NAD(P)H oxidase Nox-4 mediates 7-ketocholesterol-induced endoplasmic reticulum stress and apoptosis in human aortic smooth muscle cells

Mol Cell Biol. 2004 Dec;24(24):10703-17. doi: 10.1128/MCB.24.24.10703-10717.2004.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aorta / cytology
  • Apoptosis / drug effects*
  • CCAAT-Enhancer-Binding Proteins / metabolism
  • Calcium / analysis
  • Calcium / metabolism
  • Cells, Cultured
  • Endoplasmic Reticulum / physiology*
  • Endoplasmic Reticulum Chaperone BiP
  • Endothelium, Vascular / cytology
  • Fluorescent Antibody Technique, Indirect
  • Gene Expression Regulation, Enzymologic*
  • Genes, Reporter
  • Heat-Shock Proteins / metabolism
  • Humans
  • Iron Regulatory Protein 1 / metabolism
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Ketocholesterols / metabolism
  • Ketocholesterols / pharmacology*
  • Kinetics
  • Luciferases / metabolism
  • Microscopy, Fluorescence
  • Molecular Chaperones / metabolism
  • Molecular Sequence Data
  • Muscle, Smooth / drug effects*
  • NADPH Oxidase 4
  • NADPH Oxidases / metabolism*
  • Oxidative Stress
  • Protein Denaturation
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / metabolism
  • Reactive Oxygen Species / analysis
  • Reactive Oxygen Species / metabolism
  • Signal Transduction
  • Transcription Factor CHOP
  • Transcription Factors / metabolism

Substances

  • CCAAT-Enhancer-Binding Proteins
  • DDIT3 protein, human
  • Endoplasmic Reticulum Chaperone BiP
  • HSPA5 protein, human
  • Heat-Shock Proteins
  • Ketocholesterols
  • Molecular Chaperones
  • RNA, Messenger
  • RNA, Small Interfering
  • Reactive Oxygen Species
  • Transcription Factors
  • Transcription Factor CHOP
  • Luciferases
  • NADPH Oxidase 4
  • NADPH Oxidases
  • NOX4 protein, human
  • JNK Mitogen-Activated Protein Kinases
  • Iron Regulatory Protein 1
  • Calcium

Associated data

  • GENBANK/AF254621
  • GENBANK/AF317889
  • GENBANK/AJ438989