BMF在缺血-再灌注致心肌线粒体分裂异常中的作用及机制研究

Ischemia/reperfusion (I/R) -induced myocardial injury severely impairs human's health and life. Currently, a key focus for the researchers is to understand how I/R induces myocardial injury. It has been demonstrated that abnormal mitochondrial fission is a key event in myocardial injury after I/R. However, the molecular mechanism by which I/R leads to abnormal mitochondrial fission remains unknown. Bcl-2-modifying factor (BMF) is a powerful inducer of apoptosis. It is sequestered to cytoskeleton under physiological condition. In response to damage stimuli, BMF is released from cytoskeleton and translocates to mitochondria thereby initiating apoptosis. We previously found that the induction of abnormal mitochondrial fission by I/R is accompanied by the upregulation of BMF expression and the translocation of BMF to mitochondria in cardiomyocytes, indicating that BMF might be involved in I/R-induced abnormal mitochondrial fission. Therefore, in this project, we focus on investigating the effect and mechanism of BMF on the abnormality of mitochondrial fission in myocardial I/R. The research aims include: (1) To clarify the role of BMF in abnormal mitochondrial fission induced by I/R. (2) To elucidate the molecular mechanism by which I/R causes the release of BMF from cytoskeleton. (3) To characterize the transcriptional pathway of BMF upregulation during myocardial I/R. (4) To delineate how BMF participates in abnormal mitochondrial fission of myocardium upon I/R. The results of this project may establish the basis and provide the rationale for future study to explore and understand the mechanisms of myocardial I/R injury.

缺血再灌注心肌损伤严重威胁人类健康和生命，其机制研究是当前研究热点。诱导线粒体分裂异常是缺血再灌注心肌损伤的关键，但是其分子机制尚不清楚。BMF是强大的促凋亡因子，正常状态下定位在胞浆的细胞骨架上，在损伤刺激作用下，其从细胞骨架释放并转位至线粒体，触发细胞凋亡。我们前期实验发现：缺血再灌注诱导心肌线粒体分裂异常的同时，上调BMF表达，并刺激其从胞浆到线粒体的转位，提示缺血再灌注致心肌线粒体分裂异常与BMF有关。因此本项目立题是：BMF在缺血再灌注致心肌线粒体分裂异常中的作用及机制研究。研究内容包括：(1) 明确BMF在缺血再灌注致心肌线粒体分裂异常中作用。(2) 探究缺血再灌注诱导BMF从细胞骨架释放的分子机制。（3）阐明缺血再灌注上调BMF的转录调控途径。（4）研究BMF如何参与缺血再灌注致心肌线粒体分裂异常。本研究将为进一步探索和认识缺血再灌注心肌损伤机制提供重要理论基础和学术思想。

缺血/再灌注性心肌损伤严重威胁人类健康和生命，其机制研究是当前研究热点。诱导线粒体分裂异常是缺血/再灌注性心肌损伤关键，但是其分子机制尚不清楚。BMF是一强大的促凋亡因子，正常状态下定位在胞浆的细胞骨架上，在损伤刺激作用下，其从细胞骨架释放并转位至线粒体，促发细胞凋亡。研究证实BMF参与缺血/再灌注诱导的心肌细胞损伤。鉴于缺血/再灌注明确的致线粒体分裂异常作用和BMF强大的促凋亡功能以及BMF 在缺血/再灌注诱导心肌细胞凋亡中的作用，我们推测：缺血/再灌注可能通过作用于BMF，诱导线粒体分裂异常来导致心肌细胞损伤。因此本项目立题是：BMF在缺血/再灌注致心肌线粒体分裂异常中的作用及机制研究。研究内容包括：(1) 明确BMF在缺血/再灌注致心肌线粒体分裂异常中作用。(2) 探究缺血/再灌注诱导BMF从细胞骨架释放的分子机制。（3）阐明缺血/再灌注上调BMF的转录调控途径。（4）研究BMF如何参与缺血/再灌注致心肌线粒体分裂异常。研究发现：(1) 在心肌细胞中过表达BMF或者抑制心肌细胞内源性BMF的表达，可以增加或减少线粒体分裂异常，增加或降低心肌细胞的凋亡。研究结果证实BMF在缺血/再灌注诱导心肌细胞线粒体分裂异常中发挥重要作用。(2) 缺血/再灌注可以激活calpain，calpain的活性变化与BMF在细胞骨架中的表达相关。上述研究表明缺血/再灌注通过激活calpain，促进BMF从细胞骨架中释放。（3）缺血/再灌注可以诱导BMF mRNA表达上调，Smad4介导了这一过程。（4）BMF通过调控Drp1的线粒体转位，影响Drp1和hFis1的结合，从而参与缺血/再灌注诱导的心肌细胞线粒体分裂。本研究将为进一步探索和认识缺血/再灌注心肌损伤机制提供重要理论基础和学术思想。