Mechanisms of progression of renal damage in lupus nephritis: pathogenesis of renal scarring

Identifying Key Genes and Their Associated Molecular Pathways in Lupus Nephritis-Osteoporosis: An In-Silico Analysis

Nephritis and osteoporosis are debilitating medical conditions that significantly impact human health and reduce quality of life. To develop potential therapeutic strategies for these disorders necessitates understanding the genetic and molecular mechanisms. Here, we employed bioinformatics techniques purposed to find key genes and associated pathways responsible for nephritis-osteoporosis comorbidity. Six microarray datasets of systemic lupus erythematosus (SLE) and osteoporosis were retrieved from the Gene Expression Omnibus (GEO) database. Post normalization of data sets LIMMA package was utilized for differential expression analysis, among the datasets 44 differentially expressed genes (DEGs) were identified. The identified 44 genes were further analyzed for gene ontology (GO) where it was found that these genes are involved in defense response, organism interactions, and response to external stimuli. In predicting the molecular function, they were involved in several biological processes including binding to lipopolysaccharides and having peptidase and hydrolase activities. Firstly, the identified genes were primarily associated with certain granules such as specific granules and secretory granules in the aspect of cellular components. Enrichment analysis pointed out the potential pathways linked to the immune system, neutrophil degranulation, innate immunity, and immune response to tuberculosis. To examine interactions among DEGs, a complex protein-protein interaction (PPI) network was built, resulting in the identification of seven hub genes, CXCL8, ELANE, LCN2, MMP8, IFIT1, MX1, and ISG15. The study suggests that these elucidated hub genes might have high potential to be exploited as promising biomarkers and therapeutic targets in nephritis-osteoporosis. Taken together, this study provided deeper insights into the genetic and molecular basis for the comorbidity of nephritis and osteoporosis.

Predicting diagnostic gene expression profiles associated with immune infiltration in patients with lupus nephritis

Objective

To identify potential diagnostic markers of lupus nephritis (LN) based on bioinformatics and machine learning and to explore the significance of immune cell infiltration in this pathology.

Methods

Seven LN gene expression datasets were downloaded from the GEO database, and the larger sample size was used as the training group to obtain differential genes (DEGs) between LN and healthy controls, and to perform gene function, disease ontology (DO), and gene set enrichment analyses (GSEA). Two machine learning algorithms, least absolute shrinkage and selection operator (LASSO) and support vector machine-recursive feature elimination (SVM-RFE), were applied to identify candidate biomarkers. The diagnostic value of LN diagnostic gene biomarkers was further evaluated in the area under the ROC curve observed in the validation dataset. CIBERSORT was used to analyze 22 immune cell fractions from LN patients and to analyze their correlation with diagnostic markers.

Results

Thirty and twenty-one DEGs were screened in kidney tissue and peripheral blood, respectively. Both of which covered macrophages and interferons. The disease enrichment analysis of DEGs in kidney tissues showed that they were mainly involved in immune and renal diseases, and in peripheral blood it was mainly enriched in cardiovascular system, bone marrow, and oral cavity. The machine learning algorithm combined with external dataset validation revealed that C1QA(AUC = 0.741), C1QB(AUC = 0.758), MX1(AUC = 0.865), RORC(AUC = 0.911), CD177(AUC = 0.855), DEFA4(AUC= 0.843)and HERC5(AUC = 0.880) had high diagnostic value and could be used as diagnostic biomarkers of LN. Compared to controls, pathways such as cell adhesion molecule cam, and systemic lupus erythematosus were activated in kidney tissues; cell cycle, cytoplasmic DNA sensing pathways, NOD-like receptor signaling pathways, proteasome, and RIG-1-like receptors were activated in peripheral blood. Immune cell infiltration analysis showed that diagnostic markers in kidney tissue were associated with T cells CD8 and Dendritic cells resting, and in blood were associated with T cells CD4 memory resting, suggesting that CD4 T cells, CD8 T cells and dendritic cells are closely related to the development and progression of LN.

Conclusion

C1QA, C1QB, MX1, RORC, CD177, DEFA4 and HERC5 could be used as new candidate molecular markers for LN. It may provide new insights into the diagnosis and molecular treatment of LN in the future.

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

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

Urinary biomarkers in lupus nephritis

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

The current role for clinical and renal histological findings as predictor for outcome in Australian patients with lupus nephritis

Objectives To investigate the current demographic, clinical and histological characteristics of patients with lupus nephritis (LN) in Western Australia (WA) with regards to their predictive value for patient and renal outcome. Methods Retrospective study of adult systemic lupus erythematosus (SLE) patients with a first renal biopsy demonstrating LN between 1997 and 2017 at a metropolitan tertiary hospital in WA. Clinical data were collected at baseline and last follow-up with renal biopsy findings classified by International Society of Nephrology (ISN) criteria. Annual incidence rates (AIRs)/100,000, Kaplan-Meyer curves and Cox regression hazard ratio for independent predictors for patient and renal survival were applied. Results The AIR was 3.3, 3.1 and 0.4 for Asian ( n = 29), Indigenous Australian (IA) ( n = 11) and Caucasian ( n = 43) patients, respectively ( p < 0.01). There was no significant subgroup difference regarding ISN class (proliferative 66%, membranous 19%, mesangial 15%), levels of proteinuria (median PCR 300 mg/mmol) or frequency of raised creatinine (31%), anti-dsDNA antibody (89%) or hypocomplementaemia (88%). Treatment included corticosteroids (91%), cyclophosphamide (30%), mycophenolate (67%) and antihypertensive drugs (67%). Five- (81%) and 10-year (70%) survival was lower for IAs than for Caucasians and Asians (95% each at both time points) ( p = 0.016). Five- and 10-year renal survival (endpoint renal replacement therapy (RRT)) was 86% and 64% for IA vs 100% for Asian, 100% and 96% for Caucasian patients ( p = 0.02). IA background was the only independent predictor for poor patient survival and together with male gender also for renal survival. Only 25% of all patients remained free of any organ damage with non-renal damage observed in 53% of survivors. Conclusions LN incidence in WA was 0.75/100,000 with the lowest rate observed in Caucasians. While Asian patients have the same favourable outlook as Caucasians, the outcome is much bleaker for IA patients. Other clinical and histological findings did not predict outcomes, and importantly more than half of all surviving patients accrued non-renal damage.

Procyanidin B2 prevents lupus nephritis development in mice by inhibiting NLRP3 inflammasome activation

Lupus nephritis (LN) is a multifactorial event that contributes to the long-term mortality of systemic lupus erythematosus (SLE). Activation of NLRP3 inflammasome has been known to play a role in SLE pathogenesis. We evaluated the renal protection effects of procyanidin B2 (PCB2) and the involvement of NLRP3 in a mouse model involving MRL/lpr and MRL/MpJ mice. Kidney injury was evaluated by measuring the renal clinical and pathological features, renal immune complex deposition, and serum anti-double-stranded (anti-dsDNA) Abs. ELISA and Western blotting were used to detect NLRP3 inflammasome activation and IL-1β/IL-18 production. NLRP3 gene silencing was introduced into MRL/lpr mice by short hairpin RNA, and the renal damage was compared with the treatment of PCB2. PCB2 remarkably reduced renal damage in MRL/lpr mice, reflected by the reduced proteinuria, and serum levels of blood urea nitrogen and creatinine, as well as pathological features with less renal injury. PCB2 significantly reduced renal immune complex deposition and serum anti-dsDNA levels, notably inhibited the NLRP3 inflammasome activation, and reduced the renal and serum levels of IL-1β and IL-18 in MRL/lpr mice compared with those of NLRP3 gene-silenced MRL-lpr mice. PCB2 significantly suppressed LN in MRL-lpr mice by inhibiting the activation of NLRP3 inflammasome and subsequent IL-1β and IL-18 production. This finding explores a novel mechanism by which procyanidin exerts inflammatory suppression effects and its clinical benefits in LN prevention.

Reno-protective effect and mechanism study of Huang Lian Jie Du Decoction on lupus nephritis MRL/lpr mice

BACKGROUND

Huang Lian Jie Du Decoction (HLJDD), a very famous traditional Chinese medicinal prescription, has been used for heat dissipation and detoxification in China. This study was aimed to evaluate the reno-protective effects of HLJDD against lupus nephritis (LN) in vivo in MRL/lpr mice.

METHODS

Animals were administered orally every day for eight consecutive weeks except the mice of normal group and model group. Organ indexes, serum interleukin-6 (IL-6), interleukin-10 (IL-10), interferon-gamma (IFN-γ) and the anti-double stranded DNA (anti-dsDNA) antibody were tested, respectively. Creatinine (Cr), blood urea nitrogen (BUN) and urine protein were measured for renal function evaluation. The expression of phosphorylated signal transducer and activator of transcription 3 (p-STAT 3) in kidney tissue was observed by western blot (WB) and immunohistochemical (IHC) method. Meanwhile, histopathological changes in the renal were studied by hematoxylin-eosin (H&E) staining.

RESULTS

The mice of HLJDD-treated group exhibited a significant reduced mortality (p < 0.05), serum anti-dsDNA level (p < 0.05) and renal immune complex deposition (p < 0.05), compared with the untreated MRL/lpr mice. In addition, HLJDD treatment remarkably reduced the levels of BUN, Cr, proteinuria (p < 0.01) and the levels of inflammatory cytokines such as IL-6, IL-10 and IFN-γ (p < 0.01). Moreover, HLJDD significantly suppressed the phosphorylations of STAT 3 (p < 0.05) and the renal pathological changes.

CONCLUSIONS

The study implied that HLJDD may be a potential agent for the therapy of LN, and the down-regulated p-STAT 3 expression suggesting that it may be one of the LN therapy targets for HLJDD.

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.

Transforming growth factor beta 1 in children with systemic lupus erythematosus: a possible relation with clinical presentation of lupus nephritis

Plasma and urinary (latent and active) TGF-β1 levels were assessed in 32 children with active lupus and compared to 15 healthy controls of matched age and sex. Plasma latent and active TGF-β1 levels in children with active disease were significantly lower than controls ( P = 0.004 and P < 0.001 respectively). Plasma active TGF-β1 correlated negatively with Systemic Lupus Erythematosus Disease Activity Index ( r =-0.38, P = 0.03). On the contrary, urinary latent and active TGF-β1 levels in children with active disease were significantly higher than controls ( P < 0.001 and P = 0.003 respectively). Urinary active TGF-β1 levels correlated positively with Anti-ds DNA titre ( r = 0.42, P = 0.015) and negatively with serum C3 levels ( r =-0.48, P = 0.005). Patients with symptomatic nephritis had significantly elevated urinary active TGF-β1 levels in comparison to those with silent nephritis ( P = 0.008). From this data we conclude that lowered plasma TGF-β1 levels may be a feature of systemic immune dysfunction in children with active lupus while increased renal production of active TGF-β1 seems to have a role in the clinical presentation of lupus nephritis.

Specific HDAC6 inhibition by ACY-738 reduces SLE pathogenesis in NZB/W mice

We sought to determine if a selective HDAC6 inhibitor (ACY-738) decreases disease in NZB/W mice. From 22 to 38weeks-of-age, mice were injected intraperitoneally with 5 or 20mg/kg of ACY-738, or vehicle control. Body weight and proteinuria were measured every 2weeks, while sera anti-dsDNA, Ig isotypes, and cytokine levels were measured every 4weeks. Kidney disease was determined by evaluation of sera, urine, immune complex deposition, and renal pathology. Flow cytometric analysis assessed thymic, splenic, bone marrow, and peripheral lymphocyte differentiation patterns. Our results showed HDAC6 inhibition decreased SLE disease by inhibiting immune complex-mediated glomerulonephritis, sera anti-dsDNA levels, and inflammatory cytokine production and increasing splenic Treg cells. Inhibition of HDAC6 increased the percentage of cells in the early-stage developmental fractions of both pro- and pre-B cells. These results suggest that specific HDAC6 inhibition may be able to decrease SLE disease by altering aberrant T and B cell differentiation.

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.

Class I and II histone deacetylase inhibition by ITF2357 reduces SLE pathogenesis in vivo

We sought to determine if a specific class I and II HDAC inhibitor (ITF2357) was able to decrease disease in lupus-prone NZB/W mice through regulation of T cell profiles. From 22 to 38 weeks-of-age, NZB/W and non-lupus NZW mice were treated with ITF2357 (5 mg/kg or 10 mg/kg), or vehicle control. Body weight and proteinuria were measured every 2 weeks, while sera anti-dsDNA and cytokine levels were measured every 4 weeks. Kidney disease was determined by sera IgG levels, immune complex deposition, and renal pathology. T lymphocyte profiles were assessed using flow cytometric analyses. Our results showed that NZB/W mice treated with the 10 mg/kgof ITF2357 had decreased renal disease and inflammatory cytokines in the sera. Treatment with ITF2357 decreased the Th17 phenotype while increasing the percentage of Tregs as well as Foxp3 acetylation. These results suggest that specific HDAC inhibition may decrease disease by altering T cell differentiation and acetylation.

MicroRNA-let-7a promotes E2F-mediated cell proliferation and NFκB activation in vitro

Epigenetic factors, including altered microRNA (miRNA) expression, may contribute to aberrant immune cell function in systemic lupus erythematosus (SLE). MiRNA-let-7a (let-7a) has been shown to directly alter cell cycle progression and proinflammatory cytokine production. Due to the crucial role of let-7a in cell division and inflammation, we investigated let-7a-mediated proliferation and NFκB translocation in J774A.1 macrophages and MES 13 mesangial cells in vitro. In immune-stimulated cells transfected with let-7a, cell proliferation was significantly increased over time. There was a significant increase in the number of immune-stimulated cells in S and G2 phases. Immune-stimulated cells overexpressing let-7a had increased nuclear translocation of NFκB. Bioinformatical analysis revealed that the E2F family, critical regulators of the G1-S transition, has potential binding sites for let-7a in their mRNA transcripts. Let-7a overexpression significantly increased the expression of the cell cycle activator E2F2 and increased retinoblastoma protein (Rb) phosphorylation in immune-stimulated cells. The cell cycle inhibitor E2F5 was significantly decreased in let-7a-transfected cells that were immune-stimulated. Bioinformatical analysis revealed E2F2 and NFκB are transcription factors predicted to regulate the let-7a promoter. We analyzed transcriptional regulation of let-7a by real-time RT-PCR using chromatin immunoprecipitation with E2F2 and NFκB antibodies. There was an increase in E2F2 and NFκB binding in DNA enriched for the let-7a promoter in immune-stimulated cells. Silencing E2F2 or NFκB significantly decreased let-7a expression and IL-6 production in immune-stimulated cells. Taken together, our results suggest that overexpression of let-7a may contribute to hyperplasia and the proinflammatory response in SLE.

Nrf2 suppresses lupus nephritis through inhibition of oxidative injury and the NF-κB-mediated inflammatory response

The generation of reactive oxygen species plays a pivotal role in both acute and chronic glomerular injuries in patients with lupus nephritis. Since the transcription factor Nrf2 is a major regulator of the antioxidant response and is a primary cellular defense mechanism we sought to determine a role of Nrf2 in the progression of lupus nephritis. Pathological analyses of renal biopsies from patients with different types of lupus nephritis showed oxidative damage in the glomeruli, accompanied by an active Nrf2 antioxidant response. A murine lupus nephritis model using Nrf2+/+ and Nrf2−/− mice was established using pristine injection. In this model, Nrf2−/− mice suffered from greater renal damage and had more severe pathological alterations in the kidney. In addition, Nrf2+/+ mice showed ameliorative renal function when treated with sulforaphane, an Nrf2 inducer. Nrf2−/− mice had higher expression of TGFβ1, fibronectin and iNOS. In primary mouse mesangial cells, the nephritogenic monoclonal antibody R4A activated the NF-κB pathway and increased the level of reactive oxygen species, iNOS, TGFβ1 and fibronectin. Knockdown of Nrf2 expression aggravated all aforementioned responses induced by R4A. Thus, these results suggest that Nrf2 improves lupus nephritis by neutralizing reactive oxygen species and by negatively regulating the NF-κB and TGFβ1 signaling pathways.

Urinary monocyte chemotactic protein-1 and transforming growth factor-β in systemic lupus erythematosus

The purpose of this investigation was to assess the correlation of two biomarkers with the occurrence of renal flares in systemic lupus erythematosus (SLE). Urine levels of monocyte chemotactic protein-1 (MCP-1) and transforming growth factor beta (TGF-β) were measured at baseline, and at two and four months in five groups of patients: 25 lupus nephritis patients with active disease (active LN), 10 lupus nephritis patients with SLE in remission (remission LN), 25 patients with clinical active SLE and without nephritis (active NLN), 10 patients without nephritis with SLE in remission (remission NLN) and 10 healthy controls. We used repeated measurement and ANOVA with Duncan's post hoc to analyze the data; the urine level of the two proteins could distinguish the groups based on the existence of lupus nephritis and/or activity of SLE disease. Furthermore we performed receiver operating curve analysis to identify a cutoff point with a good sensitivity and specificity to diagnose lupus nephritis with either one of the urine proteins. Finally the samples from active LN were grouped according to whether they were Class IV or other classes. Baseline urinary MCP-1, but not TGF-β, was significantly different between the classes. Further investigation into the use of these cytokines in a prospective study is needed to determine their capacity as diagnostic tools for renal flares.

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

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

Anti-DNA antibody induction of protein kinase C phosphorylation and fibronectin synthesis in human and murine lupus and the effect of mycophenolic acid

OBJECTIVE

To examine fibronectin (FN) expression in human lupus nephritis and the effect of anti-DNA antibodies on transforming growth factor beta1 (TGFbeta1) and FN synthesis in cultured human mesangial cells. The effects of mycophenolic acid (MPA) on this pathway, and the effects of mycophenolate mofetil (MMF) treatment in (NZB x NZW)F(1)/J mice were also studied.

METHODS

Immunohistochemical analyses of renal biopsy samples from patients with active diffuse proliferative lupus nephritis were performed. Cultured human mesangial cells were incubated with human polyclonal anti-DNA antibodies, with or without MPA. (NZB x NZW)F(1)/J mice with active nephritis were randomized to receive either MMF (100 mg/kg/day) or vehicle treatment for 12 weeks.

RESULTS

Glomerular FN expression was increased in patients with lupus nephritis, and it colocalized with IgG deposition. Anti-DNA antibodies induced protein kinase Calpha (PKCalpha), PKCbetaI, and PKCbetaII activation, increased levels of bioactive TGFbeta1, and increased FN synthesis in human mesangial cells (P < 0.001 for each comparison versus control conditions). Pretreatment of anti-DNA antibodies with exogenous DNA reduced their cellular binding and abrogated their induction of TGFbeta1 and FN synthesis. Inhibition of PKC activation in human mesangial cells prior to anti-DNA antibody stimulation had no effect on cell proliferation, but resulted in significantly reduced antibody-mediated TGFbeta1 secretion and FN synthesis. MPA treatment down-regulated PKCalpha, PKCbetaI, and PKCbetaII phosphorylation, reduced levels of TGFbeta1 bioactivation, and decreased FN synthesis and deposition into the extracellular matrix. MMF treatment in (NZB x NZW)F(1)/J mice resulted in a reduction in glomerular IgG deposition, PKC activation, and FN expression, as well as an amelioration of proteinuria.

CONCLUSION

Human polyclonal anti-DNA antibodies induce TGFbeta1 and FN synthesis in human mesangial cells through PKC activation, which is inhibited by MPA.

Poly(ADP-ribose) polymerase-1 regulates the progression of autoimmune nephritis in males by inducing necrotic cell death and modulating inflammation

Necrotic lesions and necrotic cell death characterize severe autoimmune nephritides, and contribute to local inflammation and to progression of the disease. Poly(ADP-ribose) polymerase-1 (PARP-1), a DNA repair enzyme, is involved in the induction of necrosis and is a key player in the acute and chronic inflammation. Therefore, we hypothesized that PARP-1 controls the severity of nephritis by mediating the induction of necrosis in the kidney. We used lupus and anti-glomerular basement membrane models of nephritis to determine the effects of PARP-1 on the inflammatory response in the kidney. We show in this study that PARP-1 is indeed activated during the course of glomerulonephritis. We also show that the absence of PARP-1 or its pharmacological inhibition results in milder nephritis, with lower blood urea nitrogen levels, reduced necrotic lesions, and higher survival rates. The relevance of PARP-1 showed a strong male sex specificity, and treatment of male mice with 17beta-estradiol prolonged their survival during the course of nephritis. PARP-1 also regulated TNF-alpha expression and up-regulation of adhesion molecules, further supporting a role of PARP-1 in the inflammatory process within the kidney. Our results demonstrate that PARP-1 activation and consequent necrotic cell death play an important role in the pathogenesis of male nephritis, and suggest that PARP-1 can be a novel therapeutic target in glomerulonephritis.

Dual roles of immunoregulatory cytokine TGF-beta in the pathogenesis of autoimmunity-mediated organ damage

Ample evidence suggests a role of TGF-beta in preventing autoimmunity. Multiorgan inflammatory disease, spontaneous activation of self-reactive T cells, and autoantibody production are hallmarks of autoimmune diseases, such as lupus. These features are reminiscent of the immunopathology manifest in TGF-beta1-deficient mice. In this study, we show that lupus-prone (New Zealand Black and White)F(1) mice have reduced expression of TGF-beta1 in lymphoid tissues, and TGF-beta1 or TGF-beta1-producing T cells suppress autoantibody production. In contrast, the expression of TGF-beta1 protein and mRNA and TGF-beta signaling proteins (TGF-beta receptor type II and phosphorylated SMAD3) increases in the target organs, i.e., kidneys, of these mice as they age and develop progressive organ damage. In fact, the levels of TGF-beta1 in kidney tissue and urine correlate with the extent of chronic lesions that represent local tissue fibrosis. In vivo TGF-beta blockade by treatment of these mice with an anti-TGF-beta Ab selectively inhibits chronic fibrotic lesions without affecting autoantibody production and the inflammatory component of tissue injury. Thus, TGF-beta plays a dual, seemingly paradoxical, role in the development of organ damage in multiorgan autoimmune diseases. According to our working model, reduced TGF-beta in immune cells predisposes to immune dysregulation and autoantibody production, which causes tissue inflammation that triggers the production of anti-inflammatory cytokines such as TGF-beta in target organs to counter inflammation. Enhanced TGF-beta in target organs, in turn, can lead to dysregulated tissue repair, progressive fibrogenesis, and eventual end-organ damage.

The role of aldosterone blockade in murine lupus nephritis

Background

The purpose of this study was to examine the effect of aldosterone receptor blockade on the immunopathogenesis and progression of nephritis in the (NZB × NZW) F₁ murine lupus model.

Methods

Female NZB/W F₁ mice (11 weeks old) were treated daily with 25 or 50 mg/kg oral spironolactone or vehicle. Proteinuria, renal function, and serum autoantibody levels were monitored. Renal histopathology, immune complex deposition, and immunohistochemistry were analyzed at various time points. Targeted microarray analysis was performed on renal tissue, with subsequent real-time PCR analysis of several differentially expressed genes.

Results

Treatment with spironolactone was well tolerated by the mice throughout the course of their disease progression, with no significant differences in azotemia or serum potassium levels between vehicle-treated and spironolactone-treated animals. By 36 weeks of age, fewer spironolactone-treated mice developed nephrotic range proteinuria as compared with the control mice (control 70.8%, 25 mg/kg spironolactone 51.3%, and 50 mg/kg spironolactone 48.6%). Compared with control mice, mice treated with 25 mg/kg spironolactone had significantly lower serum anti-single-stranded DNA levels (2,042 μg/ml versus 1,036 μg/ml; P = 0.03) and anti-double-stranded DNA levels (3,433 μg/ml versus 614 μg/ml; P = 0.05). Spironolactone-treated mice exhibited decreased histopathologic evidence of inflammation and tissue damage, as compared with control mice. Additionally, spironolactone treatment resulted in decreased expression in the kidney of several inflammatory and proapoptotic genes, including those encoding interferon-γ, B lymphocyte stimulator (BlyS), tumor necrosis factor related apoptosis inducing ligand (TRAIL), tumor necrosis factor related weak inducer of apoptosis (TWEAK), and Fas ligand.

Conclusion

Aldosterone receptor blockade is safe and well tolerated in progressive murine lupus nephritis, and it results in decreased levels of clinical proteinuria, lower serum levels of autoantibodies, and decreased kidney damage. It appears to modulate inflammatory changes during the progression of glomerulonephritis and may also have a previously undescribed role in attenuating apoptosis.

Urinary N-acetyl-beta-D-glucosaminidase (NAG) in lupus nephritis and rheumatoid arthritis

Increased activity of urinary N-acetyl-beta-D-glucosaminidase (NAG) can be used as an early indicator of damage to the tubular epithelium. Systemic lupus erythematosus (SLE) is a multisystem autoimmune rheumatic disease. Nephritis is known as the most serious complication of SLE and the strongest predictor of poor outcome. In this study urinary NAG excretion was investigated in 24 SLE patients with normal renal function (serum creatinine < or =1.2 mg/dL) and the results were compared with those from 26 untreated patients with rheumatoid arthritis (RA) and 27 healthy controls. The SLE patients were divided into two groups according to their urinary total protein levels: group A consisted of 16 patients with < or =3.5 g/day proteinuria, and group B consisted of eight patients with nephrotic-range proteinuria (>3.5 g/day). Serum and urinary creatinine, total urinary protein levels, and urinary NAG excretion were measured in patients with SLE and RA. In addition, serum C3 and C4 levels were determined in the SLE patients. Renal biopsies were performed in all of the SLE patients. Glomerular lesions were classified according to WHO criteria for lupus nephritis (LN) I-V. The Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) was used to assess disease activity. Urinary NAG excretion was significantly higher in the SLE groups than in the healthy controls (P<0.001). In urinary NAG excretion there was also significant difference between SLE groups and RA patients (P<0.001). However, there was no significant difference in NAG excretion between the RA and control groups (P=0.062). Urinary NAG excretion was significantly higher (P<0.05) in group B compared to group A. There were no differences in SLEDAI scores, ages, and serum creatinine levels between study groups (P=0.601, P=0.285, P=0.669, respectively). Elevated SLEDAI values and hypocomplementemia were detected more often in younger patients (P<0.010, r=-0.529 and P<0.010, r=-0.569, respectively). There was a strong positive correlation between proteinuria and urinary NAG activity (P<0.001, r=0.759). These results suggest that the determination of urinary NAG activity may be a useful supplement to the routine biochemical analysis performed on the urine in cases of SLE.

Deficiency of P-selectin or P-selectin glycoprotein ligand-1 leads to accelerated development of glomerulonephritis and increased expression of CC chemokine ligand 2 in lupus-prone mice

The selectins and their ligands mediate leukocyte rolling on endothelial cells, the initial step in the emigration cascade leading to leukocyte infiltration of tissue. These adhesion molecules have been shown to be key promoters of acute leukocyte emigration events; however, their roles in the development of long-term inflammatory responses, including those that occur during chronic inflammatory diseases such as systemic lupus erythematosus, are unclear. To assess participation of P-selectin in such disorders, we studied the progression of systemic lupus erythematosus-like disease in P-selectin-deficient and control MRL/MpJ-Fas(lpr) (Fas(lpr)) mice. Surprisingly, we found that P-selectin deficiency resulted in significantly earlier mortality, characterized by a more rapid development of glomerulonephritis and dermatitis. Expression of CCL2 (MCP-1) was increased in the kidneys of P-selectin mutant mice and in supernatants of LPS-stimulated primary renal endothelial cell cultures from these mice. A closely similar phenotype, including elevated renal expression of CCL2, was also observed in Fas(lpr) mice deficient in the major P-selectin ligand, P-selectin glycoprotein ligand-1. These results indicate that P-selectin and P-selectin glycoprotein ligand-1 are not required for leukocyte infiltration and the development of autoimmune disease in Fas(lpr) mice, but rather expression of these adhesion molecules is important for modulating the progression of glomerulonephritis, possibly through down-regulation of endothelial CCL2 expression.

Measurement of urinary chemokine and growth factor messenger RNAs: A noninvasive monitoring in lupus nephritis

Noninvasive molecular tests of urine cells have been developed to monitor the activity of kidney diseases. We evaluate whether measurement of urinary messenger RNA (mRNA) levels of chemokine and growth factor genes could distinguish between diffuse proliferative lupus nephritis (class IV LN) and others and whether it is able to predict the response to therapy. Prebiopsy urine samples were collected from 26 LN patients. Urine specimens were serially collected over a period of 6 months from class IV LN patients who were receiving standard immunosuppressive treatments. Urinary interferon-producing protein 10 and its CXC chemokine receptor (CXCR)3, transforming growth factor-beta (TGF-beta), and vascular endothelial growth factor (VEGF) mRNA levels were analyzed by quantitative real-time polymerase chain reactions. Levels of chemokine or growth factor mRNAs in urine could distinguish class IV LN from others, with a sensitivity of 85% and a specificity of 94%. The receiver-operative characteristic curve demonstrated that urine mRNA levels of these genes could identify active class IV LN with an accuracy greater than the current available clinical markers, namely systemic lupus erythematosus (SLE) disease activity index, proteinuria, renal function, or urinalysis. A significant reduction of interferon-producing protein 10 (IP-10), CXCR3, TGF-beta, and VEGF mRNA levels from baselines was observed in patients who responded to therapy, whereas the levels tended to increase in those who resisted to treatment. Measurement of urinary chemokine and growth factor mRNAs can precisely distinguish class IV LN from others. Temporal association between these markers and therapeutic response is demonstrated. This noninvasive approach serves as a practical tool in diagnosis and management of LN.

Cytokine expression in lupus kidneys

Although far from complete, the picture of cytokines present in systemic lupus erythematosus (SLE) glomerulonephritis is already complex. Proinflammatory cytokines, such as TNF, IL-6, IL-1, and IL-18 are upregulated, as are both Th1 and Th2 cytokines, with different implications. In many instances, the local effects may be different from the systemic immunoregulatory ones. For some proinflammatory cytokines, and TNF in particular, the local proinflammatory ones may be more relevant to the disease. This may help solve discrepancies between different murine models of the disease and provide a better rationale for targeting certain cytokines in human SLE.

An ACE inhibitor reduces Th2 cytokines and TGF-beta1 and TGF-beta2 isoforms in murine lupus nephritis

BACKGROUND

Angiotensin-converting enzyme (ACE) inhibitors, such as captopril, are used to control hypertension. In patients and animals with primary nephropathies, these agents improve renal function more than that would be expected from their control of hypertension. Here, we examine the effects of treatment with captopril on lupus nephritis and discuss the potential mechanism(s) by which this agent exerts its renoprotective effects.

METHODS

Lupus-prone, NZB/NZW F1 and MRL-lpr/lpr, mice were treated with captopril or with a control antihypertensive agent, verapamil. Mice were monitored for nephritis, and their sera and tissues analyzed for cytokine and transforming growth factor-beta (TGF-beta) expression.

RESULTS

Captopril treatment delayed the onset of proteinuria when administered to prenephritic mice, whereas verapamil did not. Captopril treatment also retarded disease progression when given to lupus mice that had early disease, and even reversed severe proteinuria in at least some older animals with advanced disease. It reduced chronic renal lesions, but had no effect on autoantibody production. The improvement in renal disease correlated with reduced TGF-beta expression, particularly of the TGF-beta1 and TGF-beta2 isoforms, in the kidneys. Interestingly, in vivo or in vitro exposure to captopril reduced splenic levels of type 2 cytokines, interleukin (IL)-4 and IL-10, suggesting a possible role of the immune system in captopril-mediated disease modulation.

CONCLUSION

Since type 2 cytokines are known to promote lupus glomerulosclerosis, decreased IL-4 and IL-10 production in captopril-treated mice may be related to this agent's renoprotective effects. We argue here that ACE inhibitors not only act as selective TGF-beta inhibitors, but also as selective immunomodulators, to improve lupus nephritis.

Susceptibility of mast cell-deficient W/Wv mice to pristane-induced experimental lupus nephritis

In many models of organ-specific autoimmune diseases, mast cells provide a critical cellular link between autoantibodies and end-organ inflammation, both initiating and propagating disease. However, their role in systemic autoimmunity remains speculative. We therefore examined the role of mast cells in a murine model of systemic immune complex-related autoimmune disease, lupus nephritis, expecting to observe the development of humoral autoimmunity in the absence of end-organ disease. Surprisingly, not only did mast cell-deficient animals develop characteristic humoral features of lupus, including hypergammaglobulinemia and autoantibodies, they also developed immune complex glomerulonephritis, as evidenced by renal immune deposits, glomerular disease, and proteinuria. These findings implicate the presence of distinct effector pathways to end-organ damage in humoral autoimmune diseases: one involving the interaction between autoantibodies and mast cells to recruit inflammation in organ-specific autoimmunity, and another involving a more direct--mast cell-independent--interaction between autoantibodies and circulating inflammatory mediators in systemic autoimmunity.

Predictors and outcome of renal flares after successful cyclophosphamide treatment for diffuse proliferative lupus glomerulonephritis

OBJECTIVE

To study the incidence, predictors, and outcome of renal flares after successful cyclophosphamide (CYC) treatment for diffuse proliferative glomerulonephritis (DPGN) in patients with systemic lupus erythematosus (SLE).

METHODS

Between 1988 and 2001, patients with biopsy-proven SLE DPGN who were treated initially with prednisone and CYC were studied. Those who responded to CYC were followed up for the occurrence of renal flares. The cumulative risk, predictors, and outcome of renal flares were evaluated.

RESULTS

We studied 189 patients (167 women; and 22 men) with SLE DPGN. All were initially treated with prednisone and CYC (49% orally; 51% by intravenous pulse). At the last dose of CYC, 103 patients (55%) and 52 patients (28%) had achieved complete and partial renal responses, respectively. Azathioprine (AZA) was given as maintenance therapy in 117 patients (75%). After a mean followup of 96.5 months, 59 patients (38%) experienced renal flares (42% nephritic; 58% proteinuric). The median time to relapse was 32 months. The cumulative risk of renal flare was 28% at 36 months and 44% at 60 months. Independent predictors of nephritic flares were persistently low C3 levels after CYC treatment and absence of AZA maintenance therapy. At the last clinic visit, 16 patients (10.3%) had developed doubling of the serum creatinine level (cumulative risk of creatinine doubling 7.4% at 5 years after renal biopsy and 14.3% at 10 years). Ten patients (6.5%) developed end-stage renal disease (ESRD). Renal survival rates at 5 and 10 years were 94.9% and 87.5%, respectively. Increasing histologic chronicity scores, failure to achieve complete response, persistent hypertension after CYC treatment, and nephritic renal flares were unfavorable factors for doubling of the serum creatinine level and for ESRD by univariate analysis. The occurrence of nephritic flares was the only predictor of creatinine doubling by Cox regression analysis.

CONCLUSION

In patients with SLE DPGN, renal flares are common despite initial responses to CYC. Nephritic renal flares are associated with a decline in renal function. Maintenance therapy with AZA reduces, but does not completely prevent, renal flares. More effective maintenance treatment for SLE DPGN after an initial response to CYC should be evaluated.

EPR imaging of reducing activity in Nrf2 transcriptional factor-deficient mice

Mice that lack the Nrf2 (NF-E2-related factor 2) transcription factor develop a lupus-like autoimmune nephritis. The tissue-reducing activity of Nrf2-deficient mice was evaluated using a combination of real-time EPR imaging and spin probe kinetic analysis. Substantial delay in the spin probe 3-carbamoyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (Carbamoyl-PROXYL) disappearance in the liver and kidneys of Nrf2-deficient mice was observed by EPR imaging. The half-life of the spin probe in the upper abdominal area was prolonged in both the Nrf2-deficient mice and in aged mice. The combination of Nrf2 deficiency and aging in female mice resulted in the most prolonged half-life of disappearance, which was four times longer than that of juvenile female mice with a wild-type genotype. These results indicate that the low reducing activity in these organs is brought about by both Nrf2 deficiency and the aging process, and it may play a key role in the onset of autoimmune nephritis. This combination of the EPR imaging and half-life analysis appears to be a very powerful tool in the real-time analysis of reducing activity.

The value of lymphocytopenia as a marker of systemic involvement in cutaneous lupus erythematosus

BACKGROUND

Some patients suffering from cutaneous lupus erythematosus (CLE) develop extracutaneous manifestations during the course of the disease: up to 5% of patients with discoid LE (DLE) and up to 30% of subacute cutaneous LE (SCLE) patients show systemic involvement. Recent studies revealed some markers indicating systemic manifestations of CLE patients. However, the significance of diminished peripheral lymphocyte numbers as a marker of systemic involvement in CLE has not been investigated before.

OBJECTIVES

To determine the value of lymphocytopenia (< 1500 cells microL(-1)) as a marker of extracutaneous manifestations in CLE patients. : Methods The records of 72 CLE patients (44 DLE; 28 SCLE) were investigated. Systemic involvement was defined in accordance with the criteria of the European Academy of Dermatology and Venereology. Analyses of peripheral lymphocyte numbers were done by fluorescence-activated cell sorter analysis.

RESULTS

Five CLE patients developed extracutaneous manifestations during the course of disease. All these patients were lymphocytopenic. Differences between peripheral lymphocyte numbers of CLE patients with and without additional systemic involvement were highly significant (P < 0.01).

CONCLUSIONS

Our results suggest that lymphocytopenia in patients with CLE is a high sensitive but low specific marker of systemic involvement.

Outcome and prognostic indicators of diffuse proliferative lupus glomerulonephritis treated with sequential oral cyclophosphamide and azathioprine

OBJECTIVE

To study the outcome and prognostic indicators of diffuse proliferative glomerulonephritis (DPGN) in patients with systemic lupus erythematosus (SLE) treated with sequential oral cyclophosphamide (CYC) and azathioprine (AZA).

METHODS

SLE patients with biopsy-proven DPGN treated with sequential oral CYC and AZA were studied. Those who achieved renal remission at 12 months were identified, and the clinical predictors of complete remission were evaluated by regression analysis. All patients were followed up until a relapse of the nephritis or a doubling of the serum creatinine level occurred. The timing and risk factors for flares and creatinine doubling were evaluated by Kaplan-Meier analysis and with the Cox proportional hazards model.

RESULTS

We studied 55 patients (47 women, 8 men; mean +/- SD age at renal biopsy 31.1 +/- 10.4 years); 25 (46%) had a serum creatinine level >106 micromoles/liter, and 29 (53%) had nephrotic syndrome. At 12 months posttreatment, 37 (67%) had complete remission and 12 (22%) had partial remission. The initial serum creatinine level was an independent predictor of complete remission. Excluding the 4 patients who were treatment- resistant or died, 21 patients (41%) had renal flares during a median followup of 4 years. The cumulative risk of renal flare was 6% at 1 year, 21% at 3 years, and 32% at 5 years. The median time to relapse was 43 months. The histologic activity score and the mean daily dose of CYC were multivariate predictors of renal flare, by Cox regression. At the last followup visit, 9 of 54 patients (17%) had a doubling of the creatinine level, 6 of whom (11%) underwent dialysis. The cumulative risk of creatinine doubling was 8.4% at 5 years and 18.2% at 10 years. An increasing chronicity index at the time of initial renal biopsy was an independent predictor of deterioration in renal function.

CONCLUSION

Sequential therapy with oral CYC followed by AZA appears to be an effective treatment regimen for DPGN in patients with SLE, with 89% of patients achieving complete or partial remission at 12 months, 62.8% remaining in remission after 5 years, and 81.8% having stable renal function after 10 years. Predictors of treatment resistance and relapse include increasing serum creatinine level, higher histologic activity scores, and a lower dose of CYC. Increasing chronicity indices predict a deterioration of renal function.

Modulation of renal disease in MRL/lpr mice by pharmacologic inhibition of inducible nitric oxide synthase

BACKGROUND

MRL-MPJFaslpr (MRL/lpr) mice spontaneously develop lupus-like disease characterized by immune complex glomerulonephritis and overproduction of nitric oxide (NO). Blocking NO production pharmacologically by a non-specific nitric oxide synthase (NOS) inhibitor ameliorated renal disease in MRL/lpr mice while genetically deficient inducible NOS (iNOS) mice developed proliferative glomerulonephritis similar to wild-type controls.

METHODS

To clarify the role of iNOS in the pathogenesis of nephritis in MRL/lpr mice, we treated mice with two different NOS inhibitors. Either NG-monomethyl-l-arginine (L-NMMA), a nonspecific NOS inhibitor, or l-N6-(1-iminoethyl)lysine (L-NIL), an iNOS specific inhibitor, was administered in the drinking water from 10 through 22 weeks of age with disease progression monitored over time. Control mice received water alone.

RESULTS

Both L-NMMA and L-NIL blocked NO production effectively in MRL/lpr mice. As expected, neither L-NNMA nor L-NIL had an effect on antibody production, immune complex deposition or complement activation. Although both NOS inhibitors decreased protein excretion, L-NMMA was more effective than L-NIL. Pathologic renal disease was significantly decreased at 19 weeks in both treatment groups. At 22 weeks the L-NIL treated mice, but not the L-NMMA mice, had significantly reduced renal disease scores compared to controls.

CONCLUSION

These results indicate that specific inhibition of iNOS blocks the development of pathologic renal disease in MRL/lpr mice.

Lupus nephritis in African Americans

Lupus nephritis is more common and severe in African American women. Despite aggressive immunosuppressive therapies employed in lupus nephritis, African Americans have a higher incidence of progression to end-stage renal disease. The reasons for the racial disparities are not clear, but seem to be due to genetic, environmental, and socioeconomic factors. Hypertension and proteinuria are well-defined prognostic factors that significantly impact the course of renal disease progression for most forms of renal disease. However, clinical trials in lupus nephritis to date have not evaluated the role of aggressive antihypertensive or antiproteinuric therapies in retarding renal disease progression. Thus, additional studies are needed to better elucidate the natural history of lupus nephritis in African Americans and to optimize therapeutic strategies for those who are identified as being at high risk.

Nrf2-deficient female mice develop lupus-like autoimmune nephritis

BACKGROUND

NF-E2-related factor 2 (Nrf2) is a basic leucine zipper transcriptional activator essential for the coordinate transcriptional induction of antioxidant enzymes and phase II drug metabolizing enzymes through the antioxidant response element/electrophile response element. The Nrf2-deficient mice were found to develop normally under standard laboratory conditions. However, upon closer examination, we found that aged female Nrf2-deficient mice displayed a shortened lifespan and developed severe glomerulonephritis. The present study investigated the glomerulonephritis findings in Nrf2-deficient mice.

METHODS

To evaluate glomerular lesions of Nrf2-deficient mice, histological and functional analyses were performed. The amounts of serum immunoglobulins, anti-double-stranded (ds) DNA antibody, and lipid peroxidation using thiobarbituric acid reactive substances (TBARS) also were measured.

RESULTS

Nrf2-deficient female mice over 60 weeks of age developed severe nephritis characterized by cellular proliferation, lobular formation, crescent formation, and subepithelial electron-dense deposits. In immunofluorescent assays, Nrf2-deficient female mice showed mesangial deposits and massive granular deposits of IgG, IgM, and C3 along the capillary walls. Higher serum levels of IgG, anti-dsDNA antibody, lower creatinine clearance, and slight splenomegaly also were found in Nrf2-deficient female mice. A higher concentration of TBARS also was found in Nrf2-deficient female mice.

CONCLUSIONS

These data indicate that the aged Nrf2-deficient female mice develop lupus-like autoimmune nephritis and suggest that nrf2 is one of the genes determining susceptibility to autoimmune disease. Analysis of nephritis in the Nrf2-deficient female mouse may clarify the mechanisms leading to the development of lupus disease.

HLA-DR modulates autoantibody repertoire, but not mortality, in a humanized mouse model of systemic lupus erythematosus

To evaluate the disease-modulating role of HLA-DR2 and DR3 molecules, which have been associated with systemic lupus erythematosus, a humanized mouse model was examined. HLA-DR2 (DRB1*1502)- and DR3 (DRB1*0301)-transgenic mice were backcrossed to the New Zealand Mixed 2410 (NZM 2410, H2(z)) strain. Seventh generation DR2 and DR3 transgene-positive animals along with their transgene-negative littermates and the parental strain NZM2410 were monitored for proteinuria, azotemia, autoantibody production, development of nephritis, and mortality. The results showed no significant differences in proteinuria, azotemia, or mortality between the backcrosses with and without HLA-DR2 or HLA-DR3. However, the genetic analysis of different backcrosses showed that heterozygosity at the endogenous H2-E locus (E(z)/E(b)) was strongly linked with acceleration of lupus nephritis in both HLA-DR2 and HLA-DR3 transgenics. More importantly, the presence of the HLA-DR2, but not the HLA-DR3, transgene significantly enhanced the production of anti-dsDNA, but not anti-ssDNA, anti-histone-dsDNA complex, or anti-histone, Abs. In contrast, neither HLA-DR2 nor HLA-DR3 influenced the development of glomerulonephritis or the degree of immune complex deposition. Moreover, nephritic kidneys from mice with and without HLA-DR2 or HLA-DR3 transgenes showed similar patterns of cytokine expression. Collectively, these findings provide molecular evidence that the association of HLA-DR2 or HLA-DR3 with lupus susceptibility is related to the type of autoantibody rather than to disease mortality. The use of a humanized mouse model provides a way of dissecting the roles of human MHC genes in systemic lupus erythematosus pathogenesis.

Hydrogen peroxide is a novel inducer of connective tissue growth factor

Connective tissue growth factor (CTGF) has recently been described as a fibrogenic factor and is greatly induced by various extracellular stimuli, such as transforming growth factor-beta (TGF-beta), dexamethasone, and serotonin. CTGF induces collagen type I and fibronectin, and the deposition of such molecules leads to fibrotic disease in many tissues. Intracellular reactive oxygen species (ROS) are generated by extracellular stress conditions and are produced as by-products of cellular metabolism. Imbalanced cellular redox status is a potent pathogenic factor that leads to various degenerative diseases, including tissue fibrosis. Since CTGF is believed to play a crucial role in fibrotic disease formation in many tissues, we examined the role of ROS in CTGF gene expression in human lens epithelial cell line B3. The results showed that CTGF was induced by reactive oxygen species such as hydrogen peroxide and hydroxyl radicals. Next, we examined whether CTGF induction by ROS is via newly synthesized TGF-beta. The results showed that ROS directly induced CTGF mRNA not via the increased TGF-beta synthesis or activation. Next, we treated AG490, which is the well-known inhibitor of Janus kinase (JAK), with hydrogen peroxide. AG490 abrogated the CTGF induction by ROS in a dose-dependent manner. The results suggest that JAK-2/-3 seems to be involved in the enhanced CTGF mRNA expression by hydrogen peroxide. In this report, we present that hydrogen peroxide is a novel inducer of CTGF gene expression and that JAK-2/-3 activation seems to play a role in CTGF induction.

Dietary phytoestrogens: a possible role in renal disease protection

There is growing evidence that dietary phytoestrogens have a beneficial role in chronic renal disease. This review summarizes the recent findings from dietary intervention studies performed in animals and humans suggesting that consumption of soy-based protein rich in isoflavones and flaxseed rich in lignans retards the development and progression of chronic renal disease. In several animal models of renal disease, both soy protein and flaxseed have been shown to limit or reduce proteinuria and renal pathological lesions associated with progressive renal failure. In studies of human subjects with different types of chronic renal disease, soy protein and flaxseed also appear to moderate proteinuria and preserve renal function. However, most of these clinical trials were of relatively short duration and involved a small number of patients. Furthermore, it is not clear whether the renal protective effects of soy protein and flaxseed are caused by the isoflavones (daidzein and genistein) and lignans (matairesinol and secoisolariciresinol) or some other component. The biochemistry, metabolism, and mechanisms of actions of isoflavones and lignans are discussed. Isoflavones and lignans appear to act through various mechanisms that modulate cell growth and proliferation, extracellular matrix synthesis, inflammation, and oxidative stress. Some of these actions have been shown in vitro, but studies of the mechanisms operative in vivo are lacking. The diversity of cellular actions of isoflavones and lignans supports their protective effects in a variety of experimental and human types of chronic renal disease. Further investigations are needed to evaluate their long-term effects on renal disease progression in patients with chronic renal failure.

Renal immunofluorescence and the prediction of renal outcome in patients with proliferative lupus nephritis

The risk for endstage renal failure in patients with proliferative lupus nephritis (PLN) depends largely on the severity and reversibility of the inflammatory process as determined by light microscopy (LM). As the intrarenal formation of immune complexes is thought to initiate this inflammation, we studied whether renal immunofluorescence microscopy (IFM) provides clinical or prognostic information in addition to LM findings. Clinical data at the time of renal biopsy and during a mean follow-up of 46 months were extracted from the records of 69 SLE patients with proliferative LN (WHO class III/IV). Biopsy specimens were analyzed by LM for AI and CI, while IFM was performed on cryostat sections with the use of antisera against IgG, IgM, IgA, C3, C1q and fibrin. IFM findings were recorded in terms of the localization (glomerular, tubular or vascular) and intensity of fluorescence (score from zero to three). IFM findings were then related to clinical and LM findings and its prognostic value studied by survival analysis. Glomerular immune deposits were present in 99% of patients, tubular deposits in 38% and vascular deposits in 17%. A 'full-house' pattern (all three Ig classes) was found in 67% of biopsies and C3 and C1q deposits in 93% and 74% respectively. Median scores for AI and CI were 6 (1-18) and 3 (0-10); aside from a negative correlation between IgA deposits and CI, we found no other correlation between the amount or type of immune deposits and AI or CI. IgM deposits were associated with high serum levels of anti-dsDNA, while IgG deposits correlated with high ESR and serum creatinin levels. IFM scores were not related to steroid dose at the time of biopsy and neither type of glomerular, tubular or overall renal immune deposits had prognostic value for renal survival. Renal immunofluorescence does not reflect light microscopy findings in patients with PLN and does not contribute prognostic information in patients with PLN. Lupus (2000) 9, 504-510.