Effects of Platycodon grandiflorum on lipopolysaccharide-stimulated production of prostaglandin E ₂, nitric oxide, and interleukin-8 in mouse microglial BV2 cells

The roots of Platycodon grandiflorum, which belongs to the Campanulaceae family, have been used as a food material and as a traditional Oriental medicine. The effect of P. grandiflorum against lipopolysaccharide (LPS)-stimulated inflammation was investigated using 3-(4,5-dimethylthiazol-2- yl)-2,5-diphenyltetrazolium bromide assay, reverse transcription-polymerase chain reaction, prostaglandin E ₂ (PGE ₂) immunoassay, nitric oxide (NO) detection assay, and interleurkin-8 (IL-8) immunoassay on BV2 microglial cells. The aqueous extract of P. grandiflorum was shown to suppress PGE ₂ synthesis and NO production by inhibiting LPS-stimulated cyclooxygenase (COX)-2 activity and expression of inducible NO synthase (iNOS) mRNAs. In addition, the treatment with P. grandiflorum reduced the LPS-induced IL-8 release. These results suggest that P. grandiflorum inhibits PGE ₂ and NO production through its suppression of LPS-induced COX-2 and iNOS expression, and also reduces IL-8 secretion by microglial cells.