Oxidative stress disturbances in erythrocytes of beta-thalassemia

A New Perspective for Potential Organ Damage Due to Iron-Mediated Oxidation in Thalassemia Major Patients

BACKGROUND

The aim of this study is to develop new perspectives to prevent or reduce potential organ damage due to iron-mediated oxidation in thalassemia major patients.

METHODS

Seventy patients were included in this study. Blood samples were taken from the patients before and after transfusion. Total thiol, native thiol, disulfide, disulfide/native thiol percentage ratio, ischemia modified albumin (IMA), total antioxidant status (TAS), total oxidant status (TOS), and ferroxidase levels were determined. Additionally, undepleted thiol level (UTL) was determined as a new parameter associated with organ damage.

RESULTS

After transfusion, the levels of native thiol, total thiol, disulfide, TAS, ferroxidase, and TOS were higher, while the IMA levels and disulfide/native thiol percent ratio were lower. Significant correlations were found between antioxidant and oxidant tests before and after transfusion. Additionally, a negative correlation was found between the TOS and UTL levels of the patients measured before the transfusion.

CONCLUSION

In the present study, transfusion therapy increased both oxidation and the antioxidant levels. In addition, the term UTL has been introduced as a parameter that enables the determination of the oxidation level that may cause potential organ damage in transfusion-dependent thalassemia patients.

Elevated serum adiponectin is related to elevated serum ferritin and interleukin-6 in β-thalassaemia major children

BACKGROUND

There is evidence that iron affects lipid metabolism and adipocyte biology. Given the effects of iron on adiponectin, the role of iron in lipid oxidation, and the potential additive effects of oxidative stress from excess iron and lipid metabolism. We aimed to investigate serum adiponectin in relation to clinical and laboratory parameters including the inflammation markers [C-reacitve protein (CRP) and interleukin-6 (IL-6)] in β-thalassaemia major children.

METHODS

We investigated 58 β-thalassaemia major children under scheduled blood transfusion and 30 controls. Routine clinical evaluation, laboratory investigations including serum ferritin as well as CRP measured by immunoturbidimetry, IL-6 and serum adiponectin measured by ELISA are performed.

RESULTS

CRP, IL-6 and serum adiponectin levels were higher in patients than controls (p<0.001, p=0.04 and p<0.001, respectively). Patients received desferoxamine showed significantly lower levels of adiponectin than those did not receive it (mean±SD=4.50±3.37 vs. 9.96±9.68, p=0.006). Serum adiponectin was significantly negatively correlated with hemoglobin (Hb) concentration (r=-0.36, p=0.005). It was significantly positively correlated with platelets count, serum ferritin, CRP and IL-6 (r=0.27, r=0.26, r=0.30, r=0.35, respectively and p=0.04, p=0.04, p=0.01, p=0.008, respectively). Serum ferritin and IL-6 were the significant predictors of serum adiponectin level (p<0.001 and p=0.003, respectively).

CONCLUSIONS

Serum adiponectin was increased in β-thalassaemia major as were pro-inflammatory markers (CRP and IL-6). Its level is directly associated with ferritin and IL-6 levels.

The role of oxidant injury in the pathophysiology of human thalassemias

The anemia in beta-thalassemia major is caused by a combination of hemolysis and ineffective erythropoiesis, with the latter being more important. Studies of the underlying cause of the hemolysis have indicated that oxidant injury to circulating red blood cells (RBCs) was of critical importance, with evidence of oxidant damage to RBC membrane proteins 4.1 and band 3. Therefore, it seemed reasonable that oxidant damage to thalassemic erythroid precursors would cause their accelerated apoptosis and ineffective erythropoiesis. However, direct analysis showed that the apoptotic programs turned on in thalassemics were not those triggered by oxidative damage but were dependent on activation of FAS/FAS-Ligand interaction. Thus, destruction of thalassemic erythroid precursors may involve different mechanisms from those that cause RBC hemolysis.

Imbalanced globin chain synthesis determines erythroid cell pathology in thalassemic mice

BACKGROUND

beta-thalassemia occurs from the imbalanced globin chain synthesis due to the absence or inadequate beta-globin chain production. The excessive unbound alpha-globin chains precipitate in erythroid precursors and mature red blood cells leading to ineffective erythropoiesis and hemolysis.

DESIGN AND METHODS

In vitro globin chain synthesis in reticulocytes from different types of thalassemic mice was performed. The effect of imbalanced globin chain synthesis was assessed from changes of red blood cell properties including increased numbers of red blood cells vesicles and apoptotic red blood cells, increased reactive oxygen species and decreased red blood cell survival.

RESULTS

The alpha/beta-globin chain ratio in beta(IVSII-654)-thalassemic mice, 1.26+/-0.03, was significantly higher than that of wild type mice, 0.96+/-0.05. The thalassemic mice show abnormal hematologic data and defective red blood cell properties. These values were improved significantly in doubly heterozygous thalassemic mice harboring 4 copies of human beta(E)-globin transgene, with a more balanced globin chain synthesis, 0.92+/-0.05. Moreover, transgenic mice harboring 8 extra copies of the human beta(E)-globin transgene showed inversely imbalanced alpha/beta-globin synthesis ratio, 0.83+/-0.01, that resulted in a mild beta-thalassemia phenotype due to the excessive beta-globin chains. The degree of ineffective erythropoiesis also correlated with the degree of imbalanced globin chain synthesis. Bone marrow and splenic erythroid precursor cells of beta(IVSII-654)-thalassemic mice showed increased phosphatidylserine exposure in basophilic and polychromatophilic stages, which was restored to the normal level in doubly heterozygous mice.

CONCLUSIONS

Imbalanced alpha/beta-globin chain as a consequence of either reduction or enhancement of beta-globin chain synthesis can cause abnormal red blood cell properties in mouse models.

Iron-chelating and free-radical scavenging activities of microwave-processed green tea in iron overload

Secondary iron overload is found in beta-thalassemia (thal) patients because of increased dietary iron absorption and multiple blood transfusions. Excessive iron catalyzes free-radical generation, leading to oxidative damage and vital organ dysfunction. Non-transferrin-bound iron (NTBI) detected in thalassemic plasma is highly toxic and chelatable. Though used to treat iron overload, desferrioxamine (DFO) and deferiprone (L1) also have adverse effects. Green tea (GT) shows many pharmacological effects, particularly antioxidative and iron-chelating capacities. This study was performed to investigate the ability of GT extracts to reduce plasma NTBI concentration and oxidative stress in vitro. The Fe(3+) was found to bind to GT crude extract and form a complex. Green tea crude extract time- and dose-dependently decreased plasma NTBI concentration and counteracted the increase of oxidative stress in both Fe(2+)-EDTA-treated human plasma and erythrocytes. Green tea is a bifunctional natural product that could be relevant for management of iron overload and oxidative stress.

Antioxidant deficit and enhanced susceptibility to oxidative damage in individuals with different forms ofα-thalassaemia

alpha-Thalassaemia is a common red cell disorder in Taiwan, affecting 6-8% of Taiwanese. Previous studies have shown that reactive oxygen species are generated in increased amounts in thalassaemic red cells. This implies the possible alteration of redox status in thalassaemic patients, which may adversely affect their health. In the present study, the redox status of patients with alpha-thalassaemia trait and haemoglobin H (Hb H) disease was investigated. Lipid peroxidation, as measured by the level of plasma thiobarbituric acid reactive substances (TBARS), was increased in alpha-thalassaemic patients, with the highest level of TBARS in Hb H disease patient. The plasma levels of vitamin A, C, and E were significantly lower in alpha-thalassaemic patients than in controls. The overall antioxidant capacity in plasma was inversely correlated with the severity of alpha-globin gene defect: the more severe the form of alpha-thalassaemia, the lower the overall antioxidant capacity in plasma. Erythrocytes isolated from alpha-thalassaemia patients had lower levels of vitamin E, glutathione, catalase and superoxide dismutase. In addition, these alpha-thalassaemic red cells were more susceptible to hydrogen peroxide-induced lipid peroxidation and decrease in deformability. All these data suggest that the alpha-thalassaemic patients suffer from increased oxidative stress and antioxidant deficit, which may complicate the pathophysiology of alpha-thalassaemia.

Pathophysiology of thalassemia

Despite discoveries concerning the molecular abnormalities that led to the thalassemic syndromes, it still is not known how accumulation of excess unmatched alpha-globin in beta thalassemia and beta-globin in alpha thalassemia leads to red blood cell hemolysis in the peripheral blood, and in the beta thalassemias particularly, premature destruction of erythroid precursors in marrow (ineffective erythropoiesis). Oxidant injury may cause hemolysis, but there is no evidence that it causes ineffective erythropoiesis. Hemoglobin E/beta thalassemia is now a worldwide clinical problem. The reasons underlying the heterogeneity and occasional severity of the syndrome remain obscure. Ineffective erythropoiesis now appears to be caused by accelerated apoptosis, in turn caused primarily by deposition of alpha-globin chains in erythroid precursors. However, it is not clear how alpha-globin deposition causes apoptosis. The author uses new observations on the control of erythropoiesis to provide a framework for studying the enhanced thalassemic erythroid apoptosis.