炎症和线粒体自噬在心肌衰老中的功能和机制研究

Advanced aging is an independent risk factor for cardiovascular complications, in particular cardiac remodeling and contractile anomalies. Elucidation of the molecular mechanism(s) underlying cardiac remodeling and contractile anomalies is essential to the proper management of age-related cardiac diseases. Aging (or senescence) is typically accompanied with chronic low grade inflammation which may serve as a culprit factor for cardiac remodeling and dysfunction. More recent evidence revealed elevated levels of the inflammasome NLRP3 with aging. However, the precise role of inflammation and inflammasome including NLRP3 in cardiac complication in aging remains largely unknown. Work from our lab and others have indicated a pivotal role for autophagy, especially the mitochondria selective autophagy (mitophagy) in cardiac remodeling and contractile dysfunction under pathological conditions including aging. Recent findings from our group indicated a role for dysregulated autophagy in impaired mitochondrial and energy homeostasis in cardiac aging although little is known with regards to the role of inflammation and inflammasome in cardiac aging. This project will take advantage of the bioengineered murine models of mitophagy and NLRP3 to evaluate the role of inflammation in particularly NLRP3-mediated inflammation in the regulation of mitophagy and cardiac aging. Both naturally occurring and senescence accelerated mice (SAM) models of aging will be utilized. Completion of this project should shed some lights towards a better understanding of the pathogenesis and management of cardiac aging.

心肌衰老是老龄人群生存质量下降和住院率、死亡率增加的重要原因，阐明心肌衰老的分子调控机制对于寻找有效干预靶点具有重要意义。炎症反应和线粒体损伤是心肌衰老的重要机制。我们前期研究证实，衰老可引起炎症小体NLPR3调节的炎症反应的亢进，且伴有受损线粒体堆积及清除障碍，即线粒体自噬障碍，进而促进心肌衰老的发生发展。但是衰老心肌中炎症反应如何参与线粒体自噬障碍的调节目前尚不清楚。本项目拟在前期工作基础上，采用线粒体自噬以及 NLRP3基因敲除、转基因小鼠模型，构建自然衰老及SAM早衰（senescence accelerated mice）小鼠模型，结合心肌细胞衰老模型，从在体和离体两方面深入探讨衰老心肌中NLRP3炎症小体介导的炎症反应对线粒体自噬的调节机制，从而明确炎症反应介导的线粒体自噬障碍在心肌衰老中的重要作用，进一步阐明炎症反应和自噬抑制这两大参与心肌衰老调控的重要机制之间的相互关系。

我们采用成年或老龄野生型及PARKIN缺失小鼠作为模型，观察心脏结构功能，心肌超微结构，自噬及线粒体自噬水平、线粒体功能。结果显示衰老诱导心肌重构、心脏功能低下、细胞内钙调节失衡、自噬和线粒体自噬水平下降，而PARKIN缺失进一步恶化衰老引起的心功能改变以及心肌重构；PARKIN缺失加剧衰老引起的心肌超微结构改变，包括肌丝消失和线粒体肿胀。衰老引起自噬水平下降，PARKIN过表达可有效改善衰老引起的自噬下降。PARKIN缺失加剧衰老引起的心肌超微结构改变。分子机制结果表明PARKIN缺失引起IRE1alpha介导的保护性UPR活性下降， 进而引起心功能下降。综上所述，我们的研究结果表明PARKIN通过依赖于内质网应激UPR关键分子IRE 1 alpha调控在衰老中的心肌重构和功能。综上所述，我们的研究结果表明PARKIN调控在衰老中的心肌重构和功能。近年来心血管疾病在阿尔兹海默症患者中的发生发展越来越受到关注。阿尔兹海默症患者具有心脏淀粉样变，心肌功能低下,心肌重构等不良病理改变。我们发现阿尔兹海默症患者与小鼠模型（APP/PS1）均表现出明显心功能不良改变，包括心脏萎缩、纤维化、心功能下降等。同时在阿尔兹海默患者及小鼠模型中均出现褪黑素水平下降、ALDH2活性下降，自噬水平尤其是线粒体自噬水平的下降，以及参与调解免疫炎症反应的cGAS-STING-TBK1信号通路的失活。线粒体DNA在胞质中堆积以及线粒体损伤在阿尔兹海默症小鼠中给与褪黑素治疗后得到明显改善，痴呆引起的心脏功能不良改变、心肌超显微结构紊乱以及心肌重构等都有不同程度改善。钝化的cGAS-STING-TBK1通路得到激活，以及淀粉样小体Aβ堆积的改善。然而，褪黑素的保护作用在敲除ALDH2后消失，同时伴有cGAS-STING-TBK1通路的激活受限以及线粒体自噬的钝化。研究提示褪黑素可以通过激活ALDH2从而实现线粒体自噬的激活，在阿尔兹海默症中实现对心肌功能的保护。本项目在前期研究基础上，进一步阐明炎症反应对衰老心肌线粒体自噬的调节在心肌衰老中所起的关键作用，并进一步阐明炎症对线粒体自噬调节的主要机制，为寻找有效的衰老心肌保护靶点提供理论依据。