Institute of Modern Physics, Chinese Academy of Sciences, 509 Nanchang Road, Lanzhou 730000, China; Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, Gansu, China; Key Laboratory of Heavy Ion Radiation Medicine of Gansu Province, Lanzhou, Gansu, China; Graduate School of University of Chinese Academy of Sciences, Beijing 100039, China.
Institute of Modern Physics, Chinese Academy of Sciences, 509 Nanchang Road, Lanzhou 730000, China; Key Laboratory of Heavy Ion Radiation Biology and Medicine of Chinese Academy of Sciences, Lanzhou, Gansu, China; Key Laboratory of Heavy Ion Radiation Medicine of Gansu Province, Lanzhou, Gansu, China.
Life Sci. 2020 Dec 15;263:118586. doi: 10.1016/j.lfs.2020.118586. Epub 2020 Oct 13.
Mitochondrial dysfunction is receiving considerable attention due to irreplaceable biological function of mitochondria. Ionizing radiation and tigecycline (TIG) alone can cause mitochondrial dysfunction, playing important role in tumor therapy. However, prior studies fail to investigate combined mechanism of carbon ion irradiation (IR) and TIG on tumor proliferation inhibition. The study aimed to explore the combined effects of both on autophagy and apoptosis.
NSCLC cells A549 and H1299 were treated with carbon ion, TIG, or both. Cell survival rate, autophagy, apoptosis, expression of mitochondrial signaling proteins were determined by clone formation assay, immunofluorescence of LC3B, flow cytometry and western blotting, respectively; ATP content, mitochondrial membrane potential (MMP) and Ca level in mitochondria were used to assessed mitochondrial function.
Results showed IR combined TIG inhibited cells proliferation by increasing apoptosis in both cells and enhancing autophagy in H1299 cells. Additionally, combination treatment induced the most severe mitochondrial dysfunction by sharply reducing ATP, MMP and increasing Ca level of mitochondria. Up-regulation and down-regulation of mitochondrial translation proteins (EF-Tu, GFM1 and MRPS12) expression affected apoptosis and autophagy, while the level of p-mTOR was consistent with their expression in both cell types. In A549 cells, p-AMPK level decreased while p-Akt and p-mTOR increased after combination treatment.
Overall, our results showed that p-Akt and p-AMPK antagonistically targeted p-mTOR to regulate mitochondrial translation proteins to affect autophagy and apoptosis. Furthermore, this study suggests that combination of carbon ion and TIG is a potential therapeutic option against tumors.
由于线粒体具有不可替代的生物学功能，因此线粒体功能障碍受到了相当多的关注。电离辐射和替加环素（TIG）单独作用即可导致线粒体功能障碍，在肿瘤治疗中发挥重要作用。然而，之前的研究未能探究碳离子照射（IR）与 TIG 联合作用对肿瘤增殖抑制的机制。本研究旨在探讨两者联合对自噬和细胞凋亡的影响。
采用碳离子、TIG 或两者联合处理 NSCLC 细胞 A549 和 H1299。通过克隆形成实验、LC3B 免疫荧光、流式细胞术和 Western blot 分别检测细胞存活率、自噬、细胞凋亡以及线粒体信号蛋白的表达；通过测定细胞内 ATP 含量、线粒体膜电位（MMP）和线粒体钙离子水平评估线粒体功能。
结果显示，IR 联合 TIG 通过增加两种细胞中的细胞凋亡和增强 H1299 细胞中的自噬来抑制细胞增殖。此外，联合处理通过急剧降低 ATP、MMP 和增加线粒体钙离子水平导致最严重的线粒体功能障碍。线粒体翻译蛋白（EF-Tu、GFM1 和 MRPS12）的上调和下调影响细胞凋亡和自噬，而两种细胞类型中 p-mTOR 的水平与其表达一致。在 A549 细胞中，联合处理后 p-AMPK 水平降低，而 p-Akt 和 p-mTOR 水平升高。
总之，我们的研究结果表明，p-Akt 和 p-AMPK 拮抗作用于 p-mTOR，以调节线粒体翻译蛋白，从而影响自噬和细胞凋亡。此外，本研究表明，碳离子和 TIG 的联合治疗可能是一种治疗肿瘤的潜在方法。
