促红细胞生成素EPO衍生物诱导大鼠肾移植免疫耐受机制研究

EPO can significantly improve renal graft function and prolong survival of recipients. We found that EPO can not only reduce graft ischemia reperfusion injury, but also induce renal transplantation immune tolerance, which may also be one of its major regulatory mechanism. By analyzing T cell subsets in rat kidney transplantation models, we found that after being treated with EPO, Treg significantly increased within peripheral blood, spleen, and kidney tissue in the recipient rats, while Th17 significantly decreased. Additionally, EPO receptor was highly expressed in T cells of peripheral blood. These results imply that EPO may induce immune tolerance by regulating T cell subsets. Unfortunately, EPO may increase the risk of thrombus due to its erythropoietic ability; however the derivative of EPO can also induce the generation of Treg but without erythropoietic ability. Based on these results, we hypothesize that EPO derivative may induce immune tolerance in transplantation recipients by regulating the phenotype and function of immune cells, which may prolong graft survival. To reveal the mechanism of molecular immune regulation of EPOD on the improvement of renal graft function, this study will systematically analyze the impact of EPOD on biological characteristics of immune cells in kidney transplantation recipients, the expression of EPO receptor in immune cells, and the activation of signal pathways. Our study can promote the conversion application of EPOD in kidney transplantation, which also will provide a theoretical basis for developing EPO derivative agonists to induce immune tolerance.

EPO能显著改善移植肾功能及延长受者术后生存期，我们发现其不仅能减轻移植肾的缺血再灌注损伤，对移植肾免疫耐受的调控可能也是其主要的作用机制：通过大鼠肾移植模型的T细胞亚群分析发现，EPO处理后受者大鼠外周血、脾脏以及肾组织的Treg明显增多而Th17显著降低；此外，外周血T细胞还高表达EPO受体，提示EPO可能通过影响T细胞亚群诱导免疫耐受。然而EPO的促造血作用会增加血栓形成的风险，EPO衍生物（EPOD）无促造血作用却具有诱导Treg增殖的作用。根据这些结果我们推测：EPOD可能通过调控免疫细胞的表型和功能进而诱导移植耐受，为移植肾长期存活提供有利环境。本研究将系统分析EPOD对移植肾免疫细胞的EPO受体表达、生物学特性及其信号通路活化情况，揭示EPOD改善移植肾功能的免疫调控机制。这将为推动EPOD在肾脏移植的转化应用以及开发EPOD类激动剂诱导机体免疫耐受新策略提供理论基础。

异体免疫反应在改善移植结局、促进移植物长期存活起重要作用。为了探究非血源性促红素衍生物氨甲酰化促红细胞生成素在调节固有免疫及适应性免疫细胞和对移植肾存活作用机制。利用MHC完全不匹配肾移植的大鼠模型，相比于单独移植对照组，CEPO给药明显延长了移植肾的存活时间。该效应可被选择性PI3K/AKT抑制剂或EPO受体抗体—LY294002所抑制，除CEPO外。体外实验证实CEPO抑制树突细胞的分化和功能，并调节它们的促炎和抗炎细胞因子的产生，同时激活PI3K / AKT信号传导途径并增加固有免疫细胞的EPOR mRNA和蛋白质表达水平。此外，在暴露于CEPO的CD4 + T细胞中，Th1 / Th2比值降低，调节性T细胞（Treg）/Th17比值增加。该效应可被LY294002或抗EPO受体抗体消除。因此，CEPO通过以EPO受体依赖性方式激活PI3K/AKT信号通路调节免疫应答并促进移植肾存活。本研究中确定的CEPO的多方面效应和特异性信号传导靶点表明CEPO可能成为免疫调节和促进移植物长期存活的制剂。