GGPPS1调控肺巨噬细胞NLRP3炎性体启动ARDS炎症瀑布的作用机制

Activation of toll like receptor-NLRP3 pathway plays a critical role in the initiation of inflammatory cascade in ARDS. Our previous study revealed that GGPPS1 had participated in the process of lung inflammation and injury in ARDS, which might exert its role by modulating the NLRP3 inflammasome activity. Additionally, GGPPS1 was found regulating the prenylation of rab proteins, a chapter protein which is essential for TLRs transmembrane location. Based on these findings, we hypothesized that GGPPS1 might regulate the initiation of ARDS inflammatory cascade through TLRs-NLRP3 pathway. To verify this hypothesis, in the present study, we aimed to investigate the effects of GGPPS1 expression on the severity of lung inflammation and injury in specific macrophage GGPPS1 depleted mice and primary macrophages. We would also test whether GGPPS1 modulate the activation of TLRs-NLRP3 pathway by modulating the Rab prenylation. The results of the study will provide new thoughts for the development of treatment targets for ARDS.

Toll样受体 (TLRs)-NLRP3炎性体信号通路激活是启动急性呼吸窘迫综合征（ARDS）的关键病理生理环节。我们前期研究发现香叶基香叶基焦磷酸合成酶1 (GGPPS1)参与ARDS早期炎症及肺损伤形成过程，其作用机制与NLRP3炎性体活性相关。近期研究发现GGPPS1调节TLRs的关键伴侣分子Rab蛋白异戊烯化水平，提示GGPPS1可能通过调节TLRs-NLRP3信号通路激活，启动ARDS的炎症瀑布。本项目拟在前期工作基础上，选用单核/巨噬细胞GGPPS1特异性敲除小鼠及原代细胞，通过体内外研究探讨GGPPS1表达状态对ARDS早期炎症及肺损伤程度的影响，观察TLRs与Rab蛋白的亚细胞分布、异戊烯化水平及TLRs-NLRP3信号通路相关分子表达，以期揭示GGPPS1以Rab蛋白调控肺巨噬细胞TLRs-NLRP3通路活性而启动ARDS的炎症瀑布机理，为探索ARDS治疗靶点提供新思路。

Toll样受体 (toll like receptor，TLRs)和炎性体相关通路异常激活是急性呼吸窘迫综合征（acute respiratory distress syndrome，ARDS）的关键，但其调控机制尚不明确。既往研究显示香叶基香叶基焦磷酸合成酶1 (GGPPS1)是ARDS早期炎症及组织损伤的重要调控因子之一，并可调节TLRs的关键伴侣分子Rab蛋白异戊烯化水平而调控相关通路。本研究显示ARDS患者肺泡巨噬细胞GGPPS1表达显著高于健康对照组，GGPPS1敲除小鼠LPS气管滴入模型死亡率、肺组织损伤严重程度、肺泡灌洗液炎症因子水平显著升高。体外实验显示，GGPPS1敲除小鼠骨髓来源巨噬细胞（bone marrow-derived macrophages，BMDMs）LPS刺激后IL-6、IL-1β和TNF-α多种炎症因子水平均显著高于对照组小鼠。进一步研究显示，GGPPS1可下调巨噬细胞内GTP-Rac1水平和NF-κB p65磷酸化及细胞核转运，负向调控LPS相关巨噬细胞TLRs及下游通路激活。在呼吸机相关急性肺损伤（ventilator-induced acute lung injury，VILI）中我们同样观察到小鼠肺泡灌洗液中GGPPS1表达增加，GGPPS1敲除小鼠肺泡灌洗液炎症因子水平、肺组织损伤程度显著低于对照组小鼠，而额外补充GGPP可逆转这一现象，进一步的研究显示，肺泡上皮细胞内GGPPS1可促进TLR2/4 – AP-1通路激活而促进细胞损伤。这提示GGPPS1在不同细胞、不同原因导致的肺组织损伤中可能通过调控不同的信号通路而参与ARDS发生、发展，对ARDS患者进一步区分亚组可能是调控该通路而改善预后的基础。