Boonkaewwan Chaiwat, Toskulkao Chaivat, Vongsakul Molvibha
Departments of Physiology and Microbiology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
J Agric Food Chem. 2006 Feb 8;54(3):785-9. doi: 10.1021/jf0523465.
Stevioside, a natural noncaloric sweetener isolated from Stevia rebaudiana Bertoni, possesses anti-inflammatory and antitumor promoting properties; however, no information is available to explain its activity. The aim of this study was to elucidate the anti-inflammatory and immunomodulatory activities of stevioside and its metabolite, steviol. Stevioside at 1 mM significantly suppressed lipopolysaccharide (LPS)-induced release of TNF-alpha and IL-1beta and slightly suppressed nitric oxide release in THP-1 cells without exerting any direct toxic effect, whereas steviol at 100 microM did not. Activation of IKKbeta and transcription factor NF-kappaB were suppressed by stevioside, as demonstrated by Western blotting. Furthermore, only stevioside induced TNF-alpha, IL-1beta, and nitric oxide release in unstimulated THP-1 cells. Release of TNF-alpha could be partially neutralized by anti-TLR4 antibody. This study suggested that stevioside attenuates synthesis of inflammatory mediators in LPS-stimulated THP-1 cells by interfering with the IKKbeta and NF-kappaB signaling pathway, and stevioside-induced TNF-alpha secretion is partially mediated through TLR4.
甜菊糖苷是一种从甜叶菊中分离出的天然无热量甜味剂，具有抗炎和抗肿瘤促进特性；然而，尚无信息可解释其活性。本研究的目的是阐明甜菊糖苷及其代谢产物甜菊醇的抗炎和免疫调节活性。1 mM的甜菊糖苷显著抑制脂多糖（LPS）诱导的THP-1细胞中TNF-α和IL-1β的释放，并轻微抑制一氧化氮的释放，且未产生任何直接毒性作用，而100 μM的甜菊醇则无此作用。蛋白质免疫印迹法显示，甜菊糖苷可抑制IKKβ和转录因子NF-κB的激活。此外，只有甜菊糖苷能诱导未受刺激的THP-1细胞释放TNF-α、IL-1β和一氧化氮。TNF-α的释放可被抗TLR4抗体部分中和。本研究表明，甜菊糖苷通过干扰IKKβ和NF-κB信号通路减弱LPS刺激的THP-1细胞中炎症介质的合成，且甜菊糖苷诱导的TNF-α分泌部分通过TLR4介导。
