Functional role of Angiopoietin-2 in diabetic heart

描述(申请人提供)：在糖尿病患者中，冠脉侧支生长和心肌血管生成明显受损，这可能导致糖尿病心肌梗死的高死亡率。糖尿病血管生成受损与高血糖诱导的血管内皮细胞凋亡和血管生成因子信号转导功能障碍密切相关，如血管内皮生长因子和eNOS/NO信号转导功能障碍。Tie-2是一种内皮特异性受体酪氨酸激酶。血管生成素-1(Ang-1，激动剂)和Ang-2(Ang-2，拮抗剂)是Tie-2受体的两个关键配体。Ang-1被证明在调节内皮细胞存活和周细胞募集中起关键作用，而Ang-2被认为是一种血管不稳定因子，在控制血管生成或血管退化方面发挥主要作用。最近的研究表明，Ang-2在动物模型和糖尿病患者中都异常升高。此外，高血糖诱导的Ang-2导致糖尿病视网膜血管周细胞的丢失。到目前为止，关于高血糖诱导的Ang-2对糖尿病心肌内皮细胞的功能影响还知之甚少。我们的初步数据显示，暴露在高糖环境中会增加Ang-2的表达，并阻断Ang-1诱导的心肌内皮细胞迁移，这表明Ang-2的异常对糖尿病心肌血管生成有不利影响。此前，我们观察到Ang-1通过上调热休克蛋白90(Hsp90)/eNOS相互作用促进猪冠状动脉内皮细胞血管生成。因此，我们认为，高血糖诱导的Ang-2破坏了Ang-1/Hsp90客户蛋白的相互作用，并导致心肌内皮细胞失稳和心肌血管生成障碍。为了探讨我们的观点，利用db/db糖尿病小鼠模型，我们将检测：(1)高血糖诱导的Ang-2是否扰乱了Ang-1介导的Hsp90/客户蛋白相互作用，导致心肌内皮细胞凋亡和失稳，周细胞丢失和血管生成障碍；(2)Ang-1预处理通过促进Hsp90/客户蛋白相互作用和周细胞募集来预防高血糖诱导的心肌内皮细胞凋亡和失稳。我们提出的研究将阐明高血糖导致血管生成障碍的重要和新的机制，并将为开发治疗糖尿病血管生成异常的新的治疗策略提供一个框架。

DESCRIPTION (provided by applicant): In patients with diabetes mellitus, coronary collateral growth and myocardial angiogenesis are significantly impaired, and these may contribute to high mortality in diabetic myocardial infarction. Diabetic impaired angiogenesis is strongly associated with hyperglycemia-induced endothelial cell apoptosis and angiogenic factors signal transduction dysfunction such as VEGF and eNOS/NO signaling. Tie-2 is an endothelial- specific receptor tyrosine kinase. Angiopoietin-1 (Ang-1, agonist) and angiopoietin-2 (Ang-2, antagonist) are the two key ligands of Tie-2 receptor. Ang-1 has been shown to play a critical role in regulating endothelial cell survival and pericytes recruitment, whereas Ang-2 has been identified as a vessel-destabilizing agent that plays a predominant role in controlling angiogenesis or vessel regression. Recent studies reveal that Ang-2 is abnormally raised both in animal models and in diabetic patients. Further, hyperglycemia-induced Ang-2 contributes to pericytes loss in diabetic retinal vasculature. So far, little is known about the functional consequences of hyperglycemia-induced Ang-2 on diabetic myocardial endothelium. Our preliminary data reveals that exposure to high glucose increases Ang-2 expression and blocks Ang-1-induced myocardial endothelial cell migration indicating that an abnormality of Ang-2 has a detrimental effect on diabetic myocardial angiogenesis. Previously, we made a novel observation that Ang-1 stimulates angiogenesis via upregulation of heat shock protein 90 (Hsp90)/eNOS interaction in porcine coronary artery endothelial cells. Therefore, we propose that hyperglycemia-induced Ang-2 disrupts Ang-1/Hsp90 client protein interactions and contributes to myocardial endothelium destabilization and impairment of myocardial angiogenesis. To explore our notion, using db/db diabetic mice model, we will examine whether: (1) Hyperglycemia-induced Ang-2 disrupts Ang-1 mediated Hsp90/client protein interactions, leads to myocardial endothelium apoptosis and destabilization, loss of pericytes and impairment of angiogenesis; and (2) Pretreatment with Ang-1 prevents hyperglycemia-induced myocardial endothelial apoptosis and destabilization via promoting Hsp90/client protein interactions and recruitment of pericytes. Our proposed studies will elucidate important and novel mechanisms underlying hyperglycemia-induced impairment of angiogenesis and should provide a framework for developing new therapeutic strategies for the treatment of diabetic abnormal angiogenesis.