Suppressive effect of an isoflavone fraction on tumor necrosis factor-α-induced interleukin-8 production in human intestinal epithelial Caco-2 cells

Abstract

This study demonstrates the effect of soybean components on the tumor necrosis factor-α (TNF-α)-induced production of interleukin-8 (IL-8), one of the major inflammatory chemokines, in intestinal epithelial-like Caco-2 cells. Among the soybean components, an isoflavone fraction (LFF) suppressed the TNF-α-induced LL-8 secretion by Caco-2 cells in a dose-dependent manner, whereas a soyasaponin fraction and soypeptide fraction had no significant effect on TNF-α-induced IL-8 secretion. The LL-8 secretion induced by hydrogen peroxide and by LL-1β was not suppressed by LFF, suggesting that the inhibitory effect of isoflavone was specific for the TNF-α-induced regulation of IL-8. The increased expression of IL-8 mRNA by TNF-α was almost completely suppressed by IFF. Furthermore, the transcriptional activity of the human LL-8 promoter was increased by the TNF-α treatment, and IFF significantly suppressed the LL-8 promoter activity. These results indicate that IFF suppressed TNF-α-induced LL-8 production at the transcriptional level in human intestinal Caco-2 cells, suggesting IFF of soybean as a promising food component for preventing intestinal inflammation such as inflammatory bowel disease.