转录因子TFEB对心肌重构的干预和机制研究

Transcription factor EB (TFEB) is a master regulator of autophagy-lysosome machinery. Our research studied the role of TFEB in DOX-induced zebrafish and mouse myocardial remodeling models. We found that TFEB exerted a protective effect on DOX-induced zebrafish myocardial damage, while in DOX-induced mouse myocardial remodeling model, TFEB aggravated the myocardial damage. Furthermore, TFEB was found to inhibit cardiac hypertrophy and fibrosis in TAC-induced mouse myocardial hypertrophy model. These results indicate a complicated role of TFEB in the heart and its different target molecules in different models. To further clarify the effect of TFEB on myocardial remodeling and its targets, we have constructed TgTFEBflox/flox/αMHC-Cre-ER mice in which by using tamoxifen, we could conditionally induce the overexpression of TFEB. Thus, we could verify the effect of TFEB on cardiac function in DOX-induced myocardial damage and TAC-induced myocardial hypertrophy model. What’s more, we would further screen target molecules of TFEB by proteomics studies and RNAseq and detect the changes in fibroblast proliferation and trans-differentiation. We expect to clarify the mechanism of TFEB in myocardial remodeling and to control the process by regulating the expression of TFEB.

TFEB是自噬调控中重要的转录因子。本课题组研究了TFEB在DOX诱导的斑马鱼和小鼠心肌重构模型中的作用,观察到在斑马鱼DOX心肌损害模型中,TFEB有保护作用; 但是在小鼠DOX心肌重构模型中, TFEB却加重了心肌损害, 此外在小鼠升主动脉狭窄(TAC)造成的心肌肥厚模型中TFEB明显抑制心肌肥厚,抑制纤维化,这些结果提示TFEB在心脏的作用机制较为复杂，在不同模型中其作用的不同的靶分子的权重不同。为进一步探究TFEB的作用靶点和对心肌重构的影响,构建TgTFEBflox/floxαMHC-Cre-ER小鼠,利用tamoxifen在不同时间诱导,验证在DOX心肌损害和TAC心肌肥厚模型中心脏功能受到的影响,进一步采用蛋白质组学研究和RNAseq的检测手段筛选TFEB的靶分子,检测TFEB对成纤维细胞增殖和转分化的影响,阐明TFEB作用机制,达到通过调控TFEB表达干预心脏重构的目的。

自噬-溶酶体通路（ALP）功能不全在心肌肥厚的发病机制中起重要作用。然而，碱性磷酸酶不足的潜在机制在很大程度上仍然未知，并且缺乏特异性地操纵碱性磷酸酶不足以治疗心肌肥厚的策略。转录因子EB（Transcription factor EB，TFEB）作为碱性磷酸酶的主要调节因子，调节自噬体和溶酶体的产生和功能。我们发现，在苯肾上腺素（PE）诱导和主动脉缩窄诱导的心肌细胞肥大和扩张型心肌病患者的衰竭心脏中，TFEB显著降低，而自噬体标记物升高。敲除TFEB可诱导ALP功能不全，表现为自噬体标志物增加、轻链3II流减少，心肌细胞肥大表现为心钠素和β-肌球蛋白重链水平增加以及细胞大小增大。TFEB敲除的效应可通过促进自噬而消除。TFEB过表达可改善自噬流，减轻PE刺激的心肌细胞肥大和主动脉缩窄诱导的肥大性重塑、纤维化和心功能不全。姜黄素类似物化合物C1是一种特异性TFEB激活剂，同样地减弱了PE诱导的ALP不足和心肌细胞肥大。TFEB敲低增加了GATA4的积累，GATA4是几个基因的转录因子，通过阻断GATA4的自噬降解导致心肌肥大，而敲低GATA4减弱了TFEB下调诱导的心肌细胞肥大。TFEB过表达和C1均可促进GATA4自噬降解，减轻PE诱导的心肌细胞肥大。总之，TFEB下调通过导致ALP不足和阻断自噬降解在压力超负荷诱导的心肌肥大的发展中发挥重要作用。激活TFEB是治疗心肌肥厚的一种潜在的治疗策略。