A novel mechanism by which smooth muscle BMAL1 regulates IL-6 and sexual dimorphism of abdominal aortic aneurysm

项目总结 腹主动脉瘤(AAA)是一种影响数百万美国人的血管疾病，占 在美国，每年有15,000人死亡。目前，开放手术或血管内手术是唯一的治疗方法。 AAA的选择，因为还没有药物被批准用于治疗这种毁灭性的疾病，突显了一个紧急的 需要对AAA进行新的机械性理解。我们最近报告说，服用盐皮质激素 受体(MR)激动剂，Aldo或脱氧皮质酮醋酸酯(DOCA)加盐，但不包括Aldo、DOCA或盐 单独对10个月大的C57BL/6雄性小鼠具有诱导AAA的作用，我们的初步数据表明 10月龄C57BL/6雄性小鼠给予血管紧张素II(Ang II)加盐，而不是单独给予Ang II 有效地诱导AAA。虽然机制仍然难以捉摸，但我们的初步数据显示，Aldo-或Ang II- 盐诱导的AAA仅或主要发生在雄性小鼠中，而雌性或去势(Orx)雄性小鼠中则不发生。至 为了阐明AAA性别二型性的机制，我们鉴定了几个基因，它们是 Aldo盐对雄性小鼠主动脉选择性上调，对雌性和雄性小鼠无明显影响。在这些基因中， 生物钟BMAL1和炎症细胞因子白介素6(IL-6)和BMAL1一样特别有希望 尽管人们普遍认为主动脉夹层和动脉瘤破裂与AAA无关 具有昼夜节律变化的特点，由于IL-6与人类AAA的关系最近很大 全基因组关联研究(GWAS)。我们的初步数据显示，BMAL1的选择性缺失 平滑肌(SM)可完全阻断DOCA盐诱导的AAA和IL-6的上调。此外，我们 发现用一种针对IL-6信号转导的新型小分子抑制剂治疗小鼠显著 减少羟醛盐诱导的AAA。根据这些具有挑衅性的初步数据和文献 睾酮(T)促进AAA，而雌激素(E2)预防AAA，我们假设T和E2 SM-BMAL1和IL-6在Aldo或Ang II盐诱导的AAA中控性二型性的作用 以IL-6信号为靶点，代表了一种新的治疗策略。 AAA。两个特定的目标验证了这一中心假设：Aim1。为了确定性激素是否对 Aldo或Ang II盐激活主动脉中的BMAL1，从而导致Aldo或Ang II盐的性别二型性- 诱导AAA。AIM2.明确SM-BMAL1转录调控IL-6的机制 靶向IL-6信号作为一种新的治疗策略来对抗Aldo或Ang II盐诱导的AAA。要实现这些目标 AIMS，我们将给10个月大的正常或去势的C57BL/6雄性动物注射Aldo或Angii盐和/或T或E2 雌性小鼠、SM-BMAL1-KO、IL-6R-KO和野生型对照小鼠诱导SM-BMAL1和IL-6信号转导 和AAA级。拟议的研究将为BMAL1和IL-6的新作用提供新的机制洞察力 AAA性二态中的信号转导。此外，这些结果将提供针对IL-1的临床前证据。 6信号转导代表了一种针对AAA的新的治疗策略。

PROJECT SUMMARY Abdominal aortic aneurysm (AAA) is a vascular disease affecting millions of Americans that accounts for 15,000 deaths per year in the United States. Currently, open or endovascular surgery is the only therapeutic option for AAA, as no drug has been approved for treatment of this devastating disease, highlighting an urgent need for new mechanistic understandings of AAA. We recently reported that administration of mineralocorticoid receptor (MR) agonists, Aldo or deoxycorticosterone acetate (DOCA) plus salt, but not Aldo, DOCA or salt alone, to 10-month-old C57BL/6 male mice potently induces AAA, and our preliminary data demonstrated that administration of angiotensin II (Ang II) plus salt, but not Ang II alone, to 10-month-old C57BL/6 male mice also potently induces AAA. While the mechanism remains elusive, our preliminary data show that Aldo- or Ang II- salt-induced AAA occurs only or mostly in male but not in female or orchidectomized (orx) male mice. To elucidate the mechanism that underlies sexual dimorphism of AAA, we identified several genes that were selectively upregulated by Aldo-salt in aorta in male but not in female or orx male mice. Among these genes, circadian clock BMAL1 and inflammatory cytokine interleukin 6 (IL-6) are particularly promising as BMAL1 has not been previously implicated in AAA despite wide recognition that aortic dissection and aneurysmal rupture are characterized by circadian variation, and as IL-6 has been associated with human AAA by recent large genome-wide association studies (GWAS). Our preliminary data show that selective deletion of BMAL1 from smooth muscle (SM) completely abolished DOCA-salt-induced AAA and IL-6 upregulation. In addition, we found that treatment of mice with a novel small molecule inhibitor targeting the IL-6 signaling significantly diminished Aldo-salt-induced AAA. Based on these provocative preliminary data and the literature that testosterone (T) promotes AAA, whereas estrogen (E2) protects against AAA, we hypothesize that T and E2 critically regulate sexual dimorphism in Aldo- or Ang II-salt-induced AAA via SM-BMAL1 and IL-6 signaling, and further, that targeting IL-6 signaling represents a novel therapeutic strategy against AAA. Two specific aims test this central hypothesis: Aim1. To determine whether sex hormone is crucial for Aldo- or Ang II-salt to activate BMAL1 in aorta and thereby result in sexual dimorphism in Aldo- or Ang II-salt- induced AAA. Aim2. To define the mechanism by which IL-6 is transcriptionally regulated by SM-BMAL1 and to target IL-6 signaling as a novel therapeutic strategy against Aldo- or Ang II-salt-induced AAA. To achieve these aims, we will administer Aldo- or AngII-salt and/or T or E2 to 10-month-old normal or castrated C57BL/6 male or female mice, SM-BMAL1-KO, IL-6R-KO, and wild-type control mice to induce SM-BMAL1 and IL-6 signaling and AAA. The proposed studies will shed new mechanistic insight into a novel role of BMAL1 and IL-6 signaling in sexual dimorphism of AAA. Moreover, the results will provide preclinical evidence that targeting IL- 6 signaling represents a novel therapeutic strategy against AAA.