title: Palmitate induces cisternal ER expansion via the activation of XBP-1/CCTα-mediated phospholipid accumulation in RAW 264.7 cells.
abstract: BACKGROUND
  Endoplasmic reticulum (ER) stress induces ER expansion. The expansion of the intracisternal space of the ER was found in macrophages associated with human atherosclerotic lesions. We also previously reported that palmitate induces cisternal ER expansion and necrosis in RAW 264.7 cells. In this study, we report on an investigation of the likely mechanism responsible for this palmitate-induced cisternal ER expansion in a mouse macrophage cell line, RAW 264.7 cells.
  
  
  METHODS
  RAW 264.7 cells were pre-treated with the designated inhibitor or siRNA, followed by treatment with palmitate. Changes in the ER structure were examined by transmission electron microscopy. The induction of ER stress was confirmed by an increase in the extent of phosphorylation of PERK, the expression of BiP and CHOP, and the splicing of XBP-1 mRNA. Phospholipid staining was performed with the LipidTOX Red phospholipidosis detection reagent. Related gene expressions were detected by quantitative real time-RT-PCR or RT-PCR.
  
  
  RESULTS
  Palmitate was found to induce ER stress and cisternal ER expansion. In addition, palmitate-induced cisternal ER expansion was attenuated by ER stress inhibitors, such as 4-phenylbutyric acid (4-PBA) and tauroursodeoxycholic acid (TUDCA). The findings also show that palmitate induced-mRNA expression of CCTα, which increases phospholipid synthesis, was attenuated by the down-regulation of XBP-1, a part of ER stress. Furthermore, palmitate-induced phospholipid accumulation and cisternal ER expansion were attenuated by the down-regulation of XBP-1 or CCTα.
  
  
  CONCLUSIONS
  The findings reported herein indicate that palmitate-induced cisternal ER expansion is dependent on the activation of XBP-1/CCTα-mediated phospholipid accumulation in RAW 264.7 cells.
authors.affiliation: Institute of Hansen's Disease, Department of Pathology, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul, 137-701, Republic of Korea.
authors.forename: Seong Keun
authors.initials: SK
authors.lastname: Kim
authors.affiliation: Institute of Hansen's Disease, Department of Pathology, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul, 137-701, Republic of Korea.
authors.forename: Eunhye
authors.initials: E
authors.lastname: Oh
authors.affiliation: Institute of Hansen's Disease, Department of Pathology, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul, 137-701, Republic of Korea.
authors.forename: Mihee
authors.initials: M
authors.lastname: Yun
authors.affiliation: Institute of Hansen's Disease, Department of Pathology, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul, 137-701, Republic of Korea. sblee@catholic.ac.kr.
authors.forename: Seong-Beom
authors.initials: SB
authors.lastname: Lee
authors.affiliation: Institute of Hansen's Disease, Department of Pathology, College of Medicine, The Catholic University of Korea, 222 Banpo-daero, Seocho-gu, Seoul, 137-701, Republic of Korea. guetae@catholic.ac.kr.
authors.forename: Gue Tae
authors.initials: GT
authors.lastname: Chae
mesh_terms: D000818:Animals; D019916:Choline-Phosphate Cytidylyltransferase / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D051379:Mice; D009336:Necrosis; D019308:Palmitic Acid / Q000494:pharmacology*; D010743:Phospholipids / Q000378:metabolism*; D000067996:RAW 264.7 Cells; D000071701:Regulatory Factor X Transcription Factors; D015398:Signal Transduction / Q000187:drug effects; D014157:Transcription Factors / Q000378:metabolism*; D014415:Tunicamycin / Q000494:pharmacology; D000071717:X-Box Binding Protein 1
chemical_list: D004268:DNA-Binding Proteins; D010743:Phospholipids; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605543:XBP1 protein, human; C000605544:Xbp1 protein, mouse; D014415:Tunicamycin; D019308:Palmitic Acid; D019916:Choline-Phosphate Cytidylyltransferase