“BRCA1-p21-细胞周期”轴通过心脏血管内皮细胞保护放射性心脏损伤的作用及机制研究

Radioactive heart disease seriously affects the living quality and survival time of patients with thoracic tumor radiotherapy. Studies confirm that vascular injury is crucial to the occurrence of radioactive heart disease, but the molecular mechanism of its damage is still poorly understood. Our previous study found that after irradiation for vascular endothelial cells HUVEC, the expression of BRCA1 and p21 protein gradually increased with the increasing radiation dose, cell cycle arrest also gradually accelerated; after silencing the expression of BRCA1, p21 was down-regulated, and cell cycle was accelerated. Combined with mitotic catastrophe theory, we hypothesized that: "BRCA1-p21-cell cycle" axis can act on cardiac vascular endothelial cells to protect radioactive heart damage. Through vascular endothelial cell lines and specific expression of BRCA1 in vascular endothelial cells deficient mice model, the project used molecular biology, imaging, histopathology and other means to confirm the protective effect of "BRCA1-p21-cell cycle" axis on radioactive heart damage and to elucidate its mechanism of action. This study laid the foundation for revealing the occurrence mechanism of radioactive heart damage from the new viewpoint of "BRCA1-p21- cell cycle" axis and provided new ideas for the prevention and treatment of radioactive heart damage.

放射性心脏病严重影响胸部肿瘤放疗患者的生活质量及生存时间。研究证实脉管损伤是放射性心脏病发生的关键，但对其损伤的分子机制目前仍知之甚少。我们前期研究发现血管内皮细胞HUVEC受放射线照射后，BRCA1及p21蛋白的表达随照射剂量的增加而逐渐增加，细胞周期阻滞也逐渐加重；沉默BRCA1表达后，p21随之下调，细胞周期加快。结合有丝分裂危象理论，我们提出假说：“BRCA1-p21-细胞周期”轴作用于心脏血管内皮细胞保护放射性心脏损伤。本项目将通过血管内皮细胞株及血管内皮细胞BRCA1特异表达缺陷小鼠模型，采用分子生物学、影像学及组织病理学等手段，从分子、细胞、组织及动物等水平证实“BRCA1-p21-细胞周期”轴对放射性心脏损伤的保护作用，并阐明其作用机理。本研究将从“BRCA1-p21-细胞周期”轴这个新视点为揭示放射性心脏损伤发生机制奠定基础，为预防和治疗放射性心脏损伤提供新的思路。

微血管内皮细胞功能障碍是放射性心脏病(RIHD)的主要原因。BRCA1在DNA损伤修复中起重要作用。然而，BRCA1在RIHD中的作用尚不清楚。本研究旨在探讨BRCA1在参与RIHD的内皮细胞中的作用。我们检测了照射后人脐静脉内皮细胞(HUVECs)和小鼠心脏组织中BRCA1和p21蛋白的表达，发现BRCA1和p21在HUVECs和心脏组织中的表达均显著高于照射后的HUVECs和心脏组织。采用MTT法、BrdU染色和流式细胞仪检测BRCA1对细胞增殖和细胞周期进程的影响。BRCA1在内皮细胞中过表达可促进细胞生长和G1/S噬菌体阻滞，而在内皮细胞中BRCA1过表达可促进细胞生长和G1/S噬菌体阻滞。BRCA1通过上调p21的表达下调内皮细胞周期相关基因cyclin A、cyclin D1、cyclin E和p-Rb的表达，且BRCA1基因敲除的人脐静脉内皮细胞对辐射更为敏感。用免疫组织化学方法检测心肌微血管密度、心肌细胞缺氧和凋亡情况。小鼠心脏组织微血管密度降低，心肌细胞缺氧和凋亡，呈时间依赖性。此外，在16Gy照射后，由于BRCA1缺失导致内皮功能障碍，EC-BRCA1-/-小鼠比EC-BRCA1+/-小鼠更容易发生严重的RIHD。提示BRCA1通过调节p21信号通路介导的血管内皮细胞周期阻滞，对放射性心脏病具有保护作用。