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Author Notes:

Correspondence: Jonathan D. Glass, MD, Emory Center for Neurodegenerative Disease, Whitehead Biomedical Research Building, 615 Michael Street, 5th Floor, Mailstop 1941007001, Atlanta, GA 30322; Phone: 404 727-3275; Fax: 404 727-3728; Email: jglas03@emory.edu

Acknowledgments: We thank Marie Csete for providing Sod1−/− breeders and for helpful discussion, Bill Liang for assistance with HPLC, and Debbie Cooper for assistance with paraffin processing and TDP-43 staining.

Subjects:

Research Funding:

This work was supported by the Robert Packard Center for ALS Research and NIH T32 ES12870.

Keywords:

  • SOD1
  • axon
  • neuromuscular junction
  • oxidative stress
  • motor neuron
  • ALS

Absence of SOD1 leads to oxidative stress in peripheral nerve and causes a progressive distal motor axonopathy

Tools:

Journal Title:

Experimental Neurology

Volume:

Volume 233, Number 1

Publisher:

, Pages 163-171

Type of Work:

Article | Post-print: After Peer Review

Abstract:

Oxidative stress is commonly implicated in the pathogenesis of motor neuron disease. However, the cause and effect relationship between oxidative stress and motor neuron degeneration is poorly defined. We recently identified denervation at the neuromuscular junction in mice lacking the antioxidant enzyme, Cu, Zn-superoxide dismutase (SOD1) (Fischer et al., 2011). These mice show a phenotype of progressive muscle atrophy and weakness in the setting of chronic oxidative stress. Here, we investigated further the extent of motor neuron pathology in this model, and the relationship between motor pathology and oxidative stress. We report preferential denervation of fast-twitch muscles beginning between 1 and 4 months of age, with relative sparing of slow-twitch muscle. Motor axon terminals in affected muscles show widespread sprouting and formation of large axonal swellings. We confirmed, as was previously reported, that spinal motor neurons and motor and sensory nerve roots in these mice are preserved, even out to 18 months of age. We also found preservation of distal sensory fibers in the epidermis, illustrating the specificity of pathology in this model for distal motor axons. Using HPLC measurement of the glutathione redox potential, we quantified oxidative stress in peripheral nerve and muscle at the onset of denervation. SOD1 knockout tibial nerve, but not gastrocnemius muscle, showed significant oxidation of the glutathione pool, suggesting that axonal degeneration is a consequence of impaired redox homeostasis in peripheral nerve. We conclude that the SOD1 knockout mouse is a model of oxidative stress-mediated motor axonopathy. Pathology in this model primarily affects motor axon terminals at the neuromuscular junction, demonstrating the vulnerability of this synapse to oxidative injury.

Copyright information:

© 2011 Elsevier Inc. All rights reserved.

This is an Open Access work distributed under the terms of the Creative Commons Attribution-NonCommerical-NoDerivs 3.0 Unported License (http://creativecommons.org/licenses/by-nc-nd/3.0/).

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