title: Streptococcus cristatus modulates the Fusobacterium nucleatum-induced epithelial interleukin-8 response through the nuclear factor-kappa B pathway.
abstract: OBJECTIVE
  We previously reported that the interleukin-8 (IL-8) response to Fusobacterum nucleatum was attenuated in the presence of Streptococcus cristatus. Here, we further examined the underlying mechanism(s) involved in the modulating effect of S. cristatus by looking specifically at its impact on the nuclear factor-kappa B (NF-κB) pathway under the toll-like receptor (TLR) signaling background.
  
  
  METHODS
  OKF6/TERT-2 and KB cells were co-cultured with F. nucleatum and S. cristatus, either alone or in combination. Secretion of IL-8 protein was measured by ELISA. The nuclear translocation of NF-κB was evaluated by confocal microscopy, while DNA-binding activity was quantified using TransAM™ ELISA kits. Western blot analysis was performed to determine whether the anti-inflammatory effect of S. cristatus is related to the modulation of the NF-κB inhibitory protein IκB-α.
  
  
  RESULTS
  Incubation with F. nucleatum significantly enhanced the nuclear translocation of NF-κB. Exposure to S. cristatus alone did not cause detectable NF-κB translocation and was able to inhibit the F. nucleatum-induced NF-κB nuclear translocation. The TransAM assay further confirmed that S. cristatus blocked the nuclear translocation of NF-κB in response to F. nucleatum stimulation. In contrast to the nearly complete degradation of IκB-α induced by F. nucleatum alone, the presence of S. cristatus stabilized IκB-α. Pre-incubation with TLR2 and TLR4 antibodies, however, did not affect the epithelial response to either species alone or in combination.
  
  
  CONCLUSIONS
  The mechanism by which S. cristatus attenuates F. nucleatum-induced proinflammatory responses in oral epithelial cells appears to involve blockade of NF-κB nuclear translocation at the level of IκB-α degradation.
authors.affiliation: Department of Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, USA.
authors.forename: G
authors.initials: G
authors.lastname: Zhang
authors.forename: R
authors.initials: R
authors.lastname: Chen
authors.forename: J D
authors.initials: JD
authors.lastname: Rudney
mesh_terms: D002461:Cell Line, Transformed; D004847:Epithelial Cells / Q000378:metabolism; D016967:Fusobacterium nucleatum / Q000502:physiology*; D054884:Host-Pathogen Interactions; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D016209:Interleukin-8 / Q000096:biosynthesis*; D007624:KB Cells; D056265:Microbial Interactions; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism; D021381:Protein Transport; D015398:Signal Transduction; D013291:Streptococcus / Q000502:physiology*; D051195:Toll-Like Receptor 2 / Q000276:immunology; D051197:Toll-Like Receptor 4 / Q000276:immunology
chemical_list: D020672:I-kappa B Proteins; D016209:Interleukin-8; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D000072000:NF-KappaB Inhibitor alpha