Multiple pathways of neuroprotection against oxidative stress and excitotoxic injury in immature primary hippocampal neurons

In the immature brain hydrogen peroxide accumulates after excitotoxic hypoxia-ischemia and is neurotoxic. Immature hippocampal neurons were exposed to N-methyl-D-aspartate (NMDA), a glutamate agonist, and hydrogen peroxide (H₂O₂) and the effects of free radical scavenging and transition metal chelation on neurotoxicity were studied. α-Phenyl-N-tert.-butylnitrone (PBN), a known superoxide scavenger, attenuated both H₂O₂ and NMDA mediated toxicity. Treatment with desferrioxamine (DFX), an iron chelator, at the time of exposure to H₂O₂ was ineffective, but pretreatment was protective. DFX also protected against NMDA toxicity. TPEN, a metal chelator with higher affinities for a broad spectrum of transition metal ions, also protected against H₂O₂ toxicity but was ineffective against NMDA induced toxicity. These data suggest that during exposure to free radical and glutamate agonists, the presence of iron and other free metal ions contribute to neuronal cell death. In the immature nervous system this neuronal injury can be attenuated by free radical scavengers and metal chelators.