A reducing redox environment promotes C2C12 myogenesis: implications for regeneration in aged muscle.

Intracellular redox potential of skeletal muscle becomes progressively more oxidized with aging, negatively impacting regenerative ability. We examined the effects of oxidizing redox potential on terminal differentiation of cultured C2C12 myoblasts. Redox potentials were manipulated by changing the culture O(2) environment, by free radical scavenging, or addition of H(2)O(2.) Intracellular reactive oxygen species (ROS) production was higher in 20% environmental O(2) and in this condition, redox potential became progressively oxidized compared to cultures in 6% O(2.) Treatment with a ROS trapping agent (phenyl-N-tert-butylnitrone, PBN) caused reducing redox potentials and enhanced C2C12 differentiation, while addition of 25 micromolar H(2)O(2) to cells in 20% O(2) dramatically slowed differentiation. Under these most oxidative conditions, quantitative PCR showed a significant decrease in myogenic basic helix-loop-helix transcription factor expression compared to cultures treated with PBN or grown in 6% O(2). Thus, oxidative intracellular environments impair myoblast differentiation, while reducing environments favor myogenesis.