[Acetylcholine suppresses microglial inflammatory response in rats via acting on microglial α7nAChR]

Microglia are the main immune cells in the central nervous system. In the present study, the mechanism for acetylcholine (ACh) inhibiting microglial inflammatory response was investigated. Primary culture of microglia was isolated from cerebral cortex of Sprague-Dawley (SD) rats. Lipopolysaccharide (LPS) was used to activate the microglia to induce inflammatory response, and then the microglia were treated with ACh for 24 h. Protein expressions of several inflammatory factors, insulin-like growth factor 1 (IGF-1) and α7 nicotinic acetylcholine receptor (α7nAChR) were detected by Western blot. Release of inflammatory factors and IGF-1 into media was detected by ELISA. After α7nAChR gene silence was achieved by lentivirus-transfection of α7nAChR-shRNA, the change of ACh effect was observed. The results showed that LPS induced microglial activation, up-regulated inducible nitric oxide synthase (iNOS) protein expression, increased the expressions and release of IL-1β and TNF-α, and decreased the expression and release of the neurotrophic factor, IGF-1. ACh could reverse these effects of LPS. Meanwhile, LPS reduced the protein expression of α7nAChR on the microglial cells, whereas ACh could reverse the effect. Silencing of α7nAChR gene in microglia abolished the ability of ACh to inhibit LPS-induced inflammatory responses. These results suggest that ACh exerts its protection against LPS-induced microglial inflammation via acting on α7nAChR on microglia, which may provide a novel target for the treatment of neuro-inflammatory diseases.