Manganese Superoxide Dismutase Protects nNOS Neurons from NMDA and Nitric Oxide-Mediated Neurotoxicity

Abstract

Neuronal nitric oxide synthase (nNOS) neurons kill adjacent neurons through the action of NMDA-glutamate receptor activation, although they remain relatively resistant to the toxic effects of NMDA and NO. The molecular basis of the resistance of nNOS neurons to toxic insults is unknown. To begin to understand the molecular mechanisms of the resistance 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 dismutase (MnSOD) is enriched in the NO-resistant PC12 cell-derived line (PC12-R). Antisense MnSOD renders PC12-R cells sensitive to NO toxicity 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 and showed that MnSOD is enriched in nNOS neurons and that antisense MnSOD renders nNOS neurons susceptible to NMDA neurotoxicity, although it 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 kainate or AMPA neurotoxicity. Furthermore, nNOS neurons from MnSOD -/- mice are markedly sensitive to NMDA toxicity. Adenoviral transfer of MnSOD to MnSOD-/- cultures restores resistance of nNOS neurons to NMDA toxicity. Thus, MnSOD is a major protective protein that appears to be essential for the resistance of nNOS neurons in cortical cultures to NMDA mediated neurotoxicity.

Analysis of the Cytosolic Proteome in a Cell Culture Model of Familial Amyotrophic Lateral Sclerosis Reveals Alterations to the Proteasome, Antioxidant Defenses, and Nitric Oxide Synthetic Pathways

“…The role of NO in ALS pathogenesis remains controversial due to its dual role as a neuroprotective and neurotoxic agent. At low concentrations NO can protect cells against oxidative stress, presumably by induction of adaptive responses in the form of up-regulation of antioxidant proteins (43,44). In contrast, inhibition of nNOS has been shown to protect rat motor neurons from cell death induced by oxidative stress (45).…”

Apoptosis-inducing factor mediates poly(ADP-ribose) (PAR) polymer-induced cell death

“…Primary cortical neuron cultures were prepared from gestational day 14-15 fetal mice, and neurons (14 days in vitro) were exposed to NMDA or PAR polymer and viability was determined by as described (23,29).…”

Dynamic regulation of metabolism and respiration by endogenously produced nitric oxide protects against oxidative stress

“…Multiple mechanisms have been proposed for the ability of nitric oxide to protect cells against oxidative stress, including biochemical reactions of nitric oxide and the induction of adaptive responses that require protein synthesis (1)(2)(3)(4)(5)(6). Nitric oxide readily complexes with reduced iron, preventing the formation of strong oxidants (1)(2)(3).…”