STX17调节自噬溶酶体融合过程在鲍曼不动杆菌脓毒症急性肺损伤中的作用机制研究

Sepsis is a systemic inflammatory response syndrome caused by infection that can lead to multiple organ failure and endanger patient's life. Studies have shown that high-intensity inflammation during Sepsis is closely related to autophagic degradation disorders. Our previous studies have found that Acinetobacter baumannii (Ab) hindered the fusion of autophagsome and lysosome, inhibited the degradation of inflammatory factors and caused cell damage. In addition, Ab interfered with the expression of STX17 that a key protein responsible for autophagic lysosome fusion. This study is based on the hypothesis that STX17 controls the fusion of autophagsome and lysosome to regulate the degradation of inflammatory factors and affect the acute lung injury (ALI) in Ab sepsis. We will adopt the peripheral blood of ALI patients with Ab sepsis, use Ab to infect human and mouse alveolar epithelial cells with STX17 overexpression/knockout, and establish a mouse model of Ab sepsis with conditional STX17 knockout. Afterwards, the effects of autophagic flux, STX17 expression and inflammatory cytokine release on lung injury were detected. This study will further clarify the mechanism of STX17 in regulating autophagic degradation to control the inflammatory lung injury, so as to provide theoretical basis and therapeutic strategies for the pathogenesis of acute lung injury in Ab sepsis.

脓毒症（Sepsis）是一种由感染引起的全身炎症反应综合征，它可导致多器官衰竭危及病人生命。研究表明Sepsis过程中高强度的炎症反应与自噬降解障碍密切相关。我们前期研究发现引起Sepsis的鲍曼不动杆菌（Acinetobacter baumannii，Ab）阻碍自噬溶酶体融合，抑制自噬对炎症因子的降解引起细胞损伤，并干扰负责自噬溶酶体融合的关键蛋白STX17表达。本研究基于“STX17控制自噬溶酶体融合来调节自噬对炎症因子的降解，影响Ab脓毒症急性肺损伤（Acute lung injury，ALI）”的假设。拟采取Ab脓毒症ALI患者外周血；利用Ab感染人和小鼠肺泡上皮细胞；建立条件性敲除STX17的小鼠Ab脓毒症模型，检测自噬流、STX17表达及炎症因子对肺损伤的影响，阐明STX17调节自噬降解控制炎性肺损伤的作用方式和机制，从而为Ab脓毒症急性肺损伤的发病机制提供理论基础和治疗策略。

前期研究发现鲍曼不动杆菌降解突触融合蛋白STX17引发宿主不完全自噬和炎症性损伤。另外，鲍曼不动杆菌感染者外周血LncRNA-GAS5表达升高，STX17表达降低，二者负相关。但是，鲍曼不动杆菌如何调节LncRNA-GAS5降解STX17引发不完全自噬及炎症性损伤还不清楚，所以我们将对这一问题开展研究并揭示其分子机制。. 通过细胞生物学、分子生物学及动物实验，我们发现鲍曼不动杆菌激活LncRNA-GAS5导致STX17降解引起自噬降解障碍和胞内菌体载量增加。另外，鲍曼不动杆菌对LncRNA-GAS5的激活依赖于转录因子YY1，YY1和LncRNA-GAS5具有相互抑制作用。鲍曼不动杆菌可以抑制YY1表达并减弱其对LncRNA-GAS5的抑制作用，进而使LncRNA-GAS5表达加速导致STX17降解。敲降LncRNA-GAS5或过表达YY1可以恢复STX17表达，进而促进自噬降解使胞内菌体载量减少。进一步我们构建了鲍曼不动杆菌脓毒症急性肺损伤模型，发现鲍曼不动杆菌感染C57BL/6小鼠导致肺组织中LncRNA-GAS5激活，并抑制YY1和STX17表达，造成肺组织炎症性损伤；LncRNA-GAS5敲降小鼠感染鲍曼不动杆菌后其肺组织中YY1和STX17的表达显著回升，提高了肺组织内巨噬细胞数量及外周血IFN-β释放，使菌体载量降低并减轻肺组织炎症性损伤。. 此项研究找到了调节鲍曼不动杆菌降解STX17的上游分子LncRNA-GAS5和YY1，并分析了它们对鲍曼不动杆菌降解STX17引发宿主炎症性损伤的调控作用，揭示了鲍曼不动杆菌引发宿主不完全自噬造成炎症性损伤的分子机制，为理解鲍曼不动杆菌脓毒症急性肺损伤发生的机理提供了理论基础，也为今后通过调控这些关键分子治疗鲍曼不动杆菌感染引发炎症性疾病开辟了可能的方法。