A germacranolide sesquiterpene lactone suppressed inducible nitric oxide synthase by downregulating NF-κB activity.

A germacranolide sesquiterpene lactone, 2α,5-epoxy-5,10-dihydroxy-6α-angeloyloxy-9β-(3-methylbutyloxy)-germacran-8α,12-olide (EDAG), isolated from Carpesium triste var. manshuricum, showed inhibitory activity in the production of nitric oxide (NO) and the expression of inducible nitric oxide synthase (iNOS) mRNA and protein in LPS-activated macrophage cells. Molecular analysis reveals that these suppressive effects are correlated with the inhibition of NF-κB activation by EDAG. Immunoblotting showed that EDAG suppressed the LPS-induced degradation of I-κBα and decreased nuclear translocation of p65. Furthermore, EDAG showed reduced phosphorylation of ERK1/2 and p38 MAPK, whereas activation of JNK was not changed. These data suggest, at least in part, that EDAG utilizes the signal cascades of ERK1/2, p38 MAPK, and NF-κB for the suppression of iNOS gene expression.