Ginsenoside Rb1 attenuates neuroflammation via activating Wnt/β-catenin signaling pathway to exert neuroprotective effect on cerebral ischemic-reperfusion injury.

Purpose: To explore the molecular mechanism of G-Rb1 regulating microglia polarization through Wnt/β-catenin signaling pathway to alleviate cerebral ischemia-reperfusion injury in mice.

Methods: C57BL/6J mouse middle cerebral artery occlusion/reperfusion (MCAO/R) model and microglia (BV2) oxygen-glucose deprivation/reoxygenation (ODG/R) model were used. The neuroprotective effect of G-Rb1 in vivo and in vitro was evaluated by measuring nerve function deficit, cerebral blood perfusion recovery, infarct volume and cell viability. Immunofluorescence, flow cytometry, Western blot and qRT-PCR were used to evaluate the effects of G-Rb1 on the Wnt/β-catenin signaling pathway and microglia phenotypic polarization mediated neuroinflammation in vivo and in vitro.

Results: Compared with the Sham group, the symptoms of neurological impairment, cerebral blood perfusion, cerebral infarction volume and inflammatory reaction were increased in the IRI group. Compared with the IRI group, G-Rb1 group showed less symptoms of neurological impairment, increased cerebral blood perfusion, decreased cerebral infarction volume, increased proportion of M2-type microglia, increased release of anti-inflammatory factors, reduced inflammatory response, and up-regulated β-catenin expression while down-regulated GSK-3β expression. It was demonstrated that G-Rb1 activates the Wnt/β-catenin signaling pathway after CIRI. Compared with G-Rb1 group, G-Rb1 + XAV939 group had more neurological impairment, increased cerebral infarction volume, increased M1 microglia proportion, and increased neuroinflammation. Meanwhile, β-catenin expression decreased while GSK-3β expression increased. The results of in vitro experiments were similar to those of in vivo, which demonstrated that G-Rb1 may alter microglial polarization phenotype through Wnt/β-catenin signaling pathway and alleviate neuroinflammatory response after CIRI.