Proteomic analyses and identification of arginine methylated proteins differentially recognized by autosera from anti-Sm positive SLE patients

Background

Antibodies against spliceosome Sm proteins (anti-Sm autoantibodies) are specific to the autoimmune disease systemic lupus erythematosus (SLE). Anti-Sm autosera have been reported to specifically recognize Sm D1 and D3 with symmetric di-methylarginines (sDMA). We investigated if anti-Sm sera from local SLE patients can differentially recognize Sm proteins or any other proteins due to their methylation states.

Results

We prepared HeLa cell proteins at normal or hypomethylation states (treated with an indirect methyltransferase inhibitor adenosine dialdehyde, AdOx). A few signals detected by the anti-Sm positive sera from typical SLE patients decreased consistently in the immunoblots of hypomethylated cell extracts. The differentially detected signals by one serum (Sm1) were pinpointed by two-dimensional electrophoresis and identified by mass spectrometry. Three identified proteins: splicing factor, proline- and glutamine-rich (SFPQ), heterogeneous nuclear ribonucleoprotein D-like (hnRNP DL) and cellular nucleic acid binding protein (CNBP) are known to contain methylarginines in their glycine and arginine rich (GAR) sequences. We showed that recombinant hnRNP DL and CNBP expressed in Escherichia coli can be detected by all anti-Sm positive sera we tested. As CNBP appeared to be differentially detected by the SLE sera in the pilot study, differential recognition of arginine methylated CNBP protein by the anti-Sm positive sera were further examined. Hypomethylated FLAG-CNBP protein immunopurified from AdOx-treated HeLa cells was less recognized by Sm1 compared to the CNBP protein expressed in untreated cells. Two of 20 other anti-Sm positive sera specifically differentiated the FLAG-CNBP protein expressed in HeLa cells due to the methylation. We also observed deferential recognition of methylated recombinant CNBP proteins expressed from E. coli by some of the autosera.

Conclusion

Our study showed that hnRNP DL and CNBP are novel antigens for SLE patients and the recognition of CNBP might be differentiated dependent on the level of arginine methylation.     

A diepitopic sequential oligopeptide carrier (SOCn) as mimic of the sm autoantigen: synthesis, conformation and biological assays.

Anti-Sm (Sm: U1-U6 RNA-protein complex) antibodies are usually considered highly specific for systemic lupus erythematosus (SLE), while anti-U1RNP (U1RNP: U1RNA-protein complex) are thought of as diagnostic criteria for the mixed connective tissue disease (MCTD). However, both antibody specificities coexist in SLE and MCTD, in varying percentages. Although the anti-Sm/anti-U1RNP immunological cross-reactivity has been initially attributed to a common motif, PPXY(Z)PP (where X, Y, Z are various amino acids), found in the Sm, U1-A and U1-C autoantigens, it appears that the conformational features of the Sm epitopes also play an important role in the immunoreactivity. The PPGMRPP and PPGIRGP main epitopes of the Sm antigen were coupled in duplicate to the tetrameric Ac-(Lys-Aib-Gly)4-OH, SOC4, carrier to form the [(PPGMRPP)2, (PPGIRGP)2]-SOC4 construct as a mimic of the native Sm. It was found that: (i) the 3(10) helical structure of SOC4 allows the epitopes to adopt an exposed orientation, similar to their free forms, that facilitates their recognition from the anti-Sm antibodies, and (ii) the U1-RNP cross-reactivity is minimized.     

Association of cerebrospinal fluid anti-Sm antibodies with acute confusional state in systemic lupus erythematosus

Introduction

Neuropsychiatric manifestation in systemic lupus erythematosus (NPSLE) is one of the most serious complications of the disease. Previous studies revealed the strong association between serum anti-Sm and organic brain syndrome, consisting mainly of acute confusional state (ACS) of diffuse psychiatric/neuropsychological syndromes (diffuse NPSLE). However, the precise mechanism by which anti-Sm causes diffuse NPSLE remains unclear. Of note, recent studies demonstrated that anti-U1 RNP antibodies (anti-RNP) in cerebrospinal fluid (CSF) are associated with NPSLE. The present study was designed to explore the association of anti-Sm antibodies in CSF with NPSLE.

Methods

Paired serum and CSF specimens were obtained from 72 patients with NPSLE (49 with diffuse NPSLE, 23 with neurological syndromes or peripheral neuropathy (focal NPSLE) and from 22 control patients with non-SLE neurological diseases. Sera were also obtained from 41 patients with active SLE without neuropsychiatric manifestations (non-NPSLE). Anti-Sm and anti-RNP were measured by enzyme-linked immunosorbent assay (ELISA). Blood-brain barrier (BBB) function and intrathecal anti-Sm production were evaluated by Q albumin and CSF anti-Sm index, respectively. Binding of anti-Sm to neuroblastoma cell lines SK-N-MC and Neuro2a was examined by flow cytometry and by cell ELISA.

Results

Anti-Sm and anti-RNP in CSF and sera were elevated in NPSLE compared with non-SLE control. CSF anti-Sm, but not CSF anti-RNP, was significantly elevated in ACS compared with non-ACS diffuse NPSLE or with focal NPSLE. By contrast, there were no significant differences in serum anti-Sm or anti-RNP among subsets of NPSLE and non-NPSLE. Whereas there were no significant differences in CSF anti-Sm index, Q albumin was elevated in ACS compared with non-ACS or with focal NPSLE. Notably, CSF anti-Sm was correlated with Q albumin (r = 0.2373, P = 0.0447) or with serum anti-Sm (r = 0.7185, P <0.0001) in 72 patients with NPSLE. Finally, monoclonal anti-Sm and purified human anti-Sm bound to the surface of SK-N-MC and Neuro2a.

Conclusions

These results demonstrate that the elevation of CSF anti-Sm through transudation from systemic circulation due to damaged BBB plays a critical role in the pathogenesis of ACS. More importantly, the data indicate that anti-Sm is yet another autoantibody with presumed neural toxicity, but might not be the last.     

A new immunoprecipitation-real time quantitative PCR assay for anti-Th/To and anti-U3RNP antibody detection in systemic sclerosis

Introduction

Classic anti-nucleolar antibodies anti-Th/To and U3 ribonucleoprotein (-U3RNP) can help in the diagnosis, prediction of organ involvement and prognosis in systemic sclerosis (SSc); however, no validated commercial assay is available. We aimed at establishing a novel quantitative real time PCR (qPCR) method to detect these antibodies.

Methods

Standard immunoprecipitation (IP) was performed using K562 cell extract and RNA components were extracted. cDNA was reverse transcribed from RNA components and Th RNA and U3 RNA were detected by qPCR using custom primers. Cycle threshold (Ct) values were compared in a titration experiment to determine the assay efficacy. The new assay was evaluated by testing 22 anti-Th/To and 12 anti-U3RNP positive samples in addition to 88 controls, and the results were compared with IP as a gold standard.

Results

By testing serial 1:8 dilutions of cell lysate as the substrate in the IP step, RNA extracted after IP, and its derived cDNA, linear dose response curves were noted for both anti-Th/To and -U3RNP. With every dilution, Ct values changed approximately three as expected, reflecting the eight-fold difference of cDNA. The Ct difference between positive and negative samples was 8 to 13, which was similar throughout the dilutions. In the specificity analysis, the Ct values of positive samples were clearly different from the negative groups and the results by qPCR had a near perfect correlation with IP.

Conclusions

Our new method readily detects these two clinically important antibodies in SSc. Making tests for anti-Th/To and -U3RNP antibodies widely available to clinicians should be helpful in the diagnosis and follow-up of SSc patients.     

Prognostic significance of hemoglobin A1c level in patients hospitalized with coronary artery disease. A systematic review and meta-analysis

Background

To estimate the incidence of complications, life expectancy and diabetes related mortality in the Mexican diabetic population over the next two decades using data from a nation-wide, population based survey and the United Kingdom Prospective Diabetes Study (UKPDS) outcome model

Methods

The cohort included all patients with type 2 diabetes evaluated during the National Health and Nutrition Survey (ENSANut) 2006. ENSANut is a probabilistic multistage stratified survey whose aim was to measure the prevalence of chronic diseases. A total of 47,152 households were visited. Results are shown stratified by gender, time since diagnosis (> or ≤ to 10 years) and age at the time of diagnosis (> or ≤ 40 years).

Results

The prevalence of diabetes in our cohort was 14.4%. The predicted 20 year-incidence for chronic complications per 1000 individuals are: ischemic heart disease 112, myocardial infarction 260, heart failure 113, stroke 101, and amputation 62. Furthermore, 539 per 1000 patients will have a diabetes-related premature death. The average life expectancy for the diabetic population is 10.9 years (95%CI 10.7-11.2); this decreases to 8.3 years after adjusting for quality of life (CI95% 8.1-8.5). Male sex and cases diagnosed after age 40 have the highest risk for developing at least one major complication during the next 20 years.

Conclusions

Based on the current clinical profile of Mexican patients with diabetes, the burden of disease related complications will be tremendous over the next two decades.     

The PPGMRPP repetitive epitope of the Sm autoantigen: Antigenic specificity induced by conformational changes. Application of the Sequential Oligopeptide Carriers (SOCs)

Summary The PPGMRPP sequence, found in several copies in the Sm and U1RNP autoantigens, is the main target of anti-Sm and anti-U1RNP antibodies in systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD) patient's sera. It is also recognized, to a lower extent, by anti-Ro/SSA and anti-La/SSB specificities. The PPGMRPP-NH₂ peptide amide and the PPGMRPP peptide, which is bound to a pentameric sequential oligopeptide carrier (SOC₅), were examined by¹H-NMR spectroscopy and ELISA assays, using sera from patients with autimmune rheumatic diseases. Among the three main conformers found for the free PPGMRPP, the extended one was also identified for PPGMRPP-NH₂ and (PPGMRPP)₅-SOC₅. This can be attributed to the absence of ionic interactions between the Arg-guanidinium and the carboxylate group in the amide and SOC₅-bound forms of the peptide. Immunoassays using sera from various specificities showed an enhanced anti-Sm and anti-U1RNP recognition of PPGMRPP-NH₂ and (PPGMRPP)₅-SOC₅, and lowering of the anti-Ro/SSA and anti-La/SSB reactivity. The presence of multiple conformers of free PPGMRPP may explain the unexpected cross-reactivity to the anti-Ro/La positive sera, while the prevalence of the extended conformation in PPGMRPP-NH₂ and (PPGMRPP)₅-SOC₅ is mainly responsible for the enhanced recognition from the anti-Sm and anti-U1RNP autoantibodies. it is concluded that the antigenic specificity of PPGMRPP-NH₂ and (PPGMRPP)₅-SOC₅ is mainly induced by conformational changes resulting from the conversion of the C-terminal carboxylate group to the amide form.     

Interferon-induced protein IFIT4 is associated with systemic lupus erythematosus and promotes differentiation of monocytes into dendritic cell-like cells

Introduction

Using oligonucleotide microarray, many IFN-inducible genes have been found to be highly expressed in peripheral blood mononuclear cells (PBMCs) from most patients with systemic lupus erythematosus (SLE). Among these IFN-inducible genes, IFN-induced protein with tetratricopeptide repeats 4 (IFIT4) is a novel gene whose function is unknown.

Methods

In this study we examined the role played by IFIT4 in monocyte differentiation and the correlation between IFIT4 expression and the clinical manifestation of SLE. To this end, we used plasmid transfection, flow cytometry, mixed leucocyte responses, ELISA, quantitative RT-PCR and Western blotting.

Results

We found that both IFIT4 mRNA and protein expression levels were significantly higher in PBMCs and monocytes from SLE patients than in those from healthy control individuals. IFIT4 expression was positively correlated with antinuclear antibodies, anti-double-stranded DNA, and anti-Sm auto-immune antibodies in SLE. Patients with SLE exhibiting higher expression of IFIT4 had a higher prevalence of leucopenia, thrombocytopenia and C3/C4 decrease. IFIT4 protein was localized exclusively to the cytoplasm, and it was significantly upregulated by IFN-α in normal PBMCs. To determine the role played by IFIT4 in monocyte differentiation, the monocytic cell line THP-1 was transfected with pEGFP-IFIT4 expression plasmid and stimulated with granulocyte-macrophage colony-stimulating factor/IL-4 to generate IFIT4-primed dendritic cell-like cells (DCLCs). IFIT4-primed DCLCs acquired morphological characteristics of dendritic cells more quickly, with greater resemblance to dendritic cells, as compared with DCLCs primed with pEGFP-C1 control plasmid trasfection. Furthermore, they exhibited higher expressions of CD40, CD86, CD80, HLA-DR and CD83, along with lower expression of CD14; increased IL-12 secretion; and an increased ability to stimulate T-cell proliferation. In addition, IFIT4-primed DCLCs enhanced IFN-γ secretion (about 2.4-fold) by T cells compared with controls.

Conclusion

Our findings suggest that IFIT4 might play roles in promoting monocyte differentiation into DCLCs and in directing DCLCs to modulate T-helper-1 cell differentiation; these actions might contribute to the autoimmunity and pathogenesis of SLE.     

The PPGMRPP repetitive epitope of the Sm autoantigen: Antigenic specificity induced by conformational changes. Application of the Sequential Oligopeptide Carriers (SOCs)

The PPGMRPP sequence, found in several copies in the Sm and U1RNPautoantigens, is the main target of anti-Sm and anti-U1RNP antibodies insystemic lupus erythematosus (SLE) and mixed connective tissue disease(MCTD) patient's sera. It is also recognized, to a lower extent, byanti-Ro/SSA and anti-La/SSB specificities. The PPGMRPP-NH₂peptide amide and the PPGMRPP peptide, which is bound to a pentamericsequential oligopeptide carrier (SOC₅), were examined by¹H-NMR spectroscopy and ELISA assays, using sera from patientswith autoimmune rheumatic diseases. Among the three main conformers foundfor the free PPGMRPP, the extended one was also identified for PPGMRPP-NH₂ and (PPGMRPP)₅-SOC₅.This can be attributed to the absence of ionic interactions between theArg-guanidinium and the carboxylate group in the amide andSOC₅-bound forms of the peptide. Immunoassays using sera fromvarious specificities showed an enhanced anti-Sm and anti-U1RNP recognitionof PPGMRPP-NH₂ and(PPGMRPP)₅-SOC₅, and lowering of the anti-Ro/SSAand anti-La/SSB reactivity. The presence of multiple conformers of freePPGMRPP may explain the unexpected cross-reactivity to the anti-Ro/Lapositive sera, while the prevalence of the extended conformation inPPGMRPP-NH₂ and (PPGMRPP)₅-SOC₅is mainly responsible for the enhanced recognition from the anti-Sm andanti-U1RNP autoantibodies. It is concluded that the antigenic specificity ofPPGMRPP-NH₂ and (PPGMRPP)₅-SOC₅ ismainly induced by conformational changes resulting from the conversion ofthe C-terminal carboxylate group to the amide form.     

Mutations in genes encoding complement inhibitors CD46 and CFH affect the age at nephritis onset in patients with systemic lupus erythematosus

Introduction

Inherited deficiencies of several complement components strongly predispose to systemic lupus erythematosus (SLE) while deficiencies of complement inhibitors are found in kidney diseases such as atypical hemolytic uremic syndrome (aHUS).

Methods

The exons of complement inhibitor genes CD46 and CFH (factor H) were fully sequenced using the Sanger method in SLE patients with nephritis originating from two cohorts from southern and mid Sweden (n = 196). All identified mutations and polymorphisms were then analyzed in SLE patients without nephritis (n = 326) and in healthy controls (n = 523).

Results

We found nonsynonymous, heterozygous mutations in CFH in 6.1% patients with nephritis, in comparison with 4.0% and 5.4% in patients without nephritis and controls, respectively. No associations of SLE or nephritis with common variants in CFH (V62I/Y402H/E936D) were found. Furthermore, we found two nonsynonymous heterozygous mutations in CD46 in SLE patients but not in controls. The A353V polymorphism, known to affect function of CD46, was found in 6.6% of nephritis patients versus 4.9% and 6.1% of the non-nephritis SLE patients and controls. The presence of mutations in CD46 and CFH did not predispose to SLE or nephritis but was associated with earlier onset of nephritis. Furthermore, we found weak indications that there is one protective and one risk haplotype predisposing to nephritis composed of several polymorphisms in noncoding regions of CD46, which were previously implicated in aHUS.

Conclusions

SLE nephritis is not associated with frequent mutations in CFH and CD46 as found in aHUS but these may be modifying factors causing earlier onset of nephritis.     

Les manifestations hématologiques du lupus érythémateux systémique. A propos de 70 cas dans une série de 80 LES

Abstract

Systemic lupus erythematosus is a non-organ specific auto-immune disease which commonly has haematological manifestations. The aim of this study was to assess the epidemiological aspects of haematological manifestations among 80 patients with systemic lupus erythematosus (SLE).

Methods

A retrospective study of 80 SLE patients covering the period between 1990 and May 2005.

Results

From among the 80 patients with SLE, 70 had haematological manifestations, of which 65 women and 5 men. Average age was 32.41 years. The most commonly-observed haematological manifestation was anaemia (83.75%), followed by bicytopaenia (63.75%) then leukocytopaenia and/or lymphocytopaenia (62.5).     

Do we need new autoantibodies in lupus?

Systemic lupus erythematosus (SLE) is a clinically and serologically complex disease that demonstrates clinical, epidemiological and genetic differences among racial and ethnic groups. Some autoantibodies are useful for diagnosis of the illness. Others are clinically important because of associations with a particular manifestation of SLE. Antibodies to RNA helicase A (anti-RHA) comprise a newly described class of SLE autoantibodies. These antibodies have so far been found only in SLE patients and differ substantially in prevalence and nature between Mexican and white American SLE patients. Study of anti-RHA may provide insights into the origin of population differences in SLE.     

Early repolarization with horizontal ST segment may be associated with aborted sudden cardiac arrest: a retrospective case control study

Background

Patients with systemic lupus erythematosus (SLE) have increased cardiovascular morbidity and mortality. Although autopsy studies have documented that the heart is affected in most SLE patients, clinical manifestations occur in less than 10%. QT dispersion is a new parameter that can be used to assess homogeneity of cardiac repolarization and autonomic function. We compared the increase in QT dispersion in SLE patients with high disease activity and mild or moderate disease activity.

Methods and Results

One hundred twenty-four patients with SLE were enrolled in the study. Complete history and physical exam, ECG, echocardiography, exercise test and SLE disease activity index (SLEDAI) were recorded. Twenty patients were excluded on the basis of our exclusion criteria. The patients were divided to two groups based on SLEDAI: 54 in the high-score group (SLEDAI > 10) and 50 in the low-score group (SLEDAI < 10). QT dispersion was significantly higher in high-score group (58.31 ± 18.66 vs. 47.90 ± 17.41 respectively; P < 0.004). QT dispersion was not significantly higher in patients who had received hydroxychloroquine (54.17 ± 19.36 vs. 50.82 ± 15.96, P = 0.45) or corticosteroids (53.58 ± 19.16 vs. 50.40 + 11.59, P = 0.47). There was a statistically significant correlation between abnormal echocardiographic findings (abnormalities of pericardial effusion, pericarditis, pulmonary hypertension and Libman-Sacks endocarditis) and SLEADI (P < 0.004).

Conclusions

QT dispersion can be a useful, simple noninvasive method for the early detection of cardiac involvement in SLE patients with active disease. Concerning high chance of cardiac involvement, cardiovascular evaluation for every SLE patient with a SLEDAI higher than 10 may be recommended.

Trial registration

Clinicaltrial.gov registration NCT01031797     

Interaction between smoking and functional polymorphism in the TGFB1 gene is associated with ischaemic heart disease and myocardial infarction in patients with rheumatoid arthritis: a cross-sectional study

Introduction

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease. Cardiovascular disease (CVD) is common and a major cause of mortality. Studies on cardiovascular morbidity are abundant, whereas mortality studies focusing on cardiovascular outcomes are scarce. The aim of this study was to investigate causes of death and baseline predictors of overall (OM), non-vascular (N-VM), and specifically cardiovascular (CVM) mortality in SLE, and to evaluate systematic coronary risk evaluation (SCORE).

Methods

208 SLE patients were included 1995-1999 and followed up after 12 years. Clinical evaluation, CVD risk factors, and biomarkers were recorded at inclusion. Death certificates and autopsy protocols were collected. Causes of death were divided into CVM (ischemic vascular and general atherosclerotic diseases), N-VM and death due to pulmonary hypertension. Predictors of mortality were investigated using multivariable Cox regression. SCORE and standardized mortality ratio (SMR) were calculated.

Results

During follow-up 42 patients died at mean age of 62 years. SMR 2.4 (CI 1.7-3.0). 48% of deaths were caused by CVM. SCORE underestimated CVM but not to a significant level. Age, high cystatin C levels and established arterial disease were the strongest predictors for all- cause mortality. After adjusting for these in multivariable analyses, only smoking among traditional risk factors, and high soluble vascular cell adhesion molecule-1 (sVCAM-1), high sensitivity C-reactive protein (hsCRP), anti-beta2 glycoprotein-1 (abeta2GP1) and any antiphospholipid antibody (aPL) among biomarkers, remained predictive of CVM.

Conclusion

With the exception of smoking, traditional risk factors do not capture the main underlying risk factors for CVM in SLE. Rather, cystatin C levels, inflammatory and endothelial markers, and antiphospholipid antibodies (aPL) differentiate patients with favorable versus severe cardiovascular prognosis. Our results suggest that these new biomarkers are useful in evaluating the future risk of cardiovascular mortality in SLE patients.     

Ibandronate increases cortical bone density in patients with systemic lupus erythematosus on long-term glucocorticoid

Introduction

The purpose of this research is to assess the effects of oral ibandronate on bone microarchitecture by using high-resolution peripheral quantitative computed tomography (HR-pQCT) in patients with systemic lupus erythematosus (SLE) taking a long-term glucocorticoid.

Methods

In this double-blind placebo-controlled study, 40 Chinese female SLE patients taking prednisolone were randomly assigned to receive either monthly oral ibandronate (150 mg) or placebo with daily 1-hydroxycholecalciferol (Alfacalcidol; 1 μg) and calcium supplement for 12 months. Assessments of bone microarchitecture by using HR-pQCT and area bone mineral density (aBMD) of the lumbar spine and hip with dual-energy x-ray absorptiometry (DXA) were performed at baseline and 12 months.

Results

No differences in baseline characteristics were found between the two groups. After 12 months, no statistical differences were noted in any of the bone densities, microarchitectural parameters, or percentage changes of these parameters, as measured with HR-pQCT or DXA between the two groups. However, within the active group, the percentage improvement was significant in cortical bone density (P = 0.023) which was absent in the placebo group. Improvement was also seen in the aBMD of both the lumbar spine (P < 0.0001) and the hip (P < 0.005). In the placebo group, the percentage increase in trabecular separation was significant (P = 0.04), and the percentage improvement in aBMD in the spine also was significant (P = 0.049).

Conclusions

Oral ibandronate treatment improves microarchitecture in SLE patients taking long-term glucocorticoid assessed with HR-pQCT, and this new technology may have a role in assessing bony changes in future longitudinal studies in SLE patients.

Trial registration

ClinicalTrials.gov identifier: NCT00668330.     

The relationship between disease activity, sleep, psychiatric distress and pain sensitivity in rheumatoid arthritis: a cross-sectional study

Introduction

Cell stimulation leads to the shedding of phosphatidylserine (PS)-rich microparticles (MPs). Because autoimmune diseases (AIDs) are characterized by cell activation, we investigated level of circulating MPs as a possible biomarker in primary Sjögren's syndrome (pSS), systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA).

Methods

We measured plasma levels of total, platelet and leukocyte MPs by prothrombinase capture assay and flow cytometry in 43 patients with pSS, 20 with SLE and 24 with RA and in 44 healthy controls (HCs). Secretory phospholipase A2 (sPLA2) activity was assessed by fluorometry. Soluble CD40 ligand (sCD40L) and soluble P-selectin (sCD62P), reflecting platelet activation, were measured by ELISA.

Results

Patients with pSS showed increased plasma level of total MPs (mean ± SEM 8.49 ± 1.14 nM PS equivalent (Eq), P < 0.0001), as did patients with RA (7.23 ± 1.05 n PS Eq, P = 0.004) and SLE (7.3 ± 1.25 nM PS Eq, P = 0.0004), as compared with HCs (4.13 ± 0.2 nM PS Eq). Patients with AIDs all showed increased level of platelet MPs (P < 0.0001), but only those with pSS showed increased level of leukocyte MPs (P < 0.0001). Results by capture assay and flow cytometry were correlated. In patients with high disease activity according to extra-glandular complications (pSS), DAS28 (RA) or SLEDAI (SLE) compared with low-activity patients, the MP level was only slightly increased in comparison with those having a low disease activity. Platelet MP level was inversely correlated with anti-DNA antibody level in SLE (r = -0.65; P = 0.003) and serum β2 microglobulin level in pSS (r = -0.37; P < 0.03). The levels of total and platelet MPs were inversely correlated with sPLA2 activity (r = -0.37, P = 0.0007; r = -0.36, P = 0.002, respectively). sCD40L and sCD62P concentrations were significantly higher in pSS than in HC (P ≤ 0.006).

Conclusions

Plasma MP level is elevated in pSS, as well as in SLE and RA, and could be used as a biomarker reflecting systemic cell activation. Level of leukocyte-derived MPs is increased in pSS only. The MP level is low in case of more severe AID, probably because of high secretory phospholipase A2 (sPLA2) activity, which leads to consumption of MPs. Increase of platelet-derived MPs, sCD40L and sCD62P, highlights platelet activation in pSS.     

Increased expression of Mer tyrosine kinase in circulating dendritic cells and monocytes of lupus patients: correlations with plasma interferon activity and steroid therapy

Introduction

The requirement for the immunoregulatory Mer tyrosine kinase (Mer) for optimal removal of apoptotic cells prompted us to look at its expression in systemic lupus erythematosus (SLE), in which apoptotic cell clearance is abnormal. We compared the levels of expression of Mer in normal human subjects and in patients with SLE.

Methods

We used flow cytometry of isolated peripheral blood mononuclear cells to compare the levels of Mer on leukocyte subsets. We used a Mer-specific enzyme-linked immunosorbent assay (ELISA) to quantify soluble Mer (sMer) in plasmas.

Results

Monocytes, CD1c⁺ myeloid dendritic cells (mDCs), and plasmacytoid dendritic cells (pDCs) from both normal individuals and from SLE patients expressed Mer. In both normal and SLE patients, the CD14⁺⁺CD16⁺ subpopulation of monocytes expressed the highest levels of Mer, with somewhat lower levels on the CD14^intCD16⁺ population. Mer levels on CD1c⁺ mDCs and pDCs, and sMer levels in blood were increased in SLE patients compared with controls. In patients, Mer levels on CD14^intCD16⁺, CD14⁺⁺CD16^- monocytes, and CD1c⁺ dendritic cells correlated positively with type I interferon (IFN-I) activity detected in blood. In SLE patients treated with corticosteroids, Mer expression on monocytes correlated with prednisone dose, CD1c⁺ myeloid dendritic cells in patients treated with prednisone had higher levels of Mer expression than those in patients not receiving prednisone.

Conclusions

We found no global defect in Mer expression in lupus blood. In contrast, we observed increased levels of Mer expression in DC populations, which could represent a response to increased IFN-I in SLE patients. Enhanced Mer expression induced by corticosteroids may contribute to its beneficial effects in SLE.     

Synovial tissues concentrate secreted APRIL

Introduction

TNF-like weak inducer of apoptosis (TWEAK) has been implicated as a mediator of chronic inflammatory processes via prolonged activation of the NF-κB pathway in several tissues, including the kidney. Evidence for the importance of TWEAK in the pathogenesis of lupus nephritis (LN) has been recently introduced. Thus, TWEAK levels may serve as an indication of LN presence and activity.

Methods

Multicenter cohorts of systemic lupus erythematosus (SLE) patients and controls were recruited for cross-sectional and longitudinal analysis of urinary TWEAK (uTWEAK) and/or serum TWEAK (sTWEAK) levels as potential biomarkers of LN. The performance of TWEAK as a biomarker for nephritis was compared with routinely used laboratory tests in lupus patients, including anti-double stranded DNA antibodies and levels of C3 and C4.

Results

uTWEAK levels were significantly higher in LN patients than in non-LN SLE patients and other disease control groups (P = 0.039). Furthermore, uTWEAK was better at distinguishing between LN and non-LN SLE patients than anti-DNA antibodies and complement levels, while high uTWEAK levels predicted LN in SLE patients with an odds ratio of 7.36 (95% confidence interval = 2.25 to 24.07; P = 0.001). uTWEAK levels peaked during LN flares, and were significantly higher during the flare than at 4 and 6 months prior to or following the flare event. A linear mixed-effects model showed a significant association between uTWEAK levels in SLE patients and their disease activity over time (P = 0.008). sTWEAK levels, however, were not found to correlate with the presence of LN or the degree of nephritis activity.

Conclusions

High uTWEAK levels are indicative of LN, as opposed to non-LN SLE and other healthy and disease control populations, and reflect renal disease activity in longitudinal follow-up. Thus, our study further supports a role for TWEAK in the pathogenesis of LN, and provides strong evidence for uTWEAK as a candidate clinical biomarker for LN.