Hydrogen peroxide as a signal for skeletal muscle adaptations to exercise: What do concentrations tell us about potential mechanisms?

Hydrogen peroxide appears to be the key reactive oxygen species involved in redox signalling, but comparisons of the low concentrations of hydrogen peroxide that are calculated to exist within cells with those previously shown to activate common signalling events in vitro indicate that direct oxidation of key thiol groups on "redox-sensitive" signalling proteins is unlikely to occur. A number of potential mechanisms have been proposed to explain how cells overcome this block to hydrogen peroxide-stimulated redox signalling and these will be discussed in the context of the redox-stimulation of specific adaptations of skeletal muscle to contractile activity and exercise. It is argued that current data implicate a role for currently unidentified effector molecules (likely to be highly reactive peroxidases) in propagation of the redox signal from sites of hydrogen peroxide generation to common adaptive signalling pathways.