Low-dose N-methyl-D-aspartate protects against amyloid-β-induced neurotoxicity by suppressing the MLK3-MKK7-JNK3 pathway and activating the PI3K-PDK1-Akt pathway.

OBJECTIVE: Oligomeric amyloid-β (Aβ) peptide-induced neuronal apoptosis is a key process in Alzheimer's disease pathogenesis. Low-dose N-methyl-D-aspartate (NMDA) has been shown to promote cell survival both in vitro and in vivo , but its effect on Aβ neurotoxicity remains largely unknown. This study aimed to investigate whether low-dose NMDA protects against Aβ-induced neurotoxicity and to elucidate the underlying molecular mechanisms.

METHODS: Primary rat cortical neurons were exposed to 10 μM Aβ25-35 to establish a neurotoxicity model. Neuronal apoptosis was assessed by 4',6-diamidino-2-phenylindole staining. The effects of low-dose NMDA (10 μM) on the PI3K-Akt and MLK3-MKK7-JNK3 signaling pathways were examined by immunoprecipitation and Western blotting. The PI3K inhibitor LY294002 was used to verify the role of PI3K signaling in NMDA-mediated regulation of the JNK3 pathway.

RESULTS: Low-dose NMDA (10 μM) significantly reduced 10 μM Aβ25-35-induced neuronal apoptosis. Mechanistically, NMDA reversed the Aβ-induced decrease in p-PDK1 and p-Akt levels and concurrently suppressed the activation of the MLK3-MKK7-JNK3 cascade. Moreover, treatment with LY294002 attenuated the inhibitory effect of NMDA on the MLK3-MKK7-JNK3 pathway.

CONCLUSION: Low-dose NMDA exerts neuroprotective effects against Aβ-induced neurotoxicity. These effects are mediated by the dual modulation of the pro-survival PI3K-PDK1-Akt pathway and the pro-apoptotic MLK3-MKK7-JNK3 pathway.