补体C3a/C5a信号介导的巨噬细胞极化在糖尿病肾病中的作用及机制研究

Diabetic Nephrology (DN) has been considered as one of main reasons that leading to the end-stage renal disease (ESDN) and renal failure. Increasing evidences suggests that macrophage induced chornic inflammation plays a key role in the onset and progression of DN. Complement and macrophage both belong to the innate immune system of human body. Previous reports and our preliminary results had showed that the abnormal activation of complement C3a and C5a in diabetes, which was highly linked to the degree of renal injury under diabetic status. Complement C3a and C5a can also cause the oxidative stress and induce the inflammation factor production in macrophages. However, the specific effect of complement C3a/C5a signals in macrophage polarization and renal inflammatory microenvironment under diabetes is still not been fully elucidated.. In this study, we are planning to measure the expression of complement C3a/C5a and the macrophage polarization in the kidney tissues obtained from DN patients and DN mouse, and assess the relationship between macrophage polarization and complement activation. Then, we investigate the effect of complement C3a/C5a blocking on the M1/M2 macrophages polarization, renal inflammation, renal fibrosis and proteinuria by using complement receptor knockout (C3aR-/- and C5aR-/-) mouse and cell models,. Furthermore, we explore the possible molecular mechanism how complement C3a/C5a signals mediate the process of macrophages polarization. This study will provide insight into the effect of complement system contributes to the development of DN, and reveal the potential therapeutic targets to inhibit renal inflammation and delay or even prevent the progression of DN.

糖尿病肾病（DN）是导致终末期肾病的重要原因，巨噬细胞介导的慢性炎症在DN发生发展过程中发挥了重要作用。补体和巨噬细胞同属机体固有免疫系统，大量文献及申请人前期研究显示：糖尿病状态下补体C3a/C5a异常活化，且与DN肾损伤程度密切相关；C3a/C5a还可诱导巨噬细胞氧化应激和炎症因子表达；但C3a/C5a信号对DN巨噬细胞极化及肾脏炎性微环境的调控作用尚未完全阐明。.本研究拟：检测DN患者和动物模型肾脏中补体活化与巨噬细胞极化情况，明确C3a/C5a激活与巨噬细胞极化间是否存在密切联系。采用补体受体敲除（C3aR-/-和C5aR-/-）动物及细胞模型，研究巨噬细胞中阻断补体C3a/C5a信号对糖尿病状态下巨噬细胞M1/M2极化及肾脏炎症和蛋白尿等指标的影响，探讨其调控巨噬细胞极化的可能分子机制。本研究有助于阐明补体系统参与DN肾损伤的作用机制，为减轻肾脏炎症、延缓DN进展提供新的靶点。

糖尿病肾病（DKD）是一种严重的糖尿病微血管并发症。已有研究显示在2型糖尿病（T2DM）中发现了补体C5表达上调和肠道生态失调，但它们在DKD中的作用尚不清楚。在本课题中，我们研究了补体C5在DKD发病过程中对肠道菌群的影响。我们检测了T2DM患者肾脏和db/db小鼠肾脏中C5a/C5a受体（C5aR）表达变化。使用C5aR拮抗剂（C5aRA）干预db/db小鼠，并分析肾功能、肠道菌群和肾脏基因组的变化。体外实验使用C5a和短链脂肪酸（short-chain fatty acids, SCFAs）干预人肾小球内皮细胞（HRGECs），探讨对信号转导因子和转录激活因子3 （signal transducer and activator of transcription 3, STAT3）通路的影响。我们的研究发现，T2DM患者和db/db小鼠肾小球内皮细胞中C5a表达上调。虽然糖脂代谢没有改变，但C5aR阻断可减轻db/db小鼠的肾功能损伤、改善细胞外基质沉积、减弱巨噬细胞浸润和促炎因子表达。C5aRA干预部分逆转了db/db小鼠肠道菌群多样性和SCFA水平下降的趋势。C5aRA同时可下调db/db小鼠肾脏中许多免疫应答相关基因的表达，如STAT3。C5aRA和SCFAs干预可抑制C5a诱导的STAT3激活。基于我们的研究结果，我们认为，C5过度活化可通过激活HRGECs中的STAT3并损害肠肾轴来促进DKD的发病和进展，这种过度激活可能是DKD治疗的一个潜在靶点。