细胞外miRNAs在脓毒症心功能障碍中的作用及机制研究

Sepsis is now defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, which has high mortality. A large portion of septic patients exhibit myocardial dysfunction and many sepsis clinical trials have yielded frustratingly negative results. Damage-associated molecule patterns (DAMP) are generated by host and can activate innate immune system through Toll-like receptors (TLRs) to induce tissue injury such as myocardial dysfunction. Our recent work has demonstrated that extracellular RNA, as a major DAMP, is pro-inflammatory and plays an important role in myocardial ischemia-reperfusion injury, but it is unclear whether extracellular miRNAs from damaged cells are involved in sepsis-induced cardiac dysfunction. We have reported that sepsis mice release cellular RNA (including some miRNAs) into the blood circulation, and the circulating RNA levels are closely associated with overall sepsis severity in mice. Specific miRNA mimics (rich in U nucleotides) can induce complement pathway activation and cytokine production by activating TLR7 pathway in macrophage. Built on these preliminary data, we hypothesize that miRNAs (rich in U nucleotides) released from damaged cells induce innate immune response and cardiomyocyte dysfunction in septic mice via TLR7 signaling pathway. We will take complementary approaches including septic patients, isolated cells, and rodent septic models, and use miRNA mimics, anti-miRNA, TLR7 antagonists in our project. We aim ① to determine the critical role of extracellular miRNAs in sepsis-induced cardiac dysfunction and the underlying molecular mechanisms, and ② to determine whether targeting these miRNAs can suppress innate immune response, reduce cardiac dysfunction and improve sepsis survival. We believe the proposed studies will help to identify new therapeutic targets for future clinical treatment of sepsis-induced cardiac dysfunction.

脓毒症常见心功能障碍，死亡率高，诸多方法疗效欠佳。损伤相关分子模式（DAMP）经Toll样受体（TLRs）激活固有免疫参与心肌损伤。以细胞外RNA为代表的DAMP在缺血再灌注心肌损伤中起关键作用，但细胞外miRNAs是否介导脓毒症心功能障碍尚未明确。我们前期发现脓毒症时受损细胞释放RNA（包括部分miRNAs）入血，其浓度与脓毒症严重程度显著相关；富含U碱基的miRNAs经TLR7通路诱导补体激活及炎症反应。据此提出假说：脓毒症所释放富含U碱基的细胞外miRNAs作为DAMP经TLR7通路激发固有免疫过度反应并诱导心肌损伤和功能障碍。拟应用miRNAs模拟物和拮抗剂、TLR7阻断剂，从脓毒症患者、细胞和动物模型三个层面进行研究。旨在①揭示富含U碱基的细胞外miRNAs在脓毒症心功能障碍中的作用和机制；②明确靶向阻断此类miRNAs对脓毒症心功能障碍及生存率的影响，为临床治疗提供新的思路。

脓毒症常见心功能障碍，死亡率高，诸多方法疗效欠佳。损伤相关分子模式（DAMP）经Toll样受体（TLRs）激活固有免疫参与心肌损伤。以细胞外RNA为代表的DAMP在缺血再灌注心肌损伤中起关键作用，但细胞外miRNAs是否介导脓毒症心功能障碍尚未明确。本研究从脓毒症患者、细胞和动物模型三个层面进行研究，观察富含U碱基的细胞外miRNA-145、miRNA-122、miRNA-146a浓度与脓毒症严重程度及心功能不全的相性；并明确靶向阻断miRNA-TLR7/MyD88通路是否抑制固有免疫过度反应，改善心功能，提高生存率。我们研究结果发现在脓毒症患者和脓毒症小鼠外周血中富含U碱基的miRNAs（miRNA-146a、miRNA-122、miRNA-145）显著增高，且miRNAs的升高程度与脓毒症严重程度和心功能损害程度显著相关。阻断miRNA-TLR7/MyD88通路，清除循环血液中释放的miRNAs，阻断miRNAs与TLR7结合，或者阻断TLR7下游的MyD88通路，可改善脓毒症所致心功能障碍并提高生存率。证实脓毒症时受损细胞所释放富含U碱基的细胞外miRNAs可作为DAMP经TLR7通路激活固有免疫系统介导心功能障碍，为探究脓毒症所致心功能障碍的发病机制提供了实验依据，为临床控制脓毒症病程和提高生存率提供了新的靶点和思路，具有一定的应用价值和社会效益。此外本研究还证实了VVI技术可早期且敏感的评估脓毒症患者和小鼠的心功能障碍，具有一定的应用价值。本研究已发表论文2篇，其中SCI1篇，CSCD论文1篇，目前数篇论著待审待发表，课题组将会尽快发表。共培养研究生3名。