Hydrogen Peroxide Induces a Long‐Lasting Inhibition of the Ca²⁺‐Dependent Glutamate Release in Cerebrocortical Synaptosomes Without Interfering with Cytosolic Ca²⁺

Abstract

We studied the action of H2O2 on the exocytosis of glutamate by cerebrocortical synaptosomes. The treatment of synaptosomes with H2O2 (50–150 µM) for a few minutes results in a long‐lasting depression of the Ca2+‐dependent exocytosis of glutamate, induced by KCl or by the K+‐channel inhibitor 4‐aminopyridine. The energy state of synaptosomes, as judged by the level of phosphocreatine and the ATP/ADP ratio, was not affected by H2O2, although a transient decrease was observed after the treatment. H2O2 did not promote peroxidation, as judged by the formation of malondialdehyde. In indo‐1‐loaded synaptosomes, the treatment with H2O2 did not modify significantly the KCl‐induced increase of [Ca2+]i. H2O2 inhibited exocytosis also when the latter was induced by increasing [Ca2+]i with the Ca2+ ionophore ionomycin. The effects of H2O2 were unchanged in the presence of superoxide dismutase and the presence of the Fe3+ chelator deferoxamine. These results appear to indicate that H2O2, apparently without damaging the synaptosomes, induces a long‐lasting inhibition of the exocytosis of glutamate by acting directly on the exocytotic process.

Glutamate release by an Na+ load and oxidative stress in nerve terminals: relevance to ischemia/reperfusion

“…Consistent with previous reports (Zoccarato et al 1995;Tretter and Adam-Vizi 1996) we found in this study that hydrogen peroxide alone failed to induce release of glutamate (Figs 1 and 2). The dominant effect of H 2 O 2 itself on the glutamate metabolism/release is an enhanced utilization of glutamate as a metabolite within nerve terminals .…”

“…An increased basal release of glutamate from synaptosomes was reported by Gilman et al (1992) whereas no change in the resting release by H 2 O 2 was found in other studies (Zoccarato et al 1995;Tretter and Adam-Vizi 1996). Furthermore, a long-lasting depression of the depolarization-induced glutamate release was also reported (Zoccarato et al 1995). In view of the release of glutamate during oxidative stress, a recent observation that under H 2 O 2 -induced oxidative stress, glutamate is used as an alternative metabolite decreasing the glutamate reserves in nerve terminals should also be considered.…”

“…Unlike the effect of veratridine, that of the H 2 O 2 -induced oxidative stress on the release of glutamate appears to be ambiguous. An increased basal release of glutamate from synaptosomes was reported by Gilman et al (1992) whereas no change in the resting release by H 2 O 2 was found in other studies (Zoccarato et al 1995;Tretter and Adam-Vizi 1996). Furthermore, a long-lasting depression of the depolarization-induced glutamate release was also reported (Zoccarato et al 1995).…”

SNAP-25 Contains Non-Acylated Thiol Pairs that can Form Intrachain Disulfide Bonds: Possible Sites for Redox Modulation of Neurotransmission

“…Oxidative stress inhibits neurotransmitter release (Gilman et al 1992;Zoccarato et al 1995;Zoccarato and Alexandre 1996;Chen et al 2001;Giniatullin and Giniatullin 2003). Moreover, oxidative stress and impaired synaptic transmission are correlates of aging and the early stages of neurodegenerative disease (Keating 2008).…”

“…Specifically, the finding that hydrogen peroxide inhibits glutamate release without affecting cytosolic Ca 2? levels (Zoccarato et al 1995) suggests that oxidative stress may inhibit neurotransmitter release by blocking the assembly and/or function of the ternary SNARE [synaptic N-ethylmaleimide-sensitive factor attachment protein (SNAP) receptor] complex required for synaptic vesicle docking and fusion. Moreover, the results of one study demonstrated that assembly of the SNARE complex from recombinant proteins in vitro was particularly sensitive to the prior exposure to H 2 O 2 /Fe 2?…”