Macrophage small RNA export to HDL protects against inflammation and atherosclerosis

总结：动脉粥样硬化是缺血性心血管疾病（CVD）的根本原因， 其特征在于响应于动脉壁中的持续脂质沉积的不受控制的炎症。尽管 炎症在动脉粥样硬化进展中的重要性，很少有治疗被设计为靶向 这一过程是由于普遍缺乏对生物活性脂质之外的致动脉粥样硬化刺激的了解。此前我们 已经报道了脂蛋白，即HDL和LDL，转运小的非编码RNA（sRNA），最近， 我们发现，脂蛋白中富含来自细菌和真菌的sRNA， 微生物与环境有趣的是，这些外来的微生物sRNA（msRNA）也是高度丰富的， 在动脉粥样硬化病变内的巨噬细胞中，并激活siRNA敏感的Toll样受体（TLR）7/8， 损伤巨噬细胞。我们证实HDL接受来自病变巨噬细胞的msRNAs，从而抑制了 TLR7/8激活和下游促炎基因表达。支持这一模型的是巨噬细胞 发现容易将msRNA输出到HDL，并且发现HDL处理阻断msRNA诱导的 activation.在CVD中，HDL获得与HDL功能障碍相关的反应性二羰基修饰。 在初步研究中，我们发现HDL上的反应性二羰基修饰，例如异evuglandins（IsoLG）， 损害HDL-msRNA输出。此外，我们发现IsoLG修饰的HDL增加了巨噬细胞的摄取， 并诱导促炎基因表达。初步研究还发现， 用反应性清除剂阻断IsoLG修饰的模型降低了动脉粥样硬化。因此，我们旨在 使用非靶向锁定核酸（ntLNA）阻断TLR7/8的msRNA活化。令人惊讶的是，我们发现， 在ApoE-/-小鼠中，ntLNA治疗在4周内显著减少动脉粥样硬化病变面积30%， 西方饮食。此外，单细胞RNA测序方法表明ntLNA治疗抑制了 促炎基因在病变巨噬细胞中的表达，并减少促炎基因的数量。 巨噬细胞在动脉粥样硬化病变。基于初步研究，我们假设HDL去除msRNA 从病变巨噬细胞通过逆向内吞作用，这是一个过程，抑制了HDL上的异LG修饰。 此外，我们证实，在病变巨噬细胞中，msRNA激活内溶酶体TLR7/8可以很容易地被激活。 用ntLNA靶向治疗以减少动脉粥样硬化。为了验证这一假设，我们的目标是（1）。确定 巨噬细胞msRNA输出到HDL的机制和后果，HDL-msRNA输出对 巨噬细胞活化，并定义体内HDL介导的反向sRNA转运（RsRT）途径，II.）定义 二羰基修饰和msRNA货物对CVD中HDL功能障碍的影响，和III.）目标 巨噬细胞msRNA受体抑制动脉粥样硬化进展并促进消退。该项目将 为脂蛋白、细胞外sRNAs、宿主/非宿主相互作用开辟了全新的研究领域， 炎症，其适用于许多其他疾病，但对CVD特别关键。

Summary: Atherosclerosis is the underlying cause for ischemic cardiovascular disease (CVD), a pathology best characterized as uncontrolled inflammation in response to continual lipid deposition in the arterial wall. Despite the importance of inflammation in the progression of atherosclerosis, very few therapies are designed to target this process due to a general lack of knowledge of atherogenic stimuli outside of bioactive lipids. Previously, we have reported that lipoproteins, namely HDL and LDL, transport small non-coding RNAs (sRNA), and recently, we discovered that lipoproteins are highly-enriched with sRNAs derived from bacterial and fungal species in the microbiome and environment. Interestingly, these foreign, microbial sRNAs (msRNAs) are also highly-abundant in macrophages within the atherosclerotic lesions and activate sRNA-sensing toll-like receptors (TLR)7/8 in lesion macrophages. We posit that HDL accepts msRNAs from lesion macrophages, and thus, suppresses TLR7/8 activation and down-stream pro-inflammatory gene expression. Supporting this model, macrophages were found to readily export msRNAs to HDL and HDL treatments were found to block msRNA-induced activation. In CVD, HDL acquire reactive dicarbonyl modifications which are associated with HDL dysfunction. In preliminary studies, we found that reactive dicarbonyl modifications on HDL, e.g. isolevuglandins (IsoLG), impair HDL-msRNA export. Moreover, we found that IsoLG-modified HDL had increased macrophage uptake and retention and induced pro-inflammatory gene expression. Preliminary studies also found that treating mouse models with reactive scavengers to block IsoLG modifications decreased atherosclerosis. Therefore, we aimed to block msRNA activation of TLR7/8 using non-targeting locked-nucleic acids (ntLNA). Strikingly, we found that ntLNA treatments significantly reduced atherosclerotic lesion area by 30% over 4 weeks in Apoe-/- mice on western diet. In addition, single-cell RNA sequencing approaches demonstrated that ntLNA therapy repressed pro-inflammatory gene expression in lesion macrophages and reduced the number of pro-inflammatory macrophages in atherosclerotic lesions. Based on preliminary studies, we hypothesize HDL removes msRNA from lesion macrophages through retro-endocytosis, a process that is inhibited by IsoLG modifications on HDL. Furthermore, we posit that msRNA activation of endo-lysosome TLR7/8 in lesion macrophages can be readily targeted with ntLNAs to reduce atherosclerosis. To test this hypothesis, we aim to I.) Determine the mechanism(s) and consequences of macrophage msRNA export to HDL, the impact of HDL-msRNA export on macrophage activation, and define the HDL-mediated reverse sRNA transport (RsRT) pathway in vivo, II.) Define the impact of dicarbonyl modifications and msRNA cargo on HDL dysfunction in CVD, and III.) Target macrophage msRNA receptors to inhibit atherosclerosis progression and promote regression. This project will open entirely new fields of study for lipoproteins, extracellular sRNAs, host/non-host interactions, and inflammation, which have applicability to many other diseases, but is particularly critical for CVD.