title: Involvement of cholesterol-enriched microdomains in class A scavenger receptor-mediated responses in human macrophages.
abstract: OBJECTIVE
  Lipid rafts are cholesterol-enriched microdomains on cell membranes. We hypothesized that these microdomains could involve modified low-density lipoprotein (LDL) uptake.
  
  
  RESULTS
  Co-localizations of cholesterol-enriched microdomains and CD204 during the uptake of acetyl LDL (AcLDL) and oxidized LDL were observed using Alexa488-labeled polyethylene glycol cholesteryl ester, which is a sensitive probe used to analyze the dynamics of cholesterol-rich lipid microdomains in living cells. The lipid raft disruptors, methyl-β cyclodextrin and filipin, inhibited the uptake of AcLDL. CD204 siRNA treatments significantly reduced AcLDL uptake by 80%. We also demonstrated the presence of CD204 in the detergent-resistant membrane fraction (DRM) by immunoblotting analysis. The ratio of CD204/flotillin-1 in DRM was increased 11.5-fold by modified LDL administration. The PI3 kinase inhibitor LY294002, but not the Src kinase inhibitor PP1 or the Gαi/o inhibitor pertussis toxin, inhibited modified LDL uptake. The production of interleukin (IL)-8, but not CCL2, CXCL2, CXCL3, IL-6 or tumor necrosis factor-α was increased by AcLDL administration. The AcLDL-induced IL-8 production was inhibited by LY294002 and filipin.
  
  
  CONCLUSIONS
  These data firstly demonstrated that PI3 kinase-associated cholesterol-enriched microdomains are involved in CD204-mediated modified LDL uptake in human macrophages. Cholesterol-enriched microdomains may play a critical role in inflammatory processes.
authors.affiliation: Department of Cardiovascular Medicine, Juntendo University School of Medicine, 2-1-1, Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kiyanagi
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Iwabuchi
authors.forename: Kazunori
authors.initials: K
authors.lastname: Shimada
authors.forename: Kuniaki
authors.initials: K
authors.lastname: Hirose
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Miyazaki
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Sumiyoshi
authors.forename: Chihiro
authors.initials: C
authors.lastname: Iwahara
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Nakayama
authors.forename: Hiromi
authors.initials: H
authors.lastname: Masuda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mokuno
authors.forename: Satoshi
authors.initials: S
authors.lastname: Sato
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Daida
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D005372:Filipin / Q000494:pharmacology; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism; D008264:Macrophages / Q000378:metabolism*; D008297:Male; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology; D051117:Scavenger Receptors, Class A / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects; D047392:beta-Cyclodextrins / Q000494:pharmacology
chemical_list: D008077:Lipoproteins, LDL; C495139:MSR1 protein, human; D051117:Scavenger Receptors, Class A; C032629:acetyl-LDL; D047392:beta-Cyclodextrins; C108732:methyl-beta-cyclodextrin; C099252:oxidized low density lipoprotein; D005372:Filipin; D019869:Phosphatidylinositol 3-Kinases