Analysis of BCL11A gene polymorphisms and hemolysis parameters in patients with sickle-cell disease / Análise dos polimorfismos do gene BCL11A e parâmetros de hemólise em pacientes com anemia falciforme

ABSTRACT Introduction: Patients with sickle-cell disease (SCD) present chronic hemolysis with increased serum biomarkers. Genetic polymorphisms of the BLC11A gene modulate fetal hemoglobin (HbF), thus reducing hemolysis Objective: To associate the polymorphisms of BCL11A gene with the hemolysis markers: reticulocyte, bilirubin, uric acid, lactate dehydrogenase (LDH), and methemoglobin (MetHb) in SCD patients. Methods: The study included 45 patients with SCD of both sexes using hydroxyurea (HU), treated at a Hospital in Fortaleza, Ceará, Brazil, along with 80 healthy individuals as the control group. MetHb, uric acid, and bilirubin measurements were carried out with the spectrophotometric method, and LDH with a kinetic method, a reticulocyte count by a manual method; and evaluation of BCL11A polymorphisms, in real time polymerase chain reaction (PCR). Data were analyzed using the statistical software GraphPad Prism. The level of significance was set at < 5%. Results: In region rs7557939 of the BCL11A gene genotype, A/G showed a significant increase of MetHb (p = 0.0297), and the A/A genotype showed high concentration of LDH (p = 0.0316) in the same region. The use of HU at doses ≥ 10 mg/kg/day showed a decrease of LDH (p = 0.02), and treatment for > 50 months was linked to the reticulocyte count (p = 0.0155). Conclusion: Polymorphisms in the rs7557939 region of the BCL11A gene appear to somehow interfere in the clinical setting of patients with SCD, suggesting relation with the concentration of MetHb and LDH. This study pioneered an investigation into the association of hemolysis biomarkers with BCL11A gene polymorphisms in SCD.

RESUMO Introdução: Pacientes com anemia falciforme (AF) apresentam hemólise crônica com biomarcadores séricos aumentados. Os polimorfismos genéticos do gene BLC11A modulam a hemoglobina fetal (HbF), reduzindo, assim, a hemólise. Objetivo: Associar os polimorfismos do gene BCL11A aos marcadores de hemólise: reticulócitos, bilirrubina, ácido úrico, lactato desidrogenase (LDH) e meta-hemoglobina (MetHb) em pacientes com AF. Métodos: O estudo incluiu 45 pacientes com AF que utilizavam hidroxiureia (HU), tratados em um hospital de Fortaleza, Ceará, Brasil, e 80 indivíduos saudáveis como grupo-controle. A dosagem de MetHb, ácido úrico e bilirrubina foi realizada por método espectrofotométrico; LDH, pelo método cinético; contagem de reticulócitos, pelo método manual; e avaliação de polimorfismos BCL11A, por reação em cadeia da polimerase (PCR) em tempo real. Os dados foram analisados usando o software estatístico GraphPad Prism. O nível de significância foi < 5%. Resultados: Na região rs7557939 do gene BCL11A, o genótipo A/G mostrou aumento significativo de MetHb (p = 0,0297), e o genótipo A/A esteve relacionado com a alta concentração de LDH (p = 0,0316). Pacientes em uso de HU em doses ≥ 10 mg/kg/dia apresentaram diminuição de LDH (p = 0,02), e o tratamento por mais de 50 meses foi relacionado com a contagem de reticulócitos (p = 0,0155). Conclusão: Polimorfismos na região rs7557939 do gene BCL11A parecem interferir de alguma forma nas manifestações clínicas de pacientes com AF, o que sugere uma relação com a concentração de MetHb e LDH. Este estudo foi pioneiro na investigação da associação de biomarcadores de hemólise com polimorfismos do gene BCL11A na AF.

Chronic inflammatory state in sickle cell anemia patients is associated with HBB(*)S haplotype.

The chronic inflammatory state in sickle cell anemia (SCA) is associated with several factors such as the following: endothelial damage; increased production of reactive oxygen species; hemolysis; increased expression of adhesion molecules by leukocytes, erythrocytes, and platelets; and increased production of proinflammatory cytokines. Genetic characteristics affecting the clinical severity of SCA include variations in the hemoglobin F (HbF) level, coexistence of alpha-thalassemia, and the haplotype associated with the HbS gene. The different haplotypes of SCA are Bantu, Benin, Senegal, Cameroon, and Arab-Indian. These haplotypes are associated with ethnic groups and also based on the geographical origin. Studies have shown that the Bantu haplotype is associated with higher incidence of clinical complications than the other haplotypes and is therefore considered to have the worst prognosis. This study aimed to evaluate the profile of the proinflammatory cytokines interleukin-6, tumor necrosis factor-α, and interleukin-17 in patients with SCA and also to assess the haplotypes associated with beta globin cluster S (HBB(*)S). We analyzed a total of 62 patients who had SCA and had been treated with hydroxyurea; they had received a dose ranging between 15 and 25 (20.0±0.6)mg/kg/day for 6-60 (18±3.4)months; their data were compared with those for 30 normal individuals. The presence of HbS was detected and the haplotypes of the beta S gene cluster were analyzed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Our study demonstrated that SCA patients have increased inflammatory profile when compared to the healthy individuals. Further, analysis of the association between the haplotypes and inflammatory profile showed that the levels of IL-6 and TNF-α were greater in subjects with the Bantu/Bantu haplotype than in subjects with the Benin/Benin haplotype. The Bantu/Benin haplotype individuals had lower levels of cytokines than those with the Bantu/Bantu haplotype and greater levels than those of subjects with the Benin/Benin haplotype. For IL-17, a slight trend toward decreased levels was observed in the subjects with the Benin/Benin haplotype, when compared to those with the Bantu/Bantu and Bantu/Benin haplotypes; however, this difference was not statistically significant. Our results show that genetic polymorphisms in sickle cell anemia are associated with the inflammatory profile.