Low-dose radiation differentially regulates protein acetylation and histone deacetylase expression in human coronary artery endothelial cells

Purpose: Ionizing radiation induces cardiovascular disease, the endothelium being the main target. The exact mechanism of the damage is unclear but the involvement of multiple signaling pathways is probable. Reversible lysine acetylation is a posttranslational protein modification that regulates activity across a broad range of signaling pathways. The aim of this study was to determine if a low radiation dose results in acetylome alteration in endothelial cells. Materials and methods: Human coronary artery endothelial cell line was irradiated with Cs-137 gamma-rays (0.5 Gy) and proteomics analysis was performed using enriched acetylated peptides and all peptides. Data were validated using immunoblotting, deacetylase activity assay, and RhoA activity assay. Results: Nearly a hundred proteins were found to have an altered acetylation status 24 h after irradiation, primarily due to an overall decrease in acetylation. The expression of specific deacetylases was significantly increased, coinciding with an enhancement in global deacetylase activity. Proteins changed in their acetylation status belonged to several pathways including protein synthesis, cytoskeleton-related processes, protein folding and calcium signaling. The predicted changes in the RhoA/actin cytoskeleton pathway were validated by immunoassay. Conclusions: This study shows that protein acetylation is an important mediator of radiation responses in human cardiac coronary endothelial cells. Increased knowledge of the endothelial response to radiation is crucial for the development of normal tissue-sparing modalities during radiation therapy.

研究目的：电离辐射可诱发心血管疾病，内皮细胞为其主要靶标。目前辐射造成血管内皮损伤的确切机制尚不明确，但多信号通路的参与具有较高可能性。可逆性赖氨酸乙酰化是一种蛋白质翻译后修饰方式，可调控广泛信号通路的活性。本研究旨在探究低剂量辐射是否会引起内皮细胞的乙酰化修饰组（acetylome）改变。

材料与方法：采用Cs-137 γ射线以0.5 Gy剂量照射人冠状动脉内皮细胞系，通过富集乙酰化肽段与全肽段进行蛋白质组学分析。实验数据通过免疫印迹法、脱乙酰酶活性测定法以及RhoA活性测定法进行验证。

结果：照射后24小时，近百种蛋白质的乙酰化状态发生改变，整体以乙酰化水平普遍下调为主。特异性脱乙酰酶的表达量显著升高，与全局脱乙酰酶活性的增强相一致。乙酰化状态发生改变的蛋白质涉及多条通路，包括蛋白质合成、细胞骨架相关过程、蛋白质折叠以及钙信号通路。通过免疫测定验证了RhoA/肌动蛋白细胞骨架通路的预测变化。

结论：本研究表明，蛋白质乙酰化是人冠状动脉内皮细胞辐射应答的重要介导因子。深入了解内皮细胞的辐射应答机制，对于开发放射治疗过程中正常组织保护方案至关重要。