Angela Maria Dias Zanette

The beta-globin gene cluster haplotypes in sickle cell anemia patients from Northeast Brazil: a clinical and molecular view.

The βS‐globin haplotypes were studied in 78 sickle cell Brazilian patients from Bahia, Northeast Brazil, that has a large population of African origin. Hemoglobin (Hb) profiles were developed by high‐performance liquid chromatography (HPLC), and βS‐globin gene haplotypes were determined by polymerase chain reaction‐restriction fragment length polymorphism (PCR‐RFLP) techniques. We identified 44 (55.0%) patients with the CAR/Ben (Central African Republic/Benin) genotype, 16 (20.0%) Ben/Ben, 13 (16.2%) CAR/CAR and seven (8.8%) with other genotypes. Analyses of the phenotypes showed clinical differences related only to Hb F levels and blood transfusion therapy; the presence of − α− 3.7‐thalassemia (thal) demonstrated statistical significance when associated with hematocrit (p = 0.044), MCV (p = 0.0007), MCH (p = 0.012) and spleen sequestration events. The haplotype diversity found in the present study can be justified by information about the origin of the slave traffic period in Bahia during the 19th century. The specific characteristics described among the Bahian sickle cell patients could be confirmed by increasing the number of patients with specific genotypes and further studies of genetic markers.

Increased concentrations of IL-18 and uric acid in sickle cell anemia: Contribution of hemolysis, endothelial activation and the inflammasome

Sickle cell anemia (SCA) is a common, severe monogenetic disorder characterized by chronic hemolysis, frequent infections, a chronic inflammatory state and recurrent occlusions of the microcirculation, resulting in painful crises, organ damage and premature death. This study evaluated associations between serum levels of IL-18, uric acid, hemolytic markers, and inflammatory molecules in SCA patients. A cross-sectional study was performed including 45 SCA patients (median age of 20.5 years) without general symptoms and who had not undergone blood transfusions. Inclusion criteria for the steady-state SCA patients were the absence of hospitalization and the absence of infections. Interleukin-18 and uric acid levels were correlated closely with markers of hemolysis, endothelial dysfunction and others cytokines levels. These findings suggest probable influences of IL-18 and uric acid in the pathophysiology of vascular occlusion in SCA. Additional studies should be performed to characterize similar prognosis markers and possible therapeutic targets.

A C677T methylenetetrahydrofolate reductase (MTHFR) polymorphism and G20210A mutation in the prothrombin gene of sickle cell anemia patients from Northeast Brazil.

The C677T methylenetetrahydrofolate reductase (MTHFR) gene polymorphism and the G20210A mutation at the 3′ untranslated region (3′UTR) of the prothrombin gene may be considered to be genetic risk factors that contribute to the clinical heterogeneity in sickle cell disease. The current study investigated a group of sickle cell (SS) patients from Salvador‐Bahia, Northeast Brazil in order to determine the prevalence of these polymorphisms, using the polymerase chain reaction (PCR) and restriction fragment length polymorphim (RFLP) techniques. Out of 69 SS patients diagnosed with the C677T MTHFR gene polymorphism, 13 (18.6%) were heterozygous and four (5.7%) homozygous. The G20210A mutation was not found in 50 SS patients investigated. These results became important once the C677T MTHFR gene polymorphism was found to be an independent risk factor for vascular disease, a common clinical event in sickle cell disease.

Ocular lesions in sickle cell disease patients from Bahia, Brazil

Objective: The present study aims to describe ocular alterations in sickle cell disease patients in Bahia, a Northeast state, with the highest prevalence of the disease in Brazil. Methods: We carried out a cross-sectional study in a group of 146 (292 eyes) sickle cell disease patients (90 HBSS and 56 HBSC). Ophthalmologic examination including indirect binocular ophthalmoscopy was performed. Examination was completed by fluorescein angiography to detect retinal lesions. Results: The most frequent ocular lesions identified were “vascular tortuosity” and “black sunburst”. Proliferative retinopathy was found in 22 (12.2%) eyes of HBSS patients and 25 (22.3%) eyes of HBSC patients (OR=2.06; CI95%: 1.5-4.06, p=0.022); Its frequency was higher among HBSS patients aged 20-39 years, while in HBSC patients, it peaked after 40 years (35.7% and 42.8%) and dropped sharply afterwards. Conclusion: Proliferative retinopathy was described as early as 10 years of age in both patients groups. Proliferative sickle retinopathy can result in blindness and the knowledge of the most prevalent ocular alterations and age risk will be important to establish a protocol of ophthalmologic follow-up, in order to prevent a severe visual loss and increase patients life quality.

Genetic modulation of HbF in Brazilians with HbSC disease and sickle cell anemia

Sickle cell anemia (homozygosity for HbS) and HbSC disease (compound heterozygosity for HbS and HbC) are the most common genotypes of sickle cell disease (SCD). Fetal hemoglobin (HbF), the major genetic modulator of SCD, interferes with deoxyHbS polymerization [1]. Patients with HbSC disease have about half the number of complications as do HbS homozygotes [1], however, their mean HbF levels were 2.4% compared with about 6% in patients with sickle cell anemia [2]. Single nucleotide polymorphisms (SNPs) in quantitative trait loci cis and trans to the β-globin gene cluster are associated with HbF. We analyzed the association of SNPs in BCL11A, (chromosome 2p), in the HBS1L-MYB intergenic region (HMIP) (chromosome 6q), and in the 5′ olfactory receptor (OR) gene cluster of chromosome 11p with HbF in Brazilian patients with SCD. 622 patients were studied. They were not treated with hydroxyurea and were aged ≥6 years. Hemoglobin was analyzed by HPLC. SNPs rs766432 and rs6732518 in BCL11A; rs35959442 and rs11759553 in HMIP; and rs4910755 and 7483122 located in OR51B5-OR51B6 were genotyped by ABI TaqMan Assays. The βS and βC globin haplotypes were investigated with PCR and restriction fragment length polymorphism techniques. Mean HbF was compared according to genotype using the additive genetic model adjusting for age, gender and HbS homozygotes versus HbSC. A dominant genetic model adjusting for age, gender and SCD genotype was used to test the association SNPs with HbF. We tested to see if there was an association between HbF and SNPs in the OR gene cluster region after adjusting for age, gender, SCD genotype and the HBB gene cluster haplotype (Central African Republic [CAR] or Bantu versus absence of a CAR haplotype). To determine if there was a synergistic effect between the SNPs or if the effect exerted on HbF was independent, we developed multivariable linear regression models adjusting for age, gender and SCD disease status and ran stepwise linear regression analyses where we added the most significant SNPs from BCL11A, HMIP one-at-a-time. Data analysis was performed using R version 2.14.1 and the cubic root transformation of HbF [3]. 392 patients were HbS homozygotes (HbF 7.4±4.4%) and 230 had HbSC disease (HbF 2.5±2.3%). The association between HbF and SNPs in the BCL11A, HMIP and the OR gene cluster for all patients combined and for HbS homozygotes and HbSC patients separately are shown in Table I a-c (on-line supplementary material). In the combined group, there is a statistically significant association between HbF levels and both BCL11A SNPs and with HMIP SNP rs11759553 after adjusting for age, gender and the SCD genotype. As the number of minor alleles increase, so does HbF level; in HbS homozygotes a similar result was found; in HbSC disease both SNPs in BCL11A and HMIP were associated with HbF. The association between HbF levels and SNPs in the OR genes, after adjusting fo r HBB haplotype was not significant (Table II, on-line supplementary material). In a stepwise linear regression analysis adding the SNPs to a multivariable linear regression model as described, after adjusting for age, gender and SCD genotype rs35959442 is still significantly associated with HbF indicating that its effect on HbF is independent of rs766432 (Table III, on-line supplementary material). We dichotomized the patients according to the HBB gene cluster haplotype. Brazilians with SCD have a higher prevalence of the CAR haplotype compared with African Americans. This haplotype is associated with lower levels of HbF than other haplotypes [4][5]. Sickle cell anemia patients were heterozygous or homozygous for the CAR haplotype chromosome or lacked a CAR haplotype chromosome; HbSC disease patients had or did not have a CAR haplotype chromosome. Most patients with a CAR haplotype had the minor allele for rs4910755 and rs7483122, both of which are located in the 5′ OR gene cluster of chromosome 11p and could be in linkage disequilibrium with SNPs characterizing this haplotype. HbSC disease patients usually have low HbF levels. Nevertheless, it is a milder condition than sickle cell anemia even though patients are more susceptible to clinical events related to high bloodviscosity. Although HbF in HbSC disease is lower than in HbS homozygotes, BCL11A and HMIP modulate HbF in both genotypes.

Endothelial Nitric Oxide Synthase ( −786T.C) and Endothelin-1 (5665G.T) Gene Polymorphisms as Vascular Dysfunction Risk Factors in Sickle Cell Anemia

Sickle cell anemia (SCA) patients have vascular complications, and polymorphisms in endothelin-1 (ET-1) and endothelial nitric oxide synthase (eNOS) genes were associated with ET-1 and nitric oxide disturbance. We investigate the association of ET-1 5665G>T and eNOS −786T>C polymorphisms with soluble adhesion molecules (sVCAM-1 and sICAM-1), biochemical markers, and medical history. We studied 101 SCA patients; carriers of eNOS minor allele (C) had the highest levels of sVCAM-1, and carriers of ET-1 minor allele had more occurrence of acute chest syndrome (ACS). The multivariate analysis suggested the influence of the ET-1 gene on ACS outcome and an association of the eNOS gene with upper respiratory tract infection. We suggest that eNOS and ET-1 gene polymorphisms can influence SCA pathophysiology and that eNOS variant in SCA patients might be important to nitric oxide activity and vascular alteration. We found an association of the ET-1 minor allele in ACS, showing the importance of genetic screening in SCA.

Association of homocysteine and inflammatory-related molecules in sickle cell anemia.

Objective: Investigate the role of homocysteine (Hcy), Th17-related cytokines, and adhesion molecules in the inflammatory state seen in the sickle cell anemia (SCA). Methods: We studied the Hcy, interleukin (IL)-17, and transforming growth factor β (TGF-β) cytokine levels of 62 SCA patients, as well as the expression levels of inflammatory and endothelial activation markers. Results: We found significant associations between Hcy levels and increased expression of IL-17 and TGF-β among SCA patients, and a positive significant correlation between Hcy and soluble vascular cellular adhesion molecules (sVCAM). SCA individuals had raised IL-17 levels when compared with controls. Discussion: These results suggest a possible role of Hyc in the induction of TGF-β and IL-17. Other authors proposed that Hcy may contribute to the initiation and progression of vascular disease by monocyte activation, resulting in the secretion of cytokines that amplify the inflammatory response. The role of Hcy in cytokine production and oxidative stress in the endothelium may explain the increase of sVCAM expression and, the vascular activation currently described among the SCA individuals with the highest Hcy serum levels. The chronic inflammation was observed in hyperhomocysteinemic mice, with an increased expression of VCAM-1 and plasma levels of tumor necrosis factor-alpha, showing an association of this inflammatory molecule and vascular changes. Conclusion: Our findings suggest that the increased levels of IL-17,Hcy and sVCAM contributes contributes to the vascular inflammation and activation presented by SCA patients, which probably have an important role in vaso-occlusion. On the basis of the presented data, IL-17 and Hcy might be considered as important components in the pathogenesis of SCA.