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Activating transcription factor 6 mediates oxidized LDL-induced cholesterol accumulation and apoptosis in macrophages by up-regulating CHOP expression.
- Source :
-
Journal of atherosclerosis and thrombosis [J Atheroscler Thromb] 2013; Vol. 20 (1), pp. 94-107. Date of Electronic Publication: 2012 Oct 03. - Publication Year :
- 2013
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Abstract
- Aim: This study was to explore whether activating transcription factor 6 (ATF6), an important sensor to endoplasmic reticulum (ER) stress, would mediate oxidized low-density lipoprotein (ox-LDL)- induced cholesterol accumulation and apoptosis in cultured macrophages and the underlying molecular mechanisms.<br />Methods: Intracellular lipid droplets and total cholesterol levels were assayed by oil red O staining and enzymatic colorimetry, respectively. Cell viability and apoptosis were determined using MTT assay and AnnexinV-FITC apoptosis detection kit, respectively. The nuclear translocation of ATF6 in cells was detected by immunofluorescence analysis. Protein and mRNA levels were examined by Western blot analysis and real time-PCR, respectively. ATF6 siRNA was transfected to RAW264.7 cells by lipofectamin.<br />Results: Exposure of cells to ox-LDL induced glucose-regulated protein 78 (GRP78). C/EBP homologous protein (CHOP), a key-signaling component of ER stress-induced apoptosis, was up-regulated in ox-LDL-treated cells. ATF6, a factor that positively regulates CHOP expression, was activated by ox-LDL in a concentration- and time- dependent manner. The role of the ATF6-mediated ER stress pathway was further confirmed through the siRNA-mediated knockdown of ATF6, which attenuated ox-LDL-induced upregulation of CHOP, cholesterol accumulation and apoptosis in macrophages. In addition, the phosphorylation of double-stranded RNA-activated protein kinase-like endoplasmic reticulum kinase (PERK), another factor that positively regulates CHOP expression, was induced in the presence of ox-LDL, and PERK-specific siRNA also inhibited the ox-LDL-induced upregulation of CHOP and apoptosis in RAW264.7 cells.<br />Conclusion: These results demonstrate that ER stress-related proteins, particularly ATF6 and its downstream molecule CHOP, are involved in ox-LDL-induced cholesterol accumulation and apoptosis in macrophages.
- Subjects :
- Activating Transcription Factor 6 genetics
Animals
Base Sequence
Blotting, Western
Cell Line
DNA Primers
Endoplasmic Reticulum Chaperone BiP
Flow Cytometry
Fluorescent Antibody Technique
Heat-Shock Proteins biosynthesis
Macrophages cytology
Mice
Polymerase Chain Reaction
RNA, Messenger genetics
Real-Time Polymerase Chain Reaction
Activating Transcription Factor 6 physiology
Apoptosis physiology
Cholesterol metabolism
Lipoproteins, LDL physiology
Macrophages metabolism
Transcription Factor CHOP metabolism
Up-Regulation physiology
Subjects
Details
- Language :
- English
- ISSN :
- 1880-3873
- Volume :
- 20
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Journal of atherosclerosis and thrombosis
- Publication Type :
- Academic Journal
- Accession number :
- 23037953
- Full Text :
- https://doi.org/10.5551/jat.13425