细胞外RNA-TLR3信号与术后认知功能障碍的关系及其机制研究

Postoperative cognitive dysfunction (POCD) is a common complication of elderly patients during perioperative period, but its pathogenesis remains unclear. We have observed elevated level of extracellular RNA (exRNA) in the cerebrospinal fluid (CSF) of the elderly patients after hip replacement surgery. Our previous animal experiments also found perioperative RNase treatment, had significally attenuated cognitive impairment after unilateral nephrectomy in aged C57BL/6 mice, and reduced both mRNA and protein expression levels of TLR3 in hippocampus. This implies that exRNA-TLR3 signaling may play an important role in the initiation of POCD. In this study, we will perform the experiments in clinical patients，aged mice and primary cultured cells. Increase of CSF exRNA level and its relationship with the POCD will be confirmed in elderly patients after sugery. Also, the importance of TLR3 activation through the binding of exRNA for the development of POCD will be determined in our designed experiments. Futher, we will explore the possible mechanism for the development of POCD mediated by the exRNA-TLR3 signaling. The successful implementation of this study will help to reveal novel mechanisms for the pathogenesis of POCD and unravel potential preventive and therapeutic targets for POCD.

术后认知功能障碍（POCD）是老年患者围术期的常见并发症, 但其发病机制仍不明确。我们前期临床研究观察到，老年患者行髋关节置换术后脑脊液中exRNA水平明显升高。同时，动物实验研究发现，围术期给予RNase处理可显著改善行单侧肾切除术的C57BL/6老年小鼠的术后认知功能，并显著降低海马组织中TLR3的mRNA和蛋白表达水平，这提示exRNA-TLR3信号可能介导了POCD的发生。本课题拟进一步从临床患者、整体动物及细胞水平，明确老年患者麻醉手术后脑脊液中的exRNA聚集及其与POCD的关系，验证exRNA可能通过与海马神经元的TLR3结合而介导POCD的产生，探讨exRNA-TLR3信号介导POCD发病的可能机制。本项目的成功实施将为探寻POCD发病的新机制及寻找新的防治措施提供线索及依据。

术后认知功能障碍（POCD）被认为是老年患者术后严重并发症之一。近期文献表明Toll样受体3 （TLR3）在海马依赖的工作记忆中具有重要作用。然而，TLR3在POCD发生发展中的作用机制仍不清。在目前研究中，我们假设在麻醉及外科手术中增多的细胞外RNA（exRNAs），尤其是双链RNA （dsRNAs），可以激活TLR3信号通路并介导POCD的发生。基于POCD的小鼠模型，我们对20-22月龄的野生型老年小鼠进行单侧肾脏切除手术并且发现在神经元细胞及小胶质细胞上升高的TLR3表达。相比于野生型小鼠，TLR3老年敲除鼠在术后表现为更好的海马依赖记忆以及明显降低的炎症反应及凋亡。同时，在体内外实验中，我们均发现exRNA及dsRNA与TLR3的共表达的增多。尤其，TLR3／dsRNAs复合物抑制剂可降低海马中dsRNA的水平以及TLR3的表达，并降低海马炎症因子产生及凋亡，后提高海马依赖记忆行为。我们的结果表明exRNAs，特别是dsRNAs，在手术麻醉等应激条件下，可引发TLR3表达的激活并启动下游炎症凋亡通路，并在POCD的发生发展中起到重要作用。