Division of Toxicology, Office of Applied Research and Safety Assessment, Center for Food Safety and Applied Nutrition, US Food and Drug Administration, Laurel, MD 20708, USA.
J Appl Toxicol. 2012 Sep;32(9):722-30. doi: 10.1002/jat.1721. Epub 2011 Sep 23.
Usnic acid, a natural botanical product, is a constituent of some dietary supplements used for weight loss. It has been associated with clinical hepatotoxicity leading to liver failure in humans. The present study was undertaken for metabolism and toxicity evaluations of usnic acid in human hepatoblastoma HepG2 cells in culture. The cells were treated with the vehicle control and usnic acid at concentrations of 0-100 µm for 24 h at 37 °C in 5% CO2 . Following the treatment period, the cells were evaluated by biochemical and toxicogenomic endpoints of toxicity that included cytochrome P450 activity, cytotoxicity, oxidative stress, mitochondrial dysfunction and changes in pathway focused gene expression profiles. Usnic acid exposure resulted in increased P450 activity, cytotoxicity, oxidative stress and mitochondrial dysfunction in HepG2 cells. The pathway-focused gene expression analysis resulted in significantly altered expression of six genes out of a total of 84 genes examined. Of the six altered genes, three genes were up-regulated and three genes down-regulated. A marked up-regulation of one gene CCL21 associated with inflammation, one gene CCNC associated with proliferation and carcinogenesis and one gene UGT1A4 associated with metabolism as well as DNA damage and repair were observed in the usnic acid-treated cells compared with the vehicle control. Also a marked down-regulation of one gene CSF2 associated with inflammation and two genes (CYP7A1 and CYP2E1) associated with oxidative metabolic stress were observed in the usnic acid-treated cells compared with the control. The biomarkers used in this study demonstrate the toxicity of usnic acid in human hepatoblastoma HepG2 cells, suggesting an oxidative mechanism of action.
松萝酸是一种天然植物产物，是一些用于减肥的膳食补充剂的成分。它已被认为与人类临床肝毒性导致肝衰竭有关。本研究旨在评估松萝酸在人肝癌细胞 HepG2 中的代谢和毒性。将细胞用载体对照和松萝酸在 37°C 和 5%CO2 下处理 24 小时，浓度为 0-100 µm。治疗期结束后，通过细胞色素 P450 活性、细胞毒性、氧化应激、线粒体功能障碍和途径相关基因表达谱变化等毒性的生化和毒理基因组学终点来评估细胞。松萝酸暴露导致 HepG2 细胞中 P450 活性、细胞毒性、氧化应激和线粒体功能障碍增加。途径相关基因表达分析导致总共 84 个检测基因中有 6 个基因的表达发生显著改变。在这 6 个改变的基因中，有 3 个基因上调，3 个基因下调。与载体对照相比，在松萝酸处理的细胞中观察到一个与炎症相关的基因 CCL21、一个与增殖和癌变相关的基因 CCNC 和一个与代谢以及 DNA 损伤和修复相关的基因 UGT1A4 明显上调，与炎症相关的基因 CSF2 和两个与氧化代谢应激相关的基因（CYP7A1 和 CYP2E1）明显下调。本研究中使用的生物标志物表明松萝酸对人肝癌细胞 HepG2 的毒性，提示其作用机制为氧化应激。
