Specific immunomodulatory and secretory activities of stevioside and steviol in intestinal cells

Abstract

Stevioside, isolated from Stevia rebaudiana, is a commercial sweetener. It was previously demonstrated that stevioside attenuates NF-κB-dependent TNF-α and IL-1β synthesis in LPS-stimulated monocytes. The present study examined the effects of stevioside and its metabolite, steviol, on human colon carcinoma cell lines. High concentrations of stevioside (2-5 mM) and steviol (0.2-0.8 mM) decreased cell viability in T84, Caco-2, and HT29 cells. Stevioside (2 mM) potentiated TNF-α-mediated IL-8 release in T84 cells. However, steviol (0.01-0.2 mM) significantly suppressed TNF-α-induced IL-8 release in all three cell lines. In T84 cells, steviol attenuated TNF-α-stimulated IκB → NF-κB signaling. Chloride transport was stimulated by steviol (0.1 mM) > stevioside (1 mM) at 30 min. Two biological effects of steviol in the colon are demonstrated for the first time: stimulation of Cl- secretion and attenuation of TNF-α-stimulated IL-8 production. The immunomodulatory effects of steviol appear to involve NF-κB signaling. In contrast, at nontoxic concentrations stevioside affects only Cl- secretion. © 2008 American Chemical Society.