title: ApoA-I induces a preferential efflux of monounsaturated phosphatidylcholine and medium chain sphingomyelin species from a cellular pool distinct from HDL(3) mediated phospholipid efflux.
abstract: Electrospray ionization tandem mass spectrometry (ESI-MS/MS) was used for a detailed analysis of cellular phospholipid and cholesterol efflux in free cholesterol (FC) loaded human primary fibroblasts and human monocyte-derived macrophages (HMDM) loaded with enzymatically modified LDL (E-LDL). Although both cell models differed significantly in their cellular lipid composition, a higher apoA-I specific efflux was found for monounsaturated phosphatidylcholine (PC) species together with a decreased contribution of polyunsaturated PC species in both cell types. Moreover, medium chain sphingomyelin (SPM) species SPM 14:0 and SPM 16:1 were translocated preferentially to apoA-I in both cell types. In contrast to fibroblasts, HMDM displayed a considerable proportion of cholesteryl esters (CE) in basal and apoA-I specific efflux media, most likely due to secretion of CE associated to apoE. Analysis of HDL(3) mediated lipid efflux from HMDM using D(9)-choline and (13)C(3)-FC stable isotope labeling revealed significantly different D(9)-PC and D(9)-SPM species pattern for apoA-I and HDL(3) specific efflux media, which indicates a contribution of distinct cellular phospholipid pools to apoA-I and HDL(3) mediated efflux. Together with a partial loading of fibroblasts and HMDM with HDL(3)-derived CE species, these data add further evidence for retroendocytosis of HDL. In summary, analysis of apoA-I/ABCA1 and HDL(3) mediated lipid efflux by ESI-MS/MS demonstrated a preferential efflux of monounsaturated PC and medium chain SPM to apoA-I. Moreover, this is the first study, which provides evidence for distinct cellular phospholipid pools used for lipid transfer to apoA-I and HDL(3) from the analysis of phospholipid species pattern in HMDM.
authors.affiliation: Institute of Clinical Chemistry, University of Regensburg, 93042 Regensburg, Germany.
authors.forename: Rainer
authors.initials: R
authors.lastname: Schifferer
authors.forename: Gerhard
authors.initials: G
authors.lastname: Liebisch
authors.forename: Sascha
authors.initials: S
authors.lastname: Bandulik
authors.forename: Thomas
authors.initials: T
authors.lastname: Langmann
authors.forename: Ashraf
authors.initials: A
authors.lastname: Dada
authors.forename: Gerd
authors.initials: G
authors.lastname: Schmitz
mesh_terms: D016632:Apolipoprotein A-I / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D002247:Carbon Isotopes; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D003470:Culture Media; D003903:Deuterium; D005347:Fibroblasts / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007553:Isotope Labeling; D053440:Lipoproteins, HDL3 / Q000494:pharmacology*; D009000:Monocytes / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization; D013109:Sphingomyelins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D016632:Apolipoprotein A-I; D002247:Carbon Isotopes; D003470:Culture Media; D053440:Lipoproteins, HDL3; D010713:Phosphatidylcholines; D013109:Sphingomyelins; D002784:Cholesterol; D003903:Deuterium