Peroxynitrite is usually considered as a neurotoxic nitric oxidederivative. However, an increasing body of evidence suggests that, at low concentrations, peroxynitrite affords transient cytoprotection, both in vitro and in vivo. Here, we addressed the signaling mechanism responsible for this effect, and found that rat cortical neurons in primary culture acutely exposed to peroxynitrite (0.1 mmol/L) rapidly elicited Akt-Ser 473 phos-
Peroxynitrite (PN), the product of the reaction between nitric oxide (NO) and superoxide (O 2•) ) (Blough and Zafiriou 1985), is spontaneously formed in mammalian cells under physiological conditions (Radi et al. 2001;Possel et al. 2002). Initial work addressing the pathophysiology of PN yielded the widely accepted notion that this compound would be the long-term cytotoxic NO-derivative (Beckman et al. 1990;Radi et al. 1991). Peroxynitrite involvement in cytotoxicity is documented by detecting protein 3-nitrotyrosination, i.e. the 'footprinting' like evidence for in situ PN formation (Ischiropoulos et al. 1992;Greenacre and Ischiropoulos 2001;Beal 2002), associated with neurodegeneration and other disorders (Bolaños et al. 1997;Lipton 1999;Guix et al. 2005). However, in apparent contradiction with Received November 8, 2006; revised manuscript received January 5, 2007; accepted January 9, 2007. Address correspondence and reprint requests to Prof. Juan P. Bolaños, Departamento de Bioquímica y Biología Molecular, Campus Miguel de Unamuno, Universidad de Salamanca, 37007 Salamanca, Spain. E-mail: jbolanos@usal.esAbbreviations used: 7-AAD, 7-amino-actinomycin D; Akt, protein kinase B; APC, allophycocyanin; BDNF, brain-derived neurotrophic factor; CAT, catalase; DAPI, 4¢-6-diamidino-2-phenylindole; GSH, glutathione ethyl ester; GFP, green fluorescent protein; Luc, luciferase; RNAi, RNA interference; PI3K, phosphoinositide-3-kinase; PFK-1, 6-phosphofructo-1-kinase; PN, peroxynitrite; PTP, protein tyrosine phosphatase; PTEN, phosphatase with tensin homology; shRNA, small hairpin RNA; SIN-1, 3-morpholinosydnonimine; SOD, superoxide dismutase; Trk, neurotrophin tyrosine kinase receptor.