Glutathione (GSH) levels progressively decline during aging and in
neurodegenerative disorders. However, the contribution of such event in mediating neuronal cell death is still uncertain. In this report, we show that, in
neuroblastoma cells as well as in primary mouse cortical neurons, GSH decrease, induced by
buthionine sulfoximine (BSO), causes
protein nitration, S-nitrosylation and
DNA strand breaks. Such alterations are also associated with inhibition of
cytochrome c oxidase activity and microtubule network disassembly, which are considered hallmarks of
nitric oxide (NO) toxicity. In
neuroblastoma cells, BSO treatment also induces cell proliferation arrest through the ERK1/2-p53 pathway that finally results in
caspase-independent apoptosis, as evident from the translocation of
apoptosis-inducing factor from mitochondria towards nuclei. A deeper analysis of the signaling processes indicates that the NO-cGMP pathway is involved in cell proliferation arrest and death. In fact, these events are completely reversed by
L-NAME, a specific
NO synthase inhibitor, indicating that NO, rather than the depletion of GSH per se, is the primary mediator of cell damage. In addition, the
guanylate cyclase (GC) inhibitor
LY83583 is able to completely block activation of ERK1/2 and counteract BSO toxicity. In cortical neurons,
NMDA (
N-methyl-D-aspartic acid) treatment results in GSH decrease and BSO-mediated NO cytotoxicity is enhanced by either
epidermal growth factor (
EGF) or
NMDA. These findings support the idea that GSH might represent the most important
buffer of NO toxicity in neuronal cells, and indicate that the disruption of cellular redox buffering controlled by GSH makes neuronal cells susceptible to endogenous physiological flux of NO.