TFMA-COXII途径在TRAP1调控缺氧心肌细胞凋亡中的作用及机制研究

In the early stage following a severe burn, cell apotosis and energy deleption caused by hypoxia lead to myocardial injury together. Tumor necrosis factor receptor-associated protein 1 (TRAP1), also named heat shock protein 75 (HSP75), is a heat shock protein which localises in mitochondria. We have proved that overexpression TRAP1 can up-regulate energy generation through increasing respiratory chain complex IV (Cytochrome c oxidase, COX) subunit II（COXII） expressing, but the specific role and mechanism of TRAP1 on cell apoptosis are not clear. COXII is encoded by mitochondrial DNA, and COX has an effect on reactive oxygen species that can induce apoptosis. Meanwhile, mitochondrial transcription factor A (TFAM) enters into mitochondria mediated by TOM complex and TIM complex, this process is the key step for mitochondrial gene transcription and requires the involvement of molecular chaperone. So we conclude TRAP1 can regulate cardiomyocytes apoptosis by TFAM-COXII pathway under hypoxic conditions, and explore the upstream and regulatory mechanisms furthermore. In this study，we first investigate the roles of TFAM and COXII in the process of TRAP1 regulating apoptosis, then we observe the effect of TRAP1 on TFAM transmision into mitochondria and the role of TOM/TIM in this process. In the end, we verify the results in animal models. The study will provide a new ideas for prevention and treatment of myocardial hypoxic injury.

严重烧伤早期缺氧引起的细胞凋亡和能量耗竭共同导致了心肌损害。肿瘤坏死因子受体相关蛋白1（TRAP1，又称HSP75）是线粒体膜上的热休克蛋白。我们证实TRAP1能通过上调呼吸链复合物IV（COX）亚基Ⅱ（COXⅡ）的表达，减少缺氧心肌细胞ATP消耗，但其对凋亡的作用及机制尚不明确。COXⅡ由线粒体基因编码，其下游的COX能够作用于凋亡信号分子活性氧。同时转录因子A（TFAM）通过TOM/TIM蛋白复合体进入线粒体是基因转录的关键环节，且该过程需要分子伴侣的参与。因此我们推断在缺氧条件下，TRAP1能通过TFAM-COXⅡ途径调节心肌细胞凋亡，并进一步探讨TOM和TIM在其中的机制。本研究首先明确TRAP1通过TFAM-COXⅡ途径调控细胞凋亡，再观察TRAP1对TFAM转运进入线粒体的影响及TOM/TIM的作用，最后在缺氧动物模型上予以验证，从而为心肌缺氧损害的防治提供新的思路。

严重烧伤早期缺氧引起的细胞凋亡和能量耗竭共同导致了心肌损害。肿瘤坏死因子受体相关蛋白1（TRAP1）是线粒体膜上的热休克蛋白，我们前期已经证实TRAP1能通过上调呼吸链复合物IV（COX）亚基Ⅱ（COXⅡ）的表达，减少缺氧心肌细胞能量消耗，但其对细胞凋亡的作用及机制尚不明确。为明确TRAP1在缺氧条件下对心肌细胞凋亡的作用及其机制，我们首先构建心肌细胞TRAP1过表达和干扰模型, 探讨TRAP1对缺氧心肌细胞凋亡的作用，然后通过干预线粒体转录因子A(TFAM）和COXII的表达，探讨TFAM在TRAP1调控COXII表达中的作用以及TFAM-COXII途径在TRAP1调控缺氧心肌细胞凋亡过程中的作用，在此基础上进一步探讨TRAP1调节缺氧心肌细胞TFAM表达的机制。最后在缺氧动物模型上观察TRAP1、TFAM、COXII变化与心肌损伤的相关性。本研究首次证明TRAP1能够调控缺氧心肌细胞的凋亡，其具体机制是TRAP1通过上调心肌细胞DNA甲基转移酶3（Dnmt3）的表达，减少DNA甲基化水平来上调TFAM的表达，然后通过TFAM-COXⅡ途径调节细胞内活性氧含量进而调控线粒体依赖的凋亡途径激活，从而最终影响缺氧心肌细胞的凋亡。本研究丰富了缺氧心肌细胞凋亡调控的机制，为临床心肌缺氧损害的防治提供新的靶点和思路。