Peroxiredoxin‐2 recycling is slower in denser and pediatric sickle cell red cells

Abstract

Peroxiredoxin‐2 (Prx‐2) is a critical antioxidant protein in red blood cells (RBC). Prx‐2 is oxidized to a disulfide covalently‐bound dimer by H2O2, and then reduced back by the NADPH‐dependent thioredoxin—thioredoxin reductase system. The reduction of oxidized Prx‐2 is relatively slow in RBCs. Since Prx‐2 is highly abundant, Prx‐2s' peroxidase catalytic cycle is not considered to be limiting under normal conditions. However, whether Prx‐2 recycling becomes limiting when RBCs are exposed to stress is not known. Using three different model systems characterized by increased oxidative damage to RBCs spanning the physiologic (endogenous RBCs of different ages), therapeutic (cold‐stored RBCs in blood banks) and pathologic (RBCs from sickle cell disease (SCD) patients and humanized SCD mice) spectrum, basal levels of Prx‐2 oxidation and Prx‐2 recycling kinetics after addition of H2O2 were determined. The reduction of oxidized Prx‐2 was significantly slower in older versuin older versus younger RBCs, in RBCs stored for 4–5 weeks compared to 1 week, and in RBC from pediatric SCD patients compared to RBCs from control non‐SCD patients. Similarly, the rate of Prx‐2 recycling was slower in humanized SCD mice compared to WT mice. Treatment of RBC with carbon monoxide (CO) to limit heme‐peroxidase activity had no effect on Prx‐2 recycling kinetics. Treatment with glucose attenuated slowed Prx‐2 recycling in older RBCs and SCD RBCs, but not stored RBCs. In conclusion, the reduction of oxidized Prx‐2 can be further slowed in RBCs, which may limit the protection afforded by this antioxidant protein in settings associated with erythrocyte stress.

Peroxiredoxin 2: An Important Element of the Antioxidant Defense of the Erythrocyte

“…The enzymatic activity of Prdx2 was increased by a factor of 3.6-fold in SCD red cells with respect to healthy erythrocytes, apparently due to phosphorylation by activated Syk kinase [137]. Recycling of Prdx2 in erythrocytes from pediatric SCD patients was not significantly changed compared to erythrocytes from controls [157].…”

“…Thus, Prdx2 is able to act as an efficient scavenger of low concentrations of H 2 O 2 without undergoing inactivation due to hyperoxidation [14]. No hyperoxidized forms of Prdx2 (as well as Prdx1 or Prdx6) were detected in old human erythrocytes (characterized by a higher density), indicating that they did not accumulate during the process of erythrocyte aging in vivo [157]. However, accumulation of hyperoxidized Prdx2 was found in old mouse erythrocytes [159].…”

“…The reduction of oxidized Prdx2 was found to be significantly slower in older versus younger erythrocytes [157]. It has been speculated that oxidation to the disulfide can serve as a regulatory switch for other Prdx2-attributed roles such as stimulation of Ca 2+activated K + transport or chaperone activity [158].…”

Ferroptosis as an emerging target in sickle cell disease

“…This decline is demonstrated by decreased levels of antioxidants such as vitamins A and E, reduced GSH, ascorbic acid, selenium, zinc, and reduced activity of enzymes like superoxide dismutase and catalase ( Antwi-Boasiako et al, 2019 , Antwi-Boasiako et al, 2020 , Dosunmu-Ogunbi et al, 2019 , Nemati et al, 2019 , Delesderrier et al, 2020 ). Additionally, the recycling of peroxiredoxin-2 (Prx-2), a key antioxidant protein, is significantly slower in sickle RBC, compromising its effectiveness against oxidative stress ( Oh et al, 2022 ).…”