title: Saturated fatty acid induction of endoplasmic reticulum stress and apoptosis in human liver cells via the PERK/ATF4/CHOP signaling pathway.
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.
authors.affiliation: Department of Gastroenterology and Hepatology, 2nd Affiliated Hospital of Chongqing Medical University, No. 74 Linjiang Road, Chongqing 400010, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Cao
authors.forename: Dong-Ling
authors.initials: DL
authors.lastname: Dai
authors.forename: Long
authors.initials: L
authors.lastname: Yao
authors.forename: Hui-Hong
authors.initials: HH
authors.lastname: Yu
authors.forename: Bo
authors.initials: B
authors.lastname: Ning
authors.forename: Qin
authors.initials: Q
authors.lastname: Zhang
authors.forename: Juan
authors.initials: J
authors.lastname: Chen
authors.forename: Wen-Hui
authors.initials: WH
authors.lastname: Cheng
authors.forename: Wei
authors.initials: W
authors.lastname: Shen
authors.forename: Zhao-Xia
authors.initials: ZX
authors.lastname: Yang
mesh_terms: D051701:Activating Transcription Factor 4 / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D005234:Fatty Liver / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D056945:Hep G2 Cells; D006801:Humans; D008099:Liver / Q000166:cytology / Q000378:metabolism; D065626:Non-alcoholic Fatty Liver Disease; D019308:Palmitic Acid / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism*; D014280:Triglycerides / Q000032:analysis; D019892:eIF-2 Kinase / Q000235:genetics / Q000378:metabolism*
chemical_list: D051701:Activating Transcription Factor 4; D019308:Palmitic Acid; D034741:RNA, Small Interfering; D051742:Transcription Factor CHOP; D014280:Triglycerides; D019892:eIF-2 Kinase; C497109:ATF4 protein, human; C497249:DDIT3 protein, human