Differential Regulation of Extracellular Signal-Regulated Kinase and Nuclear Factor-κB Signal Transduction Pathways by Hydrogen Peroxide and Tumor Necrosis Factor

Reactive oxygen metabolites are increasingly recognized for their ability to stimulate signal transduction pathways. This is important because these oxidants are frequently generated at sites of inflammation. However, little is known about the manner in which reactive oxygen species may selectively stimulate distinct signaling pathways. We have examined this question by stimulating mesothelial cells with hydrogen peroxide (H2O2) as a model oxidant stimulus. The response to H2O2was examined by measuring the activation of the extracellular signal-regulated kinase (ERK1/2) and the nuclear factor-κB (NF-κB) signal transduction pathways. We found that H2O2stimulated activity of the ERK1/2 pathway in a dose- and time-dependent manner. The ability of H2O2to activate ERK1/2 was similar to that found with tumor necrosis factor (TNF) stimulation. The oxidant effect was inhibited by various reactive oxygen scavengers. An inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase, the upstream kinase that activates ERK1/2, inhibited the oxidant effect. The superoxide anion (O2−) also stimulated ERK1/2 activity. In contrast, H2O2did not stimulate proteolysis of IκB-α and induced only a small degree of NF-κB nuclear translocation. Stimulation of the cells with O2−also induced a minimal degree of NF-κB activation. TNF was a potent stimulus for IκB-α proteolysis and NF-κB activation, demonstrating that the cells did have a functional NF-κB pathway. These results suggest that oxidants may selectively stimulate certain pathways, thereby preserving some specificity of the signaling process. Furthermore, different cell types and distinct signaling pathways within cells may demonstrate unique profiles in the manner in which they respond to oxidant stimulation.