Tamara Mucenic

The role of mannose-binding lectin in systemic lupus erythematosus

Susceptibility to systemic lupus erythematosus (SLE) is associated with genetic, hormonal, immunological, and environmental factors. Many genes have been related with the appearance of SLE, including several loci that code different complement components and their receptors. Some genetic deficiencies of complement molecules are strongly associated with SLE, probably because these deficiencies could cause decreased clearance of apoptotic cell material. As a consequence of the apoptotic material accumulation, high levels of autoantigens can be presented inappropriately to the immune system in an inflammatory context, resulting in an imbalance on the mechanisms of immunological tolerance, immune system activation, and autoantibody production. Recent studies proposed a role to the mannose-binding lectin (MBL) in the SLE physiopathogenesis. This protein activates the complement system, and the presence of several polymorphisms at the promoter and coding regions of the MBL-2 gene determines alterations at the plasma levels of MBL. Some of these polymorphisms have been associated with SLE susceptibility, as well as with clinical and laboratory typical features of this disease, cardiovascular events, and infections. Besides, it has been described that the presence of anti-MBL autoantibodies in sera of SLE patients can influence MBL plasma levels and its functional activity.

Expression of CD55 and CD59 on peripheral blood cells from systemic lupus erythematosus (SLE) patients.

CD55 and CD59 are glycosylphosphatidylinositol-anchored proteins with complement inhibitory properties. CD55 inhibits the formation of C3 convertases, and CD59 prevents the terminal polymerisation of the membrane attack complex. It has been reported that SLE patients seems to have an acquired deficiency of these proteins associated with secondary autoimmune haemolytic anaemia and lymphopenia. The aim of this study was to evaluate the presence of altered CD55 and CD59 expression on peripheral blood cells from SLE patients. Flow cytometric analyses were performed on red and white blood cells from 23 SLE patients and 23 healthy controls. We observed more CD55- and CD59-lymphocytes (p=0.005 and p=0.019, respectively), and CD59-granulocytes (p=0.045) in SLE patients than in controls. These results suggest there is an altered pattern of CD55 and CD59 expression on the peripheral blood cells of SLE patients, and it may play a role in the cytopenias in these patients.

Mannose-binding lectin gene polymorphisms in Brazilian patients with systemic lupus erythematosus

The mannose-binding lectin gene (MBL-2) has emerged as a candidate for systemic lupus erythematosus susceptibility, but studies in Brazilian population have not been conducted. To examine potential associations of mannose-binding lectin alleles G57E, G54D, IVSnt5, R52C and R52H with susceptibility to and clinical expression of systemic lupus erythematosus in southern Brazilian patients, we conducted a case—control study with 327 consecutive patients with diagnosis of systemic lupus erythematosus and 345 healthy controls. Genotyping was performed by restriction fragment length polymorphism—polymerase chain reaction assay. A statistically significant difference in the frequencies of allele R52C was observed in European-derived systemic lupus erythematosus patients when compared with controls (9.6% vs. 3.3%, p < 0.001, odds ratio: 3.15, 95% confidence interval: 1.76—5.62, p < 0.05). The frequencies of alleles G54D and G57E were not different between European-derived systemic lupus erythematosus patients and controls. There were no differences between clinical and laboratory features in systemic lupus erythematosus patients according to the presence or absence of mannose-binding lectin allelic variants. These results support an increased risk of systemic lupus erythematosus in European-derived individuals carrying allele R52C. Patients carrying this allele have an approximately three-fold higher odds ratio of developing systemic lupus erythematosus when compared with controls. Our data do not support associations between the mannose-binding lectin allelic variants studied and clinical expression of systemic lupus erythematosus. Lupus (2010) 19, 280—287.

ABCB1 C1236T, G2677T/A and C3435T polymorphisms in systemic lupus erythematosus patients

P-glycoprotein (Pgp), the ABCB1 gene product, acts as an efflux pump that transports a large variety of substrates and is a mechanism of cell protection against xenobiotics. An increasing number of studies have shown that some ABCB1 polymorphisms may affect Pgp expression and activity, as well as affecting the development and susceptibility to diseases and pharmacological response. High activity of Pgp has been detected in systemic lupus erythematosus (SLE) patients. The C1236T, G2677T/A, and C3435T are the most commonly studied single nucleotide polymorphisms in the ABCB1 gene. Therefore, their frequencies were determined in Brazilian individuals with European ancestry (N = 143) and in SLE patients (N = 137). Genotyping was performed by PCR-RFLP analysis using specific primers followed by incubation with the appropriate restriction enzymes. The resulting DNA fragments were visualized on agarose or polyacrylamide gels. No statistically significant differences were observed in allelic and genotypic frequencies between SLE and healthy subjects (Fisher exact test). Nevertheless, the 2677A allelic frequency was lower in SLE patients with malar rash (0.007) compared with patients without this feature (0.04; P = 0.0054), while the frequency of this variant was higher in SLE patients with pleuritis (0.07) compared with patients without this feature (0.01; P = 0.0156). We suggest that although the ABCB1 polymorphisms do not directly interfere in SLE susceptibility, their evaluation, especially the 2677A allele, in other immunological processes may be interesting since they can interfere in clinical features of this disease.

O papel das proteínas reguladoras do complemento CD55/CD59 em células de sangue periférico de pacientes com lúpus eritematoso sistêmico

CD55 and CD59 are glycosylphosphatidylinositol-anchored proteins with regulatory properties on the activating cascades of the complement system. This regulation occurs through inhibition of the C3-convertase formation by CD55, and prevention of the terminal polymerization of the membrane attack complex by CD59. Deficiency in the expression of these proteins can be associated with increased susceptibility to complement-mediated cell death. Systemic lupus erythematosus patients with hemolytic anemia and lymphopenia seem to have an acquired deficiency of CD55 and CD59 proteins. However, the mechanisms involved in this deficiency and its impact on the clinical manifestation of SLE needs to be further investigated.

Glu298Asp eNOS polymorphism is not associated with SLE.

To examine potential associations of the Glu298Asp polymorphism in the coding region of the endothelial nitric oxide synthase (eNOS) gene with susceptibility to and clinical expression of systemic lupus erythematosus (SLE). One hundred thirteen consecutive patients of European ancestry with diagnosis of SLE, satisfying the American College of Rheumatology criteria, from the outpatient clinic of the Serviço de Reumatologia of the Hospital de Clínicas de Porto Alegre, and 206 healthy controls from the same geographic area were genotyped by polymerase chain reaction for the Glu298Asp polymorphism in the coding region of the eNOS gene. Clinical, demographic, and laboratorial data were collected. Clinical manifestations of SLE and related diseases were evaluated for the association with specific genotypes. The allelic and genotypic distribution of the Glu298Asp did not differ significantly between SLE patients and controls. We found no association of the polymorphism with lupus nephritis, antiphospholipid syndrome, cardiovascular disease (CVD), and risk factors to CVD. The presented results in this study do not provide support for a major role of eNOS Glu298Asp neither in the susceptibility for SLE or clinical manifestations, although there was low statistical power for the latter evaluation.