Critical role of the JNK-p53-GADD45α apoptotic cascade in mediating oxidative cytotoxicity in hippocampal neurons.

BACKGROUND AND
PURPOSE: Glutamate-induced oxidative stress plays a critical role in the induction of neuronal cell death in a number of disease states. We sought to determine the role of the c-Jun NH(2) -terminal kinase (JNK)-p53-growth arrest and DNA damage-inducible gene (GADD) 45α apoptotic cascade in mediating glutamate-induced oxidative cytotoxicity in hippocampal neuronal cells. EXPERIMENTAL APPROACH: HT22 cells, a mouse hippocampal neuronal cell line, were treated with glutamate to induce oxidative stress in vitro. Kainic acid-induced oxidative damage to the hippocampus in rats was used as an in vivo model. The signalling molecules along the JNK-p53-GADD45α cascade were probed with various means to determine their contributions to oxidative neurotoxicity. KEY
RESULTS: Treatment of HT22 cells with glutamate increased the mRNA and protein levels of GADD45α, and these increases were suppressed by p53 knock-down. Knock-down of either p53 or GADD45α also prevented glutamate-induced cell death. Glutamate-induced p53 activation was preceded by accumulation of reactive oxygen species, and co-treatment with N-acetyl-cysteine prevented glutamate-induced p53 activation and GADD45α expression. Knock-down of MKK4 or JNK, or the presence of SP600125 (a JNK inhibitor), each inhibited glutamate-induced p53 activation and GADD45α expression. In addition, we also confirmed the involvement of GADD45α in mediating kainic acid-induced hippocampal oxidative neurotoxicity in vivo.
CONCLUSIONS: AND IMPLICATIONS Activation of the JNK-p53-GADD45α cascade played a critical role in mediating oxidative cytotoxicity in hippocampal neurons. Pharmacological inhibition of this signalling cascade may provide an effective strategy for neuroprotection.