Anti-inflammatory effects of saponins derived from the roots of Platycodon grandiflorus in lipopolysaccharide-stimulated BV2 microglial cells

Abstract

Radix platycodi is the root of Platycodon grandiflorus A. DC, which has been widely used as a food material and for the treatment of a number of chronic inflammatory diseases in traditional oriental medicine. In this study, the anti‑inflammatory effects of the saponins isolated from radix platycodi (PGS) on the production of inflammatory mediators and cytokines in lipopolysaccharide (LPS)-stimulated BV2 murine microglial cells were examined. We also investigated the effects of PGS on LPS‑induced nuclear factor‑κB (NF-κB) activation and phosphoinositide 3-kinase (PI3K)/AKT and mitogen-activated protein kinase (MAPK) signaling pathways. Following stimulation with LPS, elevated nitric oxide (NO), prostaglandin E2 (PGE2) and pro-inflammatory cytokine production was detected in the BV2 microglial cells. However, PGS significantly inhibited the excessive production of NO, PGE2 and pro‑inflammatory cytokines, including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in a concentration-dependent manner without causing any cytotoxic effects. In addition, PGS suppressed NF-κB translocation and inhibited the LPS-induced phosphorylation of AKT and MAPKs. Our results indicate that the inhibitory effect of PGS on LPS-stimulated inflammatory response in BV2 microglial cells is associated with the suppression of NF-κB activation and the PI3K/AKT and MAPK signaling pathways. Therefore, these findings suggest that PGS may be useful in the treatment of neurodegenerative diseases by inhibiting inflammatory responses in activated microglial cells.