Constitutive Expression of IL-18 and IL-18R in Differentiated IEC-6 Cells: Effect of TNF-αand IFN-γTreatment

Abstract

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 IL-18, 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 proteinswere detected in IEC-6 cells. The biologically active form of IL-18 was released in response to TNF-␣ and IFN-␥ treatment. 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. 287

The probiotic Lactobacillus plantarum counteracts TNF-α-induced downregulation of SMCT1 expression and function

“…In parallel studies, we measured Na ϩ -coupled butyrate uptake and SMCT1 mRNA levels in IEC-6 cells in response to TNF-␣ treatments. Earlier studies have shown TNF-␣ effects on IEC-6 cells, indicating expression of TNF-␣ receptors in this cell line (4,23). Our results showed that TNF-␣ inhibited Na ϩ -coupled butyrate uptake in a dose-dependent manner (Fig.…”

Protective effect of Clostridium tyrobutyricum in acute dextran sodium sulphate-induced colitis: differential regulation of tumour necrosis factor-α and interleukin-18 in BALB/c and severe combined immunodeficiency mice

“…In BALB/c and C57BL/6 mice DSS-induced colitis induces increased expression of IL-18 in the colonic mucosa, where it polarizes CD4 + T cells toward T helper cell type 1 (Th1)-mediated immune response [35] and thus increased production of the proinflammatory cytokine interferon (IFN)-g. IFN-g stimulated secretion of IL-18 from enterocyte-like IEC-6 cells has been correlated with IFN-g-increased expression of caspase-1 activity [36], an enzyme required for cleavage of the precursor form of IL-18 into mature biologically active IL-18. Indeed, inhibition of caspase-1 by the specific inhibitor pralnacasan [26] attenuated DSS-induced colitis, this effect being mediated by suppression of proinflamatory IL-18 and IFN-g.…”

Interleukin-22 Induces Interleukin-18 Expression from Epithelial Cells during Intestinal Infection

“…Although activation of certain innate immune signaling receptors enhances IL-18 transcription in myeloid cells, IL-18 is generally considered to be constitutively expressed and stored as intracellular proIL-18 protein in most other cells (Kolinska et al, 2008;Nakanishi et al, 2001). Pro-inflammatory signals, through the activation of inflammasomes and caspases, trigger the proteolytical processing of proIL-18 to its active form, which is subsequently secreted by cells through a non-classical secretion pathway (Dinarello, 2009).…”

“…Although it does not play a dominant protective role in the lowdose model (Cai et al, 2000), IL-18 contributes to the development of small intestinal immunopathology after oral high-dose infection of T. gondii, partially through the induction of IFN-g production (Vossenkä mper et al, 2004). Previous studies suggest that Il18 mRNA as well as proIL-18 are constitutively produced by myeloid cells and intestinal epithelial cells (Kolinska et al, 2008). The generation of the active form of IL-18 requires inflammasome activation and caspase-mediated enzymatic cleavage (Gu et al, 1997).…”