Microparticles from splenectomized β-thalassemia/HbE patients play roles on procoagulant activities with thrombotic potential

Thromboembolic events including cerebral thrombosis, deep vein thrombosis, and pulmonary embolism are major complications in β-thalassemia. Damaged red blood cells and chronic platelet activation in splenectomized β-thalassemia/HbE patients were associated with increased microparticles (MPs) releases into blood circulation. MPs are small membrane vesicles, which play important roles on coagulation. However, the role of MP in thalassemia is poorly understood. In this study, the effects of splenectomized-MPs on platelet activation and aggregation were investigated. The results showed that isolated MPs from fresh platelet-free plasma of patients and normal subjects directly induce platelet activation, platelet aggregation, and platelet-neutrophil aggregation in a dose-dependent manner. Interestingly, MPs obtained from splenectomized patients are more efficient in induction of platelet activation (P-selectin⁺) when compared to MPs from normal subjects (P < 0.05), tenfold lower than pathophysiological level, at 1:0.1 platelet MP ratio. Co-incubation of splenectomized-MPs with either normal-, non-splenectomized- or splenectomized-platelets at 1:10 platelet MP ratio increased platelet activation up to 5.1 ± 2.2, 5.6 ± 3.7, and 9.5 ± 3.0%, respectively, when normalized with individual baseline. These findings suggest that splenectomized patients were proned to be activated by MPs, and splenectomized-MPs could play an important role on chronic platelet activation and aggregation, leading to thrombus formation in β-thalassemia/HbE patients.     

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.     

Comparison of erythrocyte antioxidative enzyme activities between two types of haemoglobin H disease.

The activities of erythrocyte antioxidative enzymes were measured in two groups of patients with different genotypes of haemoglobin (Hb) H disease: 21 with alpha-thalassaemia 1 or alpha-thalassaemia 2 (alpha-thalassaemia 1/2) and 21 with alpha-thalassaemia 1/Hb Constant Spring (HbCS). They were compared with 21 normal subjects. Both genotypes of Hb H disease had increased activities of erythrocyte superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase when compared with those of controls. Comparison of the two genotypes showed that subjects with alpha-thalassaemia 1/Hb CS, the more severe disease, had higher SOD and GSH-Px activities but lower catalase activity than those with alpha-thalassaemia 1/2. This indicates that there are compensatory mechanisms in Hb H erythrocytes to cope with increased generation of oxygen free radicals as a result of increased excess beta chain.     

Beta-globin gene cluster polymorphisms are strongly associated with severity of HbE/beta(0)-thalassemia

We evaluated the contribution of 67 single nucleotide polymorphisms (SNPs) within the beta-globin gene cluster to disease severity in groups of 207 mild- and 305 severe unrelated patients from Thailand with Hemoglobin E (HbE)/beta(0)-thalassemia and normal alpha-globin genes. Our analysis showed that these SNPs comprise two distinct linkage disequilibrium blocks, one containing the beta-globin gene and the other extending from the locus control region (LCR) to the delta gene, which are separated by a recombination hotspot in the narrow region of the beta-globin gene promoter. Forty-five SNPs within the interval including the LCR region and the delta gene showed strong association with disease severity. The strongest association was observed with the XmnI polymorphism located 158-bp upstream to the G gamma gene (p = 4.6E-12). Carriers of the T allele of XmnI were more likely to have a milder disease course and higher level of fetal hemoglobin (HbF) in both the mild (p = 0.005) and severe (p = 8.7E-06) patient groups. Haplotype analysis revealed that the T allele of XmnI was nearly always in cis with the HbE allele. The high frequency of this haplotype may be favored by positive selection against malarial infection. Further studies are needed to validate this hypothesis and determine whether XmnI or another closely linked variant modulates severity and HbF levels in patients with beta(0)-thalassemia/HbE disease.     

Effect of the maternal betaE-globin gene on hematologic responses to iron supplementation during pregnancy

BACKGROUND: It is customary in Southeast Asia to treat pregnant anemic women with iron supplements, but anemia in this region may be complicated by thalassemia and hemoglobinopathies, which lead to an ineffective response. OBJECTIVE: The aim was to determine whether routine iron supplementation during pregnancy in this area, which has a high prevalence of thalassemia and hemoglobinopathies, is an effective control strategy for iron deficiency anemia. DESIGN: A prospective study was conducted. Seventy-six pregnant women, including 43 who were heterozygous for the hemoglobin E (Hb E) gene, 20 who were heterozygous for Hb E and had alpha-thalassemia, and 13 who were homozygous Hb E, as well as 77 pregnant women who had no thalassemia gene, participated in this investigation. All pregnant women received a daily dose of 120 mg elemental Fe for an average of 133.5 d. Hematologic variables and serum ferritin concentrations were measured before supplementation and after supplementation at the gestational age of 28-32 wk. Differences in hematologic variables and serum ferritin were assessed. RESULTS: Significant differences in hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin responses were found between the nonthalassemia group and the 3 groups with the Hb E gene after adjustment for the following baseline values: age, body mass index, duration of iron supplementation, and ferritin concentration. Significant differences in the improvements in mean corpuscular volume and mean corpuscular hemoglobin values between the 3 groups indicate a poorer response at the cellular level in the pregnant women with the Hb E gene. Further analysis showed a significant difference in the hemoglobin response only for women who were homozygous for Hb E. CONCLUSION: Iron supplementation during pregnancy is not beneficial for pregnant women who are homozygous for Hb E, but a routine intervention should not cause iron overload, as judged from this short observation period.     

Molecular analysis of haemoglobin E in Southeast Asian populations

Haemoglobin (Hb) E is the most common Hb variant in Asia where its gene frequency approaches 0.3 in some areas. We studied genetic background of Hb E genes among Southeast Asian populations. This study examined β-globin gene haplotypes linked to haemoglobin E (Hb E) in diverse groups of Southeast Asian populations. The study was conducted on southern Thai (22 alleles), Cambodian (84 alleles), Laotian (120 alleles), Vietnamese (87 alleles) and Burmese (one allele) subjects. Results were compared with those of previous studies in northeast Thailand, the Yunnan of China, West India and Europe. Ten different haplotypes were observed. The four most common haplotypes were haplotypes 1 (–?+?–?+?+?+?–) and 2 (+?–?–?–?–?+?–) on chromosomes with framework 2 and haplotypes 6 (–?+?–?+?+?–?+) and 7 (+?– – – – –?+) on chromosomes with framework 3 variety. Phylogenetic analysis indicated that haplotype 1 is a relatively recent haplotype found in all populations, whereas haplotype 6 is found predominately in Cambodians. The results indicate that at least two genetic origins of Hb E are responsible for the high prevalence and spread of Hb E among Southeast Asian populations.