Author(s): Hisamatsu T, Suzuki M, Reinecker HC, Nadeau WJ, McCormick BA,
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Abstract BACKGROUND & AIMS: Mutations in the CARD15/NOD2 gene, a putative intracellular pattern recognition receptor, have been linked to the risk for Crohn's disease. Because intestinal epithelial cells play a role as the barrier to luminal microorganisms, we investigated the expression and function of CARD15/NOD2 in intestinal epithelial cells. METHODS: Expression of CARD15/NOD2 messenger RNA (mRNA) in intestinal epithelial cell lines and primary intestinal epithelial cells was assessed by reverse-transcription polymerase chain reaction (RT-PCR). Regulation of expression of CARD15/NOD2 by cytokines was determined by Northern blot using the SW480 cell line. Active CARD15/NOD2 protein in SW480 cells was assessed by the combination of immunoprecipitation and immunoblotting using anti-CARD15/NOD2 antisera. To identify the functional role of CARD15/NOD2 in intestinal epithelial cells, gentamicin protection assays of Salmonella typhimurium were performed using Caco2 cells stably transfected with either wild-type CARD15/NOD2 or the 3020insC mutant associated with Crohn's disease. RESULTS: CARD15/NOD2 mRNA was expressed in both intestinal epithelial cell lines and primary intestinal epithelial cells. CARD15/NOD2 mRNA and protein were up-regulated by tumor necrosis factor alpha (TNFalpha) in SW480 cells. The number of viable internalized S. typhimurium in Caco2 cells stably transfected with CARD15/NOD2 expression plasmid was lower than untransfected Caco2 cells or MOCK transfectant. In contrast, expression of a variant associated with Crohn's disease was unable to constrain bacterial survival. CONCLUSIONS: CARD15/NOD2 is expressed in intestinal epithelial cells and may serve as a key component of innate mucosal responses to luminal bacteria as an antibacterial factor. Failure in this activity may contribute to the development of Crohn's disease.
This article was published in Gastroenterology
and referenced in Journal of Bacteriology & Parasitology