Polymorphisms in the heme oxygenase-1 and bone morphogenetic protein receptor type 1b genes and estimated glomerular filtration rate in Brazilian sickle cell anemia patients

ABSTRACT Introduction Mutations affecting genes involved in oxidative and signaling pathways may be associated with kidney disease in sickle cell anemia. We determined the allele and genotype frequencies of some polymorphisms in the promoter regions of the Heme Oxygenase-1 (HMOX1) [rs2071746 (A > T) and (GT)n repeats, short (S) and long (L) alleles] and Bone Morphogenetic Protein Receptor type-1B (BMPR1B) [rs17022863 (A > G), rs4331783 (A > G) and rs1470409 (A > G)] genes in 75 adult patients with sickle cell anemia and 160 healthy controls and investigated whether these polymorphisms may influence the estimated glomerular filtration rate for the patients. Methods The single nucleotide polymorphisms were genotyped using the TaqMan assays, the HMOX1(GT)n repeats were determined by polymerase chain reaction fragment size analysis and the estimated glomerular filtration rate was calculated by the Modification of Diet in Renal Disease formula. Results Regarding the HMOX1rs2071746, the estimated glomerular filtration rate median was significantly higher in TT patients (p = 0.019), including when TT was compared with AT + AA (p = 0.009); for the (GT)n repeats, the estimated glomerular filtration rate medians of SS, SL and LL significantly differed (p = 0.009), being the LL estimated glomerular filtration rate median significantly higher, when compared with the LS + SS (p = 0.005). These results suggest that both the homozygotes, TT for rs2071746 and LL for (GT)n repeats, lead to a higher risk of developing renal complications. Concerning the BMPR1B, the frequencies of GG for rs17022863 and AA for rs4331783 were significantly higher in patients than in controls (p = 0.002 and p = 0.008, respectively), however no association with estimated glomerular filtration rate was found. Conclusion These results contribute to a better understanding of the genetic factors related to the development of nephropathy in sickle cell anemia patients.

Investigating alpha-globin structural variants: a retrospective review of 135000 Brazilian individuals

Background: Brazil has a multiethnic population with a high diversity of hemoglobinopathies. While screenings for beta-globin mutations are far more common, alterations affecting alpha-globin genes are usually more silent and less well known. The aim of this study was to describe the results of a screening program for alpha-globin gene mutations in a representative sample of the Southeastern Brazilian population. Methods: A total of 135,000 individuals, including patients with clinical suspicion of hemoglobinopathies and their family members, randomly chosen individuals submitted to blood tests and blood donors who were abnormal hemoglobin carriers were analyzed. The variants were screened by alkaline and acid electrophoreses, isoelectric focusing and cation-exchange high performance liquid chromatography (HPLC) and the abnormal chains were investigated by reverse-phase high performance liquid chromatography (RP-HPLC). Mutations were identified by molecular analyses, and the oxygen affinity, heme-heme cooperativity and Bohr effect of the variants were evaluated by functional tests. Results: Four new and 22 rare variants were detected in 98 families. Some of these variants were found in co-inheritance with other hemoglobinopathies. Of the rare hemoglobins, Hasharon, Stanleyville II and J-Rovigo were the most common, the first two being S-like and associated with alpha-thalassemia. Conclusion: The variability of alpha-globin alterations reflects the high degree of racial miscegenation and an intense internal migratory flow between different Brazilian regions. This diversity highlights the importance of programs for diagnosing hemoglobinopathies and preventing combinations that may lead to important clinical manifestations in multiethnic populations.

Genótipos da haptoglobina e aspectos inflamatórios na anemia falciforme / Haptoglobin genotypes and inflammatory aspects in sickle cell anemia

Estudos recentes sobre o papel da inflamação na fisiopatologia da anemia falciforme (AF) sugerem que o equilíbrio da resposta imune Th1/Th2, relacionado ao perfil de citocinas produzidas, pode influenciar a morbidade nos portadores dessa doença. A haptoglobina (Hp) é uma glicoproteína plasmática cuja função primordial é ligar-se à hemoglobina (Hb) livre no plasma para prevenir a excreção renal de ferro e os efeitos oxidativos resultantes de sua presença no vaso. Além disso, é uma proteína de fase aguda positiva, com propriedades imunomodulatórias. Dois alelos codominantes, HP1 e HP2, resultam em três genótipos/fenótipos principais, Hp1-1, Hp2-1 e Hp2-2, que correspondem a proteínas com características físico-químicas e eficiências distintas. O objetivo do presente estudo foi avaliar se os genótipos da Hp poderiam influenciar o estado inflamatório na AF por meio da comparação dos níveis de determinados parâmetros a ele relacionados. Para isso, foram comparados os níveis plasmáticos ou séricos e/ou as taxas de expressão gênica (em células mononucleares) dos mediadores imunológicos IL-1β, IL-6, IL-8, IL-10 e TNF-α, das moléculas de adesão sVCAM-1, sICAM-1 e sL-selectina, do antígeno do Fator de Von Willebrand (FvW:Ag), dos Dímeros-D, da proteína C reativa (CRP), do microRNA-155 (miRNA-155) e do gene HP (ambos em células mononucleares e polimorfonucleares) em 92 pacientes adultos com AF acompanhados no Hemocentro de Pernambuco, subdivididos em Hp1-1 (n=27), Hp2-1 (n=37) e Hp2-2 (n=28). Os valores obtidos e os genótipos de Hp foram ainda comparados com dados clínicos e laboratoriais (hematológicos e bioquímicos) oriundos dos prontuários dos pacientes. Além disso, a presença do polimorfismo CCR532, relacionado à resposta inflamatória, foi investigada nesses pacientes.

Recent studies on the role of inflammation in the pathophysiology of sickle cell anemia (SCA) suggest the Th1/Th2 balance of the immune response, relating to the profile of cytokines produced, may influence the morbidity in patients with SCA. Haptoglobin (Hp) is a plasma glycoprotein whose primary function is to bind to free hemoglobin (Hb) in the plasma, preventing excretion of iron by the kidneys and protecting blood vessels from its oxidative effects. Moreover, it is also an acute phase positive protein with immunomodulatory properties. Two codominant alleles, HP1 and HP2, result in three main genotypes/phenotypes, Hp1-1, Hp2-1 and Hp2-2, which correspond to proteins with different functional characteristics. The aim of this study was to evaluate whether the Hp genotypes may influence the inflammatory state in SCA by comparing the levels of certain parameters related to it. For this purpose, we compared the plasma or serum and/or rates of gene expression (in mononuclear cells) of immune mediators IL-1 β, IL-6, IL-8, IL-10 and TNF-α, adhesion molecules sVCAM-1, sICAM-1 and sL-selectin, antigen von Willebrand Factor (vWF: Ag), D-dimers, C-reactive protein (CRP), microRNA-155 (miRNA-155) and Hp gene (both in mononuclear and polymorphonuclear cells) in 92 adult patients with SCA followed up at the Blood Center of Pernambuco, subdivided in Hp1-1 (n = 27), Hp2-1 (n = 37) and Hp2-2 (n = 28). The values obtained and the Hp genotypes were also compared to clinical and laboratory (hematology and biochemistry) data from patients' records. Furthermore, the presence of polymorphism CCR532, related to inflammatory response, was investigated in these patients. The rates of gene expression and serum/plasma were quantified by real time PCR (qPCR) and ELISA, respectively, while the Hp genotypes of polymorphism and CCR532 were investigated by PCR reactions.

Triagem familiar para o gene HBB*S e detecção de novos casos de traço falciforme em Pernambuco / Family screening for HBB*S gene and detection of new cases of sickle cell trait in Northeastern Brazil

OBJETIVO: Estimar o incremento no número adicional de afetados com base na prevalência de síndromes falciformes em familiares de casos-índice. MÉTODOS: Estudo transversal em familiares de amostra aleatória dos casos-índice identificados por programa de triagem neonatal em Pernambuco, no período de 2001 a 2005. O modelo de triagem familiar ampliado incluiu 463 membros familiares de 21 casos-índice. Os familiares foram categorizados como: núcleo reduzido (NR -pai, mãe e irmãos); de primeiro grau (N1 - avós, tios e primos de primeiro grau); de segundo grau (N2 - filhos dos primos de primeiro grau); ampliado (NA - NR+N1+N2) e ampliado de primeiro grau (NA1 -NR+N1). A confirmação da presença de HBB*S e detecção de hemoglobinas anormais foram realizadas por meio da High Performance Liquid Chromathgraphy. A associação entre a presença de HBB*S e variáveis foi testada pelo cálculo da razão de prevalência e respectivos IC 95 por cento e a diferença entre médias verificadas pelo teste t de Student, ao nível de significância de 5 por cento. RESULTADOS: A anemia falciforme era desconhecida por 81 por cento dos familiares; o gene HBB*S esteve presente em 114 familiares. Observou-se que 53,3 por cento da população estudada estava na faixa considerada reprodutiva e 80 por cento das pessoas portadoras do gene HBB*S já tinham gerado filhos. A freqüência foi maior no núcleo NR (69 por cento), mas também elevada no N1 (22,8 por cento). O NA1 resultou na detecção de 69 portadores adicionais (aumento de 172 por cento). CONCLUSÕES: Os resultados indicam que a triagem familiar para identificação de portadores de síndrome falciforme deve ser estendida para os familiares até o primeiro grau.

OBJECTIVE: To estimate the additional number of affected individuals based on the prevalence of sickle-cell syndromes among relatives of index cases. METHODS: Cross-sectional study of relatives of a random sample of index cases identified through a neonatal screening program in Northeastern Brazil, between 2001 and 2005. The extended family trial model included 463 relatives of 21 index cases. Relatives were classified as nuclear family (NF: father, mother, and siblings); first degree extended family (N1: grandparents, uncles and aunts, and first cousins); second degree extended family (N2: children of first cousins); extended family (NA: NF+N1+N2); and extended nuclear family (NA1: NF+N1). The presence of HBB*S and other abnormal hemoglobins was confirmed by high-performance liquid chromatography. The association between the presence of HBB*S and other variables was calculated using prevalence ratios and their respective 95 percent confidence intervals, and differences between means were calculated using Student's t test with a 5 percent significance level. RESULTS: Of relatives, 81 percent had no knowledge of sickle-cell anemia and HBB*S was present in 114 family members. A total of 53.3 percent of the studied population was considered as of reproductive age, and 80 percent of HBB*S carriers had already had children. Frequency was higher among NF (69 percent), but was also high in N1 (22.8 percent). NA1 screening resulted in the detection of 69 carriers additional (a 172 percent increase). CONCLUSIONS: These results indicate that family screening for the identification of sickle-cell carriers should be extended to first degree relatives.