title: Effect of advanced glycation end products on lectin-like oxidized low density lipoprotein receptor-1 expression in endothelial cells.
abstract: OBJECTIVE
  Lectin-like oxidized LDL receptor-1 (LOX-1) is a class E oxidized LDL specific scavenger receptor that recognizes multiple ligands. Advanced glycation end products (AGEs) have been recently identified as other ligands to LOX-1 and shown to increase LOX-1 expressions in diabetes; therefore, we investigated the underlying mechanism involved.
  
  
  METHODS
  Confluent human aortic endothelial cells were treated with a fixed concentration of AGE-BSA or BSA as a control in the presence or absence of either antibody of the receptor for advanced glycation end products, mammalian target of rapamycin (mTOR) inhibitor rapamycin, NF-kB inhibitor, phosphoinositide 3-kinases (PI3K) inhibitor or anti-diabetic drug metformin. After stimulation, cells were lysed and Western blot protein expression on LOX-1, rapamycin-insensitive companion of mTOR (RICTOR), the phosphorylation status of p-mTOR, p-P70S6 kinase and p-Akt were determined.
  
  
  RESULTS
  AGEs induced LOX-1 expression in endothelial cells. Pretreatment either with anti-RAGE antibody or LY294002 prior to AGE-BSA decreases LOX-1 and p-mTOR expressions. Incubating endothelial cells with AGE-BSA in the presence of rapamycin down-regulated the protein expression-level of p-mTOR by 41% (p<0.05) and LOX-1 expression by 61.5% (p<0.01). Knockdown of RICTOR by RNA silencing showed a 41.5% (p<0.01) and 71.2% (p<0.01) reduction in LOX-1 and p-Akt expressions, respectively. Preincubation of endothelial cells with AGE-BSA and metformin, an anti-diabetic drug known to have an mTOR inhibition effect, significantly reduced AGE-stimulated LOX-1 expression.
  
  
  CONCLUSIONS
  Our results indicated that LOX-1 up-regulation induced by AGE-BSA was a receptor mediated through RAGE and is via the PI3K/PDK1/mTORC2 pathway. Metformincan reduce AGE-stimulated LOX-1 expression in endothelial cells in vitro.
authors.affiliation: Department of Medicine, University of Hong Kong, Hong Kong.
authors.forename: Sammy W M
authors.initials: SW
authors.lastname: Shiu
authors.forename: Ying
authors.initials: Y
authors.lastname: Wong
authors.forename: Kathryn C B
authors.initials: KC
authors.lastname: Tan
mesh_terms: D001011:Aorta / Q000166:cytology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D017127:Glycation End Products, Advanced / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D008687:Metformin / Q000494:pharmacology; D008954:Models, Biological; D000081082:Phosphoinositide-3 Kinase Inhibitors; D034741:RNA, Small Interfering / Q000378:metabolism; D051127:Scavenger Receptors, Class E / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism; D014162:Transfection; D015854:Up-Regulation
chemical_list: D017127:Glycation End Products, Advanced; D008024:Ligands; D000081082:Phosphoinositide-3 Kinase Inhibitors; D034741:RNA, Small Interfering; D051127:Scavenger Receptors, Class E; C081628:advanced glycation end products-bovine serum albumin; D012710:Serum Albumin, Bovine; D008687:Metformin; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases