Santo-Domingo Jaime, Chareyron Isabelle, Broenimann Charlotte, Lassueur Steve, Wiederkehr Andreas
Mitochondrial Function, Nestlé Institute of Health Sciences, 1015 Lausanne, Switzerland.
Mitochondrial Function, Nestlé Institute of Health Sciences, 1015 Lausanne, Switzerland.
Exp Cell Res. 2017 Aug 15;357(2):170-180. doi: 10.1016/j.yexcr.2017.05.013. Epub 2017 May 17.
Chloramphenicol and several other antibiotics targeting bacterial ribosomes inhibit mitochondrial protein translation. Inhibition of mitochondrial protein synthesis leads to mitonuclear protein imbalance and reduced respiratory rates as confirmed here in HeLa and PC12 cells. Unexpectedly, respiration in INS-1E insulinoma cells and primary human islets was unaltered in the presence of chloramphenicol. Resting respiratory rates and glucose stimulated acceleration of respiration were also not lowered when a range of antibiotics including, thiamphenicol, streptomycin, gentamycin and doxycycline known to interfere with bacterial protein synthesis were tested. However, chloramphenicol efficiently reduced mitochondrial protein synthesis in INS-1E cells, lowering expression of the mtDNA encoded COX1 subunit of the respiratory chain but not the nuclear encoded ATP-synthase subunit ATP5A. Despite a marked reduction of the essential respiratory chain subunit COX1, normal respiratory rates were maintained in INS-1E cells. ATP-synthase dependent respiration was even elevated in chloramphenicol treated INS-1E cells. Consistent with these findings, glucose-dependent calcium signaling reflecting metabolism-secretion coupling in beta-cells, was augmented. We conclude that antibiotics targeting mitochondria are able to cause mitonuclear protein imbalance in insulin secreting cells. We hypothesize that in contrast to other cell types, compensatory mechanisms are sufficiently strong to maintain normal respiratory rates and surprisingly even result in augmented ATP-synthase dependent respiration and calcium signaling following glucose stimulation. The result suggests that in insulin secreting cells only lowering COX1 below a threshold level may result in a measurable impairment of respiration. When focusing on mitochondrial function, care should be taken when including antibiotics targeting translation for long-term cell culture as depending on the sensitivity of the cell type analyzed, respiration, mitonuclear protein imbalance or down-stream signaling may be altered.
氯霉素和其他几种靶向细菌核糖体的抗生素会抑制线粒体蛋白质翻译。线粒体蛋白质合成的抑制会导致线粒体-细胞核蛋白失衡，并降低呼吸速率，这在HeLa细胞和PC12细胞中得到了证实。出乎意料的是，在氯霉素存在的情况下，INS-1E胰岛素瘤细胞和原代人胰岛的呼吸并未改变。当测试包括甲砜霉素、链霉素、庆大霉素和强力霉素在内的一系列已知会干扰细菌蛋白质合成的抗生素时，静息呼吸速率和葡萄糖刺激的呼吸加速也没有降低。然而，氯霉素有效地降低了INS-1E细胞中的线粒体蛋白质合成，降低了呼吸链中mtDNA编码的COX1亚基的表达，但没有降低核编码的ATP合酶亚基ATP5A的表达。尽管必需的呼吸链亚基COX1明显减少，但INS-1E细胞仍维持正常的呼吸速率。在氯霉素处理的INS-1E细胞中，ATP合酶依赖性呼吸甚至升高。与这些发现一致，反映β细胞代谢-分泌偶联的葡萄糖依赖性钙信号增强。我们得出结论，靶向线粒体的抗生素能够在胰岛素分泌细胞中引起线粒体-细胞核蛋白失衡。我们假设，与其他细胞类型不同，补偿机制足够强大，能够维持正常的呼吸速率，令人惊讶的是，在葡萄糖刺激后甚至会导致ATP合酶依赖性呼吸和钙信号增强。结果表明，在胰岛素分泌细胞中，只有将COX1降低到阈值水平以下才可能导致可测量的呼吸损伤。在关注线粒体功能时，当将靶向翻译的抗生素用于长期细胞培养时应谨慎，因为根据所分析细胞类型的敏感性，呼吸、线粒体-细胞核蛋白失衡或下游信号可能会改变。
