SNX10调控溶酶体酸性脂肪酶活性在巨噬细胞极化及动脉粥样硬化中的作用

The effects of macrophage polarization on the occurrence, development and prognosis of atherosclerosis (AS) has become an immediate area of research focus, gathered widespread attention. The beneficial effects have been demonstrated in animal models of AS by manipulating macrophage to the anti-inflammatory M2-type polarization. However, the molecular mechanisms involved in the controlling macrophage polarization is still largely unknown. The latest study found that lysosomal acid lipase (LAL) generates fatty acids for M2 polarization which is dependent on fatty acid oxidation (FAO) by lipolysis of triacylglycerols, and plays an essential role in increasing mitochondrial oxidative phosphorylation capacity and promoting M2 polarization. Our previous study found that sorting nexin 10 (SNX10), an protein involving in the endosome homeostasis and transport, can regulate LAL activity. SNX10 knockout enhanced the lysosomal acidity of macrophages, increased the mRNA level and activity of LAL. Macrophages with SNX10 deficiency presents M2-type phenotype; and easily polarized to M2 macrophages by IL-4 induction. Therefore, we hypothesized that SNX10 is likely new regulator of the function and phenotype polarization of macrophages, and that manipulating macrophage polarization targeting SNX10 may be an attractive new strategy for AS treatment. In this project, we will take advantage of SNX10 knockout mice to elucidate the molecular mechanisms of SNX10 in regulating macrophage function and phenotypic transformation through the research of energy metabolism, and specifically its impact on the development of experimental AS. Our findings may contribute a new therapeutic target for drug screening of AS.

巨噬细胞极化对动脉粥样硬化(atherosclerosis, AS)发生、发展及预后的影响已成为研究热点。通过诱导巨噬细胞向M2型极化改善AS病情已在动物模型中得到证实。然而参与控制巨噬细胞极化的分子实体及关键机制在很大程度上仍然是未知的。最新研究发现M2型巨噬细胞依赖溶酶体酸性脂肪酶（LAL）脂解三酰基甘油产生脂肪酸进行脂肪酸氧化，在促进M2型极化中发挥关键作用。我们在前期研究中发现内体转运调控蛋白SNX10具有调控LAL活性的功能。缺失SNX10的巨噬细胞溶酶体酸性明显增强，LAL基因表达上调，活性增强，呈现M2型巨噬细胞特征。因此，我们推测：靶向干预SNX10操控巨噬细胞向M2型极化很可能成为AS治疗的新途径。本项目将从能量代谢角度研究SNX10调控巨噬细胞极化的分子机制，以及对实验性AS发生、发展的影响，有可能为AS的治疗提供新的方法和药物筛选靶点。

我们以往研究发现分选连接蛋白10 (SNX10)在调节巨噬细胞功能和脂质代谢中发挥重要作用。本项目进一步探讨SNX10在动脉粥样硬化疾病中的确切作用及其机制。我们比较了健康人血管和颈动脉粥样硬化斑块中SNX10的表达。将骨髓细胞特异性SNX10敲低小鼠与 APOE-/-小鼠进行杂交，观察高胆固醇饮食诱导16周对动脉粥样硬化形成的影响。结果发现在人和APOE-/-小鼠主动脉粥样硬化病变标本中SNX10表达升高。髓系特异性敲低SNX10(ΔKO)减轻APOE -/-小鼠动脉粥样硬化的进展。抗炎型单核/巨噬细胞在外周血和ΔKO小鼠动脉粥样硬化病变部分数量增多。体外实验表明，SNX10缺失通过阻断CD36的内化来抑制泡沫细胞的形成，其机制主要依赖SNX10介导的Lyn-AKT的相互作用。SNX10缺乏导致Lyn-AKT活化减少，从而促进了TFEB的核转位，增强溶酶体的生物发生和溶酶体酸性脂肪酶（LAL）的活性，导致游离脂肪酸增加，促进线粒体新生和脂肪酸氧化，驱动巨噬细胞重编程，使其向抗炎表型转移。我们的数据首次表明，SNX10通过之前未知的Lyn-Akt-TFEB信号通路介导巨噬细胞重编程，在高脂饮食诱导的动脉粥样硬化形成中发挥重要作用，提示SNX10可能是动脉粥样硬化治疗的潜在治疗靶点。