title: Differential effects of varying concentrations of clostridium difficile toxin A on epithelial barrier function and expression of cytokines.
abstract: BACKGROUND
  Presentation after Clostridium difficile infection may depend on the level of epithelial exposure to toxins. We investigated epithelial barrier function and expression of interleukin (IL)-8 and transforming growth factor (TGF)-beta in response to varying concentrations of C. difficile toxin A.
  
  
  METHODS
  T84 cells were either preexposed or continuously exposed to C. difficile toxin A (0.01-1000 ng/mL). Barrier function was assessed by measurements of transepithelial electrical resistance.
  
  
  RESULTS
  Preexposure to < or =10 ng/mL toxin A led to an increase in the release of TGF-beta 1, but there was no change in the expression of IL-8. In contrast, after preexposure to >10 ng/mL toxin A, there was enhanced expression of IL-8, but release of TGF-beta 1 was similar to that in control monolayers. After preexposure to >10 ng/mL toxin A, there was complete and irreversible loss of electrical resistance. At lower concentrations, loss of resistance across monolayers was followed by recovery, which was enhanced by all 3 recombinant isoforms of TGF-beta. Pretreatment with recombinant isoforms of TGF-beta or coculture with TGF-beta 3-expressing colonic subepithelial myofibroblasts was also protective.
  
  
  CONCLUSIONS
  In C. difficile infection, the development and severity of colonic inflammation may depend on the exposure of intestinal epithelial cells to toxins and the expression of proinflammatory (IL-8) and protective (TGF-beta) factors.
authors.affiliation: Division of Gastroenterology, University Hospital, Queen's Medical Centre, Nottingham, United Kingdom.
authors.forename: Shawinder S
authors.initials: SS
authors.lastname: Johal
authors.forename: Katie
authors.initials: K
authors.lastname: Solomon
authors.forename: Sue
authors.initials: S
authors.lastname: Dodson
authors.forename: S Peter
authors.initials: SP
authors.lastname: Borriello
authors.forename: Yashwant R
authors.initials: YR
authors.lastname: Mahida
mesh_terms: D001427:Bacterial Toxins / Q000494:pharmacology*; D001681:Biological Assay; D016360:Clostridioides difficile / Q000737:chemistry*; D018920:Coculture Techniques; D017097:Electric Impedance; D004768:Enterotoxins / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D005347:Fibroblasts; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000378:metabolism; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D020033:Protein Isoforms; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000378:metabolism
chemical_list: D001427:Bacterial Toxins; D004768:Enterotoxins; D016209:Interleukin-8; D020033:Protein Isoforms; D016212:Transforming Growth Factor beta; C041348:tcdA protein, Clostridium difficile