Pan M H, Lin-Shiau S Y, Lin J K
Institute of Biochemistry, College of Medicine, National Taiwan University, Taipei, Taiwan.
Biochem Pharmacol. 2000 Dec 1;60(11):1665-76. doi: 10.1016/s0006-2952(00)00489-5.
Nitric oxide (NO) plays an important role in inflammation and in the multiple stages of carcinogenesis. In this study, we investigated the inhibitory effects of curcumin and its metabolites, tetrahydrocurcumin, hexahydrocurcumin, and octahydrocurcumin, on the induction of NO synthase (NOS) in RAW 264.7 cells activated with lipopolysaccharide (LPS). Western blotting and northern blotting analyses demonstrated that curcumin strongly reduced 130-kDa protein and 4.5-kb mRNA levels of iNOS in LPS-activated macrophages compared with its metabolites, tetrahydrocurcumin, hexahydrocurcumin, and octahydrocurcumin. Moreover, electrophoretic mobility shift assay (EMSA) experiments indicated that curcumin blocked the LPS-induced binding of nuclear factor-kappaB (NFkappaB), a transcription factor necessary for iNOS induction to its (32)P-labeled double-stranded oligonucleotide probe. The inhibition of NFkappaB activation occurred through the prevention of inhibitor kappaB (IkappaB) degradation. Transient transfection experiments also showed that curcumin inhibited NFkappaB-dependent transcriptional activity. Curcumin blocked the disappearance of inhibitory kappaBalpha (IkappaBalpha) and p65 from the cytosolic fraction, and inhibited the phosphorylation of IkappaBalpha. Furthermore, we showed that curcumin could inhibit the IkappaB kinase 1 (IKK1) and IkappaB kinase 2 (IKK2) activities induced by LPS, but tetrahydrocurcumin, hexahydrocurcumin, and octahydrocurcumin were less active. These results suggest that curcumin may exert its anti-inflammatory and anti-carcinogenic properties by suppressing the activation of NFkappaB through inhibition of IKK activity.
一氧化氮（NO）在炎症和癌症发生的多个阶段中发挥着重要作用。在本研究中，我们调查了姜黄素及其代谢产物四氢姜黄素、六氢姜黄素和八氢姜黄素对脂多糖（LPS）激活的RAW 264.7细胞中一氧化氮合酶（NOS）诱导的抑制作用。蛋白质免疫印迹法和Northern印迹分析表明，与四氢姜黄素、六氢姜黄素和八氢姜黄素这些代谢产物相比，姜黄素能显著降低LPS激活的巨噬细胞中诱导型一氧化氮合酶（iNOS）的130 kDa蛋白水平和4.5 kb mRNA水平。此外，电泳迁移率变动分析（EMSA）实验表明，姜黄素可阻断LPS诱导的核因子-κB（NFκB）与iNOS诱导所必需的转录因子的（32）P标记双链寡核苷酸探针的结合。NFκB激活的抑制是通过防止抑制蛋白κB（IkappaB）降解而发生的。瞬时转染实验还表明，姜黄素可抑制NFκB依赖性转录活性。姜黄素可阻止抑制蛋白κBα（IkappaBα）和p65从胞质部分消失，并抑制IkappaBα的磷酸化。此外，我们发现姜黄素可抑制LPS诱导的IkappaB激酶1（IKK1）和IkappaB激酶2（IKK2）活性，但四氢姜黄素、六氢姜黄素和八氢姜黄素的活性较低。这些结果表明，姜黄素可能通过抑制IKK活性来抑制NFκB的激活，从而发挥其抗炎和抗癌特性。
