Redox regulation in skeletal muscle during contractile activity and aging.

Skeletal muscle has the ability to adapt and remodel after functional, mechanical, and metabolic stresses by activation of different adaptation mechanisms that induce gene expression, biochemical changes, and structural remodeling. Skeletal muscle cells continuously generate reactive oxygen and nitrogen species (RONS), which can act as mediators in cellular signaling pathways that regulate the adaptation mechanisms. There is strong evidence that indicates that RONS are generated in skeletal muscle cells during contractile activity and this induces the activation of transcription factors which modulate gene expression of antioxidant and protective proteins. Thus, it has been proposed that RONS act as signals that modulate the adaptation mechanisms in skeletal muscle and other cells. Structural and functional changes occur in skeletal muscle during aging and are characterized by a reduction of muscle mass and force (sarcopenia). The causes are known, however, there is considerable support for an involvement of RONS in the process of aging and sarcopenia. Several studies indicate that adaptive responses of skeletal muscle that are activated and regulated by RONS are disrupted during aging. This reduction of skeletal muscle adaptation to contractile activity during aging might be responsible for the loss of muscle mass and function and the progressive deterioration of this organ. In summary, there is sufficient evidence that indicates that cellular redox regulation in skeletal muscle is crucial in the physiology and pathology of skeletal muscle. However, new methodologies and experimental models are required for understanding the complex biology of RONS in the cell. This will provide future interventions that mitigate pathologies and aging of skeletal muscle.