title: Enhanced translocation of bacteria across metabolically stressed epithelia is reduced by butyrate.
abstract: BACKGROUND
  The gut microflora in some patients with Crohn's disease can be reduced in numbers of butyrate-producing bacteria and this could result in metabolic stress in the colonocytes. Thus, we hypothesized that the short-chain fatty acid, butyrate, is important in the maintenance and regulation of the barrier function of the colonic epithelium.
  
  
  METHODS
  Confluent monolayers of the human colon-derived T84 or HT-29 epithelial cell lines were exposed to dinitrophenol (DNP (0.1 mM), uncouples oxidative phosphorylation) + Escherichia coli (strain HB101, 10(6) cfu) +/- butyrate (3-50 mM). Transepithelial resistance (TER), and bacterial internalization and translocation were assessed over a 24-hour period. Epithelial ultrastructure was assessed by transmission electron microscopy.
  
  
  RESULTS
  Epithelia under metabolic stress display decreased TER and increased numbers of pseudopodia that is consistent with increased internalization and translocation of the E. coli. Butyrate (but not acetate) significantly reduced the bacterial translocation across DNP-treated epithelia but did not ameliorate the drop in TER in the DNP+E. coli exposed monolayers. Inhibition of bacterial transcytosis across metabolically stressed epithelia was associated with reduced I-kappaB phosphorylation and hence NF-kappaB activation.
  
  
  CONCLUSIONS
  Reduced butyrate-producing bacteria could result in increased epithelial permeability particularly in the context of concomitant exposure to another stimulus that reduces mitochondria function. We speculate that prebiotics, the substrate for butyrate synthesis, is a valuable prophylaxis in the regulation of epithelial permeability and could be of benefit in preventing relapses in IBD.
authors.affiliation: Gastrointestinal Research Group, Department of Physiology & Pharmacology, Calvin, Phoebe and Joan Snyder Institute of Infection, Inflammation and Immunology, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Kimberley
authors.initials: K
authors.lastname: Lewis
authors.forename: Femke
authors.initials: F
authors.lastname: Lutgendorff
authors.forename: Van
authors.initials: V
authors.lastname: Phan
authors.forename: Johan D
authors.initials: JD
authors.lastname: Söderholm
authors.forename: Philip M
authors.initials: PM
authors.lastname: Sherman
authors.forename: Derek M
authors.initials: DM
authors.lastname: McKay
mesh_terms: D018988:Bacterial Translocation / Q000187:drug effects*; D002087:Butyrates / Q000494:pharmacology*; D002460:Cell Line; D002463:Cell Membrane Permeability; D003106:Colon / Q000166:cytology; D004140:Dinitrophenols / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000502:physiology*; D005947:Glucose / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007413:Intestinal Mucosa / Q000378:metabolism / Q000382:microbiology*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D016328:NF-kappa B / Q000378:metabolism; D010766:Phosphorylation; D012486:Salmonella typhimurium / Q000502:physiology*; D013312:Stress, Physiological
chemical_list: D002087:Butyrates; D004140:Dinitrophenols; D016328:NF-kappa B; D005947:Glucose