Inhibitory effects of cynaropicrin and related sesquiterpene lactones from leaves of artichoke (Cynara scolymus L.) on induction of iNOS in RAW264.7 cells and its high-affinity proteins

Abstract

The methanolic extract of the leaves of artichoke (Cynara scolymus L.) was found to inhibit nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Among the constituents of the extract, six sesquiterpene lactones (cynaropicrin, grosheimin, 11 beta,13-dihydrocynaropicrin, 3 beta-hydroxy-8 alpha-[(S)-3-hydroxy-2-methylpropionyloxy]guaia-4(15),10(14),11(13)-trien-1 alpha,5 alpha,6 beta H-12,6-olide, 3 beta-hydroxy-8 alpha-[2-methoxymethyl-2-propenoyloxy]guaia-4(15),10(14),11(13)-trien-1 alpha,5 alpha,6 beta H-12,6-olide, and deacylcynaropicrin) inhibited NO production and/or inducible nitric oxide synthase (iNOS) induction. The acyl group having an alpha,beta-unsaturated carbonyl group at the 8-position and the alpha-methylene-gamma-butyrolactone moiety were important for the strong inhibitory activity. Our results suggested that these sesquiterpene lactones inhibited the LPS-induced iNOS expression via the suppression of the JAK-STAT signaling pathway in addition to the kappa NF-kappa B signaling pathway. With regard to the target molecules of the sesquiterpene lactones, high-affinity proteins of cynaropicrin were purified from the cell extract. ATP/ADP translocase 2 and tubulin were identified and suggested to be involved in the cytotoxic effects of cynaropicrin, although the target molecules for the inhibition of iNOS expression were not clarified.