• Comparison of whole body SOD1 knockout with muscle specific SOD1 knockout mice reveals a role for nerve redox signaling in regulation of degenerative pathways in skeletal muscle.

      Nye, Gareth; Sakellariou, Giorgos; McDonagh, Brian; Porter, Helen; Giakoumaki, Ifigeneia; Earl, Kate; Vasilaki, Aphrodite; Brooks, Susan; Richardson, Arlan; Van Remmen, Holly; et al. (Mary Ann Liebert, 2017-12-12)
      Aims: Lack of Cu,Zn-superoxide dismutase (CuZnSOD) in homozygous knockout mice (Sod1−/−) leads to accelerated age-related muscle loss and weakness, but specific deletion of CuZnSOD in skeletal muscle (mSod1KO mice) or neurons (nSod1KO mice) resulted in only mild muscle functional deficits and failed to recapitulate the loss of mass and function observed in Sod1−/− mice. To dissect any underlying cross-talk between motor neurons and skeletal muscle in the degeneration in Sod1−/− mice, we characterized neuromuscular changes in the Sod1−/− model compared with mSod1KO mice and examined degenerative molecular mechanisms and pathways in peripheral nerve and skeletal muscle. Results: In contrast to mSod1KO mice, myofiber atrophy in Sod1−/− mice was associated with increased muscle oxidative damage, neuromuscular junction degeneration, denervation, nerve demyelination, and upregulation of proteins involved in maintenance of myelin sheaths. Proteomic analyses confirmed increased proteasomal activity and adaptive stress responses in muscle of Sod1−/− mice that were absent in mSod1KO mice. Peripheral nerve from neither Sod1−/− nor mSod1KO mice showed increased oxidative damage or molecular responses to increased oxidation compared with wild type mice. Differential cysteine (Cys) labeling revealed a specific redox shift in the catalytic Cys residue of peroxiredoxin 6 (Cys47) in the peripheral nerve from Sod1−/− mice. Innovation and Conclusion: These findings demonstrate that neuromuscular integrity, redox mechanisms, and pathways are differentially altered in nerve and muscle of Sod1−/− and mSod1KO mice. Results support the concept that impaired redox signaling, rather than oxidative damage, in peripheral nerve plays a key role in muscle loss in Sod1−/− mice and potentially sarcopenia during aging. Antioxid. Redox Signal. 28, 275–295. Innovation This is the first study to compare the molecular mechanisms and pathways that occur in both skeletal muscle and peripheral nerve of Sod1−/− and mSod1KO mice in an effort to examine the relative cross-talk and role of pre- and postsynaptic changes in redox homeostasis in loss of neuromuscular integrity and function that occurs with aging. This study highlights that impaired redox signaling in peripheral nerve rather than oxidative damage appears to play a key role in altering the integrity of peripheral nerves and motor neurons and potentially age-associated muscle atrophy and functional deficits. These results are potentially clinically significant and have widespread implications for the understanding of sarcopenia during aging.