Department of Neurology, The First Affiliated Hospital, Yijishan Hospital of Wannan Medical College, No. 92 Zheshan West Road, Wuhu, Anhui Province, 241000, People's Republic of China.
Guangdong Key Laboratory for Diagnosis and Treatment of Major Neurological Diseases, Department of Neurology, National Key Clinical Department and Key Discipline of Neurology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, Guangdong Province, 510080, People's Republic of China.
Mol Neurobiol. 2017 Dec;54(10):7777-7788. doi: 10.1007/s12035-016-0255-y. Epub 2016 Nov 14.
Activated microglia are classified into two specific states: classically activated (M1) and alternatively activated (M2) subtypes. It is believed that the polarization of M1/M2 phenotype plays an important role in Alzheimer's disease (AD). However, the mechanisms regulating this process remain unclear. Thus, we addressed this question focusing on milk fat globule epidermal growth factor 8 (MFG-E8). MFG-E8 is a unique protein which can bind to microglia and regulate its inflammatory responses. It is speculated that it might play a role in the balance of microglial polarization. In the current study, we used fibril Aβ42 in vitro to stimulate mouse primary microglial cultures and found subsequent M1 marker expression, along with retained M2 marker production. Then, we discovered that MFG-E8 pretreatment reversed the increased trend of M1 markers and the decreased expression of M2 markers, which were induced by Aβ42. Moreover, MFG-E8 effects could be effectively blocked by an MFG-E8 antibody. Further analysis on the signaling pathways showed that NF-κB upregulation and Akt downregulation in microglial cultures were observed after Aβ42 incubation. And the alteration of these pathways could also be reversed by MFG-E8. We then assessed the effects of NF-κB and PI3K-Akt on M1/M2 alteration using their specific inhibitors. Pyrrolidine dithiocarbamate, a NF-κB inhibitor, inhibited M1 marker expression; moreover, LY294002, an Akt inhibitor, enhanced M1 marker expression. Our study indicated the regulatory role of MFG-E8 on microglia M1/M2 alteration for the first time, providing a basis for understanding the potential role of microglia activation in AD.
经典激活（M1）和交替激活（M2）亚型。据信，M1/M2 表型的极化在阿尔茨海默病（AD）中起着重要作用。然而，调节这一过程的机制尚不清楚。因此，我们专注于牛奶脂肪球表皮生长因子 8（MFG-E8）来解决这个问题。MFG-E8 是一种独特的蛋白质，它可以与小胶质细胞结合并调节其炎症反应。据推测，它可能在小胶质细胞极化的平衡中发挥作用。在本研究中，我们使用纤维状 Aβ42 在体外刺激小鼠原代小胶质细胞培养物，并发现随后 M1 标志物的表达，同时保留 M2 标志物的产生。然后，我们发现 MFG-E8 预处理逆转了 Aβ42 诱导的 M1 标志物增加趋势和 M2 标志物表达降低。此外，MFG-E8 效应可被 MFG-E8 抗体有效阻断。对信号通路的进一步分析表明，在 Aβ42 孵育后观察到小胶质细胞培养物中 NF-κB 上调和 Akt 下调。MFG-E8 也可以逆转这些途径的改变。然后，我们使用 NF-κB 和 PI3K-Akt 的特异性抑制剂评估它们对 M1/M2 改变的影响。NF-κB 抑制剂吡咯烷二硫代氨基甲酸盐抑制 M1 标志物的表达；此外，Akt 抑制剂 LY294002 增强了 M1 标志物的表达。我们的研究首次表明 MFG-E8 对小胶质细胞 M1/M2 改变的调节作用，为理解小胶质细胞激活在 AD 中的潜在作用提供了依据。
