Targeting NMDAR2A in microglia: esketamine suppresses M1 polarization in BV2 cells.

Objective: Microglial polarization toward the M1 phenotype is a key contributor to the initiation and progression of neuroinflammatory diseases, primarily through the release of pro-inflammatory cytokines that exacerbate central nervous system-associated injury. Activation of N-methyl-D-aspartic acid receptors (NMDARs) is implicated in microglial overactivation and cytotoxicity. This study aimed to investigate the role of esketamine, a non-competitive NMDAR antagonist, on microglial polarization.

Methods: BV2 microglial cells were used as an in vitro model. Inhibitors and agonists were applied to modulate the mammalian target of rapamycin (mTOR) and brain-derived neurotrophic factor (BDNF)-tyrosine kinase receptor B (TrkB) signaling pathways. Small interfering RNA, Western blotting, enzyme-linked immunosorbent assay, and immunofluorescence staining were performed to investigate the regulatory effects and molecular targets of esketamine on BV2 cells.

Results: Esketamine enhanced mTOR phosphorylation and activated the BDNF-TrkB signaling pathway through NMDAR inhibition. This effect attenuated lipopolysaccharide-induced M1 polarization in BV2 microglia and reduced pro-inflammatory cytokine expression. Further analysis revealed that the anti-inflammatory effects of esketamine were primarily mediated by the NMDAR2A subtype, while the NMDAR2B subtype was not involved.

Conclusion: Esketamine suppressed proinflammatory microglial polarization by selectively modulating the NMDAR2A subtype, leading to the activation of the mTOR signaling pathway and enhancement of the BDNF-TrkB signaling pathway.