Rebalancing liver-infiltrated CCR3+ and CD206+ monocytes improves diet induced NAFLD. Rebalancing liver-infiltrated CCR3+ and CD206+ monocytes improves diet induced NAFLD

Melatonin has been reported to improve NAFLD, exploring the underlying mechanisms will be beneficial for better treatment of NAFLD. CDHFD- and MCD-fed mice with melatonin intervention exhibited significantly decreased liver steatosis, lobular inflammation, and focal liver necrosis. Single-cell RNA sequencing revealed melatonin selectively inhibited proinflammatory CCR3+ MoMFs, and upregulated anti-inflammatory CD206+ MoMFs in NAFLD mice. Hepatic infiltrated CCR3+CD14+ MoMFs is also significantly increased in patients with NAFLD. Mechanistically, melatonin receptor independent BTG2-ATF4 signaling plays a vital role in the regulation of CCR3+ MoMFs endoplasmic reticulum stress, survival, and proinflammation by melatonin. In contrast, melatonin upregulated CD206+ MoMFs survival and polarization via MT1/2 receptors. Melatonin stimulation also regulates human CCR3+ MoMFs and CD206+ MoMFs survival and inflammation in vitro. Furthermore, CCR3 depletion antibody monotherapy decreased liver inflammation and improved NAFLD in mice. Thus, Therapies targeting CCR3+ MoMFs may have potential benefits in NAFLD treatment. Overall design: Mice were fed with either methionine/choline-deficient diet (MCD), or MCD diet with melatonin. 7AAD-CD45+Ly6G-CD11bintF4/80hi monocytes obtained from MCD-fed mice liver which was treated with or without melatonin, and each treatment was repeated twice.

已有研究证实褪黑素可改善非酒精性脂肪性肝病（non-alcoholic fatty liver disease, NAFLD），深入探究其潜在作用机制将有助于优化NAFLD的临床治疗策略。经胆碱缺乏高脂膳食（choline-deficient high-fat diet, CDHFD）和蛋氨酸-胆碱缺乏膳食（methionine/choline-deficient diet, MCD）喂养并接受褪黑素干预的小鼠，其肝脏脂肪变性、小叶炎症及局灶性肝坏死均显著减轻。单细胞RNA测序（single-cell RNA sequencing, scRNA-seq）结果显示，褪黑素可选择性抑制非酒精性脂肪性肝病小鼠体内的促炎型CCR3+单核细胞源性巨噬细胞（monocyte-derived macrophages, MoMFs），并上调抗炎型CD206+单核细胞源性巨噬细胞的水平。临床非酒精性脂肪性肝病患者的肝脏浸润CCR3+CD14+单核细胞源性巨噬细胞水平同样显著升高。从分子机制来看，不依赖褪黑素受体的BTG2-ATF4信号通路在褪黑素调控CCR3+单核细胞源性巨噬细胞的内质网应激、存活状态及促炎功能中发挥关键作用；与之相反，褪黑素可通过褪黑素受体MT1/2上调CD206+单核细胞源性巨噬细胞的存活与极化水平。体外实验证实，褪黑素刺激同样可调控人源CCR3+及CD206+单核细胞源性巨噬细胞的存活与炎症状态。此外，单用CCR3耗竭性抗体可减轻小鼠肝脏炎症并改善非酒精性脂肪性肝病。因此，靶向CCR3+单核细胞源性巨噬细胞的治疗策略有望为非酒精性脂肪性肝病的临床治疗提供潜在获益途径。实验设计概况：实验小鼠分为两组，分别给予蛋氨酸-胆碱缺乏膳食（MCD）喂养，或同时给予MCD膳食与褪黑素干预。从经褪黑素处理或未处理的MCD喂养小鼠肝脏中分离得到7AAD-CD45+Ly6G-CD11bintF4/80hi单核细胞，每组处理重复两次。