The naturally occurring flavolignan, deoxypodophyllotoxin, inhibits lipopolysaccharide-induced iNOS expression through the NF-kappaB activation in RAW264.7 macrophage cells.

Deoxypodophyllotoxin (DPT), a naturally occurring flavolignan with anti-inflammatory activity, was isolated from Anthriscus sylvestris HOFFM., and we examined its effects on the expression of inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-stimulated, murine macrophage-like RAW264.7 cells. Western blot analysis performed with specific anti-iNOS antibodies showed that a decrease in nitric oxide (NO) was accompanied by a decrease in the iNOS protein level. To clarify the mechanistic basis for DPT's ability to inhibit iNOS induction, we examined the effect of DPT on nuclear factor (NF)-kappaB transcriptional activity and DNA binding activity. DPT potently suppressed both reporter gene activity and DNA binding activity. These findings suggest that DPT in RAW264.7 cells abolished LPS-induced iNOS expression by inhibiting the transcription factor, NF-kappaB.