Survey of peroxynitrite scavengers and its application for pathophysiolgy

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In this research project, we have attempted to survey scavengers specific for peroxynitrite and to apply them to investigation for clarification of pathophysiological role of peroxynitrite in neuronal cell injury. Prior to the survey of peroxynitrite scavengers, we have investigated the roles of peroxynitrite in release of neurotransmitters such as γ-aminobutyric acid (GABA) and acetylcholine and its mechanisms, because we attempts to use the potential of peroxynitrite to induce neurotransmitter release as a tool to confirm the activity of its scavengers.We confirmed that peroxynitrite enhanced the release of GABA and acetylcholine from mouse cerebral cortical neurons in primary culture. Using this experimental system we have examined mechanisms for peroxynitrite-evoked GABA release. Peroxynitrite-induced GABA release was abolished by inhibitors of neuronal membrane depolarization, suggesting the activity of peroxynitrite to depolarize neuronal membrane. Peroxynitrite also increased Ca … More ^<2+> influx into neurons. Each of nifedipine and ω-agatoxin VIA (ω-ATX), inhibitors specific for L- and P/Q-type voltage-dependent Ca^<2+> channels (VDCCs) respectively, inhibited significantly GABA release by peroxynitrite and the concomitant presence of these inhibitors completely abolished the influx induced by peroxynitrite, whereas ω-conotoxin GVIA (ω-CTX), an inhibitor for N-type VDCCs affected no changes. From these results it is concluded that peroxynitrite induced GABA release consequent to opening L- and P/Q-type VDCCs and did not modify the function of N-type VDCCs.Hydroxyl radical scavengers also facilitated peroxynitrite-evoked GABA release and this inhibitory action of hydroxyl radical formed from peroxynitrite during its degradation is due to its inhibition of L-type VDCCs, indicating hydroxyl radical modifies the apparent peroxynitrite-induced neurotransmitter release. In addition, the activity of peroxynitrite to induce Ca^<2+> influx into the neurons by MnTBPA, a known scavenger for peroxynitrite. In present, we are trying to survey scavengers for peroxynitrite using the experimental system described above for checking activities of candidates to abolish peroxynitrite activity. Less