Oxygen and differentiation status modulate the effect of X-ray irradiation on physiology and mitochondrial proteome of human neuroblastoma cells

Cytotoxic effects, including oxidative stress, of low linear energy transfer (LET)-ionizing radiation are often underestimated and studies of their mechanisms using cell culture models are widely conducted with cells cultivated at atmospheric oxygen that does not match its physiological levels in body tissues. Also, cell differentiation status plays a role in the outcome of experiments. We compared effects of 2 Gy X-ray irradiation on the physiology and mitochondrial proteome of nondifferentiated and human neuroblastoma (SH-SY5Y) cells treated with retinoic acid cultivated at 21% and 5% O₂. Irradiation did not affect the amount of subunits of OxPhos complexes and other non-OxPhos mitochondrial proteins, except for heat shock protein 70, which was increased depending on oxygen level and differentiation status. These two factors were proven to modulate mitochondrial membrane potential and the bioenergetic status of cells. We suggest, moreover, that oxygen plays a role in the differentiation of human SH-SY5Y cells.

低线性能量传递（linear energy transfer, LET）电离辐射所诱导的包括氧化应激在内的细胞毒性效应，常被低估。现有利用细胞培养模型探究其作用机制的研究，大多采用大气氧浓度下培养的细胞，此类环境与人体组织内的生理氧浓度并不匹配。此外，细胞分化状态同样会影响实验结果。本研究对比了2 Gy X射线照射对分别在21%与5%氧气浓度下培养的未分化、以及经视黄酸诱导分化的人神经母细胞瘤（SH-SY5Y）细胞的生理学特性与线粒体蛋白质组的影响。结果显示，X射线照射并未改变氧化磷酸化（oxidative phosphorylation, OxPhos）复合物亚基及其他非氧化磷酸化线粒体蛋白的表达水平，仅热休克蛋白70（heat shock protein 70, Hsp70）的丰度随氧浓度与分化状态的差异出现上调。研究证实，上述两个因素可调控细胞的线粒体膜电位与生物能学状态。此外，本研究还表明氧浓度对人SH-SY5Y细胞的分化过程具有调控作用。