Arctigenin, a phenylpropanoid dibenzylbutyrolactone lignan, inhibits MAP kinases and AP-1 activation via potent MKK inhibition: the role in TNF-alpha inhibition.
Arctigenin, naturally occurring in Bardanae fructus, Saussurea medusa, Arctium lappa L., Torreya nucifera and Ipomea cairica, is a phenylpropanoid dibenzylbutyrolactone lignan with antioxidant and anti-inflammatory activities. Previously, we showed that arctigenin potently inhibited the induction of nitric oxide synthase (iNOS) by lipopolysaccharide (LPS), which involved suppression of NF-kappaB activation. In the present study, we examined the effects of arctigenin on mitogen-activated protein (MAP) kinase activation in Raw264.7 cells and MAP kinase kinase (MKK) activity. The effect of arctigenin on activator protein-1 (AP-1) activation was also studied in association with tumor necrosis factor-alpha (TNF-alpha) expression. Immunoblot analysis showed that arctigenin inhibited phosphorylation of MAP kinases ERK1/2, p38 kinase and JNK and their activities in Raw264.7 cells treated with LPS. Arctigenin potently inhibited the activity of MKK1 in vitro with the IC(50) value of 1 nM. Gel shift and reporter gene analyses revealed that arctigenin inhibited LPS-inducible AP-1 binding to the AP-1 consensus oligonucleotide and AP-1-mediated reporter gene expression. In view of the potential role of AP-1 in the induction of TNF-alpha, we next examined the inhibitory effects of arctigenin on the expression of TNF-alpha. Arctigenin blocked TNF-alpha production and decreased the level of TNF-alpha mRNA in the cells exposed to LPS. These results showed that arctigenin inhibited activation of MAP kinases including ERK1/2, p38 kinase and JNK through the inhibition of MKK activities, leading to AP-1 inactivation, which might, at least in part, contribute to the inhibition of TNF-alpha production.
College of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul 151-742, South Korea.
Min Kyung
MK
Cho
Young Pyo
YP
Jang
Young Choong
YC
Kim
Sang Geon
SG
Kim
D000818:Animals; D002460:Cell Line; D005663:Furans / Q000494:pharmacology*; D015151:Immunoblotting; D017705:Lignans / Q000494:pharmacology*; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors*; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D018808:Transcription Factor AP-1 / Q000037:antagonists & inhibitors*; D014158:Transcription, Genetic; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000096:biosynthesis
D005663:Furans; D017705:Lignans; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C071942:arctigenin