Cyanide-induced apoptosis involves oxidative-stress-activated NF-kappaB in cortical neurons

The central nervous system is one of the main target organs in cyanide toxicity. Primary cultured cortical neurons were used to study the cellular mechanisms underlying cyanide-induced cytotoxicity. After exposure to KCN (100-300 microM) for 24 h, cortical neurons underwent apoptosis as characterized by positive TUNEL staining. Reactive oxygen species (ROS) play an important role in cyanide-induced neuronal apoptosis; immediately after cyanide (100-300 microM) treatment, ROS generation was observed and continued to be elevated for up to 3 h. NMDA receptor activation and subsequent Ca(2+) influx contribute in part to cyanide-induced ROS formation, since the selective NMDA receptor antagonist MK801 and intracellular Ca(2+) chelator BAPTA blocked ROS generation. Interestingly, caspases, recently reported to be involved in neuronal apoptosis, play a role in the late phase of ROS production after cyanide stimulation. Z-VAD, a nonspecific caspase inhibitor, blocked ROS generated 1 h after cyanide treatment, but it had no effect on ROS generated immediately after cyanide treatment. Nuclear factor kappaB (NF-kappaB), a redox-sensitive transcription factor, was activated dose dependently after cyanide treatment. Blockade of ROS generation by MK801, Z-VAD, and various antioxidants also blocked the activation of NF-kappaB. SN50, a synthetic peptide which inhibits the nuclear translocation of NF-kappaB, blocked cyanide-induced apoptotic cell death. These results indicate that NF-kappaB plays an important role in cyanide-induced apoptosis in cortical neurons, and the caspases may contribute in part to the activation of NF-kappaB after cyanide treatment by inducing the late phase of ROS generation.