Protectin DX调节中性粒细胞活化在脓毒症致急性肺损伤中的作用及其机制研究

Uncontrolled inflammatory response caused by neutrophil hyperactivation are the main pathological features of acute lung injury induced by sepsis. Our previous study had shown that Protectin DX(PDX), a newly identified lipid mediator, increased survival in a mouse model of sepsis and protected lung injury from sepsis. And our preliminary experiment and other’s repor suggested that PDX could limit inflammatory response through depressing neutrophil hyperactivation mediated by the inhibition of Ser345-p47phox phosphorylation of NADPH-oxidase and the upstream MAPKs signal pathway. However, it still needs to be elucidated. According to these findings we hypothesize that PDX could protect acute lung injury in sepsis through inhibiting neutrophil activation by targeting the MAPKinase/Ser345-p47phox-axis. So, we will test this hypothesis in present proposal by performing cecal ligation and puncture(CLP) in mice to establish model of sepsis-induced acute lung injury, applying diverse of experimental techniques. Firstly, we will observe the effects of PDX on acute lung injury induced by sepsis. Secondly, we are going to investigate the influence of Protectin DX in regulating neutrophil activation in sepsis-induced acute lung injury. Finally, to verify whether PDX regulates neutrophil activation is mediated by the MAPKs/ser345-p47phox signaling pathway.The finding of present proposal will provide a novel therapeutic strategy in treating acute lung injury induced by sepsis.

中性粒细胞过度活化导致失控性炎症反应是脓毒症致急性肺损伤的主要病理特征。我们的前期结果表明Protectin DX（ PDX）作为新发现的炎症消退介质能提高脓毒症小鼠生存率，并改善肺组织病理损伤。我们的预实验和其他研究提示PDX可通过MAPKs信号通路抑制NADPH氧化酶的p47phox亚基ser345位点磷酸化，进而抑制中性粒细胞活化，但仍需要充分论证。因此，我们提出研究假设：PDX可通过调节MAPKs／ser345-p47phox信号通路抑制中性粒细胞活化保护脓毒症致急性肺损伤。本项目拟采用小鼠盲肠结扎穿孔建立脓毒症致急性肺损伤模型并结合多种技术手段，首先研究PDX对小鼠急性肺损伤的影响；然后观察PDX调节中性粒细胞活化对急性肺损伤的影响；最后明确PDX调节中性粒细胞活化是否通过MAPKs/ser345-p47phox信号通路介导。本项目将为治疗脓毒症致急性肺损伤提供新的理论依据。

脓毒症病程早期就可出现急性肺损伤（ALI）和急性呼吸窘迫综合征（ARDS），其发⽣率及死亡率较高，已成为脓毒症患者死亡的⾸位原因。中性粒细胞活化并迁移到炎症部位这一过程在ALI的发展早期阶段起着重要作用。我们之前的研究表明促炎症消退介质Protectin DX（PDX）能够增强巨噬细胞吞噬功能并且促进巨噬细胞由促炎的M1型分化为抑炎的M2型从而减轻流感病毒诱导急性肺损伤，提高模型小鼠的生存率，但作用机制尚不清楚。新的研究提示，中性粒细胞活化是通过细胞内NADPH氧化酶来实现的，而NADPH氧化酶的激活是一个多步骤有序的连续过程，其中P47phox-ser345亚基已被证实在细胞质蛋白向膜转运中起主导作用，被称为NADPH氧化酶激活过程的组织者。我们推测PDX是通过抑制P47phox-ser345亚基信号途径来抑制中性粒细胞活化发挥肺保护作用的。为了确认这种推测，首先明确PDX是否能减轻脓毒症小鼠急性肺损伤，再分别进行体内体外实验探究PDX能否减轻中性粒细胞活化及其具体作用机制。我们的研究表明（1）PDX能够减轻脓毒症⼩鼠急性肺损伤。（2）PDX是通过抑制中性粒细胞活化对脓毒症致急性肺损伤产⽣作⽤。（3）PDX调节中性粒细胞活化的具体分⼦机制是通过MAPKs(p38MAPK,ERK1/2)／p47 phox -Ser 345 信号通路介导。我们的研究结果为脓毒症相关肺损伤提供了新的研究方向和治疗靶点.