NF-kappa B activation by oxidative stress and inflammation suppresses contractility in colonic circular smooth muscle cells.

Abstract

Transcription factor nuclear factor kappa B (NF-kappa B) plays a critical role in transcriptional changes in several diseases, including inflammation. The aim of this study was to investigate whether NF-kappa B is activated by inflammation and oxidative stress in colonic circular smooth muscle cells and whether that leads to suppression of their contractility. The experiments were performed on freshly dissociated single cells using electrophoretic mobility shift assay, Western immunoblotting, and immunofluorescence imaging. The NF-kappa B DNA binding was approximately 6-fold greater in cells from the inflamed colon vs. those from the normal colon. Supershift assay indicated that the antibodies to p65, p50, and c-Rel, but not that to p52, shifted the NF-kappa B band. Western immunoblotting and immunofluorescence imaging also demonstrated the presence of p65, p50, and c-Rel proteins in the cytoplasm and their translocation to the nucleus by H(2)O(2)-induced oxidative stress. H(2)O(2) treatment degraded I kappa B(beta), but not I kappa B(alpha), to translocate NF-kappa B to the nucleus. Hydrogen peroxide concentration and time dependently activated NF-kappa B DNA binding and suppressed cell contraction to acetylcholine. NF-kappa B inhibitors significantly inhibited these effects. Inhibition of NF-kappa B prior to and during inflammation in intact dogs also reversed the suppression of contractility. Transcription factor NF-kappa B is activated in colonic circular muscle cells by inflammation and oxidative stress. This activation of NF-kappa B mediates the suppression of cell contractility.