Isoliquiritigenin regulates microglial M1/M2 polarisation by mediating the P38/MAPK pathway in cerebral stroke

Objectives Regulation of microglia polarisation may be a new way to treat ischaemic stroke based on its effects on brain injury. Isoliquiritigenin (ILG) is a flavonoid with neuroprotective function. The study investigated whether ILG regulated microglial polarisation and affects brain injury. Methods Here, a transient middle cerebral artery occlusion (tMCAO) model in vivo and lipopolysaccharide (LPS)-induced BV2 cells in vitro were established. Brain damage was assessed using a 2,3,5-triphenyl-tetrazolium-chloride staining assay. Microglial polarisation was analysed using enzyme linked immunosorbent assay, quantitative real-time polymerase chain reaction, and immunofluorescence assay. The levels of p38/MAPK pathway-related factors were measured by western blot. Key findings ILG suppressed infarct volume and neurological function of tMCAO rats. Moreover, ILG facilitated M2 microglia polarisation and suppressed M1 polarisation in the tMCAO model and LPS-induced BV2 cells. Moreover, ILG reduced the phosphorylation of p38, MAPK activated protein kinase 2, and heat shock protein 27 induced by LPS. Rescue study showed that activating the p38/MAPK pathway reversed the microglia polarisation induced by ILG and inactivating the p38/MAPK pathway enchanced the microglia polarisation. Conclusion ILG promoted microglia M2 polarisation by inactivating the p38/MAPK pathway, suggesting that ILG has the potential for the treatment of ischaemic stroke.