Yue Na, Huang Huijie, Zhu Xiaocang, Han Qiuqin, Wang Yalin, Li Bing, Liu Qiong, Wu Gencheng, Zhang Yuqiu, Yu Jin
Department of Integrative Medicine and Neurobiology, School of Basic Medical Sciences, Institues of Brain Science, State Key Laboratory of Medical Neurobiology and Collaborative Innovation Center for Brain Science, Fudan University, Shanghai, 200032, China.
Department of Anatomy, Histology and Embryology, School of Basic Medical Sciences, Shanghai Medical College, Fudan University, Shanghai, 200032, China.
J Neuroinflammation. 2017 May 10;14(1):102. doi: 10.1186/s12974-017-0865-y.
In recent years, proinflammatory cytokine interleukin-1β (IL-1β) was considered to play a critical role in the pathogenesis of depression. In addition, P2X7 receptor (P2X7R), a member of the purinergic receptor family, which is predominantly present on microglia, as well as on astrocytes and neurons in lesser amounts in the central nervous system, was suggested to be involved in the processing and releasing of IL-1β. Here, we investigated the role of P2X7R in the pathogenesis of depression.
Male Sprague-Dawley rats were subjected to chronic unpredictable stressors (CUS) for 3 weeks. At the end of week 1, 2, and 3, extracellular ATP, caspase 1, IL-1β, and components and activation of NLRP3 inflammasome (nucleotide-binding, leucine-rich repeat, pyrin domain containing 3) were evaluated as biomarker of neuroinflammation. In separate experiments, the rats were microinjected with P2X7R agonists ATP, BzATP, and saline into the hippocampus, respectively, or exposed to CUS combined with hippocampal microinjection with P2X7R antagonist, BBG and A438079, and saline, respectively, for 3 weeks, followed by exposed to forced swimming test and open-field test. Moreover, we also evaluated the depressive and anxiety-like behavior of P2X7-null mice in forced swimming test, open-field test, and elevated plus maze.
Along with stress accumulation, extracellular ATP, cleaved-caspase 1, IL-1β, and ASC were significantly enhanced in the hippocampus, but P2X7R and NLRP3 were not. Immunoprecipitation assay indicated that along with the accumulation of stress, assembly of NLRP3 inflammasome and cleaved caspase 1 in NLRP3 inflammasome were significantly increased. Moreover, antagonists of P2X7R, either BBG or A438079, prevented the development of depressive-like behaviors induced by chronic unpredictable stress in rats. Meanwhile, we could not observe any depressive-like or anxiety-like behaviors of P2X7-null mice after they had been exposed to CUS. The results implied that P2X7 knockout could impede the development of depressive-like and anxiety-like behaviors induced by CUS. In contrast, chronic administration of agonists of P2X7R, either ATP or BzATP, could induce depressive-like behaviors.
The activation of P2X7R and subsequent NLRP3 inflammasome in hippocampal microglial cells could mediate depressive-like behaviors, which suggests a new therapeutic target for the prevention and treatment of depression.
近年来，促炎细胞因子白细胞介素 -1β（IL -1β）被认为在抑郁症发病机制中起关键作用。此外，嘌呤能受体家族成员P2X7受体（P2X7R）主要存在于小胶质细胞上，在中枢神经系统中也少量存在于星形胶质细胞和神经元上，提示其参与IL -1β的加工和释放。在此，我们研究了P2X7R在抑郁症发病机制中的作用。
雄性Sprague - Dawley大鼠接受3周的慢性不可预测应激（CUS）。在第1、2和3周结束时，评估细胞外ATP、半胱天冬酶1、IL -1β以及NLRP3炎性小体（含核苷酸结合、富含亮氨酸重复序列、吡啉结构域的3）的成分和激活情况，作为神经炎症的生物标志物。在单独的实验中，分别向大鼠海马内微量注射P2X7R激动剂ATP、BzATP和生理盐水，或者将大鼠暴露于CUS并分别联合海马内微量注射P2X7R拮抗剂BBG和A438079以及生理盐水，持续3周，随后进行强迫游泳试验和旷场试验。此外，我们还评估了P2X7基因敲除小鼠在强迫游泳试验、旷场试验和高架十字迷宫中的抑郁样和焦虑样行为。
随着应激积累，海马中细胞外ATP、裂解的半胱天冬酶1、IL -1β和ASC显著升高，但P2X7R和NLRP3没有升高。免疫沉淀试验表明，随着应激积累，NLRP3炎性小体的组装以及NLRP3炎性小体中裂解的半胱天冬酶1显著增加。此外，P2X7R拮抗剂BBG或A438079可预防慢性不可预测应激诱导的大鼠抑郁样行为的发展。同时，我们未观察到P2X7基因敲除小鼠在暴露于CUS后出现任何抑郁样或焦虑样行为。结果表明，P2X7基因敲除可阻碍CUS诱导的抑郁样和焦虑样行为的发展。相反，长期给予P2X7R激动剂ATP或BzATP可诱导抑郁样行为。
海马小胶质细胞中P2X7R的激活及随后的NLRP3炎性小体可介导抑郁样行为，这提示了预防和治疗抑郁症的新治疗靶点。
