Ca²⁺-mediated activation of c-Jun N-terminal kinase and nuclear factor κB by NMDA in cortical cell cultures

We examined the possibility that c-Jun N-terminal kinase (JNK) and nuclear factor κB (NF-κB) might be involved in intracellular signaling cascades that mediate NMDA-initiated neuronal events. Exposure of cortical neurons to 100 μM NMDA induced activation of JNK within 1 min. Activity of JNK was further increased over the next 5 rain and then declined by 30 min. Similarly, ionomycin, a selective Ca²⁺ ionophore, induced activation of JNK. The NMDA-induced activation of JNK was abrogated in the absence of extracellular Ca²⁺, suggesting that Ca²⁺ entry is necessary and sufficient for the JNK activation. Immunohistochemistry with anti-NF-κB antibody demonstrated nuclear translocation of NF-κB within 5 min following NMDA treatment. NMDA treatment also enhanced the DNA binding activity of nuclear NF-κB in a Ca²⁺-dependent manner. Treatment with 3 mM aspirin blocked the NMDA-induced activation of JNK and NF-κB. Neuronal death following a brief exposure to 100 μM NMDA was Ca²⁺ dependent and attenuated by addition of aspirin or sodium salicylate. The present study suggests that Ca²⁺ influx is required for NMDA-induced activation of JNK and NF-κB as well as NMDA neurotoxicity. This study also implies that aspirin may exert its neuroprotective action against NMDA through blocking the NMDA-induced activation of NF-κB and JNK.