Reticulocyte Antioxidant Enzymes mRNA Levels versus Reticulocyte Maturity Indices in Hereditary Spherocytosis, β-Thalassemia and Sickle Cell Disease

Abstract

The antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and peroxiredoxin 2 (Prx2) are particularly important in erythroid cells. Reticulocytes and other erythroid precursors may adapt their biosynthetic mechanisms to cell defects or to changes in the bone marrow environment. Our aim was to perform a comparative study of the mRNA levels of CAT, GPX1, PRDX2 and SOD1 in reticulocytes from healthy individuals and from patients with hereditary spherocytosis (HS), sickle cell disease (SCD) and β-thalassemia (β-thal), and to study the association between their transcript levels and the reticulocyte maturity indices. In controls, the enzyme mRNA levels were significantly correlated with reticulocyte maturity indices for all genes except for SOD1. HS, SCD and β-thal patients showed younger reticulocytes, with higher transcript levels of all enzymes, although with different patterns. β-thal and HS showed similar reticulocyte maturity, with different enzyme mRNA levels; SCD and HS, with different reticulocyte maturity, presented similar enzyme mRNA levels. Our data suggest that the transcript profile for these antioxidant enzymes is not entirely related to reticulocyte maturity; it appears to also reflect adaptive mechanisms to abnormal erythropoiesis and/or to altered erythropoietic environments, leading to reticulocytes with distinct antioxidant potential according to each anemia.

Keywords: antioxidant enzymes; hereditary spherocytosis; reticulocyte; sickle cell disease; β-thalassemia.

Figure 1

Reticulocyte mRNA levels of catalase (CAT, (A)), glutathione peroxidase 1 (GPX1, (B)), peroxiredoxin 2 (PRDX2, (C)), superoxide dismutase 1 (SOD1, (D)) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH, (E)) in the control (n = 31), hereditary spherocytosis (n = 22), sickle cell disease (n = 6) and β-thalassemia (n = 20) groups. The embedded table (F) shows the comparison between the average mRNA transcript levels for each disease in relation to the control group (ratios). Data are presented as median (interquartile range) for (A–E). Mann–Whitney U test was used to compare differences between groups; p < 0.05 was considered statistically significant. * p < 0.05 vs. control group; ^a p < 0.05 vs. HS patients; ^b p < 0.05 vs. sickle cell disease patients. β-thal, β-thalassemia; HS, hereditary spherocytosis; SCD, sickle cell disease.

Figure 2

Percentage of low-fluorescence reticulocytes (LFR, %) versus mRNA levels of catalase (CAT, (A)), glutathione peroxidase 1 (GPX1, (B)), peroxiredoxin 2 (PRDX2, (C)), superoxide dismutase 1 (SOD1, (D)) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH, (E)) for the control (n = 21), hereditary spherocytosis (n = 13), sickle cell disease (n = 4) and β-thalassemia (n = 14) groups. Spearman’s rank correlation coefficient was used to evaluate relationships between sets of data; p < 0.05 was considered statistically significant. β-thal, β-thalassemia; HS, hereditary spherocytosis; SCD, sickle cell disease.

Figure 3

Percentage of immature reticulocyte fraction (IRF, %) versus mRNA levels of catalase (CAT, (A)), glutathione peroxidase 1 (GPX1, (B)), peroxiredoxin 2 (PRDX2, (C)), superoxide dismutase 1 (SOD1, (D)) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH, (E)) for the control (n = 21), hereditary spherocytosis (n = 13), sickle cell disease (n = 4) and β-thalassemia (n = 14) groups. Spearman’s rank correlation coefficient was used to evaluate relationships between sets of data; p < 0.05 was considered statistically significant. β-thal, β-thalassemia; HS, hereditary spherocytosis; SCD, sickle cell disease.