1. ¹Department of Physiology and Biophysics, University of Alabama at Birmingham, Birmingham, AL, USA
2. ²Burke/Cornell Medical Research Institute, White Plains, NY, USA
3. ³Department of Pharmacology and Toxicology, University of Alabama at Birmingham, Birmingham, AL, USA
4. ⁴Department of Neurobiology, University of Alabama at Birmingham, Birmingham, AL, USA
5. ⁵Center for Free Radical Biology, University of Alabama at Birmingham, Birmingham, AL, USA
6. ⁶Current address: Division of Neuropathology, Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
7. ⁷Current address: Burke/Cornell Medical Research Institute, White Plains, NY 10605, USA

Correspondence: AG Estévez, Laboratory of Motor Neuron Biology, Burke/Cornell Medical Research Institute, 785 Mamaroneck Ave, White Plains, NY 10605, USA. Tel: +1 914 597 5221; Fax: +1 914 597 5222; E-mail: aestevez@burke.org

Received 28 February 2005; Revised 25 October 2005; Accepted 2 November 2005; Published online 20 January 2006.

Abstract

The mechanisms of peroxynitrite-induced apoptosis are not fully understood. We report here that peroxynitrite-induced apoptosis of PC12 cells requires the simultaneous activation of p38 and JNK MAP kinase, which in turn activates the intrinsic apoptotic pathway, as evidenced by Bax translocation to the mitochondria, cytochrome c release to the cytoplasm and activation of caspases, leading to cell death. Peroxynitrite induces inactivation of the Akt pathway. Furthermore, overexpression of constitutively active Akt inhibits both peroxynitrite-induced Bax translocation and cell death. Peroxynitrite-induced death was prevented by overexpression of Bcl-2 and by cyclosporin A, implicating the involvement of the intrinsic apoptotic pathway. Selective inhibition of mixed lineage kinase (MLK), p38 or JNK does not attenuate the decrease in Akt phosphorylation showing that inactivation of the Akt pathway occurs independently of the MLK/MAPK pathway. Together, these results reveal that peroxynitrite-induced activation of the intrinsic apoptotic pathway involves interactions with the MLK/MAPK and Akt signaling pathways.