Increased excretions of beta2-microglobulin, IL-6, and IL-8 and decreased excretion of Tamm-Horsfall glycoprotein in urine of patients with active lupus nephritis

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.

Interaction of uromodulin and complement factor H enhances C3b inactivation

Recent studies suggest that uromodulin plays an important role in chronic kidney diseases. It can interact with several complement components, various cytokines and immune system cells. Complement factor H (CFH), as a regulator of the complement alternative pathway, is also associated with various renal diseases. Thus, we have been suggested that uromodulin regulates complement activation by interacting with CFH during tubulointerstitial injury. We detected co‐localization of uromodulin and CFH in the renal tubules by using immunofluorescence. Next, we confirmed the binding of uromodulin with CFH in vitro and found that the affinity constant (K_D) of uromodulin binding to CFH was 4.07 × 10⁻⁶M based on surface plasmon resonance results. The binding sites on CFH were defined as the short consensus repeat (SCR) units SCR1–4, SCR7 and SCR19–20. The uromodulin‐CFH interaction enhanced the cofactor activity of CFH for factor I‐mediated cleavage of C3b to iC3b. These results indicate that uromodulin plays a role via binding and enhancing the function of CFH.

Serum and Urinary Interleukin-6 in Assessment of Renal Activity in Egyptian Patients with Systemic Lupus Erythematosus

AIM OF THE WORK

This study investigates whether serum and urinary interleukin-6 (IL-6) represent an early marker of kidney involvement and assesses the difference between them and renal biopsy in lupus nephritis (LN).

PATIENTS AND METHODS

A total of 60 systemic lupus erythematosus (SLE) patients were compared to 20 healthy controls. Urinary and serum IL-6 were measured in both patients and controls. In addition, renal biopsy was done prior or shortly after urine and blood sampling; the results were classified according to the International Society of Nephrology/Renal Pathology Society classification of LN by recording the activity score and chronicity score for each sample.

RESULTS

There was a significant higher level of urinary IL-6 in the SLE patients with biopsy-proven LN than in those without LN and those of the control group. However, no significant difference was reported between the three groups as regards serum IL-6. A strong positive correlation was found between urinary IL-6 and renal disease activity based on the renal SLE disease activity index (SLEDAI) score with no significant correlation regarding the extra renal SLEDAI. Urinary IL-6 was positively correlated with renal biopsy results and with its activity scores but weakly correlated with the chronicity scores.

CONCLUSION

Urinary IL-6 may provide a simple noninvasive potential marker of disease activity of renal involvement in adult patients with SLE.

The Implication and Significance of Beta 2 Microglobulin: A Conservative Multifunctional Regulator

OBJECTIVE

This review focuses on the current knowledge on the implication and significance of beta 2 microglobulin (β2M), a conservative immune molecule in vertebrate.

DATA SOURCES

The data used in this review were obtained from PubMed up to October 2015. Terms of β2M, immune response, and infection were used in the search.

STUDY SELECTIONS

Articles related to β2M were retrieved and reviewed. Articles focusing on the characteristic and function of β2M were selected. The exclusion criteria of articles were that the studies on β2M-related molecules.

RESULTS

β2M is critical for the immune surveillance and modulation in vertebrate animals. The dysregulation of β2M is associated with multiple diseases, including endogenous and infectious diseases. β2M could directly participate in the development of cancer cells, and the level of β2M is deemed as a prognostic marker for several malignancies. It also involves in forming major histocompatibility complex (MHC class I or MHC I) or like heterodimers, covering from antigen presentation to immune homeostasis.

CONCLUSIONS

Based on the characteristic of β2M, it or its signaling pathway has been targeted as biomedical or therapeutic tools. Moreover, β2M is highly conserved among different species, and overall structures are virtually identical, implying the versatility of β2M on applications.

Anti-C1q Autoantibodies from Systemic Lupus Erythematosus Patients Induce a Proinflammatory Phenotype in Macrophages

Anti-C1q autoantibodies (anti-C1q) are frequently found in patients with systemic lupus erythematosus (SLE) and correlate with the occurrence of proliferative lupus nephritis. A previous study of anti-C1q in experimental lupus nephritis demonstrated an important role for FcγRs in the pathogenesis of lupus nephritis, suggesting a direct effect on phagocytes. Therefore, we developed an in vitro model to study the effect of SLE patient-derived anti-C1q bound to immobilized C1q (imC1q) on human monocyte-derived macrophages (HMDMs) obtained from healthy donors and SLE patients. HMDMs were investigated by analyzing the cell morphology, LPS-induced cytokine profile, surface marker expression, and phagocytosis rate of apoptotic Jurkat cells. Morphologically, bound anti-C1q induced cell aggregations of HMDMs compared with imC1q or IgG alone. In addition, anti-C1q reversed the effect of imC1q alone, shifting the LPS-induced cytokine release toward a proinflammatory response. FcγR-blocking experiments revealed that the secretion of proinflammatory cytokines was mediated via FcγRII. The anti-C1q-induced inflammatory cytokine profile was accompanied by a downregulation of CD163 and an upregulation of LPS-induced CD80, CD274, and MHC class II. Finally, HMDMs primed on bound anti-C1q versus imC1q alone displayed a significantly lower phagocytosis rate of early and late apoptotic cells accompanied by a reduced Mer tyrosine kinase expression. Interestingly, anti-C1q-dependent secretion of proinflammatory cytokines was similar in SLE patient-derived cells, with the exception that IL-10 was slightly increased. In conclusion, anti-C1q induced a proinflammatory phenotype in HMDMs reversing the effects of imC1q alone. This effect might exacerbate underlying pathogenic mechanisms in lupus nephritis.

Progress with the use of monoclonal antibodies for the treatment of systemic lupus erythematosus

In recent years, significant progress has been made in the use of monoclonal antibodies in the treatment of systemic lupus erythematosus (SLE). Advances in our understanding of the complexity of SLE immunopathogenesis have led to the testing of several biologic agents in clinical trials. Monoclonal therapies currently emerging or under development include B-cell depletion therapies, agents targeting B-cell survival factors, blockade of T-cell co-stimulation and anticytokine therapies. Issues remain, however, regarding clinical trial design and outcome measures in SLE which need to be addressed to optimize translation of these promising therapies into clinical practice.

Biomarkers in lupus nephritis

Lupus nephritis (LN) has significant impact on the outcome of patients with systemic lupus erythematosus (SLE). In the absence of any new breakthrough for management of LN over the last few years, using existing treatment modalities in a more effective manner is the mainstay of improving outcomes. For effectively using the drugs, disease activity needs to be assessed accurately and more objectively, which is not possible with present clinical assessment tools. Biomarkers help in accurate assessment of disease activity and enable the physician to individualize the therapy. Conventional disease activity markers have limitations which need to be addressed and research in the area of biomarker discovery in LN has immensely expanded over the last two decades as evident by the literature. Moreover, biomarkers for LN should be different from the markers of overall disease activity as LN requires significant immunosuppression, unlike other non-renal manifestations of SLE. Newly discovered biomarkers exhibit qualities pertaining to different aspects of disease activity and damage. In this review, we discuss the established as well as new biomarkers of SLE in the light of their role in LN diagnosis, follow-up, prediction of renal flare and correlation with renal histology findings.

Key issues in the management of patients with systemic lupus erythematosus: latest developments and clinical implications

Systemic lupus erythematous (SLE) is a chronic multisystem disease with significant associated morbidity and mortality. A deeper understanding of the pathogenesis of SLE has led to the development of biologic agents, primarily targeting B cells and others inhibiting costimulatory molecules, type I interferons and cytokines such as interleukin-6. Several of these agents have been studied in clinical trials; some have shown promise while others have yielded disappointing results. Economic and regulatory issues continue to hamper the availability of such therapies for SLE patients. With increasing recognition that recurrent flares of disease activity lead to long-term damage accrual, one of the most important recent developments in patient management has been the concept of treat-to-target in SLE while minimizing patient exposure to excessive corticosteroid and other immunosuppressive therapy. This article reviews these key issues in SLE management, outlining recent developments and clinical implications for patients.

Pathogenic Inflammation and Its Therapeutic Targeting in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE, lupus) is a highly complex and heterogeneous autoimmune disease that most often afflicts women in their child-bearing years. It is characterized by circulating self-reactive antibodies that deposit in tissues, including skin, kidneys, and brain, and the ensuing inflammatory response can lead to irreparable tissue damage. Over many years, clinical trials in SLE have focused on agents that control B- and T-lymphocyte activation, and, with the single exception of an agent known as belimumab which targets the B-cell survival factor BAFF, they have been disappointing. At present, standard therapy for SLE with mild disease is the agent hydroxychloroquine. During disease flares, steroids are often used, while the more severe manifestations with major organ involvement warrant potent, broad-spectrum immunosuppression with cyclophosphamide or mycophenolate. Current treatments have severe and dose-limiting toxicities and thus a more specific therapy targeting a causative factor or signaling pathway would be greatly beneficial in SLE treatment. Moreover, the ability to control inflammation alongside B-cell activation may be a superior approach for disease control. There has been a recent focus on the innate immune system and associated inflammation, which has uncovered key players in driving the pathogenesis of SLE. Delineating some of these intricate inflammatory mechanisms has been possible with studies using spontaneous mouse mutants and genetically engineered mice. These strains, to varying degrees, exhibit hallmarks of the human disease and therefore have been utilized to model human SLE and to test new drugs. Developing a better understanding of the initiation and perpetuation of disease in SLE may uncover suitable novel targets for therapeutic intervention. Here, we discuss the involvement of inflammation in SLE disease pathogenesis, with a focus on several key proinflammatory cytokines and myeloid growth factors, and review the known outcomes or the potential for targeting these factors in SLE.

A multicenter photoprovocation study to identify potential biomarkers by global peptide profiling in cutaneous lupus erythematosus

Cutaneous lupus erythematosus (CLE) is an inflammatory autoimmune skin disease in which abnormal photosensitivity is an important pathogenetic factor but is difficult to predict, creating a challenge in determining treatment efficacy. Although photosensitivity in CLE patients may change over time, photoprovocation testing with ultraviolet (UV) A and UVB irradiation can be a helpful tool to explore differences between responders and nonresponders during photoprovocation. To identify biomarkers that could substitute for the clinical endpoint lesion development, we performed a global peptidomics profiling analysis of CLE subjects in a controlled photoprovocation study. Plasma and skin biopsy samples were collected before and after UV-irradiation from 13 healthy volunteers and 47 CLE subjects. Twenty-two of the 47 CLE subjects developed skin lesions. The samples were analyzed using a label-free quantitative peptidomics workflow combined with univariate and multivariate statistical analyses. The primary finding was identification of a specific plasma peptide signature separating responders versus nonresponders at baseline. The peptide signature consisted of beta 2-microglobulin (B2MG), human beta-defensin-1, and peptides derived from CD99, polymeric immunoglobulin receptor, and immunoglobulin kappa light chains. In skin, elevated B2MG levels correlated with lesion formation. Our results show that the peptidome is a rich source of potential biomarkers for predicting photosensitivity in CLE.

The role of serum IL-17 and IL-6 as biomarkers of disease activity and predictors of remission in patients with lupus nephritis

AIM

To determine the role of IL-17 and IL-6 in the pathogenesis of SLE as biomarkers of disease activity and predictors of remission and outcome of therapy in patients with active lupus nephritis.

METHODS

The study was carried out on 72 SLE female patients and 70 sex- and age-matched normal healthy subjects as controls. SLE disease activity was assessed in all patients with (SLEDAI-2k scores). Plasma levels of IL-6, and IL-17 were measured by enzyme linked immunosorbent assay and their levels were correlated with clinical manifestations of the disease and (SLEDAI-2k). ROC curve analysis was performed to determine the validity of both cytokines in prediction of activity and remission of active lupus nephritis.

RESULTS

SLE patients were found to have significantly higher levels of IL-17 (p<0.001) and IL-6 (p<0.001), in relation to normal subjects. Active group of patients had higher levels of both cytokines than the inactive one (P<0.001). Elevated serum levels of both cytokines were associated with active lupus nephritis, anemia and positively correlated with SLEDAI-2k scores (P=0.025 for IL-17 and P<0.001 for IL-6). There was a significant positive correlation between IL-6 and IL-17 serum concentrations during periods of disease activity (r=0.497, P=0.005) as well as during remission (r=0.662, P<0.001). ROC curve analysis for IL-6 and IL-17, as predictor of disease activity reviled, optimal cutoff level of 12.3 pg/ml and 19.7 pg/ml, with AUC=0.93, and 0.95, for both cytokines respectively, while as predictors of remission of active lupus nephritis, provide a cutoff value of IL-6 at 20.8 pg/ml, with AUC 0.80, and a cutoff value of IL-17 at 27.0 pg/ml, with AUC 0.82.

CONCLUSION

In conjunction with their major role in pathogenesis of SLE, baseline serum levels of IL-6 and IL-17 can be used as sensitive biomarkers for disease activity, as well as predictors of remission of lupus nephritis.

HMGB1 Promotes Systemic Lupus Erythematosus by Enhancing Macrophage Inflammatory Response

Background/Purpose. HMGB1, which may act as a proinflammatory mediator, has been proposed to contribute to the pathogenesis of multiple chronic inflammatory and autoimmune diseases including systemic lupus erythematosus (SLE); however, the precise mechanism of HMGB1 in the pathogenic process of SLE remains obscure. Method. The expression of HMGB1 was measured by ELISA and western blot. The ELISA was also applied to detect proinflammatory cytokines levels. Furthermore, nephritic pathology was evaluated by H&E staining of renal tissues. Results. In this study, we found that HMGB1 levels were significantly increased and correlated with SLE disease activity in both clinical patients and murine model. Furthermore, gain- and loss-of-function analysis showed that HMGB1 exacerbated the severity of SLE. Of note, the HMGB1 levels were found to be associated with the levels of proinflammatory cytokines such as TNF-α and IL-6 in SLE patients. Further study demonstrated that increased HMGB1 expression deteriorated the severity of SLE via enhancing macrophage inflammatory response. Moreover, we found that receptor of advanced glycation end products played a critical role in HMGB1-mediated macrophage inflammatory response. Conclusion. These findings suggested that HMGB1 might be a risk factor for SLE, and manipulation of HMGB1 signaling might provide a therapeutic strategy for SLE.

[Biologics therapy for systemic lupus erythematosus. Current situation]

BACKGROUND

Improved understanding of the immunopathogenesis of systemic lupus erythematosus (SLE) has paved the way for new specific immune interventions for this inflammatory disease similar to those for rheumatoid arthritis and spondylarthritides.

METHODS

New biologics were developed on this basis or are in the process of clinical development and open up new therapy options for patients. In this context belimumab is of particular importance. As an innovative biologic the monoclonal antibody against the cytokine BAFF/BLyS (belimumab) has been approved for the treatment of serologically active SLE. A number of other biologics against other cytokines are in the clinical development phase and appear to be promising for further improvement of the current therapeutic possibilities in SLE. This article addresses the current aspects of immune interventions with biologics for SLE and the specific challenges of this disease.

Urine β2-microglobulin is associated with clinical disease activity and renal involvement in female patients with systemic lupus erythematosus

Objective

We investigated the association of serum and urine β2-microglobulin (β2MG) with renal involvement and clinical disease activity in systemic lupus erythematosus (SLE).

Methods

Sixty-four female patients with SLE were enrolled. We assessed SLE disease activity (SLEDAI)-2K and measured serum and urine β2MG levels, as well as complement (C3 and C4) and anti-dsDNA levels. According to the SLEDAI scores, two groups were categorized: low (0–5 of SLEDAI) and high (6–19 of SLEDAI) disease activity groups. The presence of renal involvement was determined by renal SLEDAI score. Statistical analysis was performed using Spearman’s correlation analysis, Mann-Whitney U test, multivariate regression analysis, and logistic regression analysis.

Results

Urine β2MG levels were significantly different between low and high SLEDAI groups ( p = 0.001), but not for serum β2MG levels ( p = 0.579). Patients with renal involvement showed higher urine β2MG levels compared to those without renal involvement ( p < 0.001), but again there was not a difference in serum β2MG levels ( p = 0.228). Urine β2MG was closely associated with SLEDAI ( r = 0.363, p = 0.003), renal SLEDAI ( r = 0.479, p < 0.001), urine protein/Cr ( r = 0.416, p = 0.001), and ESR ( r = 0.347, p = 0.006), but not serum β2MG ( r = 0.245, p = 0.051). Urine β2MG level was identified as a surrogate for renal involvement ( p = 0.009, OR = 1.017, 95% CI 1.004–1.030) and overall disease activity ( p = 0.009, OR = 1.020, 95% CI 1.005–1.036).

Conclusions

We demonstrated that urine β2MG levels are associated with renal involvement and overall clinical disease activity in SLE.

Improved prognostic diagnosis of systemic lupus erythematosus in an early stage of disease by a combination of different predictive biomarkers identified by proteome analysis

Background

Since the original characterizations of the pathological features defining glomerulonephritis in systemic lupus erythematosus (SLE) were reported, numerous studies have linked the development of pathology to the abnormal expression of protein in urine. The determination of proteinuria is important and necessary; however, this alone is not predictive enough to confirm a suspected diagnosis, especially in an early state of disease when symptoms are not yet observed. Furthermore, several studies have already highlighted the pitfalls of proteinuria both as a clinical prognostic marker and as a factor predicting the progressive loss of renal function. Therefore, the identification of more accurate and predictive biomarkers is urgently needed. To address this, comparative urinary and kidney profiling was performed in the MRL-lpr/lpr mouse as a model of lupus tubulointerstitial nephritis and lupus glomerulonephritis corresponding to SLE in humans.

Results

Tamm-Horsfall glycoprotein (THG; uromodulin) and beta2-microglubulin (β2M) were identified as immune process-related molecules in the urine and kidney of the MRL-lpr/lpr mouse model. Furthermore, we show that the combinatory expression profile of THG and β2M as biomarkers, normalized by the proteinuria level, is more predictive than proteinuria determination alone. Data were confirmed by comparative urinary profiling of SLE in mice by Western blot and quantitative polymerase chain reaction (qPCR) analysis.

Conclusion

Based on our results, we are able to diagnose SLE in the MRL-lpr/lpr mouse in a very early state of disease, when the proteinuria level alone is not able to confirm a suspected diagnosis. The pre-validation of our urinary biomarkers is associated with clinical outcomes of glomerulonephritis in humans and merits additional investigation. Further conformations of our predictive biomarkers in the urine of SLE patients in the course of a clinical study are still ongoing.

IL-37 inhibits the production of inflammatory cytokines in peripheral blood mononuclear cells of patients with systemic lupus erythematosus: its correlation with disease activity

Background

Interleukin-37 (IL-37), a new member of IL-1 family cytokine, is recently identified as a natural inhibitor of innate immunity. This study aimed to measure the peripheral blood mononuclear cells (PBMCs) and serum levels of IL-37 in patients with systemic lupus erythematosus (SLE) and to investigate its role in SLE, including its correlation with disease activity, organ disorder and the regulation of inflammatory cytokines.

Methods

The expressions of IL-37 mRNAs in PBMCs and serum IL-37 levels in 66 SLE patients were measured by real-time polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). SLE patients PBMCs were stimulated with recombinant IL-37, levels of cytokines TNF-α, IL-1β, IL-6 and IL-10 were detected by RT-PCR and ELISA.

Results

IL-37 mRNAs and serum protein levels were higher in patients with SLE compared with healthy controls. Patients with active disease showed higher IL-37 mRNAs and serum protein levels compared with those with inactive disease as well as healthy controls. Serum IL-37 levels correlated with SLEDAI and inversely with C3 and C4. Serum IL-37 levels were higher in SLE patients with renal involvement compared with those without renal disease. In vitro, IL-37 inhibited the production of TNF-α, IL-1β and IL-6 in PBMCs of patients with SLE, whereas the production of IL-10 was unaffected.

Conclusions

IL-37 associated with SLE disease activity, especially related with SLE renal disease activity. IL-37 is an important cytokine in the control of SLE pathogenesis by suppressing the production of inflammatory cytokines. Thus, IL-37 may provide a novel research target for the pathogenesis and therapy of SLE.

Recent developments in the treatment of patients with systemic lupus erythematosus: focusing on biologic therapies

INTRODUCTION

Major trials hoping to obtain optimal disease control in systemic lupus erythematosus (SLE) are ongoing. Given its complex aetiology and pathogenesis, it is not surprising that multiple therapeutic targets have emerged and that none are uniformly successful.

AREAS COVERED

In this review, we highlight the recent, more significant studies focusing on the use of biologic therapies. There has been great emphasis on the role of B cells in SLE and many uncontrolled studies have encouraged the use of rituximab (an anti-CD20 monoclonal). Disappointingly, two major trials, EXPLORER and LUNAR did not confirm its utility, although doubts have been expressed on their trial design, and other trials using this drug are commencing. In contrast, belimumab, which blocks a B-cell activating factor, did meet its end points in two major randomised controlled clinical trials and has been approved for use in SLE by both the FDA and the European Medicines Agency. Encouraging, albeit preliminary, results with epratuzumab (which blocks CD22) have also been reported.

EXPERT OPINION

In addition to targeting B cells, other approaches including biologics, which modulate T-cell function and block interleukin-6 and interferon-α, have been explored. Finally, we review the recent developments in the use of conventional drugs, such as cyclophosphamide and mycophenolate.

Pathology of systemic lupus erythematosus: the challenges ahead

Many studies have explored the pathology of systemic lupus erythematosus (SLE), an autoimmune rheumatic disorder with a striking female predominance. Numerous autoimmune phenomena are present in this disease, which ultimately result in organ damage. However, the specific cellular and humoral mechanisms underlying the immune dysfunction are not yet fully understood. It is postulated that autoimmunity is based on the interaction of genetic predisposition, hormonal and environmental triggers that result in reduced tolerance to self-tissues. These phenomena could occur because of altered antigen presentation, abnormalities in B cell responses, increases in the function of T-helper cells, abnormal cytokine production, exaggerated effector responses, or loss of regulatory T cells or B cells. Abnormalities in all of these components of the immune response have been implicated to varying degrees in the pathogenesis of SLE. This chapter will attempt to provide a "state-of-the-art" review of the evidence about the mechanisms underlying the pathology of SLE.

The role of cytokines in the pathogenesis of systemic lupus erythematosus - from bench to bedside

The pathogenesis of systemic lupus erythematosus (SLE) entails a complex interaction between the different arms of the immune system. While autoantibodies production and immune complex deposition are cornered as hallmark features of SLE, there is growing evidence to propose the pathogenic role of cytokines in this disease. Examples of these cytokines include BLys, interleukin-6, interleukin-17, interleukin-18, type I interferons and tumour necrosis factor alpha. These cytokines all assume pivotal functions to orchestrate the differentiation, maturation and activation of various cell types, which would mediate local inflammatory process and tissue injury. The knowledge on these cytokines not only fosters our understanding of the disease, but also provides insights in devising biomarkers and targeted therapies. In this review, we focus on cytokines which have substantial pathogenic significance and also highlight the possible clinical applications of these cytokines.

Systemic lupus erythematosus and other autoimmune rheumatic diseases: challenges to treatment

Increased understanding of the molecular mechanisms underlying the pathogenenesis of autoimmune rheumatic diseases has led to targeted biological treatments that modulate various aspects of the immune response. These new treatments, together with more judicious use of other immunosuppressive drugs, have resulted in marked improvements in morbidity and mortality. Although belimumab, an agent that inhibits B-cell survival, is the first drug to be approved by the US Food and Drug Administration for the treatment of systemic lupus erythematosus in 50 years, many other immunological targets are under investigation. We discuss the recent advances in the biological treatment of autoimmune rheumatic diseases, with a particular focus on systemic lupus erythematosus.

Urinary uromodulin excretion predicts progression of chronic kidney disease resulting from IgA nephropathy

BACKGROUND

Uromodulin, or Tamm-Horsfall protein, is the most abundant urinary protein in healthy individuals. Recent studies have suggested that uromodulin may play a role in chronic kidney diseases. We examined an IgA nephropathy cohort to determine whether uromodulin plays a role in the progression of IgA nephropathy.

METHODS

A total of 344 IgA nephropathy patients were involved in this study. Morphological changes were evaluated with the Oxford classification of IgA nephropathy. Enzyme Linked Immunosorbent Assay (ELISA) measured the urinary uromodulin level on the renal biopsy day. Follow up was done regularly on 185 patients. Time-average blood pressure, time-average proteinuria, estimated glomerular filtration rate (eGFR) and eGFR decline rate were caculated. Association between the urinary uromodulin level and the eGFR decline rate was analyzed with SPSS 13.0.

RESULTS

We found that lower baseline urinary uromodulin levels (P = 0.03) and higher time-average proteinuria (P = 0.04) were risk factors for rapid eGFR decline in a follow-up subgroup of the IgA nephropathy cohort. Urinary uromodulin level was correlated with tubulointerstitial lesions (P = 0.016). Patients that had more tubular atrophy/interstitial fibrosis on the surface had lower urinary uromodulin levels (P = 0.02).

CONCLUSIONS

Urinary uromodulin level is associated with interstitial fibrosis/tubular atrophy and contributes to eGFR decline in IgA nephropathy.

Novel therapeutic agents in clinical development for systemic lupus erythematosus

Conventional immunosuppressive therapies have radically transformed patient survival in systemic lupus erythematosus (SLE), but their use is associated with considerable toxicity and a substantial proportion of patients remain refractory to treatment. A more comprehensive understanding of the complexity of SLE immunopathogenesis has evolved over the past decade and has led to the testing of several biologic agents in clinical trials. There is a clear need for new therapeutic agents that overcome these issues, and biologic agents offer exciting prospects as future SLE therapies.An array of promising new therapies are currently emerging or are under development including B-cell depletion therapies, agents targeting B-cell survival factors, blockade of T-cell co-stimulation and anti-cytokine therapies, such as monoclonal antibodies against interleukin-6 and interferon-α.

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.

Novel future therapeutic options in myasthenia gravis

BACKGROUND

Myasthenia Gravis (MG) is an autoimmune disease caused by complement-fixing antibodies against the acetylcholine receptors (AChR). Antigen-specific CD4+ T cells, Tregs and Th17+ are also necessary. Consequently, antibodies, B cells, molecules associated with signalling pathways on T helper cells, cytokines and complement are targets for more specific treatment options.

OBJECTIVES

Because available immunosuppressive therapies cause unacceptable side effects after long-term use or are not always effective in inducing remission, novel biological agents directed against the following targets might be options for future therapies in MG: 1) T cell Intracellular Signaling Pathways associated with T cell activation, such as monoclonal antibodies against CD52, Interleukin 2-receptor (IL-2 R), co-stimulatory molecules or compounds inhibiting Janus tyrosine kinases JAK1, JAK3; 2) B cells, against key B cell-surface molecules or trophic factors B cell activation factor (BAFF) and a proliferating inducing ligand (APRIL); 3) Complement, against C3 or C5 that intercept membranolytic attack complex formation; 4) Cytokines and cytokine receptors, including IL-6, IL-17, the p40 subunit of IL12/1L-23, and GM-CSF; and 5) Lymphocyte migration molecules. Construction of recombinant AChR antibodies that block the binding of the pathogenic antibodies, can be a future molecular tool.

CONCLUSION

New biological agents are in the offing for future therapies in MG. Their efficacy needs to be secured with vigorously controlled clinical trials and weighted against excessive cost and rare complications.

Serum Beta 2-microglobulin/cystatin C index: a useful biomarker in lupus nephritis?

BACKGROUND

Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease with frequent flares. Our aim was to evaluate the beta 2-microglobulin/cystatin C (β2M/CysC) index versus other markers as a predictor factor for assessment of SLE reactivation.

METHODS

We prospectively analyzed 42 patients with lupus nephritis. Disease activity was classified using SLEDAI-2K and BILAG. Routine renal function and laboratory markers of SLE activity were performed, as well as serum β2M (Sβ2M)/serum CysC (SCysC) and Sβ2M/serum creatinine (SCreat) indexes determinations.

RESULTS

The 42 enrolled patients had a mean age of 37.7 ± 13.1 years, 88% were female and 67% Caucasians; mean estimated glomerular filtration rate was 61.9 ± 20.0 ml/min/1.73 m(2). There was a strong correlation between SCreat versus SCysC (r = 0.887), SCreat versus Sβ2M (r = 0.865), and SCysC versus Sβ2M (r = 0.880). Multivariate analysis showed that the Sβ2M/SCreat index is a prognostic factor predicting active lupus nephritis.

CONCLUSION

As SCysC is a good marker of renal function, it would be expected that the Sβ2M/SCysC index could be a better indicator of renal activity than Sβ2M/SCreat, but in the present study it did not add relevant clinical information in the assessment of renal activity in SLE.

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.

Successful use of interleukin 6 antagonist tocilizumab in a patient with refractory cutaneous lupus and urticarial vasculitis

Tocilizumab (Actemra; Genentech, Inc) is the first biologic therapy targeting the cytokine interleukin 6 (IL-6). It is a humanized monoclonal immunoglobulin G1 antibody against the α-chain of the IL-6 receptor that prevents the binding of IL-6 to membrane-bound and -soluble IL-6 receptor. It was approved by the US Food and Drug Administration in January 2010 for rheumatoid arthritis refractory to other approved therapies and in April 2011 for systemic juvenile idiopathic arthritis. It has been used as an off-label treatment in many autoimmune diseases, where IL-6 plays a major role in pathogenesis. We report a case of refractory systemic lupus erythematosus in a 22-year-old woman with recurrent high-grade fever, polyarthritis, diffuse rash with urticarial vasculitis, and tumid lupus who did not respond to topical corticosteroids, photoprotection, antimalarials, methotrexate, anakinra, mycophenolate mofetil, etanercept, and intravenous immunoglobulin therapy. Symptoms recurred after corticosteroid tapers below 10 mg. She was noted to have an elevated IL-6 level, and tocilizumab was started. She responded favorably with remission of fever, arthritis, and skin manifestations and was able to taper corticosteroid therapy successfully.

Beneficial effect of Bupleurum polysaccharides on autoimmune-prone MRL-lpr mice

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease leading to inflammatory tissue damage in multiple organs. The crude polysaccharides (BPs) isolated from the roots of Bupleurum smithii var. parvifolium have anticomplementary activity and immunomodulatory functions on macrophages. To study its potential benefit on SLE, we examined effects of BPs on MRL-lpr mice, which have similar disease features to human SLE. MRL-lpr mice were treated orally with BPs 15, 30, or 60 mg kg⁻¹ day⁻¹ for 12 weeks and their SLE characteristics were evaluated. The results revealed that BPs elongated life span, improved kidney function, delayed lymphadenopathy, and reduced autoantibodies. It seemed to be mediated by inhibition of complement and macrophages activation and suppression of interferon-γ (IFN-γ) and interleukin-6 (IL-6) gene expression in the kidney. These results implicate that BPs may be an immunomodulator for the treatment of autoimmune diseases like SLE.

Heat shock protein 90 inhibition by 17-DMAG lessens disease in the MRL/lpr mouse model of systemic lupus erythematosus

Elevated expression of heat shock protein 90 (HSP90) has been found in kidneys and serum of systemic lupus erythematosus (SLE) patients and MRL/Mp-Fas(lpr)/Fas(lpr) (MRL/lpr) autoimmune mice. We investigated if inhibition of HSP90 would reduce disease in MRL/lpr mice. In vitro, pretreatment of mesangial cells with HSP90 inhibitor Geldanamycin prior to immune-stimulation showed reduced expression of IL-6, IL-12 and NO. In vivo, we found HSP90 expression was elevated in MRL/lpr kidneys when compared to C57BL/6 mice and MRL/lpr mice treated with HSP90 inhibitor 17-DMAG. MRL/lpr mice treated with 17-DMAG showed decreased proteinuria and reduced serum anti-dsDNA antibody production. Glomerulonephritis and glomerular IgG and C3 were not significantly affected by administration of 17-DMAG in MRL/lpr. 17-DMAG increased CD8(+) T cells, reduced double-negative T cells, decreased the CD4/CD8 ratio and reduced follicular B cells. These studies suggest that HSP90 may play a role in regulating T-cell differentiation and activation and that HSP90 inhibition may reduce inflammation in lupus.

Tamm-Horsfall protein regulates circulating and renal cytokines by affecting glomerular filtration rate and acting as a urinary cytokine trap

Although few organ systems play a more important role than the kidneys in cytokine catabolism, the mechanism(s) regulating this pivotal physiological function and how its deficiency affects systemic cytokine homeostasis remain unclear. Here we show that elimination of Tamm-Horsfall protein (THP) expression from mouse kidneys caused a marked elevation of circulating IFN-γ, IL1α, TNF-α, IL6, CXCL1, and IL13. Accompanying this were enlarged spleens with prominent white-pulp macrophage infiltration. Lipopolysaccharide (LPS) exacerbated the increase of serum cytokines without a corresponding increase in their urinary excretion in THP knock-out (KO) mice. This, along with the rise of serum cystatin C and the reduced inulin and creatinine clearance from the circulation, suggested that diminished glomerular filtration may contribute to reduced cytokine clearance in THP KO mice both at the baseline and under stress. Unlike wild-type mice where renal and urinary cytokines formed specific in vivo complexes with THP, this "trapping" effect was absent in THP KO mice, thus explaining why cytokine signaling pathways were activated in renal epithelial cells in such mice. Our study provides new evidence implicating an important role of THP in influencing cytokine clearance and acting as a decoy receptor for urinary cytokines. Based on these and other data, we present a unifying model that underscores the role of THP as a major regulator of renal and systemic immunity.

Roles of pro- and anti-inflammatory cytokines in the pathogenesis of SLE

SLE is an autoimmune inflammatory disease in which various pro- and anti-inflammatory cytokines, including TGF-β, IL-10, BAFF, IL-6, IFN-α, IFN-γ, IL-17, and IL-23, play crucial pathogenic roles. Virtually, all these cytokines can be generated by both innate and adaptive immune cells and exert different effects depending on specific local microenvironment. They can also interact with each other, forming a complex network to maintain delicate immune homeostasis. In this paper, we elaborate on the abnormal secretion and functions of these cytokines in SLE, analyze their potential pathogenic roles, and probe into the possibility of them being utilized as targets for therapy.

Tocilizumab for the treatment of rheumatoid arthritis and other systemic autoimmune diseases: current perspectives and future directions

Interleukin (IL)-6 is a cytokine featuring redundancy and pleiotropic activity. While IL-6, when transiently produced, contributes to host defense against acute environmental stress, continuous dysregulated IL-6 production plays a significant pathological role in several systemic autoimmune diseases. In response to the expectation that IL-6 blockade would constitute a novel therapeutic strategy for the treatment of these diseases, tocilizumab, a humanized anti-IL-6 receptor antibody, was developed. Clinical trials have verified the efficacy and the safety of tocilizumab for patients with rheumatoid arthritis, resulting in approval of this innovative biologic for the treatment of rheumatoid arthritis in more than 90 countries worldwide. Pathological analyses of the effect of IL-6 on the development of autoimmune diseases and a considerable number of case reports and pilot studies have also indicated the beneficial effects of this antibody on other systemic autoimmune diseases, including systemic lupus erythematosus, systemic sclerosis, polymyositis, and large-vessel vasculitis.

Inflammatory cytokines in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown origin affecting virtually all organ systems. Beyond genetic and environmental factors, cytokine imbalances contribute to immune dysfunction, trigger inflammation, and induce organ damage. The key cytokine that is involved in SLE pathogenesis is interferon alpha. Interferon secretion is induced by immune complexes and leads to upregulation of several inflammatory proteins, which account for the so-called IFN signature that can be found in the majority of SLE PBMCs. Additionally IL-6 and IFN-y as well as T-cell-derived cytokines like IL-17, IL-21, and IL-2 are dysregulated in SLE. The latter induce a T-cell phenotype that is characterized by enhanced B-cell help and enhanced secretion of proinflammatory cytokines but reduced induction of suppressive T cells and activation-induced cell death. This paper will focus on these cytokines and highlights pathophysiological approaches and therapeutic potential.

Novel treatments for systemic lupus erythematosus

There are many new therapeutic directions for the disease systemic lupus erythematosus (SLE). Despite this, the US Food and Drug Administration (FDA) has approved only one biological agent and it involves B cells, now thought to play a significant role in the pathogenesis of SLE. The name of the drug is belimumab, which is an agent that removes the B-cell cytokine called B lymphocyte stimulation factor (BLyS). Rituximab did not achieve its primary endpoints, even though the consensus is that it may be effective in some forms of SLE including renal disease. The anticytokine therapies against interleukin (IL)-6, IL-10, IL-17 and tumor necrosis factor (TNF) are effective in their own ways and phase II and III trials are in progress. Of particular interest to immunologists are the anti-interferon alpha and gamma drugs, which show promise in the animal models. Modulation of costimulatory molecules; specifically, the anti CD40, CTLA-***Ig and ICOS/B7RP blockade agents offer possibilities for the future using new pathways heretofore limited to rheumatoid arthritis. Finally, the use of tyrosine kinase inhibitors is another direction that has been successful in the inhibition of SLE in the murine model; early trials in human SLE have begun.

Urinary biomarkers in lupus nephritis

Renal involvement in patients with systemic lupus erythematosus in the form of severe lupus nephritis is associated with a significant burden of morbidity and mortality. Conventional laboratory biomarkers in current use have not been very successful in anticipating disease flares, predicting renal histology, or decreasing unwanted outcomes. Since early treatment is associated with improved clinical results, it is thus essential to identify new biomarkers with substantial predictive power to reduce the serious sequelae of this difficult to control lupus manifestation. Indeed, considerable efforts and progress have been made over the last few years in the search for novel biomarkers. Since urinary biomarkers are more easily obtainable with much less risk to the patient than repeat renal biopsies, and these may more accurately discern between renal disease and other organ manifestations than their serum counterparts, there has been tremendous interest in studying new candidate urine biomarkers. Below, we review several promising urinary biomarkers under investigation, including total proteinuria and microalbuminuria, urinary proteomic signatures, and the individual inflammatory mediators interleukin-6, vascular cell adhesion molecule-1, CXCL16, IP-10, and tumor necrosis factor-like weak inducer of apoptosis.

The role of cytokines in the pathogenesis and treatment of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease that is characterized by a defect in immune tolerance and exacerbated by both the innate and adaptive arms of the immune response. SLE-associated immune hyperactivity can be detected systemically as elevations in levels of cytokines along with their upregulated receptors expressed by hematopoietic cells. Importantly, increased levels of cytokines and their receptors can be observed in target organs, and it is clear that they have important roles in disease pathogenesis. Recent therapeutic strategies have focused on proximal cytokines, such as interferon-α, interleukin (IL)-1, IL-6, and tumor necrosis factor as a result of the efficacious use of biologic agents for intervention in rheumatoid arthritis and other autoimmune diseases. Despite the recent advances in understanding the cytokine networks involved in autoimmune diseases and more specifically in SLE, the diagnosis and prognosis of lupus remain a challenge. Lupus is heterogeneous and unpredictable; moreover, the frequency and severity of flares can be difficult to determine and treat. A better understanding of the regulation of expression of key cytokines and their receptors can likely provide important clues to the pathogenic mechanisms underlying specific forms of SLE, and pave the way toward more effective therapeutics.

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.

The dynamics of urinary N-acetyl-β-D-glucosaminidase (NAG), a marker of renal tubular dysfunction, in patients with lupus nephritis undergoing oral prednisone therapy

INTRODUCTION AND AIMS

N-Acetyl-β-D-glucosaminidase (NAG), a marker of renal tubular dysfunction, is increased in patients with lupus nephritis. In addition to the toxic effects of proteinuria, patients with lupus nephritis may exhibit other factors that contribute to tubular dysfunction, such as pathogenic antitubular basement membrane antibodies. The aim of our study was to assess urinary NAG, proteinuria, and glomerular filtration rate (GFR) before treatment and after 7 and 30 days of oral prednisone therapy in patients with lupus nephritis.

METHODS

Ten patients with lupus nephritis, all females, mean age: 29.4 ± 10.17 years, were enrolled into the study. All the patients received oral prednisone 1 mg/kg. Twenty healthy subjects served as controls. We measured urinary NAG before treatment and after 7 and 30 days of oral prednisone therapy. Proteinuria, GFR, blood pressure, and side effects of therapy were also followed up. Urinary NAG was measured using the colorimetrical method and expressed as units per gram of creatinine (U/gCr). Statistical analysis (Wilcoxon signed ranks test and Wilcoxon rank sum test) was performed using SPSS 17.

RESULTS

In the 10 patients with lupus nephritis, urinary NAG before treatment was 16.9 ± 13.39 U/gCr (P = 0.005 compared with controls). NAG in controls was 1.73 ± 0.51 U/gCr. Proteinuria before treatment was 3.84 ± 1.93 g/24 h. The GFR before treatment was 50.48 ± 11.98 mL/min/1.73 m². After 7 days of prednisone, urinary NAG was 23.55 ± 25.25 U/gCr (P = 0.878 compared with baseline, and P = 0.02 compared with controls). Proteinuria was 2.94 ± 1.3 g/24 h (P = 0.005 compared with baseline), and the GFR was 58.11 ± 13.64 mL/min/1.73 m² (P = 0.005 compared with baseline). After 30 days of prednisone, urinary NAG was 11.77 ± 12.18 U/gCr (P = 0.203 compared with baseline, P = 0.022 compared with the value after 7 days of prednisone, and P = 0.01 compared with controls). Proteinuria was 1.73 ± 0.68 g/24 h (P = 0.005 compared with baseline, and P = 0.005 compared with the value after 7 days of prednisone), and the GFR was 67.49 ± 16.42 mL/min/1.73 m² (P = 0.005 compared with baseline and P = 0.009 compared with the value after 7 days of prednisone). Blood pressure measurements did not show any significant changes. No major side effects of steroid therapy were noticed.

CONCLUSIONS

Urinary NAG showed a significant reduction between 7 and 30 days of therapy. The reduction in urinary NAG set in later than the decline in proteinuria and the improvement in GFR. Further studies incorporating a longer follow-up are needed to observe whether the reduction in NAG persists upon continuation of prednisone therapy.

Interleukin-6 promoter polymorphism -174 G/C is associated with nephritis in Portuguese Caucasian systemic lupus erythematosus patients

Interleukin-6 (IL-6) is a multifunctional cytokine with an important pathophysiological role in systemic lupus erythematosus (SLE). The polymorphism of the IL-6 gene promoter at position -174, which appears to influence the production of this cytokine, has been associated with susceptibility to some rheumatic diseases. The aim of this study is to investigate whether the IL-6 -174 G/C polymorphism associates with lupus susceptibility or affects disease characteristics in Portuguese patients with SLE. The association between -174 G/C and lupus diagnosis was studied in 115 adult SLE patients (95.7% females) and 152 healthy controls (94.7% females), all Caucasians. There were no significant differences in genotype or allele frequency between patients and controls. The -174 C/C genotype was independently associated with renal disease and the C allele with the presence of irreversible damage. The IL-6 gene promoter polymorphism at position -174 does not contribute to SLE susceptibility in Portuguese Caucasian patients but may predispose to specific manifestations of the disease.

Progressive renal papillary calcification and ureteral stone formation in mice deficient for Tamm-Horsfall protein

Mammalian urine contains a range of macromolecule proteins that play critical roles in renal stone formation, among which Tamm-Horsfall protein (THP) is by far the most abundant. While THP is a potent inhibitor of crystal aggregation in vitro and its ablation in vivo predisposes one of the two existing mouse models to spontaneous intrarenal calcium crystallization, key controversies remain regarding the role of THP in nephrolithiasis. By carrying out a long-range follow-up of more than 250 THP-null mice and their wild-type controls, we demonstrate here that renal calcification is a highly consistent phenotype of the THP-null mice that is age and partially gene dosage dependent, but is gender and genetic background independent. Renal calcification in THP-null mice is progressive, and by 15 mo over 85% of all the THP-null mice develop spontaneous intrarenal crystals. The crystals consist primarily of calcium phosphate in the form of hydroxyapatite, are located more frequently in the interstitial space of the renal papillae than intratubularly, particularly in older animals, and lack accompanying inflammatory cell infiltration. The interstitial deposits of hydroxyapatite observed in THP-null mice bear strong resemblances to the renal crystals found in human kidneys bearing idiopathic calcium oxalate stones. Compared with 24-h urine from the wild-type mice, that of THP-null mice is supersaturated with brushite (calcium phosphate), a stone precursor, and has reduced urinary excretion of citrate, a stone inhibitor. While less frequent than renal calcinosis, renal pelvic and ureteral stones and hydronephrosis occur in the aged THP-null mice. These results provide direct in vivo evidence indicating that normal THP plays an important role in defending the urinary system against calcification and suggest that reduced expression and/or decreased function of THP could contribute to nephrolithiasis.