Baicalein inhibits the polarization of microglia/macrophages to the M1 phenotype by targeting STAT1 in EAE mice

Microglia/macrophage polarization modulation plays a key role in the pathogenesis of multiple sclerosis (MS)/ experimental autoimmune encephalomyelitis (EAE). M1 microglia/macrophages secrete a variety of cytokines that cause inflammation and facilitate demyelination in the central nervous system (CNS). Baicalein (5,6,7-tri-hydroxyflavone, C15H10O5, BAI), a natural flavonoid isolated from the roots of the traditional Chinese medicine Scutellaria baicalensis Georgi, has been suggested to have a wide range of biological effects, including antioxidant, anti-inflammatory, and neuroprotective properties. In this study, flow cytometry, Western blotting, immuno-fluorescence and other methods were used to investigate whether BAI could reduce the demyelination and in-flammatory response of the spinal cord in EAE mice induced by MOG35-55 and affect the polarization of spinal microglia/macrophages. Our results showed that BAI treatment delayed the onset of EAE and alleviated clinical symptoms, demyelination and inflammatory cell infiltration. Meanwhile, BAI inhibited the overactivation of M1 microglia/macrophages in vivo and in vitro, significantly decreased the expression of proinflammatory cytokines in M1 microglia/macrophages, and inhibited the activation of STAT1. Subsequently, molecular docking, pull -down and immunofluorescence experiments confirmed that BAI has the ability to bind to the SH2 domain of STAT1 and that BAI colocalizes with p-STAT1 in the cytoplasm rather than being transferred to the nucleus during inflammatory stimulation. This study showed that BAI might inhibit the polarization of microglia/mac-rophages to the M1 phenotype in EAE mice by targeting STAT1. This new discovery lays a theoretical and experimental foundation for the clinical application of BAI in the treatment of MS.