H2O2 impairs inflammatory mediator release from immunologically stimulatedRBL-2H3 cells through a redox-sensitive, calcium-dependent mechanism

Objectives: In this study we examined the effects of the inflammatory agent hydrogen peroxide (H2O2) on IgE-mediated mast cell responses. Materials and methods: Release of preformed granular mediators and newly sy nthesised TNF-alpha were measured in the RBL-2H3 mast cell line stimulated through IgE receptors (Fc epsilon RI) in the presence of varying concentrat ions 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 profou nd inhibition of the calcium response. Calcium fluxes from both intra- and extracellular sources were impaired. H2O2 action was dependent on the intra cellular redox state. Receptor activation directly stimulated intracellular H2O2 production. Conclusion: While in many cells H2O2 induces potent inflammatory responses we show that it can be an antiinflammatory agent by not only inhibiting the release of preformed mediators but also by affecting the secretion of newl y synthesized TNF-alpha. Inhibition is a consequence of the profound effect on intracellular calcium levels. The activation of an intracellular oxidat ive burst by Fc epsilon RI aggregation and the sensitivity of intracellular responses to redox-altering agents point to an important regulatory mechan ism of mast cell responses in inflammatory tissues.