游离泛素激活CXCR4通路在缺血心肌修复中的作用和机制研究

Regeneration and repair of cardiac myocytes is an important way for limiting morbidity and mortality of myocardial infarction(MI) and subsequent heart failure. In our preliminary study, we identified that levels of free ubiquitin increase in the serum under acute myocardial infarction. Overexpression of free ubiquitin could inhibit apoptosis of ischemic cardiac myocytes in vitro; improve cardiac function and reduce infarct area after MI in vivo. Informed researches suggest that CXCR4 as a receptor of free ubiquitin. We further detected the interaction between free ubiquitin and CXCR4 by molecular dynamic technique and found that the two proteins were tightly bound by charge. Thus, we hypothesize that free ubiquitin secreted by injured cardiac myocytes activating anti-apoptotic PI3K/Akt pathway to promote proliferation and survival after MI through CXCR4 pathway. While liposome targeting free UB is delivered to the infarct area after MI, to observe the therapeutic effect and safety of targeted delivery. This project is expected to reveal the protective effect and molecular mechanism of free ubiquitin on myocardial infarction, which may contribute to new strategies and therapeutic targets for MI prevention and treatment.

心肌梗死后心肌再生与修复是降低心梗及后继心力衰竭发生率和死亡率的重要途径。我们前期工作发现游离泛素在急性心肌梗死患者中表达显著升高。外源性上调游离泛素水平可明显减少心肌细胞凋亡、小鼠心梗面积，改善心功能。近年来人们发现游离泛素的细胞膜受体为CXCR4，我们进一步采用分子动力学技术模拟了游离泛素与CXCR4的相互作用，发现了两者通过电荷作用紧密结合。据此我们拟在小鼠心梗模型和原代心肌细胞上通过多种分子生物学手段和基因敲除小鼠验证科学假说：心梗后细胞分泌的游离泛素（free UB）通过激活心肌上CXCR4受体，活化抗凋亡的PI3K/AKT信号通路，启动细胞的损伤修复机制，减轻心梗后心肌损伤。同时采用脂质体靶向投递free UB至心脏梗死区域，观测其治疗效果和安全性。本项目有望揭示游离泛素在心梗中的保护作用及分子机制，为心肌细胞修复提供理论依据和治疗策略。

心肌梗死（Myocardial infarction,MI）是全球致死率最高的疾病之一，其进展而来的心衰，给社会经济发展造成沉重负担。当前药物治疗、冠脉介入、冠脉搭桥手术乃至心脏辅助装置植入、心脏移植等，虽可缓解部分病情，但心梗后心衰的死亡率仍居高不下。近年来干细胞移植是提高缺血心肌生存的重要手段，受其旁分泌机制效应启发，我们前期工作基础提示，游离泛素（free UB）,一种细胞外及血清中天然存在的分子，可结合其配体CXCR4发挥对缺血心肌的保护作用。为验证游离泛素在缺血/再灌注中的保护作用，本项目采集临床冠心病患者血清，检测游离泛素、SDF-1（另一CXCR4配体）、心肌损伤标志物的表达量，并通过统计学分析得出游离泛素与心肌损伤严重程度相关，并是鉴别急性冠脉综合征与稳定性心绞痛的潜在标志之一。为进一步研究游离泛素对缺血心肌的作用机制，本项目分别从体内、体外两个维度，细胞、分子、动物组织三个层面进行研究。体外实验结果表明，心肌细胞的缺血/再灌注损伤诱导游离泛素分子水平的动态表达。外源性加入游离泛素激活了CXCR4通路，抑制了心肌细胞缺血再灌注后GSK-3β/JNK介导的线粒体凋亡，细胞自噬的表达。体内研究建立小鼠心梗模型，证实外源性给予游离泛素对心梗小鼠有明显的心脏保护作用，可提高左室射血分数，降低自噬小体聚集，改善心肌纤维化等，具有潜在的临床的转化及应用价值。