Tang Run-Hong, Qi Rui-Qun, Liu Hua-Yan
Department of Neurology, the First Hospital of China Medical University, Shenyang, Liaoning Province, China.
Department of Dermatology, Key Laboratory of Immunodermatology, the First Hospital of China Medical University, Shenyang, Liaoning Province, China.
Neural Regen Res. 2019 Sep;14(9):1594-1602. doi: 10.4103/1673-5374.255975.
Interleukin-4 plays an important protective role in Alzheimer's disease by regulating microglial phenotype, phagocytosis of amyloid-β, and secretion of anti-inflammatory and neurotrophic cytokines. Recently, increasing evidence has suggested that autophagy regulates innate immunity by affecting M1/M2 polarization of microglia/macrophages. However, the role of interleukin-4 in microglial autophagy is unknown. In view of this, BV2 microglia were treated with 0, 10, 20 or 50 ng/mL interleukin-4 for 24, 48, or 72 hours. Subsequently, light chain 3-II and p62 protein expression levels were detected by western blot assay. BV2 microglia were incubated with interleukin-4 (20 ng/mL, experimental group), 3-methyladenine (500 μM, autophagy inhibitor, negative control group), rapamycin (100 nM, autophagy inductor, positive control group), 3-methyladenine + interleukin-4 (rescue group), or without treatment for 24 hours, and then exposed to amyloid-β (1 μM, model group) or vehicle control (control) for 24 hours. LC3-II and p62 protein expression levels were again detected by western blot assay. In addition, expression levels of multiple markers of M1 and M2 phenotype were assessed by real-time fluorescence quantitative polymerase chain reaction, while intracellular and supernatant amyloid-β protein levels were measured by enzyme-linked immunosorbent assay. Our results showed that interleukin-4 induced microglial autophagic flux, most significantly at 20 ng/mL for 48 hours. Interleukin-4 pretreated microglia inhibited blockade of amyloid-β-induced autophagic flux, and promoted amyloid-β uptake and degradation partly through autophagic flux, but inhibited switching of amyloid-β-induced M1 phenotype independent on autophagic flux. These results indicate that interleukin-4 pretreated microglia increases uptake and degradation of amyloid-β in a process partly mediated by autophagy, which may play a protective role against Alzheimer's disease.
白细胞介素-4通过调节小胶质细胞表型、β-淀粉样蛋白的吞噬作用以及抗炎和神经营养细胞因子的分泌，在阿尔茨海默病中发挥重要的保护作用。最近，越来越多的证据表明自噬通过影响小胶质细胞/巨噬细胞的M1/M2极化来调节先天免疫。然而，白细胞介素-4在小胶质细胞自噬中的作用尚不清楚。鉴于此，用0、10、20或50 ng/mL白细胞介素-4处理BV2小胶质细胞24、48或72小时。随后，通过蛋白质免疫印迹法检测轻链3-II和p62蛋白表达水平。将BV2小胶质细胞与白细胞介素-4（20 ng/mL，实验组）、3-甲基腺嘌呤（500 μM，自噬抑制剂，阴性对照组）、雷帕霉素（100 nM，自噬诱导剂，阳性对照组）、3-甲基腺嘌呤 + 白细胞介素-4（拯救组）孵育24小时，或不进行处理，然后暴露于β-淀粉样蛋白（1 μM，模型组）或溶剂对照（对照组）24小时。再次通过蛋白质免疫印迹法检测LC3-II和p62蛋白表达水平。此外，通过实时荧光定量聚合酶链反应评估M1和M2表型的多个标志物的表达水平，同时通过酶联免疫吸附测定法测量细胞内和上清液中的β-淀粉样蛋白水平。我们的结果表明，白细胞介素-4诱导小胶质细胞自噬通量，在20 ng/mL处理48小时时最为显著。白细胞介素-4预处理的小胶质细胞抑制β-淀粉样蛋白诱导的自噬通量的阻断，并部分通过自噬通量促进β-淀粉样蛋白的摄取和降解，但抑制β-淀粉样蛋白诱导的M1表型的转换，且不依赖于自噬通量。这些结果表明，白细胞介素-4预处理的小胶质细胞在部分由自噬介导的过程中增加了β-淀粉样蛋白的摄取和降解，这可能对阿尔茨海默病起到保护作用。
