Differential Mechanisms of Nitric Oxide- and Peroxynitrite-Induced Cell Death

Abstract

Nitric oxide (NO) contributes to cellular degeneration in various disorders, particularly in the nervous system. NO targets cell proteins such as soluble guanylyl cyclase, but its detrimental effects are generally attributed to its reaction product with superoxide, peroxynitrite. To understand the mechanisms of NO-induced cell stress, we studied the effects of the NO donors diethylenetriamine and spermine NONOate and the peroxynitrite donor 5-amino-3-(4-morpholinyl)-1,2,3-oxadiazolium chloride (SIN-1) in SH-SY5Y and NG108-15 neuroblastoma cells. All three compounds induced a dose-and time-dependent decrease in viable cells, which was not blocked by the soluble guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. The two NONOates were ϳ15-fold more potent in SH-SY5Y than in NG108-15 cells, whereas the EC 50 values of SIN-1 in SH-SY5Y and NG108-15 cells were in the same order. This led us to conclude that the mechanisms of NO and peroxynitrite did not converge. This was supported by our other findings. NONOates induced DNA fragmentation and an increase in cellular caspase-3 activity that preceded the gradual decline in cell viability. In contrast, SIN-1 induced a transient decline in ATP levels and a delayed loss of cell viability with no significant increase in caspase-3 activity or DNA laddering. Moreover, post-treatment with insulin inhibited caspase-3 activation and loss of cell viability in NONOate-but not in SIN-1-exposed cells. These findings suggest that NO is a potent toxin independent of peroxynitrite formation.

Reactive Macrophages Increase Oxidative Stress and Alpha-Synuclein Nitration During Death of Dopaminergic Neuronal Cells in Co-Culture: Relevance to Parkinson’s Disease

“…This observation further authenticate that what we measured with H 2 DCF-DA was peroxynitrite anions but not other oxidant species (35,36). Previous studies from our laboratory have suggested that NO and peroxynitrite ions are toxic to dopaminergic neurons (37,38). Furthermore, LPS also is known to activate protein kinase C, protein-tyrosine kinases, MAP kinases and NF-kB all have been implicated in the release of several cytotoxic factors such as NO and various cytokines (39)(40)(41)(42).…”

Protective Effects of Flavonoids Against Oxidative Stress Induced by Simulated Microgravity in SH-SY5Y Cells

“…In the Fenton reaction, reduction of H 2 O 2 by iron results in the production of the highly reactive and toxic hydroxyl radical [32]. SIN-1 generates NO and superoxide in equimolar amounts, thereby producing [33]; moreover, NO is thought to be a potent toxin independent of peroxynitrite formation [34]. Both isorhamnetin and luteolin inhibited neuronal cell damage induced by H 2 O 2 or SIN-1; in these experiments, isorhamnetin was weaker in ROS scavenging activity but better at inhibiting NO formation than luteolin (Figs.…”

Preventive effects of propofol and ketamine on renal injury in unilateral ureteral obstruction

“…However, excessive, unregulated NO production can also lead to the formation of reactive nitrogen species that can oxidize lipids, damage DNA, and cause protein modifications of important cellular proteins and enzymes [27]. The ability of NO or reactive nitrogen species to alter mitochondrial function and damage proteins may result in NO-mediated apoptosis or necrosis depending on the amount of NO and reactive nitrogen species generated [28].…”