EFFECT OF DENERVATION ON REDOX‐REGULATION IN SKELETAL MUSCLE

Abstract

Changes in skeletal muscle mass and function occur during aging and are accompanied by loss of integrity and stability of the neuromuscular junction. Previous studies from our group have shown a significant increase in the mitochondrial generation of hydrogen peroxide (H202) and other peroxides in denervated muscle fibers. The mechanisms of generation of these peroxides and the effect on muscle responses are unknown. Our aim was to determine the effect of denervation on proteins that may contribute to peroxide release and proteins that regulate redox responses.The Anterior Tibialis (AT) and Extensor Digitorum Longus (EDL) muscles of wild type mice were denervated under anaesthesia by surgical removal of a small section of the peroneal nerve. Western blotting and immunohistochemical techniques were used to examine protein contents. AT and EDL muscles of thy‐1YFP mice, in which YFP expression in neuronal cells allow visualisation of the muscle innervation, were also denervated and used for morphological examination and analysis of muscle mitochondrial peroxide release.Previous work from our group has shown that, following denervation, hydrogen peroxide can be generated by several sources within mitochondria (Pollock et al, Free Rad. Biol. Med 2017) and the current data show that the increased peroxide generation was maintained to 21 days and was associated with a significant increase in Monoamine Oxidase A and NADPH Oxidase components. An increased content of proteins involved in the activation of the NADPH oxidase complex such as Peroxiredoxin 6 and Phospholipase A2 was also observed together with a significant increase in the content of several enzymes involved in the protection of cells against oxidative damage. Oxyblot analysis to assess the levels of carbonylation, showed that by 7 days post‐denervation there was a significant increase in protein carbonylation of low molecular weight (25–35 kDa) proteins. Morphological analysis indicated a progressive significant loss of muscle mass in the AT muscle from 7 days up to 21 days following denervation due to fiber atrophy without fiber loss. These results support the possibility that (at least initially) the increase in peroxide production may stimulate adaptations to protect the muscle fibers but, together with data on structural changes indicating significant fiber atrophy from 7 days after denervation, increased peroxide generation over the longer term may activate degenerative processes, such as apoptosis of the denervated muscle fibers.Support or Funding InformationThis project was funded by the US National Institutes of Health (NIA) and the Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, UK.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.