Oxidized DNA repair enzymes protect skeletal muscle from oxidative stress during differentiation and contractile activity

Mitochondria play a central role in maintaining skeletal muscle homeostasis. Beyond energy production, mitochondria serve as the primary source of reactive oxygen species (ROS) during muscle fiber contraction. An imbalance between ROS production and clearance leads to oxidative stress, a phenomenon previously observed during myoblast differentiation and muscle fiber contraction. As the mitochondrial electron transport chain (ETC) produces a significant amount of ROS, mitochondrial DNA (mtDNA), due to its proximity, is particularly susceptible to damage from these ROS. Oxidized mtDNA released into the cytosol has emerged as one of the key mitochondrial damage-associated molecular patterns (mtDAMPs), capable of activating inflammatory signaling pathways involved in myofibril regeneration. However, excessive release of mtDAMPs can overstimulate inflammatory signaling, resulting in maladaptive responses and impaired muscle recovery. This necessitates the importance of the removal of mtDAMPs to maintain muscle health. Thus, the objective of this study is to decipher if exercise can modulate the levels of oxidized mtDNA repair enzymes, thereby mitigating the level and release of oxidized mtDNA. To address this, we investigated the expression of key antioxidant enzymes and oxidized DNA repair enzymes, such as OGG1 and YB1, during skeletal muscle differentiation and acute muscle fiber contraction using C2C12 myoblasts and their differentiated myotubes. Our findings revealed a more than 2-fold increase in both mRNA and protein levels of YB1 and OGG1 in differentiated myotubes compared to myoblasts, accompanied by a concurrent 4-fold decrease in oxidized mtDNA levels. Western blot analyses further demonstrated the progressive mitochondrial translocation of OGG1 protein from mitochondria to cytosol as differentiation proceeds. Additionally, after 3 hours of acute contractile activity, protein levels of both YB1 and OGG1 were elevated by 2-fold and 3-fold respectively, despite no detectable changes in their mRNA levels. Collectively, these initial findings suggest that both myoblasts and myotubes adapt oxidized mtDNA repair mechanisms as a protective measure against oxidative stress during differentiation and acute contractile activity. Supported by NSERC Canada This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.