A Critical Role of Autophagy in Regulating Microglia Polarization in Neurodegeneration
A Critical Role of Autophagy in Regulating Microglia Polarization in Neurodegeneration
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自噬在调节神经退行性小胶质细胞极化中的关键作用
DOI：
10.3389/fnagi.2018.00378
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发表时间：
2018-11-20
影响因子：
4.8
通讯作者：
Liu, Chun-Feng
中科院分区：
文献类型：
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作者：
Jin, Meng-meng;Wang, Fen;Liu, Chun-Feng
神经炎症和自噬功能障碍与帕金森病等神经退行性疾病的发生发展密切相关。然而，自噬在小胶质细胞极化和神经炎症中的作用知之甚少。TNF-α对多巴胺能神经元具有高度毒性，是PD中神经炎症的主要介质。在这项研究中，我们发现TNF-α导致小胶质细胞自噬通量受损。同时，在TNF-α攻击的小胶质细胞中观察到M1标志物（iNOS/NO、IL-1 β和IL-6）表达增加和M2标志物（精氨酸酶1、Ym 1/2和IL-10）表达减少。通过血清剥夺或药理学激活剂（雷帕霉素和白藜芦醇）上调自噬促进小胶质细胞向M2表型极化，如抑制M1和升高M2基因表达所证明的，而用3-MA或Atg 5 siRNA抑制自噬一贯加重TNF-α诱导的M1极化。此外，单独的Atg 5敲低足以触发小胶质细胞活化朝向M1状态。更重要的是，TNF-α刺激的小胶质细胞条件培养基在加入神经元细胞时引起神经毒性。在BV 2细胞中，Atg 5敲低后神经毒性进一步加重，但用雷帕霉素预处理小胶质细胞后神经毒性减轻。AKT/mTOR信号传导的激活可能有助于自噬和炎症的变化，因为AKT特异性抑制剂perifosine阻止了TNF-α刺激的小胶质细胞中LC 3 II（自噬标志物）的增加。总之，我们的研究结果表明，TNF-α通过AKT/mTOR信号通路抑制小胶质细胞的自噬，自噬增强可以促进小胶质细胞向M2表型极化和炎症消退。
Neuroinflammation and autophagy dysfunction are closely related to the development of neurodegeneration such as Parkinson's disease (PD). However, the role of autophagy in microglia polarization and neuroinflammation is poorly understood. TNF-alpha, which is highly toxic to dopaminergic neurons, is implicated as a major mediator of neuroinflammation in PD. In this study, we found that TNF-alpha resulted in an impairment of autophagic flux in microglia. Concomitantly, an increase of M1 marker (iNOS/NO, IL-1 beta, and IL-6) expression and reduction of M2 marker (Arginase1, Ym1/2, and IL-10) were observed in TNF-alpha challenged microglia. Upregulation of autophagy via serum deprivation or pharmacologic activators (rapamycin and resveratrol) promoted microglia polarization toward M2 phenotype, as evidenced by suppressed M1 and elevated M2 gene expression, while inhibition of autophagy with 3-MA or Atg5 siRNA consistently aggravated the M1 polarization induced by TNF-alpha. Moreover, Atg5 knockdown alone was sufficient to trigger microglia activation toward M1 status. More important, TNF-alpha stimulated microglia conditioned medium caused neurotoxicity when added to neuronal cells. The neurotoxicity was further aggravated when Atg5 knockdown in BV2 cells but alleviated when microglia pretreatment with rapamycin. Activation of AKT/mTOR signaling may contribute to the changes of autophagy and inflammation as the AKT specific inhibitor perifosine prevented the increase of LC3II (an autophagic marker) in TNF-alpha stimulated microglia. Taking together, our results demonstrate that TNF-alpha inhibits autophagy in microglia through AKT/mTOR signaling pathway, and autophagy enhancement can promote microglia polarization toward M2 phenotype and inflammation resolution.