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

由不稳定的动脉粥样硬化斑块破裂或侵蚀引起的动脉粥样硬化血栓形成是动脉粥样硬化的主要原因。 全世界的死亡然而，调节晚期动脉粥样硬化病变稳定性的机制仍然存在 不太了解。其教条是：1）斑块包含一个大的坏死核心，一个薄的纤维帽， CD 68+细胞相对于Acta 2+细胞的数量[假定为巨噬细胞（M+）和平滑肌细胞 (SMC)更容易破裂; 2）SMC发挥有益作用，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 涉及同时进行SMC谱系追踪和SMC特异性敲除（KO）干细胞多能性基因 Oct 4或Klf 4，提供令人信服的证据挑战这一教条，包括显示SMC可以有重大的 对晚期病变发病机制的有益或有害作用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， 并假设用抗IL 1 β抗体（Ab）治疗以全面抑制炎症 会引发这样的变化。然而，与预期完全相反，我们的SMC谱系追踪治疗 在18-26周的西方饮食中，具有抗IL 1 β Ab的ApoE-/-小鼠导致多种有害变化 包括纤维帽厚度和胶原含量的显著减少，纤维帽SMC的快速损失， 替换为多发性骨髓瘤和受损的向外重塑。本提案中的研究将检验以下假设： SMC中的IL 1 β信号传导在晚期病变发病机制中起着关键的有益作用， 这是形成和维持保护性纤维帽所需的。目标1将确定持续性IL 1 R1 SMC内的信号传导是维持富含SMC的纤维帽所必需的。研究将包括确定 IL 1 R1配体IL 1 β和IL 1 α以及IL 1 Ra各自的贡献。我们还将确定SMC是否- 特异性他莫昔芬条件性KO的IL 1 R1受体，建立晚期动脉粥样硬化后，通过16- WD喂养18周，导致SMC纤维帽覆盖丧失和其他有害变化一致 斑块不稳定。最后，我们将确定是否观察到SMC的IL 1 β依赖性表型变化， 在我们的小鼠研究中，发生在人类病变中的这些变化是否预示着斑块破裂或糜烂。 目的2将明确影响IL 1 β中和作用于晚期肿瘤的关键变量和机制 病变的发病机制，包括那些可能有助于协调我们的研究结果与最近的积极成果， CANTOS临床试验这将包括检验对抗IL 1 β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/或并发症 心肌梗死/心力衰竭。总之，拟议的研究将提供以下方面的关键见解 调节晚期病变发病机制的基本机制，并可能有助于 用于治疗晚期动脉粥样硬化患者的改进疗法。

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.