Abstract
Peroxiredoxin II, a cytosolic isoform of the antioxidant enzyme family, has been implicated in cancer-associated cell death and apoptosis, but its functional role in the heart remains to be elucidated. Interestingly, the expression levels of peroxiredoxin II were decreased in mouse hearts upon ischemia-reperfusion, while they were elevated in two genetically modified hyperdynamic hearts with phospholamban ablation or protein phosphatase 1 inhibitor 1 overexpression. To delineate the functional significance of altered peroxiredoxin II expression, adenoviruses encoding sense or antisense peroxiredoxin II were generated; cardiomyocytes were infected, and then subjected to H(2)O(2) treatment to mimic oxidative stress-induced cell death and apoptosis. H(2)O(2) stimulation resulted in a significant decrease of endogenous peroxiredoxin II expression, along with reduced cell viability in control cells. However, overexpression of peroxiredoxin II significantly protected from H(2)O(2)-induced apoptosis and necrosis, while downregulation of this enzyme promoted the detrimental effects of oxidative stress in cardiomyocytes. The beneficial effects of peroxiredoxin II were associated with increased Bcl-2 expression, decreased expression of Bax and attenuated activity of caspases 3, 9 and 12. Furthermore, there were no significant alterations in the expression levels of the other five isoforms of peroxiredoxin, as well as active catalase or glutathione peroxidase-1 after ischemia-reperfusion or H(2)O(2) treatment. These findings suggest that peroxiredoxin II may be a unique antioxidant in the cardiac system and may represent a potential target for cardiac protection from oxidative stress-induced injury.