| Abstract |
Hydrogen peroxide (H2O2) at moderate steady-state concentrations synergizes with INF-alpha, leading to increased nuclear levels of NF-kappa B p65 subunit and to a cell-type specific up-regulation of a limited number of NF-kappa B-dependent genes. Here, we address how H2O2 achieves this molecular specificity. HeLa and MCF-7 cells were exposed to steady-state H2O2 and/or TNF-alpha and levels of c-Rel, p65, I kappa B-alpha, I kappa B-beta and I kappa B-epsilon were determined. For an extracellular concentration of 25 mu M H2O2, the intracellular H2O2 concentration is 3.7 mu M and 12.5 mu M for respectively HeLa and MCF-7 cells. The higher cytosolic H2O2 concentration present in MCF-7 cells may be a contributing factor for the higher activation of NF-kappa B caused by H2O2 in this cell line, when compared to HeLa cells. In both cells lines, H2O2 precludes the recovery of TNF-alpha-dependent I kappa B-alpha degradation, which may explain the observed synergism between H2O2 and TNIF-tx concerning p65 nuclear translocation. In MCF-7 cells, H2O2, in the presence of TNIF-alpha, tripled the induction of c-Rd l triggered either by TN F-tx or H2O2. Conversely, in HeLa cells, H2O2 had a small antagonistic effect on INF-alpha-induced c-Rd l nuclear levels, concomitantly with a 50 \% induction of la-epsilon, the preferential inhibitor protein of c-Rd l dimers. The 6-fold higher c-RefilK13-K ratio found in MCI7 cells when compared with HeLa cells, may be a contributing factor for the cell-type dependent modulation of c-Rd l by H2O2. Our results suggest that H2O2 might have an important cell-type specific role in the regulation of c-Rdl-dependent processes, e.g. cancer or wound healing. (C) 2013 Published by Elsevier B.V. Open access under CC BY-NC-ND hems |
