ATF6-PGC1α协同作用在心肌慢性缺氧适应中的作用及机制研究

Chronic hypoxia is the main patho-physiological feature of cyanotic congenital heart disease. Hypoxia induces energetic stress and ER stress, and promotes mitochondrial biogenesis and UPR activation. In previous study, we found that the activity of ATF6 was upregulated, and the expression of PGC1α and autophagy were increased in the myocardium of cyanotic patients. Activated ATF6 could interact with PGC1α. When the activation of ATF6 was inhibited, the autophagy was blocked and apoptosis was increased in cardiomyocytes cultured under long period of hypoxia. Based on these results, we postulate that the ATF6/PGC1α complex could up-regulate the expression of redox associated proteins to reconstruct ER homeostasis. It could also modulate the activity of autophagy to monitor the quality of mitochondria. This complex is critical for myocardial adaptation to chronic hypoxia. In this project, we plan to feed ATF6 knockout mice and ATF6 inactivated transgenic mice under hypoxia for 4 to 8 weeks, and test the effect of ATF6 in heart function under chronic hypoxia. After isolating the primary neonate rat cardiomyocyte, we culture it under hypoxia and study the molecular mechanisms of ATF6/PGC1α complex in autophagy regulation and myocardial adaptation to chronic hypoxia. The results of this project might give a new molecular mechanism of myocardial adaptation to chronic hypoxia, and provide a new method to improve clinical therapy for patients with cyanotic congenital heart disease.

慢性缺氧是紫绀型先心病的共同病理生理过程。低氧导致心肌细胞能量应激和内质网应激，促进线粒体生物合成和UPR激活。前期研究发现：心肌慢性缺氧时，ATF6持续活化、PGC1α表达和细胞自噬增强；活化的ATF6与PGC1α存在相互作用，干涉其表达会减弱细胞自噬，增加低氧诱导细胞凋亡的发生。推测：慢性缺氧时，高表达的PGC1α与活化的ATF6协同作用，转录上调氧化应激相关蛋白以恢复内质网平衡；促进细胞自噬，完成对增生线粒体的质量控制，是心肌细胞慢性缺氧适应的重要调控因素。基于该假设，拟采用ATF6基因敲除小鼠和ATF6失活转基因小鼠建立慢性缺氧模型，评价ATF6在慢性缺氧时对心功能的影响；建立细胞缺氧模型，采用RNA干涉、EMSA、免疫共沉淀等技术研究PGC1α与ATF6相互作用参与自噬调控的分子机制。研究结果预期能发现一种心肌慢性缺氧适应的新机制，为改善复杂先心病的临床治疗提供新策略。

慢性缺氧是紫绀型先心病的共同病理生理过程。低氧导致心肌细胞能量应激和内质网应激，促进线粒体生物合成和UPR激活。我们推测：慢性缺氧时，高表达的PGC1α与活化的ATF6协同作用，转录上调氧化应激相关蛋白以恢复内质网平衡；促进细胞自噬，完成对增生线粒体的质量控制，是心肌细胞慢性缺氧适应的重要调控因素。基于该假设，我们通过采用ATF6基因敲除小鼠建立慢性缺氧模型，评价ATF6在慢性缺氧时对心功能的影响；建立细胞缺氧模型，采用RNA干涉、EMSA、免疫共沉淀等技术研究PGC1α与ATF6相互作用参与自噬调控的分子机制。研究结果发现：1、ATF6在缺氧时心肌保护中有不可替代的作用，缺失ATF6会明显促进心肌细胞死亡，增强ATF6活性能显著改善缺氧后心肌缺血再灌注损伤；同时，在慢性缺氧时，心肌细胞内线粒体自噬现象显著增加，调节线粒体自噬能改善慢性缺氧条件下心肌细胞存活。AMPK在心肌细胞线粒体自噬中发挥关键性作用，增强AMPK活性能增强心肌细胞自噬，改善心肌细胞存活；抑制AMPK活性则显著减轻线粒体自噬，诱导心肌细胞死亡增加。上述研究结果将为进一步研究心肌细胞的损伤保护提供新的治疗靶点。累计发表SCI论文 6篇, 累计影响因子 18.3, 单篇最高影响因子 9.547; 国内统计源期刊 论著3篇。 培养毕业博士研究生3名，硕士研究生3名。

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