Anti-inflammation effect of rebaudioside a by inhibition of the mapk and NF-κB signal pathway in raw264.7 macrophage

Abstract

Rebaudioside A is a natural sweetener isolated from Stevia rebaudiana Bertoni, one of the glycosides based on steviol. Recent studies have shown that rebaudioside A inhibits the inflammatory response by inhibiting cytokines secretion such as interleukin-1α/1β in activated RAW264.7 mouse macrophage cells by LPS. However, the inhibitory mechanism of inflammation by rebaudioside A in the presence of LPS has not been fully elucidated. Therefore, in this study, we tried to investigate the anti-inflammatory activity of rebaudioside A at the protein level when RAW264.7 cells were stimulated by LPS. The inducible nitric oxide synthase protein expression level was reduced in the group treated with 250 μM rebaudioside A compared to the LPS-treated group. In addition, the mRNA expression level of NF-κB, which is a representative nuclear transcription factor by inflammatory signal, was also decreased as compared with that of LPS-treated group. In addition, NF-κB and inhibitor-κB (I-κB) complexes that are known to be dissociated by I-κB phosphorylation and ubiquitination were less phosphorylated than LPS treated group in the presence rebaudioside A. Finally, we could find that rebaudioside A was involved in the NF-κB pathway through reducing extracellular signal-regulated kinase1/2 phosphorylation in a concentration-dependent manner. These results suggest that rebaudioside A might suppress inflammatory reaction through MAPK and NF-κB regulation in LPS-stimulated RAW264.7.