Mary K. Crow

Toll-like receptor 9–dependent activation by DNA-containing immune complexes is mediated by HMGB1 and RAGE

Increased concentrations of DNA-containing immune complexes in the serum are associated with systemic autoimmune diseases such as lupus. Stimulation of Toll-like receptor 9 (TLR9) by DNA is important in the activation of plasmacytoid dendritic cells and B cells. Here we show that HMGB1, a nuclear DNA-binding protein released from necrotic cells, was an essential component of DNA-containing immune complexes that stimulated cytokine production through a TLR9–MyD88 pathway involving the multivalent receptor RAGE. Moreover, binding of HMGB1 to class A CpG oligodeoxynucleotides considerably augmented cytokine production by means of TLR9 and RAGE. Our data demonstrate a mechanism by which HMGB1 and RAGE activate plasmacytoid dendritic cells and B cells in response to DNA and contribute to autoimmune pathogenesis.

Increased expression of CD40 ligand on systemic lupus erythematosus lymphocytes.

The specificity of T cell help for B cell activation and differentiation is maintained by the brief expression on the T cell surface, following T cell receptor-mediated triggering, of CD40 ligand (CD40L). Interaction of T helper (Th) cell CD40L with B cell CD40 induces B cell activation, cell surface expression of activation antigens, proliferation, and initiation of immunoglobulin isotype switch. We predicted that in patients with systemic lupus erythematosus (SLE), in whom Th cell-dependent production of autoantibodies results in immune complex-mediated tissue damage, CD40L expression might be augmented, prolonged, or abnormally regulated. Baseline expression of CD40L was increased in some SLE patients studied, when compared with control subjects. While Th cells from normal subjects (n = 14) and rheumatic disease control patients (n = 9) showed maximal expression of CD40L, after in vitro activation with phorbol myristate acetate (PMA) and ionomycin, at 6 h of culture with diminished levels observed at 24 and 48 h, Th cells from SLE patients (n = 19) maintained high level cell surface expression of CD40L through 24 and 48 h of culture. The prolonged expression of CD40L was functionally significant, as 24 h-activated SLE T cells, when cocultured with target B cells, induced greater B cell surface CD80 (B7-1) expression than did 24 h-activated normal T cells. These results document impaired regulation of CD40L expression in SLE T cells and identify an important potential target for therapy in this systemic autoimmune disease.

High serum IFN-alpha activity is a heritable risk factor for systemic lupus erythematosus.

Interferon α (IFN-α) levels are elevated in many patients with systemic lupus erythematosus (SLE); however it is not known whether high serum IFN-α activity is a cause or a result of the disease. We studied 266 SLE patients and 405 of their healthy relatives, and frequently found high serum IFN-α activity in both patients and healthy relatives as compared to healthy unrelated individuals. High IFN-α activity was clustered in specific families in both SLE patients and their healthy first-degree relatives, suggesting a heritable trait. Heritability was also supported by quantitative familial correlation of IFN-α activity, concordance in affected sib pairs and frequent transmission of the high IFN-α activity trait from parents to offspring. Autoantibodies to RNA-binding proteins and double-stranded DNA were associated with high IFN-α activity in SLE patients; however these autoantibodies were very uncommon in healthy family members and did not explain the observed familial correlations. The frequency of high IFN-α activity was similar across all studied ethnic backgrounds. These data suggest that high serum IFN-α activity is a complex heritable trait, which plays a primary role in SLE pathogenesis.

Preclinical Carotid Atherosclerosis in Patients with Rheumatoid Arthritis

Context Patients with rheumatoid arthritis are prone to premature death from coronary heart disease despite few risk factors. Researchers have wondered if chronic inflammation is a trigger. Content The authors measured inflammatory markers and risk factors for coronary heart disease in 98 matched case-patients and controls (mean age, 48 years). Carotid ultrasonography revealed that 44% of case-patients and 15% of controls had atherosclerotic plaque. Independent predictors of plaque were age, smoking, and rheumatoid arthritis. In patients with rheumatoid arthritis, inflammatory mediators did not predict plaque. Limitations This cross-sectional study cannot prove that rheumatoid arthritis accelerates atherosclerosis. Interpretation Carotid atherosclerotic plaque is much more common in patients with rheumatoid arthritis than in controls. The mechanism remains unknown. The Editors Compared with the general population, patients with rheumatoid arthritis die prematurely (1, 2), primarily because of cardiovascular disease (1-3). Women with this disease have high rates of nonfatal myocardial infarction (4-6), even in the absence of traditional risk factors for atherosclerosis (4, 5, 7). Although markers of disease severity have been linked to an increase in overall mortality rates (1), researchers have not been able to clearly identify specific aspects of rheumatoid arthritis or its treatment that might heighten the risk for cardiovascular disease. Use of corticosteroids or disease-modifying antirheumatic drugs does not appear to increase the risk for cardiovascular events (2). In fact, a large longitudinal study recently reported that death rates from myocardial infarction among North American patients with rheumatoid arthritis had declined to the level seen in the general population (thereby yielding a greater magnitude of decline) in the setting of increased methotrexate use (8). In another U.S. study, methotrexate use was associated with lower all-cause mortality rates in rheumatoid arthritis, mostly because cardiovascular mortality rates were decreased (9). Early diagnosis of atherosclerosis in this population might trigger more aggressive prophylaxis, but we have not determined the prevalence of preclinical atherosclerosis or identified markers for the disease. In this study, we examined the prevalence of atherosclerosis in patients with rheumatoid arthritis by using ultrasonogram-defined carotid artery plaque as a direct measure and proxy for generalized atherosclerosis and as a surrogate for coronary atherosclerosis; we also examined those features of rheumatoid arthritis that predict plaque presence. Previous studies reported that plaque prevalence in rheumatoid arthritis is statistically similar to that of control populations (10, 11). However, in systemic lupus erythematosus, another autoimmune disease characterized by chronic inflammation, cross-sectional studies that were conducted by us and by others showed a marked increase in plaque compared with that seen in carefully matched controls (12, 13). The increased plaque rate in systemic lupus erythematosus is associated with chronic inflammation (not with treatment or with traditional atherosclerosis risk factors), suggesting that similar factors may be at work in rheumatoid arthritis. Preclinical disease may also be identified by using ultrasonography to determine carotid intimamedia thickness, an indirect measure of atherosclerosis. Intimamedia thickness was increased in 2 studies of East Asian patients with rheumatoid arthritis (14, 15) but not in a U.S. study (11). Intimamedia thickness varied more with disease duration (14, 15), but an association with serum C-reactive protein levels and erythrocyte sedimentation rate (2 markers of inflammation) has not been established because of conflicting reports (11, 15). Intimamedia thickness does not always correlate with atherosclerosis, particularly in relatively young individuals with chronic inflammatory disease (12, 13), and it may measure other aspects of vascular disease. Discrete atherosclerotic plaque is a potent independent predictor of incident cardiovascular disease, whereas intimamedia thickness in areas free of discrete plaque has limited value as a marker after traditional risk factors for cardiovascular disease are considered (16-18). Because of conflicting data regarding premature preclinical atherosclerosis in rheumatoid arthritis, we chose to use the direct measure of plaque to examine the prevalence of carotid atherosclerosis in consecutive unselected, nonhospitalized patients with rheumatoid arthritis and matched controls. For our other primary outcome, we sought to determine those clinical and biological measures that best predict the presence of plaque. Methods Study Sample We consecutively recruited patients who met the American College of Rheumatologys classification criteria for a diagnosis (possessing at least 4 of 7 criteria) of rheumatoid arthritis (19) and who were enrolled in the Rheumatoid Arthritis Registry at the Hospital for Special Surgery in New York. Patients were recruited at regular visits with their rheumatologists during a 15-month period (participation rate, 94%). Exclusion criteria were age younger than 18 years, serum creatinine level of 270 mol/L or greater (3.0 mg/dL) or creatinine clearance of 0.50 mL/s or less (30 mL/min), or current or recent (within the past 3 months) pregnancy. We quantified extent of disease by recording extra-articular manifestations (for example, the Sjgren syndrome, leg ulcers, and evidence of vasculitis, such as nail fold infarcts, splinter hemorrhages, and motor neuropathy), active joint count (number of tender or swollen joints), number of joints irreversibly damaged (fixed deformity or surgical replacement) (20), and the patients score on the Multidimensional Health Assessment Questionnaire (21). We recorded treatment by patient interview and chart review. Because treatment is often intermittent or at varying dosages, we tabulated medication use as never, former, or current. An 83-year-old woman had a previous stroke that was documented by magnetic resonance imaging, and a 45-year-old man had had coronary artery bypass surgery; we calculated our results both including and excluding these 2 patients. Patients were matched to controls on the basis of age (within 5 years), sex, and ethnicity. Controls were normotensive and hypertensive individuals who participated in longitudinal studies funded by the National Institutes of Health (22, 23) at the Hypertension Center of The New York Hospital and who underwent similar imaging protocols. We assessed patients for traditional cardiovascular disease risk factors: family history of myocardial infarction in first-degree male relatives younger than 55 years of age or first-degree female relatives younger than 65 years of age, smoking, hypertension (defined as blood pressure of 140/90 mm Hg or higher or the prescribed use of antihypertensive medications), diabetes mellitus (self-reported diagnosis), and fasting serum cholesterol levels. Hypertensive controls were studied after antihypertensive medications had been withheld for 3 or more weeks, whereas antihypertensive medications were not systematically withheld in hypertensive patients with rheumatoid arthritis. Brachial blood pressure was obtained at the end of the ultrasonographic studies after patients had remained in the supine position for 45 to 60 minutes in a quiet, darkened room. Of 100 patients with rheumatoid arthritis, a 74-year-old man was unable to be matched to a suitable control and a woman was excluded because she met diagnostic criteria for systemic lupus erythematosus. The institutional review board approved the study protocol, and all participants gave written informed consent. Carotid Ultrasonography All study participants underwent carotid ultrasonography, which was performed by experienced research sonographers who used an identical protocol. A single cardiologist, who was blinded to the identity of the study participants, interpreted the results. In brief, as previously described (22, 23), participants were studied in the supine position with slight hyperextension of the neck. Both extracranial carotid arterial systems were extensively scanned in multiple planes to optimize identification of atherosclerosis, which was defined as discrete plaque protruding into the lumen at least 50% beyond the diameter of the surrounding wall. Doppler interrogation was performed to evaluate the presence of significant (50% diameter reduction) obstruction. Intimamedia thickness was measured from end-diastolic (minimum dimension) M-mode images of the far wall of the distal common carotid artery. Intimamedia thickness was not measured in a location containing plaque. Mean values of right and left intimamedia thicknesses are presented. Reproducibility of intimamedia thickness and detection of plaque has been well documented (24-26). Carotid ultrasonographic studies were performed in the control group before 1999, whereas studies in the patients with rheumatoid arthritis were performed between 2000 and 2002. Laboratory Assessment Laboratory assessment of the patients with rheumatoid arthritis included routine chemistries and serum rheumatoid factor level. A high-sensitivity assay to determine serum levels of C-reactive protein was analyzed with a Cobas Integra system (Roche Diagnostics, Basel, Switzerland). Serum lipoprotein(a) levels were measured with an immunoturbidometric reagent (Diasorin, Stillwater, Minnesota) on a Roche Diagnostics Cobas Fara II system. Serum interleukin-6 levels were measured by automated enzyme immunoassay (Biosource International, Camarilo, California) on a Roche Diagnostics Cobas Core II analyzer. Serum levels of soluble intracellular adhesion molecule-1 and vascular cell adhesion molecule-1 were measured by enzyme-linked immunosorbent assay (Caltag, Burlingame, California, and R&D Systems, Minneapolis, Minnesota,

Arterial Stiffness in Chronic Inflammatory Diseases

Chronic inflammatory diseases are associated with premature atherosclerosis; however, it is unknown whether arterial stiffness is increased in this setting, possibly as a manifestation of vascular disease preceding and/or independent of atherosclerosis. Carotid ultrasonography and radial applanation tonometry were performed in 101 patients with systemic lupus erythematosus, 80 patients with rheumatoid arthritis, and 105 healthy control subjects. The 3 groups were comparable in age, gender, and carotid artery absolute and relative wall thickness. Atherosclerotic plaque was more common in lupus (46%) and rheumatoid arthritis (38%) patients than in controls (23%) (P<0.003). Although control subjects had higher central and peripheral blood pressures, arterial stiffness was increased in patient groups compared with controls (lupus, rheumatoid arthritis, controls, respectively: &bgr;: 3.36 versus 3.22 versus 2.60, P<0.001; Young’s modulus: 441 versus 452 versus 366 mm Hg/cm, P=0.004; Peterson’s elastic modulus: 278 versus 273 versus 216 mm Hg, P<0.001) after adjustment for differences in mean brachial pressure. In multivariate analysis involving the entire population, arterial stiffness was independently related to age, serum glucose, and the presence of chronic inflammatory disease. In multivariate analysis restricted to the patients, arterial stiffness was independently related to age at diagnosis, disease duration, serum cholesterol, and C-reactive protein (and IL-6, when substituted for C-reactive protein). When analyses were repeated in the 186 study subjects without carotid plaque, arterial stiffness remained significantly elevated in patient groups after adjustment for differences in age and mean brachial pressure. In conclusion, arterial stiffness is increased in chronic inflammatory disorders independent of the presence of atherosclerosis and is related to disease duration, cholesterol, and the inflammatory mediator C-reactive protein and the cytokine that stimulates its production, IL-6.

Association of the IRF5 risk haplotype with high serum interferon-α activity in systemic lupus erythematosus patients

OBJECTIVE A haplotype of the interferon regulatory factor 5 (IRF5) gene has been associated with the risk of developing systemic lupus erythematosus (SLE), and our previous studies have demonstrated that high levels of serum interferon-alpha (IFNalpha) activity are a heritable risk factor for SLE. The aim of this study was to determine whether the IRF5 SLE risk haplotype mediates the risk of SLE by predisposing patients to the development of high levels of serum IFNalpha activity. METHODS IFNalpha levels in 199 SLE patients of European and Hispanic ancestry were measured with a sensitive functional reporter cell assay. The rs2004640, rs3807306, rs10488631, and rs2280714 single-nucleotide polymorphisms (SNPs) in IRF5 were genotyped in these patients. Haplotypes were categorized as SLE risk, neutral, or protective based on published data. RESULTS SLE patients with risk/risk and risk/neutral IRF5 genotypes had higher serum IFNalpha activity than did those with protective/protective and neutral/protective genotypes (P = 0.025). This differential effect of IRF5 genotype on serum IFNalpha levels was driven largely by SLE patients who were positive for either anti-RNA binding protein (anti-RBP) or anti-double-stranded DNA (anti-dsDNA) autoantibodies (P = 0.012 for risk/risk or risk/neutral versus protective/protective or neutral/protective). The rs3807306 genotype was independently associated with high serum IFNalpha in this autoantibody group. We found no difference in IFNalpha activity according to IRF5 genotype in patients lacking either type of autoantibody or in patients positive for both classes of autoantibody. CONCLUSION The IRF5 SLE risk haplotype is associated with higher serum IFNalpha activity in SLE patients, and this effect is most prominent in patients positive for either anti-RBP or anti-dsDNA autoantibodies. This study demonstrates the biologic relevance of the SLE risk haplotype of IRF5 at the protein level.

Systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that can affect many organs, including the skin, joints, the central nervous system and the kidneys. Women of childbearing age and certain racial groups are typically predisposed to developing the condition. Rare, inherited, single-gene complement deficiencies are strongly associated with SLE, but the disease is inherited in a polygenic manner in most patients. Genetic interactions with environmental factors, particularly UV light exposure, Epstein–Barr virus infection and hormonal factors, might initiate the disease, resulting in immune dysregulation at the level of cytokines, T cells, B cells and macrophages. Diagnosis is primarily clinical and remains challenging because of the heterogeneity of SLE. Classification criteria have aided clinical trials, but, despite this, only one drug (that is, belimumab) has been approved for use in SLE in the past 60 years. The 10-year mortality has improved and toxic adverse effects of older medications such as cyclophosphamide and glucocorticoids have been partially offset by newer drugs such as mycophenolate mofetil and glucocorticoid-sparing regimes. However, further improvements have been hampered by the adverse effects of renal and neuropsychiatric involvement and late diagnosis. Adding to this burden is the increased risk of premature cardiovascular disease in SLE together with the risk of infection made worse by immunosuppressive therapy. Challenges remain with treatment-resistant disease and symptoms such as fatigue. Newer therapies may bring hope of better outcomes, and the refinement to stem cell and genetic techniques might offer a cure in the future.

Microarray analysis of interferon-regulated genes in SLE.

Altered regulation of interferon-α (IFNα) in systemic lupus erythematosus (SLE) was first demonstrated nearly 25 years ago. However, only recently has due attention been directed towards the central role of this cytokine family in SLE. Several laboratories have used large-scale microarray technology to study global gene expression patterns in heterogeneous populations of peripheral blood cells from lupus patients and control subjects. The results of these studies demonstrate that IFN-regulated genes are among the most significantly overexpressed in SLE mononuclear cells. In view of the protean effects of IFNs on immune system function, increased activity of IFNs may account for many of the immune system alterations that characterize SLE and contribute to autoimmunity. Definition of the nature of the major IFNs, or other factors, that drive the IFN-regulated gene expression signature noted in SLE is an important area for investigation that may lead to new approaches to targeted therapy of SLE.

LIGATION OF CD40 ON FIBROBLASTS INDUCES CD54 (ICAM-1) AND CD106 (VCAM-1) UP-REGULATION AND IL-6 PRODUCTION AND PROLIFERATION

CD40 was originally described as a functionally significant B cell surface molecule. However, CD40 is also expressed on monocytes, dendritic cells, epithelial cells, and basophils. We now report that synovial membrane (SM) or dermal fibroblasts also express cell surface CD40 in vitro. Fibroblast CD40 expression declines with increasing time in culture and recombinant interferon‐γ (rINF‐γ) induces fibroblast CD40 up‐regulation. This effect of rINF‐γ is augmented by recombinant interleukinlα or recombinant tumor necrosis factor‐α. CD40 expression on fibroblasts is functionally significant because CD40L‐CD40 interactions induce SM fibroblast CD54 (intercellular adhesion molecule‐1) and CD106 (vascular cell adhesion molecule‐1) up‐regulation. Moreover, ligation of CD40 augments IL‐6 production by SM fibroblasts and induces fibroblasts to proliferate. In addition, rINF‐γ enhances the effect of CD40L‐CD40 interactions on fibroblast proliferation. Taken together, these studies show that fibroblasts can express CD40, cytokines can regulate fibroblast CD40 expression, and CD40 ligation induces fibroblast activation and proliferation. J. Leukoc. Biol. 58: 209–216; 1995.

Cutting Edge: Autoimmune Disease Risk Variant of STAT4 Confers Increased Sensitivity to IFN-α in Lupus Patients In Vivo

Increased IFN-α signaling is a primary pathogenic factor in systemic lupus erythematosus (SLE). STAT4 is a transcription factor that is activated by IFN-α signaling, and genetic variation of STAT4 has been associated with risk of SLE and rheumatoid arthritis. We measured serum IFN-α activity and simultaneous IFN-α-induced gene expression in PBMC in a large SLE cohort. The risk variant of STAT4 (T allele; rs7574865) was simultaneously associated with both lower serum IFN-α activity and greater IFN-α-induced gene expression in PBMC in SLE patients in vivo. Regression analyses confirmed that the risk allele of STAT4 was associated with increased sensitivity to IFN-α signaling. The IFN regulatory factor 5 SLE risk genotype was associated with higher serum IFN-α activity; however, STAT4 showed dominant influence on the sensitivity of PBMC to serum IFN-α. These data provide biologic relevance for the risk variant of STAT4 in the IFN-α pathway in vivo.