Received for publication May 20, 2008.
Revised August 1, 2008.
Accepted for publication August 1, 2008.

REACTIVE OXYGEN SPECIES MEDIATE p53 ACTIVATION AND APOPTOSIS INDUCED BY SODIUM NITROPRUSSIDE IN SH-SY5Y CELLS

Abstract

Sodium nitroprusside (SNP) is a water soluble iron nitrosyl complex clinically used as a powerful vasodilator for treatment of hypertension and, in basic research, to mainly investigate the cytotoxic effects of nitrosative stress. Although nitric oxide (NO) is considered a pharmacologically active molecule, not all the biological effects of SNP are dependent on its NO moiety. In order to elucidate the molecular executioner(s) responsible for SNP cytotoxicity, this study determines the involvement of oxidative stress in p53 activation and apoptotic induction elicited by SNP in SH-SY5Y neuroblastoma cells. We demonstrate that pro-apoptotic activity of SNP is independent on NO production, because SNP and its two-day light exhausted compound (SNPex) trigger apoptosis at the same extent. We provide evidence for the occurrence of oxidative stress and oxidative damages during both SNP and SNPex exposure and demonstrate that iron-derived reactive oxygen species (ROS) are the genuine mediators of their cytotoxicity. We show that p53 is equally activated upon both SNP and SNP_ex treatments. Moreover, as demonstrated by siRNA experiments, we indicate its primary role in the induction of apoptosis, suggesting the ineffectiveness of NO in its engagement. The attenuation of p53 levels, obtained by oxy-radical scavengers, consistently with the recovery of cell viability and ROS decrease, demonstrate that SNP-mediated p53 activation is an event triggered by ROS and/or ROS-mediated damages. Altogether our results suggest that investigations on the physio-pathological effects of SNP should consider the role of ROS, other than NO, particularly in some conditions such as apoptotic induction and p53 activation.

Key words: Apoptosis, Glutathione, Metals and chelators, Oxidative stress/antioxidants, Radical intermediates