MANGANESE SUPEROXIDE-DISMUTASE PROTECTS NNOS NEURONS FROM NMDA AND NITRIC OXIDE-MEDIATED NEUROTOXICITY

Neuronal nitric oxide synthase (nNOS) neurons kill adjacent neurons th rough the action of NMDA-glutamate receptor activation, although they remain relatively resistant to the toxic effects of NMDA and NO. The m olecular basis of the resistance of nNOS neurons to toxic insults is u nknown. To begin to understand the molecular mechanisms of the resista nce of nNOS neurons, we developed a pheochromacytoma-derived cell line (PC12) that is resistant to the toxic effects of NO. We found through serial analysis of gene expression (SAGE) that manganese superoxide d ismutase (MnSOD) is enriched in the NO-resistant PC12 cell-derived lin e (PC12-R). Antisense MnSOD renders PC12-R cells sensitive to NO toxic ity and increases the sensitivity to NO in the parental, NO-sensitive PC12 line (PC12-S), Adenoviral transfer of MnSOD protects PC12-S cells against NO toxicity. We extended these studies to cortical cultures a nd showed that MnSOD is enriched in nNOS neurons and that antisense Mn SOD renders nNOS neurons susceptible to NMDA neurotoxicity, although i t has little effect on the overall susceptibility of cortical neurons to NMDA toxicity. Overexpression of MnSOD provides dramatic protection against NMDA and NO toxicity in cortical cultures, but not against ka inate or AMPA neurotoxicity. Furthermore, nNOS neurons from MnSOD-/- m ice are markedly sensitive to NMDA toxicity. Adenoviral transfer of Mn SOD to MnSOD-/- cultures restores resistance of nNOS neurons to NMDA t oxicity. Thus, MnSOD is a major protective protein that appears to be essential for the resistance of nNOS neurons in cortical cultures to N MDA mediated neurotoxicity.