title: Free cholesterol alters macrophage morphology and mobility by an ABCA1 dependent mechanism.
abstract: OBJECTIVE
  To investigate whether the morphological and functional changes typical of cell immobilization induced by free cholesterol (FC) accumulation in macrophages is related to the activity of the ATP-binding cassette transporter (ABCA1).
  
  
  RESULTS
  FC loading induced actin rearrangement with ruffling and cell spreading in macrophages that normally express ABCA1, but to a significant lesser extent in ABCA1-KO mouse peritoneal macrophages (MPMs) and in normal cells upon pharmacological inhibition of ABCA1 with probucol. In ABCA1-KO MPMs and in probucol-treated J774 cell migration was inhibited to a lower extent by FC as compared to control cells. Similar results were found in stably ABCA1 knocked down J774 (ABCA1-KD-J774) obtained by RNA interference. FC accessible to cholesterol oxidase, a measure of plasma membrane FC content, was significantly higher in FC-loaded WT MPMs and control J774 than in FC-loaded ABCA1-KO MPMs, ABCA1-KD-J774 or probucol-treated J774. In parallel plasma membrane total phospholids and sphingomyelin increased after cholesterol loading in control J774 but not in ABCA1-KD-J774. In addition, apoA-I, that removes FC from ABCA1 specific pool, partially restored chemotactic response in FC-loaded control J774. No effect was observed with HDL(2) that does not interact with ABCA1. Finally, FC-induced Rac activation was more efficient in control J774 than in ABCA1-KD-J774. and was prevented by probucol and apoA-I in control J774.
  
  
  CONCLUSIONS
  In macrophages ABCA1 activity mediates FC ability to alter plasma membrane organization, to inhibit cell migration, and to activate a Rac-mediated signaling pathway.
authors.affiliation: Department of Pharmacological and Biological Sciences, Parco Area delle Scienze 27/A, 43124 Parma, University of Parma, Italy.
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Adorni
authors.forename: Elda
authors.initials: E
authors.lastname: Favari
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Ronda
authors.forename: Agnese
authors.initials: A
authors.lastname: Granata
authors.forename: Stefano
authors.initials: S
authors.lastname: Bellosta
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Arnaboldi
authors.forename: Alberto
authors.initials: A
authors.lastname: Corsini
authors.forename: Rita
authors.initials: R
authors.lastname: Gatti
authors.forename: Franco
authors.initials: F
authors.lastname: Bernini
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000502:physiology*; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects; D054443:Cell Migration Assays; D002784:Cholesterol / Q000378:metabolism / Q000494:pharmacology*; D055785:Gene Knockdown Techniques; D006801:Humans; D017737:Macrophages, Peritoneal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015398:Signal Transduction / Q000187:drug effects; D020744:rac GTP-Binding Proteins / Q000502:physiology
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D002784:Cholesterol; D020744:rac GTP-Binding Proteins