Eupatolide inhibits lipopolysaccharide-induced COX-2 and iNOS expression in RAW264.7 cells by inducing proteasomal degradation of TRAF6.
Inula britannica is a traditional medicinal plant used to treat bronchitis, digestive disorders, and inflammation in Eastern Asia. Here, we identified eupatolide, a sesquiterpene lactone from I. britannica, as an inhibitor of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression. Eupatolide inhibited the production of nitric oxide (NO) and prostaglandin E(2) (PGE(2)) as well as iNOS and COX-2 protein expression in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Eupatolide dose-dependently decreased the mRNA levels and the promoter activities of COX-2 and iNOS in LPS-stimulated RAW264.7 cells. Moreover, eupatolide significantly suppressed the LPS-induced expression of nuclear factor-kappa B (NF-kappaB) and activator protein-1 (AP-1) reporter genes. Pretreatment of eupatolide inhibited LPS-induced phosphorylation and degradation of I kappaB alpha, and phosphorylation of RelA/p65 on Ser-536 as well as the activation of mitogen-activated protein kinases (MAPKs) and Akt in LPS-stimulated RAW264.7 cells. Eupatolide induced proteasomal degradation of tumor necrosis factor receptor-associated factor-6 (TRAF6), and subsequently inhibited LPS-induced TRAF6 polyubiquitination. These results suggest that eupatolide blocks LPS-induced COX-2 and iNOS expression at the transcriptional level through inhibiting the signaling pathways such as NF-kappaB and MAPKs via proteasomal degradation of TRAF6. Taken together, eupatolide may be a novel anti-inflammatory agent that induces proteasomal degradation of TRAF6, and a valuable compound for modulating inflammatory conditions.
Lee
Jongkyu
J
Department of Biochemistry, College of Natural Sciences, Kangwon National University, Chuncheon 200-701, Republic of Korea.
Tae
Nara
N
Lee
Jung Joon
JJ
Kim
Taeho
T
Lee
Jeong-Hyung
JH
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D001688:Biological Products / Q000494:pharmacology; D002460:Cell Line; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D052246:Cyclooxygenase 2 Inhibitors / Q000494:pharmacology; D015232:Dinoprostone / Q000096:biosynthesis; D015536:Down-Regulation / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D020935:MAP Kinase Signaling System / Q000187:drug effects; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D012717:Sesquiterpenes / Q000494:pharmacology*; D048029:TNF Receptor-Associated Factor 6 / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects; D054875:Ubiquitination / Q000187:drug effects
D000893:Anti-Inflammatory Agents; D001688:Biological Products; D052246:Cyclooxygenase 2 Inhibitors; D008070:Lipopolysaccharides; D016328:NF-kappa B; D012717:Sesquiterpenes; D048029:TNF Receptor-Associated Factor 6; D009569:Nitric Oxide; C001200:eupatolide; D052247:Nitric Oxide Synthase Type II; D051546:Cyclooxygenase 2; D020928:Mitogen-Activated Protein Kinases; D046988:Proteasome Endopeptidase Complex; D015232:Dinoprostone