精胺基于自噬通路调控在未成熟心肌保护中的作用及其机制

The physiological and metabolic characteristics of immature myocardium are very different from mature myocardium. The protection of immature myocardium is of much importance since pediatric cardiac surgery in infant and newborn is increasing. Our previous studies found that autophagy existed in the immature myocardium of newborn rabbit. However, the mechanism of autophagy in immature myocardium is not clear. Spermine is a kind of small molecules that has a wide range of biological functions. Our previous studies found that spermine decreased the apoptosis of newborn rabbit myocardium and protected myocardium. Spermine can also induce autophagy in yeast cells and a wide variety of mammalian cells. And autophagy can protect myocardium. Therefore, we speculate that spermine can induce autophagy in immature myocardium and then protect immature myocardium. To confirm this hypothesis, this study will search in the influence of spermine to autophagy in immature myocardium. And we will research the autophagy in the immature myocardium at different levels and in different pathways. We hope that this study can confirm our theory and find the target molecules and target pathways that spermine acted on. This study research in the mechanism of spermine and autophagy in the protection of immature myocardium at organ, cell and molecule levels for the first time. And it may provide a new strategy in the protection of immature myocardium.

未成熟心肌生理代谢特点不同于成熟心肌，随着婴幼儿心脏手术日益增多，探索更好的未成熟心肌保护方法迫在眉睫。我们前期研究发现自噬存在于新生兔未成熟心肌中，但是自噬在其中的作用机制目前还不清楚。精胺是一种具有广泛生物学功能的小分子，我们前期研究观察到新生兔心脏中精胺能够减少心肌细胞凋亡，保护IRI未成熟心肌。且精胺可诱导培养的酵母细胞和多种哺乳动物细胞发生自噬，而自噬具有心肌保护功能。因此，我们推测精胺可通过诱导未成熟心肌细胞自噬而起到心肌保护作用。为证实这个假说，本课题将进一步观察精胺对IRI未成熟心肌细胞自噬、细胞损伤的影响，并在自噬的不同水平和对不同自噬通路进行干预，探讨精胺能否通过诱导自噬而保护未成熟心肌，并在分子水平上探讨精胺发挥作用的准确靶点及所依赖的自噬信号通路。本课题首次在器官、细胞及分子水平上探讨精胺、自噬在未成熟心肌保护中的作用及机制，为未成熟心肌的保护提供一种新思路。

心肌梗死可能导致高的发病率和致死率，婴幼儿心脏病现在也比较普遍。精胺用于治疗未成熟心肌细胞的机制暂时还不清楚。研究旨在探讨精胺预处理对心肌缺血/再灌注损伤(IRI)的保护作用。方法：通过低氧联合缺血清培养然后再正常培养基培养新生大鼠心肌细胞建立一个模拟体内缺血/再灌注损伤的细胞模型，并采用精胺和雷帕霉素等分别进行干预。结果提示：精胺预处理可以显著的降低细胞凋亡和增加细胞活性，通过共聚焦显微镜和投射电子显微镜提示精胺预处理还可以来增加自噬的发生；而且在IRI损伤期间，精胺预处理可以通过抑制mTOR通路上调自噬蛋白的表达；精胺预处理后再雷帕霉素处理也可以显著性增加细胞活性和降低凋亡，而3-MA则相反；而雷帕霉素和3-MA预处理未成熟心肌细胞后，再IRI，最后再精胺处理，细胞活性和凋亡无显著性差异。因此，本研究表面精胺预处理可能是一个潜在预防IRI方法，特别是对婴幼儿。