肌萎缩侧索硬化蛋白激活小胶质细胞NLRP3炎性体

The microglial NLRP3 inflammasome is activated by amyotrophic lateral sclerosis proteins

小胶质细胞NLRP3炎症小体激活正在成为神经退行性变期间神经炎症的关键因素。β-淀粉样蛋白和α-突触核蛋白等致病蛋白的聚集体可触发小胶质细胞NLRP3激活,并导致半胱氨酸天冬氨酸酶激活和白介素-1β分泌。半胱氨酸天冬氨酸酶和白介素-1β均促进肌萎缩侧索硬化(ALS)小鼠SOD1G93A模型的疾病进展,这提示小胶质细胞NLRP3在该进程中起作用。然而,先前的研究表明SOD1G93A模型小鼠的小胶质细胞并不表达NLRP3,并且SOD1G93A蛋白在小胶质细胞中产生白介素-1β不依赖于NLRP3。本研究展示了使用Nlrp3-GFP基因敲入小鼠,在SOD1G93A小鼠中小胶质细胞表达NLRP3。结果表明,聚集和可溶性SOD1G93A均以剂量和时间依赖性方式激活小鼠原代小胶质细胞中的炎性体,导致半胱氨酸天冬氨酸酶和白介素-1β裂解、ASC斑点形成和白介素-1β分泌。重要的是,SOD1G93A不能诱导缺乏Nlrp3的小胶质细胞或用特异性NLRP3抑制剂MCC950预处理的小胶质细胞分泌白介素-1β,这证实NLRP3是介导SOD1诱导的小胶质细胞白介素-1β分泌的关键炎性体复合物。在TDP-43Q331K ALS小鼠模型中也观察到小胶质细胞NLRP3上调,并且TDP-43野生型和突变蛋白也能以NLRP3依赖性方式激活小胶质细胞炎症小体。从机制上,本研究确定活性氧簇和ATP的产生是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,病理性ALS蛋白激活了小胶质细胞NLRP3炎性体。因此,抑制NLRP3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 activa-tion,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 de-ficient for Nlrp3,or pretreated with the specific NLRP3 inhibitor MCC950,confirming NLRP3 as the key inflamma-some complex mediating SOD1-induced microglial IL-1βsecretion.Microglial NLRP3 upregulation was also ob-served in the TDP-43Q331K ALS mouse model,and TDP-43 wild-type and mutant proteins could also activate microg-lial 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 demon-strate that ALS microglia express NLRP3,and that pathological ALS proteins activate the microglial NLRP3 inflamma-some.NLRP3 inhibition may therefore be a potential therapeutic approach to arrest microglial neuroinflammation and ALS disease progression.