GDF11调控线粒体OPA1剪切介导在脓毒症心功能障碍中的作用及机制研究

Sepsis induced cardiac dysfunction is a common complication that seriously affects the prognosis of patients with sepsis, but its current treatment is limited. Recent studies have shown that the imbalance of mitochondrial fusion and fission process is one of the main mechanisms of cardiac dysfunction. Therefore, searching for a new therapeutic target for sepsis cardiac dysfunction is a scientific question that needs to be solved urgently. Growth factor 11(GDF11) , a member of the TGFβsuperfamily, has been shown to have cardioprotective effects. Our preliminary results have found that GDF11 expression is decreased in myocardial tissue of septic mice, While the overexpression of GDF11 in cardiomyocytes increases the ratio of long/short forms of mitochondrial fusion protein OPA1, and the level of cleavage protease YME1L is also up-regulated. Thus, we hypothesis that GDF11 relieve sepsis cardiac dysfunction through regulating the mitochondrial OPA1 cleavage by up-regulating the expression of YME1L. The purpose of this project is to explore the mechanism and role of GDF11 in regulating mitochondrial dynamic imbalance in sepsis induced cardiac dysfunction, and provide new insight and for sepsis cardiac dysfunction by using GDF11 myocardial-specific knockout and overexpression mice, gene overexpression/knockout and pathway inhibitor in cardiomyocytes.

脓毒症心功能障碍是严重影响脓毒症患者预后的常见并发症，目前对其治疗效果有限。近来研究表明线粒体融合分裂过程的失衡是心功能障碍的主要机制之一，因此寻找脓毒症心功能障碍新的治疗靶点是急待解决的科学问题。转化生长因子11（GDF11）是TGF-β超家族的一员，已被证实具有多种心脏保护作用。预实验发现脓毒症小鼠心肌组织中GDF11表达降低，而心肌细胞过表达GDF11增加了线粒体融合蛋白OPA1长/短亚型的比值，并上调剪切蛋白酶YME1L的表达。据此提出假说：GDF11通过上调YME1L的表达调节线粒体OPA1的剪切，发挥对脓毒症心功能障碍的保护作用。本项目拟从分子、细胞和动物水平，采用GDF11心肌特异性敲除和过表达小鼠，结合基因过表达/敲除及信号通路抑制等方法，阐明GDF11调控线粒体动力学稳态的分子机制及其在减轻心功能障碍中的作用，为临床防治脓毒症心功能障碍提供新的靶点及理论依据。

转化生长因子11（GDF11）是TGF-β超家族的一员，其对心肌急性和慢性损伤过程中的保护作用及机制尚不清。本项目从分子、细胞和动物水平，采用GDF11心肌特异性敲除和AAV9过表达小鼠，结合基因过表达/敲除及信号通路抑制、RNA-seq等方法，结果发现，心肌细胞特异性敲除GDF11后加重主动脉缩窄（TAC）诱导的小鼠心功能减退，导致小鼠较早进入心功能失代偿期，心脏纤维化明显，血管新生减少。基于送检的RNA-seq数据发现，GDF11通过p-AKT-VEGF-A信号通路促进代偿性血管生成作用，对心肌损伤具有保护作用。其次，在心梗后心功能障碍的干细胞治疗中发现，GDF11可通过激活TGF-β-Smad2/3通路，上调YME1L表达后促进L-OPA1的聚集，促使线粒体融合增加而保护线粒体形态的完整及功能的维持，起到对细胞的抗凋亡作用。最后在心功能障碍的急性炎症过程中发现，GDF11可抑制心肌细胞中CCL2趋化因子的产生，减少心肌损伤后局部炎性巨噬细胞（M1型表型）的浸润，降低炎性因子表达，发挥对心脏保护作用，且可通过直接抑制巨噬细胞内NF-κB通路以减轻其炎症表型。综上结果证实GDF11通过自分泌和旁分泌作用共同促进心功能障碍后的心肌修复。