title: NAD(P)H oxidase Nox-4 mediates 7-ketocholesterol-induced endoplasmic reticulum stress and apoptosis in human aortic smooth muscle cells.
abstract: The mechanisms involved in the cytotoxic action of oxysterols in the pathogenesis of atherosclerosis still remain poorly understood. Among the major oxysterols present in oxidized low-density lipoprotein, we show here that 7-ketocholesterol (7-Kchol) induces oxidative stress and/or apoptotic events in human aortic smooth muscle cells (SMCs). This specific effect of 7-Kchol is mediated by a robust upregulation (threefold from the basal level) of Nox-4, a reactive oxygen species (ROS)-generating NAD(P)H oxidase homologue. This effect was highlighted by silencing Nox-4 expression with a specific small interfering RNA, which significantly reduced the 7-Kchol-induced production of ROS and abolished apoptotic events. Furthermore, the 7-Kchol activating pathway included an early triggering of endoplasmic reticulum stress, as assessed by transient intracellular Ca(2+) oscillations, and the induction of the expression of the cell death effector CHOP and of GRP78/Bip chaperone via the activation of IRE-1, all hallmarks of the unfolded protein response (UPR). We also showed that 7-Kchol activated the IRE-1/Jun-NH(2)-terminal kinase (JNK)/AP-1 signaling pathway to promote Nox-4 expression. Silencing of IRE-1 and JNK inhibition downregulated Nox-4 expression and subsequently prevented the UPR-dependent cell death induced by 7-Kchol. These findings demonstrate that Nox-4 plays a key role in 7-Kchol-induced SMC death, which is consistent with the hypothesis that Nox-4/oxysterols are involved in the pathogenesis of atherosclerosis.
authors.affiliation: INSERM U479, Faculté de Médecine Xavier Bichat, BP416, 75870 Paris Cedex 18, France.
authors.forename: Eric
authors.initials: E
authors.lastname: Pedruzzi
authors.forename: Cécile
authors.initials: C
authors.lastname: Guichard
authors.forename: Véronique
authors.initials: V
authors.lastname: Ollivier
authors.forename: Fathi
authors.initials: F
authors.lastname: Driss
authors.forename: Michèle
authors.initials: M
authors.lastname: Fay
authors.forename: Céline
authors.initials: C
authors.lastname: Prunet
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Marie
authors.forename: Cécile
authors.initials: C
authors.lastname: Pouzet
authors.forename: Mohammad
authors.initials: M
authors.lastname: Samadi
authors.forename: Carole
authors.initials: C
authors.lastname: Elbim
authors.forename: Yvonne
authors.initials: Y
authors.lastname: O'dowd
authors.forename: Marcelle
authors.initials: M
authors.lastname: Bens
authors.forename: Alain
authors.initials: A
authors.lastname: Vandewalle
authors.forename: Marie-Anne
authors.initials: MA
authors.lastname: Gougerot-Pocidalo
authors.forename: Gérard
authors.initials: G
authors.lastname: Lizard
authors.forename: Eric
authors.initials: E
authors.lastname: Ogier-Denis
mesh_terms: D001011:Aorta / Q000166:cytology; D017209:Apoptosis / Q000187:drug effects*; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism; D002118:Calcium / Q000032:analysis / Q000378:metabolism; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000502:physiology*; D000091342:Endoplasmic Reticulum Chaperone BiP; D004730:Endothelium, Vascular / Q000166:cytology; D019084:Fluorescent Antibody Technique, Indirect; D015971:Gene Expression Regulation, Enzymologic; D017930:Genes, Reporter; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D035941:Iron Regulatory Protein 1 / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007653:Ketocholesterols / Q000378:metabolism / Q000494:pharmacology*; D007700:Kinetics; D008156:Luciferases / Q000378:metabolism; D008856:Microscopy, Fluorescence; D018832:Molecular Chaperones / Q000378:metabolism; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000187:drug effects*; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000378:metabolism*; D018384:Oxidative Stress; D011489:Protein Denaturation; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000032:analysis / Q000378:metabolism; D015398:Signal Transduction; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D022762:CCAAT-Enhancer-Binding Proteins; C497249:DDIT3 protein, human; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D007653:Ketocholesterols; D018832:Molecular Chaperones; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; D014157:Transcription Factors; D051742:Transcription Factor CHOP; D008156:Luciferases; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; D048031:JNK Mitogen-Activated Protein Kinases; D035941:Iron Regulatory Protein 1; D002118:Calcium