Sculpting the atherosclerotic plaque by neurotrophins

动脉粥样硬化的发展部分受到生长因子的局部表达的调节，这些生长因子促进造血细胞以及血管平滑肌细胞募集到新生内膜中。我们以前证明了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度表达。已经确定了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种特定作用： (1)神经营养因子介导表达Trk B的心脏内皮细胞的存活;（2）神经营养因子诱导表达Trk A和Trk B的血管平滑肌细胞向损伤后发育中的新生内膜的募集;（3）神经营养因子诱导的新生内膜中表达p75NTR的平滑肌细胞的活化诱导凋亡性细胞死亡。神经营养因子在血管系统中的作用，介导促生存和促死亡的结果，最近已经澄清了我们的鉴定，神经营养因子的前体形式选择性结合促凋亡p75 NTR，而成熟的配体选择性激活趋化和生存促进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表达，选择性MMP和 纤溶酶可以将前体切割成成熟形式。本项目的长期目标是了解神经营养因子的前体和成熟形式的差异表达如何调节病变形成和血管重塑的动力学。特定目标1的研究将确定人病变和动脉粥样硬化形成的小鼠模型中神经营养因子的原和成熟形式的空间和时间表达，并将它们的表达与p75 NTR和Trk受体以及MMP和神经营养因子的组分的协同表达相关联。 纤溶酶原蛋白酶系统。特定目标2中的研究将使用体外趋化性、存活和凋亡分析来确定前神经营养因子对血管平滑肌细胞、单核细胞/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，在具体目标3中，我们将通过以下方式从基因上剖析来自成熟神经营养因子的前神经营养因子在体内损伤形成中的作用： 用抗切割突变体替换天然BDNF编码外显子以仅产生BDNF原。将评估BDNF原过表达在血管损伤的鼠模型中的作用。这些研究的结果可能会确定独特的目标，以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.