title: Lipopolysaccharide preconditioning protects hepatocytes from ischemia/reperfusion injury (IRI) through inhibiting ATF4-CHOP pathway in mice.
abstract: BACKGROUND
  Low-dose lipopolysaccharide (LPS) preconditioning-induced liver protection has been demonstrated during ischemia-reperfusion injury (IRI) in several organs but has not been sufficiently elucidated underlying causal mechanism. This study investigated the role of low-dose LPS preconditioning on ATF4-CHOP pathway as well as the effects of the pathway on tissue injury and inflammation in a mouse model of liver partial-warm IRI.
  
  
  METHODS
  LPS (100 µg/kg/d) was injected intraperitoneally two days before ischemia. Hepatic injury was evaluated based on serum alanine aminotransferase levels, histopathology, and caspase-3 activity. The ATF4-CHOP pathway and its related apoptotic molecules were investigated after reperfusion. The role of LPS preconditioning on apoptosis and ATF4-CHOP pathway was examined in vitro. Moreover, the effects of the ATF4-CHOP pathway on apoptosis, Caspase-12, and Caspase-3 were determined with ATF4 small interfering RNA (siRNA). Inflammatory cytokine expression was also checked after reperfusion. Inflammatory cytokines and related signaling pathways were analyzed in vitro in macrophages treated by LPS preconditioning or ATF4 siRNA.
  
  
  RESULTS
  LPS preconditioning significantly attenuated liver injury after IRI. As demonstrated by in vitro experiments, LPS preconditioning significantly reduced the upregulation of the ATF4-CHOP pathway and inhibited Caspase-12 and Caspase-3 activation after IRI. Later experiments showed that ATF4 knockdown significantly suppressed CHOP, cleaved caspase-12 and caspase-3 expression, as well as inhibited hepatocellular apoptosis. In addition, in mice pretreated with LPS, TNF-α and IL-6 were inhibited after reperfusion, whereas IL-10 was upregulated. Similarly, low-dose LPS significantly inhibited TNF-α, IL-6, ATF4-CHOP pathway, NF-κB pathway, and ERK1/2 in high-dose LPS-stimulated macrophages, whereas IL-10 and cytokine signaling (SOCS)-3 suppressor were induced. Importantly, ATF4 siRNA is consistent with results of LPS preconditioning in macrophages.
  
  
  CONCLUSIONS
  This work is the first time to provide evidence for LPS preconditioning protects hepatocytes from IRI through inhibiting ATF4-CHOP pathway, which may be critical to reducing related apoptosis molecules and modulating innate inflammation.
authors.affiliation: Liver Transplantation Center, The First Affiliated Hospital of Nanjing Medical University, Key Laboratory of Living Donor Liver Transplantation of Ministry of Public Health, Nanjing, PR China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Rao
authors.forename: Jianjie
authors.initials: J
authors.lastname: Qin
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Qian
authors.forename: Ling
authors.initials: L
authors.lastname: Lu
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.forename: Zhengshan
authors.initials: Z
authors.lastname: Wu
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhai
authors.forename: Feng
authors.initials: F
authors.lastname: Zhang
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Li
authors.forename: Xuehao
authors.initials: X
authors.lastname: Wang
mesh_terms: D051701:Activating Transcription Factor 4 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053454:Caspase 12 / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D022781:Hepatocytes / Q000187:drug effects* / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D019194:Ischemic Preconditioning; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D015427:Reperfusion Injury / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D015398:Signal Transduction / Q000187:drug effects*; D051742:Transcription Factor CHOP / Q000378:metabolism*
chemical_list: C081452:Atf4 protein, mouse; C497250:Ddit3 protein, mouse; D008070:Lipopolysaccharides; D016328:NF-kappa B; D051701:Activating Transcription Factor 4; D051742:Transcription Factor CHOP; D006861:Hydrogen Peroxide; D020928:Mitogen-Activated Protein Kinases; D053454:Caspase 12; D053148:Caspase 3