Nuclear factor κB is activated in macrophages and epithelial cells of inflamed intestinal mucosa

Background & Aims: Transcription factors of the nuclear factor kappa B (NF-kappa B) family play an important role in the regulation of genes involved in inflammation. In inflammatory bowel diseases, proinflammatory cytokines known to be regulated by NF-kappa B are involved. The aim of this study was to investigate the role of NF-kappa B activation during mucosal inflammation in situ. Methods: A monoclonal antibody, alpha-p65mAb, was applied for immunofluorescence and immunohistochemical analysis that recognizes activated NF-kappa B. Electrophoretic mobility shift assay was used to directly demonstrate the presence of active DNA-binding NF-kappa B. Results: Using the alpha-p65mAb antibody, activated NF-kappa B could be found in biopsy specimens from inflamed mucosa but was almost absent in uninflamed mucosa. The number of cells showing NF-kappa B activation correlated with the degree of mucosal inflammation but was not significantly different between inflamed mucosa from patients with Crohn's disease, ulcerative colitis, and nonspecific colitis or diverticulitis. NF-kappa B activation was localized in macrophages and in epithelial cells as identified by double-labeling techniques. Electrophoretic mobility shift assay with isolated lamina propria mononuclear cells and epithelial cells confirmed these results. Conclusions: This study shows for the first time the activation of NF-kappa B during human mucosal inflammation in situ. In addition to macrophages, epithelial cells contained activated NF-kappa B, indicating an involvement in the inflammatory process.