title: Induction of ATF3 gene network by triglyceride-rich lipoprotein lipolysis products increases vascular apoptosis and inflammation.
abstract: OBJECTIVE
  Elevation of triglyceride-rich lipoproteins (TGRLs) contributes to the risk of atherosclerotic cardiovascular disease. Our work has shown that TGRL lipolysis products in high physiological to pathophysiological concentrations cause endothelial cell injury; however, the mechanisms remain to be delineated.
  
  
  RESULTS
  We analyzed the transcriptional signaling networks in arterial endothelial cells exposed to TGRL lipolysis products. When human aortic endothelial cells in culture were exposed to TGRL lipolysis products, activating transcription factor 3 (ATF3) was identified as a principal response gene. Induction of ATF3 mRNA and protein was confirmed by quantitative reverse-transcription polymerase chain reaction and Western blot respectively. Immunofluorescence analysis showed that ATF3 accumulated in the nuclei of cells treated with lipolysis products. Nuclear expression of phosphorylated c-Jun N-terminal kinase (JNK), previously shown to be an initiator of the ATF3 signaling cascade, also was demonstrated. Small interfering RNA (siRNA)-mediated inhibition of ATF3 blocked lipolysis products-induced transcription of E-selectin and interleukin-8, but not interleukin-6 or nuclear factor-κB. c-Jun, a downstream protein in the JNK pathway, was phosphorylated, whereas expression of nuclear factor-κB-dependent JunB was downregulated. Additionally, JNK siRNA suppressed ATF3 and p-c-Jun protein expression, suggesting that JNK is upstream of the ATF3 signaling pathway. In vivo studies demonstrated that infusion of TGRL lipolysis products into wild-type mice induced nuclear ATF3 accumulation in carotid artery endothelium. ATF3(-/-) mice were resistant to vascular apoptosis precipitated by treatment with TGRL lipolysis products. Also peripheral blood monocytes isolated from postprandial humans had increased ATF3 expression as compared with fasting monocytes.
  
  
  CONCLUSIONS
  This study demonstrates that TGRL lipolysis products activate ATF3-JNK transcription factor networks and induce endothelial cells inflammatory response.
authors.affiliation: Division of Cardiovascular Medicine, Department of Internal Medicine, School of Medicine, University of California, Davis, CA 95616, USA.
authors.forename: Hnin H
authors.initials: HH
authors.lastname: Aung
authors.forename: Michael W
authors.initials: MW
authors.lastname: Lame
authors.forename: Kishorchandra
authors.initials: K
authors.lastname: Gohil
authors.forename: Chung-Il
authors.initials: CI
authors.lastname: An
authors.forename: Dennis W
authors.initials: DW
authors.lastname: Wilson
authors.forename: John C
authors.initials: JC
authors.lastname: Rutledge
mesh_terms: D051700:Activating Transcription Factor 3 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002478:Cells, Cultured; D019040:E-Selectin / Q000378:metabolism; D042783:Endothelial Cells / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D004789:Enzyme Activation; D005455:Fluorescent Antibody Technique; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation; D006801:Humans; D007249:Inflammation / Q000235:genetics / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D018836:Inflammation Mediators / Q000378:metabolism; D016209:Interleukin-8 / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008066:Lipolysis; D008071:Lipoprotein Lipase / Q000378:metabolism; D008074:Lipoproteins / Q000097:blood / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D014280:Triglycerides / Q000097:blood / Q000378:metabolism*
chemical_list: C490449:ATF3 protein, human; D051700:Activating Transcription Factor 3; C103002:Atf3 protein, mouse; C508606:CXCL8 protein, human; D019040:E-Selectin; D018836:Inflammation Mediators; D016209:Interleukin-8; D008074:Lipoproteins; D012333:RNA, Messenger; C546936:SELE protein, human; D014280:Triglycerides; D048031:JNK Mitogen-Activated Protein Kinases; C548261:LPL protein, human; D008071:Lipoprotein Lipase
keywords: activating transcription factor 3; inflammation; lipolysis; lipoproteins; oligonucleotide arrays