HSP27对AApoAII淀粉样蛋白所致心肌损伤保护作用的机制研究

Amyloidosis is a group of diseases characterized by the deposition of insoluble materials in various organs and tissues, and further results in the organ dysfunction. The heart is one of the most commonly involved organs in amyloidosis. Cardiac amyloidosis is associated with the most critical and fatal manifestation and usually causes a rapid decline in cardiac function. Since it is unresponsive to current therapies, most patients have a very bad prognosis. From diagnosis, its median survival time is only 1.3 years and the 5-year survival rate is less than 10%. The mechanisms underlying this disorder, however, remain unknown. In our previous study, we found that the overexpression of heat shock transcription factor-1(HSF1) can inhibit the deposition of AApoAII amyloidosis in the heart. At the same time, we also observed that the expression of α-actin in the heart with amyloidosis was significantly less than the control mice without amyloid deposition. Subsequently, the cardiac contractile dysfunction was also proved by echocardiography. So, we postulate that AApoAII amyloid protein can injury the cardiac myocytes through impairing the integrity of myocardial cytoskeletal. In addition, the overexpression of heat shock protein (HSP)27 induced by HSF1 can maintain the integrity of myocardial cytoskeletal and subsequently protect the cardiac function by the mechanism involving the RhoA-ROCK signal pathway. In this study, we culture the cardiac myocytes and observe the level and distribution of α-actin under the stimulation of AApoAII amyloid protein. Further, we also observe if the overexpression of HSP27 can inhibit the cytoskeletal disruption and protect the cardiac myocytes from the injury induced by the AApoAII amyloidosis through the RhoA-ROCK pathway. Based on these rusults, we can partially clarify the mechanisms of cardiac amyloidosis and provide a possible new therapeutic method for this lethal disease.

淀粉样变性是不可溶性淀粉样物质沉积于器官或组织，导致功能障碍的一组疾病。心脏是淀粉样变性常累及的器官，由于其对治疗反应不佳，使患者预后极差，而目前发病机制尚不明确。我们在前期的研究中发现过表达热休克转录因子1（HSF1）可有效抑制淀粉样物质在心脏沉积。同时也观察到随着淀粉样物质在心脏的沉积，心肌细胞骨架蛋白α-actin的表达明显减少，心肌的收缩能力也显著下降。因此我们推测淀粉样物质可以通过影响心肌细胞骨架的完整性损伤心肌细胞。而HSF1可增加热休克蛋白(HSP)27表达，进而通过RhoA-ROCK信号途径保护细胞骨架的完整性而减少心肌的损伤。在该研究中我们利用培养的大鼠心肌细胞，观察在淀粉样物质AApoAII的刺激下，心肌细胞α-actin的表达变化及收缩能力的改变，以及过表达HSP27后对α-actin及心肌细胞收缩功能的影响及可能机制，为心脏淀粉样变性的治疗提供新的思路。

阿尔兹海默病（Alzheimer disease, AD）是老年期痴呆最常见一种类型，随着我国人口老龄化，AD已成为一个重要的医学和社会问题。近年无论是临床观察还是动物实验均发现AD与心功能不全存在紧密联系。在患有心脏淀粉样变性的心肌中含有β-淀粉样蛋白（Aβ），提示心脏有可能是除中枢神经系统之外另一个Aβ累及的器官。目前越来越多证据表明前体蛋白及其聚集体可以独立于纤维沉积本身而直接造成器官功能损伤。基于上述研究背景，我们推测Aβ可以在体外直接作用于心肌细胞导致其损伤。本研究利用体外培养的大鼠心肌细胞观察了Aβ对心肌细胞的毒性作用及其可能机制，并探讨了热休克反应对心肌细胞的保护作用。.首先利用培养的大鼠心肌细胞，发现Aβ25-35以浓度依赖的方式促进心肌细胞的凋亡，促凋亡相关蛋白（Bax, cleaved Caspase-3, cleaved Caspase-7和cleaved PARP）随Aβ25-35浓度的升高而表达增加，而抗凋亡因子Bcl-2则随着Aβ25-35浓度的升高表达减少。在进一步探讨心肌细胞凋亡的可能分子途径时发现给予Aβ25-35后大鼠心肌细胞p-p38MAPK表达明显增加，而内质网应激反应标志蛋白GRP78, CHOP的表达也明显增加，提示P38MAPK途径及内质网应激反应可能参与了Aβ25-35导致的心肌细胞凋亡。另外基于前期研究结果，进一步观察了Aβ25-35是否同AApoAII淀粉样蛋白一样能够引起心肌细胞骨架蛋白的变化。采用鬼笔环肽免疫荧光法证实Aβ25-35能够导致骨架蛋白解聚，也通过ROCK抑制剂的干预进一步证明RhoA-ROCK途径参与了心肌细胞的凋亡。.本研究进一步探讨了热休克反应与Aβ25-35所致心肌细胞凋亡的关系。发现Aβ25-35作用于心肌细胞可抑制HSF1及HSP70，HSP27，HSP90的表达。而过表达HSF1在促进热休克蛋白表达的同时，能够显著抑制心肌细胞凋亡，同时抑制RhoA-ROCK途径的激活及内质网应激反应。以上结果提示Aβ25-35对热休克反应的抑制可能参与了心肌细胞的凋亡，反之促进热休克反应可能成为减轻Aβ25-35导致心肌损伤的有效手段。.本研究首次证实Aβ对心肌细胞的损伤作用，并部分阐明其可能机制，证实热休克反应有可能成为减轻心肌损伤的手段。为AD相关性心肌损伤的发病机制和保护策略提供新的思路。