GlyT1 inhibition promotes neuroprotection in the middle cerebral artery occlusion model through the activation of GluN2A-containing NMDAR

Abstract

Glycine Transporter Type 1 (GlyT1) inhibition confers neuroprotection against different forms of cerebral damage. This effect occurs through the elevation of synaptic glycine concentrations, which enhances N-methyl-d-aspartate receptor (NMDAR) activation by glutamate. To investigate the neuroprotective mechanism of GlyT1 inhibition, we used the Middle Cerebral Artery Occlusion (MCAO) model in male C57BL/6 mice, aged 10–12 weeks. We administered N-[3-(4′-fluorophenyl)-3-(4′-phenylphenoxy)propyl] sarcosine (NFPS), a GlyT1 inhibitor, 24 h prior to ischemia induction. NFPS pretreatment provided significant neuroprotection in the MCAO model, associated with modulation of pathways related to long-term potentiation. Specifically, GluN2A subunit expression was upregulated, while GluN2B subunit expression was downregulated in cortical areas, correlating with enhanced phosphorylation of CaMKIV and CREB proteins. Coadministration with the GluN2B antagonist Eliprodil or the CREB inhibitor C646 did not affect the neuroprotective effects of NFPS pretreatment, but TCN-201, a specific GluN2A antagonist, disrupted these effects. These findings suggest that GlyT1 inhibition mediates neuroprotection through activation of GluN2A-containing NMDARs and the GluN2A/CaMKIV/CREB signaling cascade, thereby modulating the balance between GluN2A and GluN2B subunits.