HMGB1-TLRs信号通路在PM2.5致呼吸道炎性损伤中的作用

High mobility group protein (HMGB1), an important late inflammatory factor, becomes a new target for anti-inflammatory therapy in recent years. Although it has been clear that TLR2 and TLR4 are important receptors of HMGB1, the HMGB1 related signal transduction mechanisms are not yet clear. We have previously found that TLR4 was involved in the induction of TNFα on human macrophage treated with silicon dioxide, which mediated the development of inflammation. However, the role of HMGB1-TLRs pathway in PM2.5 induced airway inflammation has not been reported. Herein, our hypothesis is that, after PM2.5 stimulation, HMGB1 was released into the extracellular, binding to TLR2 and/or TLR4 as both a stress signal and an inflammatory mediator via a MyD88 dependent or independent pathway, and then activated the downstream inflammation related signaling pathways, finally leading to inflammation of the respiratory system. In our study, transgenic mice model (TLR4-/-, TLR2-/- and MyD88-/-) were used and treated accordingly before a series of molecular biological tests, including ELISA, Western blot, IP, immunofluorescence staining, HE staining and so on. Based on our study, new ideas and targets would be provided for the future prevention and treatment of PM2.5 induced airway inflammation.

高迁移率族蛋白B1（HMGB1）是一种重要晚期炎症因子，也是近年来抗炎治疗的新靶向分子。虽然已明确TLR2和TLR4是HMGB1的重要受体，但目前HMGB1相关信号转导机制尚不清楚。我们前期发现TLR4参与诱导二氧化硅对人巨噬细胞TNFα合成，介导炎症发生发展过程，但HMGB1-TLRs通路在PM2.5所致呼吸道炎症中的作用还未见报道。为此，我们提出假设：PM2.5刺激后，HMGB1作为应激信号和炎性介质释放到胞外，与TLR2或（和）TLR4结合，通过MyD88依赖或非依赖途径，最终激活下游炎症相关信号通路而导致呼吸系统炎症。本研究拟采用转基因小鼠模型（TLR4-/-，TLR2-/-和MyD88-/-），利用ELISA、Western Blot、co-IP、免疫荧光和HE染色等技术检测炎症相关指标，为将来治疗和预防PM2.5致呼吸道炎症提供新的靶点和思路。

背景：环境颗粒物（PM）是大气污染物的主要组成部分，对人体健康有多种危害。TLRs是一种非催化的跨膜蛋白，可以从微生物中识别保守分子。当微生物突破皮肤和粘膜等物理屏障时，TLR可以识别它们并激活免疫细胞反应。然而，TLR4的调节机制及其对PM所致肺、肝炎症的影响目前尚不清楚。..方法：野生型小鼠和TLR4-/-小鼠（C57BL/10JNju，混合性别，8-10周龄），随机分为两组（每组8只，共32只）。隔日气管内注入生理盐水或PM2.5（4mg/kg），连续10d（共5次）。收集BALF、血清、肝组织和肺组织，然后检测肺和肝的炎症相关指标。..结果：在肺部炎症方面，PM2.5使BCA、LDH水平升高，TLR4 KO小鼠BCA较野生型小鼠降低（P=0.08）。PM2.5处理组炎性细胞因子（HMGB1、TNFα、MCP-1/CCL2、CCR2）的表达明显高于salin处理组（P<0.05），且有减弱的趋势。HE染色显示PM2.5可引起严重的炎症损伤，TLR4 KO可减轻炎症过程。在肝脏方面，仅野生型小鼠经PM2.5处理后LDH和AKP显著升高。与肺组织相似，PM2.5刺激可诱导促炎基因的表达水平，TLR4 KO可减轻肝脏炎症的进展。..结论：TLR4对PM2.5引起的肺、肝炎症反应具有重要的调节作用。