Nitric oxide availability is increased in contracting skeletal muscle from aged mice, but does not differentially decrease muscle superoxide

• Published in: Free radical biology & medicine Vol. 78; pp. 82 - 88
• Main Authors: Pearson, T., McArdle, A., Jackson, M.J.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-01-2015; Elsevier Science
• Subjects: Aging; Aging - physiology; Animals; Blotting, Western; Cells, Cultured; Cytosol - metabolism; Fluorescent confocal microscopy; Mice; Mice, Inbred C57BL; Microscopy, Confocal; Mitochondria - metabolism; Mitochondria, Muscle - metabolism; Muscle Contraction - physiology; Muscle Fibers, Skeletal - metabolism; Muscle, Skeletal - cytology; Muscle, Skeletal - metabolism; Nitric Oxide - metabolism; Original Contribution; Peroxiredoxins - metabolism; Peroxynitrous Acid - metabolism; ROS; Skeletal muscle; Superoxides - metabolism; Tyrosine - analogs & derivatives; Tyrosine - metabolism; DHE; NO; NOS; MEM; Fluorescent confocal microscopy; 3-NT; ROS; Aging; Prx5; Skeletal muscle
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2014.10.505

Reactive oxygen and nitrogen species have been implicated in the loss of skeletal muscle mass and function that occurs during aging. Nitric oxide (NO) and superoxide are generated by skeletal muscle and where these are generated in proximity their chemical reaction to form peroxynitrite can compete with the superoxide dismutation to hydrogen peroxide. Changes in NO availability may therefore theoretically modify superoxide and peroxynitrite activities in tissues, but published data are contradictory regarding aging effects on muscle NO availability. We hypothesised that an age-related increase in NO generation might increase peroxynitrite generation in muscles from old mice, leading to an increased nitration of muscle proteins and decreased superoxide availability. This was examined using fluorescent probes and an isolated fiber preparation to examine NO content and superoxide in the cytosol and mitochondria of muscle fibers from adult and old mice both at rest and following contractile activity. We also examined the 3-nitrotyrosine (3-NT) and peroxiredoxin 5 (Prx5) content of muscles from mice as markers of peroxynitrite activity. Data indicate that a substantial age-related increase in NO levels occurred in muscle fibers during contractile activity and this was associated with an increase in muscle eNOS. Muscle proteins from old mice also showed an increased 3-NT content. Inhibition of NOS indicated that NO decreased superoxide bioavailability in muscle mitochondria, although this effect was not age related. Thus increased NO in muscles of old mice was associated with an increased 3-NT content that may potentially contribute to age-related degenerative changes in skeletal muscle.
•We studied NO in contracting and resting muscle fibers from adult and old mice.•Contracting fibers from old mice had greater NO than those from adult mice.•Muscle proteins from old mice contained increased 3-nitrotyrosine residues.•Nitric oxide synthase inhibition decreased mitochondrial superoxide in both groups.•Increased NO in muscle of old mice increases peroxynitrite and protein nitration.