p21 inducers are neuroprotective against oxidative stress-induced neuron death. A-F, E14.5 mouse cortical neurons were treated with the p21 inducers alone (closed bars) or with HCA (5 mM, open bars), which inhibits cystine uptake causing the depletion of intraneuronal glutathione. This causes neuron death which was assessed by MTT reduction after 24 h. Viability of HCA-treated neurons in the absence of neuroprotective compounds was significantly less than controls, P<0.001, *=P<0.01 vs. +HCA only, two-way ANOVA-Bonferroni’s post test, n=6.