Urine chemokines as biomarkers of human systemic lupus erythematosus activity

Single-cell mass cytometry in immunological skin diseases

Immune-related skin diseases represent a collective of dermatological disorders intricately linked to dysfunctional immune system processes. These conditions are primarily characterized by an immoderate activation of the immune system or deviant immune responses, involving diverse immune components including immune cells, antibodies, and inflammatory mediators. However, the precise molecular dysregulation underlying numerous individual cases of these diseases and unique subsets respond under disease conditions remains elusive. Comprehending the mechanisms and determinants governing the homeostasis and functionality of diseases could offer potential therapeutic opportunities for intervention. Mass cytometry enables precise and high-throughput quantitative measurement of proteins within individual cells by utilizing antibodies labeled with rare heavy metal isotopes. Imaging mass cytometry employs mass spectrometry to obtain spatial information on cell-to-cell interactions within tissue sections, simultaneously utilizing more than 40 markers. The application of single-cell mass cytometry presents a unique opportunity to conduct highly multiplexed analysis at the single-cell level, thereby revolutionizing our understanding of cell population heterogeneity and hierarchy, cellular states, multiplexed signaling pathways, proteolysis products, and mRNA transcripts specifically in the context of many autoimmune diseases. This information holds the potential to offer novel approaches for the diagnosis, prognostic assessment, and monitoring responses to treatment, thereby enriching our strategies in managing the respective conditions. This review summarizes the present-day utilization of single-cell mass cytometry in studying immune-related skin diseases, highlighting its advantages and limitations. This technique will become increasingly prevalent in conducting extensive investigations into these disorders, ultimately yielding significant contributions to their accurate diagnosis and efficacious therapeutic interventions.

Urinary Biomarkers for Lupus Nephritis: A Systems Biology Approach

Systemic lupus erythematosus (SLE) is the prototypical systemic autoimmune disorder. Kidney involvement, termed lupus nephritis (LN), is seen in 40-60% of patients with systemic lupus erythematosus (SLE). After the diagnosis, serial measurement of proteinuria is the most common method of monitoring treatment response and progression. However, present treatments for LN-corticosteroids and immunosuppressants-target inflammation, not proteinuria. Furthermore, subclinical renal inflammation can persist despite improving proteinuria. Serial kidney biopsies-the gold standard for disease monitoring-are also not feasible due to their inherent risk of complications. Biomarkers that reflect the underlying renal inflammatory process and better predict LN progression and treatment response are urgently needed. Urinary biomarkers are particularly relevant as they can be measured non-invasively and may better reflect the compartmentalized renal response in LN, unlike serum studies that are non-specific to the kidney. The past decade has overseen a boom in applying cutting-edge technologies to dissect the pathogenesis of diseases at the molecular and cellular levels. Using these technologies in LN is beginning to reveal novel disease biomarkers and therapeutic targets for LN, potentially improving patient outcomes if successfully translated to clinical practice.

Lupus Nephritis Biomarkers: A Critical Review

Lupus nephritis (LN), a major complication in individuals diagnosed with systemic lupus erythematosus, substantially increases morbidity and mortality. Despite marked improvements in the survival of patients with severe LN over the past 50 years, complete clinical remission after immunosuppressive therapy is achieved in only half of the patients. Therefore, timely detection of LN is vital for initiating prompt therapeutic interventions and improving patient outcomes. Biomarkers have emerged as valuable tools for LN detection and monitoring; however, the complex role of these biomarkers in LN pathogenesis remains unclear. Renal biopsy remains the gold standard for the identification of the histological phenotypes of LN and guides disease management. However, the molecular pathophysiology of specific renal lesions remains poorly understood. In this review, we provide a critical, up-to-date overview of the latest developments in the field of LN biomarkers.

Biomarkers for systemic lupus erythematosus - a focus on organ damage

INTRODUCTION

Systemic lupus erythematosus (SLE) is complex autoimmune disease with heterogenous manifestations, unpredictable disease course and response to treatment. One of the critical needs in SLE management is the identification of reliable biomarkers that can aid in early diagnosis, accurate monitoring of disease activity, and assessment of treatment response.

AREAS COVERED

In the current review, we focus on the commonly affected organs (skin, kidney, and nervous system) in SLE to summarize the emerging biomarkers that show promise in disease diagnosis, monitoring and treatment response assessment. The subtitles within each organ domain were determined based on the most relevant and promising biomarkers for that specific organ damage.

EXPERT OPINION

Biomarkers have the potential to significantly benefit the management of SLE by aiding in diagnosis, disease activity monitoring, prognosis, and treatment response assessment. However, despite decades of research, none has been validated and implemented for routine clinical use. Novel biomarkers could lead to the development of precision medicine for SLE, guide personalized treatment, and improve patient outcomes. Challenges in biomarker research in SLE include defining clear and clinically relevant questions, accounting for the heterogeneity of SLE, and confirming initial findings in larger, multi-center, multi-ethnic, independent cohorts that reflect real-world clinical scenarios.

Decipher the Immunopathological Mechanisms and Set Up Potential Therapeutic Strategies for Patients with Lupus Nephritis

Lupus nephritis (LN) is one of the most severe complications in patients with systemic lupus erythematosus (SLE). Traditionally, LN is regarded as an immune complex (IC) deposition disease led by dsDNA-anti-dsDNA-complement interactions in the subendothelial and/or subepithelial basement membrane of glomeruli to cause inflammation. The activated complements in the IC act as chemoattractants to chemically attract both innate and adaptive immune cells to the kidney tissues, causing inflammatory reactions. However, recent investigations have unveiled that not only the infiltrating immune-related cells, but resident kidney cells, including glomerular mesangial cells, podocytes, macrophage-like cells, tubular epithelial cells and endothelial cells, may also actively participate in the inflammatory and immunological reactions in the kidney. Furthermore, the adaptive immune cells that are infiltrated are genetically restricted to autoimmune predilection. The autoantibodies commonly found in SLE, including anti-dsDNA, are cross-reacting with not only a broad spectrum of chromatin substances, but also extracellular matrix components, including α-actinin, annexin II, laminin, collagen III and IV, and heparan sulfate proteoglycan. Besides, the glycosylation on the Fab portion of IgG anti-dsDNA antibodies can also affect the pathogenic properties of the autoantibodies in that α-2,6-sialylation alleviates, whereas fucosylation aggravates their nephritogenic activity. Some of the coexisting autoantibodies, including anti-cardiolipin, anti-C1q, anti-ribosomal P autoantibodies, may also enhance the pathogenic role of anti-dsDNA antibodies. In clinical practice, the identification of useful biomarkers for diagnosing, monitoring, and following up on LN is quite important for its treatments. The development of a more specific therapeutic strategy to target the pathogenic factors of LN is also critical. We will discuss these issues in detail in the present article.

Interleukin-33 Ameliorates Murine Systemic Lupus Erythematosus and Is Associated with Induction of M2 Macrophage Polarisation and Regulatory T Cells

The innate cytokine IL-33 is increasingly recognised to possess biological effects on various immune cells. We have previously demonstrated elevated serum level of soluble ST2 in patients with active systemic lupus erythematosus suggesting involvement of IL-33 and its receptor in the lupus pathogenesis. This study sought to examine the effect of exogenous IL-33 on disease activity of pre-disease lupus-prone mice and the underlying cellular mechanisms. Recombinant IL-33 was administered to MRL/lpr mice for 6 weeks, whereas control group received phosphate-buffered saline. IL-33-treated mice displayed less proteinuria, renal histological inflammatory changes, and had lower serum levels of pro-inflammatory cytokines including IL-6 and TNF-α. Renal tissue and splenic CD11b+ extracts showed features of M2 polarisation with elevated mRNA expression of Arg1, FIZZI, and reduced iNOS. These mice also had increased IL-13, ST2, Gata3, and Foxp3 mRNA expression in renal and splenic tissues. Kidneys of these mice displayed less CD11b+ infiltration, had downregulated MCP-1, and increased infiltration of Foxp3-expressing cells. Splenic CD4+ T cells showed increased ST2-expressing CD4+Foxp3+ population and reduced IFN-γ+ population. There were no differences in serum anti-dsDNA antibodies and renal C3 and IgG2a deposit in these mice. Exogenous IL-33 was found to ameliorate disease activity in lupus-prone mice with induction of M2 polarisation, Th2 response, and expansion of regulatory T cells. IL-33 likely orchestrated autoregulation of these cells through upregulation of ST2 expression.

Low nephron endowment increases susceptibility to renal stress and chronic kidney disease

Preterm birth results in low nephron endowment and increased risk of acute kidney injury (AKI) and chronic kidney disease (CKD). To understand the pathogenesis of AKI and CKD in preterm humans, we generated potentially novel mouse models with a 30%-70% reduction in nephron number by inhibiting or deleting Ret tyrosine kinase in the developing ureteric bud. These mice developed glomerular and tubular hypertrophy, followed by the transition to CKD, recapitulating the renal pathological changes seen in humans born preterm. We injected neonatal mice with gentamicin, a ubiquitous nephrotoxic exposure in preterm infants, and detected more severe proximal tubular injury in mice with low nephron number compared with controls with normal nephron number. Mice with low nephron number had reduced proliferative repair with more rapid development of CKD. Furthermore, mice had more profound inflammation with highly elevated levels of MCP-1 and CXCL10, produced in part by damaged proximal tubules. Our study directly links low nephron endowment with postnatal renal hypertrophy, which in this model is maladaptive and results in CKD. Underdeveloped kidneys are more susceptible to gentamicin-induced AKI, suggesting that AKI in the setting of low nephron number is more severe and further increases the risk of CKD in this vulnerable population.

The first-year course of urine MCP-1 and its association with response to treatment and long-term kidney prognosis in lupus nephritis

OBJECTIVES

The present study aims to assess the course of uMCP-1 and its association with response to therapy and long-term kidney function in a prospective cohort of adults who received a kidney biopsy for suspicion of active lupus nephritis (LN).

METHODS

Subjects were segregated into a histologically active LN group and a histologically chronic LN group. Both groups were followed for > = 36 months and urine were collected at flare, 3, 6, and 12 months of follow-up. The association between the course of uMCP-1, response to treatment, and progression to 30% loss of the eGFR was evaluated by linear mixed models for repeated measures.

RESULTS

A kidney biopsy was performed on 125 subjects. In 114, the report was consistent with histologically active LN; in 11, with histologically chronic LN. Urine MCP-1 levels were significantly higher in the active LN than in the chronic LN group. Urine MCP-1 levels correlated with the histological findings of cellular crescents, endocapillary hypercellularity, interstitial inflammation, glomerular sclerosis, interstitial fibrosis, and tubular atrophy. The mean estimates of uMCP-1 at flare were higher in the non-response group than in the complete response group, and decreased in the complete/partial response groups by the third month, while they remained elevated in the non-response group. The mean estimates for uMCP-1 were higher at LN flare and remained elevated in patients who progressed to loss of 30% of the eGFR, while they decreased in patients with stable kidney function.

CONCLUSION

The first-year course of uMCP-1 is associated with response to therapy and kidney survival in LN. Key Points •Urine MCP-1 levels differentiate histologically-active lupus nephritis from histologically-chronic lupus nephritis •Urine MCP-1 levels decrease by 3 months of therapy in subjects with a favorable response whose kidney function remains stable long-term •Urine MCP-1 levels remain elevated during the first year of therapy in subjects the will later lose kidney function.

Molecular profiling of kidney compartments from serial biopsies differentiate treatment responders from non-responders in lupus nephritis

The immune pathways that define treatment response and non-response in lupus nephritis (LN) are unknown. To characterize these intra-kidney pathways, transcriptomic analysis was done on protocol kidney biopsies obtained at flare (initial biopsy (Bx1)) and after treatment (second biopsy (Bx2)) in 58 patients with LN. Glomeruli and tubulointerstitial compartments were isolated using laser microdissection. RNA was extracted and analyzed by nanostring technology with transcript expression from clinically complete responders, partial responders and non-responders compared at Bx1 and Bx2 and to the healthy controls. Top transcripts that differentiate clinically complete responders from non-responders were validated at the protein level by confocal microscopy and urine ELISA. At Bx1, cluster analysis determined that glomerular integrin, neutrophil, chemokines/cytokines and tubulointerstitial chemokines, T cell and leukocyte adhesion genes were able to differentiate non-responders from clinically complete responders. At Bx2, glomerular monocyte, extracellular matrix, and interferon, and tubulointerstitial interferon, complement, and T cell transcripts differentiated non-responders from clinically complete responders. Protein analysis identified several protein products of overexpressed glomerular and tubulointerstitial transcripts at LN flare, recapitulating top transcript findings. Urine complement component 5a and fibronectin-1 protein levels reflected complement and fibronectin expression at flare and after treatment. Thus, transcript analysis of serial LN kidney biopsies demonstrated how gene expression in the kidney changes with clinically successful and unsuccessful therapy. Hence, these insights into the molecular landscape of response and non-response may help align LN management with the pathogenesis of kidney injury.

The nephropathy of sickle cell trait and sickle cell disease

Sickle cell syndromes, including sickle cell disease (SCD) and sickle cell trait, are associated with multiple kidney abnormalities. Young patients with SCD have elevated effective renal plasma flow and glomerular filtration rates, which decrease to normal ranges in young adulthood and subnormal levels with advancing age. The pathophysiology of SCD-related nephropathy is multifactorial - oxidative stress, hyperfiltration and glomerular hypertension are all contributing factors. Albuminuria, which is an early clinical manifestation of glomerular damage, is common in individuals with SCD. Kidney function declines more rapidly in individuals with SCD than in those with sickle cell trait or in healthy individuals. Multiple genetic modifiers, including APOL1, HMOX1, HBA1 and HBA2 variants are also implicated in the development and progression of SCD-related nephropathy. Chronic kidney disease and rapid decline in estimated glomerular filtration rate are associated with increased mortality in adults with SCD. Renin-angiotensin-aldosterone system inhibitors are the standard of care treatment for albuminuria in SCD, despite a lack of controlled studies demonstrating their long-term efficacy. Multiple studies of novel therapeutic agents are ongoing, and patients with SCD and kidney failure should be evaluated for kidney transplantation. Given the high prevalence and severe consequences of kidney disease, additional studies are needed to elucidate the pathophysiology, natural history and treatment of SCD-related nephropathy.

Identification and Validation of a Urinary Biomarker Panel to Accurately Diagnose and Predict Response to Therapy in Lupus Nephritis

Background

We have previously shown that 15 urinary biomarkers (of 129 tested by Luminex), discriminate between active Lupus Nephritis (ALN) and non-LN patients. The aim of this study was to evaluate the ability of these 15 previously-identified urinary biomarkers to predict treatment responses to conventional therapy, and for the most predictive of these biomarkers to validate their utility to identify ALN patients in an independent prospectively-acquired lupus cohort.

Methods

Our study had a 3-stage approach. In stage 1, we used Luminex to examine whether our previously identified urinary biomarkers at the time of the renal flare ( ± 3 months) or 12 ± 3 months after treatment of biopsy-proven ALN could predict treatment responses. In stage 2, a larger prospectively-acquired cross-sectional cohort was used to further validate the utility of the most predictive urinary biomarkers (identified in stage 1) to detect ALN patients. In this 2^nd stage, cut-offs with the best operating characteristics to detect ALN patients were produced for each biomarker and different combinations and/or numbers of elevated biomarkers needed to accurately identify ALN patients were analyzed. In stage 3, we aimed to further corroborate the sensitivity of the cut-offs created in stage 2 to detect ALN patients in a biopsy-proven ALN cohort who had a urine sample collection within 3 months of their biopsy.

Results

Twenty-one patients were included in stage 1. Twelve (57.1%), 4 (19.1%), and 5 (23.8%) patients had a complete (CR), partial (PR) and no (NR) remission at 24 ± 3 months, respectively. The percentage decrease following 12 ± 3 months of treatment for Adiponectin, MCP-1, sVCAM-1, PF4, IL-15 and vWF was significantly higher in patients with CR in comparison to those with PR/NR. In stage 2, a total of 247 SLE patients were included, of which 24 (9.7%) had ALN, 79 (31.9%) had LN in remission (RLN) and 144 (58.3%) were non-LN (NLN) patients. Based on the combinations of biomarkers with the best operating characteristics we propose “rule out” and “rule in” ALN criteria. In stage 3, 53 biopsy-proven ALN patients were included, 35 with proliferative LN and 18 with non-proliferative ALN, demonstrating that our “rule in ALN” criteria operate better in detecting active proliferative than non-proliferative classes.

Conclusions

Our results provide further evidence to support the role of Adiponectin, MCP-1, sVCAM-1 and PF4 in the detection of proliferative ALN cases. We further show the clinical utility of measuring multiple rather than a single biomarker and we propose novel “rule in” and “rule out” criteria for the detection of proliferative ALN with excellent operating characteristics.

Clinical Impact of Subclinical Interstitial Fibrosis or Tubular Atrophy in 1-Hour Allograft Biopsy for Remnant Renal Function in Living Kidney Donors: A Prospective Observational Study

BACKGROUND

Preservation of remnant renal function (RRF) is one of the major concerns among living kidney donors (LKDs). A comprehensive assessment is needed to predict the RRF. In this prospective study, we investigated the roles of histologic findings from a 1-hour allograft biopsy in predicting the RRF.

METHODS

Our prospective study included 116 LKDs who underwent donor nephrectomy (DN) at our institute. Clinical and radiographic data were obtained from their medical charts. Renal volume parameters were calculated using the preoperative computed tomographic images in the volume analyzer SYNAPSE VINCENT image analysis system. Tissues obtained from allograft biopsy were examined. RRF was defined as the estimated glomerular filtration rate (eGFR) 12 months after DN.

RESULTS

Of 116 LKDs, 95 were finally evaluated. The median age of the LKDs at DN and the preoperative eGFR were 57 years and 80.0 mL/min/1.73 m², respectively. In the histologic analysis, 68 allografts (71.6%) had nonspecific findings involving the glomerulus, vessel, and tubulointerstitium. Interstitial fibrosis or tubular atrophy (IF/TA) was the only significant predictive factor for RRF (P = .039). No significant association was found between renal volume parameters and IF/TA, whereas remnant renal volume adjusted by body weight (RRV/BW) tended to be relatively correlated with IF/TA (P = .072). Furthermore, LKDs with subclinical IF/TA tended to have decreased RRV/BW compared with those without subclinical IF/TA (P = .088).

CONCLUSIONS

Our findings suggested that the presence of IF/TA could be a predictive factor for RRF after DN. Further research establishing the predictive model for RRF is warranted to improve the outcomes of LKDs.

The lupus nephritis management renaissance

Over the past year, and for the first time ever, the US Food and Drug Administration approved 2 drugs specifically for the treatment of lupus nephritis (LN). As the lupus community works toward understanding how to best use these new therapies, it is also an ideal time to begin to rethink the overall management strategy of LN. In addition to new drugs, this must include how to use kidney biopsies for management and not just diagnosis, how molecular technologies can be applied to interrogate biopsies and how such data can impact management, and how to incorporate LN biomarkers into management paradigms. Herein, we will review new developments in these areas of LN and put them into perspective for disease management now and in the future.

Biomarkers Associated with Organ-Specific Involvement in Juvenile Systemic Lupus Erythematosus

Juvenile systemic lupus erythematosus (JSLE) is characterised by onset before 18 years of age and more severe disease phenotype, increased morbidity and mortality compared to adult-onset SLE. Management strategies in JSLE rely heavily on evidence derived from adult-onset SLE studies; therefore, identifying biomarkers associated with the disease pathogenesis and reflecting particularities of JSLE clinical phenotype holds promise for better patient management and improved outcomes. This narrative review summarises the evidence related to various traditional and novel biomarkers that have shown a promising role in identifying and predicting specific organ involvement in JSLE and appraises the evidence regarding their clinical utility, focusing in particular on renal biomarkers, while also emphasising the research into cardiovascular, haematological, neurological, skin and joint disease-related JSLE biomarkers, as well as genetic biomarkers with potential clinical applications.

A longitudinal multiethnic study of biomarkers in systemic lupus erythematosus: Launching the GLADEL 2.0 Study Group

Introduction: After more than 20 years of sustained work, the Latin American Group for the Study of Lupus (GLADEL) has made a significant number of contributions to the field of lupus, not only in the differential role that race/ethnicity plays in its course and outcome but also in several other studies including the beneficial effects of using antimalarials in lupus patients and the development of consensus guidelines for the treatment of lupus in our region. Methods: A new generation of "Lupus Investigators" in more than 40 centers throughout Latin America has been constituted in order to continue the legacy of the investigators of the original cohort and to launch a novel study of serum and urinary biomarkers in patients with systemic lupus erythematosus. Results: So far, we have recruited 807 patients and 631 controls from 42 Latin-American centers including 339 patients with SLE without renal involvement, 202 patients with SLE with prevalent but inactive renal disease, 176 patients with prevalent and active renal disease and 90 patients with incident lupus nephritis. Conclusions: The different methodological aspects of the GLADEL 2.0 cohort are discussed in this manuscript, including the challenges and difficulties of conducting such an ambitious project.

New biomarkers in SLE: from bench to bedside

Biomarkers may have a diagnostic or monitoring value, or may predict response to therapy or disease course. The aim of this review is to discuss new serum and urinary biomarkers recently proposed for the diagnosis and management of SLE patients. Novel sensitive and specific assays have been proposed to evaluate complement proteins, ‘old’ biomarkers that are still a cornerstone in the management of this disease. Chemokines and lectins have been evaluated as surrogate biomarkers of IFN signature. Other cytokines like the B cell activating factor (BAFF) family cytokines are directly related to perturbations of the B cell compartment as key pathogenetic mechanism of the disease. A large number of urine biomarkers have been proposed, either related to the migration and homing of leukocytes to the kidney or to the local regulation of inflammatory circuits and the survival of renal intrinsic cells. The combination of traditional disease-specific biomarkers and novel serum or urine biomarkers may represent the best choice to correctly classify, stage and treat patients with SLE.

Association Between Urinary Epidermal Growth Factor and Renal Prognosis in Lupus Nephritis

OBJECTIVE

To evaluate the role of urinary epidermal growth factor (EGF) as a biomarker of chronic kidney damage in lupus nephritis (LN).

METHODS

A proteomics approach was used to identify urinary EGF as a biomarker of interest in a discovery cohort of patients with LN. The expression of urinary EGF was characterized in 2 large multiethnic LN cohorts, and the association between urinary EGF levels at the time of flare and kidney outcomes was evaluated in a subset of 120 patients with long-term follow-up data. For longitudinal studies, the expression of urinary EGF over time was determined in 2 longitudinal cohorts of patients with LN from whom serial urine samples were collected.

RESULTS

Discovery analysis showed the urinary EGF levels as being low in patients with active LN (median peptide count 8.4, interquartile range [IQR] 2.8-12.3 in patients with active LN versus median 48.0, IQR 45.3-64.6 in healthy controls). The peptide sequence was consistent with that of proEGF, and this was confirmed by immunoblotting. The discovery findings were verified by enzyme-linked immunosorbent assay. Patients with active LN had a significantly lower level of urinary EGF compared to that in patients with active nonrenal systemic lupus erythematosus (SLE), patients with inactive SLE, and healthy kidney donors (each P < 0.05). The urinary EGF level was inversely correlated with the chronicity index of histologic features assessed in kidney biopsy tissue (Spearman's r = -0.67, P < 0.001). Multivariate survival analysis showed that the urinary EGF level was associated with time to doubling of the serum creatinine level (DSCr), a marker of future end-stage kidney disease (ESKD) (hazard ratio 0.88, 95% confidence interval 0.77-0.99, P = 0.045). Patients whose LN symptoms progressed to DSCr and those who experienced progression to ESKD had a lower urinary EGF level at the time of flare, and urinary EGF levels decreased over the 12 months following flare. All patients who experienced progression to ESKD were identified based on a urinary EGF cutoff level of <5.3 ng/mg.

CONCLUSION

Urinary EGF levels are correlated with histologic kidney damage in patients with LN. Low urinary EGF levels at the time of flare and decreasing urinary EGF levels over time are associated with adverse long-term kidney outcomes.

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 levels of ceruloplasmin and monocyte chemoattractant protein-1 correlate with extra-capillary proliferation and chronic damage in patients with lupus nephritis

BACKGROUND AND AIM

There are few studies of urinary biomarkers and histopathologic features in lupus nephritis (LN). The aim was to analyze the correlation between a wide panel of urinary biomarkers and serum concentrations of anti C1q antibodies with histological items of activity and chronicity on kidney biopsy in LN patients.

METHODS

Patients with systemic lupus erythematosus (SLE) according to American College of Rheumatology (ACR) criteria were included. LN diagnosis was based on ACR criteria. Histologic features of activity and chronicity indices were analyzed according to the Austin classification. Serum Anti C1q levels were determined by commercial ELISA. Urinary levels of transferrin, ceruloplasmin (CP), VCAM-1, TWEAK, monocyte chemoattractant protein-1 (MCP-1), neutrophil gelatinase-associated lipocalin (NGAL), and alpha-1-acid glycoprotein were measured by commercial ELISA.

RESULTS

We included 120 SLE patients (81% female, mean age 33.1 ± 9.3 years, 59.4% Mestizo, 37.8% Afro-Latin American): 64% had LN. Kidney biopsy was performed in 55 patients, but only 37 were made in our center. Anti C1q antibodies were associated with endocapillary proliferation. In patients with cellular crescents, urinary concentrations of CP were significantly higher. In patients with a chronicity index (CI) ≥ 4, fibrous crescents, tubular atrophy, and interstitial fibrosis, urinary MCP-1 levels were higher.

CONCLUSIONS

In SLE patients, serum anti C1q antibodies and urinary CP were associated with activity on kidney biopsy and MCP-1 with chronic damage. This panel of biomarkers could be validated in larger, multi-ethnic population as a complementary tool for better stratification of LN patients. Key Points • Urinary biomarkers are complementary useful tools for the assessment of SLE patients. • Urinary levels of CP correlated with activity findings on kidney biopsy in LN patients. • Urinary levels of MCP-1 correlated with chronic damage, especially with fibrous crescents, tubular atrophy, and interstitial fibrosis.

Quantitative planar array screen of 1000 proteins uncovers novel urinary protein biomarkers of lupus nephritis

OBJECTIVE

The goal of these studies is to discover novel urinary biomarkers of lupus nephritis (LN).

METHODS

Urine from systemic lupus erythematosus (SLE) patients was interrogated for 1000 proteins using a novel, quantitative planar protein microarray. Hits were validated in an independent SLE cohort with inactive, active non-renal (ANR) and active renal (AR) patients, in a cohort with concurrent renal biopsies, and in a longitudinal cohort. Single-cell renal RNA sequencing data from LN kidneys were examined to deduce the cellular origin of each biomarker.

RESULTS

Screening of 1000 proteins revealed 64 proteins to be significantly elevated in SLE urine, of which 17 were ELISA validated in independent cohorts. Urine Angptl4 (area under the curve (AUC)=0.96), L-selectin (AUC=0.86), TPP1 (AUC=0.84), transforming growth factor-β1 (TGFβ1) (AUC=0.78), thrombospondin-1 (AUC=0.73), FOLR2 (AUC=0.72), platelet-derived growth factor receptor-β (AUC=0.67) and PRX2 (AUC=0.65) distinguished AR from ANR SLE, outperforming anti-dsDNA, C3 and C4, in terms of specificity, sensitivity and positive predictive value. In multivariate regression analysis, urine Angptl4, L-selectin, TPP1 and TGFβ1 were highly associated with disease activity, even after correction for demographic variables. In SLE patients with serial follow-up, urine L-selectin (followed by urine Angptl4 and TGFβ1) were best at tracking concurrent or pending disease flares. Importantly, several proteins elevated in LN urine were also expressed within the kidneys in LN, either within resident renal cells or infiltrating immune cells, based on single-cell RNA sequencing analysis.

CONCLUSION

Unbiased planar array screening of 1000 proteins has led to the discovery of urine Angptl4, L-selectin and TGFβ1 as potential biomarker candidates for tracking disease activity in LN.

Clinical Use of Complement, Inflammation, and Fibrosis Biomarkers in Autoimmune Glomerulonephritis

Introduction

Complement activation, inflammation, and fibrosis play central roles in the mechanisms of injury in autoimmune glomerulonephritis (GN) but they are seldom assessed in epidemiologic studies. The measurement of urinary biomarkers of these pathways of injury could parallel disease activity and add clinical value beyond proteinuria.

Methods

We performed a prospective cohort study of 100 patients with focal and segmental glomerulosclerosis (FSGS), membranous nephropathy (MN), IgA nephropathy (IgAN), lupus nephritis (LN), anti-neutrophil cytoplasmic autoantibody-associated vasculitis (AAV), and membranoproliferative GN (MPGN) followed for 33 (18-54) months. Repeated urinary samples were collected throughout their follow-up to determine proteinuria, urinary sC5b-9, monocyte chemoattractant protein-1 (MCP-1), and transforming growth factor-beta 1 (TGF-β1), expressed as creatinine ratios. We identified 177 periods of active and inactive disease based on current remission definitions for each disease.

Results

Urinary sC5b-9, MCP-1, and TGF-β1 were present in each disease. In periods leading to a remission, the reduction of urinary sC5b-9 was 91%, greater than for proteinuria with 76%. During inactive periods, those who did not experience a relapse maintained lower levels of biomarkers compared with those who relapsed. At that time, the increase in urinary sC5b-9 was significantly greater than the rise in proteinuria (8.5-fold increase compared with 3.2-fold) and urinary MCP-1 and TGF-β1. Using current remission definitions for each disease, thresholds for each biomarker were determined using receiver operating characteristic curves. Individuals who averaged levels below these cutoffs during their follow-up had better renal outcomes.

Conclusion

In autoimmune glomerular diseases, urinary sC5b-9, MCP-1, and TGF-β1 are present and parallel disease activity and outcomes. Urinary sC5b-9 appears to be a more discerning marker of immunologic remissions and relapses.

Urinary Soluble CD163: a Novel Noninvasive Biomarker of Activity for Lupus Nephritis

BACKGROUND

Clinical distinction between patients with lupus nephritis who have active inflammation or chronic kidney damage is challenging. Studies have shown soluble CD163, which derives from cleavage of the CD163 M2c macrophage receptor and can be quantified in urine, correlates with active lupus nephritis.

METHODS

We measured urine CD163 at lupus nephritis flares in patients from a Mexican cohort and cross-sectional and longitudinal United States cohorts. We also performed serial urine CD163 measurements during the treatment of flares in a subset of patients from the Mexican and longitudinal United States cohorts, and assessed response to therapy at 12 months. In addition, we evaluated urinary CD163 agreement with histologic activity in 19 patients from the Mexican cohort who had repeated kidney biopsies on follow-up.

RESULTS

Urinary CD163 levels were significantly higher in patients with active lupus nephritis than in patients with active extrarenal SLE, inactive SLE, and other glomerular diseases, and correlated with disease clinical severity, histologic class, and the histologic activity index. Urinary CD163 increased from 6 months preflare to flare, diminishing progressively in complete and partial responders, whereas it remained elevated in nonresponders. Urinary CD163 <370 ng/mmol at 6 months predicted complete renal response at 12 months with >87% sensitivity and >87% specificity. Urinary CD163 <370 ng/mmol or >370 ng/mmol perfectly agreed (κ=1.0) with a histologic activity index ≤1 or >1 in repeated biopsies, respectively. Evaluation of urinary CD163 in patients with persistent proteinuria at 6 months improved the prediction of who would achieve complete renal response at 12 months.

CONCLUSIONS

Urinary CD163 reflects histologic inflammation in lupus nephritis and is a promising activity biomarker that varies over time with lupus nephritis activity and treatment.

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.

Lupus nephritis

Lupus nephritis (LN) is a form of glomerulonephritis that constitutes one of the most severe organ manifestations of the autoimmune disease systemic lupus erythematosus (SLE). Most patients with SLE who develop LN do so within 5 years of an SLE diagnosis and, in many cases, LN is the presenting manifestation resulting in the diagnosis of SLE. Understanding of the genetic and pathogenetic basis of LN has improved substantially over the past few decades. Treatment of LN usually involves immunosuppressive therapy, typically with mycophenolate mofetil or cyclophosphamide and with glucocorticoids, although these treatments are not uniformly effective. Despite increased knowledge of disease pathogenesis and improved treatment options, LN remains a substantial cause of morbidity and death among patients with SLE. Within 10 years of an initial SLE diagnosis, 5-20% of patients with LN develop end-stage kidney disease, and the multiple comorbidities associated with immunosuppressive treatment, including infections, osteoporosis and cardiovascular and reproductive effects, remain a concern. Clearly, early and accurate diagnosis of LN and prompt initiation of therapy are of vital importance to improve outcomes in patients with SLE.

Design and application of single-cell RNA sequencing to study kidney immune cells in lupus nephritis

The immune mechanisms that cause tissue injury in lupus nephritis have been challenging to define. The advent of high-dimensional cellular analyses, such as single-cell RNA sequencing, has enabled detailed characterization of the cell populations present in small biopsy samples of kidney tissue. In parallel, the development of methods that cryopreserve kidney biopsy specimens in a manner that preserves intact, viable cells, has enabled the uniform analysis of tissue samples collected at multiple sites and across many geographic areas and demographic cohorts with high-dimensional platforms. The application of these methods to kidney biopsy samples from patients with lupus nephritis has begun to define the phenotypes of both infiltrating and resident immune cells, as well as parenchymal cells, present in nephritic kidneys. The detection of similar immune cell populations in urine suggests that it might be possible to non-invasively monitor immune activation in kidneys. Once applied to large patient cohorts, these high-dimensional studies might enable patient stratification according to patterns of immune cell activation in the kidney or identify disease features that can be used as surrogate measures of efficacy in clinical trials. Applied broadly across multiple inflammatory kidney diseases, these studies promise to enormously expand our understanding of renal inflammation in the next decade.

Utilization of Biomarkers in Lupus Nephritis

Lupus nephritis (LN) occurs in up to 60% of SLE patients, and is a leading cause of disability and death. Current treatment of LN consists of a combination of high dose corticosteroids that non-specifically decrease inflammation and cytotoxic medications that reduce auto-antibody production. That combination of therapy is associated with significant side effects while remission rates remain inadequate. Since the introduction of biologics into the pharmacological armamentarium, there has been hope for less toxic and more effective therapies for LN. Unfortunately, after multiple clinical trials, no biologic has improved efficacy over standard of care therapies for LN. This is likely, in part, due to disease heterogeneity. The utilization of biomarkers in LN may provide a way to stratify patients and guide therapeutic options. In this review, we summarize traditional and novel LN biomarkers and discuss how they may be used to diagnose, stratify, and guide therapy in patients with LN, bringing precision medicine to the forefront of LN therapy.

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.

Proteomic profiling of urine: implications for lupus nephritis

INTRODUCTION

Lupus nephritis (LN) is a common and significant manifestation, affecting 60% of adults and 80% of children with systemic lupus erythematosus, with up to 30% of patients progressing to end stage renal disease. There remains an unmet need for non-invasive markers of disease activity, damage, and response to therapy. In addition, non-invasive biomarkers that predict therapeutic efficacy are needed to enable cost-effective clinical trials of novel agents. Areas covered: This review examines the methodological aspects of urinary proteomics, the role of proteome profiling in identifying promising urinary biomarkers in LN, and the translation of research findings into clinically useful tools in the management of LN. Expert opinion: Targeted and unbiased proteomics have identified several promising urinary biomarkers that predict LN activity, damage (chronicity), and response to therapy. In particular, a combination of biologically plausible urinary biomarkers termed as RAIL (Renal Activity Index for Lupus) has emerged as an excellent predictor of LN activity as well as response to therapy, being able to predict efficacy within 3 months of therapy. If validated in additional large prospective studies, the RAIL biomarkers will transform the care of patients with LN, allowing for a personalized and predictive approach and improved outcomes.

Urinary biomarkers for lupus nephritis: the role of the vascular cell adhesion molecule-1

Renal involvement is one of the main complications of systemic lupus erythematosus, causing a significant impact on patients' morbidity and mortality. Renal biopsy is still the gold standard of diagnosis, but it has many limitations. In this sense, several recent studies aim to identify biomarkers that not only predict disease activity and renal histology, but also lead to earlier treatment. In previous studies, the soluble vascular cell adhesion molecule-1 measured in urine showed a strong association with the presence of lupus nephritis, with clinical and histological activity indexes of the disease and with more severe renal lesions. This paper reviews the main urinary biomarkers of lupus nephritis that have been studied, with special emphasis on vascular cell adhesion molecule-1 results.

Discovery and Qualification of Candidate Urinary Biomarkers of Disease Activity in Lupus Nephritis

Lupus nephritis (LN) is a severe clinical manifestation of systemic lupus erythematosus (SLE) associated with significant morbidity and mortality. Assessment of severity and activity of renal involvement in SLE requires a kidney biopsy, an invasive procedure with limited prognostic value. Noninvasive biomarkers are needed to inform treatment decisions and to monitor disease activity. Proteinuria is associated with disease progression in LN; however, the composition of the LN urinary proteome remains incompletely characterized. To address this, we profiled LN urine samples using complementary mass spectrometry-based methods:  protein gel fractionation, chemical labeling using tandem mass tags, and data-independent acquisition. Combining results from these approaches yielded quantitative information on 2573 unique proteins in urine from LN patients. A multiple-reaction monitoring (MRM) method was established to confirm eight proteins in an independent cohort of LN patients, and seven proteins (transferrin, α-2-macroglobulin, haptoglobin, afamin, α-1-antitrypsin, vimentin, and ceruloplasmin) were confirmed to be elevated in LN urine compared to healthy controls. In this study, we demonstrate that deep mass spectrometry profiling of a small number of patient samples can identify high-quality biomarkers that replicate in an independent LN disease cohort. These biomarkers are being used to inform clinical biomarker strategies to support longitudinal and interventional studies focused on evaluating disease progression and treatment efficacy of novel LN therapeutics.

Precision medicine in lupus nephritis: can biomarkers get us there?

Patients with systemic lupus erythematosus frequently develop lupus nephritis (LN), a condition that can lead to end-stage kidney disease. Multiple serum and urine biomarkers for LN have been proposed in recent years, yet none have become incorporated into clinical use. The majority of studies have been single center with significant variability in cohorts, assays, and sample storage, leading to inconclusive results. It has become clear that no single biomarker is likely to be sufficient to diagnose LN, identify flares, and define the response to therapy and prognosis. A more likely scenario is a panel of urine, serum, tissue, and genetic biomarkers. In this review, we summarize traditional and novel biomarkers and discuss how they may be utilized in order to bring precision medicine to clinical practice in LN.

Podocytes contribute, and respond, to the inflammatory environment in lupus nephritis

Lupus nephritis (LN) affects up to 80% of juvenile onset systemic lupus erythematosus patients, leading to end stage renal failure requiring dialysis or transplantation in 10-15%. Podocytes are specialized epithelial cells of the glomerulus known to be a key site of damage in glomerular diseases. However, their roles in LN have yet to be fully identified. This project aims to identify structural and functional roles of podocytes in an in vitro model of LN. Conditionally immortalized podocytes were treated with proinflammatory cytokines (IL-1β, TNF-α, IFN-α, and IFN-γ) alone and in combination in an in vitro model of LN and were assessed for their structural and functional characteristics. Podocytes produce TNF-α, IL-6, IL-8, VEGF, granulocyte-monocyte colony stimulating factor (GM-CSF), and macrophage colony stimulating factor (M-CSF) at relatively low levels under basal conditions; stimulation with IL-1β led to increased secretion of IL-6 ( P = 0.011), IL-8 ( P = 0.05), VEGF ( P = 0.02), and M-CSF ( P = 0.03). Stimulation with TNF-α led to increased secretion of M-CSF ( P = 0.049) and stimulation with IFN-γ led to novel production of IL-10 ( P = 0.036) and interferon-γ-inducible protein-10 ( P = 0.036). Podocytes demonstrate a reduction in the area covered by filamentous-actin in response to IL-1β treatment within 1 h ( P = 0.011), which is restored by 24 h, associated with an increase in the level of intracellular calcium but not with increased cell death. Podocytes contribute to the inflammatory milieu in LN through cytokine/chemokine secretion and respond to the inflammatory milieu via rearrangement of the actin cytoskeleton leading to effacement, a well-known method of protection against apoptosis in these cells. This demonstrates that podocytes are involved in the pathogenesis of LN.

Association between MCP-1 2518 A>G gene polymorphism and chronic kidney disease

Monocyte chemoattractant protein-1 (MCP-1) is involved in the pathogenesis of chronic kidney diseases (CKD). MCP-1 2518 A>G gene polymorphism is associated with MCP-1 status. We performed a meta-analysis to assess the association between MCP-1 2518 A>G gene polymorphism and CKD risk. The eligible studies regarding the relationship between MCP-1 2518 A>G gene polymorphism and CKD risk were searched through electronic databases. The pooled odds ratios (ORs) and its 95% confidence intervals (CIs) were calculated by using a fixed-effects model, or in the presence of heterogeneity, a random-effects model. A total of 2415 cases and 2011 controls were recruited in our investigation. A allele/GG genotype was not associated with CKD risk in overall populations, Asians, Caucasians, and Africans. AA/AG genotype was not associated with the risk of CKD in overall populations, Asians, Caucasians, and Africans. AA genotype was associated with a lower risk of CKD in Caucasians (OR 0.816, 95% CI 0.703-0.947). AG genotype was associated with a higher risk of CKD in Caucasians (OR 1.230, 95% CI 1.042-1.452). There was no marked publication bias. In conclusion, AA genotype may be a protective factor against CKD susceptibility in Caucasians. AG genotype may be a risk factor for CKD risk in Caucasians. However, more studies are needed in the future.

Composite urinary biomarkers to predict pathological tubulointerstitial lesions in lupus nephritis

Objective This study aimed to evaluate the clinical value of urinary biomarkers including kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and monocyte chemoattractant protein-1 (MCP-1) in lupus nephritis. Methods A total of 109 biopsy-proven lupus nephritis patients were included and 50 healthy individuals were used as normal controls. Urinary KIM-1, NGAL, and MCP-1 levels were measured by ELISA and their correlations with clinical and histological features were assessed. Receiver operating characteristic curves were performed and the Cox regression model was applied to identify prognostic factors associated with renal outcomes. Results Active lupus nephritis patients exhibited elevated urinary levels of KIM-1, NGAL, and MCP-1 compared with lupus nephritis patients in remission ( P < 0.001) and normal controls ( P < 0.001). The urinary KIM-1 level was correlated with pathological tubular atrophy ( r = 0.208, P < 0.05) and increased significantly in the presence of interstitial inflammatory lesions ( P = 0.031). Urinary KIM-1, NGAL, and MCP-1 levels were higher in patients with active tubulointerstitial lesions than in those with only chronic lesions ( P = 0.015, P = 0.230, and P = 0.086, respectively). A combination of KIM-1, NGAL, and MCP-1 was a good indicator for diagnosing active tubulointerstitial lesions (area under the curve: 0.796). The combination of KIM-1 and NGAL was identified as an independent risk factor for renal outcomes (hazard ratio = 7.491, P < 0.05). Conclusion Urinary KIM-1, NGAL, and MCP-1 levels were associated with kidney injury indices in lupus nephritis. The combination of the three biomarkers showed increased power in predicting tubulointerstitial lesions and renal outcomes.

Urinary cytokines and mRNA expression as biomarkers of disease activity in lupus nephritis

Introduction

Renal involvement is one of the most serious manifestations of systemic lupus erythematosus, but non-invasive assessment of inflammatory response in kidneys is challenging. In this study we aimed to validate markers of active lupus nephritis (LN) using urine immune profiling.

Methods

Urine and serum cytokines (17-plex array) and urine mRNA expression (∼40 immune and glomerular injury genes) were measured in LN patients with active disease ( n = 17) during remission ( n = 16) and in healthy subjects ( n = 18).

Results

Urine and serum levels of CCL2, CCL5 and CXCL10 were elevated in active LN as compared with disease remission (best discrimination for urine CXCL10 and CCL2) and correlated with LN activity. In the active disease, urinary cell transcriptome showed marked upregulation of proinflammatory cytokines (e.g. TNF, CCL2, CCL5, CXCL10), and type-1 immunity-related genes (e.g. CD3G, CD4, TBX21, IFNG). An active pattern of gene expression was also observed in four patients in remission, who had moderately increased urinary leucocyte count. Two patients from this group developed renal exacerbation during the following 3 months. Markers of type-17 immune axis (e.g. IL-17A) were not significantly increased in active LN.

Conclusions

Active LN patients were characterized by marked increase of proinflammatory mediators in the urine. Urine cytokines (CCL2 and CXCL10) and type-1 T-cell-related gene markers in the urine sediment had similar diagnostic performance in detection of active LN.

Salivary biomarkers of inflammation in systemic lupus erythematosus

Saliva is currently used as a reliable diagnostic fluid in a wide range of local and systemic diseases. However, the link between salivary diagnosis and the inflammatory process in autoimmune diseases has not yet been explored. The aim of our study is to assess possible correlations between salivary inflammatory markers and systemic lupus erythematosus (SLE). Patients fulfilling the Systemic Lupus International Collaborating Clinics (SLICC) diagnosis criteria were included. Salivary and serum levels of interleukin-6 (IL-6), leptin, monocyte chemoattractant protein-1 (MCP-1) and plasminogen activator inhibitor-1 (PAI-1) were determined using stochastic sensors. Serum leptin and IL-6 had significantly higher levels in SLE patients compared to non-SLE. Also, salivary IL-6 levels highly correlated with the serum IL-6 levels. A positive correlation was found between salivary and serum levels of IL-6, signaling salivary IL-6 as a reliable marker for assessing the inflammation process in SLE.

Urinary MCP-1 as a biomarker for lupus nephritis: a meta-analysis

OBJECTIVE

This study aimed to evaluate whether urinary monocyte chemoattractant protein-1 (MCP-1) could serve as a biomarker for lupus nephritis (LN).

METHODS

We performed a meta-analysis to examine the relationship between urinary MCP-1 level and LN in three comparisons: active LN versus inactive LN, active LN versus control, and inactive LN versus control.

RESULTS

Eight studies of a total of 399 patients with LN (204 with active LN, and 195 with inactive LN) and 130 controls were available for this meta-analysis. The meta-analysis revealed that the urinary MCP-1 level was significantly higher in the active-LN group than in the inactive-LN group (standard mean difference [SMD] = 1.883, 95 % confidence interval [CI] = 0.811-2.954, p = 0.001). The meta-analysis showed that the urinary MCP-1 level was significantly higher in the active-LN group than in the control group (SMD = 3.085, 95 % CI = 1.684-4.485, p = 1.6 × 10^-5). Furthermore, stratification by ethnicity showed significantly elevated urinary MCP-1 levels in the active-LN group in Caucasian, Asian, and Egyptian populations (SMD = 2.408, 95 % CI = 1.711-3.105, p < 1.0 × 10^-8; SMD = 1.020, 95 % CI = 0.623-2.153, p = 4.6 × 10^-7; and SMD = 7.370, 95 % CI = 1.467-2.157, p = 5.9 × 10^-5, respectively). The meta-analysis indicated that the urinary MCP-1 level was also significantly higher in the inactive-LN group than in the control group (SMD = 1.812, 95 % CI = 0.628-2.996, p = 0.003).

CONCLUSIONS

The meta-analysis demonstrated that urinary MCP-1 was significantly higher in patients with active LN than in those with inactive LN and control subjects, and the patients with inactive LN showed significantly higher urinary MCP-1 levels than the controls.

Effects of age and gender on reference levels of biomarkers comprising the pediatric Renal Activity Index for Lupus Nephritis (p-RAIL)

BACKGROUND

Systemic Lupus Erythematosus (SLE) is a multisystem autoimmune disease that disproportionately effects women and children of minorities. Renal involvement (lupus nephritis, or LN) occurs in up to 80% of children with SLE and is a major determinant of poor prognosis. We have developed a non-invasive pediatric Renal Activity Index for Lupus (p-RAIL) that consists of laboratory measures that reflect histologic LN activity. These markers are neutrophil gelatinase associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), monocyte chemotactic protein (MCP-1), adiponectin (APN), ceruloplasmin (CP) and hemopexin (HPX). A major gap in the knowledge base and a barrier to clinical utility is how these markers behave in healthy children. We set out to establish a reference range for the p-RAIL markers in a population of healthy children, and to determine if levels of these markers fluctuate with age or gender.

METHODS

Urine was collected from 368 healthy children presenting to Cincinnati Children's primary care clinic for well child visits and assayed for NGAL, KIM-1, MCP-1, APN, CP and HPX using commercially available kits or assay materials.

RESULTS

Specimens were grouped by age (0-5 years (n = 94); 5-10 (n = 89); 10-15 (n = 93); 15-20 (n = 91)) and gender (M = 184, F = 184). For age and gender comparisons, values were log transformed prior to analysis. The medians (minimums, maximums) of each marker in the combined population were as follows: NGAL 6.65 (0.004, 391.52) ng/ml, KIM-1416.84 (6.22, 2512.43) pg/ml, MCP-1209.36 (9.49, 2237.06) pg/ml, APN 8.05 (0.07, 124.50) ng/ml, CP 465.15 (8.02, 7827.00) ng/ml, HPX 588.70 (6.85, 17,658.40)ng/ml. All p-RAIL biomarkers but adiponectin had weak but significant positive correlations with age, with NGAL being the strongest (r = 0.33, p < 0.001). For gender comparisons, NGAL, CP and HPX were elevated in females vs males (86%, p < 0.0001; 3%, p = 0.007, and 5%, p = 0.0005 elevation of the log transformed mean, respectively).

CONCLUSIONS

We have established a reference range for the p-RAIL biomarkers and have highlighted age and gender differences. This information is essential for rational interpretation of studies and clinical trials utilizing the p-RAIL algorithm.

Urine Biomarkers to Predict Response to Lupus Nephritis Therapy in Children and Young Adults

OBJECTIVE

To delineate urine biomarkers that forecast response to therapy of lupus nephritis (LN).

METHODS

Starting from the time of kidney biopsy, patients with childhood-onset systemic lupus erythematosus who were diagnosed with LN were studied serially. Levels of 15 biomarkers were measured in random spot urine samples, including adiponectin, α-1-acid glycoprotein (AGP), ceruloplasmin, hemopexin, hepcidin, kidney injury molecule 1, monocyte chemotactic protein-1, lipocalin-like prostaglandin D synthase (LPGDS), transforming growth factor-β (TGF-β), transferrin, and vitamin D binding protein (VDBP).

RESULTS

Among 87 patients (mean age 15.6 yrs) with LN, there were 37 treatment responders and 50 nonresponders based on the American College of Rheumatology criteria. At the time of kidney biopsy, levels of TGF-β (p < 0.0001) and ceruloplasmin (p = 0.006) were significantly lower among responders than nonresponders; less pronounced differences were present for AGP, hepcidin, LPGDS, transferrin, and VDBP (all p < 0.05). By Month 3, responders experienced marked decreases of adiponectin, AGP, transferrin, and VDBP (all p < 0.01) and mean levels of these biomarkers were all outstanding (area under the receiver-operating characteristic curve ≥ 0.9) for discriminating responders from nonresponders. Patient demographics and extrarenal disease did not influence differences in biomarker levels between response groups.

CONCLUSION

Low urine levels of TGF-β and ceruloplasmin at baseline and marked reduction of AGP, LPGDS, transferrin, or VDBP and combinations of other select biomarkers by Month 3 are outstanding predictors for achieving remission of LN. If confirmed, these results can be used to help personalize LN therapy.

Development of a Novel Renal Activity Index of Lupus Nephritis in Children and Young Adults

OBJECTIVE

Noninvasive estimation of the degree of inflammation seen on kidney biopsy with lupus nephritis (LN) remains difficult. The objective of this study was to develop a Renal Activity Index for Lupus (RAIL) that, based solely on laboratory measures, accurately reflects histologic LN activity.

METHODS

We assayed traditional LN laboratory tests and 16 urine biomarkers (UBMs) in children (n = 47) at the time of kidney biopsy. Histologic LN activity was measured by the National Institutes of Health activity index (NIH-AI) and the tubulointerstitial activity index (TIAI). High LN-activity status (versus moderate/low) was defined as NIH-AI scores >10 (versus ≤10) or TIAI scores >5 (versus ≤5). RAIL algorithms that predicted LN-activity status for both NIH-AI and TIAI were derived by stepwise multivariate logistic regression, considering traditional biomarkers and UBMs as candidate components. The accuracy of the RAIL for discriminating by LN-activity status was determined.

RESULTS

The differential excretion of 6 UBMs (neutrophil gelatinase-associated lipocalin, monocyte chemotactic protein 1, ceruloplasmin, adiponectin, hemopexin, and kidney injury molecule 1) standardized by urine creatinine was considered in the RAIL. These UBMs predicted LN-activity (NIH-AI) status with >92% accuracy and LN-activity (TIAI) status with >80% accuracy. RAIL accuracy was minimally influenced by concomitant LN damage. Accuracies between 71% and 85% were achieved without standardization of the UBMs. The strength of these UBMs to reflect LN-activity status was confirmed by principal component and linear discriminant analyses.

CONCLUSION

The RAIL is a robust and highly accurate noninvasive measure of LN activity. The measurement properties of the RAIL, which reflect the degree of inflammatory changes as seen on kidney biopsy, will require independent validation.

Identification of potential biomarkers for systemic lupus erythematosus diagnosis using two-dimensional differential gel electrophoresis (2D-DIGE) and mass spectrometry

Systemic lupus erythematosus (SLE) is an autoimmune disease of the connective tissue with a large spectrum of clinical manifestations. Immune deregulation leads to autoantibody and immune complexes overproduction, complement activation, and persistent tissue inflammation. Considering that the current diagnosis depends on the interpretation of the complex criteria established by the American College of Rheumatology and that the disease course is characterized by unpredictable activations and remissions, each patient develops different manifestations, and therefore, the discovery of specific biomarkers is urgently required. Therefore, this study aimed to identify putative biomarkers for active and inactive SLE potentially capable in distinguishing laboratorial SLE from other autoimmune diseases. The 2D-DIGE proteomics technique was used to evaluate the differential abundance of proteins between patients with active SLE, inactive SLE, patients with other autoimmune disease, and healthy individuals. Six proteins showed increased abundance in active SLE (A) and inactive SLE (I) compared to the C and O groups, but not between groups A and I. There were two transthyretin (TTR) fragments or proteins with a structure similar to TTR (accession numbers: PDB: 1GKO_A and 2PAB_A), retinol-binding protein 4 (RBP4) isoform X1 (no information in databases such as UNIPROT), and antibody fragments. Two proteins, APO-AIV and SP-40,40, were upregulated in group A than in O and C and in group I versus C, but not in group I versus O. Therefore, we suggest these proteins to be considered as candidates for the diagnosis of SLE.

Systemic lupus erythematosus biomarkers: the challenging quest

SLE, a multisystem heterogeneous disease, is characterized by production of antibodies to cellular components, with activation of both the innate and the adaptive immune system. Decades of investigation of blood biomarkers has resulted in incremental improvements in the understanding of SLE. Owing to the heterogeneity of immune dysregulation, no single biomarker has emerged as a surrogate for disease activity or prediction of disease. Beyond identification of surrogate biomarkers, a multitude of clinical trials have sought to inhibit elevated SLE biomarkers for therapeutic benefit. Armed with new -omics technologies, the necessary yet daunting quest to identify better surrogate biomarkers and successful therapeutics for SLE continues with tenacity.

Urine peptidomic biomarkers for diagnosis of patients with systematic lupus erythematosus

Background Systematic lupus erythematosus (SLE) is characterized with various complications which can cause serious organ damage in the human body. Despite the significant improvements in disease management of SLE patients, the non-invasive diagnosis is entirely missing. In this study, we used urinary peptidomic biomarkers for early diagnosis of disease onset to improve patient risk stratification, vital for effective drug treatment. Methods Urine samples from patients with SLE, lupus nephritis (LN) and healthy controls (HCs) were analyzed using capillary electrophoresis coupled to mass spectrometry (CE-MS) for state-of-the-art biomarker discovery. Results A biomarker panel made up of 65 urinary peptides was developed that accurately discriminated SLE without renal involvement from HC patients. The performance of the SLE-specific panel was validated in a multicentric independent cohort consisting of patients without SLE but with different renal disease and LN. This resulted in an area under the receiver operating characteristic (ROC) curve (AUC) of 0.80 ( p < 0.0001, 95% confidence interval (CI) 0.65-0.90) corresponding to a sensitivity and a specificity of 83% and 73%, respectively. Based on the end terminal amino acid sequences of the biomarker peptides, an in silico methodology was used to identify the proteases that were up or down-regulated. This identified matrix metalloproteinases (MMPs) as being mainly responsible for the peptides fragmentation. Conclusions A laboratory-based urine test was successfully established for early diagnosis of SLE patients. Our approach determined the activity of several proteases and provided novel molecular information that could potentially influence treatment efficacy.

Urinary Albumin Levels are Independently Associated with Renal Lesion Severity in Patients with Lupus Nephritis and Little or No Proteinuria

Background

Systemic lupus erythematosus (SLE) leads to renal lesions, which may be clinically silent in patients with little or no proteinuria. Early detection of these lesions may improve prognosis, but early markers are controversial. This study aimed to determine renal marker proteins associated with renal lesion severity in patients with lupus nephropathy (LN) and little or no proteinuria.

Material/Methods

Patients with LN and little or no proteinuria (<0.5 g/24 hours) (n=187) that underwent kidney biopsy were grouped according to: low severity (Class I or II; n=116) versus high severity (Class III, IV, or V; n=71). Disease status was determined according to the SLE disease activity index (SLEDAI). Renal marker proteins (serum β2-macroglobulin, urinary β2-macroglobulin, albumin, IgG, and α1-macroglobulin) were measured using radioimmunoassay.

Results

Compared with the low severity group, patients in the high severity group had higher urinary albumin (11.60±8.94 versus 7.08±10.07 μg/mL, p=0.008) and urinary IgG (13.21±9.35 versus 8.74±8.90 μg/mL, p=0.007) levels. Multivariate conditional logistic regression analysis showed that urinary albumin (odds ratio (OR)=1.417, 95% confidence interval (95% CI): 1.145–1.895, p=0.001) and SLEDAI (OR=2.004, 95% CI: 1.264–3.178, p=0.003) were independently associated with severe renal lesions in these patients. Using an optimal cutoff point of urinary albumin of 7.53 μg/mL resulted in 67% sensitivity and 82% specificity for the detection of high severity renal lesions.

Conclusions

Urinary albumin levels and SLEDAI were independently associated with histological severity of renal lesions in patients with LN and little or no proteinuria. These parameters could be used to help select patients for renal biopsy.