Modulation of NF-κB-Dependent Gene Expression by H2O2: A Major Role for a Simple Chemical Process in a Complex Biological Response

We recently observed that H2O2 regulates inflammation via upexpression of a few NF-kappa B-dependent genes, while leaving expression of most NF-kappa B-dependent genes unaltered. Here we test the hypothesis that this differential gene expression depends on the apparent affinity of kappa B sites in the gene-promoter regions toward NF-kappa B. Accordingly, cells were transfected with three reporter plasmids containing kappa B sequences with different affinities for NF-kappa B. It was observed that the lower the affinity, the higher the range of TNF-alpha concentrations where H2O2 upregulated gene expression. Mathematical models reproduced the key experimental observations indicating that H2O2 upregulation ceased when NF-kappa B fully occupied the kappa B sites. In vivo, it is predicted that genes with high-affinity sites remain insensitive to H2O2, whereas genes with lower-affinity sites are upregulated by H2O2. In conclusion, a simple chemical mechanism is at the root of a complex biologic process such as differential gene expression caused by H2O2. Antioxid. Redox Signal. 11, 2043-2053.