Hydrogen peroxide modulates immunoglobulin expression by targeting the 3′Igh regulatory region through an NFκB-dependent mechanism

Abstract

Reactive oxygen species such as hydrogen peroxide (H2O2) appear to play a role in signal transduction in immune cells and have been shown to be synthesized upon antigen-mediated activation and to facilitate cellular activation in B- and T-cells. However, an effect of H2O2 on B-cell function (i.e. immunoglobulin (Ig) expression) has been less well-characterized. The effects of H2O2 exposure on lymphocytes may be partly mediated by oxidative modulation of the NFκB signal transduction pathway, which also plays a role in Ig heavy chain (Igh) gene expression. Igh transcription in B lymphocytes is an essential step in antibody production and is governed through a complex interaction of several regulatory elements, including the 3′Igh regulatory region (3′IghRR). Utilizing an in vitro mouse B-cell line model, this study demonstrates that exposure to low μM concentrations of H2O2 can enhance 3′IghRR-regulated transcriptional activity and Igh gene expression, while either higher concentrations of H2O2 or the expression of a degradation resistant inhibitory κB (IκBα super-repressor) can abrogate this effect. Furthermore, suppressive H2O2 concentrations increased protein levels of the p50 NFκB sub-unit, IκBα, and an IκBα immunoreactive band which was previously characterized as an IκBα cleavage product exhibiting stronger inhibitory function than native IκBα. Taken together, these observations suggest that exposure of B lymphocytes to H2O2 can alter Igh transcriptional activity and Ig expression in a complex biphasic manner which appears to be mediated by NFκB and altered 3′IghRR activity. These results may have significant implications to disease states previously associated with the 3′IghRR.