EPHRIN-B2 EXPRESSION IN THE ASTROCYTE MEMBRANE AROUND MOUSE BRAIN INJURIES AND THE NEUROPROTECTIVE EFFECT CONFERRED AFTER EPHRIN-B2 KNOCKOUT

Objective: To analyze Ephrin-B2 ligand expression in the astrocyte membrane around brain injuries in mice and the neuroprotective effect conferred after Ephrin-B2 knockout. Methods: A mouse brain injury model was established, and Ephrin-B2 gene knockout mice were cultured. The Ephrin-B2 gene knockout mice expressed glial fibrillary acidic protein (GFAP)-positive astrocytes. Ephrin-B2 and GFAP protein expression was detected by western blotting, and GFAP gene expression was detected by polymerase chain reaction (PCR). Results: Western blotting results showed good initial astrocyte growth with no significant difference in Ephrin-B2 knockout mice and control mice. After the brain trauma model was established, GFAP expression in the cerebral cortex of Ephrin-B2 knockout mice was significantly higher than that in the control group (P<0.05). Western blotting results showed that phosphorylated Ephrin-B2 protein expression increased significantly after brain injury in the control group, reached the highest level on the seventh day after injury, and subsequently declined until the 21st day; however, it remained higher than that in mice without brain injury (P<0.05). On the third day after brain injury, the total Ephrin-B2 protein in the control group decreased to a level slightly lower than that in mice without brain injury, after which Ephrin-B2 protein expression increased gradually. In Ephrin-B2 knockout mice, the expression of GFAP increased significantly after brain injury. On the seventh day after brain injury, the astrocyte volume was significantly increased in the knockout mice, and the processes were thickened. On the 21st day after brain injury, astrocytes were evenly distributed to fill the injured area, resulting in very small injury holes. Real-time quantitative polymerase chain reaction results showed that within 21 days after brain injury, GFAP expression in the hippocampus and ipsilateral hippocampus of Ephrin-B2 knockout mice and control mice was significantly different (P<0.05). On the seventh day after brain injury, GFAP mRNA expression was the highest in the hippocampus and around the injured area in the control group, after which the levels decreased gradually. In Ephrin-B2 knockout mice, GFAP expression was the highest in the ipsilateral hippocampus on the seventh day post-injury and remained significantly increased around the injured area on the 21st day, when the expression level was three times higher than that in control mice. Conclusion: After brain injury, Ephrin-B2 ligand expression in the astrocyte membrane and GFAP mRNA expression around the injured area were significantly increased. The resulting reactive astrocytes provided an increased neuroprotective effect.