Mucosal NOD2 expression and NF-κB activation in pediatric Crohn's disease

Background: Recent advances in the pathogenesis of Crohn's disease (CD) have suggested that an aberrant innate immune response initiates the cascade of events leading to T-cell activation and to disease development. NOD2 protein, which is mainly expressed by innate immunity cells, appears to play a key role against bacteria by triggering a host defense response through the activation of the transcriptor factor NF-κB and a consequent proinflammatory cytokine production. The present study was aimed at investigating the expression and activity of NOD2, NF-κB, and of 2 proinflammatory cytokines, TNFα and IL-1β, in mucosal biopsies of CD affected children compared to healthy controls. Methods: In all, 22 children with active CD and 10 matched controls were entered in the study. mRNA and protein expressions were detected using reverse-transcriptase polymerase chain reaction (RT-PCR) and Western blot; NF-κB binding activity was assessed by electromobility gel shift assay (EMSA). Results: NOD2 and IL-1β mRNAs were upregulated in CD children. Protein levels of NOD2, TNFα, and nuclear NF-κB, as well as the binding activity of NF-κB to a consensus DNA sequence, were significantly increased in inflamed mucosa of patients as compared to controls. Moreover, NF-κB activity was strongly upregulated in patients also when bound to the NOD2 promoter site. No difference was seen between patients and controls when NF-κB binding activity was determined in the uninflamed tissue. Conclusions: This study suggests that altered mechanisms regulating NOD2 induction, NF-κB activation and cytokine production may contribute to dysregulate the innate immune response underlying pediatric CD. Copyright © 2007 Crohn's & Colitis Foundation of America, Inc.