Mechanism of action of DNA-hydrolyzing antibodies to DNA from blood of patients with systemic lupus erythematosus

Four fractions of IgG antibodies to native DNA (nDNA) were obtained from blood of patients with systemic lupus erythematosus (SLE). These antibodies displayed a thermostable DNA-hydrolyzing activity and were different in affinity for DNA-cellulose and sorption on DEAE-cellulose. DNA-hydrolyzing antibodies to nDNA are metal-dependent endonucleases, cause mainly single-strand breaks in DNA, and are active over a wide range of pH. By atomic-force microscopy, three-dimensional images of DNA complexes with DNA-hydrolyzing antibodies to nDNA were obtained with nanometer resolution, and a nonprocessive action mechanism was shown for the DNase activity of antibodies to nDNA.     

Inhibition of adenovirus DNA synthesis in vitro by sera from patients with systemic lupus erythematosus

Sera containing antinuclear antibodies from patients with systemic lupus erythematosus (SLE) and related disorders were tested for their effect on the synthesis of adenovirus (Ad) DNA in an in vitro replication system. After being heated at 60 degrees C for 1 h, some sera from patients with SLE inhibited Ad DNA synthesis by 60 to 100%. Antibodies to double-stranded DNA were present in 15 of the 16 inhibitory sera, and inhibitory activity copurified with anti-double-stranded DNA in the immunoglobulin G fraction. These SLE sera did not inhibit the DNA polymerases alpha, beta, gamma and had no antibody to the 72,000-dalton DNA-binding protein necessary for Ad DNA synthesis. The presence of antibodies to single-stranded DNA and a variety of saline-extractable antigens (Sm, Ha, nRNP, and rRNP) did not correlate with SLE serum inhibitory activity. Methods previously developed for studying the individual steps in Ad DNA replication were used to determine the site of inhibition by the SLE sera that contained antibody to double-stranded DNA. Concentrations of the SLE inhibitor that decreased the elongation of Ad DNA by greater than 85% had no effect on either the initiation of Ad DNA synthesis or the polymerization of the first 26 deoxyribonucleotides.     

A subset of lupus anti-DNA antibodies cross-reacts with the NR2 glutamate receptor in systemic lupus erythematosus.

In systemic lupus erythematosus, antibodies against double-stranded DNA are a major contributor to renal disease. We have previously demonstrated that the pentapeptide Asp/Glu-Trp-Asp/Glu-Tyr-Ser/Gly is a molecular mimic of double-stranded DNA. This sequence is also present in the extracellular domain of murine and human NMDA (N-methyl-D-aspartate) receptor subunits NR2a and NR2b. Here we show that the NR2 receptor is recognized by both murine and human anti-DNA antibodies. Moreover, anti-DNA antibodies with this cross-reactivity mediate apoptotic death of neurons in vivo and in vitro. Finally, we show that the cerebrospinal fluid of a patient with systemic lupus erythematosus contains these antibodies and also mediates neuronal death via an apoptotic pathway. These observations indicate that lupus antibodies cross-react with DNA and NMDA receptors, gain access to cerebrospinal fluid and may mediate non-thrombotic and non-vasculitic abnormalities of the central nervous system.     

Autoantibodies from patients with systemic lupus erythematosus can affect DNA and RNA synthesis in cultured cells

Sera reacting positively for anti-DNA antibodies from systemic lupus erythematosus (SLE) patients were tested for their effect on DNA and RNA synthesis in permeabilized cultured cells and isolated nuclei. The immunoglobulin fraction obtained by ammonium sulfate precipitation of serum was shown to exert considerable influence on DNA and RNA synthesis in cultured cells and nuclei. A component of this antibody population is anti-DNA. These antibodies exert different effects on DNA template activity which is a function of their conformational specificity. Intracellular penetration of autoantibodies as noted in SLE may be one of the reasons for clinical manifestations of disease in these patients.     

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.     

Neuropsychological patterns in systemic lupus erythematosus patients with depression

Thirteen patients with systemic lupus erythematosus and depression (Depressed-SLE), 10 Depressed-Control subjects, and 25 Healthy Control subjects completed cognitive testing and self-report questionnaires of pain, depression, and fatigue. The Depressed-SLE group scored higher on the American College of Rheumatology Neuropsychological Battery for systemic lupus erythematosus cognitive impairment index compared to Depressed-Control and Healthy Control subjects (p < 0.05 and p < 0.02, respectively). No correlations between cognitive impairment and pain, fatigue, or perceived cognitive failures were observed in the Depressed-SLE participants. Moderate agreement (86.4%) was found between a comprehensive neuropsychology battery cognitive impairment index and the ACR-SLE impairment index in the Depressed-SLE patients. Overall, the magnitude and pattern of cognitive impairment in Depressed-SLE patients cannot be explained by depression alone.     

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.     

High prevalence of autoantibodies to RNA helicase A in Mexican patients with systemic lupus erythematosus

Introduction

Autoantibodies to RNA helicase A (RHA) were reported as a new serological marker of systemic lupus erythematosus (SLE) associated with early stage of the disease. Anti-RHA and other autoantibodies in Mexican SLE patients and their correlation with clinical and immunological features were examined.

Methods

Autoantibodies in sera from 62 Mexican SLE patients were tested by immunoprecipitation of ³⁵S-labeled K562 cell extract and enzyme-linked immunosorbent assay (anti-U1RNP/Sm, ribosomal P, β2GPI, and dsDNA). Anti-RHA was screened based on the immunoprecipitation of the 140-kDa protein, the identity of which was verified by Western blot using rabbit anti-RHA serum. Clinical and immunological characteristics of anti-RHA-positive patients were analyzed.

Results

Anti-RHA was detected in 23% (14/62) of patients, a prevalence higher than that of anti-Sm (13%, 8/62). Prevalence and levels of various autoantibodies were not clearly different between anti-RHA (+) vs. (-) cases, although there was a trend of higher levels of anti-RHA antibodies in patients without anti-U1RNP/Sm (P = 0.07). Both anti-RHA and -Sm were common in cases within one year of diagnosis; however, the prevalence and levels of anti-RHA in patients years after diagnosis did not reduce dramatically, unlike a previous report in American patients. This suggests that the high prevalence of anti-RHA in Mexican patients may be due to relatively stable production of anti-RHA.

Conclusions

Anti-RHA was detected at high prevalence in Mexican SLE patients. Detection of anti-RHA in races in which anti-Sm is not common should be clinically useful. Racial difference in the clinical significance of anti-RHA should be clarified in future studies.     

Substrate specificity of IgGs with peroxidase and oxidoreductase activities from sera of patients with systemic lupus erythematosus and multiple sclerosis

The analysis of IgGs to protect humans from oxidative stress through oxidation of harmful compounds was carried out. We have compared here for the first time peroxidase (in the presence of H₂O₂) and oxidoreductase (in the absence of H₂O₂) activities of IgGs from sera of healthy humans and patients with systemic lupus erythematosus (SLE) and multiple sclerosis (MS). In addition, substrate specificity of SLE and MS IgG preparations in the oxidation of different compounds was analyzed: 2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS), 3,3′‐diaminobenzidine (DAB), homovanillic acid (HVA), o‐phenylenediamine (OPD), α‐naphthol, 3‐amino‐9‐ethylcarbazole (AEC), p‐hydroquinone (pHQ), and adrenaline. IgGs of healthy humans and SLE and MS patients oxidized DAB, ABTS, and OPD due to their peroxidase and oxidoreductase activities, while other compounds were substrates of IgGs only in the presence of H₂O₂: adrenaline was not oxidized by both activities of IgGs. The average SLE IgGs peroxidase activity increased statistically significant in comparison with abzymes from healthy humans in the order (‐fold): OPD (1.2) <  DAB (1.7) < α‐naphtol (2.2) ≤ AEC (2.4) < ABTS (4.5) < 5‐ASA (10.6), while with oxidoreductase activity: OPD (1.8) ≤ DAB (2.1‐fold) < ABTS (5.0). Only HVA was oxidized by IgGs with peroxidase activity of healthy donors faster than by SLE (1.3‐fold) and MS abzymes (2.4‐fold). In the oxidation of several substrates, only three IgGs of MS patients were used. The data speak of a tendency to increase the peroxidase and oxidoreductase activities of MS IgGs in comparison with healthy donors, but to a lesser extent: OPD (1.1 to 1.2‐fold) ≤ ABTS (1.2 to 1.8‐fold). It was shown that development of SLE and MS leads to increase in peroxidase and oxidoreductase activities of IgGs toward most of classical substrates. Thus, abzymes can serve as an additional factor of reactive oxygen species detoxification protecting of patients with SLE and MS from some harmful compounds somewhat better than healthy peoples.     

Increased serum interleukin 17 in patients with systemic lupus erythematosus

Interleukin 17 (IL-17) is a Th17 cytokine associated with inflammation, autoimmunity and defense against some bacteria, it has been implicated in many chronic autoimmune diseases including psoriasis, multiple sclerosis and systemic sclerosis. However, whether IL-17 plays a role in the pathogenesis of systemic lupus erythematosus (SLE) remains unclear. In the present study, we aimed to investigate the serum IL-17 level in patients with SLE and it’s associations with disease manifestations and activity. Fifty-seven patients with SLE and 30 healthy volunteers were recruited. Serum IL-17 levels were examined by enzyme linked immunosorbent assay (ELISA). Statistic analyzes were performed by SPSS 10.01. Results show that serum IL-17 levels were significantly elevated in SLE patients as compared with normal controls. Nevertheless, no associations of serum IL-17 level with clinical and laboratory parameters were found; no significant difference regarding serum IL-17 level between SLE patients with nephritis and those without nephritis was found; no significant difference was found between Less active SLE and More active SLE; Correlation analysis between serum IL-17 levels and SLEDAI showed no association. Taken together, our results indicate increased serum IL-17 levels in SLE patients, suggesting that this cytokine may trigger the inflammatory process in SLE. However, no associations of serum IL-17 level with disease manifestations were found. Therefore, further studies are required to confirm this preliminary data.     

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.     

Predictors of clinical outcomes in patients with neuropsychiatric systemic lupus erythematosus

IntroductionNeuropsychiatric systemic lupus erythematosus (NPSLE), a serious organ disorder with a variety of symptoms, has diverse therapeutic outcomes because of the variability of NPSLE manifestations. A comprehensive association study of NPSLE among clinical and immunopathogenic aspects and outcomes has not been conducted.MethodsWe analyzed the laboratory data, NPSLE symptoms, and clinical outcomes at 1 yr post-treatment and the profiles of 27 cytokines, chemokines and growth factors in cerebrospinal fluid (CSF) samples using the Bio-Plex Human 27-plex panel from 28 NPSLE patients. Univariate and multivariable competing risks regression analyses were used to determine the predictive factors of clinical response. We also tried to predict the outcome of NPSLE by the 27 cytokines/chemokines/growth factors using a weighted-voting (WV) algorithm.ResultsOf the two males and 26 females (92.9%), 16 were non-responders at 1 yr post-treatment; in the final model, the independent predictors of non-responders were longer disease durations of SLE (odds ratio [OR]: 1.490, 95% confidence interval [CI]: 1.143–2.461, p = 0.0003) and patients with more than one NPSLE symptom types (OR: 15.14, 95% CI: 1.227–452.1, p = 0.0334). The pretreatment CSF interleukin (IL)-6, IL-10, interferon-gamma (IFN-γ) and tumor necrosis factor-alpha (TNF-α) levels were significantly higher in the non-responders (p = 0.0207, p = 0.0054, p = 0.0242 and p = 0.0077, respectively). We identified six “minimum predictive markers:” IL-10, TNF-α, IL-6, IFN-γ, IL-4 and IL-13 by a WV algorithm that showed the highest accuracy (70.83%) and highest Matthews correlation coefficient (54.23%).ConclusionsWe have devised a numerical prediction scoring system that was able to separate the non-responders from responders. The patients with longer disease durations of SLE and those with more than one NPSLE symptom types had poorer outcomes. Our findings may indicate both the importance of making a diagnosis at an earlier phase for better therapeutic response and the usefulness of measuring multiple cytokines to predict NPSLE therapeutic outcomes.