NAD(P)H oxidase Nox-4 mediates 7-ketocholesterol-induced endoplasmic reticulum stress and apoptosis in human aortic smooth muscle cells.
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.
Pedruzzi
Eric
E
INSERM U479, Faculté de Médecine Xavier Bichat, BP416, 75870 Paris Cedex 18, France.
Guichard
Cécile
C
Ollivier
Véronique
V
Driss
Fathi
F
Fay
Michèle
M
Prunet
Céline
C
Marie
Jean-Claude
JC
Pouzet
Cécile
C
Samadi
Mohammad
M
Elbim
Carole
C
O'dowd
Yvonne
Y
Bens
Marcelle
M
Vandewalle
Alain
A
Gougerot-Pocidalo
Marie-Anne
MA
Lizard
Gérard
G
Ogier-Denis
Eric
E
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
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