Molecular and Cellular Biochemistry

, Volume 381, Issue 1–2, pp 127–137 | Cite as

Endoplasmic reticulum stress leads to lipid accumulation through upregulation of SREBP-1c in normal hepatic and hepatoma cells

  • Dian-liang Fang
  • Ying Wan
  • Wei Shen
  • Jie Cao
  • Zhong-xin Sun
  • Hui-hong Yu
  • Qin Zhang
  • Wen-hui Cheng
  • Juan Chen
  • Bo Ning
Article

Abstract

Endoplasmic reticulum stress (ERS) has been found in non-alcoholic fatty liver disease. The study was to further explore the mechanistic relationship between ERS and lipid accumulation. To induce ERS, the hepatoblastoma cell line HepG2 and the normal human L02 cell line were exposed to Tg for 48 h. RT-PCR and Western blot were performed to evaluate glucose-regulated protein (GRP-78) expression as a marker of ERS. ER ultrastructure was assessed by electron microscopy. Triglyceride content was examined by Oil Red O staining and quantitative intracellular triglyceride assay. The hepatic nuclear sterol regulatory element-binding protein (SREBP-1c), liver X receptor (LXRs), fatty acid synthase (FAS), and acetyl-coA carboxylase (ACC1) expressions were examined by real-time PCR and Western blot. 4-(2-aminoethyl) benzenesulfonyl fluoride (AEBSF) was used to inhibit S1P serine protease inhibitor, and SREBP-1c cleavage was evaluated under ERS. SREBP-1c was knockdown and its effect on lipid metabolism was observed. Tg treatment upregulated GRP-78 expression and severely damaged the ER structure in L02 and HepG2 cells. ERS increased triglyceride deposition and enhanced the expression of SREBP-1c, FAS, and ACC1, but have no influence on LXR. AEBSF pretreatment abolished Tg-induced SREBP-1c cleavage. Moreover, SREBP-1c silencing reduced triglycerides and downregulated FAS expression. Pharmacological ERS induced by Tg leads to lipid accumulation through upregulation of SREBP-1c in L02 and HepG2 cells.

Keywords

Endoplasmic reticulum stress SREBP-1c Hepatic steatosis 

Abbreviations

ERS

Endoplasmic reticulum stress

GRP-78

Glucose-regulated protein

NAFLD

Non-alcoholic fatty liver disease

Tg

Thapsigargin

ACC1

Acetyl-CoA carboxylase

FAS

Fatty acid synthase

LXR

Liver X receptor

S1P

Site 1 protease

SCAP

SREBP cleavage-activating protein

SREBP-1c

Sterol regulatory element-binding protein 1c

Insig-1

Insulin-induced gene 1

AEBSF

4-(2-Aminoethyl) benzenesulfonyl fluoride hydrochloride

UPR

Unfolded protein response

Notes

Acknowledgments

This study was supported by the Natural Science Foundation of China (no. 81000357). We thank the staff of the Department of Gastroenterology and Hepatology of the Second Affiliated Hospital of Chongqing Medical University for their help. We also thank Ms. Yingxia Xiang and Mr. Jing Wang for the consistent technical assistance and Medjaden Bioscience for assisting in the preparation of this manuscript.

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Copyright information

© Springer Science+Business Media New York 2013

Authors and Affiliations

  • Dian-liang Fang
    • 1
  • Ying Wan
    • 1
  • Wei Shen
    • 1
  • Jie Cao
    • 1
  • Zhong-xin Sun
    • 1
  • Hui-hong Yu
    • 1
  • Qin Zhang
    • 2
  • Wen-hui Cheng
    • 1
  • Juan Chen
    • 1
  • Bo Ning
    • 1
  1. 1.Department of Gastroenterology and Hepatology2nd Affiliated Hospital of Chongqing Medical UniversityChongqingChina
  2. 2.Department of Digestive DiseasesThe First People’s Hospital of LiangshanLiangshanChina

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