BMP4, Inflammation and Atherosclerosis

动脉粥样硬化主要发生在分支或弯曲动脉中暴露于不稳定剪应力条件下的病变易发区域，而暴露于单向层流剪切(LS)的动脉区域相对无病变。现在公认的是，动脉粥样硬化是一种炎症性疾病，动脉粥样硬化形成的早期阶段的特征是黏附分子的表达和随后单核细胞在病变易发区域的募集。此外，不稳定的剪切条件，如振荡剪切(OS)，会导致活性氧(ROS)的产生和炎症反应。尽管进行了大量的努力，但不稳定的切变条件引起炎症和动脉粥样硬化的确切机制尚不清楚。在这一应用中，我们提出了一种新的机制，通过OS通过调节ROS来促进炎症反应和动脉粥样硬化。 表达一种独特的血管基因产物-骨形态发生蛋白-4(BMP4)。我们的初步数据显示，与LS暴露的细胞相比，OS暴露的小鼠主动脉内皮细胞(MAEC)中BMP4基因的表达显著增加。此外，我们还发现OS产生的BMP4诱导内皮细胞间黏附分子-1(ICAM-1)的表面表达以及随后的单核细胞黏附。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可诱导BMP4的表达，而BMP4在TOM中以ROS和NFkappaB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。在第一个特定目标中，我们将确定BMP4诱导ICAM-1表达和单核细胞黏附的信号通路。NFkappanB、MAP激酶和SMAD蛋白的作用将被研究。在第二个目标中，我们计划根据我们的初步结果确定ROS在BMP4诱导的ICAM-1表达和单核细胞黏附中的作用，初步结果表明抗氧化剂可以阻断这些BMP4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。具体地说，在目标3中，我们将确定BMP4在ApoE-/-小鼠巨噬细胞募集和动脉粥样硬化中的作用。 而目标4将集中在确定BMP4受体(ALK)在内皮靶向ALK-/-.ApoE-/-小鼠巨噬细胞募集和动脉粥样硬化中的作用。BMP4作为一种炎性细胞因子的发现，不仅为研究动脉粥样硬化局灶性病变的发病机制提供了新的思路，也可能为动脉粥样硬化的新的诊断和治疗提供新的途径。

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.