This project is designed to increase our knowledge of the inflammatory response that follows toxic insults to the brain, especially the role of N0. It is hypothesized that inducible N0 synthase (N0S II) in astrocytes provides a tonic source of N0 tat contributes to neuronal degeneration. Towards that end, the principal investigator will characterize the induction of N0S II (No production, N0S II mRNA, protein and activity) in cultured astrocytes and the V1 cell line. This project will make extensive use of the chemical synthetic core to evaluation the ability of newly synthesized inhibitors of N0S II to selectively inhibit astrocyte versus macrophage N0S II. Such inhibitors would provide the ability to manipulate the production of N0 in the brain following injury. The principal investigator will also evaluate the contribution of astrocyte-derived N0 to neuronal injury and death. The effects of lead on N0S II will also be evaluated. N0 generating agents will be evaluated for alterations in the survival and growth of PC12 cells and cerebral cortical neurons in culture after acute and chronic exposures, and for their concentration and time dependent effects. Astrocytes and macrophages will also be compared for their N0S II induction by N0 generating agents. The principal investigator will also evaluate the ability of newly-synthesized N0S II and N0 trapping agents and lead to alter the toxicity of astrocytes and macrophages in culture.
The third aim i s to evaluate the role of N) in an in vivo model of inflammation following neuronal injury. Preliminary data indicate an increase in N)S I and N)S Ii following a discrete stab wound to the cerebral cortex and striatum. The investigator proposes to evaluate changes in the levels of all N0S isoforms following injury using Western and Northern blots as well as immunocytochemistry, followed by the evaluation of the effects of N0S II antagonists on the gliotic response or neuronal cell death following injury.
The fourth aim continues to be the evaluation of inflammatory responses in transgenic mice that have knocked out IFN receptor expression. Preliminary data indicated that these mice have reduced levels of iN0S following trauma as compared to wild type activity. The inflammatory response in IFN receptor knockouts will also be assessed in mice with normal astrocyte grafts. Overall, these studies seek to increase knowledge of the role of N0 in neural degeneration, and to identify strategies by which the toxic effects of N0 can be limited.
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