转录因子FoxO4在心肌缺血再灌注损伤中调控促凋亡蛋白Bim介导的自噬与凋亡对话的作用及其机制

Overactivation of autophagy in myocardium subjected to ischemia/reperfusion (I/R) sensitizes cardiomyocytes to apoptosis. Pro-apoptosis protein Bim is a key molecular in the crosstalk between autophagy and apoptosis. Transcription factors FoxOs regulates autopahgy related genes(Atg). Autophagy specifically regulates Bim in a CHOP-dependent manner. Our previous work found the correlation between the overexpression of Bim and the activation of FoxO4 in hypoxic neonatal rat ventricular cardiomyocyte. We thus hypothesize that, in cardiomyocytes subjected to ischemia/reperfusion, FoxO4 induces overactivation of autophagy via interaction with its Atg, which upregulats trascription of CHOP gene or interacts with CHOP protein. In order to prove our hypothesis, autophagy inhibitors and cardiomyocytes transfected with recombinant lentivirus to get gene silencing or overexpression will be applied to investigate the role of FoxO4 in overactivation of autophagy and Bim overexpression in myocardium ischemia reperfusion-induced apoptosis. Foxo4 targeting gene Atg will be identified by CHIP and EMSA techniques. The interaction between FoxO4 and CHOP will be confirmed by Co-IP and GST-pulldown techniques. In vivo, the results will be confirmed in hearts of rats. This project aims to reveal the mechanisms of Bim mediated crosstalk between autophagy and apoptosis, and will provide new mind for treatment of myocardium ischemia reperfusion injury.

心肌缺血再灌注（I/R）损伤时过度自噬促发凋亡。促凋亡蛋白Bim是自噬与凋亡对话的交点，转录因子FoxOs调控自噬相关基因（Atg），而自噬时转录因子CHOP特异性调控Bim表达。本团队新近发现心肌细胞缺氧时Bim表达与FoxO4活化呈正相关。我们推测：心肌I/R损伤时FoxO4通过调控靶基因Atg引发过度自噬，上调CHOP转录或与CHOP蛋白相互作用，上调Bim表达促发凋亡。本项目拟构建基因沉默及过表达的慢病毒载体，转染心肌细胞，通过自噬抑制剂干预，观察FoxO4对心肌I/R损伤过度自噬及通过Chop调控Bim促发凋亡的作用；结合CHIP、EMSA技术明确FoxO4调控靶基因的机制；应用Co-IP、GST-Pulldown方法探讨FoxO4与CHOP交互作用调控Bim表达。并在动物水平加以验证。研究结果有望揭示心肌I/R损伤时Bim介导自噬与凋亡对话机制，为防治心肌I/R损伤提供新思路。

心肌缺血再灌注（I/R）损伤时过度自噬促发凋亡。促凋亡蛋白Bim 是自噬与凋亡对话的交点。本课题组拟从两个方面来探索IR损伤时自噬和凋亡增高的新机制。首先，我们用自噬抑制剂3-MA和CQ干预IR损伤大鼠，从内质网应激和自噬角度明确过度自噬促进心脏凋亡作用。我们采用基因沉默技术siRNA-FOXO4，明确FOXO4在心肌IR损伤中自噬和凋亡中扮演重要作用。实验结果表明，自噬抑制剂干预后，大鼠心肌自噬和凋亡水平均明显下；心肌FOXO4沉默后，自噬和凋亡水平亦明显下降。这些研究结果表明，IR损伤后，心肌过度自噬促进细胞凋亡，FOXO4是心肌IR损伤中自噬和凋亡升高的重要原因。该研究结果为防治心肌I/R 损伤提供了新思路。