SRA调控Notch通路对巨噬细胞功能影响及其在酒精性肝病中的意义

Scavenger receptor A (SRA), also known as macrophage scavenger receptor 1 (Msr1), is an important innate immune molecule which preferentially expressed on myeloid cells. Our previous studies have demonstrated SRA is a key regulator of liver homeostasis. Recently, we observed that SRA is highly up-regulated in the livers of mice with alcoholic liver disease (ALD). Strikingly, genetic SRA ablation strongly sensitizes mice to alcohol-induced liver injury. SRA loss increased liver pathology correlated with heavy hepatic macrophage mitochondrial damage and heightened activation of Notch signaling pathway. On the basis of these findings, we propose the present grant. The regulation mechanism of SRA on the activation of Notch signaling pathway and its influences on macrophage metabolism and function will be studied. Alcohol-induced liver injury, inflammation, hepatic macrophage function and Notch signaling pathway activation were compared between wild-type and SRA deficient mice. The effects of SRA on the initiation and activation of Notch pathway as well as the underlying mechanisms will be investigated in vitro. Human liver tissues and blood from patients with ALD and healthy participants will be collected. The activation of Notch pathway, as well as the level of SRA in hepatic macrophages and peripheral blood mononuclear cells will be examined, and the association among SRA levels, Notch pathway and disease severity will be analyzed. The study will elucidate the relationship among SRA levels, Notch pathway activation, macrophage function, and the pathogenesis of ALD, which provides a new understanding about the development of ALD and regulation of Notch pathway activation. Most importantly, this study will substantiate the concept that SRA is a vital regulator of liver homeostasis, thus making it a potential target for modulation in the clinical settings of alcohol and other risk factors-caused liver damage.

清道夫受体A（SRA，又称Msr1）是主要表达于髓系细胞的天然免疫分子。我们前期研究表明SRA在维持肝脏免疫稳态中发挥重要作用。最近发现，酒精性肝病（ALD）模型小鼠肝内巨噬细胞（MΦ）SRA表达上调；与WT小鼠相比，SRA-/-小鼠酒精性肝损伤加剧、肝内MΦ线粒体损伤严重且Notch通路活化增强。据此提出假说：SRA通过Notch信号通路影响MΦ功能进而调节ALD病变。拟开展以下研究：①动物：利用WT和SRA-/-小鼠建立ALD模型，研究SRA、Notch通路及MΦ功能相互关联及其与ALD病变的关系；②体外：SRA调控Notch通路的机制；③临床：SRA与Notch通路及ALD病变的关系。研究将揭示SRA水平—Notch通路活化—MΦ功能—ALD病变的关系，为深入理解ALD的发病机制和Notch信号通路的调控增添新内容，并为靶向SRA调节MΦ功能以治疗ALD及相关炎症性疾病提供实验依据。

清道夫受体A（SRA）是天然免疫中一个重要的模式识别受体，参与多种生理和病理过程。我们前期研究提示SRA在维持肝脏免疫稳态中发挥重要作用。本项目中，我们重点关注SRA对酒精性肝脏疾病的影响，利用细胞学实验及动物模型实验，分析SRA对酒精性肝脏疾病发病机制的调节，以期为基于SRA为靶点的酒精性肝病治疗研究提供依据。主要研究结果有：(1)利用疾病模型研究发现：Lieber-DeCarli液体饲料加暴饮酒精喂养的方法诱导小鼠酒精性肝损伤，模拟酒精性肝脏疾病的肝炎症状。SRA基因缺陷小鼠较野生型WT小鼠肝组织损伤明显加重。(2) 对巨噬细胞研究发现：酒精刺激条件下，SRA通过调控巨噬细胞内Notch通路活化，上调NICD的水平，进而影响巨噬细胞Ly6C+比例增加，促进炎症因子释放，加重小鼠肝病症状。对信号通路研究发现，SRA可通过与Notch1直接结合，抑制Notch1谷胱甘肽化，最终导致Nocth1活化水平降低，Ly6C+细胞比例降低，进而抑制炎症因子的释放。(3) 机制研究表明：SRA通过与Trx-1结合抑制Notch1的谷胱甘肽化水平，从而降低Notch通路的活化，减少炎症损伤。（4）基于SRA的治疗研究：SRA配体褐藻糖胶可有效减轻小鼠酒精性肝损伤。综上，SRA调控机体对酒精性肝脏疾病的炎症应答，缓解肝损伤。本项目还探究了SRA影响TBK1激酶活化的分子机制，阐释了巨噬细胞SRA调控干扰素通路影响肝脏免疫微环境的分子机制，为免疫失衡相关的肝脏疾病研究提供了新的思考角度。在项目的资助下，申请人分析了多种天然小分子对肝脏免疫及炎症应答的调控作用，揭示了其精细的免疫学机理和分子结构基础，为相关疾病的治疗研究提供了潜在的新策略。项目基本完成既定研究目标，部分工作尚未发表。在项目资助下，目前已发表SCI论文8篇，培养研究生3名、博士后1名，项目直接研究结果参与国内会议交流1次。