Sculpting the atherosclerotic plaque by neurotrophins

动脉粥样硬化的发展在一定程度上是由生长因子的局部表达调节的，这些生长因子促进造血细胞和血管平滑肌细胞向新生内膜的募集。我们先前已经证明神经营养因子及其受体，受体酪氨酸激酶的trk家族和p75神经营养因子受体(P75NTR)在动脉粥样硬化病变中高表达。神经营养因子在调节血管发育和调节血管对损伤的反应中的三个具体作用已被确定： (1)神经营养素介导表达Trk B的心脏内皮细胞存活；(2)神经营养素诱导表达Trk A和Trk B的血管平滑肌细胞在损伤后向发育中的新生内膜募集；(3)神经营养素诱导新生内膜中表达p75NTR的血管平滑肌细胞激活，诱导细胞凋亡。神经营养因子在血管系统中作用的悖论，既介导了有利于生存的结果，也调节了有利于死亡的结果，最近我们的发现澄清了神经营养因子的前体选择性地与促凋亡的p75NTR结合，而成熟的配体选择性地激活趋化和促进生存的Trk受体。我们的初步研究表明，神经营养因子NGF和BDNF的前体和成熟形式在人类动脉粥样硬化病变和小鼠模型的动脉粥样硬化中都有表达，选择性MMPs和 纤溶酶可以将前体裂解成成熟的形式。该项目的长期目标是了解前和成熟形式的神经营养因子的差异表达如何调节病变形成和血管重塑的动力学。具体目标1的研究将确定神经营养因子的前和成熟形式在人类病变和小鼠动脉粥样硬化形成模型中的时空表达，并将它们的表达与p75NTR和trk受体的协同表达以及MMPs和MMPs的成分相关联。 纤溶酶原蛋白酶系统。通过体外趋化、存活和凋亡分析，鉴定神经营养因子前体对血管平滑肌细胞、单核/巨噬细胞和内皮细胞的生物学作用，并将其与成熟神经营养因子的作用进行比较。最后，在特定的目标3中，我们将通过以下方式从基因上剖析成熟神经营养因子在体内病变形成中的作用 用抗切割突变体替换天然的BDNF编码外显子，以仅产生前BDNF。在小鼠血管损伤模型中，将评估PRO-BDNF过表达的影响。这些研究的结果可能确定独特的靶点来调节发展中的动脉粥样硬化的微环境。

The development of atheroma is regulated in part by the localized expression of growth factors that promote the recruitment of hematopoietic cells as well as vascular smooth muscle cells into the neointima. We previously demonstrated that the neurotrophins and their receptors, the trk family of receptor tyrosine kinases and the p75 neurotrophin receptor (p75NTR), are highly expressed in atherosclerotic lesions. Three specific roles for the neurotrophins in regulating vessel development and in modulating the vascular response to injury have been identified: (1) neurotrophin-mediates survival of Trk B-expressing cardiac endothelial cells (2) neurotrophin-induced recruitment of Trk A and Trk B-expressing vascular smooth muscle cells to the developing neointima following injury; (3) neurotrophin-induced activation of p75NTR-expressing smooth muscle cells in the neointima induces apoptotic cell death. The paradox of neurotrophin actions in the vasculature, mediating both pro-survival and pro-death outcomes, has recently been clarified by our identification that the pro-forms of the neurotrophins selectively bind to the proapoptotic p75NTR, whereas the mature ligand selectively activates the chemotactic and survival promoting Trk receptors. Our preliminary studies indicate that both the pro- and mature forms of the neurotrophins NGF and BDNF are expressed in human atherosclerotic lesions and atheroma from murine models, and that selective MMPs and plasmin can cleave pro-forms to mature forms. The long term goals of this project are to understand how the differential expression of pro- and mature forms of neurotrophins regulate the dynamics of lesion formation and vascular remodeling. Studies in Specific Aim 1 will define the spatial and temporal expression of the pro- and mature forms of the neurotrophins in human lesions and in murine models of atheromata formation and correlate their expression with the co-ordinate expression of p75NTR and Trk receptors, as well as MMPs and components of the plasminogen protease system. Studies in Specific Aim 2 will identify the biological actions of the pro-neurotrophins on vascular smooth muscle cells, monocytes/macrophages and endothelial cells using in vitro analysis of chemotaxis, survival and apoptosis and compare them to the actions of the mature neurotrophins. Finally, in Specific Aim 3, we will genetically dissect the actions of the pro-neurotrophins from mature neurotrophins in lesion formation in vivo by replacing the native BDNF coding exon with a cleavage resistant mutant to generate only pro-BDNF. The effects of pro-BDNF overexpression in murine models of vascular injury will be assessed. The results of these studies may identify unique targets to regulate the microenvironment of the developing atheroma.