多胺稳态失衡在心力衰竭中的作用和外源性精胺心肌保护机制

Heart failure is a principal causing death reason for myocardial infarction， hypertension and myocardiopathy(MC)，which precise mechanism is not yet clear, and lack in satisfactory treatment. Therefore we must search new targets. The polyamines(PA), including spermidine, spermine and putrescine, naturally occur in eukaryotic cells. PA play important roles in both physiological and pathophysiologic processes. But the relationship between PA dyshomeostasis and heart failure haven't be reported yet. In previous studies, we found that disorder of PA metabolism appeared during cardiac ischemia/ reperfusion injury(IRI); the increase of PA content is involved in myocardial hypertrophy induced by ISO; the exogenous spermine have protective effect on cardiac IRI and diabetic MC. So we presume that heart failure is related with PA dyshomeostasis：in acute heart failure, the decrease of spermine content induce apoptosis and excess autophagy, and increased spermine in chronic heart failure could cause the proliferation, fibration and hypertrophy of cardiomyocytes. To demonstrate our hypothesis, we will establish rat myocardial infarction and diabetic cardiomyopathy by coronary ligation or high-fat and high-sugar diet with injection of low dose of streptozotocin, and relative cellular models, apply gene silencing technique etc, observe different characteristics and rule of myocardial polyamine metabolism (including the rate-limiting enzymes ODC and SSAT) in rat acute and chronic heart failure, explore the key role of polyamine dyshomoestasis in development of heart failure and cellular mechanism, put focal point on mPTP and autophagy, and provide theory and experiment foundation for clinic use of spermine in prevention and treatment of heart failure in the future.

心力衰竭是心肌梗死、高血压病和心肌病的主要致死原因，确切机制未明，无满意疗法，需寻新靶点。多胺存在于真核细胞内，在生理功能和病理过程中均发挥关键作用。但多胺稳态失衡和心力衰竭的关系，尚无报道。我们前期研究发现：心肌缺血-再灌注时出现多胺代谢紊乱；心肌肥厚与多胺增加有关；外源性精胺对心肌缺血再灌注损伤和糖尿病心肌病有保护作用。我们推测心力衰竭的发生与多胺代谢失衡有关：急性心衰时精胺减少引起细胞凋亡和过度自噬；慢性心衰相反，出现心肌细胞增殖、纤维化和肥大。为证实该假说，本课题拟用冠脉结扎和高糖高脂（小剂量链脲菌素）复制冠心病和糖尿病心肌病及细胞模型，采用基因沉默等技术，观察大鼠急性和慢性心衰时心肌多胺代谢（包括限速酶ODC和SSAT表达）的不同特点和规律，以效应靶点（mPTP）和信号级联（自噬）为核心，揭示多胺稳态失衡在心衰中的核心作用和分子机制，为精胺用于临床防治心力衰竭提供理论和实验依据。

心力衰竭是冠心病、心肌病、高血压病等心血管疾病死亡的主要原因，确切机制不详，多胺代谢和心力衰竭的关系尚无报道。. 本课题采用冠脉结扎和高糖高脂饮食+大剂量链脲菌素注射等方法，制备了急性心力衰竭和糖尿病心肌病性慢性心力衰竭大鼠模型以及心肌细胞缺氧和高糖损伤模型，观察了心衰（缺血、缺氧和高糖）时心肌多胺代谢的特点和规律，除了按原定计划从细胞凋亡（线粒体通路）、自噬、线粒体通透转换孔、氧化应激的角度，还进一步从内质网应激以及gp78-泛素-蛋白酶体对心肌线粒体融合蛋白和缝隙连接蛋白的调控，揭示多胺稳态失衡在心力衰竭中的作用和外源性精胺心肌保护机制。. 本研究发现：（1）大鼠急性心力衰竭模型、慢性心力衰竭模型以及缺氧和高糖心肌细胞损伤模型均发生了多胺代谢紊乱，表现为多胺代谢池减少和精胺含量降低，其发生机制为多胺合成关键酶（鸟氨酸脱羧酶，ODC）表达下调，降解关键酶（精咪精胺乙酰转移酶，SSAT）表达上调。（2）多胺代谢紊乱可引起心肌细胞凋亡增加和自噬减少，这是导致心力衰竭的重要机制。（3）外源性精胺预处理具有显著的心肌保护作用，其机制与外源性精胺激活线粒体自噬通路、使AMPK↑→mTOR↓→自噬↑、恢复溶酶体功能和促进自噬流有关；也与抑制线粒体凋亡通路、内质网应激通路和Calpain1对ATG5的N端剪切及活性氧产生减少有关；还与外源性精胺通过激活钙敏感受体（CaSR），抑制gp78-泛素-蛋白酶体对线粒体融合蛋白和缝隙连接蛋白的降解，促进心肌能量代谢有关 。（4）缺氧性肺动脉高压是导致右心衰竭的重要机制。本研究发现化学诱导性缺氧可影响PASMC多胺代谢关键酶的表达（ODC↓，SSAT↑）；外源性精胺可通过抑制ERK1 / 2和PI3K/Akt相关通路抑制缺氧性肺动脉平滑肌细胞增殖。. 上述研究成果，从新的视角进一步揭示了心力衰竭的发生机制，为心力衰竭的防治提供了新手段、新靶点和相应的理论依据。