循环microRNA-21对脓毒症时肾小管上皮细胞脂肪酸氧化代谢的影响及相应机制

The functional and metabolic abnormalities had become the hot spots as the pathogenesis of sepsis-associated acute kidney injury, and the effects of circulating microRNAs on the metabolism of renal tubular epithelial cells and its corresponding mechanism need to be further clarified. Recent studies indicated that microRNA-21 can mediate cellular fatty acid metabolism disorders, our preliminary study demonstrated that circulating microRNA-21 level increased significantly during sepsis and renal tubular epithelial cells suffered from fatty acid oxidation disorders at the mean time. Furthermore, we found that circulating microRNA-21 binds to Ago 2, whereas tubular epithelial cells express Nrp-1, an important membrane receptor that mediates the internalization of microRNA-Ago 2 complexes, and in renal tubular epithelium microRNA-21 down-regulates the expression of Sirt-1, an important protein responsible for fatty acids oxidation. Accordingly, we assume that increased circulating microRNA-21 can enter renal tubular epithelial cells via receptor-mediated internalization pathway and regulate its fatty acid oxidation. Therefore, the present study is designed to reveal the process mentioned above and associated mechanism using cell biology, immunology and genetic engineering techniques, while exploring the relationship between this pathophysiological process and the development of acute kidney injury. Thus, the present study will provide a new insight for the pathogenesis of sepsis-associated acute kidney injury.

肾小管上皮细胞的功能及代谢异常成为脓毒症相关性急性肾损伤发病机制研究的热点，而此时循环中特定的microRNA对该细胞代谢的影响及机制亟待进一步明确。研究指出microRNA-21可介导细胞脂代谢异常，我们前期的研究发现脓毒症时循环中microRNA-21水平显著增高，而此时肾小管上皮细胞出现脂肪酸氧化代谢障碍。进一步研究发现，脓毒症时循环中的microRNA-21与Ago 2结合，而肾小管上皮细胞表达可以介导microRNA-Ago 2复合物内化的重要膜受体Nrp-1，且microRNA-21可以下调在肾小管上皮细胞中调控脂肪酸氧化代谢的重要蛋白Sirt-1的表达水平。据此我们假设：脓毒症时循环中的microRNA-21可通过受体介导的内化途径进入肾小管上皮细胞并调控其脂肪酸氧化代谢。本课题将深入探讨上述过程及机制，揭示其与急性肾损伤的联系，为脓毒症相关急性肾损伤的发病机制提供新的视角。

脓毒症是危重症患者的常见临床综合征，其发病凶险、致死率高，是ICU中最常见的致死性原因。脓毒症往往合并多个器官的功能障碍，其中肾脏是最易受累的器官之一。脓毒症急性肾损伤是脓毒症死亡的独立危险因素。目前对于脓毒症急性肾损伤的发病机制仍不清楚，肾小管上皮细胞在脓毒症急性肾损伤中的损伤及代谢障碍的发生过程及具体机制仍未阐明，本课题即通过动物及细胞试验两个方面对脓毒症相关关键分子对肾小管上皮细胞代谢、蛋白表达及命运的影响进行深入的研究。通过细胞分子生物学试验及基因工程等技术手段，我们发现脂多糖(LPS)通过调控RhoT1/SMAD-4/JAM-3途径介导肾小管上皮细胞间的紧密连接的破坏，这是脓毒症可以直接导致急性肾损伤的重要机制之一；通过进一步的研究我们发现脓毒症时循环中的miR-21/Ago2可以通过肾小管上皮细胞表达的Nrp-1所介导的受体介导的内化作用在细胞中聚积，而进入细胞的miR-21通过降低细胞内AKT/CDK2水平导致FOXO1水平上升进而介导肾小管上皮细胞的脂肪酸氧化过程障碍，该过程是导致脓毒症急性肾损伤的重要机制。本研究的成果进一步完善了对脓毒症急性肾损伤发生发展机制的理解，为今后的研究提供的坚实的基础，为临床疾病的防治提供了新的视角。