肾小管上皮细胞固有修复受体抑制缺血再灌注损伤、促进修复及介导细胞靶向治疗的作用及机制

Acute kidney injury (AKI) has high morbidity and mortality. AKI may also predispose to chronic kidney disease. Currently, there is no cause-specific treatment. A leading cause of AKI is ischemia-reperfusion injury (IRI), in which tubular epithelial cells (TECs) are not only the most vulnerable victims, but also important local innate immune cells that regulate injury, repair or potential fibrosis. Erythropoietin (EPO) derived helix B surface peptide (HBSP), ligand of the innate repair receptor, EPO receptor/β common receptor (EPOR/βcR), remains the tissue protective property of EPO against renal IRI, without erythropoiesis. We recently revealed that the expression of EPOR/βcR was increased in mouse early IRI kidneys, which were associated with caspase-3 and the degree of renal injury. Small interfering RNA (siRNA) down-regulating caspase-3 reduced injury and fibrosis. We, therefore, hypothesise that IRI initiates highly expressed EROR/βcR that promotes TEC phagocytosing damaged cells and limited inflammation, as well as TEC dedifferentiation, proliferation and regeneration, resulting in self-repair; and also can guide TEC target delivery of caspase-3 siRNA-HBSP conjugate as a novel treatment to further ameliorate injury and enhance recovery. The new mechanistic insights potentially facilitate precise intervention of IR-induced AKI to reduce mortality and prevent fibrosis.

急性肾损伤(AKI) 发病率及死亡率高，可进展为慢性，尚无病因特异治疗。缺血再灌注损伤（IRI） 为AKI的主要病因，肾小管上皮细胞（TEC) 不仅最易受损， 亦为肾IRI局部固有免疫细胞, 主导IRI、修复或纤维化的调节。 促红细胞生成素（EPO）衍生肽（HBSP) 为固有修复受体（EPOR/βcR）的配体，仅保护受损组织，无红细胞生成。我们发现小鼠肾脏早期IRI诱发 EPOR/βcR表达，并与 caspase-3（C3）和损伤程度相关。小干扰核苷酸（siRNA）抑制C3，减轻肾脏IRI及纤维化。我们推测：损伤上调EPOR/βcR表达，促进TEC吞噬损伤细胞抑制炎症和TEC去分化增殖再生,以致自我修复，并能介导与HBSP偶联 C3 siRNA的TEC靶向治疗，加速修复及防止纤维化。此新机制研究将有利于AKI的早期精准治疗，降低死亡率和防止纤维化。

急性肾损伤（AKI）具有高发病率和高死亡率的特征，尚无早期病因特异性治疗。本课题基于固有修复受体EPOR/βcR在缺血再灌注（IR）所致AKI中的保护作用，进一步探讨其在AKI后早、晚期的动态分布，保护机制及信号通路的异同，以及在体内外探索了其配体多肽偶联的小干扰核糖核酸靶向肾小管上皮细胞（TEC）给药的效应及优势。.我们建立了小鼠肾IR损伤多时点的在体模型，双侧肾缺血30 min再灌注6-72 h及1-2 w；EPOR/βcR特异性配体环肽CHBP/线肽HBSP及caspase-3 siRNA（CASP3siRNA）治疗干预小鼠肾IR 48 h及2 w模型；铱（Iridium, Ir）标记HBSP（HBSP-Ir）在IR小鼠多脏器的分布；以及CHBP/HBSP-CASP3siRNA偶联物在离体猪肾脏再灌注模型的保护效应。我们还建立了H2O2诱导小鼠肾TEC损伤的体外模型，追踪HBSP-Ir的定位；以及HBSP介导的TEC吞噬功能。.在多时点模型中，IR诱导肾脏表达EPOR/βcR水平显著高于心、肝、肺，EPOR蛋白染色及HBSP-Ir体内追踪显示该异聚受体主要表达在损伤肾脏的TEC，体外的损伤TEC培养亦证实了其表达EPOR/βcR升高，为后期研究中EPOR/βcR介导的靶向性肾脏/TEC干预提供了重要依据。另外，HBSP/CHBP与CASP3siRNA的联合治疗小鼠肾IR损伤48 h和2 w进一步显著改善了肾组织结构损伤，基因组学提示了其协同作用的潜在机制，表明HBSP/CHBP与CASP3siRNA的协同及靶向性治疗方案在IR后不同阶段的意义。在体外，HBSP促进了TEC的吞噬。再者，CASP3siRNA-HBSP 或CHBP偶联物显著改善了离体猪肾脏的血流灌注，为后期小干扰的器官/细胞靶向性治疗铺垫了坚实的道路。.以上研究结果进一步诠释了EPOR/βcR的组织保护作用机制，以及与CASP3siRNA协同治疗的优势，更利用IR时TEC高表达EPOR/βcR 为靶点介导与其配体HBSP 偶联的CASP3siRNA肾脏/TEC靶向给药，及临床AKI早期精准治疗，提供了殷实依据。