Metabolic pathways related to oxidative stress in patients with hemoglobin h disease and iron overload

Telomere shortening correlates with disease severity in hemoglobin H disease patients

Hemoglobin H (Hb H) disease is the most significant health problem of the α-thalassemia syndromes. The Hb disease patients are categorized based on their genotype to deletional and nondeletional, with the latter genotype presents the more severe clinical symptoms. Since telomere length is an indicator of biological aging and health, we hypothesized that telomere length could reflect Hb H disease's severity. In this study, we recruited 48 deletional and 47 nondeletional Hb H disease patients, along with 109 normal controls, for telomere length assessment. The leukocyte telomere length was assessed by monochromatic multiplex real-time PCR and reported as the telomere to single-copy gene (T/S) ratio. When telomere length was adjusted for age, the analysis of covariance between the control and the two Hb H disease groups revealed no significant difference. However, the telomere shortening rate was more rapid in the nondeletional Hb H disease group than those of the control and deletional Hb H disease groups. Gender analysis found that male patients have a significantly lower T/S ratio than females in the nondeletional group but not in the control and deletional groups. In the two disease groups, the T/S ratio was not influenced by ferritin level or transfusion burden but was positively correlated with the absolute reticulocyte count.

Hypoxic storage of erythrocytes slows down storage lesions and prolongs shelf-life

Conventional storage conditions of erythrocytes cause storage lesions. We propose that hypoxic storage conditions, involving removal of oxygen and replacement with helium, the changes in stored erythrocytes under hypoxic condition were observed and assessed. Erythrocytes were divided into two equal parts, then stored in conventional and hypoxic conditions, separately. Blood gas analysis, hemorheology, and hemolysis were performed once a week. Energy metabolism and membrane damage were monitored by enzyme-linked immunosorbent assay. Phosphatidylserine exposure was measured by flow cytometry. P₅₀ was measured and the oxygen dissociation curve (ODC) plotted accordingly. Erythrocyte morphology was observed microscopically. In the 9th week of storage, the hemolysis of the hypoxia group was 0.7%; lower (p < .05) than that of the control group and still below the threshold of quality requirements. The dissolved oxygen and pO₂ were only 1/4 of that in the control group (p < .01); the adenosine triphosphate, glucose, and lactic acid levels were decreased (p < .05), while the 2,3-diphosphoglycerate levels were increased relative to that in the control group (p < .01). There were no statistically significant differences in membrane damage, deformability, and aggregation between the two groups. In addition, the ODC of the two groups was shifted to the left but this difference was not statistically different. Basically similar to the effect of completely anaerobic conditions. Erythrocytes stored under hypoxic conditions could maintain a relatively stable state with a significant decrease in hemolysis, reduction of storage lesions, and an increase in shelf-life.

miR-144 regulates oxidative stress tolerance of thalassemic erythroid cell via targeting NRF2

Thalassemia has a high prevalence in Thailand. Oxidative damage to erythroid cells is known to be one of the major etiologies in thalassemia pathophysiology. Oxidative stress status of thalassemia is potentiated by the heme, nonheme iron, and free iron resulting from imbalanced globin synthesis. In addition, levels of antioxidant proteins are reduced in α-thalassemia and β-thalassemia erythrocytes. However, the primary molecular mechanism for this phenotype remains unknown. Our study showed a high expression of miR-144 in β- and α-thalassemia. An increased miR-144 expression leads to decreased expression of nuclear factor erythroid 2-related factor 2 (NRF2) target, especially in α-thalassemia. In α-thalassemia, miR-144 and NRF2 target are associated with glutathione level and anemia severity. To study the effect of miR-144 expression, the gain-loss of miR-144 expression was performed by miR inhibitor and mimic transfection in the erythroblastic cell line. This study reveals that miR-144 expression was upregulated, whereas NRF2 expression and glutathione levels were decreased in comparison with the untreated condition after miR mimic transfection, while the reduction of miR-144 expression contributed to the increased NRF2 expression and glutathione level compared with the untreated condition after miR inhibitor transfection. Moreover, miR-144 overexpression leads to significantly increased sensitivity to oxidative stress at indicated concentrations of hydrogen peroxide (H₂O₂) and rescued by miR-144 inhibitor. Taken together, our findings suggest that dysregulation of miR-144 may play a role in the reduced ability of erythrocyte to deal with oxidative stress and increased RBC hemolysis susceptibility especially in thalassemia.

Abnormal red blood cell morphological changes in thalassaemia associated with iron overload and oxidative stress

AIMS

Iron overload is a major factor contributing to the overall pathology of thalassaemia, which is primarily mediated by ineffective erythropoiesis and shorter mature red blood cell (RBC) survival. Iron accumulation in RBCs generates reactive oxygen species (ROS) that cause cellular damage such as lipid peroxidation and RBC membrane deformation. Abnormal RBCs in patients with thalassaemia are commonly known as microcytic hypochromic anaemia with poikilocytosis. However, iron and ROS accumulation in RBCs as related to RBC morphological changes in patients with thalassaemia has not been reported.

METHODS

Twenty-one patients with thalassaemia, including HbH, HbH with Hb Constant Spring and β-thalassaemia/HbE (splenectomy and non-splenectomy) genotypes, and five normal subjects were recruited. RBC morphology was analysed by light and scanning electron microscopy. Systemic and RBC iron status and oxidative stress were examined.

RESULTS

Decreased normocytes were observed in the samples of patients with thalassaemia, with RBC morphological abnormality being related to the type of disease (α-thalassaemia or β-thalassaemia) and splenic status. Target cells and crenated cells were mainly found in splenectomised patients with β-thalassaemia/HbE, while target cells and teardrop cells were found in non-splenectomised patients. Patients with thalassaemia had high levels of serum ferritin, red cell ferritin and ROS in RBCs compared with normal subjects (p<0.05). Negative correlations between the amount of normocytes and serum ferritin (r_s=-0.518, p=0.011), red cell ferritin (r_s=-0.467, p=0.025) or ROS in RBCs (r_s=-0.672, p<0.001) were observed.

CONCLUSIONS

Iron overload and its consequent intracellular oxidative stress in RBCs were associated with reduce normocytes in patients with thalassaemia.

Iron Metabolism and Oxidative Status in Patients with Hb H Disease

To evaluate the iron metabolism and oxidative status in patients with Hb H disease, we investigated 43 patients with Hb H disease, including eight deletional Hb H disease patients and 35 nondeletional Hb H disease patients and 20 healthy controls. The levels of hematological parameters, serum ferritin, hepcidin, superoxide dismutase (SOD), malondialdehyde (MDA) and total antioxidant capacity (TAC), were examined. We found higher serum ferritin levels and lower hepcidin, MDA and TAC levels in Hb H disease patients than in controls. The hepcidin level in Hb H disease patients was positively correlated with MDA and TAC levels but not with serum ferritin and SOD levels. The patients with nondeletional Hb H disease showed higher serum ferritin and Hb H concentrations than those patients with deletional Hb H disease. However, no statistically significant differences in SOD, MDA and TAC levels were found in patients with deletional and nondeletional Hb H disease. Oxidative stress and antioxidant defense were related to hepcidin levels. Our study indicated that hepcidin might be an important parameter for monitoring the iron metabolism and oxidative status of Hb H disease patients.

Ischemia-modified albumin as a marker of vascular dysfunction and subclinical atherosclerosis in β-thalassemia major

BACKGROUND

Ischemia-modified albumin (IMA) is an altered type of serum albumin that forms under conditions of oxidative stress and an independent predictor of major adverse cardiovascular events.

OBJECTIVES

To measure the levels of IMA in 45 children and adolescents with β-thalassemia major (β-TM) compared with 30 healthy controls and assess its relation to lipid peroxidation, vascular complications and subclinical atherosclerosis.

METHODS

β-TM patients without symptoms of heart disease were studied focusing on transfusion history, chelation therapy, serum ferritin, malondialdehyde (MDA) and IMA levels. Echocardiography was performed and carotid intima media thickness (CIMT) was assessed.

RESULTS

IMA and MDA levels were significantly higher in β-TM patients compared with controls (p < 0.001). IMA was higher among patients with heart disease, pulmonary hypertension risk and serum ferritin ≥2500 µg/l than those without. TM patients compliant to chelation had significantly lower IMA levels. IMA levels were positively correlated to MDA and CIMT while negatively correlated to ejection fraction and fractional shortening.

CONCLUSION

Our results highlight the role of oxidative stress in the pathophysiology of vascular complications in thalassemia. IMA could be useful for screening of β-TM patients at risk of cardiopulmonary complications and atherosclerosis because its alteration occurs in early subclinical disease.