白细胞抗原相关蛋白酪氨酸磷酸酶对糖尿病小鼠下肢缺血性血管新生的作用及机制

Peripheral arterial disease is highly prevalent in patients with diabetes mellitus and characterized by reduced blood flow to the lower limb, resulting in chronic ischemia in these muscles, which can lead to eventual amputation of the affected limb. Deficient angiogenesis after ischemia contributes to worse outcomes of peripheral arterial disease in patients with diabetes. Diabetes can diminish the responsiveness to angiogenic factors important for the treatment of ischemic diseases. Improving angiogenesis and revascularization are therapeutic goals to rescue tissues from critical ischaemia. Protein kinases and phosphatases are involved in specific signaling pathways regulating angiogenesis. Protein phosphorylation and dephosphorylation serve as molecular switches for modulating this processe. Tyrosine phosphorylation events are controlled by the balance of activation of protein tyrosine kinases and protein tyrosine phosphatases (PTP). PTP serves to alter the duration of phosphorylation by kinases. PTPs constitute a large and structurally diverse family of signaling enzymes that control the cellular levels of protein tyrosine phosphorylation. however, despite the fact that PTPs have been garnering attention as novel therapeutic targets, they remain largely an untapped resource. Leukocyte antigen-related tyrosine phosphatase (LAR), a typical receptor like transmembrane protein tyrosine phosphatase, has been involved in the regulation of metabolic signaling and its substracts insulin-related growth factor (IGF-1) and cadherin were involved in angiogensis. In preliminary studies, we found that LAR function as a negative regulator of IGF-1 singnaling in endothelial cells. Blood perfusion of ischemic hind limbs was promoted in LAR knock out mice compared with wild-type mice in a mouse ischemia hindlimb model. Here, our hypothesis is LAR may play an important role in regulating angiogenesis in response to tissue ischemia. To determine the function of LAR on the angiogenesis of endothelial cell, we will examine IGF-1 receptor autophosphorylation via binding to the LAR, which in turn inhibits downstream phosphorylation and EC proliferation., migration and sprouting capability of endothelial cell in vitro using overexpression and knockdown strategies. To examine wether LAR expression could affect neovascularization in ischemic diseases, we test the angiogenic repair of ischemic hind limb in LAR knock out mice as evaluated by laser Doppler flow method and capillary density analyses. Intramuscular injection of an lentivirus encoding LAR siRNA is used to test the effect of LAR in limb perfusion of hind-limb ischemia in the murine B6.BKS-Lepr (db/db) diabetic model. The role of LAR modulating neovascularization in diabetic mice suffering from ischemia offering this approach could have utility for human diabetics. Therefore, LAR may be a therapeutic target to promote neovascularization in ischemic cardiovascular diseases.

糖尿病所致的下肢血管病是糖尿病的严重并发症之一, 其主要病理基础是侧枝血管新生能力受损而使肢端血液灌流不足, 促血管新生是治疗该类疾病的主要手段。生长因子通过内皮受体酪氨酸激酶(PTK)促进细胞内蛋白磷酸化, 在血管新生中发挥重要作用。 通过拮抗PTK的功能而调节蛋白质磷酸化水平的蛋白酪氨酸磷酸酶（PTP）, 是细胞各种生理活动的一类重要调控因子。白细胞抗原相关蛋白酪氨酸磷酸酶(LAR)是一种典型的受体型PTP。LAR可负性调节胰岛素的信号转导系统,其底物均参与血管新生, 最近本实验室发现LAR是内皮细胞上IGF-1受体的负性调节因子, 我们推测LAR对糖尿病缺血性血管新生具有重要的调节作用。本工作拟研究其表达对内皮细胞和小鼠缺血下肢的调节作用，并在小鼠糖尿病模型上观察LAR对缺血性血管新生的影响, 从而了解受体型PTP对糖尿病缺血性血管新生的调控特点，为治疗糖尿病外周血管病提供新的思路。

糖尿病所致的下肢血管病变是糖尿病的严重并发症之一, 促血管新生是治疗该类缺血性疾病的主要手段。多肽生长因子通过其内皮受体酪氨酸激酶(PTK)家族促进细胞内蛋白酪氨酸磷酸化, 在血管新生中发挥重要的作用。 通过拮抗PTK的功能而达到调节蛋白质酪氨酸磷酸化水平的蛋白酪氨酸磷酸酶（PTP）, 是细胞各种生理活动的一个重要调控因子。白细胞抗原相关蛋白酪氨酸磷酸酶(LAR)是一种典型的受体型PTP。鉴于LAR可负性调节胰岛素的信号传导系统,其底物均参与血管新生, 我们推测LAR对糖尿病缺血性血管新生具有重要的调节作用。本工作拟从LAR入手，研究其表达对离体内皮细胞, Matrigel种植体、小鼠缺血下肢血管再生的调节作用，并在糖尿病小鼠模型上观察LAR表达对糖尿病缺血性血管新生的影响, 从而了解受体型PTP对糖尿病缺血性血管新生的调控特点，为糖尿病缺血后的促血管新生疗法提供新的思路。