天冬酰胺内肽酶AEP在低剂量辐射诱发心脏损伤中的作用及机制研究

For breast cancer patients, the excess mortality after radiotherapy was mainly from radiation-related heart diseases. Intensity-modulated radiotherapy (IMRT) has been used as a new technique in breast cancer radiotherapy, which caused changes in irradiation dose of heart (decrease the high dose-volume, while increase low dose-volume). Our previous studies found that administration of IMRT is not safe, and increased low dose–volume of heart irradiation were significantly associated with increased early cardiac toxicity in patients with breast cancer. However, until now there is no guideline of dose limitation for heart in administration of IMRT in breast cancer patients. As a result, it is important to clarify the effect of changes in the dose of heart irradiation caused by IMRT and related mechanism. Our preliminary experiment suggested that Asparaginyl Endopeptidase (AEP) might play an important role in low-dose induced heart damage. Based on what we have found, in this project we plan to establish animal model of New Zealand White rabbits and primary cardiomyocytes, and to explore the damage effect of low dose irradiation on the heart and related mechanism, especially focus on the role of AEP. We also plan to explore the possibility of early detection of heart damage using serum AEP and other biomarker. We hope that the findings of this project could help to establish guideline of dose limitation for heart in administration of IMRT in breast cancer patients.

放射相关心脏疾病显著影响乳腺癌放疗生存获益。调强放疗技术在乳腺癌中的应用，带来了心脏辐射剂量模式改变（高剂量降低，低剂量暴露增加）。我们的前期研究发现乳腺癌调强放疗并不安全，并首次提示放射性心脏损伤风险与低剂量暴露程度显著相关。但调强放疗的心脏剂量限制标准在国内外指南中均为空白。因此，阐明调强放疗应用下心脏辐射剂量模式改变对放射性心脏损伤的影响及其机制具有重要临床价值。本课题预实验发现天冬酰胺内肽酶AEP极可能参与了心脏低剂量放射性损伤作用。基于上述研究发现，本课题拟通过构建新西兰大耳兔动物模型及原代心肌细胞实验，探索低剂量分次照射对心脏放射性损伤的影响及机制，重点关注天冬酰胺内肽酶AEP在其中的作用及机制，并探索血清AEP及血清心脏生物标志物早期检测放射性心脏损伤的可能性。为填补乳腺癌调强放疗的心脏剂量限制标准空白提供依据。

放射相关心脏疾病显著影响乳腺癌放疗生存获益。调强放疗技术在乳腺癌中的应用，带来了心脏辐射剂量模式改变(高剂量降低，低剂量暴露增加)。我们的前期研究发现乳腺癌调强放疗并不安全，并首次提示放射性心脏损伤风险与低剂量暴露程度显著相关。但调强放疗的心脏剂量限制标准在国内外指南中均为空白。因此，阐明调强放疗应用下心脏辐射剂量模式改变对放射性心脏损伤的影响及其机制具有重要临床价值。本课题预实验发现天冬酰胺内肽酶AEP极可能参与了心脏低剂量放射性损伤作用。基于上述研究发现，本课题通过C57 WT小鼠模型、人/鼠心肌细胞实验，探索低剂量分次照射对心脏放射性损伤的影响及机制。结果发现：1.辐射对早期心脏收缩功能无显著影响，舒张功能异常对早期心脏损伤更敏感。辐照后早期阶段，心肌细胞形态即可发生显著损伤性变化。辐照可能通过促进凋亡、G2/M期细胞周期阻滞和DNA损伤等机制造成心肌细胞损伤。微血管病变是放射性心脏损伤的重要病生机制。2. AEP是急性放射性心脏损伤过程中的重要分子。低剂量辐照后心肌细胞的AEP表达水平显著上升，并可通过抑制凋亡和促进增殖等途径增加心肌细胞的放射抵抗性。3. 血清心脏生物学指标pro-BNP对放射性心脏损伤的早期监测的敏感性，为其临床应用提供理论基础。在应用ELISA检测方法的情况下，外周血AEP水平可作为放射性心脏损伤的重要分子标志物。上述研究明确了乳腺癌调强放疗下低剂量心脏辐射的损伤作用，并初步确定AEP在低剂量辐射心脏损伤中的作用机制，为外周血AEP作为的放射性心脏损伤早期监测手段提供初步依据。