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Liposomal sphingomyelin influences the cellular lipid profile of human lymphoblastic leukemia cells without effect on

Nadine C L Zembruski1, Chi D L Nguyen, Dirk Theile

  • 1Department of Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, Im Neuenheimer Feld 410, 69120 Heidelberg, Germany.

Molecular Pharmaceutics
|February 6, 2013
PubMed

Insights

Sphingomyelin (SM) liposomes, investigated for cancer therapy, did not alter P-glycoprotein (P-gp) activity or multidrug resistance in CEM cells. This study found no impact on drug sensitivity or P-gp function when using SM liposomes.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Pharmacology

Background:

  • Sphingomyelin (SM)/cholesterol liposomes are explored as cancer drug carriers.
  • The impact of SM on P-glycoprotein (P-gp)-mediated multidrug resistance remains unknown.
  • P-gp localization in lipid rafts suggests membrane lipid composition influences its activity.

Purpose of the Study:

  • To investigate the effect of liposomal SM on P-gp activity, distribution, and SM content in cell membrane microdomains.
  • To determine the influence of liposomal SM on the sensitivity of human lymphoblastic CEM cells to cytotoxic drugs.
  • To assess changes in P-gp localization within raft and non-raft membrane domains.

Main Methods:

  • Utilized CEM and multidrug-resistant CEM/ADR5000 cells.
  • Prepared and characterized SM-only liposomes using an ethanol injection protocol.
  • Assessed SM incorporation via fluorescence microscopy and flow cytometry.
  • Measured P-gp activity using rhodamine efflux and calcein assays.
  • Analyzed drug sensitivity with 7-AAD staining.
  • Determined P-gp distribution using Western blot after density gradient centrifugation.
  • Quantified SM species (16:0, 18:0, 24:1) by LC-MS/MS.

Main Results:

  • P-gp was primarily found in non-raft fractions, with no change after liposome treatment.
  • Liposomes increased SM 16:0 and SM 24:1 content in non-raft domains of resistant cells, but not in raft domains.
  • SM-only liposomes did not affect P-gp activity or cellular chemosensitivity.
  • No significant influence of SM liposomes on P-gp mediated multidrug resistance was observed.

Conclusions:

  • Therapeutic doses of SM-only liposomes do not modulate P-gp activity or multidrug resistance in CEM cells.
  • Liposomal SM incorporation into non-raft domains does not alter P-gp function or drug sensitivity.
  • These findings suggest SM liposomes may not exacerbate P-gp mediated drug resistance in this cellular model.

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