DNA methylation similarities in genes of black South Africans with systemic lupus erythematosus and systemic sclerosis

Background

Systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) are systemic autoimmune connective tissue diseases that share overlapping clinico-pathological features. It is highly probable that there is an overlap in epigenetic landscapes of both diseases. This study aimed to identify similarities in DNA methylation changes in genes involved in SLE and SSc. Global DNA methylation and twelve genes selected on the basis of their involvement in inflammation, autoimmunity and/or fibrosis were analyzed using PCR arrays in three groups, each of 30 Black South Africans with SLE and SSc, plus 40 healthy control subjects.

Results

Global methylation in both diseases was significantly lower (<25 %) than in healthy subjects (>30 %, p = 0.0000001). In comparison to healthy controls, a similar gene-specific methylation pattern was observed in both SLE and SSc. Three genes, namely; PRF1, ITGAL and FOXP3 were consistently hypermethylated while CDKN2A and CD70 were hypomethylated in both diseases. The other genes (SOCS1, CTGF, THY1, CXCR4, MT1-G, FLI1, and DNMT1) were generally hypomethylated in SLE whereas they were neither hyper- nor hypo-methylated in SSc.

Conclusions

SSc and SLE patients have a higher global hypomethylation than healthy subjects with specific genes being hypomethylated and others hypermethylated. The majority of genes studied were hypomethylated in SLE compared to SSc. In addition to the commonly known hypomethylated genes in SLE and SSc, there are other hypomethylated genes (such as MT-1G and THY-1) that have not previously been investigated in SLE and SSc though are known to be hypermethylated in cancer.     

DNA typing of HLA-DR antigens in systemic lupus erythematosus

HLA-DR typing is technically difficult in systemic lupus erythematosus (SLE), where patients have low numbers of peripheral B cells, often of poor viability and weak in antigenic expression. In this series, one third of SLE patients could not be HLA-DR typed by serological techniques, highlighting the potential for systematic bias in DR antigen assignment in studies of HLA and SLE. This potential bias was examined by comparing serological DR results with DNA-DR typing, achieved by examining Taq I fragments of DR, DQ, and DQ which permitted unequivocal DR phenotyping of all patients, including the 35% for whom conventional DR typing was technically impossible. This showed the success of serological DR antigen assignment was indeed nonrandom, with HLA-DR2 and -DR3 significantly more readily identifiable than DR5 and DRw13. Our study suggests that technical problems may well have contributed to conflicting reports regarding the association of DR2 or DR3 with SLE. Here, DNA-DR phenotyping showed HLA-DR3 is significantly (P<.05) associated with an increased risk for SLE (54% in 46 patients, 36% in 134 controls) and HLA-DR2 is not.     

Aberrant processing of oxidative DNA damage in systemic lupus erythematosus

Defective DNA damage processing has been reported in systemic lupus erythematosus (SLE). Vitamin C may modulate formation/removal of the oxidative DNA lesion 8-oxo-2'-deoxyguanosine (8-oxodG). Baseline levels of 8-oxodG measured in SLE serum, urine and PBMC DNA did not differ significantly from healthy subjects. In contrast to healthy subjects, no significant decrease in PBMC 8-oxodG or increase in urinary 8-oxodG was noted in vitamin C supplemented SLE patients. A significant, although attenuated, increase in serum 8-oxodG was detected in SLE patients, compared to healthy subjects. These data support putative abnormalities in the repair/processing of 8-oxodG in SLE.     

Complement and systemic lupus erythematosus

Complement is implicated in the pathogenesis of systemic lupus erythematosus (SLE) in several ways and may act as both friend and foe. Homozygous deficiency of any of the proteins of the classical pathway is causally associated with susceptibility to the development of SLE, especially deficiency of the earliest proteins of the activation pathway. However, complement is also implicated in the effector inflammatory phase of the autoimmune response that characterizes the disease. Complement proteins are deposited in inflamed tissues and, in experimental models, inhibition of C5 ameliorates disease in a murine model. As a further twist to the associations between the complement system and SLE, autoantibodies to some complement proteins, especially to C1q, develop as part of the autoantibody response. The presence of anti-C1q autoantibodies is associated with severe illness, including glomerulonephritis. In this chapter the role of the complement system in SLE is reviewed and hypotheses are advanced to explain the complex relationships between complement and lupus.     

DNA repair synthesis-related enzymes during spermatogenesis in the mouse

To assess whether uracil DNA glycosylase and dUTP nucleotidohydrolase (dUTPase) can be involved in repair-type DNA synthesis associated to crossing-over or induced by UV and X-ray treatments, we have studied these enzyme activities in male mouse germ cells at specific stages of differentiation.Although the highest uracil DNA glycosylase activity was observed in dividing germ cells (spermatogonia and preleptotene spermatocytes), some activity was also detected in meiotic (3.5%) and post-meiotic (1.0%) cells with a relative maximum of activity at pachytene stage (4.7%) when meiotic crossing-over takes place. These findings suggest that uracil DNA glycosylase is involved, in this biological system, in DNA replication and in repair-type DNA synthesis.dUTPase is present at all the stages of spermatogenesis studied but, unlike thymidylate synthetase which is mainly associated with replicating germ cells, dUTPase activity is maximal in spermatocytes at pachytene stages. The data reported suggest that, in this biological system, the main role of dUTPase is to degrade dUTP to prevent misincorporation of uracil into DNA during crossing-over, rather than to participate in the biosynthetic pathway of dTTP.     

Potential Z-DNA-forming elements in serum DNA from human systemic lupus erythematosus

DNA fragments were isolated from serum of a patient with systemic lupus erythematosus. The majority of the DNA was between 150 and 250 base pairs in length. The DNA was cloned into phage M13, and 10 recombinants were sequenced. The average GC content of the DNA was higher than total human DNA (43% against 38%), with some fragments as high as 63%. This DNA is rich in alternating purine-pyrimidine segments that are potentially Z-DNA-forming regions.     

Role of epigenetic DNA alterations in the pathogenesis of systemic lupus erythematosus

Epigenetic alternations in genomic DNA encompass cytosine methylation in cytosine and guanine (CpG) dinucleotide islands, which are usually extended in the promoter and first exon of genes. The DNA methylation is carried out by DNA methyltransferases (DNMT) and it serves as an epigenetic method of gene expression modulation. The epigenetic alternations in genomic DNA have been implicated in the development of malignant and autoimmune diseases. The epigenetic aberration in regulatory DNA sequences may also be responsible for the emergence of changes in the immune system in patients with systemic lupus erythematosus (SLE). The agents 5-azacytidine (azacitidine) and 5-aza-2'-deoxycytidine (decitabine) belong to inhibitors of methyltransferase. These compounds affect the methylation level of promoter sequences and cause phenotypic changes in peripheral blood mononuclear cells (PBMC), which are similar to those observed in PBMC of SLE patients. The lack of methylcytosine in CpG dinucleotides may be responsible for the antigenic properties of microbial DNA. The presence of low-apoptotic methylated DNA fragments has been identified in plasma of SLE patients. These DNA fragments exhibit antigenic properties and may elicit the humoral response responsible for the flare of SLE. The low methylation of CpG residues in the regulatory sequences may also contribute to the elevated expression of human endogenous retroviruses (HERVs) in PBMC of SLE patients. The HERV components exhibit a profound similarity with nuclear antigens and may be responsible for the enhancement of the production of anti-antinuclear antibodies (ANA). Recent advances in the investigation of epigenetic DNA changes have formed the basis of improved understanding of etiopathogenesis of SLE, which may thereby facilitate improvement in therapeutic principles of this disease.     

系统性红斑狼疮合并隐球菌脑膜炎1例

1临床资料 患者女,42岁。因“反复关节痛、口腔溃疡4年,头痛10d”于2008年1月急诊入院,患者4a前因反复关节痛、口腔溃疡,当地医院查自身抗体：ANA（＋）,nRNP／Sm、SSA、组蛋白均阳性。血常规中白细胞2．4×10^9／L,红细胞3．42×10^12／L,血红蛋白73g/L。诊断为系统性红斑狼疮,给予强的松40mg／d口服1个月后病情好转,3a内逐渐将强的松减量为10mg／d维持已1a。     

Deoxyribonuclease-Inhibitory antibodies in systemic lupus erythematosus

Deoxyribonucleases (DNases) are key enzymes for digesting DNA. Abnormalities in the function of these enzymes may contribute to the development of anti-DNA antibodies in systemic lupus erythematosus (SLE). In this study, we used bovine DNase 1-coated ELISA plates to screen anti-DNase antibodies in SLE patients. About 62% of the sera of SLE patients (63/101) were positive for anti-DNase antibodies compared to only 8% of normal controls (8/98). A positive correlation was also found between the concentrations of anti-DNase and anti-DNA antibodies in sera of SLE patients. Affinity-purified anti-DNase immunoglobulin G (IgG) from pooled sera of SLE patients bound to bovine DNase as well as DNA. A synthetic peptide, corresponding to the catalytic site of DNase, was able to completely inhibit the binding of anti-DNase IgG to DNase. In addition to bovine DNase, the anti-DNase IgG also bound to and inhibited the enzymatic activities of DNase present in streptococcal supernatants and human urine. Immunization of lupus-prone NZB/NZW mice with bovine DNase enhanced the production of anti-DNase and DNA antibodies, and accelerated the occurrence of proteinuria. Taken together, these results suggest that DNase-inhibitory antibodies which recognize a conserved epitope near the catalytic site of DNase may act in the pathogenesis of SLE.     

Cytokine disturbances in systemic lupus erythematosus

The pathogenesis of systemic lupus erythematosus (SLE) is complex, and the resulting disease manifestations are heterogeneous. Cytokine dysregulation is pervasive, and their protein and gene expression profiles may serve as markers of disease activity and severity. Importantly, biologic agents that target specific cytokines may represent novel therapies for SLE. Four cytokines (IL-6, TNFα, IFNα, and BLyS) are being evaluated as therapeutic targets in SLE. The present review will examine the roles of each of these cytokines in murine and human SLE, and will summarize results from clinical trials of agents that target these cytokines.     

Lipid peroxidation in systemic lupus erythematosus

Lipid peroxidation is an important process in oxygen toxicity. Free radicals inflict this damage by attacking polyunsaturated fatty acids, thus setting off a deleterious chain reaction that ultimately results in their disintegration into malondialdehye, 4 hydroxy-2-nonenal and other harmful by-products. Peroxidation of lipids has been implicated in several diseases including systemic lupus erythematosus (SLE). SLE is an autoimmune disorder with unknown aetiology, characterized by the presence of autoantibodies to self-antigens. There is a significant increase in the production of free radicals like superoxide and hydroxyl radicals in SLE. Indices of lipid peroxidation, like conjugated dienes, malondialdehyde, 8-isoprostaglandin F2 alpha are significantly elevated in SLE. Increased ceruloplasmin levels and decreased transferrin levels in the sera of SLE patients have also been described. The activities of the antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase and the amounts of the antioxidant reduced glutathione are also significantly altered in this disease. In addition, there are significant changes in the essential fatty acid profile in the sera of those affected with the disease. In animal models of the disease, immunization of mice with peptides derived from autoantigens induces SLE like disease. Immunization with an oxidatively modified autoantigen led to the rapid development of autoimmunity compared to immunization with the unmodified autoantigen. Thus, oxidative damage appears to play an important role in SLE pathogenesis.     

Anti-elastin antibodies in systemic lupus erythematosus

Immunological response to elastin-derived peptides may cause tissue damage with subsequent degradation of the elastic fibres. Therefore, an incidence of anti-elastin antibodies in sera of patients with the systemic lupus erythematosus was studied. Sixty sera from 50 patients with systemic lupus erythematosus and 50 healthy subjects were assayed with dot-immunobinding technique. Titre 1:10 was considered diagnostically significant. Anti-elastin antibodies were diagnosed in 19 patients (31%) where as they were absent in the control group. In all cases anti-elastin antibodies were IgG.     

Effects of the mTOR and AKT genes polymorphisms on systemic lupus erythematosus risk

Molecular Biology Reports - The systemic lupus erythematosus (SLE) is an autoimmune disease, leading to inflammatory response and systemic consequences. The mammalian target of rapamycin (mTOR) is...     

Linking susceptibility genes and pathogenesis mechanisms using mouse models of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) represents a challenging autoimmune disease from a clinical perspective because of its varied forms of presentation. Although broad-spectrum steroids remain the standard treatment for SLE, they have many side effects and only provide temporary relief from the symptoms of the disease. Thus, gaining a deeper understanding of the genetic traits and biological pathways that confer susceptibility to SLE will help in the design of more targeted and effective therapeutics. Both human genome-wide association studies (GWAS) and investigations using a variety of mouse models of SLE have been valuable for the identification of the genes and pathways involved in pathogenesis. In this Review, we link human susceptibility genes for SLE with biological pathways characterized in mouse models of lupus, and discuss how the mechanistic insights gained could advance drug discovery for the disease.KEY WORDS: Lupus, SLE, Human genetics, Mouse models, Susceptibility genes     

Differential contribution of C4 and HLA-DQ genes to systemic lupus erythematosus susceptibility

The particular histocompatability antigen (HLA) gene(s) that may confer systemic lupus erythematosus (SLE) susceptibility remains unknown. In the present study, 58 unrelated patients and 69 controls have been analyzed for their class I and class II serologic antigens, class II (DR and DQ) DNA restriction fragment length polymorphism, their deduced DQA1 and B1 exon 2 nucleotide sequences and their corresponding amino acid residues. By using the etiologic fraction () as an almost absolute measure of the strongest linkage disequilibrium of an HLA marker to the putative SLE susceptibility locus, it has been found that the strength of association of the HLA marker may be quantified as follows: DQA1^*0501 (associated to DR3) or DQB1^*0201 (associated to DR3) > non Asp 57 DQ/Arg 52 DQ > DR3 > non Asp 57 DQ. Thus, molecular HLA DQ markers tend to be more accurate as susceptibility markers than the classical serologic markers (DR3). However, dominant or recessive non Asp 57 DQ susceptibility theories, as previously postulated for insulin-dependent diabetes mellitus, do not hold in our SLE nephritic population; indeed, three patients bear neither Arg 52 DQ nor Asp 57 DQ susceptibility factors. On the other hand, nonsusceptibility factors are included in our population in the A30B18CF130-DR3DQ2(Dw25) haplotype and not in A1B8CS01-DR3DQ2(Dw24); this distinctive association has also been recorded in type I diabetes mellitus and may reflect the existence of common pathogenic HLA-linked factors for both diseases only in the A30B18CF10DR3DQ2-(Dw 25) haplotype. Finally, the observed increase of deleted C4 genes (and not null C4 proteins) in nephritic patients shows that C4 genes are disease markers, but probably without a pathogenic role.