Patients with systemic lupus erythematosus (SLE) are at excess risk of cardiovascular events (CVEs). There is uncertainty regarding the relative importance of SLE disease activity, medications, or traditional risk factors in this increased risk. To gain insight into this, the authors analyzed data from a cohort of 1,874 patients with SLE who were seen quarterly at a single clinical center (April 1987–June 2010) using pooled logistic regression analysis. In 9,485 person-years of follow-up, the authors observed 134 CVEs (rate = 14.1/1,000 person-years). This was 2.66 times what would be expected in the general population based on Framingham risk scores (95% confidence interval: 2.16, 3.16). After adjustment for age, CVE rates were not associated with duration of SLE. However, they were associated with average past levels of SLE disease activity and recent levels of circulating anti-double-stranded DNA. Past use of corticosteroids (in the absence of current use) was not associated with CVE rates. However, persons currently using 20 mg/day or more of corticosteroids had a substantial increase in risk even after adjustment for disease activity. Thus, consistent with findings in several recent publications among cohorts with other diseases, current use of corticosteroids was associated with an increased risk of CVEs. These results suggest a short-term impact of corticosteroids on CVE risk.
angina pectoris; coronary artery bypass surgery; intermittent claudication; lupus erythematosus, systemic; myocardial infarction, prednisone; risk factors; stroke
Immunoregulatory cytokine interleukin-10 (IL-10) is elevated in sera from patients with systemic lupus erythematosus (SLE) correlating with disease activity. The established association of IL10 with SLE and other autoimmune diseases led us to fine map causal variant(s) and to explore underlying mechanisms. We assessed 19 tag SNPs, covering the IL10 gene cluster including IL19, IL20 and IL24, for association with SLE in 15,533 case and control subjects from four ancestries. The previously reported IL10 variant, rs3024505 located at 1 kb downstream of IL10, exhibited the strongest association signal and was confirmed for association with SLE in European American (EA) (P = 2.7×10−8, OR = 1.30), but not in non-EA ancestries. SNP imputation conducted in EA dataset identified three additional SLE-associated SNPs tagged by rs3024505 (rs3122605, rs3024493 and rs3024495 located at 9.2 kb upstream, intron 3 and 4 of IL10, respectively), and SLE-risk alleles of these SNPs were dose-dependently associated with elevated levels of IL10 mRNA in PBMCs and circulating IL-10 protein in SLE patients and controls. Using nuclear extracts of peripheral blood cells from SLE patients for electrophoretic mobility shift assays, we identified specific binding of transcription factor Elk-1 to oligodeoxynucleotides containing the risk (G) allele of rs3122605, suggesting rs3122605 as the most likely causal variant regulating IL10 expression. Elk-1 is known to be activated by phosphorylation and nuclear localization to induce transcription. Of interest, phosphorylated Elk-1 (p-Elk-1) detected only in nuclear extracts of SLE PBMCs appeared to increase with disease activity. Co-expression levels of p-Elk-1 and IL-10 were elevated in SLE T, B cells and monocytes, associated with increased disease activity in SLE B cells, and were best downregulated by ERK inhibitor. Taken together, our data suggest that preferential binding of activated Elk-1 to the IL10 rs3122605-G allele upregulates IL10 expression and confers increased risk for SLE in European Americans.
Systemic lupus erythematosus (SLE), a debilitating autoimmune disease characterized by the production of pathogenic autoantibodies, has a strong genetic basis. Variants of the IL10 gene, which encodes cytokine interleukin-10 (IL-10) with known function of promoting B cell hyperactivity and autoantibody production, are associated with SLE and other autoimmune diseases, and serum IL-10 levels are elevated in SLE patients correlating with increased disease activity. In this study, to discover SLE-predisposing causal variant(s), we assessed variants within the genomic region containing IL10 and its gene family member IL19, IL20 and IL24 for association with SLE in case and control subjects from diverse ancestries. We identified SLE-associated SNP rs3122605 located at 9.2 kb upstream of IL10 as the most likely causal variant in subjects of European ancestry. The SLE-risk allele of rs3122605 was dose-dependently associated with elevated IL10 expression at both mRNA and protein levels in peripheral blood samples from SLE patients and controls, which could be explained, at least in part, by its preferential binding to Elk-1, a transcription factor activated in B cells during active disease of SLE patients. Elk-1-mediated IL-10 overexpression could be downregulated by inhibiting activation of mitogen-activated protein kinases, suggesting a potential therapeutic target for SLE.
Protein tyrosine phosphatase non-receptor type 22 (PTPN22) is a negative regulator of T-cell activation associated with several autoimmune diseases, including systemic lupus erythematosus (SLE). Missense rs2476601 is associated with SLE in individuals with European ancestry. Since the rs2476601 risk allele frequency differs dramatically across ethnicities, we assessed robustness of PTPN22 association with SLE and its clinical sub-phenotypes across four ethnically diverse populations. Ten SNPs were genotyped in 8220 SLE cases and 7369 controls from in European-Americans (EA), African-Americans (AA), Asians (AS), and Hispanics (HS). We performed imputation-based association followed by conditional analysis to identify independent associations. Significantly associated SNPs were tested for association with SLE clinical sub-phenotypes, including autoantibody profiles. Multiple testing was accounted for by using false discovery rate. We successfully imputed and tested allelic association for 107 SNPs within the PTPN22 region and detected evidence of ethnic-specific associations from EA and HS. In EA, the strongest association was at rs2476601 (P = 4.7×10−9, OR = 1.40 (95% CI = 1.25–1.56)). Independent association with rs1217414 was also observed in EA, and both SNPs are correlated with increased European ancestry. For HS imputed intronic SNP, rs3765598, predicted to be a cis-eQTL, was associated (P = 0.007, OR = 0.79 and 95% CI = 0.67–0.94). No significant associations were observed in AA or AS. Case-only analysis using lupus-related clinical criteria revealed differences between EA SLE patients positive for moderate to high titers of IgG anti-cardiolipin (aCL IgG >20) versus negative aCL IgG at rs2476601 (P = 0.012, OR = 1.65). Association was reinforced when these cases were compared to controls (P = 2.7×10−5, OR = 2.11). Our results validate that rs2476601 is the most significantly associated SNP in individuals with European ancestry. Additionally, rs1217414 and rs3765598 may be associated with SLE. Further studies are required to confirm the involvement of rs2476601 with aCL IgG.
Little is known about the genetic etiology of systemic lupus erythematosus (SLE) in individuals of African ancestry, despite its higher prevalence and greater disease severity. Overproduction of nitric oxide (NO) and reactive oxygen species are implicated in the pathogenesis and severity of SLE, making NO synthases and other reactive intermediate related genes biological candidates for disease susceptibility. This study analyzed variation in reactive intermediate genes for association with SLE in two populations with African ancestry.
A total of 244 SNPs from 53 regions were analyzed in non-Gullah African Americans (AA; 1432 cases and 1687 controls) and the genetically more homogeneous Gullah of the Sea Islands of South Carolina (133 cases and 112 controls) and. Single-marker, haplotype, and two-locus interaction tests were computed for these populations.
The glutathione reductase gene GSR (rs2253409, P=0.0014, OR [95% CI]=1.26 [1.09–1.44]) was the most significant single-SNP association in AA. In the Gullah, the NADH dehydrogenase NDUFS4 (rs381575, P=0.0065, OR [95%CI]=2.10 [1.23–3.59]) and nitric oxide synthase gene NOS1 (rs561712, P=0.0072, OR [95%CI]=0.62 [0.44–0.88]) were most strongly associated with SLE. When both populations were analyzed together, GSR remained the most significant effect (rs2253409, P=0.00072, OR [95%CI]=1.26 [1.10–1.44]). Haplotype and two-locus interaction analyses also uncovered different loci in each population.
These results suggest distinct patterns of association with SLE in African-derived populations; specific loci may be more strongly associated within select population groups.
systemic lupus erythematosus; African Americans; genetic association studies; oxygen compounds; single nucleotide polymorphism
To investigate the relationship of urinary biomarkers (UBM) and established measures of renal function (EMRF) to the histological findings with lupus nephritis (LN); and to test whether certain combinations of the above mentioned laboratory measures are diagnostic of specific histological features of LN.
Urine samples of 76 patients were collected within 2 months of a kidney biopsy and assayed for the UBM: lipocalin-like prostaglandin-D synthetase (LPGDS), α1-acid-glycoprotein (AAG), transferrin (TF), ceruloplasmin (CP), neutrophil-gelatinase associated lipocalin (NGAL), and monocyte chemotactic factor 1 (MCP1). Using non-parametric analyses, UBM and EMRF levels were compared to histological features seen with LN: mesangial expansion, capillary proliferation, crescent formation, necrosis, wire loops, fibrosis, tubular atrophy, and epimembranous deposits. The area under the receiver operating characteristic (AUC) curve was calculated to predict LN activity, chronicity or membranous LN.
There was a differential increase of the UBM that formed a pattern reflective of specific histological features seen with active LN. The combination of MCP1, AAG, CP plus protein:creatinine ratio were excellent in predicting LN activity (AUC=0.85). NGAL together with creatinine clearance plus MCP1 was an excellent (AUC=0.83) and MCP1, AAG, creatinine clearance plus C4 (AUC=0.75) a good diagnostic test of LN chronicity and membranous LN, respectively.
Select UBM are associated with specific tissue changes observed with LN activity and chronicity. Especially in combination with select EMRF, UBM are well-suited to non-invasively quantify LN activity, LN chronicity, and the presence of membranous LN.
SLE; lupus nephritis; kidney biopsy; biomarker
The Systemic Lupus Collaborating Clinics (SLICC) revised and validated the American College of Rheumatology (ACR) SLE classification criteria in order to improve clinical relevance, meet stringent methodology requirements and incorporate new knowledge in SLE immunology.
The classification criteria were derived from a set of 702 expert-rated patient scenarios. Recursive partitioning was used to derive an initial rule that was simplified and refined based on SLICC physician consensus. SLICC validated the classification criteria in a new validation sample of 690 SLE patients and controls.
Seventeen criteria were identified. The SLICC criteria for SLE classification requires: 1) Fulfillment of at least four criteria, with at least one clinical criterion AND one immunologic criterion OR 2) Lupus nephritis as the sole clinical criterion in the presence of ANA or anti-dsDNA antibodies. In the derivation set, the SLICC classification criteria resulted in fewer misclassifications than the current ACR classification criteria (49 versus 70, p=0.0082), had greater sensitivity (94% versus 86%, p<0.0001) and equal specificity (92% versus 93%, p=0.39). In the validation set, the SLICC Classification criteria resulted in fewer misclassifications (62 versus 74, p=0.24), had greater sensitivity (97% versus 83%, p<0.0001) but less specificity (84% versus 96%, p<0.0001).
The new SLICC classification criteria performed well on a large set of patient scenarios rated by experts. They require that at least one clinical criterion and one immunologic criterion be present for a classification of SLE. Biopsy confirmed nephritis compatible with lupus (in the presence of SLE autoantibodies) is sufficient for classification.
The Hopkins lupus cohort is a longitudinal cohort study of over 2,000 systemic lupus erythematosus (SLE) patients, who are seen quarterly. This review covers ten important clinically-relevant studies of the cohort. These studies include the function of prednisone in atherosclerosis and thrombosis, the preventive function of hydroxychloroquine, new insights into rare neurological manifestations, and treatment of flares with bursts of steroids rather than maintenance steroids.
Systemic lupus erythematosus; SLE; Hopkins lupus cohort; Prednisone; Organ damage; Hydroxychloroquine; Thrombosis; Lupus nephritis; Lupus anticoagulant; Cardiovascular disease; Cognitive impairment; SLE myelitis; Small fiber neuropathy; Vitamin D; Flares
Which serologic and clinical findings predict adverse pregnancy outcome (APO) in patients with antiphospholipid antibody (aPL) is controversial.
PROMISSE is a multicenter, prospective observational study of risk factors for APO in patients with aPL (lupus anticoagulant [LAC], anticardiolipin antibody [aCL] and/or antibody to β2 glycoprotein I [anti-β2-GP-I]). We tested the hypothesis that a pattern of clinical and serological variables can identify women at highest risk for APO.
Between 2003 and 2011 we enrolled 144 pregnant patients, of whom 28 had APO. Thirty-nine percent of patients with LAC had APO, compared to 3% who did not have LAC (p < 0.0001). Only 8% of women with IgG aCL ≥40 u/mL but not LAC suffered APO, compared to 43% of those with LAC (p = 0.002). IgM aCL or IgG or IgM anti-β2-GP-I did not predict APO. In bivariate analysis, APO occurred in 52% of patients with and 13% of patients without prior thrombosis (p = 0.00005), and in 23% with SLE compared to 17% without SLE (not significant); SLE was a predictor in multivariate analysis. Prior pregnancy loss did not predict APO, nor did maternal race. Simultaneous aCL, anti-β2-GP-I, and LAC did not predict APO better than did LAC alone.
LAC is the primary predictor of APO after 12 weeks gestation in aPL-associated pregnancies. ACL and anti-β2-GP-I, if LAC is not also present, do not predict APO.
Systemic lupus erythematosus (SLE) is an autoimmune disease of diverse manifestations, with onset usually in young women in the third to fourth decade of life. The chronic nature of this relapsing remitting disease leads to organ damage accrual over time. Mortality and morbidity are increased in patients with SLE compared with the general population. Therapeutic advances over the last few decades have led to significant improvements in patient outcomes. Five-year survival has improved to over 90% from a low of 50% in the 1950s. However, multiple aspects of the management of SLE patients are still far from optimal. Early diagnosis remains a challenge; diagnostic delays leading to delay in definitive treatment are common. Monitoring treatment remains problematic due to the paucity of sensitive biomarkers. Current treatment regimens rely heavily on corticosteroids, even though corticosteroids are well known to cause organ damage. Treatment of refractory disease manifestations such as nephritis, recalcitrant cutaneous lesions and neurological involvement require new approaches with greater efficacy. Cognitive dysfunction is common in SLE patients, but early recognition and adequate treatment are yet to be established. Premature accelerated atherosclerosis remains a leading cause of morbidity and mortality. Fatigue is one of the most disabling symptoms, and contributes to the poor quality of life in patients with SLE. Ongoing research in SLE faces many challenges, including enrollment of homogeneous patient populations, use of reliable outcome measures and a standard control arm. The current review will highlight some of the outstanding unmet challenges in the management of this complex disease.
Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease with significant immune system aberrations resulting from complex heritable genetics as well as environmental factors. TRAF6 is a candidate gene for SLE, which has a major role in several signaling pathways that are important for immunity and organ development.
Fifteen single-nucleotide polymorphisms (SNPs), across TRAF6 were evaluated in 7,490 SLE and 6,780 control subjects from different ancestries. Population-based case-control association analyses and meta-analyses were performed. P values, false discovery rate q values, and odds ratios with 95% confidence intervals were calculated.
Evidence of associations in multiple SNPs was detected. The best overall p values were obtained for SNPs rs5030437 and rs4755453 (p=7.85×10−5 and p=4.73×10−5, respectively) without significant heterogeneity among populations (p=0.67 and p=0.50 in Q-statistic). In addition, rs540386 previously reported to be associated with RA was found to be in LD with these two SNPs (r2= 0.95) and demonstrated evidence of association with SLE in the same direction (meta-analysis p=9.15×10−4, OR=0.89, 95%CI=0.83–0.95). Thrombocytopenia improved the overall results in different populations (meta-analysis p=1.99×10−6, OR=0.57, 95%CI=0.45–0.72, for rs5030470). Finally evidence of family based association in 34 African-American pedigrees with the presence of thrombocytopenia were detected in one available SNP rs5030437 with Z score magnitude of 2.28 (p=0.02) under a dominant model.
Our data indicate the presence of association of TRAF6 with SLE in agreement with the previous report of association with RA. These data provide further support for the involvement of TRAF6 in the pathogenesis of autoimmunity.
TRAF6; polymorphism; systemic lupus erythematosus
Systemic lupus erythematosus (SLE) is a sexually dimorphic autoimmune disease which is more common in women, but affected men often experience a more severe disease. The genetic basis of sexual dimorphism in SLE is not clearly defined. A study was undertaken to examine sex-specific genetic effects among SLE susceptibility loci.
A total of 18 autosomal genetic susceptibility loci for SLE were genotyped in a large set of patients with SLE and controls of European descent, consisting of 5932 female and 1495 male samples. Sex-specific genetic association analyses were performed. The sex–gene interaction was further validated using parametric and nonparametric methods. Aggregate differences in sex-specific genetic risk were examined by calculating a cumulative genetic risk score for SLE in each individual and comparing the average genetic risk between male and female patients.
A significantly higher cumulative genetic risk for SLE was observed in men than in women. (P = 4.52×10−8) A significant sex–gene interaction was seen primarily in the human leucocyte antigen (HLA) region but also in IRF5, whereby men with SLE possess a significantly higher frequency of risk alleles than women. The genetic effect observed in KIAA1542 is specific to women with SLE and does not seem to have a role in men.
The data indicate that men require a higher cumulative genetic load than women to develop SLE. These observations suggest that sex bias in autoimmunity could be influenced by autosomal genetic susceptibility loci.
To determine the clinical manifestations and disease damage associated with discoid rash in a large multiethnic systemic lupus erythematosus (SLE) cohort.
SLE patients (per ACR criteria), age ≥ 16 years, disease duration ≤ 10 years at enrollment, and defined ethnicity (African American, Hispanic or Caucasian), from a longitudinal cohort were studied. Socioeconomic-demographic features, clinical manifestations and disease damage [as per the Systemic Lupus International Collaborating Clinics Damage Index (SDI)] were determined. The association of DLE with clinical manifestations and disease damage was examined using multivariable logistic regression.
A total of 2,228 SLE patients were studied. The mean (standard deviation, SD) age at diagnosis was 34.3 (12.8) years and the mean (SD) disease duration was 7.9 (6.0) years; 91.8% were women. Discoid lupus was observed in 393 (17.6%) of patients with SLE. In the multivariable analysis, patients with discoid lupus were more likely to be smokers and of African-American ethnicity, and to have malar rash, photosensitivity, oral ulcers, leukopenia and vasculitis. DLE patients were less likely to be of Hispanic (from Texas) ethnicity, and to have arthritis, end-stage renal disease (ESRD), and antinuclear, anti-dsDNA and anti-phospholipid antibodies. Patients with DLE had more damage accrual, particularly chronic seizures, scarring alopecia, scarring of the skin, and skin ulcers.
In this cohort of SLE patients, discoid lupus was associated with several clinical features including serious manifestations such as vasculitis and chronic seizures.
discoid rash; systemic lupus erythematosus; disease damage
Emerging evidence suggests that there are IgM-autoantibodies that may play protective roles in SLE. While IgM are often considered polyreactive, we postulate that there are distinct sets of IgM-autoantibodies of defined autoreactive specificities relevant to different features of SLE. We examined the relationships between levels of IgM natural autoantibodies (NAbs) to apoptosis-associated phosphorylcholine (PC) or malondialdehyde (MDA) antigens, with lupus-associated autoantibodies and features of disease, in 120 SLE patients. IgM anti-PC was significantly higher in patients with low disease activity and less organ damage determined by the SELENA-SLEDAI, the physician's evaluation and the SLICC damage score. Furthermore, IgM anti-PC was significantly higher in patients without cardiovascular events. In contrast, IgM anti-cardiolipin and IgM anti-dsDNA were significantly higher in patients without renal disease. These results support the hypothesis that some IgM autoantibodies are part of a natural immune repertoire that provide homeostatic functions and protection from certain clinical lupus features.
Systemic lupus erythematosus; Natural antibodies; IgM; Cardiovascular disease; Renal disease
Corticosteroids are the mainstay for treatment of systemic lupus erythematosus (SLE). The potential role of corticosteroid use on the pathogenesis of permanent organ damage requires appropriate adjustment for confounding by disease activity. We estimate the effect of corticosteroids (prednisone dose) on permanent organ damage among persons with SLE.
We identified 525 incident SLE patients in the Hopkins Lupus Cohort. At each visit, clinical activity indices, laboratory data, and treatment were recorded. The study population was followed from the month after the first visit until June 29 2006, irreversible organ damage, death, loss to follow-up, or receipt of pulse methylprednisolone therapy. We estimated the effect of cumulative average dose of prednisone on organ damage using a marginal structural model to adjust for time-dependent confounding by indication due to SLE disease activity.
Compared with non prednisone use, the hazard ratio (95% confidence interval) of organ damage for prednisone was 1.16 (0.59, 2.20) for cumulative average doses >0–180 mg/month, 1.50 (0.67, 3.39) for >180–360 mg/month, 1.64 (0.67, 4.06) for >360–540 mg/month, and 2.51 (1.02, 6.19) for >540 mg/month. In contrast, standard Cox regression models estimated higher hazard ratios at all dose levels.
Our results suggest that low doses of prednisone do not result in a substantially increased risk of irreversible organ damage.
causal modeling; marginal structural model; systemic lupus erythematosus; corticosteroid treatment; long-term prednisone therapy; permanent organ damage
Vascular cell adhesion molecule-1 (VCAM-1), an adhesion molecule, is involved in the progression of glomerular and tubulointerstitial injury. Neutrophil gelatinase-associated lipocalin (NGAL), a member of the lipocalin superfamily, has been shown to rise in both acute and chronic kidney damage. Both VCAM-1 and NGAL have been found at high levels in the urine of patients with active lupus nephritis. We investigated both as potential biomarkers for lupus nephritis.
VCAM-1 and NGAL were measured by ELISA during 1 to 8 clinic visits in 107 patients with systemic lupus erythematosus (SLE; 91% women, 51% black, 36% white, 4% Asian, 4% Hispanic, and 5% others) for a total of 190 visits. Patients’ mean age was 41 years. We analyzed the relationship between these potential urine biomarkers and the urine protein/creatinine ratio (urine Pr/Cr), the Systemic Lupus International Collaborating Clinics (SLICC) renal activity score, SLE Disease Activity Index renal descriptors, and other clinical variables.
VCAM-1 levels were strongly associated with the physician’s global estimate of disease activity (p = 0.0002), the renal visual analog scale (p < 0.0001), the urine Pr/Cr (p < 0.0001), and SLICC renal activity score (p < 0.0001). VCAM-1 levels were also associated with a urine Pr/Cr ≥ 0.5 (p < 0.0001). NGAL was not associated with any measure of disease activity or with lupus serologies.
Urine VCAM-1 had a strong association with measures of disease activity, including multiple renal activity descriptors. In contrast to previous SLE studies, NGAL failed to show any association with lupus nephritis.
SYSTEMIC LUPUS ERYTHEMATOSUS; VASCULAR CELL ADHESION MOLECULE; NEUTROPHIL GELATINASE-ASSOCIATED LIPOCALIN; LIPOCALIN; LUPUS NEPHRITIS
Male patients with systemic lupus erythematosus (SLE) are thought to be similar to female patients with SLE, but key clinical characteristics may differ. Comparisons were made between male and female patients with SLE in the Hopkins Lupus Cohort.
A total of 1979 patients in the Hopkins Lupus Cohort were included in the analysis.
The cohort consisted of 157 men (66.2% white, 33.8% African American) and 1822 women (59.8% white, 40.2% African American). The mean followup was 6.02 years (range 0–23.73). Men were more likely than women to have disability, hypertension, thrombosis, and renal, hematological, and serological manifestations. Men were more likely to be diagnosed at an older age and to have a lower education level. Women were more likely to have malar rash, photosensitivity, oral ulcers, alopecia, Raynaud’s phenomenon, or arthralgia. Men were more likely than women to have experienced end organ damage including neuropsychiatric, renal, cardiovascular, peripheral vascular disease, and myocardial infarction, and to have died. In general, differences between males and females were more numerous and striking in whites, especially with respect to lupus nephritis, abnormal serologies, and thrombosis.
Our study suggests that there are major clinical differences between male and female patients with SLE. Differences between male and female patients also depend on ethnicity. Future SLE studies will need to consider both ethnicity and gender to understand these differences.
SYSTEMIC LUPUS ERYTHEMATOSUS; GENDER; MALE LUPUS
A major cause of morbidity and mortality in systemic lupus erythematosus (SLE) is accelerated coronary atherosclerosis. New technology (computed tomographic angiography) can measure noncalcified coronary plaque (NCP), which is more prone to rupture. We report on a study of semiquantified NCP in SLE.
Patients with SLE (n = 147) with no history of cardiovascular disease underwent 64-slice coronary multidetector computed tomography (MDCT). The MDCT scans were evaluated quantitatively by a radiologist, using dedicated software.
The group of 147 patients with SLE was 86% female, 70% white, 29% African American, and 3% other ethnicity. The mean age was 51 years. In our univariate analysis, the major traditional cardiovascular risk factors associated with noncalcified plaque were age (p = 0.007), obesity (p = 0.03; measured as body mass index), homocysteine (p = 0.05), and hypertension (p = 0.04). Anticardiolipin (p = 0.026; but not lupus anticoagulant) and anti-dsDNA (p = 0.03) were associated with higher noncalcified plaque. Prednisone and hydroxychloroquine therapy had no effect, but methotrexate (MTX) use was associated with higher noncalcified plaque (p = 0.0001). In the best multivariate model, age, current MTX use, and history of anti-dsDNA remained significant.
Our results suggest that serologic SLE (anti-dsDNA) and traditional cardiovascular risk factors contribute to semiquantified noncalcified plaque in SLE. The association with MTX is not understood, but should be replicated in larger studies and in multiple centers.
SYSTEMIC LUPUS ERYTHEMATOSUS; CARDIOVASCULAR DISEASE; RISK FACTORS; COMORBIDITY
Currently, 3 antiphospholipid assays are widely used clinically [lupus anticoagulant (LAC), anticardiolipin (aCL), and anti-β2-glycoprotein I (anti-β2-GPI)]. LAC is the most specific assay, conferring the highest risk of thrombosis and pregnancy loss, but it cannot be validly performed in an anticoagulated patient. We investigated the usefulness of antiphosphatidyl-serine/prothrombin (anti-PS/PT) and its association with thrombosis. Anti-PS/PT is strongly associated with the presence of LAC. We also studied the association of IgA antiphospholipid isotypes and specific domains of β2-GPI with thrombosis in systemic lupus erythematosus (SLE).
Stored samples from patients with SLE, with and without past thrombosis, were assayed for antibodies to the whole β2-GPI protein (IgG/IgM/IgA), to β2-GPI domain 1 (IgG), to β2-GPI domain 4/5 (IgA), aCL (IgG/IgM/IgA), and anti-PS/PT (IgG, IgM, and IgG/M). LAC was detected using the dilute Russell’s viper venom time (dRVVT) with confirmatory testing.
Anti-PS/PT IgG and IgG/M and anti-β2-GPI IgG, IgM, and IgA were highly associated with a history of LAC by dRVVT (p < 0.0001). For all thrombosis, of the traditional ELISA assays, anti-β2-GPI IgA, IgG, and aCL IgA were most associated. Anti-PS/PT IgG and IgG/M had a similar magnitude of association to the traditional ELISA. For venous thrombosis, of the traditional ELISA, anti-β2-GPI (IgG and IgA), anti-PS/PT (IgG and IgG/M), and aCL IgA were associated. Again, anti-PS/PT (IgG and IgG/M) had the same magnitude of association as the traditional ELISA. For stroke, significant association was seen with anti-β2-GPI IgA D4/5.
In anticoagulated patients, where LAC testing is not valid, anti-PS/PT, either IgG or IgG/IgM, might serve as useful alternative tests to predict a higher risk of thrombosis. Anti-PS/PT antibodies were associated with all thrombosis and with venous thrombosis. IgA isotypes in secondary antiphospholipid syndrome are associated with thrombosis. Anti-β2-glycoprotein domain 1 was not shown to be associated with thrombosis in SLE.
ANTI-PHOSPHATIDYLSERINE/PROTHROMBIN; ANTI-β2-GLYCOPROTEIN I; DOMAIN 4/5 IgA; ANTICARDIOLIPIN
Accelerated atherosclerosis is a major cause of mortality in SLE. Mycophenolate mofetil (MMF) has been shown to suppress growth factor-induced proliferation of vascular smooth muscle and endothelial cells in animal models. We hypothesized that MMF might modify the inflammatory component of atherosclerosis in SLE. We examined the effect of MMF on atherosclerosis as measured by changes in carotid intima–media thickness (IMT) or coronary artery calcium (CAC) over 2 years. CAC and carotid IMT were measured at baseline and 2 years later in a cohort of 187 patients with SLE. The cohort was 91% women, 59% Caucasian, and 35% African-American, with a mean age of 45 ± 11 years. Of these, 12.5% (n = 25) received MMF during follow-up. The daily dose ranged from 500 to 3,000 mg/day, and duration ranged from 84 days to the entire 2 years. We divided MMF users into three groups: low exposure (<1,500 mg average daily dose), high exposure (≥1,500 average daily dose), and any exposure of MMF (<1,500 or ≥1,500 average daily dose) for 2 years. The mean CAC increased in all four groups: no MMF: 1.17–1.28, low MMF: 1.02–1.13, high MMF: 1.44–1.61, and any MMF: 1.21–1.34 log-Agatston units. Compared to no MMF, there was no statistically different change between the three groups (p = 0.99, 0.87, and 0.91). Similarly, mean carotid IMT increased in all four groups: no MMF: 0.58–0.66, low MMF: 0.55–0.60, high MMF: 0.56–0.71, and any MMF: 0.56–0.66. We then adjusted for statin use, lupus nephritis, body mass index, systolic blood pressure, cholesterol, and age during the 2-year follow-up. The association between MMF exposure and change in CAC or carotid IMT was not statistically significant (p = 0.63 for CAC, and p = 0.085 for carotid IMT). There was no evidence that MMF slowed or decreased the progression of atherosclerosis as measured by carotid IMT or CAC. Because the number of patients taking MMF was only twenty-five, larger studies for longer time periods are needed to explore any effect of MMF on subclinical atherosclerosis in SLE.
Systemic lupus erythematosus; Mycophenolate mofetil; Atherosclerosis
To determine whether there is any seasonal variation in the activity of systemic lupus erythematosus (SLE) overall and by individual organs.
The study group comprised 2102 patients with SLE who were followed in a prospective longitudinal cohort study. In this cohort, 92.3% of the patients were women. The mean ± SD age of the patients was 47.9 ± 13.9 years, 56.3% were white, 37.1% were African American, and 3.1% were Asian. Global disease activity was recorded by the Safety of Estrogens in Lupus Erythematosus National Assessment – Systemic Lupus Erythematosus Disease Activity Index (SELENA-SLEDAI) and the physician's global assessment. Activity of each organ was also recorded using SLEDAI terms and a visual analog scale (VAS; 0 to 3).
There was significant seasonal variation in photosensitive rash (p < 0.0001), which was more frequent in the spring and summer months (p < 0.0001). There was significantly more arthritis activity in spring and summer, as measured by both SELENA-SLEDAI (p = 0.0057) and the joint VAS (p = 0.0047). A decrease in renal activity was found in the summer months compared to the rest of the year (p = 0.0397). Serositis recorded by VAS had higher activity from August to October (p = 0.0392). Anti-dsDNA levels were significantly higher during October and November (p < 0.0001). There was significant seasonal variation in antiphospholipid antibody levels (p < 0.0001) and lupus anticoagulant (p = 0.0003). We found a significant variation in activity through the year in global disease activity as measured by SELENA-SLEDAI (p = 0.048).
In the Hopkins Lupus Cohort, skin and joint activity is increased during the spring and summer, but other organs have different patterns. These seasonal variations likely reflect environmental factors that influence disease activity, including ultraviolet light and infections.
SYSTEMIC LUPUS ERYTHEMATOSUS; DISEASE ACTIVITY; SEASONAL VARIATION
Accelerated atherosclerosis is a major cause of death in systemic lupus erythematosus (SLE), yet little is known about the effect of socioeconomic status. We investigated whether education or income levels are associated with cardiovascular risk factors and outcomes in SLE.
Our study involved a longitudinal cohort of all patients with SLE enrolled in the Hopkins Lupus Cohort from 1987 through September 2011. Socioeconomic status was measured by education level (≥ 12 years or < 12) and income tertiles (> $60,000, $25,000–$60,000, or < $25,000).
A total of 1752 patients with SLE were followed prospectively every 3 months. There were 1052 whites and 700 African Americans. Current smoking, obesity, hypertension, and diabetes mellitus were more common in African Americans (p < 0.01 for all), but there was no statistical difference in the frequency of myocardial infarction or stroke. In multivariate analyses stratified by ethnicity, low income was strongly associated with most traditional cardiovascular risk factors in whites, but only with smoking and diabetes in African Americans. In whites, low income increased the risk of both myocardial infarction (OR 3.24, 95% CI 1.41–7.45, p = 0.006) and stroke (OR 2.85, 95% CI 1.56–5.21, p = 0.001); in African Americans, these relationships were not seen. Low education, in contrast, was associated with smoking in both ethnic groups.
Low income, not low education, is the socioeconomic status variable associated with cardiovascular risk factors and events. This association is most clearly demonstrable in whites.
SYSTEMIC LUPUS ERYTHEMATOSUS; SOCIOECONOMIC STATUS; EDUCATION INCOME; CARDIOVASCULAR DISEASE; MYOCARDIAL INFARCTION
High serum interferon α (IFNα) activity is a heritable risk factor for systemic lupus erythematosus (SLE). Auto-antibodies found in SLE form immune complexes which can stimulate IFNα production by activating endosomal Toll-like receptors and interferon regulatory factors (IRFs), including IRF5. Genetic variation in IRF5 is associated with SLE susceptibility; however, it is unclear how IRF5 functional genetic elements contribute to human disease.
1034 patients with SLE and 989 controls of European ancestry, 555 patients with SLE and 679 controls of African–American ancestry, and 73 patients with SLE of South African ancestry were genotyped at IRF5 polymorphisms, which define major haplotypes. Serum IFNα activity was measured using a functional assay.
In European ancestry subjects, anti-double-stranded DNA (dsDNA) and anti-Ro antibodies were each associated with different haplotypes characterised by a different combination of functional genetic elements (OR > 2.56, p >003C; 1.9×10−14 for both). These IRF5 haplotype-auto-antibody associations strongly predicted higher serum IFNα in patients with SLE and explained > 70% of the genetic risk of SLE due to IRF5. In African–American patients with SLE a similar relationship between serology and IFNα was observed, although the previously described European ancestry-risk haplotype was present at admixture proportions in African–American subjects and absent in African patients with SLE.
The authors define a novel risk haplotype of IRF5 that is associated with anti-dsDNA antibodies and show that risk of SLE due to IRF5 genotype is largely dependent upon particular auto-antibodies. This suggests that auto-antibodies are directly pathogenic in human SLE, resulting in increased IFNα in cooperation with particular combinations of IRF5 functional genetic elements.
SLE is a systemic autoimmune disorder affecting multiple organ systems including the skin, musculoskeletal, renal and haematopoietic systems. Humoral autoimmunity is a hallmark of SLE, and patients frequently have circulating auto-antibodies directed against dsDNA, as well as RNA binding proteins (RBP). Anti-RBP autoantibodies include antibodies which recognize Ro, La, Smith (anti-Sm), and ribonucleoprotein (anti-nRNP), collectively referred to as anti-retinol-binding protein). Anti-retinol-binding protein and anti-dsDNA auto-antibodies are rare in the healthy population.1 These auto-antibodies can be present in sera for years preceding the onset of clinical SLE illness2 and are likely pathogenic in SLE.34
The Xq28 region containing IRAK1 and MECP2 has been identified as a risk locus for systemic lupus erythematosus (SLE) in previous genetic association studies. However, due to the strong linkage disequilibrium between IRAK1 and MECP2, it remains unclear which gene is affected by the underlying causal variant(s) conferring risk of SLE.
We fine-mapped ≥136 SNPs in a ~227kb region on Xq28, containing IRAK1, MECP2 and 7 adjacent genes (L1CAM, AVPR2, ARHGAP4, NAA10, RENBP, HCFC1 and TMEM187), for association with SLE in 15,783 case-control subjects derived from 4 different ancestral groups.
Multiple SNPs showed strong association with SLE in European Americans, Asians and Hispanics at P<5×10−8 with consistent association in subjects with African ancestry. Of these, 6 SNPs located in the TMEM187-IRAK1-MECP2 region captured the underlying causal variant(s) residing in a common risk haplotype shared by all 4 ancestral groups. Among them, rs1059702 best explained the Xq28 association signals in conditional testings and exhibited the strongest P value in trans-ancestral meta-analysis (Pmeta=1.3×10−27, OR=1.43), and thus was considered to be the most-likely causal variant. The risk allele of rs1059702 results in the amino acid substitution S196F in IRAK1 and had previously been shown to increase NF-κB activity in vitro. We also found that the homozygous risk genotype of rs1059702 was associated with lower mRNA levels of MECP2, but not IRAK1, in SLE patients (P=0.0012) and healthy controls (P=0.0064).
These data suggest contributions of both IRAK1 and MECP2 to SLE susceptibility.
Systemic Lupus Erythematosus; Gene Polymorphism; Xq28; IRAK1; MECP2
We previously reported that the G allele of rs3853839 at 3′untranslated region (UTR) of Toll-like receptor 7 (TLR7) was associated with elevated transcript expression and increased risk for systemic lupus erythematosus (SLE) in 9,274 Eastern Asians [P = 6.5×10−10, odds ratio (OR) (95%CI) = 1.27 (1.17–1.36)]. Here, we conducted trans-ancestral fine-mapping in 13,339 subjects including European Americans, African Americans, and Amerindian/Hispanics and confirmed rs3853839 as the only variant within the TLR7-TLR8 region exhibiting consistent and independent association with SLE (Pmeta = 7.5×10−11, OR = 1.24 [1.18–1.34]). The risk G allele was associated with significantly increased levels of TLR7 mRNA and protein in peripheral blood mononuclear cells (PBMCs) and elevated luciferase activity of reporter gene in transfected cells. TLR7 3′UTR sequence bearing the non-risk C allele of rs3853839 matches a predicted binding site of microRNA-3148 (miR-3148), suggesting that this microRNA may regulate TLR7 expression. Indeed, miR-3148 levels were inversely correlated with TLR7 transcript levels in PBMCs from SLE patients and controls (R2 = 0.255, P = 0.001). Overexpression of miR-3148 in HEK-293 cells led to significant dose-dependent decrease in luciferase activity for construct driven by TLR7 3′UTR segment bearing the C allele (P = 0.0003). Compared with the G-allele construct, the C-allele construct showed greater than two-fold reduction of luciferase activity in the presence of miR-3148. Reduced modulation by miR-3148 conferred slower degradation of the risk G-allele containing TLR7 transcripts, resulting in elevated levels of gene products. These data establish rs3853839 of TLR7 as a shared risk variant of SLE in 22,613 subjects of Asian, EA, AA, and Amerindian/Hispanic ancestries (Pmeta = 2.0×10−19, OR = 1.25 [1.20–1.32]), which confers allelic effect on transcript turnover via differential binding to the epigenetic factor miR-3148.
Systemic lupus erythematosus (SLE) is a debilitating autoimmune disease contributed to by excessive innate immune activation involving toll-like receptors (TLRs, particularly TLR7/8/9) and type I interferon (IFN) signaling pathways. TLR7 responds against RNA–containing nuclear antigens and activates IFN-α pathway, playing a pivotal role in the development of SLE. While a genomic duplication of Tlr7 promotes lupus-like disease in the Y-linked autoimmune accelerator (Yaa) murine model, the lack of common copy number variations at TLR7 in humans led us to identify a functional single nucleotide polymorphism (SNP), rs3853839 at 3′ UTR of the TLR7 gene, associated with SLE susceptibility in Eastern Asians. In this study, we fine-mapped the TLR7-TLR8 region and confirmed rs3853839 exhibiting the strongest association with SLE in European Americans, African Americans, and Amerindian/Hispanics. Individuals carrying the risk G allele of rs3853839 exhibited increased TLR7 expression at the both mRNA and protein level and decreased transcript degradation. MicroRNA-3148 (miR-3148) downregulated the expression of non-risk allele (C) containing transcripts preferentially, suggesting a likely mechanism for increased TLR7 levels in risk-allele carriers. This trans-ancestral mapping provides evidence for the global association with SLE risk at rs3853839, which resides in a microRNA–gene regulatory site affecting TLR7 expression.
Systemic lupus erythematosus (SLE) is an inflammatory autoimmune disease with a strong genetic component. African-Americans (AA) are at increased risk of SLE, but the genetic basis of this risk is largely unknown. To identify causal variants in SLE loci in AA, we performed admixture mapping followed by fine mapping in AA and European-Americans (EA). Through genome-wide admixture mapping in AA, we identified a strong SLE susceptibility locus at 2q22–24 (LOD = 6.28), and the admixture signal is associated with the European ancestry (ancestry risk ratio ∼1.5). Large-scale genotypic analysis on 19,726 individuals of African and European ancestry revealed three independently associated variants in the IFIH1 gene: an intronic variant, rs13023380 [Pmeta = 5.20×10−14; odds ratio, 95% confidence interval = 0.82 (0.78–0.87)], and two missense variants, rs1990760 (Ala946Thr) [Pmeta = 3.08×10−7; 0.88 (0.84–0.93)] and rs10930046 (Arg460His) [Pdom = 1.16×10−8; 0.70 (0.62–0.79)]. Both missense variants produced dramatic phenotypic changes in apoptosis and inflammation-related gene expression. We experimentally validated function of the intronic SNP by DNA electrophoresis, protein identification, and in vitro protein binding assays. DNA carrying the intronic risk allele rs13023380 showed reduced binding efficiency to a cellular protein complex including nucleolin and lupus autoantigen Ku70/80, and showed reduced transcriptional activity in vivo. Thus, in SLE patients, genetic susceptibility could create a biochemical imbalance that dysregulates nucleolin, Ku70/80, or other nucleic acid regulatory proteins. This could promote antibody hypermutation and auto-antibody generation, further destabilizing the cellular network. Together with molecular modeling, our results establish a distinct role for IFIH1 in apoptosis, inflammation, and autoantibody production, and explain the molecular basis of these three risk alleles for SLE pathogenesis.
African-Americans (AA) are at increased risk of systemic lupus erythematosus (SLE), but the genetic basis of this risk increase is largely unknown. We used admixture mapping to localize disease-causing genetic variants that differ in frequency across populations. This approach is advantageous for localizing susceptibility genes in recently admixed populations like AA. Our genome-wide admixture scan identified seven admixture signals, and we followed the best signal at 2q22–24 with fine-mapping, imputation-based association analysis and experimental validation. We identified two independent coding variants and a non-coding variant within the IFIH1 gene associated with SLE. Together with molecular modeling, our results establish a distinct role for IFIH1 in apoptosis, inflammation, and autoantibody production, and explain the molecular basis of these three risk alleles for SLE pathogenesis.