Activation of the alpha 7 nicotinic receptor promotes lipopolysaccharide-induced conversion of M1 microglia to M2

作者：Zhang, Qichun; Lu, Ying; Bian, Huimin; Guo, Liwei; Zhu, Huaxu^*

来源：American Journal of Translational Research, 2017, 9(3): 971-985.

• Microglia
• lipopolysaccharides
• acetylcholine
• alpha 7 nAChR
• polarization

The alpha 7 subtype of the nicotinic acetylcholine receptor (alpha 7 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 alpha 7 nAChRs. We used lentivirus-mediated shRNA to knockdown the expression of alpha 7 nAChR in BV-2 microglia incubated with lipopolysaccharides (LPS, 0.1 mu g/mL) and measured the acetylcholine (Ach, 1 mu g/mL)-mediated release of cytokines, such as IL-1 beta, 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-1 beta and IL-6 elevation and promoted IL-4 and IL-10 production and that knockdown of the a7 nAChR abolished these effects of Ach. In addition, Ach decreased LPS-induced Iba-1 expression and increased Arg-1 levels in an alpha 7 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 alpha 7 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/EBP alpha and PU.1 were significantly enhanced in LPS-treated BV-2 microglia, and the effect of Ach on this signaling pathway was blocked by alpha 7 nAChR knockdown as expected. Overall, our data demonstrate that activation of alpha 7 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.

• 出版日期2017
• 单位南京中医药大学