An unexplored role for Peroxiredoxin in exercise-induced redox signalling?

Peroxiredoxin (PRDX) is a ubiquitous oxidoreductase protein with a conserved ionised thiol that permits catalysis of hydrogen peroxide (H(2)O(2)) up to a million times faster than any thiol-containing signalling protein. The increased production of H(2)O(2) within active tissues during exercise is thought to oxidise conserved cysteine thiols, which may in turn facilitate a wide variety of physiological adaptations. The precise mechanisms linking H(2)O(2) with the oxidation of signalling thiol proteins (phosphates, kinases and transcription factors) are unclear due to these proteins' low reactivity with H(2)O(2) relative to abundant thiol peroxidases such as PRDX. Recent work has shown that following exposure to H(2)O(2) in vitro, the sulfenic acid of the PRDX cysteine can form mixed disulphides with transcription factors associated with cell survival. This implicates PRDX as an ‘active’ redox relay in transmitting the oxidising equivalent of H(2)O(2) to downstream proteins. Furthermore, under oxidative stress, PRDX can form stable oxidised dimers that can be secreted into the extracellular space, potentially acting as an extracellular ‘stress’ signal. There is extensive literature assessing non-specific markers of oxidative stress in response to exercise, however the PRDX catalytic cycle may offer a more robust approach for measuring changes in redox balance following exercise. This review discusses studies assessing PRDX-mediated cellular signalling and integrates the recent advances in redox biology with investigations that have examined the role of PRDX during exercise in humans and animals. Future studies should explore the role of PRDX as a key regulator of peroxide mediated-signal transduction during exercise in humans.