HIF-1α-ID1/miR-27a在缺血再灌注损伤所致急性肾损伤中的作用及机制研究

Acute kidney injury(AKI) is a common clinical critical disease, which has become an important cause of end stage renal disease(ESRD). Understanding the repair process of AKI could provide scientific proof for better prognosis. Based on literature reports and the preliminary works of our research group, we believe that hypoxia inducible factor 1α(HIF-1α) plays an important role in repair process of AKI. We found firstly that HIF-1α can regulate inhibitor of differentiation 1(ID1) in vitro experiments, and ID1 could down-regulate E-cadherin, promoting the dedifferentiation of renal tubular epithelial cell(TEC), showing that HIF-1α may mediate the dedifferentiation of TEC through ID1. Besides, HIF-1α is a transcription factor of miR-27a, while the target genes of miR-27a such as EGFR have important functions during AKI repairation, so HIF-1α may also regulate AKI repairation through signal pathways which are related to miR-27a. Therefore, clarifying the HIF-1α-ID1/miR-27a signal pathways by in vivo AKI model of conditional gene knockout mouse and in vitro experiments is crucial to definite AKI repairation related molecular mechanisms, and provide novel clinical targets for intervention, which has important scientific value and clinical significance.

急性肾损伤（AKI）是临床常见危重病症，已成为终末期肾脏疾病（ESRD）的重要病因。明确AKI修复过程能为改善预后提供科学依据。基于文献报道和本课题组前期工作，我们认为低氧诱导因子1α（HIF-1α）在AKI修复中具有重要作用。在体外实验中，我们首次发现HIF-1α可以调控分化抑制因子1(ID1)，ID1可下调钙粘蛋白E（E-cadherin)，具有促进肾小管上皮细胞（TEC）去分化作用，提示HIF-1α可能通过ID1介导TEC去分化。此外，HIF-1α是miR-27a的转录因子，而miR-27a的靶基因如EGFR对AKI修复具有重要作用，故HIF-1α也可通过miR-27a所涉及的信号通路调控AKI修复。因此，通过条件性基因敲除小鼠AKI模型及体外实验，阐明HIF-1α调控ID1和miR-27a的信号通路，对于明确AKI修复相关分子机制，提供新的临床干预靶点，具有重要科学价值和临床意义。

本研究成功构建肾小管条件性敲除低氧诱导因子-1α（Hypoxia induced factor1a, HIF-1α）小鼠的缺血-再灌注急性肾损伤（Acute kidney injury, AKI）模型和人近端小管细胞（human proximal tubular cells, HK2）的低氧-复氧损伤模型。利用成功构建的动物和细胞模型，验证肾小管条件性敲除HIF-1α对缺血缺氧打击后肾小管上皮细胞损伤修复的影响。通过对缺血性AKI小鼠肾皮质标本和低氧-复氧损伤的HK2细胞进行检测，发现HIF-1α敲除后体内及体外肾小管上皮细胞线粒体自噬水平明显减低、细胞凋亡加重且活性氧（ROS）生成增加。同时，I/R与H/R也诱导了HIF-1α下游基因Bcl-2 19-kDa互作蛋白3（BNIP3）表达。进一步实验证实，BNIP3过表达逆转了HIF-1α敲除对缺血缺氧打击后肾小管上皮细胞内线粒体自噬的抑制作用，并且减轻了HIF-1α敲除引起的缺血缺氧打击后肾小管上皮细胞凋亡及ROS生成增加，从而促进缺血再灌注损伤后肾脏修复。