Role of MMPs in AngII induced abdominal aortic aneurysms

需要检验的中心假设是血管紧张素II(AngII)诱导的腹主动脉瘤(AAA)的启动和成熟是由一种特定的基质金属蛋白酶(MMPs)介导的，这种MMPs是通过白细胞特异性机制分泌和/或激活的。为了验证这一假说，我们提出了以下目标：目的1.确定特定的基质金属蛋白酶是否与血管紧张素转换酶诱导的AAA有关。为了确定特定基质金属蛋白酶的作用，我们将使用具有特定基质金属蛋白酶基因工程缺陷的小鼠。我们将集中精力研究基质金属蛋白酶-2、-9和-12，基于它们在动脉瘤组织中的存在以及它们先前在疾病过程中的推测作用。此外，我们还将确定MMPs及其内源性抑制物在演化和成熟的动脉瘤组织中表达的时间序列。目的2.确定血管紧张素转换酶是否能诱导白细胞释放MMPs和/或增强邻近血管细胞分泌的MMPs的活性。为了确定Angii在基质金属蛋白酶介导的AAA形成中的直接贡献，我们将进行骨髓移植研究，其中来自基质金属蛋白酶+/+或-/-小鼠的骨髓细胞将用于重新繁殖基质金属蛋白酶+/+受体小鼠。目的3.探讨血管紧张素转换酶抑制剂对白细胞依赖性基质金属蛋白酶活性的调节机制。我们将确定Angii是否对培养细胞中特定MMPs的合成和分泌产生直接影响。此外，我们将确定血管紧张素转换酶是否导致基质金属蛋白酶的激活增加。目的4.观察腹主动脉硬化形成后给予选择性抑制剂对基质金属蛋白酶的抑制作用。在初步研究中，我们证明了抑制MMPs可以阻止血管紧张素Ⅱ诱导的AAA的启动。然而，在人类疾病中，超声波被用来检测已经形成的AAA，因此有效的药物治疗必须要么减缓AAA的进展，要么逆转已经形成的AAA的病理。可以想象，MMPs在已建立的AAA的重塑过程中扮演着不同的角色，而不是它们在疾病的启动中所起的作用。因此，初步研究将确定广泛特异性的基质金属蛋白酶抑制剂对已经形成的AAA成熟过程的影响。随后的研究将根据在特定目标1-3中获得的数据，使用更具选择性的MMPs抑制剂。本研究的意义在于阐明再生障碍性贫血的形成和成熟机制，并着重于该病的药物治疗的潜在发展。

The central hypothesis to be tested is that the initiation and maturation of angiotensin II (AngII)-induced abdominal aortic aneurysms (AAAs is mediated by a specific matrix metalloproteinase (MMP) that is secreted and/or activated via a leukocyte-specific mechanism. To test this hypothesis, we propose the following aims: Aim 1. Determine whether a specific MMP is responsible for AngII- induced AAA.. To identify the action of a specific MMP, we will use mice with genetically engineered deficiencies of specific MMPs. We will focus our efforts on MMP-2, -9, and -12, based on the demonstration of their presence in aneurysmal tissue and their previous inferred roles in the disease process. Further, we will define the temporal sequence of elaboration of MMPs and their endogenous inhibitors in evolving and mature aneurysmal tissue. Aim 2. Determine whether AngII induces the release of MMPs from leukocytes and/or enhances the activation of MMPs secreted by neighboring vascular cells. To determine the direct contribution of AngII on MMP mediated AAA formation, we will perform bone marrow transplantation studies in which bone marrow cells from MMP+/+ or -/- mice will be used to repopulate MMP+/+ recipient mice. Aim 3. Determine the mechanism of AngII on leukocyte-dependent regulation of MMP activity. We will determine whether AngII exerts a direct effect on the synthesis and secretion of specific MMPs in cultured cells. Further, we will define whether AngII results in increased activation of MMPs. Aim 4. Determine the effects of MMP inhibition when selective inhibitors are administrated after the formation of AAAs. In preliminary studies we demonstrated that inhibition of MMPs prevented the initiation of AngII-induced AAA. However, in the human disease ultrasound is used to detect an already formed AAA, and thus an effective pharmacologic treatment would have to either reduce the progression or reverse the pathology of an established AAA. It is conceivable that MMPs play a different role in the remodeling process in established AAAs, as compared to their role in the initiation of the disease. Therefore, initial studies will determine the effects of broad specificity MMP inhibitors on the maturation process of an already formed AAA. Subsequent studies will use more selective inhibitors of MMPs based on data obtained in Specific Aims 1-3. The significance of this research relates to delineation of mechanism for AA formation and maturation, with emphasis on potential development of pharmacological treatments of the disease.