■实验研究补充了低剂量和电离辐射剂量率的生物学效应的流行病学数据,并有助于确定剂量和剂量率有效性因子。
■人类VH10皮肤成纤维细胞以1.6、8、12mGy/h的速度暴露于25、50和100mGy的137Csγ辐射,在23.4Gy/h的高剂量率下,分析了辐射引起的短期和长期影响。两个样本队列,即,发现(n=30)和验证(n=12),进行RNA测序。在共享条件下(1.6mGy/h;24h)的这六个实验的结果库,加上较早的时间点(0小时),构成第三个队列(n=12)。
■在所有上述剂量率下暴露于100mGy的细胞,在暴露后0/24小时和21天收获,显示没有强烈的基因表达变化。DMXL2参与NOTCH信号通路的调节,在发现和验证队列中呈现一致的上调,并通过qPCR进行验证。基因集富集分析显示,NOTCH途径在合并队列中上调(p=0.76,归一化富集评分(NES)=0.86)。除了上调的顶端连接和下调的DNA修复,在暴露队列中,很少有途径发生持续变化.令人惊讶的是,细胞活力测定,在照射后1、3和6天进行,和菌落形成试验,就在暴露后播种,没有发现对细胞生长或存活模式的任何统计学上显著的早期影响。在12mGy/h和23.4Gy/min时观察到生存力增加(第6天)和菌落大小减小(第21天)的趋势。此外,在暴露后70天内,未观察到细胞生长曲线的长期变化。
■总而言之,以低剂量率给予低剂量的γ辐射对放射抗性VH10细胞没有强烈的细胞毒性作用.
Experimental studies complement epidemiological data on the biological effects of low doses and dose rates of ionizing radiation and help in determining the dose and dose rate effectiveness factor.
Human VH10 skin fibroblasts exposed to 25, 50, and 100 mGy of 137Cs gamma radiation at 1.6, 8, 12 mGy/h, and at a high dose rate of 23.4 Gy/h, were analyzed for radiation-induced short- and long-term effects. Two sample cohorts, i.e., discovery (n = 30) and validation (n = 12), were subjected to RNA sequencing. The pool of the results from those six experiments with shared conditions (1.6 mGy/h; 24 h), together with an earlier time point (0 h), constituted a third cohort (n = 12).
The 100 mGy-exposed cells at all abovementioned dose rates, harvested at 0/24 h and 21 days after exposure, showed no strong gene expression changes. DMXL2, involved in the regulation of the NOTCH signaling pathway, presented a consistent upregulation among both the discovery and validation cohorts, and was validated by qPCR. Gene set enrichment analysis revealed that the NOTCH pathway was upregulated in the pooled cohort (p = 0.76, normalized enrichment score (NES) = 0.86). Apart from upregulated apical junction and downregulated DNA repair, few pathways were consistently changed across exposed cohorts. Concurringly, cell viability assays, performed 1, 3, and 6 days post irradiation, and colony forming assay, seeded just after exposure, did not reveal any statistically significant early effects on cell growth or survival patterns. Tendencies of increased viability (day 6) and reduced colony size (day 21) were observed at 12 mGy/h and 23.4 Gy/min. Furthermore, no long-term changes were observed in cell growth curves generated up to 70 days after exposure.
In conclusion, low doses of gamma radiation given at low dose rates had no strong cytotoxic effects on radioresistant VH10 cells.