胞浆脱氧鸟苷激酶介导巨噬细胞炎症的兴起与消亡调控NAFLD的进展与转归

Hepatic macrophages drive development of NAFLD. Therefore, it is important to illustrate the intrinsic mechanisms about the initiation and resolution of hepatic inflammation. In the present study, we demonstrated that cytoplasmic deoxyguanosine kinase (dGK) might be a critical modulator controlling macrophage-induced inflammation and NAFLD progression. Based on these foundations, we will further confirm the important role of cytoplasmic dGK in NAFLD by analyzing the functions of dGK in hepatic macrophage inflammation, in hepatocyte steatosis and in hepatic stellate cell activation. We have detected that cytoplasmic dGK participated in JAK2-STAT1 signal transduction. In this project, we will continue to clarify the structural basis for dGK and STAT1 protein interaction, elucidate the contribution of dGK in classic JAK2-STAT1 signals, investigate the autophagic degradation of dGK, and design the signaling network of cytoplasmic dGK in macrophage inflammatory response. According to the study, cytoplasmic dGK will be considered as a novel target for NAFLD treatment with high efficiency and safety, and we will screen the ligand compounds. This project is the first time to reveal the function of cytoplasmic dGK in macrophages, and to provide new strategies for NAFLD depending on the intervention of hepatic inflammatory signals.

肝脏巨噬细胞的功能决定了NAFLD的进展与转归，因此挖掘肝脏巨噬细胞炎症兴起与消亡的内在机制对改善NAFLD尤为重要。前期首次发现胞浆脱氧鸟苷激酶(dGK)的波动变化能够调控巨噬细胞炎症反应的爆发和消亡，参与NAFLD的进程。在此基础上，本项目将进一步明确胞浆dGK在NAFLD中的重要作用，观察胞浆dGK对肝脏巨噬细胞功能的调节，及其对肝细胞脂肪变性和肝星状细胞活化的影响；阐明胞浆dGK在JAK2-STAT1通路中的贡献，揭示胞浆dGK与STAT1蛋白互作的结构基础；探讨胞浆dGK进行自噬性降解的机制，绘制dGK在巨噬细胞炎症反应中的信号网络；通过上述研究确立胞浆dGK作为NAFLD的药物靶标具有高效且安全的特点，筛选新型配体分子，寻找NAFLD的新治疗策略和候选化合物。本项目首次揭示胞浆dGK在巨噬细胞炎症反应中的功能，从干预肝脏炎症信号出发为NAFLD提供新的研究方向和潜在靶点。

巨噬细胞介导的炎症具有爆发期和恢复期，这表明炎症有内在的修复机制。肝脏巨噬细胞决定了NAFLD的进展与转归，因此挖掘肝脏巨噬细胞炎症兴起与消亡的内在机制对改善NAFLD尤为重要。本项目中，我们首次发现脱氧鸟苷激酶(dGK)的波动变化能够调控肝脏巨噬细胞炎症反应的爆发和消亡，控制NAFLD的进程。并且证实胞浆dGK的表达与巨噬细胞M1极化水平呈正相关。进一步研究发现，在炎症爆发期，dGK通过结合STAT1 C端TAD结构域来维持Tyr701 pSTAT1的持续磷酸化，阻断STAT1与磷酸酶TC45的相互作用，促进炎症因子表达增加。然而，在炎症消退阶段，巨噬细胞内自噬水平增加，诱导dGK发生自噬性降解进而解除对STAT1持续磷酸化的维系作用，炎症因子表达下降，巨噬细胞介导的炎症得到修复。在此基础上，我们筛选了多种小分子化合物，发现黄酮类化合物PMFA通过自噬介导dGK降解进而改善炎症，表现为修复NAFLD肝损伤。除此之外，我们还证实内源性小分子蛋白Annexin A5具有调节肝脏巨噬细胞表型改善脂肪性肝炎的作用。综上，本项目首次揭示胞浆dGK在巨噬细胞炎症以及NAFLD进程中的功能，从干预肝脏炎症信号出发为NAFLD提供新的研究方向和潜在靶点。