肌萎缩性侧索硬化蛋白激活小胶质细胞NLRP3炎性小体

The microglial NLRP3 inflammasome is activated by amyotrophic lateral sclerosis proteins

小胶质细胞NLRP3炎性小体激活正在成为神经退行性变过程中神经炎症的关键因素。诸如β-淀粉样蛋白和α-突触核蛋白之类的致病性蛋白质聚集体触发小胶质NLRP3激活,从而导致半胱天冬酶-1激活和IL-1β的分泌。在小鼠肌萎缩性侧索硬化症(ALS)的SOD1G93A模型中,半胱天冬酶-1和IL-1β均促进疾病进展,提示小胶质NLRP3在该进程中发挥作用。然而先前的研究表明,SOD1G93A小鼠小胶质细胞不表达NLRP3,SOD1G93A蛋白在小胶质细胞中产生独立于NLRP3的IL-1β。本研究论证了使用Nlrp3-GFP基因敲入小鼠,在SOD1G93A小鼠中小胶质细胞表达NLRP3。本研究显示聚集和可溶性SOD1G93A均可激活小鼠原代小胶质细胞中的炎性小体,导致半胱天冬酶-1和IL-1β裂解,ASC斑点形成以及呈剂量和时间依赖性的IL-1β分泌。重要的是,SOD1G93A无法从缺乏Nlrp3的小胶质细胞或者用特异性NLRP3抑制剂MCC950预处理的小胶质细胞中诱导IL-1β分泌,从而证实NLRP3是介导SOD1诱导的小胶质细胞IL-1β分泌的关键炎症小体复合物。在TDP-43Q331K ALS小鼠模型中也观察到小胶质NLRP3上调,TDP-43野生型和突变蛋白亦可以NLRP3依赖性的方式激活小胶质炎性小体。从机制上讲,本研究确定了活性氧簇和ATP的生成是SOD1G93A介导的NLRP3激活所需的关键事件。总之,本研究的数据表明ALS小胶质细胞表达NLRP3,而病理ALS蛋白激活小胶质NLRP3炎性小体。因此,NLRP3抑制可能是阻止小胶质细胞神经炎症和ALS疾病进展的潜在治疗方法。

Microglial NLRP3 inflammasome activation is emerging as a key contributor to neuroinflammation during neurodegeneration.Pathogenic protein aggregates such asβ-amyloid andα-synuclein trigger microglial NLRP3 activation,leading to caspase-1 activation and IL-1βsecretion.Both caspase-1 and IL-1βcontribute to disease progression in the mouse SOD1G93A model of amyotrophic lateral sclerosis(ALS),suggesting a role for microglial NLRP3.Prior studies,however,suggested SOD1G93A mice microglia do not express NLRP3,and SOD1G93A protein generated IL-1βin microglia independent to NLRP3.Here,we demonstrate using Nlrp3-GFP gene knock-in mice that microglia express NLRP3 in SOD1G93A mice.We show that both aggregated and soluble SOD1G93A activates inflammasome in primary mouse microglia leading caspase-1 and IL-1βcleavage,ASC speck formation,and the secretion of IL-1βin a dose-and time-dependent manner.Importantly,SOD1G93A was unable to induce IL-1βsecretion from microglia deficient for Nlrp3,or pretreated with the specific NLRP3 inhibitor MCC950,confirming NLRP3 as the key inflammasome complex mediating SOD1-induced microglial IL-1βsecretion.Microglial NLRP3 upregulation was also observed in the TDP-43Q331K ALS mouse model,and TDP-43 wild-type and mutant proteins could also activate microglial inflammasomes in a NLRP3-dependent manner.Mechanistically,we identified the generation of reactive oxygen species and ATP as key events required for SOD1G93A-mediated NLRP3 activation.Taken together,our data demonstrate that ALS microglia express NLRP3,and that pathological ALS proteins activate the microglial NLRP3 inflammasome.NLRP3 inhibition may therefore be a potential therapeutic approach to arrest microglial neuroinflammation and ALS disease progression.