Researchers found that schwannoma cells produce an oxidant and nitrating agent,
peroxynitrite, which modifies an amino acid, tyrosine, in proteins.
Nitrotyrosine is formed by the interaction of
peroxynitrite with the tyrosine residues of proteins, and it can be used to evaluate the potential cytotoxic effects of nitric oxide.
The toxic one is
peroxynitrite that inflicts blood vessel damage.
[H.sub.2]S may easily react with certain compounds, especially with reactive oxygen and nitrogen species, such as superoxide radical anion ([O.sub.2-]), [H.sub.2][O.sub.2],
peroxynitrite (ONOO-), and hypochlorite (CIO-) (22-24).
Furthermore, NO easily reacts with superoxide, forming
peroxynitrite, and reduces NO bioavailability [28, 29].
The over-produced iNOS-dependent formation of NO may cause serious lung damage though the formation of
peroxynitrite (reactive nitrogen species - RNS) combining with superoxide [36, 39, 40].
For instance, hydroxyl radicals and
peroxynitrite bursts generated in some acute disease and more in degenerative disease create more and larger PPPs.
This eliminates the possibility of interaction between NO and superoxide with the formation of toxic
peroxynitrite.
Superoxide radicals augment apoptosis, cause formation of
peroxynitrite and can lead to dysfunction of the endothelium (5,8,9).
[17, 18] have showed that the contractile carotid hyperreactivity underlying cerebrovascular complication in stressed diabetic animals involves the upregulation of NADPH/Nox4 oxidase-driven generation of hydrogen peroxide ([H.sub.2][O.sub.2]) [17] and inducible nitric oxide synthase (iNOS)-driven generation of
peroxynitrite (ONOO-) [18].
Peroxynitrite. The product of the superoxide anion and NO chemical reaction is another factor that inhibits effector T cells [20].