Suppression by a sesquiterpene lactone from Carpesium divaricatum of inducible nitric oxide synthase by inhibiting nuclear factor-kappa B activation

Excessive nitric oxide (NO) produced by inducible NO synthase (iNOS) acts a s a causative regulator in various inflammatory disease states. Carpesium d ivaricatum has been used in Korean traditional herbal medicine for its anti pyretic, analgesic, vermifugic, and anti-inflammatory properties. We invest igated the molecular mechanism for the suppression of lipopolysaccharide/in terferon-gamma (LPS/IFN gamma)-induced NO production in RAW 264.7 macrophag es by the sesquiterpene lactone 2 beta ,5-epoxy-5,10-dihydroxy-6 alpha -ang eloyloxy-9 beta -isobutyloxy-germacran-8 alpha ,12-olide (C-l), which has b een identified recently as a new compound from C. divaricatum. C-1 decrease d NO production in LPS/IFN-gamma -stimulated RAW 264.7 cells in a concentra tion-dependent manner, with an IC50 of approximately 2.16 muM; however, it had no direct effect on the iNOS activity of fully IPS/IFN-gamma -stimulate d RAW 264.7 cells. Furthermore, treatment with C-1 led to a decrease in iNO S protein and mRNA. These effects appear to be due to inhibition of nuclear factor-kappaB (NF-kappaB) activation through a mechanism involving stabili zation of the NF-kappaB/inhibitor of the kappaB (I-kappaB) complex, since i nhibition of NF-kappaB DNA binding activity by C-1 was accompanied by a par allel reduction of nuclear translocation of subunit p65 of NF-kappaB and I- kappaB alpha degradation. Taken together, the results suggest that the abil ity of C-1 to inhibit iNOS gene expression may be responsible, in part, for its anti-inflammatory effects. (C) 2001 Elsevier Science Inc. All rights r eserved.