DPP-4对非酒精性脂肪肝性肝炎Kupffer细胞的活化及调控机制

The activation of Kupffer cells (KCs) was confirmed to play a central role in the development of NASH. Our previous studies demonstrated that: 89% macrophages are DPP-4 positive macrophages in liver. Furthermore, DPP-4 positive classically activated macrophage (M1 macrophages) were significantly increased in NASH mice, while DPP-4 positive alternatively activated macrophage (M2 macrophages) were decreased, when compared with the normal mice. Meanwhile, inhibition of DPP-4 activity regulated macrophage polarization and ameliorated NASH in mice. In this study, primary KCs and bone marrow derived macrophages will be used to examine the role of DPP-4 positive macrophages on the pathogenesis of NASH. Furthermore, MIP-1α (one of the DPP-4 substrates) deficiency mice will be used to investigate the role and the mechanism of DPP-4 on the pathogenesis of NASH via regulating macrophage polarization. Finally, the effect of MIP-1α receptor CCR1/CCR5 antagonist on NASH progression will be evaluated as the potential candidate therapeutic drugs. In summary, we will clarify the role and mechanism of DPP-4 in the pathogenesis of NASH by regulating macrophages polarization, which may contribute to the better understanding and more scientific approaches for the prevention and treatment of NASH.

肝脏巨噬细胞活化在非酒精性脂肪性肝炎(NASH)发生发展中起着重要作用。本项目在前期实验中发现：在小鼠肝脏中有89%的巨噬细胞为DPP-4阳性巨噬细胞，且NASH小鼠肝脏DPP-4阳性的炎性M1巨噬细胞含量上调，DPP-4阳性的抗炎性M2巨噬细胞含量下调，而抑制DPP-4活性能调控巨噬细胞M1/M2极性并改善NASH炎症相关症状。本项目拟进一步研究DPP-4影响NASH进程的作用及分子机制。本项目将在细胞水平研究DPP-4阳性巨噬细胞极性在NASH进程中的作用；并利用DPP-4靶点之一MIP-1α敲除的小鼠，在体内研究DPP-4调控M1/M2巨噬细胞极性影响NASH进程的作用机制；同时探讨MIP-1α受体CCR1/CCR5拮抗剂作为治疗NASH药物候选的潜在可能性。该研究有助于我们了解在巨噬细胞M1/M2极化过程中DPP-4的调控作用及其分子机制，为NASH的治疗提供理论基础和分子手段。

二肽基肽酶4（Dipeptidyl peptidase-4），也被称为CD26，广泛表达于免疫细胞等的细胞表面上。我们前期的研究中发现，DPP-4可以调控巨噬细胞极化水平。但是其对巨噬细胞相关炎症、胰岛素抵抗的作用及其相关机制尚不明确。在本项目中，我们发现非酒精性脂肪肝性肝炎（NASH）小鼠血清及肝脏DPP-4活性显著增加，流式分析发现小鼠肝脏DPP-4阳性的炎性M1巨噬细胞含量上调，DPP-4阳性的抗炎性M2巨噬细胞含量下调。抑制DPP-4活性能调控巨噬细胞M1/M2极性并改善NASH小鼠炎症、胰岛素抵抗等相关症状。研究表明，在众多趋化因子中，CCL3，也被称为MIP-1α，经DPP-4催化后，成为最有效的单核细胞趋化剂，增强与其受体CCR1、CCR5结合能力。我们的实验结果发现，在MIP-1α缺失条件下，可以阻断DPP-4对巨噬细胞的调控作用，进而阻断其对NASH进程的影响。CCR1/CCR5作为MIP-1α受体，其相关拮抗剂可以调控巨噬细胞极化，改善NASH小鼠炎症及胰岛素抵抗，进而改善NASH。由此我们认为DPP-4-MIP1α-CCR1/CCR5信号通路通过调控巨噬细胞极化水平进而改善NASH相关炎症及胰岛素抵抗。