Interleukin (IL)-8 plays a central role in the initiation and maintenance of inflammatory responses in the inflammatory bowel disease. The proinflammatory cytokine-mediated production of IL-8 requires activation of various kinases, which leads to the IκB degradation and NF-κB activation. We investigated the role of 18β-glycyrrhetinic acid (GA), a saponin isolated from licorice roots, on TNF-α-induced IL-8 production in human colonic epithelial cells. HT29 cells were stimulated with TNF-α in the presence or absence of GA (1, 5 or 10 µM). IL-8 production was measured by enzyme-linked immunosorbent assay (ELISA) and reverse transcriptase-polymerase chain reaction analysis, and the mitogen-activated protein kinases (MAPKs) activation and IκBα degradation were determined by Western blot analysis. GA suppressed TNF-α-induced IL-8 production in a concentration-dependent manner. In addition, GA inhibited TNF-α-induced phosphorylation of p38 MAPK and extracellular-regulated kinases (ERK), IκBα degradation, and NF-κB activation. These results suggest that GA has the inhibitory effects on TNF-α-induced IL-8 production in the intestinal epithelial cells through blockade in the phosphorylation of MAPKs, following IκBα degradation and NF-κB activation.

Related Articles