Constitutive expression of IL-18 and IL-18R in differentiated IEC-6 cells: Effect of TNF-α and IFN-Î3 treatment

The multifunctional cytokine interleukin-18 (IL-18) is an important mediator in intestinal inflammatory processes. The aim of this study was to evaluate the constitutive expression of IL-18 and its receptors (IL-18R and IL-18R ) in intestinal epithelial cells (IEC) stimulated by tumor necrosis factor(TNF) and interferon(IFN). In addition, cellular proliferation and evaluation of brush border enzymes as differentiation markers were studied. Nontransformed rat intestinal epithelial IEC-6 cells were grown on an extracellular matrix (ECM) in medium with or without TNF, IFN, or a combination of both. Gene expression of IL18, its receptors and apoptotic markers was evaluated using real-time PCR. Expression of IL-18R protein was demonstrated by flow cytometry and Western blot. Enzymatic activities of brush border enzymes and caspase-1 were determined. The constitutive expression of IL-18, IL-18R and IL-18R mRNAs and proteins were detected in IEC-6 cells. The biologically active form of IL-18 was released in response to TNFand IFNtreatment. Exogenous IL-18 had no effect on cellular proliferation, brush border enzyme activities, and gene expression of apoptotic markers. However, the addition of IL-18 stimulated production and release of the chemokine IL-8. These data suggest that IEC-6 cells may be not only a source of IL-18 but also a target for its action.