title: Inflammation and Apoptosis: Dual Mediator Role for Toll-like Receptor 4 in the Development of Necrotizing Enterocolitis.
abstract: Necrotizing enterocolitis (NEC) is the leading cause of neonatal gastrointestinal mortality; effective interventions are lacking with limited understanding of the pathogenesis of NEC. The importance of Toll-like receptor 4 (TLR4) signaling in NEC is well documented; however, the potential mechanisms that regulate enterocyte inflammation and apoptosis remain unclear. The aim of this study was to characterize the role of TLR4-mediated inflammation and apoptosis in the development of NEC and to determine the major apoptotic pathways and regulators in the process.
  
  
  
  TLR4-deficient C57BL/10ScNJ mice and lentivirus-mediated stable TLR4-silent cell line (IEC-6) were used. NEC was induced by formula gavage, cold, hypoxia, combined with lipopolysaccharide in vivo or lipopolysaccharide stimulation in vitro. Enterocyte apoptosis was evaluated by TUNEL or Annexin analysis. The expression of TLR4, caspase3, caspase8, caspase9, Bip, Bax, Bcl-2, and RIP was detected by Western blot and immunofluorescence. Inflammatory factors such as tumor necrosis factor-α and interleukin-2 were examined by Luminex.
  
  
  
  Defect of TLR4 led to suppressed enterocytes apoptosis both in vitro and in vivo; the expression of caspase3, caspase8, Bip, and Bax was decreased; and caspase9 and Bcl-2 were increased. NEC severity was attenuated in TLR4-deficient mice compared with wild-type counterparts, and enterocytes apoptosis was correlated with NEC severity. RIP and cytokine level of tumor necrosis factor-α and interleukin-2 were also decreased.
  
  
  
  TLR4-induced inflammation and apoptosis play a critical role in the pathogenesis of NEC. TLR4 inhibition, combined with extrinsic (caspase8) and/or endoplasmic reticulum stress (Bip) apoptosis signaling blockade could serve as a potential effective treating strategy for NEC.
authors.affiliation: *Department of Pediatric Surgery, West China Hospital, Sichuan University, Chengdu, China; †Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China; and ‡Division of Oncology, Department of Clinical and Experimental Medicine Faculty of Health Sciences, Country Council of Östergötland, University of Linköping, Linköping, Sweden.
authors.forename: Yin
authors.initials: Y
authors.lastname: Zhou
authors.forename: Yibo
authors.initials: Y
authors.lastname: Li
authors.forename: Bin
authors.initials: B
authors.lastname: Zhou
authors.forename: Keling
authors.initials: K
authors.lastname: Chen
authors.forename: Zhaoying
authors.initials: Z
authors.lastname: Lyv
authors.forename: Dongmei
authors.initials: D
authors.lastname: Huang
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.forename: Zhicheng
authors.initials: Z
authors.lastname: Xu
authors.forename: Bo
authors.initials: B
authors.lastname: Xiang
authors.forename: Shuguang
authors.initials: S
authors.lastname: Jin
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Sun
authors.forename: Yuan
authors.initials: Y
authors.lastname: Li
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000276:immunology*; D002460:Cell Line; D020345:Enterocolitis, Necrotizing / Q000276:immunology*; D020895:Enterocytes / Q000276:immunology*; D007249:Inflammation / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D051197:Toll-Like Receptor 4 / Q000502:physiology*
chemical_list: C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4