Peroxiredoxins as Markers of Oxidative Stress in Circulating Blood Cells

The peroxiredoxins (Prxs) are a family of thiol peroxidases that effectively reduce cellular hydroperoxides. Treatment of erythrocytes with hydrogen peroxide oxidizes their Prx 2, and we have previously shown that erythrocyte Prx 2 oxidation occurs in blood containing activated neutrophils, and in blood stored for transfusion. We hypothesize that measurement of the redox status of Prxs in blood cells will be a marker of oxidative stress, either due to increased generation of endogenous hydroperoxides or impairment of cellular reductive mechanisms. In order to determine baseline parameters, blood samples were obtained from a healthy human population. The redox status of cytoplasmic Prx 2 and mitochondrial Prx 3 was measured in platelets, lymphocytes and monocytes, and compared with Prx 2 in erythrocytes. We also treated isolated cells with hydrogen peroxide and compared the sensitivity of their Prxs to oxidation with inhibition of mitochondrial metabolic activity using a Seahorse XF Analyser. Lymphocyte mitochondrial activity was most sensitive to hydrogen peroxide, while platelets displayed significant resilience. This coincided with Prx 3 in platelets being relatively resistant to oxidation by hydrogen peroxide, despite Prx 2 being completely oxidized under these conditions. We conclude that the redox status of Prxs varies between different blood cell types and between cytoplasm and mitochondria of the same cells. These parameters warrant further investigation in disease populations.