BMP4, Inflammation and Atherosclerosis

动脉粥样硬化优先发生在分支或弯曲动脉中暴露于不稳定剪切应力条件的病变易发区域，而暴露于单向层流剪切（LS）的动脉区域相对无病变。现在公认动脉粥样硬化是一种炎症性疾病，动脉粥样硬化形成的最早阶段的标志是粘附分子表达和随后在病变易感区域中单核细胞的募集。此外，不稳定的剪切条件，如振荡剪切（OS）诱导产生活性氧（ROS）和炎症反应。尽管付出了巨大的努力，但不稳定的剪切条件诱导炎症和动脉粥样硬化的确切机制尚不清楚。在本申请中，我们提出了一种新的机制，通过该机制，OS以ROS依赖的方式通过调节 一种独特的血管基因产物骨形态发生蛋白4（BMP 4）的表达。我们的初步数据表明，BMP 4基因表达显着增加，在小鼠主动脉内皮细胞（MAEC）暴露于OS相比，细胞暴露于LS。此外，我们发现，骨形成蛋白4产生的OS诱导表面表达的内皮细胞间粘附分子-1（ICAM-1）和随后的单核细胞粘附。基于这些发现，我们提出了一个中心假设，即内皮细胞暴露于OS诱导BMP 4表达，这反过来又以ROS和NF κ B依赖的方式启动炎症级联反应，导致单核细胞募集，泡沫细胞形成和随后的动脉粥样硬化。在第一个具体目标中，我们将确定BMP 4诱导ICAM-1表达和单核细胞粘附的信号通路。将研究NF κ B、MAP激酶和SMAD蛋白的作用。在第二个目标中，我们计划确定ROS在BMP 4诱导的ICAM-1表达和单核细胞粘附中的作用，基于我们的初步结果，抗氧化剂阻断了这些BMP 4诱导的炎症反应。在目标3和4中，我们将在动脉粥样硬化的动物模型中测试这些概念。具体而言，在目标3中，我们将确定BMP 4在ApoE -/-小鼠中巨噬细胞募集和动脉粥样硬化中的作用， 而目标4将集中于确定内皮靶向ALK-/-、ApoE-/-小鼠中BMP 4受体（ALK）在巨噬细胞募集和动脉粥样硬化中的作用。BMP 4作为炎症细胞因子的鉴定不仅将为在病变易发区域中动脉粥样硬化的局灶性发展的机制提供新的见解，而且还可以确定动脉粥样硬化的新的诊断和治疗方法。

Atherosclerosis preferentially occurs in lesion-prone areas exposed to unstable shear stress conditions in branched or curved arteries, while the arterial regions exposed to unidirectional laminar shear (LS) are relatively lesion-free. It is now well accepted that atherosclerosis is an inflammatory disease and that the hallmarks of the earliest stages of atherogenesis are adhesion molecule expression and subsequent recruitment of monocytes in the lesion prone areas. In addition, unstable shear conditions such as oscillatory shear (OS) induce production of reactive oxygen species (ROS) and inflammatory responses. Despite intense efforts, the precise mechanisms by which unstable shear conditions induce inflammation and atherosclerosis are not clear. In this application, we propose a novel mechanism by which OS promotes inflammatory responses and atherosclerosis in a ROS-dependent manner via regulation of the expression of a unique vascular gene product, bone morphogenic protein-4 (BMP4). Our preliminary data show that BMP4 gene expression is dramatically increased in mouse aortic endothelial cells (MAEC) exposed to OS when compared to cells exposed to LS. Moreover, we found that BMP4 produced by OS induced surface expression of endothelial intercellular adhesion molecule-1 (ICAM-1) and subsequent monocyte adhesion. Based on these findings, we propose the central hypothesis that exposure of endothelial cells to OS induces BMP4 expression, which in tum initiates an inflammatory cascade in a ROS- and NFkappaB-dependent manner resulting in monocyte recruitment, foam cell formation, and subsequent atherosclerosis. In the first specific aim, we will determine the signaling pathways by which BMP4 induces expression of ICAM-1 and monocytes adhesion. The role of the NFkappanB, MAP kinases and SMAD proteins will be investigated. In the second aim, we plan to determine the role of ROS in BMP4-induced expression of ICAM-1 and monocyte adhesion, based on our preliminary results showing that antioxidants block these BMP4-induced inflammatory responses. In aims 3 and 4, we will test these concepts in an animal model of atherosclerosis. Specifically in aim 3, we will determine the role of BMP4 in the macrophage recruitment and atherosclerosis in ApoE -/- mice, while aim 4 will center on determining the role of the BMP4 receptor (ALK) in macrophage recruitment and atherosclerosis in endothelial-targeted ALK-/-.ApoE-/- mice. The identification of BMP4 as an inflammatory cytokine will not only provide novel insight into the mechanisms underlying the focal development of atherosclerosis in lesion-prone areas, but also may identify novel diagnostic and therapeutic approaches in atherosclerosis.