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

Abstract

In this study we examined the effects of the inflammatory agent hydrogen peroxide (H2O2) on IgE-mediated mast cell responses. 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. 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. 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.