Effects of p53 inhibitor on survival and death of cells subjected to oxidative stress.

Our previous data indicate that ischemia and amyloid beta peptide (A beta) cause an oxidative damage to macromolecules. In the present study we investigated the role of p53 protein in cell survival and death after administration of A beta. The experiments were carried out on pheochromocytoma cells (PC-12) and cortical primary neurons in culture. The cortical neurons were exposed (48 h, 10 microM) to the action of a short A beta 25-35 neurotoxic fragment and the involvement of p53 was evaluated after addition of the p53 inhibitor pifithrin-alpha. Changes in cell morphology were evaluated by 4', 6-diamidino-2-phenylindole staining and the concentration-dependent effect of pifithrin-alpha on cells viability was determined. Additionally, we studied the effect of pifithrin-alpha on neuronal survival in vivo after a 5-min global brain ischemia followed by 7 days' reperfusion in gerbils. We found that A beta enhanced apoptotic cell death in cortical primary neurons. Pifithrin-alpha, at a 10 microM final concentration, protected the neuronal cells from the apoptotic death. However, at concentrations of 0.1 and 1 mM, the p53 inhibitor decreased PC-12 cells' viability in a dose-dependent manner. In in vivo experiments we did not observe any neuroprotection by pifithrin-alpha in the CA1 hippocampal layer, which suggests that its effects strongly depend on the duration and type of an ischemic insult. Our data indicate that pifithrin-alpha affects neuronal cells in a dual manner. It has a protective effect at a low concentration, but becomes neurotoxic at higher concentrations.