Notch信号通路在腹主动脉瘤发生中作用及调控炎性反应的分子机理

Abdominal aortic aneurysm (AAA) has become a common vascular disease in aging society. Once rupture occurs, which is the most widely recognized complication of AAA, mortality is extremely high due to rapid exsanguination. The pathological features of AAA include inflammatory process related to migration of lymphocytes and macrophages, extracellular matrix remodeling and medial disruption, cellular apoptosis, medial neovascularization, et al. Recent evidences indicate that Notch signaling contributes to inflammatory process, deterioration of extracellular matrix, tissue remodeling and cellular apoptosis; meanwhile, Notch signaling plays a pivotal role in the accumulation of inflammatory cells, overproduction of cytokines，polarization of macrophages, and medial neovascularization. Nevertheless, the effect of Notch signaling pathway in the AAA formation has not being elucidated and the molecular mechanisms of Notch function in the AAA formation remain obscure. We has found in the pre-experiment that increased expression of Notch receptors and their cognate ligands in the aortic tissue of AAA patients and experimental animal model，and the pilot study also demonstrated the accumulation of inflammatory cells and ectopic activation of relative cytokines, implicating an important role for Notch signaling pathways in AAA development.. The project intends to study the expression of Notch signaling pathway components in AAA and the mechanism of Notch signaling pathway in regulating the inflammatory process, apoptosis and medial neovascularization from multiple aspects, expecting to have an impact on the potential for diagnostic markers and intervention targets, and provide a theoretical basis for the pathogenesis of AAA formation.

腹主动脉瘤（AAA）是严重危害老年人的动脉扩张性疾病。免疫炎症反应是其主要病理特征之一。Notch信号是调节炎症反应、细胞凋亡及血管新生的主要通路。但是Notch信号通路在AAA发生发展中的作用以及调节炎症反应的分子机制仍不清楚。申请人前期研究发现AAA患者主动脉组织和动物模型Notch信号通路中NICD和配体HES1表达水平明显增高、巨噬细胞等浸润增加，提示Notch信号通路可能在AAA发生中起重要作用。本项目拟采用Notch基因敲除小鼠、γ-促分泌酶抑制剂处理小鼠及体外培养的平滑肌细胞、巨噬细胞和T淋巴细胞，采用过表达Notch激活片段NICD腺病毒转染和分子细胞生物学技术，研究Notch信号通路在AAA发生发展及其逆转中的作用机制。探讨Notch信号调控细胞炎症反应、细胞凋亡及血管新生等的分子机制，寻找AAA潜在的诊断标记物和干预靶点, 为阐释AAA发病的新机制提供理论依据。

腹主动脉瘤（AAA）是老龄化社会的常见病，一旦破裂死亡率达60~80%。本课题通过动物实验发现AAA形成过程中Notch信号通路的异常激活，其抑制剂dibenzazepine（DBZ）可抑制AAA形成。进一步研究发现DBZ可减轻血管壁的炎性增厚与胶原纤维的异常沉积；DBZ可抑制主动脉壁内巨噬细胞浸润及相关炎症因子的分泌；DBZ可抑制腹主动脉瘤中CD4+T细胞的聚集和Th2的分化；DBZ可抑制主动脉壁内MMP-2、MMP-9及MCP-1表达；DBZ可抑制Ang II诱导的主动脉壁内血管新生。该研究首次在体内实验层面明确了Notch信号通路激活可促进AAA形成及其作用机制，为AAA的临床干预提供新的参考靶点。本课题组进一步通过搜集临床病例标本，运用酶联免疫荧光实验测定血浆中的Notch信号通路相关蛋白表达，发现血浆 Notch1和 TACE浓度在AAA患者较正常对照显著增高；通过绘制ROC曲线分析，发现同时检测Notch1和TACE血浆水平可提高AAA的预测值。该研究为临床筛查、检测AAA提供了新的潜在生物学标记物。本课题组在既往实验基础之上，进一步进行动物实验研究，发现AAA形成过程中泛素-蛋白酶体系统的异常激活，蛋白酶体抑制剂Bortezomib（BTZ）可抑制AAA形成，主要机制包括：BTZ可抑制腹主动脉组织的炎性重塑及弹力纤维断裂；BTZ抑制主动脉壁内MMP-2及MMP-9活性；BTZ抑制主动脉壁内T淋巴细胞、巨噬细胞等炎症细胞浸润及炎症因子分泌；BTZ可逆转Ang II诱导的主动脉壁内平滑肌细胞表型转化。该研究首次在体内实验层面明确了蛋白酶体激活可促进AAA形成及其作用机制。本课题组发现血清促血管生成素相关生长因子（AGF）表达水平在AAA患者血浆中升高，其升高程度随瘤体的增大更为明显。同时发现高AGF水平是下肢外周动脉疾病（LEPAD）的潜在危险因素，并且与LEPAD患者的疾病严重性和不良结果相关。为临床评估AAA、下肢缺血患者的预后提供新的监测指标。通过总结研究成果，课题在研期间本课题组共发表相关SCI论著5篇，累计影响因子15.99，指导4名博士研究生毕业。研究成果得到业界认可，获得华夏医学科技奖一次。