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Molecular and Cellular Biochemistry

, Volume 364, Issue 1–2, pp 115–129 | Cite as

Saturated fatty acid induction of endoplasmic reticulum stress and apoptosis in human liver cells via the PERK/ATF4/CHOP signaling pathway

  • Jie Cao
  • Dong-Ling Dai
  • Long Yao
  • Hui-Hong Yu
  • Bo Ning
  • Qin Zhang
  • Juan Chen
  • Wen-Hui Cheng
  • Wei ShenEmail author
  • Zhao-Xia YangEmail author
Article

Abstract

Accumulation of saturated fatty acids in the liver can cause nonalcoholic fatty liver disease (NAFLD). This study investigated saturated fatty acid induction of endoplasmic reticulum (ER) stress and apoptosis in human liver cells and the underlying causal mechanism. Human liver L02 and HepG2 cell lines were exposed to the saturated fatty acid sodium palmitate. MTT assay was used for cell viability, flow cytometry and Hoechst 33258 staining for apoptosis, RT-PCR for mRNA expression, and Western blot for protein expression. Silence of PRK-like ER kinase (PERK) expression in liver cells was through transient transfection of PERK shRNA. Treatment of L02 and HepG2 cells with sodium palmitate reduced cell viability through induction of apoptosis. Sodium palmitate also induced ER stress in the cells, indicated by upregulation of PERK phosphorylation and expression of BiP, ATF4, and CHOP proteins. Sodium palmitate had little effect on activating XBP-1, a common target of the other two canonical sensors of ER stress, ATF6, and IRE1. Knockdown of PERK gene expression suppressed the PERK/ATF4/CHOP signaling pathway during sodium palmitate-induced ER stress and significantly inhibited sodium palmitate-induced apoptosis in L02 and HepG2 cells. Saturated fatty acid-induced ER stress and apoptosis in these human liver cells were enacted through the PERK/ATF4/CHOP signaling pathway. Future study is warranted to investigate the role of these proteins in mediating saturated fatty acid-induced NAFLD in animal models.

Keywords

Saturated fatty acid ER stress Apoptosis PERK expression 

Abbreviations

7-AAD

7-Amino-actinomycin D

ATF4

Activated transcription factor 4

BCA

Bicinchoninic acid

BiP

Binding immunoglobulin protein

BSA

Bovine serum albumin

ER

Endoplasmic reticulum

GRP78

Glucose-regulated protein 78

FFA

Free fatty acid

JNK

c-Jun NH2-terminal kinase

MTT

Methyl-thiazolyl-tetrazolium

NAFLD

Nonalcoholic fatty liver disease

NASH

Nonalcoholic steatohepatitis

PBS

Phosphate-buffered saline

PKR

Protein kinase dependent on RNA

PERK

PKR-like ER kinase

PVDF

Polyvinylidene difluoride

RIPA

Radioimmunoprecipitation

TBS

Tris-buffered saline

TBST

Triton X-100-TBS

UPR

Unfolded protein response

XBP-1

X-box-binding protein 1

CHOP

C/EBP-homologous protein

Notes

Acknowledgments

Our study was supported by grants from the Natural Science Foundation of China (#30871160), the Natural Science Foundation of Chongqing, China (#CSTC-2008BB5404) and the Project of Medical Science and Technology of Chongqing (#2008-2-401). We sincerely thank the staff of the Department of Gastroenterology and Hepatology at the Second Affiliated Hospital of Chongqing Medical University for their constant and unselfish help. We thank Ms. Yingxia Xiang and Mr. Jing Wang for their consistent and illuminating technical assistance. We also thank Medjaden Bioscience, Hong Kong, China, for assistance in the preparation of this manuscript.

Conflict of interest

None.

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Copyright information

© Springer Science+Business Media, LLC. 2012

Authors and Affiliations

  • Jie Cao
    • 1
  • Dong-Ling Dai
    • 2
  • Long Yao
    • 3
  • Hui-Hong Yu
    • 1
  • Bo Ning
    • 1
  • Qin Zhang
    • 4
  • Juan Chen
    • 1
  • Wen-Hui Cheng
    • 1
  • Wei Shen
    • 1
    Email author
  • Zhao-Xia Yang
    • 1
    Email author
  1. 1.Department of Gastroenterology and Hepatology2nd Affiliated Hospital of Chongqing Medical UniversityChongqingChina
  2. 2.Department of Internal MedicineThe Children’s Hospital of ShenzhenShenzhenChina
  3. 3.Department of Intensive-Care MedicineThe Central Hospital of JiangjinChongqingChina
  4. 4.Department of Digestive DiseasesThe First People’s Hospital of LiangshanLiangshanChina

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