细胞内RAS激活在PMN-MDSC诱导的ESRD免疫缺陷中的作用和机制研究

End-stage renal disease (ESRD) patients present anti-infection immune deficiency without explicit mechanism. Myeloid-derived suppressor cell (MDSC) is the major criminal in inducing immune deficiency. However, its role in ESRD related immune deficiency is unclear. In our previous studies, we found that polymorphonuclear cell myeloid-derived suppressor cell (PMN-MDSC) increased and was activated in ESRD patients. And, ESRD related PMN-MDSC raised the risk of infection diseases (Kidney Int.2017). Furthermore, we found that intracellular renin-angiotensin system (iRAS) was activated in PMN-MDSC with elevated S100A9, and, inhibition of iRAS led to decrease of PMN-MDSC and S100A9. Thus, a scientific question was raised to us that "PMN-MDSC induced by iRAS activation through S100A9 might cause the anti-infection immune deficiency among ESRD patients". In the present project, this presumption will be tested in the following parts: Firstly, we will determine the role of iRAS in ESRD related PMN-MDSC caused the anti-infection immune deficiency; then, the regulative role of S100A9 in this process will be investigated; furthermore, the regulatory mechanism of iRAS and S100A9 will be tested by ways including protein mass spectrometry; finally, the clinical usage of iRAS/S100A9/PMN-MDSC pathway in ESRD patients will be tested in predicting infectious events. The present project will reveal a new mechanism for ESRD related immune deficiency and find a new target for immuno-therapy.

终末期肾病（ESRD）患者存在抗感染免疫缺陷，但其机制尚不明确。髓系抑制性细胞（MDSC）是导致免疫抑制的重要元凶，而其在ESRD相关免疫缺陷中的作用并不明确。我们前期研究发现ESRD患者存在PMN-MDSC异常扩增及活化，增加了患者的感染风险(Kidney Int.2017)；进而发现其胞内RAS（iRAS）异常激活、S100A9上调，拮抗iRAS可以逆转PMN-MDSC和S100A9的上升，因而提出“iRAS通过S100A9诱导的PMN-MDSC介导了ESRD抗感染免疫缺陷”的假说。本项目拟进行以下验证：明确iRAS在ESRD相关PMN-MDSC介导抗感染免疫缺陷中的调控作用；研究S100A9的介导作用；进而通过蛋白质谱等方法，研究iRAS调控S100A9的分子机制；再利用前瞻性队列研究明确此通路的临床应用价值。本项目将揭示ESRD患者免疫缺陷的新机制，为其免疫治疗提供新靶点。

在本项目支持下，我们针对ESRD免疫紊乱和MDSC的调控进行了系列研究。我们发现PMN-MDSC与透析患者总生存无关，可能与PMN-MDSC缺乏特异性标记有关。这是PMN-MDSC领域的重大科学问题。我们首先验证PMN-MDSC特异性表面标记LOX-1。最近的一项研究表明，LOX-1是人类PMN-MDSC的独特表面标记。我们发现HCC患者LOX-1+CD15+PMN-MDSC明显高于健康对照组和良性疾病患者，并能浸润肿瘤组织。LOX-1+CD15+PMN-MDSCs显著抑制T细胞增殖和活化。内质网应激/ROS-精氨酸酶是其关键机制。进而，我们发现患有CHB的鼻咽癌幸存者有高水平的LOX-1+PMN-MDSCs。LOX-1+PMN-MDSCs显著降低T细胞的增殖和激活。有慢性乙型肝炎的鼻咽癌幸存者EBV DNA阳性率高于无慢性乙型肝炎的鼻咽癌患者。EBV DNA阳性的患者LOX-1+PMN-MDSC水平较高。LOX-1+PMN-MDSCs抑制CD8+T细胞对EBV的应答。本研究揭示了LOX-1是PMN-MDSC特异性表面标记。.我们发现PMN-MDSC与透析患者总生存无关，但是发现血液透析患者M-MDSC升高，进而我们发现血液透析患者M-MDSCs水平明显高于健康对照组。M-MDSCs高水平患者OS降低，卒中和急性心力衰竭事件增加。M-MDSC是血液透析患者OS和卒中事件的独立预测因子。血液透析相关的M-MDSCs显著消除了T细胞的增殖。与单核细胞相比，M-MDSCs的CXCR4和VLA-4水平更高。与单核细胞组相比，与M-MDSCs共培养的人冠状动脉内皮细胞(HCAECs)迁移能力增强。精氨酸酶抑制剂和l-精氨酸可解除血液透析相关M-MDSC的免疫抑制功能和诱导HCAECs迁移。血液透析患者血浆IFN-γ、TNF-α和IL-6水平均高于健康对照组。血液透析患者M-MDSC水平与IL-6水平呈正相关。IL-6诱导M-MDSC，IFN-γ和TNF-α激活M-MDSC。血液透析患者M-MDSCs水平升高，且与心脑血管疾病发生风险密切相关。血液透析相关的M-MDSC可促进动脉粥样硬化病变，其可能通过消耗局部l -精氨酸促进内皮细胞迁移。