title: Overexpression of human 15(S)-lipoxygenase-1 in RAW macrophages leads to increased cholesterol mobilization and reverse cholesterol transport.
abstract: OBJECTIVE
  The purpose of this study was to determine the effect of 15-lipoxygenase-1 (15-LO-1) on cholesterol mobilization from macrophages.
  
  
  RESULTS
  Overexpression of human 15-LO-1 in RAW mouse macrophages led to enhanced cholesterol efflux, increased cholesteryl ester (CE) hydrolysis, and increased reverse cholesterol transport (RCT). Efflux studies comparing 15-LO-1 overexpressing cells to mock-transfected RAW macrophages resulted in a 3- to 7-fold increase in cholesterol efflux to apolipoprotein A-I and a modest increase in efflux to HDL. Additional experiments revealed an increase in mRNA and protein levels of ABCA1 and ABCG1 in the RAW expressing 15-LO-1 compared to controls. Efforts to examine whether the arachidonic acid metabolite of 15-LO-1, (15S)-hydroxyeicosatetraenoic acid (HETE), was responsible for the enhanced efflux revealed this eicosanoid metabolite did not play a role. Enhanced steryl ester hydrolysis was observed in 15-LO-1 overexpressing cells suggesting that the CE produced in the 15-LO-1 expressing cells was readily mobilized. To measure RCT, RAW macrophages overexpressing 15-LO-1 or mock-transfected cells were cholesterol enriched by exposure to acetylated low-density lipoprotein and [(3)H]-cholesterol. These macrophages were injected into wild-type animals and RCT was measured as a percent of injected dose of (3)H appearing in the feces at 48 hours. We found 7% of the injected (3)H in the feces of mice that received macrophages overexpressing 15-LO-1 and 4% in the feces of mice that received mock-transfected cells.
  
  
  CONCLUSIONS
  These data are consistent with a model in which overexpression of human 15-LO-1 in RAW macrophages promotes RCT through increased CE hydrolysis and ABCA1-mediated cholesterol efflux.
authors.affiliation: Division of Gastroenterology and Nutrition, The Children's Hospital of Philadelphia, 3615 Civic Center Blvd, ARC1102, Philadelphia, PA 19104-4399, USA. weibel@email.chop.edu
authors.forename: Ginny L
authors.initials: GL
authors.lastname: Weibel
authors.forename: Michelle R
authors.initials: MR
authors.lastname: Joshi
authors.forename: Eric T
authors.initials: ET
authors.lastname: Alexander
authors.forename: Peijuan
authors.initials: P
authors.lastname: Zhu
authors.forename: Ian A
authors.initials: IA
authors.lastname: Blair
authors.forename: George H
authors.initials: GH
authors.lastname: Rothblat