Loss of BMP receptor II, inflammation, and atherosclerosis

动脉粥样硬化是一种炎性疾病，优先发生在与扰动血流相关的动脉区域，而不影响未扰动血流区域。我们已经表明，内皮细胞（EC）暴露于扰动流动条件刺激骨形态发生蛋白4（BMP 4）的产生，其诱导骨形成。 内皮细胞炎症反应和小鼠高血压。最近，在研究BMP 4作用机制时，我们发现了一个令人惊讶的矛盾现象，即siRNA介导的BMP II型受体（BMPRII）的敲除，而不是我们最初假设的阻断炎症反应，诱导了一个显著的炎症反应。 EC炎症反应。我们还发现，BMPRII的表达随着冠状动脉粥样硬化病变的进展而减少。在Apo-E基因敲除小鼠中使用颈动脉部分结扎的流动诱导的动脉粥样硬化的新模型中进行了类似的观察。我们的初步结果进一步表明，在使用BMPRir'ApoE''小鼠的部分结扎模型中，BMPRII缺乏显著加速动脉粥样硬化的发展，而在p47 phox缺陷型ApoE缺失小鼠（P47'^APOE）中，BMPRII和NADPH氧化酶在血流诱导的动脉粥样硬化中起关键作用。 动脉粥样硬化模型我们还发现，促炎细胞因子TNF α降低BMPRII表达，而降低胆固醇的他汀类药物增加它在培养的内皮细胞。这些有趣的发现让我们 提出BMPRII缺失可能是血流紊乱部位病变发生和进展的中心事件。定义BMPRII参与血管炎症的潜在机制， 动脉粥样硬化是本申请的具体目标。BMPRII在血管炎症和动脉粥样硬化中的病理生理学重要性尚不清楚。然而，BMPRII基因突变是家族性原发性肺动脉高压的主要原因。BMPRII含有长的细胞质尾，其结合超过34种蛋白质，包括p50 b NF κ B、蛋白激酶Cp和cSrc。研究表明，BMPRII可能是一种支架蛋白，它使结合的蛋白质保持不活动，直到被激动剂结合激活，就像 caveolin-1功能。在这里，我们将研究的假设，BMPRII表达下调的促动脉粥样硬化因子，包括TNF α和上调的抗动脉粥样硬化条件和药物，如他汀类药物。BMPRII表达的减少释放了正常情况下结合的信号蛋白 与受体结合并保持非活性，导致血管炎症的不受控制的激活和随后的动脉粥样硬化以NADPH氧化酶依赖性方式发展。我们将在四个目标中使用EC和小鼠模型来检验假设。目的1将定义BMPRII表达的变化， ApoE小鼠中血流紊乱的动脉粥样硬化病变，喂食高脂饮食，颈动脉部分结扎或不结扎。目的2：探讨他汀类药物和TNF α对内皮细胞和ApoE基因敲除小鼠BMPRII表达的调控机制。目的3将确定BMPRII敲低诱导细胞凋亡的机制。 EC炎症。目的4将使用喂食高脂肪饮食的BMPRir_ApoE缺失小鼠确定BMPRII表达降低对炎症和动脉粥样硬化的影响。这些研究的成功完成将为理解血管壁中BMPRII缺失引起的致动脉粥样硬化机制以及致动脉粥样硬化条件如何改变内皮细胞中BMPRII水平提供新的见解。这一新的知识将为治疗和预防动脉粥样硬化提供新的治疗和诊断靶点。

Atherosclerosis is an inflammatory disease, occurring preferentially in arterial regions associated with disturbed flow while sparing the undisturbed flow regions. We have shown that exposure of endothelial cells (EC) to disturbed flow conditions stimulates production of bone morphogenic protein 4 {BMP4), which induces inflammatory responses in ECs and hypertension in mice. Recently, while studying the mechanism of BMP4 action, we made the surprising paradoxical observation that siRNA-mediated knockdown of the BMP receptor type II (BMPRII), instead of blocking the inflammatory response as we initially hypothesized, induces a striking inflammatory response in EC. We also found that BMPRII expression decreases as the atherosclerotic lesion advances in human coronary arteries. Similar observations were made in a novel model of flow-induced atherosclerosis using a partial ligation of the carotid artery in Apo-E null mice. Our preliminary results further show that BMPRII deficiency dramatically accelerates the development of atherosclerosis in the partially liqated model using BMPRir'ApoE'' mice, while it is significantly blunted in p47phox-deficient ApoE-null mice (P47'^APOE )¿ demonstrating the critical role of BMPRII and NADPH oxidases in the flow-induced atherosclerosis model. We also found that the pro-inflammatory cytokine TNFa decreases BMPRII expression, whereas the cholesterol lowering statins increase it in cultured endothelial cells. These intriguing findings led us to propose that loss of BMPRII may be a central event in lesion initiation and progression at sites of disturbed flow. Defining the underlying mechanisms through which BMPRII is involved in vascular inflammation and atherosclerosis is the specific goal of this application. The pathophysiological importance of BMPRII in vascular inflammation and atherosclerosis is not known. However, genetic mutations of BMPRII are a major cause of familial primary pulmonary hypertension. BMPRII contains a long cytoplasmic tail that binds more than 34 proteins including p50b NFKB, protein kinase Cp and cSrc. Studies suggest that the BMPRII may be a scaffolding protein that keeps the bound proteins inactive until activated by agonist binding, much like how caveolin-1 functions. Here, we will examine the hypothesis that BMPRII expression is downregulated by pro-atherogenic factors including TNFa and upregulated by anti-atherogenic conditions and drugs such as statins. The decrease in BMPRII expression unleashes the signaling proteins that are normally bound to the receptor and kept inactive, resulting in uncontrolled activation of vascular inflammation and subsequent atherosclerosis development in a NADPH oxidase-dependent manner. We will test the hypothesis using ECs and mouse models in four Aims. Aim 1 will define the changes in BMPRII expression in flow-disturbed atherosclerotic lesions in ApoE''' mice fed a high fat diet with or without a partial ligation of the carotid artery. Aim 2 will determine the mechanisms by which statins and TNFa regulate BMPRII expression in ECs and ApoE-null mice. Aim 3 will detennine the mechanisms by which BMPRII knockdown induces inflammation in ECs. Aim 4 will determine the effect of reduced BMPRII expression on inflammation and atherosclerosis using BMPRir''_ApoE-null mice fed a high fat diet. Successful completion of these studies will provide novel insight into understanding the atherogenic mechanisms caused by the loss of BMPRII in the vessel wall, and how atherogenic conditions alter BMPRII levels in endothelial cells. This new knowledge will provide a novel therapeutic and diagnostic target to treat and prevent atherosclerosis.