ABSTRACT
Neuroinflammation is a common pathological feature of neurodegenerative diseases （NDs）. Microglia （MG）， a resident macrophage in the brain with a unique developmental origin， is the core driver of neuroinflammation. It can participate in the occurrence and development of NDs through different polarization states and play a key role in regulating neurogenesis and synapse shaping and maintaining homeostasis. MG can be divided into M1 pro-inflammatory phenotype and M2 anti-inflammatory phenotype according to its function. The inflammatory mediators released by the M1 phenotype can lead to nerve degeneration and myelin sheath damage， while the activation of the M2 phenotype is required to inhibit the inflammatory response and promote tissue repair. With the advantages of multi-pathway， multi-target， and bidirectional regulation， traditional Chinese medicine can regulate the polarization balance of MG and has dual effects on NDs such as Alzheimer's disease， Parkinson's disease， and multiple sclerosis. The active components of traditional Chinese medicine and its compound can inhibit the activation of MG by regulating phosphatidylinositol-3-kinases/protein kinase B（PI3K/Akt）， NOD-like receptor thermal protein domain associated protein 3（NLRP3）， signal transducer and activator of transcription factor1（STAT1）， nuclear transcription factor kappa B（NF-κB）， and other pathways， promote the polarization of M1 phenotype to M2 phenotype， reduce the expression of interleukin（IL）-6， tumor necrosis factor-α（TNF-α）， and other pro-inflammatory factors， and increase the secretion of IL-10， arginase-1（Arg-1）， and other anti-inflammatory factors. It can also reduce β-amyloid deposition and tau protein expression in Alzheimer's disease， alleviate dopaminergic neuronal damage in Parkinson's disease， and relieve demyelination， inflammatory cell infiltration， and related clinical symptoms of multiple sclerosis. The bidirectional regulation of the M1/M2 polarization balance of MG by traditional Chinese medicine is a potential strategy for the treatment of NDs. This paper focused on the targets of the regulation of MG polarization balance by traditional Chinese medicine monomer and its compound in the treatment of NDs， so as to further study and summarize the existing research results and provide ideas and basis for the future treatment of NDs.