Background: Interleukin (IL)-22 is a recently identified cytokine that is suggested to play pivotal roles in various inflammatory diseases. Although the IL-22 receptor 1 (IL-22R1) is restrictively expressed in epithelial cells in the colon, the role of IL-22 in colonic diseases still remains unclear. In this study microarray analyses revealed that deleted in malignant brain tumors 1 (DMBT1) is a novel upregulated gene in IL-22-stimulated colon cancer cells. Therefore, we investigated the involvement of DMBT1 and IL-22 in ulcerative colitis (UC) tissues and examined the mechanism regulating the expression of DMBT1 in response to IL-22 stimulation.
Methods: Changes of gene expression in IL-22-stimulated SW403 cells were investigated by microarray analyses. The effects of IL-22 on DMBT1 expression were examined in SW403 cells using a small interfering RNA (si)RNA for STAT3 or inhibitors for MEK, PI3K, and nuclear factor kappa B (NF-κB). The element responsible for IL-22-induced DMBT1 promoter activation was determined by a promoter deletion and electrophoretic mobility shift assay (EMSA). Expression of IL-22, IL-22R1, and DMBT1 in UC tissues was analyzed by real-time reverse-transcription polymerase chain reaction (RT-PCR) and immunohistochemistry.
Results: IL-22 treatment enhanced the expression of DMBT1 through STAT3 tyrosine phosphorylation and NF-κB activation in colon cancer cells. The IL-22-responsive element was located between -187 and -179 in the DMBT1 promoter region. In the UC mucosa the levels of DMBT1 and IL-22 mRNA expression were significantly enhanced and positively correlated, the numbers of IL-22-positive lymphocytes were increased, and the expression of IL-22R1 and DMBT1 was enhanced in the inflamed epithelium.
Conclusions: The IL-22/DMBT1 axis may play a pivotal role in the pathophysiology of UC.
Copyright © 2010 Crohn's & Colitis Foundation of America, Inc.