Oxidative stress modulates heme synthesis and induces peroxiredoxin-2 as a novel cytoprotective response in ?-thalassemic erythropoiesis.

ABSTRACT: ?-thalassemic syndromes are inherited red cell disorders characterized by severe ineffective erythropoiesis and increased levels of reactive oxygen species whose contribution to ?-thalassemic anemia is only partially understood.We studied erythroid precursors from normal and ?-thalassemic peripheral CD34(+) cells in two-phase liquid culture by proteomic, reverse transcriptase polymerase chain reaction and immunoblot analyses. We measured intracellular reactive oxygen species, heme levels and the activity of ?-aminolevulinate-synthase-2. We exposed normal cells and K562 cells with silenced peroxiredoxin-2 to H(2)O(2) and generated a recombinant peroxiredoxin-2 for kinetic measurements in the presence of H(2)O(2) or hemin.In ?-thalassemia the increased production of reactive oxygen species was associated with down-regulation of heme oxygenase-1 and biliverdin reductase and up-regulation of peroxiredoxin-2. In agreement with these observations in ?-thalassemic cells we found decreased heme levels related to significantly reduced activity of the first enzyme of the heme pathway, ?-aminolevulinate synthase-2 without differences in its expression. We demonstrated that the activity of recombinant ?-aminolevulinate synthase-2 is inhibited by both reactive oxygen species and hemin as a protective mechanism in ?-thalassemic cells. We then addressed the question of the protective role of peroxiredoxin-2 in erythropoiesis by exposing normal cells to oxidative stress and silencing peroxiredoxin-2 in human erythroleukemia K562 cells. We found that peroxiredoxin-2 expression is up-regulated in response to oxidative stress and required for K562 cells to survive oxidative stress. We then showed that peroxiredoxin-2 binds heme in erythroid precursors with high affinity, suggesting a possible multifunctional cytoprotective role of peroxiredoxin-2 in ?-thalassemia.In ?-thalassemic erythroid cells the reduction of ?-aminolevulinate synthase-2 activity and the increased expression of peroxiredoxin-2 might represent two novel stress-response protective systems.

SUBMITTER: De Franceschi L 

PROVIDER: S-EPMC3208676 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature