title: Does propofol alter membrane fluidity at clinically relevant concentrations? An ESR spin label study.
abstract: General anesthetics have been shown to perturb the membrane properties of excitable tissues. Due to their lipid solubility, anesthetics dissolve in every membrane, penetrate into organelles and interact with numerous cellular structures in multiple ways. Several studies indicate that anesthetics alter membrane fluidity and decrease the phase-transition temperature. However, the required concentrations to induce such effects on the properties of membrane lipids are by far higher than clinically relevant concentrations. In the present study, the fluidizing effect of the anesthetic agent propofol (2,6-diisopropyl phenol: PPF), a general anesthetic extensively used in clinical practice, has been investigated on liposome dimyristoyl-L-alpha phosphatidylcholine (DMPC) and cell (erythrocyte, Neuro-2a) membranes using electron spin resonance spectroscopy (ESR) of nitroxide labeled fatty acid probes (5-, 16-doxyl stearic acid). A clear effect of PPF at concentrations higher than the clinically relevant ones was quantified both in liposome and cell membranes, while no evident fluidity effect was measured at the clinical PPF doses. However, absorption spectroscopy of merocyanine 540 (MC540) clearly indicates a PPF fluidizing capacity in liposome membrane even at these clinical concentrations. PPF may locally influence the structure and dynamics of membrane domains, through the formation of small-scale lipid domains, which would explain the lack of ESR information at low PPF concentrations.
authors.affiliation: Laboratory of Experimental Medical Imaging, Department of Physics, Institute of Physics B5, University of Liège, Sart-Tilman, B-4000 Liège, Belgium. M.Bahri@ulg.ac.be
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Bahri
authors.forename: Alain
authors.initials: A
authors.lastname: Seret
authors.forename: Pol
authors.initials: P
authors.lastname: Hans
authors.forename: Jacques
authors.initials: J
authors.lastname: Piette
authors.forename: Ginette
authors.initials: G
authors.lastname: Deby-Dupont
authors.forename: Maryse
authors.initials: M
authors.lastname: Hoebeke
mesh_terms: D004305:Dose-Response Relationship, Drug; D004578:Electron Spin Resonance Spectroscopy; D004910:Erythrocyte Membrane / Q000187:drug effects* / Q000648:ultrastructure; D004912:Erythrocytes / Q000187:drug effects / Q000648:ultrastructure; D006801:Humans; D008081:Liposomes; D008560:Membrane Fluidity / Q000187:drug effects*; D021962:Membrane Microdomains / Q000187:drug effects*; D015742:Propofol / Q000494:pharmacology*; D011744:Pyrimidinones; D013057:Spectrum Analysis; D013113:Spin Labels
chemical_list: D008081:Liposomes; D011744:Pyrimidinones; D013113:Spin Labels; C003954:merocyanine dye; D015742:Propofol