Cerium oxide nanoparticle administration to skeletal muscle cells under different gravity and radiation conditions

For their remarkable biomimetic properties implying strong modulation of the intracellular and extracellular redox state, cerium oxide nanoparticles (also termed 'nanoceria') were hypothesized to exert a protective role against oxidative stress associated to the harsh environmental conditions of spaceflight, characterized by microgravity and highly energetic radiations. Nanoparticles were supplied to proliferating C2C12 mouse skeletal muscle cells under different gravity and radiation levels (microgravity+cosmic radiations or Earth gravity+cosmic radiations on board the International Space Station; Earth gravity on ground). Biological responses were thus investigated at a transcriptional level by RNA next-generation sequencing. Lists of differentially expressed genes (DEGs) were generated and intersected by taking into consideration relevant comparisons, which led to the observation of prevailing effects of the space environment over those induced by nanoceria, possibly due to its administration during spaceflight. In space, up-regulation of transcription was slightly preponderant over down-regulation, and it implied involvement of intracellular compartments, with the majority of DEGs being consistently over- or under-expressed whenever present. Cosmic radiations regulated a higher number of DEGs than microgravity and seemed to promote increased cellular catabolism. By taking into consideration space physical stressors alone, microgravity and cosmic radiations appeared to have opposite effects at transcriptional level despite partial sharing of molecular pathways. Interestingly, gene ontology denoted some enrichment in terms related to vision, when only effects of radiation were assessed. The regulation of mitochondrial uncoupling protein 2 in space-relevant samples suggests perturbation of the intracellular redox homeostasis, and leaves open opportunities to antioxidant treatment for oxidative stress reduction in harsh environments. RNA-seq/miRNA-seq of C2C12 proliferating mouse myoblasts, cultured in the following conditions (n of 3): A (without nanoceria, in space without gravity), B (with nanoceria, in space without gravity), C (without nanoceria, in space with gravity), D (with nanoceria, in space with gravity), E (without nanoceria, on land), and F (with nanoceria, on land).

鉴于氧化铈纳米颗粒（cerium oxide nanoparticles，又称纳米铈（nanoceria））具备优异的仿生特性，可强效调控细胞内外的氧化还原稳态，研究人员推测其能够对抗航天严苛环境（以微重力与高能辐射为典型特征）引发的氧化应激，发挥保护作用。本研究将纳米铈施加于增殖中的C2C12小鼠骨骼肌细胞，并设置三类培养条件以模拟不同重力与辐射水平：国际空间站内的微重力+宇宙辐射组、国际空间站内的常重力+宇宙辐射组，以及地面常重力对照组。随后通过RNA下一代测序（RNA next-generation sequencing）技术，在转录组层面探究细胞的生物学响应。研究人员生成了差异表达基因（differentially expressed genes, DEGs）列表，并通过关联相关比较组进行交集分析，结果显示航天环境的调控效应显著强于纳米铈诱导的效应，这可能与航天任务中纳米铈的给药时机相关。在航天环境中，基因转录上调的趋势略占主导，且该过程涉及多种细胞内区室；绝大多数差异表达基因在检测到表达变化时，均呈现一致的上调或下调模式。宇宙辐射调控的差异表达基因数量多于微重力，且似乎可促进细胞分解代谢水平升高。仅单独考量航天物理应激因子时，尽管微重力与宇宙辐射共享部分分子通路，但二者在转录组层面呈现出截然相反的调控效应。值得关注的是，仅针对辐射效应进行富集分析时，基因本体（gene ontology, GO）注释显示出与视觉相关的术语富集现象。航天相关样本中线粒体解偶联蛋白2的表达调控，提示细胞内氧化还原稳态受到扰动，这为在严苛环境中通过抗氧化治疗减轻氧化应激提供了潜在研究方向。本数据集包含C2C12增殖小鼠成肌细胞的RNA-seq/miRNA-seq数据，所有样本均设置3次生物学重复，培养条件分为以下6组：A组：无纳米铈，太空微重力环境；B组：添加纳米铈，太空微重力环境；C组：无纳米铈，太空常重力+宇宙辐射环境；D组：添加纳米铈，太空常重力+宇宙辐射环境；E组：无纳米铈，地面常重力环境；F组：添加纳米铈，地面常重力环境。