title: H2O2 impairs inflammatory mediator release from immunologically stimulated RBL-2H3 cells through a redox-sensitive, calcium-dependent mechanism.
abstract: OBJECTIVE
  In this study we examined the effects of the inflammatory agent hydrogen peroxide (H2O2) on IgE-mediated mast cell responses.
  
  
  METHODS
  Release of preformed granular mediators and newly synthesised TNF-alpha were measured in the RBL-2H3 mast cell line stimulated through IgE receptors (FcepsilonRI) in the presence of varying concentrations of H2O2. The sensitivity of the intracellular calcium response to H2O2 exposure was investigated.
  
  
  RESULTS
  We found that H2O2 treatment impaired the release of preformed and newly synthesised mediators. H2O2 treatment simultaneously led to a profound inhibition of the calcium response. Calcium fluxes from both intra- and extracellular sources were impaired. H2O2 action was dependent on the intracellular redox state. Receptor activation directly stimulated intracellular H2O2 production.
  
  
  CONCLUSIONS
  While in many cells H2O2 induces potent inflammatory responses we show that it can be an anti-inflammatory agent by not only inhibiting the release of preformed mediators but also by affecting the secretion of newly synthesized TNF-alpha. Inhibition is a consequence of the profound effect on intracellular calcium levels. The activation of an intracellular oxidative burst by FcepsilonRI aggregation and the sensitivity of intracellular responses to redox-altering agents point to an important regulatory mechanism of mast cell responses in inflammatory tissues.
authors.affiliation: Unité Immuno-Allergie, Institut Pasteur, Paris, France. clobert@pasteur.fr
authors.forename: C
authors.initials: C
authors.lastname: Guerin-Marchand
authors.forename: H
authors.initials: H
authors.lastname: Sénéchal
authors.forename: C
authors.initials: C
authors.lastname: Pelletier
authors.forename: H
authors.initials: H
authors.lastname: Fohrer
authors.forename: R
authors.initials: R
authors.lastname: Olivier
authors.forename: B
authors.initials: B
authors.lastname: David
authors.forename: B
authors.initials: B
authors.lastname: Berthon
authors.forename: U
authors.initials: U
authors.lastname: Blank
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D000941:Antigens / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D002460:Cell Line; D003600:Cytosol / Q000378:metabolism; D003864:Depression, Chemical; D005434:Flow Cytometry; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D015151:Immunoblotting; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D018836:Inflammation Mediators / Q000378:metabolism*; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction; D011233:Precipitin Tests; D012333:RNA, Messenger / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D001619:beta-N-Acetylhexosaminidases / Q000378:metabolism
chemical_list: D000276:Adjuvants, Immunologic; D000941:Antigens; D007202:Indicators and Reagents; D018836:Inflammation Mediators; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D006861:Hydrogen Peroxide; D001619:beta-N-Acetylhexosaminidases; D002118:Calcium