Mild hyperbaric oxygen modulates selected proteolytic and mitochondrial markers during cast immobilization in mice

Skeletal muscle atrophy impairs physical performance and increases mortality risk. Mild hyperbaric oxygen (MHO) attenuates disuse-related muscle impairments and improves mitochondrial function, but whether these effects require repeated exposure or can be achieved with a single, brief exposure remains unknown. Male ICR mice were subjected to cast immobilization and assigned to control (CON), cast immobilization (Cast), or cast immobilization with MHO (Cast + MHO). In the acute experiment, mice were immobilized for 3 days and exposed to MHO (1.3 ATA, 38% O₂) for 3 h. In the repeated experiment, mice were immobilized for 14 days and received MHO exposure (6 h/day). A single MHO exposure attenuated increases in Fbxo32 , and Trim63 mRNA in the soleus muscle and reduced Bnip3 and Map1lc3b mRNA in the plantaris muscle ( P < 0.05). Repeated MHO exposure attenuated the increase in Atrogin-1 in the plantaris muscle ( P < 0.05). Immobilization reduced muscle fiber cross-sectional area and FOXO1 phosphorylation in the plantaris muscle, but neither outcome differed significantly between the Cast and Cast + MHO groups. Repeated MHO exposure attenuated the reduction in Complex IV in the plantaris muscle (P < 0.05). These findings suggest that MHO exposure modulates proteolytic and mitochondrial regulatory pathways during immobilization.