β-thalassemia is a worldwide distributed monogenic red cell disorder, characterized by an absent or reduced beta globin chain synthesis. The unbalance of alpha-gamma chain and the presence of pathological free iron promote severe oxidative damage, playing crucial a role in erythrocyte hemolysis, exacerbating ineffective erythropoiesis and decreasing the lifespan of red blood cells (RBC). Catalase, glutathione peroxidase and peroxiredoxins act together to protect RBCs from hydrogen peroxide insult. Among them, peroxiredoxins stand out for their overall abundance and reactivity. In RBCs, Prdx2 is the third most abundant protein, although Prdxs 1 and 6 isoforms are also found in lower amounts. Despite the importance of these enzymes, Prdx1 and Prdx2 may have their peroxidase activity inactivated by hyperoxidation at high hydroperoxide concentrations, which also promotes the molecular chaperone activity of these proteins. Some studies have demonstrated the importance of Prdx1 and Prdx2 for the development and maintenance of erythrocytes in hemolytic anemia. Now, we performed a global analysis comparatively evaluating the expression profile of several antioxidant enzymes and their physiological reducing agents in patients with beta thalassemia intermedia (BTI) and healthy individuals. Furthermore, increased levels of ROS were observed not only in RBC, but also in neutrophils and mononuclear cells of BTI patients. The level of transcripts and the protein content of Prx1 were increased in reticulocyte and RBCs of BTI patients and the protein content was also found to be higher when compared to beta thalassemia major (BTM), suggesting that this peroxidase could cooperate with Prx2 in the removal of H2O2. Furthermore, Prdx2 production is highly increased in RBCs of BTM patients that present high amounts of hyperoxidized species. A significant increase in the content of Trx1, Srx1 and Sod1 in RBCs of BTI patients suggested protective roles for these enzymes in BTI patients. Finally, the upregulation of Nrf2 and Keap1 transcription factors found in BTI patients may be involved in the regulation of the antioxidant enzymes analyzed in this work.

Summary Beta‐thalassaemia (BT) is classified according to blood transfusion requirement as minor (BTMi), intermedia (BTI) and major (BTM). BTM is the most severe form, requiring regular transfusions while transfusion need is only occasional in BTI. Differential gene expression between patients has not been assessed so far. Here, we evaluated the global gene expression profiles during differentiation of human erythroid cells of two patients carrying the same mutation [CD39, (C → T)], though displaying different phenotypes (BTI and BTM). Considering the role of reactive oxygen species (ROS) in the pathophysiology of thalassaemia, we focused on differentially expressed genes involved in metabolic pathways triggered by ROS, such as inflammation and apoptosis, and, from these, we selected the Apurinic/Apyrimidinic Endodeoxyribonuclease 1 (APEX1) and High Mobility Group Box1 (HMGB1) genes, whose role in BT is not well established. An in‐depth expression analysis of transcriptional and protein levels in patients carrying a range of mutations associated with BT phenotypes indicated that APEX1 was increased in both BTI and BTM. Furthermore, higher amounts of HMGB1 was found in the plasma of BTI patients. Our findings suggest that these proteins have important roles in BT and could represent new targets for further studies aiming to improve the management of the disease.

The yeast Saccharomyces cerevisiae is a model organism for biochemical and genetic studies, and several very important discoveries of fundamental biological processes have been conducted using this yeast as an experimental organism. An emerging concept, which is validated by several works using this organism, relies on the biological importance of oxidant species, specially the hydroperoxides. These molecules were formed during aerobic biological process and control several intracellular mechanisms such as a range of signaling pathways, cell cycle, programmed cell death, circadian rhythm, aging, and lifespan extension. Thereby, cellular homeostasis depends on a refined control of hydroperoxides levels and low-molecular-weight molecules in combination with antioxidant enzymes playing a role in this equilibrium. This proposal is focused on the S. cerevisiae peroxiredoxins and their role in peroxide decomposition, signal transduction, circadian clocks, and aging as model enzymes for the study and comprehension of these biological processes in living organisms, including humans.

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