Cui Yong-Qiang, Liu Yan-Jun, Zhang Fan
Catheterization Center, Zhumadian Central Hospital, Henan 463000, China.
Catheterization Center, Zhumadian Central Hospital, Henan 463000, China.
Biochem Biophys Res Commun. 2018 Mar 11;497(3):916-923. doi: 10.1016/j.bbrc.2017.12.144. Epub 2017 Dec 27.
Britannin (Bri), isolated from Inula aucheriana, is a sesquiterpene lactone (SL), a class of secondary metabolites. Previous studies have suggested the anti-cancer potential of Bri; however, the molecular mechanism remains elusive. The present study investigated the effects of Bri on liver cancer progression. Our findings indicated that Bri significantly suppressed the growth of liver cancer cell lines. Mechanistic researches revealed that Bri induced apoptosis through the extrinsic and intrinsic apoptotic pathways, as evidenced by the increase of Caspase-8, -9 and -3 cleavages. In addition, Bri-triggered autophagy in liver cancer cells, supported by the up-regulation of light chain 3 (LC3) II, p62, autophagy-related 5 (ATG5) and Beclin 1, as well as the occurrence of autophagic vacuoles. Importantly, Bri increased AMPK activation, while decreased the activity of its down-streaming signal, mTOR. Of note, suppression of AMP-activated protein kinase (AMPK) activation using its inhibitor, Compound C, could inhibit both apoptosis and autophagy induced by Bri. Furthermore, Bri was found to induce reactive oxygen species (ROS) generation in hepatic cancer cells. Notably, reducing ROS production by its scavenger, N-acetyl cysteine (NAC), could down-regulate p-AMPK levels, while up-regulate the phosphorylated mechanistic target of rapamycin (p-mTOR) expressions, accompanied with the restored cell viability, as well as the reduced apoptosis and autophagy in Bri-treated liver cancer cells. Finally, Bri inhibited the tumor growth in vivo without side effects. In conclusion, our study illustrated that Bri could induce apoptosis and autophagy by activating AMPK regulated by ROS in liver cancer cells, supplying molecular bases for developing Bri into an effective candidate against liver cancer.
大花旋覆花素（Bri）是从大花旋覆花中分离得到的一种倍半萜内酯（SL），属于一类次生代谢产物。先前的研究表明Bri具有抗癌潜力；然而，其分子机制仍不清楚。本研究调查了Bri对肝癌进展的影响。我们的研究结果表明，Bri显著抑制肝癌细胞系的生长。机制研究表明，Bri通过外源性和内源性凋亡途径诱导细胞凋亡，Caspase-8、-9和-3裂解增加证明了这一点。此外，Bri在肝癌细胞中引发自噬，这由轻链3（LC3）II、p62、自噬相关5（ATG5）和Beclin 1的上调以及自噬空泡的出现所支持。重要的是，Bri增加了AMPK的激活，同时降低了其下游信号mTOR的活性。值得注意的是，使用其抑制剂化合物C抑制AMP激活的蛋白激酶（AMPK）的激活，可以抑制Bri诱导的细胞凋亡和自噬。此外，发现Bri在肝癌细胞中诱导活性氧（ROS）的产生。值得注意的是，用其清除剂N-乙酰半胱氨酸（NAC）减少ROS的产生，可以下调p-AMPK水平，同时上调磷酸化的雷帕霉素靶蛋白（p-mTOR）的表达，伴随着细胞活力的恢复，以及Bri处理的肝癌细胞中凋亡和自噬的减少。最后，Bri在体内抑制肿瘤生长且无副作用。总之，我们的研究表明，Bri可以通过激活肝癌细胞中由ROS调节的AMPK来诱导细胞凋亡和自噬，为将Bri开发成一种有效的抗肝癌候选药物提供了分子基础。
