Increased release of von Willebrand factor antigen from endothelial cells by anti-DNA autoantibodies

Effects of anti-β2GPI antibodies on VWF release from human umbilical vein endothelial cells and ADAMTS13 activity

BACKGROUND

Antiphospholipid syndrome (APS) is characterized by recurrent thromboembolic events in the setting of pathologic autoantibodies, some of which are directed to β2-Glycoprotein 1 (β2GPI). The mechanisms of thrombosis in APS appear to be multifactorial and likely include a component of endothelial activation. Among other things, activated endothelium secretes von Willebrand factor, a hemostatic protein that in excess can increase the risk of thrombosis.

OBJECTIVE

We hypothesized that anti-β2GPI antibodies could regulate the release and modulation of VWF from endothelial cells.

PATIENTS/METHODS

Isolated anti-β2GPI antibodies from patients with APS were assayed for their ability to induced VWF release from HUVECs and modulate the effects of ADAMTS13 in a shear-dependent assay.

RESULTS

We observed that anti-β2GPI antibodies from some patients with APS induced VWF release from human endothelial cells but did not induce formation of cell-anchored VWF-platelet strings. Finally, we also determined that one of the Anti-β2GPI antibodies tested can inhibit the function of ADAMTS13, the main modulator of extracellular VWF.

CONCLUSIONS

These results suggest that VWF and ADAMTS13 may play a role in the prothrombotic phenotype of APS.

Anti-dsDNA antibodies and resident renal cells - Their putative roles in pathogenesis of renal lesions in lupus nephritis

Lupus nephritis affects up to 70% of patients with systemic lupus erythematosus and is an important treatable cause of kidney failure. Cardinal features of lupus nephritis include loss of self-tolerance, production of autoantibodies, immune complex deposition and immune-mediated injury to the kidney, resulting in increased cell proliferation, apoptosis, and induction of inflammatory and fibrotic processes that destroy normal nephrons. The production anti-dsDNA antibodies is a cardinal feature in lupus and their level correlates with disease activity. In addition to the formation of immune complexes thereby triggering complement activation, how anti-dsDNA antibodies home to the kidney and induce pathological processes in the renal parenchyma remain to be fully elucidated. Data from our laboratory and other investigators show that the properties of anti-dsDNA antibodies vary between patients and change over time, and that anti-dsDNA antibodies could bind directly to integral cell surface molecules such as annexin II or α-actinin, or indirectly through chromatin material deposited on the cell surface. The binding of anti-dsDNA antibodies to mesangial cells and proximal renal tubular epithelial cells triggers downstream inflammatory and fibrotic pathways, which include the activation of the PKC and MAPK signaling pathways, increased secretion of pro-inflammatory cytokines and matrix protein deposition that contribute to pathological processes in the renal parenchyma.

Increased von Willebrand factor levels in patients with systemic lupus erythematosus reflect inflammation rather than increased propensity for platelet activation

Background

von Willebrand factor (VWF) is involved in platelet plug formation and protein transport. Increased VWF levels in systemic lupus erythematous (SLE) are considered risk factors for vascular events. VWF protein levels, however, do not accurately reflect its platelet-aggregating function, which has not been examined in SLE.

Methods

Cross-sectional study with clinical and laboratory data obtained in patients with SLE (n=92) from a regional lupus registry. VWF function was determined by ristocetin-induced platelet aggregation (VWF ristocetin cofactor, VWF:RCo) and VWF levels by turbidimetric assay (VWF antigen, VWF:Ag). The platelet-aggregating activity per VWF unit was estimated by the VWF RCo/Ag ratio. Healthy controls served as comparators and associations were evaluated by non-parametric methods.

Results

VWF:Ag (142% vs 107%, p=0.001) and VWF:RCo levels (123% vs 78%, p<0.041) were increased in patients with SLE, but VWF RCo/Ag ratio was similar as in controls (0.83 vs 0.82, p=0.8). VWF:Ag levels were higher in patients experiencing serositis but unrelated to other manifestations, thrombotic disease, Systemic Lupus Erythematous Disease Activity Index 2000 or Systemic Lupus International Collaborative Clinics-Damage Index. VWF:Ag levels correlated significantly with VWF:RCo levels (Rs 0.8, p<0.001), erythrocyte sedimentation rate (ESR) (Rs 0.32, p<0.01), anti-dsDNA Ab (Rs 0.27, p<0.01), total IgG (Rs 0.33 p<0.01), fibrinogen (Rs 0.28, p<0.01) and ceruloplasmin (Rs 0.367, p<0.01) levels. VWF:RCo levels were not related to clinical findings but were correlated with ESR, anti-dsDNA and transferrin levels. No serological associations existed for VWF RCo/Ag ratio (all p>0.2).

Conclusions

In this SLE cohort, VWF:Ag behaved similarly to acute-phase reactants, but VWF:Ag increases were not matched by increases in functional activity per unit of VWF. Thus, more VWF did not increase the propensity for platelet aggregation in SLE.

Pathogenesis of renal disease in systemic lupus erythematosus--the role of autoantibodies and lymphocytes subset abnormalities

Lupus nephritis (LN) is a common and severe organ manifestation of systemic lupus erythematosus (SLE), and is associated with significant patient morbidity and mortality. Autoantibodies and aberrations in lymphocyte subsets have putative roles in the pathogenesis of SLE and LN, and might reflect disease activity and are amenable to immunosuppressive treatments. Anti-DNA is one of the well-studied autoantibodies, which correlates with disease activity and has direct nephritogenic effects on resident renal cells and various glomerular components. Other important autoantibodies in the pathogenesis of LN include anti-C1q, anti-α-actinin and anti-nucleosome antibodies. Changes in naive and memory B cells and plasma cells have been observed in SLE and LN patients. These B cell subsets exert diverse effects during pathogenesis of LN such as production of autoantibodies, secretion of proinflammatory and anti-inflammatory cytokines and presentation of auto-antigens to effector cells. Aberration of T lymphocytes, especially the T-helper subsets, is also highly pertinent in the development of LN. In this context, important T helper subsets include Th1, Th2, Th9, Th17, T_Reg and follicular T-helper cells. The growing knowledge on these autoantibodies and lymphocyte subset abnormalities will enhance our understanding of SLE and LN, and hence help devise better strategies for disease monitoring and treatment.

Definitions of and contributions to cardiovascular disease in systemic lupus erythematosus

Patients with systemic lupus erythematosus (SLE) have a significantly increased risk of cardiovascular disease (CVD). Increased prevalence of atherosclerosis may explain part of this enhanced risk, but SLE related CVD can also result from other mechanisms. Vascular events may be the result of several pathophysiologic mechanisms; some can be caused by atherosclerosis, others may be primarily thrombotic, and some may be due to ongoing inflammation. The traditional risk factors are of importance for the development of CVD in lupus. However, lupus-related factors, such as endothelial dysfunction and inflammation, renal impairment and disease activity, lupus phenotype, autoantibodies and genetic predisposition are equally or even more important. Risk factors may also contribute separately or in combination to increase the risk of atherosclerosis and clinical CVD in SLE. Studies investigating risk factors for CVD in SLE vary with respect to definition of outcome, it is, e.g. common that the terms atherosclerosis and clinical CVD are used interchangeably. Varying definitions and outcomes may thus explain divergent results of different studies and make comparisons difficult. This review summarizes some of the current knowledge regarding risk factors and mechanisms for atherosclerosis and clinical CVD in SLE. Aspects on the importance of CVD definitions and outcomes are briefly discussed.

Autoantibodies and resident renal cells in the pathogenesis of lupus nephritis: getting to know the unknown

Systemic lupus erythematosus is characterized by a breakdown of self-tolerance and production of autoantibodies. Kidney involvement (i.e., lupus nephritis) is both common and severe and can result in permanent damage within the glomerular, vascular, and tubulo-interstitial compartments of the kidney, leading to acute or chronic renal failure. Accumulating evidence shows that anti-dsDNA antibodies play a critical role in the pathogenesis of lupus nephritis through their binding to cell surface proteins of resident kidney cells, thereby triggering the downstream activation of signaling pathways and the release of mediators of inflammation and fibrosis. This paper describes the mechanisms through which autoantibodies interact with resident renal cells and how this interaction plays a part in disease pathogenesis that ultimately leads to structural and functional alterations in lupus nephritis.

Prospective cohort studies on risk factors for cardiovascular events in systemic lupus erythematosus: a major challenge

Cardiovascular disease (CVD) has been identified as a major contributor to morbidity and mortality in patients with systemic lupus erythematosus (SLE). The etiology of premature CVD in SLE is supposed to have many factors, including traditional coronary artery disease (CAD) risk factors, antiphospholipid antibodies, and metabolic and inflammatory factors. Despite the overwhelming interest in CVD in SLE research, prospective studies evaluating risk factors for hard endpoints (that is, cardiovascular events) are relatively scarce. The article by Gustafsson and colleagues suggests that prothrombotic factors play an important role in SLE-related CVD and that the influence of traditional CAD risk factors might be limited.

Predictors of the first cardiovascular event in patients with systemic lupus erythematosus - a prospective cohort study

Introduction

Cardiovascular disease (CVD) is a major cause of premature mortality among Systemic lupus erythematosus (SLE) patients. Many studies have measured and evaluated risk factors for premature subclinical atherosclerosis, but few studies are prospective and few have evaluated risk factors for hard endpoints, i.e. clinically important cardiovascular events (CVE). We investigated the impact of traditional and lupus associated risk factors for the first ever CVE in a longitudinal cohort of SLE patients.

Methods

A total of 182 SLE patients (mean age 43.9 years) selected to be free of CVE were included. Cardiovascular and autoimmune biomarkers were measured on samples collected after overnight fasting at baseline. Clinical information was collected at baseline and at follow up. End point was the first ever CVE (ischemic heart, cerebrovascular or peripheral vascular disease or death due to CVD). Impact of baseline characteristics/biomarkers on the risk of having a first CVE was evaluated with Cox regression.

Results

Follow up was 99.5% after a mean time of 8.3 years. Twenty-four patients (13%) had a first CVE. In age-adjusted Cox regression, any positive antiphospholipid antibody (aPL), elevated markers of endothelial activation (von Willebrand factor (vWf), soluble vascular cellular adhesion molecule-1 (sVCAM-1)) and fibrinogen predicted CVEs. Of SLE manifestations, arthritis, pleuritis and previous venous occlusion were positively associated with future CVEs while thrombocytopenia was negatively associated. Among traditional risk factors only age and smoking were significant predictors. In a multivariable Cox regression model age, any positive aPL, vWf and absence of thrombocytopenia were all predictors of the first CVE.

Conclusions

In addition to age, positive aPL, biomarkers indicating increased endothelial cell activity/damage, and absence of thrombocytopenia were independent predictors of CVEs in this prospective study. Our results indicate that activation of the endothelium and the coagulation system are important features in SLE related CVD. Furthermore, we observed that the risk of CVEs seems to differ between subgroups of SLE patients.

The Tie2 receptor antagonist angiopoietin 2 facilitates vascular inflammation in systemic lupus erythematosus

OBJECTIVE

To investigate the role of the angiopoietin-tyrosine kinase with Ig-like and epidermal growth factor-like domains (Ang-Tie) system in systemic lupus erythematosus (SLE). Endothelial activation is emerging as a key event for leukocyte recruitment and accelerated atherosclerosis in SLE. Recently, the endothelial-specific Ang-Tie ligand-receptor system has been identified as a major regulator of vascular responsiveness to inflammatory stimuli.

METHODS

Ang1 (by immunoradiometric sandwich assay (IRMA)) and Ang2 (by ELISA) were measured in sera of 43 patients with SLE and 30 healthy controls. Expression of Ang2 was studied by immunohistochemistry in biopsies of human lupus nephritis.

RESULTS

Circulating Ang2 concentrations were increased and concentrations of Ang1 decreased in patients with active SLE compared to healthy controls. This tendency was still present in inactive SLE, although less pronounced. Individual Ang2 concentrations correlated well with SLE Disease Activity Index (SLEDAI) score, proteinuria, double-stranded DNA (dsDNA) titre and soluble vascular cell adhesion molecule 1 (sVCAM-1). In a multivariate regression analysis, renal involvement was the only independent predictor for elevated Ang2. Serum Ang2 was identified as a strong predictor for disease activity by receiver operating characteristic (ROC) procedures and regression tree models. Protein expression of Ang2 was upregulated in glomeruli of patients with lupus nephritis.

CONCLUSIONS

These data indicate that Ang2-mediated disruption of protective Ang1/Tie2 signalling is operational in SLE. Ang2 might facilitate endothelial inflammation, permeability and contribute to premature atherosclerosis. Furthermore, circulating Ang2 may be a valuable new biomarker for disease activity in SLE. Strategies to control the deleterious effects of Ang2 may open new perspectives to prevent endothelial inflammation in SLE.

Dendritic cells from lupus-prone mice are defective in repressing immunoglobulin secretion

Autoimmunity results from a breakdown in tolerance mechanisms that regulate autoreactive lymphocytes. We recently showed that during innate immune responses, secretion of IL-6 by dendritic cells (DCs) maintained autoreactive B cells in an unresponsive state. In this study, we describe that TLR4-activated DCs from lupus-prone mice are defective in repressing autoantibody secretion, coincident with diminished IL-6 secretion. Reduced secretion of IL-6 by MRL/lpr DCs reflected diminished synthesis and failure to sustain IL-6 mRNA production. This occurred coincident with lack of NF-kappaB and AP-1 DNA binding and failure to sustain IkappaBalpha phosphorylation. Analysis of individual mice showed that some animals partially repressed Ig secretion despite reduced levels of IL-6. This suggests that in addition to IL-6, DCs secrete other soluble factor(s) that regulate autoreactive B cells. Collectively, the data show that MRL/lpr mice are defective in DC/IL-6-mediated tolerance, but that some individuals maintain the ability to repress autoantibody secretion by an alternative mechanism.

Pathogenesis of lupus nephritis: an update

Lupus nephritis (LN) is a prototypic autoimmune disease. Its immunopathogenesis is characterized by the loss of self-tolerance. In this article, we review our current understanding of the disease mediators of LN. There is ample evidence to suggest a pathogenic role of nephritogenic autoantibodies. These antibodies cross react with nucleosomal epitopes, and the in vivo generation of nucleosomes requires apoptosis. Furthermore, there is an intriguing and paradoxical relationship between complement and systemic lupus erythematosus (SLE). Immune complex-mediated activation of complement through the classic pathway is traditionally believed to be a major mechanism by which tissue injury occurs. In contrast, hereditary deficiencies of complement components increase the risk of SLE. Finally, the roles of reactive nitrogen and oxygen species are emphasized.

Tubular expression of angiotensin II receptors and their regulation in IgA nephropathy

Enhanced renal expression for the renin-angiotensin system (RAS) is detected in IgA nephropathy (IgAN). Previous data showed an altered glomerular expression of angiotensin II type 1 receptor (AT1R), suggesting a regulatory response to high intrarenal angiotensin II (Ang II) concentration in IgAN. In this study, the expression and regulation of Ang II receptors were examined in human proximal tubular epithelial cells (PTEC) in IgAN. Tubular expression of AT1R and Ang II type 2 receptor (AT2R) was increased in IgAN. In vitro culture experiment showed that the upregulation of Ang II receptors was not due to the direct effect of IgA but the indirect effect after IgA deposition on human mesangial cell. When PTEC were cultured with conditioned culture medium from human mesangial cells activated with IgA, Ang II production was upregulated, leading to inflammation and apoptosis via the AT1R and AT2R, respectively. Sequential expression of Ang II receptors determined the injury of PTEC induced by mediators in the conditioned medium. The initial interaction between Ang II and AT1R activated both protein kinase C and mitogen-activated protein kinase pathways, leading to inflammatory responses. This early AT1R-dependent event was followed by upregulation of AT2R expression and continued Ang II release. The interaction between Ang II and AT2R subsequently led to expression of cleaved poly[ADP-ribose] polymerase through downregulation of the mitogen-activated protein kinase pathway. The data suggest that appropriate control of Ang II receptor activities in PTEC may ameliorate tubulointerstitial injury in IgAN.

Rationale for interleukin-6 blockade in systemic lupus erythematosus

Interleukin-6 (IL-6) is a pleiotropic cytokine with a wide range of biological activities that plays an important role in immune regulation and inflammation. Among other actions, it induces terminal differentiation of B lymphocytes into antibody-forming cells and the differentiation of T cells into effector cells. IL-6 also has multiple potent proinflammatory effects. An association between IL-6 and lupus was demonstrated in murine models of SLE and blocking IL-6 improved lupus in all models tested. Data from several studies suggest that IL-6 plays a critical role in the B cell hyperactivity and immunopathology of human SLE, and may have a direct role in mediating tissue damage. Based on these data, we propose that blocking the effect of IL-6 in humans may improve lupus by interacting with the autoinflammatory process both systemically and locally.

Effect of maternal anti-HPA-1a antibodies and polyclonal IVIG on the activation status of vascular endothelial cells

Maternal anti-HPA-1a antibodies can cause severe fetal and neonatal alloimmune thrombocytopenia (FNAIT), complicated by intracranial haemorrhage (ICH). Antenatal treatment with maternal intravenous immunoglobulin (IVIG) seems to protect against ICH even when thrombocytopenia persists. The aim of this study was to investigate if anti-HPA-1a antibodies and IVIG potentially affect vascular endothelial cells (ECs) in order to identify susceptibility for ICH. Human umbilical cord endothelial cells (HUVEC) were incubated with anti-HPA-1a antibodies with or without polyclonal IVIG and evaluated for EC activation. Maternal sera with anti-HPA-1a antibodies affected neither the EC expression of intracellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1) and tissue factor (TF) nor the release of van Willebrand factor (vWF) or interleukin (IL)-8 nor the integrity of ECs. Maternal sera obtained after IVIG treatment and polyclonal IVIG decrease constitutive and cytokine-induced ICAM-1 and VCAM-1 expression on ECs. The results show that maternal anti-HPA-1a antibodies cause no activation or damage of ECs in this model. The clinical relevance of the de-activating properties of IVIG on EC activation with respect to ICH deserves further investigation.

New approaches to the renal pathogenicity of anti-DNA antibodies in systemic lupus erythematosus

Autoantibodies against double stranded (ds) DNA are not only a helpful serological marker for diagnosis of systemic lupus erythematosus (SLE), but have also been shown to be crucial in the pathogenesis of lupus nephritis. However, the question of how anti-dsDNA antibodies contribute to renal damage is unresolved. Many authorities believe that indirect binding (mediated by nuclear antigens) or direct cross-reactivity of anti-dsDNA antibodies with kidney antigens are important determinants of anti-dsDNA nephritogenicity. An alternative hypothesis for the renal pathogenicity of anti-dsDNA antibodies was proposed more than 20 years ago, namely that certain autoantibodies could penetrate into living cells and thus induce damage. Work from several laboratories has recently provided firm support for this iconoclastic theory, which contradicted prevailing immunologic dogma that cell interiors are inaccessible to antibodies. Here, we review the evidence that anti-dsDNA antibodies may penetrate into living cells, and discuss which intracellular events may follow from binding of anti-dsDNA antibodies to the cell surface and subsequent intracellular penetration. Determining the mechanism by which anti-dsDNA antibodies induce renal injury is important for understanding a major disease manifestation of lupus, and may lead to the development of novel approaches to the treatment of lupus renal disease.

Endothelial cell activation, injury, damage and dysfunction: separate entities or mutual terms?

The loss of well-regulated endothelial cell functioning is followed by adverse changes in a variety of physiological systems, such as the expression of adhesion molecules, maintenance of adequate blood vessel tone and haemostasis. Therefore, a full understanding of endothelial cell biology is essential if the losses of normal function of these systems are to be avoided. The viewpoint presented in this paper suggests that a spectrum between endothelial cell health and disease can be drawn: midway between these two extremes is immunological activation (by, for example, cytokines), which is reversible. Endothelial cell damage or injury (which may be the result of chronic inflammatory activation, hypercholesterolaemia, and/or smoking) are invariably associated with clinical conditions such as hypertension and oedema (and, ultimately, thrombosis and infarction), and are more difficult to reverse. A better understanding of the events, including apoptosis, that lead to vascular dysfunction may be useful in developing our understanding of vascular biology.

Monoclonal anti-double-stranded DNA autoantibody stimulates the expression and release of IL-1beta, IL-6, IL-8, IL-10 and TNF-alpha from normal human mononuclear cells involving in the lupus pathogenesis

In our previous reports, we found polyclonal anti-double-stranded DNA antibodies (anti-dsDNA) purified from patients with active systemic lupus erythematosus (SLE) exerted inhibitory effect on [3H]thymidine incorporation of human mononuclear cells (MNC). However, the other immunological effects of anti-dsDNA on the functions of MNC have not yet been reported. In this study, two monoclonal antibodies, 12B3 and 9D7, with different anti-dsDNA activity were evaluated for their effects on the expression and release of different cytokines from human MNC. We confirmed absence of endotoxin in the two monoclonal antibody preparations and the used medium as detected by Limulus amoebocyte lysate test. The mRNA expression and release of different cytokines including interleukin (IL)-1beta, IL-2, IL-4, IL-6, IL-8, IL-10, tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) were measured. We found the two monoclonal anti-dsDNA not only dose-responsively suppressed the phytohaemagglutinin (PHA)-induced thymidine uptake of human MNC but stimulated the mRNA expression of IL-1beta, IL-6 and IL-8 in normal human MNC detected by reverse transcription-polymerase chain reaction (RT-PCR). Enzyme-linked immunosorbent assay (ELISA) measurement of cytokines in MNC culture supernatants revealed that anti-dsDNA enhanced IL-1beta, IL-8, TNF-alpha and IL-10 release from resting MNC. These effects of anti-dsDNA antibodies were not affected by polymyxin B, a potent binder and neutralizer of lipopolysaccharide (LPS). These in vitro studies suggest that anti-dsDNA possess a dual effect on normal human MNC: (a) to enhance the release of proinflammatory cytokines (IL-1beta, IL-8 and TNF-alpha) from MNC to augment inflammatory reaction; and (b) to polarize the immune reaction towards the T helper 2 (Th2) (increased IL-10 production) pathway. This unique effect of anti-dsDNA may play a role in lupus pathogenesis by augmenting inflammatory reactions and autoantibody production which are commonly found in patients with active SLE.

Effect of anti-DNA autoantibodies on the gene expression of interleukin 8, transforming growth factor-beta, and nitric oxide synthase in cultured endothelial cells

Our study aims to determine whether anti-dsDNA exerts any effect on the gene expression of IL-8 or TGF-beta in cultured HUVEC. Both cytokines have angiogenic effect on endothelial cells. IgG was purified from 19 patients with SLE and from 19 healthy controls. Anti-dsDNA-depleted polyclonal IgG was also prepared from serum IgG of lupus patients by affinity chromatography with DNA cellulose column. Compared with either control IgG or anti-dsDNA-dep-IgG, HUVEC incubated with anti-dsDNA-containing-IgG expressed higher levels of IL-8 mRNA (p = 0.0001) and TGF-beta 1 mRNA (p = 0.0014). We demonstrated a significant increase in the percentage of cells with fragmented DNA in HUVEC incubated with anti-dsDNA-containing-IgG compared with those incubated with anti-dsDNA-dep-IgG, supporting the notion that anti-dsDNA may exert a direct apoptotic effect on cultured endothelial cells. Our study provides in vitro evidence that anti-dsDNA could play an important pathogenetic role in inducing inflammatory injury of vascular endothelium in SLE.

Increased nitric oxide production accompanied by the up-regulation of inducible nitric oxide synthase in vascular endothelium from patients with systemic lupus erythematosus

OBJECTIVE

To investigate whether systemic lupus erythematosus (SLE) is accompanied by increased serum nitrite levels, whether active compared with inactive disease is associated with greater nitric oxide (NO) production, and whether endothelial cells or keratinocytes serve as cellular sources of NO by virtue of their increased expression of either constitutive nitric oxide synthase (cNOS) or inducible NOS (iNOS).

METHODS

Fifty-one serum samples (46 from patients with SLE) were analyzed for NO production by measuring nitrite levels in a calorimetric assay. Skin biopsy samples from 21 SLE patients and 11 healthy volunteers were evaluated immunohistochemically, using monoclonal antibodies, for endothelial cell and keratinocyte cNOS and iNOS expression.

RESULTS

Serum nitrite levels were significantly elevated in the 46 patients with SLE (mean +/- SEM 37 +/- 6 microM/liter) compared with controls (15 +/- 7 microM/liter; P < 0.01), and were elevated in patients with active SLE compared with those with inactive disease (46 +/- 7 microM/liter versus 30 +/- 7 microM/liter; P < 0.01). Serum nitrite levels correlated with disease activity (r = 0.47, P = 0.04) and with levels of antibodies to double-stranded DNA (r = 0.35, P = 0.02). Endothelial cell expression of iNOS in SLE patients (mean +/- SEM score 1.5 +/- 0.2) was significantly greater compared with controls (0.6 +/- 0.2; P < 0.01), and higher in patients with active disease compared with those with inactive SLE (1.7 +/- 0.2 versus 1.2 +/- 0.2; P < 0.01). Keratinocyte expression of iNOS was also significantly elevated in SLE patients (0.9 +/- 0.1) compared with controls (0.4 +/- 0.1; P < 0.001). With regard to expression of cNOS, there were no differences between patients with active SLE, those with inactive SLE, and normal controls in either the vascular endothelium or the keratinocytes.

CONCLUSION

NO production is increased in patients with SLE, and 2 potential sources of excessive NO are activated endothelial cells and keratinocytes via up-regulated iNOS.

Thrombosis and systemic lupus erythematosus: the Hopkins Lupus Cohort perspective

Vascular damage in systemic lupus erythematosus (SLE) occurs through vasculitis, premature atherosclerosis, and hypercoagulability (predominantly due to the antiphospholipid antibody syndrome). In the Hopkins Lupus Cohort, a prospective cohort study, the incidence of thrombosis is 2 per 100 person-years of follow-up. Markers of immune-complex mediated injury (high anti-dsDNA and low C3), atherosclerosis (hypertension, hyperlipidemia, homocysteine) and antiphospholipid antibodies (lupus anticoagulant or anticardiolipin) are independent predictors of thrombosis. Hydroxychloroquine use is protective against future thrombosis.