title: Sab (Sh3bp5) dependence of JNK mediated inhibition of mitochondrial respiration in palmitic acid induced hepatocyte lipotoxicity.
abstract: OBJECTIVE
  Sustained c-Jun N-terminal kinase (JNK) activation by saturated fatty acids plays a role in lipotoxicity and the pathogenesis of non-alcoholic steatohepatitis (NASH). We have reported that the interaction of JNK with mitochondrial Sab leads to inhibition of respiration, increased reactive oxygen species (ROS), cell death and hepatotoxicity. We tested whether this pathway underlies palmitic acid (PA)-induced lipotoxicity in hepatocytes.
  
  
  METHODS
  Primary mouse hepatocytes (PMH) from adeno-shlacZ or adeno-shSab treated mice and HuH7 cells were used.
  
  
  RESULTS
  In PMH, PA dose-dependently up to 1mM stimulated oxygen consumption rate (OCR) due to mitochondrial β-oxidation. At ⩾1.5mM, PA gradually reduced OCR, followed by cell death. Inhibition of JNK, caspases or treatment with antioxidant butylated hydroxyanisole (BHA) protected PMH against cell death. Sab knockdown or a membrane permeable Sab blocking peptide prevented PA-induced mitochondrial impairment, but inhibited only the late phase of both JNK activation (beyond 4h) and cell death. In PMH, PA increased p-PERK and its downstream target CHOP, but failed to activate the IRE-1α arm of the UPR. However, Sab silencing did not affect PA-induced PERK activation. Conversely, specific inhibition of PERK prevented JNK activation and cell death, indicating a major role upstream of JNK activation.
  
  
  CONCLUSIONS
  The effect of p-JNK on mitochondria plays a key role in PA-mediated lipotoxicity. The interplay of p-JNK with mitochondrial Sab leads to impaired respiration, ROS production, sustained JNK activation, and apoptosis.
authors: University of Southern California Research Center for Liver Diseases, Division of Gastrointestinal and Liver Diseases, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089-9121, USA.
authors: Sanda
authors: S
authors: Win
authors: University of Southern California Research Center for Liver Diseases, Division of Gastrointestinal and Liver Diseases, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089-9121, USA.
authors: Tin Aung
authors: TA
authors: Than
authors: University of Southern California Research Center for Liver Diseases, Division of Gastrointestinal and Liver Diseases, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089-9121, USA.
authors: Bao Han Allison
authors: BH
authors: Le
authors: Southern California Research Center for ALPD and Cirrhosis, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA; Department of Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), Consejo Superior Investigaciones Cientificas (CSIC) and Liver Unit-Hospital Clinic and CIBEREHD, Barcelona, Spain.
authors: Carmen
authors: C
authors: García-Ruiz
authors: Southern California Research Center for ALPD and Cirrhosis, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA; Department of Cell Death and Proliferation, Institute of Biomedical Research of Barcelona (IIBB), Consejo Superior Investigaciones Cientificas (CSIC) and Liver Unit-Hospital Clinic and CIBEREHD, Barcelona, Spain.
authors: Jose C
authors: JC
authors: Fernandez-Checa
authors: University of Southern California Research Center for Liver Diseases, Division of Gastrointestinal and Liver Diseases, Keck School of Medicine, University of Southern California, Los Angeles, CA 90089-9121, USA; Southern California Research Center for ALPD and Cirrhosis, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA. Electronic address: kaplowit@usc.edu.
authors: Neil
authors: N
authors: Kaplowitz
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D055785:Gene Knockdown Techniques; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D065626:Non-alcoholic Fatty Liver Disease / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects; D019308:Palmitic Acid / Q000008:administration & dosage / Q000633:toxicity*; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000975:Antioxidants; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; D017382:Reactive Oxygen Species; C112230:SH3BP5 protein, human; C568472:Sab protein, mouse; D019308:Palmitic Acid; D048031:JNK Mitogen-Activated Protein Kinases
keywords: Apoptosis; Hepatocytes; Mitochondria; Palmitic acid; Reactive oxygen species