Zhang Qichun, Lu Ying, Bian Huimin, Guo Liwei, Zhu Huaxu
Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, Nanjing University of Chinese MedicineNanjing 210023, PR China; Jiangsu Botanical Medicine Refine Engineering Research Center, Nanjing University of Chinese MedicineNanjing 210023, PR China; Department of Pharmacology, School of Pharmacy, Nanjing University of Chinese MedicineNanjing 210023, PR China.
Department of Pharmacology, School of Pharmacy, Nanjing University of Chinese Medicine Nanjing 210023, PR China.
Am J Transl Res. 2017 Mar 15;9(3):971-985. eCollection 2017.
The α7 subtype of the nicotinic acetylcholine receptor (α7 nAChR) plays an essential role in the cholinergic anti-inflammatory pathway that regulates macrophage/microglia function in inflammation. Similar to M1 and M2 macrophages, M1 and M2 microglia exhibit pro-inflammation and anti-inflammation properties, respectively. In the present study, we analyzed function-associated phenotypes to detect the transformation of microglia with activation of α7 nAChRs. We used lentivirus-mediated shRNA to knockdown the expression of α7 nAChR in BV-2 microglia incubated with lipopolysaccharides (LPS, 0.1 μg/mL) and measured the acetylcholine (Ach, 1 μg/mL)-mediated release of cytokines, such as IL-1β, IL-4, IL-6, and IL-10, in the culture supernatant via radioimmunoassay. After stimulation with Ach, the expression of typical biomarkers for different microglia phenotypes, Iba-1 and Arg-1, was determined by cellular immunofluorescence. Furthermore, the expression of signaling molecules, including p38, JAK2/STAT3, PI3K/Akt and miR-124, was analyzed via western blotting and real-time PCR. We found that Ach inhibited LPS-induced IL-1β and IL-6 elevation and promoted IL-4 and IL-10 production and that knockdown of the α7 nAChR abolished these effects of Ach. In addition, Ach decreased LPS-induced Iba-1 expression and increased Arg-1 levels in an α7 nAChR-dependent manner. The LPS-inhibited activation of JAK2/STAT3 and PI3K/Akt was also rescued by Ach, an effect that was blocked by knockdown of the α7 nAChR. In contrast, Ach triggered the phosphorylation of JAK2 and STAT3 that was otherwise inactivated by LPS in BV-2 cells. Finally, the levels of miR-124 and downstream targets C/EBPα and PU.1 were significantly enhanced in LPS-treated BV-2 microglia, and the effect of Ach on this signaling pathway was blocked by α7 nAChR knockdown as expected. Overall, our data demonstrate that activation ofα7 nAChRs inhibits the transformation of M1 microglia and promotes the M2 phenotype, contributing to the modulation of vagus nerve neuroinflammation during several central nervous system diseases.
烟碱型乙酰胆碱受体的α7亚型(α7 nAChR)在调节炎症中巨噬细胞/小胶质细胞功能的胆碱能抗炎途径中发挥着重要作用。与M1和M2巨噬细胞类似,M1和M2小胶质细胞分别表现出促炎和抗炎特性。在本研究中,我们分析了与功能相关的表型,以检测随着α7 nAChRs激活小胶质细胞的转变。我们使用慢病毒介导的短发夹RNA(shRNA)敲低与脂多糖(LPS,0.1 μg/mL)孵育的BV-2小胶质细胞中α7 nAChR的表达,并通过放射免疫测定法测量培养上清液中乙酰胆碱(Ach,1 μg/mL)介导的细胞因子如IL-1β、IL-4、IL-6和IL-10的释放。在用Ach刺激后,通过细胞免疫荧光法测定不同小胶质细胞表型的典型生物标志物Iba-1和Arg-1的表达。此外,通过蛋白质印迹法和实时聚合酶链反应分析包括p38、JAK2/STAT3、PI3K/Akt和miR-124在内的信号分子的表达。我们发现Ach抑制LPS诱导的IL-1β和IL-6升高,并促进IL-4和IL-10的产生,并且α7 nAChR的敲低消除了Ach的这些作用。此外,Ach以α7 nAChR依赖的方式降低LPS诱导的Iba-1表达并增加Arg-1水平。Ach还挽救了LPS抑制的JAK2/STAT3和PI3K/Akt的激活,α7 nAChR的敲低阻断了这一作用。相反,Ach触发了BV-2细胞中原本被LPS失活的JAK2和STAT3的磷酸化。最后,在LPS处理的BV-2小胶质细胞中,miR-124及其下游靶点C/EBPα和PU.1的水平显著升高,正如预期的那样,α7 nAChR的敲低阻断了Ach对该信号通路的作用。总体而言,我们的数据表明α7 nAChRs的激活抑制M1小胶质细胞的转变并促进M2表型,有助于在几种中枢神经系统疾病期间调节迷走神经神经炎症。