title: Four types of Bifidobacteria trigger autophagy response in intestinal epithelial cells.
abstract: OBJECTIVE
  To investigate the influence of gut microbiota on autophagy activation in intestinal epithelial cells (IEC) and to evaluate the IEC autophagy response to different types of Bifidobacteria.
  
  
  METHODS
  IEC-18 cells were treated with lipopolysaccharide (LPS) derived from enteropathogenic Escherichia coli (EPEC) O127:B8 and culture medium supernatants of four types of Bifidobacteria. Transepithelial electrical resistance (TEER) was measured using an epithelial voltohmmeter. Autophagy was determined by transmission electron microscopy (TEM), the ratio of LC3-II to LC3-I and the persistence of both green fluorescent protein (GFP) and mCherry signals using a tandem mCherry-GFP-LC3 construct. The expression of Atg12-Atg5-Atg16 complex was measured by quantitative real-time polymerase chain reaction.
  
  
  RESULTS
  EPEC-LPS significantly diminished the TEER of IEC compared with untreated controls by 45-55%. This reduction was not observed after treated with Bifidobacteria at all time points. Bifidobacteria could initiate the activation of autophagy in IEC, based on both the ratio of LC3-II to LC3-I and TEM. There was no difference in the influence of the four types of Bifidobacteria on the autophagy response. Compared with Bifidobacteria, IEC reacted to EPEC-LPS much more intensively by autophagy accumulation. More mCherry(+) LC3 autophagic puncta and increased expressions of autophagy genes Atg5, Atg12 and Atg16 could be detected after being treated with Bifidobacteria and EPEC-LPS.
  
  
  CONCLUSIONS
  Bifidobacteria initiate autophagy activation in IEC. The Atg12-Atg5-Atg16 multimeric complex might participate in the activation of Bifidobacteria-induced cell autophagy.
authors.affiliation: Division of Gastroenterology, Union Hospital, Wuhan, Hubei Province, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Lin
authors.forename: Ye
authors.initials: Y
authors.lastname: Jiang
authors.forename: Xin Yan
authors.initials: XY
authors.lastname: Zhao
authors.forename: Yang
authors.initials: Y
authors.lastname: Guan
authors.forename: Wei
authors.initials: W
authors.lastname: Qian
authors.forename: Xiao Chao
authors.initials: XC
authors.lastname: Fu
authors.forename: Hun Yu
authors.initials: HY
authors.lastname: Ren
authors.forename: Xiao Hua
authors.initials: XH
authors.lastname: Hou
mesh_terms: D000818:Animals; D001343:Autophagy; D000071187:Autophagy-Related Protein 5; D001644:Bifidobacterium / Q000235:genetics / Q000502:physiology*; D002460:Cell Line; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology; D004926:Escherichia coli / Q000502:physiology; D007413:Intestinal Mucosa / Q000378:metabolism / Q000382:microbiology*; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism; D019936:Probiotics; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D051381:Rats
chemical_list: D000071187:Autophagy-Related Protein 5; D008869:Microtubule-Associated Proteins; D011506:Proteins; C545865:Atg5 protein, rat; C526109:Anxa3 protein, rat
keywords: autophagy; inflammatory bowel diseases; intestinal epithelial cell; probiotics