Table_1_Monocyte and Macrophage Lipid Accumulation Results in Down-Regulated Type-I Interferon Responses.docx

Macrophages are critical components of atherosclerotic lesions and their pro- and anti-inflammatory responses influence atherogenesis. Type-I interferons (IFNs) are cytokines that play an essential role in antiviral responses and inflammatory activation and have been shown to promote atherosclerosis. Although the impact of type-I IFNs on macrophage foam cell formation is well-documented, the effect of lipid accumulation in monocytes and macrophages on type-I IFN responses remains unknown. Here we examined IFN stimulated (ISG) and non-ISG inflammatory gene expression in mouse and human macrophages that were loaded with acetylated LDL (acLDL), as a model for foam cell formation. We found that acLDL loading in mouse and human macrophages specifically suppressed expression of ISGs and IFN-β secretion, but not other pro-inflammatory genes. The down regulation of ISGs could be rescued by exogenous IFN-β supplementation. Activation of the cholesterol-sensing nuclear liver X receptor (LXR) recapitulated the cholesterol-initiated type-I IFN suppression. Additional analyses of murine in vitro and in vivo generated foam cells confirmed the suppressed IFN signaling pathways and suggest that this phenotype is mediated via down regulation of interferon regulatory factor binding at gene promoters. Finally, RNA-seq analysis of monocytes of familial hypercholesterolemia (FH) patients also showed type-I IFN suppression which was restored by lipid-lowering therapy and not present in monocytes of healthy donors. Taken together, we define type-I IFN suppression as an athero-protective characteristic of foamy macrophages. These data provide new insights into the mechanisms that control inflammatory responses in hyperlipidaemic settings and can support future therapeutic approaches focusing on reprogramming of macrophages to reduce atherosclerotic plaque progression and improve stability.

巨噬细胞（Macrophages）是动脉粥样硬化斑块（atherosclerotic lesions）的关键组成部分，其促炎与抗炎应答可影响动脉粥样硬化发生（atherogenesis）过程。I型干扰素（Type-I interferons, IFNs）是一类在抗病毒应答及炎症激活中发挥核心作用的细胞因子，且已被证实可促进动脉粥样硬化进展。尽管I型干扰素对巨噬细胞泡沫细胞形成的影响已有充分研究，但单核细胞（monocytes）与巨噬细胞内的脂质蓄积对I型干扰素应答的调控作用仍未明确。本研究以乙酰化低密度脂蛋白（acetylated LDL, acLDL）构建泡沫细胞模型，检测了小鼠及人源巨噬细胞中干扰素刺激基因（Interferon Stimulated Genes, ISG）与非ISG炎症基因的表达情况。研究发现，小鼠及人源巨噬细胞经acLDL负载后，可特异性抑制ISG的表达及β干扰素（IFN-β）的分泌，但对其他促炎基因无显著影响。外源性补充IFN-β可逆转ISG的下调现象。胆固醇感应核受体肝X受体（liver X receptor, LXR）的激活可模拟胆固醇介导的I型干扰素抑制效应。对小鼠体外及体内来源的泡沫细胞的进一步分析证实，I型干扰素信号通路受到抑制，且该表型可能通过下调基因启动子区域的干扰素调节因子（interferon regulatory factor）结合活性所介导。最后，对家族性高胆固醇血症（familial hypercholesterolemia, FH）患者单核细胞的RNA测序分析显示，其I型干扰素通路同样受到抑制，且该抑制效应可通过降脂治疗得以恢复，而健康供者的单核细胞未出现该现象。综上，本研究明确I型干扰素抑制是泡沫巨噬细胞的抗动脉粥样硬化特性。上述研究结果为高脂血症环境下炎症应答的调控机制提供了新视角，可为未来以重编程巨噬细胞为靶点、延缓动脉粥样硬化斑块进展并提升斑块稳定性的治疗策略提供理论支撑。