Urine osteoprotegerin and monocyte chemoattractant protein-1 in lupus nephritis

Urine proteomic signatures of histological class, activity, chronicity, and treatment response in lupus nephritis

Lupus nephritis (LN) is a pathologically heterogenous autoimmune disease linked to end-stage kidney disease and mortality. Better therapeutic strategies are needed as only 30%-40% of patients completely respond to treatment. Noninvasive biomarkers of intrarenal inflammation may guide more precise approaches. Because urine collects the byproducts of kidney inflammation, we studied the urine proteomic profiles of 225 patients with LN (573 samples) in the longitudinal Accelerating Medicines Partnership in RA/SLE cohort. Urinary biomarkers of monocyte/neutrophil degranulation (i.e., PR3, S100A8, azurocidin, catalase, cathepsins, MMP8), macrophage activation (i.e., CD163, CD206, galectin-1), wound healing/matrix degradation (i.e., nidogen-1, decorin), and IL-16 characterized the aggressive proliferative LN classes and significantly correlated with histological activity. A decline of these biomarkers after 3 months of treatment predicted the 1-year response more robustly than proteinuria, the standard of care (AUC: CD206 0.91, EGFR 0.9, CD163 0.89, proteinuria 0.8). Candidate biomarkers were validated and provide potentially treatable targets. We propose these biomarkers of intrarenal immunological activity as noninvasive tools to diagnose LN and guide treatment and as surrogate endpoints for clinical trials. These findings provide insights into the processes involved in LN activity. This data set is a public resource to generate and test hypotheses and validate biomarkers.

Gene expression profiling in skin reveals strong similarities between subacute and chronic cutaneous lupus that are distinct from lupus nephritis

Subacute cutaneous lupus erythematosus (SCLE) and chronic cutaneous lupus erythematosus (CCLE) are represented in the majority of cutaneous lupus subtypes, each of which has variable implications for systemic manifestations such as lupus nephritis. On dermatologic exam, SCLE and CCLE are distinct. However, it is often difficult to diagnose the subtype from histology alone. Our study utilized whole-genome microarray expression analysis on human skin samples of SCLE, CCLE, and healthy controls, along with human samples of lupus nephritis and normal kidney tissue to compare cutaneous lupus subtypes to each other, as well as lupus nephritis. The data revealed that cutaneous lupus subtypes were distinct from healthy control skin, with gene expression predominantly characterized by upregulation of type 1 interferon and T-cell chemotactic genes. However, the cutaneous lupus subtypes were very similar to one another; comparative analyses revealed few statistically significant differences in gene expression. There were also distinct differences between the gene signatures of cutaneous lupus and lupus nephritis. Cutaneous lupus samples revealed gene signatures demonstrating a prominent inflammatory component that may suggest the skin as an early site of initiation of lupus pathogenesis, while lupus nephritis reflected recruitment and activation of M2 macrophages and a wound healing signature.

Systemic lupus erythematosus: The search for the ideal biomarker

During the last decades, there has been an increased interest in the discovery and validation of biomarkers that reliably reflect specific aspects of lupus. Although many biomarkers have been developed, few of them have been validated and used in clinical practice, but with unsatisfactory performances. Thus, there is still a need to rigorously validate many of these novel promising biomarkers in large-scale longitudinal studies and also identify better biomarkers not only for lupus diagnosis but also for monitoring and predicting upcoming flares and response to treatment. Besides serological biomarkers, urinary and cerebrospinal fluid biomarkers have emerged for assessing both renal and central nervous system involvement in systemic lupus erythematosus, respectively. Also, novel omics techniques help us to understand the molecular basis of the disease and also allow the identification of novel biomarkers which may be potentially useful for guiding new therapeutic targets.

Urinary biomarkers in lupus nephritis

Systemic lupus erythematosus (SLE) is the prototypical autoimmune disease that can affect any organ of the body. Multiple mechanisms may contribute to the pathophysiology of systemic lupus, including failure to remove apoptotic bodies, hyperactivity of self-reactive B and T lymphocytes, abnormal exposure to autoantigens, and increased levels of B-cell stimulatory cytokines. The involvement of the kidney, called lupus nephritis (LN), during the course of the disease affects between 30% and 60% of adult SLE patients, and up to 70% of children. LN is an immune-mediated glomerulonephritis that is a common and serious finding in patients with SLE. Nowadays, renal biopsy is considered the gold standard for classifying LN, besides its degree of activity or chronicity. Nevertheless, renal biopsy lacks the ability to predict which patients will respond to immunosuppressive therapy and is a costly and risky procedure that is not practical in the monitoring of LN because serial repetitions would be necessary. Consequently, many serum and urinary biomarkers have been studied in SLE patients for the complementary study of LN, existing conventional biomarkers like proteinuria, protein/creatinine ratio in spot urine, 24 ​h urine proteinuria, creatinine clearance, among others and non-conventional biomarkers, like Monocyte chemoattractant protein-1 (MCP-1), have been correlated with the histological findings of the different types of LN. In this article, we review the advances in lupus nephritis urinary biomarkers. Such markers ideally should be capable of predicting early sub-clinical flares and could be used to follow response to therapy. In addition, some of these markers have been found to be involved in the pathogenesis of lupus nephritis.

Serum RANKL, osteoprotegerin (OPG) and RANKL/OPG ratio in children with systemic lupus erythematosus

Background

Systemic lupus erythematosus (SLE) patients have lower bone mineral density (BMD) compared with healthy individuals because of general, genetic, disease and medication-related factors. The disturbance of the receptor activator of nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG) ratio has been reported to be associated with low BMD in many disorders in adults and children alike.

Objectives

The objectives of this study were (i) to assess serum OPG, RANKL and RANKL/OPG ratio levels in SLE children and controls, (ii) to determine whether the cumulative glucocorticoid (CGCS) dose had any effect on the concentration of serum RANKL, OPG and RANKL/OPG ratio, and (iii) to determine the relation of these parameters to BMD.

Methods

We evaluated 50 SLE children and 50 age- and sex-matched healthy controls. RANKL and OPG were assessed in serum and compared between patients and controls. For SLE patients, a univariate followed by multivariable analysis were carried out to detect the possible predictors of the changes in RANKL, OPG and RANKL/OPG ratio levels. Lumbar BMD for all patients was assessed by dual-energy X-ray absorptiometry (DXA) scan and then correlated to different probable correlated factors.

Results

RANKL, OPG and RANKL/OPG ratio were significantly higher in SLE patients ( p ≤ 0.001). Univariate analysis showed significant correlations of RANKL with CGCS ( p ≤ 0.001) and with DXA scan z-score ( p = 0.007): OPG was significantly correlated to Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score ( p = 0.001) and anti-double-stranded DNA ( p = 0.001), whereas RANKL/OPG was significantly correlated to duration of illness and DXA z-score ( p = 0.002). The multivariable analysis showed that DXA z-score was an independent predictor of RANKL and RANKL/OPG ratio ( p = 0.019 and 0.008, respectively), whereas SLEDAI score was an independent predictor of OPG levels. BMD was negatively correlated to disease duration ( p = 0.008) and CGCS dose ( p = 0.015), but no significant correlation has been found between BMD and cumulative SLEDAI score ( p = 0.29).

Conclusions

Serum RANKL/OPG ratio is elevated in Egyptian children with SLE and is considered a risk factor for reduced bone mass in these children. Other risk factors for low BMD include high CGCS dose and disease duration, supporting that osteoporosis in SLE is multifactorial.

Lupus: the new epidemic

Is systemic lupus erythematosus (SLE) is occurring more frequently now than in decades past? Despite improvements in the identification of patients with SLE, the development of new classification criteria, and the recognition of several biomarkers used alone or in combination, the diagnosis of SLE is still a challenge for clinicians, in particular early in the course of the disease, which makes the recognition of secular trends difficult to ascertain. Lacking a uniform definition of preclinical lupus or incomplete lupus, it is difficult to predict accurately which patients would go on to develop SLE. We will briefly review the classification criteria, early or preclinical SLE, the epidemiology of SLE, antinuclear antibodies-negative SLE, and biomarkers of the disease.

TRAIL, OPG, and TWEAK in kidney disease: biomarkers or therapeutic targets?

Ligands and receptors of the tumor necrosis factor (TNF) superfamily regulate immune responses and homeostatic functions with potential diagnostic and therapeutic implications. Kidney disease represents a global public health problem, whose prevalence is rising worldwide, due to the aging of the population and the increasing prevalence of diabetes, hypertension, obesity, and immune disorders. In addition, chronic kidney disease is an independent risk factor for the development of cardiovascular disease, which further increases kidney-related morbidity and mortality. Recently, it has been shown that some TNF superfamily members are actively implicated in renal pathophysiology. These members include TNF-related apoptosis-inducing ligand (TRAIL), its decoy receptor osteoprotegerin (OPG), and TNF-like weaker inducer of apoptosis (TWEAK). All of them have shown the ability to activate crucial pathways involved in kidney disease development and progression (e.g. canonical and non-canonical pathways of the transcription factor nuclear factor-kappa B), as well as the ability to regulate cell proliferation, differentiation, apoptosis, necrosis, inflammation, angiogenesis, and fibrosis with double-edged effects depending on the type and stage of kidney injury. Here we will review the actions of TRAIL, OPG, and TWEAK on diabetic and non-diabetic kidney disease, in order to provide insights into their full clinical potential as biomarkers and/or therapeutic options against kidney disease.

Soluble TNF-R1, VEGF and other cytokines as markers of disease activity in systemic lupus erythematosus and lupus nephritis

Background

Current non-invasive methods of assessing disease activity in systemic lupus erythematosus (SLE) are of limited sensitivity and specificity. Testing includes acute phase markers, autoantibodies and complement levels. Although measurements of dsDNA antibodies and complement C3/C4 levels are routine, they remain of limited value. Improved blood and urine markers may help in early detection of flare, distinction between flare and chronic damage, and monitoring response to therapy.

Methods

A total of 87 patients with SLE were tested for the following cytokines in serum and urine: monocyte chemoattractant protein 1 (MCP-1), regulated upon activation, normal T cell expressed and secreted (RANTES), soluble tumour necrosis factor receptor 1 (sTNF-R1), interferon-inducible protein 10 (IP-10), monocyte inhibitory protein 1α (MIP-1α) and vascular endothelial growth factor (VEGF). Patients attending the Lupus Unit at St Thomas’ Hospital, London, UK were divided into active lupus nephritis (LN), inactive LN and non-renal SLE groups based on their renal pathology and SLE disease activity index (SLEDAI). Cytokine testing was performed using the FIDIS multiplex bead assay.

Results

The mean level of serum sTNF-R1 was higher in the active LN group compared with both inactive LN and non-renal SLE groups ( p < 0.001). For urine measurements there were significant differences between active LN and non-renal SLE for VEGF ( p = 0.016), after statistical correction for multiple testing. Both urinary and serum sTNF-R1 and IP-10 levels correlated with SLEDAI scores ( p < 0.001), while serum VEGF correlated weakly with SLEDAI ( p = 0.025). The optimum combination for differentiating active from inactive LN patients was serum VEGF, sTNF-R1, MCP-1 and glomerular filtration rate plus urinary sTNF-R1 and protein-creatinine ratio.

Conclusion

These results indicate that for active LN, sTNF-R1 could be a useful serum cytokine marker, with potential for VEGF in the urine. This study has confirmed the ability of the multiplex bead technique to detect cytokines in a good analytical range, including very low and high levels, in both serum and urine. Combining serum and urine markers provided additional sensitivity in distinguishing active from inactive LN.

Serum osteoprotegrin (OPG) in subclinical atherosclerosis in systemic lupus erythematosus

Introduction Osteoprotegerin (OPG) is a member of the tumor necrosis factor (TNF) receptor family. It has recently been demonstrated that OPG is produced by a variety of tissues, including the cardiovascular system (heart, arteries, veins), lung, kidney, immune tissues, and bone. The OPG-RANKL signaling pathway is strongly related to vascular calcification. We determined the association of this biomarker with subclinical atherosclerosis in systemic lupus erythematous (SLE). Methods We measured OPG and markers of subclinical atherosclerosis (coronary artery calcium (CAC), carotid intima-media thickness (cIMT) carotid plaque) in 166 SLE patients (91% female, 64% Caucasian, 31% African American, 5% others, mean age 45 years). Subgroups of patients with different levels of OPG level were compared with respect to average levels of CAC, cIMT, and with respect to presence of carotid plaque. Age was adjusted for using multiple regression. Results OPG was highly correlated with age ( p < 0.0001). Individuals with higher levels of OPG tended to have higher measures of CAC, cIMT, and more carotid plaque. However, after adjustment for age, these associations, while still positive, were no longer statistically significant. Conclusion In our study much of the association observed was due to confounding by age, and after adjusting for age, our findings do not rule out the possibility of a null association.

Monocyte chemoattractant protein-1 and the kidney

PURPOSE OF REVIEW

Recently, initial studies have been carried out in patients using monocyte chemoattractant protein-1 (MCP-1) inhibitors. This review summarizes the known function of MCP-1 in regulating monocytes during inflammation and its role in inflammatory disease of the kidney.

RECENT FINDINGS

MCP-1 is one of the first chemokines described and plays an important role in renal inflammatory disease. The function of MCP-1 has been investigated and analyzed in both animal models of renal disease and renal patients. MCP-1 mediates firstly the release of monocytes from the bone marrow, and then generates a gradient in the endothelial glycocalyx to direct monocytes to sites of inflammation, thereby alleviating the migration of blood leukocytes into the inflamed tissue. In addition, MCP-1 has direct signaling effects in monocytes and influences migration, proliferation, and differentiation of leukocytes. Blockade of MCP-1 in several models of renal disease has ameliorated the disease, suggesting that inhibition of MCP-1 is a promising and valid strategy to treat patients with renal inflammatory disease.

SUMMARY

Understanding the role of MCP-1 in monocyte homeostasis and the implications of MCP-1 inhibition in renal disease will help in designing better diagnostic and therapeutic strategies in patients with inflammatory renal disease.

Lupus nephritis biomarkers

Lupus nephritis (LN), a potentially destructive outcome of SLE, is a real challenge in the management of SLE because of the difficulty in diagnosing its subclinical onset and identifying relapses before serious complications set in. Conventional clinical parameters such as proteinuria, GFR, urine sediments, anti-dsDNA and complement levels are not sensitive or specific enough for detecting ongoing disease activity in lupus kidneys and early relapse of nephritis. There has long been a need for biomarkers of disease activity in LN. Such markers ideally should be capable of predicting early sub-clinical flares and could be used to gauge response to therapy, thus obviating the need for serial renal biopsies with their possible hazardous complications. Since urine can be readily obtained, it lends itself as an obvious biological substrate. In this review, the use of urine and serum as sources of lupus nephritis biomarkers is described, and the results of biomarker discovery studies using candidate and proteomic approaches are summarized.

Development of Biomarker Models to Predict Outcomes in Lupus Nephritis

OBJECTIVE

The American College of Rheumatology guidelines for the treatment of lupus nephritis recommend change in induction therapy when response to therapy has not occurred within 6 months. Response is not defined, and renal fibrosis can occur while waiting for this end point. Therefore, a decision support tool to better define response is needed to guide clinicians when starting patients on therapy. This study was undertaken to identify biomarker models with sufficient predictive power to develop such a tool.

METHODS

Urine samples from 140 patients with biopsy-proven lupus nephritis who had not yet started induction therapy were analyzed for a panel of urinary biomarkers. Univariate receiver operating characteristic (ROC) curves were generated for each individual biomarker and compared to the ROC area under the curve values from machine learning models developed using random forest algorithms. Biomarker models of outcome developed with novel markers in addition to clinical markers were compared to those developed with traditional clinical markers alone.

RESULTS

Models developed with the combined traditional and novel biomarker panels demonstrated clinically meaningful predictive power. Markers most predictive of response were chemokines, cytokines, and markers of cellular damage.

CONCLUSION

This is the first study to demonstrate the power of low-abundance biomarker panels and machine learning algorithms for predicting lupus nephritis outcomes. This is a critical first step in research to develop clinically meaningful decision support tools.

Urinary biomarkers in childhood lupus nephritis

Juvenile-onset systemic lupus erythematosus (JSLE) is a rare, severe multisystem autoimmune disease affecting the kidney (Lupus Nephritis, LN) in up to 80% of children. LN is more severe in children than adults, with potential for irreversible kidney damage requiring dialysis or transplant. Renal biopsy is currently the gold standard for diagnosing and monitoring LN, however, it is invasive and associated with complications. Urine biomarkers have been shown to be better than serum biomarkers in differentiating renal disease from other organ manifestations. Over the past decade, there have been an increasing number of studies investigating specific candidate biomarkers implicated in the pathogenesis of LN or screening for urinary biomarkers using hypothesis free methods. In this review, developments in urine biomarkers for LN will be reviewed, highlighting those that are of relevance to children and have gone through validation in independent international patient cohorts, bringing them close to clinical translation.

Effects of Minocycline on Urine Albumin, Interleukin-6, and Osteoprotegerin in Patients with Diabetic Nephropathy: A Randomized Controlled Pilot Trial

Background

We tested minocycline as an anti-proteinuric adjunct to renin-angiotensin-aldosterone system inhibitors (RAASi) in diabetic nephropathy (DN) and measured urinary biomarkers to evaluate minocycline’s biological effects.

Methods

Design: Prospective, single center, randomized, placebo-controlled, intention-to-treat pilot trial. Inclusion. Type 2 diabetes/DN; Baseline creatinine clearance > 30 mL/min; proteinuria ≥ 1.0 g/day; Age ≥30 years; BP <150/95 mm Hg; intolerant of/at maximum RAASi dose. Protocol. 3-wk screening; Baseline randomization; Urine and blood measures at months 1, 2, 4, and Month 6 study completion. Urine interleukin-6 (IL-6) and osteoprotegerin were measured in a subset. Primary outcome. Natural log of urine protein/creatinine (ln U P:Cr) ratio at Month 6 vs Baseline.

Results

30 patients completed the study. The 15% decline in U P: Cr in minocycline patients (6 month P:Cr ÷ Baseline P:Cr, 0.85 vs. 0.92) was not significant (p = 0.27). Creatinine clearance did not differ in the 2 groups. Urine IL-6:Cr (p = 0.03) and osteoprotegerin/Cr (p = 0.046) decrements were significant. Minocycline modified the relationship between urine IL-6 and proteinuria, suggesting a protective biological effect.

Conclusions

Although the decline in U P:Cr in minocycline patients was not statistically significant, the significant differences in urine IL-6 and osteoprotegerin suggest that minocycline may confer cytoprotection in patients with DN, providing a rationale for further study.

Trial Registration

Clinicaltrials.gov NCT01779089

Biomarkers for kidney involvement in pediatric lupus

Lupus nephritis (LN), the renal involvement in systemic lupus erythematosus, is currently diagnosed by histopathology obtained by percutaneous renal biopsy and is associated with increased morbidity and mortality in both adults and children. LN is more prevalent and severe in children, requiring aggressive and prolonged immunosuppression. The consequences of the diagnosis and its treatment have devastating long-term effects on the growth, well-being and quality of life of affected children. The paucity of reliable clinical indicators of the presence and severity of renal involvement have contributed to a halt in the reduction of progression to end-stage renal disease in recent years. Here, we discuss the recent development of biomarkers in the management of LN and their role as therapeutic targets.

Urinary osteoprotegerin: a potential biomarker of lupus nephritis disease activity

OBJECTIVES

Urinary biomarkers may help in identification, treatment and assessment of response in patients with lupus nephritis (LN). Osteoprotegerin (OPG) is produced by the kidneys and lymphoid cells and may reflect renal disease activity better. The data on its utility are sparse.

METHODS

Fifty-eight patients with active LN (AN), 24 with active non-renal disease (ANR) and 39 with inactive disease (ID) were included. Median disease duration was 32 (1-204) months and median age was 27 (12-50) years. AN patients were followed up every three months for one year. Urine and serum samples were collected for OPG measurement by ELISA (pg/ml) and urinary values were normalised for creatinine excretion (pg/mg). Urine samples from 24 healthy individuals (HCs) and 20 patients each of rheumatoid arthritis (RA) and diabetic nephropathy (DM) served as controls. Variables were expressed as median (range).

RESULTS

At baseline, normalised urinary OPG (uOPG) was significantly higher (p < 0.001) in AN (1229 (0-8577)) than ANR (236 (0-14713)), ID (463 (7-4253)), HCs (366 (120-2849)) and DM (350 (127-1577)) but it was not different from RA (1511 (122-8849)). uOPG correlated modestly with rSLEDAI (r = 0.4, p < 0.001) and SLEDAI (r = 0.31, p < 0.001) but not with serum OPG (sOPG). uOPG but not sOPG could differentiate between AN and ANR groups. In the longitudinal study, uOPG and sOPG decreased significantly with treatment at all follow-up visits but the trend of fall in sOPG was erratic. uOPG values at baseline, 3, 6, 9 and 12 months were 1229 (0-8577), 466 (3-4874), 104 (0-1598), 325 (0-4025) and 555 (6-6771) pg/mg, respectively. uOPG but not sOPG rose before conventional markers in three patients who had a relapse of LN. In two patients who developed chronic kidney disease, uOPG remained persistently high. For differentiating AN from ANR patients, uOPG performed the best on receiver operator characteristics analysis (AUC = 0.72) when compared with anti-dsDNA antibodies, C3, C4 and sOPG.

CONCLUSION

uOPG is derived from kidneys and helps differentiate active SLE patients with and without LN. It shows modest correlation with disease activity and has a potential to predict poor response to therapy and relapse of LN.

Urine Monocyte Chemoattractant Protein-1 and Lupus Nephritis Disease Activity: Preliminary Report of a Prospective Longitudinal Study

Objective. This longitudinal study aimed to determine the urine monocyte chemoattractant protein-1 (uMCP-1) levels in patients with biopsy-proven lupus nephritis (LN) at various stages of renal disease activity and to compare them to current standard markers. Methods. Patients with LN—active or inactive—had their uMCP-1 levels and standard disease activity markers measured at baseline and 2 and 4 months. Urinary parameters, renal function test, serological markers, and renal SLE disease activity index-2K (renal SLEDAI-2K) were analyzed to determine their associations with uMCP-1. Results. A hundred patients completed the study. At each visit, uMCP-1 levels (pg/mg creatinine) were significantly higher in the active group especially with relapses and were significantly associated with proteinuria and renal SLEDAI-2K. Receiver operating characteristic (ROC) curves showed that uMCP-1 was a potential biomarker for LN. Whereas multiple logistic regression analysis showed that only proteinuria and serum albumin and not uMCP-1 were independent predictors of LN activity. Conclusion. uMCP-1 was increased in active LN. Although uMCP-1 was not an independent predictor for LN activity, it could serve as an adjunctive marker when the clinical diagnosis of LN especially early relapse remains uncertain. Larger and longer studies are indicated.

Predictors of kidney disease in a cohort of pediatric patients with lupus

INTRODUCTION

Children with systemic lupus erythematosus (SLE) have an increased prevalence of kidney disease compared to their adult counterparts. Our goal was to identify potential clinical and laboratory predictors of renal disease.

METHODS

We performed a cohort study of incident and prevalent patients with SLE aged ≤19 years. Retrospective data from initial presentation until study enrollment was also collected. Laboratory and clinic data were recorded from each clinic visit including disease activity indices, autoantibodies, urinalyses, blood counts, and metabolic profile. Kidney disease was defined as the presence of abnormal renal biopsy or by American College of Rheumatology case definition for lupus nephritis. Logistic regression analyses were used to determine the association between clinical and laboratory data with kidney disease in those who had renal involvement within 30 days of SLE diagnosis. We also performed a time to event analysis to identify antecedents of renal disease.

RESULTS

Forty-seven children and adolescents with SLE were followed in the cohort, 91% female and 68% black. All of the males in the cohort developed renal disease, and all within one month of the diagnosis of SLE. In logistic regression, low serum albumin (odds ratio (OR): 4.8, 95% CI: 1.9-12.5) and positive dsDNA antibodies (OR: 3.2, 95% CI: 1.7-5.9) were associated with kidney disease. In longitudinal analyses, isolated sterile pyuria (hazard ratio (HR): 3, 95% CI: 1.1-6.4) and low serum albumin (HR: 3.4, 95% CI: 1.7-6.9) were predictors of future kidney disease. The presence of antibodies against Ro were protective against renal disease (HR: 0.2, 95% CI: 0.05-0.5).

CONCLUSION

We identified variables associated with kidney disease, both at initial diagnosis of SLE and in longitudinal follow-up in a cohort of children with SLE. The recognition of these abnormal laboratory values may help clinicians identify patients at risk for kidney disease before its onset thus preventing long-term complications.

Biomarkers for childhood-onset systemic lupus erythematosus

Childhood-onset systemic lupus erythematosus (cSLE) is a systemic autoimmune disease characterized by the presence of autoantibodies. cSLE often affects multiple organs in the body and is known to have a poorer prognosis than adult-onset disease (Azevedo et al. 2014). Current laboratory tests are clearly insufficient for identifying and monitoring the disease. Recent studies have yielded novel biomarkers for cSLE which can be used for monitoring disease activity and response to treatment. The most encouraging biomarkers will be discussed herein and include cell-bound complement activation products, some genomic profiles, and urinary proteins such as neutrophil gelatinase-associated lipocalin, monocyte chemoattractant protein-1, and others. Previous studies suggested that a combination of the novel biomarkers might help to enhance sensitivity and specificity for early diagnosis, disease monitoring, and prediction of cSLE flares.

Advances in biomarkers for paediatric rheumatic diseases

The search for biomarkers in paediatric rheumatic diseases, particularly juvenile idiopathic arthritis (JIA), childhood lupus nephritis (LN), and juvenile idiopathic inflammatory myopathies (JIIMs) is attracting increased interest. In JIA, a number of biomarkers have shown potential for predicting clinical phenotype, disease activity and severity, clinical remission and relapse, response to treatment, and disease course over time. In systemic JIA, measurement of biomarkers that reflect the degree of activation and expansion of T cells and macrophages might be helpful for detecting subclinical macrophage activation syndrome. Urine biomarkers for childhood LN hold promise for facilitating early diagnosis and improving disease monitoring and assessment of response to therapy. Myositis-specific autoantibodies define distinct serological subgroups of JIIMs, albeit with similar clinical features, responses to therapy, and prognoses. Use of biomarkers may potentially help to avoid invasive procedures, such as renal biopsy in systemic lupus erythematosus and muscle biopsy in juvenile dermatomyositis. Incorporation of effective and reliable biomarkers into routine practice might facilitate adoption of a stratified approach to investigation and management, foster the implementation of research into the design of personalized and targeted therapies, and ultimately lead to more rational and effective clinical care.

Bone disease in newly diagnosed lupus nephritis patients

Introduction

Bone loss in Lupus Nephritis (LN) patients is common and multifactorial. The aim of this study was to evaluate the bone status of newly diagnosed LN patients and their correlation with inflammatory factors involved in LN physiopathology.

Methods

We studied 15 pre-menopausal patients with ≤2 months of diagnosed SLE and LN. Patients with prior kidney or bone disease were excluded. In addition to biochemical evaluation (including 25-hydroxyvitamin D₃ [25(OH)D] and Monocyte Chemotactic Protein (MCP1) dosage), we performed bone biopsies followed by osteoblast culture, histomorphometric and immunohistochemistry analysis.

Results

LN patients presented a mean age of 29.5±10 years, a proteinuria of 4.7±2.9 g/day and an estimated glomerular filtration rate (GFR) of 37(31–87) ml/min/1,73 m². They were on glucocorticoid therapy for 34±12 days. All patients presented vitamin D insufficiency (9.9±4.4 ng/ml, range 4–20). Urinary MCP1 correlated negatively with 25(OH)D (r = −0.53, p = 0.003) and positively with serum deoxypyridinoline (r = 0.53, p = 0.004). Osteoblasts isolated from LN bone biopsies presented a significantly higher expression of MCP-1 when compared to controls (32.0.±9.1 vs. 22.9±5.3 mean fluorescence intensities, p = 0.01). LN patients presented a significantly reduced osteoid volume, osteoid thickness, osteoid surface, mineralization surface and bone formation rate, associated with an increased eroded surface and osteoclast surface. Patient’s bone specimens demonstrated a reduced immunostaining for osteoprotegerin (0.61±0.82 vs. 1.08±0.50%, p = 0.003), and an increased expression of Receptor Activator of NF-κB ligand (RANKL) (1.76±0.92 vs. 0.41±0.28%, p<0.001) when compared to controls.

Discussion

Newly diagnosed LN patients presented a significant disturbance in bone metabolism, characterized by an impaired bone formation and mineralization, associated with an increase in resorption parameters. Glucocorticoid use, vitamin D insufficiency and inflammation might be involved in the physiopathology of bone metabolism disturbance.

Osteoprotegerin and kidney disease

Vascular calcification in chronic kidney disease (CKD) patients is associated to increased mortality. Osteoprotegerin (OPG) is a soluble tumor necrosis factor (TNF) superfamily receptor that inhibits the actions of the cytokines receptor activator of nuclear factor kappa-B ligand (RANKL) and TNF-related apoptosis-inducing ligand (TRAIL) by preventing their binding to signaling receptors in the cell membrane. OPG-deficient mice display vascular calcification while OPG prevented calcification of cultured vascular smooth muscle cells and protected kidney cells from TRAIL-induced death. OPG may be a biomarker in patients with kidney disease. Circulating OPG is increased in predialysis, dialysis and transplant CKD patients and may predict vascular calcification progression and patient survival. By contrast, circulating OPG is decreased in nephrotic syndrome. In addition, free and exosome-bound urinary OPG is increased in human kidney disease. Increased urinary OPG has been associated with lupus nephritis activity. Despite the association of high OPG levels with disease, experimental functional information available suggests that OPG might be protective in kidney disease and in vascular injury in the context of uremia. Thus, tissue injury results in increased OPG, while OPG may protect from tissue injury. Recombinant OPG was safe in phase I randomized controlled trials. Further research is needed to fully define the therapeutic and biomarker potential of OPG in patients with kidney disease.

A study of hepcidin and monocyte chemoattractant protein-1 in Egyptian females with systemic lupus erythematosus

BACKGROUND

Lupus nephritis is one of the most serious manifestations of systemic lupus erythematosus (SLE). Novel biomarkers are necessary to enhance the diagnostic accuracy, prognostic stratification, monitoring of treatment response, and detection of early renal flares.

METHODS

Our study was conducted on 90 participants. They were divided into three groups, group I (controls) encompassed 30 ages and sex-matched healthy personnel. Group II included 30 non-nephritic SLE patients and finally group III included 30 SLE nephritic patients. Urinary monocyte chemoattractant protein-1 (UMCP-1) and hepcidin were evaluated by ELISA technique, compared and correlated in different groups, with each other and with other routine variables and with renal biopsy done to study group (III).

RESULTS

Both UMCP-1 and hepcidin in group III showed significant increase compared to other two groups (controls and group II) (468 ± 128, 111 ± 12, 252 ± 56 pg/ml, respectively, for UMCP-1 and 40 ± 12, 11 ± 2, 20 ± 5 ng/ml, respectively, for hepcidin, P < 0.01). Also both UMCP-1 and hepcidin in group III showed significant increase in diffuse proliferative subgroup compared to focal proliferative and mesangioproliferative subgroups (580 ± 43, 502 ± 46, and 352.6 ± 100 pg/ml, respectively, for UMCP-1 and 47.8 ± 9.5, 41.4 ± 6, and 32.9 ± 10.8 ng/ml, respectively, for urinary hepcidin, P < 0.05).

CONCLUSION

UMCP-1 and hepcidin could be associated with the susceptibility of lupus nephritis.

Systemic lupus erythematosus diagnostics in the 'omics' era

Systemic lupus erythematosus is a complex autoimmune disease affecting multiple organ systems. Currently, diagnosis relies upon meeting at least four out of eleven criteria outlined by the ACR. The scientific community actively pursues discovery of novel diagnostics in the hope of better identifying susceptible individuals in early stages of disease. Comprehensive studies have been conducted at multiple biological levels including: DNA (or genomics), mRNA (or transcriptomics), protein (or proteomics) and metabolites (or metabolomics). The 'omics' platforms allow us to re-examine systemic lupus erythematosus at a greater degree of molecular resolution. More importantly, one is hopeful that these 'omics' platforms may yield newer biomarkers for systemic lupus erythematosus that can help clinicians track the disease course with greater sensitivity and specificity.

Biomarkers in systemic lupus erythematosus: challenges and prospects for the future

The search for lupus biomarkers to diagnose, monitor, stratify, and predict individual response to therapy is currently more intense than ever before. This effort is essential for several reasons. First, epidemic overdiagnosis and underdiagnosis of lupus, even by certified rheumatologists, leads to errors in therapy with concomitant side effects which may be more serious than the disease itself. Second, identification of lupus flares remains as much an art as it is a science. Third, the capacity to stratify patients so as to predict those who will develop specific patterns of organ involvement is not currently possible but would potentially lead to preventive therapeutic strategies. Fourth, only one new drug for the treatment of lupus has been approved by the US Food and Drug Administration in over 50 years. A major obstacle in this pipeline is the dearth of biomarkers available to prove a patient has responded to an experimental therapeutic intervention. This review will summarize the challenges faced in the discovery and validation of lupus biomarkers, the most promising lupus biomarkers identified to date, and the promise of future directions.

Biomarkers and updates on pediatrics lupus nephritis

Lupus nephritis is a common complication of systemic lupus erythematosus in children and adolescents. This article reviews the clinical relevance of lupus nephritis and its current treatment. The reader is introduced to novel biomarkers that are expected to improve the management of lupus nephritis in the future, and support the testing of novel medication regimens.

Urinary CXCL-10/IP-10 and MCP-1 as markers to assess activity of lupus nephritis

Objective

IP-10 and MCP-1 are pro-inflammatory chemokines which are involved in the immunopathogenesis of lupus nephritis and may thus be useful biomarkers.

Methods

SLE patients fulfilling ACR 1997 criteria were included. SLEDAI was calculated and blood and urine samples collected. Active lupus was defined as SLEDAI ≥4. Active patients were divided into active renal (proteinuria ≥ 500 mg/day or active sediment in urine) and active non-renal lupus. Patients with active renal lupus were followed until the nephritis became inactive, when a second sample was collected. Serum and urinary levels of MCP-1 and IP-10 (pg/ml) were measured by ELISA. Urinary values were normalized for urinary spot creatinine (in mg/dL. Thus the values were expressed as pg/mg creatinine × 100 creatinine).

Results

A total of 136 patients with SLE including 78 active (46 active renal and 32 active non-renal) were included. Median age was 25 (10–55) years and SLE duration was 23 (six to 48) months. Both serum (data not shown) and urinary levels of MCP-1 (35.2 (12.7–71.7), 9.4 (4.4–17), p < 0.001) and IP-10 (9.5 (4.4–17.9), 3.9 (1.9–9.3), p < 0.001) were higher in active compared to inactive SLE. However, in active renal compared to active non-renal SLE, there was no difference in serum levels; only urinary levels of MCP-1 (46.2 (19.9–125), 12.7 (5.8–43.9), p < 0.001) and IP-10 (12.5 (5.6–22.7), 5.2 (2.3–12.2), p < 0.05) were higher. On longitudinal follow-up of active renal patients ( n = 24), there was a decrease in urinary levels of MCP-1 and IP-10 ( p = 0.005). On ROC analysis, urinary MCP-1 outperformed C4 and urinary IP-10, but was similar to dsDNA and C3 in differentiating active renal from non-renal SLE.

Conclusions

Urinary and serum IP-10 and MCP-1 are potentially useful markers of lupus activity; however, only the urinary levels are indicative of renal activity. However, on ROC analysis, they are not better than conventional markers.

Urinary angiostatin--a novel putative marker of renal pathology chronicity in lupus nephritis

There is a critical need to identify biomarkers for Systemic Lupus Erythematosus (SLE) which has a high prevalence of renal failure. When urine from patients with lupus nephritis was recently screened for the levels of ∼280 molecules using an exploratory array-based proteomic platform, elevated angiostatin levels were noted. Angiostatin is a bioactive fragment of plasminogen, and has been known to have modulatory function in angiogenesis and inflammation. The significant elevation in urinary angiostatin was next validated in an independent cohort of SLE patients (n = 100) using ELISA. Among patients with SLE, urine angiostatin was significantly increased in active SLE compared with inactive SLE, correlating well with the SLEDAI disease activity index and SLICC renal activity score (r = 0.66, p < 0.0001). ROC curve analysis further confirmed that urinary angiostatin had the capacity to discriminate patients with active SLE from those with inactive disease. Patients with Class IV lupus nephritis exhibited the highest levels of urinary angiostatin. Immunohistochemistry staining localized angiostatin expression to the renal tubular cells in these patients. Finally, when paired urine-kidney samples procured concurrently from patients with LN were next examined, urine angiostatin levels correlated strongly with the renal pathology chronicity index, but not with the activity index. Given that Class IV lupus nephritis and renal pathology chronicity changes forebode poor renal and patient survival, urinary angiostatin emerges as a novel noninvasive marker of renal disease in SLE. Longitudinal studies are in progress to further assess the disease-predictive potential of urinary angiostatin.

Urinary chemokine (C-C motif) ligand 2 (monocyte chemotactic protein-1) as a tubular injury marker for early detection of cisplatin-induced nephrotoxicity

Because of the difficulty in detecting segment-specific response in the kidney, we investigated the molecular events underlying acute kidney injury in the proximal tubules of rats with cisplatin (cis-diamminedichloroplatinum II)-induced nephrotoxicity. Microarray analysis revealed that mRNA levels of several cytokines and chemokines, such as interleukin-1beta, chemokine (C-C motif) ligand (CCL) 2, CCL20, chemokine (C-X-C motif) ligand (CXCL) 1, and CXCL10 were significantly increased after cisplatin treatment in both isolated proximal tubules and whole kidney. Interestingly, tubular CCL2 mRNA levels increased soon after cisplatin administration, whereas CCL2 mRNA levels in whole kidney first decreased and then increased. Levels of both CCL2 and kidney injury molecule-1 (KIM-1) in the whole kidney increased after cisplatin administration. Immunofluorescence analysis revealed CCL2 changes in the proximal tubular cells initially and then in the medullary interstitium. Urinary CCL2 excretion significantly increased approximately 3-fold compared with controls the day after cisplatin administration (5mg/kg), when no changes were observed plasma creatinine and blood urea nitrogen levels. Urinary levels of KIM-1 also increased 3-fold after cisplatin administration. In addition, urinary CCL2 rather than KIM-1 increased in chronic renal failure rats after administration of low-dose cisplatin (2mg/kg), suggesting that urinary CCL2 was selective for cisplatin-induced nephrotoxicity in renal impairment. These results indicated that the increase in cytokine and chemokine expression in renal epithelial cells might be responsible for kidney deterioration in cisplatin-induced nephrotoxicity, and that urinary CCL2 is associated with tubular injury and serves as a sensitive and noninvasive marker for the early detection of cisplatin-induced tubular injury.

MCP-1 in urine as biomarker of disease activity in Systemic Lupus Erythematosus

Conventional clinical parameters are not sensitive or specific enough for detecting ongoing disease activity in the Systemic Lupus Erythematosus (SLE). Measurement of cytokines in urine is an encouraging approach to detection of early flares in this disease. Here we have profiled 27 different cytokines, chemokines and celular growth factors in the urine of 48 patients previously diagnosed of SLE as potential biomarkers of disease activity. Correlation analysis with Bonferroni correction showed that MCP-1 was the only immune mediator which levels in urine correlated directly with the SLE Disease Activity Index 2000 (SLEDAI-2K) score (correlation coefficient, p): MCP-1 (0.45,0.003). MCP-1 correlated inversely with levels of C3 complement protein in serum (-0.50,0.001). MCP-1 showed significant higher levels in patients with severe disease activity in comparison with those exhibiting mild activity. Levels of this chemokine were also higher in patients with severe disease activity in comparison with patients with inactive disease and healthy controls. Areas under receiver operating characteristic curves (AUROC) for detection of severe disease (SLEDAI⩾8) was as follows for MCP-1: [AUROC, (IC95%), p]: [0.81 (0.65-0.96) 0.003]. In addition, MCP-1 showed a good result in the AUROC analysis for detecting renal involvement [0.70 (0.52-0.87) 0.050]. When correlation analysis were repeated excluding those patients with active renal disease (n=14), levels of MCP-1 in urine kept on showing a significant positive association with SLEDAI-2K score. In conclusion, multiplex-based cytokine profiling in urine demonstrated the superiority of MCP-1 over a wide range of cytokines as biomarker of disease activity in SLE.

Biomarkers for systemic lupus erythematosus

In recent years, biomarkers have shown significant promise in helping decision-making in drug development. Systemic lupus erythematosus (SLE) is a complicated and highly heterogeneous disease that involves all organs. Only one drug, belimumab, has been approved by the US Food and Drug Administration to treat SLE during the last 50 years and there remains a high unmet medical need to develop new and effective therapies to benefit different patient populations in SLE. Due to the extreme heterogeneity of the disease and the complex and rigorous process to validate individual biomarkers, there is currently a very limited number of consensus biomarkers to aid the treatment decision-making in SLE. This review provides a snapshot of some biomarkers in the field that have the potential to make a big impact on drug development and/or treatment decisions by physicians. These include: type I interferon (IFN) gene signature as a pharmacodynamic marker and potential predictive marker for anti-type I IFN therapy; anti-double stranded DNA as a disease marker and potential predictive marker for flares; the complements and neutrophil signatures as disease marker of SLE; and TWEAK (a tumor necrosis factor family member produced by macrophages) and MCP-1 as potential markers to predict renal flares. Most of these markers need carefully planned and prospective studies with high statistical power to confirm their respective utilities. With the development and application of powerful new technologies, more successful biomarkers will emerge in SLE. This could improve the management of patients in the clinic and facilitate the development of novel and more effective therapeutics for this difficult-to-treat disease.

Role of TWEAK in lupus nephritis: a bench-to-bedside review

There is significant unmet need in the treatment of lupus nephritis (LN) patients. In this review, we highlight the role of the TWEAK/Fn14 pathway in mediating key pathologic processes underlying LN involving both glomerular and tubular injury, and thus the potential for renal protection via blockade of this pathway. The specific pathological mechanisms of TWEAK - namely promoting inflammation, renal cell proliferation and apoptosis, vascular activation and fibrosis - are described, with supporting data from animal models and in vitro systems. Furthermore, we detail the translational relevance of these mechanisms to clinical readouts in human LN. We present the opportunity for an anti-TWEAK therapeutic as a renal protective agent to improve efficacy relative to current standard of care treatments hopefully without increased safety risk, and highlight a phase II trial with BIIB023, an anti-TWEAK neutralizing antibody, designed to assess efficacy in LN patients. Taken together, targeting the TWEAK/Fn14 axis represents a potential new therapeutic paradigm for achieving renal protection in LN patients.

Biomarkers for systemic lupus erythematosus

The urgent need for lupus biomarkers was demonstrated in September 2011 during a Workshop sponsored by the Food and Drug Administration: Potential Biomarkers Predictive of Disease Flare. After 2 days of discussion and more than 2 dozen presentations from thought leaders in both industry and academia, it became apparent that highly sought biomarkers to predict lupus flare have not yet been identified. Even short of the elusive biomarker of flare, few biomarkers for systemic lupus erythematosus (SLE) diagnosis, monitoring, and stratification have been validated and employed for making clinical decisions. This lack of reliable, specific biomarkers for SLE hampers proper clinical management of patients with SLE and impedes development of new lupus therapeutics. As such, the intensity of investigation to identify lupus biomarkers is climbing a steep trajectory, lending cautious optimism that a validated panel of biomarkers for lupus diagnosis, monitoring, stratification, and prediction of flare may soon be in hand.

Mechanisms of tissue injury in lupus nephritis

Systemic lupus erythematosus is a prototypic autoimmune disease characterized by autoantibody production and immune complex formation/deposition in target organs such as the kidney. Resultant local inflammation then leads to organ damage. Nephritis, a major cause of morbidity and mortality in patients with lupus, occurs in approximately 50% of lupus patients. In the present review, we provide an overview of the current research and knowledge concerning mechanisms of renal injury in both lupus-prone mouse models and human lupus patients.

Soluble receptor activator of nuclear factor κB ligand/osteoprotegerin ratio is increased in systemic lupus erythematosus patients

INTRODUCTION

Systemic lupus erythematosus (SLE) patients have lower bone mineral density and increased fracture risk when compared with healthy individuals, due to distinct factors and mechanisms. Bone remodeling is a tightly orchestrated process dependent on several factors, including the balance between receptor activator of nuclear factor κB ligand (RANKL) and osteoprotegerin (OPG). Our aim was to assess serum OPG and soluble RANKL (sRANKL) levels as well as sRANKL/OPG ratio in female SLE patients and compare it with female controls.

METHODS

We have evaluated 103 SLE patients and 114 healthy controls, all Caucasian females. All participants underwent a clinical and laboratory evaluation. sRANKL and OPG were quantified in serum by ELISA based methods. sRANKL, OPG and sRANKL/OPG ratio levels were compared between SLE patients and age, sex and race matched healthy controls. For SLE patients, a multivariate analysis was performed, to find the possible predictors of the changes in sRANKL, OPG and sRANKL/OPG ratio levels.

RESULTS

Although sRANKL levels did not differ between the two groups, serum OPG was lower in SLE patients (P < 0.001). This led to an increased sRANKL/OPG ratio (P = 0.010) in the patients' group.The multivariate analysis was performed considering age and other clinical and laboratorial potential confounders for these variations in the SLE patients group. We have showed that age (P = 0.001) and levels of anti-Sm antibodies (P = 0.016) were independent predictors of sRANKL/OPG ratio variations in SLE patients. No relationship with therapy or disease activity measured by SLEDAI2K was found.

CONCLUSIONS

These results are suggestive of increased osteoclastic stimuli driven by the SLE disease mechanisms.

Urinary monocyte chemoattractant protein-1 in renal disease

Monocyte chemoattractant protein-1 (MCP-1/CCL2) has a critical role in the development of various renal diseases. Data from disease specific experimental animal models and clinical studies confirm that MCP-1 plays an important part in the pathogenesis of renal diseases. The action of MCP-1 in these studies has been shown to be more complex than the traditional concept of monocyte/macrophage recruitment to the inflammatory site. MCP-1 is expressed in renal tissues and it is detectable in urine of patients with a variety of renal diseases. Measurement of urinary levels of MCP-1 can provide valuable information not only for the diagnosis of active renal disease, but also for monitoring of response to therapy. Urinary MCP-1 measurement can provide help with evaluation of the prognosis in various renal diseases. Furthermore, selective targeting of MCP-1 could be an effective treatment in suppressing a number of renal diseases as blocking MCP-1 has already been shown to ameliorate renal diseases in experimental animal models. The advantage of measuring urinary MCP-1 rather than the conventional markers must now be validated using a larger cohort of patients in different renal diseases. Also the therapeutic potential of MCP-1 targeting agents needs to be investigated in clinical studies.

Correlations of urinary biomarkers, TNF-like weak inducer of apoptosis (TWEAK), osteoprotegerin (OPG), monocyte chemoattractant protein-1 (MCP-1), and IL-8 with lupus nephritis

OBJECTIVE

This case-controlled study was designed to correlate urinary biomarkers, TNF-like weak inducer of apoptosis (TWEAK), osteoprotegerin (OPG), monocyte chemoattractant protein-1 (MCP-1), and interleukin-8 (IL-8) levels, with renal involvement in a cohort of systemic lupus erythematosus (SLE) patients to examine their diagnostic performance.

PATIENTS AND METHODS

In 73 SLE patients, and in 23 healthy volunteers, urinary levels of TWEAK, OPG, MCP-1, and IL-8 levels were measured. Disease activity was assessed by total SLE disease activity index, and renal activity by renal activity index (rSLEDAI), and both were correlated with urinary biomarkers. Sensitivity, specificity, and predictive values of individual biomarkers to predict lupus nephritis were also calculated.

RESULTS

Significantly higher levels of urinary biomarkers were observed in SLE patients with lupus nephritis (LN) compared with those without LN (TWEAK, p < 0.001; MCP-1, p < 0.001; OPG, p < 0.001; IL-8, p < 0.032). Other significantly higher levels were observed in SLE patients with LN compared with control subjects (TWEAK, MCP-1, OPG, and IL-8 p < 0.001). Positive correlations were observed between rSLEDAI and TWEAK (r = 0.612 and p < 0.001), MCP-1 (r = 0.635 and p < 0.001), and OPG (r = 0.505 and p < 0.001).

CONCLUSIONS

Urinary levels of TWEAK, OPG, and MCP-1 positively correlate with renal involvement as assessed by rSLEDAI with reasonable sensitivity, specificity, and predictive values to detect lupus nephritis while IL-8 was not significantly associated with global or rSLEDAI.

Review: Serum and urine biomarkers of kidney disease: A pathophysiological perspective

The use of reliable biomarkers is becoming increasingly important for the improved management of patients with acute and chronic kidney diseases. Recent developments have identified a number of novel biomarkers in serum or urine that can determine the potential risk of kidney damage, distinguish different types of renal injury, predict the progression of disease and have the potential to assess the efficacy of therapeutic intervention. Some of these biomarkers can be used independently while others are more beneficial when used in combination with knowledge of other clinical risk factors. Advances in gene expression analysis, chromatography, mass spectrometry and the development of sensitive enzyme-linked immunosorbent assays have facilitated accurate quantification of many biomarkers. This review primarily focuses on describing new and established biomarkers, which identify and measure the various pathophysiological processes that promote kidney disease. It provides an overview of some of the different classes of renal biomarkers that can be assessed in serum/plasma and urine, including markers of renal function, oxidative stress, structural and cellular injury, immune responses and fibrosis. However, it does not explore the current status of these biomarkers in terms of their clinical validation.

Biomarkers in lupus nephritis

Biomarkers have the potential to be useful tools for noninvasively evaluating and managing patients with lupus nephritis. Many candidate biomarkers have been identified, but they require validation in larger cohorts. It is likely that combinations or biomarker profiles, rather than individual markers, will emerge to help better predict the severity of inflammation, the extent of fibrosis, degree of drug responsiveness, and other variables. This approach has the potential to reduce the use of the renal biopsy, improve therapeutic efficacy, and limit toxicity. We predict algorithms based on genotype and biomarkers combined with clinical presentation will emerge to help guide physicians in management. Assays that show the most potential include serum erythrocyte bound complement C4d, interleukin 17, interleukin 23, interferon score/chemokine score ratio, and anti-C1q antibodies. Such urinary biomarkers as fractional excretion of endothelial-1, monocyte chemoattractant protein-1, vascular cell adhesion molecule-1, and TWEAK (tumor necrosis factor-like weak inducer of apoptosis) may also be useful but require validations.

[MCP-1 in urine as biomarker of renal lupus in absence of cytokines, interferon-γ and growth factors]

OBJECTIVE

To characterize 17 immunological markers in the Urine of patients with SLE.

INTRODUCTION

Lupus nephritis is an inflammatory disease affecting the renal parenchyma. Cytokines and chemokines are key immune mediators that have been related with the pathogenesis of the disease. Obtaining non invasive prognosis markers is a highly desirable objective in order to improve the clinical management of these patients.

PATIENTS AND METHODS

In this study we profiled 17 immune mediators (Th1, Th2, Th17 cytokines, chemokines and growth factors) in the urine of 25 patients with systemic lupus erythematosus with active renal disease by using a Biorad© 17-plex kit on a Luminex© platform. A group of healthy volunteers of similar age and comparable sex distribution was recruited as control (n=10).

RESULTS

Results evidenced that the only detectable mediators in urine were IL-8, MCP-1 and MIP-1 β. When levels of these mediators were compared between patients and controls, significantly higher levels of MCP-1 were observed in the urine of the patients. MCP-1 levels in urine correlated positively with the SLEDAI score in a significant way and negatively with plasma levels of complement C4.

CONCLUSIONS

Our results reinforce the role of MCP-1 in urine as biomarker of disease activity in renal lupus, excluding the detection of other soluble immune mediators such as Th1, Th2 ,Th17 cytokines and growth factors as suitable markers in this non invasive sample.

Biomarkers for lupus nephritis: a critical appraisal

Kidney disease is one of the most serious manifestations of systemic lupus erythematosus (SLE). Despite the improvement in the medical care of SLE in the past two decades, the prognosis of lupus nephritis remains unsatisfactory. Besides exploring more effective but less toxic treatment modalities that will further improve the remission rate, early detection and treatment of renal activity may spare patients from intensive immunosuppressive therapies and reduce renal damage. Conventional clinical parameters such as creatinine clearance, proteinuria, urine sediments, anti-dsDNA, and complement levels are not sensitive or specific enough for detecting ongoing disease activity in the lupus kidneys and early relapse of nephritis. Thus, novel biomarkers are necessary to enhance the diagnostic accuracy and sensitivity of lupus renal disease, prognostic stratification, monitoring of treatment response, and detection of early renal flares. This paper reviews promising biomarkers that have recently been evaluated in longitudinal studies of lupus nephritis.