Chen Chien-Chih, Tsai Pei-Chung, Wei Bai-Luh, Chiou Wen-Fei
National Research Institute of Chinese Medicine, Taipei, Taiwan, ROC.
Eur J Pharmacol. 2008 Aug 20;590(1-3):430-6. doi: 10.1016/j.ejphar.2008.05.018. Epub 2008 May 24.
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.
8-异戊烯基山奈酚是一种从具有抗炎特性的中国草药苦参根中分离出的异戊烯基黄酮。然而，8-异戊烯基山奈酚本身是否具有抗炎活性仍不清楚。在本研究中，我们评估了8-异戊烯基山奈酚对脂多糖（LPS）诱导的RAW264.7巨噬细胞中一氧化氮（NO）产生的影响。8-异戊烯基山奈酚通过在蛋白质和mRNA水平上抑制诱导型NO合酶（iNOS）的表达，显著抑制了LPS诱导的NO产生，但未能影响硝普钠引发的NO产生、iNOS酶活性和细胞活力。对其机制的进一步研究表明，8-异戊烯基山奈酚抑制了LPS诱导的c-Jun磷酸化（激活蛋白-1（AP-1）的主要成分），但并未减弱IkB-α的降解或NF-κB的核转位。使用包括2'-氨基-3'-甲氧基黄酮（PD98059，MEK1/2抑制剂）、4-[5-（4-氟苯基）-2-[4-（甲基磺酰基）苯基]-1H-咪唑-4-基]吡啶（SB203580，p38激酶抑制剂）和蒽[1-9-cd]吡唑-6（2H）-酮（SP600125，c-Jun N端激酶抑制剂）的丝裂原活化蛋白激酶（MAPK）抑制剂进行的细胞信号分析表明，细胞外信号调节激酶1/2（ERK1/2）、p38和JNK均参与了LPS刺激的iNOS表达和NO产生，但8-异戊烯基山奈酚选择性地干扰了JNK的磷酸化。另一方面，在存在SP600125的情况下，LPS诱导的c-Jun磷酸化减弱。我们认为，干扰JNK介导的c-Jun磷酸化并因此阻断AP-1激活可能有助于8-异戊烯基山奈酚对iNOS的抑制作用。这些发现为8-异戊烯基山奈酚是一种减轻促炎性NO诱导的有效药物提供了首个分子基础。
