8-Prenylkaempferol suppresses inducible nitric oxide synthase expression through interfering with JNK-mediated AP-1 pathway in murine macrophages.
8-Prenylkaempferol is a prenylflavonoid isolated from the roots of Sophora flavescens, a Chinese herb with anti-inflammatory properties. However whether 8-prenylkaempferol itself displayed an anti-inflammatory activity remained unclear. In this study, we evaluated the effect of 8-prenylkaempferol on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 macrophages. 8-Prenylkaempferol inhibited significantly LPS-induced NO production through suppressing inducible NO synthase (iNOS) expression at both protein and mRNA levels but failed to affect sodium nitroprusside-triggered NO production, iNOS enzyme activity, and cell viability. Further investigation of the mechanisms revealed that 8-prenylkaempferol inhibited LPS-induced c-Jun phosphorylation (a major component of activator protein-1, AP-1), but did not attenuate IkB-alpha degradation nor NF-kappaB nuclear translocation. Cellular signaling analysis using mitogen-activating protein kinase (MAPK) inhibitors including 2'-amino-3'-methoxyflavone (PD98059, MEK1/2 inhibitor), 4-[5-(4-fluorophenyl)-2-[4-(methylsulfonyl)phenyl]-1H-imidazol-4-yl]pyridine (SB203580, p38 kinase inhibitor) and anthra[1-9-cd]pyrazol-6(2H)-one (SP600125, c-Jun N-terminal kinase inhibitor) demonstrated that extracellular signal-regulated kinase1/2 (ERK1/2), p38 and JNK all participated in LPS-stimulated iNOS expression and NO production, but 8-prenylkaempferol interfered selectively with JNK phosphorylation. On the other hand, LPS-induced c-Jun phosphorylation was attenuated in the presence of SP600125. We suggested that interfering with JNK-mediated c-Jun phosphorylation and thus blocking AP-1 activation might contribute to the suppression effects of 8-prenylkaempferol on iNOS. These findings provided the first molecular basis that 8-prenylkaempferol is an effective agent for attenuating pro-inflammatory NO induction.
Chen
Chien-Chih
CC
National Research Institute of Chinese Medicine, Taipei, Taiwan, ROC.
Tsai
Pei-Chung
PC
Wei
Bai-Luh
BL
Chiou
Wen-Fei
WF
D000818:Animals; D002478:Cells, Cultured; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D020672:I-kappa B Proteins / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D044949:Kaempferols / Q000494:pharmacology*; D008070:Lipopolysaccharides / Q000494:pharmacology; D020935:MAP Kinase Signaling System; D008264:Macrophages / Q000201:enzymology; D051379:Mice; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors*; D010766:Phosphorylation; D021381:Protein Transport; D015398:Signal Transduction / Q000187:drug effects; D029909:Sophora / Q000737:chemistry*; D018808:Transcription Factor AP-1 / Q000502:physiology*
C532177:8-prenylkaempferol; D004365:Drugs, Chinese Herbal; D020672:I-kappa B Proteins; D044949:Kaempferols; D008070:Lipopolysaccharides; D016328:NF-kappa B; C000606205:Nfkbia protein, mouse; D018808:Transcription Factor AP-1; D000072000:NF-KappaB Inhibitor alpha; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D048031:JNK Mitogen-Activated Protein Kinases