基于关联网络的空间辐射防护分子靶标的辨识与预测

Identification and prediction of molecular targets related to space radiation protection based on associated networks

空间辐射对航天员健康的危害制约人类的空间探索活动,对其中重离子成分的医学防护研究是对抗空间辐射人体健康威胁的关键之一.本研究以地面装置模拟空间辐射环境,用0.5和2 Gy剂量的碳离子(12C^6+)辐照正常人淋巴母细胞AHH-1,照前0.5 h分别用两种已知的辐射防护药物处理细胞,照后4 h用基因表达芯片测量细胞基因表达谱,构建辐射损伤相关基因表达量调节网络.运用基于模拟退火的迭代搜索算法辨识不同剂量12C^6+辐照及防护药物作用下的辐射相关基因激活子网,依据节点的连接度预测出PPM1A, RIF1, CASP3, TFE3和RIN1等潜在的空间辐射损伤防护高关联度基因.进一步的富集分析表明,这些基因显著富集的分子功能类别主要与转录调节、激活子活性等有关;细胞定位类别主要是核体、染色体等;生物过程类别主要与信号转导、RNA代谢和细胞定位调节等有关.进一步在Hela细胞上通过Western blotting实验证明, 0.5和2 Gy剂量12C^6+辐照后, RIF1基因表达量显著上升,辐照后4 h的相对表达率达到对照组的2倍以上.这种辨识方法通过计算分析理性预测和发掘潜在的辐射损伤防护高关联度人类基因,为重离子辐射损伤医学防护研究提供了新的策略和内容.辨识所得分子靶标为有针对性地进行空间辐射损伤防护药物的研发提供了候选靶标,为细胞响应电离辐射及防护药物作用的分子机制研究提供了线索与支持,对于空间辐射损伤防护技术的提升具有重要的意义.

The effect of cosmic radiation on astronauts is a major barrier for human space exploration. In particular, medical protection against heavy ion radiation-induced injury is one of the key approaches in counteracting cosmic radiation to humans. In recent years, with the rapid accumulation of high-throughput data including gene expression profiles and omics-based data such as protein-protein interactions(PPI), large-scaled network pharmacology analyses can now be conducted. Exploring human genes with potentially high correlation to protection against radiation is becoming an important component and a new approach in heavy ion radiation study owing to advances in rational computational methods based on systems biology techniques.In this study, heavy ion accelerators were employed to simulate cosmic radiation and a pipeline was constructed to identify activated subnetworks of significantly differentially expressed genes and to predict essential genes related to radiation-induced injury protection. Human lymphoblastoid AHH-1 cells were irradiated with 0.5 or 2 Gy of carbon ions(12C^6+). Two kinds of existing radioprotective agents 523 and VND3207 were separately used in vitro 0.5 h before irradiation. Gene expression profiles of the cells were obtained by microarray 4 h after irradiation without and with the treatment of radioprotective agents. The networks of gene expression regulation were constructed based on PPI integrated from Human Protein Reference Database(HPRD). Simulated annealing algorithm was then used to extract activated subnetworks and potential candidate molecular targets including PPM1 A, RIF1, CASP3, TFE3 and RIN1 were proposed according to their degrees of connection. Further gene set enrichment analysis(GSEA) indicated significantly enriched clusters of the identified genes in molecular functions including transcription regulator activity, transcription activator activity, enzyme activator activity, protein kinase activity and zinc ion binding. The most enriched clusters in cell components included nuclear body, transcription factor complex, cell junction, chromosome and cytoplasmic side of membrane. The most enriched biological processes were regulation of RNA metabolism, intracellular signal transduction,regulation of neuron death, regulation of cellular component and phosphorylation. We further investigated the expression of RIF1 before and after irradiation with 0.5 and 2 Gy of 12C^6+ in Hela cells by western blotting. Expression of RIF1 increased significantly after irradiation and the relative expression in cells 4 h after irradiation was greater than 2-fold that of the control. This study took gene correlation into consideration in addition to their differential expression. It provides promising candidates for further discovery of anti-radiation drugs and will be of importance in promoting cosmic radiation protection techniques in long-term manned space programs and deep space exploration missions. In addition, considerable support and clues may also be revealed from the data generated in this study for future research on the underlying mechanisms in radiation-induced injury and medical protection against cosmic radiation.