes did not influence P-gp activity and chemosensitivity. In conclusion, SM-only liposomes in therapeutic amounts did not influence P-gp mediated multidrug resistance in CEM cells.

PMID: 23379426 [PubMed - as supplied by publisher]