Peroxynitrite, formed by the reaction between
nitric oxide and
superoxide, leads to the oxidation of
proteins,
lipids, and
DNA, and
nitrates thiols such as
cysteine and
glutathione, and
amino acids like
tyrosine. Previous in vitro studies have shown
glutathione to be an efficient scavenger of
peroxynitrite, protecting synaptosomal membranes from
protein oxidation, the
enzyme glutamine synthetase from inactivation, and preventing the death of hippocampal neurons in culture. The current study was undertaken to see if in vivo modulation of
glutathione levels would affect brain cortical synaptosomal
membrane proteins and their subsequent reaction with
peroxynitrite.
Glutathione levels were depleted, in vivo, by injecting animals with
2-cyclohexen-1-one (CHX, 100 mg/kg
body weight), and levels of
glutathione were enhanced by injecting animals with
N-acetylcysteine (NAC, 200 mg/kg
body weight), which gets metabolized to
cysteine, a precursor of
glutathione. Changes in
membrane protein conformation and structure in synaptosomes subsequently isolated from these animals were examined using electron paramagnetic resonance, before and after in vitro addition of
peroxynitrite. The animals injected with the
glutathione depletant CHX showed greater damage to the
membrane proteins both before and after
peroxynitrite treatment, compared to the non-injected controls. The
membrane proteins from animals injected with NAC were comparable to controls before
peroxynitrite treatment and were partially protected against
peroxynitrite-induced damage. This study showed that modulation of endogenous
glutathione levels can affect the degree of
peroxynitrite-induced brain membrane damage and may have potential therapeutic significance for oxidative stress-associated
neurodegenerative disorders.