Serum Amyloid A, Inflammasome Activation, and Abdominal Aortic Aneurysms

最近的估计表明，在美国65-79岁的男性中有5%-10%，女性中有1%-2%是 患有腹主动脉瘤(AAA)。每年大约有15,000人死于腹主动脉破裂。 由于缺乏其他已证实有效的治疗方法，AAA的治疗仅限于手术干预。 尽管大多数AAA患者没有症状，但由于破裂而死亡的风险大大增加 AAAS扩大规模。对AAA进展的机制的洞察将对 通过提供新的生物标记物来预测AAA的扩张和因此AAA的风险 主动脉破裂，以及新的干预策略。我们实验室最近发表的研究结果 为详细评估血清淀粉样蛋白A(SAA)在AAA进展中的作用提供动力：1)SAA缺乏 在小鼠模型中减弱AAA；2)在小鼠中，SAA存在于AAA中具有实质性弹性蛋白的区域 降解、巨噬细胞浸润和基质金属蛋白酶(MMP)活性；3)SAA 在人类AAA中。在未发表的工作中，我们还确定了SA诱导IL-1β和NLRP3的表达，AS 巨噬细胞中IL-1β的分泌，与NLRP3炎症小体的启动和激活一致。 这些发现值得注意，因为最近认识到NLRP3炎症小体激活是一个关键事件 在小鼠的AAA发育过程中。因此，我们的中心假设是SAA激活了NLRP3炎症体， 从而放大局部炎症反应，增强病理组织重塑，促进 AAA级。目的1：探讨NLRP3炎性小体在SAA促进AAA中的作用 老鼠。目标1a。使用缺乏各种炎症体成分的小鼠(NLRP3-/-，ASC-/-，caspase-1-/-小鼠) 或IL-1β信号转导(IL-1R-/-小鼠)，我们将确定SAA介导的氨基酸是否依赖于NLRP3 炎症者。我们还将调查小分子阴离子磺酸盐，一种阻止 SAA在组织中的沉积，能有效地降低小鼠体内的AAA。目标1b。利用巨噬细胞培养， 我们将调查是否有任何已知的生物活性归因于SAA，包括活性氧 物种生成或与高密度脂蛋白结合，参与SAA介导的NLRP3炎症体激活。 目的2：检验全身性SAA促进AAA进展的假说。目标2a。 我们的方法将是在特定的时间间隔内瞬时增加小鼠肝脏中SAA的表达 通过使用病毒载体和可诱导的转基因进行血管紧张素Ⅱ输注的过程。作为补充 方法，SAA的表达将被抑制使用反义寡核苷酸。SAA对指数的影响 AAA进展与主动脉炎症和重塑的关系将被确定。目标2b。为了调查 唾液酸与炎性小体激活在人再障中的作用及其与IL-1β的关系 AAA在人类中的扩张率将在N-TA3CT前瞻性试验中确定。这些研究 有潜力确定AAA临床管理的新策略。

Recent estimates indicate that 5-10% of men and 1-2% of women 65-79 years of age in the United States are living with an abdominal aortic aneurysm (AAA). Approximately 15,000 will die each year due to AAA rupture. The treatment for AAA is limited to surgical intervention due to lack of other therapies with proven benefit. Although most patients with AAAs are asymptomatic, the risk of death due to rupture increases greatly as AAAs expand. Insights into mechanisms contributing to AAA progression would have a major impact on the clinical management of AAA by providing new biomarkers that predict AAA expansion and thus the risk for aortic rupture, as well as novel strategies for intervention. Recent published findings from our laboratory provide the impetus for a detailed evaluation of serum amyloid A (SAA) in AAA progression: 1) SAA deficiency attenuates AAA in a mouse model; 2) in mice, SAA is present in AAA in regions with substantial elastin degradation, macrophage infiltration, and matrix metalloproteinase (MMP) activity; and 3) SAA can be detected in human AAA. In unpublished work, we also determined that SAA induces IL-1β and NLRP3 expression, as well as IL-1β secretion, in macrophages, consistent with priming and activation of the NLRP3 inflammasome. These findings are notable, given the recent recognition that NLRP3 inflammasome activation is a critical event in AAA development in mice. Thus, our central hypothesis is that SAA activates the NLRP3 inflammasome, thereby amplifying local inflammatory responses that enhance pathological tissue remodeling and promote AAA progression. AIM 1: Investigate the role of the NLRP3 inflammasome in SAA's ability to promote AAA in mice. Aim 1a. Using mice deficient in various inflammasome components (NLRP3-/-, ASC-/-, caspase-1-/- mice) or IL-1β signaling (IL-1R-/- mice), we will determine whether SAA-mediated AAA is dependent on the NLRP3 inflammasome. We will also investigate whether small-molecule anionic sulphonates, a treatment that blocks the deposition of SAA in tissues, is effective in reducing AAA in mice. Aim 1b. Using macrophage cell cultures, we will investigate whether any of the known biological activities attributed to SAA, including reactive oxygen species generation or association with HDL, are involved in SAA-mediated NLRP3 inflammasome activation. AIM 2: To test the hypothesis that systemic SAA promotes the progression of an established AAA. Aim 2a. Our approach will be to transiently increase SAA expression in livers of mice at specific intervals during the course of AngII infusion through the use of viral vectors and an inducible transgene. As a complementary approach, SAA expression will be suppressed using antisense oligonucleotides. The impact of SAA on indices of AAA progression and aortic inflammation and remodeling will be determined. Aim 2b. To investigate the potential role of SAA and inflammasome activation in human AAA, the relationship between plasma SAA, IL-1β and the rate of AAA expansion in humans will be determined in the prospective N-TA3CT trial. These studies hold the potential for identifying new strategies for the clinical management of AAA.