Gene expression profiling of PBL in response to ionising radiation and modeled microgravity

BACKGROUND: Ionizing radiation (IR) can be extremely harmful for human cells since an improper DNA-damage response (DDR) to IR can contribute to carcinogenesis initiation. Perturbations in DDR pathway can originate from alteration in the functionality of the microRNA-mediated gene regulation being microRNAs (miRNAs) small noncoding RNA that act as post-transcriptional regulators of gene expression. In this study we gained insight into the role of miRNAs in the regulation of DDR to IR under microgravity a condition of weightlessness experienced by astronauts during space missions which could have a synergistic action on cells increasing the risk of radiation exposure. METHODOLOGY/PRINCIPAL FINDINGS: We analyzed miRNA expression profile of human peripheral blood lymphocytes (PBL) incubated for 4 and 24 h in normal gravity (1 g) and in modeled microgravity (MMG) during the repair time after irradiation with 0.2 and 2Gy of gamma-rays. Our results show that MMG alters miRNA expression signature of irradiated PBL by decreasing the number of radio-responsive miRNAs. Moreover let-7i* miR-7 miR-7-1* miR-27a miR-144 miR-200a miR-598 miR-650 are deregulated by the combined action of radiation and MMG. Integrated analyses of miRNA and mRNA expression profiles carried out on PBL of the same donors identified significant miRNA-mRNA anti-correlations of DDR pathway. Gene Ontology analysis reports that the biological category of Response to DNA damage is enriched when PBL are incubated in 1 g but not in MMG. Moreover some anti-correlated genes of p53-pathway show a different expression level between 1 g and MMG. Functional validation assays using luciferase reporter constructs confirmed miRNA-mRNA interactions derived from target prediction analyses. CONCLUSIONS/SIGNIFICANCE: On the whole by integrating the transcriptome and microRNome we provide evidence that modeled microgravity can affects the DNA-damage response to IR in human PBL. Overall Design: Gene expression signature was defined in PBL irradiated with gamma-rays (2.0 Gy) and incubated in modeled microgravity (mmg) and in parallel ground conditions (1g) for 24h. Five independent experiments were performed for each donor to address which mRNAs were regulated on IR stress. The level of each transcript was represented as Log2.

背景：电离辐射（IR）对人类细胞具有极大的危害性，因为对IR的不当DNA损伤反应（DDR）可能促进致癌过程的启动。DDR途径的扰动可能源于微RNA（miRNA）介导的基因调控功能的改变，miRNA是一种小型的非编码RNA，作为基因表达转录后调控因子。在本研究中，我们深入探讨了miRNA在微重力条件下对IR调节的作用，微重力是宇航员在太空任务期间经历的失重状态，它可能对细胞产生协同作用，增加辐射暴露的风险。方法/主要发现：我们分析了在正常重力（1g）和模拟微重力（MMG）条件下，经过0.2和2Gy伽马射线照射后修复时间内的外周血淋巴细胞（PBL）在4小时和24小时内的miRNA表达谱。我们的结果显示，MMG通过减少放射敏感miRNA的数量，改变了照射PBL的miRNA表达特征。此外，let-7i*、miR-7、miR-7-1*、miR-27a、miR-144、miR-200a、miR-598、miR-650等miRNA在辐射和MMG的共同作用下发生失调。对同一供体的PBL进行的miRNA和mRNA表达谱的集成分析，发现了DDR途径中miRNA-mRNA的显著负相关性。基因本体分析报告指出，当PBL在1g条件下培养时，“DNA损伤反应”的生物类别富集，而在MMG条件下则不是。此外，一些与p53途径负相关的基因在1g和MMG条件下表现出不同的表达水平。使用荧光素酶报告构建体的功能验证实验证实了来自目标预测分析的miRNA-mRNA相互作用。结论/意义：总体而言，通过整合转录组和miRNome，我们提供了模拟微重力可以影响人类PBL对IR DNA损伤反应的证据。总体设计：在2.0 Gy伽马射线照射后，PBL在模拟微重力（mmg）和并行地面条件（1g）下培养24小时，定义了基因表达特征。对每个供体进行了五个独立的实验，以确定哪些mRNA在IR应激下被调节。每个转录物的水平以Log2表示。