Endothelial Nitric Oxide Synthase (eNOS) Gene Polymorphisms and Markers of Hemolysis, Inflammation and Endothelial Dysfunction in Brazilian Sickle Cell Anemia Patients

The impaired bioavailability of endogenous nitric oxide (NO) in sickle cell anemia (SCA) may be influenced by polymorphisms in the endothelial nitric oxide synthase gene (eNOS). We compared allelic/genotypic frequencies of the eNOS polymorphisms T-786C, VNTR4a/b and G894T between 89 adult SCA patients and 100 healthy controls, and investigated the relationship between these SNPs and markers of hemolysis [lactate dehydrogenase (LDH), indirect bilirubin (IB) and reticulocyte counts], inflammation [interleukins IL-1β, IL-6, IL-8, Tumor Necrosis Factor (TNF-α) and C-reactive protein (CRP)] and endothelial dysfunction (ED) [soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 (sICAM-1), soluble L-selectin (sL-selectin), von Willebrand Factor (vWF) antigen and D-dimers] in the patients. The frequencies of the mutant -786C allele and -786C/C genotype were significantly higher in patients (p = 0.02 and p = 0.04, respectively) but not significantly correlated with the markers. For VNTR4a/b and G894T, the allelic/genotypic frequencies did not statistically differ between patient and control groups. Patients carrying the 4a allele and those with the 894G/G genotype showed a significant decrease in IB (p = 0.02 and p = 0.04, respectively), and only patients with the 4a allele exhibited reduced IL-1β (p = 0.01). The correlation profiles between markers of inflammation and ED significantly differed between patients carrying the mutant alleles and those with wild-type genotypes. This appears to be the first report on the relationship between eNOS gene polymorphisms and markers of hemolysis, inflammation and ED in Brazilian SCA patients. Our results indicate that the SNPs analyzed may influence the phenotypic variability of these patients.

Association of variant alleles of MBL2 gene with vasoocclusive crisis in children with sickle cell anemia

Vasoocclusive crisis (VOC) is the major cause of morbidity and mortality in sickle cell anemia (SCA), which is caused by the occlusion of blood vessels, followed by ischemia or infarct, resulting in progressive damage to organs. However, this clinical manifestation is variable, indicating that this process could be influenced by modifier genes. The gene MBL2 which codes for mannose-binding lectin (MBL) has been associated with modifications in the progression of infectious and inflammatory vascular diseases. The aim of this study was to determine the frequency of the polymorphisms of exon 1 (alleles A/O) and promoter region -221 (alleles Y/X) of MBL2 in children with SCA and to verify their association with VOC. The determination of the polymorphism of exon 1 and the promoter region of MBL2 was performed by SYBR GREEN((R)) and Taqman((R)) system, respectively. In the patients with SCA, the frequency of the genotype related to high production of MBL was 0.46 (YA/YA) and for intermediate/low production was 0.54 (YA/XA, XA/XA, YA/YO, XA/YO, YO/YO). The frequency of the genotypes and haplotypes of MBL2 in patients with SCA did not differ from control individuals. The populations were in Hardy-Weinberg equilibrium. The patients were divided into two groups. The groups were separated by the frequency of VOC, which was defined by the total of VOC episodes divided by the age of the children at the end of this study. Since, we choose a cut point in FVOC <1 (n=48) (which we considered of mild presentation of disease) and FVOC >or=1 (n=39) (higher severity). In children with SCA, the frequency of the genotypes of MBL2 of intermediate/low expression for MBL was associated with FVOC >or=1 (p=0.0188 OR=3.15 CI=1.19-8.50). The results suggest that MBL2 polymorphism at promoter and first exon of MBL2 associated with low serum levels and structural alterations of MBL could modify the phenotype of the child with SCA related to VOC.