[abstract] NEURONAL NOS AND GLUTAMATE DECARBOXYLASE S-NITROSYLATION BEFORE OXYGEN SEIZURES.

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[abstract] NEURONAL NOS AND GLUTAMATE DECARBOXYLASE S-NITROSYLATION BEFORE OXYGEN SEIZURES.

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Title: [abstract] NEURONAL NOS AND GLUTAMATE DECARBOXYLASE S-NITROSYLATION BEFORE OXYGEN SEIZURES.
Author: Demchenko, IT; Atochin, DN; Suliman, HB; Tatro, L; Allen, BA; Huang, PL; Piantadosi, CA
Abstract: BACKGROUND: Glutamic acid decarboxylase (GAD) is inhibited by HBO2, but the inhibitory mechanisms and their effect on the pathogenesis of oxygen seizures are unknown. Using rats, we have found that HBO2-stimulated NO production inhibits GAD activity by S-nitrosylation. Here, mice lacking eNOS or nNOS were used to examine isoform-specific contributions to brain NO production in protein S-nitrosylation of GAD-65 in HBO2. MATERIALS AND METHODS: Two series of experiments were conducted. First, anesthetized C57BL/6 wild type (WT) and eNOS-/- or nNOS-/- mice were exposed to HBO2 at 5 ATA for 60 min. NO metabolites (NOx), an indicator of brain NO bioactivity, and 3-nitrotyrosine (3-NT), a marker of peroxynitrite (ONOO-), were measured in striatum by microdialysis coupled with NO-chemiluminescence or HPLC-ED. Second, awake WT and nNOS-/- mice were exposed to 4 ATA HBO2 for 60 min and brain homogenates assayed by the Biotin-switch method in which cysteine and S-nitrosylated cysteine were derivitized by MMTS and biotin-HPDP, respectively. Western blot was performed with streptavidin immunoprecipitated proteins using an antibody to GAD-65 (rabbit polyclonal IgG). Total GAD activity was assayed fluorometrically. RESULTS: HBO2 increased NOx and 3-NT during the HBO2 exposures in WT and eNOS-/- mice. In contrast, striatal NOx and 3-NTyr did not change significantly in nNOS-/- mice, and seizure latency was extended. Endogenous S-nitrosylation of GAD-65 was detectable at low levels in brain protein of WT mice and were substantially increased at 0 and 60 min after HBO2. In nNOS-/- mice, GAD-65 S-nitrosylation was reduced. S-nitrosylation of GAD-65 protein was associated with inhibition of total GAD activity in WT mice. CONCLUSIONS: Our data show that: 1) nNOS-derived NO generates the bulk of brain NOx and ONOO-, and 2) HBO2-stimulated neuronal NO production inhibits GAD-65 activity by S-nitrosylation that contributes to an excitatory-inhibitory imbalance, which predisposes to HBO2-induced seizures. (Supported by the Office Naval Research)
Description: Abstract of the Undersea and Hyperbaric Medical Society, Inc. Annual Scientific Meeting held June 14-16, 2007. Ritz-Carlton Kapalua Maui, Hawaii (http:www.uhms.org)
URI: http://archive.rubicon-foundation.org/5208
Date: 2007

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  • UHMS Meeting Abstracts
    This is a collection of the published abstracts from the Undersea and Hyperbaric Medical Society (UHMS) annual meetings.

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