Lupus-prone New Zealand Black/New Zealand White F1 mice display endothelial dysfunction and abnormal phenotype and function of endothelial progenitor cells

Metabolic Modulators in Cardiovascular Complications of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a multifactorial disorder with contributions from hormones, genetics, and the environment, predominantly affecting young women. Cardiovascular disease is the primary cause of mortality in SLE, and hypertension is more prevalent among SLE patients. The dysregulation of both innate and adaptive immune cells in SLE, along with their infiltration into kidney and vascular tissues, is a pivotal factor contributing to the cardiovascular complications associated with SLE. The activation, proliferation, and differentiation of CD4+ T cells are intricately governed by cellular metabolism. Numerous metabolic inhibitors have been identified to target critical nodes in T cell metabolism. This review explores the existing evidence and knowledge gaps concerning whether the beneficial effects of metabolic modulators on autoimmunity, hypertension, endothelial dysfunction, and renal injury in lupus result from the restoration of a balanced immune system. The inhibition of glycolysis, mitochondrial metabolism, or mTORC1 has been found to improve endothelial dysfunction and prevent the development of hypertension in mouse models of SLE. Nevertheless, limited information is available regarding the potential vasculo-protective effects of drugs that act on immunometabolism in SLE patients.

Perivascular adipose tissue promotes vascular dysfunction in murine lupus

Introduction

Patients with systemic lupus erythematosus (SLE) are at elevated risk for Q10 cardiovascular disease (CVD) due to accelerated atherosclerosis. Compared to heathy control subjects, lupus patients have higher volumes and densities of thoracic aortic perivascular adipose tissue (PVAT), which independently associates with vascular calcification, a marker of subclinical atherosclerosis. However, the biological and functional role of PVAT in SLE has not been directly investigated.

Methods

Using mouse models of lupus, we studied the phenotype and function of PVAT, and the mechanisms linking PVAT and vascular dysfunction in lupus disease.

Results and discussion

Lupus mice were hypermetabolic and exhibited partial lipodystrophy, with sparing of thoracic aortic PVAT. Using wire myography, we found that mice with active lupus exhibited impaired endothelium-dependent relaxation of thoracic aorta, which was further exacerbated in the presence of thoracic aortic PVAT. Interestingly, PVAT from lupus mice exhibited phenotypic switching, as evidenced by "whitening" and hypertrophy of perivascular adipocytes along with immune cell infiltration, in association with adventitial hyperplasia. In addition, expression of UCP1, a brown/beige adipose marker, was dramatically decreased, while CD45-positive leukocyte infiltration was increased, in PVAT from lupus mice. Furthermore, PVAT from lupus mice exhibited a marked decrease in adipogenic gene expression, concomitant with increased pro-inflammatory adipocytokine and leukocyte marker expression. Taken together, these results suggest that dysfunctional, inflamed PVAT may contribute to vascular disease in lupus.

Cardiovascular disease risk and pathogenesis in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) often features extensive cardiovascular (CV) comorbidity and patients with SLE are at significantly increased risk of CV event occurrence and CV-related mortality. While the specific mechanisms leading to this increased cardiovascular disease (CVD) risk remain to be fully characterized, this heightened risk cannot be fully explained by traditional CV risk factors and is likely driven by immunologic and inflammatory features of SLE. Widespread innate and adaptive immune dysregulation characterize SLE, and factors including excessive type I interferon burden, inappropriate formation and ineffective clearance of neutrophil extracellular traps, and autoantibody formation have been linked to clinical and metabolic features impacting CV risk in SLE and may represent pathogenic drivers of SLE-related CVD. Indeed, functional and phenotypic aberrations in almost every immune cell type are present in SLE and may impact CVD progression. As understanding of the contribution of SLE-specific factors to CVD in SLE improves, improved screening and monitoring of CV risk alongside development of therapeutic treatments aimed at prevention of CVD in SLE patients are required and remain the focus of several ongoing studies and lines of inquiry.

Vascular Inflammation in Mouse Models of Systemic Lupus Erythematosus

Vascular inflammation mediated by overly activated immune cells is a significant cause of morbidity and mortality in systemic lupus erythematosus (SLE). Several mouse models to study the pathogenesis of SLE are currently in use, many of which have different mechanisms of pathogenesis. The diversity of these models allows interrogation of different aspects of the disease pathogenesis. To better determine the mechanisms by which vascular inflammation occurs in SLE, and to assist future researchers in choosing the most appropriate mouse models to study cardiovascular complications in SLE, we suggest that direct comparisons of vascular inflammation should be conducted among different murine SLE models. We also propose the use of in vitro vascular assays to further investigate vascular inflammation processes prevalent among different murine SLE models.

Cardiovascular disease risk and pathogenesis in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) often features extensive cardiovascular (CV) comorbidity and patients with SLE are at significantly increased risk of CV event occurrence and CV-related mortality. While the specific mechanisms leading to this increased cardiovascular disease (CVD) risk remain to be fully characterized, this heightened risk cannot be fully explained by traditional CV risk factors and is likely driven by immunologic and inflammatory features of SLE. Widespread innate and adaptive immune dysregulation characterize SLE, and factors including excessive type I interferon burden, inappropriate formation and ineffective clearance of neutrophil extracellular traps, and autoantibody formation have been linked to clinical and metabolic features impacting CV risk in SLE and may represent pathogenic drivers of SLE-related CVD. Indeed, functional and phenotypic aberrations in almost every immune cell type are present in SLE and may impact CVD progression. As understanding of the contribution of SLE-specific factors to CVD in SLE improves, improved screening and monitoring of CV risk alongside development of therapeutic treatments aimed at prevention of CVD in SLE patients are required and remain the focus of several ongoing studies and lines of inquiry.

Animal models of systemic lupus erythematosus and their applications in drug discovery

INTRODUCTION

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease with substantial phenotypic heterogeneity. Currently, our understanding of the pathogenesis is still limited, and as a result, specific and efficacious therapies are lacking. Various mouse models have been established to serve as powerful tools that will promote a better understanding of the disease and the ability to test novel drugs before clinical application.

AREAS COVERED

The authors review the existing mouse models of SLE in terms of pathogenesis and manifestations, as well as their applications in drug discovery and development. The areas of focus include promising novel therapeutics that could benefit patients in the future and the contribution of mouse models used in preclinical studies.

EXPERT OPINION

Given the diversity of SLE mouse models with different characteristics, researchers must select a suitable model based on the mechanism involved. The use of multiple models is needed for drug testing studies to evaluate drug efficacy on different genetic backgrounds and other mechanisms to provide a reference for clinical trials.

Vascular Inflammation and Dysfunction in Lupus-Prone Mice-IL-6 as Mediator of Disease Initiation

BACKGROUND

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease and patients are under an increased risk for cardiovascular (CV) events and mortality. The increased CV risk for patients with SLE seems to be caused by a premature and accelerated atherosclerosis, attributable to lupus-specific risk factors (i.e., increased systemic inflammation, altered immune status), apart from traditional CV risk factors. To date, there is no established experimental model to explore the pathogenesis of this increased CV risk in SLE patients.

METHODS

Here we investigated whether MRL-Fas^lpr mice, which develop an SLE-like phenotype, may serve as a model to study lupus-mediated vascular disease. Therefore, MRL-Fas^lpr, MRL-++, and previously generated Il6^-/- MRL-Fas^lpr mice were used to evaluate vascular changes and possible mechanisms of vascular dysfunction and damage.

RESULTS

Contrary to MRL-++ control mice, lupus-prone MRL-Faslpr mice exhibited a pronounced vascular and perivascular leukocytic infiltration in various organs; expression of pro-inflammatory cytokines in the aorta and kidney was augmented; and intima-media thickness of the aorta was increased. IL-6 deficiency reversed these changes and restored aortic relaxation.

CONCLUSION

Our findings demonstrate that the MRL-Fas^lpr mouse model is an excellent tool to investigate vascular damage in SLE mice. Moreover, IL-6 promotes vascular inflammation and damage and could potentially be a therapeutic target for the treatment of accelerated arteriosclerosis in SLE.

IFN-I Mediates Dysfunction of Endothelial Progenitor Cells in Atherosclerosis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a multi-system autoimmune disease including the cardiovascular system. Atherosclerosis is the most common cardiovascular complication of SLE and a significant risk factor for morbidity and mortality. Vascular damage/protection mechanism in SLE patients is out of balance, caused by the cascade reaction among oxidative stress, proinflammatory cytokines, Neutrophil Extracellular Traps, activation of B cells and autoantibodies and abnormal T cells. As a precursor cell repairing vascular endothelium, endothelial progenitor cells (EPCs) belong to the protective mechanism and show the reduced number and impaired function in SLE. However, the pathological mechanism of EPCs dysfunction in SLE remains ill-defined. This paper reviews the latest SLE epidemiology and pathogenesis, discusses the changes in the number and function of EPCs in SLE, expounds the role of EPCs in SLE atherosclerosis, and provides new guidance and theoretical basis for exploring novel targets for SLE treatment.

Type-I interferons in atherosclerosis

Chen et al. review the effects of type-I IFNs and the potential of anti–type-I IFN therapies in atherosclerosis.

The contribution of dyslipidemia and inflammation in atherosclerosis is well established. Along with effective lipid-lowering treatments, the recent success of clinical trials with anti-inflammatory therapies and the accelerated atherosclerosis in many autoimmune diseases suggest that targeting inflammation may open new avenues for the prevention and the treatment for cardiovascular diseases (CVDs). In the past decades, studies have widened the role of type-I interferons (IFNs) in disease, from antivirus defense to autoimmune responses and immuno-metabolic syndromes. While elevated type-I IFN level in serum is associated with CVD incidence in patients with interferonopathies, experimental data have attested that type-I IFNs affect plaque-residing macrophages, potentiate foam cell and extracellular trap formation, induce endothelial dysfunction, alter the phenotypes of dendritic cells and T and B lymphocytes, and lead to exacerbated atherosclerosis outcomes. In this review, we discuss the production and the effects of type-I IFNs in different atherosclerosis-associated cell types from molecular biology studies, animal models, and clinical observations, and the potential of new therapies against type-I IFN signaling for atherosclerosis.

Accelerated model of lupus autoimmunity and vasculopathy driven by toll-like receptor 7/9 imbalance

Objectives

Activation of endosomal toll-like receptor (TLR)7 or TLR9 has been proposed as a critical step for the initiation and development of SLE. Traditional spontaneous lupus models normally introduce multiple risk alleles, thereby adding additional confounding factors. In the induced lupus models, the role of TLR9 remains unclear. In the present study, we explored the role of an imbalance between TLR7 and TLR9 pathways in the pathogenesis of lupus and its associated vasculopathy using the imiquimod model in TLR9 KO/B6 background.

Methods

Wild type (WT) and Tlr9^-/- mice were epicutaneously treated with imiquimod cream 5% on both ears three times per week for indicated times. At euthanasia, mice were analysed for organ involvement, endothelium-dependent vasorelaxation, serum autoantibodies, and innate and adaptive immune responses.

Results

Compared with the lupus-like phenotype that develops in imiquimod-treated WT mice, Tlr9^-/- mice exposed to imiquimod have increased severity of autoimmunity features and inflammatory phenotype that develops at earlier stages. These abnormalities are characterised by enhanced TLR7 expression and immune activation, increased immune complex deposition, Th1 T cells and dendritic cell kidney infiltration and significant impairments in endothelial function. Modulation of TLR7 expression was observed in the Tlr9^-/- mice.

Conclusions

These findings further underscore the protective role of TLR9 in TLR7-driven autoimmunity and also in the development of vasculopathy, further strengthening the importance of tightly manipulating TLRs in putative therapeutic strategies. This study provides a new model of accelerated lupus phenotype driven by danger-associated molecular patterns.

Novel Insights in Systemic Lupus Erythematosus and Atherosclerosis

Introduction

The systemic inflammatory nature of systemic lupus erythematosus (SLE) is well patent not only in the diverse clinical manifestations of the disease but also in the increased risk of premature atherosclerosis and cardiovascular events (CVE), making SLE one of the most complex diseases to study and manage in clinical practice.

Aim

To travel from old aspects to modern insights on the physiopathology, new molecular biomarkers, imaging methods of atherosclerosis assessment, and the potential treatments of atherosclerosis in SLE.

Methods

We conducted a literature search using PubMed database and performed a critical review.

Conclusion/discussion

Several developments have taken place in the understanding of the relationship between SLE and premature atherosclerosis. Nevertheless, cardiovascular diseases are still the major cause of reduced life expectancy in SLE and the main cause of death. The lack of standardization methods for the imaging assessment of atherosclerosis in SLE and the multifactorial nature of the disease are well patriated in the difficulty of achieving consistent and reproducible results among studies that focus in cardiovascular risk assessment and prediction. A raising number of molecular biomarkers of atherosclerosis have been proposed, but the combination of several biomarkers and risk factors may better estimate cardiovascular disease risk. Moreover, the development of effective therapies to prevent progression of atherosclerosis and CVE shall address systemic inflammation.

A role for muscarinic receptors in neutrophil extracellular trap formation and levamisole-induced autoimmunity

Levamisole, an anthelmintic drug with cholinergic properties, has been implicated in cases of drug-induced vasculitis when added to cocaine for profit purposes. Neutrophil extracellular trap (NET) formation is a cell death mechanism characterized by extrusion of chromatin decorated with granule proteins. Aberrant NET formation and degradation have been implicated in idiopathic autoimmune diseases that share features with levamisole-induced autoimmunity as well as in drug-induced autoimmunity. This study's objective was to determine how levamisole modulates neutrophil biology and its putative effects on the vasculature. Murine and human neutrophils exposed to levamisole demonstrated enhanced NET formation through engagement of muscarinic subtype 3 receptor. Levamisole-induced NETosis required activation of Akt and the RAF/MEK/ERK pathway, ROS induction through the nicotinamide adenine dinucleotide phosphate oxidase, and peptidylarginine deiminase activation. Sera from two cohorts of patients actively using levamisole-adulterated cocaine displayed autoantibodies against NET components. Cutaneous biopsy material obtained from individuals exposed to levamisole suggests that neutrophils produce NETs in areas of vasculitic inflammation and thrombosis. NETs generated by levamisole were toxic to endothelial cells and impaired endothelium-dependent vasorelaxation. Stimulation of muscarinic receptors on neutrophils by cholinergic agonists may contribute to the pathophysiology observed in drug-induced autoimmunity through the induction of inflammatory responses and neutrophil-induced vascular damage.

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.

Endothelial progenitor dysfunction associates with a type I interferon signature in primary antiphospholipid syndrome

OBJECTIVES

Patients with antiphospholipid syndrome (APS) are at risk for subclinical endothelial injury, as well as accelerated atherosclerosis. In the related disease systemic lupus erythematosus, there is a well-established defect in circulating endothelial progenitors, which leads to an accrual of endothelial damage over time. This defect has been at least partially attributed to exaggerated expression of type I interferons (IFNs). We sought to determine whether these pathways are important in APS.

METHODS

We studied 68 patients with primary APS. Endothelial progenitors were assessed by flow cytometry and functional assay. Type I IFN activity was determined by a well-accepted bioassay, while peripheral blood mononuclear cells were scored for expression of IFN-responsive genes.

RESULTS

Endothelial progenitors from patients with APS demonstrated a marked defect in the ability to differentiate into endothelial cells, a phenotype which could be mimicked by treating control progenitors with APS sera. Elevated type I IFN activity was detected in the circulation of patients with APS (a finding that was then replicated in an independent cohort). While IgG depletion from APS sera did not rescue endothelial progenitor function, the dysfunction was successfully reversed by a type I IFN receptor-neutralising antibody.

CONCLUSIONS

We describe, for the first time to our knowledge, an IFN signature in primary APS and show that this promotes impaired endothelial progenitor function. This work opens the door to novel approaches that may mitigate vascular damage in APS, such as anti-IFN drugs.

Why are kids with lupus at an increased risk of cardiovascular disease?

Juvenile-onset systemic lupus erythematosus (SLE) is an aggressive multisystem autoimmune disease. Despite improvements in outcomes for adult patients, children with SLE continue to have a lower life expectancy than adults with SLE, with more aggressive disease, a higher incidence of lupus nephritis and there is an emerging awareness of their increased risk of cardiovascular disease (CVD). In this review, we discuss the evidence for an increased risk of CVD in SLE, its pathogenesis, and the clinical approach to its management.

Understanding mechanisms of hypertension in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder that predominately affects women of reproductive age. Hypertension is an important cardiovascular risk factor that is prevalent in this patient population. Despite the high incidence of hypertension in women with SLE, the pathophysiological mechanisms underlying the development of hypertension remain poorly understood. This review will focus on disease-related factors, including inflammation, autoantibodies, and sex hormones that may contribute to hypertension in patients with SLE. In addition, we will highlight studies performed by our laboratory using the female NZBWF1 (F1 hybrid of New Zealand Black and New Zealand White strains) mouse model, a spontaneous model of SLE that mimics human disease and develops hypertension and renal injury. Specifically, using female NZBWF1 mice, we have demonstrated that multiple factors contribute to the pathogenesis of hypertension, including the inflammatory cytokine, tumor necrosis factor (TNF)-α, oxidative stress, as well as B-cell hyperactivity and autoantibody production.

Aortic aneurysm association with SLE - a case-control study

OBJECTIVES

Aortic aneurysm is a life threatening cardiovascular complication in patients with systemic lupus erythematosus (SLE).The purpose of this study was to investigate the association between SLE and occurrence of aortic aneurysms.

METHODS

Patients with SLE were compared with age- and sex-matched controls regarding the proportion of aortic aneurysm in a case-control study. Chi-square and t-tests were used for univariate analysis and a logistic regression model was used for multivariate analysis. The study was performed utilizing the medical database of Clalit Health Services.

RESULTS

The study included 5018 patients with SLE and 25,090 age- and sex-matched controls. The proportion of aortic aneurysm in patients with SLE was increased compared with the proportion in controls (0.6% and 0.1%, respectively, p < 0.001). In a multivariate analysis SLE was associated with the coexistence of aortic aneurysms (odds ratio 2.06, 95% confidence interval 1.21-3.51).

CONCLUSIONS

Patients with SLE have a higher proportion of aortic aneurysms as compared with matched controls. Therefore, physicians treating patients with SLE should be aware of this life threatening association.

Early treatment with hydroxychloroquine prevents the development of endothelial dysfunction in a murine model of systemic lupus erythematosus

Introduction

Accelerated atherosclerosis is one of the major causes of morbidity in patients with systemic lupus erythematosus (SLE). Endothelial dysfunction (ED) is considered an early marker of atherosclerosis. It is a reversible alteration, thus representing an attractive target for prevention strategies against cardiovascular disease. Studies have shown that ED occurs in patients with SLE even in the absence of severe, active disease. Hydroxychloroquine (HCQ) is widely used in SLE to control disease activity, but its use is also associated with an improvement in long-term prognosis. Beyond the beneficial effect in well-established disease, our hypothesis is that treatment with HCQ might have a beneficial impact on ED prevention in SLE. The aim of this study was to assess the impact of early treatment with HCQ on ED in a murine model of SLE.

Methods

Twelve-week-old NZB/W F1 (NZ) and C57BL/6 J mice (controls) were allocated to receive HCQ or vehicle for 6, 12, or 18 weeks. Proteinuria and anti–double-stranded DNA autoantibodies were determined. ED was assessed in mesenteric arteries (pressurized myography). Nitric oxide (NO) availability and reactive oxygen species (ROS) production were evaluated. Vascular ROS production was measured with dihydroethidium (DHE) fluorescent dye.

Results

Starting from 18 weeks of age, NZ mice showed a progressive reduction in NO availability, which was normalized by ascorbic acid and apocynin in the up to 24-week-old group, and partly ameliorated in older animals. HCQ administration normalized the NO availability in the up to 24-week-old group, with a partial amelioration in the 30-week-old group. DHE analysis revealed a progressive increment of vascular ROS generation among NZ groups, which was prevented by apocynin. Similarly, in the NZ HCQ-treated group, vascular ROS production was abrogated.

Conclusions

The ED that characterizes this mouse model of SLE is caused by the nicotinamide adenine dinucleotide phosphate oxidase–driven ROS excess. Very early treatment with HCQ is able to exert vascular protection via an antioxidant effect.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0790-3) contains supplementary material, which is available to authorized users.

CD47 deficiency ameliorates autoimmune nephritis in Fas(lpr) mice by suppressing IgG autoantibody production

CD47, a self-recognition marker, plays an important role in both innate and adaptive immune responses. To explore the potential role of CD47 in activation of autoreactive T and B cells and the production of autoantibodies in autoimmune disease, especially systemic lupus erythematosus (SLE), we have generated CD47 knockout Fas(lpr) (CD47(-/-) -Fas(lpr) ) mice and examined histopathological changes in the kidneys, cumulative survival rates, proteinuria, extent of splenomegaly and autoantibodies, serum chemistry and immunological parameters. In comparison with Fas(lpr) mice, CD47(-/-) -Fas(lpr) mice exhibit a prolonged lifespan and delayed autoimmune nephritis, including glomerular cell proliferation, basement membrane thickening, acute tubular atrophy and vacuolization. CD47(-/-) -Fas(lpr) mice have lower levels of proteinuria, associated with reduced deposition of complement C3 and C1q, and IgG but not IgM in the glomeruli, compared to age-matched Fas(lpr) mice. Serum levels of antinuclear antibodies and anti-double-stranded DNA antibodies are significantly lower in CD47(-/-) -Fas(lpr) than in Fas(lpr) mice. CD47(-/-) -Fas(lpr) mice also display less pronounced splenomegaly than Fas(lpr) mice. The mechanistic studies further suggest that CD47 deficiency impairs the antigenic challenge-induced production of IgG but not IgM, and that this effect is associated with reduction of T follicular cells and impairment of germinal centre development in lymphoid tissues. In conclusion, our results demonstrate that CD47 deficiency ameliorates lupus nephritis in Fas(lpr) mice via suppression of IgG autoantibody production.

Type I IFNs as biomarkers in rheumatoid arthritis: towards disease profiling and personalized medicine

RA (rheumatoid arthritis) is a chronic rheumatic condition hallmarked by joint inflammation and destruction by self-reactive immune responses. Clinical management of RA patients is often hampered by its heterogeneous nature in both clinical presentation and outcome, thereby highlighting the need for new predictive biomarkers. In this sense, several studies have recently revealed a role for type I IFNs (interferons), mainly IFNα, in the pathogenesis of a subset of RA patients. Genetic variants associated with the type I IFN pathway have been linked with RA development, as well as with clinical features. Moreover, a role for IFNα as a trigger for RA development has also been described. Additionally, a type I IFN signature has been associated with the early diagnosis of RA and clinical outcome prediction in patients undergoing biological drug treatment, two challenging issues for decision-making in the clinical setting. Moreover, these cytokines have been related to endothelial damage and vascular repair failure in different autoimmune disorders. Therefore, together with chronic inflammation and disease features, they could probably account for the increased cardiovascular disease morbidity and mortality of these patients. The main aim of the present review is to provide recent evidence supporting a role for type I IFNs in the immunopathology of RA, as well as to analyse their possible role as biomarkers for disease management.

Interleukin 10 hampers endothelial cell differentiation and enhances the effects of interferon α on lupus endothelial cell progenitors

OBJECTIVE

SLE is an autoimmune disease characterized by autoantibody generation, organ damage and an increased risk of cardiovascular disease. Generally considered an anti-inflammatory cytokine, IL-10 is increased in SLE and correlates with poor cardiovascular outcomes in the general population. The aim of this study was to explore the putative role of IL-10 in modulating endothelial function in SLE by examining the effects of this cytokine on endothelial progenitor cell/circulating angiogenic cell (EPC/CAC) differentiation.

METHODS

Human and murine control and lupus EPCs/CACs were differentiated into mature endothelial cells (ECs) in the presence or absence of graded concentrations of recombinant IL-10 with or without recombinant IFN-α or a neutralizing antibody to IL-10. IL-10-deficient mice were examined to assess the role of this cytokine in type I IFN-mediated inhibition of EC differentiation and neo-angiogenesis using an in vivo Matrigel plug assay. Serum IL-10 concentrations were measured via ELISA.

RESULTS

IL-10 hampers EC differentiation in a dose-dependent manner. In murine EPC cultures, IL-10 is required to observe the inhibitory effects of type I IFNs on EPC function and neo-angiogenesis. In human SLE EPC/CAC cultures, neutralization of IL-10 significantly improved the differentiation of EPCs, and IL-10 enhanced type I IFN-mediated EPC/CAC dysfunction. The presence of IL-10 in serum inversely correlated with EPC/CAC function in SLE but not in control cells.

CONCLUSION

IL-10 interferes with endothelial differentiation and may enhance the effects of type I IFN on vascular repair in SLE. IL-10 may be a relevant target for improving cardiovascular risk in SLE.

Peptidylarginine deiminase inhibition disrupts NET formation and protects against kidney, skin and vascular disease in lupus-prone MRL/lpr mice

OBJECTIVES

An imbalance between neutrophil extracellular trap (NET) formation and degradation has been described in systemic lupus erythematosus (SLE), potentially contributing to autoantigen externalisation, type I interferon synthesis and endothelial damage. We have demonstrated that peptidylarginine deiminase (PAD) inhibition reduces NET formation and protects against lupus-related vascular damage in the New Zealand Mixed model of lupus. However, another strategy for inhibiting NETs--knockout of NOX2--accelerates lupus in a different murine model, MRL/lpr. Here, we test the effects of PAD inhibition on MRL/lpr mice in order to clarify whether some NET inhibitory pathways may be consistently therapeutic across models of SLE.

METHODS

NET formation and autoantibodies to NETs were characterised in lupus-prone MRL/lpr mice. MRL/lpr mice were also treated with two different PAD inhibitors, Cl-amidine and the newly described BB-Cl-amidine. NET formation, endothelial function, interferon signature, nephritis and skin disease were examined in treated mice.

RESULTS

Neutrophils from MRL/lpr mice demonstrate accelerated NET formation compared with controls. MRL/lpr mice also form autoantibodies to NETs and have evidence of endothelial dysfunction. PAD inhibition markedly improves endothelial function, while downregulating the expression of type I interferon-regulated genes. PAD inhibition also reduces proteinuria and immune complex deposition in the kidneys, while protecting against skin disease.

CONCLUSIONS

PAD inhibition reduces NET formation, while protecting against lupus-related damage to the vasculature, kidneys and skin in various lupus models. The strategy by which NETs are inhibited will have to be carefully considered if human studies are to be undertaken.

Imbalance between endothelial damage and repair: a gateway to cardiovascular disease in systemic lupus erythematosus

Atherosclerosis is accelerated in patients with systemic lupus erythematosus (SLE) and it leads to excessive cardiovascular complications in these patients. Despite the improved awareness of cardiovascular disease and advent of clinical diagnostics, the process of atherogenesis in most patients remains clinically silent until symptoms and signs of cardiovascular complications develop. As evidence has demonstrated that vascular damage is already occurring before clinically overt cardiovascular disease develops in lupus patients, intervention at the preclinical stage of atherogenesis would be plausible. Indeed, endothelial dysfunction, one of the earliest steps of atherogenesis, has been demonstrated to occur in lupus patients even when they are naïve for cardiovascular disease. Currently known “endothelium-toxic” factors including type 1 interferon, proinflammatory cytokines, inflammatory cells, immune complexes, costimulatory molecules, neutrophils extracellular traps, lupus-related autoantibodies, oxidative stress, and dyslipidemia, coupled with the aberrant functions of the endothelial progenitor cells (EPC) which are crucial to vascular repair, likely tip the balance towards endothelial dysfunction and propensity to develop cardiovascular disease in lupus patients. In this review, altered physiology of the endothelium, factors leading to perturbed vascular repair contributed by lupus EPC and the impact of proatherogenic factors on the endothelium which potentially lead to atherosclerosis in lupus patients will be discussed.

An essential role of caspase 1 in the induction of murine lupus and its associated vascular damage

OBJECTIVE

Systemic lupus erythematosus (SLE) is a systemic autoimmune syndrome associated with organ damage and an elevated risk of cardiovascular disease resulting from activation of both innate and adaptive immune pathways. Recently, increased activation of the inflammasome machinery in SLE has been described. Using the mouse model of pristane-induced lupus, we undertook this study to explore whether caspase 1, the central enzyme of the inflammasome, plays a role in the development of SLE and its associated vascular dysfunction.

METHODS

Eight-week-old wild-type (WT) or caspase 1(-/-) mice were injected intraperitoneally with phosphate buffered saline or pristane. Six months after injection, mice were euthanized, and the development of a lupus phenotype and vascular dysfunction was assessed.

RESULTS

While WT mice exposed to pristane developed autoantibodies and a strong type I interferon response, mice lacking caspase 1 were significantly protected against these features as well as against pristane-induced vascular dysfunction. Further, the development of immune complex glomerulonephritis, which was prominent after pristane exposure in WT mice, was significantly abrogated in caspase 1(-/-) mice.

CONCLUSION

These results indicate that caspase 1 is an essential component in the development of lupus and its associated vascular dysfunction and that it may play an important role in the cross-talk between environmental exposures and autoimmunity development, thus identifying a novel pathway for therapeutic targeting.

Cardiovascular disease in lupus: insights and updates

PURPOSE OF REVIEW

With improved management of the classical disease manifestations of systemic lupus erythematosus (SLE), cardiovascular disease (CVD) has emerged as one of the most important causes of morbidity and mortality. This review in particular focuses on progress over the past year in clinical and basic aspects of SLE-driven accelerated atherosclerosis.

RECENT FINDINGS

Both subclinical CVD and CV events continue to be recognized at increased frequency in previously unstudied lupus cohorts and populations. Novel associations have been identified between lupus CVD and cognitive impairment, depression, and low-income status. In terms of pathogenesis, there is an ever-increasing focus on the innate immune system and, in particular, type I interferons (IFNs). Recent studies have drawn connections in both human and murine models between neutrophils, plasmacytoid dendritic cells, type I IFNs, and endothelial dysfunction. Whether treatments such as mycophenolate mofetil or statins have a role in prevention of lupus CVD is an area of intensive study.

SUMMARY

CVD is a major complication of lupus and is now a leading cause of death among people living with this disease. As such, additional studies are needed in order to identify the most effective preventive strategies and most predictive vascular risk biomarkers. Type I IFNs may play a critical role in lupus CVD pathogenesis, and it is recommended that vascular outcomes be included in ongoing trials testing the efficacy of anti-IFN biologics.

The effect of type 1 IFN on human aortic endothelial cell function in vitro: relevance to systemic lupus erythematosus

Cardiovascular disease (CVD) is an important cause of morbidity and mortality in patients with systemic lupus erythematosus. The etiopathogenesis of premature CVD is not fully understood, but recently interferon-alpha (IFNα) has been implicated as a contributing factor. Since IFNα has been associated with both disease activity and endothelial dysfunction in lupus patients, we aimed to determine whether IFNα has direct effects on human aortic endothelial cell (HAoEC) function in vitro. We studied the function of IFNα2b-treated HAoECs in terms of cell proliferation, capillary-like network formation, and nitric oxide (NO) generation. Changes in gene expression were also analyzed using an exon gene array. IFNα2b regulated the expression of 198 genes, including recognized interferon-stimulated genes (ISGs). Gene ontology analysis showed over-representation of genes involved in antigen presentation and host response to virus but no significant changes in clusters of genes recognized as important in endothelial cell activation or dysfunction. HAoEC proliferation, tubule formation, and NO bioavailability were unchanged, suggesting that IFNα in isolation does not have a direct impact on aortic endothelial cell function.

Peptidylarginine deiminase inhibition reduces vascular damage and modulates innate immune responses in murine models of atherosclerosis

RATIONALE

Neutrophil extracellular trap (NET) formation promotes vascular damage, thrombosis, and activation of interferon-α-producing plasmacytoid dendritic cells in diseased arteries. Peptidylarginine deiminase inhibition is a strategy that can decrease in vivo NET formation.

OBJECTIVE

To test whether peptidylarginine deiminase inhibition, a novel approach to targeting arterial disease, can reduce vascular damage and inhibit innate immune responses in murine models of atherosclerosis.

METHODS AND RESULTS

Apolipoprotein-E (Apoe)(-/-) mice demonstrated enhanced NET formation, developed autoantibodies to NETs, and expressed high levels of interferon-α in diseased arteries. Apoe(-/-) mice were treated for 11 weeks with daily injections of Cl-amidine, a peptidylarginine deiminase inhibitor. Peptidylarginine deiminase inhibition blocked NET formation, reduced atherosclerotic lesion area, and delayed time to carotid artery thrombosis in a photochemical injury model. Decreases in atherosclerosis burden were accompanied by reduced recruitment of netting neutrophils and macrophages to arteries, as well as by reduced arterial interferon-α expression.

CONCLUSIONS

Pharmacological interventions that block NET formation can reduce atherosclerosis burden and arterial thrombosis in murine systems. These results support a role for aberrant NET formation in the pathogenesis of atherosclerosis through modulation of innate immune responses.

Differential expression of functional Fc-receptors and additional immune complex receptors on mouse kidney cells

The precise mechanisms by which circulating immune complexes accumulate in the kidney to form deposits in glomerulonephritis are not well understood. In particular, the role of resident cells within glomeruli of the kidney has been widely debated. Immune complexes have been shown to bind one glomerular cell type (mesangial cells) leading to functional responses such as pro-inflammatory cytokine production. To further assess the presence of functional immunoreceptors on resident glomerular cells, cultured mouse renal epithelial, endothelial, and mesangial cells were treated with heat-aggregated mouse IgG or preformed murine immune complexes. Mesangial and renal endothelial cells were found to bind IgG complexes, whereas glomerular epithelial cell binding was minimal. A blocking antibody for Fc-gamma receptors reduced binding to mesangial cells but not renal endothelial cells, suggesting differential immunoreceptor utilization. RT-PCR and immunostaining based screening of cultured renal endothelial cells showed limited low-level expression of known Fc-receptors and Ig binding proteins. The interaction between mesangial cells and renal endothelial cells and immune complexes resulted in distinct, cell-specific patterns of chemokine and cytokine production. This novel pathway involving renal endothelial cells likely contributes to the predilection of circulating immune complex accumulation within the kidney and to the inflammatory responses that drive kidney injury.

Peptidylarginine deiminase inhibition is immunomodulatory and vasculoprotective in murine lupus

Recent evidence suggests that enhanced neutrophil extracellular trap (NET) formation activates plasmacytoid dendritic cells and serves as a source of autoantigens in SLE. We propose that aberrant NET formation is also linked to organ damage and to the premature vascular disease characteristic of human SLE. Here, we demonstrate enhanced NET formation in the New Zealand mixed 2328 (NZM) model of murine lupus. NZM mice also developed autoantibodies to NETs as well as the ortholog of human cathelicidin/LL37 (CRAMP), a molecule externalized in the NETs. NZM mice were treated with Cl-amidine, an inhibitor of peptidylarginine deiminases (PAD), to block NET formation and were evaluated for lupus-like disease activity, endothelial function, and prothrombotic phenotype. Cl-amidine treatment inhibited NZM NET formation in vivo and significantly altered circulating autoantibody profiles and complement levels while reducing glomerular IgG deposition. Further, Cl-amidine increased the differentiation capacity of bone marrow endothelial progenitor cells, improved endothelium-dependent vasorelaxation, and markedly delayed time to arterial thrombosis induced by photochemical injury. Overall, these findings suggest that PAD inhibition can modulate phenotypes crucial for lupus pathogenesis and disease activity and may represent an important strategy for mitigating cardiovascular risk in lupus patients.

Aortic Atherosclerosis in Systemic Lupus Erythematosus

Aortic atherosclerosis (AoA) defined as intima-media thickening or plaques and aortic stiffness (AoS) also considered an atherosclerotic process and defined as decreased vessel distensibility (higher pulse pressure to achieve similar degree of vessel distension) are common in patients with SLE.

Immune-mediated inflammation, thrombogenesis, traditional atherogenic factors, and therapy-related metabolic abnormalities are the main pathogenic factors of AoA and AoS.

Pathology of AoA and AoS suggests an initial subclinical endothelialitis or vasculitis, which is exacerbated by thrombogenesis and atherogenic factors and ultimately resulting in AoA and AoS.

Computed tomography (CT) for detection of arterial wall calcifications and arterial tonometry for detection of increased arterial pulse wave velocity are the most common diagnostic methods for detecting AoA and AoS, respectively. MRI may become a more applicable and accurate technique than CT. Although transesophageal echocardiography accurately detects earlier and advanced stages of AoA and AoS, it is semi-invasive and cannot be used as a screening method.

Although imaging techniques demonstrate highly variable prevalence rates, on average about one third of adult SLE patients may have AoA or AoS.

Age at SLE diagnosis; SLE duration; activity and damage; corticosteroid therapy; metabolic syndrome; chronic kidney disease; and mitral annular calcification are common independent predictors of AoA and AoS. Also, AoA and AoS are highly associated with carotid and coronary atherosclerosis.

Earlier stages of AoA and AoS are usually subclinical. However, earlier stages of disease may be causally related or contribute to peripheral or cerebral embolism, pre-hypertension and hypertension, and increased left ventricular afterload resulting in left ventricular hypertrophy and diastolic dysfunction. Later stages of disease predisposes to visceral ischemia, aortic aneurysms and aortic dissection.

Even earlier stages of AoA and AoS have been associated with increased cardiovascular and cerebrovascular morbidity and mortality of SLE patients.

Aggressive non-steroidal immunosuppressive therapy and non-pharmacologic and pharmacologic interventions for control of atherogenic risk factors may prevent the development or progression of AoA and AoS and may decrease cardiovascular and cerebrovascular morbidity and mortality in SLE.

Type I interferons modulate vascular function, repair, thrombosis, and plaque progression in murine models of lupus and atherosclerosis

OBJECTIVE

Patients with systemic lupus erythematosus (SLE) have a notable increase in atherothrombotic cardiovascular disease (CVD) which is not explained by the Framingham risk equation. In vitro studies indicate that type I interferons (IFNs) may play prominent roles in increased CV risk in SLE. However, the in vivo relevance of these findings, with regard to the development of CVD, has not been characterized. This study was undertaken to examine the role of type I IFNs in endothelial dysfunction, aberrant vascular repair, and atherothrombosis in murine models of lupus and atherosclerosis.

METHODS

Lupus-prone New Zealand mixed 2328 (NZM) mice and atherosclerosis-prone apolipoprotein E- knockout (apoE(-/-) ) mice were compared to mice lacking type I IFN receptor (INZM and apoE(-/-) IFNAR(-/-) mice, respectively) with regard to endothelial vasodilatory function, endothelial progenitor cell (EPC) function, in vivo neoangiogenesis, plaque development, and occlusive thrombosis. Similar experiments were performed using NZM and apoE(-/-) mice exposed to an IFNα-containing or empty adenovirus.

RESULTS

Loss of type I IFN receptor signaling improved endothelium-dependent vasorelaxation, lipoprotein parameters, EPC numbers and function, and neoangiogenesis in lupus-prone mice, independent of disease activity or sex. Further, acute exposure to IFNα impaired endothelial vasorelaxation and EPC function in lupus-prone and non-lupus-prone mice. Decreased atherosclerosis severity and arterial inflammatory infiltrates and increased neoangiogenesis were observed in apoE(-/-) IFNAR(-/-) mice, compared to apoE(-/-) mice, while NZM and apoE(-/-) mice exposed to IFNα developed accelerated thrombosis and platelet activation.

CONCLUSION

These results support the hypothesis that type I IFNs play key roles in the development of premature CVD in SLE and, potentially, in the general population, through pleiotropic deleterious effects on the vasculature.

Circulating endothelial cells and their progenitors in systemic lupus erythematosus and early rheumatoid arthritis patients

OBJECTIVE

The aim of this study was to investigate the endothelial progenitor cell population in SLE and early RA patients and its potential relationships with disease features and cytokine serum levels.

METHODS

Endothelial progenitor cells (EPCs), mature EPCs (mEPCs) and endothelial cells (ECs) were measured in peripheral blood samples from 83 SLE and 85 early RA patients and 39 healthy controls by flow cytometry on the basis of CD34, VEGF receptor 2 and CD133 expression. Serum levels of IL-1β, IL-6, IL-8, IL-17, VEGF-A, IFN-α, TGF-β and GM-CSF were quantified by immunoassays. Clinical and immunological data were obtained by reviewing clinical histories.

RESULTS

Circulating EPCs were increased in SLE but not in early RA patients associated with an enhanced CD34(+) bone marrow-progenitor cell release but unrelated to disease features. The amount of mEPCs, however, was significantly higher in SLE patients presenting anti-SSA/SSB antibodies and/or malar rash, whereas the presence of specific autoantibodies was associated with EC counts in early RA and SLE patients. As expected, most cytokines tested were altered in both diseases but, interestingly, IFN-α levels, and to a lesser extent IL-6 and IL-1β, were associated with CD133 loss and increased mEPC number, whereas VEGF and TGF-β seem to exert an opposite effect.

CONCLUSION

Our results show that high IFN-α levels and/or the presence of disease-specific antibodies may identify a group of SLE patients with increased mEPC and EC counts, and consequently probably defective endothelial repair, thus supporting their use as surrogate biomarkers of endothelial damage and high cardiovascular risk.

Type I interferons are associated with subclinical markers of cardiovascular disease in a cohort of systemic lupus erythematosus patients

BACKGROUND

Systemic lupus erythematosus (SLE) patients have a striking increase in cardiovascular (CV) comorbidity not fully explained by the Framingham risk score. Recent evidence from in vitro studies suggests that type I interferons (IFN) could promote premature CV disease (CVD) in SLE. We assessed the association of type I IFN signatures with functional and anatomical evidence of vascular damage, and with biomarkers of CV risk in a cohort of lupus patients without overt CVD.

METHODOLOGY/PRINCIPAL FINDINGS

Serum type I IFN activity (induction of five IFN-inducible genes; IFIGs) from 95 SLE patient and 38 controls was quantified by real-time PCR. Flow mediated dilatation (FMD) of the brachial artery and carotid intima media thickness (CIMT) were quantified by ultrasound, and coronary calcification by computed tomography. Serum vascular biomarkers were measured by ELISA. We evaluated the effect of type I IFNs on FMD, CIMT and coronary calcification by first applying principal components analysis to combine data from five IFIGs into summary components that could be simultaneously modeled. Three components were derived explaining 97.1% of the total IFIG variation. Multivariable linear regression was utilized to investigate the association between the three components and other covariates, with the outcomes of FMD and CIMT; zero-inflated Poisson regression was used for modeling of coronary calcification. After controlling for traditional CV risk factors, enhanced serum IFN activity was significantly associated with decreased endothelial function in SLE patients and controls (p<0.05 for component 3), increased CIMT among SLE patients (p<0.01 for components 1 and 2), and severity of coronary calcification among SLE patients (p<0.001 for component 3).

CONCLUSIONS

Type I IFNs are independently associated with atherosclerosis development in lupus patients without history of overt CVD and after controlling for Framingham risk factors. This study further supports the hypothesis that type I IFNs promote premature vascular damage in SLE.

Endothelial progenitor cells: a new player in lupus?

Patients with systemic lupus erythematosus (SLE) have a greatly increased risk of cardiovascular disease. There is growing interest in the link between vascular damage and lupus-specific inflammatory factors. Impaired endothelial repair could account for the endothelial dysfunction in this patient group. This review describes the contribution that endothelial progenitor cells could play in the pathogenesis of premature vascular damage in this disease. The methods of isolation, detection, and characterization of endothelial progenitor cells, together with their potential role in repair of the endothelium and as a therapeutic target in SLE, are discussed.

Activation of type I interferon pathway in systemic lupus erythematosus: association with distinct clinical phenotypes

Growing evidence over the last few years suggests a central role of type I IFN pathway in the pathogenesis of systemic autoimmune disorders. Data from clinical and genetic studies in patients with systemic lupus erythematosus (SLE) and lupus-prone mouse models, indicates that the type I interferon system may play a pivotal role in the pathogenesis of several lupus and associated clinical features, such as nephritis, neuropsychiatric and cutaneous lupus, premature atherosclerosis as well as lupus-specific autoantibodies particularly against ribonucleoproteins. In the current paper, our aim is to summarize the latest findings supporting the association of type I IFN pathway with specific clinical manifestations in the setting of SLE providing insights on the potential use of type I IFN as a therapeutic target.

Inflammasome activation of IL-18 results in endothelial progenitor cell dysfunction in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease with heterogeneous manifestations including severe organ damage and vascular dysfunction leading to premature atherosclerosis. IFN-α has been proposed to have an important role in the development of lupus and lupus-related cardiovascular disease, partly by repression of IL-1 pathways leading to impairments in vascular repair induced by endothelial progenitor cells (EPCs) and circulating angiogenic cells (CACs). Counterintuitively, SLE patients also display transcriptional upregulation of the IL-1β/IL-18 processing machinery, the inflammasome. To understand this dichotomy and its impact on SLE-related cardiovascular disease, we examined cultures of human and murine control or lupus EPC/CACs to determine the role of the inflammasome in endothelial differentiation. We show that caspase-1 inhibition improves dysfunctional SLE EPC/CAC differentiation into mature endothelial cells and blocks IFN-α-mediated repression of this differentiation, implicating inflammasome activation as a crucial downstream pathway leading to aberrant vasculogenesis. Furthermore, serum IL-18 levels are elevated in SLE and correlate with EPC/CAC dysfunction. Exogenous IL-18 inhibits endothelial differentiation in control EPC/CACs and neutralization of IL-18 in SLE EPC/CAC cultures restores their capacity to differentiate into mature endothelial cells, supporting a deleterious effect of IL-18 on vascular repair in vivo. Upregulation of the inflammasome machinery was operational in vivo, as evidenced by gene array analysis of lupus nephritis biopsies. Thus, the effects of IFN-α are complex and contribute to an elevated risk of cardiovascular disease by suppression of IL-1β pathways and by upregulation of the inflammasome machinery and potentiation of IL-18 activation.

High dietary fat promotes visceral obesity and impaired endothelial function in female mice with systemic lupus erythematosus

BACKGROUND

Inflammation contributes to metabolic and cardiovascular disease. Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disorder that predominantly affects young women. Cardiovascular disease is a major cause of mortality in patients with SLE. We recently reported that a model of SLE (female New Zealand Black/White F1 [NZBWF1] mice) developed characteristics of the metabolic syndrome.

OBJECTIVES

In the present study, we tested the hypothesis that high dietary fat with SLE accelerated development of cardiovascular risk factors such as central obesity and vascular dysfunction.

METHODS

Twenty-four-week-old female SLE mice (NZBWF1) were fed either a control diet (SLE, 10% kcal) or a high-fat (HF) diet (SLE + HF, 45% kcal) for a total of 14 weeks.

RESULTS

Body weight was similar between SLE (42 [1] g, n = 5) and SLE + HF (45 [2] g, n = 6) mice, and weight gain was not different in the SLE + HF mice (+18.0 [3.0]%) compared with controls (+15.8 [3.6]%); food intake was not different (SLE, 2.2 [0.3] vs SLE + HF, 2.1 [0.2] g/24 hours). At the end of the experiment, 57% of the SLE + HF mice exhibited signs of albuminuria (>100 mg/dL) compared with only 20% of the control SLE mice. Endothelial-dependent relaxation in isolated carotid arteries was impaired in the SLE + HF group compared with that in the SLE group. Ovarian fat increased in SLE + HF mice (6.6 [0.5] g) compared with that in the control SLE mice (5.4 [0.1] g, P < 0.05), and liver weight decreased in SLE + HF (1.6 [0.1] g) mice compared with that in control mice (1.9 [0.1] g, P < 0.03).

CONCLUSIONS

These data suggest that dietary fat accelerates renal injury and peripheral vascular dysfunction and promotes visceral obesity in a disease model with chronic inflammation.

Blood pressure and renal hemodynamic responses to acute angiotensin II infusion are enhanced in a female mouse model of systemic lupus erythematosus

Inflammation and immune system dysfunction contributes to the development of cardiovascular and renal disease. Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disorder that carries a high risk for both renal and cardiovascular disease. While hemodynamic changes that may contribute to increased cardiovascular risk have been reported in humans and animal models of SLE, renal hemodynamics have not been widely studied. The renin-angiotensin system (RAS) plays a central role in renal hemodynamic control, and although RAS blockade is a common therapeutic strategy, the role of RAS in hemodynamic function during SLE is not clear. This study tested whether mean arterial pressure (MAP) and renal hemodynamic responses to acute infusions of ANG II in anesthetized animals were enhanced in an established female mouse model of SLE (NZBWF1). Baseline MAP was not different between anesthetized SLE and control (NZWLacJ) mice, while renal blood flow (RBF) was significantly lower in mice with SLE. SLE mice exhibited an enhanced pressor response and greater reduction in RBF after ANG II infusion. An acute infusion of the ANG II receptor blocker losartan increased RBF in control mice but not in mice with SLE. Renin and ANG II type 1 receptor expression was significantly lower, and ANG II type 2 receptor expression was increased in the renal cortex from SLE mice compared with controls. These data suggest that there are fewer ANG II receptors in the kidneys from mice with SLE but that the existing receptors exhibit an enhanced sensitivity to ANG II.

Opposing effects of monomeric and pentameric C-reactive protein on endothelial progenitor cells

C-reactive protein (CRP) has been linked to the pathogenesis of atherosclerosis. The dissociation of native, pentameric (p)CRP to monomeric (m)CRP on the cell membrane of activated platelets has recently been demonstrated. The dissociation of pCRP to mCRP may explain local pro-inflammatory reactions at the site of developing atherosclerotic plaques. As a biomarker, pCRP predicts cardiovascular adverse events and so do reduced levels and function of circulating endothelial progenitor cells (EPCs). We hypothesised that mCRP and pCRP exert a differential effect on EPC function and differentiation. EPCs were treated with mCRP or pCRP for 72 h, respectively. Phenotypical characterisation was done by flow cytometry and immunofluorescence microscopy, while the effect of mCRP and pCRP on gene expression was examined by whole-genome gene expression analysis. The functional capacity of EPCs was determined by colony forming unit (CFU) assay and endothelial tube formation assay. Double staining for acetylated LDL and ulex lectin significantly decreased in cells treated with pCRP. The length of tubuli in a matrigel assay with HUVECs decreased significantly in response to pCRP, but not to mCRP. The number of CFUs increased after pCRP treatment. RNA expression profiling demonstrated that mCRP and pCRP cause highly contradictory gene regulation. Interferon-responsive genes (IFI44L, IFI44, IFI27, IFI 6, MX1, OAS2) were among the highly up-regulated genes after mCRP, but not after pCRP treatment. In conclusion, EPC phenotype, genotype and function were differentially affected by mCRP and pCRP, strongly arguing for differential roles of these two CRP conformations. The up-regulation of interferon-inducible genes in response to mCRP may constitute a mechanism for the local regulation of EPC function.

The interplay of inflammation and cardiovascular disease in systemic lupus erythematosus

Patients with systemic lupus erythematosus have up to a 50-fold increased risk of developing atherosclerotic cardiovascular disease. Recent advances in the etiology of vascular damage in this disease stress the interplay of lupus-specific inflammatory factors with traditional cardiac risk factors, leading to increased endothelial damage. This review analyzes the putative role that immune dysregulation and lupus-specific factors may play in the pathogenesis of premature vascular damage in this disease. The potential role of various cytokines, in particular type I interferons, in the development of accelerated atherosclerosis is examined. Potential therapeutic targets are discussed.

The detrimental effects of IFN-α on vasculogenesis in lupus are mediated by repression of IL-1 pathways: potential role in atherogenesis and renal vascular rarefaction

Systemic lupus erythematosus (SLE) is characterized by increased vascular risk due to premature atherosclerosis independent of traditional risk factors. We previously proposed that IFN-α plays a crucial role in premature vascular damage in SLE. IFN-α alters the balance between endothelial cell apoptosis and vascular repair mediated by endothelial progenitor cells (EPCs) and myeloid circulating angiogenic cells (CACs). In this study, we demonstrate that IFN-α promotes an antiangiogenic signature in SLE and control EPCs/CACs, characterized by transcriptional repression of IL-1α and β, IL-1R1, and vascular endothelial growth factor A, and upregulation of IL-1R antagonist and the decoy receptor IL-1R2. IL-1β promotes significant improvement in the functional capacity of lupus EPCs/CACs, therefore abrogating the deleterious effects of IFN-α. The beneficial effects from IL-1 are mediated, at least in part, by increases in EPC/CAC proliferation, by decreases in EPC/CAC apoptosis, and by preventing the skewing of CACs toward nonangiogenic pathways. IFN-α induces STAT2 and 6 phosphorylation in EPCs/CACs, and JAK inhibition abrogates the transcriptional antiangiogenic changes induced by IFN-α in these cells. Immunohistochemistry of renal biopsies from patients with lupus nephritis, but not anti-neutrophil cytoplasmic Ab-positive vasculitis, showed this pathway to be operational in vivo, with increased IL-1R antagonist, downregulation of vascular endothelial growth factor A, and glomerular and blood vessel decreased capillary density, compared with controls. Our study introduces a novel putative pathway by which type I IFNs may interfere with vascular repair in SLE through repression of IL-1-dependent pathways. This could promote atherosclerosis and loss of renal function in this disease.