title: Itinerary of high density lipoproteins in endothelial cells.
abstract: High density lipoprotein (HDL) and its main protein component apolipoprotein A-I (ApoA-I) have multiple anti-atherogenic functions. Some of them are exerted within the vessel wall, so that HDL needs to pass the endothelial barrier. To elucidate their itinerary through endothelial cells (ECs), we labelled ApoA-I and HDL either fluorescently or with 1.4 nm nanogold and investigated their cellular localization by using immunofluorescent microscopy (IFM) and electron microscopy (EM). HDL as well as ApoA-I is taken up by ECs into the same route of intracellular trafficking. Time kinetics and pulse chase experiments revealed that HDL is trafficked through different vesicles. HDL partially co-localized with LDL, albumin, and transferrin. HDL did not co-localize with clathrin and caveolin-1. Fluorescent HDL was recovered at small proportions in early endosomes and endosome to trans-golgi network vesicles but not at all in recycling endosomes, in late endosomes or lysosomes. EM identified HDL mainly in large filled vesicles which however upon IFM did not colocalize with markers of multivesicular bodies or autophagosomes. The uptake or cellular distribution of HDL was altered upon pharmacological interference with cytochalasine D, colchicine and dynasore. Blockage of fluid phase uptake with Amiloride or EIPA did not reduce the uptake of HDL. Neither did we observe any co-localization of HDL with dextran as the marker of fluid phase uptake. In conclusion, HDL and ApoA-I are internalized and trafficked by endothelial cells through a non-classical endocytic route.
authors.affiliation: Institute of Clinical Chemistry, University and University Hospital of Zurich, Switzerland; Competence Center for Integrated Human Physiology, University of Zurich, Switzerland.
authors.forename: Damir
authors.initials: D
authors.lastname: Perisa
authors.affiliation: Institute of Clinical Chemistry, University and University Hospital of Zurich, Switzerland; Competence Center for Integrated Human Physiology, University of Zurich, Switzerland.
authors.forename: Lucia
authors.initials: L
authors.lastname: Rohrer
authors.affiliation: Center for Microscopy and Image Analysis, University of Zürich, Switzerland.
authors.forename: Andres
authors.initials: A
authors.lastname: Kaech
authors.affiliation: Institute of Clinical Chemistry, University and University Hospital of Zurich, Switzerland; Competence Center for Integrated Human Physiology, University of Zurich, Switzerland. Electronic address: arnold.voneckardstein@usz.ch.
authors.forename: Arnold
authors.initials: A
authors.lastname: von Eckardstein
mesh_terms: D000818:Animals; D001011:Aorta / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016632:Apolipoprotein A-I / Q000378:metabolism*; D001692:Biological Transport; D002417:Cattle; D051242:Caveolin 1 / Q000378:metabolism; D002966:Clathrin / Q000378:metabolism; D003078:Colchicine / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D004705:Endocytosis; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005456:Fluorescent Dyes; D006046:Gold; D006835:Hydrazones / Q000494:pharmacology; D007700:Kinetics; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000378:metabolism; D049329:Nanostructures / Q000737:chemistry; D061251:Primary Cell Culture; D012709:Serum Albumin / Q000378:metabolism; D014168:Transferrin / Q000378:metabolism; D022161:Transport Vesicles / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D021601:trans-Golgi Network / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*
chemical_list: D016632:Apolipoprotein A-I; D051242:Caveolin 1; D002966:Clathrin; D005456:Fluorescent Dyes; D006835:Hydrazones; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; C511794:N'-(3,4-dihydroxybenzylidene)-3-hydroxy-2-naphthahydrazide; D012709:Serum Albumin; D014168:Transferrin; D015638:Cytochalasin D; D006046:Gold; D003078:Colchicine
keywords: Endocytosis; Endothelial cells; High density lipoproteins; Multivesicular bodies