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

项目摘要 腹主动脉瘤（AAA）是一种影响数百万美国人的血管疾病， 美国每年有15,000人死亡。目前，开放或血管内手术是唯一的治疗方法， AAA的选择，因为没有药物被批准用于治疗这种毁灭性的疾病，突出了一个紧迫的问题。 需要对AAA的新的机械理解。我们最近报道，盐皮质激素的管理， 受体（MR）激动剂，Aldo或醋酸脱氧皮质酮（DOCA）加盐，但不包括Aldo、DOCA或盐 对10月龄C57 BL/6雄性小鼠单独使用，有效地诱导AAA，我们的初步数据表明， 对10个月大的C57 BL/6雄性小鼠施用血管紧张素II（Ang II）加盐，而不是单独施用Ang II，也 有效诱发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仅发生或主要发生在雄性小鼠中，而不发生在雌性小鼠或去卵巢（orx）雄性小鼠中。到 为了阐明AAA性二型性的机制，我们鉴定了几个基因， Aldo盐选择性上调雄性小鼠的主动脉，但不上调雌性或orx雄性小鼠的主动脉。在这些基因中， 生物钟BMAL 1和炎性细胞因子白细胞介素6（IL-6）特别有希望，因为BMAL 1具有 尽管广泛认识到主动脉夹层和动脉瘤破裂 以昼夜节律变化为特征，并且由于IL-6与人类AAA相关，最近的大规模研究表明， 全基因组关联研究（GWAS）。我们的初步数据表明，选择性缺失BMAL 1， 平滑肌（SM）完全消除DOCA盐诱导的AAA和IL-6上调。另外我们 发现用一种新的靶向IL-6信号传导的小分子抑制剂治疗小鼠， 减少醛盐诱导的AAA。根据这些挑衅性的初步数据和文献， 睾酮（T）促进AAA，而雌激素（E2）保护AAA，我们假设T和E2 通过SM-BMAL 1和IL-6在Aldo或Ang II盐诱导的AAA中关键调节性二态性 此外，靶向IL-6信号转导代表了一种新的治疗策略， AAA。两个具体的目标测试这个中心假设：目标1。为了确定性激素是否对 Aldo-或Ang II-盐激活主动脉中的BMAL 1，从而导致Aldo-或Ang II-盐中的性二型性。 诱发AAA。目标2。确定IL-6受SM-BMAL 1转录调控的机制， 靶向IL-6信号传导作为针对Aldo或Ang II盐诱导的AAA的新治疗策略。实现这些 目的，我们将Aldo-或AngII-盐和/或T或E2给予10个月大的正常或去势的C57 BL/6雄性 或雌性小鼠、SM-BMAL 1-KO、IL-6 R-KO和野生型对照小鼠诱导SM-BMAL 1和IL-6信号传导 和AAA。这些研究将为BMAL 1和IL-6的新作用提供新的机制见解 AAA的性二型性信号。此外，这些结果将提供临床前证据，靶向IL-10， 6信号转导代表了针对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.