IL1beta signaling in SMCpromotes beneficial changes in late stage atherosclerotic lesion pathogenesis

动脉粥样硬化血栓形成，由不稳定的动脉粥样硬化斑块破裂或侵蚀引起，是 世界范围内的死亡。然而，调节晚期动脉粥样硬化病变稳定性的机制仍然存在。 人们对此知之甚少。教义是：1)斑块包含一个大的坏死核，一个薄的纤维帽，和一个大的 CD68+细胞相对于Acta2+细胞的数量[推测为巨噬细胞(MФ)和平滑肌细胞 (分别为SMC)更容易破裂；和2)SMC发挥有益的作用，因为它们是主要的 负责形成富含基质的保护性纤维帽的细胞类型。然而，我们实验室最近的研究 同时涉及SMC谱系追踪和干细胞多能性基因的SMC特异性敲除(KO) 10月4日或KLF4，提供了令人信服的证据挑战这一教条，包括表明SMC可以有主要的 对晚期皮损发病的有利或不利影响取决于其表型的性质 过渡。因此，我们试图确定促进有益(动脉粥样硬化保护)SMC表型的机制。 转变，并假设用抗IL-1β抗体(Ab)治疗可以全局抑制炎症 会引发这样的变化。然而，与预期完全相反的是，对待我们的SMC血统追踪 ApoE-/-小鼠在18-26周的西方饮食中使用抗IL-1β抗体导致多种有害变化 包括纤维帽厚度和胶原含量显著减少，纤维帽SMC和 替换为MФS，并损害外向重塑。这项提案中的研究将检验这一假设 IL-1β信号在晚期病变的发病机制中起着重要的有益作用，包括 形成和维护保护性纤维帽所必需的。目标1将确定持久性IL1R1 SMC内的信令是维持SMC富含纤维帽所必需的。研究将包括确定 IL1R1配体IL1β、IL1α以及IL1Ra各自的贡献。我们还将确定SMC是否- 他莫昔芬条件KO的IL1R1受体，在建立晚期动脉粥样硬化后，16- WD喂养18周后，SMC纤维帽覆盖范围的丧失与其他有害变化一致 斑块不稳定。最后，我们将确定IL-1β是否依赖于观察到的SMC的表型变化 在我们的小鼠中，研究发生在人类的病变中，如果这些变化是斑块破裂或侵蚀的预测。 目标2将确定影响IL1β中和晚期效果的关键变量和机制 病变发病机制，包括那些可能有助于将我们的发现与最近的阳性结果相一致的病变发病机制 坎托斯临床试验。这将包括验证对抗IL-1β治疗的反应是 高度依赖于是否存在持续性高脂血症/未消退的炎症和/或并发 心肌梗塞/心力衰竭。综上所述，拟议的研究将提供以下关键见解 调节晚期病变发病机制的基本机制，并可能有助于 改善治疗晚期动脉粥样硬化患者的治疗方法。

Atherothrombosis, resulting from rupture or erosion of unstable atherosclerotic plaques, is the leading cause of death worldwide. However, the mechanisms that regulate the stability of late stage atherosclerotic lesions remain poorly understood. The dogma is that: 1) plaques containing a large necrotic core, a thin fibrous cap, and large numbers of CD68+ cells relative to Acta2+ cells [presumed to be macrophages (MФ) and smooth muscle cells (SMC) respectively] are more prone to rupture; and 2) SMC play a beneficial role because they are the primary cell type responsible for formation of a matrix-rich protective fibrous cap. However, recent studies by our lab involving simultaneous SMC lineage tracing and SMC-specific knockout (KO) of the stem cell pluripotency genes Oct4 or Klf4, provide compelling evidence challenging this dogma including showing that SMC can have major beneficial or detrimental effects on late stage lesion pathogenesis depending on the nature of their phenotypic transitions. As such, we sought to identify mechanisms to promote beneficial (atheroprotective) SMC phenotypic transitions, and hypothesized that treatment with an anti-IL1β antibody (Ab) to globally suppress inflammation would induce such changes. However, completely contrary to expectations, treatment of our SMC lineage-tracing ApoE-/- mice with the anti-IL1β Ab between 18-26 weeks of Western diet resulted in multiple detrimental changes including a marked reduction in fibrous cap thickness and collagen content, rapid loss of fibrous cap SMC and replacement with MФs, and impaired outward remodeling. Studies in this proposal will test the hypothesis that that IL1β signaling in SMC plays a critical beneficial role in late stage lesion pathogenesis including being required for formation and maintenance of a protective fibrous cap. Aim 1 will determine if persistent IL1R1 signaling within SMC is required for maintenance of a SMC rich fibrous cap. Studies will include determining the contributions of each of the IL1R1 ligands IL1β, and IL1α, as well as IL1Ra. We will also determine if SMC- specific tamoxifen conditional KO of the IL1R1 receptor, after establishment of advanced atherosclerosis by 16- 18 weeks of WD feeding, results in loss of SMC fibrous cap coverage and other detrimental changes consistent with plaque destabilization. Finally, we will determine if IL1β dependent phenotypic changes of SMC observed in our mouse studies occur in human lesions and if these changes are predictive of plaque rupture or erosion. Aim 2 will define critical variables and mechanisms that influence the effects of IL1β neutralization on late stage lesion pathogenesis including those that may help to reconcile our findings with the recent positive outcomes of the CANTOS Clinical Trial. This will include testing the hypotheses that the response to anti-IL1β therapy is highly dependent on whether there is persistent hyperlipidemia/unresolved inflammation, and/or concurrent myocardial infarction/heart failure. Taken together, the proposed studies will provide key insights regarding fundamental mechanisms that regulate late stage lesion pathogenesis, and may contribute to development of improved therapies for treating patients with advanced atherosclerosis.