Oxidant-regulation of Gene Expression in the Chronically Inflamed Intestine

Abstract

It is becoming increasingly apparent that the chronic gut inflammation observed in the idiopathic inflammatory bowel diseases (e.g. ulcerative colitis, Crohn's disease) is associated with enhanced production of leukocyte-derived oxidants. Oxidants such as hydrogen peroxide are known to activate certain transcription factors such as nuclear transcription factor κ beta. Nuclear transcription factor kB (NF-κB) is a ubiquitous transcription factor and pleiotropic regulator of numerous genes involved in the immune and inflammatory responses. This transcription factor is activated via the selective phosphorylation, ubiquination and degradation of its inhibitor protein I-kB thereby allowing translocation of NF-κB into the nucleus where it upregulates the transcription of a variety of adhesion molecules (e.g. ICAM-1, VCAM-1), cytokines (TNF, IL-1, IL-6) and enzymes (iNOS). The proteolytic degradation of the post-translationally modified I-κB is known to be mediated by the 26S proteasome complex. Based upon work from our laboratory, we propose that inhibition of NF-κB activation produces significant anti-inflammatory activity which may be mediated by the inhibition of transcription of certain pro-inflammatory mediators and adhesion molecules.