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

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-kappaB and a consequent proinflammatory cytokine production. The present study was aimed at investigating the expression and activity of NOD2, NF-kappaB, and of 2 proinflammatory cytokines, TNFalpha and IL-1beta, in mucosal biopsies of CD affected children compared to healthy controls.

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-kappaB binding activity was assessed by electromobility gel shift assay (EMSA).

NOD2 and IL-1beta mRNAs were upregulated in CD children. Protein levels of NOD2, TNFalpha, and nuclear NF-kappaB, as well as the binding activity of NF-kappaB to a consensus DNA sequence, were significantly increased in inflamed mucosa of patients as compared to controls. Moreover, NF-kappaB activity was strongly upregulated in patients also when bound to the NOD2 promoter site. No difference was seen between patients and controls when NF-kappaB binding activity was determined in the uninflamed tissue.

This study suggests that altered mechanisms regulating NOD2 induction, NF-kappaB activation and cytokine production may contribute to dysregulate the innate immune response underlying pediatric CD.