The Ubiquitination and Degradation of SH2B3 Mediated by MEF2A/WWP2 Axis Restores Microglial Homeostasis to Alleviate Cerebral Microvascular Endothelial Cell Injury in Ischemic Stroke.

Ischemic stroke (IS) is a severe disease. The altered activation states of microglia play important roles in IS. In present study, a total of 125 C57BL/6 mice was used (N = 6 per group). Middle cerebral artery occlusion (MCAO) and oxygen-glucose deprivation (OGD) were performed for in vivo and in vitro model construction. The infarct size was detected using TTC staining. The nerve injury was evaluated by a neurological deficit score. OGD-treated brain microvascular endothelial cells (BMECs) were co-cultured with BV2 cells. Cell viability was determined by CCK-8 assay, and the apoptosis rate was identified by flow cytometry analysis. Transendothelial electronic resistance (TEER) of the cells was measured by TEER measurement. Molecular interactions were analyzed using dual-luciferase reporter gene, ChIP, and Co-IP assays. All in vitro experiments were conducted with three replicates, and each experiment was performed in triplicate. We found that Src Homology 2B Adaptor Protein 3 (SH2B3) was overexpressed in the cerebral cortex tissues of MCAO treated mice (P < 0.01), and BMECs co-cultured with BV-2 cells under OGD conditions (P < 0.01). SH2B3 knockdown or Myocyte Enhancer Factor 2 A (MEF2A) overexpression reduced infarct size and improved neurological function in MCAO mice. SH2B3 knockdown enhanced OGD-treated cell viability (P < 0.05), inhibited cell apoptosis (P < 0.05) in BMECs, and ameliorated BBB (P < 0.01). Moreover, SH2B3 knockdown changed the activation status of microglia. MEF2A promoted the transcriptional activation of WW Domain Containing E3 Ubiquitin Protein Ligase 2 (WWP2) and WWP2 promoted the ubiquitination and degradation of SH2B3. SH2B3 overexpression reversed the effects of MEF2A overexpression on microglia states, BMECs injury and BBB function. In summary, MEF2A promoted the ubiquitination-mediated degradation of SH2B3 via transcription up-regulating WWP2, then changed the activation status of microglia, thus ameliorating BMEC injury, and finally ameliorating IS injury.