TREM-1/NLRP3炎症小体正反馈环路在ALI炎症级联反应中的作用

In the previous studies, we found TREM-1, a membrane bound receptor, was overexpressed in lungs of acute lung injury (ALI) mice. Blocking TREM-1 reduced the expression of NLRP3 inflammasome and impaired the activity of it, thus leading to the attenuation of ALI. It indicated that a cross-talk between TREM-1 and NLRP3 might exist and play a role in promoting the inflammation cascade in ALI. In this study, we propose TREM-1 could activate NLRP3 inflammasome via DAP12/ITAM/Syk pathway; and the downstream cytokines of NLRP3 inflammasome, IL-1β and HMGB1, could regulate the expression and function of TREM-1. The interaction of TREM-1 and NLRP3 inflammasome forms a positive feedback, which contribute to the mechanism of inflammation cascade in ALI. To test our hypothesis, we will investigate: ①effect of TREM-1 on the activation of NLRP3 inflammsome and its underlying mechanism; ②effect of NLRP3 inflammasome on the function/expression of TREM-1 and its mechanism; ③effect of the positive feedback between TREM-1/NLRP3 inflammasome on inflammation cascade in ALI.

申请人在2015年结题的NSFC资助下，观察到固有免疫系统的胞膜受体TREM-1在急性肺损伤（ALI）小鼠肺内表达显著增加，而阻断TREM-1使ALI小鼠肺内胞浆模式识别受体NLRP3炎症小体的表达和活性下降，减轻ALI，提示TREM-1与NLRP3炎症小体在肺内炎症网络中存在分子对话，可能是ALI炎症失控的新机制。因此，申请人提出TREM-1激活后可能通过DAP12/ITAM/Syk通路活化NLRP3炎症小体，反之NLRP3炎症小体活化产物IL-1β和HMGB1可调控TREM-1的表达与功能，二者形成正反馈环路，导致ALI炎症级联反应。本项目拟从动物、细胞和分子水平探讨：①ALI小鼠肺内TREM-1激活对NLRP3炎症小体活化的影响及机制；②ALI小鼠肺内NLRP3炎症小体活化对TREM-1表达和功能的影响及机制；③TREM-1/NLRP3炎症小体正反馈环路在ALI炎症中的作用。

急性肺损伤（ALI）仍然是严重危害人类健康的急危重症，有效治疗措施不足。复杂的肺内炎症级联反应网络是ALI的重要病理特征之一。在本项目的资助下，课题组系统阐明髓样细胞表达的触发受体-1（TREM-1）和NLRP3炎症小体正反馈环路在小鼠ALI肺内炎症级联放大反应中的作用，并围绕TREM-1和NLRP3炎症小体探讨其参与ALI炎症失控的分子机制和可能的干预措施，为临床治疗ALI提供新启示。本项目开展的研究如下：①本项目首次观察阻断TREM-1受体激活可减轻脂多糖（LPS）诱导的小鼠ALI，其机制与抑制NLRP3炎症小体活化有关。直接激活TREM-1可诱导小鼠原代巨噬细胞NLRP3炎症小体的活化；而巨噬细胞NLRP3炎症小体活化后促进HMGB1和IL-18分泌，以旁/自分泌的形式上调 TREM-1表达。采用不同靶点切断TREM-1/NLRP3炎症小体正反馈环路均可减轻小鼠ALI。②进一步探讨TREM-1加重ALI机制的研究，观察到诱导糖代谢重编程参与ALI炎症级联放大反应：TREM-1受体激活可诱导巨噬细胞糖酵解，而阻断糖酵解可通过抑制NLRP3炎症小体活化，减轻小鼠ALI。③深入探讨TREM-1和NLRP3炎症小体的内源性调控机制，首次观察到环氧二十碳三烯酸（EETs）和血管活性肠肽（VIP）可抑制TREM-1的表达与NLRP3炎症小体活化，减轻LPS诱导的小鼠ALI。花生四烯酸的CYPs/COX-2代谢失稳态参与ALI炎症失控，靶向干预通过抑制NLRP3炎性小体活化治疗ALI。本项目探讨了TREM-1/NLRP3炎症小体在ALI炎症失控中的作用，进一步阐明了糖脂代谢紊乱是TREM-1/NLRP3炎症小体炎症级联放大反应的新机制，拓展了TREM-1/NLRP3炎症小体的应用范围，为ALI等炎症性疾病的治疗提供新的思路。