The present study illustrates mitochondria-mediated impact of ionizing radiation which is paralleled by activation of several pro-adaptive responses in normal human dermal fibroblast cells. Irradiation of cells with X-rays (5 Gy) led to an increase in fragmentation and mitochondrial mass. Distinct temporal changes in cytosolic and mitochondrial reactive oxygen species (ROS) were noted in response to radiation, which was associated with depletion in mitochondrial membrane potential followed by decrease in ATP levels. Long Amplicon-Polymerase Chain Reaction (LA-PCR) analysis showed time-dependent increase in mitochondrial DNA damage that preceded mitochondrial ROS generation. Irradiation of cells led to an initial G2/M arrest at 8 h that persisted till 16 h, with subsequent block at G0/G1 measured at 48 and 72 h time points. Interestingly, cells activated autophagy as a countermeasure against radiation-mediated cellular insults and aided in removal of damaged mitochondria. Blocking autophagy using 3-methyladenine led to cell death via activation of enhanced ROS, PARP-1 and caspase 3 cleavage. Upregulation of mitochondrial biogenesis factors Nrf1/PGC-1α, following irradiation was observed. Irradiated cells exhibited an increase in the phosphorylation of GCN2, PERK and eIF2α that might be responsible for the up-regulation of ATF4 and CHOP thereby regulating autophagy and components of integrated stress response. Apart from this, we measured accumulation of mitochondrial chaperones (HSP60/HSP10) and ATF5 which is a major molecule involved in mitochondrial stress. Taken together, mitochondria are one of the major cytoplasmic targets for ionizing radiation and possibly act as an early indicator of cellular insult. The findings also show that stressed mitochondria might influence endoplasmic reticulum (ER)-related signalling leading to the activation of adaptive mechanisms like cytoprotective autophagy, and molecules responsible for mitochondrial biogenesis and protein quality control in order to replenish mitochondrial pool and maintain cellular homeostasis.

中文翻译：

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刺激细胞保护性自噬和线粒体生物发生/蛋白稳态的组成部分作为可靠的生存策略，以响应电离辐射。

本研究说明了线粒体介导的电离辐射影响，这与正常人真皮成纤维细胞中几种促适应性反应的激活相平行。用X射线（5 Gy）照射细胞会导致碎片和线粒体质量增加。注意到辐射对胞质和线粒体活性氧（ROS）有明显的时间变化，这与线粒体膜电位的耗竭以及ATP含量的降低有关。长扩增子-聚合酶链反应（LA-PCR）分析表明，线粒体ROS产生之前，线粒体DNA损伤的时间依赖性增加。细胞辐照导致最初的G2 / M阻滞在8 h持续到16 h，随后在48和72 h时间点的G0 / G1阻滞。有趣的是 细胞激活自噬作为对辐射介导的细胞损伤的对策，并有助于清除受损的线粒体。使用3-甲基腺嘌呤阻断自噬通过激活增强的ROS，PARP-1和caspase 3裂解导致细胞死亡。观察到辐射后线粒体生物发生因子Nrf1 /PGC-1α的上调。受辐照的细胞显示GCN2，PERK和eIF2α的磷酸化增加，这可能是ATF4和CHOP上调的原因，从而调节自噬和整合应激反应的成分。除此之外，我们还测量了线粒体伴侣蛋白（HSP60 / HSP10）和ATF5的积累，ATF5是参与线粒体应激的主要分子。在一起 线粒体是电离辐射的主要细胞质靶标之一，可能是细胞损伤的早期指标。研究结果还表明，紧张的线粒体可能会影响内质网（ER）相关信号，从而激活诸如细胞保护性自噬以及负责线粒体生物发生和蛋白质质量控​​制的分子以补充线粒体池并维持细胞稳态。