title: Hepatocyte autophagy is linked to C/EBP-homologous protein, Bcl2-interacting mediator of cell death, and BH3-interacting domain death agonist gene expression.
abstract: BACKGROUND
  Endoplasmic reticulum (ER) stress and autophagy each play important roles in hepatocyte cell injury. We hypothesized that gene expression of C/EBP-homologous protein (CHOP) and the BH3 proteins Bcl2-interacting mediator of cell death (BIM) and BH3-interacting domain death agonist (BID) are involved in a complex interplay that regulates ER stress-induced autophagy and cell death.
  
  
  METHODS
  Hepatocytes were cultured from lean Zucker rats. Confluent hepatocytes were incubated with single or combined small interfering RNA for CHOP, BIM, and/or BID for 24 h providing gene inhibition. Incubation with tunicamycin (TM) for another 24 h stimulated ER stress. Quantitative real-time polymerase chain reaction determined the expression levels of CHOP, BIM, and BID. Immunostaining with microtubule-associated protein 1 light chain 3 measured autophagy activity. Trypan blue exclusion determined the cell viability.
  
  
  RESULTS
  TM treatment increased the messenger RNA levels of CHOP and BIM but decreased the messenger RNA levels of BID. TM increased autophagy and decreased cell viability. Individual inhibition of CHOP, BIM, or BID protected against autophagy and cell death. However, simultaneous treatment with any combination of CHOP, BIM, and BID small interfering RNAs reduced autophagy activity but increased cell death independent of ER stress induction.
  
  
  CONCLUSIONS
  Autophagy in hepatocytes results from acute ER stress and involves interplay, at the gene expression level, of CHOP, BIM, and BID. Inhibition of any one of these individual genes during acute ER stress is protective against cell death. Conversely, inhibition of any two of the three genes results in increased nonautophagic cell death independent of ER stress induction. This study suggests interplay between CHOP, BIM, and BID expression that can be leveraged for protection against ER stress-related cell death. However, disruption of the CHOP/BH3 gene expression homeostasis is detrimental to cell survival independent of other cellular stress.
authors.affiliation: Department of Surgery, University of Mississippi Medical Center, Jackson, Mississippi.
authors.forename: Junlin
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Surgery, University of Mississippi Medical Center, Jackson, Mississippi.
authors.forename: Nitesh
authors.initials: N
authors.lastname: Singh
authors.affiliation: Department of Surgery, University of Mississippi Medical Center, Jackson, Mississippi.
authors.forename: Kendra S
authors.initials: KS
authors.lastname: Robinson-Taylor
authors.affiliation: Department of Surgery, University of Mississippi Medical Center, Jackson, Mississippi.
authors.forename: Wanda A
authors.initials: WA
authors.lastname: Dorsett-Martin
authors.affiliation: Department of Surgery, University of Mississippi Medical Center, Jackson, Mississippi.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Morris
authors.affiliation: Department of Surgery, University of Mississippi Medical Center, Jackson, Mississippi.
authors.forename: Truman M
authors.initials: TM
authors.lastname: Earl
authors.affiliation: Department of Surgery, University of Mississippi Medical Center, Jackson, Mississippi. Electronic address: cdanderson@umc.edu.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Anderson
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000502:physiology*; D001343:Autophagy / Q000502:physiology*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000235:genetics / Q000502:physiology*; D000072224:Bcl-2-Like Protein 11; D002478:Cells, Cultured; D059865:Endoplasmic Reticulum Stress; D005786:Gene Expression Regulation; D022781:Hepatocytes / Q000502:physiology*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D011924:Rats, Zucker; D051742:Transcription Factor CHOP / Q000235:genetics / Q000502:physiology*
chemical_list: D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; D000072224:Bcl-2-Like Protein 11; C000606778:Bcl2l11 protein, rat; C494816:Bid protein, rat; C497251:Ddit3 protein, rat; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D051742:Transcription Factor CHOP
keywords: Autophagy; BID; BIM; CHOP; Endoplasmic reticulum stress; Hepatocyte