Beta-肾上腺素能受体通过Hippo信号通路介导扩张型心肌病的机制

Dilated cardiomyopathy is the most common form of cardiomyopathies and a major cause of heart failure (HF). Fundamental histopathology of cardiomyopathy and failing heart is cardiomyocyte death and fibrosis. Identifying the mechanisms that drive the progression of cardiomyopathy is the pre-requisite for development of new therapies. Enhanced activity of the sympatho-beta-adrenergic receptor (beta-AR) system is a hallmark of heart disease and HF, contributing to myocyte death and fibrosis. But our understanding on the beta-AR signaling remains incomplete. .Our recent research have demonstrated that stimulation of beta-AR increases cardiac expression of Mst1, the key upstream kinase of the Hippo pathway, and that Mst1 activation leads to upregulation of the pro-apoptotic BIM and pro-fibrotic galectin-3. Our central hypothesis is that activation of Mst1-Hippo pathway in leads to upregulation of BIM and galectin-3 thereby contributing to cardiomyopathy. We will test our hypothesis by integrated physiological approaches utilizing 2 mouse models of cardiomyopathy and 3 bi-genic models generated through cross-breeding to deplete galectin-3 or BIM. Comprehensive cardiac phenotyping will be conducted to determine the severity of cardiomyopathy. Genetic and biochemical assays will be conducted to delineate the beta-AR/Mst1-Hippo/BIM and galectin-3 signaling in the heart. .This project would document, for the first time, coupling of beta-AR signalling to the Mst1-Hippo pathway leading to adverse biological consequences, particularly cardiomyocyte death and myocardial fibrosis. The outcomes would be invaluable for the development of new therapies of cardiomyopathy and HF to suppress expression BIM and galectin-3 via intervening the Mst1-Hippo pathway.

扩张型心肌病（DCM）是最常见的原发性心肌病类型，是心力衰竭（HF）的重要病因，开辟治疗DCM和HF的新途径是临床的迫切需要。进行性心肌细胞凋亡和心肌纤维化是导致DCM恶化并引起HF的重要机制。交感神经系统beta-肾上腺素能受体（β-AR）的激活伴随心肌病和HF，并导致心肌细胞凋亡和纤维化，但具体机制尚不清楚。本项目拟阐明β-AR/Hippo信号通路在心肌病和HF中的病理生理和治疗意义。我们的科研假设是：β-AR激活Mst1-Hippo通路引起转录调节异常，致使BIM和Gal-3表达升高，进而促进心肌病的发展。利用多个小鼠心肌病模型和小鼠品系杂交手段，我们将探讨Mst1、BIM和Gal-3 在心肌病中的作用以及失活这些分子的心脏保护作用。这一系列研究将为心脏Hippo信号通路的病理生理意义增加全新的内涵，并验证该通路作为心肌病治疗的可能靶点。

我们如期完成了规划的全部研究，证实了主要科研假设，即刺激β-肾上腺素能受体（βAR）能够激活心脏Hippo信号通路，上调疾病相关基因表达，同时显著抑制了线粒体代谢和质量控制相关基因的表达，造成心肌能量代谢障碍，由此促进了心肌病的发生和发展。共发表8篇论文和3篇相关的综述文章。.首先，证明了βAR激动剂异丙基肾上腺素（ISO）能够有效地激活心肌Mst1-Hippo信号通路。这一作用呈ISO剂量和时间依赖性，β1-AR和β2-AR均参与Hippo通路的激活，该作用可以被β-受体阻断剂或者蛋白激酶A抑制剂所阻断。Mst1是。利用心肌特异性高表达Hippo通路上游重要激酶Mst1（Mst1-TG）或显性失活Mst1（dnMst1-TG）小鼠模型的研究发现，激活βAR-Hippo通路依赖于Mst1的活性。.第二，进一步研究了βAR-Hippo通路激活的心脏生物学效应，发现若干促纤维化、炎症或凋亡基因（如Galectin-3）的表达水平显著升高，呈ISO剂量和时间依赖性，可被β-受体阻滞剂所抑制。同时还发现，βAR-Hippo通路激活能够显著抑制心肌线粒体相关基因的表达。.第三，利用不同的心肌病动物模型，研究了βAR-Hippo信号通路的作用。首先，在大剂量ISO（7天）造成的心肌病模型中，野生型小鼠心肌病表型明显，心肌Gal-3表达升高8倍，而Gal-3基因敲除（Gal-KO）动物心肌病表型显著减轻。其次，心肌特异性高表达β2-AR小鼠（β2-TG）出现显著细胞凋亡、纤维化和心功能减退的表型。β2-TG小鼠心脏Hippo通路显著激活，同时有Gal-3、CTGF和BIM的显著高表达。利用了Mst1-TG心肌病小鼠模型研究了Gal-3 的作用。在敲除Gal-3基因后，心肌病小鼠心肌纤维化程度显著减轻，心室功能和心力衰竭表型有显著改善。.第四，我们首次证明了βAR-Hippo信号通路-线粒体损伤是应激性心肌病（TCM，该模型通过ISO处理造成）和抗肿瘤药物所致心肌病的重要发病机制。在这两种心肌病模型中，除心肌Hippo信号通路显著激活之外，动物发生显著的线粒体损伤、线粒体质量控制机制异常、能量代谢障碍（心肌ATP水平显著降低）、心室收缩功能减退。而这些改变在Hippo通路失活（dnMst1-TG）小鼠中有显著减轻。研究发现提示：针对Hippo信号通路的干预治疗有望获得心脏