title: Punicalagin attenuates palmitate-induced lipotoxicity in HepG2 cells by activating the Keap1-Nrf2 antioxidant defense system.
abstract: Free fatty acids (FFA) could induce hepatocyte lipotoxicity, which plays an important role in the initiation of nonalcoholic fatty liver disease (NAFLD). Inhibition of FFA-induced lipotoxicity is suggested as a potential treatment for nonalcoholic fatty liver disease. The aim of the current study is to explore the effect of punicalagin, a polyphenol abundant in pomegranate, on FFA-induced hepatic lipotoxicity and its potential mechanisms.
  
  
  
  HepG2 cells were exposed to 250 μM palmitate for 24 h with or without punicalagin pretreatment. Punicalagin pretreatment attenuated palmitate-induced mitochondrial membrane potential lost, ATP depletion, and reactive oxygen species production. Punicalagin also increased hepatocyte viability by blocking mitochondria-mediated caspase-dependent apoptosis. The hepatoprotective effect was associated with an exaggerated phosphorylation of extracellular signal regulated kinase as well as significant nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation and target genes induction. Blockage of extracellular signal regulated kinase by a pharmacological inhibitor abrogated the cytoprotective effect of punicalagin and its induction of Nrf2 pathway. Knockdown of Nrf2 by specific small interfering RNA also diminished the protective effects of punicalagin, while knockdown of Kelch-like ECH-associated protein 1 (Keap1) with small interfering RNA could promote Nrf2 nuclear translocation and exert similar protection as punicalagin treatment.
  
  
  
  These findings suggest that punicalagin could effectively attenuate FFA-induced lipotoxicity by activating Keap1-Nrf2 cytoprotective signaling pathway.
authors.affiliation: Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Chunhong
authors.initials: C
authors.lastname: Yan
authors.affiliation: Department of Nutrition and Food Security, School of Public Health, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Wenyan
authors.initials: W
authors.lastname: Sun
authors.affiliation: Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Xun
authors.initials: X
authors.lastname: Wang
authors.affiliation: Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Jiangang
authors.initials: J
authors.lastname: Long
authors.affiliation: Laboratory of Nutrition and Functional Factors, College of Food Science and Engineering, Northwest A & F University, Yangling, China.
authors.forename: Xuebo
authors.initials: X
authors.lastname: Liu
authors.affiliation: Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Feng
authors.affiliation: Center for Mitochondrial Biology and Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Frontier Institute of Science and Technology, Xi'an Jiaotong University, Xi'an, China.
authors.forename: Jiankang
authors.initials: J
authors.lastname: Liu
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D047348:Hydrolyzable Tannins / Q000494:pharmacology*; D000072019:Kelch-Like ECH-Associated Protein 1 / Q000235:genetics / Q000378:metabolism*; D050356:Lipid Metabolism / Q000187:drug effects*; D029561:Lythraceae / Q000737:chemistry; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D010168:Palmitates / Q000633:toxicity*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000975:Antioxidants; D047348:Hydrolyzable Tannins; C431364:KEAP1 protein, human; D000072019:Kelch-Like ECH-Associated Protein 1; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D010168:Palmitates; D017382:Reactive Oxygen Species; C115642:punicalagin
keywords: Hepatocyte; Lipotoxicity; Mitochondrial function; Nrf2; Punicalagin