Activation of M3 muscarinic ameliorates experimental autoimmune encephalomyelitis by restoring microglial quiescence

The cholinergic system serves as a crucial signaling mediator in neuroimmune regulation. Our previous study has shown that muscarinic acetylcholine receptors (mAChRs) contributed to microglial inflammatory response. However, its role in autoimmune neurodegeneration, such as multiple sclerosis (MS) remains unclear. In this study, we investigated the role of microglial mAChRs in MS pathology. For downstream analysis, we employed high-throughput transcriptomic sequencing in lipopolysaccharide (LPS)-stimulated BV2 microglia cells treated with pilocarpine (Pilo), a agonist of mAChRs. LPS+Pilo-treated cells displayed a transcriptional profile with similarity to that of normal cells. Alterations in cell chemotaxis and immune responses, with the activation of multiple GPCR downstream signaling pathways and TNF signaling pathways are also seen in LPS+Pilo-treated cells compared with LPS-stimulated cells, with significantly different expression of Msr1, Cybb, Ccl12, and Nr4a1. The results revealed that activation of mAChRs in microglia significantly upregulates Nr4a1 expression, which subsequently suppresses NF-κB-mediated inflammatory signaling.