Laxifolone A suppresses LPS/IFN-gamma-induced NO synthesis by attenuating NF-kappaB translocation: role of NF-kappaB p105 level.
Laxifolone A is a triterpene isolated from Euonymus laxiflorus Champ. Exposure of RAW264.7 macrophages to laxifolone A concentration-dependently suppressed lipopolysaccharide/interferon-gamma (LPS/IFN-gamma)-induced nitrite production (IC50 = 0.37 +/- 0.05 microM), inducible NO synthase (iNOS) protein, and iNOS mRNA expression. Translocation of nuclear factor-kappaB (NF-kappaB) into the nucleus with subsequent activation of iNOS gene transcription is essential in NO signaling. Western blot analysis indicated that the cytosolic NF-kappaB/p65 was obviously decreased after LPS/IFN-gamma stimulation for 30 min and this phenomenon could be reversed by laxifolone A. Similarly, a time-related NF-kappaB/p65 nuclear translocation induced by LPS/IFN-gamma was diminished in the presence of laxifolone A. However, laxifolone A failed to interfere in LPS/IFN-gamma-evoked IkappaB degradation. Our results also showed that LPS/IFN-gamma-stimulation resulted in the degradation of NF-kappaB p105, the NF-kappaB precursor, and laxifolone A treatment significantly counteracted this effect. Furthermore, laxifolone A itself was able to enhance NF-kappaB p105 protein expression. In summary, these results suggest that inhibition of NF-kappaB p105 degradation in cytoplasm may participate in the abrogation of LPS/IFN-gamma-induced NF-kappaB translocation and subsequent NO synthesis by laxifolone A.
Ko
Han-Chieh
HC
Division of Basic Chinese Medical Research, National Research Institute of Chinese Medicine, Taipei, Taiwan, ROC.
Kuo
Yao-Haur
YH
Wei
Bai-Luh
BL
Chiou
Wen-Fei
WF
D000818:Animals; D015153:Blotting, Western; D004305:Dose-Response Relationship, Drug; D029756:Euonymus; D020128:Inhibitory Concentration 50; D007371:Interferon-gamma; D008070:Lipopolysaccharides; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000235:genetics; D052247:Nitric Oxide Synthase Type II; D008517:Phytotherapy; D010936:Plant Extracts / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D018547:Plant Stems; D012333:RNA, Messenger / Q000032:analysis; D014315:Triterpenes / Q000008:administration & dosage / Q000494:pharmacology* / Q000627:therapeutic use
D008070:Lipopolysaccharides; D016328:NF-kappa B; D010936:Plant Extracts; D012333:RNA, Messenger; D014315:Triterpenes; C477581:laxifolone A; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse