Mediators of injury in lupus nephritis

Nitric-Oxide-Mediated Signaling in Podocyte Pathophysiology

Nitric oxide (NO) is a potent signaling molecule involved in many physiological and pathophysiological processes in the kidney. NO plays a complex role in glomerular ultrafiltration, vasodilation, and inflammation. Changes in NO bioavailability in pathophysiological conditions such as hypertension or diabetes may lead to podocyte damage, proteinuria, and rapid development of chronic kidney disease (CKD). Despite the extensive data highlighting essential functions of NO in health and pathology, related signaling in glomerular cells, particularly podocytes, is understudied. Several reports indicate that NO bioavailability in glomerular cells is decreased during the development of renal pathology, while restoring NO level can be beneficial for glomerular function. At the same time, the compromised activity of nitric oxide synthase (NOS) may provoke the formation of peroxynitrite and has been linked to autoimmune diseases such as systemic lupus erythematosus. It is known that the changes in the distribution of NO sources due to shifts in NOS subunits expression or modifications of NADPH oxidases activity may be linked to or promote the development of pathology. However, there is a lack of information about the detailed mechanisms describing the production and release of NO in the glomerular cells. The interaction of NO and other reactive oxygen species in podocytes and how NO-calcium crosstalk regulates glomerular cells’ function is still largely unknown. Here, we discuss recent reports describing signaling, synthesis, and known pathophysiological mechanisms mediated by the changes in NO homeostasis in the podocyte. The understanding and further investigation of these essential mechanisms in glomerular cells will facilitate the design of novel strategies to prevent or manage health conditions that cause glomerular and kidney damage.

Role of vitamin D/VDR nuclear translocation in down-regulation of NF-κB/NLRP3/caspase-1 axis in lupus nephritis

BACKGROUND

Vitamin D receptor (VDR) and NLRP3 inflammasome play critical roles in lupus nephritis (LN) pathogenesis.

AIM OF THE STUDY

This study explored the therapeutic effect of VDR agonist on LN and its molecular mechanism to inhibit NLRP3 signalling.

METHODS

C57BL/6 mice, lupus-prone MRL/lpr mice, and VDR agonist paricacitol-treated MRL/lpr mice (300 ng/kg/mouse per dose, 5 times/week for 8 weeks from 8 weeks old) were used to assess kidney histopathology and measure proteinuria, serum anti-ds-DNA antibody and expression of NF-κB/NLRP3/caspase-1/IL-1β/IL-18 axis. We used mouse renal tubular epithelial cells (mRTECs) to identify protein-protein interactions and examine the effects of paricalcitol.

RESULTS AND CONCLUSION

LN pathogenesis decreased after paricalcitol treatment. We observed a marked improvement in renal pathology and a time-dependent decrease urine protein and serum anti-dsDNA antibody levels. In 16-week-old MRL/lpr LN mice, the upregulated expression of NLRP3/caspase-1/IL-1β/IL-18 axis was significantly downregulated after paricalcitol treatment. Paricalcitol can reverse the apoptosis induced by anti-dsDNA antibody via the NF-κB/NLRP3/caspase-1/IL-1β/IL-18 axis in mRTECs. Furthermore, paricalcitol suppressed NF-κB nuclear translocation by competitively binding to importin-4. In summary, the VDR agonist can alleviate LN by modulating the NF-κB/NLRP3/caspase-1/IL-1β/IL-18 axis and suppressing the NF-κB nuclear translocation.

Cryptotanshinone ameliorates the pathogenesis of systemic lupus erythematosus by blocking T cell proliferation

Systemic lupus erythematosus (SLE) is a chronic, devastating autoimmune disorder associated with severe organ damage. Recently, the role of Signal Transducer and Activator of Transcription 3 (STAT3) in murine lupus has been described, suggesting the involvement of STAT3 signaling in the development of SLE. Cryptotanshinone (CTS) is an effective inhibitor of STAT3; however its potential as a SLE treatment remains to be explored. To determine the function of CTS in SLE, we treated MRL/lpr female mice with CTS. Firstly, we found CTS treatment reversed the elevated STAT3 signaling of spleens in lupus-prone MRL/lpr mice, accompanying with a dramatically decreased number of T cells, especially double-negative (DN) T cells. Further research showed that CTS inhibited T cell proliferation via suppressing of STAT3 activation in vitro and in vivo. Consistently, we also proved that CTS treatment significantly alleviated autoimmune response including notably diminished skin lesions, reduced spleen size and increased life span. In addition, CTS treatment decreased the levels of auto-antibodies and pro-inflammatory cytokines, as well as normalized structure and function of kidneys. All these data suggested that CTS treatment depressed STAT3 phosphorylation, which resulted in blocked DN T cell proliferation and finally attenuated the spontaneous SLE development. Taken together, our data identify CTS as a potential therapeutic drug for SLE patients.

Pro-inflammatory S100 proteins are associated with glomerulonephritis and anti-dsDNA antibodies in systemic lupus erythematosus

Objectives Systemic lupus erythematosus (SLE) is associated with elevated levels of S100A8/A9, pro-inflammatory proteins mainly secreted by activated polymorphonuclear neutrophils (PMNs). The underlying mechanisms for increased S100A8/A9 levels and their relation to the clinical phenotype have not been carefully investigated. We assessed S100A8/A9 and S100A12 levels in SLE patient sera in relation to disease activity, clinical phenotype, presence of anti-dsDNA antibodies and ability to promote phagocytosis of necrotic cells (NCs) by PMNs. Methods Serum levels of S100A8/A9 and S100A12 were measured by ELISA in paired samples of 100 SLE patients at time points of higher and lower disease activity. Serum-mediated phagocytosis of NCs by PMNs was analysed by flow cytometry. Clinical data were recorded at time points of blood sampling. Results Serum levels of S100A8/A9 and S100A12 were increased in SLE patients with high disease activity compared to paired samples at low disease activity ( p = 0.01 and p = 0.008, respectively). Elevated levels of S100A8/A9 were particularly seen in patients with anti-dsDNA antibodies ( p = 0.01) and glomerulonephritis before treatment ( p = 0.02). Immunosuppressive therapy was associated with a reduction of S100A8/A9 serum levels ( p = 0.002). The ability of serum to support phagocytosis of NCs by PMNs was related to increased S100A8/A9 levels ( p = 0.01). Conclusions Elevated serum levels of S100A8/A9 may be used to monitor disease activity and response to treatment in SLE patients, especially in patients with glomerulonephritis. S100A12 may be a marker of disease activity in SLE. Increased S100A8/A9 levels may reflect immune-pathological processes involving phagocytosis of immune complexes by PMNs.

Ethnic, clinical and immunological factors in systemic lupus erythematosus and the development of lupus nephritis: results from a multi-ethnic New Zealand cohort

The aim of this study was to identify risk factors for lupus nephritis including clinical, laboratory, and ethnic factors in a cohort of lupus patients in New Zealand. A retrospective study of patients from two teaching hospitals in Auckland, New Zealand. Patients were selected if they had attended as either an inpatient, or a rheumatology outpatient between 2000 and 2005. 170 patients had SLE according to ACR classification. Lupus nephritis (LN) was diagnosed according to ACR criteria. Clinical, laboratory, and ethnic data were gathered from the patient notes. Twenty-four patients had LN at diagnosis and 32 patients developed LN after diagnosis. LN was associated with serositis ( P = 0.008), cutaneous vasculitis ( P = 0.026), anaemia ( P = 0.005), CRP elevation >6 months ( P < 0.001), hypocomplementaemia >6 months ( P < 0.0001). Patients with elevated doublestranded DNA (dsDNA) (>5 × normal) were more likely to develop type IV LN ( P = 0.0096). Forty-one percent of patients were Caucasian, 12% Maori, 23% Pacific People, 16% Asian, 6% Indian. Maori patients with SLE (odds ratio (OR) = 8.47, 95% confidence interval (CI) = 2.11—33.96, P = 0.002), and Pacific People (OR = 3.11, 95% CI = 1.29—11.48, P = 0.014) had increased risk for developing LN. Anaemia at presentation (hazard ratio (HR) 3.2, 95% CI = 1.4—7.1, P = 0.004), and low complement >6 months (HR = 3.4, 95% CI = 1.4—8.7, P = 0.008) were independent risk factors for developing LN after SLE diagnosis. In New Zealand, Pacific People and Maori patients with SLE have a higher incidence of LN, and patients with anaemia and hypocomplementaemia are more likely to develop LN after diagnosis. Patients with high dsDNA levels are more likely to develop Type IV lupus nephritis. Lupus (2007) 16, 830—837.

Placebo-controlled randomized clinical trial of fish oil's impact on fatigue, quality of life, and disease activity in Systemic Lupus Erythematosus

Introduction

A recent metabolomic screen of sera from patients with Systemic Lupus Erythematosus (SLE) found reduction of antioxidants and substrates for energy generation. These metabolic alterations may underlie one of the most common features of SLE - fatigue. The metabolomic studies also noted reduced omega-3 fatty acids, which are powerful anti- oxidants. This deficiency may be causally related to oxidative stress, inflammation, disease activity, and fatigue in SLE. Supplementation of omega-3 fatty acids using fish oil in SLE has been shown to reduce oxidative stress in other studies. The objective of this study is to evaluate the effect of fish oil supplementation on clinical measures of fatigue, quality of life, and disease activity as part of a randomized clinical trial.

Methods

Fifty SLE patients recruited in outpatient clinics were randomized 1:1 to fish oil supplementation or olive oil placebo, and blinded to their treatment group. At baseline and after 6 months of treatment, RAND Short Form-36 (RAND SF-36), Fatigue Severity Scale (FSS), SLE Disease Activity Index (SLEDAI), and Physician Global Assessment (PGA) were completed; serum was also collected for soluble mediator analysis.

Results

Thirty-two patients completed the study. PGA improved significantly in the fish oil group compared with the placebo group (p = 0.015). The RAND SF-36 Energy/fatigue and Emotional well-being scores demonstrated improvement trends (p = 0.092 and 0.070). No clear difference was seen in FSS and SLEDAI (p = 0.350 and p = 0.417). Erythrocyte sedimentation rate and serum IL-12 were reduced (p = 0.008 and p = 0.058); while serum IL-13 was increased by fish oil supplementation (p = 0.033).

Conclusions

In this randomized, placebo-controlled 6-month trial, SLE patients randomized to fish oil supplementation demonstrated improvement in their PGA, RAND SF-36, and some circulating inflammatory markers.

Trial registration

ClinicalTrials.gov Identifier: NCT02021513 (registered 13 December 2013).

Interleukin-6 deficiency corrects nephritis, lymphocyte abnormalities, and secondary Sjögren's syndrome features in lupus-prone Sle1.Yaa mice

OBJECTIVE

To assess disease features in Sle1.Yaa mice with genetic interleukin-6 (IL-6) deficiency.

METHODS

Sera and tissues were collected from C57BL/6 (B6), Sle1.Yaa, and Sle1.Yaa.IL-6(-/-) mice and analyzed for various features of disease. Using serum samples, autoantibody specificities were determined by enzyme-linked immunosorbent assay (ELISA) and indirect immunofluorescence, cytokine production was analyzed by Luminex and ELISA, and levels of blood urea nitrogen were determined by ELISA. Renal, lung, and salivary gland tissue sections were evaluated for pathologic changes. Lymphocyte phenotypes, including CD4+ T cell cytokine production, and those of follicular and extrafollicular T helper subsets, germinal center B cells, and plasma cells, were determined using flow cytometry.

RESULTS

IL-6 deficiency not only ameliorated autoantibody production and renal disease in this model, but also effectively reduced inflammation of lungs and salivary glands. Furthermore, IL-6 deficiency abrogated differentiation of Th1 and extrafollicular T helper cells, germinal center B cells, and plasma cells in the spleen and eliminated renal T cells with IL-17, interferon-γ, and IL-21 production potential.

CONCLUSION

Our findings highlight IL-6-mediated T cell aberrations in Yaa-driven autoimmunity and support the concept of therapeutic IL-6/IL-6 receptor blockade in systemic lupus erythematosus and Sjögren's syndrome by impairing the production of autoantibodies and lymphocytic infiltration of the kidneys, lungs, and salivary glands.

MicroRNA-let-7a expression is increased in the mesangial cells of NZB/W mice and increases IL-6 production in vitro

Recent evidence supports a role for epigenetic alterations in the pathogenesis of systemic lupus erythematosus (SLE). MicroRNAs (miRNAs or miRs) are endogenous epigenetic regulators whose expression is altered in many diseases, including SLE. IL-6 is an inflammatory cytokine produced by mesangial cells during lupus nephritis (LN). IL-6 contains a potential binding site for miRNA-let-7a (let-7a) in its 3' untranslated region (UTR). We found let-7a expression was significantly increased in the mesangial cells of pre-diseased and actively diseased New Zealand Black/White (NZB/W) mice compared to age-matched New Zealand White (NZW) mice. Overexpression of let-7a in vitro increased IL-6 production in stimulated mesangial cells compared to non-transfected controls. Inhibition of let-7a did not significantly affect immune-stimulated IL-6 production. When stimulated mesangial cells overexpressing let-7a were treated with the transcription inhibitor Actinomycin D (ActD), IL-6 was degraded faster, consistent with the direct targeting of the 3' UTR of IL-6 by let-7a. Overexpression of let-7a increased the expression of tristetraprolin (TTP), an RNA-binding protein (RBP) that has 5 potential binding regions in the 3' UTR of IL-6. ActD inhibited the transcription of proteins including TTP that may contribute to the let-7a-mediated increase in immune-stimulated IL-6 production. These data show that NZB/W mice have higher let-7a expression than NZW mice and that increased let-7a expression in vitro increases IL-6 production in stimulated mesangial cells. Further studies examining the role of let-7a expression in inflammation are warranted.

Cellular and urinary microRNA alterations in NZB/W mice with hydroxychloroquine or prednisone treatment

Determining alterations to disease-associated miRNAs induced by specific therapeutics may allow the use of tailored therapy in lupus. We determined miRNA alterations in female NZB/W lupus mice treated with hydroxychloroquine (HCQ) or prednisone (PRED) for 12 weeks beginning at 24 weeks-of-age. B cell, PBMC, and urinary miR-let-7a expression were decreased with HCQ or PRED treatment. HCQ or PRED treatment reduced miR-21 expression in mesangial cells, T cells, pDCs, PBMCs, and the urine. MiR-146a expression was reduced in mesangial cells with HCQ treatment and in pDCs with HCQ or PRED treatment. PRED treatment increased miR-155 expression in mesangial, B, and T cells and PBMCs yet decreased miR-155 expression in pDCs and the urine. In vitro studies confirmed that HCQ or PRED's anti-inflammatory actions are dependent on their ability to inhibit miRNA expression. Our studies indicate that lupus therapeutics may work, in part, by altering the expression of disease-associated miRNAs.

MicroRNAs implicated in the immunopathogenesis of lupus nephritis

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the deposition of immune complexes due to widespread loss of immune tolerance to nuclear self-antigens. Deposition in the renal glomeruli results in the development of lupus nephritis (LN), the leading cause of morbidity and mortality in SLE. In addition to the well-recognized genetic susceptibility to SLE, disease pathogenesis is influenced by epigenetic regulators such as microRNAs (miRNAs). miRNAs are small, noncoding RNAs that bind to the 3′ untranslated region of target mRNAs resulting in posttranscriptional gene modulation. miRNAs play an important and dynamic role in the activation of innate immune cells and are critical in regulating the adaptive immune response. Immune stimulation and the resulting cytokine milieu alter miRNA expression while miRNAs themselves modify cellular responses to stimulation. Here we examine dysregulated miRNAs implicated in LN pathogenesis from human SLE patients and murine lupus models. The effects of LN-associated miRNAs in the kidney, peripheral blood mononuclear cells, macrophages, mesangial cells, dendritic cells, and splenocytes are discussed. As the role of miRNAs in immunopathogenesis becomes delineated, it is likely that specific miRNAs may serve as targets for therapeutic intervention in the treatment of LN and other pathologies.

Combination of autoantibodies against different histone proteins influences complement-dependent phagocytosis of necrotic cell material by polymorphonuclear leukocytes in systemic lupus erythematosus

OBJECTIVE

Polymorphonuclear leukocytes (PMN) with autoantibody-coated engulfed necrotic cell material (NC) are frequently seen in systemic lupus erythematosus (SLE). We evaluated the roles of complement, different antihistone antibodies (anti-H ab), and oxidative burst in the phagocytosis of NC by PMN, as well as association to disease activity and clinical phenotype in SLE.

METHODS

ELISA and immunoblot were used to measure antibodies to different histone proteins in sera from patients with SLE and complement-deficient individuals. Phagocytosis of NC by PMN and oxidative burst activity was assessed by flow cytometry.

RESULTS

A clearly increased phagocytosis of NC was seen in patients with active SLE, which was associated with high levels of anti-H ab concentrations and oxidative burst activity. The complement system contributed to efficient phagocytosis of NC by PMN through activation of the classical pathway, and the phagocytosis was mediated by FcγRIIA, FcγRIIIB, and CR1 in combination. A pattern of high phagocytosis, consumption of classical pathway components, and a broad anti-H ab repertoire was seen particularly in patients with nephritis and serositis. The combination of antibodies to several different histone proteins, often with anti-DNA antibodies, promoted an efficient uptake of NC, whereas antibodies against only histone H1 or a few histones seemed to be of less importance.

CONCLUSION

The distributions of specificities among anti-H ab are of great importance in the complement-dependent phagocytosis of debris from NC in SLE. Measurement of anti-H ab could be useful in monitoring of this disease and contribute to improved understanding of the autoimmune process.

The ambiguity in immunology

In the present article, we discuss the various ambiguous aspects of the immune system that render this complex biological network so highly flexible and able to defend the host from different external invaders. This ambiguity stems mainly from the property of the immune system to be both protective and harmful. Immunity cannot be fully protective without producing a certain degree of damage (immunopathology) to the host. The balance between protection and tissue damage is, therefore, critical for the establishment of immune homeostasis and protection. In this review, we will consider as ambiguous, various immunological tactics including: (a) the opposing functions driving immune responses, immune-regulation, and contra-regulation, as well as (b) the phenomenon of chronic immune activation as a result of a continuous cross-presentation of apoptotic T cells by dendritic cells. All these plans participate principally to maintain a state of chronic low-level inflammation during persisting infections, and ultimately to favor the species survival.

Activation-induced deaminase-deficient MRL/lpr mice secrete high levels of protective antibodies against lupus nephritis

OBJECTIVE

We previously generated MRL/lpr mice deficient in activation-induced deaminase (AID) that lack isotype switching and immunoglobulin hypermutation. These mice have high levels of unmutated (germline) autoreactive IgM, yet they experienced an increase in survival and an improvement in lupus nephritis that exceeded that of MRL/lpr mice lacking IgG. The purpose of the present study was to test the hypothesis that high levels of germline autoreactive IgM in these mice confer protection against lupus nephritis.

METHODS

Autoreactive IgM antibodies of various specificities, including antibodies against double-stranded DNA (dsDNA), from AID-deficient MRL/lpr mice were given to asymptomatic MRL/lpr mice, and the levels of cytokines, proteinuria, immune complex deposition in the kidneys, and glomerulonephritis were examined. Novel AID-deficient MRL/lpr mice that lack any antibodies were generated for comparison to AID-deficient MRL/lpr mice that secrete only IgM.

RESULTS

Treatment with IgM anti-dsDNA resulted in a dramatic improvement in lupus nephritis. Other autoreactive IgM antibodies, such as antiphospholipid and anti-Sm, did not alter the pathologic changes. Secretion of proinflammatory cytokines by macrophages and the levels of inflammatory cells and apoptotic debris in the kidneys were lower in mice receiving IgM anti-dsDNA. Protective IgM derived from AID-deficient MRL/lpr mice displayed a distinct B cell repertoire, with a bias toward members of the V(H) 7183 family.

CONCLUSION

IgM anti-dsDNA protected MRL/lpr mice from lupus nephritis, likely by stopping the inflammatory cascade leading to kidney damage. A distinct repertoire of V(H) usage in IgM anti-dsDNA hybridomas from AID-deficient mice suggests that there is enrichment of a dedicated B cell population that secretes unmutated protective IgM in these mice.

A GA microsatellite in the Fli1 promoter modulates gene expression and is associated with systemic lupus erythematosus patients without nephritis

INTRODUCTION

The transcription factor Fli1 is implicated in the pathogenesis of systemic lupus erythematosus (SLE). Recently, a GA(n) polymorphic microsatellite was characterized in the mouse Fli1 promoter that modulates promoter activity and is truncated in two lupus mouse models compared to non-autoimmune prone mice. In this work, we characterize a homologous GA(n) microsatellite in the human Fli1 promoter. The purpose of this study is to determine the effect of the microsatellite length on Fli1 promoter activity in vitro and to determine if the length of the GA(n) microsatellite is associated with SLE and/or specific disease characteristics.

METHODS

Constructs with variable lengths of the GA(n) microsatellite in the Fli1 promoter were generated and analyzed in promoter/reporter (P/R) assays in a human T cell line. Using three SLE patient cohorts and matched controls, microsatellite length was measured and association with the presence of disease and the occurrence of specific disease manifestations was assessed.

RESULTS

P/R assays demonstrated that the presence of a shorter microsatellite resulted in higher Fli1 promoter activity. A significant association was observed in the lupus cohort SLE in Gullah Health (SLEIGH) between the GA(26) base pair allele and absence of nephritis.

CONCLUSIONS

This study demonstrates that a GA(n) microsatellite in the human Fli1 promoter is highly polymorphic. The length of the microsatellite is inversely correlated to Fli1 promoter activity in a human T cell line. Although no association between microsatellite length and lupus was observed, an association between a specific microsatellite length and patients without nephritis in the SLEIGH cohort was observed.

Deficiency of activating Fcγ-receptors reduces hepatic clearance and deposition of IC and increases CIC levels in mercury-induced autoimmunity

Background

Inorganic mercury (Hg) induces a T-cell dependent, systemic autoimmune condition (HgIA) where activating Fcγ-receptors (FcγRs) are important for the induction. In this study we examined the influence of activating FcγRs on circulating levels and organ localization of immune complexes (IC) in HgIA.

Methods and Principal Findings

Mercury treated BALB/c wt mice showed a significant but modest increase of circulating IC (CIC) from day 12 until day 18 and day 35 for IgG2a- and IgG1- CIC, respectively. Mercury-treated mice lacking the trans-membrane γ-chain of activating FcγRs (FcRγ^−/−) had significantly higher CIC levels of both IgG1-CIC and IgG2a-CIC than wt mice during the treatment course. The hepatic uptake of preformed CIC was significantly more efficient in wt mice compared to FcγR^−/− mice, but also development of extrahepatic tissue IC deposits was delayed in FcRγ^−/− mice. After 35 days of Hg treatment the proportion of immune deposits, as well as the amounts was significantly reduced in vessel FcRγ^−/− mice compared to wt mice.

Conclusions

We conclude that mice lacking functional activating FcγRs respond to Hg with increased levels and altered quality of CIC compared with wt mice. Lack of functional activating FcγRs delayed the elimination of CIC, but also significantly reduced extrahepatic tissue localization of CIC.

Regulatory effect of melatonin on cytokine disturbances in the pristane-induced lupus mice

Systemic lupus erythematosus (SLE) develops in relation to many environmental factors. In our opinion, it is more important to investigate the effect of melatonin on the environmental- related SLE. In the present study, 0.5 ml pristane were used to induce SLE in female BALB/c mice. Melatonin (0.01, 0.1, 1.0 mg/kg) was orally administered immediately after pristane-injection for 24 weeks. IgM anti ssDNA and histone antibodies were detected after 0, 1, 2, 4, 8 weeks pristane injection. The levels of IL-2, IL-6 and IL-13 were detected after 24 weeks. Renal lesions were also observed. The results showed that melatonin antagonized the increasing levels of IgM anti ssDNA and histone autoantibodies. Melatonin could also decrease the IL-6 and IL-13 production and increase the IL-2 production. Besides, melatonin could lessen the renal lesions caused by pristane. These results suggested that melatonin has a beneficial effect on pristane-induced lupus through regulating the cytokines disturbances.

The mouse and human Fli1 genes are similarly regulated by Ets factors in T cells

Fli1 is a member of the Ets family of transcription factors and is preferentially expressed in hematopoietic cell lineages. Its expression level is linked to the pathogenesis of lupus. In this study, we identified mechanisms involved in the transcriptional regulation of the mouse and human Fli1 promoters. We show that the Fli1 promoter is upregulated by Ets factors Ets1, Ets2, Fli1 and Elf1 either alone or in combination with GATA factors, but is inhibited by Tel. In vitro binding studies show that Elf1, Tel and Fli1 in T cells bind the three Ets-binding sites in the murine Fli1 proximal promoter. We identified transcription factor-binding sites in the human Fli1 promoter region that function in T cells in a similar manner to those in the mouse promoter. Furthermore, we show similar binding of Ets factors to the endogenous mouse and human Fli1 promoters in T cells and knocking down Ets1 results in an upregulation of Fli1 expression. Together, these results suggest that the human and mouse genes are regulated similarly and that Ets1 may be important in preventing the overexpression of Fli1 in T cells. This report lays the groundwork for identifying targets for manipulating Fli1 expression as a possible therapeutic approach.

Renal disease in systemic lupus erythematosus with emphasis on classification of lupus glomerulonephritis: advances and implications

CONTEXT

Systemic lupus erythematosus is an autoimmune disease with protean clinical and pathologic manifestations involving almost all organs in the body. There is a high incidence of renal involvement during the course of the disease, with varied renal pathologic lesions and diverse clinical features. A renal biopsy examined by routine light microscopy, immunofluorescence, and electron microscopy contributes toward diagnosis, prognostic information, and appropriate management.

OBJECTIVES

(1) To review the clinical and various pathologic features of renal lesions in systemic lupus erythematosus patients. (2) To introduce the International Society of Nephrology and Renal Pathology Society Classification of Lupus Glomerulonephritis.

DATA SOURCES

A literature review, illustrations with original artwork, and tabulation of clinical and pathologic data of cases obtained from the authors' renal biopsy files examined during the last 8 years were used.

CONCLUSIONS

The International Society of Nephrology/ Renal Pathology Society-sponsored Classification of Lupus Glomerulonephritis proposes standardized definitions of the various pathologic findings, describes clinically relevant lesions, incorporates prognostic parameters, and recommends a uniform way of reporting the renal biopsy findings. Lupus glomerulonephritis is divided into 6 classes primarily based on the morphologic lesions, extent and severity of the involvement, immune complex deposition, and activity and chronicity. Special emphasis is laid on describing qualitative as well as quantitative morphologic data and to include the accompanying tubulointerstitial disease and different vascular lesions, which have prognostic and therapeutic significance. This classification is intended to facilitate a higher degree of reproducibility, resulting in better patient care and more effective future clinical and translational research. Renal biopsy findings in systemic lupus erythematosus add new and independent parameters of prognostic significance to established clinical and genetic factors.

Increased survival and reduced renal injury in MRL/lpr mice treated with a novel sphingosine-1-phosphate receptor agonist

Agonists of the type 1 sphingosine-1-phosphate (S1P) receptor inhibit lymphocyte migration, causing their sequestration in lymphoid tissue. The S1P agonist FTY720 prolongs the survival of organ allografts and blocks T-cell mediated autoimmune diseases in experimental models; however, it is a non-selective agonist of four of the five S1P receptors. In this study female MRL/lpr mice, which develop an aggressive form of spontaneous autoimmune kidney disease, were treated with a more selective agonist of the type 1 receptor (KRP-203) or vehicle at 12 or 16 weeks of age. Eighty percent of the mice treated at 12 weeks, before the onset of visible disease, survived to the 24 weeks end point with decreased tubulointerstitial disease and significantly fewer infiltrating CD4(+) and CD8(+) T-cells. Only half of the control vehicle-treated mice survived. All of the mice treated at 16 weeks survived with reduced proteinuria. Mice in both groups had significant reductions in circulating lymphocytes. Mice receiving KRP-203 for 8-12 weeks had significant reductions in T-cells and consequently less adenopathy. Ex vivo treatment of lymphocytes from MRL/lpr mice with KRP-203 enhanced their apoptosis. Our study indicates that KRP-203 attenuates kidney injury in MRL/lpr mice, in part, by reducing T-cell infiltrates.

Immunological memory stabilizing autoreactivity

The etiopathologies of autoimmune diseases are complex. A broad variety of cell types and gene products are involved. However, clinical and experimental evidence suggests that the importance of an individual factor changes during the course of the disease. Factors and cell types that induce acute autoreactivity and initiate an autoimmune disease could be distinct from those that drive a chronic course of that disease. Autoreactive immunological memory, in particular B cell and plasma cell memory, contributes to chronicity through several mechanisms. Formation of autoreactive memory B cells leads to an increase in the numbers of autoreactive cells. In comparison to naive B cells, these memory B cells show a decreased threshold for activation. Additionally, a fraction of memory B cells express the chemokine receptor CXCR3, which supports their accumulation within chronically inflamed tissues. This may allow their escape from mechanisms for induction of peripheral tolerance. Within the inflamed tissue, inflammatory cytokines and autoantigens provide activation signals that promote plasma cell differentiation and survival. The autoantibodies produced locally by these plasma cells contribute to the severity of inflammation. Together, an autoreactive loop of autoantibody-induced inflammation is formed. Another integral part of immunological memory are long-lived plasma cells. These cells provide persistent humoral antibody memory. Though not all autoantibodies are produced by long-lived plasma cells, these cells have a special impact on immune pathology. Long-lived plasma cells are relatively resistant to existing therapies of immunosuppression and continuously secrete antibodies, without need for restimulation. Long-lived plasma cells provide titers of autoantibodies even during clinically quiescent phases and after immunosuppression. These persisting autoantibody titers, though often low and not causing acute clinical symptoms, are likely to maintain a low level of chronic inflammation and progressive tissue destruction, which reduces the threshold for another break of immunological tolerance.

Models of systemic lupus erythematosus: development of autoimmunity following peptide immunizations of noninbred pedigreed rabbits

Reported in this study are the initial results from studies to develop rabbit models of systemic lupus erythematosus (SLE) by immunizations using two distinct peptides on branched polylysine backbones (multiple Ag peptide)-peptides. Eleven rabbits received a peptide from the Sm B/B' spliceosomal complex previously shown to be immunogenic in rabbits, and 13 rabbits received a peptide from the rabbit N-methyl-d-aspartate receptor NR2b. All 24 animals in different generations of pedigreed, noninbred rabbits produced peptide-specific responses. Anti-nuclear autoantibody responses, including anti-dsDNA, were seen in 17 of 24 rabbits. To date, two rabbits have been observed to have seizure-like events and a third nystagmus. A model for eliciting development of SLE in genetically related yet heterogeneous rabbits may more closely resemble development of human SLE than do some models in inbred mice. Through selective breeding, it may also ultimately provide additional information about the genetics and etiology of SLE and serve as a model for assessing new treatment options.

Increased prevalence of activated CD70+CD4+ T cells in the periphery of patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by loss of immune tolerance. A hallmark of SLE is the presence of autoantibodies resulting from B cell hyperactivity. Previous studies have shown that the presence of abnormal B cell subsets in the periphery, such as CD27highCD20- B cells, correlate with disease activity. We examined the relationship between the expression of CD70, the ligand for CD27 expressed by activated T cells, and indicators of disease activity. A significant increase in median CD70+CD4+ T cell frequencies and memory CD45RA-CD4+ T cell frequencies was observed in SLE samples as compared to healthy controls. The frequencies of CD70+CD4+ T cells correlated with disease duration but not age, treatment, or disease activity. Although a majority of CD70+CD4+ T cells appeared to be effector memory cells, mitogen-stimulated CD70+CD4+ T cells were capable of secreting a full repertoire of effector cytokines. Despite the presence of activated CD4+ T cells, no increase in immunosenescent CD4+ T cells, as defined by the loss of CD28 and/or the acquisition of CD57 was observed in samples from SLE patients. These studies indicate that increased CD70 expression might serve as a useful marker of abnormal T cell activity in SLE.

Inducible nitric oxide synthase inhibitors reduce urinary markers of systemic oxidant stress in murine proliferative lupus nephritis

BACKGROUND

Proliferative lupus nephritis (PLN) is characterized by increased expression of inducible nitric oxide (NO) synthase (iNOS). Inhibition of iNOS with NG-monomethyl L-arginine (L-NMMA) abrogates renal disease in two models of murine PLN, but the mechanism of this effect is unknown. Reactive oxygen species have both direct and indirect pathogenic effects in inflammatory lesions and are therefore potentially an important therapeutic target in PLN. We hypothesized that inhibition of iNOS activity would reduce ROS production in murine PLN.

METHODS

A dose escalation of L-NMMA (0, 20, 100, and 500 mg/kg/day) was performed in New Zealand Black x New Zealand White F1 (NZB/W) mice with active renal disease. Twenty-four-hour urine nitrate + nitrite (NOX) was measured with a chemiluminescence NO analyzer. Twenty-four-hour urine 8-isoprostane F2alpha (8-iso-PGF2alpha) was measured by gas chromatography-negative ion chemical ionization mass spectrometry. MRL-MpJFASlpr (MRL/lpr) and NZB/W mice were divided into three groups and given either L-NMMA, L-N6-iminoethyl-lysine (L-NIL), or distilled water for 2 weeks. Urine NOX and 8-iso-PGF2alpha were determined after 2 weeks.

RESULTS

L-NMMA reduced both urine NOX and 8-iso-PGF2alpha levels in a dose-dependent fashion in NZB/W and MRL/lpr mice. Urine NOX and 8-iso-PGF2alpha levels were highly correlated. Both specific (L-NIL) and nonspecific (L-NMMA) iNOS inhibition reduced urine NOX and 8-iso-PGF2alpha levels in both models of murine PLN.

CONCLUSION

These findings suggest that iNOS activity is a major source of reactive oxidant stress in these models of murine PLN. Future studies will address the pathogenic role of reactive oxygen stress in PLN.

Interferon-β: A Therapeutic for Autoimmune Lupus in MRL-Faslpr Mice

Type I interferons are associated with lupus. Genes that are regulated by IFN-alpha are upregulated in pediatric lupus patients. Gene deletion of the IFN-alpha/beta receptor in experimental lupus-like NZB mice results in reduced disease activity. Conversely, IFN-beta is a well-established treatment in multiple sclerosis, another autoimmune disease. For determining whether IFN-beta treatment is harmful or beneficial in lupus, MRL-Fas(lpr) mice were injected with this type I IFN. Treatment was initiated in MRL-Fas(lpr) mice with mild and advanced disease. IFN-beta was highly effective in prolonging survival and ameliorating the clinical (renal function, proteinuria, splenomegaly, and skin lesions), serologic (autoantibodies and cytokines), and histologic parameters of the lupus-like disease in mice that had mild and advanced disease. Several underlying mechanisms of IFN-beta therapy involving cellular (decreased T cell proliferation and infiltration of leukocytes into the kidney) and humoral (decrease in IgG3 isotypes) immune responses and a reduction in nephrogenic cytokines were identified. In conclusion, IFN-beta treatment of lupus nephritis in MRL-Fas(lpr) mice is remarkably beneficial and suggests that IFN-beta may be an appealing therapeutic candidate for subtypes of human lupus.

Identification and validation of the mitochondrial F1F0-ATPase as the molecular target of the immunomodulatory benzodiazepine Bz-423

Bz-423 is a 1,4-benzodiazepine that suppresses disease in lupus-prone mice by selectively killing pathogenic lymphocytes, and it is less toxic compared to current lupus drugs. Cells exposed to Bz-423 rapidly generate O(2)(-) within mitochondria, and this reactive oxygen species is the signal initiating apoptosis. Phage display screening revealed that Bz-423 binds to the oligomycin sensitivity conferring protein (OSCP) component of the mitochondrial F(1)F(0)-ATPase. Bz-423 inhibited the F(1)F(0)-ATPase in vitro, and reconstitution experiments demonstrated that inhibition was mediated by the OSCP. This target was further validated by generating cells with reduced OSCP expression using RNA interference and studying the sensitivity of these cells to Bz-423. Our findings help explain the efficacy and selectivity of Bz-423 for autoimmune lymphocytes and highlight the OSCP as a target to guide the development of novel lupus therapeutics.

Strong association of a functional polymorphism in the monocyte chemoattractant protein 1 promoter gene with lupus nephritis

OBJECTIVE

Lupus nephritis (LN) is a major contributor to morbidity and mortality in patients with systemic lupus erythematosus (SLE). There is evidence that polymorphisms in the genes of inflammatory mediators may predispose to the development of LN in patients with SLE. In this study, we examined the role of a functional monocyte chemoattractant protein 1 (MCP-1) polymorphism in SLE and LN.

METHODS

DNA and paired urine and serum samples were obtained from 134 SLE patients (> or =4 American College of Rheumatology criteria for SLE; 49 with and 85 without LN) and 118 controls. MCP-1 genomic variants were detected by polymerase chain reaction followed by restriction enzyme-fragment analysis. Urinary and serum MCP-1 levels and MCP-1 production by peripheral blood macrophages were measured by enzyme-linked immunosorbent assay.

RESULTS

The A/A genotype was more common in controls than in SLE patients (P = 0.0002), whereas both the A/G (P = 0.009) and G/G (P = 0.0212) genotypes were more frequent in SLE patients. The A/A genotype was observed in only 23% of the patients with LN compared with 58% of those without LN (P < 0.0001). MCP-1 production by peripheral blood mononuclear cells from patients with the A/G and G/G phenotypes was markedly higher than the production by cells from patients with the A/A genotype. Urinary levels of MCP-1 were significantly higher in patients with LN.

CONCLUSION

These results suggest that an A/G or G/G genotype may predispose to the development of SLE and further indicate that SLE patients with these genotypes may be at higher risk of developing LN. Moreover, measurement of urinary levels of MCP-1 may be a useful tool for the detection and management of LN.

Immune deposition of C1q and anti-C1q antibodies in the kidney is dependent on the presence of glomerular IgG

Anti-C1q autoantibodies are found frequently in patients with Systemic Lupus Erythematosus (SLE) and several studies indicate that these autoantibodies are associated with renal involvement. We have shown earlier that administration of anti-C1q antibodies to normal BALB/c mice results in the deposition of these antibodies and C1q in the kidney. In the present study we have investigated which factors are essential for this C1q-anti-C1q deposition. Injection of anti-C1q antibodies in C57BL/6 mice results in deposition of both C1q and anti-C1q in glomeruli, while administration of equal concentrations of anti-C1q to immunoglobulin deficient Rag2-/- mice did not result in deposition of anti-C1q antibodies. Analysis of renal sections of naive Rag2-/- mice revealed absence of mouse IgG and C1q in the glomeruli, while circulating C1q was within normal levels. Reconstitution of Rag2-/- mice with IgG, either by injection with purified mouse IgG or by splenocyte transfer, resulted in restored localization of mouse IgG together with C1q in the kidney. Subsequent injection of anti-C1q antibodies in these IgG reconstituted mice resulted in clear deposition of C1q together with anti-C1q in the kidneys comparable to that found in C57BL/6 mice receiving anti-C1q. We propose that the continuous presence of serum derived non-immune IgG in the glomerulus serves as a target for low affinity interactions with C1q, which then can serve as antigen for anti-C1q antibodies. Therefore we hypothesize that high and fluctuating levels of IgG as observed in patients with SLE may contribute to flares of renal inflammation in those patients with anti-C1q autoantibodies.

Diagnostic and prognostic significance of anti-C1q antibodies in systemic lupus erythematosus

PURPOSE OF REVIEW

The presence of a wide variety of autoantibodies is a characteristic finding in systemic lupus erythematosus. Autoantibodies against nuclear proteins, such as anti-nuclear and anti-double-stranded DNA antibodies, are used as diagnostic markers in systemic lupus erythematosus. Renal involvement is frequently found in systemic lupus erythematosus and is an important risk factor for death. Therefore, markers for the diagnosis and follow-up of nephritis are very important. Anti-C1q autoantibodies are strongly associated with renal involvement in systemic lupus erythematosus. This study will review recent findings on the pathogenic role and clinical importance of anti-C1q antibodies in lupus nephritis.

RECENT FINDINGS

Recent clinical studies have clearly emphasized the diagnostic relevance of anti-C1q autoantibody levels in patients with lupus nephritis. With a possible negative predictive value of 100%, anti-C1q autoantibodies are the only exclusive antibodies associated with the involvement of a single organ in systemic lupus erythematosus. Next to the clinical findings, the pathogenic significance of anti-C1q antibodies has been shown in an animal model. The deposition of autologous C1q in healthy glomeruli of mice after the infusion of anti-C1q antibodies induces moderate tissue damage.

SUMMARY

The latest insight into the pathogenesis of anti-C1q autoantibodies in the development of lupus nephritis and the recently demonstrated clinical importance of anti-C1q autoantibodies for the diagnosis of lupus nephritis support the value of further investigations. New diagnostic methods for the detection of anti-C1q and an accurate follow-up of antibody levels might be of use in clinical practice.