线粒体calpain-1调控活性氧产生在糖尿病心肌病发生中的作用

Globally, the number of adults affected with diabetes is rapidly growing and it is estimated to increase to nearly 400 million by 2030. Diabetes can directly affect cardiac structure and function, a condition called diabetic cardiomyopathy, independent of coronary artery disease and hypertension, and characterized by ventricular insufficiency and failure. Diabetic cardiomyopathy is a serious clinical condition. It is a tremendous personal struggle for Chinese and a significant financial burden for our health care system. However, the mechanisms by which this occurs remain incompletely understood and no cure is available for this disease. Thus, further investigations are urgently needed to understand its pathogenesis, identify new therapeutic targets and develop effective therapeutic strategies. In recent years, we have demonstrated that genetic inhibition of calpain by over-expression of calpastatin or capn4 knockout prevents cardiac apoptosis, hypertrophy, fibrosis and dysfunction in mouse models of type-1 and type-2 diabetes. These studies highlight a crucial role of calpain in development of diabetic cardiomyopathy and suggest that calpain may be a novel therapeutic target for this disease. To further understand the role of calpain in great depth, our preliminary study found that diabetes increased calpain-1 in mitochondria and mitochondrial calpain-1 accumulation correlated with mitochondrial reactive oxygen species (ROS) generation in diabetic hearts. Thus, our GOAL in this grant is to investigate whether and how mitochondrial calpain-1 induces ROS generation, contributing to diabetic cardiomyopathy. We HYPOTHESIZE that mitochondrial calpain-1 targets and impairs ATP synthase activity. Disruption of ATP synthase promotes ROS generation, which mediates cardiac injury in diabetes. Accordingly, we put forth the following SPECIFIC AIMS to test our hypotheses: (1) To determine whether calpain-1 accumulation in mitochondria contributes to ROS generation in development of diabetic cardiomyopathy; (2) To investigate whether mitochondrial calpain-1 targets and impairs ATP synthase in diabetic cardiomyopathy; (3) To define whether calpain-1 mediated ATP synthase disruption plays a role in mitochondrial ROS generation and diabetic cardiomyopathy. A combination of "loss and gain of function" approaches will be taken to investigate the roles of mitochondrial calpain-1 on ROS generation and subsequent cardiac injury both in vitro and in vivo. Both streptozocin-induced mice and db/db mice will be employed as a model of type-1 and type-2 diabetes, respectively. Thus, the proposed studies will provide important information about how mitochondrial calpain-1 induces ROS generation in mediating diabetic cardiomyopathy. Further understanding of calpain-mediated diabetic cardiomyopathy will be of great significance in identifying new therapeutic targets and developing new therapy for this disease, which may potentially have significance in clinic settings

糖尿病是主要致死和致残疾病之一，严重影响人们的键康。糖尿病心肌病是严重的糖尿病并发症，它的发病机理没有完全清楚，目前尚缺乏有效的防治措施。我们近来的研究发现钙依赖性蛋白酶calpain在糖尿病心肌病发生中起重要作用。本项目是在前期研究的基础上进一步探讨线粒体中calpain-1的增高如何通过损害ATP合成酶活性，从而促进线粒体活性氧的过量产生和导致糖尿病心肌病变。为此，我们将开展如下研究内容：（1）确认线粒体内calpain-1对糖尿病心肌线粒体活性氧过量产生和在糖尿病心肌病发生中的作用；（2）明确在糖尿病心肌线粒体内calpain-1靶向裂解ATP5A1和损伤ATP合成酶；（3）阐明calpain-1介导ATP合成酶损伤在线粒体活性氧过量产生和糖尿病心肌病发生中的作用。本研究将从新的角度认识calpain-1及其下游通路在糖尿病心肌病发生中作用机制，为治疗提供新的靶点，具有重要的意义。

糖尿病是主要致死和致残疾病之一，严重影响人们的键康。糖尿病心肌病是严重的糖尿病并发症，它的发病机理没有完全清楚，目前尚缺乏有效的防治措施。我们近来的研究发现钙依赖性蛋白酶calpain在糖尿病心肌病发生中起重要作用。本项目研究了线粒体中calpain-1的增高通过损害ATP合成酶活性，从而促进线粒体活性氧的过量产生和导致糖尿病心肌病变。我们发现：（1）在培养心肌细胞和小鼠模型上，糖尿病条件引起calpain-1转移到心肌细胞线粒体内和导致心肌细胞线粒体内活性氧的过量产生；而靶向抑制线粒体内calpain或活性氧能够减轻糖尿病对心肌细胞的损伤；（2）糖尿病心肌细胞线粒体内calpain-1靶向裂解ATP5A1和损伤ATP合成酶；而上调ATP5A1减少线粒体活性氧的产生并保护糖尿病对心肌细胞的损伤；（3）转基因靶向上调线粒体内calpain-1足够引起ATP5A1下调、损伤ATP合成酶活性、诱导线粒体活性氧过量产生和心肌损伤，而选择性抑制线粒体活性氧则有效减轻心肌损伤。因此，本研究阐明了calpain-1及其下游通路在糖尿病心肌病发生中作用机制，为治疗提供新的靶点，具有重要的意义。