title: Critical role of myeloid differentiation factor 88 in necrotizing enterocolitis.
abstract: BACKGROUND
  The importance of toll-like receptor 4 in necrotizing enterocolitis (NEC) has been intensively studied, but its downstream signaling and the potential regulatory mechanisms remain unidentified. Our study focused on the role of myeloid differentiation factor 88 (MyD88), the first downstream adaptor of toll-like receptor 4 inflammatory and apoptotic signaling in the pathogenesis of NEC.
  
  
  METHODS
  MyD88 knockout (MyD88(-/-)-Ko) mice and lentivirus-mediated stable MyD88-knockdown cell line (IEC-6) were used. NEC was induced by formula gavage, cold, hypoxia, combined with lipopolysaccharide (LPS) in vivo, or LPS stimulation in vitro. NEC was evaluated by histology and multiple inflammatory cytokines. Enterocyte apoptosis was evaluated by terminal-deoxynucleoitidyl transferase-mediated nick end labeling (TUNEL) or Annexin analysis. Inflammatory or apoptotic molecules including NF-κB, Toll/IL-1R domain-containing adaptor-inducing IFN-β, interferon regulatory factor 3, Bax, Bcl-2, and caspases were examined by quantitative real-time PCR (qRT-PCR).
  
  
  RESULTS
  In the MyD88-Ko group, NEC severity and intestinal enterocyte apoptosis rate were reduced, the expression of NF-κB, caspases, and Bax, were all downregulated, while Toll/IL-1R domain-containing adaptor-inducing IFN-β and were upregulated, and antiapoptotic gene Bcl-2 remained stable. Cytokine levels of interleukin (IL)-6, IL-1β, and tumor necrosis factor-α (TNF-α) were also all decreased.
  
  
  CONCLUSIONS
  MyD88-dependent signaling is the prevailing inflammatory and apoptotic signaling in toll-like receptor 4 downstream signaling; MyD88-Ko resulted in reduced inflammatory severity and apoptosis, though MyD88-independent signaling can also be activated, but is of less dominant for the development of NEC.
authors.affiliation: 1] Department of Pediatric Surgery, West China Hospital, Sichuan University, Chengdu, China [2] Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Guozhu
authors.initials: G
authors.lastname: Yang
authors.affiliation: 1] Department of Pediatric Surgery, West China Hospital, Sichuan University, Chengdu, China [2] Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Pingqian
authors.initials: P
authors.lastname: Bao
authors.affiliation: 1] Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China [2] Department of Gastrointestinal Surgery, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Lie
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Zhaoying
authors.initials: Z
authors.lastname: Lyu
authors.affiliation: Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhou
authors.affiliation: Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Keling
authors.initials: K
authors.lastname: Chen
authors.affiliation: 1] Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China [2] Department of Gastrointestinal Surgery, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Su
authors.initials: S
authors.lastname: Peng
authors.affiliation: 1] Department of Pediatric Surgery, West China Hospital, Sichuan University, Chengdu, China [2] Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: 1] Department of Pediatric Surgery, West China Hospital, Sichuan University, Chengdu, China [2] Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Longpei
authors.initials: L
authors.lastname: Yao
authors.affiliation: 1] Department of Pediatric Surgery, West China Hospital, Sichuan University, Chengdu, China [2] Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: 1] Department of Pediatric Surgery, West China Hospital, Sichuan University, Chengdu, China [2] Institute of Digestive Surgery, State Key Laboratory of Biotherapy, West China Hospital, Sichuan University, Chengdu, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Li
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism; D020345:Enterocolitis, Necrotizing / Q000378:metabolism / Q000503:physiopathology*; D020895:Enterocytes / Q000473:pathology; D020287:In Situ Nick-End Labeling; D008070:Lipopolysaccharides; D051379:Mice; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D051197:Toll-Like Receptor 4 / Q000378:metabolism
chemical_list: D016207:Cytokines; D008070:Lipopolysaccharides; D053594:Myeloid Differentiation Factor 88; D051197:Toll-Like Receptor 4