HAX-1 对阿霉素诱导的急性及慢性心肌损伤的保护作用及其机制研究

Doxorubicin is a powerful anthracycline antibiotic used to treat divergent human neoplasms. However, its clinical use is limited because of severe cardiotoxic side effects. HS-1-associated protein X-1 (HAX-1), with homology to Bcl-2 domains BH1 and BH2, is a newly identified anti-apoptotic factor. Recently, it was shown that HAX-1 is a binding partner of phospholamban (PLN) and SERCA2a and this interaction was postulated to inhibit cell apoptosis and promote cell survival through modulation of ER Ca2+ stores. In vitro study showed that HAX-1 protected cardiomyocytes from hypoxia-reoxygenation-induced injury. However, the cardioprotection of HAX-1 in vivo, especially under stress conditions, remains unclear. To investigate the cardioprotection of HAX-1 against Doxorubicin-induced cardiotoxicity, HAX-1 will be up-regulated and down-regulated by ex vivo adenovirus-mediated gene delivery in isolated adult rat cardiomyocytes, and in vivo transgenic mice with cardiac specific overexpression of HAX-1 or HAX-1 deficiency, followed by acute and chronic Doxorubicin treatment. This is the first study to elucidate that: 1) HAX-1 protects against Doxrubicin-induced acute and chronic cardiac injury both ex vivo and in vivo; 2) the cardioprotection of HAX-1 is associated with the specific interactions between HAX-1 and its molecular targets in both mitochondria and ER; and 3) The cardioprotection of HAX-1 is associated with SR calcium homeostasis. These studies will, for the first time, provide a detail mechanism of HAX-1's cardioprotection against Doxorubicin-triggered cardiac injury at the subcellular and moleclular levels, indicating HAX-1's beneficial effect to treat cardiomyopathy and heart failure.

阿霉素是一种高效广谱抗肿瘤药物,但有可能引起严重的心脏毒性反应而限制了其临床应用。HAX-1 是最近发现的与Bcl-2 结构具同源性的抗凋亡蛋白，同时存在于心肌细胞的线粒体和肌浆网，并与心肌肌浆网钙泵SERCA2a及其调控蛋白PLN相互作用而参与调节心肌收缩性和肌浆网钙转运。目前尚不清楚，HAX-1能否有效抑制阿霉素所致的心脏毒性作用。本研究首次基于体外大鼠心肌细胞水平，以及在体HAX-1基因过表达和基因敲除小鼠模型中，通过上调和下调心肌特异性的HAX-1表达水平，观察其对急性和慢性阿霉素诱导的心肌损伤的影响及其机制，以期阐明：1.HAX-1 对阿霉素诱导的心肌损伤具有显著保护作用；2. HAX-1抗凋亡的保护作用与其在线粒体和内质网双重通路相关；3.HAX-1对肌浆网钙稳态的调控在其双重心肌保护作用中是否也发挥重要作用。本研究将为临床阿霉素诱导的心肌损伤和心力衰竭提供新的治疗靶标。

阿霉素是一种高效广谱抗肿瘤药，但可引起心脏不良反应从而限制了其临床应用。本项目在体外实验中发现HAX-1水平下调可加重阿霉素诱导的心肌细胞损伤，但上调HAX-1水平减轻阿霉素诱导的心肌细胞毒性。在整体动物实验中发现HAX-1过表达可保护阿霉素诱导的急性心肌细胞损伤和心功能异常，但HAX-1基因敲除加重阿霉素诱导的急性心肌细胞损伤和心功能异常。研究还发现HAX-1的过表达可抑制线粒体凋亡通路，并与 PLN及SERCA2a结合调节细胞内钙转运，从而改善阿霉素诱导的心肌损伤。本项目在国内外首次通过体（内）外实验系统深入地研究了HAX-1在阿霉素诱导的心肌细胞损伤中的保护作用。特别是从线粒体和内质网介导的凋亡通路以及肌浆网/内质网中的主要钙调节蛋白角度，在亚细胞水平和分子水平阐明了HAX-1 对阿霉素诱导的心肌细胞损伤的双重保护作用机制。本项目将为临床上防治严重威胁人类生命健康的心力衰竭和阿霉素心脏不良反应提供新策略。