NLRP3炎症小体在吗啡镇痛耐受形成中的作用

Recent studies indicate that microglia-mediated inflammation plays an important role in morphine tolerance. However, the underlying mechanism remains largely unknown. Nucleotide-binding domain-like protein 3 (NLRP3) is an important member of nucleotide-binding oligomerization domain-like receptor (NLR) family, which could recognize a variety of pathogen-and host-derived "danger" signals. NLPR3 can form inflammasome with adaptor protein ASC and pro-caspase-1, which is a multiprotein complexe that can activate caspase-1 and ultimately lead to the processing and secretioin of interleukin (IL)-1β and IL-18. Recently, we found that the expression of NLRP3 in activated microglia was increased after morphine treatment. The transfection of pAdeno- NLRP3-shRNA-EGFP vector in spinal cord significantly inhibited morphine tolerance. These results suggest that NLRP3 inflammasome in the microglia is associated with morphine tolerance. Using behavioral test and molecular biological methods, the aim of the project is to explore the role of NLRP3 in morphine tolerance in vivo and in vitro. To further clarify the molecular mechanisms that morphine activates NLRP3 inflammasome, toll-like receptor 2 and P2X7R signaling pathways are interrupted. Our project will provide a novel therapeutic target for morphine tolerance.

近年研究显示脊髓小胶质细胞介导的炎症反应参与吗啡镇痛耐受，但其调控机制未明。NLRP3作为最重要的模式识别受体NLR家族成员，能够识别细胞内的病原体以及细胞自身产生的危险信号，进而与接头蛋白ASC以及pro-caspase-1形成称为"炎症小体"的蛋白复合物，从而对pro-IL-1和pro-IL-18进行切割使其成熟并释放到胞外，参与免疫调节。我们最近发现，吗啡激活小胶质细胞NLRP3炎症小体；鞘内注射干扰NLRP3表达的腺病毒能抑制吗啡耐受的形成。以上预实验提示小胶质细胞NLRP3炎症小体可能参与吗啡镇痛耐受。因此本项目将在整体动物和细胞水平，结合行为学及分子生物学技术，研究小胶质细胞NLRP3炎症小体在吗啡镇痛耐受形成中的作用；并通过进一步干预Toll样受体2和嘌呤受体P2X7的信号通路，揭示吗啡激活NLRP3炎症小体的信号通路。本项目可为吗啡镇痛耐受的防治提供新颖的作用靶点。

小胶质细胞作为中枢神经系统重要的免疫细胞，参与吗啡镇痛耐受的形成过程。然而，在吗啡镇痛耐受中脊髓小胶质细胞活化的机制，以及吗啡诱导炎症因子过度激活的机制，目前还不十分清楚。本研究在整体动物和细胞水平上，采用行为学、细胞生物学和分子生物学的技术， 首次发现：（1）吗啡可以增加小胶质细胞NLRP3炎症小体的活性；（2） 抑制小胶质细胞NLRP3炎症小体的活性可以减缓吗啡镇痛耐受的形成；（3）吗啡通过诱导ROS的产生和K+外流，并通过激活P2X7受体信号通路活化小胶质细胞NLRP3炎症小体，从而促进IL-1β和IL-18的成熟与释放。上述结果证实了小胶质细胞NLRP3炎症小体活化参与吗啡镇痛耐受的形成，并阐明了吗啡激活NLRP3炎症小体的信号通路， 为有效防治吗啡镇痛耐受的形成提供了一个新靶点。