A novel GSK-3β inhibitor YQ138 prevents neuronal injury induced by glutamate and brain ischemia through activation of the Nrf2 signaling pathway.

Aim: To discover neuroprotective compounds and to characterize the discovered active compound YQ138 as a novel GSK-3β inhibitor.

Methods: Primary rat cerebellar granule cells (CGCs) were treated with glutamate, and cell viability was analyzed with MTT assay, which was used as in vitro model for screening neuroprotective compounds. Active compound was further tested in OGD- or serum deprivation-induced neuronal injury models. The expression levels of GSK-3β downstream proteins (Nrf2, HO-1, NQO1, Tau and β-catenin) were detected with Western blotting. For evaluating the neuroprotective effects in vivo, adult male rats were subjected to transient middle cerebral artery occlusion (tMCAO), then treated with YQ138 (10 mg/kg, iv) at 2, 4 and 6 h after ischemia onset.

Results: From a compound library consisting of about 2000 potential kinase inhibitors, YQ138 was found to exert neuroprotective effects: pretreatment with YQ138 (0.1-40 μmol/L) dose-dependently inhibited glutamate-induced neuronal death. Furthermore, pretreatment with YQ138 (10 μmol/L) significantly inhibited OGD- or serum deprivation-induced neuronal death. Among a panel of seven kinases tested, YQ138 selectively inhibited the activity of GSK-3β (IC50=0.52 nmol/L). Furthermore, YQ138 dose-dependently increased the expression of β-catenin, and decreased the phosphorylation of Tau in CGCs. Moreover, YQ138 significantly increased the expression of GSK-3β downstream antioxidative proteins Nrf2, HO-1, NQO1, GSH and SOD in CGCs. In rats with tMCAO, administration of YQ138 significantly decreased infarct volume, improved the neurological deficit, and increased the expression of Nrf2 and HO-1 and the activities of SOD and GSH in the cerebral cortex.

Conclusion: A novel GSK-3β inhibitor YQ138 effectively suppresses brain ischemic injury in vitro and in vivo.