Dong Yuan, Li Shuoshuo, Lu Yiming, Li Xiaoheng, Liao Yajin, Peng Zhixin, Li Yunfeng, Hou Lin, Yuan Zengqiang, Cheng Jinbo
Department of Biochemistry, Medical College, Qingdao University, Qingdao, 266071, Shandong, China.
The Brain Science Center, Beijing Institute of Basic Medical Sciences, No. 27 Taiping Road, Haidian District, Beijing, 100850, China.
J Neuroinflammation. 2020 Jul 7;17(1):205. doi: 10.1186/s12974-020-01842-0.
Persistent inflammation dysregulation and cognitive decline have been associated with several trauma- and stress-related disorders such as posttraumatic stress disorder (PTSD) and anxiety disorder. Despite the abundant discoveries of neuroinflammation in such disorders, the underlying mechanisms still remain unclear.
Wild-type and Nlrp3 mice were exposed to the electric foot shocks in the contextual fear memory paradigm. Three hours after the electric foot shocks, activation of the NLRP3 inflammasome was investigated through immunoblotting and ELISA. Microglia were isolated and analyzed by quantitative real-time PCR. Hippocampal tissues were collected 3 h and 72 h after the electric foot shocks and subjected to RNA sequencing. MCC950 was administrated to mice via intraperitoneal (i.p.) injection. Interleukin-1 receptor antagonist (IL-ra) and interleukin-1β (IL-1β) were delivered via intracerebroventricular (i.c.v.) infusion. Contextual fear responses of mice were tested on 4 consecutive days (test days 1-4) starting at 48 h after the electric foot shocks. Anxiety-like behaviors were examined by elevated plus maze and open-field test.
We demonstrated that, in the contextual fear memory paradigm, the NLRP3 inflammasome was activated 3 h after electric foot shocks. We also found an upregulation in toll-like receptor and RIG-I-like receptor signaling, and a decrease in postsynaptic density (PSD) related proteins, such as PSD95 and Shank proteins, in the hippocampus 72 h after the electric foot shocks, indicating an association between neuroinflammation and PSD protein loss after stress encounter. Meanwhile, Nlrp3 knockout could significantly prevent both neuroinflammation and loss of PSD-related proteins, suggesting a possible protective role of NLRP3 deletion during this process. For further studies, we demonstrated that both genetic knockout and pharmaceutical inhibition of the NLRP3 inflammasome remarkably enhanced the extinction of contextual fear memory and attenuated anxiety-like behavior caused by electric foot shocks. Moreover, cytokine IL-1β administration inhibited the extinction of contextual fear memory. Meanwhile, IL-1ra significantly enhanced the extinction of contextual fear memory and attenuated anxiety-like behavior.
Taken together, our data revealed the pivotal role of NLRP3 inflammasome activation in the regulation of fear memory and the development of PTSD and anxiety disorder, providing a novel target for the clinical treatment of such disorders.
持续性炎症失调和认知衰退与多种创伤及应激相关障碍有关，如创伤后应激障碍（PTSD）和焦虑症。尽管在这些障碍中对神经炎症有大量发现，但其潜在机制仍不清楚。
将野生型和Nlrp3基因敲除小鼠置于情境恐惧记忆范式中接受足部电击。足部电击3小时后，通过免疫印迹和酶联免疫吸附测定（ELISA）研究NLRP3炎性小体的激活情况。分离小胶质细胞并通过定量实时聚合酶链反应（qRT-PCR）进行分析。在足部电击后3小时和72小时收集海马组织并进行RNA测序。通过腹腔注射将MCC950给予小鼠。通过脑室内注入白细胞介素-1受体拮抗剂（IL-ra）和白细胞介素-1β（IL-1β）。从足部电击后48小时开始，连续4天（测试日1 - 4）测试小鼠的情境恐惧反应。通过高架十字迷宫和旷场试验检查焦虑样行为。
我们证明，在情境恐惧记忆范式中，足部电击后NLRP3炎性小体在3小时被激活。我们还发现，在足部电击72小时后，海马中Toll样受体和RIG-I样受体信号上调，且突触后致密物（PSD）相关蛋白如PSD95和Shank蛋白减少，这表明应激后神经炎症与PSD蛋白丢失之间存在关联。同时，Nlrp3基因敲除可显著预防神经炎症和PSD相关蛋白的丢失，表明在此过程中NLRP3缺失可能具有保护作用。进一步研究表明，NLRP3炎性小体的基因敲除和药物抑制均显著增强了情境恐惧记忆的消退，并减轻了足部电击引起的焦虑样行为。此外，给予细胞因子IL-1β抑制了情境恐惧记忆的消退。同时，IL-1ra显著增强了情境恐惧记忆的消退并减轻了焦虑样行为。
综上所述，我们的数据揭示了NLRP3炎性小体激活在恐惧记忆调节以及PTSD和焦虑症发展中的关键作用，为这些疾病的临床治疗提供了新靶点。
